diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index c61d15ed446b4..0c2c21335a806 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -8,6 +8,7 @@ docs/compilers @dotnet/roslyn-compiler
 docs/ide @dotnet/roslyn-ide
 
 eng/ @dotnet/roslyn-infrastructure
+eng/SourceBuild* @dotnet/source-build-internal
 scripts/ @dotnet/roslyn-infrastructure
 
 src/Analyzers/ @dotnet/roslyn-ide
diff --git a/.gitignore b/.gitignore
index 1b5de22f73c67..960bf567817ac 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,6 +20,7 @@
 .dotnet/
 .tools/
 .packages/
+.nuget/
 
 # Enable "build/" folder in the NuGet Packages folder since NuGet packages use it for MSBuild targets
 !packages/*/build/
diff --git a/Roslyn.sln b/Roslyn.sln
index e68230672e34d..290580925c9e5 100644
--- a/Roslyn.sln
+++ b/Roslyn.sln
@@ -523,10 +523,16 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.CodeAnalysis.Exte
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.CodeAnalysis.ExternalAccess.RazorCompiler.UnitTests", "src\Tools\ExternalAccess\RazorCompilerTest\Microsoft.CodeAnalysis.ExternalAccess.RazorCompiler.UnitTests.csproj", "{828FD0DB-9927-42AC-B6C2-D1514965D6C3}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.CodeAnalysis.LanguageServer", "src\Features\LanguageServer\Microsoft.CodeAnalysis.LanguageServer\Microsoft.CodeAnalysis.LanguageServer.csproj", "{2A3C94F7-5B5E-4CDC-B645-672815E61DEB}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.CodeAnalysis.LanguageServer.UnitTests", "src\Features\LanguageServer\Microsoft.CodeAnalysis.LanguageServer.UnitTests\Microsoft.CodeAnalysis.LanguageServer.UnitTests.csproj", "{9A90AA02-4275-40ED-B1F1-731AF17E675C}"
+EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Net.Compilers.Toolset.Framework.Package", "src\NuGet\Microsoft.Net.Compilers.Toolset\Framework\Microsoft.Net.Compilers.Toolset.Framework.Package.csproj", "{521ADC3E-CC15-414B-9356-D87C5BCF3A24}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "LanguageServer", "LanguageServer", "{D449D505-CC6A-4E0B-AF1B-976E2D0AE67A}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.VisualStudio.LanguageServices.DevKit", "src\VisualStudio\DevKit\Impl\Microsoft.VisualStudio.LanguageServices.DevKit.csproj", "{9B7AC5C2-293D-438D-B9A2-1EDDC2C6BF00}"
+EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.CodeAnalysis.CSharp.Features.UnitTests", "src\Features\CSharpTest\Microsoft.CodeAnalysis.CSharp.Features.UnitTests.csproj", "{E645B517-5766-46FB-AA4A-D4D30C9E3BE6}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.CodeAnalysis.Features.UnitTests", "src\Features\Test\Microsoft.CodeAnalysis.Features.UnitTests.csproj", "{9296F799-5DE4-4E12-A68E-AAC39B0EB90A}"
@@ -1295,10 +1301,22 @@ Global
 		{828FD0DB-9927-42AC-B6C2-D1514965D6C3}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{828FD0DB-9927-42AC-B6C2-D1514965D6C3}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{828FD0DB-9927-42AC-B6C2-D1514965D6C3}.Release|Any CPU.Build.0 = Release|Any CPU
+		{2A3C94F7-5B5E-4CDC-B645-672815E61DEB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2A3C94F7-5B5E-4CDC-B645-672815E61DEB}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2A3C94F7-5B5E-4CDC-B645-672815E61DEB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2A3C94F7-5B5E-4CDC-B645-672815E61DEB}.Release|Any CPU.Build.0 = Release|Any CPU
+		{9A90AA02-4275-40ED-B1F1-731AF17E675C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9A90AA02-4275-40ED-B1F1-731AF17E675C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9A90AA02-4275-40ED-B1F1-731AF17E675C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9A90AA02-4275-40ED-B1F1-731AF17E675C}.Release|Any CPU.Build.0 = Release|Any CPU
 		{521ADC3E-CC15-414B-9356-D87C5BCF3A24}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{521ADC3E-CC15-414B-9356-D87C5BCF3A24}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{521ADC3E-CC15-414B-9356-D87C5BCF3A24}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{521ADC3E-CC15-414B-9356-D87C5BCF3A24}.Release|Any CPU.Build.0 = Release|Any CPU
+		{9B7AC5C2-293D-438D-B9A2-1EDDC2C6BF00}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9B7AC5C2-293D-438D-B9A2-1EDDC2C6BF00}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9B7AC5C2-293D-438D-B9A2-1EDDC2C6BF00}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9B7AC5C2-293D-438D-B9A2-1EDDC2C6BF00}.Release|Any CPU.Build.0 = Release|Any CPU
 		{E645B517-5766-46FB-AA4A-D4D30C9E3BE6}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{E645B517-5766-46FB-AA4A-D4D30C9E3BE6}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{E645B517-5766-46FB-AA4A-D4D30C9E3BE6}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -1565,7 +1583,10 @@ Global
 		{8BC50AFF-1EBF-4E9A-AEBB-04F387AA800F} = {FD0FAF5F-1DED-485C-99FA-84B97F3A8EEC}
 		{E5E0BF73-95F7-4BC3-8443-2336C4FF4297} = {8977A560-45C2-4EC2-A849-97335B382C74}
 		{828FD0DB-9927-42AC-B6C2-D1514965D6C3} = {8977A560-45C2-4EC2-A849-97335B382C74}
+		{2A3C94F7-5B5E-4CDC-B645-672815E61DEB} = {D449D505-CC6A-4E0B-AF1B-976E2D0AE67A}
+		{9A90AA02-4275-40ED-B1F1-731AF17E675C} = {D449D505-CC6A-4E0B-AF1B-976E2D0AE67A}
 		{521ADC3E-CC15-414B-9356-D87C5BCF3A24} = {C52D8057-43AF-40E6-A01B-6CDBB7301985}
+		{9B7AC5C2-293D-438D-B9A2-1EDDC2C6BF00} = {8DBA5174-B0AA-4561-82B1-A46607697753}
 		{E645B517-5766-46FB-AA4A-D4D30C9E3BE6} = {3E5FE3DB-45F7-4D83-9097-8F05D3B3AEC6}
 		{9296F799-5DE4-4E12-A68E-AAC39B0EB90A} = {3E5FE3DB-45F7-4D83-9097-8F05D3B3AEC6}
 		{57B7C0AA-E14A-41F6-AD06-FB3937F66FC2} = {3E5FE3DB-45F7-4D83-9097-8F05D3B3AEC6}
@@ -1624,6 +1645,8 @@ Global
 		src\Compilers\Server\VBCSCompiler\VBCSCompilerCommandLine.projitems*{9508f118-f62e-4c16-a6f4-7c3b56e166ad}*SharedItemsImports = 5
 		src\Compilers\VisualBasic\vbc\VbcCommandLine.projitems*{975cd834-45f4-4ea0-a395-cb60dbd0e214}*SharedItemsImports = 5
 		src\Workspaces\SharedUtilitiesAndExtensions\Workspace\Core\WorkspaceExtensions.projitems*{99f594b1-3916-471d-a761-a6731fc50e9a}*SharedItemsImports = 13
+		src\Dependencies\Collections\Microsoft.CodeAnalysis.Collections.projitems*{9b7ac5c2-293d-438d-b9a2-1eddc2c6bf00}*SharedItemsImports = 5
+		src\Dependencies\PooledObjects\Microsoft.CodeAnalysis.PooledObjects.projitems*{9b7ac5c2-293d-438d-b9a2-1eddc2c6bf00}*SharedItemsImports = 5
 		src\Analyzers\VisualBasic\CodeFixes\VisualBasicCodeFixes.projitems*{9f9ccc78-7487-4127-9d46-db23e501f001}*SharedItemsImports = 13
 		src\Analyzers\CSharp\CodeFixes\CSharpCodeFixes.projitems*{a07abcf5-bc43-4ee9-8fd8-b2d77fd54d73}*SharedItemsImports = 5
 		src\Workspaces\SharedUtilitiesAndExtensions\Workspace\CSharp\CSharpWorkspaceExtensions.projitems*{a07abcf5-bc43-4ee9-8fd8-b2d77fd54d73}*SharedItemsImports = 5
diff --git a/azure-pipelines-official.yml b/azure-pipelines-official.yml
index d4c303b6fefaa..ddd44ed2beb85 100644
--- a/azure-pipelines-official.yml
+++ b/azure-pipelines-official.yml
@@ -5,6 +5,7 @@ trigger:
     - main-vs-deps
     - release/dev16.*-vs-deps
     - release/dev17.*
+    - features/lsp_tools_host
     exclude:
     - release/dev17.0
 pr: none
@@ -81,7 +82,7 @@ stages:
   displayName: Build and Test
   pool:
     name: NetCore1ESPool-Svc-Internal
-    demands: ImageOverride -equals windows.vs2022.amd64
+    demands: ImageOverride -equals windows.vs2022preview.amd64
 
   jobs:
   - ${{ if eq(variables['Build.SourceBranch'], 'refs/heads/release/dev17.7') }}:
@@ -130,6 +131,12 @@ stages:
     - powershell: Write-Host "##vso[task.setvariable variable=VisualStudio.DropName]Products/$(System.TeamProject)/$(Build.Repository.Name)/$(SourceBranchName)/$(Build.BuildNumber)"
       displayName: Setting VisualStudio.DropName variable
 
+    - task: NodeTool@0
+      inputs:
+        versionSpec: '16.x'
+      displayName: 'Install Node.js'
+
+
     - task: NuGetToolInstaller@0
       inputs:
         versionSpec: '4.9.2'
@@ -303,6 +310,21 @@ stages:
         ArtifactName: 'PackageArtifacts'
       condition: succeeded()
 
+    # Publish language server package
+    - powershell: Write-Host "##vso[task.setvariable variable=NPMFileName]$((ls -file $(Build.SourcesDirectory)\artifacts\packages\Release\NPM\ | select -First 1).FullName)"
+      displayName: Setting NPM Package Variable
+
+    # Authenticates the .npmrc file for publishing to the internal AzDO feed.
+    # See: https://learn.microsoft.com/azure/devops/pipelines/tasks/package/npm-authenticate?view=azure-devops
+    - task: npmAuthenticate@0
+      displayName: Authenticate NPM Feed
+      inputs:
+        workingFile: $(Build.SourcesDirectory)/src/VisualStudio/DevKit/Impl/.npmrc
+        customEndpoint: devdiv-vs-green-npm-package-feed
+
+    - script: npm publish --userconfig $(Build.SourcesDirectory)\src\VisualStudio\DevKit\Impl\.npmrc $(NPMFileName)
+      displayName: Publish Language Server NPM Package
+
     # Publish Asset Manifests for Build Asset Registry job
     - task: PublishBuildArtifacts@1
       displayName: Publish Asset Manifests
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index e4f0fff4f588b..8282e102b2294 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -29,6 +29,61 @@ pr:
       - CONTRIBUTING.md
       - README.md
 
+variables:
+  # This value is conditionally overriden by the variable group DotNet-HelixApi-Access.
+  # ADO only lets us conditionally include a variable group on individual stages.
+  - name: HelixApiAccessToken
+    value: ''
+
+  # Set pool / queue name variables depending on which instance we're running in.
+  - name: PoolName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: NetCore-Public
+    ${{ else }}:
+      value: NetCore1ESPool-Internal
+
+  - name: Vs2022PreviewQueueName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: windows.vs2022preview.amd64.open
+    ${{ else }}:
+      value: windows.vs2022preview.amd64
+
+  - name: Vs2022QueueName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: windows.vs2022.amd64.open
+    ${{ else }}:
+      value: windows.vs2022.amd64
+
+  - name: UbuntuQueueName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: Build.Ubuntu.1804.Amd64.Open
+    ${{ else }}:
+      value: Build.Ubuntu.1804.Amd64
+
+  - name: HelixWindowsQueueName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: Windows.10.Amd64.Open
+    ${{ else }}:
+      value: Windows.10.Amd64
+
+  - name: HelixWindowsSpanishQueueName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: Windows.10.Amd64.Server2022.ES.Open
+    ${{ else }}:
+      value: Windows.10.Amd64.Server2022.ES
+
+  - name: HelixUbuntuQueueName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: Ubuntu.1804.Amd64.Open
+    ${{ else }}:
+      value: Ubuntu.1804.Amd64
+
+  - name: HelixMacOsQueueName
+    ${{ if eq(variables['System.TeamProject'], 'public') }}:
+      value: OSX.1015.Amd64.Open
+    ${{ else }}:
+      value: OSX.1015.Amd64
+
 stages:
 - stage: Windows_Debug_Build
   dependsOn: []
@@ -38,7 +93,8 @@ stages:
       jobName: Build_Windows_Debug
       testArtifactName: Transport_Artifacts_Windows_Debug
       configuration: Debug
-      queueName: windows.vs2022preview.amd64.open
+      poolName: $(PoolName)
+      queueName: $(Vs2022PreviewQueueName)
       restoreArguments: -msbuildEngine dotnet /p:UsingToolVSSDK=false /p:GenerateSatelliteAssemblies=false
       buildArguments: -msbuildEngine dotnet /p:UsingToolVSSDK=false /p:GenerateSatelliteAssemblies=false /p:PublishReadyToRun=false
 
@@ -50,7 +106,8 @@ stages:
       jobName: Build_Windows_Release
       testArtifactName: Transport_Artifacts_Windows_Release
       configuration: Release
-      queueName: windows.vs2022preview.amd64.open
+      poolName: $(PoolName)
+      queueName: $(Vs2022PreviewQueueName)
       restoreArguments: -msbuildEngine dotnet /p:UsingToolVSSDK=false /p:GenerateSatelliteAssemblies=false
       buildArguments: -msbuildEngine dotnet /p:UsingToolVSSDK=false /p:GenerateSatelliteAssemblies=false /p:PublishReadyToRun=false
 
@@ -62,7 +119,8 @@ stages:
       jobName: Build_Unix_Debug
       testArtifactName: Transport_Artifacts_Unix_Debug
       configuration: Debug
-      queueName: Build.Ubuntu.1804.Amd64.Open
+      poolName: $(PoolName)
+      queueName: $(UbuntuQueueName)
 
 - stage: Source_Build
   dependsOn: []
@@ -90,6 +148,9 @@ stages:
 
 - stage: Windows_Debug_Desktop
   dependsOn: Windows_Debug_Build
+  variables:
+  - ${{ if ne(variables['System.TeamProject'], 'public') }}:
+    - group: DotNet-HelixApi-Access
   jobs:
   - ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
     - template: eng/pipelines/test-windows-job.yml
@@ -99,6 +160,8 @@ stages:
         testArtifactName: Transport_Artifacts_Windows_Debug
         configuration: Debug
         testArguments: -testDesktop -testArch x86
+        helixQueueName: $(HelixWindowsQueueName)
+        helixApiAccessToken: $(HelixApiAccessToken)
 
   - template: eng/pipelines/test-windows-job.yml
     parameters:
@@ -107,9 +170,14 @@ stages:
       testArtifactName: Transport_Artifacts_Windows_Debug
       configuration: Debug
       testArguments: -testDesktop -testArch x64
+      helixQueueName: $(HelixWindowsQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
 - stage: Windows_Release_Desktop
   dependsOn: Windows_Release_Build
+  variables:
+  - ${{ if ne(variables['System.TeamProject'], 'public') }}:
+    - group: DotNet-HelixApi-Access
   jobs:
   - template: eng/pipelines/test-windows-job.yml
     parameters:
@@ -118,6 +186,8 @@ stages:
       testArtifactName: Transport_Artifacts_Windows_Release
       configuration: Release
       testArguments: -testDesktop -testArch x86
+      helixQueueName: $(HelixWindowsQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
   - ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
     - template: eng/pipelines/test-windows-job.yml
@@ -127,6 +197,8 @@ stages:
         testArtifactName: Transport_Artifacts_Windows_Release
         configuration: Release
         testArguments: -testDesktop -testArch x64
+        helixQueueName: $(HelixWindowsQueueName)
+        helixApiAccessToken: $(HelixApiAccessToken)
 
   - template: eng/pipelines/test-windows-job.yml
     parameters:
@@ -134,10 +206,15 @@ stages:
       jobName: Test_Windows_Desktop_Spanish_Release_64
       testArtifactName: Transport_Artifacts_Windows_Release
       configuration: Release
-      testArguments: -testDesktop -testArch x64 -helixQueueName Windows.10.Amd64.Server2022.ES.Open
+      testArguments: -testDesktop -testArch x64
+      helixQueueName: $(HelixWindowsSpanishQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
 - stage: Windows_Debug_CoreClr
   dependsOn: Windows_Debug_Build
+  variables:
+  - ${{ if ne(variables['System.TeamProject'], 'public') }}:
+    - group: DotNet-HelixApi-Access
   jobs:
   - template: eng/pipelines/test-windows-job.yml
     parameters:
@@ -146,6 +223,8 @@ stages:
       testArtifactName: Transport_Artifacts_Windows_Debug
       configuration: Debug
       testArguments: -testCoreClr
+      helixQueueName: $(HelixWindowsQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
   - ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
     - template: eng/pipelines/test-windows-job-single-machine.yml
@@ -154,6 +233,8 @@ stages:
         jobName: Test_Windows_CoreClr_Debug_Single_Machine
         testArtifactName: Transport_Artifacts_Windows_Debug
         configuration: Debug
+        poolName: $(PoolName)
+        queueName: $(Vs2022QueueName)
         testArguments: -testCoreClr
 
   - template: eng/pipelines/test-windows-job.yml
@@ -163,6 +244,8 @@ stages:
       testArtifactName: Transport_Artifacts_Windows_Debug
       configuration: Debug
       testArguments: -testCoreClr -testIOperation -testCompilerOnly
+      helixQueueName: $(HelixWindowsQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
   # This leg runs almost all the compiler tests supported on CoreCLR, but
   #  with additional validation for used assemblies and GetEmitDiagnostics
@@ -173,9 +256,14 @@ stages:
       testArtifactName: Transport_Artifacts_Windows_Debug
       configuration: Debug
       testArguments: -testCoreClr -testUsedAssemblies -testCompilerOnly
+      helixQueueName: $(HelixWindowsQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
 - stage: Windows_Release_CoreClr
   dependsOn: Windows_Release_Build
+  variables:
+  - ${{ if ne(variables['System.TeamProject'], 'public') }}:
+    - group: DotNet-HelixApi-Access
   jobs:
   - template: eng/pipelines/test-windows-job.yml
     parameters:
@@ -184,9 +272,14 @@ stages:
       testArtifactName: Transport_Artifacts_Windows_Release
       configuration: Release
       testArguments: -testCoreClr
+      helixQueueName: $(HelixWindowsQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
 - stage: Unix_Debug_CoreClr
   dependsOn: Unix_Build
+  variables:
+  - ${{ if ne(variables['System.TeamProject'], 'public') }}:
+    - group: DotNet-HelixApi-Access
   jobs:
   - template: eng/pipelines/test-unix-job.yml
     parameters:
@@ -194,7 +287,9 @@ stages:
       jobName: Test_Linux_Debug
       testArtifactName: Transport_Artifacts_Unix_Debug
       configuration: Debug
-      testArguments: --testCoreClr --helixQueueName Ubuntu.1804.Amd64.Open
+      testArguments: --testCoreClr
+      helixQueueName: $(HelixUbuntuQueueName)
+      helixApiAccessToken: $(HelixApiAccessToken)
 
   - ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
     - template: eng/pipelines/test-unix-job-single-machine.yml
@@ -204,7 +299,8 @@ stages:
         testArtifactName: Transport_Artifacts_Unix_Debug
         configuration: Debug
         testArguments: --testCoreClr
-        queueName: Build.Ubuntu.1804.Amd64.Open
+        poolName: $(PoolName)
+        queueName: $(UbuntuQueueName)
 
   - ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
     - template: eng/pipelines/test-unix-job.yml
@@ -213,7 +309,9 @@ stages:
         jobName: Test_macOS_Debug
         testArtifactName: Transport_Artifacts_Unix_Debug
         configuration: Debug
-        testArguments: --testCoreClr --helixQueueName OSX.1015.Amd64.Open
+        testArguments: --testCoreClr 
+        helixQueueName: $(HelixMacOsQueueName)
+        helixApiAccessToken: $(HelixApiAccessToken)
 
 - stage: Correctness
   dependsOn: []
@@ -221,6 +319,7 @@ stages:
   - template: eng/pipelines/evaluate-changed-files.yml
     parameters:
       jobName: Determine_Changes
+      poolName: $(PoolName)
       vmImageName: ubuntu-latest
       paths:
         - subset: compilers
@@ -234,8 +333,8 @@ stages:
   - job: Correctness_Build_Artifacts
     dependsOn: Determine_Changes
     pool:
-      name: NetCore-Public
-      demands: ImageOverride -equals windows.vs2022preview.amd64.open
+      name: $(PoolName)
+      demands: ImageOverride -equals $(Vs2022PreviewQueueName)
     timeoutInMinutes: 90
     variables:
       - template: eng/pipelines/variables-build.yml
@@ -284,8 +383,8 @@ stages:
     dependsOn: Determine_Changes
     condition: or(ne(variables['Build.Reason'], 'PullRequest'), eq(dependencies.Determine_Changes.outputs['SetPathVars_compilers.containsChange'], 'true'))
     pool:
-      name: NetCore-Public
-      demands: ImageOverride -equals windows.vs2022preview.amd64.open
+      name: $(PoolName)
+      demands: ImageOverride -equals $(Vs2022PreviewQueueName)
     timeoutInMinutes: 90
     variables:
       - template: eng/pipelines/variables-build.yml
@@ -306,8 +405,8 @@ stages:
     dependsOn: Determine_Changes
     condition: or(ne(variables['Build.Reason'], 'PullRequest'), eq(dependencies.Determine_Changes.outputs['SetPathVars_compilers.containsChange'], 'true'))
     pool:
-      name: NetCore-Public
-      demands: ImageOverride -equals windows.vs2022preview.amd64.open
+      name: $(PoolName)
+      demands: ImageOverride -equals $(Vs2022PreviewQueueName)
     timeoutInMinutes: 90
     variables:
       - template: eng/pipelines/variables-build.yml
@@ -322,8 +421,8 @@ stages:
     dependsOn: Determine_Changes
     condition: ne(variables['Build.Reason'], 'Pull Request')
     pool:
-      name: NetCore-Public
-      demands: ImageOverride -equals windows.vs2022preview.amd64.open
+      name: $(PoolName)
+      demands: ImageOverride -equals $(Vs2022PreviewQueueName)
     timeoutInMinutes: 90
     variables:
       - template: eng/pipelines/variables-build.yml
@@ -348,8 +447,8 @@ stages:
     dependsOn: Determine_Changes
     condition: or(ne(variables['Build.Reason'], 'PullRequest'), eq(dependencies.Determine_Changes.outputs['SetPathVars_compilers.containsChange'], 'true'))
     pool:
-      name: NetCore-Public
-      demands: ImageOverride -equals windows.vs2022preview.amd64.open
+      name: $(PoolName)
+      demands: ImageOverride -equals $(Vs2022PreviewQueueName)
     timeoutInMinutes: 90
     variables:
       - template: eng/pipelines/variables-build.yml
@@ -377,8 +476,8 @@ stages:
 
   - job: Correctness_Analyzers
     pool:
-      name: NetCore-Public
-      demands: ImageOverride -equals Build.Ubuntu.1804.Amd64.Open
+      name: $(PoolName)
+      demands: ImageOverride -equals $(UbuntuQueueName)
     timeoutInMinutes: 35
     variables:
       - template: eng/pipelines/variables-build.yml
diff --git a/docs/Language Feature Status.md b/docs/Language Feature Status.md
index df3a8363fa991..6bc04b2854ab2 100644
--- a/docs/Language Feature Status.md	
+++ b/docs/Language Feature Status.md	
@@ -19,7 +19,7 @@ efforts behind them.
 | [Default in deconstruction](https://github.com/dotnet/roslyn/pull/25562) | [decon-default](https://github.com/dotnet/roslyn/tree/features/decon-default) | [In Progress](https://github.com/dotnet/roslyn/issues/25559) | [jcouv](https://github.com/jcouv) | [gafter](https://github.com/gafter) |  | [jcouv](https://github.com/jcouv) |
 | [Collection Literals](https://github.com/dotnet/csharplang/issues/5354) | [CollectionLiterals](https://github.com/dotnet/roslyn/tree/features/CollectionLiterals) | [In Progress](https://github.com/dotnet/roslyn/issues/66418) | [cston](https://github.com/cston) | [333fred](https://github.com/333fred), [RikkiGibson](https://github.com/RikkiGibson) | [CyrusNajmabadi](https://github.com/CyrusNajmabadi) | [CyrusNajmabadi](https://github.com/CyrusNajmabadi) |
 | [Roles/Extensions](https://github.com/dotnet/csharplang/issues/5497) | [roles](https://github.com/dotnet/roslyn/tree/features/roles) | [In Progress](https://github.com/dotnet/roslyn/issues/66722) | [jcouv](https://github.com/jcouv) | [AlekseyTs](https://github.com/AlekseyTs), [jjonescz](https://github.com/jjonescz) |  | [MadsTorgersen](https://github.com/MadsTorgersen) |
-| [Interceptors](https://github.com/dotnet/csharplang/issues/7009) | [interceptors](https://github.com/dotnet/roslyn/tree/features/interceptors) | [In Progress](https://github.com/dotnet/roslyn/issues/67421) | [RikkiGibson](https://github.com/RikkiGibson) | [cston](https://github.com/cston), [jcouv](https://github.com/jcouv) | [beccamc](https://github.com/beccamc) | [RikkiGibson](https://github.com/RikkiGibson) |
+| [Interceptors](https://github.com/dotnet/csharplang/issues/7009) | [interceptors](https://github.com/dotnet/roslyn/tree/features/interceptors) | [In Progress](https://github.com/dotnet/roslyn/issues/67421) | [RikkiGibson](https://github.com/RikkiGibson) | [cston](https://github.com/cston), [jcouv](https://github.com/jcouv) | [akhera99](https://github.com/akhera99) | [RikkiGibson](https://github.com/RikkiGibson) |
 | [Inline Arrays](https://github.com/dotnet/csharplang/blob/main/proposals/inline-arrays.md) | [InlineArrays](https://github.com/dotnet/roslyn/tree/features/InlineArrays) | [In Progress](https://github.com/dotnet/roslyn/issues/67826) | [AlekseyTs](https://github.com/AlekseyTs) | [cston](https://github.com/cston), [jjonescz](https://github.com/jjonescz) |  |  |
 | [ref readonly parameters](https://github.com/dotnet/csharplang/issues/6010) | | [In Progress](https://github.com/dotnet/roslyn/issues/68056) | [jjonescz](https://github.com/jjonescz) | [jcouv](https://github.com/jcouv), [AlekseyTs](https://github.com/AlekseyTs) | [akhera99](https://github.com/akhera99) | [jaredpar](https://github.com/jaredpar)
 
diff --git a/docs/features/interceptors.md b/docs/features/interceptors.md
new file mode 100644
index 0000000000000..83ec2dd26a944
--- /dev/null
+++ b/docs/features/interceptors.md
@@ -0,0 +1,195 @@
+# Interceptors
+
+## Summary
+[summary]: #summary
+
+*Interceptors* are an experimental compiler feature planned to ship in .NET 8. The feature may be subject to breaking changes or removal in a future release.
+
+An *interceptor* is a method which can declaratively substitute a call to an *interceptable* method with a call to itself at compile time. This substitution occurs by having the interceptor declare the source locations of the calls that it intercepts. This provides a limited facility to change the semantics of existing code by adding new code to a compilation (e.g. in a source generator).
+
+```cs
+using System;
+using System.Runtime.CompilerServices;
+
+var c = new C();
+c.InterceptableMethod(1); // (L1,C1): prints "interceptor 1"
+c.InterceptableMethod(1); // (L2,C2): prints "other interceptor 1"
+c.InterceptableMethod(2); // (L3,C3): prints "other interceptor 2"
+c.InterceptableMethod(1); // prints "interceptable 1"
+
+class C
+{
+    public void InterceptableMethod(int param)
+    {
+        Console.WriteLine($"interceptable {param}");
+    }
+}
+
+// generated code
+static class D
+{
+    [InterceptsLocation("Program.cs", line: /*L1*/, character: /*C1*/)] // refers to the call at (L1, C1)
+    public static void InterceptorMethod(this C c, int param)
+    {
+        Console.WriteLine($"interceptor {param}");
+    }
+
+    [InterceptsLocation("Program.cs", line: /*L2*/, character: /*C2*/)] // refers to the call at (L2, C2)
+    [InterceptsLocation("Program.cs", line: /*L3*/, character: /*C3*/)] // refers to the call at (L3, C3)
+    public static void OtherInterceptorMethod(this C c, int param)
+    {
+        Console.WriteLine($"other interceptor {param}");
+    }
+}
+```
+
+## Detailed design
+[design]: #detailed-design
+
+### InterceptsLocationAttribute
+
+A method indicates that it is an *interceptor* by adding one or more `[InterceptsLocation]` attributes. These attributes refer to the source locations of the calls it intercepts.
+
+```cs
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+    public sealed class InterceptsLocationAttribute(string filePath, int line, int character) : Attribute
+    {
+    }
+}
+```
+
+Any "ordinary method" (i.e. with `MethodKind.Ordinary`) can have its calls intercepted.
+
+`[InterceptsLocation]` attributes included in source are emitted to the resulting assembly, just like other custom attributes.
+
+PROTOTYPE(ic): We may want to recognize `file class InterceptsLocationAttribute` as a valid declaration of the attribute, to allow generators to bring the attribute in without conflicting with other generators which may also be bringing the attribute in. See open question in [User opt-in](#user-opt-in).
+https://github.com/dotnet/roslyn/issues/67079 is a bug which causes file-local source declarations of well-known attributes to be generally treated as known. When that bug is fixed, we may want to single out `InterceptsLocationAttribute` as "recognized, even though they are file-local".
+
+#### File paths
+
+File paths used in `[InterceptsLocation]` are expected to have `/pathmap` substitution already applied. Generators should accomplish this by locally recreating the file path transformation performed by the compiler:
+
+```cs
+using Microsoft.CodeAnalysis;
+
+string GetInterceptorFilePath(SyntaxTree tree, Compilation compilation)
+{
+    return compilation.Options.SourceReferenceResolver?.NormalizePath(tree.FilePath, baseFilePath: null) ?? tree.FilePath;
+}
+```
+
+The file path given in the attribute must be equal by ordinal comparison to the value given by the above function.
+
+The compiler does not map `#line` directives when determining if an `[InterceptsLocation]` attribute intercepts a particular call in syntax.
+
+#### Position
+
+Line and column numbers in `[InterceptsLocation]` are 1-indexed to match existing places where source locations are displayed to the user. For example, in `Diagnostic.ToString`.
+
+The location of the call is the location of the simple name syntax which denotes the interceptable method. For example, in `app.MapGet(...)`, the name syntax for `MapGet` would be considered the location of the call. For a static method call like `System.Console.WriteLine(...)`, the name syntax for `WriteLine` is the location of the call. If we allow intercepting calls to property accessors in the future (e.g `obj.Property`), we would also be able to use the name syntax in this way.
+
+#### Attribute creation
+
+The goal of the above decisions is to make it so that when source generators are filling in `[InterceptsLocation(...)]`, they simply need to read `nameSyntax.SyntaxTree.FilePath` and `nameSyntax.GetLineSpan().Span.Start` for the exact file path and position information they need to use.
+
+We should provide samples of recommended coding patterns for generator authors to show correct usage of these, including the "translation" from 0-indexed to 1-indexed positions.
+
+### Non-invocation method usages
+
+Conversion to delegate type, address-of, etc. usages of methods cannot be intercepted.
+
+Interception can only occur for calls to ordinary member methods--not constructors, delegates, properties, local functions, operators, etc. Support for more member kinds may be added in the future.
+
+### Arity
+
+Interceptors cannot have type parameters or be declared in generic types at any level of nesting.
+
+This limitation prevents interceptors from matching the signature of an interceptable call in cases where the interceptable call uses type parameters which are not in scope at the interceptor declaration. We can consider adjusting the rules to alleviate this limitation if compelling scenarios arise for it in the future.
+
+```cs
+using System.Runtime.CompilerServices;
+
+class C
+{
+    public static void InterceptableMethod<T1>(T1 t) => throw null!;
+}
+
+static class Program
+{
+    public static void M<T2>(T2 t)
+    {
+        C.InterceptableMethod(t);
+    }
+}
+
+static class D
+{
+    [InterceptsLocation("Program.cs", 12, 11)]
+    public static void Interceptor1(object s) => throw null!;
+}
+```
+
+### Signature matching
+
+When a call is intercepted, the interceptor and interceptable methods must meet the signature matching requirements detailed below:
+- When an interceptable instance method is compared to a classic extension method, we use the extension method in reduced form for comparison. The extension method parameter with the `this` modifier is compared to the instance method `this` parameter.
+- The returns and parameters, including the `this` parameter, must have the same ref kinds and types.
+- A warning is reported instead of an error if a type difference is found where the types are not distinct to the runtime. For example, `object` and `dynamic`.
+- No warning or error is reported for a *safe* nullability difference, such as when the interceptable method accepts a `string` parameter, and the interceptor accepts a `string?` parameter.
+- Method names and parameter names are not required to match.
+- Parameter default values are not required to match. When intercepting, default values on the interceptor method are ignored.
+- `params` modifiers are not required to match.
+- `scoped` modifiers and `[UnscopedRef]` must be equivalent.
+- In general, attributes which normally affect the behavior of the call site, such as `[CallerLineNumber]` are ignored on the interceptor of an intercepted call.
+  - The only exception to this is when the attribute affects "capabilities" of the method in a way that affects safety, such as with `[UnscopedRef]`. Such attributes are required to match across interceptable and interceptor methods.
+
+Arity does not need to match between intercepted and interceptor methods. In other words, it is permitted to intercept a generic method with a non-generic interceptor.
+
+### Conflicting interceptors
+
+If more than one interceptor refers to the same location, it is a compile-time error.
+
+If an `[InterceptsLocation]` attribute is found in the compilation which does not refer to the location of an explicit method call, it is a compile-time error.
+
+### Interceptor accessibility
+
+An interceptor must be accessible at the location where interception is occurring.
+
+An interceptor contained in a file-local type is permitted to intercept a call in another file, even though the interceptor is not normally *visible* at the call site.
+
+This allows generator authors to avoid *polluting lookup* with interceptors, helps avoid name conflicts, and prevents use of interceptors in *unintended positions* from the interceptor author's point-of-view.
+
+We may also want to consider adjusting behavior of `[EditorBrowsable]` to work in the same compilation.
+
+### Editor experience
+
+Interceptors are treated like a post-compilation step in this design. Diagnostics are given for misuse of interceptors, but some diagnostics are only given in the command-line build and not in the IDE. There is limited traceability in the editor for which calls in a compilation are actually being intercepted. If this feature is brought forward past the experimental stage, this limitation will need to be re-examined.
+
+### User opt-in
+
+Interceptors will require a feature flag during the experimental phase. The flag can be enabled with `/features=InterceptorsPreview` on the command line or `<Features>InterceptorsPreview</Features>` in msbuild.
+
+### Implementation strategy
+
+During the binding phase, `InterceptsLocationAttribute` usages are decoded and the related data for each usage are collected in a `ConcurrentSet` on the compilation:
+- intercepted file-path and location
+- attribute location
+- attributed method symbol
+
+At this time, diagnostics are reported for the following conditions:
+- problems specific to the attributed interceptor method itself, for example, that it is not an ordinary method.
+- syntactic problems specific to the referenced location, for example, that it does not refer to an applicable simple name as defined in [Position](#position) subsection.
+
+During the lowering phase, when a given `BoundCall` is lowered:
+- we check if its syntax contains an applicable simple name
+- if so, we lookup whether it is being intercepted, based on data about `InterceptsLocationAttribute` collected during the binding phase.
+- if it is being intercepted, we perform an additional step after lowering of the receiver and arguments is completed:
+  - substitute the interceptable method with the interceptor method on the `BoundCall`.
+  - if the interceptor is a classic extension method, and the interceptable method is an instance method, we adjust the `BoundCall` to use the receiver as the first argument of the call, "pushing" the other arguments forward, similar to the way it would have bound if the original call were to an extension method in reduced form.
+
+At this time, diagnostics are reported for the following conditions:
+- incompatibility between the interceptor and interceptable methods, for example, in their signatures.
+- *duplicate* `[InterceptsLocation]`, that is, multiple interceptors which intercept the same call.
+- interceptor is not accessible at the call site.
\ No newline at end of file
diff --git a/docs/wiki/EnC-Supported-Edits.md b/docs/wiki/EnC-Supported-Edits.md
index deb3a47a412c3..c05d40b1121ce 100644
--- a/docs/wiki/EnC-Supported-Edits.md
+++ b/docs/wiki/EnC-Supported-Edits.md
@@ -1,5 +1,8 @@
-# Supported Edits in Edit & Continue (EnC)
-Edit & Continue lets you modify/add to your source code in break-mode while debugging without ever having to restart your debugging session. 
+# Supported Edits in Edit & Continue (EnC) and Hot Reload on .NET 8
+Hot Reload lets you modify/add to your source code while the application is running, either with debugger attached to the process (F5) or not attached (Ctrl+F5).
+Edit & Continue lets you modify/add to your source code in break-mode while debugging without having to restart your debugging session.
+
+This document captures the current state. Potential future improvements in this area are tracked by https://github.com/dotnet/roslyn/issues/49001.
 
 **Definitions**
 * [Variable Capturing](http://blogs.msdn.com/b/matt/archive/2008/03/01/understanding-variable-capturing-in-c.aspx) is the mechanism in which the lambda/delegate which is defined inline is able to hold on to any variables within its lexical scope
@@ -12,50 +15,38 @@ Edit & Continue lets you modify/add to your source code in break-mode while debu
 ### Supported Edits
 | Edit operation | Additional Info |
 | ------------------- |--------------------|
-| Add methods, fields, constructors, properties, events, indexers, field and property initializers, nested types and top-level types (including delegates, enums, interfaces, abstract and generic types, and anonymous types) to an existing type  | The existing type cannot be a generic or an interface. <br/> <br/> Adding or modifying [enum members](https://msdn.microsoft.com/en-us/library/sbbt4032.aspx) within an existing enum is not supported. |
-| Add and modify iterators  | Changing a regular method to an iterator method *is* supported |
-| Add async/await expressions  |  Adding an await expression into an existing async method is not supported. <br/><br/> Adding an await expression around an active statement is not supported. <br/><br/> Changing a regular method to async *is* supported. |
-| Modify async/await expressions  |  Modifying await expressions wrapped inside other expressions (e.g. ```G(await F());```) is not supported |
+| Add methods, fields, constructors, properties, events, indexers, field and property initializers, nested types and top-level types (including delegates, enums, interfaces, abstract and generic types, and anonymous types) to an existing type  | The existing type cannot be an interface. <br/> <br/> Adding or modifying [enum members](https://msdn.microsoft.com/en-us/library/sbbt4032.aspx) within an existing enum is not supported. |
+| Add and modify iterators, `yield` statements | Changing a regular method to an iterator method *is* supported |
+| Add and modify async methods, `await` expressions | Modifying await expressions wrapped inside other expressions (e.g. ```G(await F());```) is not supported. <br/><br/> Changing a regular method to async *is* supported. |
 | Add and modify operations with dynamic objects | - |
-| Add and modify C# 6.0 language features like string interpolation and null-conditional operators | - |
 | Add lambda expressions | Lambda expressions can only be added if they are static, access the “this” reference that has already been captured, or access captured variables from a single scope |
+| Modify generic code | Enabled in .NET 8 and Visual Studio 17.7 |
 | Modify lambda expressions | The following rules guarantee that the structure of the emitted closure tree will not change--thus ensuring that lambdas in the new body are mapped to the corresponding generated CLR methods that implemented their previous versions: <ul><li>Lambda signatures cannot be modified (this includes names, types, ref-ness of parameters, and return types)</li><li>The set of variables captured by the lambda expression cannot be modified (a variable that has not been captured before cannot be captured after modification and vice versa)</li><li>The scope of captured variables cannot be modified</li><li>The set of captured variables accessed by the lambda expression cannot be modified</li></ul> |
 | Add LINQ expressions | LINQ expressions contain implicitly-declared anonymous functions. This means the edit rules for lambdas and LINQ will be the same. |
 | Modify LINQ expressions | LINQ expressions contain implicitly-declared anonymous functions. This means the edit rules for lambdas and LINQ will be the same. |
 | Modifying async lambda and LINQ expressions in combination | You can edit various nested expressions provided that they otherwise satisfy the EnC rules | 
-| Edit partial class * | https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes#:~:text=it%20is%20now%20possible%20to%20apply%20changes%20in%20code%20that%20is%20within%20a%20partial%20class. |
-| Edit Source Generated File * | https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes#:~:text=you%20can%20now%20apply%20changes%20within%20a%20source%20generated)%20file. |
-| Add using statement * | https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes#:~:text=it%20is%20now%20possible%20to%20add%20and%2For%20change%20a%20using%20directive. |
-
-* = As of Visual Studio 2019 Version 16.10
-
-
+| Edit partial class | Enabled in [VS 16.10](https://learn.microsoft.com/en-us/visualstudio/releases/2019/release-notes-v16.10) |
+| Edit Source Generated File | Enabled in [VS 16.10](https://learn.microsoft.com/en-us/visualstudio/releases/2019/release-notes-v16.10). |
+| Add using directive | Enabled in [VS 16.10](https://learn.microsoft.com/en-us/visualstudio/releases/2019/release-notes-v16.10). |
+| Deleting members other than fields | Enabled in [VS 17.3](https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes-v17.3) |
+| Renaming members other than fields | Enabled in [VS 17.4](https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes-v17.4) |
+| Rename method parameters | Enabled in [VS 17.0](https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes-v17.0) | 
+| Modify method parameter types | Enabled in [VS 17.4](https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes-v17.4) |
+| Change return type of a method/event/property/operator/indexer | Enabled in [VS 17.4](https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes-v17.4) |
+| Add and modify custom attributes | Enabled in [VS 17.0](https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes-v17.0) | 
+| Adding and modifying namespace declarations | Enabled in [VS 17.3](https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes-v17.3) |
 
 ### Not Supported Edits
 | Edit operation      | Additional Info |
 | ------------------- |-----------------|
-| Modify [method signatures](https://msdn.microsoft.com/en-us/library/ms173114.aspx) | - |
-| Add or modify [generics](https://msdn.microsoft.com/en-us/library/512aeb7t.aspx) | - |
 | Modify interfaces | - |
 | Add a method body such that an abstract method becomes non-abstract | - |
 | Add new abstract, virtual, or override member to a type | You CAN add a non-abstract member to an abstract type |
 | Add [destructor](https://msdn.microsoft.com/en-us/library/66x5fx1b.aspx) to an existing type |  - |
-| Modify a type parameter, base type, delegate type, or return type of an event/property/operator/indexer | - |
+| Modify a type parameter, base type, delegate type | - |
 | Modify a catch-block if it contains an active statement (leaf or internal) | - |
 | Modify a try-catch-finally block if the finally clause contains an active statement | - |
-| Renaming of any kind | - |
-| Delete members, types, namespaces | - |
-| Delete entire method bodies | Not supported because deleting an entire method body would make the method “abstract”—which is not currently supported |
-| Add using statements | Allowed in Visual Studio 2019 Version 16.10 | 
-| Add a namespace | - |
+| Delete types | - |
 | Edit a member referencing an embedded interop type | - |
 | Edit a member with On Error or Resume statements | Specific to Visual Basic |
 | Edit a member containing an Aggregate, Group By, Simple Join, or Group Join LINQ query clause | Specific to Visual Basic |
-| Edit an async method/lambda in a project that doesn't define or reference AsyncStateMachineAttribute type (e.g. projects targeting .NET Framework 4.0 and lower) | - |
-| Edit an iterator method/lambda in a project that doesn't define or reference IteratorStateMachineAttribute type (e.g. projects targeting .NET Framework 4.0 and lower) | - |
-
-### App Model EnC Support
-
-| Support EnC | Do Not Support EnC | 
-| ------------------ |------------------------------| 
-| <ul><li>Apps that support the 4.6 desktop version of the CLR for both x86 and x64 (e.g., Console, WPF, Windows 8.1 apps)</li><li>UWP in Windows 10</li><ul> | <ul><li>ASP.NET 5 apps</li><li>Silverlight 5</li><li>Windows Phone 8.1</li><li>Windows Phone 10</li><li>Windows Phone emulator scenarios</li><li>Windows Store 8.1</li></ul>|
diff --git a/dotnet-tools.json b/dotnet-tools.json
index b81fdc2997f8c..4577fa79bb69f 100644
--- a/dotnet-tools.json
+++ b/dotnet-tools.json
@@ -2,7 +2,7 @@
   "isRoot": true,
   "tools": {
     "dotnet-format": {
-      "version": "6.4.326609",
+      "version": "7.0.360304",
       "commands": [
         "dotnet-format"
       ]
diff --git a/eng/Signing.props b/eng/Signing.props
index a3b096a15d715..c857d4d1cf656 100644
--- a/eng/Signing.props
+++ b/eng/Signing.props
@@ -42,6 +42,7 @@
     <FileSignInfo Include="Nerdbank.Streams.dll" CertificateName="3PartySHA2" />
     <FileSignInfo Include="Newtonsoft.Json.dll" CertificateName="3PartySHA2" />
     <FileSignInfo Include="Validation.dll" CertificateName="3PartySHA2" />
+    <FileSignInfo Include="Humanizer.dll" CertificateName="3PartySHA2" />
 
     <!-- Sign VS/Microsoft dlls we crossgen'd and included in the vsix for our .NET remote host with Microsoft cert -->
     <FileSignInfo Include="Microsoft.CodeAnalysis.Elfie.dll" CertificateName="MicrosoftSHA2" />
diff --git a/eng/SourceBuild.props b/eng/SourceBuild.props
index a8b55f352ade9..c0ca9b21c9bb5 100644
--- a/eng/SourceBuild.props
+++ b/eng/SourceBuild.props
@@ -1,3 +1,5 @@
+<!-- Whenever altering this or other Source Build files, please include @dotnet/source-build-internal as a reviewer. -->
+
 <Project>
 
   <PropertyGroup>
diff --git a/eng/SourceBuildPrebuiltBaseline.xml b/eng/SourceBuildPrebuiltBaseline.xml
index a6de405305083..6fc9593ba0f39 100644
--- a/eng/SourceBuildPrebuiltBaseline.xml
+++ b/eng/SourceBuildPrebuiltBaseline.xml
@@ -1,3 +1,6 @@
+<!-- Whenever altering this or other Source Build files, please include @dotnet/source-build-internal as a reviewer. -->
+<!-- See aka.ms/dotnet/prebuilts for guidance on what pre-builts are and how to eliminate them. -->
+
 <UsageData>
   <IgnorePatterns>
     <UsagePattern IdentityGlob="Microsoft.SourceBuild.Intermediate.*/*" />
diff --git a/eng/Version.Details.xml b/eng/Version.Details.xml
index 2f91f1ce3627c..d8d7a25d52160 100644
--- a/eng/Version.Details.xml
+++ b/eng/Version.Details.xml
@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Dependencies>
   <ProductDependencies>
-    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-externals" Version="8.0.0-alpha.1.23251.2">
+    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-externals" Version="8.0.0-alpha.1.23319.1">
       <Uri>https://github.com/dotnet/source-build-externals</Uri>
-      <Sha>7133c4310e0df9b425455a54bcd6816f46b79465</Sha>
+      <Sha>0d04efdab9f26bad07edc881dc7fa088337b8562</Sha>
       <SourceBuild RepoName="source-build-externals" ManagedOnly="true" />
     </Dependency>
     <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-reference-packages" Version="8.0.0-alpha.1.23211.4">
@@ -13,22 +13,22 @@
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>
-    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="8.0.0-beta.23220.2">
+    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="8.0.0-beta.23326.5">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>d75baf71a09ed067b48f484f29efc4e7f3e3df13</Sha>
+      <Sha>c0e0c6d3e5b5fd90084486f11f0a7cb3d4577e4f</Sha>
       <SourceBuild RepoName="arcade" ManagedOnly="true" />
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.XliffTasks" Version="1.0.0-beta.23165.1" CoherentParentDependency="Microsoft.DotNet.Arcade.Sdk">
+    <Dependency Name="Microsoft.DotNet.XliffTasks" Version="1.0.0-beta.23319.1" CoherentParentDependency="Microsoft.DotNet.Arcade.Sdk">
       <Uri>https://github.com/dotnet/xliff-tasks</Uri>
-      <Sha>b7fb98b199d0b1b6188da4f4bf4f5accddac98d4</Sha>
+      <Sha>b0368bfd6df87d2e30b1191d81c477b5419a9f29</Sha>
       <SourceBuild RepoName="xliff-tasks" ManagedOnly="true" />
     </Dependency>
-    <Dependency Name="Microsoft.SourceLink.GitHub" Version="1.2.0-beta-23165-02" CoherentParentDependency="Microsoft.DotNet.Arcade.Sdk">
+    <Dependency Name="Microsoft.SourceLink.GitHub" Version="8.0.0-beta.23314.2" CoherentParentDependency="Microsoft.DotNet.Arcade.Sdk">
       <Uri>https://github.com/dotnet/sourcelink</Uri>
-      <Sha>3f43bf1b2dead2cb51f20dc47f6dfd7981248820</Sha>
+      <Sha>4d2c8bf58e8cb7900ec2d9077c155572e2d3cd88</Sha>
       <SourceBuild RepoName="sourcelink" ManagedOnly="true" />
     </Dependency>
-    <Dependency Name="Microsoft.DiaSymReader" Version="2.0.0" CoherentParentDependency="Microsoft.Net.Compilers.Toolset">
+    <Dependency Name="Microsoft.DiaSymReader" Version="2.0.0">
       <Uri>https://github.com/dotnet/symreader</Uri>
       <Sha>27e584661980ee6d82c419a2a471ae505b7d122e</Sha>
     </Dependency>
@@ -36,9 +36,9 @@
       <Uri>https://github.com/dotnet/roslyn</Uri>
       <Sha>5d10d428050c0d6afef30a072c4ae68776621877</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.Helix.Sdk" Version="8.0.0-beta.23220.2">
+    <Dependency Name="Microsoft.DotNet.Helix.Sdk" Version="8.0.0-beta.23326.5">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>d75baf71a09ed067b48f484f29efc4e7f3e3df13</Sha>
+      <Sha>c0e0c6d3e5b5fd90084486f11f0a7cb3d4577e4f</Sha>
     </Dependency>
     <Dependency Name="Microsoft.CodeAnalysis.NetAnalyzers" Version="8.0.0-preview.23251.1">
       <Uri>https://github.com/dotnet/roslyn-analyzers</Uri>
diff --git a/eng/Versions.props b/eng/Versions.props
index 95deeab853a94..aed92e872beca 100644
--- a/eng/Versions.props
+++ b/eng/Versions.props
@@ -15,25 +15,25 @@
       Keep the setting conditional. The toolset sets the assembly version to 42.42.42.42 if not set explicitly.
     -->
     <AssemblyVersion Condition="'$(OfficialBuild)' == 'true' or '$(DotNetUseShippingVersions)' == 'true'">$(MajorVersion).$(MinorVersion).0.0</AssemblyVersion>
-    <MicrosoftNetCompilersToolsetVersion>4.5.0</MicrosoftNetCompilersToolsetVersion>
+    <MicrosoftNetCompilersToolsetVersion>4.7.0-1.final</MicrosoftNetCompilersToolsetVersion>
   </PropertyGroup>
   <PropertyGroup>
     <!-- Versions used by several individual references below -->
-    <RoslynDiagnosticsNugetPackageVersion>3.3.5-beta1.23204.1</RoslynDiagnosticsNugetPackageVersion>
-    <MicrosoftCodeAnalysisNetAnalyzersVersion>8.0.0-preview.23251.1</MicrosoftCodeAnalysisNetAnalyzersVersion>
+    <RoslynDiagnosticsNugetPackageVersion>3.3.5-beta1.23307.1</RoslynDiagnosticsNugetPackageVersion>
+    <MicrosoftCodeAnalysisNetAnalyzersVersion>8.0.0-preview.23307.1</MicrosoftCodeAnalysisNetAnalyzersVersion>
     <MicrosoftCodeAnalysisTestingVersion>1.1.2-beta1.23163.2</MicrosoftCodeAnalysisTestingVersion>
     <MicrosoftVisualStudioExtensibilityTestingVersion>0.1.149-beta</MicrosoftVisualStudioExtensibilityTestingVersion>
     <!-- CodeStyleAnalyzerVersion should we updated together with version of dotnet-format in dotnet-tools.json -->
-    <CodeStyleAnalyzerVersion>4.3.0-1.final</CodeStyleAnalyzerVersion>
-    <VisualStudioEditorPackagesVersion>17.6.252</VisualStudioEditorPackagesVersion>
+    <CodeStyleAnalyzerVersion>4.6.0</CodeStyleAnalyzerVersion>
+    <VisualStudioEditorPackagesVersion>17.7.38-preview</VisualStudioEditorPackagesVersion>
     <!-- This should generally be set to $(VisualStudioEditorPackagesVersion),
          but sometimes EditorFeatures.Cocoa specifically requires a newer editor build. -->
     <VisualStudioMacEditorPackagesVersion>$(VisualStudioEditorPackagesVersion)</VisualStudioMacEditorPackagesVersion>
     <ILAsmPackageVersion>6.0.0-rtm.21518.12</ILAsmPackageVersion>
     <ILDAsmPackageVersion>6.0.0-rtm.21518.12</ILDAsmPackageVersion>
-    <MicrosoftVisualStudioLanguageServerClientPackagesVersion>17.6.26-preview</MicrosoftVisualStudioLanguageServerClientPackagesVersion>
+    <MicrosoftVisualStudioLanguageServerClientPackagesVersion>17.7.4-preview</MicrosoftVisualStudioLanguageServerClientPackagesVersion>
     <MicrosoftVisualStudioLanguageServerProtocolPackagesVersion>17.7.8-preview-g8c33dc3a76</MicrosoftVisualStudioLanguageServerProtocolPackagesVersion>
-    <MicrosoftVisualStudioShellPackagesVersion>17.6.35829</MicrosoftVisualStudioShellPackagesVersion>
+    <MicrosoftVisualStudioShellPackagesVersion>17.7.35038-preview.1</MicrosoftVisualStudioShellPackagesVersion>
     <RefOnlyMicrosoftBuildPackagesVersion>16.10.0</RefOnlyMicrosoftBuildPackagesVersion>
     <!-- The version of Roslyn we build Source Generators against that are built in this
          repository. This must be lower than MicrosoftNetCompilersToolsetVersion,
@@ -41,7 +41,7 @@
          the generators we build would load on the command line but not load in IDEs. -->
     <SourceGeneratorMicrosoftCodeAnalysisVersion>4.1.0</SourceGeneratorMicrosoftCodeAnalysisVersion>
     <MicrosoftILVerificationVersion>7.0.0-alpha.1.22060.1</MicrosoftILVerificationVersion>
-    <MicrosoftVisualStudioThreadingPackagesVersion>17.6.40</MicrosoftVisualStudioThreadingPackagesVersion>
+    <MicrosoftVisualStudioThreadingPackagesVersion>17.7.1-preview</MicrosoftVisualStudioThreadingPackagesVersion>
     <MicrosoftTestPlatformVersion>17.4.0-preview-20220707-01</MicrosoftTestPlatformVersion>
   </PropertyGroup>
   <!--
@@ -53,6 +53,7 @@
     <BasicReferenceAssembliesNet50Version>1.2.4</BasicReferenceAssembliesNet50Version>
     <BasicReferenceAssembliesNet60Version>1.2.4</BasicReferenceAssembliesNet60Version>
     <BasicReferenceAssembliesNet70Version>1.3.0</BasicReferenceAssembliesNet70Version>
+    <BasicReferenceAssembliesNet80Version>1.4.2</BasicReferenceAssembliesNet80Version>
     <BasicReferenceAssembliesNet461Version>1.3.0</BasicReferenceAssembliesNet461Version>
     <BasicReferenceAssembliesNetStandard13Version>1.2.4</BasicReferenceAssembliesNetStandard13Version>
     <BenchmarkDotNetVersion>0.13.0</BenchmarkDotNetVersion>
@@ -78,6 +79,7 @@
     <RefOnlyMicrosoftBuildUtilitiesCoreVersion>$(RefOnlyMicrosoftBuildPackagesVersion)</RefOnlyMicrosoftBuildUtilitiesCoreVersion>
     <NuGetVisualStudioContractsVersion>6.0.0-preview.0.15</NuGetVisualStudioContractsVersion>
     <MicrosoftVisualStudioRpcContractsVersion>17.5.14-alpha</MicrosoftVisualStudioRpcContractsVersion>
+    <MicrosoftAspNetCoreRazorExternalAccessRoslynWorkspaceVersion>7.0.0-preview.23251.2</MicrosoftAspNetCoreRazorExternalAccessRoslynWorkspaceVersion>
     <!--
       Since the Microsoft.CodeAnalysis.Analyzers package is a public dependency of our NuGet
       packages we will keep it untied to the RoslynDiagnosticsNugetPackageVersion we use for
@@ -107,11 +109,13 @@
     <MicrosoftDiaSymReaderNativeVersion>17.0.0-beta1.21524.1</MicrosoftDiaSymReaderNativeVersion>
     <MicrosoftDiaSymReaderPortablePdbVersion>1.7.0-beta-21528-01</MicrosoftDiaSymReaderPortablePdbVersion>
     <MicrosoftExtensionsLoggingVersion>6.0.0</MicrosoftExtensionsLoggingVersion>
+    <MicrosoftExtensionsLoggingAbstractionsVersion>6.0.2</MicrosoftExtensionsLoggingAbstractionsVersion>
     <MicrosoftExtensionsLoggingConsoleVersion>6.0.0</MicrosoftExtensionsLoggingConsoleVersion>
     <MicrosoftIdentityModelClientsActiveDirectoryVersion>3.13.8</MicrosoftIdentityModelClientsActiveDirectoryVersion>
     <MicrosoftInternalPerformanceCodeMarkersDesignTimeVersion>15.8.27812-alpha</MicrosoftInternalPerformanceCodeMarkersDesignTimeVersion>
-    <MicrosoftInternalVisualStudioInteropVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftInternalVisualStudioInteropVersion>
+    <MicrosoftInternalVisualStudioInteropVersion>17.7.35038-preview.1</MicrosoftInternalVisualStudioInteropVersion>
     <MicrosoftInternalVisualStudioShellFrameworkVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftInternalVisualStudioShellFrameworkVersion>
+    <MicrosoftIORedistVersion>6.0.0</MicrosoftIORedistVersion>
     <MicrosoftmacOSRefVersion>12.3.300-rc.3.83</MicrosoftmacOSRefVersion>
     <MicrosoftIORedistVersion>6.0.0</MicrosoftIORedistVersion>
     <MicrosoftMetadataVisualizerVersion>1.0.0-beta3.21075.2</MicrosoftMetadataVisualizerVersion>
@@ -127,8 +131,8 @@
     <MicrosoftNetSdkVersion>2.0.0-alpha-20170405-2</MicrosoftNetSdkVersion>
     <MicrosoftNuGetBuildTasksVersion>0.1.0</MicrosoftNuGetBuildTasksVersion>
     <MicrosoftPortableTargetsVersion>0.1.2-dev</MicrosoftPortableTargetsVersion>
-    <MicrosoftServiceHubClientVersion>4.2.1009</MicrosoftServiceHubClientVersion>
-    <MicrosoftServiceHubFrameworkVersion>4.2.100</MicrosoftServiceHubFrameworkVersion>
+    <MicrosoftServiceHubClientVersion>4.2.1017</MicrosoftServiceHubClientVersion>
+    <MicrosoftServiceHubFrameworkVersion>4.2.102</MicrosoftServiceHubFrameworkVersion>
     <MicrosoftSourceLinkToolsVersion>1.1.1-beta-21566-01</MicrosoftSourceLinkToolsVersion>
     <MicrosoftTeamFoundationServerClientVersion>16.170.0</MicrosoftTeamFoundationServerClientVersion>
     <MicrosoftTestPlatformTranslationLayerVersion>$(MicrosoftTestPlatformVersion)</MicrosoftTestPlatformTranslationLayerVersion>
@@ -137,8 +141,8 @@
     <MicrosoftVisualStudioCacheVersion>17.3.26-alpha</MicrosoftVisualStudioCacheVersion>
     <MicrosoftVisualStudioCallHierarchyPackageDefinitionsVersion>15.8.27812-alpha</MicrosoftVisualStudioCallHierarchyPackageDefinitionsVersion>
     <MicrosoftVisualStudioCodeAnalysisSdkUIVersion>15.8.27812-alpha</MicrosoftVisualStudioCodeAnalysisSdkUIVersion>
-    <MicrosoftVisualStudioComponentModelHostVersion>17.6.199-preview</MicrosoftVisualStudioComponentModelHostVersion>
-    <MicrosoftVisualStudioCompositionVersion>17.6.6</MicrosoftVisualStudioCompositionVersion>
+    <MicrosoftVisualStudioComponentModelHostVersion>17.6.256</MicrosoftVisualStudioComponentModelHostVersion>
+    <MicrosoftVisualStudioCompositionVersion>17.7.1-preview</MicrosoftVisualStudioCompositionVersion>
     <MicrosoftVisualStudioCoreUtilityVersion>$(VisualStudioEditorPackagesVersion)</MicrosoftVisualStudioCoreUtilityVersion>
     <MicrosoftVisualStudioDebuggerUIInterfacesVersion>17.6.0-beta.23252.1</MicrosoftVisualStudioDebuggerUIInterfacesVersion>
     <MicrosoftVisualStudioDebuggerContractsVersion>17.6.0-beta.23252.1</MicrosoftVisualStudioDebuggerContractsVersion>
@@ -158,7 +162,8 @@
     <MicrosoftVisualStudioImageCatalogVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioImageCatalogVersion>
     <MicrosoftVisualStudioImagingVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioImagingVersion>
     <MicrosoftVisualStudioImagingInterop140DesignTimeVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioImagingInterop140DesignTimeVersion>
-    <MicrosoftVisualStudioInteropVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioInteropVersion>
+    <MicrosoftVisualStudioInternalMicroBuildNpmPackVersion>2.0.93</MicrosoftVisualStudioInternalMicroBuildNpmPackVersion>
+    <MicrosoftVisualStudioInteropVersion>17.7.35038-preview.1</MicrosoftVisualStudioInteropVersion>
     <MicrosoftVisualStudioLanguageVersion>$(VisualStudioEditorPackagesVersion)</MicrosoftVisualStudioLanguageVersion>
     <MicrosoftVisualStudioLanguageCallHierarchyVersion>15.8.27812-alpha</MicrosoftVisualStudioLanguageCallHierarchyVersion>
     <MicrosoftVisualStudioLanguageIntellisenseVersion>$(VisualStudioEditorPackagesVersion)</MicrosoftVisualStudioLanguageIntellisenseVersion>
@@ -181,11 +186,11 @@
     <MicrosoftVisualStudioRemoteControlVersion>16.3.52</MicrosoftVisualStudioRemoteControlVersion>
     <MicrosoftVisualStudioSDKAnalyzersVersion>16.10.10</MicrosoftVisualStudioSDKAnalyzersVersion>
     <MicrosoftVisualStudioSearchVersion>17.5.0-preview-2-33111-081</MicrosoftVisualStudioSearchVersion>
-    <MicrosoftVisualStudioSetupConfigurationInteropVersion>3.6.2080</MicrosoftVisualStudioSetupConfigurationInteropVersion>
+    <MicrosoftVisualStudioSetupConfigurationInteropVersion>3.6.2111</MicrosoftVisualStudioSetupConfigurationInteropVersion>
     <MicrosoftVisualStudioShell150Version>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioShell150Version>
     <MicrosoftVisualStudioShellFrameworkVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioShellFrameworkVersion>
     <MicrosoftVisualStudioShellDesignVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioShellDesignVersion>
-    <MicrosoftVisualStudioTelemetryVersion>17.6.46</MicrosoftVisualStudioTelemetryVersion>
+    <MicrosoftVisualStudioTelemetryVersion>17.7.55</MicrosoftVisualStudioTelemetryVersion>
     <MicrosoftVisualStudioTemplateWizardInterfaceVersion>8.0.0.0-alpha</MicrosoftVisualStudioTemplateWizardInterfaceVersion>
     <MicrosoftVisualStudioTextDataVersion>$(VisualStudioEditorPackagesVersion)</MicrosoftVisualStudioTextDataVersion>
     <MicrosoftVisualStudioTextInternalVersion>$(VisualStudioEditorPackagesVersion)</MicrosoftVisualStudioTextInternalVersion>
@@ -196,6 +201,7 @@
     <MicrosoftVisualStudioThreadingAnalyzersVersion>$(MicrosoftVisualStudioThreadingPackagesVersion)</MicrosoftVisualStudioThreadingAnalyzersVersion>
     <MicrosoftVisualStudioThreadingVersion>$(MicrosoftVisualStudioThreadingPackagesVersion)</MicrosoftVisualStudioThreadingVersion>
     <MicrosoftVisualStudioUtilitiesVersion>$(MicrosoftVisualStudioShellPackagesVersion)</MicrosoftVisualStudioUtilitiesVersion>
+    <MicrosoftVisualStudioUtilitiesInternalVersion>16.3.42</MicrosoftVisualStudioUtilitiesInternalVersion>
     <MicrosoftVisualStudioValidationVersion>17.6.11</MicrosoftVisualStudioValidationVersion>
     <MicrosoftVisualStudioInteractiveWindowVersion>4.0.0</MicrosoftVisualStudioInteractiveWindowVersion>
     <MicrosoftVisualStudioVsInteractiveWindowVersion>4.0.0</MicrosoftVisualStudioVsInteractiveWindowVersion>
@@ -207,7 +213,7 @@
     <MDbgVersion>0.1.0</MDbgVersion>
     <MonoOptionsVersion>6.6.0.161</MonoOptionsVersion>
     <MoqVersion>4.10.1</MoqVersion>
-    <NerdbankStreamsVersion>2.9.112</NerdbankStreamsVersion>
+    <NerdbankStreamsVersion>2.9.116</NerdbankStreamsVersion>
     <NuGetVisualStudioVersion>6.0.0-preview.0.15</NuGetVisualStudioVersion>
     <NuGetSolutionRestoreManagerInteropVersion>4.8.0</NuGetSolutionRestoreManagerInteropVersion>
     <MicrosoftDiaSymReaderPdb2PdbVersion>1.1.0-beta1-62506-02</MicrosoftDiaSymReaderPdb2PdbVersion>
@@ -221,7 +227,7 @@
       is expected by the NET SDK used in the Workspace.MSBuild UnitTests. In order to test against the same verion of NuGet
       as our configured SDK, we must set the version to be the same.
      -->
-    <NuGetCommonVersion>6.6.0-preview.3.57</NuGetCommonVersion>
+    <NuGetCommonVersion>6.7.0-preview.2.50</NuGetCommonVersion>
     <NuGetConfigurationVersion>$(NuGetCommonVersion)</NuGetConfigurationVersion>
     <NuGetFrameworksVersion>$(NuGetCommonVersion)</NuGetFrameworksVersion>
     <NuGetPackagingVersion>$(NuGetCommonVersion)</NuGetPackagingVersion>
@@ -233,8 +239,9 @@
     <SystemBuffersVersion>4.5.1</SystemBuffersVersion>
     <SystemCompositionVersion>7.0.0</SystemCompositionVersion>
     <SystemCodeDomVersion>7.0.0</SystemCodeDomVersion>
-    <SystemCommandLineVersion>2.0.0-beta1.20574.7</SystemCommandLineVersion>
+    <SystemCommandLineVersion>2.0.0-beta4.22272.1</SystemCommandLineVersion>
     <SystemCommandLineExperimentalVersion>0.3.0-alpha.19577.1</SystemCommandLineExperimentalVersion>
+    <SystemCommandLineNamingConventionBinderVersion>$(SystemCommandLineVersion)</SystemCommandLineNamingConventionBinderVersion>
     <SystemComponentModelCompositionVersion>7.0.0</SystemComponentModelCompositionVersion>
     <SystemConfigurationConfigurationManagerVersion>7.0.0</SystemConfigurationConfigurationManagerVersion>
     <SystemDrawingCommonVersion>7.0.0</SystemDrawingCommonVersion>
@@ -291,7 +298,7 @@
       create a test insertion in Visual Studio to validate.
     -->
     <NewtonsoftJsonVersion>13.0.3</NewtonsoftJsonVersion>
-    <StreamJsonRpcVersion>2.15.26</StreamJsonRpcVersion>
+    <StreamJsonRpcVersion>2.15.29</StreamJsonRpcVersion>
     <!--
       When updating the S.C.I or S.R.M version please let the MSBuild team know in advance so they
       can update to the same version. Version changes require a VS test insertion for validation.
diff --git a/eng/build.ps1 b/eng/build.ps1
index 300b675bad461..88ed9a10ae5a4 100644
--- a/eng/build.ps1
+++ b/eng/build.ps1
@@ -68,6 +68,7 @@ param (
   [switch]$sequential,
   [switch]$helix,
   [string]$helixQueueName = "",
+  [string]$helixApiAccessToken = "",
 
   [parameter(ValueFromRemainingArguments=$true)][string[]]$properties)
 
@@ -260,6 +261,8 @@ function BuildSolution() {
   # https://github.com/NuGet/Home/issues/12373
   $restoreUseStaticGraphEvaluation = if ($ci) { $false } else { $true }
   
+  $isNpmAvailable = IsNpmAvailable
+
   try {
     MSBuild $toolsetBuildProj `
       $bl `
@@ -282,6 +285,7 @@ function BuildSolution() {
       /p:RestoreUseStaticGraphEvaluation=$restoreUseStaticGraphEvaluation `
       /p:VisualStudioIbcDrop=$ibcDropName `
       /p:VisualStudioDropAccessToken=$officialVisualStudioDropAccessToken `
+      /p:IsNpmPackable=$isNpmAvailable `
       $suppressExtensionDeployment `
       $msbuildWarnAsError `
       $buildFromSource `
@@ -401,7 +405,7 @@ function TestUsingRunTests() {
   $args += " --configuration $configuration"
 
   if ($testCoreClr) {
-    $args += " --tfm net6.0 --tfm net7.0"
+    $args += " --tfm net6.0 --tfm net7.0 --tfm net8.0"
     $args += " --timeout 90"
     if ($testCompilerOnly) {
       $args += GetCompilerTestAssembliesIncludePaths
@@ -461,6 +465,10 @@ function TestUsingRunTests() {
     $args += " --helixQueueName $helixQueueName"
   }
 
+  if ($helixApiAccessToken) {
+    $args += " --helixApiAccessToken $helixApiAccessToken"
+  }
+
   try {
     Write-Host "$runTests $args"
     Exec-Console $dotnetExe "$runTests $args"
@@ -705,6 +713,14 @@ function List-Processes() {
   Get-Process -Name "devenv" -ErrorAction SilentlyContinue | Out-Host
 }
 
+function IsNpmAvailable() {
+  if (Get-Command "npm" -ErrorAction SilentlyContinue) {
+    return $true
+  }
+
+  return $false;
+}
+
 try {
   if ($PSVersionTable.PSVersion.Major -lt "5") {
     Write-Host "PowerShell version must be 5 or greater (version $($PSVersionTable.PSVersion) detected)"
diff --git a/eng/build.sh b/eng/build.sh
index d49ebf7de670b..c160b5e887752 100755
--- a/eng/build.sh
+++ b/eng/build.sh
@@ -68,6 +68,7 @@ binary_log=false
 ci=false
 helix=false
 helix_queue_name=""
+helix_api_access_token=""
 bootstrap=false
 run_analyzers=false
 skip_documentation=false
@@ -140,6 +141,11 @@ while [[ $# > 0 ]]; do
       args="$args $1"
       shift
       ;;
+    --helixapiaccesstoken)
+      helix_api_access_token=$2
+      args="$args $1"
+      shift
+      ;;
     --bootstrap)
       bootstrap=true
       # Bootstrap requires restore
@@ -320,6 +326,10 @@ if [[ "$test_core_clr" == true ]]; then
     runtests_args="$runtests_args --helixQueueName $helix_queue_name"
   fi
 
+  if [[ -n "$helix_api_access_token" ]]; then
+    runtests_args="$runtests_args --helixApiAccessToken $helix_api_access_token"
+  fi
+
   if [[ "$helix" == true ]]; then
     runtests_args="$runtests_args --helix"
   fi
diff --git a/eng/common/cross/build-rootfs.sh b/eng/common/cross/build-rootfs.sh
index 1deadcc676e30..9caf9b021dbdd 100755
--- a/eng/common/cross/build-rootfs.sh
+++ b/eng/common/cross/build-rootfs.sh
@@ -27,6 +27,7 @@ __AlpineArch=armv7
 __FreeBSDArch=arm
 __FreeBSDMachineArch=armv7
 __IllumosArch=arm7
+__HaikuArch=arm
 __QEMUArch=arm
 __UbuntuArch=armhf
 __UbuntuRepo="http://ports.ubuntu.com/"
@@ -70,7 +71,7 @@ __AlpinePackages+=" krb5-dev"
 __AlpinePackages+=" openssl-dev"
 __AlpinePackages+=" zlib-dev"
 
-__FreeBSDBase="12.3-RELEASE"
+__FreeBSDBase="12.4-RELEASE"
 __FreeBSDPkg="1.17.0"
 __FreeBSDABI="12"
 __FreeBSDPackages="libunwind"
@@ -85,8 +86,12 @@ __IllumosPackages+=" mit-krb5"
 __IllumosPackages+=" openssl"
 __IllumosPackages+=" zlib"
 
-__HaikuPackages="gmp"
+__HaikuPackages="gcc_syslibs"
+__HaikuPackages+=" gcc_syslibs_devel"
+__HaikuPackages+=" gmp"
 __HaikuPackages+=" gmp_devel"
+__HaikuPackages+=" icu66"
+__HaikuPackages+=" icu66_devel"
 __HaikuPackages+=" krb5"
 __HaikuPackages+=" krb5_devel"
 __HaikuPackages+=" libiconv"
@@ -95,6 +100,10 @@ __HaikuPackages+=" llvm12_libunwind"
 __HaikuPackages+=" llvm12_libunwind_devel"
 __HaikuPackages+=" mpfr"
 __HaikuPackages+=" mpfr_devel"
+__HaikuPackages+=" openssl"
+__HaikuPackages+=" openssl_devel"
+__HaikuPackages+=" zlib"
+__HaikuPackages+=" zlib_devel"
 
 # ML.NET dependencies
 __UbuntuPackages+=" libomp5"
@@ -210,6 +219,7 @@ while :; do
             __FreeBSDArch=amd64
             __FreeBSDMachineArch=amd64
             __illumosArch=x86_64
+            __HaikuArch=x86_64
             __UbuntuRepo="http://archive.ubuntu.com/ubuntu/"
             ;;
         x86)
@@ -330,7 +340,7 @@ while :; do
             ;;
         freebsd13)
             __CodeName=freebsd
-            __FreeBSDBase="13.0-RELEASE"
+            __FreeBSDBase="13.2-RELEASE"
             __FreeBSDABI="13"
             __SkipUnmount=1
             ;;
@@ -340,7 +350,6 @@ while :; do
             ;;
         haiku)
             __CodeName=haiku
-            __BuildArch=x64
             __SkipUnmount=1
             ;;
         --skipunmount)
@@ -559,67 +568,54 @@ elif [[ "$__CodeName" == "illumos" ]]; then
 elif [[ "$__CodeName" == "haiku" ]]; then
     JOBS=${MAXJOBS:="$(getconf _NPROCESSORS_ONLN)"}
 
-    echo "Building Haiku sysroot for x86_64"
+    echo "Building Haiku sysroot for $__HaikuArch"
     mkdir -p "$__RootfsDir/tmp"
-    cd "$__RootfsDir/tmp"
-    git clone -b hrev56235  https://review.haiku-os.org/haiku
-    git clone -b btrev43195 https://review.haiku-os.org/buildtools
-    cd "$__RootfsDir/tmp/buildtools" && git checkout 7487388f5110021d400b9f3b88e1a7f310dc066d
-
-    # Fetch some unmerged patches
-    cd "$__RootfsDir/tmp/haiku"
-    ## Add development build profile (slimmer than nightly)
-    git fetch origin refs/changes/64/4164/1 && git -c commit.gpgsign=false cherry-pick FETCH_HEAD
-
-    # Build jam
-    cd "$__RootfsDir/tmp/buildtools/jam"
-    make
-
-    # Configure cross tools
-    echo "Building cross-compiler"
-    mkdir -p "$__RootfsDir/generated"
-    cd "$__RootfsDir/generated"
-    "$__RootfsDir/tmp/haiku/configure" -j"$JOBS" --sysroot "$__RootfsDir" --cross-tools-source "$__RootfsDir/tmp/buildtools" --build-cross-tools x86_64
-
-    # Build Haiku packages
-    echo "Building Haiku"
-    echo 'HAIKU_BUILD_PROFILE = "development-raw" ;' > UserProfileConfig
-    "$__RootfsDir/tmp/buildtools/jam/jam0" -j"$JOBS" -q '<build>package' '<repository>Haiku'
-
-    BaseUrl="https://depot.haiku-os.org/__api/v2/pkg/get-pkg"
-
-    # Download additional packages
-    echo "Downloading additional required packages"
+    pushd "$__RootfsDir/tmp"
+
+    mkdir "$__RootfsDir/tmp/download"
+
+    echo "Downloading Haiku package tool"
+    git clone https://github.com/haiku/haiku-toolchains-ubuntu --depth 1 $__RootfsDir/tmp/script
+    wget -O "$__RootfsDir/tmp/download/hosttools.zip" $($__RootfsDir/tmp/script/fetch.sh --hosttools)
+    unzip -o "$__RootfsDir/tmp/download/hosttools.zip" -d "$__RootfsDir/tmp/bin"
+
+    DepotBaseUrl="https://depot.haiku-os.org/__api/v2/pkg/get-pkg"
+    HpkgBaseUrl="https://eu.hpkg.haiku-os.org/haiku/master/$__HaikuArch/current"
+
+    # Download Haiku packages
+    echo "Downloading Haiku packages"
     read -ra array <<<"$__HaikuPackages"
     for package in "${array[@]}"; do
         echo "Downloading $package..."
         # API documented here: https://github.com/haiku/haikudepotserver/blob/master/haikudepotserver-api2/src/main/resources/api2/pkg.yaml#L60
         # The schema here: https://github.com/haiku/haikudepotserver/blob/master/haikudepotserver-api2/src/main/resources/api2/pkg.yaml#L598
-        hpkgDownloadUrl="$(wget -qO- --post-data='{"name":"'"$package"'","repositorySourceCode":"haikuports_x86_64","versionType":"LATEST","naturalLanguageCode":"en"}' \
-            --header='Content-Type:application/json' "$BaseUrl" | jq -r '.result.versions[].hpkgDownloadURL')"
-        wget -P "$__RootfsDir/generated/download" "$hpkgDownloadUrl"
+        hpkgDownloadUrl="$(wget -qO- --post-data='{"name":"'"$package"'","repositorySourceCode":"haikuports_'$__HaikuArch'","versionType":"LATEST","naturalLanguageCode":"en"}' \
+            --header='Content-Type:application/json' "$DepotBaseUrl" | jq -r '.result.versions[].hpkgDownloadURL')"
+        wget -P "$__RootfsDir/tmp/download" "$hpkgDownloadUrl"
+    done
+    for package in haiku haiku_devel; do
+        echo "Downloading $package..."
+        hpkgVersion="$(wget -qO- $HpkgBaseUrl | sed -n 's/^.*version: "\([^"]*\)".*$/\1/p')"
+        wget -P "$__RootfsDir/tmp/download" "$HpkgBaseUrl/packages/$package-$hpkgVersion-1-$__HaikuArch.hpkg"
     done
 
-    # Setup the sysroot
-    echo "Setting up sysroot and extracting needed packages"
+    # Set up the sysroot
+    echo "Setting up sysroot and extracting required packages"
     mkdir -p "$__RootfsDir/boot/system"
-    for file in "$__RootfsDir/generated/objects/haiku/x86_64/packaging/packages/"*.hpkg; do
-        "$__RootfsDir/generated/objects/linux/x86_64/release/tools/package/package" extract -C "$__RootfsDir/boot/system" "$file"
-    done
-    for file in "$__RootfsDir/generated/download/"*.hpkg; do
-        "$__RootfsDir/generated/objects/linux/x86_64/release/tools/package/package" extract -C "$__RootfsDir/boot/system" "$file"
+    for file in "$__RootfsDir/tmp/download/"*.hpkg; do
+        echo "Extracting $file..."
+        LD_LIBRARY_PATH="$__RootfsDir/tmp/bin" "$__RootfsDir/tmp/bin/package" extract -C "$__RootfsDir/boot/system" "$file"
     done
 
+    # Download buildtools
+    echo "Downloading Haiku buildtools"
+    wget -O "$__RootfsDir/tmp/download/buildtools.zip" $($__RootfsDir/tmp/script/fetch.sh --buildtools --arch=$__HaikuArch)
+    unzip -o "$__RootfsDir/tmp/download/buildtools.zip" -d "$__RootfsDir"
+
     # Cleaning up temporary files
     echo "Cleaning up temporary files"
+    popd
     rm -rf "$__RootfsDir/tmp"
-    for name in "$__RootfsDir/generated/"*; do
-        if [[ "$name" =~ "cross-tools-" ]]; then
-            : # Keep the cross-compiler
-        else
-            rm -rf "$name"
-        fi
-    done
 elif [[ -n "$__CodeName" ]]; then
 
     if [[ "$__SkipSigCheck" == "0" ]]; then
diff --git a/eng/common/cross/toolchain.cmake b/eng/common/cross/toolchain.cmake
index 1c9d212d13592..a88d643c8a765 100644
--- a/eng/common/cross/toolchain.cmake
+++ b/eng/common/cross/toolchain.cmake
@@ -6,6 +6,7 @@ unset(FREEBSD)
 unset(ILLUMOS)
 unset(ANDROID)
 unset(TIZEN)
+unset(HAIKU)
 
 set(TARGET_ARCH_NAME $ENV{TARGET_BUILD_ARCH})
 if(EXISTS ${CROSS_ROOTFS}/bin/freebsd-version)
@@ -16,6 +17,7 @@ elseif(EXISTS ${CROSS_ROOTFS}/usr/platform/i86pc)
   set(ILLUMOS 1)
 elseif(EXISTS ${CROSS_ROOTFS}/boot/system/develop/headers/config/HaikuConfig.h)
   set(CMAKE_SYSTEM_NAME Haiku)
+  set(HAIKU 1)
 else()
   set(CMAKE_SYSTEM_NAME Linux)
   set(LINUX 1)
@@ -67,13 +69,25 @@ elseif(TARGET_ARCH_NAME STREQUAL "armv6")
   endif()
 elseif(TARGET_ARCH_NAME STREQUAL "ppc64le")
   set(CMAKE_SYSTEM_PROCESSOR ppc64le)
-  set(TOOLCHAIN "powerpc64le-linux-gnu")
+  if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/powerpc64le-alpine-linux-musl)
+    set(TOOLCHAIN "powerpc64le-alpine-linux-musl")
+  else()
+    set(TOOLCHAIN "powerpc64le-linux-gnu")
+  endif()
 elseif(TARGET_ARCH_NAME STREQUAL "riscv64")
   set(CMAKE_SYSTEM_PROCESSOR riscv64)
-  set(TOOLCHAIN "riscv64-linux-gnu")
+  if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/riscv64-alpine-linux-musl)
+    set(TOOLCHAIN "riscv64-alpine-linux-musl")
+  else()
+    set(TOOLCHAIN "riscv64-linux-gnu")
+  endif()
 elseif(TARGET_ARCH_NAME STREQUAL "s390x")
   set(CMAKE_SYSTEM_PROCESSOR s390x)
-  set(TOOLCHAIN "s390x-linux-gnu")
+  if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/s390x-alpine-linux-musl)
+    set(TOOLCHAIN "s390x-alpine-linux-musl")
+  else()
+    set(TOOLCHAIN "s390x-linux-gnu")
+  endif()
 elseif(TARGET_ARCH_NAME STREQUAL "x64")
   set(CMAKE_SYSTEM_PROCESSOR x86_64)
   if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/x86_64-alpine-linux-musl)
@@ -88,11 +102,15 @@ elseif(TARGET_ARCH_NAME STREQUAL "x64")
   elseif(ILLUMOS)
     set(TOOLCHAIN "x86_64-illumos")
   elseif(HAIKU)
-    set(TOOLCHAIN "x64_64-unknown-haiku")
+    set(TOOLCHAIN "x86_64-unknown-haiku")
   endif()
 elseif(TARGET_ARCH_NAME STREQUAL "x86")
   set(CMAKE_SYSTEM_PROCESSOR i686)
-  set(TOOLCHAIN "i686-linux-gnu")
+  if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/i586-alpine-linux-musl)
+    set(TOOLCHAIN "i586-alpine-linux-musl")
+  else()
+    set(TOOLCHAIN "i686-linux-gnu")
+  endif()
   if(TIZEN)
     set(TIZEN_TOOLCHAIN "i586-tizen-linux-gnu/9.2.0")
   endif()
@@ -198,10 +216,8 @@ elseif(HAIKU)
             return()
         endif()
 
-        set(SEARCH_PATH "${CROSS_ROOTFS}/generated/cross-tools-x86_64/bin")
-
         find_program(EXEC_LOCATION_${exec}
-            PATHS ${SEARCH_PATH}
+            PATHS "${CROSS_ROOTFS}/cross-tools-x86_64/bin"
             NAMES
             "${TOOLSET_PREFIX}${exec}${CLR_CMAKE_COMPILER_FILE_NAME_VERSION}"
             "${TOOLSET_PREFIX}${exec}")
@@ -266,8 +282,11 @@ elseif(TARGET_ARCH_NAME MATCHES "^(arm64|x64)$")
     add_toolchain_linker_flag("-Wl,--rpath-link=${CROSS_ROOTFS}/usr/lib64/gcc/${TIZEN_TOOLCHAIN}")
   endif()
 elseif(TARGET_ARCH_NAME STREQUAL "x86")
+  if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/i586-alpine-linux-musl)
+    add_toolchain_linker_flag("--target=${TOOLCHAIN}")
+    add_toolchain_linker_flag("-Wl,--rpath-link=${CROSS_ROOTFS}/usr/lib/gcc/${TOOLCHAIN}")
+  endif()
   add_toolchain_linker_flag(-m32)
-
   if(TIZEN)
     add_toolchain_linker_flag("-B${CROSS_ROOTFS}/usr/lib/gcc/${TIZEN_TOOLCHAIN}")
     add_toolchain_linker_flag("-L${CROSS_ROOTFS}/lib")
@@ -277,6 +296,9 @@ elseif(TARGET_ARCH_NAME STREQUAL "x86")
 elseif(ILLUMOS)
   add_toolchain_linker_flag("-L${CROSS_ROOTFS}/lib/amd64")
   add_toolchain_linker_flag("-L${CROSS_ROOTFS}/usr/amd64/lib")
+elseif(HAIKU)
+  add_toolchain_linker_flag("-lnetwork")
+  add_toolchain_linker_flag("-lroot")
 endif()
 
 # Specify compile options
@@ -307,6 +329,9 @@ if(TARGET_ARCH_NAME MATCHES "^(arm|armel)$")
     add_compile_options(-mfloat-abi=softfp)
   endif()
 elseif(TARGET_ARCH_NAME STREQUAL "x86")
+  if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/i586-alpine-linux-musl)
+    add_compile_options(--target=${TOOLCHAIN})
+  endif()
   add_compile_options(-m32)
   add_compile_options(-Wno-error=unused-command-line-argument)
 endif()
diff --git a/eng/common/cross/x64/sources.list.bionic b/eng/common/cross/x64/sources.list.bionic
new file mode 100644
index 0000000000000..a71ccadcffaf8
--- /dev/null
+++ b/eng/common/cross/x64/sources.list.bionic
@@ -0,0 +1,11 @@
+deb http://archive.ubuntu.com/ubuntu/ bionic main restricted universe
+deb-src http://archive.ubuntu.com/ubuntu/ bionic main restricted universe
+
+deb http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe
+deb-src http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe
+
+deb http://archive.ubuntu.com/ubuntu/ bionic-backports main restricted
+deb-src http://archive.ubuntu.com/ubuntu/ bionic-backports main restricted
+
+deb http://archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse
+deb-src http://archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse
diff --git a/eng/common/dotnet-install.sh b/eng/common/dotnet-install.sh
index abd045a3247f0..7e69e3a9e24a7 100755
--- a/eng/common/dotnet-install.sh
+++ b/eng/common/dotnet-install.sh
@@ -54,6 +54,10 @@ cpuname=$(uname -m)
 case $cpuname in
   arm64|aarch64)
     buildarch=arm64
+    if [ "$(getconf LONG_BIT)" -lt 64 ]; then
+        # This is 32-bit OS running on 64-bit CPU (for example Raspberry Pi OS)
+        buildarch=arm
+    fi
     ;;
   loongarch64)
     buildarch=loongarch64
diff --git a/eng/common/native/init-compiler.sh b/eng/common/native/init-compiler.sh
index 7aee4213e1b06..517401b688bf7 100644
--- a/eng/common/native/init-compiler.sh
+++ b/eng/common/native/init-compiler.sh
@@ -64,7 +64,7 @@ if [ -z "$CLR_CC" ]; then
     if [ -z "$majorVersion" ]; then
         # note: gcc (all versions) and clang versions higher than 6 do not have minor version in file name, if it is zero.
         if [ "$compiler" = "clang" ]; then versions="16 15 14 13 12 11 10 9 8 7 6.0 5.0 4.0 3.9 3.8 3.7 3.6 3.5"
-        elif [ "$compiler" = "gcc" ]; then versions="12 11 10 9 8 7 6 5 4.9"; fi
+        elif [ "$compiler" = "gcc" ]; then versions="13 12 11 10 9 8 7 6 5 4.9"; fi
 
         for version in $versions; do
             _major="${version%%.*}"
diff --git a/eng/common/sdk-task.ps1 b/eng/common/sdk-task.ps1
index e10a596879746..6c4ac6fec1a99 100644
--- a/eng/common/sdk-task.ps1
+++ b/eng/common/sdk-task.ps1
@@ -64,7 +64,7 @@ try {
       $GlobalJson.tools | Add-Member -Name "vs" -Value (ConvertFrom-Json "{ `"version`": `"16.5`" }") -MemberType NoteProperty
     }
     if( -not ($GlobalJson.tools.PSObject.Properties.Name -match "xcopy-msbuild" )) {
-      $GlobalJson.tools | Add-Member -Name "xcopy-msbuild" -Value "17.4.1" -MemberType NoteProperty
+      $GlobalJson.tools | Add-Member -Name "xcopy-msbuild" -Value "17.6.0-2" -MemberType NoteProperty
     }
     if ($GlobalJson.tools."xcopy-msbuild".Trim() -ine "none") {
         $xcopyMSBuildToolsFolder = InitializeXCopyMSBuild $GlobalJson.tools."xcopy-msbuild" -install $true
diff --git a/eng/common/templates/job/job.yml b/eng/common/templates/job/job.yml
index a21533fdd31d2..e20ee3a983cb0 100644
--- a/eng/common/templates/job/job.yml
+++ b/eng/common/templates/job/job.yml
@@ -75,6 +75,10 @@ jobs:
   - ${{ if eq(parameters.enableRichCodeNavigation, 'true') }}:
     - name: EnableRichCodeNavigation
       value: 'true'
+  # Retry signature validation up to three times, waiting 2 seconds between attempts.
+  # See https://learn.microsoft.com/en-us/nuget/reference/errors-and-warnings/nu3028#retry-untrusted-root-failures
+  - name: NUGET_EXPERIMENTAL_CHAIN_BUILD_RETRY_POLICY
+    value: 3,2000
   - ${{ each variable in parameters.variables }}:
     # handle name-value variable syntax
     # example:
@@ -83,7 +87,7 @@ jobs:
     - ${{ if ne(variable.name, '') }}:
       - name: ${{ variable.name }}
         value: ${{ variable.value }}
-    
+
     # handle variable groups
     - ${{ if ne(variable.group, '') }}:
       - group: ${{ variable.group }}
@@ -158,16 +162,18 @@ jobs:
   - template: /eng/common/templates/steps/component-governance.yml
     parameters:
       ${{ if eq(parameters.disableComponentGovernance, '') }}:
-        ${{ if and(ne(variables['System.TeamProject'], 'public'), notin(variables['Build.Reason'], 'PullRequest'), eq(parameters.runAsPublic, 'false'), or(contains(variables['Build.SourceBranch'], 'internal/release'), eq(variables['Build.SourceBranch'], 'main'))) }}:
+        ${{ if and(ne(variables['System.TeamProject'], 'public'), notin(variables['Build.Reason'], 'PullRequest'), eq(parameters.runAsPublic, 'false'), or(startsWith(variables['Build.SourceBranch'], 'refs/heads/release/'), startsWith(variables['Build.SourceBranch'], 'refs/heads/dotnet/'), startsWith(variables['Build.SourceBranch'], 'refs/heads/microsoft/'), eq(variables['Build.SourceBranch'], 'refs/heads/main'))) }}:
           disableComponentGovernance: false
         ${{ else }}:
           disableComponentGovernance: true
+      ${{ else }}:
+        disableComponentGovernance: ${{ parameters.disableComponentGovernance }}
       componentGovernanceIgnoreDirectories: ${{ parameters.componentGovernanceIgnoreDirectories }}
 
   - ${{ if eq(parameters.enableMicrobuild, 'true') }}:
     - ${{ if and(eq(parameters.runAsPublic, 'false'), ne(variables['System.TeamProject'], 'public'), notin(variables['Build.Reason'], 'PullRequest')) }}:
       - task: MicroBuildCleanup@1
-        displayName: Execute Microbuild cleanup tasks  
+        displayName: Execute Microbuild cleanup tasks
         condition: and(always(), in(variables['_SignType'], 'real', 'test'), eq(variables['Agent.Os'], 'Windows_NT'))
         continueOnError: ${{ parameters.continueOnError }}
         env:
@@ -217,7 +223,7 @@ jobs:
       displayName: Publish XUnit Test Results
       inputs:
         testResultsFormat: 'xUnit'
-        testResultsFiles: '*.xml' 
+        testResultsFiles: '*.xml'
         searchFolder: '$(Build.SourcesDirectory)/artifacts/TestResults/$(_BuildConfig)'
         testRunTitle: ${{ coalesce(parameters.testRunTitle, parameters.name, '$(System.JobName)') }}-xunit
         mergeTestResults: ${{ parameters.mergeTestResults }}
@@ -228,7 +234,7 @@ jobs:
       displayName: Publish TRX Test Results
       inputs:
         testResultsFormat: 'VSTest'
-        testResultsFiles: '*.trx' 
+        testResultsFiles: '*.trx'
         searchFolder: '$(Build.SourcesDirectory)/artifacts/TestResults/$(_BuildConfig)'
         testRunTitle: ${{ coalesce(parameters.testRunTitle, parameters.name, '$(System.JobName)') }}-trx
         mergeTestResults: ${{ parameters.mergeTestResults }}
diff --git a/eng/common/templates/steps/source-build.yml b/eng/common/templates/steps/source-build.yml
index a97a185a367a9..1100521834a94 100644
--- a/eng/common/templates/steps/source-build.yml
+++ b/eng/common/templates/steps/source-build.yml
@@ -68,6 +68,11 @@ steps:
       runtimeOsArgs='/p:RuntimeOS=${{ parameters.platform.runtimeOS }}'
     fi
 
+    baseOsArgs=
+    if [ '${{ parameters.platform.baseOS }}' != '' ]; then
+      baseOsArgs='/p:BaseOS=${{ parameters.platform.baseOS }}'
+    fi
+
     publishArgs=
     if [ '${{ parameters.platform.skipPublishValidation }}' != 'true' ]; then
       publishArgs='--publish'
@@ -86,6 +91,7 @@ steps:
       $internalRestoreArgs \
       $targetRidArgs \
       $runtimeOsArgs \
+      $baseOsArgs \
       /p:SourceBuildNonPortable=${{ parameters.platform.nonPortable }} \
       /p:ArcadeBuildFromSource=true \
       /p:AssetManifestFileName=$assetManifestFileName
diff --git a/eng/common/tools.ps1 b/eng/common/tools.ps1
index 8ad03be3eccb2..c9eced9f7df4c 100644
--- a/eng/common/tools.ps1
+++ b/eng/common/tools.ps1
@@ -287,6 +287,25 @@ function InstallDotNet([string] $dotnetRoot,
   [string] $runtimeSourceFeedKey = '',
   [switch] $noPath) {
 
+  $dotnetVersionLabel = "'sdk v$version'"
+
+  if ($runtime -ne '' -and $runtime -ne 'sdk') {
+    $runtimePath = $dotnetRoot
+    $runtimePath = $runtimePath + "\shared"
+    if ($runtime -eq "dotnet") { $runtimePath = $runtimePath + "\Microsoft.NETCore.App" }
+    if ($runtime -eq "aspnetcore") { $runtimePath = $runtimePath + "\Microsoft.AspNetCore.App" }
+    if ($runtime -eq "windowsdesktop") { $runtimePath = $runtimePath + "\Microsoft.WindowsDesktop.App" }
+    $runtimePath = $runtimePath + "\" + $version
+  
+    $dotnetVersionLabel = "runtime toolset '$runtime/$architecture v$version'"
+
+    if (Test-Path $runtimePath) {
+      Write-Host "  Runtime toolset '$runtime/$architecture v$version' already installed."
+      $installSuccess = $true
+      Exit
+    }
+  }
+
   $installScript = GetDotNetInstallScript $dotnetRoot
   $installParameters = @{
     Version = $version
@@ -323,18 +342,18 @@ function InstallDotNet([string] $dotnetRoot,
     } else {
       $location = "public location";
     }
-    Write-Host "Attempting to install dotnet from $location."
+    Write-Host "  Attempting to install $dotnetVersionLabel from $location."
     try {
       & $installScript @variation
       $installSuccess = $true
       break
     }
     catch {
-      Write-Host "Failed to install dotnet from $location."
+      Write-Host "  Failed to install $dotnetVersionLabel from $location."
     }
   }
   if (-not $installSuccess) {
-    Write-PipelineTelemetryError -Category 'InitializeToolset' -Message "Failed to install dotnet from any of the specified locations."
+    Write-PipelineTelemetryError -Category 'InitializeToolset' -Message "Failed to install $dotnetVersionLabel from any of the specified locations."
     ExitWithExitCode 1
   }
 }
@@ -360,13 +379,13 @@ function InitializeVisualStudioMSBuild([bool]$install, [object]$vsRequirements =
   }
 
   # Minimum VS version to require.
-  $vsMinVersionReqdStr = '16.8'
+  $vsMinVersionReqdStr = '17.6'
   $vsMinVersionReqd = [Version]::new($vsMinVersionReqdStr)
 
   # If the version of msbuild is going to be xcopied,
   # use this version. Version matches a package here:
-  # https://dev.azure.com/dnceng/public/_packaging?_a=package&feed=dotnet-eng&package=RoslynTools.MSBuild&protocolType=NuGet&version=17.4.1&view=overview
-  $defaultXCopyMSBuildVersion = '17.4.1'
+  # https://dev.azure.com/dnceng/public/_artifacts/feed/dotnet-eng/NuGet/RoslynTools.MSBuild/versions/17.6.0-2
+  $defaultXCopyMSBuildVersion = '17.6.0-2'
 
   if (!$vsRequirements) {
     if (Get-Member -InputObject $GlobalJson.tools -Name 'vs') {
@@ -399,7 +418,8 @@ function InitializeVisualStudioMSBuild([bool]$install, [object]$vsRequirements =
   # Locate Visual Studio installation or download x-copy msbuild.
   $vsInfo = LocateVisualStudio $vsRequirements
   if ($vsInfo -ne $null) {
-    $vsInstallDir = $vsInfo.installationPath
+    # Ensure vsInstallDir has a trailing slash
+    $vsInstallDir = Join-Path $vsInfo.installationPath "\"
     $vsMajorVersion = $vsInfo.installationVersion.Split('.')[0]
 
     InitializeVisualStudioEnvironmentVariables $vsInstallDir $vsMajorVersion
diff --git a/eng/common/tools.sh b/eng/common/tools.sh
index cf9fb1ea2d32b..e8d478943341d 100755
--- a/eng/common/tools.sh
+++ b/eng/common/tools.sh
@@ -184,6 +184,35 @@ function InstallDotNetSdk {
 function InstallDotNet {
   local root=$1
   local version=$2
+  local runtime=$4
+
+  local dotnetVersionLabel="'$runtime v$version'"
+  if [[ -n "${4:-}" ]] && [ "$4" != 'sdk' ]; then
+    runtimePath="$root"
+    runtimePath="$runtimePath/shared"
+    case "$runtime" in
+      dotnet)
+        runtimePath="$runtimePath/Microsoft.NETCore.App"
+        ;;
+      aspnetcore)
+        runtimePath="$runtimePath/Microsoft.AspNetCore.App"
+        ;;
+      windowsdesktop)
+        runtimePath="$runtimePath/Microsoft.WindowsDesktop.App"
+        ;;
+      *)
+        ;;
+    esac
+    runtimePath="$runtimePath/$version"
+
+    dotnetVersionLabel="runtime toolset '$runtime/$architecture v$version'"
+
+    if [ -d "$runtimePath" ]; then
+      echo "  Runtime toolset '$runtime/$architecture v$version' already installed."
+      local installSuccess=1
+      return
+    fi
+  fi
 
   GetDotNetInstallScript "$root"
   local install_script=$_GetDotNetInstallScript
@@ -228,17 +257,17 @@ function InstallDotNet {
   for variationName in "${variations[@]}"; do
     local name="$variationName[@]"
     local variation=("${!name}")
-    echo "Attempting to install dotnet from $variationName."
+    echo "  Attempting to install $dotnetVersionLabel from $variationName."
     bash "$install_script" "${variation[@]}" && installSuccess=1
     if [[ "$installSuccess" -eq 1 ]]; then
       break
     fi
 
-    echo "Failed to install dotnet from $variationName."
+    echo "  Failed to install $dotnetVersionLabel from $variationName."
   done
 
   if [[ "$installSuccess" -eq 0 ]]; then
-    Write-PipelineTelemetryError -category 'InitializeToolset' "Failed to install dotnet SDK from any of the specified locations."
+    Write-PipelineTelemetryError -category 'InitializeToolset' "Failed to install $dotnetVersionLabel from any of the specified locations."
     ExitWithExitCode 1
   fi
 }
diff --git a/eng/config/PublishData.json b/eng/config/PublishData.json
index 7821aedd7985e..a249886a2c134 100644
--- a/eng/config/PublishData.json
+++ b/eng/config/PublishData.json
@@ -14,11 +14,13 @@
       "Microsoft.CodeAnalysis.Workspaces.Common": "vssdk",
       "Microsoft.CodeAnalysis.Workspaces.MSBuild": "arcade",
       "Microsoft.CodeAnalysis.Workspaces.Desktop": "arcade",
+      "Microsoft.CodeAnalysis.Compiler.Test.Resources": "vs-impl",
       "Microsoft.CodeAnalysis.CSharp": "vssdk",
       "Microsoft.CodeAnalysis.CSharp.CodeStyle": "arcade",
       "Microsoft.CodeAnalysis.CSharp.Features": "arcade",
       "Microsoft.CodeAnalysis.CSharp.Scripting": "arcade",
       "Microsoft.CodeAnalysis.CSharp.Workspaces": "vssdk",
+      "Microsoft.CodeAnalysis.Test.Utilities": "vs-impl",
       "Microsoft.CodeAnalysis.VisualBasic": "vssdk",
       "Microsoft.CodeAnalysis.VisualBasic.CodeStyle": "arcade",
       "Microsoft.CodeAnalysis.VisualBasic.Features": "arcade",
@@ -43,6 +45,8 @@
       "Microsoft.CodeAnalysis.EditorFeatures.Wpf": "vssdk",
       "Microsoft.CodeAnalysis.EditorFeatures.Cocoa": "vssdk",
       "Microsoft.VisualStudio.IntegrationTest.Utilities": "vs-impl",
+      "Microsoft.VisualStudio.LanguageServices.DevKit": "npm",
+      "Microsoft.CodeAnalysis.LanguageServer": "vs-impl",
       "Microsoft.CodeAnalysis.LanguageServer.Protocol": "vs-impl",
       "Microsoft.CodeAnalysis.CSharp.LanguageServer.Protocol": "vs-impl",
       "Microsoft.CodeAnalysis.VisualBasic.LanguageServer.Protocol": "vs-impl",
@@ -186,6 +190,16 @@
       "vsMajorVersion": 17,
       "insertionCreateDraftPR": true,
       "insertionTitlePrefix": "[Validation]"
+    },
+    "dev/andrha/telemetry": {
+      "nugetKind": [
+        "Shipping",
+        "NonShipping"
+      ],
+      "vsBranch": "main",
+      "vsMajorVersion": 17,
+      "insertionCreateDraftPR": true,
+      "insertionTitlePrefix": "[Telemetry Validation]"
     }
   }
 }
diff --git a/eng/config/runtimeconfig.template.json b/eng/config/runtimeconfig.template.json
index 384e2f49e4b29..e46db7a06283c 100644
--- a/eng/config/runtimeconfig.template.json
+++ b/eng/config/runtimeconfig.template.json
@@ -1,3 +1,3 @@
 {
-  "rollForwardOnNoCandidateFx": 2
+  "rollForward": "Major"
 } 
diff --git a/eng/pipelines/build-unix-job.yml b/eng/pipelines/build-unix-job.yml
index 20bbe8f070684..8f9316d88885e 100644
--- a/eng/pipelines/build-unix-job.yml
+++ b/eng/pipelines/build-unix-job.yml
@@ -9,6 +9,9 @@ parameters:
 - name: configuration
   type: string
   default: 'Debug'
+- name: poolName
+  type: string
+  default: ''
 - name: queueName
   type: string
   default: ''
@@ -20,7 +23,7 @@ jobs:
 - job: ${{ parameters.jobName }}
   pool:
     ${{ if ne(parameters.queueName, '') }}:
-      name: NetCore-Public
+      name: ${{ parameters.poolName}}
       demands: ImageOverride -equals ${{ parameters.queueName }}
 
     ${{ if ne(parameters.vmImageName, '') }}:
diff --git a/eng/pipelines/build-windows-job.yml b/eng/pipelines/build-windows-job.yml
index 606ec1c431bbf..457ccbe2ba61d 100644
--- a/eng/pipelines/build-windows-job.yml
+++ b/eng/pipelines/build-windows-job.yml
@@ -9,6 +9,9 @@ parameters:
 - name: configuration
   type: string
   default: 'Debug'
+- name: poolName
+  type: string
+  default: ''
 - name: queueName
   type: string
   default: ''
@@ -26,7 +29,7 @@ jobs:
 - job: ${{ parameters.jobName }}
   pool:
     ${{ if ne(parameters.queueName, '') }}:
-      name: NetCore-Public
+      name: ${{ parameters.poolName }}
       demands: ImageOverride -equals ${{ parameters.queueName }}
 
     ${{ if ne(parameters.vmImageName, '') }}:
diff --git a/eng/pipelines/checkout-unix-task.yml b/eng/pipelines/checkout-unix-task.yml
index e65175caf5a7d..f63c1b433e975 100644
--- a/eng/pipelines/checkout-unix-task.yml
+++ b/eng/pipelines/checkout-unix-task.yml
@@ -1,14 +1,13 @@
 # Shallow checkout sources on Unix
 
+parameters:
+- name: depth
+  type: number
+  default: 1
+
 steps:
-  - checkout: none
+  - checkout: self
+    fetchDepth: ${{ parameters.depth }}
+    fetchTags: false
 
-  - script: |
-      set -x
-      git init
-      git config --local checkout.workers 0
-      git config --local fetch.parallel 0
-      git remote add origin "$(Build.Repository.Uri)"
-      git fetch --no-tags --no-auto-maintenance --depth=1 origin "$(Build.SourceVersion)"
-      git checkout "$(Build.SourceVersion)"
-    displayName: Shallow Checkout
+  
diff --git a/eng/pipelines/checkout-windows-task.yml b/eng/pipelines/checkout-windows-task.yml
index 304aa7868a5f9..f66c019d37942 100644
--- a/eng/pipelines/checkout-windows-task.yml
+++ b/eng/pipelines/checkout-windows-task.yml
@@ -1,16 +1,13 @@
 # Shallow checkout sources on Windows
 
-# Git path based on https://github.com/microsoft/azure-pipelines-agent/blob/f98a479ab3cc323ff17b8cb75d5ab5f953f342cc/src/Agent.Plugins/GitCliManager.cs#L90
+parameters:
+- name: depth
+  type: number
+  default: 1
+
 steps:
-  - checkout: none
+  - checkout: self
+    fetchDepth: ${{ parameters.depth }}
+    fetchTags: false
 
-  - script: |
-      set PATH=$(Agent.HomeDirectory)\externals\git\cmd;%PATH%
-      @echo on
-      git init
-      git config --local checkout.workers 0
-      git config --local fetch.parallel 0
-      git remote add origin "$(Build.Repository.Uri)"
-      git fetch --no-tags --no-auto-maintenance --depth=1 origin "$(Build.SourceVersion)"
-      git checkout "$(Build.SourceVersion)"
-    displayName: Shallow Checkout
+  
diff --git a/eng/pipelines/evaluate-changed-files.yml b/eng/pipelines/evaluate-changed-files.yml
index ff61d577afe38..8d2aab8e685d1 100644
--- a/eng/pipelines/evaluate-changed-files.yml
+++ b/eng/pipelines/evaluate-changed-files.yml
@@ -3,6 +3,9 @@ parameters:
 - name: jobName
   type: string
   default: ''
+- name: poolName
+  type: string
+  default: ''
 - name: queueName
   type: string
   default: ''
@@ -17,7 +20,7 @@ jobs:
 - job: ${{ parameters.jobName }}
   pool:
     ${{ if ne(parameters.queueName, '') }}:
-      name: NetCore-Public
+      name: ${{ parameters.poolName }}
       demands: ImageOverride -equals ${{ parameters.queueName }}
 
     ${{ if ne(parameters.vmImageName, '') }}:
@@ -25,17 +28,9 @@ jobs:
   timeoutInMinutes: 10
 
   steps:
-  - checkout: none
-
-  - script: |
-      set -x
-      git init
-      git config --local checkout.workers 0
-      git config --local fetch.parallel 0
-      git remote add origin "$(Build.Repository.Uri)"
-      git fetch --no-tags --no-auto-maintenance --depth=2 origin "$(Build.SourceVersion)"
-      git checkout "$(Build.SourceVersion)"
-    displayName: Shallow Checkout
+  - template: checkout-unix-task.yml
+    parameters:
+      depth: 2
   
   - ${{ if ne(parameters.paths[0], '') }}:
     - ${{ each path in parameters.paths }}:
diff --git a/eng/pipelines/test-unix-job-single-machine.yml b/eng/pipelines/test-unix-job-single-machine.yml
index 040ec4f2dde86..789a4eaf35f1f 100644
--- a/eng/pipelines/test-unix-job-single-machine.yml
+++ b/eng/pipelines/test-unix-job-single-machine.yml
@@ -15,6 +15,9 @@ parameters:
 - name: testArguments
   type: string
   default: ''
+- name: poolName
+  type: string
+  default: ''
 - name: queueName
   type: string
   default: ''
@@ -26,7 +29,7 @@ jobs:
 - job: ${{ parameters.jobName }}
   pool:
     ${{ if ne(parameters.queueName, '') }}:
-      name: NetCore-Public
+      name: ${{ parameters.poolName }}
       demands: ImageOverride -equals ${{ parameters.queueName }}
 
     ${{ if ne(parameters.vmImageName, '') }}:
diff --git a/eng/pipelines/test-unix-job.yml b/eng/pipelines/test-unix-job.yml
index 398f950798a93..a7eb2dc72fb9c 100644
--- a/eng/pipelines/test-unix-job.yml
+++ b/eng/pipelines/test-unix-job.yml
@@ -1,5 +1,7 @@
 # Test on Unix using Helix
 parameters:
+- name: helixQueueName
+  type: string
 - name: testRunName
   type: string
   default: ''
@@ -15,6 +17,9 @@ parameters:
 - name: testArguments
   type: string
   default: ''
+- name: helixApiAccessToken
+  type: string
+  default: ''
 
 jobs:
 - job: ${{ parameters.jobName }}
@@ -43,7 +48,7 @@ jobs:
     - task: ShellScript@2
       inputs:
         scriptPath: ./eng/build.sh
-        args: --ci --helix --configuration ${{ parameters.configuration }} ${{ parameters.testArguments }}
+        args: --ci --helix --configuration ${{ parameters.configuration }} --helixQueueName ${{ parameters.helixQueueName }} ${{ parameters.testArguments }}
       displayName: Test
       env:
         SYSTEM_ACCESSTOKEN: $(System.AccessToken)
diff --git a/eng/pipelines/test-windows-job-single-machine.yml b/eng/pipelines/test-windows-job-single-machine.yml
index 8a1ce755e0415..45b482ca26f2e 100644
--- a/eng/pipelines/test-windows-job-single-machine.yml
+++ b/eng/pipelines/test-windows-job-single-machine.yml
@@ -15,6 +15,9 @@ parameters:
 - name: testArguments
   type: string
   default: ''
+- name: poolName
+  type: string
+  default: ''
 - name: queueName
   type: string
   default: 'windows.vs2022.amd64.open'
@@ -22,7 +25,7 @@ parameters:
 jobs:
 - job: ${{ parameters.jobName }}
   pool:
-    name: NetCore-Public
+    name: ${{ parameters.poolName }}
     demands: ImageOverride -equals ${{ parameters.queueName }}
   timeoutInMinutes: 120
   variables:
diff --git a/eng/pipelines/test-windows-job.yml b/eng/pipelines/test-windows-job.yml
index 5484f13af74cf..4cec724dbcf6f 100644
--- a/eng/pipelines/test-windows-job.yml
+++ b/eng/pipelines/test-windows-job.yml
@@ -1,5 +1,7 @@
 # Test on Windows Desktop using Helix
 parameters:
+- name: helixQueueName
+  type: string
 - name: testRunName
   type: string
   default: ''
@@ -15,6 +17,9 @@ parameters:
 - name: testArguments
   type: string
   default: ''
+- name: helixApiAccessToken
+  type: string
+  default: ''
 
 jobs:
 - job: ${{ parameters.jobName }}
@@ -44,7 +49,7 @@ jobs:
       displayName: Run Unit Tests
       inputs:
         filePath: eng/build.ps1
-        arguments: -ci -helix -configuration ${{ parameters.configuration }} ${{ parameters.testArguments }} -collectDumps
+        arguments: -ci -helix -configuration ${{ parameters.configuration }} -helixQueueName ${{ parameters.helixQueueName }} ${{ parameters.testArguments }} -collectDumps
       env:
         SYSTEM_ACCESSTOKEN: $(System.AccessToken)
 
diff --git a/eng/publish-assets.ps1 b/eng/publish-assets.ps1
index a3d2dfaa4fd61..7cc3a725ea64e 100644
--- a/eng/publish-assets.ps1
+++ b/eng/publish-assets.ps1
@@ -92,6 +92,11 @@ function Publish-Nuget($publishData, [string]$packageDir) {
         continue
       }
 
+      if ($feedName.equals("npm")) {
+        Write-Host "Skipping publishing for $nupkg as it is published in a separate step as an NPM package"
+        continue
+      }
+
       # Use the feed name to get the source to upload the package to.
       if (-not (Get-Member -InputObject $feedData -Name $feedName)) {
         throw "$feedName has no configured source feed"
@@ -101,6 +106,7 @@ function Publish-Nuget($publishData, [string]$packageDir) {
       $apiKey = Get-PublishKey $uploadUrl
 
       if (-not $test) {
+        Write-Host "Publishing $nupkg"
         Exec-Console $dotnet "nuget push $nupkg --source $uploadUrl --api-key $apiKey"
       }
     }
diff --git a/eng/targets/Imports.targets b/eng/targets/Imports.targets
index 4da62950a42f5..13118e1464a26 100644
--- a/eng/targets/Imports.targets
+++ b/eng/targets/Imports.targets
@@ -265,10 +265,11 @@
       <_InternalsVisibleToAttribute Include="System.Runtime.CompilerServices.RestrictedInternalsVisibleToAttribute">
         <_Parameter1>%(RestrictedInternalsVisibleTo.Identity)</_Parameter1>
         <_Parameter2 Condition="'%(RestrictedInternalsVisibleTo.Partner)' != ''">Microsoft.CodeAnalysis.ExternalAccess.%(RestrictedInternalsVisibleTo.Partner).Api</_Parameter2>
+        <_Parameter2 Condition="'%(RestrictedInternalsVisibleTo.Namespace)' != ''">%(RestrictedInternalsVisibleTo.Namespace)</_Parameter2>
       </_InternalsVisibleToAttribute>
     </ItemGroup>
 
-    <Warning Condition="'%(RestrictedInternalsVisibleTo.Partner)' == ''" Text="RestrictedInternalsVisibleTo items must specify the 'Partner' attribute. Target assembly: %(Identity)" />
+    <Warning Condition="'%(RestrictedInternalsVisibleTo.Partner)' == '' and '%(RestrictedInternalsVisibleTo.Namespace)' == ''" Text="RestrictedInternalsVisibleTo items must specify the 'Partner' or 'Namespace' attribute. Target assembly: %(Identity)" />
   </Target>
 
   <!-- Make sure expected compile items are included -->
diff --git a/eng/targets/Settings.props b/eng/targets/Settings.props
index 62882152a5c7a..b6b963f87df58 100644
--- a/eng/targets/Settings.props
+++ b/eng/targets/Settings.props
@@ -51,6 +51,11 @@
     <PublishWindowsPdb>false</PublishWindowsPdb>
     <EnforceExtendedAnalyzerRules>false</EnforceExtendedAnalyzerRules>
     <EnforceExtendedAnalyzerRules Condition="'$(IsAnalyzer)' == 'true'">true</EnforceExtendedAnalyzerRules>
+
+    <!-- NPM packaging settings -->
+    <NpmPackageOutputPath>$(ArtifactsDir)\packages\$(Configuration)\NPM\</NpmPackageOutputPath>
+    <!-- By default don't attempt to do npm packaging during pack since it requires NPM to be installed -->
+    <IsNpmPackable Condition="'$(IsNpmPackable)'==''">false</IsNpmPackable>
   </PropertyGroup>
 
   <!-- 
diff --git a/eng/targets/XUnit.targets b/eng/targets/XUnit.targets
index e2e574a4290b6..e803a80906a25 100644
--- a/eng/targets/XUnit.targets
+++ b/eng/targets/XUnit.targets
@@ -7,7 +7,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="xunit.analyzers" Version="$(xunitanalyzersVersion)" IsImplicitlyDefined="true" PrivateAssets="all" />
     <PackageReference Include="XunitXml.TestLogger" Version="$(XunitXmlTestLoggerVersion)" />
   </ItemGroup>
 
diff --git a/global.json b/global.json
index 869516829253a..e51413af0e5ce 100644
--- a/global.json
+++ b/global.json
@@ -1,18 +1,18 @@
 {
   "sdk": {
-    "version": "8.0.100-preview.3.23178.7",
+    "version": "8.0.100-preview.5.23303.2",
     "allowPrerelease": false,
     "rollForward": "latestPatch"
   },
   "tools": {
-    "dotnet": "8.0.100-preview.3.23178.7",
+    "dotnet": "8.0.100-preview.5.23303.2",
     "vs": {
-      "version": "17.4.1"
+      "version": "17.6.0"
     },
-    "xcopy-msbuild": "17.4.1"
+    "xcopy-msbuild": "17.6.0-2"
   },
   "msbuild-sdks": {
-    "Microsoft.DotNet.Arcade.Sdk": "8.0.0-beta.23220.2",
-    "Microsoft.DotNet.Helix.Sdk": "8.0.0-beta.23220.2"
+    "Microsoft.DotNet.Arcade.Sdk": "8.0.0-beta.23326.5",
+    "Microsoft.DotNet.Helix.Sdk": "8.0.0-beta.23326.5"
   }
 }
diff --git a/src/Analyzers/CSharp/Analyzers/InlineDeclaration/CSharpInlineDeclarationDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/InlineDeclaration/CSharpInlineDeclarationDiagnosticAnalyzer.cs
index 82373e90ac6de..814c93498da1a 100644
--- a/src/Analyzers/CSharp/Analyzers/InlineDeclaration/CSharpInlineDeclarationDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/InlineDeclaration/CSharpInlineDeclarationDiagnosticAnalyzer.cs
@@ -152,6 +152,10 @@ private void AnalyzeSyntaxNode(SyntaxNodeAnalysisContext context, INamedTypeSymb
                 return;
             }
 
+            // Bail out early if the localDeclaration is outside the context's analysis span.
+            if (!context.ShouldAnalyzeSpan(localDeclaration.Span))
+                return;
+
             if (localDeclarator.SpanStart >= argumentNode.SpanStart)
             {
                 // We have an error situation where the local was declared after the out-var.  
diff --git a/src/Analyzers/CSharp/Analyzers/MakeStructFieldsWritable/CSharpMakeStructFieldsWritableDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/MakeStructFieldsWritable/CSharpMakeStructFieldsWritableDiagnosticAnalyzer.cs
index 20da6321fa0a9..2a659ec462fd8 100644
--- a/src/Analyzers/CSharp/Analyzers/MakeStructFieldsWritable/CSharpMakeStructFieldsWritableDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/MakeStructFieldsWritable/CSharpMakeStructFieldsWritableDiagnosticAnalyzer.cs
@@ -57,15 +57,22 @@ public static void CreateAndRegisterActions(CompilationStartAnalysisContext cont
                     if (namedTypeSymbol.TypeKind != TypeKind.Struct)
                         return;
 
-                    //We check if struct contains any 'readonly' fields
+                    // We check if struct contains any 'readonly' fields
                     if (!HasReadonlyField(namedTypeSymbol))
                         return;
 
+                    // Check if diagnostic location is within the analysis span
+                    if (!context.ShouldAnalyzeLocation(GetDiagnosticLocation(namedTypeSymbol)))
+                        return;
+
                     var symbolAnalyzer = new SymbolAnalyzer(namedTypeSymbol);
                     symbolAnalyzer.RegisterActions(context);
                 }, SymbolKind.NamedType);
             }
 
+            private static Location GetDiagnosticLocation(INamedTypeSymbol namedTypeSymbol)
+                => namedTypeSymbol.Locations[0];
+
             private static bool HasReadonlyField(INamedTypeSymbol namedTypeSymbol)
             {
                 return namedTypeSymbol
@@ -105,7 +112,7 @@ private void SymbolEndAction(SymbolAnalysisContext context)
                 {
                     var diagnostic = Diagnostic.Create(
                                     s_diagnosticDescriptor,
-                                    _namedTypeSymbol.Locations[0]);
+                                    GetDiagnosticLocation(_namedTypeSymbol));
                     context.ReportDiagnostic(diagnostic);
                 }
             }
diff --git a/src/Analyzers/CSharp/Analyzers/MakeStructMemberReadOnly/CSharpMakeStructMemberReadOnlyAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/MakeStructMemberReadOnly/CSharpMakeStructMemberReadOnlyAnalyzer.cs
index e133d8a295c94..241375026254e 100644
--- a/src/Analyzers/CSharp/Analyzers/MakeStructMemberReadOnly/CSharpMakeStructMemberReadOnlyAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/MakeStructMemberReadOnly/CSharpMakeStructMemberReadOnlyAnalyzer.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
 using System.Threading;
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.CodeStyle;
@@ -38,6 +39,15 @@ protected override void InitializeWorker(AnalysisContext context)
                 return;
 
             context.RegisterSymbolStartAction(context =>
+            {
+                if (!ShouldAnalyze(context, out var option))
+                    return;
+
+                context.RegisterOperationBlockAction(
+                    context => AnalyzeBlock(context, option.Notification.Severity));
+            }, SymbolKind.NamedType);
+
+            static bool ShouldAnalyze(SymbolStartAnalysisContext context, [NotNullWhen(true)] out CodeStyleOption2<bool>? option)
             {
                 // Only run on non-readonly structs.  If the struct is already readonly, no need to make the members readonly.
                 if (context.Symbol is not INamedTypeSymbol
@@ -47,19 +57,41 @@ protected override void InitializeWorker(AnalysisContext context)
                         DeclaringSyntaxReferences: [var reference, ..],
                     } structType)
                 {
-                    return;
+                    option = null;
+                    return false;
                 }
 
                 var cancellationToken = context.CancellationToken;
                 var declaration = reference.GetSyntax(cancellationToken);
                 var options = context.GetCSharpAnalyzerOptions(declaration.SyntaxTree);
-                var option = options.PreferReadOnlyStructMember;
+                option = options.PreferReadOnlyStructMember;
                 if (!option.Value)
-                    return;
+                    return false;
 
-                context.RegisterOperationBlockAction(
-                    context => AnalyzeBlock(context, option.Notification.Severity));
-            }, SymbolKind.NamedType);
+                // Skip analysis if the analysis filter span does not contain the primary location where we would report a diagnostic.
+                if (context.FilterSpan is not null)
+                {
+                    Contract.ThrowIfNull(context.FilterTree);
+                    var shouldAnalyze = false;
+                    foreach (var member in structType.GetMembers())
+                    {
+                        if (member is not IMethodSymbol method)
+                            continue;
+
+                        var (location, _) = GetDiagnosticLocation(method, cancellationToken);
+                        if (location != null && context.ShouldAnalyzeLocation(location))
+                        {
+                            shouldAnalyze = true;
+                            break;
+                        }
+                    }
+
+                    if (!shouldAnalyze)
+                        return false;
+                }
+
+                return true;
+            }
         });
 
     private void AnalyzeBlock(
@@ -68,18 +100,12 @@ private void AnalyzeBlock(
     {
         var cancellationToken = context.CancellationToken;
 
-        // if it's not a method, or it's already readonly, nothing to do.
-        if (context.OwningSymbol is not IMethodSymbol
-            {
-                MethodKind: MethodKind.Ordinary or MethodKind.ExplicitInterfaceImplementation or MethodKind.PropertyGet or MethodKind.PropertySet,
-                IsReadOnly: false,
-                IsStatic: false,
-                IsImplicitlyDeclared: false,
-                DeclaringSyntaxReferences: [var methodReference, ..],
-            } owningMethod)
-        {
+        if (context.OwningSymbol is not IMethodSymbol owningMethod)
+            return;
+
+        var (location, additionalLocation) = GetDiagnosticLocation(owningMethod, cancellationToken);
+        if (location == null || !context.ShouldAnalyzeSpan(location.SourceSpan))
             return;
-        }
 
         foreach (var blockOperation in context.OperationBlocks)
         {
@@ -93,6 +119,28 @@ private void AnalyzeBlock(
                 return;
         }
 
+        context.ReportDiagnostic(DiagnosticHelper.Create(
+            Descriptor,
+            location,
+            severity,
+            additionalLocations: ImmutableArray.Create(additionalLocation),
+            properties: null));
+    }
+
+    private static (Location? location, Location? additionalLocation) GetDiagnosticLocation(
+        IMethodSymbol owningMethod,
+        CancellationToken cancellationToken)
+    {
+        // if it's not a method, or it's already readonly, nothing to do.
+        if (owningMethod.MethodKind is not (MethodKind.Ordinary or MethodKind.ExplicitInterfaceImplementation or MethodKind.PropertyGet or MethodKind.PropertySet)
+            || owningMethod.IsReadOnly
+            || owningMethod.IsStatic
+            || owningMethod.IsImplicitlyDeclared)
+        {
+            return (null, null);
+        }
+
+        var methodReference = owningMethod.DeclaringSyntaxReferences[0];
         var declaration = methodReference.GetSyntax(cancellationToken);
 
         var nameToken = declaration switch
@@ -109,14 +157,9 @@ private void AnalyzeBlock(
             declaration = declaration.GetRequiredParent();
 
         if (nameToken is null)
-            return;
+            return (null, null);
 
-        context.ReportDiagnostic(DiagnosticHelper.Create(
-            Descriptor,
-            nameToken.Value.GetLocation(),
-            severity,
-            additionalLocations: ImmutableArray.Create(declaration.GetLocation()),
-            properties: null));
+        return (nameToken.Value.GetLocation(), declaration.GetLocation());
     }
 
     private static bool BlockOperationPotentiallyMutatesThis(
diff --git a/src/Analyzers/CSharp/Analyzers/MakeStructReadOnly/CSharpMakeStructReadOnlyDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/MakeStructReadOnly/CSharpMakeStructReadOnlyDiagnosticAnalyzer.cs
index a62c8f1190346..d4343e2f1f97f 100644
--- a/src/Analyzers/CSharp/Analyzers/MakeStructReadOnly/CSharpMakeStructReadOnlyDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/MakeStructReadOnly/CSharpMakeStructReadOnlyDiagnosticAnalyzer.cs
@@ -38,7 +38,7 @@ protected override void InitializeWorker(AnalysisContext context)
             context.RegisterSymbolStartAction(context =>
             {
                 // First, see if this at least strongly looks like a struct that could be converted.
-                if (!IsCandidate(context, out var typeDeclaration, out var option))
+                if (!IsCandidate(context, out var location, out var additionalLocation, out var option))
                     return;
 
                 // Looks good.  However, we have to make sure that the struct has no code which actually overwrites 'this'
@@ -60,9 +60,9 @@ protected override void InitializeWorker(AnalysisContext context)
 
                     context.ReportDiagnostic(DiagnosticHelper.Create(
                         Descriptor,
-                        typeDeclaration.Identifier.GetLocation(),
+                        location,
                         option.Notification.Severity,
-                        additionalLocations: ImmutableArray.Create(typeDeclaration.GetLocation()),
+                        additionalLocations: ImmutableArray.Create(additionalLocation),
                         properties: null));
                 });
             }, SymbolKind.NamedType);
@@ -70,13 +70,15 @@ protected override void InitializeWorker(AnalysisContext context)
 
     private static bool IsCandidate(
         SymbolStartAnalysisContext context,
-        [NotNullWhen(true)] out TypeDeclarationSyntax? typeDeclaration,
+        [NotNullWhen(true)] out Location? primaryLocation,
+        [NotNullWhen(true)] out Location? additionalLocation,
         [NotNullWhen(true)] out CodeStyleOption2<bool>? option)
     {
         var typeSymbol = (INamedTypeSymbol)context.Symbol;
         var cancellationToken = context.CancellationToken;
 
-        typeDeclaration = null;
+        primaryLocation = null;
+        additionalLocation = null;
         option = null;
         if (typeSymbol.TypeKind is not TypeKind.Struct)
             return false;
@@ -87,7 +89,7 @@ private static bool IsCandidate(
         if (typeSymbol.DeclaringSyntaxReferences.Length == 0)
             return false;
 
-        typeDeclaration = typeSymbol.DeclaringSyntaxReferences[0].GetSyntax(cancellationToken) as TypeDeclarationSyntax;
+        var typeDeclaration = typeSymbol.DeclaringSyntaxReferences[0].GetSyntax(cancellationToken) as TypeDeclarationSyntax;
         if (typeDeclaration is null)
             return false;
 
@@ -111,6 +113,12 @@ private static bool IsCandidate(
         if (!hasField)
             return false;
 
+        // Check if the primary location for the diagnostic is part of the analysis span.
+        primaryLocation = typeDeclaration.Identifier.GetLocation();
+        if (!context.ShouldAnalyzeLocation(primaryLocation))
+            return false;
+
+        additionalLocation = typeDeclaration.GetLocation();
         return true;
     }
 }
diff --git a/src/Analyzers/CSharp/Analyzers/RemoveUnnecessaryNullableDirective/CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/RemoveUnnecessaryNullableDirective/CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer.cs
index 9b0df4f3af4ab..0d0256b6bb3b1 100644
--- a/src/Analyzers/CSharp/Analyzers/RemoveUnnecessaryNullableDirective/CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/RemoveUnnecessaryNullableDirective/CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer.cs
@@ -277,6 +277,12 @@ public void AnalyzeCodeBlock(CodeBlockAnalysisContext context)
                 if (IsIgnoredCodeBlock(context.CodeBlock))
                     return;
 
+                var root = context.GetAnalysisRoot(findInTrivia: true);
+
+                // Bail out if the root contains no nullable directives.
+                if (!root.ContainsDirective(SyntaxKind.NullableDirectiveTrivia))
+                    return;
+
                 var syntaxTreeState = GetOrCreateSyntaxTreeState(context.CodeBlock.SyntaxTree, defaultCompleted: false, context.SemanticModel, context.CancellationToken);
                 if (!syntaxTreeState.TryProceedWithInterval(context.CodeBlock.FullSpan))
                     return;
diff --git a/src/Analyzers/CSharp/Analyzers/RemoveUnusedParametersAndValues/CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/RemoveUnusedParametersAndValues/CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs
index 18256c7780995..b5831f3f2a73f 100644
--- a/src/Analyzers/CSharp/Analyzers/RemoveUnusedParametersAndValues/CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/RemoveUnusedParametersAndValues/CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs
@@ -6,8 +6,10 @@
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
+using Microsoft.CodeAnalysis.CSharp.LanguageService;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Operations;
 using Microsoft.CodeAnalysis.RemoveUnusedParametersAndValues;
 
@@ -22,6 +24,8 @@ public CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer()
         {
         }
 
+        protected override ISyntaxFacts SyntaxFacts => CSharpSyntaxFacts.Instance;
+
         protected override bool SupportsDiscard(SyntaxTree tree)
             => tree.Options.LanguageVersion() >= LanguageVersion.CSharp7;
 
diff --git a/src/Analyzers/CSharp/Analyzers/UseLocalFunction/CSharpUseLocalFunctionDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/UseLocalFunction/CSharpUseLocalFunctionDiagnosticAnalyzer.cs
index f9d205e23feae..3d97a34deeeee 100644
--- a/src/Analyzers/CSharp/Analyzers/UseLocalFunction/CSharpUseLocalFunctionDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/UseLocalFunction/CSharpUseLocalFunctionDiagnosticAnalyzer.cs
@@ -100,6 +100,13 @@ private void SyntaxNodeAction(SyntaxNodeAnalysisContext syntaxContext, INamedTyp
             if (localDeclaration.GetDiagnostics().Any(d => d.Severity == DiagnosticSeverity.Error))
                 return;
 
+            // Bail out if none of possible diagnostic locations are within the analysis span
+            var anonymousFunctionStatement = anonymousFunction.GetAncestor<StatementSyntax>();
+            var shouldReportOnAnonymousFunctionStatement = anonymousFunctionStatement != null
+                && localDeclaration != anonymousFunctionStatement;
+            if (!IsInAnalysisSpan(syntaxContext, localDeclaration, anonymousFunctionStatement, shouldReportOnAnonymousFunctionStatement))
+                return;
+
             var cancellationToken = syntaxContext.CancellationToken;
             var local = semanticModel.GetDeclaredSymbol(localDeclaration.Declaration.Variables[0], cancellationToken);
             if (local == null)
@@ -151,17 +158,34 @@ private void SyntaxNodeAction(SyntaxNodeAnalysisContext syntaxContext, INamedTyp
                     additionalLocations,
                     properties: null));
 
-                var anonymousFunctionStatement = anonymousFunction.GetAncestor<StatementSyntax>();
-                if (anonymousFunctionStatement != null && localDeclaration != anonymousFunctionStatement)
+                if (shouldReportOnAnonymousFunctionStatement)
                 {
                     syntaxContext.ReportDiagnostic(DiagnosticHelper.Create(
                         Descriptor,
-                        anonymousFunctionStatement.GetLocation(),
+                        anonymousFunctionStatement!.GetLocation(),
                         severity,
                         additionalLocations,
                         properties: null));
                 }
             }
+
+            static bool IsInAnalysisSpan(
+                SyntaxNodeAnalysisContext context,
+                LocalDeclarationStatementSyntax localDeclaration,
+                StatementSyntax? anonymousFunctionStatement,
+                bool shouldReportOnAnonymousFunctionStatement)
+            {
+                if (context.ShouldAnalyzeSpan(localDeclaration.Span))
+                    return true;
+
+                if (shouldReportOnAnonymousFunctionStatement
+                    && context.ShouldAnalyzeSpan(anonymousFunctionStatement!.Span))
+                {
+                    return true;
+                }
+
+                return false;
+            }
         }
 
         private static bool CheckForPattern(
diff --git a/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpAsAndNullCheckDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpAsAndNullCheckDiagnosticAnalyzer.cs
index 37c224050220f..64e0999273fd0 100644
--- a/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpAsAndNullCheckDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpAsAndNullCheckDiagnosticAnalyzer.cs
@@ -113,6 +113,10 @@ private void SyntaxNodeAction(SyntaxNodeAnalysisContext syntaxContext)
                 return;
             }
 
+            // Bail out if the potential diagnostic location is outside the analysis span.
+            if (!syntaxContext.ShouldAnalyzeSpan(localStatement.Span))
+                return;
+
             // Don't convert if the as is part of a using statement
             // eg using (var x = y as MyObject) { }
             if (localStatement is UsingStatementSyntax)
diff --git a/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpIsAndCastCheckDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpIsAndCastCheckDiagnosticAnalyzer.cs
index 64536165cd602..682cd8c22a753 100644
--- a/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpIsAndCastCheckDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpIsAndCastCheckDiagnosticAnalyzer.cs
@@ -80,6 +80,10 @@ private void SyntaxNodeAction(SyntaxNodeAnalysisContext syntaxContext)
                 return;
             }
 
+            // Bail out if the potential diagnostic location is outside the analysis span.
+            if (!syntaxContext.ShouldAnalyzeSpan(localDeclarationStatement.Span))
+                return;
+
             // It's of the form:
             //
             //     if (expr is Type)
diff --git a/src/Analyzers/CSharp/Analyzers/UsePrimaryConstructor/CSharpUsePrimaryConstructorDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/UsePrimaryConstructor/CSharpUsePrimaryConstructorDiagnosticAnalyzer.cs
index 3bbf9ca80b22e..2bcfc3e768c71 100644
--- a/src/Analyzers/CSharp/Analyzers/UsePrimaryConstructor/CSharpUsePrimaryConstructorDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/UsePrimaryConstructor/CSharpUsePrimaryConstructorDiagnosticAnalyzer.cs
@@ -5,6 +5,8 @@
 // Ignore Spelling: kvp
 
 using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
@@ -13,7 +15,6 @@
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
-using Microsoft.CodeAnalysis.CSharp.LanguageService;
 using Microsoft.CodeAnalysis.CSharp.Shared.Extensions;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -23,415 +24,501 @@
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Roslyn.Utilities;
 
-namespace Microsoft.CodeAnalysis.CSharp.UsePrimaryConstructor
+namespace Microsoft.CodeAnalysis.CSharp.UsePrimaryConstructor;
+
+/// <summary>
+/// Looks for code of the forms:
+/// <code>
+///     class Point
+///     {
+///         private int x;
+///         private int y;
+/// 
+///         public C(int x, int y)
+///         {
+///             this.x = x;
+///             this.y = y;
+///         }
+///     }
+/// </code>
+/// and converts it to:
+/// <code>
+///     class Point(int x, int y)
+///     {
+///     }
+/// </code>
+/// </summary>
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+internal sealed class CSharpUsePrimaryConstructorDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
 {
+    // Deliberately using names that could not be actual field/property names in the properties dictionary.
+    public const string AllFieldsName = "<>AllFields";
+    public const string AllPropertiesName = "<>AllProperties";
+
+    private static readonly ObjectPool<ConcurrentSet<ISymbol>> s_concurrentSetPool = new(() => new());
+
+    public CSharpUsePrimaryConstructorDiagnosticAnalyzer()
+        : base(IDEDiagnosticIds.UsePrimaryConstructorDiagnosticId,
+               EnforceOnBuildValues.UsePrimaryConstructor,
+               CSharpCodeStyleOptions.PreferPrimaryConstructors,
+               new LocalizableResourceString(
+                    nameof(CSharpAnalyzersResources.Use_primary_constructor), CSharpAnalyzersResources.ResourceManager, typeof(CSharpAnalyzersResources)))
+    {
+    }
 
-    /// <summary>
-    /// Looks for code of the forms:
-    /// <code>
-    ///     class Point
-    ///     {
-    ///         private int x;
-    ///         private int y;
-    /// 
-    ///         public C(int x, int y)
-    ///         {
-    ///             this.x = x;
-    ///             this.y = y;
-    ///         }
-    ///     }
-    /// </code>
-    /// and converts it to:
-    /// <code>
-    ///     class Point(int x, int y)
-    ///     {
-    ///     }
-    /// </code>
-    /// </summary>
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
-    internal sealed class CSharpUsePrimaryConstructorDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
+    public override DiagnosticAnalyzerCategory GetAnalyzerCategory()
+        => DiagnosticAnalyzerCategory.SemanticDocumentAnalysis;
+
+    protected override void InitializeWorker(AnalysisContext context)
     {
-        // Deliberately using names that could not be actual field/property names in the properties dictionary.
-        public const string AllFieldsName = "<>AllFields";
-        public const string AllPropertiesName = "<>AllProperties";
-
-        private static readonly ObjectPool<ConcurrentSet<ISymbol>> s_concurrentSetPool = new(() => new());
-
-        public CSharpUsePrimaryConstructorDiagnosticAnalyzer()
-            : base(IDEDiagnosticIds.UsePrimaryConstructorDiagnosticId,
-                   EnforceOnBuildValues.UsePrimaryConstructor,
-                   CSharpCodeStyleOptions.PreferPrimaryConstructors,
-                   new LocalizableResourceString(
-                        nameof(CSharpAnalyzersResources.Use_primary_constructor), CSharpAnalyzersResources.ResourceManager, typeof(CSharpAnalyzersResources)))
+        context.RegisterCompilationStartAction(context =>
         {
-        }
+            // "x is not Type y" is only available in C# 9.0 and above. Don't offer this refactoring
+            // in projects targeting a lesser version.
+            if (!context.Compilation.LanguageVersion().IsCSharp12OrAbove())
+                return;
 
-        public override DiagnosticAnalyzerCategory GetAnalyzerCategory()
-            => DiagnosticAnalyzerCategory.SemanticDocumentAnalysis;
+            // Mapping from a named type to a particular analyzer we have created for it. Needed because nested
+            // types need to update the information for their containing types while they themselves are being
+            // analyzed.
+            var namedTypeToAnalyzer = new ConcurrentDictionary<INamedTypeSymbol, Analyzer>();
+            context.RegisterSymbolStartAction(context => Analyzer.AnalyzeNamedTypeStart(this, context, namedTypeToAnalyzer), SymbolKind.NamedType);
+        });
+    }
 
-        protected override void InitializeWorker(AnalysisContext context)
-        {
-            context.RegisterCompilationStartAction(context =>
-            {
-                // "x is not Type y" is only available in C# 9.0 and above. Don't offer this refactoring
-                // in projects targeting a lesser version.
-                if (!context.Compilation.LanguageVersion().IsCSharp12OrAbove())
-                    return;
+    public static bool IsViableMemberToAssignTo(
+        INamedTypeSymbol namedType,
+        [NotNullWhen(true)] ISymbol? member,
+        [NotNullWhen(true)] out SyntaxNode? nodeToRemove,
+        CancellationToken cancellationToken)
+    {
+        nodeToRemove = null;
+        if (member is not IFieldSymbol and not IPropertySymbol)
+            return false;
 
-                context.RegisterSymbolStartAction(context => Analyzer.AnalyzeNamedTypeStart(this, context), SymbolKind.NamedType);
-            });
-        }
+        if (member.IsImplicitlyDeclared)
+            return false;
 
-        public static bool IsViableMemberToAssignTo(
-            INamedTypeSymbol namedType,
-            [NotNullWhen(true)] ISymbol? member,
-            [NotNullWhen(true)] out SyntaxNode? nodeToRemove,
-            CancellationToken cancellationToken)
+        if (member.IsStatic)
+            return false;
+
+        if (!namedType.Equals(member.ContainingType))
+            return false;
+
+        if (member.DeclaringSyntaxReferences is not [var memberReference, ..])
+            return false;
+
+        nodeToRemove = memberReference.GetSyntax(cancellationToken);
+        if (nodeToRemove is not VariableDeclaratorSyntax and not PropertyDeclarationSyntax)
+            return false;
+
+        // If it's a property, then it has to be an auto property in order for us to be able to initialize is
+        // directly outside of a constructor.
+        if (nodeToRemove is PropertyDeclarationSyntax property)
         {
-            nodeToRemove = null;
-            if (member is not IFieldSymbol and not IPropertySymbol)
+            if (property.AccessorList is null ||
+                property.AccessorList.Accessors.Any(static a => a.ExpressionBody != null || a.Body != null))
+            {
                 return false;
+            }
+        }
 
-            if (member.IsImplicitlyDeclared)
-                return false;
+        return true;
+    }
 
-            if (member.IsStatic)
-                return false;
+    /// <summary>
+    /// Helper type we create that encapsulates all the state we need while processing.
+    /// </summary>
+    private sealed class Analyzer
+    {
+        private readonly CSharpUsePrimaryConstructorDiagnosticAnalyzer _diagnosticAnalyzer;
 
-            if (!namedType.Equals(member.ContainingType))
-                return false;
+        private readonly CodeStyleOption2<bool> _styleOption;
+        private readonly INamedTypeSymbol _namedType;
+        private readonly ConstructorDeclarationSyntax _primaryConstructorDeclaration;
 
-            if (member.DeclaringSyntaxReferences is not [var memberReference, ..])
-                return false;
+        private readonly PooledDictionary<ISymbol, IParameterSymbol> _candidateMembersToRemove;
+        private readonly ConcurrentDictionary<INamedTypeSymbol, Analyzer> _namedTypeToAnalyzer;
 
-            nodeToRemove = memberReference.GetSyntax(cancellationToken);
-            if (nodeToRemove is not VariableDeclaratorSyntax and not PropertyDeclarationSyntax)
-                return false;
+        /// <summary>
+        /// Needs to be concurrent as we can process members in parallel in <see
+        /// cref="AnalyzeFieldOrPropertyReference"/>.
+        /// </summary>
+        private readonly ConcurrentSet<ISymbol> _membersThatCannotBeRemoved = s_concurrentSetPool.Allocate();
+
+        public Analyzer(
+            CSharpUsePrimaryConstructorDiagnosticAnalyzer diagnosticAnalyzer,
+            CodeStyleOption2<bool> styleOption,
+            INamedTypeSymbol namedType,
+            ConstructorDeclarationSyntax primaryConstructorDeclaration,
+            PooledDictionary<ISymbol, IParameterSymbol> candidateMembersToRemove,
+            ConcurrentDictionary<INamedTypeSymbol, Analyzer> namedTypeToAnalyzer)
+        {
+            _diagnosticAnalyzer = diagnosticAnalyzer;
+            _styleOption = styleOption;
+            _namedType = namedType;
+            _primaryConstructorDeclaration = primaryConstructorDeclaration;
+            _candidateMembersToRemove = candidateMembersToRemove;
+            _namedTypeToAnalyzer = namedTypeToAnalyzer;
+        }
 
-            // If it's a property, then it has to be an auto property in order for us to be able to initialize is
-            // directly outside of a constructor.
-            if (nodeToRemove is PropertyDeclarationSyntax property)
+        public bool HasCandidateMembersToRemove => _candidateMembersToRemove.Count > 0;
+
+        private void OnSymbolEnd(SymbolAnalysisContext context)
+        {
+            // Pass along a mapping of field/property name to the constructor parameter name that will replace it.
+            var properties = _candidateMembersToRemove
+                .Where(kvp => !_membersThatCannotBeRemoved.Contains(kvp.Key))
+                .ToImmutableDictionary(
+                    static kvp => kvp.Key.Name,
+                    static kvp => (string?)kvp.Value.Name);
+
+            // To provide better user-facing-strings, keep track of whether or not all the members we'd be
+            // removing are all fields or all properties.
+            if (_candidateMembersToRemove.Any(kvp => kvp.Key is IFieldSymbol) &&
+                _candidateMembersToRemove.All(kvp => kvp.Key is IFieldSymbol))
             {
-                if (property.AccessorList is null ||
-                    property.AccessorList.Accessors.Any(static a => a.ExpressionBody != null || a.Body != null))
-                {
-                    return false;
-                }
+                properties = properties.Add(AllFieldsName, AllFieldsName);
             }
+            else if (
+                _candidateMembersToRemove.Any(kvp => kvp.Key is IPropertySymbol) &&
+                _candidateMembersToRemove.All(kvp => kvp.Key is IPropertySymbol))
+            {
+                properties = properties.Add(AllPropertiesName, AllPropertiesName);
+            }
+
+            context.ReportDiagnostic(DiagnosticHelper.Create(
+                _diagnosticAnalyzer.Descriptor,
+                _primaryConstructorDeclaration.Identifier.GetLocation(),
+                _styleOption.Notification.Severity,
+                ImmutableArray.Create(_primaryConstructorDeclaration.GetLocation()),
+                properties));
+
+            _candidateMembersToRemove.Free();
+            s_concurrentSetPool.ClearAndFree(_membersThatCannotBeRemoved);
 
-            return true;
+            _namedTypeToAnalyzer.TryRemove(_namedType, out _);
         }
 
-        /// <summary>
-        /// Helper type we create that encapsulates all the state we need while processing.
-        /// </summary>
-        private sealed class Analyzer
+        public static void AnalyzeNamedTypeStart(
+            CSharpUsePrimaryConstructorDiagnosticAnalyzer diagnosticAnalyzer,
+            SymbolStartAnalysisContext context,
+            ConcurrentDictionary<INamedTypeSymbol, Analyzer> namedTypeToAnalyzer)
         {
-            private readonly CSharpUsePrimaryConstructorDiagnosticAnalyzer _diagnosticAnalyzer;
+            var compilation = context.Compilation;
+            var cancellationToken = context.CancellationToken;
 
-            private readonly CodeStyleOption2<bool> _styleOption;
+            var startSymbol = (INamedTypeSymbol)context.Symbol;
+            var options = context.Options;
 
-            private readonly IMethodSymbol _primaryConstructor;
-            private readonly ConstructorDeclarationSyntax _primaryConstructorDeclaration;
+            // Ensure that any analyzers for containing types are created and they hear about any reference to their
+            // fields in this nested type.
 
-            private readonly PooledDictionary<ISymbol, IParameterSymbol> _candidateMembersToRemove;
+            var hadContainingTypeAnalyzer = false;
+            for (var containingType = startSymbol.ContainingType; containingType != null; containingType = containingType.ContainingType)
+            {
+                var containgTypeAnalyzer = TryGetOrCreateAnalyzer(containingType);
+                RegisterFieldOrPropertyAnalysisIfNecessary(containgTypeAnalyzer);
+                hadContainingTypeAnalyzer = hadContainingTypeAnalyzer || containgTypeAnalyzer != null;
+            }
 
-            /// <summary>
-            /// Needs to be concurrent as we can process members in parallel in <see
-            /// cref="AnalyzeFieldOrPropertyReference"/>.
-            /// </summary>
-            private readonly ConcurrentSet<ISymbol> _membersThatCannotBeRemoved = s_concurrentSetPool.Allocate();
+            // Now try to make the analyzer for this type.
+            var analyzer = TryGetOrCreateAnalyzer(startSymbol);
+            if (analyzer != null)
+            {
+                RegisterFieldOrPropertyAnalysisIfNecessary(analyzer);
+                context.RegisterSymbolEndAction(analyzer.OnSymbolEnd);
+            }
+            else if (hadContainingTypeAnalyzer)
+            {
+                // We didn't create an analyze for this type.  But we have containing types with analyzers. Ensure
+                // we register a symbol-end analyzer for us.  The analysis subsystem needs this to ensure that outer
+                // analyzers don't complete until its nested types are done.
+                context.RegisterSymbolEndAction(static _ => { });
+            }
 
-            public Analyzer(
-                CSharpUsePrimaryConstructorDiagnosticAnalyzer diagnosticAnalyzer,
-                CodeStyleOption2<bool> styleOption,
-                IMethodSymbol primaryConstructor,
-                ConstructorDeclarationSyntax primaryConstructorDeclaration,
-                PooledDictionary<ISymbol, IParameterSymbol> candidateMembersToRemove)
+            return;
+
+            void RegisterFieldOrPropertyAnalysisIfNecessary(Analyzer? analyzer)
             {
-                _diagnosticAnalyzer = diagnosticAnalyzer;
-                _styleOption = styleOption;
-                _primaryConstructor = primaryConstructor;
-                _primaryConstructorDeclaration = primaryConstructorDeclaration;
-                _candidateMembersToRemove = candidateMembersToRemove;
+                if (analyzer is { HasCandidateMembersToRemove: true })
+                {
+                    // Look to see if we have trivial `_x = x` or `this.x = x` assignments.  If so, then the field/prop
+                    // could be a candidate for removal (as long as we determine that all use sites of the field/prop would
+                    // be able to use the captured primary constructor parameter).
+                    context.RegisterOperationAction(
+                        analyzer.AnalyzeFieldOrPropertyReference,
+                        OperationKind.FieldReference, OperationKind.PropertyReference);
+                }
             }
 
-            private void OnSymbolEnd(SymbolAnalysisContext context)
+            Analyzer? TryGetOrCreateAnalyzer(
+                INamedTypeSymbol namedType)
             {
-                // See if the constructor analysis found a viable constructor to convert to a primary constructor.
-                if (_primaryConstructor is not null)
+                if (!namedTypeToAnalyzer.TryGetValue(namedType, out var analyzer))
                 {
-                    // Pass along a mapping of field/property name to the constructor parameter name that will replace it.
-                    var properties = _candidateMembersToRemove
-                        .Where(kvp => !_membersThatCannotBeRemoved.Contains(kvp.Key))
-                        .ToImmutableDictionary(
-                            static kvp => kvp.Key.Name,
-                            static kvp => (string?)kvp.Value.Name);
-
-                    // To provide better user-facing-strings, keep track of whether or not all the members we'd be
-                    // removing are all fields or all properties.
-                    if (_candidateMembersToRemove.Any(kvp => kvp.Key is IFieldSymbol) &&
-                        _candidateMembersToRemove.All(kvp => kvp.Key is IFieldSymbol))
-                    {
-                        properties = properties.Add(AllFieldsName, AllFieldsName);
-                    }
-                    else if (
-                        _candidateMembersToRemove.Any(kvp => kvp.Key is IPropertySymbol) &&
-                        _candidateMembersToRemove.All(kvp => kvp.Key is IPropertySymbol))
-                    {
-                        properties = properties.Add(AllPropertiesName, AllPropertiesName);
-                    }
+                    analyzer = TryCreateAnalyzer(namedType);
+                    if (analyzer != null)
+                        namedTypeToAnalyzer.TryAdd(namedType, analyzer);
 
-                    context.ReportDiagnostic(DiagnosticHelper.Create(
-                        _diagnosticAnalyzer.Descriptor,
-                        _primaryConstructorDeclaration.Identifier.GetLocation(),
-                        _styleOption.Notification.Severity,
-                        ImmutableArray.Create(_primaryConstructorDeclaration.GetLocation()),
-                        properties));
+                    // If another thread beat us, defer to that.
+                    namedTypeToAnalyzer.TryGetValue(namedType, out analyzer);
                 }
 
-                _candidateMembersToRemove.Free();
-                s_concurrentSetPool.ClearAndFree(_membersThatCannotBeRemoved);
+                return analyzer;
             }
 
-            public static void AnalyzeNamedTypeStart(
-                CSharpUsePrimaryConstructorDiagnosticAnalyzer diagnosticAnalyzer,
-                SymbolStartAnalysisContext context)
+            Analyzer? TryCreateAnalyzer(INamedTypeSymbol namedType)
             {
-                var compilation = context.Compilation;
-                var cancellationToken = context.CancellationToken;
-
                 // Bail immediately if the user has disabled this feature.
-                var namedType = (INamedTypeSymbol)context.Symbol;
                 if (namedType.DeclaringSyntaxReferences is not [var reference, ..])
-                    return;
+                    return null;
 
-                var styleOption = context.Options.GetCSharpAnalyzerOptions(reference.SyntaxTree).PreferPrimaryConstructors;
+                var styleOption = options.GetCSharpAnalyzerOptions(reference.SyntaxTree).PreferPrimaryConstructors;
                 if (!styleOption.Value)
-                    return;
+                    return null;
 
                 // only classes/structs can have primary constructors (not interfaces, enums or delegates).
                 if (namedType.TypeKind is not (TypeKind.Class or TypeKind.Struct))
-                    return;
+                    return null;
 
                 // Don't want to offer on records.  It's completely fine for records to not use primary constructs and
                 // instead use init-properties.
                 if (namedType.IsRecord)
-                    return;
+                    return null;
 
                 // No need to offer this if the type already has a primary constructor.
                 if (namedType.TryGetPrimaryConstructor(out _))
-                    return;
+                    return null;
 
                 // Need to see if there is a single constructor that either calls `base(...)` or has no constructor
                 // initializer (and thus implicitly calls `base()`), and that all other constructors call `this(...)`.
-                if (!TryFindPrimaryConstructorCandidate(out var primaryConstructor, out var primaryConstructorDeclaration))
-                    return;
+                if (!TryFindPrimaryConstructorCandidate(namedType, out var primaryConstructor, out var primaryConstructorDeclaration))
+                    return null;
 
                 if (primaryConstructor.Parameters.Length == 0)
-                    return;
+                    return null;
 
                 if (primaryConstructor.DeclaredAccessibility != Accessibility.Public)
-                    return;
+                    return null;
 
                 // Constructor has to have a real body (can't be extern/etc.).
                 if (primaryConstructorDeclaration is { Body: null, ExpressionBody: null })
-                    return;
+                    return null;
 
                 if (primaryConstructorDeclaration.Parent is not TypeDeclarationSyntax)
-                    return;
+                    return null;
 
                 if (primaryConstructor.Parameters.Any(static p => p.RefKind is RefKind.Ref or RefKind.Out))
-                    return;
+                    return null;
 
                 // Now ensure the constructor body is something that could be converted to a primary constructor (i.e.
                 // only assignments to instance fields/props on this).
-                var semanticModel = compilation.GetSemanticModel(primaryConstructorDeclaration.SyntaxTree);
                 var candidateMembersToRemove = PooledDictionary<ISymbol, IParameterSymbol>.GetInstance();
-                if (!AnalyzeConstructorBody())
+                if (!AnalyzeConstructorBody(namedType, primaryConstructorDeclaration, candidateMembersToRemove))
                 {
                     candidateMembersToRemove.Free();
-                    return;
+                    return null;
                 }
 
-                var analyzer = new Analyzer(diagnosticAnalyzer, styleOption, primaryConstructor, primaryConstructorDeclaration, candidateMembersToRemove);
-
-                // Look to see if we have trivial `_x = x` or `this.x = x` assignments.  If so, then the field/prop
-                // could be a candidate for removal (as long as we determine that all use sites of the field/prop would
-                // be able to use the captured primary constructor parameter).
-
-                if (candidateMembersToRemove.Count > 0)
-                    context.RegisterOperationAction(analyzer.AnalyzeFieldOrPropertyReference, OperationKind.FieldReference, OperationKind.PropertyReference);
+                return new Analyzer(
+                    diagnosticAnalyzer,
+                    styleOption,
+                    namedType,
+                    primaryConstructorDeclaration,
+                    candidateMembersToRemove,
+                    namedTypeToAnalyzer);
+            }
 
-                context.RegisterSymbolEndAction(analyzer.OnSymbolEnd);
+            bool TryFindPrimaryConstructorCandidate(
+                INamedTypeSymbol namedType,
+                [NotNullWhen(true)] out IMethodSymbol? primaryConstructor,
+                [NotNullWhen(true)] out ConstructorDeclarationSyntax? primaryConstructorDeclaration)
+            {
+                primaryConstructor = null;
+                primaryConstructorDeclaration = null;
 
-                return;
+                var constructors = namedType.InstanceConstructors;
 
-                bool TryFindPrimaryConstructorCandidate(
-                    [NotNullWhen(true)] out IMethodSymbol? primaryConstructor,
-                    [NotNullWhen(true)] out ConstructorDeclarationSyntax? primaryConstructorDeclaration)
+                foreach (var constructor in constructors)
                 {
-                    primaryConstructor = null;
-                    primaryConstructorDeclaration = null;
-
-                    var constructors = namedType.InstanceConstructors;
+                    // Can ignore the implicit struct constructor.  It doesn't block us making a real constructor
+                    // into a primary constructor.
+                    if (namedType.IsStructType() && constructor.IsImplicitlyDeclared)
+                        continue;
 
-                    foreach (var constructor in constructors)
-                    {
-                        // Can ignore the implicit struct constructor.  It doesn't block us making a real constructor
-                        // into a primary constructor.
-                        if (namedType.IsStructType() && constructor.IsImplicitlyDeclared)
-                            continue;
+                    // Needs to just have a single declaration
+                    if (constructor.DeclaringSyntaxReferences is not [var constructorReference])
+                        return false;
 
-                        // Needs to just have a single declaration
-                        if (constructor.DeclaringSyntaxReferences is not [var constructorReference])
-                            return false;
+                    if (constructorReference.GetSyntax(cancellationToken) is not ConstructorDeclarationSyntax constructorDeclaration)
+                        return false;
 
-                        if (constructorReference.GetSyntax(cancellationToken) is not ConstructorDeclarationSyntax constructorDeclaration)
+                    if (constructorDeclaration.Initializer is null or (kind: SyntaxKind.BaseConstructorInitializer))
+                    {
+                        // Can only have one candidate
+                        if (primaryConstructor != null)
                             return false;
 
-                        if (constructorDeclaration.Initializer is null or (kind: SyntaxKind.BaseConstructorInitializer))
-                        {
-                            // Can only have one candidate
-                            if (primaryConstructor != null)
-                                return false;
-
-                            primaryConstructor = constructor;
-                            primaryConstructorDeclaration = constructorDeclaration;
-                        }
-                        else
-                        {
-                            Debug.Assert(constructorDeclaration.Initializer.Kind() == SyntaxKind.ThisConstructorInitializer);
-                        }
+                        primaryConstructor = constructor;
+                        primaryConstructorDeclaration = constructorDeclaration;
                     }
-
-                    return primaryConstructor != null;
-                }
-
-                bool AnalyzeConstructorBody()
-                {
-                    return primaryConstructorDeclaration switch
+                    else
                     {
-                        { ExpressionBody.Expression: AssignmentExpressionSyntax assignmentExpression } => IsAssignmentToInstanceMember(assignmentExpression, out _),
-                        { Body: { } body } => AnalyzeBlockBody(body),
-                        _ => false,
-                    };
+                        Debug.Assert(constructorDeclaration.Initializer.Kind() == SyntaxKind.ThisConstructorInitializer);
+                    }
                 }
 
-                bool AnalyzeBlockBody(BlockSyntax block)
+                return primaryConstructor != null;
+            }
+
+            bool AnalyzeConstructorBody(
+                INamedTypeSymbol namedType,
+                ConstructorDeclarationSyntax primaryConstructorDeclaration,
+                Dictionary<ISymbol, IParameterSymbol> candidateMembersToRemove)
+            {
+                var semanticModel = compilation.GetSemanticModel(primaryConstructorDeclaration.SyntaxTree);
+
+                var body = primaryConstructorDeclaration.ExpressionBody ?? (SyntaxNode?)primaryConstructorDeclaration.Body;
+                if (body?.ContainsDirectives is true)
+                    return false;
+
+                return primaryConstructorDeclaration switch
                 {
-                    // Quick pass.  Must all be assignment expressions.  Don't have to do any more analysis if we see anything beyond that.
-                    if (!block.Statements.All(static s => s is ExpressionStatementSyntax { Expression: AssignmentExpressionSyntax }))
-                        return false;
+                    { ExpressionBody.Expression: AssignmentExpressionSyntax assignmentExpression }
+                        => IsAssignmentToInstanceMember(namedType, semanticModel, assignmentExpression, candidateMembersToRemove, out _),
+                    { Body: { } block }
+                        => AnalyzeBlockBody(namedType, semanticModel, block, candidateMembersToRemove),
+                    _ => false,
+                };
+            }
 
-                    using var _ = PooledHashSet<ISymbol>.GetInstance(out var assignedMembers);
+            bool AnalyzeBlockBody(
+                INamedTypeSymbol namedType,
+                SemanticModel semanticModel,
+                BlockSyntax block,
+                Dictionary<ISymbol, IParameterSymbol> candidateMembersToRemove)
+            {
+                // Quick pass.  Must all be assignment expressions.  Don't have to do any more analysis if we see anything beyond that.
+                if (!block.Statements.All(static s => s is ExpressionStatementSyntax { Expression: AssignmentExpressionSyntax }))
+                    return false;
 
-                    foreach (var statement in block.Statements)
-                    {
-                        if (statement is not ExpressionStatementSyntax { Expression: AssignmentExpressionSyntax assignmentExpression } ||
-                            !IsAssignmentToInstanceMember(assignmentExpression, out var member))
-                        {
-                            return false;
-                        }
+                using var _ = PooledHashSet<ISymbol>.GetInstance(out var assignedMembers);
 
-                        // Only allow a single write to the same member
-                        if (!assignedMembers.Add(member))
-                            return false;
+                foreach (var statement in block.Statements)
+                {
+                    if (statement is not ExpressionStatementSyntax { Expression: AssignmentExpressionSyntax assignmentExpression } ||
+                        !IsAssignmentToInstanceMember(namedType, semanticModel, assignmentExpression, candidateMembersToRemove, out var member))
+                    {
+                        return false;
                     }
 
-                    return true;
+                    // Only allow a single write to the same member
+                    if (!assignedMembers.Add(member))
+                        return false;
                 }
 
-                bool IsAssignmentToInstanceMember(
-                    AssignmentExpressionSyntax assignmentExpression, [NotNullWhen(true)] out ISymbol? member)
-                {
-                    member = null;
+                return true;
+            }
 
-                    if (assignmentExpression.Kind() != SyntaxKind.SimpleAssignmentExpression)
-                        return false;
+            bool IsAssignmentToInstanceMember(
+                INamedTypeSymbol namedType,
+                SemanticModel semanticModel,
+                AssignmentExpressionSyntax assignmentExpression,
+                Dictionary<ISymbol, IParameterSymbol> candidateMembersToRemove,
+                [NotNullWhen(true)] out ISymbol? member)
+            {
+                member = null;
 
-                    // has to be of the form:
-                    //
-                    // x = ...      // or
-                    // this.x = ...
-                    var leftIdentifier = assignmentExpression.Left switch
-                    {
-                        IdentifierNameSyntax identifierName => identifierName,
-                        MemberAccessExpressionSyntax(kind: SyntaxKind.SimpleMemberAccessExpression) { Expression: (kind: SyntaxKind.ThisExpression), Name: IdentifierNameSyntax identifierName } => identifierName,
-                        _ => null,
-                    };
+                if (assignmentExpression.Kind() != SyntaxKind.SimpleAssignmentExpression)
+                    return false;
 
-                    if (leftIdentifier is null)
-                        return false;
+                // has to be of the form:
+                //
+                // x = ...      // or
+                // this.x = ...
+                var leftIdentifier = assignmentExpression.Left switch
+                {
+                    IdentifierNameSyntax identifierName => identifierName,
+                    MemberAccessExpressionSyntax(kind: SyntaxKind.SimpleMemberAccessExpression) { Expression: (kind: SyntaxKind.ThisExpression), Name: IdentifierNameSyntax identifierName } => identifierName,
+                    _ => null,
+                };
 
-                    // Quick syntactic lookup.
-                    if (namedType.GetMembers(leftIdentifier.Identifier.ValueText).IsEmpty)
-                        return false;
+                if (leftIdentifier is null)
+                    return false;
 
-                    // Has to bind to a field/prop on this type.
-                    member = semanticModel.GetSymbolInfo(leftIdentifier, cancellationToken).GetAnySymbol()?.OriginalDefinition;
-                    if (!IsViableMemberToAssignTo(namedType, member, out _, cancellationToken))
-                        return false;
+                // Quick syntactic lookup.
+                if (namedType.GetMembers(leftIdentifier.Identifier.ValueText).IsEmpty)
+                    return false;
 
-                    // Left side looks good.  Now check the right side.  It cannot reference 'this' (as that is not
-                    // legal once we move this to initialize the field/prop in the rewrite).
-                    var rightOperation = semanticModel.GetOperation(assignmentExpression.Right);
-                    foreach (var operation in rightOperation.DescendantsAndSelf())
-                    {
-                        if (operation is IInstanceReferenceOperation)
-                            return false;
-                    }
+                // Has to bind to a field/prop on this type.
+                member = semanticModel.GetSymbolInfo(leftIdentifier, cancellationToken).GetAnySymbol()?.OriginalDefinition;
+                if (!IsViableMemberToAssignTo(namedType, member, out _, cancellationToken))
+                    return false;
 
-                    // Looks good, both the left and right sides are legal.
+                // Left side looks good.  Now check the right side.  It cannot reference 'this' (as that is not
+                // legal once we move this to initialize the field/prop in the rewrite).
+                var rightOperation = semanticModel.GetOperation(assignmentExpression.Right);
+                foreach (var operation in rightOperation.DescendantsAndSelf())
+                {
+                    if (operation is IInstanceReferenceOperation)
+                        return false;
+                }
 
-                    // If we have an assignment of the form `private_member = param`, then that member can be a candidate for removal.
-                    if (member.DeclaredAccessibility == Accessibility.Private &&
-                        !member.GetAttributes().Any() &&
-                        semanticModel.GetSymbolInfo(assignmentExpression.Right, cancellationToken).GetAnySymbol() is IParameterSymbol parameter &&
-                        parameter.Type.Equals(member.GetMemberType()))
-                    {
-                        candidateMembersToRemove[member] = parameter;
-                    }
+                // Looks good, both the left and right sides are legal.
 
-                    return true;
+                // If we have an assignment of the form `private_member = param`, then that member can be a candidate for removal.
+                if (member.DeclaredAccessibility == Accessibility.Private &&
+                    !member.GetAttributes().Any() &&
+                    semanticModel.GetSymbolInfo(assignmentExpression.Right, cancellationToken).GetAnySymbol() is IParameterSymbol parameter &&
+                    parameter.Type.Equals(member.GetMemberType()))
+                {
+                    candidateMembersToRemove[member] = parameter;
                 }
+
+                return true;
             }
+        }
 
-            private void AnalyzeFieldOrPropertyReference(OperationAnalysisContext context)
-            {
-                var operation = (IMemberReferenceOperation)context.Operation;
-                var semanticModel = operation.SemanticModel;
-                Contract.ThrowIfNull(semanticModel);
+        private void AnalyzeFieldOrPropertyReference(OperationAnalysisContext context)
+        {
+            var operation = (IMemberReferenceOperation)context.Operation;
+            var semanticModel = operation.SemanticModel;
+            Contract.ThrowIfNull(semanticModel);
 
-                var member = operation.Member.OriginalDefinition;
-                var instance = operation.Instance;
+            var instance = operation.Instance;
 
-                // static field/property.  not something we're interested in.
-                if (instance is null)
-                    return;
+            // static field/property.  not something we're interested in.
+            if (instance is null)
+                return;
 
-                // we only care about reference to members in our candidate-removal set.  Can ignore everything else.
-                if (!_candidateMembersToRemove.TryGetValue(member, out var parameter))
-                    return;
+            var member = operation.Member.OriginalDefinition;
 
-                // not a reference off of 'this'.  e.g. `== other.fieldName`, we could not remove this member.
-                if (instance is not IInstanceReferenceOperation)
-                {
-                    _membersThatCannotBeRemoved.Add(member);
-                    return;
-                }
+            // Don't need to analyze this again, if it's already in the list of members we can't remove.
+            if (_membersThatCannotBeRemoved.Contains(member))
+                return;
 
-                // it's either `this.field` or just `field`.  We can replace with a reference to 'paramName' *if* that
-                // name in the current location doesn't bind to something else.
-                var symbols = semanticModel.LookupSymbols(operation.Syntax.SpanStart, name: parameter.Name);
-                if (symbols.Any(s => !Equals(s, parameter) && !Equals(s, member)))
-                {
-                    _membersThatCannotBeRemoved.Add(member);
-                    return;
-                }
+            // we only care about reference to members in our candidate-removal set.  Can ignore everything else.
+            if (!_candidateMembersToRemove.TryGetValue(member, out var parameter))
+                return;
+
+            // not a reference off of 'this'.  e.g. `== other.fieldName`, we could not remove this member.
+            if (instance is not IInstanceReferenceOperation)
+            {
+                _membersThatCannotBeRemoved.Add(member);
+                return;
+            }
 
-                // looks good.  We should be able to remove this.
+            // it's either `this.field` or just `field`.  We can replace with a reference to 'paramName' *if* that
+            // name in the current location doesn't bind to something else.
+            var symbols = semanticModel.LookupSymbols(operation.Syntax.SpanStart, name: parameter.Name);
+            if (symbols.Any(s => !Equals(s, parameter) && !Equals(s, member)))
+            {
+                _membersThatCannotBeRemoved.Add(member);
+                return;
             }
+
+            // looks good.  We should be able to remove this.
         }
     }
 }
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.cs.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.cs.xlf
index bf6ea2c0dbabe..b485bfe17c5b5 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.cs.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.cs.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">Člena je možné nastavit jako readonly</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Použít primární konstruktor</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.de.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.de.xlf
index 8d79d878d8634..6ff3705cc68a5 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.de.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.de.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">Member kann als "readonly" festgelegt werden</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Primären Konstruktor verwenden</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.es.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.es.xlf
index 11daab06b2aad..b6d67d308c8d5 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.es.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.es.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">El miembro se puede hacer "readonly"</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Usar constructor principal</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.fr.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.fr.xlf
index c162eb14c9e8f..270a3f05a8fa7 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.fr.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.fr.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">Le membre peut être défini en 'readonly'</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Utiliser le constructeur principal</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.it.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.it.xlf
index 69faa2d5192fa..13dbd08e7716a 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.it.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.it.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">Il membro può essere impostato come 'readonly'</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Usa costruttore primario</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ja.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ja.xlf
index b2dc9d7ac5cc8..374f99f4b75d0 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ja.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ja.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">メンバーを 'readonly' にすることができます</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">プライマリ コンストラクターの使用</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ko.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ko.xlf
index 2b3cc11dda55d..85f2d27edae89 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ko.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ko.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">멤버를 'readonly'로 만들 수 있음</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">기본 생성자 사용</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pl.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pl.xlf
index 78ce181489267..17825648087f7 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pl.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pl.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">Element członkowski można określić jako „readonly”</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Użyj konstruktora podstawowego</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pt-BR.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pt-BR.xlf
index 20a4f1ad94d9a..6c2efc3a35f31 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pt-BR.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.pt-BR.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">O membro pode se tornar 'readonly'</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Usar construtor primário</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ru.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ru.xlf
index 32697d6e8c7f5..caa0742ff2280 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ru.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.ru.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">Элемент можно сделать "readonly"</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Использовать основной конструктор</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.tr.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.tr.xlf
index 0b1ea7cd7efe0..b009bdd608b86 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.tr.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.tr.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">Üye 'readonly' yapılabilir</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">Birincil oluşturucuyu kullan</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hans.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hans.xlf
index 904774dca1e96..1f964aab79bae 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hans.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hans.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">可将成员设为“readonly”</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">使用主构造函数</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hant.xlf b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hant.xlf
index c1be03f414364..0feb0aa243ef3 100644
--- a/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hant.xlf
+++ b/src/Analyzers/CSharp/Analyzers/xlf/CSharpAnalyzersResources.zh-Hant.xlf
@@ -104,7 +104,7 @@
       </trans-unit>
       <trans-unit id="Member_can_be_made_readonly">
         <source>Member can be made 'readonly'</source>
-        <target state="new">Member can be made 'readonly'</target>
+        <target state="translated">成員可以設為 'readonly'</target>
         <note>{Locked="readonly"} "readonly" is a C# keyword and should not be localized.</note>
       </trans-unit>
       <trans-unit id="Misplaced_using_directive">
@@ -389,7 +389,7 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor">
         <source>Use primary constructor</source>
-        <target state="new">Use primary constructor</target>
+        <target state="translated">使用主要建構函式</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_range_operator">
diff --git a/src/Analyzers/CSharp/CodeFixes/Iterator/CSharpAddYieldCodeFixProvider.cs b/src/Analyzers/CSharp/CodeFixes/Iterator/CSharpAddYieldCodeFixProvider.cs
index c09ccdc1d6488..47d8aa3651a2e 100644
--- a/src/Analyzers/CSharp/CodeFixes/Iterator/CSharpAddYieldCodeFixProvider.cs
+++ b/src/Analyzers/CSharp/CodeFixes/Iterator/CSharpAddYieldCodeFixProvider.cs
@@ -117,7 +117,7 @@ private static bool TryGetMethodReturnType(
             return methodReturnType != null;
         }
 
-        private bool IsCorrectTypeForYieldReturn(ITypeSymbol typeArgument, ITypeSymbol returnExpressionType, ITypeSymbol methodReturnType, SemanticModel model)
+        private static bool IsCorrectTypeForYieldReturn(ITypeSymbol typeArgument, ITypeSymbol returnExpressionType, ITypeSymbol methodReturnType, SemanticModel model)
         {
             var ienumerableSymbol = model.Compilation.GetTypeByMetadataName(typeof(IEnumerable).FullName!);
             var ienumeratorSymbol = model.Compilation.GetTypeByMetadataName(typeof(IEnumerator).FullName!);
@@ -151,7 +151,7 @@ private bool IsCorrectTypeForYieldReturn(ITypeSymbol typeArgument, ITypeSymbol r
             return true;
         }
 
-        private bool CanConvertTypes(ITypeSymbol typeArgument, ITypeSymbol returnExpressionType, SemanticModel model)
+        private static bool CanConvertTypes(ITypeSymbol typeArgument, ITypeSymbol returnExpressionType, SemanticModel model)
         {
             // return false if there is no conversion for the top level type
             if (!model.Compilation.ClassifyConversion(typeArgument, returnExpressionType).Exists)
diff --git a/src/Analyzers/CSharp/CodeFixes/MakeLocalFunctionStatic/MakeLocalFunctionStaticCodeFixHelper.cs b/src/Analyzers/CSharp/CodeFixes/MakeLocalFunctionStatic/MakeLocalFunctionStaticCodeFixHelper.cs
index 74f6be529eea5..77bc273b5683f 100644
--- a/src/Analyzers/CSharp/CodeFixes/MakeLocalFunctionStatic/MakeLocalFunctionStaticCodeFixHelper.cs
+++ b/src/Analyzers/CSharp/CodeFixes/MakeLocalFunctionStatic/MakeLocalFunctionStaticCodeFixHelper.cs
@@ -169,7 +169,7 @@ public static async Task MakeLocalFunctionStaticAsync(
 
 #if CODE_STYLE
             var info = new CSharpCodeGenerationContextInfo(
-                CodeGenerationContext.Default, CSharpCodeGenerationOptions.Default, new CSharpCodeGenerationService(document.Project.Services), root.SyntaxTree.Options.LanguageVersion());
+                CodeGenerationContext.Default, CSharpCodeGenerationOptions.Default, new CSharpCodeGenerationService(document.Project.GetExtendedLanguageServices().LanguageServices), root.SyntaxTree.Options.LanguageVersion());
 #else
             var info = await document.GetCodeGenerationInfoAsync(CodeGenerationContext.Default, fallbackOptions, cancellationToken).ConfigureAwait(false);
 #endif
diff --git a/src/Analyzers/CSharp/CodeFixes/MakeMemberRequired/CSharpMakeMemberRequiredCodeFixProvider.cs b/src/Analyzers/CSharp/CodeFixes/MakeMemberRequired/CSharpMakeMemberRequiredCodeFixProvider.cs
index 0ed289d499713..d5d82a8275b37 100644
--- a/src/Analyzers/CSharp/CodeFixes/MakeMemberRequired/CSharpMakeMemberRequiredCodeFixProvider.cs
+++ b/src/Analyzers/CSharp/CodeFixes/MakeMemberRequired/CSharpMakeMemberRequiredCodeFixProvider.cs
@@ -58,6 +58,12 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
 
         var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
+        if (semanticModel.Compilation.GetBestTypeByMetadataName("System.Runtime.CompilerServices.RequiredMemberAttribute") is null)
+        {
+            // The attribute necessary to support required members is not present
+            return;
+        }
+
         var fieldOrPropertySymbol = semanticModel.GetDeclaredSymbol(node, cancellationToken);
         if (fieldOrPropertySymbol is IPropertySymbol propertySymbol)
         {
diff --git a/src/Analyzers/CSharp/CodeFixes/RemoveUnnecessaryCast/CSharpRemoveUnnecessaryCastCodeFixProvider.cs b/src/Analyzers/CSharp/CodeFixes/RemoveUnnecessaryCast/CSharpRemoveUnnecessaryCastCodeFixProvider.cs
index 5ea27bba40f25..a460cedecd4d1 100644
--- a/src/Analyzers/CSharp/CodeFixes/RemoveUnnecessaryCast/CSharpRemoveUnnecessaryCastCodeFixProvider.cs
+++ b/src/Analyzers/CSharp/CodeFixes/RemoveUnnecessaryCast/CSharpRemoveUnnecessaryCastCodeFixProvider.cs
@@ -62,7 +62,7 @@ await editor.ApplyExpressionLevelSemanticEditsAsync(
                 cancellationToken).ConfigureAwait(false);
         }
 
-        private ExpressionSyntax Recurse(ExpressionSyntax old)
+        private static ExpressionSyntax Recurse(ExpressionSyntax old)
         {
             if (old is ParenthesizedExpressionSyntax parenthesizedExpression)
             {
diff --git a/src/Analyzers/CSharp/CodeFixes/UseLocalFunction/CSharpUseLocalFunctionCodeFixProvider.cs b/src/Analyzers/CSharp/CodeFixes/UseLocalFunction/CSharpUseLocalFunctionCodeFixProvider.cs
index 4b4b3a84b3ef8..8f299272ff5f1 100644
--- a/src/Analyzers/CSharp/CodeFixes/UseLocalFunction/CSharpUseLocalFunctionCodeFixProvider.cs
+++ b/src/Analyzers/CSharp/CodeFixes/UseLocalFunction/CSharpUseLocalFunctionCodeFixProvider.cs
@@ -93,7 +93,7 @@ protected override async Task FixAllAsync(
             {
 #if CODE_STYLE
                 var info = new CSharpCodeGenerationContextInfo(
-                    CodeGenerationContext.Default, CSharpCodeGenerationOptions.Default, new CSharpCodeGenerationService(document.Project.Services), root.SyntaxTree.Options.LanguageVersion());
+                    CodeGenerationContext.Default, CSharpCodeGenerationOptions.Default, new CSharpCodeGenerationService(document.Project.GetExtendedLanguageServices().LanguageServices), root.SyntaxTree.Options.LanguageVersion());
 #else
                 var info = await document.GetCodeGenerationInfoAsync(CodeGenerationContext.Default, fallbackOptions, cancellationToken).ConfigureAwait(false);
 #endif
diff --git a/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider.cs b/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider.cs
index c2554c10b8963..59b98f9a02fb4 100644
--- a/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider.cs
+++ b/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider.cs
@@ -119,12 +119,10 @@ private static async Task UsePrimaryConstructorAsync(
         var namedType = semanticModel.GetRequiredDeclaredSymbol(typeDeclaration, cancellationToken);
         var constructor = semanticModel.GetRequiredDeclaredSymbol(constructorDeclaration, cancellationToken);
 
-        using var _1 = PooledDictionary<ISymbol, SyntaxNode>.GetInstance(out var removedMembers);
-
         // If we're removing members, first go through and update all references to that member to use the parameter name.
         var typeDeclarationNodes = namedType.DeclaringSyntaxReferences.Select(r => (TypeDeclarationSyntax)r.GetSyntax(cancellationToken));
         var namedTypeDocuments = typeDeclarationNodes.Select(r => solution.GetRequiredDocument(r.SyntaxTree)).ToImmutableHashSet();
-        await RemoveMembersAsync().ConfigureAwait(false);
+        var removedMembers = await RemoveMembersAsync().ConfigureAwait(false);
 
         // If the constructor has a base-initializer, then go find the base-type in the inheritance list for the
         // typedecl and move it there.
@@ -151,9 +149,6 @@ private static async Task UsePrimaryConstructorAsync(
         var constructorDocumentEditor = await solutionEditor.GetDocumentEditorAsync(document.Id, cancellationToken).ConfigureAwait(false);
         constructorDocumentEditor.RemoveNode(constructorDeclaration);
 
-        var finalTrivia = CreateFinalTypeDeclarationLeadingTrivia(
-            typeDeclaration, constructorDeclaration, constructor, properties, removedMembers);
-
         // Finally move the constructors parameter list to the type declaration.
         constructorDocumentEditor.ReplaceNode(
             typeDeclaration,
@@ -173,8 +168,8 @@ private static async Task UsePrimaryConstructorAsync(
                         a => a.WithTarget(AttributeTargetSpecifier(Token(SyntaxKind.MethodKeyword))).WithoutTrivia().WithAdditionalAnnotations(Formatter.Annotation)));
 
                 // When moving the parameter list from the constructor to the type, we will no longer have nested types
-                // in scope.  So rewrite references to them if that's the case.
-                var parameterList = UpdateReferencesToNestedTypes(constructorDeclaration.ParameterList);
+                // or member constants in scope.  So rewrite references to them if that's the case.
+                var parameterList = UpdateReferencesToNestedMembers(constructorDeclaration.ParameterList);
 
                 parameterList = RemoveElementIndentation(
                     typeDeclaration, constructorDeclaration, parameterList,
@@ -182,6 +177,9 @@ private static async Task UsePrimaryConstructorAsync(
 
                 parameterList = RemoveInModifierIfMemberIsRemoved(parameterList);
 
+                var finalTrivia = CreateFinalTypeDeclarationLeadingTrivia(
+                    currentTypeDeclaration, constructorDeclaration, constructor, properties, removedMembers);
+
                 return currentTypeDeclaration
                     .WithLeadingTrivia(finalTrivia)
                     .WithAttributeLists(finalAttributeLists)
@@ -216,22 +214,37 @@ ParameterListSyntax RemoveInModifierIfMemberIsRemoved(ParameterListSyntax parame
                 });
         }
 
-        ParameterListSyntax UpdateReferencesToNestedTypes(ParameterListSyntax parameterList)
+        ParameterListSyntax UpdateReferencesToNestedMembers(ParameterListSyntax parameterList)
         {
             return parameterList.ReplaceNodes(
                 parameterList.DescendantNodes().OfType<SimpleNameSyntax>(),
-                (typeSyntax, updatedTypeSyntax) =>
+                (nameSyntax, currentNameSyntax) =>
                 {
-                    // Don't have to update if the type is already qualified.
-                    if (typeSyntax.Parent is QualifiedNameSyntax qualifiedNameSyntax && qualifiedNameSyntax.Right == typeSyntax)
-                        return updatedTypeSyntax;
+                    // Don't have to update if the member is already qualified.
 
-                    var typeSymbol = semanticModel.GetTypeInfo(typeSyntax, cancellationToken).Type;
-                    if (typeSymbol is not INamedTypeSymbol { ContainingType: not null } || !namedType.Equals(typeSymbol.ContainingType.OriginalDefinition))
-                        return updatedTypeSyntax;
+                    if (nameSyntax.Parent is not QualifiedNameSyntax qualifiedNameSyntax || qualifiedNameSyntax.Right != nameSyntax)
+                    {
+                        var symbol = semanticModel.GetSymbolInfo(nameSyntax, cancellationToken).GetAnySymbol();
+                        if (symbol is INamedTypeSymbol { ContainingType: not null } &&
+                            namedType.Equals(symbol.ContainingType.OriginalDefinition))
+                        {
+                            // reference to a nested type in an unqualified fashion.  Have to qualify this.
+                            return QualifiedName(namedType.GenerateNameSyntax(), currentNameSyntax);
+                        }
+                    }
 
-                    // reference to a nested type in an unqualified fashion.  Have to qualify this.
-                    return QualifiedName(namedType.GenerateNameSyntax(), updatedTypeSyntax);
+                    if (nameSyntax.Parent is not MemberAccessExpressionSyntax memberAccessExpression || memberAccessExpression.Name != nameSyntax)
+                    {
+                        var symbol = semanticModel.GetSymbolInfo(nameSyntax, cancellationToken).GetAnySymbol();
+                        if (symbol is IFieldSymbol { ContainingType: not null } &&
+                            namedType.Equals(symbol.ContainingType.OriginalDefinition))
+                        {
+                            // reference to a member field an unqualified fashion.  Have to qualify this.
+                            return MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, namedType.GenerateNameSyntax(), currentNameSyntax);
+                        }
+                    }
+
+                    return currentNameSyntax;
                 });
         }
 
@@ -349,36 +362,39 @@ SyntaxNode UpdateDeclaration(SyntaxNode declaration, AssignmentExpressionSyntax
             }
         }
 
-        async ValueTask RemoveMembersAsync()
+        async ValueTask<ImmutableDictionary<ISymbol, SyntaxNode>> RemoveMembersAsync()
         {
-            if (!removeMembers)
-                return;
-
-            // Go through each pair of member/parameterName.  Update all references to member to now refer to
-            // parameterName. This is safe as the analyzer ensured that all existing locations would safely be able
-            // to do this.  Then once those are all done, actually remove the members.
-            foreach (var (memberName, parameterName) in properties)
+            var removedMembers = ImmutableDictionary<ISymbol, SyntaxNode>.Empty;
+            if (removeMembers)
             {
-                Contract.ThrowIfNull(parameterName);
+                // Go through each pair of member/parameterName.  Update all references to member to now refer to
+                // parameterName. This is safe as the analyzer ensured that all existing locations would safely be able
+                // to do this.  Then once those are all done, actually remove the members.
+                foreach (var (memberName, parameterName) in properties)
+                {
+                    Contract.ThrowIfNull(parameterName);
 
-                var (member, nodeToRemove) = GetMemberToRemove(memberName);
-                if (member is null)
-                    continue;
+                    var (member, nodeToRemove) = GetMemberToRemove(memberName);
+                    if (member is null)
+                        continue;
 
-                removedMembers[member] = nodeToRemove;
-                await ReplaceReferencesToMemberWithParameterAsync(
-                    member, CSharpSyntaxFacts.Instance.EscapeIdentifier(parameterName)).ConfigureAwait(false);
-            }
+                    removedMembers = removedMembers.Add(member, nodeToRemove);
+                    await ReplaceReferencesToMemberWithParameterAsync(
+                        member, CSharpSyntaxFacts.Instance.EscapeIdentifier(parameterName)).ConfigureAwait(false);
+                }
 
-            foreach (var group in removedMembers.Values.GroupBy(n => n.SyntaxTree))
-            {
-                var syntaxTree = group.Key;
-                var memberDocument = solution.GetRequiredDocument(syntaxTree);
-                var documentEditor = await solutionEditor.GetDocumentEditorAsync(memberDocument.Id, cancellationToken).ConfigureAwait(false);
+                foreach (var group in removedMembers.Values.GroupBy(n => n.SyntaxTree))
+                {
+                    var syntaxTree = group.Key;
+                    var memberDocument = solution.GetRequiredDocument(syntaxTree);
+                    var documentEditor = await solutionEditor.GetDocumentEditorAsync(memberDocument.Id, cancellationToken).ConfigureAwait(false);
 
-                foreach (var memberToRemove in group)
-                    documentEditor.RemoveNode(memberToRemove);
+                    foreach (var memberToRemove in group)
+                        documentEditor.RemoveNode(memberToRemove);
+                }
             }
+
+            return removedMembers;
         }
 
         (ISymbol? member, SyntaxNode nodeToRemove) GetMemberToRemove(string memberName)
@@ -401,7 +417,8 @@ async ValueTask ReplaceReferencesToMemberWithParameterAsync(ISymbol member, stri
             var references = await SymbolFinder.FindReferencesAsync(
                 member, solution, namedTypeDocuments, cancellationToken).ConfigureAwait(false);
 
-            using var _ = PooledHashSet<SyntaxNode>.GetInstance(out var nodesToReplace);
+            using var _1 = PooledHashSet<SyntaxNode>.GetInstance(out var nodesToReplace);
+            using var _2 = PooledHashSet<XmlEmptyElementSyntax>.GetInstance(out var seeTagsToReplace);
             foreach (var reference in references)
             {
                 foreach (var location in reference.Locations)
@@ -409,10 +426,16 @@ async ValueTask ReplaceReferencesToMemberWithParameterAsync(ISymbol member, stri
                     if (location.IsImplicit)
                         continue;
 
-                    if (location.Location.FindNode(getInnermostNodeForTie: true, cancellationToken) is not IdentifierNameSyntax identifier)
+                    if (location.Location.FindNode(findInsideTrivia: true, getInnermostNodeForTie: true, cancellationToken) is not IdentifierNameSyntax identifier)
                         continue;
 
-                    if (identifier.IsRightSideOfDot())
+                    var xmlElement = identifier.AncestorsAndSelf().OfType<XmlEmptyElementSyntax>().FirstOrDefault();
+                    if (xmlElement is { Name.LocalName.ValueText: "see" })
+                    {
+                        // reference to member in a `<see cref="name"/>` tag.  Switch to a paramref tag instead.
+                        seeTagsToReplace.Add(xmlElement);
+                    }
+                    else if (identifier.IsRightSideOfDot())
                     {
                         if (identifier.GetRequiredParent() is ExpressionSyntax expression)
                             nodesToReplace.Add(expression);
@@ -439,6 +462,24 @@ async ValueTask ReplaceReferencesToMemberWithParameterAsync(ISymbol member, stri
                         parameterNameNode.WithTriviaFrom(nodeToReplace));
                 }
             }
+
+            foreach (var group in seeTagsToReplace.GroupBy(n => n.SyntaxTree))
+            {
+                var document = solution.GetDocument(group.Key);
+                if (document is null)
+                    continue;
+
+                var documentEditor = await solutionEditor.GetDocumentEditorAsync(document.Id, cancellationToken).ConfigureAwait(false);
+
+                foreach (var seeTag in group)
+                {
+                    var paramRefTag = seeTag
+                        .ReplaceToken(seeTag.Name.LocalName, Identifier("paramref").WithTriviaFrom(seeTag.Name.LocalName))
+                        .WithAttributes(SingletonList<XmlAttributeSyntax>(XmlNameAttribute(parameterName)));
+
+                    documentEditor.ReplaceNode(seeTag, paramRefTag);
+                }
+            }
         }
     }
 }
diff --git a/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider_DocComments.cs b/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider_DocComments.cs
index f1ddeb843ebf8..95209b70f148d 100644
--- a/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider_DocComments.cs
+++ b/src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider_DocComments.cs
@@ -66,7 +66,7 @@ private static SyntaxTriviaList CreateFinalTypeDeclarationLeadingTrivia(
         ConstructorDeclarationSyntax constructorDeclaration,
         IMethodSymbol constructor,
         ImmutableDictionary<string, string?> properties,
-        Dictionary<ISymbol, SyntaxNode> removedMembers)
+        ImmutableDictionary<ISymbol, SyntaxNode> removedMembers)
     {
         // First, take the constructor doc comments and merge those into the type's doc comments.
         // Then, take any removed fields/properties and merge their comments into the type's doc comments.
@@ -164,7 +164,7 @@ static SyntaxTrivia MergeDocComments(SyntaxTrivia typeDeclarationDocComment, Syn
         static SyntaxTriviaList MergeTypeDeclarationAndRemovedMembersDocComments(
             IMethodSymbol constructor,
             ImmutableDictionary<string, string?> properties,
-            Dictionary<ISymbol, SyntaxNode> removedMembers,
+            ImmutableDictionary<ISymbol, SyntaxNode> removedMembers,
             SyntaxTriviaList typeDeclarationLeadingTrivia)
         {
             // now, if we're removing any members, and they had doc comments, and we don't already have doc comments for
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.cs.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.cs.xlf
index 5f24975c3c70c..db8b06771dad9 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.cs.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.cs.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Použít primární konstruktor (a odebrat pole)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Použít primární konstruktor (a odebrat členy)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Použít primární konstruktor (a odebrat vlastnosti)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.de.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.de.xlf
index 17d95e1828324..21890de80e14d 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.de.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.de.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Primären Konstruktor verwenden (und Felder entfernen)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Primären Konstruktor verwenden (und Member entfernen)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Primären Konstruktor verwenden (und Eigenschaften entfernen)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.es.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.es.xlf
index 62a03402585e5..f1bee74d61072 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.es.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.es.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Usar constructor principal (y quitar campos)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Usar constructor principal (y quitar miembros)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Usar constructor principal (y quitar propiedades)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.fr.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.fr.xlf
index 3870a29067c88..c20e7aefbcf58 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.fr.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.fr.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Utiliser le constructeur principal (et supprimer les champs)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Utiliser le constructeur principal (et supprimer des membres)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Utiliser le constructeur principal (et supprimer les propriétés)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.it.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.it.xlf
index 701ffdac8657b..e39865d50da00 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.it.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.it.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Usa costruttore primario (e rimuovi campi)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Usa costruttore primario (e rimuovi membri)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Usa costruttore primario (e rimuovi proprietà)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ja.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ja.xlf
index 3ccace73e3352..e6cc199616399 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ja.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ja.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">プライマリ コンストラクターを使用する (そしてフィールドを削除する)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">プライマリ コンストラクターを使用する (そしてメンバーを削除する)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">プライマリ コンストラクターを使用する (そしてプロパティを削除する)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ko.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ko.xlf
index 02ad09a93a169..bc69a0acfab63 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ko.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ko.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">기본 생성자 사용(및 필드 제거)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">기본 생성자 사용(및 멤버 제거)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">기본 생성자 사용(및 속성 제거)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pl.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pl.xlf
index 48e9d6f08c622..a83177f7fa24d 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pl.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pl.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Użyj konstruktora podstawowego (i usuń pola)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Użyj konstruktora podstawowego (i usuń elementy członkowskie)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Użyj konstruktora podstawowego (i usuń właściwości)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pt-BR.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pt-BR.xlf
index 10ead2956d8ec..1fff187c61b0c 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pt-BR.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.pt-BR.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Usar construtor primário (e remover campos)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Usar construtor primário (e remover membros)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Usar construtor primário (e remover propriedades)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ru.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ru.xlf
index 56ee32aad6a3c..3cb45509ab68f 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ru.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.ru.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Использовать основной конструктор (и удалять поля)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Использовать основной конструктор (и удалять элементы)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Использовать основной конструктор (и удалять свойства)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.tr.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.tr.xlf
index 57db5cf504dc5..5c703a64834db 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.tr.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.tr.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">Birincil oluşturucuyu kullan (ve alanları kaldır)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">Birincil oluşturucuyu kullan (ve üyeleri kaldır)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">Birincil oluşturucuyu kullan (ve özellikleri kaldır)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hans.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hans.xlf
index 289d693f605c9..7260b7ece20d4 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hans.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hans.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">使用主构造函数(并删除字段)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">使用主构造函数(并删除成员)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">使用主构造函数(并删除属性)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hant.xlf b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hant.xlf
index f2e6dfd5aa7fe..1af63ee6e1db8 100644
--- a/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hant.xlf
+++ b/src/Analyzers/CSharp/CodeFixes/xlf/CSharpCodeFixesResources.zh-Hant.xlf
@@ -199,17 +199,17 @@
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_fields">
         <source>Use primary constructor (and remove fields)</source>
-        <target state="new">Use primary constructor (and remove fields)</target>
+        <target state="translated">使用主要建構函式 (並移除欄位)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_members">
         <source>Use primary constructor (and remove members)</source>
-        <target state="new">Use primary constructor (and remove members)</target>
+        <target state="translated">使用主要建構函式 (並移除成員)</target>
         <note />
       </trans-unit>
       <trans-unit id="Use_primary_constructor_and_remove_properties">
         <source>Use primary constructor (and remove properties)</source>
-        <target state="new">Use primary constructor (and remove properties)</target>
+        <target state="translated">使用主要建構函式 (並移除屬性)</target>
         <note />
       </trans-unit>
       <trans-unit id="Warning_colon_Adding_parameters_to_local_function_declaration_may_produce_invalid_code">
diff --git a/src/Analyzers/CSharp/Tests/HideBase/HideBaseTests.cs b/src/Analyzers/CSharp/Tests/HideBase/HideBaseTests.cs
index ae95adef076ec..4bf97282ed7ca 100644
--- a/src/Analyzers/CSharp/Tests/HideBase/HideBaseTests.cs
+++ b/src/Analyzers/CSharp/Tests/HideBase/HideBaseTests.cs
@@ -159,8 +159,8 @@ class A { internal const int i = 0; }
         }
 
         [Fact]
-        public async Task TestAddNewToDisorderedModifiers() =>
-            await TestInRegularAndScript1Async(
+        public async Task TestAddNewToDisorderedModifiers()
+            => await TestInRegularAndScript1Async(
                 """
                 class Application
                 {
@@ -185,8 +185,8 @@ class App : Application
                 """);
 
         [Fact]
-        public async Task TestAddNewToOrderedModifiersWithTrivia() =>
-            await TestInRegularAndScript1Async(
+        public async Task TestAddNewToOrderedModifiersWithTrivia()
+            => await TestInRegularAndScript1Async(
                 """
                 class Application
                 {
diff --git a/src/Analyzers/CSharp/Tests/MakeLocalFunctionStatic/MakeLocalFunctionStaticTests.cs b/src/Analyzers/CSharp/Tests/MakeLocalFunctionStatic/MakeLocalFunctionStaticTests.cs
index ca45dbf7f6c6d..7289625e6804f 100644
--- a/src/Analyzers/CSharp/Tests/MakeLocalFunctionStatic/MakeLocalFunctionStaticTests.cs
+++ b/src/Analyzers/CSharp/Tests/MakeLocalFunctionStatic/MakeLocalFunctionStaticTests.cs
@@ -25,7 +25,7 @@ public MakeLocalFunctionStaticTests(ITestOutputHelper logger)
         }
 
         internal override (DiagnosticAnalyzer, CodeFixProvider) CreateDiagnosticProviderAndFixer(Workspace workspace)
-            => (new MakeLocalFunctionStaticDiagnosticAnalyzer(), GetMakeLocalFunctionStaticCodeFixProvider());
+            => (new MakeLocalFunctionStaticDiagnosticAnalyzer(), new MakeLocalFunctionStaticCodeFixProvider());
 
         private static readonly ParseOptions CSharp72ParseOptions = CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.CSharp7_2);
         private static readonly ParseOptions CSharp8ParseOptions = CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.CSharp8);
diff --git a/src/Analyzers/CSharp/Tests/MakeMemberRequired/MakeMemberRequiredTests.cs b/src/Analyzers/CSharp/Tests/MakeMemberRequired/MakeMemberRequiredTests.cs
index 43980d15d497d..2dfb732c425ca 100644
--- a/src/Analyzers/CSharp/Tests/MakeMemberRequired/MakeMemberRequiredTests.cs
+++ b/src/Analyzers/CSharp/Tests/MakeMemberRequired/MakeMemberRequiredTests.cs
@@ -8,6 +8,7 @@
 using Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Microsoft.CodeAnalysis.Testing;
+using Roslyn.Test.Utilities;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.CSharp.Analyzers.UnitTests.MakeMemberRequired
@@ -119,6 +120,28 @@ public static IEnumerable<object[]> AccessorAccessibilityModifierCombinationsWhe
             yield return new[] { "internal", "private protected" };
         }
 
+        [Fact]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68478")]
+        public async Task SimpleSetPropertyMissingRequiredAttribute()
+        {
+            var code =
+                """
+                #nullable enable
+                class MyClass
+                {
+                    public string {|CS8618:MyProperty|} { get; set; }
+                }
+                """;
+
+            await new VerifyCS.Test
+            {
+                TestCode = code,
+                FixedCode = code,
+                LanguageVersion = LanguageVersion.CSharp11,
+                ReferenceAssemblies = ReferenceAssemblies.Net.Net60,
+            }.RunAsync();
+        }
+
         [Fact]
         public async Task SimpleSetProperty()
         {
diff --git a/src/Analyzers/CSharp/Tests/UseConditionalExpression/UseConditionalExpressionForAssignmentTests.cs b/src/Analyzers/CSharp/Tests/UseConditionalExpression/UseConditionalExpressionForAssignmentTests.cs
index 232d7852ef1ed..cabf22483c332 100644
--- a/src/Analyzers/CSharp/Tests/UseConditionalExpression/UseConditionalExpressionForAssignmentTests.cs
+++ b/src/Analyzers/CSharp/Tests/UseConditionalExpression/UseConditionalExpressionForAssignmentTests.cs
@@ -2044,5 +2044,63 @@ class C
                 }
                 """);
         }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68578")]
+        public async Task TestMissingWhenAssignmentReferencesPatternVariable()
+        {
+            await TestMissingAsync("""
+                using System;
+
+                public class Class1
+                {
+                    public int i;
+                }
+
+                public class Program
+                {
+                    public static void Test(object obj)
+                    {
+                        if (obj is Class1 c)
+                        {
+                            c.i = 1;
+                        }
+                        else
+                        {
+                            throw new Exception();
+                        }
+                    }
+                }
+                """);
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68578")]
+        public async Task TestMissingWhenAssignmentReferencesOutVariable()
+        {
+            await TestMissingAsync("""
+                using System;
+
+                public class Class1
+                {
+                    public int i;
+                }
+
+                public class Program
+                {
+                    public static void Test(object obj)
+                    {
+                        if (TryGetValue(out var c))
+                        {
+                            c.i = 1;
+                        }
+                        else    
+                        {
+                            throw new Exception();
+                        }
+                    }
+
+                    private static bool TryGetValue(out Class1 c) => throw new NotImplementedException();
+                }
+                """);
+        }
     }
 }
diff --git a/src/Analyzers/CSharp/Tests/UseLocalFunction/UseLocalFunctionTests.cs b/src/Analyzers/CSharp/Tests/UseLocalFunction/UseLocalFunctionTests.cs
index 173f28d7f06f6..5ec4e570fc965 100644
--- a/src/Analyzers/CSharp/Tests/UseLocalFunction/UseLocalFunctionTests.cs
+++ b/src/Analyzers/CSharp/Tests/UseLocalFunction/UseLocalFunctionTests.cs
@@ -24,7 +24,7 @@ public UseLocalFunctionTests(ITestOutputHelper logger)
         }
 
         internal override (DiagnosticAnalyzer, CodeFixProvider) CreateDiagnosticProviderAndFixer(Workspace workspace)
-            => (new CSharpUseLocalFunctionDiagnosticAnalyzer(), GetCSharpUseLocalFunctionCodeFixProvider());
+            => (new CSharpUseLocalFunctionDiagnosticAnalyzer(), new CSharpUseLocalFunctionCodeFixProvider());
 
         private static readonly ParseOptions CSharp72ParseOptions = CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.CSharp7_2);
 
diff --git a/src/Analyzers/CSharp/Tests/UsePrimaryConstructor/UsePrimaryConstructorTests.cs b/src/Analyzers/CSharp/Tests/UsePrimaryConstructor/UsePrimaryConstructorTests.cs
index 121b3d6b0d585..e7afa56401c1a 100644
--- a/src/Analyzers/CSharp/Tests/UsePrimaryConstructor/UsePrimaryConstructorTests.cs
+++ b/src/Analyzers/CSharp/Tests/UsePrimaryConstructor/UsePrimaryConstructorTests.cs
@@ -737,20 +737,20 @@ class C
         }.RunAsync();
     }
 
-    [Fact(Skip = "Currently broken due to nested type IOp callbacks not running")]
-    public async Task TestDoNotRemoveMembersUsedInNestedTypes()
+    [Fact]
+    public async Task DoNotRemoveMembersUsedInNestedTypes()
     {
         await new VerifyCS.Test
         {
             TestCode = """
                 using System;
 
-                class C
+                class OuterType
                 {
                     private int _i;
                     private int _j;
 
-                    public [|C|](int i, int j)
+                    public [|OuterType|](int i, int j)
                     {
                         _i = i;
                         _j = j;
@@ -760,7 +760,7 @@ public struct Enumerator
                     {
                         private int _i;
 
-                        public Enumerator(C c)
+                        public Enumerator(OuterType c)
                         {
                             _i = c._i;
                             Console.WriteLine(c);
@@ -771,17 +771,17 @@ public Enumerator(C c)
             FixedCode = """
                 using System;
 
-                class C(int i, int j)
+                class OuterType(int i, int j)
                 {
-                    private int I { get; } = i;
+                    private int _i = i;
 
                     public struct Enumerator
                     {
                         private int _i;
                 
-                        public Enumerator(C c)
+                        public Enumerator(OuterType c)
                         {
-                            _i = c.I;
+                            _i = c._i;
                             Console.WriteLine(c);
                         }
                     }
@@ -2606,4 +2606,418 @@ class C(int i)
             LanguageVersion = LanguageVersion.Preview,
         }.RunAsync();
     }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion1()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    public C(int i)
+                    {
+                #if NET6
+                        Console.WriteLine();
+                #endif
+                    }
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion2()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    public C(int i)
+                    {
+                #if false
+                        Console.WriteLine();
+                #endif
+                    }
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion3()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    private int _i;
+
+                    public C(int i)
+                #if NET6
+                        => _i = i;
+                #else
+                        => this._i = i;
+                #endif
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion4()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    private int _i;
+
+                    public C(int i)
+                #if true
+                        => _i = i;
+                #else
+                        => this._i = i;
+                #endif
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion5()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    private int _i;
+
+                    public C(int i)
+                #if false
+                        => _i = i;
+                #else
+                        => this._i = i;
+                #endif
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion6()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    private int _i;
+
+                    public C(int i)
+                    {
+                #if true
+                        _i = i;
+                #endif
+                    }
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion7()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    private int _i;
+
+                    public C(int i)
+                    {
+                #if true
+                        _i = i;
+                #else
+                        this._i = i;
+                #endif
+                    }
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestNotWithPreprocessorRegion8()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+
+                class C
+                {
+                    private int _i;
+
+                    public C(int i)
+                    {
+                #if false
+                        _i = i;
+                #else
+                        this._i = i;
+                #endif
+                    }
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestWithRegionDirective1()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                class C
+                {
+
+                    #region constructors
+
+                    public [|C|](int i)
+                    {
+                    }
+
+                    #endregion
+
+                }
+                """,
+            FixedCode = """
+                class C(int i)
+                {
+                
+                    #region constructors
+
+                    #endregion
+
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestWithRegionDirective2()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                class C
+                {
+
+                    #region constructors
+
+                    public [|C|](int i)
+                    {
+                    }
+
+                    public C(string s) : this(s.Length)
+                    {
+                    }
+
+                    #endregion
+
+                }
+                """,
+            FixedCode = """
+                class C(int i)
+                {
+
+                    #region constructors
+
+                    public C(string s) : this(s.Length)
+                    {
+                    }
+
+                    #endregion
+
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestSeeTag1()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                /// <summary>
+                /// Provides strongly typed wrapper around <see cref="_i"/>.
+                /// </summary>
+                class C
+                {
+                    private int _i;
+
+                    public [|C|](int i)
+                    {
+                        _i = i;
+                    }
+                }
+                """,
+            FixedCode = """
+                /// <summary>
+                /// Provides strongly typed wrapper around <see cref="_i"/>.
+                /// </summary>
+                class C(int i)
+                {
+                    private int _i = i;
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestSeeTag2()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                /// <summary>
+                /// Provides strongly typed wrapper around <see cref="_i"/>.
+                /// </summary>
+                class C
+                {
+                    private int _i;
+
+                    public [|C|](int i)
+                    {
+                        _i = i;
+                    }
+                }
+                """,
+            FixedCode = """
+                /// <summary>
+                /// Provides strongly typed wrapper around <paramref name="i"/>.
+                /// </summary>
+                class C(int i)
+                {
+                }
+                """,
+            CodeActionIndex = 1,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestReferenceToConstantInParameterInitializer1()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                class C
+                {
+                    private const int Default = 0;
+                    private int _i;
+
+                    public [|C|](int i = Default)
+                    {
+                        _i = i;
+                    }
+                }
+                """,
+            FixedCode = """
+                class C(int i = C.Default)
+                {
+                    private const int Default = 0;
+                    private int _i = i;
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestReferenceToConstantInParameterInitializer2()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                class C
+                {
+                    private const int Default = 0;
+                    private int _i;
+
+                    public [|C|](int i = C.Default)
+                    {
+                        _i = i;
+                    }
+                }
+                """,
+            FixedCode = """
+                class C(int i = C.Default)
+                {
+                    private const int Default = 0;
+                    private int _i = i;
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
+
+    [Fact]
+    public async Task TestReferenceToConstantInParameterInitializer3()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                class C<T>
+                {
+                    private const int Default = 0;
+                    private int _i;
+
+                    public [|C|](int i = Default)
+                    {
+                        _i = i;
+                    }
+                }
+                """,
+            FixedCode = """
+                class C<T>(int i = C<T>.Default)
+                {
+                    private const int Default = 0;
+                    private int _i = i;
+                }
+                """,
+            LanguageVersion = LanguageVersion.Preview,
+        }.RunAsync();
+    }
 }
diff --git a/src/Analyzers/Core/Analyzers/MakeFieldReadonly/AbstractMakeFieldReadonlyDiagnosticAnalyzer.cs b/src/Analyzers/Core/Analyzers/MakeFieldReadonly/AbstractMakeFieldReadonlyDiagnosticAnalyzer.cs
index 7e5d7af549400..e1bffa85961ca 100644
--- a/src/Analyzers/Core/Analyzers/MakeFieldReadonly/AbstractMakeFieldReadonlyDiagnosticAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/MakeFieldReadonly/AbstractMakeFieldReadonlyDiagnosticAnalyzer.cs
@@ -63,6 +63,9 @@ protected override void InitializeWorker(AnalysisContext context)
 
                 context.RegisterSymbolStartAction(context =>
                 {
+                    if (!ShouldAnalyze(context, (INamedTypeSymbol)context.Symbol))
+                        return;
+
                     context.RegisterOperationAction(AnalyzeOperation, OperationKind.FieldReference);
 
                     // Can't allow changing the fields to readonly if the struct overwrites itself.  e.g. `this = default;`
@@ -86,7 +89,11 @@ protected override void InitializeWorker(AnalysisContext context)
                 // Local functions.
                 void AnalyzeFieldSymbol(SymbolAnalysisContext symbolContext)
                 {
-                    _ = TryGetOrInitializeFieldState((IFieldSymbol)symbolContext.Symbol, symbolContext.Options, symbolContext.CancellationToken);
+                    var field = (IFieldSymbol)symbolContext.Symbol;
+                    if (!symbolContext.ShouldAnalyzeLocation(GetDiagnosticLocation(field)))
+                        return;
+
+                    _ = TryGetOrInitializeFieldState(field, symbolContext.Options, symbolContext.CancellationToken);
                 }
 
                 void AnalyzeOperation(OperationAnalysisContext operationContext)
@@ -119,7 +126,7 @@ void OnSymbolEnd(SymbolAnalysisContext symbolEndContext)
                                 var option = GetCodeStyleOption(field, symbolEndContext.Options);
                                 var diagnostic = DiagnosticHelper.Create(
                                     Descriptor,
-                                    field.Locations[0],
+                                    GetDiagnosticLocation(field),
                                     option.Notification.Severity,
                                     additionalLocations: null,
                                     properties: null);
@@ -129,6 +136,26 @@ void OnSymbolEnd(SymbolAnalysisContext symbolEndContext)
                     }
                 }
 
+                bool ShouldAnalyze(SymbolStartAnalysisContext context, INamedTypeSymbol namedType)
+                {
+                    // Check if we have at least one candidate field in analysis scope.
+                    foreach (var member in namedType.GetMembers())
+                    {
+                        if (member is IFieldSymbol field
+                            && IsCandidateField(field, threadStaticAttribute, dataContractAttribute, dataMemberAttribute)
+                            && context.ShouldAnalyzeLocation(GetDiagnosticLocation(field)))
+                        {
+                            return true;
+                        }
+                    }
+
+                    // We have to analyze nested types if containing type contains a candidate field in analysis scope.
+                    if (namedType.ContainingType is { } containingType)
+                        return ShouldAnalyze(context, containingType);
+
+                    return false;
+                }
+
                 static bool IsCandidateField(IFieldSymbol symbol, INamedTypeSymbol? threadStaticAttribute, INamedTypeSymbol? dataContractAttribute, INamedTypeSymbol? dataMemberAttribute)
                         => symbol is
                         {
@@ -202,6 +229,9 @@ void UpdateFieldStateOnWrite(IFieldSymbol field)
             });
         }
 
+        private static Location GetDiagnosticLocation(IFieldSymbol field)
+            => field.Locations[0];
+
         private static bool IsFieldWrite(IFieldReferenceOperation fieldReference, ISymbol owningSymbol)
         {
             // Check if the underlying member is being written or a writable reference to the member is taken.
@@ -259,6 +289,6 @@ private static bool IsFieldWrite(IFieldReferenceOperation fieldReference, ISymbo
         }
 
         private static CodeStyleOption2<bool> GetCodeStyleOption(IFieldSymbol field, AnalyzerOptions options)
-            => options.GetAnalyzerOptions(field.Locations[0].SourceTree!).PreferReadonly;
+            => options.GetAnalyzerOptions(GetDiagnosticLocation(field).SourceTree!).PreferReadonly;
     }
 }
diff --git a/src/Analyzers/Core/Analyzers/RemoveUnusedMembers/AbstractRemoveUnusedMembersDiagnosticAnalyzer.cs b/src/Analyzers/Core/Analyzers/RemoveUnusedMembers/AbstractRemoveUnusedMembersDiagnosticAnalyzer.cs
index fa1e87c8112b1..24dcf854cdd9d 100644
--- a/src/Analyzers/Core/Analyzers/RemoveUnusedMembers/AbstractRemoveUnusedMembersDiagnosticAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/RemoveUnusedMembers/AbstractRemoveUnusedMembersDiagnosticAnalyzer.cs
@@ -116,6 +116,9 @@ private CompilationAnalyzer(
                 _attributeSetForMethodsToIgnore = ImmutableHashSet.CreateRange(GetAttributesForMethodsToIgnore(compilation));
             }
 
+            private static Location GetDiagnosticLocation(ISymbol symbol)
+                => symbol.Locations[0];
+
             private static IEnumerable<INamedTypeSymbol> GetAttributesForMethodsToIgnore(Compilation compilation)
             {
                 // Ignore methods with special serialization attributes, which are invoked by the runtime
@@ -181,6 +184,9 @@ private void RegisterActions(CompilationStartAnalysisContext compilationStartCon
                 Action<ISymbol, ValueUsageInfo> onSymbolUsageFound = OnSymbolUsage;
                 compilationStartContext.RegisterSymbolStartAction(symbolStartContext =>
                 {
+                    if (!ShouldAnalyze(symbolStartContext, (INamedTypeSymbol)symbolStartContext.Symbol))
+                        return;
+
                     var hasUnsupportedOperation = false;
                     symbolStartContext.RegisterOperationAction(AnalyzeMemberReferenceOperation, OperationKind.FieldReference, OperationKind.MethodReference, OperationKind.PropertyReference, OperationKind.EventReference);
                     symbolStartContext.RegisterOperationAction(AnalyzeFieldInitializer, OperationKind.FieldInitializer);
@@ -202,12 +208,32 @@ private void RegisterActions(CompilationStartAnalysisContext compilationStartCon
                     // Register custom language-specific actions, if any.
                     _analyzer.HandleNamedTypeSymbolStart(symbolStartContext, onSymbolUsageFound);
                 }, SymbolKind.NamedType);
+
+                bool ShouldAnalyze(SymbolStartAnalysisContext context, INamedTypeSymbol namedType)
+                {
+                    // Check if we have at least one candidate symbol in analysis scope.
+                    foreach (var member in namedType.GetMembers())
+                    {
+                        if (IsCandidateSymbol(member.OriginalDefinition)
+                            && context.ShouldAnalyzeLocation(GetDiagnosticLocation(member)))
+                        {
+                            return true;
+                        }
+                    }
+
+                    // We have to analyze nested types if containing type contains a candidate field in analysis scope.
+                    if (namedType.ContainingType is { } containingType)
+                        return ShouldAnalyze(context, containingType);
+
+                    return false;
+                }
             }
 
             private void AnalyzeSymbolDeclaration(SymbolAnalysisContext symbolContext)
             {
                 var symbol = symbolContext.Symbol.OriginalDefinition;
-                if (IsCandidateSymbol(symbol))
+                if (IsCandidateSymbol(symbol)
+                    && symbolContext.ShouldAnalyzeLocation(GetDiagnosticLocation(symbol)))
                 {
                     lock (_gate)
                     {
@@ -474,7 +500,7 @@ member is IPropertySymbol property &&
                             // We report the diagnostic on the first location of the member.
                             var diagnostic = DiagnosticHelper.CreateWithMessage(
                                 rule,
-                                member.Locations[0],
+                                GetDiagnosticLocation(member),
                                 rule.GetEffectiveSeverity(symbolEndContext.Compilation.Options),
                                 additionalLocations: null,
                                 properties: null,
diff --git a/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.BlockAnalyzer.cs b/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.BlockAnalyzer.cs
index 9d019f1dfcbf5..c711df7259e03 100644
--- a/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.BlockAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.BlockAnalyzer.cs
@@ -5,6 +5,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Immutable;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CodeStyle;
@@ -65,29 +66,7 @@ private BlockAnalyzer(SymbolStartAnalyzer symbolStartAnalyzer, Options options)
 
                 public static void Analyze(OperationBlockStartAnalysisContext context, SymbolStartAnalyzer symbolStartAnalyzer)
                 {
-                    if (HasSyntaxErrors() || context.OperationBlocks.IsEmpty)
-                        return;
-
-                    // Bail out in presence of conditional directives
-                    // This is a workaround for https://github.com/dotnet/roslyn/issues/31820
-                    // Issue https://github.com/dotnet/roslyn/issues/31821 tracks
-                    // reverting this workaround.
-                    if (HasConditionalDirectives())
-                        return;
-
-                    // All operation blocks for a symbol belong to the same tree.
-                    var firstBlock = context.OperationBlocks[0];
-                    if (!symbolStartAnalyzer._compilationAnalyzer.TryGetOptions(firstBlock.Syntax.SyntaxTree,
-                                                                                context.Options,
-                                                                                out var options))
-                    {
-                        return;
-                    }
-
-                    // Ignore methods that are just a single-throw method.  These are often
-                    // in-progress pieces of work and we don't want to force the user to fixup other
-                    // issues before they've even gotten around to writing their code.
-                    if (firstBlock.IsSingleThrowNotImplementedOperation())
+                    if (!ShouldAnalyze(context, symbolStartAnalyzer, out var options))
                         return;
 
                     var blockAnalyzer = new BlockAnalyzer(symbolStartAnalyzer, options);
@@ -96,10 +75,62 @@ public static void Analyze(OperationBlockStartAnalysisContext context, SymbolSta
                     context.RegisterOperationAction(blockAnalyzer.AnalyzeLocalOrParameterReference, OperationKind.LocalReference, OperationKind.ParameterReference);
                     context.RegisterOperationAction(_ => blockAnalyzer._hasInvalidOperation = true, OperationKind.Invalid);
                     context.RegisterOperationBlockEndAction(blockAnalyzer.AnalyzeOperationBlockEnd);
-
                     return;
 
                     // Local Functions.
+                    bool ShouldAnalyze(
+                        OperationBlockStartAnalysisContext context,
+                        SymbolStartAnalyzer symbolStartAnalyzer,
+                        [NotNullWhen(true)] out Options? options)
+                    {
+                        options = null;
+                        if (HasSyntaxErrors() || context.OperationBlocks.IsEmpty)
+                            return false;
+
+                        // Bail out in presence of conditional directives
+                        // This is a workaround for https://github.com/dotnet/roslyn/issues/31820
+                        // Issue https://github.com/dotnet/roslyn/issues/31821 tracks
+                        // reverting this workaround.
+                        if (HasConditionalDirectives())
+                            return false;
+
+                        // All operation blocks for a symbol belong to the same tree.
+                        var firstBlock = context.OperationBlocks[0];
+                        if (!symbolStartAnalyzer._compilationAnalyzer.TryGetOptions(firstBlock.Syntax.SyntaxTree,
+                                                                                    context.Options,
+                                                                                    out options))
+                        {
+                            return false;
+                        }
+
+                        // Ignore methods that are just a single-throw method.  These are often
+                        // in-progress pieces of work and we don't want to force the user to fixup other
+                        // issues before they've even gotten around to writing their code.
+                        if (firstBlock.IsSingleThrowNotImplementedOperation())
+                            return false;
+
+                        // If we are analyzing a specific filter tree, skip operation blocks in unrelated trees.
+                        if (symbolStartAnalyzer._symbolStartAnalysisContext.FilterTree is { } filterTree &&
+                            firstBlock.Syntax.SyntaxTree != filterTree)
+                        {
+                            return false;
+                        }
+
+                        // If we are analyzing a specific filter span, skip operation blocks outside the filter span.
+                        if (context.FilterSpan.HasValue)
+                        {
+                            Contract.ThrowIfFalse(context.FilterSpan != symbolStartAnalyzer._symbolStartAnalysisContext.FilterSpan);
+                            Contract.ThrowIfNull(symbolStartAnalyzer._symbolStartAnalysisContext.FilterTree);
+                            var root = firstBlock.Syntax.SyntaxTree.GetRoot(context.CancellationToken);
+                            var spanStart = firstBlock.Syntax.SpanStart;
+                            var memberDecl = symbolStartAnalyzer._compilationAnalyzer.SyntaxFacts.GetContainingMemberDeclaration(root, spanStart, useFullSpan: false);
+                            if (memberDecl != null && !context.ShouldAnalyzeSpan(memberDecl.Span))
+                                return false;
+                        }
+
+                        return true;
+                    }
+
                     bool HasSyntaxErrors()
                     {
                         foreach (var operationBlock in context.OperationBlocks)
diff --git a/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.cs b/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.cs
index c468742899f66..7d24cfb30a869 100644
--- a/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.cs
@@ -31,6 +31,7 @@ private sealed partial class SymbolStartAnalyzer
             private readonly DeserializationConstructorCheck _deserializationConstructorCheck;
             private readonly ConcurrentDictionary<IMethodSymbol, bool> _methodsUsedAsDelegates;
             private readonly INamedTypeSymbol _iCustomMarshaler;
+            private readonly SymbolStartAnalysisContext _symbolStartAnalysisContext;
 
             /// <summary>
             /// Map from unused parameters to a boolean value indicating if the parameter has a read reference or not.
@@ -44,7 +45,8 @@ public SymbolStartAnalyzer(
                 INamedTypeSymbol eventArgsTypeOpt,
                 ImmutableHashSet<INamedTypeSymbol> attributeSetForMethodsToIgnore,
                 DeserializationConstructorCheck deserializationConstructorCheck,
-                INamedTypeSymbol iCustomMarshaler)
+                INamedTypeSymbol iCustomMarshaler,
+                SymbolStartAnalysisContext symbolStartAnalysisContext)
             {
                 _compilationAnalyzer = compilationAnalyzer;
 
@@ -54,6 +56,7 @@ public SymbolStartAnalyzer(
                 _unusedParameters = new ConcurrentDictionary<IParameterSymbol, bool>();
                 _methodsUsedAsDelegates = new ConcurrentDictionary<IMethodSymbol, bool>();
                 _iCustomMarshaler = iCustomMarshaler;
+                _symbolStartAnalysisContext = symbolStartAnalysisContext;
             }
 
             public static void CreateAndRegisterActions(
@@ -77,7 +80,8 @@ public static void CreateAndRegisterActions(
                     // to ensure there is no shared state (such as identified unused parameters within the type),
                     // as that would lead to duplicate diagnostics being reported from symbol end action callbacks
                     // for unrelated named types.
-                    var symbolAnalyzer = new SymbolStartAnalyzer(analyzer, eventsArgType, attributeSetForMethodsToIgnore, deserializationConstructorCheck, iCustomMarshaler);
+                    var symbolAnalyzer = new SymbolStartAnalyzer(analyzer, eventsArgType, attributeSetForMethodsToIgnore,
+                        deserializationConstructorCheck, iCustomMarshaler, symbolStartContext);
                     symbolAnalyzer.OnSymbolStart(symbolStartContext);
                 }, SymbolKind.NamedType);
 
diff --git a/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs b/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs
index 2eb696e61c24b..fec9c5d2f262d 100644
--- a/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.cs
@@ -8,6 +8,7 @@
 using System.Diagnostics;
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Operations;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -99,6 +100,7 @@ protected AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer(
         {
         }
 
+        protected abstract ISyntaxFacts SyntaxFacts { get; }
         protected abstract Location GetDefinitionLocationToFade(IOperation unusedDefinition);
         protected abstract bool SupportsDiscard(SyntaxTree tree);
         protected abstract bool MethodHasHandlesClause(IMethodSymbol method);
diff --git a/src/Analyzers/Core/Analyzers/SimplifyTypeNames/SimplifyTypeNamesDiagnosticAnalyzerBase.cs b/src/Analyzers/Core/Analyzers/SimplifyTypeNames/SimplifyTypeNamesDiagnosticAnalyzerBase.cs
index a87d651c4702a..00c78b4c31b39 100644
--- a/src/Analyzers/Core/Analyzers/SimplifyTypeNames/SimplifyTypeNamesDiagnosticAnalyzerBase.cs
+++ b/src/Analyzers/Core/Analyzers/SimplifyTypeNames/SimplifyTypeNamesDiagnosticAnalyzerBase.cs
@@ -107,7 +107,7 @@ private void AnalyzeCompilation(CompilationStartAnalysisContext context)
         /// blocks may be analyzed by <see cref="AnalyzeCodeBlock"/>, and any remaining spans can be analyzed by
         /// <see cref="AnalyzeSemanticModel"/>.</returns>
         protected abstract bool IsIgnoredCodeBlock(SyntaxNode codeBlock);
-        protected abstract ImmutableArray<Diagnostic> AnalyzeCodeBlock(CodeBlockAnalysisContext context);
+        protected abstract ImmutableArray<Diagnostic> AnalyzeCodeBlock(CodeBlockAnalysisContext context, SyntaxNode root);
         protected abstract ImmutableArray<Diagnostic> AnalyzeSemanticModel(SemanticModelAnalysisContext context, SyntaxNode root, SimpleIntervalTree<TextSpan, TextSpanIntervalIntrospector>? codeBlockIntervalTree);
 
         public bool TrySimplify(SemanticModel model, SyntaxNode node, [NotNullWhen(true)] out Diagnostic? diagnostic, TSimplifierOptions options, CancellationToken cancellationToken)
@@ -237,10 +237,11 @@ public void AnalyzeCodeBlock(CodeBlockAnalysisContext context)
                 if (!TryProceedWithInterval(addIfAvailable: false, context.CodeBlock.FullSpan, completed, intervalTree))
                     return;
 
-                var diagnostics = _analyzer.AnalyzeCodeBlock(context);
+                var root = context.GetAnalysisRoot(findInTrivia: true);
+                var diagnostics = _analyzer.AnalyzeCodeBlock(context, root);
 
                 // After this point, cancellation is not allowed due to possible state alteration
-                if (!TryProceedWithInterval(addIfAvailable: true, context.CodeBlock.FullSpan, completed, intervalTree))
+                if (!TryProceedWithInterval(addIfAvailable: root == context.CodeBlock, context.CodeBlock.FullSpan, completed, intervalTree))
                     return;
 
                 foreach (var diagnostic in diagnostics)
diff --git a/src/Analyzers/Core/Analyzers/UseAutoProperty/AbstractUseAutoPropertyAnalyzer.cs b/src/Analyzers/Core/Analyzers/UseAutoProperty/AbstractUseAutoPropertyAnalyzer.cs
index 5777d49230970..f8c99eea05161 100644
--- a/src/Analyzers/Core/Analyzers/UseAutoProperty/AbstractUseAutoPropertyAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/UseAutoProperty/AbstractUseAutoPropertyAnalyzer.cs
@@ -86,20 +86,9 @@ protected sealed override void InitializeWorker(AnalysisContext context)
             => context.RegisterSymbolStartAction(context =>
             {
                 var namedType = (INamedTypeSymbol)context.Symbol;
-                if (namedType.TypeKind is not TypeKind.Class and not TypeKind.Struct and not TypeKind.Module)
+                if (!ShouldAnalyze(context, namedType))
                     return;
 
-                // Don't bother running on this type unless at least one of its parts has the 'prefer auto props' option
-                // on, and the diagnostic is not suppressed.
-                if (!namedType.DeclaringSyntaxReferences.Select(d => d.SyntaxTree).Distinct().Any(tree =>
-                    {
-                        var preferAutoProps = context.Options.GetAnalyzerOptions(tree).PreferAutoProperties;
-                        return preferAutoProps.Value && preferAutoProps.Notification.Severity != ReportDiagnostic.Suppress;
-                    }))
-                {
-                    return;
-                }
-
                 var fieldNames = _fieldNamesPool.Allocate();
                 var analysisResults = s_analysisResultPool.Allocate();
                 var ineligibleFields = s_fieldSetPool.Allocate();
@@ -140,6 +129,45 @@ protected sealed override void InitializeWorker(AnalysisContext context)
                         s_fieldWriteLocationPool.ClearAndFree(nonConstructorFieldWrites);
                     }
                 });
+
+                static bool ShouldAnalyze(SymbolStartAnalysisContext context, INamedTypeSymbol namedType)
+                {
+                    if (namedType.TypeKind is not TypeKind.Class and not TypeKind.Struct and not TypeKind.Module)
+                        return false;
+
+                    // Don't bother running on this type unless at least one of its parts has the 'prefer auto props' option
+                    // on, and the diagnostic is not suppressed.
+                    if (!namedType.DeclaringSyntaxReferences.Select(d => d.SyntaxTree).Distinct().Any(tree =>
+                    {
+                        var preferAutoProps = context.Options.GetAnalyzerOptions(tree).PreferAutoProperties;
+                        return preferAutoProps.Value && preferAutoProps.Notification.Severity != ReportDiagnostic.Suppress;
+                    }))
+                    {
+                        return false;
+                    }
+
+                    // If we are analyzing a sub-span (lightbulb case), then check if the filter span
+                    // has a field/property declaration where a diagnostic could be reported.
+                    if (context.FilterSpan.HasValue)
+                    {
+                        Contract.ThrowIfNull(context.FilterTree);
+                        var shouldAnalyze = false;
+                        var analysisRoot = context.GetAnalysisRoot(findInTrivia: false);
+                        foreach (var node in analysisRoot.DescendantNodes())
+                        {
+                            if (node is TPropertyDeclaration or TFieldDeclaration && context.ShouldAnalyzeSpan(node.Span, node.SyntaxTree))
+                            {
+                                shouldAnalyze = true;
+                                break;
+                            }
+                        }
+
+                        if (!shouldAnalyze && analysisRoot.FirstAncestorOrSelf<SyntaxNode>(node => node is TPropertyDeclaration or TFieldDeclaration) == null)
+                            return false;
+                    }
+
+                    return true;
+                }
             }, SymbolKind.NamedType);
 
         private void AnalyzePropertyDeclaration(
diff --git a/src/Analyzers/Core/Analyzers/UseConditionalExpression/ForAssignment/UseConditionalExpressionForAssignmentHelpers.cs b/src/Analyzers/Core/Analyzers/UseConditionalExpression/ForAssignment/UseConditionalExpressionForAssignmentHelpers.cs
index 684534c12609d..d4b38e5e4c038 100644
--- a/src/Analyzers/Core/Analyzers/UseConditionalExpression/ForAssignment/UseConditionalExpressionForAssignmentHelpers.cs
+++ b/src/Analyzers/Core/Analyzers/UseConditionalExpression/ForAssignment/UseConditionalExpressionForAssignmentHelpers.cs
@@ -2,9 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Operations;
+using Microsoft.CodeAnalysis.PooledObjects;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 
 namespace Microsoft.CodeAnalysis.UseConditionalExpression
 {
@@ -68,6 +71,9 @@ public static bool TryMatchPattern(
                 return false;
             }
 
+            if (ReferencesDeclaredVariableInAssignment(ifOperation.Condition, trueAssignment?.Target, falseAssignment?.Target))
+                return false;
+
             isRef = trueAssignment?.IsRef == true;
             return UseConditionalExpressionHelpers.CanConvert(
                 syntaxFacts, ifOperation, trueStatement, falseStatement);
@@ -83,6 +89,49 @@ static bool AreEqualOrHaveImplicitConversion(ITypeSymbol? firstType, ITypeSymbol
                 return compilation.ClassifyCommonConversion(firstType, secondType).IsImplicit
                      ^ compilation.ClassifyCommonConversion(secondType, firstType).IsImplicit;
             }
+
+            static bool ReferencesDeclaredVariableInAssignment(IOperation condition, IOperation? trueTarget, IOperation? falseTarget)
+            {
+                if (trueTarget is not null || falseTarget is not null)
+                {
+                    using var _1 = PooledHashSet<ILocalSymbol>.GetInstance(out var symbolsDeclaredInConditional);
+                    foreach (var operation in condition.DescendantsAndSelf())
+                    {
+                        // `if (x is String s)`
+                        if (operation is IDeclarationPatternOperation { DeclaredSymbol: ILocalSymbol local })
+                            symbolsDeclaredInConditional.AddIfNotNull(local);
+
+                        // `if (Goo(out String s))`
+                        if (operation is IDeclarationExpressionOperation { Expression: ILocalReferenceOperation localReference })
+                            symbolsDeclaredInConditional.AddIfNotNull(localReference.Local);
+                    }
+
+                    if (symbolsDeclaredInConditional.Count > 0)
+                    {
+                        return ContainsLocalReference(symbolsDeclaredInConditional, trueTarget) ||
+                               ContainsLocalReference(symbolsDeclaredInConditional, falseTarget);
+                    }
+                }
+
+                return false;
+            }
+
+            static bool ContainsLocalReference(HashSet<ILocalSymbol> declaredPatternSymbols, IOperation? target)
+            {
+                if (target is not null)
+                {
+                    foreach (var operation in target.DescendantsAndSelf())
+                    {
+                        if (operation is ILocalReferenceOperation { Local: var local } &&
+                            declaredPatternSymbols.Contains(local))
+                        {
+                            return true;
+                        }
+                    }
+                }
+
+                return false;
+            }
         }
 
         private static bool TryGetAssignmentOrThrow(
diff --git a/src/Analyzers/Core/Analyzers/UseSystemHashCode/UseSystemHashCodeDiagnosticAnalyzer.cs b/src/Analyzers/Core/Analyzers/UseSystemHashCode/UseSystemHashCodeDiagnosticAnalyzer.cs
index 9c9d39f83095f..1cb37be3f5fe7 100644
--- a/src/Analyzers/Core/Analyzers/UseSystemHashCode/UseSystemHashCodeDiagnosticAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/UseSystemHashCode/UseSystemHashCodeDiagnosticAnalyzer.cs
@@ -43,6 +43,10 @@ private void AnalyzeOperationBlock(HashCodeAnalyzer analyzer, OperationBlockAnal
                 return;
 
             var owningSymbol = context.OwningSymbol;
+            var diagnosticLocation = owningSymbol.Locations[0];
+            if (!context.ShouldAnalyzeSpan(diagnosticLocation.SourceSpan))
+                return;
+
             var operation = context.OperationBlocks[0];
             var (accessesBase, hashedMembers, statements) = analyzer.GetHashedMembers(owningSymbol, operation);
             var elementCount = (accessesBase ? 1 : 0) + (hashedMembers.IsDefaultOrEmpty ? 0 : hashedMembers.Length);
@@ -74,7 +78,7 @@ private void AnalyzeOperationBlock(HashCodeAnalyzer analyzer, OperationBlockAnal
             var declarationLocation = context.OwningSymbol.DeclaringSyntaxReferences[0].GetSyntax(cancellationToken).GetLocation();
             context.ReportDiagnostic(DiagnosticHelper.Create(
                 Descriptor,
-                owningSymbol.Locations[0],
+                diagnosticLocation,
                 option.Notification.Severity,
                 new[] { operationLocation, declarationLocation },
                 ImmutableDictionary<string, string?>.Empty));
diff --git a/src/Analyzers/Core/Analyzers/UseThrowExpression/AbstractUseThrowExpressionDiagnosticAnalyzer.cs b/src/Analyzers/Core/Analyzers/UseThrowExpression/AbstractUseThrowExpressionDiagnosticAnalyzer.cs
index 9e9cc07e62a75..d0a3775bdb00d 100644
--- a/src/Analyzers/Core/Analyzers/UseThrowExpression/AbstractUseThrowExpressionDiagnosticAnalyzer.cs
+++ b/src/Analyzers/Core/Analyzers/UseThrowExpression/AbstractUseThrowExpressionDiagnosticAnalyzer.cs
@@ -165,7 +165,7 @@ private static bool ValueIsAccessed(SemanticModel semanticModel, IConditionalOpe
 
         protected abstract bool IsInExpressionTree(SemanticModel semanticModel, SyntaxNode node, INamedTypeSymbol? expressionTypeOpt, CancellationToken cancellationToken);
 
-        private bool TryFindAssignmentExpression(
+        private static bool TryFindAssignmentExpression(
             IBlockOperation containingBlock, IConditionalOperation ifOperation, ISymbol localOrParameter,
             [NotNullWhen(true)] out IExpressionStatementOperation? expressionStatement,
             [NotNullWhen(true)] out IAssignmentOperation? assignmentExpression)
@@ -206,7 +206,7 @@ private bool TryFindAssignmentExpression(
             return false;
         }
 
-        private bool TryDecomposeIfCondition(
+        private static bool TryDecomposeIfCondition(
             IConditionalOperation ifStatement,
              [NotNullWhen(true)] out ISymbol? localOrParameter)
         {
@@ -238,7 +238,7 @@ private bool TryDecomposeIfCondition(
             return false;
         }
 
-        private bool TryGetLocalOrParameterSymbol(
+        private static bool TryGetLocalOrParameterSymbol(
             IOperation operation,
             [NotNullWhen(true)] out ISymbol? localOrParameter)
         {
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.cs.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.cs.xlf
index 115a2de2cbcc1..783b82502cec7 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.cs.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.cs.xlf
@@ -51,18 +51,18 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Přidejte do souboru projektu MSBuild následující skupinu PropertyGroup, aby se při sestavení povolila funkce IDE0005 (Odebrat nepotřebné direktivy usings nebo imports):
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
+      Dbejte na to, aby se při buildu kontrolovala syntaxe všech komentářů dokumentace, které jsou součástí kódu, ale
+      neohlašujte varování pro chybějící komentáře.
       CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
       CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
       CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
     --&gt;
-    &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
+     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
-  &lt;/PropertyGroup&gt;
+ &lt;/PropertyGroup&gt;
     </target>
         <note />
       </trans-unit>
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">Nastavit vlastnost MSBuild GenerateDocumentationFile na true</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Nastavte vlastnost MSBuild GenerateDocumentationFile v souboru projektu na true, aby se povolila funkce IDE0005 (odebrat nepotřebné direktivy using/imports) při sestavení</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.de.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.de.xlf
index efa62afd84999..ad65305a6d402 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.de.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.de.xlf
@@ -51,16 +51,16 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Fügen Sie die folgende PropertyGroup zu Ihrer MSBuild-Projektdatei hinzu, um IDE0005 (Nicht benötigte Using-Direktiven/Importe entfernen) beim Build zu aktivieren:
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Stellen Sie sicher, dass alle Dokumentationskommentare, die im Code enthalten sind, während des Builds auf Syntax geprüft werden,
+      aber melden Sie keine Warnungen für fehlende Kommentare.
+      CS1573: Der Parameter 'parameter' hat kein passendes param-Tag im XML-Kommentar für 'parameter' (andere Parameter jedoch schon)
+      CS1591: Fehlender XML-Kommentar für öffentlich sichtbaren Typ oder Member 'Type_or_Member'
+      CS1712: Der Typparameter 'type_parameter' hat kein passendes typeparam-Tag im XML-Kommentar zu 'type_or_member' (andere Typparameter jedoch schon)
     --&gt;
-    &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
+    &lt;GenerateDocumentationFile&gt;TRUE&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </target>
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">MSBuild-Eigenschaft "GenerateDocumentationFile" auf "true" festlegen</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Legen Sie die MSBuild-Eigenschaft "GenerateDocumentationFile" in der Projektdatei auf "true" fest, um IDE0005 (Nicht benötigte Using-Direktiven/Importe entfernen) beim Build zu aktivieren.</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.es.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.es.xlf
index 51bbf57b6c93f..b0f143d75f44e 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.es.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.es.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Agregue el siguiente PropertyGroup al archivo de proyecto de MSBuild para habilitar IDE0005 (Quitar instrucciones using o importaciones innecesarias) en la compilación:
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Asegúrese de que los comentarios de documentación que se incluyen en el código se comprueban para comprobar la sintaxis durante la compilación, pero no
+ notificar advertencias para los comentarios que faltan.
+       CS1573: El parámetro 'parameter' no tiene ninguna etiqueta de parámetro coincidente en el comentario XML para 'parameter' (pero otros parámetros sí)
+      CS1591: Falta un comentario XML para el tipo o miembro visible públicamente 'Type_or_Member'
+      CS1712:El parámetro de tipo 'type_parameter' no tiene ninguna etiqueta typeparam coincidente en el comentario XML en 'type_or_member' (pero sí otros parámetros de tipo)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">Establecer la propiedad de MSBuild "GenerateDocumentationFile" en "true"</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Establecer la propiedad de MSBuild "GenerateDocumentationFile" en "true" en el archivo de proyecto para habilitar IDE0005 (quitar instrucciones using o importaciones innecesarias) en la compilación</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.fr.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.fr.xlf
index e11c2ad4c8d9f..a104342f0da5b 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.fr.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.fr.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Ajoutez le PropertyGroup suivant à votre fichier de projet MSBuild pour activer IDE0005 (supprimer les utilisations/importations inutiles) lors de la construction :
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Vérifiez que la syntaxe des commentaires de documentation inclus dans le code est vérifiée pendant la génération, mais
+      ne signale pas d’avertissements pour les commentaires manquants.
+      CS1573 : le paramètre 'parameter' n’a pas de balise param correspondante dans le commentaire XML pour 'parameter' (contrairement à d’autres paramètres)
+      CS1591 : commentaire XML manquant pour le type visible publiquement ou le membre 'Type_or_Member'
+      CS1712 : le paramètre de type 'type_parameter' n’a pas de balise typeparam correspondante dans le commentaire XML sur 'type_or_member' (contrairement à d’autres paramètres de type)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">Définissez la propriété MSBuild 'GenerateDocumentationFile' sur 'true'</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Définissez la propriété MSBuild 'GenerateDocumentationFile' sur 'true' dans le fichier projet pour activer IDE0005 (supprimer les utilisations/importations inutiles) lors de la construction</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.it.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.it.xlf
index d7dc1d890cd13..3dd221c998368 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.it.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.it.xlf
@@ -51,17 +51,17 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Aggiungere il PropertyGroup seguente al file di progetto MSBuild per abilitare IDE0005 (Rimuovere using/imports non necessari) nella compilazione:
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Assicurarsi che durante la compilazione sia controllata la sintassi dei commenti della documentazione inclusi nel codice, ma
+      non segnalare avvisi per i commenti mancanti.
+      CS1573: il parametro 'parameter' non contiene il tag param corrispondente nel commento XML per 'parameter' (a differenza di altri parametri)
+      CS1591: manca il commento XML per il tipo o il membro 'Type_or_Member' visibili pubblicamente
+      CS1712: il parametro del tipo 'type_parameter' non contiene il tag typeparam corrispondente nel commento XML su 'type_or_member' (a differenza di altri parametri)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
-    &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
+    &lt;NoWarn&gt;$(NoWarn),1573.1591.1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </target>
         <note />
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">Imposta la proprietà 'GenerateDocumentationFile' di MSBuild su 'true'</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Impostare la proprietà MSBuild 'GenerateDocumentationFile' su 'true' nel file di progetto per abilitare IDE0005 (rimuovere using/imports non necessari) nella compilazione</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ja.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ja.xlf
index 1b5686d68195f..187e5e137d9f7 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ja.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ja.xlf
@@ -51,14 +51,15 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">MSBuild プロジェクト ファイルに次の PropertyGroup を追加して、ビルドで IDE0005 (不要な usings/imports を削除する) を有効にします。
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      コードにドキュメント コメントが含まれている場合には、ビルド中に構文チェックが行われるようにしますが、
+。
+      抜けているコメントに関する警告は報告しません。
+      CS1573: パラメーター 'parameter' には、'parameter' の XML コメントに一致するパラメーター タグがありません (ただし、他のパラメーターにはあります)。
+      CS1591: 公開されている型またはメンバー 'Type_or_Member'
+      CS1712: 型パラメーター 'type_parameter' には、'type_or_member' の XML コメントに一致する typeparam タグがありません (ただし、他の型パラメーターにはあります)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +344,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">MSBuild プロパティ 'GenerateDocumentationFile' を 'true' に設定します</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">ビルドで IDE0005 (不要な usings/imports を削除する) を有効にするには、プロジェクト ファイルで MSBuild プロパティ 'GenerateDocumentationFile' を 'true' に設定します</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ko.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ko.xlf
index 01d6e219e55b0..bf7482fa9dac3 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ko.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ko.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">빌드 시 IDE0005(불필요한 using/imports 제거)를 사용하도록 설정하려면 MSBuild 프로젝트 파일에 다음 PropertyGroup을 추가합니다.
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      빌드하는 동안 코드에 포함된 설명서 주석이 구문을 확인하지만, 주석 누락에 대한
+      경고를 보고하지 않습니다.
+      CS1573: 'parameter' 매개 변수의 XML 주석에 'parameter'에 일치하는 매개 변수 태그가 없습니다(하지만 다른 매개 변수는 일치함.)
+      CS1591: 공개적으로 표시되는 형식 또는 멤버 'Type_or_Member'에 대한 XML 주석이 없습니다.
+      CS1712: 형식 매개 변수 'type_parameter'에 'type_or_member'의 XML 주석에 일치하는 형식 매개 변수 태그가 없습니다(하지만 다른 형식 매개 변수는 일치함).
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">MSBuild 속성 'GenerateDocumentationFile'을 'true'로 설정</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">빌드 시 IDE0005(불필요한 using/imports 제거)를 사용하도록 설정하려면 프로젝트 파일에서 MSBuild 속성 'GenerateDocumentationFile'을 'true'로 설정합니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pl.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pl.xlf
index 898cd3d967f4d..48f6db3801bcf 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pl.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pl.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Dodaj następującą grupę właściwości do pliku projektu MSBuild, aby włączyć środowisko IDE0005 (usuń niepotrzebne operacje użycia/importu) w kompilacji:
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Sprawdź komentarze do dokumentacji zawarte w kodzie pod kątem składni, ale
+      nie zgłaszaj ostrzeżeń dla brakujących komentarzy.
+      CS1573: Parametr „parameter” nie ma pasującej etykiety parametru w komentarzu XML dla „parameter” (ale inne parametry mają taką etykietę)
+      CS1591: Brak komentarza XML dla publicznie widocznego typu lub członka „Type_or_Member”
+      CS1712: Parametr typu „type_parameter” nie ma pasującej etykiety typeparam w komentarzu XML dla  „type_or_member” (ale inne parametry typu mają taką etykietę)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">Ustaw właściwość MSBuild „GenerateDocumentationFile” na wartość „true”</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Ustaw właściwość MSBuild „GenerateDocumentationFile” na wartość „true” w pliku projektu, aby włączyć środowisko IDE0005 (usuń niepotrzebne operacje użycia/importu) w kompilacji</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pt-BR.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pt-BR.xlf
index be6f44229d358..6bc52c076ab6f 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pt-BR.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.pt-BR.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Adicione o PropertyGroup a seguir ao arquivo de projeto do MSBuild para habilitar IDE0005 (Remover usos/importações desnecessários) no build:
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Verifique se todos os comentários de documentação incluídos no código são verificados para sintaxe durante a compilação, mas
+      não relatar avisos para comentários ausentes.
+      CS1573: o parâmetro 'parameter' não tem marca de parâmetro correspondente no comentário XML para 'parameter' (mas outros parâmetros têm)
+      CS1591: Comentário XML ausente para o tipo ou membro publicamente visível 'Type_or_Member'
+      CS1712: o parâmetro de tipo 'type_parameter' não tem marca typeparam correspondente no comentário XML em 'type_or_member' (mas outros parâmetros de tipo têm)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">Definir a propriedade 'GenerateDocumentationFile' do MSBuild como 'true'</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Defina a propriedade 'GenerateDocumentationFile' do MSBuild como 'true' no arquivo de projeto para habilitar IDE0005 (Remover usos/importações desnecessários) no build</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ru.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ru.xlf
index 39e2c548d565a..4e8b7cd4df423 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ru.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.ru.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Добавьте следующую группу свойств в файл проекта MSBuild, чтобы включить IDE0005 (удалить ненужное использование или импорт) при сборке:
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Убедитесь, что любые комментарии к документации, включенные в код, проверяются на синтаксис во время сборки, но
+      не сообщайте о предупреждениях об отсутствующих комментариях.
+      CS1573: у параметра 'parameter' нет соответствующего тега param в комментарии XML для 'parameter' (но у других параметров есть)
+      CS1591: отсутствует комментарий XML для общедоступного типа или члена 'Type_or_Member'
+      CS1712: у параметра типа 'type_parameter' нет соответствующего тега typeparam в комментарии XML для 'type_or_member' (но у других параметров типа есть)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">Установите для свойства MSBuild "GenerateDocumentationFile" значение "ИСТИНА"</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Установите для свойства MSBuild "GenerateDocumentationFile" значение "ИСТИНА" в файле проекта, чтобы включить IDE0005 (удалить ненужное использование или импорт) при сборке.</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.tr.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.tr.xlf
index adbd53f35275d..cb77bb7ac663e 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.tr.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.tr.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">Derlemede IDE0005'i (Gereksiz kullanımları/içe aktarmaları kaldır) etkinleştirmek için MSBuild proje dosyanıza aşağıdaki PropertyGroup'u ekleyin:
   &lt;PropertyGroup&gt;
     &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+      Kodda yer alan, belge hakkındaki yorumlar, derleme sırasında söz dizimi açısından kontrol edilmelidir. 
+      Eksik yorumlar için uyarılar bildirilmemelidir.
+      CS1573: 'parameter' parametresi, ‘parameter’ için XML yorumunda param etiketine sahip değil (Diğer parametrelerin aksine)
+      CS1591: Herkese açık tür veya üye 'Type_or_Member' için XML yorumu eklenmemiş
+      CS1712: Tür parametresi 'type_parameter’, 'type_or_member' hakkındaki XML yorumunda eşleşen typeparam etiketine sahip değil (Diğer parametrelerin aksine)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">'GenerateDocumentationFile' MSBuild özelliğini 'true' olarak ayarlayın</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">Derlemede IDE0005'i (Gereksiz kullanımları/içe aktarmaları kaldırın) etkinleştirmek için proje dosyasında MSBuild özelliğini 'GenerateDocumentationFile' 'true' olarak ayarlayın</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hans.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hans.xlf
index 905c03f297c1d..f5d7fc08b5ef2 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hans.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hans.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">将以下 PropertyGroup 添加到 MSBuild 项目文件，以便在生成时启用 IDE0005 (删除不必要的使用/导入):
   &lt;PropertyGroup&gt;
-    &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+     &lt;!--
+      请确保在生成期间对代码中包含的任何文档注释进行了语法检查，但
+      没有报告关于缺少注释的警告。
+      CS1573: 参数 'parameter' 在 'parameter' 的 XML 注释中没有匹配的 param 标记(但其他参数有)
+      CS1591: 公开可见类型或成员 'Type_or_Member' 缺少 XML 注释
+      CS1712: 类型参数 'type_parameter' 在 'type_or_member' 的 XML 注释中没有匹配的 typeparam 标记(但其他类型参数有)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">将 MSBuild 属性 "GenerateDocumentationFile" 设置为 "true"</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">在项目文件中将 MSBuild 属性 "GenerateDocumentationFile" 设置为 "true"，以在生成时启用 IDE0005 (删除不必要的使用/导入)</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hant.xlf b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hant.xlf
index 7859c31daefe8..b69c3d9e738ad 100644
--- a/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hant.xlf
+++ b/src/Analyzers/Core/Analyzers/xlf/AnalyzersResources.zh-Hant.xlf
@@ -51,14 +51,14 @@
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
   &lt;/PropertyGroup&gt;
     </source>
-        <target state="new">Add the following PropertyGroup to your MSBuild project file to enable IDE0005 (Remove unnecessary usings/imports) on build:
+        <target state="translated">將下列 PropertyGroup 新增至 MSBuild 專案檔，以在組建上啟用 IDE0005 (移除不必要的 using/import):
   &lt;PropertyGroup&gt;
-    &lt;!--
-      Make sure any documentation comments which are included in code get checked for syntax during the build, but do
-      not report warnings for missing comments.
-      CS1573: Parameter 'parameter' has no matching param tag in the XML comment for 'parameter' (but other parameters do)
-      CS1591: Missing XML comment for publicly visible type or member 'Type_or_Member'
-      CS1712: Type parameter 'type_parameter' has no matching typeparam tag in the XML comment on 'type_or_member' (but other type parameters do)
+   &lt;!--
+      請務必確認程式碼中包含的任何文件註解在組建期間皆經過語法檢查，但
+      不要回報遺漏註解的警告。
+      CS1573: 參數 'parameter' 在 'parameter' 的 XML 註解中沒有相符的參數標籤 (不過其他參數有)
+      CS1591: 遺漏公開可見類型或成員 'Type_or_Member' 的 XML 註解
+      CS1712: 型別參數 'type_parameter' 在 'type_or_member' 的 XML 註解中沒有相符的型別參數標籤 (不過其他型別參數有)
     --&gt;
     &lt;GenerateDocumentationFile&gt;True&lt;/GenerateDocumentationFile&gt;
     &lt;NoWarn&gt;$(NoWarn),1573,1591,1712&lt;/NoWarn&gt;
@@ -343,12 +343,12 @@
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true'</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true'</target>
+        <target state="translated">將 MSBuild 屬性 'GenerateDocumentationFile' 設為 'true'</target>
         <note />
       </trans-unit>
       <trans-unit id="Set_MSBuild_Property_GenerateDocumentationFile_to_true_in_project_file_to_enable_IDE0005_Remove_unnecessary_usings_imports_on_build">
         <source>Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</source>
-        <target state="new">Set MSBuild property 'GenerateDocumentationFile' to 'true' in project file to enable IDE0005 (Remove unnecessary usings/imports) on build</target>
+        <target state="translated">如要在組建上啟用 IDE0005 (移除不必要的 using/import)，請在專案檔中將 MSBuild 屬性 'GenerateDocumentationFile' 設為 'true'</target>
         <note />
       </trans-unit>
       <trans-unit id="Simplify_LINQ_expression">
diff --git a/src/Analyzers/Core/CodeFixes/AddExplicitCast/InheritanceDistanceComparer.cs b/src/Analyzers/Core/CodeFixes/AddExplicitCast/InheritanceDistanceComparer.cs
index b383407bf32de..be47400543e4d 100644
--- a/src/Analyzers/Core/CodeFixes/AddExplicitCast/InheritanceDistanceComparer.cs
+++ b/src/Analyzers/Core/CodeFixes/AddExplicitCast/InheritanceDistanceComparer.cs
@@ -61,7 +61,7 @@ public int Compare((TExpressionSyntax syntax, ITypeSymbol symbol) x,
         /// <summary>
         /// Calculate the inheritance distance between baseType and derivedType.
         /// </summary>
-        private int GetInheritanceDistanceRecursive(ITypeSymbol baseType, ITypeSymbol? derivedType)
+        private static int GetInheritanceDistanceRecursive(ITypeSymbol baseType, ITypeSymbol? derivedType)
         {
             if (derivedType == null)
                 return int.MaxValue;
diff --git a/src/Analyzers/Core/CodeFixes/UseConditionalExpression/ForAssignment/AbstractUseConditionalExpressionForAssignmentCodeFixProvider.cs b/src/Analyzers/Core/CodeFixes/UseConditionalExpression/ForAssignment/AbstractUseConditionalExpressionForAssignmentCodeFixProvider.cs
index 870f991246fa7..ac471ca3c2299 100644
--- a/src/Analyzers/Core/CodeFixes/UseConditionalExpression/ForAssignment/AbstractUseConditionalExpressionForAssignmentCodeFixProvider.cs
+++ b/src/Analyzers/Core/CodeFixes/UseConditionalExpression/ForAssignment/AbstractUseConditionalExpressionForAssignmentCodeFixProvider.cs
@@ -150,7 +150,7 @@ private bool TryConvertWhenAssignmentToLocalDeclaredImmediateAbove(
             return true;
         }
 
-        private bool TryFindMatchingLocalDeclarationImmediatelyAbove(
+        private static bool TryFindMatchingLocalDeclarationImmediatelyAbove(
             IConditionalOperation ifOperation,
             ISimpleAssignmentOperation? trueAssignment,
             ISimpleAssignmentOperation? falseAssignment,
@@ -246,7 +246,7 @@ private bool TryFindMatchingLocalDeclarationImmediatelyAbove(
             return !ReferencesLocalVariable(ifOperation.Condition, variable);
         }
 
-        private bool ReferencesLocalVariable(IOperation operation, ILocalSymbol variable)
+        private static bool ReferencesLocalVariable(IOperation operation, ILocalSymbol variable)
         {
             if (operation is ILocalReferenceOperation localReference &&
                 Equals(variable, localReference.Local))
diff --git a/src/Analyzers/VisualBasic/Analyzers/RemoveUnusedParametersAndValues/VisualBasicRemoveUnusedParametersAndValuesDiagnosticAnalyzer.vb b/src/Analyzers/VisualBasic/Analyzers/RemoveUnusedParametersAndValues/VisualBasicRemoveUnusedParametersAndValuesDiagnosticAnalyzer.vb
index eda6eb7173b02..2db8e309c3066 100644
--- a/src/Analyzers/VisualBasic/Analyzers/RemoveUnusedParametersAndValues/VisualBasicRemoveUnusedParametersAndValuesDiagnosticAnalyzer.vb
+++ b/src/Analyzers/VisualBasic/Analyzers/RemoveUnusedParametersAndValues/VisualBasicRemoveUnusedParametersAndValuesDiagnosticAnalyzer.vb
@@ -4,6 +4,7 @@
 
 Imports Microsoft.CodeAnalysis.CodeStyle
 Imports Microsoft.CodeAnalysis.Diagnostics
+Imports Microsoft.CodeAnalysis.LanguageService
 Imports Microsoft.CodeAnalysis.Operations
 Imports Microsoft.CodeAnalysis.RemoveUnusedParametersAndValues
 Imports Microsoft.CodeAnalysis.VisualBasic.CodeStyle
@@ -21,6 +22,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.RemoveUnusedParametersAndValues
                        unusedValueAssignmentOption:=VisualBasicCodeStyleOptions.UnusedValueAssignment)
         End Sub
 
+        Protected Overrides ReadOnly Property SyntaxFacts As ISyntaxFacts = VisualBasicSyntaxFacts.Instance
+
         Protected Overrides Function GetUnusedValueExpressionStatementOption(provider As AnalyzerOptionsProvider) As CodeStyleOption2(Of UnusedValuePreference)
             Return CType(provider, VisualBasicAnalyzerOptionsProvider).UnusedValueExpressionStatement
         End Function
diff --git a/src/CodeStyle/BannedSymbols.txt b/src/CodeStyle/BannedSymbols.txt
index 6dbaf50c3c35b..47d012bef5484 100644
--- a/src/CodeStyle/BannedSymbols.txt
+++ b/src/CodeStyle/BannedSymbols.txt
@@ -1,4 +1,5 @@
 P:Microsoft.CodeAnalysis.Project.LanguageServices; Use 'GetExtendedLanguageServices' instead
+P:Microsoft.CodeAnalysis.Project.Services; Use 'GetExtendedLanguageServices' instead
 M:Microsoft.CodeAnalysis.Host.HostWorkspaceServices.GetLanguageServices(System.String); Use 'GetExtendedLanguageServices' or directly get the language service by invoking 'GetLanguageService' or 'GetRequiredLanguageService'
 T:Microsoft.CodeAnalysis.Options.OptionSet; 'OptionSet' is not available in CodeStyle layer. Add a using/Imports statement defining 'OptionSet = Microsoft.CodeAnalysis.Diagnostics.AnalyzerConfigOptions' when preprocessor variable 'CODE_STYLE' is defined
 T:Microsoft.CodeAnalysis.Options.OptionKey; Use 'Microsoft.CodeAnalysis.Options.OptionKey2' instead
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs b/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
index 4d1474ecd7e4b..856ff3d8acad0 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
@@ -733,6 +733,28 @@ internal bool CheckValueKind(SyntaxNode node, BoundExpression expr, BindValueKin
                             throw ExceptionUtilities.UnexpectedValue(implicitIndexer.IndexerOrSliceAccess.Kind);
                     }
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)expr;
+
+                        if (elementAccess.IsValue || elementAccess.GetItemOrSliceHelper is WellKnownMember.System_Span_T__Slice_Int_Int or WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int)
+                        {
+                            // Strict RValue
+                            break;
+                        }
+
+                        var getItemOrSliceHelper = (MethodSymbol)Compilation.GetWellKnownTypeMember(elementAccess.GetItemOrSliceHelper);
+
+                        if (getItemOrSliceHelper is null)
+                        {
+                            return true;
+                        }
+
+                        getItemOrSliceHelper = getItemOrSliceHelper.AsMember(getItemOrSliceHelper.ContainingType.Construct(ImmutableArray.Create(elementAccess.Expression.Type.TryGetInlineArrayElementField().TypeWithAnnotations)));
+
+                        return CheckMethodReturnValueKind(getItemOrSliceHelper, elementAccess.Syntax, node, valueKind, checkingReceiver, diagnostics);
+                    }
+
                 case BoundKind.ImplicitIndexerReceiverPlaceholder:
                     break;
 
@@ -763,6 +785,10 @@ internal bool CheckValueKind(SyntaxNode node, BoundExpression expr, BindValueKin
                     var assignment = (BoundAssignmentOperator)expr;
                     return CheckSimpleAssignmentValueKind(node, assignment, valueKind, diagnostics);
 
+                case BoundKind.ValuePlaceholder:
+                    // Strict RValue
+                    break;
+
                 default:
                     Debug.Assert(expr is not BoundValuePlaceholderBase, $"Placeholder kind {expr.Kind} should be explicitly handled");
                     break;
@@ -1983,7 +2009,11 @@ bool isRefEscape
 
                     if (!valid)
                     {
-                        ReportInvocationEscapeError(syntax, symbol, parameter, checkingReceiver, diagnostics);
+                        if (symbol is not SignatureOnlyMethodSymbol)
+                        {
+                            ReportInvocationEscapeError(syntax, symbol, parameter, checkingReceiver, diagnostics);
+                        }
+
                         return false;
                     }
                 }
@@ -2049,7 +2079,7 @@ private bool CheckInvocationEscapeWithUpdatedRules(
                         // For consistency with C#10 implementation, we don't report an additional error
                         // for the receiver. (In both implementations, the call to Check*Escape() above
                         // will have reported a specific escape error for the receiver though.)
-                        if ((object)((argument as BoundCapturedReceiverPlaceholder)?.Receiver ?? argument) != receiver)
+                        if ((object)((argument as BoundCapturedReceiverPlaceholder)?.Receiver ?? argument) != receiver && symbol is not SignatureOnlyMethodSymbol)
                         {
                             ReportInvocationEscapeError(syntax, symbol, param, checkingReceiver, diagnostics);
                         }
@@ -3133,6 +3163,33 @@ internal uint GetRefEscape(BoundExpression expr, uint scopeOfTheContainingExpres
                     }
                     break;
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)expr;
+
+                        if (elementAccess.GetItemOrSliceHelper is not (WellKnownMember.System_ReadOnlySpan_T__get_Item or WellKnownMember.System_Span_T__get_Item) || elementAccess.IsValue)
+                        {
+                            Debug.Assert(GetInlineArrayAccessEquivalentSignatureMethod(elementAccess, out _, out _).RefKind == RefKind.None);
+                            break;
+                        }
+
+                        ImmutableArray<BoundExpression> arguments;
+                        ImmutableArray<RefKind> refKinds;
+                        SignatureOnlyMethodSymbol equivalentSignatureMethod = GetInlineArrayAccessEquivalentSignatureMethod(elementAccess, out arguments, out refKinds);
+
+                        Debug.Assert(equivalentSignatureMethod.RefKind != RefKind.None);
+
+                        return GetInvocationEscapeScope(
+                            equivalentSignatureMethod,
+                            receiver: null,
+                            equivalentSignatureMethod.Parameters,
+                            arguments,
+                            refKinds,
+                            argsToParamsOpt: default,
+                            scopeOfTheContainingExpression,
+                            isRefEscape: true);
+                    }
+
                 case BoundKind.PropertyAccess:
                     var propertyAccess = (BoundPropertyAccess)expr;
 
@@ -3387,6 +3444,37 @@ internal bool CheckRefEscape(SyntaxNode node, BoundExpression expr, uint escapeF
                     }
                     break;
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)expr;
+
+                        if (elementAccess.GetItemOrSliceHelper is not (WellKnownMember.System_ReadOnlySpan_T__get_Item or WellKnownMember.System_Span_T__get_Item) || elementAccess.IsValue)
+                        {
+                            Debug.Assert(GetInlineArrayAccessEquivalentSignatureMethod(elementAccess, out _, out _).RefKind == RefKind.None);
+                            break;
+                        }
+
+                        ImmutableArray<BoundExpression> arguments;
+                        ImmutableArray<RefKind> refKinds;
+                        SignatureOnlyMethodSymbol equivalentSignatureMethod = GetInlineArrayAccessEquivalentSignatureMethod(elementAccess, out arguments, out refKinds);
+
+                        Debug.Assert(equivalentSignatureMethod.RefKind != RefKind.None);
+
+                        return CheckInvocationEscape(
+                            elementAccess.Syntax,
+                            equivalentSignatureMethod,
+                            receiver: null,
+                            equivalentSignatureMethod.Parameters,
+                            argsOpt: arguments,
+                            argRefKindsOpt: refKinds,
+                            argsToParamsOpt: default,
+                            checkingReceiver,
+                            escapeFrom,
+                            escapeTo,
+                            diagnostics,
+                            isRefEscape: true);
+                    }
+
                 case BoundKind.FunctionPointerInvocation:
                     var functionPointerInvocation = (BoundFunctionPointerInvocation)expr;
 
@@ -3691,6 +3779,25 @@ internal uint GetValEscape(BoundExpression expr, uint scopeOfTheContainingExpres
                             throw ExceptionUtilities.UnexpectedValue(implicitIndexerAccess.IndexerOrSliceAccess.Kind);
                     }
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)expr;
+
+                        ImmutableArray<BoundExpression> arguments;
+                        ImmutableArray<RefKind> refKinds;
+                        SignatureOnlyMethodSymbol equivalentSignatureMethod = GetInlineArrayAccessEquivalentSignatureMethod(elementAccess, out arguments, out refKinds);
+
+                        return GetInvocationEscapeScope(
+                            equivalentSignatureMethod,
+                            receiver: null,
+                            equivalentSignatureMethod.Parameters,
+                            arguments,
+                            refKinds,
+                            argsToParamsOpt: default,
+                            scopeOfTheContainingExpression,
+                            isRefEscape: false);
+                    }
+
                 case BoundKind.PropertyAccess:
                     var propertyAccess = (BoundPropertyAccess)expr;
 
@@ -3745,6 +3852,23 @@ internal uint GetValEscape(BoundExpression expr, uint scopeOfTheContainingExpres
                         return GetInterpolatedStringHandlerConversionEscapeScope(conversion.Operand, scopeOfTheContainingExpression);
                     }
 
+                    if (conversion.Conversion.IsInlineArray)
+                    {
+                        ImmutableArray<BoundExpression> arguments;
+                        ImmutableArray<RefKind> refKinds;
+                        SignatureOnlyMethodSymbol equivalentSignatureMethod = GetInlineArrayConversionEquivalentSignatureMethod(conversion, out arguments, out refKinds);
+
+                        return GetInvocationEscapeScope(
+                            equivalentSignatureMethod,
+                            receiver: null,
+                            equivalentSignatureMethod.Parameters,
+                            arguments,
+                            refKinds,
+                            argsToParamsOpt: default,
+                            scopeOfTheContainingExpression,
+                            isRefEscape: false);
+                    }
+
                     return GetValEscape(conversion.Operand, scopeOfTheContainingExpression);
 
                 case BoundKind.AssignmentOperator:
@@ -4147,6 +4271,29 @@ internal bool CheckValEscape(SyntaxNode node, BoundExpression expr, uint escapeF
                             throw ExceptionUtilities.UnexpectedValue(implicitIndexerAccess.IndexerOrSliceAccess.Kind);
                     }
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)expr;
+
+                        ImmutableArray<BoundExpression> arguments;
+                        ImmutableArray<RefKind> refKinds;
+                        SignatureOnlyMethodSymbol equivalentSignatureMethod = GetInlineArrayAccessEquivalentSignatureMethod(elementAccess, out arguments, out refKinds);
+
+                        return CheckInvocationEscape(
+                            elementAccess.Syntax,
+                            equivalentSignatureMethod,
+                            receiver: null,
+                            equivalentSignatureMethod.Parameters,
+                            argsOpt: arguments,
+                            argRefKindsOpt: refKinds,
+                            argsToParamsOpt: default,
+                            checkingReceiver,
+                            escapeFrom,
+                            escapeTo,
+                            diagnostics,
+                            isRefEscape: false);
+                    }
+
                 case BoundKind.PropertyAccess:
                     var propertyAccess = (BoundPropertyAccess)expr;
 
@@ -4228,6 +4375,27 @@ internal bool CheckValEscape(SyntaxNode node, BoundExpression expr, uint escapeF
                         return CheckInterpolatedStringHandlerConversionEscape(conversion.Operand, escapeFrom, escapeTo, diagnostics);
                     }
 
+                    if (conversion.Conversion.IsInlineArray)
+                    {
+                        ImmutableArray<BoundExpression> arguments;
+                        ImmutableArray<RefKind> refKinds;
+                        SignatureOnlyMethodSymbol equivalentSignatureMethod = GetInlineArrayConversionEquivalentSignatureMethod(conversion, out arguments, out refKinds);
+
+                        return CheckInvocationEscape(
+                            conversion.Syntax,
+                            equivalentSignatureMethod,
+                            receiver: null,
+                            equivalentSignatureMethod.Parameters,
+                            argsOpt: arguments,
+                            argRefKindsOpt: refKinds,
+                            argsToParamsOpt: default,
+                            checkingReceiver,
+                            escapeFrom,
+                            escapeTo,
+                            diagnostics,
+                            isRefEscape: false);
+                    }
+
                     return CheckValEscape(node, conversion.Operand, escapeFrom, escapeTo, checkingReceiver: false, diagnostics: diagnostics);
 
                 case BoundKind.AssignmentOperator:
@@ -4461,6 +4629,106 @@ internal bool CheckValEscape(SyntaxNode node, BoundExpression expr, uint escapeF
             }
         }
 
+        private SignatureOnlyMethodSymbol GetInlineArrayAccessEquivalentSignatureMethod(BoundInlineArrayAccess elementAccess, out ImmutableArray<BoundExpression> arguments, out ImmutableArray<RefKind> refKinds)
+        {
+            RefKind resultRefKind;
+            RefKind parameterRefKind;
+
+            if (elementAccess.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__get_Item or WellKnownMember.System_Span_T__get_Item)
+            {
+                // inlineArray[index] is equivalent to calling a method with the signature:
+                // - ref T GetItem(ref inlineArray), or
+                // - ref readonly T GetItem(in inlineArray), or
+                // - T GetItem(inlineArray)
+
+                if (elementAccess.IsValue)
+                {
+                    resultRefKind = RefKind.None;
+                    parameterRefKind = RefKind.None;
+                }
+                else
+                {
+                    resultRefKind = elementAccess.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__get_Item ? RefKind.In : RefKind.Ref;
+                    parameterRefKind = resultRefKind;
+                }
+            }
+            else if (elementAccess.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int or WellKnownMember.System_Span_T__Slice_Int_Int)
+            {
+                // inlineArray[Range] is equivalent to calling a method with the signature:
+                // - Span<T> Slice(ref inlineArray), or
+                // - ReadOnlySpan<T> Slice(in inlineArray)
+                resultRefKind = RefKind.None;
+                parameterRefKind = elementAccess.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int ? RefKind.In : RefKind.Ref;
+            }
+            else
+            {
+                throw ExceptionUtilities.Unreachable();
+            }
+
+            var equivalentSignatureMethod = new SignatureOnlyMethodSymbol(
+                name: "",
+                this._symbol.ContainingType,
+                MethodKind.Ordinary,
+                Cci.CallingConvention.Default,
+                ImmutableArray<TypeParameterSymbol>.Empty,
+                ImmutableArray.Create<ParameterSymbol>(new SignatureOnlyParameterSymbol(
+                                                            TypeWithAnnotations.Create(elementAccess.Expression.Type),
+                                                            ImmutableArray<CustomModifier>.Empty,
+                                                            isParams: false,
+                                                            parameterRefKind
+                                                            )),
+                resultRefKind,
+                isInitOnly: false,
+                isStatic: true,
+                returnType: TypeWithAnnotations.Create(elementAccess.Type),
+                ImmutableArray<CustomModifier>.Empty,
+                ImmutableArray<MethodSymbol>.Empty);
+
+            arguments = ImmutableArray.Create(elementAccess.Expression);
+            refKinds = ImmutableArray.Create(parameterRefKind);
+
+            return equivalentSignatureMethod;
+        }
+
+        private SignatureOnlyMethodSymbol GetInlineArrayConversionEquivalentSignatureMethod(BoundConversion conversion, out ImmutableArray<BoundExpression> arguments, out ImmutableArray<RefKind> refKinds)
+        {
+            Debug.Assert(conversion.Conversion.IsInlineArray);
+            return GetInlineArrayConversionEquivalentSignatureMethod(inlineArray: conversion.Operand, resultType: conversion.Type, out arguments, out refKinds);
+        }
+
+        private SignatureOnlyMethodSymbol GetInlineArrayConversionEquivalentSignatureMethod(BoundExpression inlineArray, TypeSymbol resultType, out ImmutableArray<BoundExpression> arguments, out ImmutableArray<RefKind> refKinds)
+        {
+            // An inline array conversion is equivalent to calling a method with the signature:
+            // - Span<T> Convert(ref inlineArray), or
+            // - ReadOnlySpan<T> Convert(in inlineArray)
+
+            RefKind parameterRefKind = resultType.OriginalDefinition.Equals(_compilation.GetWellKnownType(WellKnownType.System_ReadOnlySpan_T), TypeCompareKind.AllIgnoreOptions) ? RefKind.In : RefKind.Ref;
+
+            var equivalentSignatureMethod = new SignatureOnlyMethodSymbol(
+                name: "",
+                _symbol.ContainingType,
+                MethodKind.Ordinary,
+                Cci.CallingConvention.Default,
+                ImmutableArray<TypeParameterSymbol>.Empty,
+                ImmutableArray.Create<ParameterSymbol>(new SignatureOnlyParameterSymbol(
+                                                            TypeWithAnnotations.Create(inlineArray.Type),
+                                                            ImmutableArray<CustomModifier>.Empty,
+                                                            isParams: false,
+                                                            parameterRefKind
+                                                            )),
+                RefKind.None,
+                isInitOnly: false,
+                isStatic: true,
+                returnType: TypeWithAnnotations.Create(resultType),
+                ImmutableArray<CustomModifier>.Empty,
+                ImmutableArray<MethodSymbol>.Empty);
+
+            arguments = ImmutableArray.Create(inlineArray);
+            refKinds = ImmutableArray.Create(parameterRefKind);
+
+            return equivalentSignatureMethod;
+        }
+
         private bool CheckTupleValEscape(ImmutableArray<BoundExpression> elements, uint escapeFrom, uint escapeTo, BindingDiagnosticBag diagnostics)
         {
             foreach (var element in elements)
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Attributes.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Attributes.cs
index 3c4a0f7b1dd33..aa5480dac9fea 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Attributes.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Attributes.cs
@@ -194,7 +194,7 @@ private BoundAttribute BindAttributeCore(AttributeSyntax node, NamedTypeSymbol a
             }
             else
             {
-                bool found = TryPerformConstructorOverloadResolution(
+                bool found = attributeArgumentBinder.TryPerformConstructorOverloadResolution(
                     attributeTypeForBinding,
                     analyzedArguments.ConstructorArguments,
                     attributeTypeForBinding.Name,
@@ -211,12 +211,12 @@ private BoundAttribute BindAttributeCore(AttributeSyntax node, NamedTypeSymbol a
 
                 if (!found)
                 {
-                    CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = GetNewCompoundUseSiteInfo(diagnostics);
+                    CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = attributeArgumentBinder.GetNewCompoundUseSiteInfo(diagnostics);
                     resultKind = resultKind.WorseResultKind(
-                        memberResolutionResult.IsValid && !IsConstructorAccessible(memberResolutionResult.Member, ref useSiteInfo) ?
+                        memberResolutionResult.IsValid && !attributeArgumentBinder.IsConstructorAccessible(memberResolutionResult.Member, ref useSiteInfo) ?
                             LookupResultKind.Inaccessible :
                             LookupResultKind.OverloadResolutionFailure);
-                    boundConstructorArguments = BuildArgumentsForErrorRecovery(analyzedArguments.ConstructorArguments, candidateConstructors);
+                    boundConstructorArguments = attributeArgumentBinder.BuildArgumentsForErrorRecovery(analyzedArguments.ConstructorArguments, candidateConstructors);
                     diagnostics.Add(node, useSiteInfo);
                 }
                 else
@@ -233,7 +233,7 @@ private BoundAttribute BindAttributeCore(AttributeSyntax node, NamedTypeSymbol a
                         diagnostics,
                         attributedMember: attributedMember);
                     boundConstructorArguments = analyzedArguments.ConstructorArguments.Arguments.ToImmutable();
-                    ReportDiagnosticsIfObsolete(diagnostics, attributeConstructor, node, hasBaseReceiver: false);
+                    attributeArgumentBinder.ReportDiagnosticsIfObsolete(diagnostics, attributeConstructor, node, hasBaseReceiver: false);
 
                     if (attributeConstructor.Parameters.Any(static p => p.RefKind == RefKind.In))
                     {
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Conversions.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Conversions.cs
index 6c564d3e9e740..aab5fed0951cc 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Conversions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Conversions.cs
@@ -131,7 +131,7 @@ BoundExpression createConversion(
                 }
 
                 // Obsolete diagnostics for method group are reported as part of creating the method group conversion.
-                reportUseSiteDiagnostics(conversion);
+                reportUseSiteDiagnostics(syntax, conversion, source, destination, diagnostics);
 
                 if (conversion.IsAnonymousFunction && source.Kind == BoundKind.UnboundLambda)
                 {
@@ -264,7 +264,10 @@ BoundExpression createConversion(
                         .WithSuppression(source.IsSuppressed);
                 }
 
-                reportUseSiteDiagnosticsForUnderlyingConversions(conversion);
+                if (!hasErrors && conversion.Exists)
+                {
+                    ensureAllUnderlyingConversionsChecked(syntax, source, conversion, wasCompilerGenerated, destination, diagnostics);
+                }
 
                 return new BoundConversion(
                     syntax,
@@ -278,7 +281,7 @@ BoundExpression createConversion(
                     hasErrors: hasErrors)
                 { WasCompilerGenerated = wasCompilerGenerated };
 
-                void reportUseSiteDiagnostics(Conversion conversion)
+                void reportUseSiteDiagnostics(SyntaxNode syntax, Conversion conversion, BoundExpression source, TypeSymbol destination, BindingDiagnosticBag diagnostics)
                 {
                     // Obsolete diagnostics for method group are reported as part of creating the method group conversion.
                     Debug.Assert(!conversion.IsMethodGroup);
@@ -287,64 +290,172 @@ void reportUseSiteDiagnostics(Conversion conversion)
                     {
                         ReportUseSite(conversion.Method, diagnostics, syntax.Location);
                     }
-                    CheckConstraintLanguageVersionAndRuntimeSupportForConversion(syntax, conversion, diagnostics);
+
+                    checkConstraintLanguageVersionAndRuntimeSupportForConversion(syntax, conversion, source, destination, diagnostics);
                 }
+            }
 
-                void reportUseSiteDiagnosticsForUnderlyingConversions(Conversion conversion)
+            void ensureAllUnderlyingConversionsChecked(SyntaxNode syntax, BoundExpression source, Conversion conversion, bool wasCompilerGenerated, TypeSymbol destination, BindingDiagnosticBag diagnostics)
+            {
+                if (conversion.IsNullable)
                 {
-                    var underlyingConversions = conversion.UnderlyingConversions;
+                    Debug.Assert(conversion.UnderlyingConversions.Length == 1);
 
-                    if (!underlyingConversions.IsDefaultOrEmpty)
+                    if (destination.IsNullableType())
                     {
-                        foreach (var underlying in underlyingConversions)
+                        switch (source.Type?.IsNullableType())
                         {
-                            reportUseSiteDiagnosticsForSelfAndUnderlyingConversions(underlying);
-
-                            if (underlying.IsUserDefined)
-                            {
-                                reportUseSiteDiagnosticsForSelfAndUnderlyingConversions(underlying.UserDefinedFromConversion);
-                                reportUseSiteDiagnosticsForSelfAndUnderlyingConversions(underlying.UserDefinedToConversion);
-                                underlying.MarkUnderlyingConversionsChecked();
-                            }
+                            case true:
+                                _ = CreateConversion(
+                                        syntax,
+                                        new BoundValuePlaceholder(source.Syntax, source.Type.GetNullableUnderlyingType()),
+                                        conversion.UnderlyingConversions[0],
+                                        isCast: false,
+                                        conversionGroupOpt: null,
+                                        wasCompilerGenerated,
+                                        destination.GetNullableUnderlyingType(),
+                                        diagnostics);
+                                break;
+
+                            case false:
+                                _ = CreateConversion(
+                                        syntax,
+                                        source,
+                                        conversion.UnderlyingConversions[0],
+                                        isCast: false,
+                                        conversionGroupOpt: null,
+                                        wasCompilerGenerated,
+                                        destination.GetNullableUnderlyingType(),
+                                        diagnostics);
+                                break;
                         }
 
+                        conversion.UnderlyingConversions[0].AssertUnderlyingConversionsChecked();
                         conversion.MarkUnderlyingConversionsChecked();
                     }
+                    else if (source.Type?.IsNullableType() == true)
+                    {
+
+                        _ = CreateConversion(
+                                syntax,
+                                new BoundValuePlaceholder(source.Syntax, source.Type.GetNullableUnderlyingType()),
+                                conversion.UnderlyingConversions[0],
+                                isCast: false,
+                                conversionGroupOpt: null,
+                                wasCompilerGenerated,
+                                destination,
+                                diagnostics);
 
-                    void reportUseSiteDiagnosticsForSelfAndUnderlyingConversions(Conversion conversion)
+                        conversion.UnderlyingConversions[0].AssertUnderlyingConversionsChecked();
+                        conversion.MarkUnderlyingConversionsChecked();
+                    }
+                }
+                else if (conversion.IsTupleConversion)
+                {
+                    ImmutableArray<TypeWithAnnotations> sourceTypes;
+                    ImmutableArray<TypeWithAnnotations> destTypes;
+
+                    if (source.Type?.TryGetElementTypesWithAnnotationsIfTupleType(out sourceTypes) == true &&
+                        destination.TryGetElementTypesWithAnnotationsIfTupleType(out destTypes) &&
+                        sourceTypes.Length == destTypes.Length)
                     {
-                        reportUseSiteDiagnostics(conversion);
-                        reportUseSiteDiagnosticsForUnderlyingConversions(conversion);
+                        var elementConversions = conversion.UnderlyingConversions;
+                        Debug.Assert(elementConversions.Length == sourceTypes.Length);
+
+                        for (int i = 0; i < sourceTypes.Length; i++)
+                        {
+                            _ = CreateConversion(
+                                    syntax,
+                                    new BoundValuePlaceholder(source.Syntax, sourceTypes[i].Type),
+                                    elementConversions[i],
+                                    isCast: false,
+                                    conversionGroupOpt: null,
+                                    wasCompilerGenerated,
+                                    destTypes[i].Type,
+                                    diagnostics);
+
+                            elementConversions[i].AssertUnderlyingConversionsChecked();
+                        }
+
+                        conversion.MarkUnderlyingConversionsChecked();
                     }
                 }
-            }
-        }
+                else if (conversion.IsDynamic)
+                {
+                    Debug.Assert(conversion.UnderlyingConversions.IsDefault);
+                    conversion.MarkUnderlyingConversionsChecked();
+                }
 
-        internal void CheckConstraintLanguageVersionAndRuntimeSupportForConversion(SyntaxNodeOrToken syntax, Conversion conversion, BindingDiagnosticBag diagnostics)
-        {
-            Debug.Assert(syntax.SyntaxTree is object);
+                conversion.AssertUnderlyingConversionsCheckedRecursive();
+            }
 
-            if (conversion.IsUserDefined && conversion.Method is MethodSymbol method && method.IsStatic)
+            void checkConstraintLanguageVersionAndRuntimeSupportForConversion(SyntaxNode syntax, Conversion conversion, BoundExpression source, TypeSymbol destination, BindingDiagnosticBag diagnostics)
             {
-                if (method.IsAbstract || method.IsVirtual)
-                {
-                    Debug.Assert(conversion.ConstrainedToTypeOpt is TypeParameterSymbol);
+                Debug.Assert(syntax.SyntaxTree is object);
 
-                    if (Compilation.SourceModule != method.ContainingModule)
+                if (conversion.IsUserDefined)
+                {
+                    if (conversion.Method is MethodSymbol method && method.IsStatic)
                     {
-                        CheckFeatureAvailability(syntax, MessageID.IDS_FeatureStaticAbstractMembersInInterfaces, diagnostics);
+                        if (method.IsAbstract || method.IsVirtual)
+                        {
+                            Debug.Assert(conversion.ConstrainedToTypeOpt is TypeParameterSymbol);
+
+                            if (Compilation.SourceModule != method.ContainingModule)
+                            {
+                                CheckFeatureAvailability(syntax, MessageID.IDS_FeatureStaticAbstractMembersInInterfaces, diagnostics);
+
+                                if (!Compilation.Assembly.RuntimeSupportsStaticAbstractMembersInInterfaces)
+                                {
+                                    Error(diagnostics, ErrorCode.ERR_RuntimeDoesNotSupportStaticAbstractMembersInInterfaces, syntax);
+                                }
+                            }
+                        }
 
-                        if (!Compilation.Assembly.RuntimeSupportsStaticAbstractMembersInInterfaces)
+                        if (SyntaxFacts.IsCheckedOperator(method.Name) &&
+                            Compilation.SourceModule != method.ContainingModule)
                         {
-                            Error(diagnostics, ErrorCode.ERR_RuntimeDoesNotSupportStaticAbstractMembersInInterfaces, syntax);
+                            CheckFeatureAvailability(syntax, MessageID.IDS_FeatureCheckedUserDefinedOperators, diagnostics);
                         }
                     }
                 }
-
-                if (SyntaxFacts.IsCheckedOperator(method.Name) &&
-                    Compilation.SourceModule != method.ContainingModule)
+                else if (conversion.IsInlineArray)
                 {
-                    CheckFeatureAvailability(syntax, MessageID.IDS_FeatureCheckedUserDefinedOperators, diagnostics);
+                    if (!Compilation.Assembly.RuntimeSupportsInlineArrayTypes)
+                    {
+                        Error(diagnostics, ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, syntax);
+                    }
+
+                    CheckFeatureAvailability(syntax, MessageID.IDS_FeatureInlineArrays, diagnostics);
+                    diagnostics.ReportUseSite(source.Type!.TryGetInlineArrayElementField(), syntax);
+
+                    if (destination.OriginalDefinition.Equals(Compilation.GetWellKnownType(WellKnownType.System_ReadOnlySpan_T), TypeCompareKind.AllIgnoreOptions))
+                    {
+                        if (CheckValueKind(syntax, source, BindValueKind.RefersToLocation, checkingReceiver: false, BindingDiagnosticBag.Discarded))
+                        {
+                            _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan, diagnostics, syntax: syntax); // This also takes care of an 'int' type
+                            _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T, diagnostics, syntax: syntax);
+                            _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T, diagnostics, syntax: syntax);
+                        }
+                        else
+                        {
+                            Error(diagnostics, ErrorCode.ERR_InlineArrayConversionToReadOnlySpanNotSupported, syntax, destination);
+                        }
+                    }
+                    else
+                    {
+                        Debug.Assert(destination.OriginalDefinition.Equals(Compilation.GetWellKnownType(WellKnownType.System_Span_T), TypeCompareKind.AllIgnoreOptions));
+
+                        if (CheckValueKind(syntax, source, BindValueKind.RefersToLocation | BindValueKind.Assignable, checkingReceiver: false, BindingDiagnosticBag.Discarded))
+                        {
+                            _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan, diagnostics, syntax: syntax); // This also takes care of an 'int' type
+                            _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T, diagnostics, syntax: syntax);
+                        }
+                        else
+                        {
+                            Error(diagnostics, ErrorCode.ERR_InlineArrayConversionToSpanNotSupported, syntax, destination);
+                        }
+                    }
                 }
             }
         }
@@ -813,6 +924,7 @@ private BoundExpression CreateUserDefinedConversion(
                     // Skip introducing the conversion from C to C?.  The "to" conversion is now wrong though,
                     // because it will still assume converting C? to D?. 
 
+                    toConversion.MarkUnderlyingConversionsCheckedRecursive();
                     toConversion = Conversions.ClassifyConversionFromType(conversionReturnType, destination, isChecked: CheckOverflowAtRuntime, ref useSiteInfo);
                     Debug.Assert(toConversion.Exists);
                 }
@@ -859,6 +971,8 @@ private BoundExpression CreateUserDefinedConversion(
                 destination: destination,
                 diagnostics: diagnostics);
 
+            conversion.AssertUnderlyingConversionsCheckedRecursive();
+
             finalConversion.ResetCompilerGenerated(source.WasCompilerGenerated);
 
             return finalConversion;
@@ -955,6 +1069,9 @@ private BoundExpression CreateMethodGroupConversion(SyntaxNode syntax, BoundExpr
                 hasErrors = true;
             }
 
+            Debug.Assert(conversion.UnderlyingConversions.IsDefault);
+            conversion.MarkUnderlyingConversionsChecked();
+
             return new BoundConversion(syntax, group, conversion, @checked: false, explicitCastInCode: isCast, conversionGroup, constantValueOpt: ConstantValue.NotAvailable, type: destination, hasErrors: hasErrors) { WasCompilerGenerated = group.WasCompilerGenerated };
         }
 
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
index 4614e0dec59f0..543f4b13e44b8 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
@@ -450,6 +450,12 @@ internal BoundFieldEqualsValue BindFieldInitializer(
             BoundExpression result = initializerBinder.BindVariableOrAutoPropInitializerValue(initializerOpt, field.RefKind,
                                                            field.GetFieldType(initializerBinder.FieldsBeingBound).Type, diagnostics);
 
+            if (field is { IsStatic: false, RefKind: RefKind.None, ContainingSymbol: SourceMemberContainerTypeSymbol { PrimaryConstructor: { } primaryConstructor } } &&
+                TryGetPrimaryConstructorParameterSubjectToDoubleStorageWarning(primaryConstructor, result) is (ParameterSymbol parameter, SyntaxNode syntax))
+            {
+                diagnostics.Add(ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer, syntax.Location, parameter);
+            }
+
             return new BoundFieldEqualsValue(initializerOpt, field, initializerBinder.GetDeclaredLocalsForScope(initializerOpt), result);
         }
 
@@ -4365,24 +4371,7 @@ private BoundExpression BindConstructorInitializerCore(
                                 continue;
                             }
 
-                            BoundParameter boundParameter;
-
-                            switch (analyzedArguments.Argument(i))
-                            {
-                                case BoundParameter param:
-                                    boundParameter = param;
-                                    break;
-
-                                case BoundConversion { Conversion.IsIdentity: true, Operand: BoundParameter param }:
-                                    boundParameter = param;
-                                    break;
-
-                                default:
-                                    continue;
-                            }
-
-                            if (boundParameter.ParameterSymbol is { } parameter &&
-                                primaryConstructor.GetCapturedParameters().ContainsKey(parameter))
+                            if (TryGetPrimaryConstructorParameterSubjectToDoubleStorageWarning(primaryConstructor, analyzedArguments.Argument(i)) is (ParameterSymbol parameter, SyntaxNode syntax))
                             {
                                 if (expanded)
                                 {
@@ -4394,7 +4383,7 @@ private BoundExpression BindConstructorInitializerCore(
                                     }
                                 }
 
-                                diagnostics.Add(ErrorCode.WRN_CapturedPrimaryConstructorParameterPassedToBase, boundParameter.Syntax.Location, parameter);
+                                diagnostics.Add(ErrorCode.WRN_CapturedPrimaryConstructorParameterPassedToBase, syntax.Location, parameter);
                             }
                         }
                     }
@@ -4473,6 +4462,33 @@ static void validateRecordCopyConstructor(MethodSymbol constructor, NamedTypeSym
             }
         }
 
+        private static (ParameterSymbol, SyntaxNode) TryGetPrimaryConstructorParameterSubjectToDoubleStorageWarning(SynthesizedPrimaryConstructor primaryConstructor, BoundExpression boundExpression)
+        {
+            BoundParameter boundParameter;
+
+            switch (boundExpression)
+            {
+                case BoundParameter param:
+                    boundParameter = param;
+                    break;
+
+                case BoundConversion { Conversion.IsIdentity: true, Operand: BoundParameter param }:
+                    boundParameter = param;
+                    break;
+
+                default:
+                    return (null, null);
+            }
+
+            if (boundParameter.ParameterSymbol is { } parameter &&
+                primaryConstructor.GetCapturedParameters().ContainsKey(parameter))
+            {
+                return (parameter, boundParameter.Syntax);
+            }
+
+            return (null, null);
+        }
+
         internal static bool IsUserDefinedRecordCopyConstructor(MethodSymbol constructor)
         {
             return constructor.ContainingType is SourceNamedTypeSymbol sourceType &&
@@ -4584,8 +4600,8 @@ BoundExpression bindElement(CollectionElementSyntax syntax, BindingDiagnosticBag
             BoundExpression bindSpreadElement(SpreadElementSyntax syntax, BindingDiagnosticBag diagnostics)
             {
                 var expression = BindRValueWithoutTargetType(syntax.Expression, diagnostics);
-                var builder = new ForEachEnumeratorInfo.Builder();
-                bool hasErrors = !GetEnumeratorInfoAndInferCollectionElementType(syntax, syntax.Expression, ref builder, ref expression, isAsync: false, diagnostics, inferredType: out _) ||
+                ForEachEnumeratorInfo.Builder builder;
+                bool hasErrors = !GetEnumeratorInfoAndInferCollectionElementType(syntax, syntax.Expression, ref expression, isAsync: false, diagnostics, inferredType: out _, out builder) ||
                     builder.IsIncomplete;
                 if (hasErrors)
                 {
@@ -5117,7 +5133,7 @@ private BoundExpression BindObjectInitializerMember(
 
                 MessageID.IDS_FeatureDictionaryInitializer.CheckFeatureAvailability(diagnostics, implicitIndexing.ArgumentList.OpenBracketToken);
 
-                boundMember = BindElementAccess(implicitIndexing, implicitReceiver, implicitIndexing.ArgumentList, diagnostics);
+                boundMember = BindElementAccess(implicitIndexing, implicitReceiver, implicitIndexing.ArgumentList, allowInlineArrayElementAccess: false, diagnostics);
 
                 resultKind = boundMember.ResultKind;
                 hasErrors = boundMember.HasAnyErrors || implicitReceiver.HasAnyErrors;
@@ -7521,7 +7537,8 @@ protected MethodGroupResolution BindExtensionMethod(
                     isMethodGroupConversion: isMethodGroupConversion,
                     allowRefOmittedArguments: allowRefOmittedArguments,
                     returnRefKind: returnRefKind,
-                    returnType: returnType);
+                    returnType: returnType,
+                    isExtensionMethodResolution: true);
                 diagnostics.Add(expression, useSiteInfo);
                 var sealedDiagnostics = diagnostics.ToReadOnlyAndFree();
 
@@ -8060,10 +8077,10 @@ private static bool IsMethodOrPropertyGroup(ArrayBuilder<Symbol> members)
         private BoundExpression BindElementAccess(ElementAccessExpressionSyntax node, BindingDiagnosticBag diagnostics)
         {
             BoundExpression receiver = BindExpression(node.Expression, diagnostics: diagnostics, invoked: false, indexed: true);
-            return BindElementAccess(node, receiver, node.ArgumentList, diagnostics);
+            return BindElementAccess(node, receiver, node.ArgumentList, allowInlineArrayElementAccess: true, diagnostics);
         }
 
-        private BoundExpression BindElementAccess(ExpressionSyntax node, BoundExpression receiver, BracketedArgumentListSyntax argumentList, BindingDiagnosticBag diagnostics)
+        private BoundExpression BindElementAccess(ExpressionSyntax node, BoundExpression receiver, BracketedArgumentListSyntax argumentList, bool allowInlineArrayElementAccess, BindingDiagnosticBag diagnostics)
         {
             AnalyzedArguments analyzedArguments = AnalyzedArguments.GetInstance();
             try
@@ -8080,7 +8097,7 @@ private BoundExpression BindElementAccess(ExpressionSyntax node, BoundExpression
                 receiver = CheckValue(receiver, BindValueKind.RValue, diagnostics);
                 receiver = BindToNaturalType(receiver, diagnostics);
 
-                return BindElementOrIndexerAccess(node, receiver, analyzedArguments, diagnostics);
+                return BindElementOrIndexerAccess(node, receiver, analyzedArguments, allowInlineArrayElementAccess, diagnostics);
             }
             finally
             {
@@ -8088,7 +8105,7 @@ private BoundExpression BindElementAccess(ExpressionSyntax node, BoundExpression
             }
         }
 
-        private BoundExpression BindElementOrIndexerAccess(ExpressionSyntax node, BoundExpression expr, AnalyzedArguments analyzedArguments, BindingDiagnosticBag diagnostics)
+        private BoundExpression BindElementOrIndexerAccess(ExpressionSyntax node, BoundExpression expr, AnalyzedArguments analyzedArguments, bool allowInlineArrayElementAccess, BindingDiagnosticBag diagnostics)
         {
             if ((object)expr.Type == null)
             {
@@ -8104,11 +8121,247 @@ private BoundExpression BindElementOrIndexerAccess(ExpressionSyntax node, BoundE
                 // able to get more semantic analysis of the indexing operation. We do not
                 // want to report cascading errors.
 
-                BoundExpression result = BindElementAccessCore(node, expr, analyzedArguments, BindingDiagnosticBag.Discarded);
-                return result;
+                diagnostics = BindingDiagnosticBag.Discarded;
+            }
+
+            bool tryInlineArrayAccess = false;
+
+            if (allowInlineArrayElementAccess &&
+                !InAttributeArgument && !InParameterDefaultValue && // These checks prevent cycles caused by attribute binding when HasInlineArrayAttribute check triggers that.
+                expr.Type.HasInlineArrayAttribute(out int length) && expr.Type.TryGetInlineArrayElementField() is FieldSymbol elementField)
+            {
+                tryInlineArrayAccess = true;
+
+                if (analyzedArguments.Arguments.Count == 1 &&
+                    tryImplicitConversionToInlineArrayIndex(node, analyzedArguments.Arguments[0], diagnostics, out WellKnownType indexOrRangeWellknownType) is { } convertedIndex)
+                {
+                    return bindInlineArrayElementAccess(node, expr, length, analyzedArguments, convertedIndex, indexOrRangeWellknownType, elementField, diagnostics);
+                }
+            }
+
+            BindingDiagnosticBag diagnosticsForBindElementAccessCore = diagnostics;
+
+            if (tryInlineArrayAccess && diagnostics.AccumulatesDiagnostics)
+            {
+                diagnosticsForBindElementAccessCore = BindingDiagnosticBag.GetInstance(diagnostics);
+            }
+
+            BoundExpression result = BindElementAccessCore(node, expr, analyzedArguments, diagnosticsForBindElementAccessCore);
+
+            if (diagnosticsForBindElementAccessCore != diagnostics)
+            {
+                Debug.Assert(tryInlineArrayAccess);
+                Debug.Assert(diagnosticsForBindElementAccessCore.DiagnosticBag is { });
+
+                if (diagnosticsForBindElementAccessCore.DiagnosticBag.AsEnumerableWithoutResolution().AsSingleton() is
+                    { Code: (int)ErrorCode.ERR_BadIndexLHS, Arguments: [TypeSymbol type] } && type.Equals(expr.Type, TypeCompareKind.ConsiderEverything))
+                {
+                    diagnosticsForBindElementAccessCore.DiagnosticBag.Clear();
+                    Error(diagnosticsForBindElementAccessCore, ErrorCode.ERR_InlineArrayBadIndex, node.Location);
+                }
+
+                diagnostics.AddRangeAndFree(diagnosticsForBindElementAccessCore);
+            }
+
+            return result;
+
+            BoundExpression tryImplicitConversionToInlineArrayIndex(ExpressionSyntax node, BoundExpression index, BindingDiagnosticBag diagnostics, out WellKnownType indexOrRangeWellknownType)
+            {
+                indexOrRangeWellknownType = WellKnownType.Unknown;
+                BoundExpression convertedIndex = TryImplicitConversionToArrayIndex(index, SpecialType.System_Int32, node, diagnostics);
+
+                if (convertedIndex is null)
+                {
+                    convertedIndex = TryImplicitConversionToArrayIndex(index, WellKnownType.System_Index, node, diagnostics);
+
+                    if (convertedIndex is null)
+                    {
+                        convertedIndex = TryImplicitConversionToArrayIndex(index, WellKnownType.System_Range, node, diagnostics);
+                        if (convertedIndex is object)
+                        {
+                            indexOrRangeWellknownType = WellKnownType.System_Range;
+                        }
+                    }
+                    else
+                    {
+                        indexOrRangeWellknownType = WellKnownType.System_Index;
+                    }
+                }
+
+                return convertedIndex;
+            }
+
+            BoundExpression bindInlineArrayElementAccess(ExpressionSyntax node, BoundExpression expr, int length, AnalyzedArguments analyzedArguments, BoundExpression convertedIndex, WellKnownType indexOrRangeWellknownType, FieldSymbol elementField, BindingDiagnosticBag diagnostics)
+            {
+                // Check required well-known members. They may not be needed
+                // during lowering, but it's simpler to always require them to prevent
+                // the user from getting surprising errors when optimizations fail
+                if (indexOrRangeWellknownType != WellKnownType.Unknown)
+                {
+                    if (indexOrRangeWellknownType == WellKnownType.System_Range)
+                    {
+                        _ = GetWellKnownTypeMember(WellKnownMember.System_Range__get_Start, diagnostics, syntax: node);
+                        _ = GetWellKnownTypeMember(WellKnownMember.System_Range__get_End, diagnostics, syntax: node);
+                    }
+
+                    _ = GetWellKnownTypeMember(WellKnownMember.System_Index__GetOffset, diagnostics, syntax: node);
+                }
+
+                if (analyzedArguments.Names.Count > 0)
+                {
+                    Error(diagnostics, ErrorCode.ERR_NamedArgumentForInlineArray, node);
+                }
+
+                ReportRefOrOutArgument(analyzedArguments, diagnostics);
+
+                WellKnownMember createSpanHelper;
+                WellKnownMember getItemOrSliceHelper;
+                bool isValue = false;
+
+                if (CheckValueKind(node, expr, BindValueKind.RefersToLocation | BindValueKind.Assignable, checkingReceiver: false, BindingDiagnosticBag.Discarded))
+                {
+                    createSpanHelper = WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan;
+                    getItemOrSliceHelper = indexOrRangeWellknownType == WellKnownType.System_Range ? WellKnownMember.System_Span_T__Slice_Int_Int : WellKnownMember.System_Span_T__get_Item;
+                }
+                else
+                {
+                    createSpanHelper = WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan;
+                    getItemOrSliceHelper = indexOrRangeWellknownType == WellKnownType.System_Range ? WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int : WellKnownMember.System_ReadOnlySpan_T__get_Item;
+
+                    _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T, diagnostics, syntax: node);
+
+                    if (!CheckValueKind(node, expr, BindValueKind.RefersToLocation, checkingReceiver: false, BindingDiagnosticBag.Discarded))
+                    {
+                        if (indexOrRangeWellknownType == WellKnownType.System_Range)
+                        {
+                            Location location;
+
+                            if (expr.Syntax.Parent is ConditionalAccessExpressionSyntax conditional &&
+                                conditional.Expression == expr.Syntax)
+                            {
+                                location = expr.Syntax.SyntaxTree.GetLocation(TextSpan.FromBounds(expr.Syntax.SpanStart, conditional.OperatorToken.Span.End));
+                            }
+                            else
+                            {
+                                location = expr.Syntax.GetLocation();
+                            }
+
+                            Error(diagnostics, ErrorCode.ERR_RefReturnLvalueExpected, location);
+                        }
+                        else
+                        {
+                            isValue = true;
+                        }
+                    }
+                }
+
+                // Check bounds
+                if (convertedIndex.ConstantValueOpt is { SpecialType: SpecialType.System_Int32, Int32Value: int constIndex })
+                {
+                    checkInlineArrayBounds(convertedIndex.Syntax, constIndex, length, excludeEnd: true, diagnostics);
+                }
+                else if (indexOrRangeWellknownType == WellKnownType.System_Index)
+                {
+                    checkInlineArrayBoundsForSystemIndex(convertedIndex, length, excludeEnd: true, diagnostics);
+                }
+                else if (indexOrRangeWellknownType == WellKnownType.System_Range && convertedIndex is BoundRangeExpression rangeExpr)
+                {
+                    if (rangeExpr.LeftOperandOpt is BoundExpression left)
+                    {
+                        checkInlineArrayBoundsForSystemIndex(left, length, excludeEnd: false, diagnostics);
+                    }
+
+                    if (rangeExpr.RightOperandOpt is BoundExpression right)
+                    {
+                        checkInlineArrayBoundsForSystemIndex(right, length, excludeEnd: false, diagnostics);
+                    }
+                }
+
+                _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T, diagnostics, syntax: node);
+                _ = GetWellKnownTypeMember(createSpanHelper, diagnostics, syntax: node);
+                var spanMethod = GetWellKnownTypeMember(getItemOrSliceHelper, diagnostics, syntax: node);
+
+                if (spanMethod is { ContainingType: { Kind: SymbolKind.NamedType } spanType })
+                {
+                    spanType.Construct(ImmutableArray.Create(elementField.TypeWithAnnotations)).CheckConstraints(new ConstraintsHelper.CheckConstraintsArgs(this.Compilation, this.Conversions, node.GetLocation(), diagnostics));
+                }
+
+                if (!Compilation.Assembly.RuntimeSupportsInlineArrayTypes)
+                {
+                    Error(diagnostics, ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, node);
+                }
+
+                CheckFeatureAvailability(node, MessageID.IDS_FeatureInlineArrays, diagnostics);
+                diagnostics.ReportUseSite(elementField, node);
+
+                TypeSymbol resultType;
+
+                if (indexOrRangeWellknownType == WellKnownType.System_Range)
+                {
+                    // The symbols will be verified as return types of 'createSpanHelper', no need to check them again
+                    resultType = Compilation.GetWellKnownType(
+                        getItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int ? WellKnownType.System_ReadOnlySpan_T : WellKnownType.System_Span_T).
+                        Construct(ImmutableArray.Create(elementField.TypeWithAnnotations));
+                }
+                else
+                {
+                    resultType = elementField.Type;
+                }
+
+                return new BoundInlineArrayAccess(node, expr, convertedIndex, isValue, getItemOrSliceHelper, resultType);
+            }
+
+            static void checkInlineArrayBounds(SyntaxNode location, int index, int end, bool excludeEnd, BindingDiagnosticBag diagnostics)
+            {
+                if (index < 0 || (excludeEnd ? index >= end : index > end))
+                {
+                    Error(diagnostics, ErrorCode.ERR_InlineArrayIndexOutOfRange, location);
+                }
+            }
+
+            void checkInlineArrayBoundsForSystemIndex(BoundExpression convertedIndex, int length, bool excludeEnd, BindingDiagnosticBag diagnostics)
+            {
+                SyntaxNode location;
+                int? constIndex = InferConstantIndexFromSystemIndex(Compilation, convertedIndex, length, out location);
+
+                if (constIndex.HasValue)
+                {
+                    checkInlineArrayBounds(location, constIndex.GetValueOrDefault(), length, excludeEnd, diagnostics);
+                }
+            }
+        }
+
+        internal static int? InferConstantIndexFromSystemIndex(CSharpCompilation compilation, BoundExpression convertedIndex, int length, out SyntaxNode location)
+        {
+            int? constIndexOpt = null;
+            location = null;
+            if (TypeSymbol.Equals(convertedIndex.Type, compilation.GetWellKnownType(WellKnownType.System_Index), TypeCompareKind.AllIgnoreOptions))
+            {
+                if (convertedIndex is BoundFromEndIndexExpression hatExpression)
+                {
+                    // `^index`
+                    if (hatExpression.Operand.ConstantValueOpt is { SpecialType: SpecialType.System_Int32, Int32Value: int constIndex })
+                    {
+                        location = hatExpression.Syntax;
+                        constIndexOpt = length - constIndex;
+                    }
+                }
+                else if (convertedIndex is BoundConversion { Operand: { ConstantValueOpt: { SpecialType: SpecialType.System_Int32, Int32Value: int constIndex } } operand })
+                {
+                    location = operand.Syntax;
+                    constIndexOpt = constIndex;
+                }
+                else if (convertedIndex is BoundObjectCreationExpression { Constructor: MethodSymbol constructor, Arguments: { Length: 2 } arguments, ArgsToParamsOpt: { IsDefaultOrEmpty: true }, InitializerExpressionOpt: null } &&
+                         (object)constructor == compilation.GetWellKnownTypeMember(WellKnownMember.System_Index__ctor) &&
+                         arguments[0] is { ConstantValueOpt: { SpecialType: SpecialType.System_Int32, Int32Value: int constIndex1 } } index &&
+                         arguments[1] is { ConstantValueOpt: { SpecialType: SpecialType.System_Boolean, BooleanValue: bool isFromEnd } })
+                {
+                    location = index.Syntax;
+                    constIndexOpt = isFromEnd ? length - constIndex1 : constIndex1;
+                }
             }
 
-            return BindElementAccessCore(node, expr, analyzedArguments, diagnostics);
+            return constIndexOpt;
         }
 
         private BoundExpression BadIndexerExpression(SyntaxNode node, BoundExpression expr, AnalyzedArguments analyzedArguments, DiagnosticInfo errorOpt, BindingDiagnosticBag diagnostics)
@@ -9275,6 +9528,7 @@ private MethodGroupResolution ResolveDefaultMethodGroup(
                     returnRefKind,
                     returnType,
                     isFunctionPointerResolution,
+                    isExtensionMethodResolution: false,
                     callingConvention);
 
                 // Note: the MethodGroupResolution instance is responsible for freeing its copy of analyzed arguments
@@ -9644,7 +9898,7 @@ private BoundExpression BindElementBindingExpression(ElementBindingExpressionSyn
         {
             BoundExpression receiver = GetReceiverForConditionalBinding(node, diagnostics);
 
-            var memberAccess = BindElementAccess(node, receiver, node.ArgumentList, diagnostics);
+            var memberAccess = BindElementAccess(node, receiver, node.ArgumentList, allowInlineArrayElementAccess: true, diagnostics);
             return memberAccess;
         }
 
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_InterpolatedString.cs b/src/Compilers/CSharp/Portable/Binder/Binder_InterpolatedString.cs
index 59cf5bace1423..5b0e71ae2647c 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_InterpolatedString.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_InterpolatedString.cs
@@ -323,6 +323,7 @@ private bool TryBindUnconvertedBinaryOperatorToDefaultInterpolatedStringHandler(
                 // This is case 1. Let the standard machinery handle it
                 return false;
             }
+
             var partsArrayBuilder = ArrayBuilder<ImmutableArray<BoundExpression>>.GetInstance();
 
             if (!binaryOperator.VisitBinaryOperatorInterpolatedString(
@@ -344,26 +345,33 @@ private bool TryBindUnconvertedBinaryOperatorToDefaultInterpolatedStringHandler(
 
             Debug.Assert(partsArrayBuilder.Count >= 2);
 
-            if (partsArrayBuilder.Count <= 4 && partsArrayBuilder.All(static parts => AllInterpolatedStringPartsAreStrings(parts)))
+            int count = 0;
+
+            foreach (var parts in partsArrayBuilder)
             {
-                // This is case 2. Let the standard machinery handle it
-                partsArrayBuilder.Free();
-                return false;
+                count += parts.Length;
+                if (count > 4 || !AllInterpolatedStringPartsAreStrings(parts))
+                {
+                    // Case 3. Bind as handler.
+                    var (appendCalls, data) = BindUnconvertedInterpolatedPartsToHandlerType(
+                        binaryOperator.Syntax,
+                        partsArrayBuilder.ToImmutableAndFree(),
+                        interpolatedStringHandlerType,
+                        diagnostics,
+                        isHandlerConversion: false,
+                        additionalConstructorArguments: default,
+                        additionalConstructorRefKinds: default);
+
+                    // Now that the parts have been bound, reconstruct the binary operators.
+                    convertedBinaryOperator = UpdateBinaryOperatorWithInterpolatedContents(binaryOperator, appendCalls, data, binaryOperator.Syntax, diagnostics);
+                    return true;
+                }
             }
 
-            // Case 3. Bind as handler.
-            var (appendCalls, data) = BindUnconvertedInterpolatedPartsToHandlerType(
-                binaryOperator.Syntax,
-                partsArrayBuilder.ToImmutableAndFree(),
-                interpolatedStringHandlerType,
-                diagnostics,
-                isHandlerConversion: false,
-                additionalConstructorArguments: default,
-                additionalConstructorRefKinds: default);
-
-            // Now that the parts have been bound, reconstruct the binary operators.
-            convertedBinaryOperator = UpdateBinaryOperatorWithInterpolatedContents(binaryOperator, appendCalls, data, binaryOperator.Syntax, diagnostics);
-            return true;
+            // Case 2. Let the standard machinery handle it.
+            Debug.Assert(count <= 4);
+            partsArrayBuilder.Free();
+            return false;
         }
 
         private BoundBinaryOperator UpdateBinaryOperatorWithInterpolatedContents(BoundBinaryOperator originalOperator, ImmutableArray<ImmutableArray<BoundExpression>> appendCalls, InterpolatedStringHandlerData data, SyntaxNode rootSyntax, BindingDiagnosticBag diagnostics)
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Lookup.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Lookup.cs
index d3cbe2574fbca..f5d2c0995d061 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Lookup.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Lookup.cs
@@ -1336,7 +1336,7 @@ internal static ImmutableArray<Symbol> GetCandidateMembers(NamespaceOrTypeSymbol
 
         private bool IsInScopeOfAssociatedSyntaxTree(Symbol symbol)
         {
-            while (symbol is not null and not NamedTypeSymbol { AssociatedFileIdentifier: not null })
+            while (symbol is not null and not NamedTypeSymbol { IsFileLocal: true })
             {
                 symbol = symbol.ContainingType;
             }
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Symbols.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Symbols.cs
index dec3baa78de6e..12ffd218658da 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Symbols.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Symbols.cs
@@ -2480,7 +2480,7 @@ private BestSymbolInfo GetBestSymbolInfo(ArrayBuilder<Symbol> symbols, out BestS
 
         private static BestSymbolLocation GetLocation(CSharpCompilation compilation, Symbol symbol)
         {
-            if (symbol is SourceMemberContainerTypeSymbol { IsFileLocal: true })
+            if (symbol is NamedTypeSymbol { IsFileLocal: true })
             {
                 return BestSymbolLocation.FromFile;
             }
diff --git a/src/Compilers/CSharp/Portable/Binder/EmbeddedStatementBinder.cs b/src/Compilers/CSharp/Portable/Binder/EmbeddedStatementBinder.cs
index e1305e287f375..fe7d39ddd0ab5 100644
--- a/src/Compilers/CSharp/Portable/Binder/EmbeddedStatementBinder.cs
+++ b/src/Compilers/CSharp/Portable/Binder/EmbeddedStatementBinder.cs
@@ -30,7 +30,7 @@ public EmbeddedStatementBinder(Binder enclosing, StatementSyntax statement)
 
         protected override ImmutableArray<LocalSymbol> BuildLocals()
         {
-            ArrayBuilder<LocalSymbol> locals = ArrayBuilder<LocalSymbol>.GetInstance();
+            ArrayBuilder<LocalSymbol> locals = ArrayBuilder<LocalSymbol>.GetInstance(DefaultLocalSymbolArrayCapacity);
             BuildLocals(this, _statement, locals);
             return locals.ToImmutableAndFree();
         }
diff --git a/src/Compilers/CSharp/Portable/Binder/ForEachEnumeratorInfo.cs b/src/Compilers/CSharp/Portable/Binder/ForEachEnumeratorInfo.cs
index 17ddcc2cf25a1..c27c93cfabed9 100644
--- a/src/Compilers/CSharp/Portable/Binder/ForEachEnumeratorInfo.cs
+++ b/src/Compilers/CSharp/Portable/Binder/ForEachEnumeratorInfo.cs
@@ -15,6 +15,10 @@ internal sealed class ForEachEnumeratorInfo
     {
         // Types identified by the algorithm in the spec (8.8.4).
         public readonly TypeSymbol CollectionType;
+
+        public readonly WellKnownType InlineArraySpanType;
+        public readonly bool InlineArrayUsedAsValue;
+
         // public readonly TypeSymbol EnumeratorType; // redundant - return type of GetEnumeratorMethod
         public readonly TypeWithAnnotations ElementTypeWithAnnotations;
         public TypeSymbol ElementType => ElementTypeWithAnnotations.Type;
@@ -45,6 +49,8 @@ internal sealed class ForEachEnumeratorInfo
 
         private ForEachEnumeratorInfo(
             TypeSymbol collectionType,
+            WellKnownType inlineArraySpanType,
+            bool inlineArrayUsedAsValue,
             TypeWithAnnotations elementType,
             MethodArgumentInfo getEnumeratorInfo,
             MethodSymbol currentPropertyGetter,
@@ -63,8 +69,14 @@ private ForEachEnumeratorInfo(
             Debug.Assert((object)currentPropertyGetter != null, $"Field '{nameof(currentPropertyGetter)}' cannot be null");
             Debug.Assert((object)moveNextInfo != null, $"Field '{nameof(moveNextInfo)}' cannot be null");
             Debug.Assert(patternDisposeInfo == null || needsDisposal);
+            Debug.Assert(inlineArraySpanType is WellKnownType.Unknown or WellKnownType.System_Span_T or WellKnownType.System_ReadOnlySpan_T);
+            Debug.Assert(inlineArraySpanType == WellKnownType.Unknown ||
+                         (collectionType.HasInlineArrayAttribute(out _) && collectionType.TryGetInlineArrayElementField() is FieldSymbol elementField && elementType.Equals(elementField.TypeWithAnnotations, TypeCompareKind.ConsiderEverything)));
+            Debug.Assert(!inlineArrayUsedAsValue || inlineArraySpanType != WellKnownType.Unknown);
 
             this.CollectionType = collectionType;
+            this.InlineArraySpanType = inlineArraySpanType;
+            this.InlineArrayUsedAsValue = inlineArrayUsedAsValue;
             this.ElementTypeWithAnnotations = elementType;
             this.GetEnumeratorInfo = getEnumeratorInfo;
             this.CurrentPropertyGetter = currentPropertyGetter;
@@ -82,6 +94,9 @@ private ForEachEnumeratorInfo(
         internal struct Builder
         {
             public TypeSymbol CollectionType;
+            public bool ViaExtensionMethod;
+            public WellKnownType InlineArraySpanType;
+            public bool InlineArrayUsedAsValue;
             public TypeWithAnnotations ElementTypeWithAnnotations;
             public TypeSymbol ElementType => ElementTypeWithAnnotations.Type;
 
@@ -108,6 +123,8 @@ public ForEachEnumeratorInfo Build(BinderFlags location)
 
                 return new ForEachEnumeratorInfo(
                     CollectionType,
+                    InlineArraySpanType,
+                    InlineArrayUsedAsValue,
                     ElementTypeWithAnnotations,
                     GetEnumeratorInfo,
                     CurrentPropertyGetter,
diff --git a/src/Compilers/CSharp/Portable/Binder/ForEachLoopBinder.cs b/src/Compilers/CSharp/Portable/Binder/ForEachLoopBinder.cs
index 605d515b12955..55008d718ae1f 100644
--- a/src/Compilers/CSharp/Portable/Binder/ForEachLoopBinder.cs
+++ b/src/Compilers/CSharp/Portable/Binder/ForEachLoopBinder.cs
@@ -191,9 +191,8 @@ internal override BoundStatement BindForEachDeconstruction(BindingDiagnosticBag
             // Use the right binder to avoid seeing iteration variable
             BoundExpression collectionExpr = originalBinder.GetBinder(_syntax.Expression).BindRValueWithoutTargetType(_syntax.Expression, diagnostics);
 
-            var builder = new ForEachEnumeratorInfo.Builder();
             TypeWithAnnotations inferredType;
-            bool hasErrors = !GetEnumeratorInfoAndInferCollectionElementType(_syntax, _syntax.Expression, ref builder, ref collectionExpr, IsAsync, diagnostics, out inferredType);
+            bool hasErrors = !GetEnumeratorInfoAndInferCollectionElementType(_syntax, _syntax.Expression, ref collectionExpr, IsAsync, diagnostics, out inferredType, builder: out _);
 
             ExpressionSyntax variables = ((ForEachVariableStatementSyntax)_syntax).Variable;
 
@@ -224,9 +223,9 @@ private BoundForEachStatement BindForEachPartsWorker(BindingDiagnosticBag diagno
             // Use the right binder to avoid seeing iteration variable
             BoundExpression collectionExpr = originalBinder.GetBinder(_syntax.Expression).BindRValueWithoutTargetType(_syntax.Expression, diagnostics);
 
-            var builder = new ForEachEnumeratorInfo.Builder();
+            ForEachEnumeratorInfo.Builder builder;
             TypeWithAnnotations inferredType;
-            bool hasErrors = !GetEnumeratorInfoAndInferCollectionElementType(_syntax, _syntax.Expression, ref builder, ref collectionExpr, IsAsync, diagnostics, out inferredType);
+            bool hasErrors = !GetEnumeratorInfoAndInferCollectionElementType(_syntax, _syntax.Expression, ref collectionExpr, IsAsync, diagnostics, out inferredType, out builder);
 
             // These occur when special types are missing or malformed, or the patterns are incompletely implemented.
             hasErrors |= builder.IsIncomplete;
@@ -347,13 +346,20 @@ private BoundForEachStatement BindForEachPartsWorker(BindingDiagnosticBag diagno
                                     throw ExceptionUtilities.UnexpectedValue(local.RefKind);
                             }
 
-                            hasErrors |= !CheckMethodReturnValueKind(
-                                builder.CurrentPropertyGetter,
-                                callSyntaxOpt: null,
-                                collectionExpr.Syntax,
-                                requiredCurrentKind,
-                                checkingReceiver: false,
-                                diagnostics);
+                            if (builder.InlineArraySpanType == WellKnownType.Unknown)
+                            {
+                                hasErrors |= !CheckMethodReturnValueKind(
+                                    builder.CurrentPropertyGetter,
+                                    callSyntaxOpt: null,
+                                    collectionExpr.Syntax,
+                                    requiredCurrentKind,
+                                    checkingReceiver: false,
+                                    diagnostics);
+                            }
+                            else
+                            {
+                                hasErrors |= !CheckValueKind(collectionExpr.Syntax, collectionExpr, requiredCurrentKind, checkingReceiver: false, diagnostics);
+                            }
                         }
 
                         break;
@@ -519,7 +525,7 @@ private BoundForEachStatement BindForEachPartsWorker(BindingDiagnosticBag diagno
 
             TypeSymbol getEnumeratorType = getEnumeratorMethod.ReturnType;
 
-            if (getEnumeratorType.IsRestrictedType() && (IsDirectlyInIterator || IsInAsyncMethod()))
+            if (builder.InlineArraySpanType == WellKnownType.Unknown && getEnumeratorType.IsRestrictedType() && (IsDirectlyInIterator || IsInAsyncMethod()))
             {
                 diagnostics.Add(ErrorCode.ERR_BadSpecialByRefIterator, foreachKeyword.GetLocation(), getEnumeratorType);
             }
@@ -604,8 +610,7 @@ internal TypeWithAnnotations InferCollectionElementType(BindingDiagnosticBag dia
             // Use the right binder to avoid seeing iteration variable
             BoundExpression collectionExpr = this.GetBinder(collectionSyntax).BindValue(collectionSyntax, diagnostics, BindValueKind.RValue);
 
-            var builder = new ForEachEnumeratorInfo.Builder();
-            GetEnumeratorInfoAndInferCollectionElementType(_syntax, collectionSyntax, ref builder, ref collectionExpr, IsAsync, diagnostics, out TypeWithAnnotations inferredType);
+            GetEnumeratorInfoAndInferCollectionElementType(_syntax, collectionSyntax, ref collectionExpr, IsAsync, diagnostics, out TypeWithAnnotations inferredType, builder: out _);
             return inferredType;
         }
     }
@@ -654,12 +659,13 @@ protected BoundExpression ConvertForEachCollection(
         internal bool GetEnumeratorInfoAndInferCollectionElementType(
             SyntaxNode syntax,
             ExpressionSyntax collectionSyntax,
-            ref ForEachEnumeratorInfo.Builder builder,
-            ref BoundExpression collectionExpr, bool isAsync,
+            ref BoundExpression collectionExpr,
+            bool isAsync,
             BindingDiagnosticBag diagnostics,
-            out TypeWithAnnotations inferredType)
+            out TypeWithAnnotations inferredType,
+            out ForEachEnumeratorInfo.Builder builder)
         {
-            bool gotInfo = GetEnumeratorInfo(syntax, collectionSyntax, ref builder, ref collectionExpr, isAsync, diagnostics);
+            bool gotInfo = GetEnumeratorInfo(syntax, collectionSyntax, ref collectionExpr, isAsync, diagnostics, out builder);
 
             if (!gotInfo)
             {
@@ -742,11 +748,11 @@ private BoundExpression UnwrapCollectionExpressionIfNullable(BoundExpression col
         /// <param name="collectionExpr">The expression over which to iterate.</param>
         /// <param name="diagnostics">Populated with binding diagnostics.</param>
         /// <returns>Partially populated (all but conversions) or null if there was an error.</returns>
-        private bool GetEnumeratorInfo(SyntaxNode syntax, ExpressionSyntax collectionSyntax, ref ForEachEnumeratorInfo.Builder builder, ref BoundExpression collectionExpr, bool isAsync, BindingDiagnosticBag diagnostics)
+        private bool GetEnumeratorInfo(SyntaxNode syntax, ExpressionSyntax collectionSyntax, ref BoundExpression collectionExpr, bool isAsync, BindingDiagnosticBag diagnostics, out ForEachEnumeratorInfo.Builder builder)
         {
-            builder.IsAsync = isAsync;
+            BoundExpression originalCollectionExpr = collectionExpr;
 
-            EnumeratorResult found = GetEnumeratorInfoCore(syntax, collectionSyntax, ref builder, ref collectionExpr, isAsync, diagnostics);
+            EnumeratorResult found = GetEnumeratorInfoCore(syntax, collectionSyntax, ref collectionExpr, isAsync, diagnostics, out builder);
             switch (found)
             {
                 case EnumeratorResult.Succeeded:
@@ -767,8 +773,7 @@ private bool GetEnumeratorInfo(SyntaxNode syntax, ExpressionSyntax collectionSyn
             }
 
             // Retry with a different assumption about whether the foreach is async
-            var ignoredBuilder = new ForEachEnumeratorInfo.Builder();
-            bool wrongAsync = GetEnumeratorInfoCore(syntax, collectionSyntax, ref ignoredBuilder, ref collectionExpr, !isAsync, BindingDiagnosticBag.Discarded) == EnumeratorResult.Succeeded;
+            bool wrongAsync = GetEnumeratorInfoCore(syntax, collectionSyntax, ref originalCollectionExpr, !isAsync, BindingDiagnosticBag.Discarded, builder: out _) == EnumeratorResult.Succeeded;
 
             var errorCode = wrongAsync
                 ? (isAsync ? ErrorCode.ERR_AwaitForEachMissingMemberWrongAsync : ErrorCode.ERR_ForEachMissingMemberWrongAsync)
@@ -786,103 +791,197 @@ private enum EnumeratorResult
             FailedAndReported
         }
 
-        private EnumeratorResult GetEnumeratorInfoCore(SyntaxNode syntax, ExpressionSyntax collectionSyntax, ref ForEachEnumeratorInfo.Builder builder, ref BoundExpression collectionExpr, bool isAsync, BindingDiagnosticBag diagnostics)
+        private EnumeratorResult GetEnumeratorInfoCore(SyntaxNode syntax, ExpressionSyntax collectionSyntax, ref BoundExpression collectionExpr, bool isAsync, BindingDiagnosticBag diagnostics, out ForEachEnumeratorInfo.Builder builder)
         {
-            TypeSymbol collectionExprType = collectionExpr.Type;
+            EnumeratorResult result;
 
-            if (collectionExprType is null) // There's no way to enumerate something without a type.
+            if (!isAsync && collectionExpr.Type?.HasInlineArrayAttribute(out _) == true && collectionExpr.Type.TryGetInlineArrayElementField() is FieldSymbol elementField)
             {
-                if (!ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                WellKnownType wellKnownSpan;
+                bool usedAsValue = false;
+
+                if (CheckValueKind(collectionExpr.Syntax, collectionExpr, BindValueKind.RefersToLocation | BindValueKind.Assignable, checkingReceiver: false, BindingDiagnosticBag.Discarded))
                 {
-                    // Anything else with a null type is a method group or anonymous function
-                    diagnostics.Add(ErrorCode.ERR_AnonMethGrpInForEach, collectionSyntax.Location, collectionExpr.Display);
+                    wellKnownSpan = WellKnownType.System_Span_T;
                 }
+                else
+                {
+                    wellKnownSpan = WellKnownType.System_ReadOnlySpan_T;
 
-                // CONSIDER: dev10 also reports ERR_ForEachMissingMember (i.e. failed pattern match).
-                return EnumeratorResult.FailedAndReported;
-            }
+                    if (!CheckValueKind(collectionExpr.Syntax, collectionExpr, BindValueKind.RefersToLocation, checkingReceiver: false, BindingDiagnosticBag.Discarded))
+                    {
+                        usedAsValue = true;
+                    }
+                }
 
-            if (collectionExpr.ResultKind == LookupResultKind.NotAValue)
-            {
-                // Short-circuiting to prevent strange behavior in the case where the collection
-                // expression is a type expression and the type is enumerable.
-                Debug.Assert(collectionExpr.HasAnyErrors); // should already have been reported
-                return EnumeratorResult.FailedAndReported;
-            }
+                NamedTypeSymbol spanType = GetWellKnownType(wellKnownSpan, diagnostics, collectionExpr.Syntax);
 
-            if (collectionExprType.Kind == SymbolKind.DynamicType && isAsync)
-            {
-                diagnostics.Add(ErrorCode.ERR_BadDynamicAwaitForEach, collectionSyntax.Location);
-                return EnumeratorResult.FailedAndReported;
+                if (spanType.IsErrorType())
+                {
+                    builder = new ForEachEnumeratorInfo.Builder();
+                    return EnumeratorResult.FailedAndReported;
+                }
+
+                spanType = spanType.Construct(ImmutableArray.Create(elementField.TypeWithAnnotations));
+                spanType.CheckConstraints(new ConstraintsHelper.CheckConstraintsArgs(this.Compilation, this.Conversions, collectionExpr.Syntax.GetLocation(), diagnostics));
+
+                var enumeratorInfoDiagnostics = BindingDiagnosticBag.GetInstance(diagnostics);
+                BoundExpression span = new BoundValuePlaceholder(collectionExpr.Syntax, spanType).MakeCompilerGenerated();
+#if DEBUG
+                var originalSpan = span;
+#endif
+
+                result = getEnumeratorInfo(syntax, collectionSyntax, ref span, isAsync: false, enumeratorInfoDiagnostics, out builder);
+
+#if DEBUG
+                Debug.Assert(span == originalSpan);
+                Debug.Assert(!builder.ViaExtensionMethod || builder.GetEnumeratorInfo.Method.IsExtensionMethod);
+#endif
+                if (!builder.ViaExtensionMethod &&
+                    ((result is EnumeratorResult.Succeeded && builder.ElementTypeWithAnnotations.Equals(elementField.TypeWithAnnotations, TypeCompareKind.AllIgnoreOptions) &&
+                      builder.CurrentPropertyGetter?.RefKind == (wellKnownSpan == WellKnownType.System_ReadOnlySpan_T ? RefKind.RefReadOnly : RefKind.Ref)) ||
+                     result is EnumeratorResult.FailedAndReported))
+                {
+                    Debug.Assert(builder.CollectionType == (object)spanType);
+                    builder.CollectionType = collectionExpr.Type;
+                    builder.InlineArraySpanType = wellKnownSpan;
+                    builder.InlineArrayUsedAsValue = usedAsValue;
+                    diagnostics.AddRangeAndFree(enumeratorInfoDiagnostics);
+
+                    CheckFeatureAvailability(collectionExpr.Syntax, MessageID.IDS_FeatureInlineArrays, diagnostics);
+
+                    if (result == EnumeratorResult.Succeeded)
+                    {
+                        if (wellKnownSpan == WellKnownType.System_ReadOnlySpan_T)
+                        {
+                            _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T, diagnostics, syntax: collectionExpr.Syntax);
+                        }
+
+                        _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T, diagnostics, syntax: collectionExpr.Syntax);
+                        _ = GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T, diagnostics, syntax: collectionExpr.Syntax);
+                    }
+
+                    return result;
+                }
+
+                enumeratorInfoDiagnostics.Free();
             }
 
-            // The spec specifically lists the collection, enumerator, and element types for arrays and dynamic.
-            if (collectionExprType.Kind == SymbolKind.ArrayType || collectionExprType.Kind == SymbolKind.DynamicType)
+#if DEBUG
+            var originalCollectionExpr = collectionExpr;
+#endif
+
+            result = getEnumeratorInfo(syntax, collectionSyntax, ref collectionExpr, isAsync, diagnostics, out builder);
+
+#if DEBUG
+            Debug.Assert(collectionExpr == originalCollectionExpr ||
+                         (originalCollectionExpr.Type?.IsNullableType() == true && originalCollectionExpr.Type.StrippedType().Equals(collectionExpr.Type, TypeCompareKind.AllIgnoreOptions)));
+            Debug.Assert(!builder.ViaExtensionMethod || builder.GetEnumeratorInfo.Method.IsExtensionMethod);
+#endif
+
+            return result;
+
+            EnumeratorResult getEnumeratorInfo(SyntaxNode syntax, ExpressionSyntax collectionSyntax, ref BoundExpression collectionExpr, bool isAsync, BindingDiagnosticBag diagnostics, out ForEachEnumeratorInfo.Builder builder)
             {
-                if (ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                builder = new ForEachEnumeratorInfo.Builder();
+                builder.IsAsync = isAsync;
+
+                TypeSymbol collectionExprType = collectionExpr.Type;
+
+                if (collectionExprType is null) // There's no way to enumerate something without a type.
                 {
+                    if (!ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                    {
+                        // Anything else with a null type is a method group or anonymous function
+                        diagnostics.Add(ErrorCode.ERR_AnonMethGrpInForEach, collectionSyntax.Location, collectionExpr.Display);
+                    }
+
+                    // CONSIDER: dev10 also reports ERR_ForEachMissingMember (i.e. failed pattern match).
                     return EnumeratorResult.FailedAndReported;
                 }
-                builder = GetDefaultEnumeratorInfo(syntax, builder, diagnostics, collectionExprType);
-                return EnumeratorResult.Succeeded;
-            }
 
-            var unwrappedCollectionExpr = UnwrapCollectionExpressionIfNullable(collectionExpr, diagnostics);
-            var unwrappedCollectionExprType = unwrappedCollectionExpr.Type;
+                if (collectionExpr.ResultKind == LookupResultKind.NotAValue)
+                {
+                    // Short-circuiting to prevent strange behavior in the case where the collection
+                    // expression is a type expression and the type is enumerable.
+                    Debug.Assert(collectionExpr.HasAnyErrors); // should already have been reported
+                    return EnumeratorResult.FailedAndReported;
+                }
 
-            if (SatisfiesGetEnumeratorPattern(syntax, collectionSyntax, ref builder, unwrappedCollectionExpr, isAsync, viaExtensionMethod: false, diagnostics))
-            {
-                collectionExpr = unwrappedCollectionExpr;
-                if (ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                if (collectionExprType.Kind == SymbolKind.DynamicType && isAsync)
                 {
+                    diagnostics.Add(ErrorCode.ERR_BadDynamicAwaitForEach, collectionSyntax.Location);
                     return EnumeratorResult.FailedAndReported;
                 }
-                return createPatternBasedEnumeratorResult(ref builder, unwrappedCollectionExpr, isAsync, viaExtensionMethod: false, diagnostics);
-            }
 
-            if (!isAsync && IsIEnumerable(unwrappedCollectionExprType))
-            {
-                collectionExpr = unwrappedCollectionExpr;
-                // This indicates a problem with the special IEnumerable type - it should have satisfied the GetEnumerator pattern.
-                diagnostics.Add(ErrorCode.ERR_ForEachMissingMember, collectionSyntax.Location, unwrappedCollectionExprType, WellKnownMemberNames.GetEnumeratorMethodName);
-                return EnumeratorResult.FailedAndReported;
-            }
-            if (isAsync && IsIAsyncEnumerable(unwrappedCollectionExprType))
-            {
-                collectionExpr = unwrappedCollectionExpr;
-                // This indicates a problem with the well-known IAsyncEnumerable type - it should have satisfied the GetAsyncEnumerator pattern.
-                diagnostics.Add(ErrorCode.ERR_AwaitForEachMissingMember, collectionSyntax.Location, unwrappedCollectionExprType, WellKnownMemberNames.GetAsyncEnumeratorMethodName);
-                return EnumeratorResult.FailedAndReported;
-            }
+                // The spec specifically lists the collection, enumerator, and element types for arrays and dynamic.
+                if (collectionExprType.Kind == SymbolKind.ArrayType || collectionExprType.Kind == SymbolKind.DynamicType)
+                {
+                    if (ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                    {
+                        return EnumeratorResult.FailedAndReported;
+                    }
+                    builder = GetDefaultEnumeratorInfo(syntax, builder, diagnostics, collectionExprType);
+                    return EnumeratorResult.Succeeded;
+                }
 
-            if (SatisfiesIEnumerableInterfaces(collectionSyntax, ref builder, unwrappedCollectionExpr, isAsync, diagnostics, unwrappedCollectionExprType) is not EnumeratorResult.FailedNotReported and var result)
-            {
-                collectionExpr = unwrappedCollectionExpr;
-                return result;
-            }
+                var unwrappedCollectionExpr = UnwrapCollectionExpressionIfNullable(collectionExpr, diagnostics);
+                var unwrappedCollectionExprType = unwrappedCollectionExpr.Type;
 
-            // COMPAT:
-            // In some rare cases, like MicroFramework, System.String does not implement foreach pattern.
-            // For compat reasons we must still treat System.String as valid to use in a foreach
-            // Similarly to the cases with array and dynamic, we will default to IEnumerable for binding purposes.
-            // Lowering will not use iterator info with strings, so it is ok.
-            if (!isAsync && collectionExprType.SpecialType == SpecialType.System_String)
-            {
-                if (ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                if (SatisfiesGetEnumeratorPattern(syntax, collectionSyntax, ref builder, unwrappedCollectionExpr, isAsync, viaExtensionMethod: false, diagnostics))
+                {
+                    collectionExpr = unwrappedCollectionExpr;
+                    if (ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                    {
+                        return EnumeratorResult.FailedAndReported;
+                    }
+                    return createPatternBasedEnumeratorResult(ref builder, unwrappedCollectionExpr, isAsync, viaExtensionMethod: false, diagnostics);
+                }
+
+                if (!isAsync && IsIEnumerable(unwrappedCollectionExprType))
+                {
+                    collectionExpr = unwrappedCollectionExpr;
+                    // This indicates a problem with the special IEnumerable type - it should have satisfied the GetEnumerator pattern.
+                    diagnostics.Add(ErrorCode.ERR_ForEachMissingMember, collectionSyntax.Location, unwrappedCollectionExprType, WellKnownMemberNames.GetEnumeratorMethodName);
+                    return EnumeratorResult.FailedAndReported;
+                }
+                if (isAsync && IsIAsyncEnumerable(unwrappedCollectionExprType))
                 {
+                    collectionExpr = unwrappedCollectionExpr;
+                    // This indicates a problem with the well-known IAsyncEnumerable type - it should have satisfied the GetAsyncEnumerator pattern.
+                    diagnostics.Add(ErrorCode.ERR_AwaitForEachMissingMember, collectionSyntax.Location, unwrappedCollectionExprType, WellKnownMemberNames.GetAsyncEnumeratorMethodName);
                     return EnumeratorResult.FailedAndReported;
                 }
 
-                builder = GetDefaultEnumeratorInfo(syntax, builder, diagnostics, collectionExprType);
-                return EnumeratorResult.Succeeded;
-            }
+                if (SatisfiesIEnumerableInterfaces(collectionSyntax, ref builder, unwrappedCollectionExpr, isAsync, diagnostics, unwrappedCollectionExprType) is not EnumeratorResult.FailedNotReported and var result)
+                {
+                    collectionExpr = unwrappedCollectionExpr;
+                    return result;
+                }
 
-            if (SatisfiesGetEnumeratorPattern(syntax, collectionSyntax, ref builder, collectionExpr, isAsync, viaExtensionMethod: true, diagnostics))
-            {
-                return createPatternBasedEnumeratorResult(ref builder, collectionExpr, isAsync, viaExtensionMethod: true, diagnostics);
-            }
+                // COMPAT:
+                // In some rare cases, like MicroFramework, System.String does not implement foreach pattern.
+                // For compat reasons we must still treat System.String as valid to use in a foreach
+                // Similarly to the cases with array and dynamic, we will default to IEnumerable for binding purposes.
+                // Lowering will not use iterator info with strings, so it is ok.
+                if (!isAsync && collectionExprType.SpecialType == SpecialType.System_String)
+                {
+                    if (ReportConstantNullCollectionExpr(collectionExpr, diagnostics))
+                    {
+                        return EnumeratorResult.FailedAndReported;
+                    }
+
+                    builder = GetDefaultEnumeratorInfo(syntax, builder, diagnostics, collectionExprType);
+                    return EnumeratorResult.Succeeded;
+                }
 
-            return EnumeratorResult.FailedNotReported;
+                if (SatisfiesGetEnumeratorPattern(syntax, collectionSyntax, ref builder, collectionExpr, isAsync, viaExtensionMethod: true, diagnostics))
+                {
+                    return createPatternBasedEnumeratorResult(ref builder, collectionExpr, isAsync, viaExtensionMethod: true, diagnostics);
+                }
+
+                return EnumeratorResult.FailedNotReported;
+            }
 
             EnumeratorResult createPatternBasedEnumeratorResult(ref ForEachEnumeratorInfo.Builder builder, BoundExpression collectionExpr, bool isAsync, bool viaExtensionMethod, BindingDiagnosticBag diagnostics)
             {
@@ -890,6 +989,7 @@ EnumeratorResult createPatternBasedEnumeratorResult(ref ForEachEnumeratorInfo.Bu
 
                 Debug.Assert(!(viaExtensionMethod && builder.GetEnumeratorInfo.Method.Parameters.IsDefaultOrEmpty));
 
+                builder.ViaExtensionMethod = viaExtensionMethod;
                 builder.CollectionType = viaExtensionMethod
                     ? builder.GetEnumeratorInfo.Method.Parameters[0].Type
                     : collectionExpr.Type;
diff --git a/src/Compilers/CSharp/Portable/Binder/LocalScopeBinder.cs b/src/Compilers/CSharp/Portable/Binder/LocalScopeBinder.cs
index 713edcfa30a66..50e1d7af388c9 100644
--- a/src/Compilers/CSharp/Portable/Binder/LocalScopeBinder.cs
+++ b/src/Compilers/CSharp/Portable/Binder/LocalScopeBinder.cs
@@ -15,6 +15,8 @@ namespace Microsoft.CodeAnalysis.CSharp
 {
     internal partial class LocalScopeBinder : Binder
     {
+        protected const int DefaultLocalSymbolArrayCapacity = 16;
+
         private ImmutableArray<LocalSymbol> _locals;
         private ImmutableArray<LocalFunctionSymbol> _localFunctions;
         private ImmutableArray<LabelSymbol> _labels;
@@ -158,7 +160,7 @@ protected ImmutableArray<LocalSymbol> BuildLocals(SyntaxList<StatementSyntax> st
             }
 #endif
 
-            ArrayBuilder<LocalSymbol> locals = ArrayBuilder<LocalSymbol>.GetInstance();
+            ArrayBuilder<LocalSymbol> locals = ArrayBuilder<LocalSymbol>.GetInstance(DefaultLocalSymbolArrayCapacity);
             foreach (var statement in statements)
             {
                 BuildLocals(enclosingBinder, statement, locals);
diff --git a/src/Compilers/CSharp/Portable/Binder/RefSafetyAnalysis.cs b/src/Compilers/CSharp/Portable/Binder/RefSafetyAnalysis.cs
index ecc9203df16c1..550426a3eddbd 100644
--- a/src/Compilers/CSharp/Portable/Binder/RefSafetyAnalysis.cs
+++ b/src/Compilers/CSharp/Portable/Binder/RefSafetyAnalysis.cs
@@ -15,7 +15,7 @@ namespace Microsoft.CodeAnalysis.CSharp
 {
     internal sealed partial class RefSafetyAnalysis : BoundTreeWalkerWithStackGuardWithoutRecursionOnTheLeftOfBinaryOperator
     {
-        internal static void Analyze(CSharpCompilation compilation, Symbol symbol, BoundNode node, BindingDiagnosticBag diagnostics)
+        internal static void Analyze(CSharpCompilation compilation, MethodSymbol symbol, BoundNode node, BindingDiagnosticBag diagnostics)
         {
             var visitor = new RefSafetyAnalysis(
                 compilation,
@@ -33,7 +33,7 @@ internal static void Analyze(CSharpCompilation compilation, Symbol symbol, Bound
             }
         }
 
-        internal static void Analyze(CSharpCompilation compilation, Symbol symbol, ImmutableArray<BoundInitializer> fieldAndPropertyInitializers, BindingDiagnosticBag diagnostics)
+        internal static void Analyze(CSharpCompilation compilation, MethodSymbol symbol, ImmutableArray<BoundInitializer> fieldAndPropertyInitializers, BindingDiagnosticBag diagnostics)
         {
             var visitor = new RefSafetyAnalysis(
                 compilation,
@@ -76,7 +76,7 @@ private static bool InUnsafeMethod(Symbol symbol)
         }
 
         private readonly CSharpCompilation _compilation;
-        private readonly Symbol _symbol;
+        private readonly MethodSymbol _symbol;
         private readonly bool _useUpdatedEscapeRules;
         private readonly BindingDiagnosticBag _diagnostics;
         private bool _inUnsafeRegion;
@@ -91,7 +91,7 @@ private static bool InUnsafeMethod(Symbol symbol)
 
         private RefSafetyAnalysis(
             CSharpCompilation compilation,
-            Symbol symbol,
+            MethodSymbol symbol,
             bool inUnsafeRegion,
             bool useUpdatedEscapeRules,
             BindingDiagnosticBag diagnostics,
@@ -995,7 +995,34 @@ private static ImmutableArray<BoundExpression> GetDeconstructionRightParts(Bound
         public override BoundNode? VisitForEachStatement(BoundForEachStatement node)
         {
             this.Visit(node.Expression);
-            uint collectionEscape = GetValEscape(node.Expression, _localScopeDepth);
+            uint collectionEscape;
+
+            if (node.EnumeratorInfoOpt is { InlineArraySpanType: not WellKnownType.Unknown and var spanType, InlineArrayUsedAsValue: false })
+            {
+                ImmutableArray<BoundExpression> arguments;
+                ImmutableArray<RefKind> refKinds;
+
+                SignatureOnlyMethodSymbol equivalentSignatureMethod = GetInlineArrayConversionEquivalentSignatureMethod(
+                    // Strip identity conversion added by compiler on top of inline array.
+                    inlineArray: node.Expression is not BoundConversion { Conversion.IsIdentity: true, ExplicitCastInCode: false, Operand: BoundExpression operand } ? node.Expression : operand,
+                    resultType: node.EnumeratorInfoOpt.GetEnumeratorInfo.Method.ContainingType,
+                    out arguments, out refKinds);
+
+                collectionEscape = GetInvocationEscapeScope(
+                    equivalentSignatureMethod,
+                    receiver: null,
+                    equivalentSignatureMethod.Parameters,
+                    arguments,
+                    refKinds,
+                    argsToParamsOpt: default,
+                    _localScopeDepth,
+                    isRefEscape: false);
+            }
+            else
+            {
+                collectionEscape = GetValEscape(node.Expression, _localScopeDepth);
+            }
+
             using var _ = new LocalScope(this, ImmutableArray<LocalSymbol>.Empty);
 
             foreach (var local in node.IterationVariables)
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversion.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversion.cs
index c6655ed853672..9046015a3a0a7 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversion.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversion.cs
@@ -214,6 +214,7 @@ private static void AssertTrivialConversion(ConversionKind kind)
                 case ConversionKind.ExplicitDynamic:
                 case ConversionKind.InterpolatedString:
                 case ConversionKind.InterpolatedStringHandler:
+                case ConversionKind.InlineArray:
                     isTrivial = true;
                     break;
 
@@ -263,6 +264,7 @@ internal static Conversion GetTrivialConversion(ConversionKind kind)
         internal static Conversion PinnedObjectToPointer => new Conversion(ConversionKind.PinnedObjectToPointer);
         internal static Conversion ImplicitPointer => new Conversion(ConversionKind.ImplicitPointer);
         internal static Conversion FunctionType => new Conversion(ConversionKind.FunctionType);
+        internal static Conversion InlineArray => new Conversion(ConversionKind.InlineArray);
 
         // trivial conversions that could be underlying in nullable conversion
         // NOTE: tuple conversions can be underlying as well, but they are not trivial 
@@ -390,14 +392,22 @@ internal void AssertUnderlyingConversionsCheckedRecursive()
                     underlying.AssertUnderlyingConversionsCheckedRecursive();
                 }
             }
+
+            if (IsUserDefined)
+            {
+                UserDefinedFromConversion.AssertUnderlyingConversionsCheckedRecursive();
+                UserDefinedToConversion.AssertUnderlyingConversionsCheckedRecursive();
+            }
         }
 
         [Conditional("DEBUG")]
         internal void MarkUnderlyingConversionsChecked()
         {
 #if DEBUG
-            Debug.Assert(_uncommonData is not null);
-            _uncommonData._nestedConversionsChecked = true;
+            if (_uncommonData is not null)
+            {
+                _uncommonData._nestedConversionsChecked = true;
+            }
 #endif
         }
 
@@ -418,6 +428,12 @@ internal void MarkUnderlyingConversionsCheckedRecursive()
                         underlying.MarkUnderlyingConversionsCheckedRecursive();
                     }
                 }
+
+                if (IsUserDefined)
+                {
+                    UserDefinedFromConversion.MarkUnderlyingConversionsCheckedRecursive();
+                    UserDefinedToConversion.MarkUnderlyingConversionsCheckedRecursive();
+                }
             }
 #endif
         }
@@ -692,6 +708,17 @@ public bool IsInterpolatedStringHandler
             }
         }
 
+        /// <summary>
+        /// Returns true if the conversion is an inline array conversion.
+        /// </summary>
+        public bool IsInlineArray
+        {
+            get
+            {
+                return Kind == ConversionKind.InlineArray;
+            }
+        }
+
         /// <summary>
         /// Returns true if the conversion is an implicit nullable conversion or explicit nullable conversion.
         /// </summary>
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKind.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKind.cs
index 499878083c7a5..47af64956263d 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKind.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKind.cs
@@ -66,5 +66,7 @@ internal enum ConversionKind : byte
         CollectionLiteral, // a conversion from a collection literal to any type
 
         InterpolatedStringHandler, // A conversion from an interpolated string literal to a type attributed with InterpolatedStringBuilderAttribute
+
+        InlineArray, // A conversion from an inline array to Span/ReadOnlySpan
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKindExtensions.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKindExtensions.cs
index ed3e5f029b635..d77d417df2edc 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKindExtensions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionKindExtensions.cs
@@ -51,6 +51,7 @@ public static bool IsImplicitConversion(this ConversionKind conversionKind)
                 case StackAllocToSpanType:
                 case ImplicitPointer:
                 case ObjectCreation:
+                case InlineArray:
                 case CollectionLiteral:
                     return true;
 
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversions.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversions.cs
index 91deb69e37352..64c5ee4452e5d 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/Conversions.cs
@@ -423,5 +423,9 @@ public override Conversion GetStackAllocConversion(BoundStackAllocArrayCreation
         {
             return (Conversions)base.WithNullability(includeNullability);
         }
+
+        protected override bool IsAttributeArgumentBinding => _binder.InAttributeArgument;
+
+        protected override bool IsParameterDefaultValueBinding => _binder.InParameterDefaultValue;
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs
index 056f6dc496c81..7bd3305b84936 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs
@@ -73,6 +73,10 @@ internal ConversionsBase WithNullability(bool includeNullability)
 
         protected abstract Conversion GetInterpolatedStringConversion(BoundExpression source, TypeSymbol destination, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo);
 
+        protected abstract bool IsAttributeArgumentBinding { get; }
+
+        protected abstract bool IsParameterDefaultValueBinding { get; }
+
         internal AssemblySymbol CorLibrary { get { return corLibrary; } }
 
 #nullable enable
@@ -592,6 +596,7 @@ private static bool IsStandardImplicitConversionFromExpression(ConversionKind ki
                 case ConversionKind.ImplicitTupleLiteral:
                 case ConversionKind.StackAllocToPointerType:
                 case ConversionKind.StackAllocToSpanType:
+                case ConversionKind.InlineArray:
                     return true;
                 default:
                     return false;
@@ -1105,6 +1110,17 @@ private Conversion ClassifyImplicitBuiltInConversionFromExpression(BoundExpressi
                     break;
             }
 
+            // Neither Span<T>, nor ReadOnlySpan<T> can be wrapped into a Nullable<T>, therefore, there is no point to check for an attempt to convert to Nullable types here. 
+            if (!IsAttributeArgumentBinding && !IsParameterDefaultValueBinding && // These checks prevent cycles caused by attribute binding when HasInlineArrayAttribute check triggers that.
+                source?.HasInlineArrayAttribute(out _) == true &&
+                source.TryGetInlineArrayElementField() is { TypeWithAnnotations: var elementType } &&
+                (destination.OriginalDefinition.Equals(Compilation.GetWellKnownType(WellKnownType.System_Span_T), TypeCompareKind.AllIgnoreOptions) ||
+                 destination.OriginalDefinition.Equals(Compilation.GetWellKnownType(WellKnownType.System_ReadOnlySpan_T), TypeCompareKind.AllIgnoreOptions)) &&
+                HasIdentityConversionInternal(((NamedTypeSymbol)destination.OriginalDefinition).Construct(ImmutableArray.Create(elementType)), destination))
+            {
+                return Conversion.InlineArray;
+            }
+
             return Conversion.NoConversion;
         }
 
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/TypeConversions.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/TypeConversions.cs
index 9af64b2054d6d..307fdacbf1f24 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/TypeConversions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/TypeConversions.cs
@@ -60,5 +60,9 @@ protected override Conversion GetInterpolatedStringConversion(BoundExpression so
         }
 
         protected override CSharpCompilation Compilation => null;
+
+        protected override bool IsAttributeArgumentBinding => false;
+
+        protected override bool IsParameterDefaultValueBinding => false;
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/UserDefinedImplicitConversions.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/UserDefinedImplicitConversions.cs
index acae729c7309c..06f7ae0686a9b 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/UserDefinedImplicitConversions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/UserDefinedImplicitConversions.cs
@@ -664,6 +664,8 @@ private static bool IsEncompassingImplicitConversionKind(ConversionKind kind)
 
                 // Added for C# 9
                 case ConversionKind.ImplicitPointer:
+                // Added for C# 12
+                case ConversionKind.InlineArray:
                     return true;
 
                 default:
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/MethodTypeInference.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/MethodTypeInference.cs
index f0a02acebfd25..c68253bbc418d 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/MethodTypeInference.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/MethodTypeInference.cs
@@ -662,16 +662,15 @@ private void MakeCollectionLiteralTypeInferences(
 
         private static bool TryGetCollectionIterationType(Binder binder, ExpressionSyntax syntax, TypeSymbol collectionType, out TypeWithAnnotations iterationType)
         {
-            var builder = new ForEachEnumeratorInfo.Builder();
             BoundExpression collectionExpr = new BoundValuePlaceholder(syntax, collectionType);
             return binder.GetEnumeratorInfoAndInferCollectionElementType(
                 syntax,
                 syntax,
-                ref builder,
                 ref collectionExpr,
                 isAsync: false,
                 BindingDiagnosticBag.Discarded,
-                out iterationType);
+                out iterationType,
+                builder: out _);
         }
 #nullable disable
 
diff --git a/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs b/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
index 0c694247f1f9e..7db9441f15d1a 100644
--- a/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
@@ -128,12 +128,14 @@ public void MethodInvocationOverloadResolution(
             RefKind returnRefKind = default,
             TypeSymbol returnType = null,
             bool isFunctionPointerResolution = false,
+            bool isExtensionMethodResolution = false,
             in CallingConventionInfo callingConventionInfo = default)
         {
             MethodOrPropertyOverloadResolution(
                 methods, typeArguments, receiver, arguments, result,
                 isMethodGroupConversion, allowRefOmittedArguments, ref useSiteInfo, inferWithDynamic,
-                allowUnexpandedForm, returnRefKind, returnType, isFunctionPointerResolution, in callingConventionInfo);
+                allowUnexpandedForm, returnRefKind, returnType, isFunctionPointerResolution: isFunctionPointerResolution,
+                isExtensionMethodResolution: isExtensionMethodResolution, in callingConventionInfo);
         }
 
         // Perform overload resolution on the given property group, with the given arguments and
@@ -168,16 +170,23 @@ internal void MethodOrPropertyOverloadResolution<TMember>(
             RefKind returnRefKind = default,
             TypeSymbol returnType = null,
             bool isFunctionPointerResolution = false,
+            bool isExtensionMethodResolution = false,
             in CallingConventionInfo callingConventionInfo = default)
             where TMember : Symbol
         {
             var results = result.ResultsBuilder;
 
+            // No need to check for overridden or hidden methods if the members were
+            // resolved as extension methods and the extension methods are defined in
+            // types derived from System.Object.
+            bool checkOverriddenOrHidden = !(isExtensionMethodResolution &&
+                members.All(static m => m.ContainingSymbol is NamedTypeSymbol { BaseTypeNoUseSiteDiagnostics.SpecialType: SpecialType.System_Object }));
+
             // First, attempt overload resolution not getting complete results.
             PerformMemberOverloadResolution(
                 results, members, typeArguments, receiver, arguments, completeResults: false, isMethodGroupConversion,
                 returnRefKind, returnType, allowRefOmittedArguments, isFunctionPointerResolution, callingConventionInfo,
-                ref useSiteInfo, inferWithDynamic, allowUnexpandedForm);
+                ref useSiteInfo, inferWithDynamic: inferWithDynamic, allowUnexpandedForm: allowUnexpandedForm, checkOverriddenOrHidden: checkOverriddenOrHidden);
 
             if (!OverloadResolutionResultIsValid(results, arguments.HasDynamicArgument))
             {
@@ -187,7 +196,7 @@ internal void MethodOrPropertyOverloadResolution<TMember>(
                     results, members, typeArguments, receiver, arguments,
                     completeResults: true, isMethodGroupConversion, returnRefKind, returnType,
                     allowRefOmittedArguments, isFunctionPointerResolution, callingConventionInfo,
-                    ref useSiteInfo, allowUnexpandedForm: allowUnexpandedForm);
+                    ref useSiteInfo, inferWithDynamic: false, allowUnexpandedForm: allowUnexpandedForm, checkOverriddenOrHidden: checkOverriddenOrHidden);
             }
         }
 
@@ -239,8 +248,9 @@ private void PerformMemberOverloadResolution<TMember>(
             bool isFunctionPointerResolution,
             in CallingConventionInfo callingConventionInfo,
             ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo,
-            bool inferWithDynamic = false,
-            bool allowUnexpandedForm = true)
+            bool inferWithDynamic,
+            bool allowUnexpandedForm,
+            bool checkOverriddenOrHidden)
             where TMember : Symbol
         {
             // SPEC: The binding-time processing of a method invocation of the form M(A), where M is a 
@@ -256,7 +266,7 @@ private void PerformMemberOverloadResolution<TMember>(
             // overriding or hiding member is not in a subtype of the type containing the
             // (potentially) overridden or hidden member.
             Dictionary<NamedTypeSymbol, ArrayBuilder<TMember>> containingTypeMapOpt = null;
-            if (members.Count > 50) // TODO: fine-tune this value
+            if (checkOverriddenOrHidden && members.Count > 50) // TODO: fine-tune this value
             {
                 containingTypeMapOpt = PartitionMembersByContainingType(members);
             }
@@ -276,7 +286,8 @@ private void PerformMemberOverloadResolution<TMember>(
                     containingTypeMapOpt,
                     inferWithDynamic: inferWithDynamic,
                     useSiteInfo: ref useSiteInfo,
-                    allowUnexpandedForm: allowUnexpandedForm);
+                    allowUnexpandedForm: allowUnexpandedForm,
+                    checkOverriddenOrHidden: checkOverriddenOrHidden);
             }
 
             // CONSIDER: use containingTypeMapOpt for RemoveLessDerivedMembers?
@@ -288,7 +299,10 @@ private void PerformMemberOverloadResolution<TMember>(
             RemoveInaccessibleTypeArguments(results, ref useSiteInfo);
 
             // SPEC: The set of candidate methods is reduced to contain only methods from the most derived types.
-            RemoveLessDerivedMembers(results, ref useSiteInfo);
+            if (checkOverriddenOrHidden)
+            {
+                RemoveLessDerivedMembers(results, ref useSiteInfo);
+            }
 
             if (Compilation.LanguageVersion.AllowImprovedOverloadCandidates())
             {
@@ -824,9 +838,12 @@ private void AddMemberToCandidateSet<TMember>(
             Dictionary<NamedTypeSymbol, ArrayBuilder<TMember>> containingTypeMapOpt,
             bool inferWithDynamic,
             ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo,
-            bool allowUnexpandedForm)
+            bool allowUnexpandedForm,
+            bool checkOverriddenOrHidden = true)
             where TMember : Symbol
         {
+            Debug.Assert(checkOverriddenOrHidden || containingTypeMapOpt is null);
+
             // SPEC VIOLATION:
             //
             // The specification states that the method group that resulted from member lookup has
@@ -856,47 +873,50 @@ private void AddMemberToCandidateSet<TMember>(
             // clever in filtering out methods from less-derived classes later, but we'll cross that
             // bridge when we come to it.
 
-            if (members.Count < 2)
-            {
-                // No hiding or overriding possible.
-            }
-            else if (containingTypeMapOpt == null)
+            if (checkOverriddenOrHidden)
             {
-                if (MemberGroupContainsMoreDerivedOverride(members, member, checkOverrideContainingType: true, ref useSiteInfo))
+                if (members.Count < 2)
                 {
-                    // Don't even add it to the result set.  We'll add only the most-overriding members.
-                    return;
+                    // No hiding or overriding possible.
                 }
+                else if (containingTypeMapOpt == null)
+                {
+                    if (MemberGroupContainsMoreDerivedOverride(members, member, checkOverrideContainingType: true, ref useSiteInfo))
+                    {
+                        // Don't even add it to the result set.  We'll add only the most-overriding members.
+                        return;
+                    }
 
-                if (MemberGroupHidesByName(members, member, ref useSiteInfo))
+                    if (MemberGroupHidesByName(members, member, ref useSiteInfo))
+                    {
+                        return;
+                    }
+                }
+                else if (containingTypeMapOpt.Count == 1)
                 {
-                    return;
+                    // No hiding or overriding since all members are in the same type.
                 }
-            }
-            else if (containingTypeMapOpt.Count == 1)
-            {
-                // No hiding or overriding since all members are in the same type.
-            }
-            else
-            {
-                // NOTE: only check for overriding/hiding in subtypes of f.ContainingType.
-                NamedTypeSymbol memberContainingType = member.ContainingType;
-                foreach (var pair in containingTypeMapOpt)
+                else
                 {
-                    NamedTypeSymbol otherType = pair.Key;
-                    if (otherType.IsDerivedFrom(memberContainingType, TypeCompareKind.ConsiderEverything, useSiteInfo: ref useSiteInfo))
+                    // NOTE: only check for overriding/hiding in subtypes of f.ContainingType.
+                    NamedTypeSymbol memberContainingType = member.ContainingType;
+                    foreach (var pair in containingTypeMapOpt)
                     {
-                        ArrayBuilder<TMember> others = pair.Value;
-
-                        if (MemberGroupContainsMoreDerivedOverride(others, member, checkOverrideContainingType: false, ref useSiteInfo))
+                        NamedTypeSymbol otherType = pair.Key;
+                        if (otherType.IsDerivedFrom(memberContainingType, TypeCompareKind.ConsiderEverything, useSiteInfo: ref useSiteInfo))
                         {
-                            // Don't even add it to the result set.  We'll add only the most-overriding members.
-                            return;
-                        }
+                            ArrayBuilder<TMember> others = pair.Value;
 
-                        if (MemberGroupHidesByName(others, member, ref useSiteInfo))
-                        {
-                            return;
+                            if (MemberGroupContainsMoreDerivedOverride(others, member, checkOverrideContainingType: false, ref useSiteInfo))
+                            {
+                                // Don't even add it to the result set.  We'll add only the most-overriding members.
+                                return;
+                            }
+
+                            if (MemberGroupHidesByName(others, member, ref useSiteInfo))
+                            {
+                                return;
+                            }
                         }
                     }
                 }
@@ -1275,7 +1295,7 @@ private static void RemoveLessDerivedMembers<TMember>(ArrayBuilder<MemberResolut
                 // work necessary to eliminate methods on base types of Mammal when we eliminated
                 // methods on base types of Cat.
 
-                if (IsLessDerivedThanAny(result.LeastOverriddenMember.ContainingType, results, ref useSiteInfo))
+                if (IsLessDerivedThanAny(index: f, result.LeastOverriddenMember.ContainingType, results, ref useSiteInfo))
                 {
                     results[f] = result.WithResult(MemberAnalysisResult.LessDerived());
                 }
@@ -1283,11 +1303,16 @@ private static void RemoveLessDerivedMembers<TMember>(ArrayBuilder<MemberResolut
         }
 
         // Is this type a base type of any valid method on the list?
-        private static bool IsLessDerivedThanAny<TMember>(TypeSymbol type, ArrayBuilder<MemberResolutionResult<TMember>> results, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
+        private static bool IsLessDerivedThanAny<TMember>(int index, TypeSymbol type, ArrayBuilder<MemberResolutionResult<TMember>> results, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
             where TMember : Symbol
         {
             for (int f = 0; f < results.Count; ++f)
             {
+                if (f == index)
+                {
+                    continue;
+                }
+
                 var result = results[f];
 
                 if (!result.Result.IsValid)
@@ -1642,7 +1667,7 @@ private void RemoveWorseMembers<TMember>(ArrayBuilder<MemberResolutionResult<TMe
         /// <summary>
         /// Returns the parameter type (considering params).
         /// </summary>
-        private TypeSymbol GetParameterType(ParameterSymbol parameter, MemberAnalysisResult result)
+        private static TypeSymbol GetParameterType(ParameterSymbol parameter, MemberAnalysisResult result)
         {
             var type = parameter.Type;
             if (result.Kind == MemberResolutionKind.ApplicableInExpandedForm &&
diff --git a/src/Compilers/CSharp/Portable/Binder/SimpleProgramBinder.cs b/src/Compilers/CSharp/Portable/Binder/SimpleProgramBinder.cs
index a7cfc5716f1cf..46744a96313ed 100644
--- a/src/Compilers/CSharp/Portable/Binder/SimpleProgramBinder.cs
+++ b/src/Compilers/CSharp/Portable/Binder/SimpleProgramBinder.cs
@@ -25,7 +25,7 @@ public SimpleProgramBinder(Binder enclosing, SynthesizedSimpleProgramEntryPointS
 
         protected override ImmutableArray<LocalSymbol> BuildLocals()
         {
-            ArrayBuilder<LocalSymbol> locals = ArrayBuilder<LocalSymbol>.GetInstance();
+            ArrayBuilder<LocalSymbol> locals = ArrayBuilder<LocalSymbol>.GetInstance(DefaultLocalSymbolArrayCapacity);
 
             foreach (var statement in _entryPoint.CompilationUnit.Members)
             {
diff --git a/src/Compilers/CSharp/Portable/BoundTree/BoundExpression.cs b/src/Compilers/CSharp/Portable/BoundTree/BoundExpression.cs
index a6e823cd3627f..891f017763792 100644
--- a/src/Compilers/CSharp/Portable/BoundTree/BoundExpression.cs
+++ b/src/Compilers/CSharp/Portable/BoundTree/BoundExpression.cs
@@ -5,6 +5,7 @@
 using System.Collections.Immutable;
 using System.Diagnostics;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Roslyn.Utilities;
 using System;
 
@@ -239,6 +240,34 @@ public override Symbol ExpressionSymbol
                 return this.Method;
             }
         }
+
+        public Location? InterceptableLocation
+        {
+            get
+            {
+                // When this assertion fails, it means a new syntax is being used which corresponds to a BoundCall.
+                // The developer needs to determine how this new syntax should interact with interceptors (produce an error, permit intercepting the call, etc...)
+                Debug.Assert(this.WasCompilerGenerated || this.Syntax is InvocationExpressionSyntax or ConstructorInitializerSyntax or PrimaryConstructorBaseTypeSyntax { ArgumentList: { } },
+                    $"Unexpected syntax kind for BoundCall: {this.Syntax.Kind()}");
+
+                if (this.WasCompilerGenerated || this.Syntax is not InvocationExpressionSyntax syntax)
+                {
+                    return null;
+                }
+
+                // If a qualified name is used as a valid receiver of an invocation syntax at some point,
+                // we probably want to treat it similarly to a MemberAccessExpression.
+                // However, we don't expect to encounter it.
+                Debug.Assert(syntax.Expression is not QualifiedNameSyntax);
+
+                return syntax.Expression switch
+                {
+                    MemberAccessExpressionSyntax memberAccess => memberAccess.Name.Location,
+                    SimpleNameSyntax name => name.Location,
+                    _ => null
+                };
+            }
+        }
     }
 
     internal partial class BoundTypeExpression
diff --git a/src/Compilers/CSharp/Portable/BoundTree/BoundExpressionExtensions.cs b/src/Compilers/CSharp/Portable/BoundTree/BoundExpressionExtensions.cs
index 2ea79fb066291..94997b44ad21c 100644
--- a/src/Compilers/CSharp/Portable/BoundTree/BoundExpressionExtensions.cs
+++ b/src/Compilers/CSharp/Portable/BoundTree/BoundExpressionExtensions.cs
@@ -42,6 +42,24 @@ public static RefKind GetRefKind(this BoundExpression node)
                 case BoundKind.ImplicitIndexerAccess:
                     return ((BoundImplicitIndexerAccess)node).IndexerOrSliceAccess.GetRefKind();
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)node;
+
+                        if (!elementAccess.IsValue)
+                        {
+                            switch (elementAccess.GetItemOrSliceHelper)
+                            {
+                                case WellKnownMember.System_Span_T__get_Item:
+                                    return RefKind.Ref;
+                                case WellKnownMember.System_ReadOnlySpan_T__get_Item:
+                                    return RefKind.RefReadOnly;
+                            }
+                        }
+
+                        return RefKind.None;
+                    }
+
                 case BoundKind.ObjectInitializerMember:
                     var member = (BoundObjectInitializerMember)node;
                     if (member.HasErrors)
diff --git a/src/Compilers/CSharp/Portable/BoundTree/BoundInlineArrayAccess.cs b/src/Compilers/CSharp/Portable/BoundTree/BoundInlineArrayAccess.cs
new file mode 100644
index 0000000000000..ad7b7188dce60
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/BoundTree/BoundInlineArrayAccess.cs
@@ -0,0 +1,76 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using Microsoft.CodeAnalysis.CSharp.Symbols;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.CSharp
+{
+    internal partial class BoundInlineArrayAccess
+    {
+        private partial void Validate()
+        {
+#if DEBUG
+            Debug.Assert(!IsValue || GetItemOrSliceHelper == WellKnownMember.System_ReadOnlySpan_T__get_Item);
+#pragma warning disable format
+            Debug.Assert(Argument.Type is
+                             { SpecialType: SpecialType.System_Int32 } or
+                             NamedTypeSymbol
+                                 {
+                                     ContainingSymbol: NamespaceSymbol
+                                                       {
+                                                           Name: "System",
+                                                           ContainingSymbol: NamespaceSymbol { IsGlobalNamespace: true }
+                                                       },
+                                     Name: "Index" or "Range",
+                                     IsGenericType: false
+                                 }
+                             );
+#pragma warning restore format
+
+            if (Argument.Type.Name == "Range")
+            {
+                Debug.Assert(GetItemOrSliceHelper is
+                                WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int or
+                                WellKnownMember.System_Span_T__Slice_Int_Int);
+
+                if (GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int)
+                {
+                    Debug.Assert(Type.Name == "ReadOnlySpan");
+                }
+                else
+                {
+                    Debug.Assert(Type.Name == "Span");
+                }
+
+#pragma warning disable format
+                Debug.Assert(Type is
+                                 NamedTypeSymbol
+                                     {
+                                         ContainingSymbol: NamespaceSymbol
+                                                           {
+                                                               Name: "System",
+                                                               ContainingSymbol: NamespaceSymbol { IsGlobalNamespace: true }
+                                                           },
+                                         Arity: 1
+                                     }
+                                 );
+#pragma warning restore format
+
+                Debug.Assert(((NamedTypeSymbol)Type).TypeArgumentsWithAnnotationsNoUseSiteDiagnostics[0].Equals(Expression.Type?.TryGetInlineArrayElementField()?.TypeWithAnnotations ?? default, TypeCompareKind.ConsiderEverything));
+            }
+            else
+            {
+                Debug.Assert(GetItemOrSliceHelper is
+                                WellKnownMember.System_ReadOnlySpan_T__get_Item or
+                                WellKnownMember.System_Span_T__get_Item);
+
+                Debug.Assert(Type.Equals(Expression.Type?.TryGetInlineArrayElementField()?.Type, TypeCompareKind.ConsiderEverything));
+            }
+#endif
+        }
+    }
+}
+
diff --git a/src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml b/src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml
index 2a933c71e00a5..e7a06f099f35e 100644
--- a/src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml
+++ b/src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml
@@ -35,6 +35,7 @@
   <ValueType Name="ErrorCode"/>
   <ValueType Name="ImmutableBindingDiagnostic"/>
   <ValueType Name="InterpolatedStringHandlerData"/>
+  <ValueType Name="WellKnownMember"/>
   <ValueType Name="CollectionLiteralTypeKind"/>
 
   <AbstractNode Name="BoundInitializer" Base="BoundNode"/>
@@ -2195,6 +2196,21 @@
     <Field Name="ArgumentPlaceholders" Type="ImmutableArray&lt;BoundImplicitIndexerValuePlaceholder&gt;" Null="disallow" SkipInVisitor="true" />
   </Node>
 
+  <Node Name="BoundInlineArrayAccess" Base="BoundExpression" HasValidate="true">
+    <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow" />
+
+    <!-- The target of the operation -->
+    <Field Name="Expression" Type="BoundExpression" Null="disallow" />
+
+    <!-- An expression with type int, Index or Range -->
+    <Field Name="Argument" Type="BoundExpression" Null="disallow" />
+
+    <!-- The access is an element access rather than a slice access, and it produces a value rather than a variable -->
+    <Field Name="IsValue" Type="bool" />
+
+    <Field Name="GetItemOrSliceHelper" Type="WellKnownMember"/>
+  </Node>
+
   <Node Name="BoundDynamicIndexerAccess" Base="BoundExpression">
     <!-- Non-null type is required for this node kind -->
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
diff --git a/src/Compilers/CSharp/Portable/CSharpResources.resx b/src/Compilers/CSharp/Portable/CSharpResources.resx
index c4a2cc5fce23b..44223e1596ebe 100644
--- a/src/Compilers/CSharp/Portable/CSharpResources.resx
+++ b/src/Compilers/CSharp/Portable/CSharpResources.resx
@@ -318,6 +318,18 @@
   <data name="IDS_SK_TYVAR" xml:space="preserve">
     <value>type parameter</value>
   </data>
+  <data name="IDS_SK_ARRAY" xml:space="preserve">
+    <value>array</value>
+  </data>
+  <data name="IDS_SK_POINTER" xml:space="preserve">
+    <value>pointer</value>
+  </data>
+  <data name="IDS_SK_FUNCTION_POINTER" xml:space="preserve">
+    <value>function pointer</value>
+  </data>
+  <data name="IDS_SK_DYNAMIC" xml:space="preserve">
+    <value>dynamic</value>
+  </data>
   <data name="IDS_SK_ALIAS" xml:space="preserve">
     <value>using alias</value>
   </data>
@@ -4794,6 +4806,9 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </value>
     <comment>Visual C# Compiler Options</comment>
   </data>
@@ -5246,7 +5261,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
     <value>Async methods cannot have by-reference locals</value>
   </data>
   <data name="ERR_RefReturningCallAndAwait" xml:space="preserve">
-    <value>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</value>
+    <value>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</value>
   </data>
   <data name="ERR_RefConditionalAndAwait" xml:space="preserve">
     <value>'await' cannot be used in an expression containing a ref conditional operator</value>
@@ -7517,10 +7532,139 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_BadCaseInSwitchArm" xml:space="preserve">
     <value>A switch expression arm does not begin with a 'case' keyword.</value>
   </data>
+  <data name="ERR_InterceptorsFeatureNotEnabled" xml:space="preserve">
+    <value>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</value>
+  </data>
+  <data name="ERR_InterceptorCannotBeGeneric" xml:space="preserve">
+    <value>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</value>
+  </data>
+  <data name="ERR_InterceptorPathNotInCompilation" xml:space="preserve">
+    <value>Cannot intercept: compilation does not contain a file with path '{0}'.</value>
+  </data>
+  <data name="ERR_InterceptorPathNotInCompilationWithCandidate" xml:space="preserve">
+    <value>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</value>
+  </data>
+  <data name="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate" xml:space="preserve">
+    <value>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</value>
+  </data>
+  <data name="ERR_InterceptorLineOutOfRange" xml:space="preserve">
+    <value>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</value>
+  </data>
+  <data name="ERR_InterceptorCharacterOutOfRange" xml:space="preserve">
+    <value>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</value>
+  </data>
+  <data name="ERR_InterceptorLineCharacterMustBePositive" xml:space="preserve">
+    <value>Line and character numbers provided to InterceptsLocationAttribute must be positive.</value>
+  </data>
+  <data name="ERR_InterceptorPositionBadToken" xml:space="preserve">
+    <value>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</value>
+  </data>
+  <data name="ERR_InterceptorMustReferToStartOfTokenPosition" xml:space="preserve">
+    <value>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</value>
+  </data>
+  <data name="ERR_InterceptorSignatureMismatch" xml:space="preserve">
+    <value>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</value>
+  </data>
+  <data name="WRN_InterceptorSignatureMismatch" xml:space="preserve">
+    <value>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</value>
+  </data>
+  <data name="WRN_InterceptorSignatureMismatch_Title" xml:space="preserve">
+    <value>Signatures of interceptable and interceptor methods do not match.</value>
+  </data>
+  <data name="ERR_InterceptorMethodMustBeOrdinary" xml:space="preserve">
+    <value>An interceptor method must be an ordinary member method.</value>
+  </data>
+  <data name="ERR_InterceptorMustHaveMatchingThisParameter" xml:space="preserve">
+    <value>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</value>
+  </data>
+  <data name="ERR_InterceptorMustNotHaveThisParameter" xml:space="preserve">
+    <value>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</value>
+  </data>
+  <data name="ERR_InterceptorFilePathCannotBeNull" xml:space="preserve">
+    <value>Interceptor cannot have a 'null' file path.</value>
+  </data>
+  <data name="ERR_InterceptorNameNotInvoked" xml:space="preserve">
+    <value>Possible method name '{0}' cannot be intercepted because it is not being invoked.</value>
+  </data>
+  <data name="ERR_InterceptorNonUniquePath" xml:space="preserve">
+    <value>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</value>
+  </data>
+  <data name="ERR_DuplicateInterceptor" xml:space="preserve">
+    <value>The indicated call is intercepted multiple times.</value>
+  </data>
+  <data name="ERR_InterceptorNotAccessible" xml:space="preserve">
+    <value>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</value>
+  </data>
+  <data name="ERR_InterceptorScopedMismatch" xml:space="preserve">
+    <value>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</value>
+  </data>
   <data name="ERR_ConstantValueOfTypeExpected" xml:space="preserve">
     <value>A constant value of type '{0}' is expected</value>
   </data>
   <data name="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny" xml:space="preserve">
     <value>Cannot use primary constructor parameter of type '{0}' inside an instance member</value>
   </data>
+  <data name="WRN_NullabilityMismatchInParameterTypeOnInterceptor" xml:space="preserve">
+    <value>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</value>
+  </data>
+  <data name="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title" xml:space="preserve">
+    <value>Nullability of reference types in type of parameter doesn't match interceptable method.</value>
+  </data>
+  <data name="WRN_NullabilityMismatchInReturnTypeOnInterceptor" xml:space="preserve">
+    <value>Nullability of reference types in return type doesn't match interceptable method '{0}'.</value>
+  </data>
+  <data name="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title" xml:space="preserve">
+    <value>Nullability of reference types in return type doesn't match interceptable method.</value>
+  </data>
+  <data name="ERR_InterceptorCannotInterceptNameof" xml:space="preserve">
+    <value>A nameof operator cannot be intercepted.</value>
+  </data>
+  <data name="ERR_InterceptorCannotUseUnmanagedCallersOnly" xml:space="preserve">
+    <value>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</value>
+  </data>
+  <data name="ERR_BadUsingStaticType" xml:space="preserve">
+    <value>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</value>
+  </data>
+  <data name="ERR_SymbolDefinedInAssembly" xml:space="preserve">
+    <value>'{0}' is defined in assembly '{1}'.</value>
+  </data>
+  <data name="WRN_CapturedPrimaryConstructorParameterInFieldInitializer" xml:space="preserve">
+    <value>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</value>
+  </data>
+  <data name="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title" xml:space="preserve">
+    <value>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</value>
+  </data>
+  <data name="ERR_InlineArrayConversionToSpanNotSupported" xml:space="preserve">
+    <value>Cannot convert expression to '{0}' because it is not an assignable variable</value>
+  </data>
+  <data name="ERR_InlineArrayConversionToReadOnlySpanNotSupported" xml:space="preserve">
+    <value>Cannot convert expression to '{0}' because it may not be passed or returned by reference</value>
+  </data>
+  <data name="IDS_FeatureInlineArrays" xml:space="preserve">
+    <value>inline arrays</value>
+  </data>
+  <data name="ERR_InlineArrayIndexOutOfRange" xml:space="preserve">
+    <value>Index is outside the bounds of the inline array</value>
+  </data>
+  <data name="ERR_InvalidInlineArrayLength" xml:space="preserve">
+    <value>Inline array length must be greater than 0.</value>
+  </data>
+  <data name="ERR_InvalidInlineArrayLayout" xml:space="preserve">
+    <value>Inline array struct must not have explicit layout.</value>
+  </data>
+  <data name="ERR_InvalidInlineArrayFields" xml:space="preserve">
+    <value>Inline array struct must declare one and only one instance field which must not be a ref field.</value>
+  </data>
+  <data name="ERR_ExpressionTreeContainsInlineArrayOperation" xml:space="preserve">
+    <value>An expression tree may not contain an inline array access or conversion</value>
+  </data>
+  <data name="ERR_RuntimeDoesNotSupportInlineArrayTypes" xml:space="preserve">
+    <value>Target runtime doesn't support inline array types.</value>
+  </data>
+  <data name="ERR_InlineArrayBadIndex" xml:space="preserve">
+    <value>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</value>
+  </data>
+  <data name="ERR_NamedArgumentForInlineArray" xml:space="preserve">
+    <value>An inline array access may not have a named argument specifier</value>
+  </data>
 </root>
\ No newline at end of file
diff --git a/src/Compilers/CSharp/Portable/CodeGen/EmitExpression.cs b/src/Compilers/CSharp/Portable/CodeGen/EmitExpression.cs
index f6e06e022773e..92e4bc9aaab62 100644
--- a/src/Compilers/CSharp/Portable/CodeGen/EmitExpression.cs
+++ b/src/Compilers/CSharp/Portable/CodeGen/EmitExpression.cs
@@ -930,9 +930,12 @@ private void EmitSideEffects(BoundSequence sequence)
         private void EmitArguments(ImmutableArray<BoundExpression> arguments, ImmutableArray<ParameterSymbol> parameters, ImmutableArray<RefKind> argRefKindsOpt)
         {
             // We might have an extra argument for the __arglist() of a varargs method.
-            Debug.Assert(arguments.Length == parameters.Length || arguments.Length == parameters.Length + 1, "argument count must match parameter count");
+            Debug.Assert(arguments.Length == parameters.Length ||
+                (arguments.Length == parameters.Length + 1 && arguments is [.., BoundArgListOperator]), "argument count must match parameter count");
             Debug.Assert(parameters.All(p => p.RefKind == RefKind.None) || !argRefKindsOpt.IsDefault, "there are nontrivial parameters, so we must have argRefKinds");
-            Debug.Assert(argRefKindsOpt.IsDefault || argRefKindsOpt.Length == arguments.Length, "if we have argRefKinds, we should have one for each argument");
+            // We might have a missing ref kind for the __arglist() of a varargs method.
+            Debug.Assert(argRefKindsOpt.IsDefault || argRefKindsOpt.Length == arguments.Length ||
+                (argRefKindsOpt.Length == arguments.Length - 1 && arguments is [.., BoundArgListOperator]), "if we have argRefKinds, we should have one for each argument");
 
             for (int i = 0; i < arguments.Length; i++)
             {
@@ -2949,7 +2952,7 @@ private void EmitAssignmentValue(BoundAssignmentOperator assignmentOperator)
 
                 // NOTE: passing "ReadOnlyStrict" here. 
                 //       we should not get an address of a copy if at all possible
-                LocalDefinition temp = EmitAddress(assignmentOperator.Right, lhs.GetRefKind() == RefKind.RefReadOnly ? AddressKind.ReadOnlyStrict : AddressKind.Writeable);
+                LocalDefinition temp = EmitAddress(assignmentOperator.Right, lhs.GetRefKind() is RefKind.RefReadOnly or RefKindExtensions.StrictIn ? AddressKind.ReadOnlyStrict : AddressKind.Writeable);
 
                 // Generally taking a ref for the purpose of ref assignment should not be done on homeless values
                 // however, there are very rare cases when we need to get a ref off a temp in synthetic code.
diff --git a/src/Compilers/CSharp/Portable/CodeGen/Optimizer.cs b/src/Compilers/CSharp/Portable/CodeGen/Optimizer.cs
index 36003e3bcf275..c70695c28cbd2 100644
--- a/src/Compilers/CSharp/Portable/CodeGen/Optimizer.cs
+++ b/src/Compilers/CSharp/Portable/CodeGen/Optimizer.cs
@@ -982,7 +982,7 @@ public override BoundNode VisitAssignmentOperator(BoundAssignmentOperator node)
                 // If the LHS is a readonly ref and the result is used later we cannot stack
                 // schedule since we may be converting a writeable value on the RHS to a readonly
                 // one on the LHS.
-                if (localSymbol.RefKind == RefKind.RefReadOnly &&
+                if (localSymbol.RefKind is RefKind.RefReadOnly or RefKindExtensions.StrictIn &&
                     (_context == ExprContext.Address || _context == ExprContext.Value))
                 {
                     ShouldNotSchedule(localSymbol);
diff --git a/src/Compilers/CSharp/Portable/CommandLine/CSharpCommandLineParser.cs b/src/Compilers/CSharp/Portable/CommandLine/CSharpCommandLineParser.cs
index d5b416367f07b..1ca2ab2df627b 100644
--- a/src/Compilers/CSharp/Portable/CommandLine/CSharpCommandLineParser.cs
+++ b/src/Compilers/CSharp/Portable/CommandLine/CSharpCommandLineParser.cs
@@ -136,6 +136,7 @@ internal sealed override CommandLineArguments CommonParse(IEnumerable<string> ar
             bool publicSign = false;
             string? sourceLink = null;
             string? ruleSetPath = null;
+            bool reportIVTs = false;
 
             // Process ruleset files first so that diagnostic severity settings specified on the command line via
             // /nowarn and /warnaserror can override diagnostic severity settings specified in the ruleset file.
@@ -1354,6 +1355,17 @@ internal sealed override CommandLineArguments CommonParse(IEnumerable<string> ar
                                 AddDiagnostic(diagnostics, ErrorCode.ERR_StdInOptionProvidedButConsoleInputIsNotRedirected);
                             }
                             continue;
+
+                        case "reportivts":
+                        case "reportivts+":
+                            if (valueMemory is not null) break;
+                            reportIVTs = true;
+                            continue;
+
+                        case "reportivts-":
+                            if (valueMemory is not null) break;
+                            reportIVTs = false;
+                            continue;
                     }
                 }
 
@@ -1576,7 +1588,8 @@ internal sealed override CommandLineArguments CommonParse(IEnumerable<string> ar
                 PreferredUILang = preferredUILang,
                 ReportAnalyzer = reportAnalyzer,
                 SkipAnalyzers = skipAnalyzers,
-                EmbeddedFiles = embeddedFiles.AsImmutable()
+                EmbeddedFiles = embeddedFiles.AsImmutable(),
+                ReportInternalsVisibleToAttributes = reportIVTs,
             };
         }
 
diff --git a/src/Compilers/CSharp/Portable/CommandLine/CSharpCompiler.cs b/src/Compilers/CSharp/Portable/CommandLine/CSharpCompiler.cs
index 10ec64d61ba5e..4b62175029b82 100644
--- a/src/Compilers/CSharp/Portable/CommandLine/CSharpCompiler.cs
+++ b/src/Compilers/CSharp/Portable/CommandLine/CSharpCompiler.cs
@@ -377,5 +377,34 @@ private protected override GeneratorDriver CreateGeneratorDriver(ParseOptions pa
         {
             return CSharpGeneratorDriver.Create(generators, additionalTexts, (CSharpParseOptions)parseOptions, analyzerConfigOptionsProvider);
         }
+
+        private protected override void DiagnoseBadAccesses(TextWriter consoleOutput, ErrorLogger? errorLogger, Compilation compilation, ImmutableArray<Diagnostic> diagnostics)
+        {
+            DiagnosticBag newDiagnostics = DiagnosticBag.GetInstance();
+            foreach (var diag in diagnostics)
+            {
+                var symbol = diag switch
+                {
+                    { Code: (int)ErrorCode.ERR_BadAccess, Arguments: [Symbol s] } => s,
+                    { Code: (int)ErrorCode.ERR_InaccessibleGetter, Arguments: [Symbol s] } => s,
+                    { Code: (int)ErrorCode.ERR_InaccessibleSetter, Arguments: [Symbol s] } => s,
+                    { Code: (int)ErrorCode.ERR_ImplicitImplementationOfInaccessibleInterfaceMember, Arguments: [_, Symbol s, _] } => s,
+                    _ => null
+                };
+
+                if (symbol is null || ReferenceEquals(compilation.Assembly, symbol.ContainingAssembly))
+                {
+                    // Can't be IVT related
+                    continue;
+                }
+
+                // '{0}' is defined in assembly '{1}'.
+                newDiagnostics.Add(new CSDiagnostic(
+                    new CSDiagnosticInfo(ErrorCode.ERR_SymbolDefinedInAssembly, symbol, symbol.ContainingAssembly),
+                    diag.Location));
+            }
+
+            ReportDiagnostics(newDiagnostics.ToReadOnlyAndFree(), consoleOutput, errorLogger, compilation);
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs b/src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs
index 3ecebb7fae368..6b77c1b8bf5b4 100644
--- a/src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs
+++ b/src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs
@@ -154,6 +154,9 @@ internal Conversions Conversions
         /// </summary>
         private readonly ConcurrentCache<TypeSymbol, NamedTypeSymbol> _typeToNullableVersion = new ConcurrentCache<TypeSymbol, NamedTypeSymbol>(size: 100);
 
+        /// <summary>Lazily caches SyntaxTrees by their mapped path. Used to look up the syntax tree referenced by an interceptor. <see cref="TryGetInterceptor"/></summary>
+        private ImmutableSegmentedDictionary<string, OneOrMany<SyntaxTree>> _mappedPathToSyntaxTree;
+
         public override string Language
         {
             get
@@ -1037,6 +1040,33 @@ internal override int GetSyntaxTreeOrdinal(SyntaxTree tree)
             }
         }
 
+        internal OneOrMany<SyntaxTree> GetSyntaxTreesByMappedPath(string mappedPath)
+        {
+            // We could consider storing this on SyntaxAndDeclarationManager instead, and updating it incrementally.
+            // However, this would make it more difficult for it to be "pay-for-play",
+            // i.e. only created in compilations where interceptors are used.
+            var mappedPathToSyntaxTree = _mappedPathToSyntaxTree;
+            if (mappedPathToSyntaxTree.IsDefault)
+            {
+                RoslynImmutableInterlocked.InterlockedInitialize(ref _mappedPathToSyntaxTree, computeMappedPathToSyntaxTree());
+                mappedPathToSyntaxTree = _mappedPathToSyntaxTree;
+            }
+
+            return mappedPathToSyntaxTree.TryGetValue(mappedPath, out var value) ? value : OneOrMany<SyntaxTree>.Empty;
+
+            ImmutableSegmentedDictionary<string, OneOrMany<SyntaxTree>> computeMappedPathToSyntaxTree()
+            {
+                var builder = ImmutableSegmentedDictionary.CreateBuilder<string, OneOrMany<SyntaxTree>>();
+                var resolver = Options.SourceReferenceResolver;
+                foreach (var tree in SyntaxTrees)
+                {
+                    var path = resolver?.NormalizePath(tree.FilePath, baseFilePath: null) ?? tree.FilePath;
+                    builder[path] = builder.ContainsKey(path) ? builder[path].Add(tree) : OneOrMany.Create(tree);
+                }
+                return builder.ToImmutable();
+            }
+        }
+
         #endregion
 
         #region References
@@ -1111,6 +1141,11 @@ internal IEnumerable<string> ExternAliases
             }
         }
 
+        internal override TSymbol? GetSymbolInternal<TSymbol>(ISymbol? symbol) where TSymbol : class
+        {
+            return (TSymbol?)(object?)symbol.GetSymbol<Symbol>();
+        }
+
         public override IEnumerable<AssemblyIdentity> ReferencedAssemblyNames
         {
             get
@@ -2307,6 +2342,60 @@ internal void AddModuleInitializerMethod(MethodSymbol method)
             LazyInitializer.EnsureInitialized(ref _moduleInitializerMethods).Add(method);
         }
 
+        // NB: the 'Many' case for these dictionary values means there are duplicates. An error is reported for this after binding.
+        private ConcurrentDictionary<(string FilePath, int Line, int Character), OneOrMany<(Location AttributeLocation, MethodSymbol Interceptor)>>? _interceptions;
+
+        internal void AddInterception(string filePath, int line, int character, Location attributeLocation, MethodSymbol interceptor)
+        {
+            Debug.Assert(!_declarationDiagnosticsFrozen);
+
+            var dictionary = LazyInitializer.EnsureInitialized(ref _interceptions);
+            dictionary.AddOrUpdate((filePath, line, character),
+                addValueFactory: static (key, newValue) => OneOrMany.Create(newValue),
+                updateValueFactory: static (key, existingValues, newValue) =>
+                {
+                    // AddInterception can be called when attributes are decoded on a symbol, which can happen for the same symbol concurrently.
+                    // If something else has already added the interceptor denoted by a given `[InterceptsLocation]`, we want to drop it.
+                    // Since the collection is almost always length 1, a simple foreach is adequate for detecting this.
+                    foreach (var (attributeLocation, interceptor) in existingValues)
+                    {
+                        if (attributeLocation == newValue.AttributeLocation && interceptor.Equals(newValue.Interceptor, TypeCompareKind.ConsiderEverything))
+                        {
+                            return existingValues;
+                        }
+                    }
+                    return existingValues.Add(newValue);
+                },
+                // Explicit tuple element names are needed here so that the names unify when this is an extension method call (netstandard2.0).
+                factoryArgument: (AttributeLocation: attributeLocation, Interceptor: interceptor));
+        }
+
+        internal (Location AttributeLocation, MethodSymbol Interceptor)? TryGetInterceptor(Location? callLocation)
+        {
+            if (_interceptions is null || callLocation is null)
+            {
+                return null;
+            }
+
+            var callLineColumn = callLocation.GetLineSpan().Span.Start;
+            Debug.Assert(callLocation.SourceTree is not null);
+            var key = (callLocation.SourceTree.FilePath, callLineColumn.Line, callLineColumn.Character);
+
+            if (_interceptions.TryGetValue(key, out var interceptionsAtAGivenLocation))
+            {
+                if (interceptionsAtAGivenLocation is [var oneInterception])
+                {
+                    return oneInterception;
+                }
+
+                // Duplicate interceptors is an error in the declaration phase.
+                // This method is only expected to be called if no such errors are present.
+                throw ExceptionUtilities.Unreachable();
+            }
+
+            return null;
+        }
+
         #endregion
 
         #region Binding
@@ -3392,7 +3481,7 @@ public override void VisitNamespace(NamespaceSymbol symbol)
             public override void VisitNamedType(NamedTypeSymbol symbol)
             {
                 Debug.Assert(symbol.ContainingSymbol.Kind == SymbolKind.Namespace); // avoid unnecessary traversal of nested types
-                if (symbol.AssociatedFileIdentifier is not null)
+                if (symbol.IsFileLocal)
                 {
                     var location = symbol.GetFirstLocation();
                     var filePath = location.SourceTree?.FilePath;
@@ -3405,12 +3494,40 @@ public override void VisitNamedType(NamedTypeSymbol symbol)
             }
         }
 
+        /// <returns><see langword="true"/> if file types are present in files with duplicate file paths. Otherwise, <see langword="false" />.</returns>
         private bool CheckDuplicateFilePaths(DiagnosticBag diagnostics)
         {
             var visitor = new DuplicateFilePathsVisitor(diagnostics);
             return visitor.CheckDuplicateFilePathsAndFree(SyntaxTrees, GlobalNamespace);
         }
 
+        /// <returns><see langword="true"/> if duplicate interceptions are present in the compilation. Otherwise, <see langword="false" />.</returns>
+        internal bool CheckDuplicateInterceptions(BindingDiagnosticBag diagnostics)
+        {
+            if (_interceptions is null)
+            {
+                return false;
+            }
+
+            bool anyDuplicates = false;
+            foreach ((_, OneOrMany<(Location, MethodSymbol)> interceptionsOfAGivenLocation) in _interceptions)
+            {
+                Debug.Assert(interceptionsOfAGivenLocation.Count != 0);
+                if (interceptionsOfAGivenLocation.Count == 1)
+                {
+                    continue;
+                }
+
+                anyDuplicates = true;
+                foreach (var (attributeLocation, _) in interceptionsOfAGivenLocation)
+                {
+                    diagnostics.Add(ErrorCode.ERR_DuplicateInterceptor, attributeLocation);
+                }
+            }
+
+            return anyDuplicates;
+        }
+
         private void GenerateModuleInitializer(PEModuleBuilder moduleBeingBuilt, DiagnosticBag methodBodyDiagnosticBag)
         {
             Debug.Assert(_declarationDiagnosticsFrozen);
diff --git a/src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs b/src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs
index 938e722167175..cb9015f31f5d7 100644
--- a/src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs
+++ b/src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs
@@ -2239,11 +2239,12 @@ protected internal virtual CSharpSyntaxNode GetBindableSyntaxNode(CSharpSyntaxNo
             return node;
         }
 
+#nullable enable
         /// <summary>
         /// If the node is an expression, return the nearest parent node
         /// with semantic meaning. Otherwise return null.
         /// </summary>
-        protected CSharpSyntaxNode GetBindableParentNode(CSharpSyntaxNode node)
+        protected CSharpSyntaxNode? GetBindableParentNode(CSharpSyntaxNode node)
         {
             if (!(node is ExpressionSyntax))
             {
@@ -2251,7 +2252,7 @@ protected CSharpSyntaxNode GetBindableParentNode(CSharpSyntaxNode node)
             }
 
             // The node is an expression, but its parent is null
-            CSharpSyntaxNode parent = node.Parent;
+            CSharpSyntaxNode? parent = node.Parent;
             if (parent == null)
             {
                 // For speculative model, expression might be the root of the syntax tree, in which case it can have a null parent.
@@ -2289,17 +2290,25 @@ protected CSharpSyntaxNode GetBindableParentNode(CSharpSyntaxNode node)
             // the node is the instance associated with the method invocation.
             // In that case, return the invocation expression so that any conversion
             // of the receiver can be included in the resulting SemanticInfo.
-            if ((bindableParent.Kind() == SyntaxKind.SimpleMemberAccessExpression) && (bindableParent.Parent.Kind() == SyntaxKind.InvocationExpression))
-            {
-                bindableParent = bindableParent.Parent;
-            }
-            else if (bindableParent.Kind() == SyntaxKind.ArrayType)
+            switch (bindableParent)
             {
-                bindableParent = SyntaxFactory.GetStandaloneExpression((ArrayTypeSyntax)bindableParent);
+                case { RawKind: (int)SyntaxKind.SimpleMemberAccessExpression, Parent.RawKind: (int)SyntaxKind.InvocationExpression }:
+                    bindableParent = bindableParent.Parent;
+                    break;
+                case ArrayTypeSyntax arrayType:
+                    bindableParent = SyntaxFactory.GetStandaloneExpression(arrayType);
+                    break;
+                case { RawKind: (int)SyntaxKind.ComplexElementInitializerExpression }:
+                    // The { "a", "b" } node in a collection initializer is marked as compiler-generated, and will never
+                    // end up in the bound node map. We don't need the parent node for any calculations here, so just return
+                    // null to avoid rebinding the initializer (which can cause exponential binding problems, see EndToEndTests.LongInitializerList).
+                    bindableParent = null;
+                    break;
             }
 
             return bindableParent;
         }
+#nullable disable
 
         internal override Symbol RemapSymbolIfNecessaryCore(Symbol symbol)
         {
diff --git a/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs b/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs
index 4139b33f4e855..655f8dbc89f6d 100644
--- a/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs
+++ b/src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs
@@ -120,6 +120,8 @@ public static void CompileMethodBodies(
             Debug.Assert(diagnostics != null);
             Debug.Assert(diagnostics.DiagnosticBag != null);
 
+            hasDeclarationErrors |= compilation.CheckDuplicateInterceptions(diagnostics);
+
             if (compilation.PreviousSubmission != null)
             {
                 // In case there is a previous submission, we should ensure
diff --git a/src/Compilers/CSharp/Portable/Emitter/Model/MethodSymbolAdapter.cs b/src/Compilers/CSharp/Portable/Emitter/Model/MethodSymbolAdapter.cs
index 7001a361d209b..8ac3c889e541d 100644
--- a/src/Compilers/CSharp/Portable/Emitter/Model/MethodSymbolAdapter.cs
+++ b/src/Compilers/CSharp/Portable/Emitter/Model/MethodSymbolAdapter.cs
@@ -72,7 +72,7 @@ Cci.ITypeReference Cci.ITypeMemberReference.GetContainingType(EmitContext contex
         {
             Debug.Assert(this.IsDefinitionOrDistinct());
 
-            var synthesizedGlobalMethod = AdaptedMethodSymbol as SynthesizedGlobalMethodSymbol;
+            var synthesizedGlobalMethod = AdaptedMethodSymbol.OriginalDefinition as SynthesizedGlobalMethodSymbol;
             if ((object)synthesizedGlobalMethod != null)
             {
                 return synthesizedGlobalMethod.ContainingPrivateImplementationDetailsType;
@@ -300,7 +300,7 @@ Cci.ITypeDefinition Cci.ITypeDefinitionMember.ContainingTypeDefinition
             {
                 CheckDefinitionInvariant();
 
-                var synthesizedGlobalMethod = AdaptedMethodSymbol as SynthesizedGlobalMethodSymbol;
+                var synthesizedGlobalMethod = AdaptedMethodSymbol.OriginalDefinition as SynthesizedGlobalMethodSymbol;
                 if ((object)synthesizedGlobalMethod != null)
                 {
                     return synthesizedGlobalMethod.ContainingPrivateImplementationDetailsType;
diff --git a/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs b/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs
index 27702b3664a69..775abe083aa8a 100644
--- a/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs
+++ b/src/Compilers/CSharp/Portable/Emitter/Model/PEModuleBuilder.cs
@@ -1858,21 +1858,34 @@ internal MethodSymbol EnsureThrowIfNullFunctionExists(SyntaxNode syntaxNode, Syn
         /// Creates the ThrowSwitchExpressionException helper if needed.
         /// </summary>
         internal MethodSymbol EnsureThrowSwitchExpressionExceptionExists(SyntaxNode syntaxNode, SyntheticBoundNodeFactory factory, DiagnosticBag diagnostics)
+        {
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionFunctionName,
+                                                      static (sourceModule, privateImplClass, factory) =>
+                                                      {
+                                                          TypeSymbol returnType = factory.SpecialType(SpecialType.System_Void);
+                                                          TypeSymbol unmatchedValueType = factory.SpecialType(SpecialType.System_Object);
+                                                          return new SynthesizedThrowSwitchExpressionExceptionMethod(sourceModule, privateImplClass, returnType, unmatchedValueType);
+                                                      },
+                                                      factory,
+                                                      diagnostics);
+        }
+
+        private MethodSymbol EnsurePrivateImplClassMethodExists<TArg>(SyntaxNode syntaxNode, string methodName, Func<SourceModuleSymbol, PrivateImplementationDetails, TArg, MethodSymbol> createMethodSymbol, TArg arg, DiagnosticBag diagnostics)
         {
             var privateImplClass = GetPrivateImplClass(syntaxNode, diagnostics);
-            var throwSwitchExpressionAdapter = privateImplClass.GetMethod(PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionFunctionName);
-            if (throwSwitchExpressionAdapter is not null)
+            var methodAdapter = privateImplClass.GetMethod(methodName);
+            if (methodAdapter is not null)
             {
-                return (MethodSymbol)throwSwitchExpressionAdapter.GetInternalSymbol()!;
+                Debug.Assert(methodAdapter.Name == methodName);
+                return (MethodSymbol)methodAdapter.GetInternalSymbol()!;
             }
 
-            TypeSymbol returnType = factory.SpecialType(SpecialType.System_Void);
-            TypeSymbol unmatchedValueType = factory.SpecialType(SpecialType.System_Object);
-            var sourceModule = SourceModule;
+            MethodSymbol methodSymbol = createMethodSymbol(SourceModule, privateImplClass, arg);
+            Debug.Assert(methodSymbol.Name == methodName);
 
             // use add-then-get pattern to ensure the symbol exists, and then ensure we use the single "canonical" instance added by whichever thread won the race.
-            privateImplClass.TryAddSynthesizedMethod(new SynthesizedThrowSwitchExpressionExceptionMethod(sourceModule, privateImplClass, returnType, unmatchedValueType).GetCciAdapter());
-            return (MethodSymbol)privateImplClass.GetMethod(PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionFunctionName)!.GetInternalSymbol()!;
+            privateImplClass.TryAddSynthesizedMethod(methodSymbol.GetCciAdapter());
+            return (MethodSymbol)privateImplClass.GetMethod(methodName)!.GetInternalSymbol()!;
         }
 
         /// <summary>
@@ -1880,24 +1893,20 @@ internal MethodSymbol EnsureThrowSwitchExpressionExceptionExists(SyntaxNode synt
         /// </summary>
         internal MethodSymbol EnsureThrowSwitchExpressionExceptionParameterlessExists(SyntaxNode syntaxNode, SyntheticBoundNodeFactory factory, DiagnosticBag diagnostics)
         {
-            var privateImplClass = GetPrivateImplClass(syntaxNode, diagnostics);
-            var throwSwitchExpressionAdapter = privateImplClass.GetMethod(PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionParameterlessFunctionName);
-            if (throwSwitchExpressionAdapter is not null)
-            {
-                return (MethodSymbol)throwSwitchExpressionAdapter.GetInternalSymbol()!;
-            }
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionParameterlessFunctionName,
+                                                      static (sourceModule, privateImplClass, factory) =>
+                                                      {
+                                                          TypeSymbol returnType = factory.SpecialType(SpecialType.System_Void);
 
-            TypeSymbol returnType = factory.SpecialType(SpecialType.System_Void);
-            var sourceModule = SourceModule;
-
-            // use add-then-get pattern to ensure the symbol exists, and then ensure we use the single "canonical" instance added by whichever thread won the race.
-            privateImplClass.TryAddSynthesizedMethod(new SynthesizedParameterlessThrowMethod(
-                sourceModule,
-                privateImplClass,
-                returnType,
-                PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionParameterlessFunctionName,
-                factory.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctor)).GetCciAdapter());
-            return (MethodSymbol)privateImplClass.GetMethod(PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionParameterlessFunctionName)!.GetInternalSymbol()!;
+                                                          return new SynthesizedParameterlessThrowMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              returnType,
+                                                              PrivateImplementationDetails.SynthesizedThrowSwitchExpressionExceptionParameterlessFunctionName,
+                                                              factory.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctor));
+                                                      },
+                                                      factory,
+                                                      diagnostics);
         }
 
         /// <summary>
@@ -1905,25 +1914,120 @@ internal MethodSymbol EnsureThrowSwitchExpressionExceptionParameterlessExists(Sy
         /// </summary>
         internal MethodSymbol EnsureThrowInvalidOperationExceptionExists(SyntaxNode syntaxNode, SyntheticBoundNodeFactory factory, DiagnosticBag diagnostics)
         {
-            var privateImplClass = GetPrivateImplClass(syntaxNode, diagnostics);
-            var throwAdapter = privateImplClass.GetMethod(PrivateImplementationDetails.SynthesizedThrowInvalidOperationExceptionFunctionName);
-            if (throwAdapter is not null)
-            {
-                return (MethodSymbol)throwAdapter.GetInternalSymbol()!;
-            }
-
-            TypeSymbol returnType = factory.SpecialType(SpecialType.System_Void);
-            var sourceModule = SourceModule;
-
-            // use add-then-get pattern to ensure the symbol exists, and then ensure we use the single "canonical" instance added by whichever thread won the race.
-            privateImplClass.TryAddSynthesizedMethod(new SynthesizedParameterlessThrowMethod(
-                sourceModule,
-                privateImplClass,
-                returnType,
-                PrivateImplementationDetails.SynthesizedThrowInvalidOperationExceptionFunctionName,
-                factory.WellKnownMethod(WellKnownMember.System_InvalidOperationException__ctor)).GetCciAdapter());
-            return (MethodSymbol)privateImplClass.GetMethod(PrivateImplementationDetails.SynthesizedThrowInvalidOperationExceptionFunctionName)!.GetInternalSymbol()!;
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedThrowInvalidOperationExceptionFunctionName,
+                                                      static (sourceModule, privateImplClass, factory) =>
+                                                      {
+                                                          TypeSymbol returnType = factory.SpecialType(SpecialType.System_Void);
+
+                                                          return new SynthesizedParameterlessThrowMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              returnType,
+                                                              PrivateImplementationDetails.SynthesizedThrowInvalidOperationExceptionFunctionName,
+                                                              factory.WellKnownMethod(WellKnownMember.System_InvalidOperationException__ctor));
+                                                      },
+                                                      factory,
+                                                      diagnostics);
+        }
+
+        internal MethodSymbol EnsureInlineArrayAsSpanExists(SyntaxNode syntaxNode, NamedTypeSymbol spanType, NamedTypeSymbol intType, DiagnosticBag diagnostics)
+        {
+            Debug.Assert(intType.SpecialType == SpecialType.System_Int32);
+
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName,
+                                                      static (sourceModule, privateImplClass, arg) =>
+                                                      {
+                                                          return new SynthesizedInlineArrayAsSpanMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName,
+                                                              arg.spanType,
+                                                              arg.intType);
+                                                      },
+                                                      (spanType, intType),
+                                                      diagnostics);
+        }
+
+        internal MethodSymbol EnsureInlineArrayAsReadOnlySpanExists(SyntaxNode syntaxNode, NamedTypeSymbol spanType, NamedTypeSymbol intType, DiagnosticBag diagnostics)
+        {
+            Debug.Assert(intType.SpecialType == SpecialType.System_Int32);
+
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName,
+                                                      static (sourceModule, privateImplClass, arg) =>
+                                                      {
+                                                          return new SynthesizedInlineArrayAsReadOnlySpanMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName,
+                                                              arg.spanType,
+                                                              arg.intType);
+                                                      },
+                                                      (spanType, intType),
+                                                      diagnostics);
+        }
+
+        internal MethodSymbol EnsureInlineArrayElementRefExists(SyntaxNode syntaxNode, NamedTypeSymbol intType, DiagnosticBag diagnostics)
+        {
+            Debug.Assert(intType.SpecialType == SpecialType.System_Int32);
+
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedInlineArrayElementRefName,
+                                                      static (sourceModule, privateImplClass, intType) =>
+                                                      {
+                                                          return new SynthesizedInlineArrayElementRefMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              PrivateImplementationDetails.SynthesizedInlineArrayElementRefName,
+                                                              intType);
+                                                      },
+                                                      intType,
+                                                      diagnostics);
+        }
+
+        internal MethodSymbol EnsureInlineArrayElementRefReadOnlyExists(SyntaxNode syntaxNode, NamedTypeSymbol intType, DiagnosticBag diagnostics)
+        {
+            Debug.Assert(intType.SpecialType == SpecialType.System_Int32);
+
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName,
+                                                      static (sourceModule, privateImplClass, intType) =>
+                                                      {
+                                                          return new SynthesizedInlineArrayElementRefReadOnlyMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName,
+                                                              intType);
+                                                      },
+                                                      intType,
+                                                      diagnostics);
+        }
+
+        internal MethodSymbol EnsureInlineArrayFirstElementRefExists(SyntaxNode syntaxNode, DiagnosticBag diagnostics)
+        {
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName,
+                                                      static (sourceModule, privateImplClass, _) =>
+                                                      {
+                                                          return new SynthesizedInlineArrayFirstElementRefMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName);
+                                                      },
+                                                      (object?)null,
+                                                      diagnostics);
+        }
+
+        internal MethodSymbol EnsureInlineArrayFirstElementRefReadOnlyExists(SyntaxNode syntaxNode, DiagnosticBag diagnostics)
+        {
+            return EnsurePrivateImplClassMethodExists(syntaxNode, PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName,
+                                                      static (sourceModule, privateImplClass, _) =>
+                                                      {
+                                                          return new SynthesizedInlineArrayFirstElementRefReadOnlyMethod(
+                                                              sourceModule,
+                                                              privateImplClass,
+                                                              PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName);
+                                                      },
+                                                      (object?)null,
+                                                      diagnostics);
         }
+
 #nullable disable
 
         public override IEnumerable<Cci.INamespaceTypeDefinition> GetAdditionalTopLevelTypeDefinitions(EmitContext context)
diff --git a/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs b/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
index 29c4bf2ea0d4a..ae886e9e7158e 100644
--- a/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
+++ b/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
@@ -2182,6 +2182,7 @@ internal enum ErrorCode
         ERR_StructLayoutCyclePrimaryConstructorParameter = 9121,
         ERR_UnexpectedParameterList = 9122,
         WRN_AddressOfInAsync = 9123,
+        WRN_CapturedPrimaryConstructorParameterInFieldInitializer = 9124,
 
         ERR_BadRefInUsingAlias = 9130,
         ERR_BadUnsafeInUsingDirective = 9131,
@@ -2192,6 +2193,46 @@ internal enum ErrorCode
         ERR_ConstantValueOfTypeExpected = 9135,
         ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny = 9136,
 
+        ERR_InterceptorsFeatureNotEnabled = 9137,
+        ERR_InterceptorCannotBeGeneric = 9138,
+        ERR_InterceptorPathNotInCompilation = 9139,
+        ERR_InterceptorPathNotInCompilationWithCandidate = 9140,
+        ERR_InterceptorPositionBadToken = 9141,
+        ERR_InterceptorLineOutOfRange = 9142,
+        ERR_InterceptorCharacterOutOfRange = 9143,
+        ERR_InterceptorSignatureMismatch = 9144,
+        ERR_InterceptorPathNotInCompilationWithUnmappedCandidate = 9145,
+        ERR_InterceptorMethodMustBeOrdinary = 9146,
+        ERR_InterceptorMustReferToStartOfTokenPosition = 9147,
+        ERR_InterceptorMustHaveMatchingThisParameter = 9148,
+        ERR_InterceptorMustNotHaveThisParameter = 9149,
+        ERR_InterceptorFilePathCannotBeNull = 9150,
+        ERR_InterceptorNameNotInvoked = 9151,
+        ERR_InterceptorNonUniquePath = 9152,
+        ERR_DuplicateInterceptor = 9153,
+        WRN_InterceptorSignatureMismatch = 9154,
+        ERR_InterceptorNotAccessible = 9155,
+        ERR_InterceptorScopedMismatch = 9156,
+        ERR_InterceptorLineCharacterMustBePositive = 9157,
+        WRN_NullabilityMismatchInReturnTypeOnInterceptor = 9158,
+        WRN_NullabilityMismatchInParameterTypeOnInterceptor = 9159,
+        ERR_InterceptorCannotInterceptNameof = 9160,
+        ERR_InterceptorCannotUseUnmanagedCallersOnly = 9161,
+
+        ERR_BadUsingStaticType = 9162,
+        ERR_SymbolDefinedInAssembly = 9163,
+
+        ERR_InlineArrayConversionToSpanNotSupported = 9164,
+        ERR_InlineArrayConversionToReadOnlySpanNotSupported = 9165,
+        ERR_InlineArrayIndexOutOfRange = 9166,
+        ERR_InvalidInlineArrayLength = 9167,
+        ERR_InvalidInlineArrayLayout = 9168,
+        ERR_InvalidInlineArrayFields = 9169,
+        ERR_ExpressionTreeContainsInlineArrayOperation = 9170,
+        ERR_RuntimeDoesNotSupportInlineArrayTypes = 9171,
+        ERR_InlineArrayBadIndex = 9172,
+        ERR_NamedArgumentForInlineArray = 9173,
+
         ERR_CollectionLiteralTargetTypeNotConstructible = 9500, // PROTOTYPE: Update error numbers.
         ERR_ExpressionTreeContainsCollectionLiteral = 9501,
         ERR_CollectionLiteralNoTargetType = 9503,
diff --git a/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs b/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs
index 0da21f2bc3025..631206ffe7a84 100644
--- a/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs
+++ b/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs
@@ -80,6 +80,8 @@ static ErrorFacts()
             nullableWarnings.Add(GetId(ErrorCode.WRN_ParameterDisallowsNull));
             nullableWarnings.Add(GetId(ErrorCode.WRN_ParameterNotNullIfNotNull));
             nullableWarnings.Add(GetId(ErrorCode.WRN_ReturnNotNullIfNotNull));
+            nullableWarnings.Add(GetId(ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor));
+            nullableWarnings.Add(GetId(ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor));
 
             NullableWarnings = nullableWarnings.ToImmutable();
         }
@@ -530,6 +532,10 @@ internal static int GetWarningLevel(ErrorCode code)
                 case ErrorCode.WRN_ParamsArrayInLambdaOnly:
                 case ErrorCode.WRN_CapturedPrimaryConstructorParameterPassedToBase:
                 case ErrorCode.WRN_UnreadPrimaryConstructorParameter:
+                case ErrorCode.WRN_InterceptorSignatureMismatch:
+                case ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor:
+                case ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor:
+                case ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer:
                     return 1;
                 default:
                     return 0;
@@ -579,6 +585,17 @@ internal static bool IsBuildOnlyDiagnostic(ErrorCode code)
                 case ErrorCode.ERR_EncUpdateFailedDelegateTypeChanged:
                 case ErrorCode.ERR_CannotBeConvertedToUtf8:
                 case ErrorCode.ERR_FileTypeNonUniquePath:
+                case ErrorCode.ERR_InterceptorSignatureMismatch:
+                case ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter:
+                case ErrorCode.ERR_InterceptorMustNotHaveThisParameter:
+                case ErrorCode.ERR_DuplicateInterceptor:
+                case ErrorCode.WRN_InterceptorSignatureMismatch:
+                case ErrorCode.ERR_InterceptorNotAccessible:
+                case ErrorCode.ERR_InterceptorScopedMismatch:
+                case ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor:
+                case ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor:
+                case ErrorCode.ERR_InterceptorCannotInterceptNameof:
+                case ErrorCode.ERR_SymbolDefinedInAssembly:
                     // Update src\EditorFeatures\CSharp\LanguageServer\CSharpLspBuildOnlyDiagnostics.cs
                     // whenever new values are added here.
                     return true;
@@ -2309,8 +2326,35 @@ internal static bool IsBuildOnlyDiagnostic(ErrorCode code)
                 case ErrorCode.ERR_BadNullableReferenceTypeInUsingAlias:
                 case ErrorCode.ERR_BadStaticAfterUnsafe:
                 case ErrorCode.ERR_BadCaseInSwitchArm:
+                case ErrorCode.ERR_InterceptorsFeatureNotEnabled:
+                case ErrorCode.ERR_InterceptorCannotBeGeneric:
+                case ErrorCode.ERR_InterceptorPathNotInCompilation:
+                case ErrorCode.ERR_InterceptorPathNotInCompilationWithCandidate:
+                case ErrorCode.ERR_InterceptorPathNotInCompilationWithUnmappedCandidate:
+                case ErrorCode.ERR_InterceptorPositionBadToken:
+                case ErrorCode.ERR_InterceptorLineOutOfRange:
+                case ErrorCode.ERR_InterceptorCharacterOutOfRange:
+                case ErrorCode.ERR_InterceptorMethodMustBeOrdinary:
+                case ErrorCode.ERR_InterceptorMustReferToStartOfTokenPosition:
+                case ErrorCode.ERR_InterceptorFilePathCannotBeNull:
+                case ErrorCode.ERR_InterceptorNameNotInvoked:
+                case ErrorCode.ERR_InterceptorNonUniquePath:
+                case ErrorCode.ERR_InterceptorLineCharacterMustBePositive:
                 case ErrorCode.ERR_ConstantValueOfTypeExpected:
                 case ErrorCode.ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny:
+                case ErrorCode.ERR_InterceptorCannotUseUnmanagedCallersOnly:
+                case ErrorCode.ERR_BadUsingStaticType:
+                case ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer:
+                case ErrorCode.ERR_InlineArrayConversionToSpanNotSupported:
+                case ErrorCode.ERR_InlineArrayConversionToReadOnlySpanNotSupported:
+                case ErrorCode.ERR_InlineArrayIndexOutOfRange:
+                case ErrorCode.ERR_InvalidInlineArrayLength:
+                case ErrorCode.ERR_InvalidInlineArrayLayout:
+                case ErrorCode.ERR_InvalidInlineArrayFields:
+                case ErrorCode.ERR_ExpressionTreeContainsInlineArrayOperation:
+                case ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes:
+                case ErrorCode.ERR_InlineArrayBadIndex:
+                case ErrorCode.ERR_NamedArgumentForInlineArray:
                 case ErrorCode.ERR_CollectionLiteralTargetTypeNotConstructible:
                 case ErrorCode.ERR_ExpressionTreeContainsCollectionLiteral:
                 case ErrorCode.ERR_CollectionLiteralNoTargetType:
diff --git a/src/Compilers/CSharp/Portable/Errors/MessageID.cs b/src/Compilers/CSharp/Portable/Errors/MessageID.cs
index 2205320a17f9e..ce8b62f4e4a2a 100644
--- a/src/Compilers/CSharp/Portable/Errors/MessageID.cs
+++ b/src/Compilers/CSharp/Portable/Errors/MessageID.cs
@@ -82,6 +82,11 @@ internal enum MessageID
         IDS_FeatureAutoPropertyInitializer = MessageBase + 12649,
 
         IDS_SK_TYPE_OR_NAMESPACE = MessageBase + 12652,
+        IDS_SK_ARRAY = MessageBase + 12653,
+        IDS_SK_POINTER = MessageBase + 12654,
+        IDS_SK_FUNCTION_POINTER = MessageBase + 12655,
+        IDS_SK_DYNAMIC = MessageBase + 12656,
+
         IDS_Contravariant = MessageBase + 12659,
         IDS_Contravariantly = MessageBase + 12660,
         IDS_Covariant = MessageBase + 12661,
@@ -267,6 +272,8 @@ internal enum MessageID
         IDS_FeatureUsingTypeAlias = MessageBase + 12834,
 
         IDS_FeatureInstanceMemberInNameof = MessageBase + 12835,
+
+        IDS_FeatureInlineArrays = MessageBase + 12836,
         IDS_FeatureCollectionLiterals = MessageBase + 12900, // PROTOTYPE: Update message number.
     }
 
@@ -453,6 +460,7 @@ internal static LanguageVersion RequiredVersion(this MessageID feature)
                 case MessageID.IDS_FeaturePrimaryConstructors: // declaration table check
                 case MessageID.IDS_FeatureUsingTypeAlias: // semantic check
                 case MessageID.IDS_FeatureInstanceMemberInNameof: // semantic check
+                case MessageID.IDS_FeatureInlineArrays: // semantic check
                 case MessageID.IDS_FeatureCollectionLiterals: // semantic check
                     return LanguageVersion.Preview;
 
diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs
index 67924df04171b..6024414d9514b 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs
@@ -567,15 +567,17 @@ protected void VisitLvalue(BoundExpression node)
                     break;
 
                 case BoundKind.PropertyAccess:
-                    var access = (BoundPropertyAccess)node;
-
-                    if (Binder.AccessingAutoPropertyFromConstructor(access, _symbol))
                     {
-                        var backingField = (access.PropertySymbol as SourcePropertySymbolBase)?.BackingField;
-                        if (backingField != null)
+                        var access = (BoundPropertyAccess)node;
+
+                        if (Binder.AccessingAutoPropertyFromConstructor(access, _symbol))
                         {
-                            VisitFieldAccessInternal(access.ReceiverOpt, backingField);
-                            break;
+                            var backingField = (access.PropertySymbol as SourcePropertySymbolBase)?.BackingField;
+                            if (backingField != null)
+                            {
+                                VisitFieldAccessInternal(access.ReceiverOpt, backingField);
+                                break;
+                            }
                         }
                     }
 
@@ -600,6 +602,12 @@ protected void VisitLvalue(BoundExpression node)
                     ((BoundTupleExpression)node).VisitAllElements((x, self) => self.VisitLvalue(x), this);
                     break;
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var access = (BoundInlineArrayAccess)node;
+                        VisitLvalue(access);
+                        break;
+                    }
                 default:
                     VisitRvalue(node);
                     break;
@@ -1681,9 +1689,15 @@ public override BoundNode VisitConversion(BoundConversion node)
                 Visit(node.Operand);
             }
 
+            AfterVisitConversion(node);
+
             return null;
         }
 
+        protected virtual void AfterVisitConversion(BoundConversion node)
+        {
+        }
+
         public override BoundNode VisitIfStatement(BoundIfStatement node)
         {
             // 5.3.3.5 If statements
@@ -2245,6 +2259,25 @@ public override BoundNode VisitArrayAccess(BoundArrayAccess node)
             return null;
         }
 
+        public override BoundNode VisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            VisitRvalue(node.Expression);
+            VisitRvalue(node.Argument);
+
+            AfterVisitInlineArrayAccess(node);
+            return null;
+        }
+
+        protected virtual void AfterVisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+        }
+
+        protected virtual void VisitLvalue(BoundInlineArrayAccess access)
+        {
+            VisitLvalue(access.Expression);
+            VisitRvalue(access.Argument);
+        }
+
         public override BoundNode VisitBinaryOperator(BoundBinaryOperator node)
         {
             if (node.OperatorKind.IsLogical())
diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractRegionDataFlowPass.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractRegionDataFlowPass.cs
index 4e51e4c6715b4..153aa9b03f482 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractRegionDataFlowPass.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractRegionDataFlowPass.cs
@@ -62,5 +62,13 @@ private void MakeSlots(ImmutableArray<ParameterSymbol> parameters)
                 GetOrCreateSlot(parameter);
             }
         }
+
+        protected override void AfterVisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+        }
+
+        protected override void AfterVisitConversion(BoundConversion node)
+        {
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/DefiniteAssignment.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/DefiniteAssignment.cs
index a58ca3cf6a41d..2b25df8da8f90 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/DefiniteAssignment.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/DefiniteAssignment.cs
@@ -472,7 +472,9 @@ protected virtual void ReportUnassignedOutParameter(ParameterSymbol parameter, S
                     Debug.Assert(thisSlot > 0);
                     if (!this.State.IsAssigned(thisSlot))
                     {
-                        foreach (var field in _emptyStructTypeCache.GetStructInstanceFields(parameter.Type))
+                        TypeSymbol parameterType = parameter.Type;
+
+                        foreach (var field in _emptyStructTypeCache.GetStructInstanceFields(parameterType))
                         {
                             if (_emptyStructTypeCache.IsEmptyStructType(field.Type)) continue;
 
@@ -500,9 +502,29 @@ protected virtual void ReportUnassignedOutParameter(ParameterSymbol parameter, S
                                 }
 
                                 this.AddImplicitlyInitializedField(field);
+                                reported = true;
+                            }
+                        }
+
+                        if (!reported)
+                        {
+                            if (parameterType.HasInlineArrayAttribute(out int length) && length > 1 && parameterType.TryGetInlineArrayElementField() is FieldSymbol elementField)
+                            {
+                                if (!compilation.IsFeatureEnabled(MessageID.IDS_FeatureAutoDefaultStructs))
+                                {
+                                    Diagnostics.Add(ErrorCode.ERR_ParamUnassigned, location, parameter.Name);
+                                }
+
+                                // Add the element field to the set of fields requiring initialization to indicate that the whole instance needs initialization.
+                                // This is done explicitly only for unreported cases, because, if something was reported, then we already have added the
+                                // element field in the set. It is the only instance field in the type.
+                                // One-length inline arrays do not need special handling because we can completely rely on the tracking around the underlying
+                                // field itself.
+                                this.AddImplicitlyInitializedField(elementField);
                             }
+
+                            reported = true;
                         }
-                        reported = true;
                     }
                 }
 
@@ -812,6 +834,13 @@ private void NoteRead(BoundNode fieldOrEventAccess)
                         NoteRead(((BoundParameter)n).ParameterSymbol);
                         return;
 
+                    case BoundKind.InlineArrayAccess:
+                        {
+                            var elementAccess = (BoundInlineArrayAccess)n;
+                            n = elementAccess.Expression;
+                            continue;
+                        }
+
                     default:
                         return;
                 }
@@ -988,6 +1017,14 @@ private void NoteWrite(BoundExpression n, BoundExpression value, bool read)
                         NoteWrite(((BoundRangeVariable)n).Value, value, read);
                         return;
 
+                    case BoundKind.InlineArrayAccess:
+                        {
+                            var elementAccess = (BoundInlineArrayAccess)n;
+                            n = elementAccess.Expression;
+                            value = null;
+                            continue;
+                        }
+
                     default:
                         return;
                 }
@@ -1214,10 +1251,9 @@ void addDiagnosticForStructThis(Symbol thisParameter, int thisSlot)
                 Debug.Assert(CurrentSymbol is MethodSymbol { MethodKind: MethodKind.Constructor, ContainingType.TypeKind: TypeKind.Struct });
                 if (TrackImplicitlyInitializedFields)
                 {
-#if DEBUG
                     bool foundUnassignedField = false;
-#endif
-                    foreach (var field in _emptyStructTypeCache.GetStructInstanceFields(thisParameter.ContainingType))
+                    NamedTypeSymbol containingType = thisParameter.ContainingType;
+                    foreach (var field in _emptyStructTypeCache.GetStructInstanceFields(containingType))
                     {
                         if (_emptyStructTypeCache.IsEmptyStructType(field.Type))
                             continue;
@@ -1229,15 +1265,22 @@ void addDiagnosticForStructThis(Symbol thisParameter, int thisSlot)
                         if (slot == -1 || !State.IsAssigned(slot))
                         {
                             AddImplicitlyInitializedField(field);
-#if DEBUG
                             foundUnassignedField = true;
-#endif
                         }
                     }
 
-#if DEBUG
+                    if (!foundUnassignedField && containingType.HasInlineArrayAttribute(out int length) && length > 1 && containingType.TryGetInlineArrayElementField() is FieldSymbol elementField)
+                    {
+                        // Add the element field to the set of fields requiring initialization to indicate that the whole instance needs initialization.
+                        // This is done explicitly only for unreported cases, because, if something was reported, then we already have added the
+                        // element field in the set. It is the only instance field in the type.
+                        // One-length inline arrays do not need special handling because we can completely rely on the tracking around the underlying
+                        // field itself.
+                        this.AddImplicitlyInitializedField(elementField);
+                        foundUnassignedField = true;
+                    }
+
                     Debug.Assert(foundUnassignedField);
-#endif
                 }
 
                 if (compilation.IsFeatureEnabled(MessageID.IDS_FeatureAutoDefaultStructs))
@@ -1363,6 +1406,12 @@ private bool IsAssigned(BoundExpression node, out int unassignedSlot)
                         break;
                     }
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)node;
+                        return IsAssigned(elementAccess.Expression, out unassignedSlot);
+                    }
+
                 case BoundKind.PropertyAccess:
                     {
                         var propertyAccess = (BoundPropertyAccess)node;
@@ -1512,6 +1561,36 @@ protected virtual void AssignImpl(BoundNode node, BoundExpression value, bool is
                         break;
                     }
 
+                case BoundKind.InlineArrayAccess:
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)node;
+                        if (written)
+                        {
+                            NoteWrite(elementAccess.Expression, value: null, read);
+                        }
+
+                        if (elementAccess.Expression.Type.HasInlineArrayAttribute(out int length) &&
+                            (elementAccess.Argument.ConstantValueOpt is { SpecialType: SpecialType.System_Int32, Int32Value: 0 } ||
+                             Binder.InferConstantIndexFromSystemIndex(compilation, elementAccess.Argument, length, out _) is 0))
+                        {
+                            int slot = MakeMemberSlot(elementAccess.Expression, elementAccess.Expression.Type.TryGetInlineArrayElementField());
+                            if (slot > 0)
+                            {
+                                SetSlotState(slot, written);
+                                break;
+                            }
+                        }
+
+                        if (!written)
+                        {
+                            AssignImpl(elementAccess.Expression, value: null, isRef, written, read);
+                            int slot = MakeSlot(elementAccess.Expression);
+                            SetSlotState(slot, written);
+                        }
+
+                        break;
+                    }
+
                 case BoundKind.Parameter:
                     {
                         var paramExpr = (BoundParameter)node;
@@ -1577,6 +1656,13 @@ private bool FieldsAllSet(int containingSlot, LocalState state)
             Debug.Assert(!state.IsAssigned(containingSlot));
             VariableIdentifier variable = variableBySlot[containingSlot];
             TypeSymbol structType = variable.Symbol.GetTypeOrReturnType().Type;
+
+            if (structType.HasInlineArrayAttribute(out int length) && length > 1 && structType.TryGetInlineArrayElementField() is object)
+            {
+                // An inline array of length > 1 cannot be considered fully initialized judging only based on fields.
+                return false;
+            }
+
             foreach (var field in _emptyStructTypeCache.GetStructInstanceFields(structType))
             {
                 if (_emptyStructTypeCache.IsEmptyStructType(field.Type)) continue;
@@ -2455,6 +2541,10 @@ protected void CheckAssigned(BoundExpression expr, SyntaxNode node)
                 case BoundKind.BaseReference:
                     CheckAssigned(MethodThisParameter, node);
                     break;
+
+                case BoundKind.InlineArrayAccess:
+                    CheckAssigned(((BoundInlineArrayAccess)expr).Expression, node);
+                    break;
             }
         }
 
@@ -2637,6 +2727,25 @@ protected override void AdjustStateForNullCoalescingAssignmentNonNullCase(BoundN
             Assign(node.LeftOperand, node.LeftOperand);
         }
 
+        protected override void AfterVisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            if (node.GetItemOrSliceHelper == WellKnownMember.System_Span_T__Slice_Int_Int)
+            {
+                // exposing ref is a potential write
+                NoteWrite(node.Expression, value: null, read: false);
+            }
+        }
+
+        protected override void AfterVisitConversion(BoundConversion node)
+        {
+            if (node.Conversion.IsInlineArray &&
+                node.Type.OriginalDefinition.Equals(compilation.GetWellKnownType(WellKnownType.System_Span_T), TypeCompareKind.AllIgnoreOptions))
+            {
+                // exposing ref is a potential write
+                NoteWrite(node.Operand, value: null, read: false);
+            }
+        }
+
         #endregion Visitors
 
         protected override string Dump(LocalState state)
diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/FlowAnalysisPass.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/FlowAnalysisPass.cs
index cf06013f5dc30..d56594ef677e3 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/FlowAnalysisPass.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/FlowAnalysisPass.cs
@@ -109,34 +109,54 @@ public static BoundBlock Rewrite(
 
         private static BoundBlock PrependImplicitInitializations(BoundBlock body, MethodSymbol method, ImmutableArray<FieldSymbol> implicitlyInitializedFields, TypeCompilationState compilationState, BindingDiagnosticBag diagnostics)
         {
+            Debug.Assert(!implicitlyInitializedFields.IsEmpty);
             Debug.Assert(method.MethodKind == MethodKind.Constructor);
-            Debug.Assert(method.ContainingType.IsStructType());
+            NamedTypeSymbol containingType = method.ContainingType;
+            Debug.Assert(containingType.IsStructType());
 
             var F = new SyntheticBoundNodeFactory(method, body.Syntax, compilationState, diagnostics);
 
             var builder = ArrayBuilder<BoundStatement>.GetInstance(implicitlyInitializedFields.Length);
-            foreach (var field in implicitlyInitializedFields)
+
+            // Inline arrays of length > 1 must be initialized completely, simply initializing the element field is not sufficient.
+            // For arrays of length == 1, initializing the element field is sufficient.
+            if (containingType.HasInlineArrayAttribute(out int length) && length > 1 && containingType.TryGetInlineArrayElementField() is FieldSymbol elementField)
             {
-                if (field.RefKind == RefKind.None)
-                {
-                    // field = default(T);
-                    builder.Add(
-                        F.ExpressionStatement(
-                            F.AssignmentExpression(
-                                F.Field(F.This(), field),
-                                F.Default(field.Type))));
-                }
-                else
+                Debug.Assert(elementField == implicitlyInitializedFields.Single());
+
+                // this = default;
+                builder.Add(
+                    F.ExpressionStatement(
+                        F.AssignmentExpression(
+                            F.This(),
+                            F.Default(containingType))));
+            }
+            else
+            {
+                foreach (var field in implicitlyInitializedFields)
                 {
-                    // field = ref *default(T*);
-                    builder.Add(
-                        F.ExpressionStatement(
-                            F.AssignmentExpression(
-                                F.Field(F.This(), field),
-                                F.NullRef(field.TypeWithAnnotations),
-                                isRef: true)));
+                    if (field.RefKind == RefKind.None)
+                    {
+                        // field = default(T);
+                        builder.Add(
+                            F.ExpressionStatement(
+                                F.AssignmentExpression(
+                                    F.Field(F.This(), field),
+                                    F.Default(field.Type))));
+                    }
+                    else
+                    {
+                        // field = ref *default(T*);
+                        builder.Add(
+                            F.ExpressionStatement(
+                                F.AssignmentExpression(
+                                    F.Field(F.This(), field),
+                                    F.NullRef(field.TypeWithAnnotations),
+                                    isRef: true)));
+                    }
                 }
             }
+
             var initializations = F.HiddenSequencePoint(F.Block(builder.ToImmutableAndFree()));
 
             return body.Update(body.Locals, body.LocalFunctions, body.HasUnsafeModifier, body.Instrumentation, body.Statements.Insert(index: 0, initializations));
diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
index b856751caf98d..1c63a614a0af4 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs
@@ -184,7 +184,7 @@ public VisitArgumentResult(VisitResult visitResult, Optional<LocalState> stateFo
         /// Invalid type, used only to catch Visit methods that do not set
         /// _result.Type. See VisitExpressionWithoutStackGuard.
         /// </summary>
-        private static readonly TypeWithState _invalidType = TypeWithState.Create(ErrorTypeSymbol.UnknownResultType, NullableFlowState.NotNull);
+        private static readonly TypeWithState _invalidType = TypeWithState.Create(new UnsupportedMetadataTypeSymbol(), NullableFlowState.NotNull);
 
         /// <summary>
         /// Contains the map of expressions to inferred nullabilities and types used by the optional rewriter phase of the
@@ -4469,6 +4469,29 @@ private static void GetArrayElements(BoundArrayInitialization node, ArrayBuilder
             return null;
         }
 
+        public override BoundNode? VisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            Debug.Assert(!IsConditionalState);
+
+            var expressionType = VisitRvalueWithState(node.Expression).Type;
+
+            Debug.Assert(!IsConditionalState);
+            Debug.Assert(expressionType is not null);
+            Debug.Assert(expressionType.IsValueType);
+
+            VisitRvalue(node.Argument);
+
+            TypeWithAnnotations type = expressionType.TryGetInlineArrayElementField()!.TypeWithAnnotations;
+
+            if (node.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int or WellKnownMember.System_Span_T__Slice_Int_Int)
+            {
+                type = TypeWithAnnotations.Create(((NamedTypeSymbol)node.Type).OriginalDefinition.Construct(ImmutableArray.Create(type)));
+            }
+
+            SetResult(node, type.ToTypeWithState(), type);
+            return null;
+        }
+
         private TypeWithState InferResultNullability(BinaryOperatorKind operatorKind, MethodSymbol? methodOpt, TypeSymbol resultType, TypeWithState leftType, TypeWithState rightType)
         {
             NullableFlowState resultState = NullableFlowState.NotNull;
@@ -7384,7 +7407,7 @@ private Conversion GenerateConversionForConditionalOperator(BoundExpression sour
             return conversion;
         }
 
-        private static Conversion GenerateConversion(Conversions conversions, BoundExpression? sourceExpression, TypeSymbol? sourceType, TypeSymbol destinationType, bool fromExplicitCast, bool extensionMethodThisArgument, bool isChecked)
+        private Conversion GenerateConversion(Conversions conversions, BoundExpression? sourceExpression, TypeSymbol? sourceType, TypeSymbol destinationType, bool fromExplicitCast, bool extensionMethodThisArgument, bool isChecked)
         {
             var discardedUseSiteInfo = CompoundUseSiteInfo<AssemblySymbol>.Discarded;
             bool useExpression = sourceType is null || UseExpressionForConversion(sourceExpression);
@@ -7412,7 +7435,7 @@ private static Conversion GenerateConversion(Conversions conversions, BoundExpre
         /// do not have an explicit type but there are several other cases as well.
         /// (See expressions handled in ClassifyImplicitBuiltInConversionFromExpression.)
         /// </summary>
-        private static bool UseExpressionForConversion([NotNullWhen(true)] BoundExpression? value)
+        private bool UseExpressionForConversion([NotNullWhen(true)] BoundExpression? value)
         {
             if (value is null)
             {
@@ -7427,6 +7450,13 @@ private static bool UseExpressionForConversion([NotNullWhen(true)] BoundExpressi
                 case BoundKind.InterpolatedString:
                     return true;
                 default:
+                    if (!_binder.InAttributeArgument && !_binder.InParameterDefaultValue && // These checks prevent cycles caused by attribute binding when HasInlineArrayAttribute check triggers that.
+                        value.Type.HasInlineArrayAttribute(out _) == true &&
+                        value.Type.TryGetInlineArrayElementField() is not null)
+                    {
+                        return true;
+                    }
+
                     return false;
             }
         }
@@ -8350,6 +8380,14 @@ private TypeWithState VisitConversion(
                     // Can reach here, with an error type.
                     break;
 
+                case ConversionKind.InlineArray:
+                    if (checkConversion)
+                    {
+                        conversion = GenerateConversion(_conversions, conversionOperand, operandType.Type, targetType, fromExplicitCast, extensionMethodThisArgument, isChecked: conversionOpt?.Checked ?? false);
+                        canConvertNestedNullability = conversion.Exists;
+                    }
+                    break;
+
                 default:
                     Debug.Assert(targetType.IsValueType || targetType.IsErrorType());
                     break;
@@ -10247,7 +10285,24 @@ protected override void VisitForEachExpression(BoundForEachStatement node)
             {
                 // Reinfer the return type of the node.Expression.GetEnumerator().Current property, so that if
                 // the collection changed nested generic types we pick up those changes.
-                reinferredGetEnumeratorMethod ??= (MethodSymbol)AsMemberOfType(convertedResult.Type, node.EnumeratorInfoOpt.GetEnumeratorInfo.Method);
+                if (reinferredGetEnumeratorMethod is null)
+                {
+                    TypeSymbol? getEnumeratorType;
+
+                    if (node.EnumeratorInfoOpt is { InlineArraySpanType: not WellKnownType.Unknown and var wellKnownSpan })
+                    {
+                        Debug.Assert(wellKnownSpan is WellKnownType.System_Span_T or WellKnownType.System_ReadOnlySpan_T);
+                        NamedTypeSymbol spanType = compilation.GetWellKnownType(wellKnownSpan);
+                        getEnumeratorType = spanType.Construct(ImmutableArray.Create(convertedResult.Type!.TryGetInlineArrayElementField()!.TypeWithAnnotations));
+                    }
+                    else
+                    {
+                        getEnumeratorType = convertedResult.Type;
+                    }
+
+                    reinferredGetEnumeratorMethod = (MethodSymbol)AsMemberOfType(getEnumeratorType, node.EnumeratorInfoOpt.GetEnumeratorInfo.Method);
+                }
+
                 var enumeratorReturnType = GetReturnTypeWithState(reinferredGetEnumeratorMethod);
 
                 if (enumeratorReturnType.State != NullableFlowState.NotNull)
diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker_Patterns.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker_Patterns.cs
index 3722c683de217..83d090d853bd9 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker_Patterns.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker_Patterns.cs
@@ -468,7 +468,9 @@ public PossiblyConditionalState Clone()
                                                 // The expression in the tuple could not be assigned a slot (for example, `a?.b`),
                                                 // so we had to create a slot for the tuple element instead.
                                                 // We'll remember that so that we can apply any learnings to the expression.
+#pragma warning disable CA1854 //Prefer a 'TryGetValue' call over a Dictionary indexer access guarded by a 'ContainsKey' check to avoid double lookup
                                                 if (!originalInputMap.ContainsKey(outputSlot))
+#pragma warning restore CA1854
                                                 {
                                                     originalInputMap.Add(outputSlot,
                                                         ((BoundTupleExpression)expression).Arguments[originalTupleElement.TupleElementIndex]);
diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/ReadWriteWalker.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/ReadWriteWalker.cs
index 3fe22a9da1144..c5a3ed6f8ab2f 100644
--- a/src/Compilers/CSharp/Portable/FlowAnalysis/ReadWriteWalker.cs
+++ b/src/Compilers/CSharp/Portable/FlowAnalysis/ReadWriteWalker.cs
@@ -150,6 +150,11 @@ private void NoteReceiverWritten(BoundFieldAccess expr)
             NoteReceiverReadOrWritten(expr, _writtenInside);
         }
 
+        private void NoteReceiverWritten(BoundInlineArrayAccess expr)
+        {
+            NoteExpressionReadOrWritten(expr.Expression, _writtenInside);
+        }
+
         private void NoteReceiverRead(BoundFieldAccess expr)
         {
             NoteReceiverReadOrWritten(expr, _readInside);
@@ -167,6 +172,11 @@ private void NoteReceiverReadOrWritten(BoundFieldAccess expr, HashSet<Symbol> re
             if (expr.FieldSymbol.IsStatic) return;
             if (expr.FieldSymbol.ContainingType.IsReferenceType) return;
             var receiver = expr.ReceiverOpt;
+            NoteExpressionReadOrWritten(receiver, readOrWritten);
+        }
+
+        private void NoteExpressionReadOrWritten(BoundExpression receiver, HashSet<Symbol> readOrWritten)
+        {
             if (receiver == null) return;
             var receiverSyntax = receiver.Syntax;
             if (receiverSyntax == null) return;
@@ -205,7 +215,14 @@ private void NoteReceiverReadOrWritten(BoundFieldAccess expr, HashSet<Symbol> re
                 case BoundKind.FieldAccess:
                     if (receiver.Type.IsStructType() && receiverSyntax.Span.OverlapsWith(RegionSpan))
                     {
-                        NoteReceiverReadOrWritten(receiver as BoundFieldAccess, readOrWritten);
+                        NoteReceiverReadOrWritten((BoundFieldAccess)receiver, readOrWritten);
+                    }
+                    break;
+                case BoundKind.InlineArrayAccess:
+                    if (receiverSyntax.Span.OverlapsWith(RegionSpan))
+                    {
+                        var elementAccess = (BoundInlineArrayAccess)receiver;
+                        NoteExpressionReadOrWritten(elementAccess.Expression, readOrWritten);
                     }
                     break;
             }
@@ -240,6 +257,17 @@ protected override void AssignImpl(BoundNode node, BoundExpression value, bool i
                         }
                     }
                     break;
+                case BoundKind.InlineArrayAccess:
+                    {
+                        base.AssignImpl(node, value, isRef, written, read);
+                        var elementAccess = (BoundInlineArrayAccess)node;
+                        if (!IsInside && node.Syntax != null && node.Syntax.Span.Contains(RegionSpan))
+                        {
+                            NoteReceiverWritten(elementAccess);
+                        }
+
+                        break;
+                    }
 
                 default:
                     base.AssignImpl(node, value, isRef, written, read);
diff --git a/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs b/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs
index f3b38546d6774..c14e46d72bbba 100644
--- a/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs
+++ b/src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs
@@ -212,6 +212,7 @@ internal enum BoundKind : byte
         EventAccess,
         IndexerAccess,
         ImplicitIndexerAccess,
+        InlineArrayAccess,
         DynamicIndexerAccess,
         Lambda,
         UnboundLambda,
@@ -264,6 +265,7 @@ internal enum BoundKind : byte
 
 
 
+
     internal abstract partial class BoundInitializer : BoundNode
     {
         protected BoundInitializer(BoundKind kind, SyntaxNode syntax, bool hasErrors)
@@ -7339,6 +7341,47 @@ public BoundImplicitIndexerAccess Update(BoundExpression receiver, BoundExpressi
         }
     }
 
+    internal sealed partial class BoundInlineArrayAccess : BoundExpression
+    {
+        public BoundInlineArrayAccess(SyntaxNode syntax, BoundExpression expression, BoundExpression argument, bool isValue, WellKnownMember getItemOrSliceHelper, TypeSymbol type, bool hasErrors = false)
+            : base(BoundKind.InlineArrayAccess, syntax, type, hasErrors || expression.HasErrors() || argument.HasErrors())
+        {
+
+            RoslynDebug.Assert(expression is object, "Field 'expression' cannot be null (make the type nullable in BoundNodes.xml to remove this check)");
+            RoslynDebug.Assert(argument is object, "Field 'argument' cannot be null (make the type nullable in BoundNodes.xml to remove this check)");
+            RoslynDebug.Assert(type is object, "Field 'type' cannot be null (make the type nullable in BoundNodes.xml to remove this check)");
+
+            this.Expression = expression;
+            this.Argument = argument;
+            this.IsValue = isValue;
+            this.GetItemOrSliceHelper = getItemOrSliceHelper;
+            Validate();
+        }
+
+        [Conditional("DEBUG")]
+        private partial void Validate();
+
+        public new TypeSymbol Type => base.Type!;
+        public BoundExpression Expression { get; }
+        public BoundExpression Argument { get; }
+        public bool IsValue { get; }
+        public WellKnownMember GetItemOrSliceHelper { get; }
+
+        [DebuggerStepThrough]
+        public override BoundNode? Accept(BoundTreeVisitor visitor) => visitor.VisitInlineArrayAccess(this);
+
+        public BoundInlineArrayAccess Update(BoundExpression expression, BoundExpression argument, bool isValue, WellKnownMember getItemOrSliceHelper, TypeSymbol type)
+        {
+            if (expression != this.Expression || argument != this.Argument || isValue != this.IsValue || getItemOrSliceHelper != this.GetItemOrSliceHelper || !TypeSymbol.Equals(type, this.Type, TypeCompareKind.ConsiderEverything))
+            {
+                var result = new BoundInlineArrayAccess(this.Syntax, expression, argument, isValue, getItemOrSliceHelper, type, this.HasErrors);
+                result.CopyAttributes(this);
+                return result;
+            }
+            return this;
+        }
+    }
+
     internal sealed partial class BoundDynamicIndexerAccess : BoundExpression
     {
         public BoundDynamicIndexerAccess(SyntaxNode syntax, BoundExpression receiver, ImmutableArray<BoundExpression> arguments, ImmutableArray<string> argumentNamesOpt, ImmutableArray<RefKind> argumentRefKindsOpt, ImmutableArray<PropertySymbol> applicableIndexers, TypeSymbol type, bool hasErrors = false)
@@ -9005,6 +9048,8 @@ internal R VisitInternal(BoundNode node, A arg)
                     return VisitIndexerAccess((BoundIndexerAccess)node, arg);
                 case BoundKind.ImplicitIndexerAccess:
                     return VisitImplicitIndexerAccess((BoundImplicitIndexerAccess)node, arg);
+                case BoundKind.InlineArrayAccess:
+                    return VisitInlineArrayAccess((BoundInlineArrayAccess)node, arg);
                 case BoundKind.DynamicIndexerAccess:
                     return VisitDynamicIndexerAccess((BoundDynamicIndexerAccess)node, arg);
                 case BoundKind.Lambda:
@@ -9275,6 +9320,7 @@ internal abstract partial class BoundTreeVisitor<A, R>
         public virtual R VisitEventAccess(BoundEventAccess node, A arg) => this.DefaultVisit(node, arg);
         public virtual R VisitIndexerAccess(BoundIndexerAccess node, A arg) => this.DefaultVisit(node, arg);
         public virtual R VisitImplicitIndexerAccess(BoundImplicitIndexerAccess node, A arg) => this.DefaultVisit(node, arg);
+        public virtual R VisitInlineArrayAccess(BoundInlineArrayAccess node, A arg) => this.DefaultVisit(node, arg);
         public virtual R VisitDynamicIndexerAccess(BoundDynamicIndexerAccess node, A arg) => this.DefaultVisit(node, arg);
         public virtual R VisitLambda(BoundLambda node, A arg) => this.DefaultVisit(node, arg);
         public virtual R VisitUnboundLambda(UnboundLambda node, A arg) => this.DefaultVisit(node, arg);
@@ -9506,6 +9552,7 @@ internal abstract partial class BoundTreeVisitor
         public virtual BoundNode? VisitEventAccess(BoundEventAccess node) => this.DefaultVisit(node);
         public virtual BoundNode? VisitIndexerAccess(BoundIndexerAccess node) => this.DefaultVisit(node);
         public virtual BoundNode? VisitImplicitIndexerAccess(BoundImplicitIndexerAccess node) => this.DefaultVisit(node);
+        public virtual BoundNode? VisitInlineArrayAccess(BoundInlineArrayAccess node) => this.DefaultVisit(node);
         public virtual BoundNode? VisitDynamicIndexerAccess(BoundDynamicIndexerAccess node) => this.DefaultVisit(node);
         public virtual BoundNode? VisitLambda(BoundLambda node) => this.DefaultVisit(node);
         public virtual BoundNode? VisitUnboundLambda(UnboundLambda node) => this.DefaultVisit(node);
@@ -10384,6 +10431,12 @@ internal abstract partial class BoundTreeWalker : BoundTreeVisitor
             this.Visit(node.Argument);
             return null;
         }
+        public override BoundNode? VisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            this.Visit(node.Expression);
+            this.Visit(node.Argument);
+            return null;
+        }
         public override BoundNode? VisitDynamicIndexerAccess(BoundDynamicIndexerAccess node)
         {
             this.Visit(node.Receiver);
@@ -11699,6 +11752,13 @@ internal abstract partial class BoundTreeRewriter : BoundTreeVisitor
             TypeSymbol? type = this.VisitType(node.Type);
             return node.Update(receiver, argument, lengthOrCountAccess, receiverPlaceholder, indexerOrSliceAccess, argumentPlaceholders, type);
         }
+        public override BoundNode? VisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            BoundExpression expression = (BoundExpression)this.Visit(node.Expression);
+            BoundExpression argument = (BoundExpression)this.Visit(node.Argument);
+            TypeSymbol? type = this.VisitType(node.Type);
+            return node.Update(expression, argument, node.IsValue, node.GetItemOrSliceHelper, type);
+        }
         public override BoundNode? VisitDynamicIndexerAccess(BoundDynamicIndexerAccess node)
         {
             BoundExpression receiver = (BoundExpression)this.Visit(node.Receiver);
@@ -14197,6 +14257,24 @@ public NullabilityRewriter(ImmutableDictionary<BoundExpression, (NullabilityInfo
             return updatedNode;
         }
 
+        public override BoundNode? VisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            BoundExpression expression = (BoundExpression)this.Visit(node.Expression);
+            BoundExpression argument = (BoundExpression)this.Visit(node.Argument);
+            BoundInlineArrayAccess updatedNode;
+
+            if (_updatedNullabilities.TryGetValue(node, out (NullabilityInfo Info, TypeSymbol? Type) infoAndType))
+            {
+                updatedNode = node.Update(expression, argument, node.IsValue, node.GetItemOrSliceHelper, infoAndType.Type!);
+                updatedNode.TopLevelNullability = infoAndType.Info;
+            }
+            else
+            {
+                updatedNode = node.Update(expression, argument, node.IsValue, node.GetItemOrSliceHelper, node.Type);
+            }
+            return updatedNode;
+        }
+
         public override BoundNode? VisitDynamicIndexerAccess(BoundDynamicIndexerAccess node)
         {
             ImmutableArray<PropertySymbol> applicableIndexers = GetUpdatedArray(node, node.ApplicableIndexers);
@@ -16412,6 +16490,17 @@ private BoundTreeDumperNodeProducer()
             new TreeDumperNode("hasErrors", node.HasErrors, null)
         }
         );
+        public override TreeDumperNode VisitInlineArrayAccess(BoundInlineArrayAccess node, object? arg) => new TreeDumperNode("inlineArrayAccess", null, new TreeDumperNode[]
+        {
+            new TreeDumperNode("expression", null, new TreeDumperNode[] { Visit(node.Expression, null) }),
+            new TreeDumperNode("argument", null, new TreeDumperNode[] { Visit(node.Argument, null) }),
+            new TreeDumperNode("isValue", node.IsValue, null),
+            new TreeDumperNode("getItemOrSliceHelper", node.GetItemOrSliceHelper, null),
+            new TreeDumperNode("type", node.Type, null),
+            new TreeDumperNode("isSuppressed", node.IsSuppressed, null),
+            new TreeDumperNode("hasErrors", node.HasErrors, null)
+        }
+        );
         public override TreeDumperNode VisitDynamicIndexerAccess(BoundDynamicIndexerAccess node, object? arg) => new TreeDumperNode("dynamicIndexerAccess", null, new TreeDumperNode[]
         {
             new TreeDumperNode("receiver", null, new TreeDumperNode[] { Visit(node.Receiver, null) }),
diff --git a/src/Compilers/CSharp/Portable/Generated/ErrorFacts.Generated.cs b/src/Compilers/CSharp/Portable/Generated/ErrorFacts.Generated.cs
index c1203a2275310..4cc64b0c8686f 100644
--- a/src/Compilers/CSharp/Portable/Generated/ErrorFacts.Generated.cs
+++ b/src/Compilers/CSharp/Portable/Generated/ErrorFacts.Generated.cs
@@ -315,6 +315,10 @@ public static bool IsWarning(ErrorCode code)
                 case ErrorCode.WRN_CapturedPrimaryConstructorParameterPassedToBase:
                 case ErrorCode.WRN_UnreadPrimaryConstructorParameter:
                 case ErrorCode.WRN_AddressOfInAsync:
+                case ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer:
+                case ErrorCode.WRN_InterceptorSignatureMismatch:
+                case ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor:
+                case ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor:
                     return true;
                 default:
                     return false;
diff --git a/src/Compilers/CSharp/Portable/Lowering/DiagnosticsPass_ExpressionTrees.cs b/src/Compilers/CSharp/Portable/Lowering/DiagnosticsPass_ExpressionTrees.cs
index 3f3e32c5b832a..2c79218eac088 100644
--- a/src/Compilers/CSharp/Portable/Lowering/DiagnosticsPass_ExpressionTrees.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/DiagnosticsPass_ExpressionTrees.cs
@@ -108,6 +108,16 @@ public override BoundNode VisitImplicitIndexerAccess(BoundImplicitIndexerAccess
             return base.VisitImplicitIndexerAccess(node);
         }
 
+        public override BoundNode VisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            if (_inExpressionLambda)
+            {
+                Error(ErrorCode.ERR_ExpressionTreeContainsInlineArrayOperation, node);
+            }
+
+            return base.VisitInlineArrayAccess(node);
+        }
+
         public override BoundNode VisitFromEndIndexExpression(BoundFromEndIndexExpression node)
         {
             if (_inExpressionLambda)
@@ -787,6 +797,13 @@ public override BoundNode VisitConversion(BoundConversion node)
                     }
                     break;
 
+                case ConversionKind.InlineArray:
+                    if (_inExpressionLambda)
+                    {
+                        Error(ErrorCode.ERR_ExpressionTreeContainsInlineArrayOperation, node);
+                    }
+                    break;
+
                 case ConversionKind.InterpolatedStringHandler:
                     if (_inExpressionLambda)
                     {
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.cs
index 53cb6205fd676..0345ba599655d 100644
--- a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.cs
@@ -222,6 +222,16 @@ private PEModuleBuilder? EmitModule
 
         private BoundExpression? VisitExpressionImpl(BoundExpression node)
         {
+            if (node is BoundNameOfOperator nameofOperator)
+            {
+                Debug.Assert(!nameofOperator.WasCompilerGenerated);
+                var nameofIdentiferSyntax = (IdentifierNameSyntax)((InvocationExpressionSyntax)nameofOperator.Syntax).Expression;
+                if (this._compilation.TryGetInterceptor(nameofIdentiferSyntax.Location) is not null)
+                {
+                    this._diagnostics.Add(ErrorCode.ERR_InterceptorCannotInterceptNameof, nameofIdentiferSyntax.Location);
+                }
+            }
+
             ConstantValue? constantValue = node.ConstantValueOpt;
             if (constantValue != null)
             {
@@ -972,6 +982,9 @@ internal static bool CanBePassedByReference(BoundExpression expr)
                     // That placeholder is always replaced with a temp local
                     return true;
 
+                case BoundKind.InlineArrayAccess:
+                    return ((BoundInlineArrayAccess)expr) is { IsValue: false, GetItemOrSliceHelper: WellKnownMember.System_Span_T__get_Item or WellKnownMember.System_ReadOnlySpan_T__get_Item };
+
                 case BoundKind.ImplicitIndexerValuePlaceholder:
                     // Implicit Index or Range indexers only have by-value parameters:
                     // this[int], Slice(int, int), Substring(int, int)
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Call.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Call.cs
index 6a9c6c147cd5b..aa36020507073 100644
--- a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Call.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Call.cs
@@ -133,6 +133,130 @@ private void EmbedIfNeedTo(BoundExpression receiver, ImmutableArray<PropertySymb
             }
         }
 
+        private void InterceptCallAndAdjustArguments(
+            ref MethodSymbol method,
+            ref BoundExpression? receiverOpt,
+            ref ImmutableArray<BoundExpression> arguments,
+            ref ImmutableArray<RefKind> argumentRefKindsOpt,
+            bool invokedAsExtensionMethod,
+            Location? interceptableLocation)
+        {
+            if (this._compilation.TryGetInterceptor(interceptableLocation) is not var (attributeLocation, interceptor))
+            {
+                // The call was not intercepted.
+                return;
+            }
+
+            Debug.Assert(interceptableLocation != null);
+            Debug.Assert(interceptor.Arity == 0);
+
+            var containingMethod = this._factory.CurrentFunction;
+            Debug.Assert(containingMethod is not null);
+
+            var useSiteInfo = this.GetNewCompoundUseSiteInfo();
+            var isAccessible = AccessCheck.IsSymbolAccessible(interceptor, containingMethod.ContainingType, ref useSiteInfo);
+            this._diagnostics.Add(attributeLocation, useSiteInfo);
+            if (!isAccessible)
+            {
+                this._diagnostics.Add(ErrorCode.ERR_InterceptorNotAccessible, attributeLocation, interceptor, containingMethod);
+                return;
+            }
+
+            // When the original call is to an instance method, and the interceptor is an extension method,
+            // we need to take special care to intercept with the extension method as though it is being called in reduced form.
+            Debug.Assert(receiverOpt is not BoundTypeExpression || method.IsStatic);
+            var needToReduce = receiverOpt is not (null or BoundTypeExpression) && interceptor.IsExtensionMethod;
+            var symbolForCompare = needToReduce ? ReducedExtensionMethodSymbol.Create(interceptor, receiverOpt!.Type, _compilation) : interceptor;
+
+            if (!MemberSignatureComparer.InterceptorsComparer.Equals(method, symbolForCompare))
+            {
+                this._diagnostics.Add(ErrorCode.ERR_InterceptorSignatureMismatch, attributeLocation, method, interceptor);
+                return;
+            }
+
+            _ = SourceMemberContainerTypeSymbol.CheckValidNullableMethodOverride(
+                _compilation,
+                method,
+                symbolForCompare,
+                _diagnostics,
+                static (diagnostics, method, interceptor, topLevel, attributeLocation) =>
+                {
+                    diagnostics.Add(ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor, attributeLocation, method);
+                },
+                static (diagnostics, method, interceptor, implementingParameter, blameAttributes, attributeLocation) =>
+                {
+                    diagnostics.Add(ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor, attributeLocation, new FormattedSymbol(implementingParameter, SymbolDisplayFormat.ShortFormat), method);
+                },
+                extraArgument: attributeLocation);
+
+            if (!MemberSignatureComparer.InterceptorsStrictComparer.Equals(method, symbolForCompare))
+            {
+                this._diagnostics.Add(ErrorCode.WRN_InterceptorSignatureMismatch, attributeLocation, method, interceptor);
+            }
+
+            method.TryGetThisParameter(out var methodThisParameter);
+            symbolForCompare.TryGetThisParameter(out var interceptorThisParameterForCompare);
+            switch (methodThisParameter, interceptorThisParameterForCompare)
+            {
+                case (not null, null):
+                case (not null, not null) when !methodThisParameter.Type.Equals(interceptorThisParameterForCompare.Type, TypeCompareKind.ObliviousNullableModifierMatchesAny)
+                        || methodThisParameter.RefKind != interceptorThisParameterForCompare.RefKind:
+                    this._diagnostics.Add(ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter, attributeLocation, methodThisParameter, method);
+                    return;
+                case (null, not null):
+                    this._diagnostics.Add(ErrorCode.ERR_InterceptorMustNotHaveThisParameter, attributeLocation, method);
+                    return;
+                default:
+                    break;
+            }
+
+            if (invokedAsExtensionMethod && interceptor.IsStatic && !interceptor.IsExtensionMethod)
+            {
+                // Special case when intercepting an extension method call in reduced form with a non-extension.
+                this._diagnostics.Add(ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter, attributeLocation, method.Parameters[0], method);
+                return;
+            }
+
+            if (SourceMemberContainerTypeSymbol.CheckValidScopedOverride(
+                method,
+                symbolForCompare,
+                this._diagnostics,
+                static (diagnostics, method, symbolForCompare, implementingParameter, blameAttributes, attributeLocation) =>
+                {
+                    diagnostics.Add(ErrorCode.ERR_InterceptorScopedMismatch, attributeLocation, method, symbolForCompare);
+                },
+                extraArgument: attributeLocation,
+                allowVariance: true,
+                // Since we've already reduced 'symbolForCompare', we compare as though it is not an extension.
+                invokedAsExtensionMethod: false))
+            {
+                return;
+            }
+
+            if (needToReduce)
+            {
+                Debug.Assert(methodThisParameter is not null);
+                arguments = arguments.Insert(0, receiverOpt!);
+                receiverOpt = null;
+
+                // CodeGenerator.EmitArguments requires that we have a fully-filled-out argumentRefKindsOpt for any ref/in/out arguments.
+                var thisRefKind = methodThisParameter.RefKind;
+                if (argumentRefKindsOpt.IsDefault && thisRefKind != RefKind.None)
+                {
+                    argumentRefKindsOpt = method.Parameters.SelectAsArray(static param => param.RefKind);
+                }
+
+                if (!argumentRefKindsOpt.IsDefault)
+                {
+                    argumentRefKindsOpt = argumentRefKindsOpt.Insert(0, thisRefKind);
+                }
+            }
+
+            method = interceptor;
+
+            return;
+        }
+
         public override BoundNode VisitCall(BoundCall node)
         {
             Debug.Assert(node != null);
@@ -175,32 +299,34 @@ public override BoundNode VisitCall(BoundCall node)
 
             BoundExpression visitArgumentsAndFinishRewrite(BoundCall node, BoundExpression? rewrittenReceiver)
             {
-                var argRefKindsOpt = node.ArgumentRefKindsOpt;
+                MethodSymbol method = node.Method;
+                ImmutableArray<int> argsToParamsOpt = node.ArgsToParamsOpt;
+                ImmutableArray<RefKind> argRefKindsOpt = node.ArgumentRefKindsOpt;
+                bool invokedAsExtensionMethod = node.InvokedAsExtensionMethod;
 
                 ArrayBuilder<LocalSymbol>? temps = null;
                 var rewrittenArguments = VisitArgumentsAndCaptureReceiverIfNeeded(
                     ref rewrittenReceiver,
                     captureReceiverMode: ReceiverCaptureMode.Default,
                     node.Arguments,
-                    node.Method,
-                    node.ArgsToParamsOpt,
+                    method,
+                    argsToParamsOpt,
                     argRefKindsOpt,
                     storesOpt: null,
                     ref temps);
 
-                var rewrittenCall = MakeArgumentsAndCall(
-                    syntax: node.Syntax,
-                    rewrittenReceiver: rewrittenReceiver,
-                    method: node.Method,
-                    arguments: rewrittenArguments,
-                    argumentRefKindsOpt: argRefKindsOpt,
-                    expanded: node.Expanded,
-                    invokedAsExtensionMethod: node.InvokedAsExtensionMethod,
-                    argsToParamsOpt: node.ArgsToParamsOpt,
-                    resultKind: node.ResultKind,
-                    type: node.Type,
-                    temps,
-                    nodeOpt: node);
+                rewrittenArguments = MakeArguments(
+                    node.Syntax,
+                    rewrittenArguments,
+                    method,
+                    node.Expanded,
+                    argsToParamsOpt,
+                    ref argRefKindsOpt,
+                    ref temps,
+                    invokedAsExtensionMethod);
+
+                InterceptCallAndAdjustArguments(ref method, ref rewrittenReceiver, ref rewrittenArguments, ref argRefKindsOpt, invokedAsExtensionMethod, node.InterceptableLocation);
+                var rewrittenCall = MakeCall(node, node.Syntax, rewrittenReceiver, method, rewrittenArguments, argRefKindsOpt, node.ResultKind, node.Type, temps.ToImmutableAndFree());
 
                 if (Instrument)
                 {
@@ -235,7 +361,7 @@ private BoundExpression MakeArgumentsAndCall(
                 ref temps,
                 invokedAsExtensionMethod);
 
-            return MakeCall(nodeOpt, syntax, rewrittenReceiver, method, arguments, argumentRefKindsOpt, invokedAsExtensionMethod, resultKind, type, temps.ToImmutableAndFree());
+            return MakeCall(nodeOpt, syntax, rewrittenReceiver, method, arguments, argumentRefKindsOpt, resultKind, type, temps.ToImmutableAndFree());
         }
 
         private BoundExpression MakeCall(
@@ -245,7 +371,6 @@ private BoundExpression MakeCall(
             MethodSymbol method,
             ImmutableArray<BoundExpression> rewrittenArguments,
             ImmutableArray<RefKind> argumentRefKinds,
-            bool invokedAsExtensionMethod,
             LookupResultKind resultKind,
             TypeSymbol type,
             ImmutableArray<LocalSymbol> temps)
@@ -281,11 +406,11 @@ private BoundExpression MakeCall(
                     rewrittenReceiver,
                     method,
                     rewrittenArguments,
-                    default(ImmutableArray<string>),
+                    argumentNamesOpt: default(ImmutableArray<string>),
                     argumentRefKinds,
                     isDelegateCall: false,
                     expanded: false,
-                    invokedAsExtensionMethod: invokedAsExtensionMethod,
+                    invokedAsExtensionMethod: false,
                     argsToParamsOpt: default(ImmutableArray<int>),
                     defaultArguments: default(BitVector),
                     resultKind: resultKind,
@@ -297,13 +422,13 @@ private BoundExpression MakeCall(
                     rewrittenReceiver,
                     method,
                     rewrittenArguments,
-                    default(ImmutableArray<string>),
+                    argumentNamesOpt: default(ImmutableArray<string>),
                     argumentRefKinds,
                     node.IsDelegateCall,
-                    false,
-                    node.InvokedAsExtensionMethod,
-                    default(ImmutableArray<int>),
-                    default(BitVector),
+                    expanded: false,
+                    invokedAsExtensionMethod: false,
+                    argsToParamsOpt: default(ImmutableArray<int>),
+                    defaultArguments: default(BitVector),
                     node.ResultKind,
                     node.Type);
             }
@@ -330,7 +455,6 @@ private BoundExpression MakeCall(SyntaxNode syntax, BoundExpression? rewrittenRe
                 method: method,
                 rewrittenArguments: rewrittenArguments,
                 argumentRefKinds: default(ImmutableArray<RefKind>),
-                invokedAsExtensionMethod: false,
                 resultKind: LookupResultKind.Viable,
                 type: type,
                 temps: default);
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_CompoundAssignmentOperator.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_CompoundAssignmentOperator.cs
index 86a3194a6ed6f..f80ed9fa146f9 100644
--- a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_CompoundAssignmentOperator.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_CompoundAssignmentOperator.cs
@@ -666,6 +666,10 @@ private BoundExpression TransformCompoundAssignmentLHS(BoundExpression originalL
                     }
                     break;
 
+                case BoundKind.InlineArrayAccess:
+                    Debug.Assert(originalLHS.GetRefKind() == RefKind.Ref);
+                    break;
+
                 case BoundKind.DynamicMemberAccess:
                     return TransformDynamicMemberAccess((BoundDynamicMemberAccess)originalLHS, stores, temps);
 
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs
index b4ea92c877b50..e6fe91ea178c2 100644
--- a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs
@@ -304,6 +304,8 @@ private BoundExpression MakeConversionNodeCore(
         {
             Debug.Assert(oldNodeOpt == null || oldNodeOpt.Syntax == syntax);
             Debug.Assert(rewrittenType is { });
+            Debug.Assert(_factory.ModuleBuilderOpt is { });
+            Debug.Assert(_diagnostics.DiagnosticBag is { });
 
             if (_inExpressionLambda && !conversion.IsUserDefined)
             {
@@ -586,6 +588,29 @@ private BoundExpression MakeConversionNodeCore(
                         }
                     }
 
+                case ConversionKind.InlineArray:
+                    {
+                        Debug.Assert(rewrittenOperand.Type is not null);
+
+                        NamedTypeSymbol spanType = (NamedTypeSymbol)rewrittenType;
+                        MethodSymbol createSpan;
+
+                        if (spanType.OriginalDefinition.Equals(_compilation.GetWellKnownType(WellKnownType.System_ReadOnlySpan_T), TypeCompareKind.AllIgnoreOptions))
+                        {
+                            createSpan = _factory.ModuleBuilderOpt.EnsureInlineArrayAsReadOnlySpanExists(syntax, spanType.OriginalDefinition, _factory.SpecialType(SpecialType.System_Int32), _diagnostics.DiagnosticBag);
+                        }
+                        else
+                        {
+                            Debug.Assert(spanType.OriginalDefinition.Equals(_compilation.GetWellKnownType(WellKnownType.System_Span_T), TypeCompareKind.AllIgnoreOptions));
+                            createSpan = _factory.ModuleBuilderOpt.EnsureInlineArrayAsSpanExists(syntax, spanType.OriginalDefinition, _factory.SpecialType(SpecialType.System_Int32), _diagnostics.DiagnosticBag);
+                        }
+
+                        createSpan = createSpan.Construct(rewrittenOperand.Type, spanType.TypeArgumentsWithAnnotationsNoUseSiteDiagnostics.Single().Type);
+                        _ = rewrittenOperand.Type.HasInlineArrayAttribute(out int length);
+
+                        return _factory.Call(null, createSpan, rewrittenOperand, _factory.Literal(length), useStrictArgumentRefKinds: true);
+                    }
+
                 default:
                     break;
             }
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ForEachStatement.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ForEachStatement.cs
index f7e56d2cdc71b..18e8730b83e7b 100644
--- a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ForEachStatement.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ForEachStatement.cs
@@ -49,6 +49,10 @@ public override BoundNode VisitForEachStatement(BoundForEachStatement node)
                     return RewriteMultiDimensionalArrayForEachStatement(node);
                 }
             }
+            else if (node.EnumeratorInfoOpt is { InlineArraySpanType: not WellKnownType.Unknown })
+            {
+                return RewriteInlineArrayForEachStatementAsFor(node);
+            }
             else if (node.AwaitOpt is null && CanRewriteForEachAsFor(node.Syntax, nodeExpressionType, out var indexerGet, out var lengthGetter))
             {
                 return RewriteForEachStatementAsFor(node, indexerGet, lengthGetter);
@@ -543,7 +547,7 @@ private BoundExpression SynthesizeCall(MethodArgumentInfo methodArgumentInfo, CS
         /// NOTE: We're assuming that sequence points have already been generated.
         /// Otherwise, lowering to for-loops would generated spurious ones.
         /// </remarks>
-        private BoundStatement RewriteForEachStatementAsFor(BoundForEachStatement node, MethodSymbol indexerGet, MethodSymbol lengthGet)
+        private BoundStatement RewriteForEachStatementAsFor<TArg>(BoundForEachStatement node, GetForEachStatementAsForPreamble? getPreamble, GetForEachStatementAsForItem<TArg> getItem, GetForEachStatementAsForLength<TArg> getLength, TArg arg)
         {
             var forEachSyntax = (CommonForEachStatementSyntax)node.Syntax;
 
@@ -558,12 +562,21 @@ private BoundStatement RewriteForEachStatementAsFor(BoundForEachStatement node,
             BoundStatement? rewrittenBody = VisitStatement(node.Body);
             Debug.Assert(rewrittenBody is { });
 
+            LocalSymbol? preambleLocal = null;
+            RefKind collectionTempRefKind = RefKind.None;
+            BoundStatement? collectionVarInitializationPreamble = getPreamble?.Invoke(this, node, ref rewrittenExpression, out preambleLocal, out collectionTempRefKind);
+
             // Collection a
-            LocalSymbol collectionTemp = _factory.SynthesizedLocal(collectionType, forEachSyntax, kind: SynthesizedLocalKind.ForEachArray);
+            LocalSymbol collectionTemp = _factory.SynthesizedLocal(collectionType, forEachSyntax, kind: SynthesizedLocalKind.ForEachArray, refKind: collectionTempRefKind);
 
             // Collection a = /*node.Expression*/;
             BoundStatement arrayVarDecl = MakeLocalDeclaration(forEachSyntax, collectionTemp, rewrittenExpression);
 
+            if (collectionVarInitializationPreamble is object)
+            {
+                arrayVarDecl = new BoundStatementList(arrayVarDecl.Syntax, ImmutableArray.Create(collectionVarInitializationPreamble, arrayVarDecl)).MakeCompilerGenerated();
+            }
+
             InstrumentForEachStatementCollectionVarDeclaration(node, ref arrayVarDecl);
 
             // Reference to a.
@@ -583,11 +596,7 @@ private BoundStatement RewriteForEachStatementAsFor(BoundForEachStatement node,
             BoundExpression iterationVarInitValue = ApplyConversionIfNotIdentity(
                 node.ElementConversion,
                 node.ElementPlaceholder,
-                BoundCall.Synthesized(
-                    syntax: forEachSyntax,
-                    receiverOpt: boundArrayVar,
-                    indexerGet,
-                    boundPositionVar));
+                getItem(this, node, boundArrayVar, boundPositionVar, arg));
 
             // V v = (V)a[p];   /* OR */   (D1 d1, ...) = (V)a[p];
             ImmutableArray<LocalSymbol> iterationVariables = node.IterationVariables;
@@ -599,10 +608,7 @@ private BoundStatement RewriteForEachStatementAsFor(BoundForEachStatement node,
                         statements: ImmutableArray.Create<BoundStatement>(arrayVarDecl, positionVarDecl));
 
             // a.Length
-            BoundExpression arrayLength = BoundCall.Synthesized(
-                syntax: forEachSyntax,
-                receiverOpt: boundArrayVar,
-                lengthGet);
+            BoundExpression arrayLength = getLength(this, node, boundArrayVar, arg);
 
             // p < a.Length
             BoundExpression exitCondition = new BoundBinaryOperator(
@@ -632,7 +638,7 @@ private BoundStatement RewriteForEachStatementAsFor(BoundForEachStatement node,
             // }
             BoundStatement result = RewriteForStatementWithoutInnerLocals(
                 original: node,
-                outerLocals: ImmutableArray.Create<LocalSymbol>(collectionTemp, positionVar),
+                outerLocals: preambleLocal is null ? ImmutableArray.Create<LocalSymbol>(collectionTemp, positionVar) : ImmutableArray.Create<LocalSymbol>(preambleLocal, collectionTemp, positionVar),
                 rewrittenInitializer: initializer,
                 rewrittenCondition: exitCondition,
                 rewrittenIncrement: positionIncrement,
@@ -646,6 +652,89 @@ private BoundStatement RewriteForEachStatementAsFor(BoundForEachStatement node,
             return result;
         }
 
+        private delegate BoundStatement? GetForEachStatementAsForPreamble(LocalRewriter rewriter, BoundForEachStatement node, ref BoundExpression rewrittenExpression, out LocalSymbol? preambleLocal, out RefKind collectionTempRefKind);
+        private delegate BoundExpression GetForEachStatementAsForItem<TArg>(LocalRewriter rewriter, BoundForEachStatement node, BoundLocal boundArrayVar, BoundLocal boundPositionVar, TArg arg);
+        private delegate BoundExpression GetForEachStatementAsForLength<TArg>(LocalRewriter rewriter, BoundForEachStatement node, BoundLocal boundArrayVar, TArg arg);
+
+        private BoundStatement RewriteForEachStatementAsFor(BoundForEachStatement node, MethodSymbol indexerGet, MethodSymbol lengthGet)
+        {
+            return RewriteForEachStatementAsFor(node,
+                                                getPreamble: null,
+                                                getItem: static (LocalRewriter rewriter, BoundForEachStatement node, BoundLocal boundArrayVar, BoundLocal boundPositionVar, (MethodSymbol indexerGet, MethodSymbol lengthGet) arg) =>
+                                                {
+                                                    return BoundCall.Synthesized(
+                                                               syntax: node.Syntax,
+                                                               receiverOpt: boundArrayVar,
+                                                               arg.indexerGet,
+                                                               boundPositionVar);
+                                                },
+                                                getLength: static (LocalRewriter rewriter, BoundForEachStatement node, BoundLocal boundArrayVar, (MethodSymbol indexerGet, MethodSymbol lengthGet) arg) =>
+                                                {
+                                                    return BoundCall.Synthesized(
+                                                               syntax: node.Syntax,
+                                                               receiverOpt: boundArrayVar,
+                                                               arg.lengthGet);
+                                                },
+                                                arg: (indexerGet, lengthGet));
+        }
+
+        private BoundStatement RewriteInlineArrayForEachStatementAsFor(BoundForEachStatement node)
+        {
+            return RewriteForEachStatementAsFor(node,
+                                                getPreamble: static (LocalRewriter rewriter, BoundForEachStatement node, ref BoundExpression rewrittenExpression, out LocalSymbol? preambleLocal, out RefKind collectionTempRefKind) =>
+                                                                    {
+                                                                        var enumeratorInfo = node.EnumeratorInfoOpt;
+                                                                        Debug.Assert(enumeratorInfo is not null);
+                                                                        Debug.Assert(rewrittenExpression.Type is not null);
+
+                                                                        BoundStatement? collectionVarInitializationPreamble = null;
+                                                                        preambleLocal = null;
+                                                                        if (enumeratorInfo.InlineArrayUsedAsValue)
+                                                                        {
+                                                                            BoundLocal boundLocal = rewriter._factory.StoreToTemp(rewrittenExpression, out BoundAssignmentOperator? valueStore);
+                                                                            rewrittenExpression = boundLocal;
+                                                                            collectionVarInitializationPreamble = rewriter._factory.ExpressionStatement(valueStore);
+                                                                            preambleLocal = boundLocal.LocalSymbol;
+                                                                        }
+
+                                                                        collectionTempRefKind = enumeratorInfo.InlineArraySpanType == WellKnownType.System_Span_T ? RefKind.Ref : RefKindExtensions.StrictIn;
+                                                                        return collectionVarInitializationPreamble;
+                                                                    },
+                                                getItem: static (LocalRewriter rewriter, BoundForEachStatement node, BoundLocal boundArrayVar, BoundLocal boundPositionVar, object? _) =>
+                                                                {
+                                                                    MethodSymbol elementRef;
+                                                                    Debug.Assert(rewriter._factory.ModuleBuilderOpt is { });
+                                                                    Debug.Assert(rewriter._diagnostics.DiagnosticBag is { });
+
+                                                                    var enumeratorInfo = node.EnumeratorInfoOpt;
+                                                                    Debug.Assert(enumeratorInfo is not null);
+
+                                                                    NamedTypeSymbol intType = rewriter._factory.SpecialType(SpecialType.System_Int32);
+                                                                    if (enumeratorInfo.InlineArraySpanType == WellKnownType.System_Span_T)
+                                                                    {
+                                                                        elementRef = rewriter._factory.ModuleBuilderOpt.EnsureInlineArrayElementRefExists(node.Syntax, intType, rewriter._diagnostics.DiagnosticBag);
+                                                                    }
+                                                                    else
+                                                                    {
+                                                                        Debug.Assert(enumeratorInfo.InlineArraySpanType == WellKnownType.System_ReadOnlySpan_T);
+                                                                        elementRef = rewriter._factory.ModuleBuilderOpt.EnsureInlineArrayElementRefReadOnlyExists(node.Syntax, intType, rewriter._diagnostics.DiagnosticBag);
+                                                                    }
+
+                                                                    TypeSymbol inlineArrayType = boundArrayVar.Type;
+                                                                    elementRef = elementRef.Construct(inlineArrayType, inlineArrayType.TryGetInlineArrayElementField()!.Type);
+
+                                                                    return rewriter._factory.Call(null, elementRef, boundArrayVar, boundPositionVar, useStrictArgumentRefKinds: true);
+                                                                },
+                                                getLength: static (LocalRewriter rewriter, BoundForEachStatement node, BoundLocal boundArrayVar, object? _) =>
+                                                                  {
+                                                                      _ = boundArrayVar.Type.HasInlineArrayAttribute(out int length);
+                                                                      Debug.Assert(length > 0);
+                                                                      BoundExpression arrayLength = rewriter._factory.Literal(length);
+                                                                      return arrayLength;
+                                                                  },
+                                                arg: null);
+        }
+
         /// <summary>
         /// Takes the expression for the current value of the iteration variable and either
         /// (1) assigns it into a local, or
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_IndexerAccess.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_IndexerAccess.cs
index 7b0bbef5edd47..4844ed07bdbc9 100644
--- a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_IndexerAccess.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_IndexerAccess.cs
@@ -167,6 +167,205 @@ private BoundExpression MakeIndexerAccess(
             }
         }
 
+        public override BoundNode? VisitInlineArrayAccess(BoundInlineArrayAccess node)
+        {
+            Debug.Assert(_factory.ModuleBuilderOpt is { });
+            Debug.Assert(_diagnostics.DiagnosticBag is { });
+            Debug.Assert(node.Expression.Type is object);
+            Debug.Assert(node.Argument.Type is object);
+
+            var rewrittenReceiver = VisitExpression(node.Expression);
+            BoundAssignmentOperator? receiverStore = null;
+
+            if (node.IsValue && node.GetItemOrSliceHelper == WellKnownMember.System_ReadOnlySpan_T__get_Item)
+            {
+                // Clone receiver because it is a value, but we need a variable to be able to get a span
+                rewrittenReceiver = _factory.StoreToTemp(rewrittenReceiver, out receiverStore);
+            }
+
+            var getItemOrSliceHelper = (MethodSymbol?)_compilation.GetWellKnownTypeMember(node.GetItemOrSliceHelper);
+            Debug.Assert(getItemOrSliceHelper is object);
+
+            BoundExpression result;
+            _ = node.Expression.Type.HasInlineArrayAttribute(out int length);
+
+            if (node.Argument.Type.SpecialType == SpecialType.System_Int32)
+            {
+                result = getElementRef(node, rewrittenReceiver, index: VisitExpression(node.Argument), getItemOrSliceHelper, length);
+            }
+            else
+            {
+                Debug.Assert(length > 0);
+
+                if (TypeSymbol.Equals(node.Argument.Type, _compilation.GetWellKnownType(WellKnownType.System_Index), TypeCompareKind.AllIgnoreOptions))
+                {
+                    BoundExpression makeOffsetInput = DetermineMakePatternIndexOffsetExpressionStrategy(node.Argument, out PatternIndexOffsetLoweringStrategy strategy);
+                    BoundExpression integerArgument = makePatternIndexOffsetExpression(makeOffsetInput, length, strategy);
+
+                    result = getElementRef(node, rewrittenReceiver, index: integerArgument, getItemOrSliceHelper, length);
+                }
+                else
+                {
+                    // createSpan(ref receiver, length).Slice(range converted to start, range converted to size)
+
+                    Debug.Assert(receiverStore is null);
+                    Debug.Assert(TypeSymbol.Equals(node.Argument.Type, _compilation.GetWellKnownType(WellKnownType.System_Range), TypeCompareKind.AllIgnoreOptions));
+
+                    MethodSymbol createSpan = getCreateSpanHelper(node, spanType: getItemOrSliceHelper.ContainingType, intType: (NamedTypeSymbol)getItemOrSliceHelper.Parameters[0].Type);
+                    getItemOrSliceHelper = getItemOrSliceHelper.AsMember((NamedTypeSymbol)createSpan.ReturnType);
+
+                    BoundRangeExpression? rangeExpr;
+                    BoundExpression? startMakeOffsetInput, endMakeOffsetInput, rewrittenRangeArg;
+                    PatternIndexOffsetLoweringStrategy startStrategy, endStrategy;
+                    RewriteRangeParts(node.Argument, out rangeExpr, out startMakeOffsetInput, out startStrategy, out endMakeOffsetInput, out endStrategy, out rewrittenRangeArg);
+
+                    var localsBuilder = ArrayBuilder<LocalSymbol>.GetInstance();
+                    var sideEffectsBuilder = ArrayBuilder<BoundExpression>.GetInstance();
+
+                    BoundExpression startExpr;
+                    BoundExpression rangeSizeExpr;
+                    if (rangeExpr is not null)
+                    {
+
+                        startExpr = makePatternIndexOffsetExpression(startMakeOffsetInput, length, startStrategy);
+                        BoundExpression endExpr = makePatternIndexOffsetExpression(endMakeOffsetInput, length, endStrategy);
+                        rangeSizeExpr = MakeRangeSize(ref startExpr, endExpr, localsBuilder, sideEffectsBuilder);
+                    }
+                    else
+                    {
+                        Debug.Assert(rewrittenRangeArg is not null);
+                        DeconstructRange(rewrittenRangeArg, _factory.Literal(length), localsBuilder, sideEffectsBuilder, out startExpr, out rangeSizeExpr);
+                    }
+
+                    BoundExpression possiblyRefCapturedReceiver = rewrittenReceiver;
+
+                    if (sideEffectsBuilder.Count != 0)
+                    {
+                        possiblyRefCapturedReceiver = _factory.StoreToTemp(possiblyRefCapturedReceiver, out var refCapture, createSpan.Parameters[0].RefKind == RefKind.In ? RefKindExtensions.StrictIn : RefKind.Ref);
+                        localsBuilder.Insert(0, ((BoundLocal)possiblyRefCapturedReceiver).LocalSymbol);
+                        sideEffectsBuilder.Insert(0, refCapture);
+                    }
+
+                    if (startExpr.ConstantValueOpt is { SpecialType: SpecialType.System_Int32, Int32Value: 0 } &&
+                        rangeSizeExpr.ConstantValueOpt is { SpecialType: SpecialType.System_Int32, Int32Value: >= 0 and int rangeSizeConst } &&
+                        rangeSizeConst <= length)
+                    {
+                        // No need to call Slice, we can create a Span of the right length from the start.
+                        result = _factory.Call(null, createSpan, possiblyRefCapturedReceiver, rangeSizeExpr, useStrictArgumentRefKinds: true);
+                    }
+                    else
+                    {
+                        result = _factory.Call(_factory.Call(null, createSpan, possiblyRefCapturedReceiver, _factory.Literal(length), useStrictArgumentRefKinds: true),
+                                           getItemOrSliceHelper, startExpr, rangeSizeExpr);
+                    }
+
+                    result = _factory.Sequence(localsBuilder.ToImmutableAndFree(), sideEffectsBuilder.ToImmutableAndFree(), result);
+                }
+            }
+
+            if (receiverStore is not null)
+            {
+                result = _factory.Sequence(ImmutableArray.Create(((BoundLocal)rewrittenReceiver).LocalSymbol),
+                                           ImmutableArray.Create((BoundExpression)receiverStore),
+                                           result);
+            }
+
+            return result;
+
+            BoundExpression makePatternIndexOffsetExpression(BoundExpression? makeOffsetInput, int length, PatternIndexOffsetLoweringStrategy strategy)
+            {
+                BoundExpression integerArgument;
+
+                if (strategy == PatternIndexOffsetLoweringStrategy.SubtractFromLength &&
+                    makeOffsetInput is { ConstantValueOpt.Int32Value: var offset })
+                {
+                    integerArgument = _factory.Literal(length - offset);
+                }
+                else
+                {
+                    integerArgument = MakePatternIndexOffsetExpression(makeOffsetInput, _factory.Literal(length), strategy);
+                }
+
+                return integerArgument;
+            }
+
+            MethodSymbol getCreateSpanHelper(BoundInlineArrayAccess node, NamedTypeSymbol spanType, NamedTypeSymbol intType)
+            {
+                Debug.Assert(node.Expression.Type is object);
+
+                MethodSymbol createSpan;
+                if (node.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int or WellKnownMember.System_ReadOnlySpan_T__get_Item)
+                {
+                    createSpan = _factory.ModuleBuilderOpt.EnsureInlineArrayAsReadOnlySpanExists(node.Syntax, spanType, intType, _diagnostics.DiagnosticBag);
+                }
+                else
+                {
+                    createSpan = _factory.ModuleBuilderOpt.EnsureInlineArrayAsSpanExists(node.Syntax, spanType, intType, _diagnostics.DiagnosticBag);
+                }
+
+                return createSpan.Construct(node.Expression.Type, node.Expression.Type.TryGetInlineArrayElementField()!.Type);
+            }
+
+            BoundExpression getElementRef(BoundInlineArrayAccess node, BoundExpression rewrittenReceiver, BoundExpression index, MethodSymbol getItemOrSliceHelper, int length)
+            {
+                Debug.Assert(node.Expression.Type is object);
+                Debug.Assert(index.Type?.SpecialType == SpecialType.System_Int32);
+
+                var intType = (NamedTypeSymbol)index.Type;
+
+                if (index.ConstantValueOpt is { SpecialType: SpecialType.System_Int32, Int32Value: int constIndex })
+                {
+                    if (constIndex == 0)
+                    {
+                        // getFirstElementRef(ref receiver)
+                        MethodSymbol elementRef;
+
+                        if (node.GetItemOrSliceHelper is WellKnownMember.System_Span_T__get_Item)
+                        {
+                            elementRef = _factory.ModuleBuilderOpt.EnsureInlineArrayFirstElementRefExists(node.Syntax, _diagnostics.DiagnosticBag);
+                        }
+                        else
+                        {
+                            Debug.Assert(node.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__get_Item);
+                            elementRef = _factory.ModuleBuilderOpt.EnsureInlineArrayFirstElementRefReadOnlyExists(node.Syntax, _diagnostics.DiagnosticBag);
+                        }
+
+                        elementRef = elementRef.Construct(node.Expression.Type, node.Expression.Type.TryGetInlineArrayElementField()!.Type);
+
+                        return _factory.Call(null, elementRef, rewrittenReceiver, useStrictArgumentRefKinds: true);
+                    }
+                    else if (constIndex > 0 && constIndex < length)
+                    {
+                        // getElementRef(ref receiver, index)
+                        MethodSymbol elementRef;
+
+                        if (node.GetItemOrSliceHelper is WellKnownMember.System_Span_T__get_Item)
+                        {
+                            elementRef = _factory.ModuleBuilderOpt.EnsureInlineArrayElementRefExists(node.Syntax, intType, _diagnostics.DiagnosticBag);
+                        }
+                        else
+                        {
+                            Debug.Assert(node.GetItemOrSliceHelper is WellKnownMember.System_ReadOnlySpan_T__get_Item);
+                            elementRef = _factory.ModuleBuilderOpt.EnsureInlineArrayElementRefReadOnlyExists(node.Syntax, intType, _diagnostics.DiagnosticBag);
+                        }
+
+                        elementRef = elementRef.Construct(node.Expression.Type, node.Expression.Type.TryGetInlineArrayElementField()!.Type);
+
+                        return _factory.Call(null, elementRef, rewrittenReceiver, index, useStrictArgumentRefKinds: true);
+                    }
+                }
+
+                Debug.Assert(index.ConstantValueOpt is null); // Binder should have reported an error due to index out of bounds, or should have handled by code above.
+
+                // createSpan(ref receiver, length)[index]
+
+                NamedTypeSymbol spanType = getItemOrSliceHelper.ContainingType;
+                MethodSymbol createSpan = getCreateSpanHelper(node, spanType, intType);
+                getItemOrSliceHelper = getItemOrSliceHelper.AsMember((NamedTypeSymbol)createSpan.ReturnType);
+                return _factory.Call(_factory.Call(null, createSpan, rewrittenReceiver, _factory.Literal(length), useStrictArgumentRefKinds: true), getItemOrSliceHelper, index);
+            }
+        }
+
         public override BoundNode? VisitListPatternIndexPlaceholder(BoundListPatternIndexPlaceholder node)
         {
             throw ExceptionUtilities.Unreachable();
@@ -518,51 +717,10 @@ private BoundExpression VisitRangePatternIndexerAccess(BoundImplicitIndexerAcces
             var receiver = VisitExpression(node.Receiver);
             var rangeArg = node.Argument;
 
-            BoundExpression? startMakeOffsetInput = null;
-            PatternIndexOffsetLoweringStrategy startStrategy = default;
-            BoundExpression? endMakeOffsetInput = null;
-            PatternIndexOffsetLoweringStrategy endStrategy = default;
-            var rangeExpr = rangeArg as BoundRangeExpression;
-            BoundExpression? rewrittenRangeArg = null;
-
-            if (rangeExpr is not null)
-            {
-                // If we know that the input is a range expression, we can
-                // optimize by pulling it apart inline, so
-                // 
-                // Range range = argumentExpr;
-                // int start = range.Start.GetOffset(length)
-                // int rangeSize = range.End.GetOffset(length) - start
-                //
-                // is, with `start..end`:
-                //
-                // int start = start.GetOffset(length)
-                // int rangeSize = end.GetOffset(length) - start
-
-                if (rangeExpr.LeftOperandOpt is BoundExpression left)
-                {
-                    startMakeOffsetInput = DetermineMakePatternIndexOffsetExpressionStrategy(left, out startStrategy);
-                }
-                else
-                {
-                    startStrategy = PatternIndexOffsetLoweringStrategy.Zero;
-                    startMakeOffsetInput = null;
-                }
-
-                if (rangeExpr.RightOperandOpt is BoundExpression right)
-                {
-                    endMakeOffsetInput = DetermineMakePatternIndexOffsetExpressionStrategy(right, out endStrategy);
-                }
-                else
-                {
-                    endStrategy = PatternIndexOffsetLoweringStrategy.Length;
-                    endMakeOffsetInput = null;
-                }
-            }
-            else
-            {
-                rewrittenRangeArg = VisitExpression(rangeArg);
-            }
+            BoundRangeExpression? rangeExpr;
+            BoundExpression? startMakeOffsetInput, endMakeOffsetInput, rewrittenRangeArg;
+            PatternIndexOffsetLoweringStrategy startStrategy, endStrategy;
+            RewriteRangeParts(rangeArg, out rangeExpr, out startMakeOffsetInput, out startStrategy, out endMakeOffsetInput, out endStrategy, out rewrittenRangeArg);
 
             var localsBuilder = ArrayBuilder<LocalSymbol>.GetInstance();
             var sideEffectsBuilder = ArrayBuilder<BoundExpression>.GetInstance();
@@ -641,7 +799,6 @@ private BoundExpression VisitRangePatternIndexerAccess(BoundImplicitIndexerAcces
                 const int captureEndOffset = 1 << 1;
                 const int useLength = 1 << 2;
                 const int captureLength = 1 << 3;
-                const int captureStartValue = 1 << 4;
 
                 int rewriteFlags;
 
@@ -659,27 +816,27 @@ private BoundExpression VisitRangePatternIndexerAccess(BoundImplicitIndexerAcces
                         break;
                     case (PatternIndexOffsetLoweringStrategy.UseAsIs, PatternIndexOffsetLoweringStrategy.Length):
                     case (PatternIndexOffsetLoweringStrategy.UseAsIs, PatternIndexOffsetLoweringStrategy.UseGetOffsetAPI):
-                        rewriteFlags = useLength | captureStartValue;
+                        rewriteFlags = useLength;
                         break;
                     case (PatternIndexOffsetLoweringStrategy.UseAsIs, PatternIndexOffsetLoweringStrategy.SubtractFromLength):
                         rewriteFlags = captureStartOffset | captureEndOffset | useLength;
                         break;
                     case (PatternIndexOffsetLoweringStrategy.UseAsIs, PatternIndexOffsetLoweringStrategy.UseAsIs):
-                        rewriteFlags = captureStartValue;
+                        rewriteFlags = 0;
                         break;
                     case (PatternIndexOffsetLoweringStrategy.SubtractFromLength, PatternIndexOffsetLoweringStrategy.Length):
                     case (PatternIndexOffsetLoweringStrategy.UseGetOffsetAPI, PatternIndexOffsetLoweringStrategy.Length):
-                        rewriteFlags = captureStartOffset | useLength | captureLength | captureStartValue;
+                        rewriteFlags = captureStartOffset | useLength | captureLength;
                         break;
                     case (PatternIndexOffsetLoweringStrategy.SubtractFromLength, PatternIndexOffsetLoweringStrategy.SubtractFromLength):
                     case (PatternIndexOffsetLoweringStrategy.SubtractFromLength, PatternIndexOffsetLoweringStrategy.UseGetOffsetAPI):
                     case (PatternIndexOffsetLoweringStrategy.UseGetOffsetAPI, PatternIndexOffsetLoweringStrategy.SubtractFromLength):
                     case (PatternIndexOffsetLoweringStrategy.UseGetOffsetAPI, PatternIndexOffsetLoweringStrategy.UseGetOffsetAPI):
-                        rewriteFlags = captureStartOffset | captureEndOffset | useLength | captureLength | captureStartValue;
+                        rewriteFlags = captureStartOffset | captureEndOffset | useLength | captureLength;
                         break;
                     case (PatternIndexOffsetLoweringStrategy.SubtractFromLength, PatternIndexOffsetLoweringStrategy.UseAsIs):
                     case (PatternIndexOffsetLoweringStrategy.UseGetOffsetAPI, PatternIndexOffsetLoweringStrategy.UseAsIs):
-                        rewriteFlags = captureStartOffset | captureEndOffset | useLength | captureStartValue;
+                        rewriteFlags = captureStartOffset | captureEndOffset | useLength;
                         break;
 
                     default:
@@ -687,7 +844,6 @@ private BoundExpression VisitRangePatternIndexerAccess(BoundImplicitIndexerAcces
                 }
 
                 Debug.Assert(startStrategy != PatternIndexOffsetLoweringStrategy.Zero || (rewriteFlags & captureStartOffset) == 0);
-                Debug.Assert(startStrategy != PatternIndexOffsetLoweringStrategy.Zero || (rewriteFlags & captureStartValue) == 0);
                 Debug.Assert((rewriteFlags & captureEndOffset) == 0 || (rewriteFlags & captureStartOffset) != 0 || startStrategy == PatternIndexOffsetLoweringStrategy.Zero);
                 Debug.Assert((rewriteFlags & captureStartOffset) == 0 || (rewriteFlags & captureEndOffset) != 0 || endStrategy == PatternIndexOffsetLoweringStrategy.Length);
                 Debug.Assert(endStrategy != PatternIndexOffsetLoweringStrategy.Length || (rewriteFlags & captureEndOffset) == 0);
@@ -732,66 +888,13 @@ private BoundExpression VisitRangePatternIndexerAccess(BoundImplicitIndexerAcces
                 }
 
                 startExpr = MakePatternIndexOffsetExpression(startMakeOffsetInput, lengthAccess, startStrategy);
-
-                if ((rewriteFlags & captureStartValue) != 0 && startExpr.ConstantValueOpt is null)
-                {
-                    var startLocal = F.StoreToTemp(startExpr, out var startStore);
-                    localsBuilder.Add(startLocal.LocalSymbol);
-                    sideEffectsBuilder.Add(startStore);
-                    startExpr = startLocal;
-                }
-
                 BoundExpression endExpr = MakePatternIndexOffsetExpression(endMakeOffsetInput, lengthAccess, endStrategy);
-
-                if (startExpr.ConstantValueOpt?.Int32Value == 0)
-                {
-                    rangeSizeExpr = endExpr;
-                }
-                else if (startExpr.ConstantValueOpt is { Int32Value: var startConst } && endExpr.ConstantValueOpt is { Int32Value: var endConst })
-                {
-                    rangeSizeExpr = F.Literal(unchecked(endConst - startConst));
-                }
-                else
-                {
-                    rangeSizeExpr = F.IntSubtract(endExpr, startExpr);
-                }
+                rangeSizeExpr = MakeRangeSize(ref startExpr, endExpr, localsBuilder, sideEffectsBuilder);
             }
             else
             {
                 Debug.Assert(rewrittenRangeArg is not null);
-                var rangeLocal = F.StoreToTemp(rewrittenRangeArg, out var rangeStore);
-                localsBuilder.Add(rangeLocal.LocalSymbol);
-                sideEffectsBuilder.Add(rangeStore);
-
-                var lengthAccess = VisitExpression(node.LengthOrCountAccess);
-
-                var lengthLocal = F.StoreToTemp(lengthAccess, out var lengthStore);
-                localsBuilder.Add(lengthLocal.LocalSymbol);
-                sideEffectsBuilder.Add(lengthStore);
-
-                var startLocal = F.StoreToTemp(
-                    F.Call(
-                        F.Call(rangeLocal, F.WellKnownMethod(WellKnownMember.System_Range__get_Start)),
-                        F.WellKnownMethod(WellKnownMember.System_Index__GetOffset),
-                        lengthLocal),
-                    out var startStore);
-
-                localsBuilder.Add(startLocal.LocalSymbol);
-                sideEffectsBuilder.Add(startStore);
-                startExpr = startLocal;
-
-                var rangeSizeLocal = F.StoreToTemp(
-                    F.IntSubtract(
-                        F.Call(
-                            F.Call(rangeLocal, F.WellKnownMethod(WellKnownMember.System_Range__get_End)),
-                            F.WellKnownMethod(WellKnownMember.System_Index__GetOffset),
-                            lengthLocal),
-                        startExpr),
-                    out var rangeSizeStore);
-
-                localsBuilder.Add(rangeSizeLocal.LocalSymbol);
-                sideEffectsBuilder.Add(rangeSizeStore);
-                rangeSizeExpr = rangeSizeLocal;
+                DeconstructRange(rewrittenRangeArg, VisitExpression(node.LengthOrCountAccess), localsBuilder, sideEffectsBuilder, out startExpr, out rangeSizeExpr);
             }
 
             Debug.Assert(node.ArgumentPlaceholders.Length == 2);
@@ -810,5 +913,126 @@ private BoundExpression VisitRangePatternIndexerAccess(BoundImplicitIndexerAcces
                 sideEffectsBuilder.ToImmutableAndFree(),
                 rewrittenIndexerAccess);
         }
+
+        private BoundExpression MakeRangeSize(ref BoundExpression startExpr, BoundExpression endExpr, ArrayBuilder<LocalSymbol> localsBuilder, ArrayBuilder<BoundExpression> sideEffectsBuilder)
+        {
+            var F = _factory;
+
+            BoundExpression rangeSizeExpr;
+
+            if (startExpr.ConstantValueOpt?.Int32Value == 0)
+            {
+                rangeSizeExpr = endExpr;
+            }
+            else if (startExpr.ConstantValueOpt is { Int32Value: var startConst } && endExpr.ConstantValueOpt is { Int32Value: var endConst })
+            {
+                rangeSizeExpr = F.Literal(unchecked(endConst - startConst));
+            }
+            else
+            {
+                if (startExpr.ConstantValueOpt is null &&
+                    startExpr is not BoundLocal { LocalSymbol.SynthesizedKind: not SynthesizedLocalKind.UserDefined })
+                {
+                    var startLocal = F.StoreToTemp(startExpr, out var startStore);
+                    localsBuilder.Add(startLocal.LocalSymbol);
+                    sideEffectsBuilder.Add(startStore);
+                    startExpr = startLocal;
+                }
+
+                rangeSizeExpr = F.IntSubtract(endExpr, startExpr);
+            }
+
+            return rangeSizeExpr;
+        }
+
+        private void DeconstructRange(BoundExpression rewrittenRangeArg, BoundExpression lengthAccess, ArrayBuilder<LocalSymbol> localsBuilder, ArrayBuilder<BoundExpression> sideEffectsBuilder, out BoundExpression startExpr, out BoundExpression rangeSizeExpr)
+        {
+            var F = _factory;
+
+            var rangeLocal = F.StoreToTemp(rewrittenRangeArg, out var rangeStore);
+            localsBuilder.Add(rangeLocal.LocalSymbol);
+            sideEffectsBuilder.Add(rangeStore);
+
+            if (lengthAccess.ConstantValueOpt is null)
+            {
+                var lengthLocal = F.StoreToTemp(lengthAccess, out var lengthStore);
+                localsBuilder.Add(lengthLocal.LocalSymbol);
+                sideEffectsBuilder.Add(lengthStore);
+                lengthAccess = lengthLocal;
+            }
+
+            var startLocal = F.StoreToTemp(
+                F.Call(
+                    F.Call(rangeLocal, F.WellKnownMethod(WellKnownMember.System_Range__get_Start)),
+                    F.WellKnownMethod(WellKnownMember.System_Index__GetOffset),
+                    lengthAccess),
+                out var startStore);
+
+            localsBuilder.Add(startLocal.LocalSymbol);
+            sideEffectsBuilder.Add(startStore);
+            startExpr = startLocal;
+
+            var rangeSizeLocal = F.StoreToTemp(
+                F.IntSubtract(
+                    F.Call(
+                        F.Call(rangeLocal, F.WellKnownMethod(WellKnownMember.System_Range__get_End)),
+                        F.WellKnownMethod(WellKnownMember.System_Index__GetOffset),
+                        lengthAccess),
+                    startExpr),
+                out var rangeSizeStore);
+
+            localsBuilder.Add(rangeSizeLocal.LocalSymbol);
+            sideEffectsBuilder.Add(rangeSizeStore);
+            rangeSizeExpr = rangeSizeLocal;
+        }
+
+        private void RewriteRangeParts(BoundExpression rangeArg, out BoundRangeExpression? rangeExpr, out BoundExpression? startMakeOffsetInput, out PatternIndexOffsetLoweringStrategy startStrategy, out BoundExpression? endMakeOffsetInput, out PatternIndexOffsetLoweringStrategy endStrategy, out BoundExpression? rewrittenRangeArg)
+        {
+            startMakeOffsetInput = null;
+            startStrategy = default;
+            endMakeOffsetInput = null;
+            endStrategy = default;
+            rewrittenRangeArg = null;
+            rangeExpr = rangeArg as BoundRangeExpression;
+
+            if (rangeExpr is not null)
+            {
+                // If we know that the input is a range expression, we can
+                // optimize by pulling it apart inline, so
+                // 
+                // Range range = argumentExpr;
+                // int start = range.Start.GetOffset(length)
+                // int rangeSize = range.End.GetOffset(length) - start
+                //
+                // is, with `start..end`:
+                //
+                // int start = start.GetOffset(length)
+                // int rangeSize = end.GetOffset(length) - start
+
+                if (rangeExpr.LeftOperandOpt is BoundExpression left)
+                {
+                    startMakeOffsetInput = DetermineMakePatternIndexOffsetExpressionStrategy(left, out startStrategy);
+                }
+                else
+                {
+                    startStrategy = PatternIndexOffsetLoweringStrategy.Zero;
+                    startMakeOffsetInput = null;
+                }
+
+                if (rangeExpr.RightOperandOpt is BoundExpression right)
+                {
+                    endMakeOffsetInput = DetermineMakePatternIndexOffsetExpressionStrategy(right, out endStrategy);
+                }
+                else
+                {
+                    endStrategy = PatternIndexOffsetLoweringStrategy.Length;
+                    endMakeOffsetInput = null;
+                }
+            }
+            else
+            {
+                rewrittenRangeArg = VisitExpression(rangeArg);
+            }
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ObjectOrCollectionInitializerExpression.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ObjectOrCollectionInitializerExpression.cs
index 4dc2b30997aa9..91faef3826194 100644
--- a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ObjectOrCollectionInitializerExpression.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ObjectOrCollectionInitializerExpression.cs
@@ -199,10 +199,10 @@ private BoundExpression MakeDynamicCollectionInitializer(BoundExpression rewritt
             {
                 Debug.Assert(temps.Count == 0);
                 temps.Free();
-                return initializer.Update(addMethod, rewrittenArguments, rewrittenReceiver, expanded: false, argsToParamsOpt: default, defaultArguments: default, initializer.InvokedAsExtensionMethod, initializer.ResultKind, rewrittenType);
+                return initializer.Update(addMethod, rewrittenArguments, rewrittenReceiver, expanded: false, argsToParamsOpt: default, defaultArguments: default, invokedAsExtensionMethod: false, initializer.ResultKind, rewrittenType);
             }
 
-            return MakeCall(null, syntax, rewrittenReceiver, addMethod, rewrittenArguments, argumentRefKindsOpt, initializer.InvokedAsExtensionMethod, initializer.ResultKind, addMethod.ReturnType, temps.ToImmutableAndFree());
+            return MakeCall(null, syntax, rewrittenReceiver, addMethod, rewrittenArguments, argumentRefKindsOpt, initializer.ResultKind, addMethod.ReturnType, temps.ToImmutableAndFree());
         }
 
         private BoundExpression VisitObjectInitializerMember(BoundObjectInitializerMember node, ref BoundExpression rewrittenReceiver, ArrayBuilder<BoundExpression> sideEffects, ref ArrayBuilder<LocalSymbol>? temps)
diff --git a/src/Compilers/CSharp/Portable/Lowering/MethodToClassRewriter.cs b/src/Compilers/CSharp/Portable/Lowering/MethodToClassRewriter.cs
index a517066593e36..6f6ab63d0bc45 100644
--- a/src/Compilers/CSharp/Portable/Lowering/MethodToClassRewriter.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/MethodToClassRewriter.cs
@@ -613,8 +613,8 @@ public override BoundNode VisitLoweredConditionalAccess(BoundLoweredConditionalA
 
             if (method.ContainingType is null)
             {
-                Debug.Assert(method is SynthesizedGlobalMethodSymbol);
-                return method;
+                Debug.Assert(method.OriginalDefinition is SynthesizedGlobalMethodSymbol);
+                return method.OriginalDefinition.ConstructIfGeneric(TypeMap.SubstituteTypes(method.TypeArgumentsWithAnnotations));
             }
             else if (method.ContainingType.IsAnonymousType)
             {
diff --git a/src/Compilers/CSharp/Portable/Lowering/SpillSequenceSpiller.cs b/src/Compilers/CSharp/Portable/Lowering/SpillSequenceSpiller.cs
index 631b689c990a8..839625364c371 100644
--- a/src/Compilers/CSharp/Portable/Lowering/SpillSequenceSpiller.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/SpillSequenceSpiller.cs
@@ -335,7 +335,7 @@ private BoundExpression Spill(
                         continue;
 
                     case BoundKind.Sequence:
-                        if (refKind != RefKind.None)
+                        if (refKind != RefKind.None || expression.Type?.IsRefLikeType == true)
                         {
                             var sequence = (BoundSequence)expression;
 
@@ -429,6 +429,47 @@ private BoundExpression Spill(
                         // later, if needed
                         return expression;
 
+                    case BoundKind.Call:
+                        var call = (BoundCall)expression;
+
+                        // If the method is known to have no observable side-effects, we can spill its receiver and arguments,
+                        // and call it later, after some other (unrelated) side-effects are evaluated.
+                        // It is similar to spilling a field/array access.
+                        if (refKind != RefKind.None)
+                        {
+                            if (call.Method.OriginalDefinition is SynthesizedInlineArrayFirstElementRefMethod or SynthesizedInlineArrayFirstElementRefReadOnlyMethod)
+                            {
+                                Debug.Assert(call.Arguments.Length == 1);
+                                return call.Update(ImmutableArray.Create(Spill(builder, call.Arguments[0], call.ArgumentRefKindsOpt[0])));
+                            }
+                            else if (call.Method.OriginalDefinition is SynthesizedInlineArrayElementRefMethod or SynthesizedInlineArrayElementRefReadOnlyMethod)
+                            {
+                                return spillInlineArrayHelperWithTwoArguments(builder, call);
+                            }
+                            else if (call.Method.OriginalDefinition == _F.Compilation.GetWellKnownTypeMember(WellKnownMember.System_Span_T__get_Item) ||
+                                call.Method.OriginalDefinition == _F.Compilation.GetWellKnownTypeMember(WellKnownMember.System_ReadOnlySpan_T__get_Item))
+                            {
+                                Debug.Assert(call.Arguments.Length == 1);
+                                return call.Update(Spill(builder, call.ReceiverOpt, ReceiverSpillRefKind(call.ReceiverOpt)),
+                                                   call.Method,
+                                                   ImmutableArray.Create(Spill(builder, call.Arguments[0])));
+                            }
+                        }
+                        else if (call.Method.OriginalDefinition is SynthesizedInlineArrayAsSpanMethod or SynthesizedInlineArrayAsReadOnlySpanMethod)
+                        {
+                            return spillInlineArrayHelperWithTwoArguments(builder, call);
+                        }
+                        else if (call.Method.OriginalDefinition == _F.Compilation.GetWellKnownTypeMember(WellKnownMember.System_Span_T__Slice_Int_Int) ||
+                                 call.Method.OriginalDefinition == _F.Compilation.GetWellKnownTypeMember(WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int))
+                        {
+                            Debug.Assert(call.Arguments.Length == 2);
+                            return call.Update(Spill(builder, call.ReceiverOpt, ReceiverSpillRefKind(call.ReceiverOpt)),
+                                               call.Method,
+                                               ImmutableArray.Create(Spill(builder, call.Arguments[0]), Spill(builder, call.Arguments[1])));
+                        }
+
+                        goto default;
+
                     default:
                         if (expression.Type.IsVoidType() || sideEffectsOnly)
                         {
@@ -452,6 +493,13 @@ private BoundExpression Spill(
                         }
                 }
             }
+
+            BoundExpression spillInlineArrayHelperWithTwoArguments(BoundSpillSequenceBuilder builder, BoundCall call)
+            {
+                Debug.Assert(call.Arguments.Length == 2);
+                return call.Update(ImmutableArray.Create(Spill(builder, call.Arguments[0], call.ArgumentRefKindsOpt[0]),
+                                                         call.Arguments[1].ConstantValueOpt is { } ? call.Arguments[1] : Spill(builder, call.Arguments[1])));
+            }
         }
 
         internal static bool IsComplexConditionalInitializationOfReceiverRef(
diff --git a/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/MethodToStateMachineRewriter.cs b/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/MethodToStateMachineRewriter.cs
index 2235b01d68c5b..c7bd2371c52dd 100644
--- a/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/MethodToStateMachineRewriter.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/MethodToStateMachineRewriter.cs
@@ -307,7 +307,8 @@ private BoundStatement PossibleIteratorScope(ImmutableArray<LocalSymbol> locals,
                 // Ref synthesized variables have proxies that are allocated in VisitAssignmentOperator.
                 if (local.RefKind != RefKind.None)
                 {
-                    Debug.Assert(local.SynthesizedKind == SynthesizedLocalKind.Spill);
+                    Debug.Assert(local.SynthesizedKind == SynthesizedLocalKind.Spill ||
+                                 (local.SynthesizedKind == SynthesizedLocalKind.ForEachArray && local.Type.HasInlineArrayAttribute(out _) && local.Type.TryGetInlineArrayElementField() is object));
                     continue;
                 }
 
@@ -489,9 +490,17 @@ private void FreeReusableHoistedField(StateMachineFieldSymbol field)
 
         private BoundExpression HoistRefInitialization(SynthesizedLocal local, BoundAssignmentOperator node)
         {
-            Debug.Assert(local.SynthesizedKind == SynthesizedLocalKind.Spill);
+            Debug.Assert(local.SynthesizedKind == SynthesizedLocalKind.Spill ||
+                         (local.SynthesizedKind == SynthesizedLocalKind.ForEachArray && local.Type.HasInlineArrayAttribute(out _) && local.Type.TryGetInlineArrayElementField() is object));
             Debug.Assert(local.SyntaxOpt != null);
-            Debug.Assert(this.OriginalMethod.IsAsync);
+#pragma warning disable format
+            Debug.Assert(local.SynthesizedKind switch
+                         {
+                             SynthesizedLocalKind.Spill => this.OriginalMethod.IsAsync,
+                             SynthesizedLocalKind.ForEachArray => this.OriginalMethod.IsAsync || this.OriginalMethod.IsIterator,
+                             _ => false
+                         });
+#pragma warning restore format
 
             var right = (BoundExpression)Visit(node.Right);
 
@@ -504,7 +513,14 @@ private BoundExpression HoistRefInitialization(SynthesizedLocal local, BoundAssi
             if (F.Compilation.Options.OptimizationLevel == OptimizationLevel.Debug)
             {
                 awaitSyntaxOpt = local.GetDeclaratorSyntax();
-                Debug.Assert(awaitSyntaxOpt.IsKind(SyntaxKind.AwaitExpression) || awaitSyntaxOpt.IsKind(SyntaxKind.SwitchExpression));
+#pragma warning disable format
+                Debug.Assert(local.SynthesizedKind switch
+                             {
+                                 SynthesizedLocalKind.Spill => awaitSyntaxOpt.IsKind(SyntaxKind.AwaitExpression) || awaitSyntaxOpt.IsKind(SyntaxKind.SwitchExpression),
+                                 SynthesizedLocalKind.ForEachArray => awaitSyntaxOpt is CommonForEachStatementSyntax,
+                                 _ => false
+                             });
+#pragma warning restore format
                 syntaxOffset = OriginalMethod.CalculateLocalSyntaxOffset(LambdaUtilities.GetDeclaratorPosition(awaitSyntaxOpt), awaitSyntaxOpt.SyntaxTree);
             }
             else
@@ -814,7 +830,8 @@ public override BoundNode VisitAssignmentOperator(BoundAssignmentOperator node)
             // Here we handle ref temps. Ref synthesized variables are the target of a ref assignment operator before
             // being used in any other way.
 
-            Debug.Assert(leftLocal.SynthesizedKind == SynthesizedLocalKind.Spill);
+            Debug.Assert(leftLocal.SynthesizedKind == SynthesizedLocalKind.Spill ||
+                         (leftLocal.SynthesizedKind == SynthesizedLocalKind.ForEachArray && leftLocal.Type.HasInlineArrayAttribute(out _) && leftLocal.Type.TryGetInlineArrayElementField() is object));
             Debug.Assert(node.IsRef);
 
             // We have an assignment to a variable that has not yet been assigned a proxy.
diff --git a/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/StateMachineRewriter.cs b/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/StateMachineRewriter.cs
index e54c9781c2378..76dc796ee859b 100644
--- a/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/StateMachineRewriter.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/StateMachineRewriter.cs
@@ -169,7 +169,8 @@ private void CreateNonReusableLocalProxies(
                     if (local.RefKind != RefKind.None)
                     {
                         // we'll create proxies for these variables later:
-                        Debug.Assert(synthesizedKind == SynthesizedLocalKind.Spill);
+                        Debug.Assert(synthesizedKind == SynthesizedLocalKind.Spill ||
+                                     (synthesizedKind == SynthesizedLocalKind.ForEachArray && local.Type.HasInlineArrayAttribute(out _) && local.Type.TryGetInlineArrayElementField() is object));
                         continue;
                     }
 
diff --git a/src/Compilers/CSharp/Portable/Lowering/SynthesizedMethodBaseSymbol.cs b/src/Compilers/CSharp/Portable/Lowering/SynthesizedMethodBaseSymbol.cs
index 4496b6fe86b11..08fc7eefd4102 100644
--- a/src/Compilers/CSharp/Portable/Lowering/SynthesizedMethodBaseSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/SynthesizedMethodBaseSymbol.cs
@@ -36,26 +36,23 @@ protected SynthesizedMethodBaseSymbol(NamedTypeSymbol containingType,
                                               string name,
                                               DeclarationModifiers declarationModifiers,
                                               bool isIterator)
-            : base(containingType, syntaxReference, location, isIterator)
+            : base(containingType, syntaxReference, location, isIterator,
+                   (declarationModifiers, MakeFlags(
+                                                    methodKind: MethodKind.Ordinary,
+                                                    refKind: baseMethod.RefKind,
+                                                    declarationModifiers,
+                                                    returnsVoid: baseMethod.ReturnsVoid,
+                                                    isExtensionMethod: false,
+                                                    isNullableAnalysisEnabled: false,
+                                                    isVarArg: baseMethod.IsVararg,
+                                                    isExpressionBodied: false,
+                                                    isExplicitInterfaceImplementation: false)))
         {
             Debug.Assert((object)containingType != null);
             Debug.Assert((object)baseMethod != null);
 
             this.BaseMethod = baseMethod;
             _name = name;
-
-            this.MakeFlags(
-                methodKind: MethodKind.Ordinary,
-                refKind: baseMethod.RefKind,
-                declarationModifiers: declarationModifiers,
-                returnsVoid: baseMethod.ReturnsVoid,
-                // Consider synthesized methods to always have bodies.
-                hasAnyBody: true,
-                isExtensionMethod: false,
-                isNullableAnalysisEnabled: false,
-                isVarArg: baseMethod.IsVararg,
-                isMetadataVirtualIgnoringModifiers: false,
-                isExpressionBodied: false);
         }
 
         protected void AssignTypeMapAndTypeParameters(TypeMap typeMap, ImmutableArray<TypeParameterSymbol> typeParameters)
diff --git a/src/Compilers/CSharp/Portable/Lowering/SyntheticBoundNodeFactory.cs b/src/Compilers/CSharp/Portable/Lowering/SyntheticBoundNodeFactory.cs
index 793786031539e..903bdb32e579f 100644
--- a/src/Compilers/CSharp/Portable/Lowering/SyntheticBoundNodeFactory.cs
+++ b/src/Compilers/CSharp/Portable/Lowering/SyntheticBoundNodeFactory.cs
@@ -788,14 +788,14 @@ public BoundCall Call(BoundExpression? receiver, MethodSymbol method)
             return Call(receiver, method, ImmutableArray<BoundExpression>.Empty);
         }
 
-        public BoundCall Call(BoundExpression? receiver, MethodSymbol method, BoundExpression arg0)
+        public BoundCall Call(BoundExpression? receiver, MethodSymbol method, BoundExpression arg0, bool useStrictArgumentRefKinds = false)
         {
-            return Call(receiver, method, ImmutableArray.Create(arg0));
+            return Call(receiver, method, ImmutableArray.Create(arg0), useStrictArgumentRefKinds);
         }
 
-        public BoundCall Call(BoundExpression? receiver, MethodSymbol method, BoundExpression arg0, BoundExpression arg1)
+        public BoundCall Call(BoundExpression? receiver, MethodSymbol method, BoundExpression arg0, BoundExpression arg1, bool useStrictArgumentRefKinds = false)
         {
-            return Call(receiver, method, ImmutableArray.Create(arg0, arg1));
+            return Call(receiver, method, ImmutableArray.Create(arg0, arg1), useStrictArgumentRefKinds);
         }
 
         public BoundCall Call(BoundExpression? receiver, MethodSymbol method, params BoundExpression[] args)
@@ -806,16 +806,35 @@ public BoundCall Call(BoundExpression? receiver, MethodSymbol method, params Bou
         public BoundCall Call(BoundExpression? receiver, WellKnownMember method, BoundExpression arg0)
             => Call(receiver, WellKnownMethod(method), ImmutableArray.Create(arg0));
 
-        public BoundCall Call(BoundExpression? receiver, MethodSymbol method, ImmutableArray<BoundExpression> args)
+        public BoundCall Call(BoundExpression? receiver, MethodSymbol method, ImmutableArray<BoundExpression> args, bool useStrictArgumentRefKinds = false)
         {
             Debug.Assert(method.ParameterCount == args.Length);
 
             return new BoundCall(
                 Syntax, receiver, method, args,
-                argumentNamesOpt: default(ImmutableArray<String>), argumentRefKindsOpt: method.ParameterRefKinds, isDelegateCall: false, expanded: false,
+                argumentNamesOpt: default(ImmutableArray<string>), argumentRefKindsOpt: getArgumentRefKinds(method, useStrictArgumentRefKinds), isDelegateCall: false, expanded: false,
                 invokedAsExtensionMethod: false, argsToParamsOpt: default(ImmutableArray<int>), defaultArguments: default(BitVector), resultKind: LookupResultKind.Viable,
                 type: method.ReturnType, hasErrors: method.OriginalDefinition is ErrorMethodSymbol)
             { WasCompilerGenerated = true };
+
+            static ImmutableArray<RefKind> getArgumentRefKinds(MethodSymbol method, bool useStrictArgumentRefKinds)
+            {
+                var result = method.ParameterRefKinds;
+
+                if (useStrictArgumentRefKinds && result.Contains(RefKind.In))
+                {
+                    var builder = ArrayBuilder<RefKind>.GetInstance(result.Length);
+
+                    foreach (var refKind in result)
+                    {
+                        builder.Add(refKind == RefKind.In ? RefKindExtensions.StrictIn : refKind);
+                    }
+
+                    return builder.ToImmutableAndFree();
+                }
+
+                return result;
+            }
         }
 
         public BoundCall Call(BoundExpression? receiver, MethodSymbol method, ImmutableArray<RefKind> refKinds, ImmutableArray<BoundExpression> args)
diff --git a/src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs b/src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs
index 56304f9a3c152..bc901b0624449 100644
--- a/src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs
+++ b/src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs
@@ -143,6 +143,8 @@ public CSharpOperationFactory(SemanticModel semanticModel)
                     return CreateBoundArrayAccessOperation((BoundArrayAccess)boundNode);
                 case BoundKind.ImplicitIndexerAccess:
                     return CreateBoundImplicitIndexerAccessOperation((BoundImplicitIndexerAccess)boundNode);
+                case BoundKind.InlineArrayAccess:
+                    return CreateBoundInlineArrayAccessOperation((BoundInlineArrayAccess)boundNode);
                 case BoundKind.NameOfOperator:
                     return CreateBoundNameOfOperatorOperation((BoundNameOfOperator)boundNode);
                 case BoundKind.ThrowExpression:
@@ -1737,6 +1739,17 @@ private IOperation CreateBoundImplicitIndexerAccessOperation(BoundImplicitIndexe
             return new ImplicitIndexerReferenceOperation(instance, argument, lengthSymbol, indexerSymbol, _semanticModel, syntax, type, isImplicit);
         }
 
+        private IInlineArrayAccessOperation CreateBoundInlineArrayAccessOperation(BoundInlineArrayAccess boundInlineArrayAccess)
+        {
+            IOperation arrayReference = Create(boundInlineArrayAccess.Expression);
+            IOperation argument = Create(boundInlineArrayAccess.Argument);
+            SyntaxNode syntax = boundInlineArrayAccess.Syntax;
+            ITypeSymbol? type = boundInlineArrayAccess.GetPublicTypeSymbol();
+            bool isImplicit = boundInlineArrayAccess.WasCompilerGenerated;
+
+            return new InlineArrayAccessOperation(arrayReference, argument, _semanticModel, syntax, type, isImplicit);
+        }
+
         private INameOfOperation CreateBoundNameOfOperatorOperation(BoundNameOfOperator boundNameOfOperator)
         {
             IOperation argument = Create(boundNameOfOperator.Argument);
@@ -1946,6 +1959,8 @@ private IForLoopOperation CreateBoundForStatementOperation(BoundForStatement bou
                                                     ((PropertySymbol)enumeratorInfoOpt.CurrentPropertyGetter.AssociatedSymbol).GetPublicSymbol(),
                                                     enumeratorInfoOpt.MoveNextInfo.Method.GetPublicSymbol(),
                                                     isAsynchronous: enumeratorInfoOpt.IsAsync,
+                                                    inlineArrayConversion: enumeratorInfoOpt.InlineArraySpanType is WellKnownType.Unknown ? null : Conversion.InlineArray,
+                                                    collectionIsInlineArrayValue: enumeratorInfoOpt.InlineArrayUsedAsValue,
                                                     needsDispose: enumeratorInfoOpt.NeedsDisposal,
                                                     knownToImplementIDisposable: enumeratorInfoOpt.NeedsDisposal ?
                                                                                      compilation.Conversions.
@@ -2016,7 +2031,11 @@ internal IOperation CreateBoundForEachStatementLoopControlVariable(BoundForEachS
         private IForEachLoopOperation CreateBoundForEachStatementOperation(BoundForEachStatement boundForEachStatement)
         {
             IOperation loopControlVariable = CreateBoundForEachStatementLoopControlVariable(boundForEachStatement);
-            IOperation collection = Create(boundForEachStatement.Expression);
+            // Strip identity conversion added by compiler on top of inline array. Conversion produces an rvalue, but we need the IOperation tree to preserve lvalue-ness of the original collection. 
+            IOperation collection = Create(boundForEachStatement.EnumeratorInfoOpt?.InlineArraySpanType is null or WellKnownType.Unknown ||
+                                           boundForEachStatement.Expression is not BoundConversion { Conversion.IsIdentity: true, ExplicitCastInCode: false, Operand: BoundExpression operand } ?
+                                               boundForEachStatement.Expression :
+                                               operand);
             var nextVariables = ImmutableArray<IOperation>.Empty;
             IOperation body = Create(boundForEachStatement.Body);
             ForEachLoopOperationInfo? info = GetForEachLoopOperatorInfo(boundForEachStatement);
diff --git a/src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt b/src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt
index 220896f5b853f..225bc3b4430ca 100644
--- a/src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt
+++ b/src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt
@@ -1,3 +1,4 @@
+Microsoft.CodeAnalysis.CSharp.Conversion.IsInlineArray.get -> bool
 Microsoft.CodeAnalysis.CSharp.Conversion.IsCollectionLiteral.get -> bool
 Microsoft.CodeAnalysis.CSharp.Syntax.CollectionExpressionSyntax
 Microsoft.CodeAnalysis.CSharp.Syntax.CollectionExpressionSyntax.AddElements(params Microsoft.CodeAnalysis.CSharp.Syntax.CollectionElementSyntax![]! items) -> Microsoft.CodeAnalysis.CSharp.Syntax.CollectionExpressionSyntax!
diff --git a/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Members.cs b/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Members.cs
index 9aeeb3524e212..858726fc1fc3f 100644
--- a/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Members.cs
+++ b/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Members.cs
@@ -277,15 +277,6 @@ public override void VisitMethod(IMethodSymbol symbol)
                 builder.Add(CreatePart(SymbolDisplayPartKind.NumericLiteral, symbol, "lambda expression"));
                 return;
             }
-            else if ((symbol as Symbols.PublicModel.MethodSymbol)?.UnderlyingMethodSymbol is SynthesizedGlobalMethodSymbol) // It would be nice to handle VB symbols too, but it's not worth the effort.
-            {
-                // Represents a compiler generated synthesized method symbol with a null containing
-                // type.
-
-                // TODO(cyrusn); Why is this a literal?
-                builder.Add(CreatePart(SymbolDisplayPartKind.NumericLiteral, symbol, symbol.Name));
-                return;
-            }
             else if (symbol.MethodKind == MethodKind.FunctionPointerSignature)
             {
                 visitFunctionPointerSignature(symbol);
diff --git a/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Types.cs b/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Types.cs
index b04e2982195f7..77264489f00bd 100644
--- a/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Types.cs
+++ b/src/Compilers/CSharp/Portable/SymbolDisplay/SymbolDisplayVisitor.Types.cs
@@ -179,14 +179,21 @@ public override void VisitDynamicType(IDynamicTypeSymbol symbol)
 
         public override void VisitNamedType(INamedTypeSymbol symbol)
         {
+            if ((format.CompilerInternalOptions & SymbolDisplayCompilerInternalOptions.IncludeFileLocalTypesPrefix) != 0
+                && symbol is Symbols.PublicModel.Symbol { UnderlyingSymbol: NamedTypeSymbol { } internalSymbol1 }
+                && internalSymbol1.GetFileLocalTypeMetadataNamePrefix() is { } fileLocalNamePrefix)
+            {
+                builder.Add(CreatePart(SymbolDisplayPartKind.ModuleName, symbol, fileLocalNamePrefix));
+            }
+
             VisitNamedTypeWithoutNullability(symbol);
             AddNullableAnnotations(symbol);
 
             if ((format.CompilerInternalOptions & SymbolDisplayCompilerInternalOptions.IncludeContainingFileForFileTypes) != 0
-                && symbol is Symbols.PublicModel.Symbol { UnderlyingSymbol: NamedTypeSymbol { AssociatedFileIdentifier: { } identifier } internalSymbol })
+                && symbol is Symbols.PublicModel.Symbol { UnderlyingSymbol: NamedTypeSymbol { AssociatedFileIdentifier: { } identifier } internalSymbol2 })
             {
                 var fileDescription = identifier.DisplayFilePath is { Length: not 0 } path ? path
-                    : internalSymbol.GetFirstLocationOrNone().SourceTree is { } tree ? $"<tree {internalSymbol.DeclaringCompilation.GetSyntaxTreeOrdinal(tree)}>"
+                    : internalSymbol2.GetFirstLocationOrNone().SourceTree is { } tree ? $"<tree {internalSymbol2.DeclaringCompilation.GetSyntaxTreeOrdinal(tree)}>"
                     : "<unknown>";
 
                 builder.Add(CreatePart(SymbolDisplayPartKind.Punctuation, symbol, "@"));
diff --git a/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/PublicSymbols/AnonymousManager.TypeOrDelegatePublicSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/PublicSymbols/AnonymousManager.TypeOrDelegatePublicSymbol.cs
index 06788db9915e5..1c4403a5ad514 100644
--- a/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/PublicSymbols/AnonymousManager.TypeOrDelegatePublicSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/PublicSymbols/AnonymousManager.TypeOrDelegatePublicSymbol.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Runtime.InteropServices;
@@ -73,6 +74,7 @@ internal sealed override bool MangleName
                 get { return false; }
             }
 
+            internal sealed override bool IsFileLocal => false;
             internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
             public sealed override int Arity
@@ -132,12 +134,12 @@ public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
                 return ImmutableArray<NamedTypeSymbol>.Empty;
             }
 
-            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
             {
                 return ImmutableArray<NamedTypeSymbol>.Empty;
             }
 
-            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
             {
                 return ImmutableArray<NamedTypeSymbol>.Empty;
             }
@@ -278,6 +280,12 @@ internal sealed override ImmutableArray<NamedTypeSymbol> GetDeclaredInterfaces(C
             {
                 return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
             }
+
+            internal sealed override bool HasInlineArrayAttribute(out int length)
+            {
+                length = 0;
+                return false;
+            }
         }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/SynthesizedSymbols/AnonymousType.TypeOrDelegateTemplateSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/SynthesizedSymbols/AnonymousType.TypeOrDelegateTemplateSymbol.cs
index ec05349c85c53..affdb89a5dea3 100644
--- a/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/SynthesizedSymbols/AnonymousType.TypeOrDelegateTemplateSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/AnonymousTypes/SynthesizedSymbols/AnonymousType.TypeOrDelegateTemplateSymbol.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
@@ -180,12 +181,12 @@ public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
                 return ImmutableArray<NamedTypeSymbol>.Empty;
             }
 
-            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
             {
                 return ImmutableArray<NamedTypeSymbol>.Empty;
             }
 
-            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+            public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
             {
                 return ImmutableArray<NamedTypeSymbol>.Empty;
             }
@@ -237,6 +238,7 @@ internal sealed override bool MangleName
                 get { return this.Arity > 0; }
             }
 
+            internal sealed override bool IsFileLocal => false;
             internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
             internal sealed override ImmutableArray<TypeWithAnnotations> TypeArgumentsWithAnnotationsNoUseSiteDiagnostics
@@ -318,6 +320,12 @@ internal sealed override AttributeUsageInfo GetAttributeUsageInfo()
             {
                 return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
             }
+
+            internal sealed override bool HasInlineArrayAttribute(out int length)
+            {
+                length = 0;
+                return false;
+            }
         }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/ArrayTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/ArrayTypeSymbol.cs
index cc5e6a277f9b4..4f88a12cb98d4 100644
--- a/src/Compilers/CSharp/Portable/Symbols/ArrayTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/ArrayTypeSymbol.cs
@@ -272,12 +272,12 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
@@ -488,6 +488,12 @@ protected sealed override ITypeSymbol CreateITypeSymbol(CodeAnalysis.NullableAnn
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
 
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
+
         /// <summary>
         /// Represents SZARRAY - zero-based one-dimensional array 
         /// </summary>
diff --git a/src/Compilers/CSharp/Portable/Symbols/AssemblySymbol.cs b/src/Compilers/CSharp/Portable/Symbols/AssemblySymbol.cs
index a3ddf233f4843..df553606ed113 100644
--- a/src/Compilers/CSharp/Portable/Symbols/AssemblySymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/AssemblySymbol.cs
@@ -428,6 +428,8 @@ public bool SupportsRuntimeCapability(RuntimeCapability capability)
                     return this.RuntimeSupportsUnmanagedSignatureCallingConvention;
                 case RuntimeCapability.VirtualStaticsInInterfaces:
                     return this.RuntimeSupportsStaticAbstractMembersInInterfaces;
+                case RuntimeCapability.InlineArrayTypes:
+                    return this.RuntimeSupportsInlineArrayTypes;
             }
 
             return false;
@@ -466,6 +468,18 @@ internal bool RuntimeSupportsNumericIntPtr
             }
         }
 
+        /// <summary>
+        /// Figure out if the target runtime supports inline array types.
+        /// </summary>
+        internal bool RuntimeSupportsInlineArrayTypes
+        {
+            // Keep in sync with VB's AssemblySymbol.RuntimeSupportsInlineArrayTypes
+            get
+            {
+                return GetSpecialTypeMember(SpecialMember.System_Runtime_CompilerServices_InlineArrayAttribute__ctor) is object;
+            }
+        }
+
         protected bool RuntimeSupportsFeature(SpecialMember feature)
         {
             // Keep in sync with VB's AssemblySymbol.RuntimeSupportsFeature
@@ -514,7 +528,19 @@ internal bool RuntimeSupportsCovariantReturnsOfClasses
         internal abstract ImmutableArray<AssemblySymbol> GetLinkedReferencedAssemblies();
         internal abstract void SetLinkedReferencedAssemblies(ImmutableArray<AssemblySymbol> assemblies);
 
+        IEnumerable<ImmutableArray<byte>> IAssemblySymbolInternal.GetInternalsVisibleToPublicKeys(string simpleName)
+            => GetInternalsVisibleToPublicKeys(simpleName);
+
         internal abstract IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicKeys(string simpleName);
+
+        IEnumerable<string> IAssemblySymbolInternal.GetInternalsVisibleToAssemblyNames()
+            => GetInternalsVisibleToAssemblyNames();
+
+        internal abstract IEnumerable<string> GetInternalsVisibleToAssemblyNames();
+
+        bool IAssemblySymbolInternal.AreInternalsVisibleToThisAssembly(IAssemblySymbolInternal otherAssembly)
+            => AreInternalsVisibleToThisAssembly((AssemblySymbol)otherAssembly);
+
         internal abstract bool AreInternalsVisibleToThisAssembly(AssemblySymbol other);
 
         /// <summary>
diff --git a/src/Compilers/CSharp/Portable/Symbols/Attributes/WellKnownAttributeData/TypeWellKnownEarlyAttributeData.cs b/src/Compilers/CSharp/Portable/Symbols/Attributes/WellKnownAttributeData/TypeWellKnownEarlyAttributeData.cs
index 55a4c25c4d093..60634a1a467ca 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Attributes/WellKnownAttributeData/TypeWellKnownEarlyAttributeData.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Attributes/WellKnownAttributeData/TypeWellKnownEarlyAttributeData.cs
@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Diagnostics;
+
 namespace Microsoft.CodeAnalysis.CSharp.Symbols
 {
     /// <summary>
@@ -26,5 +28,32 @@ public bool HasInterpolatedStringHandlerAttribute
             }
         }
         #endregion
+
+        #region InlineArrayAttribute
+
+        private int _inlineArrayLength;
+        public int InlineArrayLength
+        {
+            get
+            {
+                VerifySealed(expected: true);
+                return _inlineArrayLength;
+            }
+            set
+            {
+                VerifySealed(expected: false);
+
+                Debug.Assert(value is -1 or > 0);
+                if (_inlineArrayLength == 0)
+                {
+                    _inlineArrayLength = value;
+                }
+
+                SetDataStored();
+            }
+        }
+
+        #endregion
+
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/DynamicTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/DynamicTypeSymbol.cs
index 4f4733a2b68dd..627e2a4ef0069 100644
--- a/src/Compilers/CSharp/Portable/Symbols/DynamicTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/DynamicTypeSymbol.cs
@@ -139,7 +139,7 @@ public override ImmutableArray<Symbol> GetMembers(string name)
             return ImmutableArray<Symbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
@@ -253,5 +253,11 @@ protected sealed override ITypeSymbol CreateITypeSymbol(CodeAnalysis.NullableAnn
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/ErrorTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/ErrorTypeSymbol.cs
index 68482459eda9e..7105bf06a2140 100644
--- a/src/Compilers/CSharp/Portable/Symbols/ErrorTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/ErrorTypeSymbol.cs
@@ -2,11 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Roslyn.Utilities;
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Runtime.InteropServices;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.Symbols
 {
@@ -190,7 +191,7 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
         /// <returns>An ImmutableArray containing all the types that are members of this symbol with the given name.
         /// If this symbol has no type members with this name,
         /// returns an empty ImmutableArray. Never returns null.</returns>
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
@@ -201,7 +202,7 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
         /// <returns>An ImmutableArray containing all the types that are members of this symbol with the given name and arity.
         /// If this symbol has no type members with this name and arity,
         /// returns an empty ImmutableArray. Never returns null.</returns>
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
@@ -555,6 +556,12 @@ protected sealed override ITypeSymbol CreateITypeSymbol(CodeAnalysis.NullableAnn
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 
     internal abstract class SubstitutedErrorTypeSymbol : ErrorTypeSymbol
@@ -578,7 +585,8 @@ internal override bool MangleName
             get { return _originalDefinition.MangleName; }
         }
 
-        internal override FileIdentifier? AssociatedFileIdentifier => _originalDefinition.AssociatedFileIdentifier;
+        internal sealed override bool IsFileLocal => _originalDefinition.IsFileLocal;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => _originalDefinition.AssociatedFileIdentifier;
 
         internal override DiagnosticInfo? ErrorInfo
         {
diff --git a/src/Compilers/CSharp/Portable/Symbols/ExtendedErrorTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/ExtendedErrorTypeSymbol.cs
index 1beb24ad71c41..74be7fa53d0a7 100644
--- a/src/Compilers/CSharp/Portable/Symbols/ExtendedErrorTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/ExtendedErrorTypeSymbol.cs
@@ -145,6 +145,7 @@ internal override bool MangleName
             }
         }
 
+        internal override bool IsFileLocal => false;
         internal override FileIdentifier? AssociatedFileIdentifier => null;
 
         public override Symbol? ContainingSymbol
diff --git a/src/Compilers/CSharp/Portable/Symbols/FunctionPointers/FunctionPointerTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/FunctionPointers/FunctionPointerTypeSymbol.cs
index 41d77b8405fda..5db3fd3bd3a4e 100644
--- a/src/Compilers/CSharp/Portable/Symbols/FunctionPointers/FunctionPointerTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/FunctionPointers/FunctionPointerTypeSymbol.cs
@@ -92,7 +92,7 @@ private FunctionPointerTypeSymbol(FunctionPointerMethodSymbol signature)
         public override ImmutableArray<Symbol> GetMembers() => ImmutableArray<Symbol>.Empty;
         public override ImmutableArray<Symbol> GetMembers(string name) => ImmutableArray<Symbol>.Empty;
         public override ImmutableArray<NamedTypeSymbol> GetTypeMembers() => ImmutableArray<NamedTypeSymbol>.Empty;
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name) => ImmutableArray<NamedTypeSymbol>.Empty;
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name) => ImmutableArray<NamedTypeSymbol>.Empty;
         internal override TResult Accept<TArgument, TResult>(CSharpSymbolVisitor<TArgument, TResult> visitor, TArgument a) => visitor.VisitFunctionPointerType(this, a);
         internal override ImmutableArray<NamedTypeSymbol> InterfacesNoUseSiteDiagnostics(ConsList<TypeSymbol>? basesBeingResolved = null) => ImmutableArray<NamedTypeSymbol>.Empty;
 
@@ -221,5 +221,11 @@ internal static bool IsCallingConventionModifier(NamedTypeSymbol modifierType)
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/FunctionTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/FunctionTypeSymbol.cs
index 94725807c68ec..0cbd87e3b03e4 100644
--- a/src/Compilers/CSharp/Portable/Symbols/FunctionTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/FunctionTypeSymbol.cs
@@ -139,7 +139,7 @@ internal void SetExpression(BoundExpression expression)
 
         public override ImmutableArray<NamedTypeSymbol> GetTypeMembers() => throw ExceptionUtilities.Unreachable();
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name) => throw ExceptionUtilities.Unreachable();
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name) => throw ExceptionUtilities.Unreachable();
 
         protected override ISymbol CreateISymbol() => throw ExceptionUtilities.Unreachable();
 
@@ -196,6 +196,12 @@ private FunctionTypeSymbol WithDelegateType(NamedTypeSymbol delegateType)
 
         internal override IEnumerable<(MethodSymbol Body, MethodSymbol Implemented)> SynthesizedInterfaceMethodImpls() => throw ExceptionUtilities.Unreachable();
 
+        internal override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
+
         internal override bool Equals(TypeSymbol t2, TypeCompareKind compareKind)
         {
             if (ReferenceEquals(this, t2))
diff --git a/src/Compilers/CSharp/Portable/Symbols/MemberSignatureComparer.cs b/src/Compilers/CSharp/Portable/Symbols/MemberSignatureComparer.cs
index 7868ec311522c..398fbc3981674 100644
--- a/src/Compilers/CSharp/Portable/Symbols/MemberSignatureComparer.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/MemberSignatureComparer.cs
@@ -141,6 +141,35 @@ internal sealed class MemberSignatureComparer : IEqualityComparer<Symbol>
             considerRefKindDifferences: true,
             typeComparison: TypeCompareKind.ObliviousNullableModifierMatchesAny);
 
+        /// <summary>
+        /// Determines if an interceptor has a compatible signature with an interceptable method.
+        /// NB: when a classic extension method is intercepting an instance method call, a normalization to 'ReducedExtensionMethodSymbol' must be performed first.
+        /// </summary>
+        public static readonly MemberSignatureComparer InterceptorsComparer = new MemberSignatureComparer(
+            considerName: false,
+            considerExplicitlyImplementedInterfaces: false,
+            considerReturnType: true,
+            considerTypeConstraints: false,
+            considerCallingConvention: false,
+            considerRefKindDifferences: true,
+            considerArity: false,
+            typeComparison: TypeCompareKind.AllIgnoreOptions);
+
+        /// <summary>
+        /// Determines if an interceptor has a compatible signature with an interceptable method.
+        /// If methods are considered equal by <see cref="InterceptorsComparer"/>, but not equal by this comparer, a warning is reported.
+        /// NB: when a classic extension method is intercepting an instance method call, a normalization to 'ReducedExtensionMethodSymbol' must be performed first.
+        /// </summary>
+        public static readonly MemberSignatureComparer InterceptorsStrictComparer = new MemberSignatureComparer(
+            considerName: false,
+            considerExplicitlyImplementedInterfaces: false,
+            considerReturnType: true,
+            considerTypeConstraints: false,
+            considerCallingConvention: false,
+            considerRefKindDifferences: true,
+            considerArity: false,
+            typeComparison: TypeCompareKind.AllNullableIgnoreOptions);
+
         /// <summary>
         /// This instance is used to check whether one member overrides another, according to the C# definition.
         /// </summary>
@@ -336,6 +365,9 @@ internal sealed class MemberSignatureComparer : IEqualityComparer<Symbol>
         // Compare the type constraints
         private readonly bool _considerTypeConstraints;
 
+        // Compare the arity (type parameter count)
+        private readonly bool _considerArity;
+
         // Compare the full calling conventions.  Still compares varargs if false.
         private readonly bool _considerCallingConvention;
 
@@ -352,9 +384,11 @@ private MemberSignatureComparer(
             bool considerTypeConstraints,
             bool considerCallingConvention,
             bool considerRefKindDifferences,
+            bool considerArity = true,
             TypeCompareKind typeComparison = TypeCompareKind.IgnoreDynamic | TypeCompareKind.IgnoreNativeIntegers)
         {
             Debug.Assert(!considerExplicitlyImplementedInterfaces || considerName, "Doesn't make sense to consider interfaces separately from name.");
+            Debug.Assert(!considerTypeConstraints || considerArity, "If you consider type constraints, you must also consider arity");
 
             _considerName = considerName;
             _considerExplicitlyImplementedInterfaces = considerExplicitlyImplementedInterfaces;
@@ -362,6 +396,7 @@ private MemberSignatureComparer(
             _considerTypeConstraints = considerTypeConstraints;
             _considerCallingConvention = considerCallingConvention;
             _considerRefKindDifferences = considerRefKindDifferences;
+            _considerArity = considerArity;
             _typeComparison = typeComparison;
             Debug.Assert((_typeComparison & TypeCompareKind.FunctionPointerRefMatchesOutInRefReadonly) == 0,
                          $"Rely on the {nameof(considerRefKindDifferences)} flag to set this to ensure all cases are handled.");
@@ -404,9 +439,12 @@ public bool Equals(Symbol member1, Symbol member2)
 
             // NB: up to, and including, this check, we have not actually forced the (type) parameters
             // to be expanded - we're only using the counts.
-            int arity = member1.GetMemberArity();
-            if ((arity != member2.GetMemberArity()) ||
-                (member1.GetParameterCount() != member2.GetParameterCount()))
+            if (_considerArity && (member1.GetMemberArity() != member2.GetMemberArity()))
+            {
+                return false;
+            }
+
+            if (member1.GetParameterCount() != member2.GetParameterCount())
             {
                 return false;
             }
diff --git a/src/Compilers/CSharp/Portable/Symbols/MergedNamespaceSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/MergedNamespaceSymbol.cs
index c0a83e98d2a5a..2f414e3e83b80 100644
--- a/src/Compilers/CSharp/Portable/Symbols/MergedNamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/MergedNamespaceSymbol.cs
@@ -43,7 +43,7 @@ internal sealed class MergedNamespaceSymbol : NamespaceSymbol
         // The cachedLookup caches results of lookups on the constituent namespaces so that
         // subsequent lookups for the same name are much faster than having to ask each of the
         // constituent namespaces.
-        private readonly CachingDictionary<string, Symbol> _cachedLookup;
+        private readonly CachingDictionary<ReadOnlyMemory<char>, Symbol> _cachedLookup;
 
         // GetMembers() is repeatedly called on merged namespaces in some IDE scenarios.
         // This caches the result that is built by asking the 'cachedLookup' for a concatenated
@@ -93,7 +93,7 @@ private MergedNamespaceSymbol(NamespaceExtent extent, NamespaceSymbol containing
             _extent = extent;
             _namespacesToMerge = namespacesToMerge;
             _containingNamespace = containingNamespace;
-            _cachedLookup = new CachingDictionary<string, Symbol>(SlowGetChildrenOfName, SlowGetChildNames, EqualityComparer<string>.Default);
+            _cachedLookup = new CachingDictionary<ReadOnlyMemory<char>, Symbol>(SlowGetChildrenOfName, SlowGetChildNames, ReadOnlyMemoryOfCharComparer.Instance);
             _nameOpt = nameOpt;
 
 #if DEBUG
@@ -132,7 +132,7 @@ internal override void ForceComplete(SourceLocation locationOpt, CancellationTok
         /// Method that is called from the CachingLookup to lookup the children of a given name.
         /// Looks in all the constituent namespaces.
         /// </summary>
-        private ImmutableArray<Symbol> SlowGetChildrenOfName(string name)
+        private ImmutableArray<Symbol> SlowGetChildrenOfName(ReadOnlyMemory<char> name)
         {
             ArrayBuilder<NamespaceSymbol> namespaceSymbols = null;
             var otherSymbols = ArrayBuilder<Symbol>.GetInstance();
@@ -166,15 +166,23 @@ private ImmutableArray<Symbol> SlowGetChildrenOfName(string name)
         /// Method that is called from the CachingLookup to get all child names. Looks in all
         /// constituent namespaces.
         /// </summary>
-        private HashSet<string> SlowGetChildNames(IEqualityComparer<string> comparer)
+        private SegmentedHashSet<ReadOnlyMemory<char>> SlowGetChildNames(IEqualityComparer<ReadOnlyMemory<char>> comparer)
         {
-            var childNames = new HashSet<string>(comparer);
+            // compute an upper bound for the final capacity of the set we'll return, to reduce heap churn
+            int childCount = 0;
+
+            foreach (var ns in _namespacesToMerge)
+            {
+                childCount += ns.GetMembersUnordered().Length;
+            }
+
+            var childNames = new SegmentedHashSet<ReadOnlyMemory<char>>(childCount, comparer);
 
             foreach (var ns in _namespacesToMerge)
             {
                 foreach (var child in ns.GetMembersUnordered())
                 {
-                    childNames.Add(child.Name);
+                    childNames.Add(child.Name.AsMemory());
                 }
             }
 
@@ -218,7 +226,7 @@ public override ImmutableArray<Symbol> GetMembers()
             return _allMembers;
         }
 
-        public override ImmutableArray<Symbol> GetMembers(string name)
+        public override ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name)
         {
             return _cachedLookup[name];
         }
@@ -233,7 +241,7 @@ public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return ImmutableArray.CreateRange<NamedTypeSymbol>(GetMembers().OfType<NamedTypeSymbol>());
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             // TODO - This is really inefficient. Creating a new array on each lookup needs to fixed!
             return ImmutableArray.CreateRange<NamedTypeSymbol>(_cachedLookup[name].OfType<NamedTypeSymbol>());
diff --git a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEAssemblySymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEAssemblySymbol.cs
index e1acaece2a20d..ba4f5fa114f72 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEAssemblySymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEAssemblySymbol.cs
@@ -247,6 +247,11 @@ internal override IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicK
             return Assembly.GetInternalsVisibleToPublicKeys(simpleName);
         }
 
+        internal override IEnumerable<string> GetInternalsVisibleToAssemblyNames()
+        {
+            return Assembly.GetInternalsVisibleToAssemblyNames();
+        }
+
         internal DocumentationProvider DocumentationProvider
         {
             get
diff --git a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEFieldSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEFieldSymbol.cs
index 6c5843faa621a..ca5bc67794aa9 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEFieldSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEFieldSymbol.cs
@@ -216,7 +216,9 @@ internal override bool IsNotSerialized
         {
             get
             {
+#pragma warning disable SYSLIB0050 // 'TypeAttributes.Serializable' is obsolete
                 return (_flags & FieldAttributes.NotSerialized) != 0;
+#pragma warning restore SYSLIB0050
             }
         }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEModuleSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEModuleSymbol.cs
index 07f3651172efb..ce1cd6f4718e5 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEModuleSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEModuleSymbol.cs
@@ -476,7 +476,7 @@ private ImmutableArray<CSharpAttributeData> GetCustomAttributesFilterCompilerAtt
         }
 
         internal void OnNewTypeDeclarationsLoaded(
-            Dictionary<string, ImmutableArray<PENamedTypeSymbol>> typesDict)
+            Dictionary<ReadOnlyMemory<char>, ImmutableArray<PENamedTypeSymbol>> typesDict)
         {
             bool keepLookingForDeclaredCorTypes = (_ordinal == 0 && _assemblySymbol.KeepLookingForDeclaredSpecialTypes);
 
@@ -691,7 +691,7 @@ internal override CharSet? DefaultMarshallingCharSet
         internal NamedTypeSymbol LookupTopLevelMetadataTypeWithNoPiaLocalTypeUnification(ref MetadataTypeName emittedName, out bool isNoPiaLocalType)
         {
             NamedTypeSymbol? result;
-            var scope = (PENamespaceSymbol?)this.GlobalNamespace.LookupNestedNamespace(emittedName.NamespaceSegments);
+            var scope = (PENamespaceSymbol?)this.GlobalNamespace.LookupNestedNamespace(emittedName.NamespaceSegmentsMemory);
 
             if ((object?)scope == null)
             {
diff --git a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.cs
index 55abe62496b5c..1b2f81feb8c56 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.cs
@@ -27,7 +27,8 @@ namespace Microsoft.CodeAnalysis.CSharp.Symbols.Metadata.PE
     /// </summary>
     internal abstract class PENamedTypeSymbol : NamedTypeSymbol
     {
-        private static readonly Dictionary<string, ImmutableArray<PENamedTypeSymbol>> s_emptyNestedTypes = new Dictionary<string, ImmutableArray<PENamedTypeSymbol>>(EmptyComparer.Instance);
+        private static readonly Dictionary<ReadOnlyMemory<char>, ImmutableArray<PENamedTypeSymbol>> s_emptyNestedTypes =
+            new Dictionary<ReadOnlyMemory<char>, ImmutableArray<PENamedTypeSymbol>>(EmptyReadOnlyMemoryOfCharComparer.Instance);
 
         private readonly NamespaceOrTypeSymbol _container;
         private readonly TypeDefinitionHandle _handle;
@@ -60,7 +61,7 @@ internal abstract class PENamedTypeSymbol : NamedTypeSymbol
         /// A map of types immediately contained within this type 
         /// grouped by their name (case-sensitively).
         /// </summary>
-        private Dictionary<string, ImmutableArray<PENamedTypeSymbol>> _lazyNestedTypes;
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<PENamedTypeSymbol>> _lazyNestedTypes;
 
         /// <summary>
         /// Lazily initialized by TypeKind property.
@@ -394,7 +395,8 @@ internal abstract override bool MangleName
             get;
         }
 
-        internal override FileIdentifier? AssociatedFileIdentifier
+        internal sealed override bool IsFileLocal => _lazyUncommonProperties is { lazyFilePathChecksum: { IsDefault: false }, lazyDisplayFileName: { } };
+        internal sealed override FileIdentifier? AssociatedFileIdentifier
         {
             get
             {
@@ -1509,7 +1511,7 @@ public override ImmutableArray<Symbol> GetMembers(string name)
 
             // nested types are not common, but we need to check just in case
             ImmutableArray<PENamedTypeSymbol> t;
-            if (_lazyNestedTypes.TryGetValue(name, out t))
+            if (_lazyNestedTypes.TryGetValue(name.AsMemory(), out t))
             {
                 m = m.Concat(StaticCast<Symbol>.From(t));
             }
@@ -1578,7 +1580,7 @@ private void EnsureNestedTypesAreLoaded()
             }
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             EnsureNestedTypesAreLoaded();
 
@@ -1592,7 +1594,7 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return GetTypeMembers(name).WhereAsArray((type, arity) => type.Arity == arity, arity);
         }
@@ -2056,14 +2058,14 @@ private static Dictionary<string, ImmutableArray<Symbol>> GroupByName(ArrayBuild
             return symbols.ToDictionary(s => s.Name, StringOrdinalComparer.Instance);
         }
 
-        private static Dictionary<string, ImmutableArray<PENamedTypeSymbol>> GroupByName(ArrayBuilder<PENamedTypeSymbol> symbols)
+        private static Dictionary<ReadOnlyMemory<char>, ImmutableArray<PENamedTypeSymbol>> GroupByName(ArrayBuilder<PENamedTypeSymbol> symbols)
         {
             if (symbols.Count == 0)
             {
                 return s_emptyNestedTypes;
             }
 
-            return symbols.ToDictionary(s => s.Name, StringOrdinalComparer.Instance);
+            return symbols.ToDictionary(s => s.Name.AsMemory(), ReadOnlyMemoryOfCharComparer.Instance);
         }
 
         internal override UseSiteInfo<AssemblySymbol> GetUseSiteInfo()
@@ -2238,7 +2240,9 @@ internal override CharSet MarshallingCharSet
 
         public override bool IsSerializable
         {
+#pragma warning disable SYSLIB0050 // 'TypeAttributes.Serializable' is obsolete
             get { return (_flags & TypeAttributes.Serializable) != 0; }
+#pragma warning restore SYSLIB0050
         }
 
         public override bool IsRefLikeType
@@ -2453,6 +2457,17 @@ private static IEnumerable<TSymbol> GetMembers<TSymbol>(ImmutableArray<Symbol> m
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
 
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            if (this.ContainingPEModule.Module.HasInlineArrayAttribute(_handle, out length) && length > 0)
+            {
+                return true;
+            }
+
+            length = 0;
+            return false;
+        }
+
         /// <summary>
         /// Specialized PENamedTypeSymbol for types with no type parameters in
         /// metadata (no type parameters on this type and all containing types).
diff --git a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamespaceSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamespaceSymbol.cs
index 4fba6d7b0c9bd..fba5a2224cb38 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamespaceSymbol.cs
@@ -27,13 +27,13 @@ internal abstract class PENamespaceSymbol
         /// A map of namespaces immediately contained within this namespace 
         /// mapped by their name (case-sensitively).
         /// </summary>
-        protected Dictionary<string, PENestedNamespaceSymbol> lazyNamespaces;
+        protected Dictionary<ReadOnlyMemory<char>, PENestedNamespaceSymbol> lazyNamespaces;
 
         /// <summary>
         /// A map of types immediately contained within this namespace 
         /// grouped by their name (case-sensitively).
         /// </summary>
-        protected Dictionary<string, ImmutableArray<PENamedTypeSymbol>> lazyTypes;
+        protected Dictionary<ReadOnlyMemory<char>, ImmutableArray<PENamedTypeSymbol>> lazyTypes;
 
         /// <summary>
         /// A map of NoPia local types immediately contained in this assembly.
@@ -87,7 +87,7 @@ private ImmutableArray<NamedTypeSymbol> GetMemberTypesPrivate()
             return StaticCast<NamedTypeSymbol>.From(_lazyFlattenedTypes);
         }
 
-        public sealed override ImmutableArray<Symbol> GetMembers(string name)
+        public sealed override ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name)
         {
             EnsureAllMembersLoaded();
 
@@ -121,7 +121,7 @@ public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return GetMemberTypesPrivate();
         }
 
-        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             EnsureAllMembersLoaded();
 
@@ -132,7 +132,7 @@ public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string nam
                 : ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return GetTypeMembers(name).WhereAsArray((type, arity) => type.Arity == arity, arity);
         }
@@ -224,12 +224,12 @@ private void LazyInitializeNamespaces(
         {
             if (this.lazyNamespaces == null)
             {
-                var namespaces = new Dictionary<string, PENestedNamespaceSymbol>(StringOrdinalComparer.Instance);
+                var namespaces = new Dictionary<ReadOnlyMemory<char>, PENestedNamespaceSymbol>(ReadOnlyMemoryOfCharComparer.Instance);
 
                 foreach (var child in childNamespaces)
                 {
                     var c = new PENestedNamespaceSymbol(child.Key, this, child.Value);
-                    namespaces.Add(c.Name, c);
+                    namespaces.Add(c.Name.AsMemory(), c);
                 }
 
                 Interlocked.CompareExchange(ref this.lazyNamespaces, namespaces, null);
@@ -276,7 +276,7 @@ private void LazyInitializeTypes(IEnumerable<IGrouping<string, TypeDefinitionHan
                     }
                 }
 
-                var typesDict = children.ToDictionary(c => c.Name, StringOrdinalComparer.Instance);
+                var typesDict = children.ToDictionary(c => c.Name.AsMemory(), ReadOnlyMemoryOfCharComparer.Instance);
                 children.Free();
 
                 if (noPiaLocalTypes != null)
diff --git a/src/Compilers/CSharp/Portable/Symbols/MissingAssemblySymbol.cs b/src/Compilers/CSharp/Portable/Symbols/MissingAssemblySymbol.cs
index 29b66de0eb31c..94c8e988007f4 100644
--- a/src/Compilers/CSharp/Portable/Symbols/MissingAssemblySymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/MissingAssemblySymbol.cs
@@ -190,6 +190,11 @@ internal override IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicK
             return SpecializedCollections.EmptyEnumerable<ImmutableArray<byte>>();
         }
 
+        internal override IEnumerable<string> GetInternalsVisibleToAssemblyNames()
+        {
+            return SpecializedCollections.EmptyEnumerable<string>();
+        }
+
         public override bool MightContainExtensionMethods
         {
             get
diff --git a/src/Compilers/CSharp/Portable/Symbols/MissingMetadataTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/MissingMetadataTypeSymbol.cs
index 29c3189a7f126..4eb2298265afe 100644
--- a/src/Compilers/CSharp/Portable/Symbols/MissingMetadataTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/MissingMetadataTypeSymbol.cs
@@ -48,7 +48,8 @@ internal override bool MangleName
             }
         }
 
-        internal override FileIdentifier? AssociatedFileIdentifier => null;
+        internal sealed override bool IsFileLocal => false;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
         /// <summary>
         /// Get the arity of the missing type.
diff --git a/src/Compilers/CSharp/Portable/Symbols/MissingNamespaceSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/MissingNamespaceSymbol.cs
index 1fba2e3465546..569973c620580 100644
--- a/src/Compilers/CSharp/Portable/Symbols/MissingNamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/MissingNamespaceSymbol.cs
@@ -4,13 +4,10 @@
 
 #nullable disable
 
-using System.Collections.Generic;
+using System;
 using System.Collections.Immutable;
-using Microsoft.CodeAnalysis.CSharp.Symbols;
-using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Text;
-using Roslyn.Utilities;
 using System.Diagnostics;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.Symbols
 {
@@ -115,12 +112,12 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
@@ -130,7 +127,7 @@ public override ImmutableArray<Symbol> GetMembers()
             return ImmutableArray<Symbol>.Empty;
         }
 
-        public override ImmutableArray<Symbol> GetMembers(string name)
+        public override ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name)
         {
             return ImmutableArray<Symbol>.Empty;
         }
diff --git a/src/Compilers/CSharp/Portable/Symbols/NamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NamedTypeSymbol.cs
index 4a87ddb735ef6..3b37a950b96e7 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NamedTypeSymbol.cs
@@ -495,6 +495,8 @@ public override string MetadataName
             }
         }
 
+        internal abstract bool IsFileLocal { get; }
+
         /// <summary>
         /// If this type is a file-local type, returns an identifier for the file this type was declared in. Otherwise, returns null.
         /// </summary>
@@ -677,21 +679,13 @@ internal virtual ImmutableArray<Symbol> GetSimpleNonTypeMembers(string name)
         /// returns an empty ImmutableArray. Never returns null.</returns>
         public abstract override ImmutableArray<NamedTypeSymbol> GetTypeMembers();
 
-        /// <summary>
-        /// Get all the members of this symbol that are types that have a particular name, of any arity.
-        /// </summary>
-        /// <returns>An ImmutableArray containing all the types that are members of this symbol with the given name.
-        /// If this symbol has no type members with this name,
-        /// returns an empty ImmutableArray. Never returns null.</returns>
-        public abstract override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name);
-
         /// <summary>
         /// Get all the members of this symbol that are types that have a particular name and arity
         /// </summary>
         /// <returns>An ImmutableArray containing all the types that are members of this symbol with the given name and arity.
         /// If this symbol has no type members with this name and arity,
         /// returns an empty ImmutableArray. Never returns null.</returns>
-        public abstract override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity);
+        public abstract override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity);
 
         /// <summary>
         /// Get all instance field and event members.
diff --git a/src/Compilers/CSharp/Portable/Symbols/NamespaceOrTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NamespaceOrTypeSymbol.cs
index 605dd64219e6b..10ec3093df81a 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NamespaceOrTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NamespaceOrTypeSymbol.cs
@@ -8,6 +8,7 @@
 using System.Diagnostics;
 using System.Linq;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Symbols;
 using Roslyn.Utilities;
 
@@ -18,6 +19,9 @@ namespace Microsoft.CodeAnalysis.CSharp.Symbols
     /// </summary>
     internal abstract class NamespaceOrTypeSymbol : Symbol, INamespaceOrTypeSymbolInternal
     {
+        protected static readonly ObjectPool<PooledDictionary<ReadOnlyMemory<char>, object>> s_nameToObjectPool =
+            PooledDictionary<ReadOnlyMemory<char>, object>.CreatePool(ReadOnlyMemoryOfCharComparer.Instance);
+
         // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
         // Changes to the public interface of this class should remain synchronized with the VB version.
         // Do not make any changes to the public interface without making the corresponding change
@@ -153,7 +157,8 @@ internal virtual ImmutableArray<NamedTypeSymbol> GetTypeMembersUnordered()
         /// <returns>An ImmutableArray containing all the types that are members of this symbol with the given name.
         /// If this symbol has no type members with this name,
         /// returns an empty ImmutableArray. Never returns null.</returns>
-        public abstract ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name);
+        public ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+            => GetTypeMembers(name.AsMemory());
 
         /// <summary>
         /// Get all the members of this symbol that are types that have a particular name and arity
@@ -161,11 +166,18 @@ internal virtual ImmutableArray<NamedTypeSymbol> GetTypeMembersUnordered()
         /// <returns>An IEnumerable containing all the types that are members of this symbol with the given name and arity.
         /// If this symbol has no type members with this name and arity,
         /// returns an empty IEnumerable. Never returns null.</returns>
-        public virtual ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+            => GetTypeMembers(name.AsMemory(), arity);
+
+        /// <inheritdoc cref="GetTypeMembers(string)"/>
+        public abstract ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name);
+
+        /// <inheritdoc cref="GetTypeMembers(string, int)"/>
+        public virtual ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             // default implementation does a post-filter. We can override this if its a performance burden, but 
             // experience is that it won't be.
-            return GetTypeMembers(name).WhereAsArray((t, arity) => t.Arity == arity, arity);
+            return GetTypeMembers(name).WhereAsArray(static (t, arity) => t.Arity == arity, arity);
         }
 
         /// <summary>
@@ -245,6 +257,7 @@ public virtual ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int a
 
             NamespaceOrTypeSymbol scope = this;
             Debug.Assert(scope is not MergedNamespaceSymbol);
+            Debug.Assert(scope is NamespaceSymbol or NamedTypeSymbol);
 
             if (scope.Kind == SymbolKind.ErrorType)
             {
@@ -265,13 +278,13 @@ public virtual ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int a
                 if (emittedTypeName.ForcedArity == -1 || emittedTypeName.ForcedArity == emittedTypeName.InferredArity)
                 {
                     // Let's handle mangling case first.
-                    namespaceOrTypeMembers = scope.GetTypeMembers(emittedTypeName.UnmangledTypeName);
+                    namespaceOrTypeMembers = scope.GetTypeMembers(emittedTypeName.UnmangledTypeNameMemory);
 
                     foreach (var named in namespaceOrTypeMembers)
                     {
                         if (emittedTypeName.InferredArity == named.Arity &&
                             named.MangleName &&
-                            named.MetadataName == emittedTypeName.TypeName)
+                            ReadOnlyMemoryOfCharComparer.Equals(named.MetadataName.AsSpan(), emittedTypeName.TypeNameMemory))
                         {
                             if (namedType is not null)
                             {
@@ -313,13 +326,13 @@ public virtual ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int a
                 }
             }
 
-            namespaceOrTypeMembers = scope.GetTypeMembers(emittedTypeName.TypeName);
+            namespaceOrTypeMembers = scope.GetTypeMembers(emittedTypeName.TypeNameMemory);
 
             foreach (var named in namespaceOrTypeMembers)
             {
                 if (!named.MangleName &&
                     (forcedArity == -1 || forcedArity == named.Arity) &&
-                    named.MetadataName == emittedTypeName.TypeName)
+                    ReadOnlyMemoryOfCharComparer.Equals(named.MetadataName.AsSpan(), emittedTypeName.TypeNameMemory))
                 {
                     if (namedType is not null)
                     {
@@ -334,6 +347,8 @@ public virtual ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int a
 Done:
             if (isTopLevel
                 && (emittedTypeName.ForcedArity == -1 || emittedTypeName.ForcedArity == emittedTypeName.InferredArity)
+                // Quick check so we don't have to realize the expensive `UnmangledTypeName` in the common case.
+                && emittedTypeName.TypeNameMemory.Span is [GeneratedNameParser.FileTypeNameStartChar, ..]
                 && GeneratedNameParser.TryParseFileTypeName(
                     emittedTypeName.UnmangledTypeName,
                     out string? displayFileName,
diff --git a/src/Compilers/CSharp/Portable/Symbols/NamespaceSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NamespaceSymbol.cs
index 9b275242c18ae..9999d50b2db2c 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NamespaceSymbol.cs
@@ -4,6 +4,7 @@
 
 #nullable disable
 
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
@@ -245,43 +246,23 @@ internal NamedTypeSymbol ImplicitType
         /// Symbol for the most nested namespace, if found. Nothing 
         /// if namespace or any part of it can not be found.
         /// </returns>
-        internal NamespaceSymbol LookupNestedNamespace(ImmutableArray<string> names)
+        internal NamespaceSymbol LookupNestedNamespace(ImmutableArray<ReadOnlyMemory<char>> names)
         {
             NamespaceSymbol scope = this;
-
-            foreach (string name in names)
+            foreach (ReadOnlyMemory<char> name in names)
             {
-                NamespaceSymbol nextScope = null;
-
-                foreach (NamespaceOrTypeSymbol symbol in scope.GetMembers(name))
-                {
-                    var ns = symbol as NamespaceSymbol;
-
-                    if ((object)ns != null)
-                    {
-                        if ((object)nextScope != null)
-                        {
-                            Debug.Assert((object)nextScope == null, "Why did we run into an unmerged namespace?");
-                            nextScope = null;
-                            break;
-                        }
-
-                        nextScope = ns;
-                    }
-                }
-
-                scope = nextScope;
-
-                if ((object)scope == null)
-                {
-                    break;
-                }
+                scope = scope.GetNestedNamespace(name);
+                if (scope is null)
+                    return null;
             }
 
             return scope;
         }
 
         internal NamespaceSymbol GetNestedNamespace(string name)
+            => GetNestedNamespace(name.AsMemory());
+
+        internal NamespaceSymbol GetNestedNamespace(ReadOnlyMemory<char> name)
         {
             foreach (var sym in this.GetMembers(name))
             {
@@ -294,6 +275,11 @@ internal NamespaceSymbol GetNestedNamespace(string name)
             return null;
         }
 
+        public abstract ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name);
+
+        public sealed override ImmutableArray<Symbol> GetMembers(string name)
+            => GetMembers(name.AsMemory());
+
         internal NamespaceSymbol GetNestedNamespace(NameSyntax name)
         {
             switch (name.Kind())
diff --git a/src/Compilers/CSharp/Portable/Symbols/NativeIntegerTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NativeIntegerTypeSymbol.cs
index 7a296e86a1722..e89c5742fdef5 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NativeIntegerTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NativeIntegerTypeSymbol.cs
@@ -141,9 +141,9 @@ ImmutableArray<Symbol> makeMembers(ImmutableArray<Symbol> underlyingMembers)
 
         public override ImmutableArray<NamedTypeSymbol> GetTypeMembers() => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name) => ImmutableArray<NamedTypeSymbol>.Empty;
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name) => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity) => ImmutableArray<NamedTypeSymbol>.Empty;
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity) => ImmutableArray<NamedTypeSymbol>.Empty;
 
         internal override NamedTypeSymbol GetDeclaredBaseType(ConsList<TypeSymbol> basesBeingResolved) => _underlyingType.GetDeclaredBaseType(basesBeingResolved);
 
@@ -177,7 +177,8 @@ internal override UseSiteInfo<AssemblySymbol> GetUseSiteInfo()
         internal sealed override NamedTypeSymbol NativeIntegerUnderlyingType => _underlyingType;
 
         // note: there is no supported way to create a native integer type whose underlying type is file-local.
-        internal override FileIdentifier? AssociatedFileIdentifier => null;
+        internal sealed override bool IsFileLocal => false;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
         internal sealed override bool IsRecord => false;
         internal sealed override bool IsRecordStruct => false;
@@ -275,6 +276,12 @@ internal static void VerifyEquality(Symbol symbolA, Symbol symbolB)
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
 
+        internal override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
+
         private sealed class NativeIntegerTypeMap : AbstractTypeMap
         {
             private readonly NativeIntegerTypeSymbol _type;
diff --git a/src/Compilers/CSharp/Portable/Symbols/NoPiaAmbiguousCanonicalTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NoPiaAmbiguousCanonicalTypeSymbol.cs
index eaecffd33c8a7..a1d83b05ff17c 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NoPiaAmbiguousCanonicalTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NoPiaAmbiguousCanonicalTypeSymbol.cs
@@ -49,7 +49,8 @@ internal override bool MangleName
             }
         }
 
-        internal override FileIdentifier? AssociatedFileIdentifier => null;
+        internal sealed override bool IsFileLocal => false;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
         public AssemblySymbol EmbeddingAssembly
         {
diff --git a/src/Compilers/CSharp/Portable/Symbols/NoPiaIllegalGenericInstantiationSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NoPiaIllegalGenericInstantiationSymbol.cs
index 06e5b8cc138af..a051fb8b976b0 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NoPiaIllegalGenericInstantiationSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NoPiaIllegalGenericInstantiationSymbol.cs
@@ -41,7 +41,8 @@ internal override bool MangleName
             }
         }
 
-        internal override FileIdentifier? AssociatedFileIdentifier => null;
+        internal sealed override bool IsFileLocal => false;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
         public NamedTypeSymbol UnderlyingSymbol
         {
diff --git a/src/Compilers/CSharp/Portable/Symbols/NoPiaMissingCanonicalTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NoPiaMissingCanonicalTypeSymbol.cs
index e785f225d49ec..14cd9b7558f85 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NoPiaMissingCanonicalTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NoPiaMissingCanonicalTypeSymbol.cs
@@ -73,7 +73,8 @@ internal override bool MangleName
             }
         }
 
-        internal override FileIdentifier? AssociatedFileIdentifier => null;
+        internal sealed override bool IsFileLocal => false;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
         public string? Guid
         {
diff --git a/src/Compilers/CSharp/Portable/Symbols/NonMissingModuleSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/NonMissingModuleSymbol.cs
index 282669d61e018..06b5511657810 100644
--- a/src/Compilers/CSharp/Portable/Symbols/NonMissingModuleSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/NonMissingModuleSymbol.cs
@@ -188,7 +188,7 @@ internal void AssertReferencesInitialized()
         internal sealed override NamedTypeSymbol? LookupTopLevelMetadataType(ref MetadataTypeName emittedName)
         {
             NamedTypeSymbol? result;
-            NamespaceSymbol? scope = this.GlobalNamespace.LookupNestedNamespace(emittedName.NamespaceSegments);
+            NamespaceSymbol? scope = this.GlobalNamespace.LookupNestedNamespace(emittedName.NamespaceSegmentsMemory);
 
             if ((object?)scope == null)
             {
diff --git a/src/Compilers/CSharp/Portable/Symbols/PlaceholderTypeArgumentSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/PlaceholderTypeArgumentSymbol.cs
index 8545ec720d59c..8ac21488f2074 100644
--- a/src/Compilers/CSharp/Portable/Symbols/PlaceholderTypeArgumentSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/PlaceholderTypeArgumentSymbol.cs
@@ -48,6 +48,7 @@ internal override bool MangleName
             }
         }
 
+        internal override bool IsFileLocal => false;
         internal override FileIdentifier? AssociatedFileIdentifier => null;
 
         internal override DiagnosticInfo? ErrorInfo
diff --git a/src/Compilers/CSharp/Portable/Symbols/PointerTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/PointerTypeSymbol.cs
index 8fdcb20a8964c..aaff1d36f2138 100644
--- a/src/Compilers/CSharp/Portable/Symbols/PointerTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/PointerTypeSymbol.cs
@@ -144,12 +144,12 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
@@ -315,5 +315,11 @@ protected override ITypeSymbol CreateITypeSymbol(CodeAnalysis.NullableAnnotation
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/PublicModel/NamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/PublicModel/NamedTypeSymbol.cs
index 8f26fefe58f55..38863cab17cb7 100644
--- a/src/Compilers/CSharp/Portable/Symbols/PublicModel/NamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/PublicModel/NamedTypeSymbol.cs
@@ -195,10 +195,10 @@ INamedTypeSymbol INamedTypeSymbol.TupleUnderlyingType
         bool INamedTypeSymbol.IsSerializable => UnderlyingNamedTypeSymbol.IsSerializable;
 
         bool INamedTypeSymbol.IsFileLocal =>
-            // Even though we round-trip the file identifier through metadata to support EE,
-            // we don't want public API to give the impression that the compiler considers a metadata type to be a file-local type.
+            // Internally we can treat a metadata type as being a file-local type for EE.
+            // For public API, only source types are considered file-local types.
             UnderlyingNamedTypeSymbol.OriginalDefinition is SourceMemberContainerTypeSymbol
-                && UnderlyingNamedTypeSymbol.AssociatedFileIdentifier is not null;
+                && UnderlyingNamedTypeSymbol.IsFileLocal;
 
         INamedTypeSymbol INamedTypeSymbol.NativeIntegerUnderlyingType => UnderlyingNamedTypeSymbol.NativeIntegerUnderlyingType.GetPublicSymbol();
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs
index c59e90fd57611..f862e7cc8f4e7 100644
--- a/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/ReducedExtensionMethodSymbol.cs
@@ -530,6 +530,12 @@ internal override bool IsExplicitInterfaceImplementation
 
         internal override bool IsEffectivelyReadOnly => _reducedFrom.Parameters[0].RefKind == RefKind.In;
 
+        internal override bool TryGetThisParameter(out ParameterSymbol thisParameter)
+        {
+            thisParameter = _reducedFrom.Parameters[0];
+            return true;
+        }
+
         public override ImmutableArray<MethodSymbol> ExplicitInterfaceImplementations
         {
             get { return ImmutableArray<MethodSymbol>.Empty; }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.cs
index 518e96213a849..08ea5170c67b5 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.cs
@@ -193,6 +193,11 @@ internal override IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicK
             return _underlyingAssembly.GetInternalsVisibleToPublicKeys(simpleName);
         }
 
+        internal override IEnumerable<string> GetInternalsVisibleToAssemblyNames()
+        {
+            return _underlyingAssembly.GetInternalsVisibleToAssemblyNames();
+        }
+
         internal override bool AreInternalsVisibleToThisAssembly(AssemblySymbol other)
         {
             return _underlyingAssembly.AreInternalsVisibleToThisAssembly(other);
diff --git a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamedTypeSymbol.cs
index 14be3d9c59bf7..b59cd587705e0 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamedTypeSymbol.cs
@@ -206,12 +206,12 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return this.RetargetingTranslator.Retarget(_underlyingType.GetTypeMembers());
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return this.RetargetingTranslator.Retarget(_underlyingType.GetTypeMembers(name));
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return this.RetargetingTranslator.Retarget(_underlyingType.GetTypeMembers(name, arity));
         }
@@ -389,6 +389,7 @@ public sealed override bool AreLocalsZeroed
             get { throw ExceptionUtilities.Unreachable(); }
         }
 
+        internal override bool IsFileLocal => _underlyingType.IsFileLocal;
         internal override FileIdentifier? AssociatedFileIdentifier => _underlyingType.AssociatedFileIdentifier;
 
         internal sealed override NamedTypeSymbol AsNativeInteger() => throw ExceptionUtilities.Unreachable();
@@ -412,5 +413,10 @@ public sealed override bool AreLocalsZeroed
                 }
             }
         }
+
+        internal override bool HasInlineArrayAttribute(out int length)
+        {
+            return _underlyingType.HasInlineArrayAttribute(out length);
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamespaceSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamespaceSymbol.cs
index dd4ae5bb262f6..145014230187b 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Retargeting/RetargetingNamespaceSymbol.cs
@@ -98,7 +98,7 @@ internal override ImmutableArray<Symbol> GetMembersUnordered()
             return RetargetMembers(_underlyingNamespace.GetMembersUnordered());
         }
 
-        public override ImmutableArray<Symbol> GetMembers(string name)
+        public override ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name)
         {
             return RetargetMembers(_underlyingNamespace.GetMembers(name));
         }
@@ -132,12 +132,12 @@ private ImmutableArray<NamedTypeSymbol> RetargetTypeMembers(ImmutableArray<Named
             return builder.ToImmutableAndFree();
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return RetargetTypeMembers(_underlyingNamespace.GetTypeMembers(name));
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return RetargetTypeMembers(_underlyingNamespace.GetTypeMembers(name, arity));
         }
diff --git a/src/Compilers/CSharp/Portable/Symbols/SignatureOnlyMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/SignatureOnlyMethodSymbol.cs
index 279464bc50d4f..d01070a2ec2cc 100644
--- a/src/Compilers/CSharp/Portable/Symbols/SignatureOnlyMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/SignatureOnlyMethodSymbol.cs
@@ -176,7 +176,7 @@ internal override bool IsMetadataFinal
 
         internal sealed override bool HasUnscopedRefAttribute => false;
 
-        internal sealed override bool UseUpdatedEscapeRules => false;
+        internal sealed override bool UseUpdatedEscapeRules => true;
 
         #endregion
     }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/ImplicitNamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/ImplicitNamedTypeSymbol.cs
index 44c30a9b85530..609b28e80b8f4 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/ImplicitNamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/ImplicitNamedTypeSymbol.cs
@@ -170,5 +170,11 @@ internal override ObsoleteAttributeData ObsoleteAttributeData
         internal sealed override NamedTypeSymbol AsNativeInteger() => throw ExceptionUtilities.Unreachable();
 
         internal sealed override NamedTypeSymbol NativeIntegerUnderlyingType => null;
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceAssemblySymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceAssemblySymbol.cs
index 1e4c41ee6eccd..b7bd00f636099 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceAssemblySymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceAssemblySymbol.cs
@@ -2119,6 +2119,16 @@ internal override IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicK
             return (result != null) ? result.Keys : SpecializedCollections.EmptyEnumerable<ImmutableArray<byte>>();
         }
 
+        internal override IEnumerable<string> GetInternalsVisibleToAssemblyNames()
+        {
+            EnsureAttributesAreBound();
+
+            if (_lazyInternalsVisibleToMap == null)
+                return SpecializedCollections.EmptyEnumerable<string>();
+
+            return _lazyInternalsVisibleToMap.Keys;
+        }
+
         internal override bool AreInternalsVisibleToThisAssembly(AssemblySymbol potentialGiverOfAccess)
         {
             // Ensure that optimistic IVT access is only granted to requests that originated on the thread
@@ -2680,7 +2690,7 @@ internal ImmutableArray<Diagnostic> GetUnusedFieldWarnings(CancellationToken can
                         handledUnreadFields.Add(field);
                     }
 
-                    if (containingType.HasStructLayoutAttribute)
+                    if (containingType.HasStructLayoutAttribute || containingType.HasInlineArrayAttribute(out _))
                     {
                         continue;
                     }
@@ -2717,7 +2727,7 @@ internal ImmutableArray<Diagnostic> GetUnusedFieldWarnings(CancellationToken can
                     }
 
                     var containingType = field.ContainingType as SourceNamedTypeSymbol;
-                    if ((object)containingType != null && !containingType.HasStructLayoutAttribute)
+                    if ((object)containingType != null && !containingType.HasStructLayoutAttribute && !containingType.HasInlineArrayAttribute(out _))
                     {
                         diagnostics.Add(ErrorCode.WRN_UnreferencedFieldAssg, field.GetFirstLocationOrNone(), field);
                     }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs
index e8f76dd887aea..0e7d9082285f4 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceComplexParameterSymbol.cs
@@ -370,11 +370,11 @@ private ConstantValue MakeDefaultExpression(BindingDiagnosticBag diagnostics, ou
             MessageID.IDS_FeatureOptionalParameter.CheckFeatureAvailability(diagnostics, defaultSyntax.EqualsToken);
 
             binder = GetDefaultParameterValueBinder(defaultSyntax);
-            Binder binderForDefault = binder.CreateBinderForParameterDefaultValue(this, defaultSyntax);
-            Debug.Assert(binderForDefault.InParameterDefaultValue);
-            Debug.Assert(binderForDefault.ContainingMemberOrLambda == ContainingSymbol);
+            binder = binder.CreateBinderForParameterDefaultValue(this, defaultSyntax);
+            Debug.Assert(binder.InParameterDefaultValue);
+            Debug.Assert(binder.ContainingMemberOrLambda == ContainingSymbol);
 
-            parameterEqualsValue = binderForDefault.BindParameterDefaultValue(defaultSyntax, this, diagnostics, out var valueBeforeConversion);
+            parameterEqualsValue = binder.BindParameterDefaultValue(defaultSyntax, this, diagnostics, out var valueBeforeConversion);
             if (valueBeforeConversion.HasErrors)
             {
                 return ConstantValue.Bad;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbol.cs
index 2119ddccd1841..eb7aa8f24dc99 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbol.cs
@@ -31,19 +31,17 @@ private SourceConstructorSymbol(
              MethodKind methodKind,
              bool isNullableAnalysisEnabled,
              BindingDiagnosticBag diagnostics) :
-             base(containingType, location, syntax, SyntaxFacts.HasYieldOperations(syntax))
+             base(containingType, location, syntax, SyntaxFacts.HasYieldOperations(syntax),
+                  MakeModifiersAndFlags(containingType, syntax, methodKind, isNullableAnalysisEnabled, location, diagnostics, out bool modifierErrors, out bool report_ERR_StaticConstructorWithAccessModifiers))
         {
-            bool hasBlockBody = syntax.Body != null;
-            bool isExpressionBodied = !hasBlockBody && syntax.ExpressionBody != null;
-            bool hasAnyBody = hasBlockBody || isExpressionBodied;
-
             _hasThisInitializer = syntax.Initializer?.Kind() == SyntaxKind.ThisConstructorInitializer;
 
-            bool modifierErrors;
-            var declarationModifiers = this.MakeModifiers(syntax.Modifiers, methodKind, hasAnyBody, location, diagnostics, out modifierErrors);
-            this.MakeFlags(
-                methodKind, RefKind.None, declarationModifiers, returnsVoid: true, hasAnyBody: hasAnyBody, isExpressionBodied: isExpressionBodied,
-                isExtensionMethod: false, isVarArg: syntax.ParameterList.Parameters.Any(static p => p.IsArgList), isNullableAnalysisEnabled: isNullableAnalysisEnabled);
+            this.CheckUnsafeModifier(DeclarationModifiers, diagnostics);
+
+            if (report_ERR_StaticConstructorWithAccessModifiers)
+            {
+                diagnostics.Add(ErrorCode.ERR_StaticConstructorWithAccessModifiers, location, this);
+            }
 
             if (syntax.Identifier.ValueText != containingType.Name)
             {
@@ -51,6 +49,8 @@ private SourceConstructorSymbol(
                 diagnostics.Add(ErrorCode.ERR_MemberNeedsType, location);
             }
 
+            bool hasAnyBody = syntax.HasAnyBody();
+
             if (IsExtern)
             {
                 if (methodKind == MethodKind.Constructor && syntax.Initializer != null)
@@ -80,6 +80,19 @@ private SourceConstructorSymbol(
                 syntax.Body, syntax.ExpressionBody, syntax, diagnostics);
         }
 
+        private static (DeclarationModifiers, Flags) MakeModifiersAndFlags(
+            NamedTypeSymbol containingType, ConstructorDeclarationSyntax syntax, MethodKind methodKind, bool isNullableAnalysisEnabled, Location location, BindingDiagnosticBag diagnostics,
+            out bool modifierErrors, out bool report_ERR_StaticConstructorWithAccessModifiers)
+        {
+            DeclarationModifiers declarationModifiers = MakeModifiers(containingType, syntax, methodKind, syntax.HasAnyBody(), location, diagnostics, out modifierErrors, out report_ERR_StaticConstructorWithAccessModifiers);
+            Flags flags = MakeFlags(
+                                    methodKind, RefKind.None, declarationModifiers, returnsVoid: true, isExpressionBodied: syntax.IsExpressionBodied(),
+                                    isExtensionMethod: false, isVarArg: syntax.IsVarArg(), isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                                    isExplicitInterfaceImplementation: false);
+
+            return (declarationModifiers, flags);
+        }
+
         internal ConstructorDeclarationSyntax GetSyntax()
         {
             Debug.Assert(syntaxReferenceOpt != null);
@@ -101,7 +114,9 @@ protected override CSharpSyntaxNode GetInitializer()
             return GetSyntax().Initializer;
         }
 
-        private DeclarationModifiers MakeModifiers(SyntaxTokenList modifiers, MethodKind methodKind, bool hasBody, Location location, BindingDiagnosticBag diagnostics, out bool modifierErrors)
+        private static DeclarationModifiers MakeModifiers(
+            NamedTypeSymbol containingType, ConstructorDeclarationSyntax syntax, MethodKind methodKind, bool hasBody, Location location, BindingDiagnosticBag diagnostics,
+            out bool modifierErrors, out bool report_ERR_StaticConstructorWithAccessModifiers)
         {
             var defaultAccess = (methodKind == MethodKind.StaticConstructor) ? DeclarationModifiers.None : DeclarationModifiers.Private;
 
@@ -112,21 +127,20 @@ private DeclarationModifiers MakeModifiers(SyntaxTokenList modifiers, MethodKind
                 DeclarationModifiers.Extern |
                 DeclarationModifiers.Unsafe;
 
-            bool isInterface = ContainingType.IsInterface;
-            var mods = ModifierUtils.MakeAndCheckNonTypeMemberModifiers(isOrdinaryMethod: false, isForInterfaceMember: isInterface, modifiers, defaultAccess, allowedModifiers, location, diagnostics, out modifierErrors);
-
-            this.CheckUnsafeModifier(mods, diagnostics);
+            bool isInterface = containingType.IsInterface;
+            var mods = ModifierUtils.MakeAndCheckNonTypeMemberModifiers(isOrdinaryMethod: false, isForInterfaceMember: isInterface, syntax.Modifiers, defaultAccess, allowedModifiers, location, diagnostics, out modifierErrors);
 
+            report_ERR_StaticConstructorWithAccessModifiers = false;
             if (methodKind == MethodKind.StaticConstructor)
             {
                 // Don't report ERR_StaticConstructorWithAccessModifiers if the ctor symbol name doesn't match the containing type name.
                 // This avoids extra unnecessary errors.
                 // There will already be a diagnostic saying Method must have a return type.
                 if ((mods & DeclarationModifiers.AccessibilityMask) != 0 &&
-                    ContainingType.Name == ((ConstructorDeclarationSyntax)this.SyntaxNode).Identifier.ValueText)
+                    containingType.Name == syntax.Identifier.ValueText)
                 {
-                    diagnostics.Add(ErrorCode.ERR_StaticConstructorWithAccessModifiers, location, this);
                     mods = mods & ~DeclarationModifiers.AccessibilityMask;
+                    report_ERR_StaticConstructorWithAccessModifiers = true;
                     modifierErrors = true;
                 }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbolBase.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbolBase.cs
index 00e94036b411f..4a5dc9b5da099 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbolBase.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceConstructorSymbolBase.cs
@@ -23,8 +23,9 @@ protected SourceConstructorSymbolBase(
             SourceMemberContainerTypeSymbol containingType,
             Location location,
             CSharpSyntaxNode syntax,
-            bool isIterator)
-            : base(containingType, syntax.GetReference(), location, isIterator)
+            bool isIterator,
+            (DeclarationModifiers declarationModifiers, Flags flags) modifiersAndFlags)
+            : base(containingType, syntax.GetReference(), location, isIterator, modifiersAndFlags)
         {
             Debug.Assert(syntax.Kind() is SyntaxKind.ConstructorDeclaration or SyntaxKind.RecordDeclaration or SyntaxKind.RecordStructDeclaration or SyntaxKind.ClassDeclaration or SyntaxKind.StructDeclaration);
         }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventAccessorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventAccessorSymbol.cs
index 33b135319d643..7ffd478df9134 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventAccessorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventAccessorSymbol.cs
@@ -32,7 +32,6 @@ internal SourceCustomEventAccessorSymbol(
                    isAdder: syntax.Kind() == SyntaxKind.AddAccessorDeclaration,
                    isIterator: SyntaxFacts.HasYieldOperations(syntax.Body),
                    isNullableAnalysisEnabled: isNullableAnalysisEnabled,
-                   hasAnyBody: syntax.Body is not null || syntax.ExpressionBody is not null,
                    isExpressionBodied: syntax is { Body: null, ExpressionBody: not null })
         {
             Debug.Assert(syntax != null);
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventSymbol.cs
index 7f379c7072076..550c97a36a93f 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceCustomEventSymbol.cs
@@ -155,9 +155,8 @@ internal SourceCustomEventSymbol(SourceMemberContainerTypeSymbol containingType,
                     diagnostics.Add(ErrorCode.ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation, this.GetFirstLocation());
                 }
 
-                // No body as this was an abstract event.
-                _addMethod = new SynthesizedEventAccessorSymbol(this, isAdder: true, hasAnyBody: false, isExpressionBodied: false, explicitlyImplementedEvent, aliasQualifierOpt);
-                _removeMethod = new SynthesizedEventAccessorSymbol(this, isAdder: false, hasAnyBody: false, isExpressionBodied: false, explicitlyImplementedEvent, aliasQualifierOpt);
+                _addMethod = new SynthesizedEventAccessorSymbol(this, isAdder: true, isExpressionBodied: false, explicitlyImplementedEvent, aliasQualifierOpt);
+                _removeMethod = new SynthesizedEventAccessorSymbol(this, isAdder: false, isExpressionBodied: false, explicitlyImplementedEvent, aliasQualifierOpt);
             }
             else
             {
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceDelegateMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceDelegateMethodSymbol.cs
index 804ee3eea2b57..1093b7f4231ce 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceDelegateMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceDelegateMethodSymbol.cs
@@ -26,12 +26,12 @@ protected SourceDelegateMethodSymbol(
             MethodKind methodKind,
             RefKind refKind,
             DeclarationModifiers declarationModifiers)
-            : base(delegateType, syntax.GetReference(), location: syntax.Identifier.GetLocation(), isIterator: false)
+            : base(delegateType, syntax.GetReference(), location: syntax.Identifier.GetLocation(), isIterator: false,
+                   (declarationModifiers, MakeFlags(
+                                                    methodKind, refKind, declarationModifiers, returnType.IsVoidType(), isExpressionBodied: false,
+                                                    isExtensionMethod: false, isVarArg: false, isNullableAnalysisEnabled: false, isExplicitInterfaceImplementation: false)))
         {
             _returnType = returnType;
-            this.MakeFlags(
-                methodKind, refKind, declarationModifiers, _returnType.IsVoidType(), hasAnyBody: false, isExpressionBodied: false,
-                isExtensionMethod: false, isVarArg: false, isNullableAnalysisEnabled: false);
         }
 
         internal sealed override ExecutableCodeBinder TryGetBodyBinder(BinderFactory binderFactoryOpt = null, bool ignoreAccessibility = false) => throw ExceptionUtilities.Unreachable();
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceDestructorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceDestructorSymbol.cs
index fe0457aee98d3..d1d3562b38e0b 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceDestructorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceDestructorSymbol.cs
@@ -20,21 +20,13 @@ internal SourceDestructorSymbol(
             DestructorDeclarationSyntax syntax,
             bool isNullableAnalysisEnabled,
             BindingDiagnosticBag diagnostics) :
-            base(containingType, syntax.GetReference(), syntax.Identifier.GetLocation(), isIterator: SyntaxFacts.HasYieldOperations(syntax.Body))
+            base(containingType, syntax.GetReference(), GetSymbolLocation(syntax, out Location location), isIterator: SyntaxFacts.HasYieldOperations(syntax.Body),
+                 MakeModifiersAndFlags(containingType, syntax, isNullableAnalysisEnabled, location, diagnostics, out bool modifierErrors))
         {
-            const MethodKind methodKind = MethodKind.Destructor;
-            Location location = this.GetFirstLocation();
-
-            bool modifierErrors;
-            var declarationModifiers = MakeModifiers(syntax.Modifiers, location, diagnostics, out modifierErrors);
+            this.CheckUnsafeModifier(DeclarationModifiers, diagnostics);
 
             bool hasBlockBody = syntax.Body != null;
-            bool isExpressionBodied = !hasBlockBody && syntax.ExpressionBody != null;
-            bool hasAnyBody = hasBlockBody || isExpressionBodied;
-
-            this.MakeFlags(
-                methodKind, RefKind.None, declarationModifiers, returnsVoid: true, hasAnyBody: hasAnyBody, isExpressionBodied: isExpressionBodied, isExtensionMethod: false,
-                isVarArg: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled);
+            bool isExpressionBodied = IsExpressionBodied;
 
             if (syntax.Identifier.ValueText != containingType.Name)
             {
@@ -69,6 +61,22 @@ internal SourceDestructorSymbol(
                 syntax.Body, syntax.ExpressionBody, syntax, diagnostics);
         }
 
+        private static (DeclarationModifiers, Flags) MakeModifiersAndFlags(NamedTypeSymbol containingType, DestructorDeclarationSyntax syntax, bool isNullableAnalysisEnabled, Location location, BindingDiagnosticBag diagnostics, out bool modifierErrors)
+        {
+            DeclarationModifiers declarationModifiers = MakeModifiers(containingType, syntax.Modifiers, location, diagnostics, out modifierErrors);
+            Flags flags = MakeFlags(
+                                    MethodKind.Destructor, RefKind.None, declarationModifiers, returnsVoid: true, isExpressionBodied: syntax.IsExpressionBodied(), isExtensionMethod: false,
+                                    isVarArg: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled, isExplicitInterfaceImplementation: false);
+
+            return (declarationModifiers, flags);
+        }
+
+        private static Location GetSymbolLocation(DestructorDeclarationSyntax syntax, out Location location)
+        {
+            location = syntax.Identifier.GetLocation();
+            return location;
+        }
+
         protected override void MethodChecks(BindingDiagnosticBag diagnostics)
         {
             var syntax = GetSyntax();
@@ -117,13 +125,11 @@ public override TypeWithAnnotations ReturnTypeWithAnnotations
             }
         }
 
-        private DeclarationModifiers MakeModifiers(SyntaxTokenList modifiers, Location location, BindingDiagnosticBag diagnostics, out bool modifierErrors)
+        private static DeclarationModifiers MakeModifiers(NamedTypeSymbol containingType, SyntaxTokenList modifiers, Location location, BindingDiagnosticBag diagnostics, out bool modifierErrors)
         {
             // Check that the set of modifiers is allowed
             const DeclarationModifiers allowedModifiers = DeclarationModifiers.Extern | DeclarationModifiers.Unsafe;
-            var mods = ModifierUtils.MakeAndCheckNonTypeMemberModifiers(isOrdinaryMethod: false, isForInterfaceMember: ContainingType.IsInterface, modifiers, DeclarationModifiers.None, allowedModifiers, location, diagnostics, out modifierErrors);
-
-            this.CheckUnsafeModifier(mods, diagnostics);
+            var mods = ModifierUtils.MakeAndCheckNonTypeMemberModifiers(isOrdinaryMethod: false, isForInterfaceMember: containingType.IsInterface, modifiers, DeclarationModifiers.None, allowedModifiers, location, diagnostics, out modifierErrors);
 
             mods = (mods & ~DeclarationModifiers.AccessibilityMask) | DeclarationModifiers.Protected; // we mark destructors protected in the symbol table
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceEventAccessorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceEventAccessorSymbol.cs
index c67ba98104cce..e553212efec5a 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceEventAccessorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceEventAccessorSymbol.cs
@@ -30,9 +30,18 @@ public SourceEventAccessorSymbol(
             bool isAdder,
             bool isIterator,
             bool isNullableAnalysisEnabled,
-            bool hasAnyBody,
             bool isExpressionBodied)
-            : base(@event.containingType, syntaxReference, location, isIterator)
+            : base(@event.containingType, syntaxReference, location, isIterator,
+                   (@event.Modifiers, MakeFlags(
+                                                isAdder ? MethodKind.EventAdd : MethodKind.EventRemove,
+                                                RefKind.None,
+                                                @event.Modifiers,
+                                                returnsVoid: false, // until we learn otherwise (in LazyMethodChecks).
+                                                isExpressionBodied: isExpressionBodied,
+                                                isExtensionMethod: false,
+                                                isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                                                isVarArg: false,
+                                                isExplicitInterfaceImplementation: @event.IsExplicitInterfaceImplementation)))
         {
             _event = @event;
 
@@ -53,19 +62,6 @@ public SourceEventAccessorSymbol(
             }
 
             _explicitInterfaceImplementations = explicitInterfaceImplementations;
-
-            this.MakeFlags(
-                isAdder ? MethodKind.EventAdd : MethodKind.EventRemove,
-                RefKind.None,
-                @event.Modifiers,
-                returnsVoid: false, // until we learn otherwise (in LazyMethodChecks).
-                hasAnyBody: hasAnyBody,
-                isExpressionBodied: isExpressionBodied,
-                isExtensionMethod: false,
-                isNullableAnalysisEnabled: isNullableAnalysisEnabled,
-                isVarArg: false,
-                isMetadataVirtualIgnoringModifiers: @event.IsExplicitInterfaceImplementation && (@event.Modifiers & DeclarationModifiers.Static) == 0);
-
             _name = GetOverriddenAccessorName(@event, isAdder) ?? name;
         }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceFieldLikeEventSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceFieldLikeEventSymbol.cs
index 0db8d93d0c41c..630336104a377 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceFieldLikeEventSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceFieldLikeEventSymbol.cs
@@ -113,11 +113,8 @@ internal SourceFieldLikeEventSymbol(SourceMemberContainerTypeSymbol containingTy
                 }
             }
 
-            // Accessors will assume that Type is available. We consider abstract/extern accessors to not have a
-            // body, but all others do have one.
-            var hasAnyBody = !IsAbstract && !IsExtern;
-            _addMethod = new SynthesizedEventAccessorSymbol(this, isAdder: true, hasAnyBody: hasAnyBody, isExpressionBodied: false);
-            _removeMethod = new SynthesizedEventAccessorSymbol(this, isAdder: false, hasAnyBody: hasAnyBody, isExpressionBodied: false);
+            _addMethod = new SynthesizedEventAccessorSymbol(this, isAdder: true, isExpressionBodied: false);
+            _removeMethod = new SynthesizedEventAccessorSymbol(this, isAdder: false, isExpressionBodied: false);
 
             if (declarationSyntax.Variables[0] == declaratorSyntax)
             {
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs
index d038c2ece3ebf..af8b99d17bd12 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs
@@ -200,11 +200,13 @@ public bool SetHasDeclaredRequiredMembers(bool value)
         private DeclaredMembersAndInitializers? _lazyDeclaredMembersAndInitializers = DeclaredMembersAndInitializers.UninitializedSentinel;
 
         private MembersAndInitializers? _lazyMembersAndInitializers;
-        private Dictionary<string, ImmutableArray<Symbol>>? _lazyMembersDictionary;
-        private Dictionary<string, ImmutableArray<Symbol>>? _lazyEarlyAttributeDecodingMembersDictionary;
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>>? _lazyMembersDictionary;
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>>? _lazyEarlyAttributeDecodingMembersDictionary;
 
-        private static readonly Dictionary<string, ImmutableArray<NamedTypeSymbol>> s_emptyTypeMembers = new Dictionary<string, ImmutableArray<NamedTypeSymbol>>(EmptyComparer.Instance);
-        private Dictionary<string, ImmutableArray<NamedTypeSymbol>>? _lazyTypeMembers;
+        private static readonly Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>> s_emptyTypeMembers =
+            new Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>>(EmptyReadOnlyMemoryOfCharComparer.Instance);
+
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>>? _lazyTypeMembers;
         private ImmutableArray<Symbol> _lazyMembersFlattened;
         private SynthesizedExplicitImplementations? _lazySynthesizedExplicitImplementations;
         private int _lazyKnownCircularStruct;
@@ -841,7 +843,7 @@ internal override ManagedKind GetManagedKind(ref CompoundUseSiteInfo<AssemblySym
 
         internal bool IsNew => HasFlag(DeclarationModifiers.New);
 
-        internal bool IsFileLocal => HasFlag(DeclarationModifiers.File);
+        internal sealed override bool IsFileLocal => HasFlag(DeclarationModifiers.File);
 
         internal bool IsUnsafe => HasFlag(DeclarationModifiers.Unsafe);
 
@@ -1267,7 +1269,7 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return GetTypeMembersDictionary().Flatten(LexicalOrderSymbolComparer.Instance);
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             ImmutableArray<NamedTypeSymbol> members;
             if (GetTypeMembersDictionary().TryGetValue(name, out members))
@@ -1278,12 +1280,12 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return GetTypeMembers(name).WhereAsArray((t, arity) => t.Arity == arity, arity);
         }
 
-        private Dictionary<string, ImmutableArray<NamedTypeSymbol>> GetTypeMembersDictionary()
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>> GetTypeMembersDictionary()
         {
             if (_lazyTypeMembers == null)
             {
@@ -1301,7 +1303,7 @@ private Dictionary<string, ImmutableArray<NamedTypeSymbol>> GetTypeMembersDictio
             return _lazyTypeMembers;
         }
 
-        private Dictionary<string, ImmutableArray<NamedTypeSymbol>> MakeTypeMembers(BindingDiagnosticBag diagnostics)
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>> MakeTypeMembers(BindingDiagnosticBag diagnostics)
         {
             var symbols = ArrayBuilder<NamedTypeSymbol>.GetInstance();
             var conflictDict = new Dictionary<(string name, int arity, SyntaxTree? syntaxTree), SourceNamedTypeSymbol>();
@@ -1346,7 +1348,7 @@ private Dictionary<string, ImmutableArray<NamedTypeSymbol>> MakeTypeMembers(Bind
 
                 Debug.Assert(s_emptyTypeMembers.Count == 0);
                 return symbols.Count > 0 ?
-                    symbols.ToDictionary(s => s.Name, StringOrdinalComparer.Instance) :
+                    symbols.ToDictionary(s => s.Name.AsMemory(), ReadOnlyMemoryOfCharComparer.Instance) :
                     s_emptyTypeMembers;
             }
             finally
@@ -1429,7 +1431,7 @@ public override ImmutableArray<Symbol> GetMembers()
         public sealed override ImmutableArray<Symbol> GetMembers(string name)
         {
             ImmutableArray<Symbol> members;
-            if (GetMembersByName().TryGetValue(name, out members))
+            if (GetMembersByName().TryGetValue(name.AsMemory(), out members))
             {
                 return members;
             }
@@ -1510,14 +1512,14 @@ internal override ImmutableArray<Symbol> GetEarlyAttributeDecodingMembers()
         internal override ImmutableArray<Symbol> GetEarlyAttributeDecodingMembers(string name)
         {
             ImmutableArray<Symbol> result;
-            return GetEarlyAttributeDecodingMembersDictionary().TryGetValue(name, out result) ? result : ImmutableArray<Symbol>.Empty;
+            return GetEarlyAttributeDecodingMembersDictionary().TryGetValue(name.AsMemory(), out result) ? result : ImmutableArray<Symbol>.Empty;
         }
 
-        private Dictionary<string, ImmutableArray<Symbol>> GetEarlyAttributeDecodingMembersDictionary()
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> GetEarlyAttributeDecodingMembersDictionary()
         {
             if (_lazyEarlyAttributeDecodingMembersDictionary == null)
             {
-                if (Volatile.Read(ref _lazyMembersDictionary) is Dictionary<string, ImmutableArray<Symbol>> result)
+                if (Volatile.Read(ref _lazyMembersDictionary) is Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> result)
                 {
                     return result;
                 }
@@ -1527,20 +1529,19 @@ private Dictionary<string, ImmutableArray<Symbol>> GetEarlyAttributeDecodingMemb
                 // NOTE: members were added in a single pass over the syntax, so they're already
                 // in lexical order.
 
-                Dictionary<string, ImmutableArray<Symbol>> membersByName;
+                Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> membersByName;
 
                 if (!membersAndInitializers.HaveIndexers)
                 {
-                    membersByName = membersAndInitializers.NonTypeMembers.ToDictionary(static s => s.Name);
+                    membersByName = ToNameKeyedDictionary(membersAndInitializers.NonTypeMembers);
                 }
                 else
                 {
                     // We can't include indexer symbol yet, because we don't know
                     // what name it will have after attribute binding (because of
                     // IndexerNameAttribute).
-                    membersByName = membersAndInitializers.NonTypeMembers.
-                        WhereAsArray(s => !s.IsIndexer() && (!s.IsAccessor() || ((MethodSymbol)s).AssociatedSymbol?.IsIndexer() != true)).
-                        ToDictionary(static s => s.Name);
+                    membersByName = ToNameKeyedDictionary(membersAndInitializers.NonTypeMembers.
+                        WhereAsArray(s => !s.IsIndexer() && (!s.IsAccessor() || ((MethodSymbol)s).AssociatedSymbol?.IsIndexer() != true)));
                 }
 
                 AddNestedTypesToDictionary(membersByName, GetTypeMembersDictionary());
@@ -1551,6 +1552,46 @@ private Dictionary<string, ImmutableArray<Symbol>> GetEarlyAttributeDecodingMemb
             return _lazyEarlyAttributeDecodingMembersDictionary;
         }
 
+        private static Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> ToNameKeyedDictionary(ImmutableArray<Symbol> symbols)
+        {
+            if (symbols is [var symbol])
+            {
+                return new Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>>(1, ReadOnlyMemoryOfCharComparer.Instance)
+                {
+                    {  symbol.Name.AsMemory(), ImmutableArray.Create(symbol) },
+                };
+            }
+
+            if (symbols.Length == 0)
+            {
+                return new Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>>(ReadOnlyMemoryOfCharComparer.Instance);
+            }
+
+            // bucketize
+            // prevent reallocation. it may not have 'count' entries, but it won't have more. 
+            //
+            // We store a mapping from keys to either a single item (very common in practice as this is used from
+            // callers that maps names to symbols with that name, and most names are unique), or an array builder of items.
+
+            var accumulator = s_nameToObjectPool.Allocate();
+            foreach (var item in symbols)
+                ImmutableArrayExtensions.AddToMultiValueDictionaryBuilder(accumulator, item.Name.AsMemory(), item);
+
+            var dictionary = new Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>>(accumulator.Count, ReadOnlyMemoryOfCharComparer.Instance);
+
+            // freeze
+            foreach (var pair in accumulator)
+            {
+                dictionary.Add(pair.Key, pair.Value is ArrayBuilder<Symbol> arrayBuilder
+                    ? arrayBuilder.ToImmutableAndFree()
+                    : ImmutableArray.Create((Symbol)pair.Value));
+            }
+
+            accumulator.Free();
+
+            return dictionary;
+        }
+
         // NOTE: this method should do as little work as possible
         //       we often need to get members just to do a lookup.
         //       All additional checks and diagnostics may be not
@@ -1653,7 +1694,7 @@ static bool isMemberInCompleteMemberList(MembersAndInitializers? membersAndIniti
             }
         }
 
-        protected Dictionary<string, ImmutableArray<Symbol>> GetMembersByName()
+        protected Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> GetMembersByName()
         {
             if (this.state.HasComplete(CompletionPart.Members))
             {
@@ -1663,7 +1704,7 @@ protected Dictionary<string, ImmutableArray<Symbol>> GetMembersByName()
             return GetMembersByNameSlow();
         }
 
-        private Dictionary<string, ImmutableArray<Symbol>> GetMembersByNameSlow()
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> GetMembersByNameSlow()
         {
             if (_lazyMembersDictionary == null)
             {
@@ -1848,7 +1889,7 @@ private void CheckRecordMemberNames(BindingDiagnosticBag diagnostics)
 
         private void CheckMemberNameConflicts(BindingDiagnosticBag diagnostics)
         {
-            Dictionary<string, ImmutableArray<Symbol>> membersByName = GetMembersByName();
+            Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> membersByName = GetMembersByName();
 
             // Collisions involving indexers are handled specially.
             CheckIndexerNameConflicts(diagnostics, membersByName);
@@ -2082,7 +2123,7 @@ private void ReportMethodSignatureCollision(BindingDiagnosticBag diagnostics, So
             diagnostics.Add(ErrorCode.ERR_MemberAlreadyExists, method1.GetFirstLocation(), methodName, this);
         }
 
-        private void CheckIndexerNameConflicts(BindingDiagnosticBag diagnostics, Dictionary<string, ImmutableArray<Symbol>> membersByName)
+        private void CheckIndexerNameConflicts(BindingDiagnosticBag diagnostics, Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> membersByName)
         {
             PooledHashSet<string>? typeParameterNames = null;
             if (this.Arity > 0)
@@ -2135,7 +2176,7 @@ private void CheckIndexerNameConflicts(BindingDiagnosticBag diagnostics, Diction
         private void CheckIndexerSignatureCollisions(
             PropertySymbol indexer,
             BindingDiagnosticBag diagnostics,
-            Dictionary<string, ImmutableArray<Symbol>> membersByName,
+            Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> membersByName,
             Dictionary<PropertySymbol, PropertySymbol> indexersBySignature,
             ref string? lastIndexerName)
         {
@@ -2159,10 +2200,12 @@ private void CheckIndexerSignatureCollisions(
 
                 if (Locations.Length == 1 || IsPartial)
                 {
-                    if (membersByName.ContainsKey(indexerName))
+#pragma warning disable CA1854 //Prefer a 'TryGetValue' call over a Dictionary indexer access guarded by a 'ContainsKey' check to avoid double lookup
+                    if (membersByName.ContainsKey(indexerName.AsMemory()))
+#pragma warning restore CA1854
                     {
                         // The name of the indexer is reserved - it can only be used by other indexers.
-                        Debug.Assert(!membersByName[indexerName].Any(SymbolExtensions.IsIndexer));
+                        Debug.Assert(!membersByName[indexerName.AsMemory()].Any(SymbolExtensions.IsIndexer));
                         diagnostics.Add(ErrorCode.ERR_DuplicateNameInClass, indexer.GetFirstLocation(), this, indexerName);
                     }
                 }
@@ -2707,9 +2750,9 @@ private static bool ContainsModifier(SyntaxTokenList modifiers, SyntaxKind modif
             return false;
         }
 
-        private Dictionary<string, ImmutableArray<Symbol>> MakeAllMembers(BindingDiagnosticBag diagnostics)
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> MakeAllMembers(BindingDiagnosticBag diagnostics)
         {
-            Dictionary<string, ImmutableArray<Symbol>> membersByName;
+            Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> membersByName;
             var membersAndInitializers = GetMembersAndInitializers();
 
             // Most types don't have indexers.  If this is one of those types,
@@ -2721,7 +2764,7 @@ private Dictionary<string, ImmutableArray<Symbol>> MakeAllMembers(BindingDiagnos
             }
             else
             {
-                membersByName = membersAndInitializers.NonTypeMembers.ToDictionary(static s => s.Name);
+                membersByName = ToNameKeyedDictionary(membersAndInitializers.NonTypeMembers);
 
                 // Merge types into the member dictionary
                 AddNestedTypesToDictionary(membersByName, GetTypeMembersDictionary());
@@ -2732,12 +2775,12 @@ private Dictionary<string, ImmutableArray<Symbol>> MakeAllMembers(BindingDiagnos
             return membersByName;
         }
 
-        private static void AddNestedTypesToDictionary(Dictionary<string, ImmutableArray<Symbol>> membersByName, Dictionary<string, ImmutableArray<NamedTypeSymbol>> typesByName)
+        private static void AddNestedTypesToDictionary(
+            Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> membersByName,
+            Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>> typesByName)
         {
-            foreach (var pair in typesByName)
+            foreach ((ReadOnlyMemory<char> name, ImmutableArray<NamedTypeSymbol> types) in typesByName)
             {
-                string name = pair.Key;
-                ImmutableArray<NamedTypeSymbol> types = pair.Value;
                 ImmutableArray<Symbol> typesAsSymbols = StaticCast<Symbol>.From(types);
 
                 ImmutableArray<Symbol> membersForName;
@@ -3476,10 +3519,10 @@ internal Binder GetBinder(CSharpSyntaxNode syntaxNode)
         }
 
         private void MergePartialMembers(
-            ref Dictionary<string, ImmutableArray<Symbol>> membersByName,
+            ref Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>> membersByName,
             BindingDiagnosticBag diagnostics)
         {
-            var memberNames = ArrayBuilder<string>.GetInstance(membersByName.Count);
+            var memberNames = ArrayBuilder<ReadOnlyMemory<char>>.GetInstance(membersByName.Count);
             memberNames.AddRange(membersByName.Keys);
 
             //key and value will be the same object
@@ -3518,7 +3561,7 @@ private void MergePartialMembers(
                             if ((object)membersByName == _lazyEarlyAttributeDecodingMembersDictionary)
                             {
                                 // Avoid mutating the cached dictionary and especially avoid doing this possibly on multiple threads in parallel.
-                                membersByName = new Dictionary<string, ImmutableArray<Symbol>>(membersByName);
+                                membersByName = new Dictionary<ReadOnlyMemory<char>, ImmutableArray<Symbol>>(membersByName, ReadOnlyMemoryOfCharComparer.Instance);
                             }
 
                             membersByName[name] = FixPartialMember(membersByName[name], prevPart, methodPart);
@@ -4065,7 +4108,7 @@ void addDeconstruct(SynthesizedPrimaryConstructor ctor, ImmutableArray<Symbol> p
 
                 if (!memberSignatures.TryGetValue(targetMethod, out Symbol? existingDeconstructMethod))
                 {
-                    members.Add(new SynthesizedRecordDeconstruct(this, ctor, positionalMembers, memberOffset: members.Count, diagnostics));
+                    members.Add(new SynthesizedRecordDeconstruct(this, ctor, positionalMembers, memberOffset: members.Count));
                 }
                 else
                 {
@@ -4134,7 +4177,7 @@ void addCopyCtor(bool primaryAndCopyCtorAmbiguity)
             void addCloneMethod()
             {
                 Debug.Assert(isRecordClass);
-                members.Add(new SynthesizedRecordClone(this, memberOffset: members.Count, diagnostics));
+                members.Add(new SynthesizedRecordClone(this, memberOffset: members.Count));
             }
 
             MethodSymbol addPrintMembersMethod(IEnumerable<Symbol> userDefinedMembers)
@@ -4160,7 +4203,7 @@ MethodSymbol addPrintMembersMethod(IEnumerable<Symbol> userDefinedMembers)
                 MethodSymbol printMembersMethod;
                 if (!memberSignatures.TryGetValue(targetMethod, out Symbol? existingPrintMembersMethod))
                 {
-                    printMembersMethod = new SynthesizedRecordPrintMembers(this, userDefinedMembers, memberOffset: members.Count, diagnostics);
+                    printMembersMethod = new SynthesizedRecordPrintMembers(this, userDefinedMembers, memberOffset: members.Count);
                     members.Add(printMembersMethod);
                 }
                 else
@@ -4234,9 +4277,7 @@ void addToStringMethod(MethodSymbol printMethod)
                         var toStringMethod = new SynthesizedRecordToString(
                             this,
                             printMethod,
-                            memberOffset: members.Count,
-                            isReadOnly: printMethod.IsEffectivelyReadOnly,
-                            diagnostics);
+                            memberOffset: members.Count);
                         members.Add(toStringMethod);
                     }
                     else
@@ -4356,7 +4397,7 @@ void addProperty(SynthesizedRecordPropertySymbol property)
 
                 bool checkMemberNotHidden(Symbol symbol, ParameterSymbol param)
                 {
-                    if (memberNames.Contains(symbol.Name) || this.GetTypeMembersDictionary().ContainsKey(symbol.Name))
+                    if (memberNames.Contains(symbol.Name) || this.GetTypeMembersDictionary().ContainsKey(symbol.Name.AsMemory()))
                     {
                         diagnostics.Add(ErrorCode.ERR_HiddenPositionalMember, param.GetFirstLocation(), symbol);
                         return false;
@@ -4367,7 +4408,7 @@ bool checkMemberNotHidden(Symbol symbol, ParameterSymbol param)
 
             void addObjectEquals(MethodSymbol thisEquals)
             {
-                members.Add(new SynthesizedRecordObjEquals(this, thisEquals, memberOffset: members.Count, diagnostics));
+                members.Add(new SynthesizedRecordObjEquals(this, thisEquals, memberOffset: members.Count));
             }
 
             MethodSymbol addGetHashCode(PropertySymbol? equalityContract)
@@ -4390,7 +4431,7 @@ MethodSymbol addGetHashCode(PropertySymbol? equalityContract)
 
                 if (!memberSignatures.TryGetValue(targetMethod, out Symbol? existingHashCodeMethod))
                 {
-                    getHashCode = new SynthesizedRecordGetHashCode(this, equalityContract, memberOffset: members.Count, diagnostics);
+                    getHashCode = new SynthesizedRecordGetHashCode(this, equalityContract, memberOffset: members.Count);
                     members.Add(getHashCode);
                 }
                 else
@@ -4488,7 +4529,7 @@ MethodSymbol addThisEquals(PropertySymbol? equalityContract)
 
                 if (!memberSignatures.TryGetValue(targetMethod, out Symbol? existingEqualsMethod))
                 {
-                    thisEquals = new SynthesizedRecordEquals(this, equalityContract, memberOffset: members.Count, diagnostics);
+                    thisEquals = new SynthesizedRecordEquals(this, equalityContract, memberOffset: members.Count);
                     members.Add(thisEquals);
                 }
                 else
@@ -4530,7 +4571,7 @@ void addBaseEquals()
                 Debug.Assert(isRecordClass);
                 if (!BaseTypeNoUseSiteDiagnostics.IsObjectType())
                 {
-                    members.Add(new SynthesizedRecordBaseEquals(this, memberOffset: members.Count, diagnostics));
+                    members.Add(new SynthesizedRecordBaseEquals(this, memberOffset: members.Count));
                 }
             }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberMethodSymbol.cs
index 7cd2ddded6a85..ada267b439872 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberMethodSymbol.cs
@@ -171,9 +171,9 @@ public Flags(
                 bool isExtensionMethod,
                 bool isNullableAnalysisEnabled,
                 bool isVararg,
-                bool isMetadataVirtualIgnoringModifiers = false)
+                bool isExplicitInterfaceImplementation)
             {
-                bool isMetadataVirtual = isMetadataVirtualIgnoringModifiers || ModifiersRequireMetadataVirtual(declarationModifiers);
+                bool isMetadataVirtual = (isExplicitInterfaceImplementation && (declarationModifiers & DeclarationModifiers.Static) == 0) || ModifiersRequireMetadataVirtual(declarationModifiers);
 
                 int methodKindInt = ((int)methodKind & MethodKindMask) << MethodKindOffset;
                 int refKindInt = ((int)refKind & RefKindMask) << RefKindOffset;
@@ -198,6 +198,29 @@ public Flags(
                     | ReturnsVoidIsSetBit;
             }
 
+            public Flags(
+                MethodKind methodKind,
+                RefKind refKind,
+                DeclarationModifiers declarationModifiers,
+                bool returnsVoid,
+                bool isExpressionBodied,
+                bool isExtensionMethod,
+                bool isNullableAnalysisEnabled,
+                bool isVararg,
+                bool isExplicitInterfaceImplementation)
+                : this(methodKind,
+                       refKind,
+                       declarationModifiers,
+                       returnsVoid: returnsVoid,
+                       hasAnyBody: false,
+                       isExpressionBodied: isExpressionBodied,
+                       isExtensionMethod: isExtensionMethod,
+                       isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                       isVararg: isVararg,
+                       isExplicitInterfaceImplementation: isExplicitInterfaceImplementation)
+            {
+            }
+
             public bool IsMetadataVirtual(bool ignoreInterfaceImplementationChanges = false)
             {
                 // This flag is immutable, so there's no reason to set a lock bit, as we do below.
@@ -241,7 +264,7 @@ public bool SetNullableContext(byte? value)
 
         protected SymbolCompletionState state;
 
-        protected DeclarationModifiers DeclarationModifiers;
+        protected readonly DeclarationModifiers DeclarationModifiers;
         protected Flags flags;
 
         private readonly NamedTypeSymbol _containingType;
@@ -273,7 +296,8 @@ protected SourceMemberMethodSymbol(
             NamedTypeSymbol containingType,
             SyntaxReference syntaxReferenceOpt,
             Location location,
-            bool isIterator)
+            bool isIterator,
+            (DeclarationModifiers declarationModifiers, Flags flags) modifiersAndFlags)
             : base(syntaxReferenceOpt, isIterator)
         {
             Debug.Assert(containingType is not null);
@@ -282,6 +306,8 @@ protected SourceMemberMethodSymbol(
 
             _containingType = containingType;
             _location = location;
+            DeclarationModifiers = modifiersAndFlags.declarationModifiers;
+            flags = modifiersAndFlags.flags;
         }
 
         protected void CheckEffectiveAccessibility(TypeWithAnnotations returnType, ImmutableArray<ParameterSymbol> parameters, BindingDiagnosticBag diagnostics)
@@ -339,20 +365,18 @@ protected void CheckFileTypeUsage(TypeWithAnnotations returnType, ImmutableArray
             }
         }
 
-        protected void MakeFlags(
+        protected static Flags MakeFlags(
             MethodKind methodKind,
             RefKind refKind,
             DeclarationModifiers declarationModifiers,
             bool returnsVoid,
-            bool hasAnyBody,
             bool isExpressionBodied,
             bool isExtensionMethod,
             bool isNullableAnalysisEnabled,
             bool isVarArg,
-            bool isMetadataVirtualIgnoringModifiers = false)
+            bool isExplicitInterfaceImplementation)
         {
-            DeclarationModifiers = declarationModifiers;
-            this.flags = new Flags(methodKind, refKind, declarationModifiers, returnsVoid, hasAnyBody, isExpressionBodied, isExtensionMethod, isNullableAnalysisEnabled, isVarArg, isMetadataVirtualIgnoringModifiers);
+            return new Flags(methodKind, refKind, declarationModifiers, returnsVoid, isExpressionBodied, isExtensionMethod, isNullableAnalysisEnabled, isVarArg, isExplicitInterfaceImplementation);
         }
 
         protected void SetReturnsVoid(bool returnsVoid)
@@ -1059,7 +1083,6 @@ protected void CheckFeatureAvailabilityAndRuntimeSupport(SyntaxNode declarationS
         /// present, this is not treated as expression-bodied.
         /// </remarks>
         internal bool IsExpressionBodied => flags.IsExpressionBodied;
-        protected bool HasAnyBody => flags.HasAnyBody;
 
         public sealed override RefKind RefKind => this.flags.RefKind;
         public sealed override bool IsVararg => this.flags.IsVararg;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceMethodSymbolWithAttributes.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceMethodSymbolWithAttributes.cs
index 79f805093c5a8..536e2438d971f 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceMethodSymbolWithAttributes.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceMethodSymbolWithAttributes.cs
@@ -13,6 +13,7 @@
 using System.Threading;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Shared.Collections;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.Symbols
@@ -596,6 +597,10 @@ private void DecodeWellKnownAttributeAppliedToMethod(ref DecodeWellKnownAttribut
                     diagnostics.Add(ErrorCode.ERR_UnscopedRefAttributeUnsupportedMemberTarget, arguments.AttributeSyntaxOpt.Location);
                 }
             }
+            else if (attribute.IsTargetAttribute(this, AttributeDescription.InterceptsLocationAttribute))
+            {
+                DecodeInterceptsLocationAttribute(arguments);
+            }
             else
             {
                 var compilation = this.DeclaringCompilation;
@@ -934,6 +939,174 @@ private void DecodeModuleInitializerAttribute(DecodeWellKnownAttributeArguments<
             }
         }
 
+        private void DecodeInterceptsLocationAttribute(DecodeWellKnownAttributeArguments<AttributeSyntax, CSharpAttributeData, AttributeLocation> arguments)
+        {
+            Debug.Assert(arguments.AttributeSyntaxOpt is object);
+            Debug.Assert(!arguments.Attribute.HasErrors);
+            var attributeData = arguments.Attribute;
+            var attributeArguments = attributeData.CommonConstructorArguments;
+            if (attributeArguments is not [
+                { Type.SpecialType: SpecialType.System_String },
+                { Kind: not TypedConstantKind.Array, Value: int lineNumberOneBased },
+                { Kind: not TypedConstantKind.Array, Value: int characterNumberOneBased }])
+            {
+                // Since the attribute does not have errors (asserted above), it should be guaranteed that we have the above arguments.
+                throw ExceptionUtilities.Unreachable();
+            }
+
+            var diagnostics = (BindingDiagnosticBag)arguments.Diagnostics;
+            var attributeSyntax = arguments.AttributeSyntaxOpt;
+            var attributeLocation = attributeSyntax.Location;
+            const int filePathParameterIndex = 0;
+            const int lineNumberParameterIndex = 1;
+            const int characterNumberParameterIndex = 2;
+
+            if (!attributeSyntax.SyntaxTree.Options.Features.ContainsKey("InterceptorsPreview"))
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorsFeatureNotEnabled, attributeSyntax);
+                return;
+            }
+
+            var attributeFilePath = (string?)attributeArguments[0].Value;
+            if (attributeFilePath is null)
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorFilePathCannotBeNull, attributeData.GetAttributeArgumentSyntaxLocation(filePathParameterIndex, attributeSyntax));
+                return;
+            }
+
+            if (Arity != 0 || ContainingType.IsGenericType)
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorCannotBeGeneric, attributeLocation, this);
+                return;
+            }
+
+            if (MethodKind != MethodKind.Ordinary)
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorMethodMustBeOrdinary, attributeLocation);
+                return;
+            }
+
+            Debug.Assert(_lazyCustomAttributesBag.IsEarlyDecodedWellKnownAttributeDataComputed);
+            var unmanagedCallersOnly = this.GetUnmanagedCallersOnlyAttributeData(forceComplete: false);
+            if (unmanagedCallersOnly != null)
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorCannotUseUnmanagedCallersOnly, attributeLocation);
+                return;
+            }
+
+            var syntaxTrees = DeclaringCompilation.SyntaxTrees;
+            var matchingTrees = DeclaringCompilation.GetSyntaxTreesByMappedPath(attributeFilePath);
+            if (matchingTrees.Count == 0)
+            {
+                var referenceResolver = DeclaringCompilation.Options.SourceReferenceResolver;
+                // if we expect '/_/Program.cs':
+
+                // we might get: 'C:\Project\Program.cs' <-- path not mapped
+                var unmappedMatch = syntaxTrees.FirstOrDefault(static (tree, filePath) => tree.FilePath == filePath, attributeFilePath);
+                if (unmappedMatch != null)
+                {
+                    diagnostics.Add(
+                        ErrorCode.ERR_InterceptorPathNotInCompilationWithUnmappedCandidate,
+                        attributeData.GetAttributeArgumentSyntaxLocation(filePathParameterIndex, attributeSyntax),
+                        attributeFilePath,
+                        mapPath(referenceResolver, unmappedMatch));
+                    return;
+                }
+
+                // we might get: '\_\Program.cs' <-- slashes not normalized
+                // we might get: '\_/Program.cs' <-- slashes don't match
+                // we might get: 'Program.cs' <-- suffix match
+                // Force normalization of all '\' to '/', but when we recommend a path in the diagnostic message, ensure it will match what we expect if the user decides to use it.
+                var suffixMatch = syntaxTrees.FirstOrDefault(static (tree, pair)
+                    => mapPath(pair.referenceResolver, tree)
+                        .Replace('\\', '/')
+                        .EndsWith(pair.attributeFilePath),
+                    (referenceResolver, attributeFilePath: attributeFilePath.Replace('\\', '/')));
+                if (suffixMatch != null)
+                {
+                    diagnostics.Add(
+                        ErrorCode.ERR_InterceptorPathNotInCompilationWithCandidate,
+                        attributeData.GetAttributeArgumentSyntaxLocation(filePathParameterIndex, attributeSyntax),
+                        attributeFilePath,
+                        mapPath(referenceResolver, suffixMatch));
+                    return;
+                }
+
+                diagnostics.Add(ErrorCode.ERR_InterceptorPathNotInCompilation, attributeData.GetAttributeArgumentSyntaxLocation(filePathParameterIndex, attributeSyntax), attributeFilePath);
+
+                return;
+            }
+            else if (matchingTrees.Count > 1)
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorNonUniquePath, attributeData.GetAttributeArgumentSyntaxLocation(filePathParameterIndex, attributeSyntax), attributeFilePath);
+                return;
+            }
+
+            SyntaxTree? matchingTree = matchingTrees[0];
+            // Internally, line and character numbers are 0-indexed, but when they appear in code or diagnostic messages, they are 1-indexed.
+            int lineNumberZeroBased = lineNumberOneBased - 1;
+            int characterNumberZeroBased = characterNumberOneBased - 1;
+
+            if (lineNumberZeroBased < 0 || characterNumberZeroBased < 0)
+            {
+                var location = attributeData.GetAttributeArgumentSyntaxLocation(lineNumberZeroBased < 0 ? lineNumberParameterIndex : characterNumberParameterIndex, attributeSyntax);
+                diagnostics.Add(ErrorCode.ERR_InterceptorLineCharacterMustBePositive, location);
+                return;
+            }
+
+            var referencedLines = matchingTree.GetText().Lines;
+            var referencedLineCount = referencedLines.Count;
+
+            if (lineNumberZeroBased >= referencedLineCount)
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorLineOutOfRange, attributeData.GetAttributeArgumentSyntaxLocation(lineNumberParameterIndex, attributeSyntax), referencedLineCount, lineNumberOneBased);
+                return;
+            }
+
+            var line = referencedLines[lineNumberZeroBased];
+            var lineLength = line.End - line.Start;
+            if (characterNumberZeroBased >= lineLength)
+            {
+                diagnostics.Add(ErrorCode.ERR_InterceptorCharacterOutOfRange, attributeData.GetAttributeArgumentSyntaxLocation(characterNumberParameterIndex, attributeSyntax), lineLength, characterNumberOneBased);
+                return;
+            }
+
+            var referencedPosition = line.Start + characterNumberZeroBased;
+            var root = matchingTree.GetRoot();
+            var referencedToken = root.FindToken(referencedPosition);
+            switch (referencedToken)
+            {
+                case { Parent: SimpleNameSyntax { Parent: MemberAccessExpressionSyntax { Parent: InvocationExpressionSyntax } memberAccess } rhs } when memberAccess.Name == rhs:
+                case { Parent: SimpleNameSyntax { Parent: InvocationExpressionSyntax invocation } simpleName } when invocation.Expression == simpleName:
+                    // happy case
+                    break;
+                case { Parent: SimpleNameSyntax { Parent: not MemberAccessExpressionSyntax } }:
+                case { Parent: SimpleNameSyntax { Parent: MemberAccessExpressionSyntax memberAccess } rhs } when memberAccess.Name == rhs:
+                    // NB: there are all sorts of places "simple names" can appear in syntax. With these checks we are trying to
+                    // minimize confusion about why the name being used is not *interceptable*, but it's done on a best-effort basis.
+                    diagnostics.Add(ErrorCode.ERR_InterceptorNameNotInvoked, attributeLocation, referencedToken.Text);
+                    return;
+                default:
+                    diagnostics.Add(ErrorCode.ERR_InterceptorPositionBadToken, attributeLocation, referencedToken.Text);
+                    return;
+            }
+
+            // Did they actually refer to the start of the token, not the middle, or in trivia?
+            if (referencedPosition != referencedToken.Span.Start)
+            {
+                var linePositionZeroBased = referencedToken.GetLocation().GetLineSpan().StartLinePosition;
+                diagnostics.Add(ErrorCode.ERR_InterceptorMustReferToStartOfTokenPosition, attributeLocation, referencedToken.Text, linePositionZeroBased.Line + 1, linePositionZeroBased.Character + 1);
+                return;
+            }
+
+            DeclaringCompilation.AddInterception(matchingTree.FilePath, lineNumberZeroBased, characterNumberZeroBased, attributeLocation, this);
+
+            static string mapPath(SourceReferenceResolver? referenceResolver, SyntaxTree tree)
+            {
+                return referenceResolver?.NormalizePath(tree.FilePath, baseFilePath: null) ?? tree.FilePath;
+            }
+        }
+
         private void DecodeUnmanagedCallersOnlyAttribute(ref DecodeWellKnownAttributeArguments<AttributeSyntax, CSharpAttributeData, AttributeLocation> arguments)
         {
             Debug.Assert(arguments.AttributeSyntaxOpt != null);
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamedTypeSymbol.cs
index e3029c48fcb94..2662c918f132a 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamedTypeSymbol.cs
@@ -1003,6 +1003,24 @@ internal override (CSharpAttributeData?, BoundAttribute?) EarlyDecodeWellKnownAt
                 return (null, null);
             }
 
+            if (CSharpAttributeData.IsTargetEarlyAttribute(arguments.AttributeType, arguments.AttributeSyntax, AttributeDescription.InlineArrayAttribute))
+            {
+                (attributeData, boundAttribute) = arguments.Binder.GetAttribute(arguments.AttributeSyntax, arguments.AttributeType, beforeAttributePartBound: null, afterAttributePartBound: null, out hasAnyDiagnostics);
+                if (!attributeData.HasErrors)
+                {
+                    int length = attributeData.GetConstructorArgument<int>(0, SpecialType.System_Int32);
+
+                    arguments.GetOrCreateData<TypeEarlyWellKnownAttributeData>().InlineArrayLength = length > 0 ? length : -1;
+
+                    if (!hasAnyDiagnostics)
+                    {
+                        return (attributeData, boundAttribute);
+                    }
+                }
+
+                return (null, null);
+            }
+
             return base.EarlyDecodeWellKnownAttribute(ref arguments);
         }
 #nullable disable
@@ -1140,6 +1158,20 @@ protected sealed override void DecodeWellKnownAttributeImpl(ref DecodeWellKnownA
             {
                 _lazyIsExplicitDefinitionOfNoPiaLocalType = ThreeState.True;
             }
+            else if (attribute.IsTargetAttribute(this, AttributeDescription.InlineArrayAttribute))
+            {
+                int length = attribute.CommonConstructorArguments[0].DecodeValue<int>(SpecialType.System_Int32);
+
+                if (length <= 0)
+                {
+                    diagnostics.Add(ErrorCode.ERR_InvalidInlineArrayLength, attribute.GetAttributeArgumentSyntaxLocation(0, arguments.AttributeSyntaxOpt));
+                }
+
+                if (TypeKind != TypeKind.Struct)
+                {
+                    diagnostics.Add(ErrorCode.ERR_AttributeOnBadSymbolType, arguments.AttributeSyntaxOpt.Name.Location, arguments.AttributeSyntaxOpt.GetErrorDisplayName(), "struct");
+                }
+            }
             else
             {
                 var compilation = this.DeclaringCompilation;
@@ -1538,6 +1570,19 @@ internal override void PostDecodeWellKnownAttributes(ImmutableArray<CSharpAttrib
             base.PostDecodeWellKnownAttributes(boundAttributes, allAttributeSyntaxNodes, diagnostics, symbolPart, decodedData);
         }
 
+        internal override bool HasInlineArrayAttribute(out int length)
+        {
+            TypeEarlyWellKnownAttributeData data = this.GetEarlyDecodedWellKnownAttributeData();
+            if (data?.InlineArrayLength is > 0 and var lengthFromAttribute)
+            {
+                length = lengthFromAttribute;
+                return true;
+            }
+
+            length = 0;
+            return false;
+        }
+
         /// <remarks>
         /// These won't be returned by GetAttributes on source methods, but they
         /// will be returned by GetAttributes on metadata symbols.
@@ -1699,6 +1744,24 @@ protected override void AfterMembersCompletedChecks(BindingDiagnosticBag diagnos
                     diagnostics.Add(ErrorCode.WRN_ObsoleteMembersShouldNotBeRequired, member.GetFirstLocation(), member);
                 }
             }
+
+            if (TypeKind == TypeKind.Struct && HasInlineArrayAttribute(out _))
+            {
+                if (Layout.Kind == LayoutKind.Explicit)
+                {
+                    diagnostics.Add(ErrorCode.ERR_InvalidInlineArrayLayout, GetFirstLocation());
+                }
+
+                if (TryGetInlineArrayElementField() is null)
+                {
+                    diagnostics.Add(ErrorCode.ERR_InvalidInlineArrayFields, GetFirstLocation());
+                }
+
+                if (!ContainingAssembly.RuntimeSupportsInlineArrayTypes)
+                {
+                    diagnostics.Add(ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, GetFirstLocation());
+                }
+            }
         }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.AliasesAndUsings.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.AliasesAndUsings.cs
index bdc398d4ddf93..da43dd8d6e7f3 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.AliasesAndUsings.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.AliasesAndUsings.cs
@@ -764,6 +764,7 @@ UsingsAndDiagnostics buildUsings(
 
                             declarationBinder ??= compilation.GetBinderFactory(declarationSyntax.SyntaxTree).GetBinder(usingDirective.NamespaceOrType).WithAdditionalFlags(flags);
                             var imported = declarationBinder.BindNamespaceOrTypeSymbol(usingDirective.NamespaceOrType, directiveDiagnostics, basesBeingResolved).NamespaceOrTypeSymbol;
+                            bool addDirectiveDiagnostics = true;
 
                             if (imported.Kind == SymbolKind.Namespace)
                             {
@@ -814,6 +815,15 @@ UsingsAndDiagnostics buildUsings(
                                     }
                                 }
                             }
+                            else if (imported.Kind is SymbolKind.ArrayType or SymbolKind.PointerType or SymbolKind.FunctionPointerType or SymbolKind.DynamicType)
+                            {
+                                diagnostics.Add(ErrorCode.ERR_BadUsingStaticType, usingDirective.NamespaceOrType.Location, imported.GetKindText());
+
+                                // Don't bother adding sub diagnostics (like that an unsafe type was referenced).  The
+                                // primary thing we want to report is simply that the using-static points to something
+                                // entirely invalid.
+                                addDirectiveDiagnostics = false;
+                            }
                             else if (imported.Kind != SymbolKind.ErrorType)
                             {
                                 // Do not report additional error if the symbol itself is erroneous.
@@ -825,7 +835,11 @@ UsingsAndDiagnostics buildUsings(
                                     MessageID.IDS_SK_TYPE_OR_NAMESPACE.Localize());
                             }
 
-                            diagnostics.AddRange(directiveDiagnostics.DiagnosticBag);
+                            if (addDirectiveDiagnostics)
+                            {
+                                diagnostics.AddRange(directiveDiagnostics.DiagnosticBag);
+                            }
+
                             directiveDiagnostics.Free();
                         }
                     }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.cs
index e4c2c7a2a0e63..1dca5c384c1f8 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.cs
@@ -28,8 +28,8 @@ internal sealed partial class SourceNamespaceSymbol : NamespaceSymbol
 
         private SymbolCompletionState _state;
         private ImmutableArray<Location> _locations;
-        private Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>> _nameToMembersMap;
-        private Dictionary<string, ImmutableArray<NamedTypeSymbol>> _nameToTypeMembersMap;
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamespaceOrTypeSymbol>> _nameToMembersMap;
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>> _nameToTypeMembersMap;
         private ImmutableArray<Symbol> _lazyAllMembers;
         private ImmutableArray<NamedTypeSymbol> _lazyTypeMembersUnordered;
 
@@ -166,7 +166,7 @@ public override ImmutableArray<Symbol> GetMembers()
             }
         }
 
-        public override ImmutableArray<Symbol> GetMembers(string name)
+        public override ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name)
         {
             ImmutableArray<NamespaceOrTypeSymbol> members;
             return this.GetNameToMembersMap().TryGetValue(name, out members)
@@ -190,7 +190,7 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return this.GetNameToTypeMembersMap().Flatten(LexicalOrderSymbolComparer.Instance);
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             ImmutableArray<NamedTypeSymbol> members;
             return this.GetNameToTypeMembersMap().TryGetValue(name, out members)
@@ -198,7 +198,7 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
                 : ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return GetTypeMembers(name).WhereAsArray((s, arity) => s.Arity == arity, arity);
         }
@@ -219,7 +219,7 @@ internal override NamespaceExtent Extent
             }
         }
 
-        private Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>> GetNameToMembersMap()
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamespaceOrTypeSymbol>> GetNameToMembersMap()
         {
             if (_nameToMembersMap == null)
             {
@@ -243,7 +243,7 @@ private Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>> GetNameToMembe
             return _nameToMembersMap;
         }
 
-        private Dictionary<string, ImmutableArray<NamedTypeSymbol>> GetNameToTypeMembersMap()
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamedTypeSymbol>> GetNameToTypeMembersMap()
         {
             if (_nameToTypeMembersMap == null)
             {
@@ -251,14 +251,15 @@ private Dictionary<string, ImmutableArray<NamedTypeSymbol>> GetNameToTypeMembers
                 // NOTE: type of the array, see comments in MakeNameToMembersMap() for details
                 Interlocked.CompareExchange(
                     ref _nameToTypeMembersMap,
-                    ImmutableArrayExtensions.GetTypesFromMemberMap<NamespaceOrTypeSymbol, NamedTypeSymbol>(GetNameToMembersMap(), StringOrdinalComparer.Instance),
+                    ImmutableArrayExtensions.GetTypesFromMemberMap<ReadOnlyMemory<char>, NamespaceOrTypeSymbol, NamedTypeSymbol>(
+                        GetNameToMembersMap(), ReadOnlyMemoryOfCharComparer.Instance),
                     comparand: null);
             }
 
             return _nameToTypeMembersMap;
         }
 
-        private Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>> MakeNameToMembersMap(BindingDiagnosticBag diagnostics)
+        private Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamespaceOrTypeSymbol>> MakeNameToMembersMap(BindingDiagnosticBag diagnostics)
         {
             // NOTE: Even though the resulting map stores ImmutableArray<NamespaceOrTypeSymbol> as
             // NOTE: values if the name is mapped into an array of named types, which is frequently
@@ -269,15 +270,15 @@ private Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>> MakeNameToMemb
             // NOTE: a name maps into values collection containing types only instead of allocating another
             // NOTE: array of NamedTypeSymbol[] we downcast the array to ImmutableArray<NamedTypeSymbol>
 
-            var builder = PooledDictionary<string, object>.GetInstance();
+            var builder = s_nameToObjectPool.Allocate();
             foreach (var declaration in _mergedDeclaration.Children)
             {
                 NamespaceOrTypeSymbol symbol = BuildSymbol(declaration, diagnostics);
-                ImmutableArrayExtensions.AddToMultiValueDictionaryBuilder(builder, symbol.Name, symbol);
+                ImmutableArrayExtensions.AddToMultiValueDictionaryBuilder(builder, symbol.Name.AsMemory(), symbol);
             }
 
-            var result = new Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>>(builder.Count);
-            ImmutableArrayExtensions.CreateNameToMembersMap<NamespaceOrTypeSymbol, NamedTypeSymbol, NamespaceSymbol>(builder, result);
+            var result = new Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamespaceOrTypeSymbol>>(builder.Count, ReadOnlyMemoryOfCharComparer.Instance);
+            ImmutableArrayExtensions.CreateNameToMembersMap<ReadOnlyMemory<char>, NamespaceOrTypeSymbol, NamedTypeSymbol, NamespaceSymbol>(builder, result);
             builder.Free();
 
             CheckMembers(this, result, diagnostics);
@@ -285,7 +286,7 @@ private Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>> MakeNameToMemb
             return result;
         }
 
-        private static void CheckMembers(NamespaceSymbol @namespace, Dictionary<string, ImmutableArray<NamespaceOrTypeSymbol>> result, BindingDiagnosticBag diagnostics)
+        private static void CheckMembers(NamespaceSymbol @namespace, Dictionary<ReadOnlyMemory<char>, ImmutableArray<NamespaceOrTypeSymbol>> result, BindingDiagnosticBag diagnostics)
         {
             var memberOfArity = new Symbol[10];
             MergedNamespaceSymbol mergedAssemblyNamespace = null;
@@ -300,7 +301,10 @@ private static void CheckMembers(NamespaceSymbol @namespace, Dictionary<string,
                 Array.Clear(memberOfArity, 0, memberOfArity.Length);
                 foreach (var symbol in result[name])
                 {
-                    var nts = symbol as NamedTypeSymbol;
+                    var nts = symbol as SourceMemberContainerTypeSymbol;
+                    // It should be impossible to have a type member of a source namespace symbol which is not a SourceMemberContainerTypeSymbol
+                    Debug.Assert((object)nts != null || symbol is not TypeSymbol);
+
                     var arity = ((object)nts != null) ? nts.Arity : 0;
                     if (arity >= memberOfArity.Length)
                     {
@@ -335,19 +339,22 @@ private static void CheckMembers(NamespaceSymbol @namespace, Dictionary<string,
 
                     if ((object)other != null)
                     {
+                        // To decide whether type declarations are duplicates, we need to access members which are only meaningful on source original definition symbols.
+                        Debug.Assert((object)nts?.OriginalDefinition == nts && (object)other.OriginalDefinition == other);
+
                         switch (nts, other)
                         {
-                            case (SourceNamedTypeSymbol left, SourceNamedTypeSymbol right) when isFileLocalTypeInSeparateFileFrom(left, right) || isFileLocalTypeInSeparateFileFrom(right, left):
+                            case ({ } left, SourceMemberContainerTypeSymbol right) when isFileLocalTypeInSeparateFileFrom(left, right) || isFileLocalTypeInSeparateFileFrom(right, left):
                                 // no error
                                 break;
-                            case (SourceNamedTypeSymbol { IsFileLocal: true }, _) or (_, SourceNamedTypeSymbol { IsFileLocal: true }):
-                                diagnostics.Add(ErrorCode.ERR_FileLocalDuplicateNameInNS, symbol.GetFirstLocationOrNone(), name, @namespace);
+                            case ({ IsFileLocal: true }, _) or (_, SourceMemberContainerTypeSymbol { IsFileLocal: true }):
+                                diagnostics.Add(ErrorCode.ERR_FileLocalDuplicateNameInNS, symbol.GetFirstLocationOrNone(), symbol.Name, @namespace);
                                 break;
-                            case (SourceNamedTypeSymbol { IsPartial: true }, SourceNamedTypeSymbol { IsPartial: true }):
+                            case ({ IsPartial: true }, SourceMemberContainerTypeSymbol { IsPartial: true }):
                                 diagnostics.Add(ErrorCode.ERR_PartialTypeKindConflict, symbol.GetFirstLocationOrNone(), symbol);
                                 break;
                             default:
-                                diagnostics.Add(ErrorCode.ERR_DuplicateNameInNS, symbol.GetFirstLocationOrNone(), name, @namespace);
+                                diagnostics.Add(ErrorCode.ERR_DuplicateNameInNS, symbol.GetFirstLocationOrNone(), symbol.Name, @namespace);
                                 break;
                         }
                     }
@@ -366,7 +373,7 @@ private static void CheckMembers(NamespaceSymbol @namespace, Dictionary<string,
                 }
             }
 
-            static bool isFileLocalTypeInSeparateFileFrom(SourceNamedTypeSymbol possibleFileLocalType, SourceNamedTypeSymbol otherSymbol)
+            static bool isFileLocalTypeInSeparateFileFrom(SourceMemberContainerTypeSymbol possibleFileLocalType, SourceMemberContainerTypeSymbol otherSymbol)
             {
                 if (!possibleFileLocalType.IsFileLocal)
                 {
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodOrUserDefinedOperatorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodOrUserDefinedOperatorSymbol.cs
index d52af621917fc..2e61931ddf8e2 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodOrUserDefinedOperatorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodOrUserDefinedOperatorSymbol.cs
@@ -21,8 +21,8 @@ internal abstract class SourceOrdinaryMethodOrUserDefinedOperatorSymbol : Source
         private ImmutableArray<ParameterSymbol> _lazyParameters;
         private TypeWithAnnotations _lazyReturnType;
 
-        protected SourceOrdinaryMethodOrUserDefinedOperatorSymbol(NamedTypeSymbol containingType, SyntaxReference syntaxReferenceOpt, Location location, bool isIterator)
-            : base(containingType, syntaxReferenceOpt, location, isIterator)
+        protected SourceOrdinaryMethodOrUserDefinedOperatorSymbol(NamedTypeSymbol containingType, SyntaxReference syntaxReferenceOpt, Location location, bool isIterator, (DeclarationModifiers declarationModifiers, Flags flags) modifiersAndFlags)
+            : base(containingType, syntaxReferenceOpt, location, isIterator, modifiersAndFlags)
         {
         }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs
index 303302cfead8f..d65c1687f6472 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs
@@ -55,21 +55,25 @@ private SourceOrdinaryMethodSymbol(
                  name,
                  location,
                  syntax,
-                 methodKind,
-                 refKind: syntax.ReturnType.SkipScoped(out _).GetRefKindInLocalOrReturn(diagnostics),
                  isIterator: SyntaxFacts.HasYieldOperations(syntax.Body),
-                 isExtensionMethod: syntax.ParameterList.Parameters.FirstOrDefault() is ParameterSyntax firstParam &&
-                                    !firstParam.IsArgList &&
-                                    firstParam.Modifiers.Any(SyntaxKind.ThisKeyword),
-                 isReadOnly: false,
-                 hasAnyBody: syntax.Body != null || syntax.ExpressionBody != null,
-                 isExpressionBodied: syntax is { Body: null, ExpressionBody: not null },
-                 isNullableAnalysisEnabled: isNullableAnalysisEnabled,
-                 isVarArg: syntax.ParameterList.Parameters.Any(p => p.IsArgList),
-                 diagnostics)
+                 MakeModifiersAndFlags(containingType, location, syntax, methodKind, isNullableAnalysisEnabled, diagnostics, out bool hasExplicitAccessMod))
         {
             Debug.Assert(diagnostics.DiagnosticBag is object);
 
+            this.CheckUnsafeModifier(DeclarationModifiers, diagnostics);
+
+            HasExplicitAccessModifier = hasExplicitAccessMod;
+            bool hasAnyBody = syntax.HasAnyBody();
+
+            CheckFeatureAvailabilityAndRuntimeSupport(syntax, location, hasAnyBody, diagnostics);
+
+            if (hasAnyBody)
+            {
+                CheckModifiersForBody(location, diagnostics);
+            }
+
+            ModifierUtils.CheckAccessibility(this.DeclarationModifiers, this, isExplicitInterfaceImplementation: methodKind == MethodKind.ExplicitInterfaceImplementation, diagnostics, location);
+
             Debug.Assert(syntax.ReturnType is not ScopedTypeSyntax);
 
             if (syntax.Arity == 0)
@@ -81,7 +85,44 @@ private SourceOrdinaryMethodSymbol(
                 syntax.Body, syntax.ExpressionBody, syntax, diagnostics);
         }
 
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
+        private static (DeclarationModifiers, Flags) MakeModifiersAndFlags(
+            NamedTypeSymbol containingType, Location location, MethodDeclarationSyntax syntax, MethodKind methodKind,
+            bool isNullableAnalysisEnabled, BindingDiagnosticBag diagnostics, out bool hasExplicitAccessMod)
+        {
+            (DeclarationModifiers declarationModifiers, hasExplicitAccessMod) = MakeModifiers(syntax, containingType, methodKind, hasBody: syntax.HasAnyBody(), location, diagnostics);
+            Flags flags = MakeFlags(
+                                    methodKind, refKind: syntax.ReturnType.SkipScoped(out _).GetRefKindInLocalOrReturn(diagnostics),
+                                    declarationModifiers,
+                                    returnsVoid: false, // The correct value will be computed lazily later and then the flags will be fixed up.
+                                    hasAnyBody: syntax.HasAnyBody(), isExpressionBodied: syntax.IsExpressionBodied(),
+                                    isExtensionMethod: syntax.ParameterList.Parameters.FirstOrDefault() is ParameterSyntax firstParam &&
+                                                       !firstParam.IsArgList &&
+                                                       firstParam.Modifiers.Any(SyntaxKind.ThisKeyword),
+                                    isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                                    isVarArg: syntax.IsVarArg(),
+                                    isExplicitInterfaceImplementation: methodKind == MethodKind.ExplicitInterfaceImplementation);
+
+            return (declarationModifiers, flags);
+        }
+
+        private static Flags MakeFlags(
+            MethodKind methodKind,
+            RefKind refKind,
+            DeclarationModifiers declarationModifiers,
+            bool returnsVoid,
+            bool hasAnyBody,
+            bool isExpressionBodied,
+            bool isExtensionMethod,
+            bool isNullableAnalysisEnabled,
+            bool isVarArg,
+            bool isExplicitInterfaceImplementation)
+        {
+            return new Flags(methodKind, refKind, declarationModifiers, returnsVoid, hasAnyBody, isExpressionBodied, isExtensionMethod, isNullableAnalysisEnabled, isVarArg, isExplicitInterfaceImplementation);
+        }
+
+        private bool HasAnyBody => flags.HasAnyBody;
+
+        private (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var syntax = GetSyntax();
             var withTypeParamsBinder = this.DeclaringCompilation.GetBinderFactory(syntax.SyntaxTree).GetBinder(syntax.ReturnType, syntax, this);
@@ -396,11 +437,10 @@ private SyntaxList<AttributeListSyntax> AttributeDeclarationSyntaxList
             }
         }
 
-        protected sealed override DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
+        private static DeclarationModifiers MakeDeclarationModifiers(MethodDeclarationSyntax syntax, NamedTypeSymbol containingType, Location location, DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
         {
-            var syntax = GetSyntax();
-            return ModifierUtils.MakeAndCheckNonTypeMemberModifiers(isOrdinaryMethod: true, isForInterfaceMember: ContainingType.IsInterface,
-                                                                    syntax.Modifiers, defaultAccess: DeclarationModifiers.None, allowedModifiers, GetFirstLocation(), diagnostics, out _);
+            return ModifierUtils.MakeAndCheckNonTypeMemberModifiers(isOrdinaryMethod: true, isForInterfaceMember: containingType.IsInterface,
+                                                                    syntax.Modifiers, defaultAccess: DeclarationModifiers.None, allowedModifiers, location, diagnostics, out _);
         }
 
         internal sealed override void ForceComplete(SourceLocation locationOpt, CancellationToken cancellationToken)
@@ -601,6 +641,284 @@ internal sealed override bool CallsAreOmitted(SyntaxTree syntaxTree)
 
         internal sealed override bool GenerateDebugInfo => !IsAsync && !IsIterator;
 
+#nullable enable
+        protected override void MethodChecks(BindingDiagnosticBag diagnostics)
+        {
+            Debug.Assert(this.MethodKind != MethodKind.UserDefinedOperator, "SourceUserDefinedOperatorSymbolBase overrides this");
+
+            var (returnType, parameters, declaredConstraints) = MakeParametersAndBindReturnType(diagnostics);
+
+            MethodSymbol? overriddenOrExplicitlyImplementedMethod = MethodChecks(returnType, parameters, diagnostics);
+
+            if (!declaredConstraints.IsDefault && overriddenOrExplicitlyImplementedMethod is object)
+            {
+                for (int i = 0; i < declaredConstraints.Length; i++)
+                {
+                    var typeParameter = this.TypeParameters[i];
+                    ErrorCode report;
+
+                    switch (declaredConstraints[i].Constraints & (TypeParameterConstraintKind.ReferenceType | TypeParameterConstraintKind.ValueType | TypeParameterConstraintKind.Default))
+                    {
+                        case TypeParameterConstraintKind.ReferenceType:
+                            if (!typeParameter.IsReferenceType)
+                            {
+                                report = ErrorCode.ERR_OverrideRefConstraintNotSatisfied;
+                                break;
+                            }
+                            continue;
+                        case TypeParameterConstraintKind.ValueType:
+                            if (!typeParameter.IsNonNullableValueType())
+                            {
+                                report = ErrorCode.ERR_OverrideValConstraintNotSatisfied;
+                                break;
+                            }
+                            continue;
+                        case TypeParameterConstraintKind.Default:
+                            if (typeParameter.IsReferenceType || typeParameter.IsValueType)
+                            {
+                                report = ErrorCode.ERR_OverrideDefaultConstraintNotSatisfied;
+                                break;
+                            }
+                            continue;
+                        default:
+                            continue;
+                    }
+
+                    diagnostics.Add(report, typeParameter.GetFirstLocation(), this, typeParameter,
+                                    overriddenOrExplicitlyImplementedMethod.TypeParameters[i], overriddenOrExplicitlyImplementedMethod);
+                }
+            }
+
+            CheckModifiers(MethodKind == MethodKind.ExplicitInterfaceImplementation, _location, diagnostics);
+        }
+#nullable disable
+
+        // Consider moving this to flags to save space
+        internal bool HasExplicitAccessModifier { get; }
+
+        private static (DeclarationModifiers mods, bool hasExplicitAccessMod) MakeModifiers(MethodDeclarationSyntax syntax, NamedTypeSymbol containingType, MethodKind methodKind, bool hasBody, Location location, BindingDiagnosticBag diagnostics)
+        {
+            bool isInterface = containingType.IsInterface;
+            bool isExplicitInterfaceImplementation = methodKind == MethodKind.ExplicitInterfaceImplementation;
+
+            // This is needed to make sure we can detect 'public' modifier specified explicitly and
+            // check it against language version below.
+            var defaultAccess = isInterface && !isExplicitInterfaceImplementation ? DeclarationModifiers.None : DeclarationModifiers.Private;
+
+            // Check that the set of modifiers is allowed
+            var allowedModifiers = DeclarationModifiers.Partial | DeclarationModifiers.Unsafe;
+            var defaultInterfaceImplementationModifiers = DeclarationModifiers.None;
+
+            if (!isExplicitInterfaceImplementation)
+            {
+                allowedModifiers |= DeclarationModifiers.New |
+                                    DeclarationModifiers.Sealed |
+                                    DeclarationModifiers.Abstract |
+                                    DeclarationModifiers.Static |
+                                    DeclarationModifiers.Virtual |
+                                    DeclarationModifiers.AccessibilityMask;
+
+                if (!isInterface)
+                {
+                    allowedModifiers |= DeclarationModifiers.Override;
+                }
+                else
+                {
+                    defaultInterfaceImplementationModifiers |= DeclarationModifiers.Sealed |
+                                                               DeclarationModifiers.Abstract |
+                                                               DeclarationModifiers.Static |
+                                                               DeclarationModifiers.Virtual |
+                                                               DeclarationModifiers.Extern |
+                                                               DeclarationModifiers.Async |
+                                                               DeclarationModifiers.Partial |
+                                                               DeclarationModifiers.AccessibilityMask;
+                }
+            }
+            else
+            {
+                Debug.Assert(isExplicitInterfaceImplementation);
+
+                if (isInterface)
+                {
+                    allowedModifiers |= DeclarationModifiers.Abstract;
+                }
+
+                allowedModifiers |= DeclarationModifiers.Static;
+            }
+
+            allowedModifiers |= DeclarationModifiers.Extern | DeclarationModifiers.Async;
+
+            if (containingType.IsStructType())
+            {
+                allowedModifiers |= DeclarationModifiers.ReadOnly;
+            }
+
+            // In order to detect whether explicit accessibility mods were provided, we pass the default value
+            // for 'defaultAccess' and manually add in the 'defaultAccess' flags after the call.
+            bool hasExplicitAccessMod;
+            DeclarationModifiers mods = MakeDeclarationModifiers(syntax, containingType, location, allowedModifiers, diagnostics);
+            if ((mods & DeclarationModifiers.AccessibilityMask) == 0)
+            {
+                hasExplicitAccessMod = false;
+                mods |= defaultAccess;
+            }
+            else
+            {
+                hasExplicitAccessMod = true;
+            }
+
+            ModifierUtils.CheckFeatureAvailabilityForStaticAbstractMembersInInterfacesIfNeeded(mods, isExplicitInterfaceImplementation, location, diagnostics);
+
+            ModifierUtils.ReportDefaultInterfaceImplementationModifiers(hasBody, mods,
+                                                                        defaultInterfaceImplementationModifiers,
+                                                                        location, diagnostics);
+
+            mods = AddImpliedModifiers(mods, isInterface, methodKind, hasBody);
+            return (mods, hasExplicitAccessMod);
+        }
+
+        private static DeclarationModifiers AddImpliedModifiers(DeclarationModifiers mods, bool containingTypeIsInterface, MethodKind methodKind, bool hasBody)
+        {
+            // Let's overwrite modifiers for interface and explicit interface implementation methods with what they are supposed to be. 
+            // Proper errors must have been reported by now.
+            if (containingTypeIsInterface)
+            {
+                mods = ModifierUtils.AdjustModifiersForAnInterfaceMember(mods, hasBody,
+                                                                         methodKind == MethodKind.ExplicitInterfaceImplementation);
+            }
+            else if (methodKind == MethodKind.ExplicitInterfaceImplementation)
+            {
+                mods = (mods & ~DeclarationModifiers.AccessibilityMask) | DeclarationModifiers.Private;
+            }
+            return mods;
+        }
+
+        private const DeclarationModifiers PartialMethodExtendedModifierMask =
+            DeclarationModifiers.Virtual |
+            DeclarationModifiers.Override |
+            DeclarationModifiers.New |
+            DeclarationModifiers.Sealed |
+            DeclarationModifiers.Extern;
+
+        private bool HasExtendedPartialModifier => (DeclarationModifiers & PartialMethodExtendedModifierMask) != 0;
+
+        private void CheckModifiers(bool isExplicitInterfaceImplementation, Location location, BindingDiagnosticBag diagnostics)
+        {
+            bool isVararg = this.IsVararg;
+
+            Debug.Assert(!IsStatic || !IsOverride); // Otherwise should have been reported and cleared earlier.
+            Debug.Assert(!IsStatic || ContainingType.IsInterface || (!IsAbstract && !IsVirtual)); // Otherwise should have been reported and cleared earlier.
+
+            bool isExplicitInterfaceImplementationInInterface = isExplicitInterfaceImplementation && ContainingType.IsInterface;
+
+            if (IsPartial && HasExplicitAccessModifier)
+            {
+                Binder.CheckFeatureAvailability(SyntaxNode, MessageID.IDS_FeatureExtendedPartialMethods, diagnostics, location);
+            }
+
+            if (IsPartial && IsAbstract)
+            {
+                diagnostics.Add(ErrorCode.ERR_PartialMethodInvalidModifier, location);
+            }
+            else if (IsPartial && !HasExplicitAccessModifier && !ReturnsVoid)
+            {
+                diagnostics.Add(ErrorCode.ERR_PartialMethodWithNonVoidReturnMustHaveAccessMods, location, this);
+            }
+            else if (IsPartial && !HasExplicitAccessModifier && HasExtendedPartialModifier)
+            {
+                diagnostics.Add(ErrorCode.ERR_PartialMethodWithExtendedModMustHaveAccessMods, location, this);
+            }
+            else if (IsPartial && !HasExplicitAccessModifier && Parameters.Any(static p => p.RefKind == RefKind.Out))
+            {
+                diagnostics.Add(ErrorCode.ERR_PartialMethodWithOutParamMustHaveAccessMods, location, this);
+            }
+            else if (this.DeclaredAccessibility == Accessibility.Private && (IsVirtual || (IsAbstract && !isExplicitInterfaceImplementationInInterface) || IsOverride))
+            {
+                diagnostics.Add(ErrorCode.ERR_VirtualPrivate, location, this);
+            }
+            else if (IsOverride && (IsNew || IsVirtual))
+            {
+                // A member '{0}' marked as override cannot be marked as new or virtual
+                diagnostics.Add(ErrorCode.ERR_OverrideNotNew, location, this);
+            }
+            else if (IsSealed && !IsOverride && !(isExplicitInterfaceImplementationInInterface && IsAbstract))
+            {
+                // '{0}' cannot be sealed because it is not an override
+                diagnostics.Add(ErrorCode.ERR_SealedNonOverride, location, this);
+            }
+            else if (IsSealed && ContainingType.TypeKind == TypeKind.Struct)
+            {
+                // The modifier '{0}' is not valid for this item
+                diagnostics.Add(ErrorCode.ERR_BadMemberFlag, location, SyntaxFacts.GetText(SyntaxKind.SealedKeyword));
+            }
+            else if (ReturnType.IsStatic)
+            {
+                // '{0}': static types cannot be used as return types
+                diagnostics.Add(ErrorFacts.GetStaticClassReturnCode(ContainingType.IsInterfaceType()), location, ReturnType);
+            }
+            else if (IsAbstract && IsExtern)
+            {
+                diagnostics.Add(ErrorCode.ERR_AbstractAndExtern, location, this);
+            }
+            else if (IsAbstract && IsSealed && !isExplicitInterfaceImplementationInInterface)
+            {
+                diagnostics.Add(ErrorCode.ERR_AbstractAndSealed, location, this);
+            }
+            else if (IsAbstract && IsVirtual)
+            {
+                diagnostics.Add(ErrorCode.ERR_AbstractNotVirtual, location, this.Kind.Localize(), this);
+            }
+            else if (IsAbstract && ContainingType.TypeKind == TypeKind.Struct)
+            {
+                // The modifier '{0}' is not valid for this item
+                diagnostics.Add(ErrorCode.ERR_BadMemberFlag, location, SyntaxFacts.GetText(SyntaxKind.AbstractKeyword));
+            }
+            else if (IsVirtual && ContainingType.TypeKind == TypeKind.Struct)
+            {
+                // The modifier '{0}' is not valid for this item
+                diagnostics.Add(ErrorCode.ERR_BadMemberFlag, location, SyntaxFacts.GetText(SyntaxKind.VirtualKeyword));
+            }
+            else if (IsStatic && IsDeclaredReadOnly)
+            {
+                // Static member '{0}' cannot be marked 'readonly'.
+                diagnostics.Add(ErrorCode.ERR_StaticMemberCantBeReadOnly, location, this);
+            }
+            else if (IsAbstract && !ContainingType.IsAbstract && (ContainingType.TypeKind == TypeKind.Class || ContainingType.TypeKind == TypeKind.Submission))
+            {
+                // '{0}' is abstract but it is contained in non-abstract type '{1}'
+                diagnostics.Add(ErrorCode.ERR_AbstractInConcreteClass, location, this, ContainingType);
+            }
+            else if (IsVirtual && ContainingType.IsSealed)
+            {
+                // '{0}' is a new virtual member in sealed type '{1}'
+                diagnostics.Add(ErrorCode.ERR_NewVirtualInSealed, location, this, ContainingType);
+            }
+            else if (!HasAnyBody && IsAsync)
+            {
+                diagnostics.Add(ErrorCode.ERR_BadAsyncLacksBody, location);
+            }
+            else if (!HasAnyBody && !IsExtern && !IsAbstract && !IsPartial && !IsExpressionBodied)
+            {
+                diagnostics.Add(ErrorCode.ERR_ConcreteMissingBody, location, this);
+            }
+            else if (ContainingType.IsSealed && this.DeclaredAccessibility.HasProtected() && !this.IsOverride)
+            {
+                diagnostics.Add(AccessCheck.GetProtectedMemberInSealedTypeError(ContainingType), location, this);
+            }
+            else if (ContainingType.IsStatic && !IsStatic)
+            {
+                diagnostics.Add(ErrorCode.ERR_InstanceMemberInStaticClass, location, Name);
+            }
+            else if (isVararg && (IsGenericMethod || ContainingType.IsGenericType || Parameters.Length > 0 && Parameters[Parameters.Length - 1].IsParams))
+            {
+                diagnostics.Add(ErrorCode.ERR_BadVarargs, location);
+            }
+            else if (isVararg && IsAsync)
+            {
+                diagnostics.Add(ErrorCode.ERR_VarargsAsync, location);
+            }
+        }
+
         private sealed class SourceOrdinaryMethodSymbolSimple : SourceOrdinaryMethodSymbol
         {
             // Avoid adding fields here if possible.  This 'simple' type handles the majority of source methods in any
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbolBase.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbolBase.cs
index 28184ed27f878..f1ade69b03ff6 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbolBase.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbolBase.cs
@@ -30,106 +30,16 @@ protected SourceOrdinaryMethodSymbolBase(
             string name,
             Location location,
             CSharpSyntaxNode syntax,
-            MethodKind methodKind,
-            RefKind refKind,
             bool isIterator,
-            bool isExtensionMethod,
-            bool isReadOnly,
-            bool hasAnyBody,
-            bool isExpressionBodied,
-            bool isNullableAnalysisEnabled,
-            bool isVarArg,
-            BindingDiagnosticBag diagnostics) :
+            (DeclarationModifiers declarationModifiers, Flags flags) modifiersAndFlags) :
             base(containingType,
                  syntax.GetReference(),
                  location,
-                 isIterator: isIterator)
+                 isIterator: isIterator,
+                 modifiersAndFlags)
         {
-            Debug.Assert(diagnostics.DiagnosticBag is object);
-            Debug.Assert(!isReadOnly || this.IsImplicitlyDeclared, "We only expect synthesized methods to use this flag to make a method readonly. Explicitly declared methods should get this value from modifiers in syntax.");
-
             _name = name;
-
-            // The following two values are used to compute and store the initial value of the flags
-            // However, these two components are placeholders; the correct value will be
-            // computed lazily later and then the flags will be fixed up.
-            const bool returnsVoid = false;
-
-            DeclarationModifiers declarationModifiers;
-            (declarationModifiers, HasExplicitAccessModifier) = this.MakeModifiers(methodKind, isReadOnly, hasAnyBody, location, diagnostics);
-
-            //explicit impls must be marked metadata virtual unless static
-            bool isExplicitInterfaceImplementation = methodKind == MethodKind.ExplicitInterfaceImplementation;
-            var isMetadataVirtualIgnoringModifiers = isExplicitInterfaceImplementation && (declarationModifiers & DeclarationModifiers.Static) == 0;
-
-            this.MakeFlags(
-                methodKind, refKind, declarationModifiers, returnsVoid, hasAnyBody: hasAnyBody, isExpressionBodied: isExpressionBodied,
-                isExtensionMethod: isExtensionMethod, isNullableAnalysisEnabled: isNullableAnalysisEnabled, isVarArg: isVarArg,
-                isMetadataVirtualIgnoringModifiers: isMetadataVirtualIgnoringModifiers);
-
-            CheckFeatureAvailabilityAndRuntimeSupport(syntax, location, hasAnyBody, diagnostics);
-
-            if (hasAnyBody)
-            {
-                CheckModifiersForBody(location, diagnostics);
-            }
-
-            ModifierUtils.CheckAccessibility(this.DeclarationModifiers, this, isExplicitInterfaceImplementation: isExplicitInterfaceImplementation, diagnostics, location);
-        }
-
-#nullable enable
-        protected override void MethodChecks(BindingDiagnosticBag diagnostics)
-        {
-            Debug.Assert(this.MethodKind != MethodKind.UserDefinedOperator, "SourceUserDefinedOperatorSymbolBase overrides this");
-
-            var (returnType, parameters, declaredConstraints) = MakeParametersAndBindReturnType(diagnostics);
-
-            MethodSymbol? overriddenOrExplicitlyImplementedMethod = MethodChecks(returnType, parameters, diagnostics);
-
-            if (!declaredConstraints.IsDefault && overriddenOrExplicitlyImplementedMethod is object)
-            {
-                for (int i = 0; i < declaredConstraints.Length; i++)
-                {
-                    var typeParameter = this.TypeParameters[i];
-                    ErrorCode report;
-
-                    switch (declaredConstraints[i].Constraints & (TypeParameterConstraintKind.ReferenceType | TypeParameterConstraintKind.ValueType | TypeParameterConstraintKind.Default))
-                    {
-                        case TypeParameterConstraintKind.ReferenceType:
-                            if (!typeParameter.IsReferenceType)
-                            {
-                                report = ErrorCode.ERR_OverrideRefConstraintNotSatisfied;
-                                break;
-                            }
-                            continue;
-                        case TypeParameterConstraintKind.ValueType:
-                            if (!typeParameter.IsNonNullableValueType())
-                            {
-                                report = ErrorCode.ERR_OverrideValConstraintNotSatisfied;
-                                break;
-                            }
-                            continue;
-                        case TypeParameterConstraintKind.Default:
-                            if (typeParameter.IsReferenceType || typeParameter.IsValueType)
-                            {
-                                report = ErrorCode.ERR_OverrideDefaultConstraintNotSatisfied;
-                                break;
-                            }
-                            continue;
-                        default:
-                            continue;
-                    }
-
-                    diagnostics.Add(report, typeParameter.GetFirstLocation(), this, typeParameter,
-                                    overriddenOrExplicitlyImplementedMethod.TypeParameters[i], overriddenOrExplicitlyImplementedMethod);
-                }
-            }
-
-            CheckModifiers(MethodKind == MethodKind.ExplicitInterfaceImplementation, HasAnyBody, _location, diagnostics);
         }
-#nullable disable
-
-        protected abstract (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics);
 
         protected sealed override void LazyAsyncMethodChecks(CancellationToken cancellationToken)
         {
@@ -186,241 +96,6 @@ public override string Name
 
         internal abstract override OneOrMany<SyntaxList<AttributeListSyntax>> GetAttributeDeclarations();
 
-        internal bool HasExplicitAccessModifier { get; }
-
-        private (DeclarationModifiers mods, bool hasExplicitAccessMod) MakeModifiers(MethodKind methodKind, bool isReadOnly, bool hasBody, Location location, BindingDiagnosticBag diagnostics)
-        {
-            bool isInterface = this.ContainingType.IsInterface;
-            bool isExplicitInterfaceImplementation = methodKind == MethodKind.ExplicitInterfaceImplementation;
-
-            // This is needed to make sure we can detect 'public' modifier specified explicitly and
-            // check it against language version below.
-            var defaultAccess = isInterface && !isExplicitInterfaceImplementation ? DeclarationModifiers.None : DeclarationModifiers.Private;
-
-            // Check that the set of modifiers is allowed
-            var allowedModifiers = DeclarationModifiers.Partial | DeclarationModifiers.Unsafe;
-            var defaultInterfaceImplementationModifiers = DeclarationModifiers.None;
-
-            if (!isExplicitInterfaceImplementation)
-            {
-                allowedModifiers |= DeclarationModifiers.New |
-                                    DeclarationModifiers.Sealed |
-                                    DeclarationModifiers.Abstract |
-                                    DeclarationModifiers.Static |
-                                    DeclarationModifiers.Virtual |
-                                    DeclarationModifiers.AccessibilityMask;
-
-                if (!isInterface)
-                {
-                    allowedModifiers |= DeclarationModifiers.Override;
-                }
-                else
-                {
-                    defaultInterfaceImplementationModifiers |= DeclarationModifiers.Sealed |
-                                                               DeclarationModifiers.Abstract |
-                                                               DeclarationModifiers.Static |
-                                                               DeclarationModifiers.Virtual |
-                                                               DeclarationModifiers.Extern |
-                                                               DeclarationModifiers.Async |
-                                                               DeclarationModifiers.Partial |
-                                                               DeclarationModifiers.AccessibilityMask;
-                }
-            }
-            else
-            {
-                Debug.Assert(isExplicitInterfaceImplementation);
-
-                if (isInterface)
-                {
-                    allowedModifiers |= DeclarationModifiers.Abstract;
-                }
-
-                allowedModifiers |= DeclarationModifiers.Static;
-            }
-
-            allowedModifiers |= DeclarationModifiers.Extern | DeclarationModifiers.Async;
-
-            if (ContainingType.IsStructType())
-            {
-                allowedModifiers |= DeclarationModifiers.ReadOnly;
-            }
-
-            // In order to detect whether explicit accessibility mods were provided, we pass the default value
-            // for 'defaultAccess' and manually add in the 'defaultAccess' flags after the call.
-            bool hasExplicitAccessMod;
-            DeclarationModifiers mods = MakeDeclarationModifiers(allowedModifiers, diagnostics);
-            if ((mods & DeclarationModifiers.AccessibilityMask) == 0)
-            {
-                hasExplicitAccessMod = false;
-                mods |= defaultAccess;
-            }
-            else
-            {
-                hasExplicitAccessMod = true;
-            }
-
-            if (isReadOnly)
-            {
-                Debug.Assert(ContainingType.IsStructType());
-                mods |= DeclarationModifiers.ReadOnly;
-            }
-
-            ModifierUtils.CheckFeatureAvailabilityForStaticAbstractMembersInInterfacesIfNeeded(mods, isExplicitInterfaceImplementation, location, diagnostics);
-
-            this.CheckUnsafeModifier(mods, diagnostics);
-
-            ModifierUtils.ReportDefaultInterfaceImplementationModifiers(hasBody, mods,
-                                                                        defaultInterfaceImplementationModifiers,
-                                                                        location, diagnostics);
-
-            mods = AddImpliedModifiers(mods, isInterface, methodKind, hasBody);
-            return (mods, hasExplicitAccessMod);
-        }
-
-        protected abstract DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics);
-
-        private static DeclarationModifiers AddImpliedModifiers(DeclarationModifiers mods, bool containingTypeIsInterface, MethodKind methodKind, bool hasBody)
-        {
-            // Let's overwrite modifiers for interface and explicit interface implementation methods with what they are supposed to be. 
-            // Proper errors must have been reported by now.
-            if (containingTypeIsInterface)
-            {
-                mods = ModifierUtils.AdjustModifiersForAnInterfaceMember(mods, hasBody,
-                                                                         methodKind == MethodKind.ExplicitInterfaceImplementation);
-            }
-            else if (methodKind == MethodKind.ExplicitInterfaceImplementation)
-            {
-                mods = (mods & ~DeclarationModifiers.AccessibilityMask) | DeclarationModifiers.Private;
-            }
-            return mods;
-        }
-
-        private const DeclarationModifiers PartialMethodExtendedModifierMask =
-            DeclarationModifiers.Virtual |
-            DeclarationModifiers.Override |
-            DeclarationModifiers.New |
-            DeclarationModifiers.Sealed |
-            DeclarationModifiers.Extern;
-
-        internal bool HasExtendedPartialModifier => (DeclarationModifiers & PartialMethodExtendedModifierMask) != 0;
-
-        private void CheckModifiers(bool isExplicitInterfaceImplementation, bool hasBody, Location location, BindingDiagnosticBag diagnostics)
-        {
-            bool isVararg = this.IsVararg;
-
-            Debug.Assert(!IsStatic || !IsOverride); // Otherwise should have been reported and cleared earlier.
-            Debug.Assert(!IsStatic || ContainingType.IsInterface || (!IsAbstract && !IsVirtual)); // Otherwise should have been reported and cleared earlier.
-
-            bool isExplicitInterfaceImplementationInInterface = isExplicitInterfaceImplementation && ContainingType.IsInterface;
-
-            if (IsPartial && HasExplicitAccessModifier)
-            {
-                Binder.CheckFeatureAvailability(SyntaxNode, MessageID.IDS_FeatureExtendedPartialMethods, diagnostics, location);
-            }
-
-            if (IsPartial && IsAbstract)
-            {
-                diagnostics.Add(ErrorCode.ERR_PartialMethodInvalidModifier, location);
-            }
-            else if (IsPartial && !HasExplicitAccessModifier && !ReturnsVoid)
-            {
-                diagnostics.Add(ErrorCode.ERR_PartialMethodWithNonVoidReturnMustHaveAccessMods, location, this);
-            }
-            else if (IsPartial && !HasExplicitAccessModifier && HasExtendedPartialModifier)
-            {
-                diagnostics.Add(ErrorCode.ERR_PartialMethodWithExtendedModMustHaveAccessMods, location, this);
-            }
-            else if (IsPartial && !HasExplicitAccessModifier && Parameters.Any(static p => p.RefKind == RefKind.Out))
-            {
-                diagnostics.Add(ErrorCode.ERR_PartialMethodWithOutParamMustHaveAccessMods, location, this);
-            }
-            else if (this.DeclaredAccessibility == Accessibility.Private && (IsVirtual || (IsAbstract && !isExplicitInterfaceImplementationInInterface) || IsOverride))
-            {
-                diagnostics.Add(ErrorCode.ERR_VirtualPrivate, location, this);
-            }
-            else if (IsOverride && (IsNew || IsVirtual))
-            {
-                // A member '{0}' marked as override cannot be marked as new or virtual
-                diagnostics.Add(ErrorCode.ERR_OverrideNotNew, location, this);
-            }
-            else if (IsSealed && !IsOverride && !(isExplicitInterfaceImplementationInInterface && IsAbstract))
-            {
-                // '{0}' cannot be sealed because it is not an override
-                diagnostics.Add(ErrorCode.ERR_SealedNonOverride, location, this);
-            }
-            else if (IsSealed && ContainingType.TypeKind == TypeKind.Struct)
-            {
-                // The modifier '{0}' is not valid for this item
-                diagnostics.Add(ErrorCode.ERR_BadMemberFlag, location, SyntaxFacts.GetText(SyntaxKind.SealedKeyword));
-            }
-            else if (ReturnType.IsStatic)
-            {
-                // '{0}': static types cannot be used as return types
-                diagnostics.Add(ErrorFacts.GetStaticClassReturnCode(ContainingType.IsInterfaceType()), location, ReturnType);
-            }
-            else if (IsAbstract && IsExtern)
-            {
-                diagnostics.Add(ErrorCode.ERR_AbstractAndExtern, location, this);
-            }
-            else if (IsAbstract && IsSealed && !isExplicitInterfaceImplementationInInterface)
-            {
-                diagnostics.Add(ErrorCode.ERR_AbstractAndSealed, location, this);
-            }
-            else if (IsAbstract && IsVirtual)
-            {
-                diagnostics.Add(ErrorCode.ERR_AbstractNotVirtual, location, this.Kind.Localize(), this);
-            }
-            else if (IsAbstract && ContainingType.TypeKind == TypeKind.Struct)
-            {
-                // The modifier '{0}' is not valid for this item
-                diagnostics.Add(ErrorCode.ERR_BadMemberFlag, location, SyntaxFacts.GetText(SyntaxKind.AbstractKeyword));
-            }
-            else if (IsVirtual && ContainingType.TypeKind == TypeKind.Struct)
-            {
-                // The modifier '{0}' is not valid for this item
-                diagnostics.Add(ErrorCode.ERR_BadMemberFlag, location, SyntaxFacts.GetText(SyntaxKind.VirtualKeyword));
-            }
-            else if (IsStatic && IsDeclaredReadOnly)
-            {
-                // Static member '{0}' cannot be marked 'readonly'.
-                diagnostics.Add(ErrorCode.ERR_StaticMemberCantBeReadOnly, location, this);
-            }
-            else if (IsAbstract && !ContainingType.IsAbstract && (ContainingType.TypeKind == TypeKind.Class || ContainingType.TypeKind == TypeKind.Submission))
-            {
-                // '{0}' is abstract but it is contained in non-abstract type '{1}'
-                diagnostics.Add(ErrorCode.ERR_AbstractInConcreteClass, location, this, ContainingType);
-            }
-            else if (IsVirtual && ContainingType.IsSealed)
-            {
-                // '{0}' is a new virtual member in sealed type '{1}'
-                diagnostics.Add(ErrorCode.ERR_NewVirtualInSealed, location, this, ContainingType);
-            }
-            else if (!hasBody && IsAsync)
-            {
-                diagnostics.Add(ErrorCode.ERR_BadAsyncLacksBody, location);
-            }
-            else if (!hasBody && !IsExtern && !IsAbstract && !IsPartial && !IsExpressionBodied)
-            {
-                diagnostics.Add(ErrorCode.ERR_ConcreteMissingBody, location, this);
-            }
-            else if (ContainingType.IsSealed && this.DeclaredAccessibility.HasProtected() && !this.IsOverride)
-            {
-                diagnostics.Add(AccessCheck.GetProtectedMemberInSealedTypeError(ContainingType), location, this);
-            }
-            else if (ContainingType.IsStatic && !IsStatic)
-            {
-                diagnostics.Add(ErrorCode.ERR_InstanceMemberInStaticClass, location, Name);
-            }
-            else if (isVararg && (IsGenericMethod || ContainingType.IsGenericType || Parameters.Length > 0 && Parameters[Parameters.Length - 1].IsParams))
-            {
-                diagnostics.Add(ErrorCode.ERR_BadVarargs, location);
-            }
-            else if (isVararg && IsAsync)
-            {
-                diagnostics.Add(ErrorCode.ERR_VarargsAsync, location);
-            }
-        }
-
         internal override void AddSynthesizedAttributes(PEModuleBuilder moduleBuilder, ref ArrayBuilder<SynthesizedAttributeData> attributes)
         {
             base.AddSynthesizedAttributes(moduleBuilder, ref attributes);
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs
index 634f427a7a537..2a4d2a396005c 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertyAccessorSymbol.cs
@@ -144,27 +144,32 @@ private SourcePropertyAccessorSymbol(
             ArrowExpressionClauseSyntax syntax,
             bool isNullableAnalysisEnabled,
             BindingDiagnosticBag diagnostics) :
-            base(containingType, syntax.GetReference(), location, isIterator: false)
+            base(containingType, syntax.GetReference(), location, isIterator: false,
+                 MakeModifiersAndFlags(property, propertyModifiers, isNullableAnalysisEnabled))
         {
             _property = property;
             _isAutoPropertyAccessor = false;
 
+            CheckFeatureAvailabilityAndRuntimeSupport(syntax, location, hasBody: true, diagnostics: diagnostics);
+            CheckModifiersForBody(location, diagnostics);
+
+            ModifierUtils.CheckAccessibility(this.DeclarationModifiers, this, property.IsExplicitInterfaceImplementation, diagnostics, location);
+
+            this.CheckModifiers(location, hasBody: true, isAutoPropertyOrExpressionBodied: true, diagnostics: diagnostics);
+        }
+
+        private static (DeclarationModifiers, Flags) MakeModifiersAndFlags(SourcePropertySymbol property, DeclarationModifiers propertyModifiers, bool isNullableAnalysisEnabled)
+        {
             // The modifiers for the accessor are the same as the modifiers for the property,
             // minus the indexer and readonly bit
             var declarationModifiers = GetAccessorModifiers(propertyModifiers);
 
             // ReturnsVoid property is overridden in this class so
             // returnsVoid argument to MakeFlags is ignored.
-            bool isExplicitInterfaceImplementation = property.IsExplicitInterfaceImplementation;
-            this.MakeFlags(MethodKind.PropertyGet, _property.RefKind, declarationModifiers, returnsVoid: false, hasAnyBody: true, isExpressionBodied: true, isExtensionMethod: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled,
-                isVarArg: false, isMetadataVirtualIgnoringModifiers: isExplicitInterfaceImplementation && (declarationModifiers & DeclarationModifiers.Static) == 0);
-
-            CheckFeatureAvailabilityAndRuntimeSupport(syntax, location, hasBody: true, diagnostics: diagnostics);
-            CheckModifiersForBody(location, diagnostics);
+            Flags flags = MakeFlags(MethodKind.PropertyGet, property.RefKind, declarationModifiers, returnsVoid: false, isExpressionBodied: true, isExtensionMethod: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                                    isVarArg: false, isExplicitInterfaceImplementation: property.IsExplicitInterfaceImplementation);
 
-            ModifierUtils.CheckAccessibility(this.DeclarationModifiers, this, isExplicitInterfaceImplementation, diagnostics, location);
-
-            this.CheckModifiers(location, hasBody: true, isAutoPropertyOrExpressionBodied: true, diagnostics: diagnostics);
+            return (declarationModifiers, flags);
         }
 
 #nullable enable
@@ -186,12 +191,12 @@ protected SourcePropertyAccessorSymbol(
             : base(containingType,
                    syntax.GetReference(),
                    location,
-                   isIterator)
+                   isIterator,
+                   MakeModifiersAndFlags(containingType, property, propertyModifiers, location, hasBlockBody, hasExpressionBody, modifiers, methodKind, isNullableAnalysisEnabled, diagnostics, out bool modifierErrors))
         {
             _property = property;
             _isAutoPropertyAccessor = isAutoPropertyAccessor;
             Debug.Assert(!_property.IsExpressionBodied, "Cannot have accessors in expression bodied lightweight properties");
-            var isExpressionBodied = !hasBlockBody && hasExpressionBody;
             var hasAnyBody = hasBlockBody || hasExpressionBody;
             _usesInit = usesInit;
             if (_usesInit)
@@ -199,23 +204,6 @@ protected SourcePropertyAccessorSymbol(
                 Binder.CheckFeatureAvailability(syntax, MessageID.IDS_FeatureInitOnlySetters, diagnostics, location);
             }
 
-            bool modifierErrors;
-            bool isExplicitInterfaceImplementation = property.IsExplicitInterfaceImplementation;
-            var declarationModifiers = this.MakeModifiers(modifiers, isExplicitInterfaceImplementation, hasAnyBody, location, diagnostics, out modifierErrors);
-
-            // Include some modifiers from the containing property, but not the accessibility modifiers.
-            declarationModifiers |= GetAccessorModifiers(propertyModifiers) & ~DeclarationModifiers.AccessibilityMask;
-            if ((declarationModifiers & DeclarationModifiers.Private) != 0)
-            {
-                // Private accessors cannot be virtual.
-                declarationModifiers &= ~DeclarationModifiers.Virtual;
-            }
-
-            // ReturnsVoid property is overridden in this class so
-            // returnsVoid argument to MakeFlags is ignored.
-            this.MakeFlags(methodKind, _property.RefKind, declarationModifiers, returnsVoid: false, hasAnyBody: hasAnyBody, isExpressionBodied: isExpressionBodied, isExtensionMethod: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled,
-                isVarArg: false, isMetadataVirtualIgnoringModifiers: isExplicitInterfaceImplementation && (declarationModifiers & DeclarationModifiers.Static) == 0);
-
             CheckFeatureAvailabilityAndRuntimeSupport(syntax, location, hasBody: hasAnyBody || isAutoPropertyAccessor, diagnostics);
 
             if (hasAnyBody)
@@ -223,7 +211,7 @@ protected SourcePropertyAccessorSymbol(
                 CheckModifiersForBody(location, diagnostics);
             }
 
-            ModifierUtils.CheckAccessibility(this.DeclarationModifiers, this, isExplicitInterfaceImplementation, diagnostics, location);
+            ModifierUtils.CheckAccessibility(this.DeclarationModifiers, this, property.IsExplicitInterfaceImplementation, diagnostics, location);
 
             if (!modifierErrors)
             {
@@ -233,6 +221,33 @@ protected SourcePropertyAccessorSymbol(
             if (modifiers.Count > 0)
                 MessageID.IDS_FeaturePropertyAccessorMods.CheckFeatureAvailability(diagnostics, modifiers[0]);
         }
+
+        private static (DeclarationModifiers, Flags) MakeModifiersAndFlags(
+            NamedTypeSymbol containingType, SourcePropertySymbolBase property, DeclarationModifiers propertyModifiers, Location location,
+            bool hasBlockBody, bool hasExpressionBody, SyntaxTokenList modifiers, MethodKind methodKind, bool isNullableAnalysisEnabled,
+            BindingDiagnosticBag diagnostics, out bool modifierErrors)
+        {
+            var isExpressionBodied = !hasBlockBody && hasExpressionBody;
+            var hasAnyBody = hasBlockBody || hasExpressionBody;
+
+            bool isExplicitInterfaceImplementation = property.IsExplicitInterfaceImplementation;
+            var declarationModifiers = MakeModifiers(containingType, modifiers, isExplicitInterfaceImplementation, hasAnyBody, location, diagnostics, out modifierErrors);
+
+            // Include some modifiers from the containing property, but not the accessibility modifiers.
+            declarationModifiers |= GetAccessorModifiers(propertyModifiers) & ~DeclarationModifiers.AccessibilityMask;
+            if ((declarationModifiers & DeclarationModifiers.Private) != 0)
+            {
+                // Private accessors cannot be virtual.
+                declarationModifiers &= ~DeclarationModifiers.Virtual;
+            }
+
+            // ReturnsVoid property is overridden in this class so
+            // returnsVoid argument to MakeFlags is ignored.
+            Flags flags = MakeFlags(methodKind, property.RefKind, declarationModifiers, returnsVoid: false, isExpressionBodied: isExpressionBodied, isExtensionMethod: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                                    isVarArg: false, isExplicitInterfaceImplementation: isExplicitInterfaceImplementation);
+
+            return (declarationModifiers, flags);
+        }
 #nullable disable
 
         private static DeclarationModifiers GetAccessorModifiers(DeclarationModifiers propertyModifiers) =>
@@ -474,7 +489,7 @@ internal sealed override bool IsDeclaredReadOnly
 
         internal sealed override bool IsInitOnly => !IsStatic && _usesInit;
 
-        private DeclarationModifiers MakeModifiers(SyntaxTokenList modifiers, bool isExplicitInterfaceImplementation,
+        private static DeclarationModifiers MakeModifiers(NamedTypeSymbol containingType, SyntaxTokenList modifiers, bool isExplicitInterfaceImplementation,
             bool hasBody, Location location, BindingDiagnosticBag diagnostics, out bool modifierErrors)
         {
             // No default accessibility. If unset, accessibility
@@ -483,14 +498,14 @@ private DeclarationModifiers MakeModifiers(SyntaxTokenList modifiers, bool isExp
 
             // Check that the set of modifiers is allowed
             var allowedModifiers = isExplicitInterfaceImplementation ? DeclarationModifiers.None : DeclarationModifiers.AccessibilityMask;
-            if (this.ContainingType.IsStructType())
+            if (containingType.IsStructType())
             {
                 allowedModifiers |= DeclarationModifiers.ReadOnly;
             }
 
             var defaultInterfaceImplementationModifiers = DeclarationModifiers.None;
 
-            bool isInterface = this.ContainingType.IsInterface;
+            bool isInterface = containingType.IsInterface;
             if (isInterface && !isExplicitInterfaceImplementation)
             {
                 defaultInterfaceImplementationModifiers = DeclarationModifiers.AccessibilityMask;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedConversionSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedConversionSymbol.cs
index 8d891bdcfe1af..50773d9f52112 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedConversionSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedConversionSymbol.cs
@@ -68,7 +68,7 @@ private SourceUserDefinedConversionSymbol(
                 syntax,
                 MakeDeclarationModifiers(methodKind, containingType.IsInterface, syntax, location, diagnostics),
                 hasAnyBody: syntax.HasAnyBody(),
-                isExpressionBodied: syntax.Body == null && syntax.ExpressionBody != null,
+                isExpressionBodied: syntax.IsExpressionBodied(),
                 isIterator: SyntaxFacts.HasYieldOperations(syntax.Body),
                 isNullableAnalysisEnabled: isNullableAnalysisEnabled,
                 diagnostics)
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbol.cs
index 647fcc7f676ef..4871e27a5c3ec 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbol.cs
@@ -73,7 +73,7 @@ private SourceUserDefinedOperatorSymbol(
                 syntax,
                 MakeDeclarationModifiers(methodKind, containingType.IsInterface, syntax, location, diagnostics),
                 hasAnyBody: syntax.HasAnyBody(),
-                isExpressionBodied: syntax.Body == null && syntax.ExpressionBody != null,
+                isExpressionBodied: syntax.IsExpressionBodied(),
                 isIterator: SyntaxFacts.HasYieldOperations(syntax.Body),
                 isNullableAnalysisEnabled: isNullableAnalysisEnabled,
                 diagnostics)
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbolBase.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbolBase.cs
index a13bf13ecb34b..7aa2ecd864bd3 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbolBase.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbolBase.cs
@@ -34,21 +34,22 @@ protected SourceUserDefinedOperatorSymbolBase(
             bool isIterator,
             bool isNullableAnalysisEnabled,
             BindingDiagnosticBag diagnostics) :
-            base(containingType, syntax.GetReference(), location, isIterator: isIterator)
+            base(containingType, syntax.GetReference(), location, isIterator: isIterator,
+                 (declarationModifiers, MakeFlags(
+                                                  methodKind, RefKind.None, declarationModifiers,
+                                                  // We will bind the formal parameters and the return type lazily. For now,
+                                                  // assume that the return type is non-void; when we do the lazy initialization
+                                                  // of the parameters and return type we will update the flag if necessary.
+                                                  returnsVoid: false,
+                                                  isExpressionBodied: isExpressionBodied,
+                                                  isExtensionMethod: false, isVarArg: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                                                  isExplicitInterfaceImplementation: methodKind == MethodKind.ExplicitInterfaceImplementation)))
         {
             _explicitInterfaceType = explicitInterfaceType;
             _name = name;
 
             this.CheckUnsafeModifier(declarationModifiers, diagnostics);
 
-            // We will bind the formal parameters and the return type lazily. For now,
-            // assume that the return type is non-void; when we do the lazy initialization
-            // of the parameters and return type we will update the flag if necessary.
-
-            this.MakeFlags(
-                methodKind, RefKind.None, declarationModifiers, returnsVoid: false, hasAnyBody: hasAnyBody, isExpressionBodied: isExpressionBodied,
-                isExtensionMethod: false, isVarArg: false, isNullableAnalysisEnabled: isNullableAnalysisEnabled);
-
             if (this.ContainingType.IsInterface &&
                 !(IsAbstract || IsVirtual) && !IsExplicitInterfaceImplementation &&
                 !(syntax is OperatorDeclarationSyntax { OperatorToken: var opToken } && opToken.Kind() is not (SyntaxKind.EqualsEqualsToken or SyntaxKind.ExclamationEqualsToken)))
diff --git a/src/Compilers/CSharp/Portable/Symbols/SubstitutedMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/SubstitutedMethodSymbol.cs
index 4e21bb16912d1..4044492bbac25 100644
--- a/src/Compilers/CSharp/Portable/Symbols/SubstitutedMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/SubstitutedMethodSymbol.cs
@@ -360,16 +360,24 @@ internal override int CalculateLocalSyntaxOffset(int localPosition, SyntaxTree l
         private int ComputeHashCode()
         {
             int code = this.OriginalDefinition.GetHashCode();
+            int containingHashCode;
 
-            // If the containing type of the original definition is the same as our containing type
-            // it's possible that we will compare equal to the original definition under certain conditions 
-            // (e.g, ignoring nullability) and want to retain the same hashcode. As such, consider only
-            // the original definition for the hashcode when we know equality is possible
-            var containingHashCode = _containingType.GetHashCode();
-            if (containingHashCode == this.OriginalDefinition.ContainingType.GetHashCode() &&
-                wasConstructedForAnnotations(this))
+            if (OriginalDefinition is SynthesizedGlobalMethodSymbol global)
             {
-                return code;
+                containingHashCode = System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(global.ContainingPrivateImplementationDetailsType);
+            }
+            else
+            {
+                // If the containing type of the original definition is the same as our containing type
+                // it's possible that we will compare equal to the original definition under certain conditions 
+                // (e.g, ignoring nullability) and want to retain the same hashcode. As such, consider only
+                // the original definition for the hashcode when we know equality is possible
+                containingHashCode = _containingType.GetHashCode();
+                if (containingHashCode == this.OriginalDefinition.ContainingType.GetHashCode() &&
+                    wasConstructedForAnnotations(this))
+                {
+                    return code;
+                }
             }
 
             code = Hash.Combine(containingHashCode, code);
diff --git a/src/Compilers/CSharp/Portable/Symbols/SubstitutedNamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/SubstitutedNamedTypeSymbol.cs
index 508d2addb26f4..5c2318e303b0b 100644
--- a/src/Compilers/CSharp/Portable/Symbols/SubstitutedNamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/SubstitutedNamedTypeSymbol.cs
@@ -195,12 +195,12 @@ public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return OriginalDefinition.GetTypeMembers().SelectAsArray((t, self) => t.AsMember(self), this);
         }
 
-        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return OriginalDefinition.GetTypeMembers(name).SelectAsArray((t, self) => t.AsMember(self), this);
         }
 
-        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return OriginalDefinition.GetTypeMembers(name, arity).SelectAsArray((t, self) => t.AsMember(self), this);
         }
@@ -429,6 +429,7 @@ internal override IEnumerable<CSharpAttributeData> GetCustomAttributesToEmit(PEM
             throw ExceptionUtilities.Unreachable();
         }
 
+        internal sealed override bool IsFileLocal => _underlyingType.IsFileLocal;
         internal sealed override FileIdentifier? AssociatedFileIdentifier => _underlyingType.AssociatedFileIdentifier;
 
         internal sealed override NamedTypeSymbol AsNativeInteger() => throw ExceptionUtilities.Unreachable();
@@ -438,5 +439,10 @@ internal override IEnumerable<CSharpAttributeData> GetCustomAttributesToEmit(PEM
         internal sealed override bool IsRecord => _underlyingType.IsRecord;
         internal sealed override bool IsRecordStruct => _underlyingType.IsRecordStruct;
         internal sealed override bool HasPossibleWellKnownCloneMethod() => _underlyingType.HasPossibleWellKnownCloneMethod();
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            return _underlyingType.HasInlineArrayAttribute(out length);
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/SymbolKindExtensions.cs b/src/Compilers/CSharp/Portable/Symbols/SymbolKindExtensions.cs
index 2ea94f086818b..4d1b8cca17800 100644
--- a/src/Compilers/CSharp/Portable/Symbols/SymbolKindExtensions.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/SymbolKindExtensions.cs
@@ -23,6 +23,14 @@ public static LocalizableErrorArgument Localize(this SymbolKind kind)
                     return MessageID.IDS_SK_TYPE.Localize();
                 case SymbolKind.TypeParameter:
                     return MessageID.IDS_SK_TYVAR.Localize();
+                case SymbolKind.ArrayType:
+                    return MessageID.IDS_SK_ARRAY.Localize();
+                case SymbolKind.PointerType:
+                    return MessageID.IDS_SK_POINTER.Localize();
+                case SymbolKind.FunctionPointerType:
+                    return MessageID.IDS_SK_FUNCTION_POINTER.Localize();
+                case SymbolKind.DynamicType:
+                    return MessageID.IDS_SK_DYNAMIC.Localize();
                 case SymbolKind.Method:
                     return MessageID.IDS_SK_METHOD.Localize();
                 case SymbolKind.Property:
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNameParser.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNameParser.cs
index 198ee7372a8a5..620df43eccb30 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNameParser.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNameParser.cs
@@ -189,8 +189,16 @@ internal static bool TryParsePrimaryConstructorParameterFieldName(string fieldNa
             return false;
         }
 
+        public const char FileTypeNameStartChar = '<';
+
         private const int sha256LengthBytes = 32;
         private const int sha256LengthHexChars = sha256LengthBytes * 2;
+        private static readonly string s_regexPatternString = $@"<([a-zA-Z_0-9]*)>F([0-9A-F]{{{sha256LengthHexChars}}})__";
+
+        static GeneratedNameParser()
+        {
+            Debug.Assert(s_regexPatternString[0] == FileTypeNameStartChar);
+        }
 
         // A full metadata name for a generic file-local type looks like:
         // <ContainingFile>FN__ClassName`A
@@ -199,7 +207,7 @@ internal static bool TryParsePrimaryConstructorParameterFieldName(string fieldNa
         //
         // The "unmangled" name of a generic file-local type looks like:
         // <ContainingFile>FN__ClassName
-        private static readonly Regex s_fileTypeOrdinalPattern = new Regex($@"<([a-zA-Z_0-9]*)>F([0-9A-F]{{{sha256LengthHexChars}}})__", RegexOptions.Compiled);
+        private static readonly Regex s_fileTypeOrdinalPattern = new Regex(s_regexPatternString, RegexOptions.Compiled);
 
         /// <remarks>
         /// This method will work with either unmangled or mangled type names as input, but it does not remove any arity suffix if present.
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedPrimaryConstructor.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedPrimaryConstructor.cs
index eb4f79ecf69a2..0577a64529cda 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedPrimaryConstructor.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedPrimaryConstructor.cs
@@ -19,26 +19,31 @@ internal sealed class SynthesizedPrimaryConstructor : SourceConstructorSymbolBas
         public SynthesizedPrimaryConstructor(
              SourceMemberContainerTypeSymbol containingType,
              TypeDeclarationSyntax syntax) :
-             base(containingType, syntax.Identifier.GetLocation(), syntax, isIterator: false)
+             base(containingType, syntax.Identifier.GetLocation(), syntax, isIterator: false, MakeModifiersAndFlags(containingType, syntax))
         {
             Debug.Assert(syntax.Kind() is SyntaxKind.RecordDeclaration or SyntaxKind.RecordStructDeclaration or SyntaxKind.ClassDeclaration or SyntaxKind.StructDeclaration);
             Debug.Assert(containingType.HasPrimaryConstructor);
             Debug.Assert(containingType is SourceNamedTypeSymbol);
             Debug.Assert(containingType is IAttributeTargetSymbol);
+        }
+
+        private static (DeclarationModifiers, Flags) MakeModifiersAndFlags(SourceMemberContainerTypeSymbol containingType, TypeDeclarationSyntax syntax)
+        {
             Debug.Assert(syntax.ParameterList != null);
 
-            this.MakeFlags(
-                MethodKind.Constructor,
-                RefKind.None,
-                containingType.IsAbstract ? DeclarationModifiers.Protected : DeclarationModifiers.Public,
-                returnsVoid: true,
-                // We consider synthesized constructors to have a body, since they effectively span the entire type, and
-                // can do things like create constructor assignments that write into the fields/props of the type.
-                hasAnyBody: true,
-                isExpressionBodied: false,
-                isExtensionMethod: false,
-                isVarArg: syntax.ParameterList.Parameters.Any(static p => p.IsArgList),
-                isNullableAnalysisEnabled: false); // IsNullableAnalysisEnabled uses containing type instead.
+            DeclarationModifiers declarationModifiers = containingType.IsAbstract ? DeclarationModifiers.Protected : DeclarationModifiers.Public;
+            Flags flags = MakeFlags(
+                                    MethodKind.Constructor,
+                                    RefKind.None,
+                                    declarationModifiers,
+                                    returnsVoid: true,
+                                    isExpressionBodied: false,
+                                    isExtensionMethod: false,
+                                    isVarArg: syntax.ParameterList.IsVarArg(),
+                                    isNullableAnalysisEnabled: false, // IsNullableAnalysisEnabled uses containing type instead.
+                                    isExplicitInterfaceImplementation: false);
+
+            return (declarationModifiers, flags);
         }
 
         internal TypeDeclarationSyntax GetSyntax()
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordBaseEquals.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordBaseEquals.cs
index ed73aa912dd53..fb23a1599653f 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordBaseEquals.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordBaseEquals.cs
@@ -16,20 +16,13 @@ namespace Microsoft.CodeAnalysis.CSharp.Symbols
     /// </summary>
     internal sealed class SynthesizedRecordBaseEquals : SynthesizedRecordOrdinaryMethod
     {
-        public SynthesizedRecordBaseEquals(SourceMemberContainerTypeSymbol containingType, int memberOffset, BindingDiagnosticBag diagnostics)
-            : base(containingType, WellKnownMemberNames.ObjectEquals, isReadOnly: false, hasBody: true, memberOffset, diagnostics)
+        public SynthesizedRecordBaseEquals(SourceMemberContainerTypeSymbol containingType, int memberOffset)
+            : base(containingType, WellKnownMemberNames.ObjectEquals, memberOffset, DeclarationModifiers.Public | DeclarationModifiers.Override | DeclarationModifiers.Sealed)
         {
             Debug.Assert(!containingType.IsRecordStruct);
         }
 
-        protected override DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
-        {
-            const DeclarationModifiers result = DeclarationModifiers.Public | DeclarationModifiers.Override | DeclarationModifiers.Sealed;
-            Debug.Assert((result & ~allowedModifiers) == 0);
-            return result;
-        }
-
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var compilation = DeclaringCompilation;
             var location = ReturnTypeLocation;
@@ -37,8 +30,7 @@ protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymb
                     Parameters: ImmutableArray.Create<ParameterSymbol>(
                                     new SourceSimpleParameterSymbol(owner: this,
                                                                     TypeWithAnnotations.Create(ContainingType.BaseTypeNoUseSiteDiagnostics, NullableAnnotation.Annotated),
-                                                                    ordinal: 0, RefKind.None, ScopedKind.None, "other", Locations)),
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                                                                    ordinal: 0, RefKind.None, ScopedKind.None, "other", Locations)));
         }
 
         protected override int GetParameterCountFromSyntax() => 1;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordClone.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordClone.cs
index af74e3e402f7e..b5355ae673f37 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordClone.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordClone.cs
@@ -21,33 +21,31 @@ internal sealed class SynthesizedRecordClone : SynthesizedRecordOrdinaryMethod
     {
         public SynthesizedRecordClone(
             SourceMemberContainerTypeSymbol containingType,
-            int memberOffset,
-            BindingDiagnosticBag diagnostics)
-            : base(containingType, WellKnownMemberNames.CloneMethodName, isReadOnly: false, hasBody: !containingType.IsAbstract, memberOffset, diagnostics)
+            int memberOffset)
+            : base(containingType, WellKnownMemberNames.CloneMethodName, memberOffset, MakeDeclarationModifiers(containingType))
         {
             Debug.Assert(!containingType.IsRecordStruct);
         }
 
-        protected override DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
+        private static DeclarationModifiers MakeDeclarationModifiers(SourceMemberContainerTypeSymbol containingType)
         {
             DeclarationModifiers result = DeclarationModifiers.Public;
 
-            if (VirtualCloneInBase() is object)
+            if (VirtualCloneInBase(containingType) is object)
             {
                 result |= DeclarationModifiers.Override;
             }
             else
             {
-                result |= ContainingType.IsSealed ? DeclarationModifiers.None : DeclarationModifiers.Virtual;
+                result |= containingType.IsSealed ? DeclarationModifiers.None : DeclarationModifiers.Virtual;
             }
 
-            if (ContainingType.IsAbstract)
+            if (containingType.IsAbstract)
             {
                 result &= ~DeclarationModifiers.Virtual;
                 result |= DeclarationModifiers.Abstract;
             }
 
-            Debug.Assert((result & ~allowedModifiers) == 0);
 #if DEBUG
             Debug.Assert(modifiersAreValid(result));
 #endif 
@@ -82,9 +80,9 @@ static bool modifiersAreValid(DeclarationModifiers modifiers)
 #endif 
         }
 
-        private MethodSymbol? VirtualCloneInBase()
+        private static MethodSymbol? VirtualCloneInBase(NamedTypeSymbol containingType)
         {
-            NamedTypeSymbol baseType = ContainingType.BaseTypeNoUseSiteDiagnostics;
+            NamedTypeSymbol baseType = containingType.BaseTypeNoUseSiteDiagnostics;
 
             if (!baseType.IsObjectType())
             {
@@ -95,13 +93,12 @@ static bool modifiersAreValid(DeclarationModifiers modifiers)
             return null;
         }
 
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
-            return (ReturnType: !ContainingAssembly.RuntimeSupportsCovariantReturnsOfClasses && VirtualCloneInBase() is { } baseClone ?
+            return (ReturnType: !ContainingAssembly.RuntimeSupportsCovariantReturnsOfClasses && VirtualCloneInBase(ContainingType) is { } baseClone ?
                                      baseClone.ReturnTypeWithAnnotations :
                                      TypeWithAnnotations.Create(isNullableEnabled: true, ContainingType),
-                    Parameters: ImmutableArray<ParameterSymbol>.Empty,
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                    Parameters: ImmutableArray<ParameterSymbol>.Empty);
         }
 
         protected override int GetParameterCountFromSyntax() => 0;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordDeconstruct.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordDeconstruct.cs
index e542fe47fc9fc..8df91cb09a940 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordDeconstruct.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordDeconstruct.cs
@@ -19,23 +19,16 @@ public SynthesizedRecordDeconstruct(
             SourceMemberContainerTypeSymbol containingType,
             SynthesizedPrimaryConstructor ctor,
             ImmutableArray<Symbol> positionalMembers,
-            int memberOffset,
-            BindingDiagnosticBag diagnostics)
-            : base(containingType, WellKnownMemberNames.DeconstructMethodName, isReadOnly: IsReadOnly(containingType, positionalMembers), hasBody: true, memberOffset, diagnostics)
+            int memberOffset)
+            : base(containingType, WellKnownMemberNames.DeconstructMethodName, memberOffset,
+                   DeclarationModifiers.Public | (IsReadOnly(containingType, positionalMembers) ? DeclarationModifiers.ReadOnly : 0))
         {
             Debug.Assert(positionalMembers.All(p => p is PropertySymbol { GetMethod: not null } or FieldSymbol));
             _ctor = ctor;
             _positionalMembers = positionalMembers;
         }
 
-        protected override DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
-        {
-            const DeclarationModifiers result = DeclarationModifiers.Public;
-            Debug.Assert((result & ~allowedModifiers) == 0);
-            return result;
-        }
-
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var compilation = DeclaringCompilation;
             var location = ReturnTypeLocation;
@@ -49,8 +42,7 @@ protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymb
                                                 ScopedKind.None,
                                                 param.Name,
                                                 locations),
-                                        arg: Locations),
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                                        arg: Locations));
         }
 
         protected override int GetParameterCountFromSyntax() => _ctor.ParameterCount;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordEquals.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordEquals.cs
index c0049393fec9c..59b03317a8b9d 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordEquals.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordEquals.cs
@@ -18,21 +18,17 @@ internal sealed class SynthesizedRecordEquals : SynthesizedRecordOrdinaryMethod
     {
         private readonly PropertySymbol? _equalityContract;
 
-        public SynthesizedRecordEquals(SourceMemberContainerTypeSymbol containingType, PropertySymbol? equalityContract, int memberOffset, BindingDiagnosticBag diagnostics)
-            : base(containingType, WellKnownMemberNames.ObjectEquals, isReadOnly: containingType.IsRecordStruct, hasBody: true, memberOffset, diagnostics)
+        public SynthesizedRecordEquals(SourceMemberContainerTypeSymbol containingType, PropertySymbol? equalityContract, int memberOffset)
+            : base(containingType, WellKnownMemberNames.ObjectEquals, memberOffset,
+                   DeclarationModifiers.Public |
+                   (containingType.IsSealed ? 0 : DeclarationModifiers.Virtual) |
+                   (containingType.IsRecordStruct ? DeclarationModifiers.ReadOnly : 0))
         {
             Debug.Assert(equalityContract is null == containingType.IsRecordStruct);
             _equalityContract = equalityContract;
         }
 
-        protected override DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
-        {
-            DeclarationModifiers result = DeclarationModifiers.Public | (ContainingType.IsSealed ? DeclarationModifiers.None : DeclarationModifiers.Virtual);
-            Debug.Assert((result & ~allowedModifiers) == 0);
-            return result;
-        }
-
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters)
             MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var compilation = DeclaringCompilation;
@@ -42,8 +38,7 @@ protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymb
                     Parameters: ImmutableArray.Create<ParameterSymbol>(
                                     new SourceSimpleParameterSymbol(owner: this,
                                                                     TypeWithAnnotations.Create(ContainingType, annotation),
-                                                                    ordinal: 0, RefKind.None, ScopedKind.None, "other", Locations)),
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                                                                    ordinal: 0, RefKind.None, ScopedKind.None, "other", Locations)));
         }
 
         protected override int GetParameterCountFromSyntax() => 1;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordGetHashCode.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordGetHashCode.cs
index f9ea532a468ae..1e44ee1e77d5f 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordGetHashCode.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordGetHashCode.cs
@@ -17,8 +17,8 @@ internal sealed class SynthesizedRecordGetHashCode : SynthesizedRecordObjectMeth
     {
         private readonly PropertySymbol? _equalityContract;
 
-        public SynthesizedRecordGetHashCode(SourceMemberContainerTypeSymbol containingType, PropertySymbol? equalityContract, int memberOffset, BindingDiagnosticBag diagnostics)
-            : base(containingType, WellKnownMemberNames.ObjectGetHashCode, memberOffset, isReadOnly: containingType.IsRecordStruct, diagnostics)
+        public SynthesizedRecordGetHashCode(SourceMemberContainerTypeSymbol containingType, PropertySymbol? equalityContract, int memberOffset)
+            : base(containingType, WellKnownMemberNames.ObjectGetHashCode, memberOffset, isReadOnly: containingType.IsRecordStruct)
         {
             Debug.Assert(containingType.IsRecordStruct == equalityContract is null);
             _equalityContract = equalityContract;
@@ -26,14 +26,13 @@ public SynthesizedRecordGetHashCode(SourceMemberContainerTypeSymbol containingTy
 
         protected override SpecialMember OverriddenSpecialMember => SpecialMember.System_Object__GetHashCode;
 
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters)
             MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var compilation = DeclaringCompilation;
             var location = ReturnTypeLocation;
             return (ReturnType: TypeWithAnnotations.Create(Binder.GetSpecialType(compilation, SpecialType.System_Int32, location, diagnostics)),
-                    Parameters: ImmutableArray<ParameterSymbol>.Empty,
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                    Parameters: ImmutableArray<ParameterSymbol>.Empty);
         }
 
         protected override int GetParameterCountFromSyntax() => 0;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjEquals.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjEquals.cs
index e944deede9a62..da1c56468ea0b 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjEquals.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjEquals.cs
@@ -15,15 +15,15 @@ internal sealed class SynthesizedRecordObjEquals : SynthesizedRecordObjectMethod
     {
         private readonly MethodSymbol _typedRecordEquals;
 
-        public SynthesizedRecordObjEquals(SourceMemberContainerTypeSymbol containingType, MethodSymbol typedRecordEquals, int memberOffset, BindingDiagnosticBag diagnostics)
-            : base(containingType, WellKnownMemberNames.ObjectEquals, memberOffset, isReadOnly: containingType.IsRecordStruct, diagnostics)
+        public SynthesizedRecordObjEquals(SourceMemberContainerTypeSymbol containingType, MethodSymbol typedRecordEquals, int memberOffset)
+            : base(containingType, WellKnownMemberNames.ObjectEquals, memberOffset, isReadOnly: containingType.IsRecordStruct)
         {
             _typedRecordEquals = typedRecordEquals;
         }
 
         protected override SpecialMember OverriddenSpecialMember => SpecialMember.System_Object__Equals;
 
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters)
             MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var compilation = DeclaringCompilation;
@@ -33,8 +33,7 @@ protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymb
                     Parameters: ImmutableArray.Create<ParameterSymbol>(
                                     new SourceSimpleParameterSymbol(owner: this,
                                                                     TypeWithAnnotations.Create(Binder.GetSpecialType(compilation, SpecialType.System_Object, location, diagnostics), annotation),
-                                                                    ordinal: 0, RefKind.None, ScopedKind.None, "obj", Locations)),
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                                                                    ordinal: 0, RefKind.None, ScopedKind.None, "obj", Locations)));
         }
 
         protected override int GetParameterCountFromSyntax() => 1;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjectMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjectMethod.cs
index 33f0639cbb216..62660a52671e8 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjectMethod.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordObjectMethod.cs
@@ -11,18 +11,12 @@ namespace Microsoft.CodeAnalysis.CSharp.Symbols
     /// </summary>
     internal abstract class SynthesizedRecordObjectMethod : SynthesizedRecordOrdinaryMethod
     {
-        protected SynthesizedRecordObjectMethod(SourceMemberContainerTypeSymbol containingType, string name, int memberOffset, bool isReadOnly, BindingDiagnosticBag diagnostics)
-            : base(containingType, name, isReadOnly: isReadOnly, hasBody: true, memberOffset, diagnostics)
+        protected SynthesizedRecordObjectMethod(SourceMemberContainerTypeSymbol containingType, string name, int memberOffset, bool isReadOnly)
+            : base(containingType, name, memberOffset,
+                   DeclarationModifiers.Public | DeclarationModifiers.Override | (isReadOnly ? DeclarationModifiers.ReadOnly : 0))
         {
         }
 
-        protected sealed override DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
-        {
-            const DeclarationModifiers result = DeclarationModifiers.Public | DeclarationModifiers.Override;
-            Debug.Assert((result & ~allowedModifiers) == 0);
-            return result;
-        }
-
         protected sealed override void MethodChecks(BindingDiagnosticBag diagnostics)
         {
             base.MethodChecks(diagnostics);
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordOrdinaryMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordOrdinaryMethod.cs
index 0306e1c830606..b2986891dbfce 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordOrdinaryMethod.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordOrdinaryMethod.cs
@@ -20,13 +20,26 @@ internal abstract class SynthesizedRecordOrdinaryMethod : SourceOrdinaryMethodSy
     {
         private readonly int _memberOffset;
 
-        protected SynthesizedRecordOrdinaryMethod(SourceMemberContainerTypeSymbol containingType, string name, bool isReadOnly, bool hasBody, int memberOffset, BindingDiagnosticBag diagnostics)
-            : base(containingType, name, containingType.GetFirstLocation(), (CSharpSyntaxNode)containingType.SyntaxReferences[0].GetSyntax(), MethodKind.Ordinary, RefKind.None,
-                   isIterator: false, isExtensionMethod: false, isReadOnly: isReadOnly, hasAnyBody: hasBody, isExpressionBodied: false, isNullableAnalysisEnabled: false, isVarArg: false, diagnostics)
+        protected SynthesizedRecordOrdinaryMethod(SourceMemberContainerTypeSymbol containingType, string name, int memberOffset, DeclarationModifiers declarationModifiers)
+            : base(containingType, name, containingType.GetFirstLocation(), (CSharpSyntaxNode)containingType.SyntaxReferences[0].GetSyntax(),
+                   isIterator: false,
+                   (declarationModifiers, MakeFlags(
+                                                    MethodKind.Ordinary, RefKind.None, declarationModifiers, returnsVoid: false, isExpressionBodied: false,
+                                                    isExtensionMethod: false, isNullableAnalysisEnabled: false, isVarArg: false,
+                                                    isExplicitInterfaceImplementation: false)))
         {
             _memberOffset = memberOffset;
         }
 
+        protected override void MethodChecks(BindingDiagnosticBag diagnostics)
+        {
+            Debug.Assert(Arity == 0);
+            var (returnType, parameters) = MakeParametersAndBindReturnType(diagnostics);
+            MethodChecks(returnType, parameters, diagnostics);
+        }
+
+        protected abstract (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics);
+
         public sealed override bool IsImplicitlyDeclared => true;
 
         protected sealed override Location ReturnTypeLocation => GetFirstLocation();
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordPrintMembers.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordPrintMembers.cs
index 3781497a6ec4a..4f463b0b29831 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordPrintMembers.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordPrintMembers.cs
@@ -23,43 +23,44 @@ internal sealed class SynthesizedRecordPrintMembers : SynthesizedRecordOrdinaryM
         public SynthesizedRecordPrintMembers(
             SourceMemberContainerTypeSymbol containingType,
             IEnumerable<Symbol> userDefinedMembers,
-            int memberOffset,
-            BindingDiagnosticBag diagnostics)
+            int memberOffset)
             : base(
                   containingType,
                   WellKnownMemberNames.PrintMembersMethodName,
-                  isReadOnly: IsReadOnly(containingType, userDefinedMembers),
-                  hasBody: true,
                   memberOffset: memberOffset,
-                  diagnostics)
+                  MakeDeclarationModifiers(containingType, userDefinedMembers))
         {
         }
 
-        protected override DeclarationModifiers MakeDeclarationModifiers(DeclarationModifiers allowedModifiers, BindingDiagnosticBag diagnostics)
+        private static DeclarationModifiers MakeDeclarationModifiers(SourceMemberContainerTypeSymbol containingType, IEnumerable<Symbol> userDefinedMembers)
         {
-            var result = (ContainingType.IsRecordStruct || (ContainingType.BaseTypeNoUseSiteDiagnostics.IsObjectType() && ContainingType.IsSealed)) ?
+            var result = (containingType.IsRecordStruct || (containingType.BaseTypeNoUseSiteDiagnostics.IsObjectType() && containingType.IsSealed)) ?
                 DeclarationModifiers.Private :
                 DeclarationModifiers.Protected;
 
-            if (ContainingType.IsRecord && !ContainingType.BaseTypeNoUseSiteDiagnostics.IsObjectType())
+            if (containingType.IsRecord && !containingType.BaseTypeNoUseSiteDiagnostics.IsObjectType())
             {
                 result |= DeclarationModifiers.Override;
             }
             else
             {
-                result |= ContainingType.IsSealed ? DeclarationModifiers.None : DeclarationModifiers.Virtual;
+                result |= containingType.IsSealed ? DeclarationModifiers.None : DeclarationModifiers.Virtual;
             }
 
-            Debug.Assert((result & ~allowedModifiers) == 0);
 #if DEBUG
             Debug.Assert(modifiersAreValid(result));
 #endif
+            if (IsReadOnly(containingType, userDefinedMembers))
+            {
+                result |= DeclarationModifiers.ReadOnly;
+            }
+
             return result;
 
 #if DEBUG
             bool modifiersAreValid(DeclarationModifiers modifiers)
             {
-                if (ContainingType.IsRecordStruct)
+                if (containingType.IsRecordStruct)
                 {
                     return modifiers == DeclarationModifiers.Private;
                 }
@@ -85,7 +86,7 @@ bool modifiersAreValid(DeclarationModifiers modifiers)
 #endif
         }
 
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var compilation = DeclaringCompilation;
             var location = ReturnTypeLocation;
@@ -94,8 +95,7 @@ protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymb
                     Parameters: ImmutableArray.Create<ParameterSymbol>(
                         new SourceSimpleParameterSymbol(owner: this,
                             TypeWithAnnotations.Create(Binder.GetWellKnownType(compilation, WellKnownType.System_Text_StringBuilder, diagnostics, location), annotation),
-                            ordinal: 0, RefKind.None, ScopedKind.None, "builder", Locations)),
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                            ordinal: 0, RefKind.None, ScopedKind.None, "builder", Locations)));
         }
 
         protected override int GetParameterCountFromSyntax() => 1;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordToString.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordToString.cs
index 33220633ece8a..dbc92b6e5b06c 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordToString.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/Records/SynthesizedRecordToString.cs
@@ -22,13 +22,12 @@ namespace Microsoft.CodeAnalysis.CSharp.Symbols
     internal sealed class SynthesizedRecordToString : SynthesizedRecordObjectMethod
     {
         private readonly MethodSymbol _printMethod;
-        public SynthesizedRecordToString(SourceMemberContainerTypeSymbol containingType, MethodSymbol printMethod, int memberOffset, bool isReadOnly, BindingDiagnosticBag diagnostics)
+        public SynthesizedRecordToString(SourceMemberContainerTypeSymbol containingType, MethodSymbol printMethod, int memberOffset)
             : base(
                   containingType,
                   WellKnownMemberNames.ObjectToString,
                   memberOffset,
-                  isReadOnly: isReadOnly,
-                  diagnostics)
+                  isReadOnly: printMethod.IsEffectivelyReadOnly)
         {
             Debug.Assert(printMethod is object);
             _printMethod = printMethod;
@@ -36,14 +35,13 @@ public SynthesizedRecordToString(SourceMemberContainerTypeSymbol containingType,
 
         protected override SpecialMember OverriddenSpecialMember => SpecialMember.System_Object__ToString;
 
-        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters, ImmutableArray<TypeParameterConstraintClause> DeclaredConstraintsForOverrideOrImplementation) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
+        protected override (TypeWithAnnotations ReturnType, ImmutableArray<ParameterSymbol> Parameters) MakeParametersAndBindReturnType(BindingDiagnosticBag diagnostics)
         {
             var compilation = DeclaringCompilation;
             var location = ReturnTypeLocation;
             var annotation = ContainingType.IsRecordStruct ? NullableAnnotation.Oblivious : NullableAnnotation.NotAnnotated;
             return (ReturnType: TypeWithAnnotations.Create(Binder.GetSpecialType(compilation, SpecialType.System_String, location, diagnostics), annotation),
-                    Parameters: ImmutableArray<ParameterSymbol>.Empty,
-                    DeclaredConstraintsForOverrideOrImplementation: ImmutableArray<TypeParameterConstraintClause>.Empty);
+                    Parameters: ImmutableArray<ParameterSymbol>.Empty);
         }
 
         protected override int GetParameterCountFromSyntax() => 0;
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedContainer.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedContainer.cs
index e8372fb269453..4d014569d51a7 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedContainer.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedContainer.cs
@@ -137,9 +137,9 @@ internal override IEnumerable<FieldSymbol> GetFieldsToEmit()
 
         public override ImmutableArray<NamedTypeSymbol> GetTypeMembers() => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name) => ImmutableArray<NamedTypeSymbol>.Empty;
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name) => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity) => ImmutableArray<NamedTypeSymbol>.Empty;
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity) => ImmutableArray<NamedTypeSymbol>.Empty;
 
         public override Accessibility DeclaredAccessibility => Accessibility.Private;
 
@@ -166,6 +166,7 @@ internal override IEnumerable<FieldSymbol> GetFieldsToEmit()
         internal override bool MangleName => Arity > 0;
 
 #nullable enable
+        internal sealed override bool IsFileLocal => false;
         internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 #nullable disable
 
@@ -206,5 +207,11 @@ internal override IEnumerable<FieldSymbol> GetFieldsToEmit()
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEmbeddedAttributeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEmbeddedAttributeSymbol.cs
index 7e0e82cf48c51..137fe6d633453 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEmbeddedAttributeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEmbeddedAttributeSymbol.cs
@@ -99,7 +99,8 @@ public SynthesizedEmbeddedAttributeSymbolBase(
 
         internal override bool MangleName => false;
 
-        internal override FileIdentifier? AssociatedFileIdentifier => null;
+        internal sealed override bool IsFileLocal => false;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
         internal override bool HasCodeAnalysisEmbeddedAttribute => true;
 
@@ -137,9 +138,9 @@ public SynthesizedEmbeddedAttributeSymbolBase(
 
         public override ImmutableArray<NamedTypeSymbol> GetTypeMembers() => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name) => ImmutableArray<NamedTypeSymbol>.Empty;
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name) => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity) => ImmutableArray<NamedTypeSymbol>.Empty;
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity) => ImmutableArray<NamedTypeSymbol>.Empty;
 
         internal override ImmutableArray<string> GetAppliedConditionalSymbols() => ImmutableArray<string>.Empty;
 
@@ -194,6 +195,12 @@ internal override void AddSynthesizedAttributes(PEModuleBuilder moduleBuilder, r
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 
     /// <summary>
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEventAccessorSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEventAccessorSymbol.cs
index 5c133e454d8d1..0ee7c2f9a4d03 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEventAccessorSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedEventAccessorSymbol.cs
@@ -24,8 +24,8 @@ internal sealed class SynthesizedEventAccessorSymbol : SourceEventAccessorSymbol
         // Since we don't have a syntax reference, we'll have to use another object for locking.
         private readonly object _methodChecksLockObject = new object();
 
-        internal SynthesizedEventAccessorSymbol(SourceEventSymbol @event, bool isAdder, bool hasAnyBody, bool isExpressionBodied, EventSymbol explicitlyImplementedEventOpt = null, string aliasQualifierOpt = null)
-            : base(@event, null, @event.Location, explicitlyImplementedEventOpt, aliasQualifierOpt, isAdder, isIterator: false, isNullableAnalysisEnabled: false, hasAnyBody: hasAnyBody, isExpressionBodied: isExpressionBodied)
+        internal SynthesizedEventAccessorSymbol(SourceEventSymbol @event, bool isAdder, bool isExpressionBodied, EventSymbol explicitlyImplementedEventOpt = null, string aliasQualifierOpt = null)
+            : base(@event, null, @event.Location, explicitlyImplementedEventOpt, aliasQualifierOpt, isAdder, isIterator: false, isNullableAnalysisEnabled: false, isExpressionBodied: isExpressionBodied)
         {
         }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedGlobalMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedGlobalMethodSymbol.cs
index 873180ce4361c..7ff0e2aa8c4b7 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedGlobalMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedGlobalMethodSymbol.cs
@@ -25,26 +25,49 @@ internal abstract class SynthesizedGlobalMethodSymbol : MethodSymbol
     {
         private readonly ModuleSymbol _containingModule;
         private readonly PrivateImplementationDetails _privateImplType;
-        private readonly TypeSymbol _returnType;
+        private TypeSymbol _returnType;
         private ImmutableArray<ParameterSymbol> _parameters;
+        private ImmutableArray<TypeParameterSymbol> _typeParameters;
         private readonly string _name;
 
-        internal SynthesizedGlobalMethodSymbol(ModuleSymbol containingModule, PrivateImplementationDetails privateImplType, TypeSymbol returnType, string name)
+        internal SynthesizedGlobalMethodSymbol(ModuleSymbol containingModule, PrivateImplementationDetails privateImplType, string name)
         {
             Debug.Assert((object)containingModule != null);
             Debug.Assert(privateImplType != null);
-            Debug.Assert((object)returnType != null);
             Debug.Assert(name != null);
 
             _containingModule = containingModule;
             _privateImplType = privateImplType;
-            _returnType = returnType;
             _name = name;
         }
 
+        internal SynthesizedGlobalMethodSymbol(ModuleSymbol containingModule, PrivateImplementationDetails privateImplType, TypeSymbol returnType, string name)
+            : this(containingModule, privateImplType, name)
+        {
+            Debug.Assert((object)returnType != null);
+            _returnType = returnType;
+            _typeParameters = ImmutableArray<TypeParameterSymbol>.Empty;
+        }
+
+        protected void SetReturnType(TypeSymbol returnType)
+        {
+            Debug.Assert(returnType is not null);
+            Debug.Assert(_returnType is null);
+            _returnType = returnType;
+        }
+
         protected void SetParameters(ImmutableArray<ParameterSymbol> parameters)
         {
-            ImmutableInterlocked.InterlockedExchange(ref _parameters, parameters);
+            Debug.Assert(!parameters.IsDefault);
+            Debug.Assert(_parameters.IsDefault);
+            _parameters = parameters;
+        }
+
+        protected void SetTypeParameters(ImmutableArray<TypeParameterSymbol> typeParameters)
+        {
+            Debug.Assert(!typeParameters.IsDefault);
+            Debug.Assert(_typeParameters.IsDefault);
+            _typeParameters = typeParameters;
         }
 
         public sealed override bool IsImplicitlyDeclared
@@ -160,7 +183,16 @@ public override bool IsVararg
 
         public override ImmutableArray<TypeParameterSymbol> TypeParameters
         {
-            get { return ImmutableArray<TypeParameterSymbol>.Empty; }
+            get
+            {
+                Debug.Assert(!_typeParameters.IsDefault, $"Expected {nameof(SetTypeParameters)} prior to accessing this property.");
+                if (_typeParameters.IsDefault)
+                {
+                    return ImmutableArray<TypeParameterSymbol>.Empty;
+                }
+
+                return _typeParameters;
+            }
         }
 
         public override ImmutableArray<ParameterSymbol> Parameters
@@ -227,7 +259,7 @@ public override Symbol AssociatedSymbol
 
         public override int Arity
         {
-            get { return 0; }
+            get { return TypeParameters.Length; }
         }
 
         public override bool ReturnsVoid
@@ -305,7 +337,15 @@ public override bool IsExtensionMethod
 
         internal override Cci.CallingConvention CallingConvention
         {
-            get { return 0; }
+            get
+            {
+                if (IsGenericMethod)
+                {
+                    return Cci.CallingConvention.Generic;
+                }
+
+                return Cci.CallingConvention.Default;
+            }
         }
 
         internal override bool IsExplicitInterfaceImplementation
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayAsReadOnlySpanMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayAsReadOnlySpanMethod.cs
new file mode 100644
index 0000000000000..ef789ef177d35
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayAsReadOnlySpanMethod.cs
@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.CodeGen;
+
+namespace Microsoft.CodeAnalysis.CSharp.Symbols
+{
+    internal sealed class SynthesizedInlineArrayAsReadOnlySpanMethod : SynthesizedGlobalMethodSymbol
+    {
+        internal SynthesizedInlineArrayAsReadOnlySpanMethod(SourceModuleSymbol containingModule, PrivateImplementationDetails privateImplType, string synthesizedMethodName, NamedTypeSymbol spanType, NamedTypeSymbol intType)
+            : base(containingModule, privateImplType, synthesizedMethodName)
+        {
+            this.SetTypeParameters(ImmutableArray.Create<TypeParameterSymbol>(new SynthesizedSimpleMethodTypeParameterSymbol(this, 0, "TBuffer"), new SynthesizedSimpleMethodTypeParameterSymbol(this, 1, "TElement")));
+            this.SetReturnType(spanType.Construct(TypeParameters[1]));
+            this.SetParameters(ImmutableArray.Create<ParameterSymbol>(SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(TypeParameters[0]), 0, RefKind.In, "buffer"),
+                                                                      SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(intType), 1, RefKind.None, "length")));
+        }
+
+        internal override void GenerateMethodBody(TypeCompilationState compilationState, BindingDiagnosticBag diagnostics)
+        {
+            SyntheticBoundNodeFactory f = new SyntheticBoundNodeFactory(this, this.GetNonNullSyntaxNode(), compilationState, diagnostics);
+            f.CurrentFunction = this;
+
+            try
+            {
+                // return MemoryMarshal.CreateReadOnlySpan<TElement>(ref Unsafe.As<TBuffer, TElement>(ref Unsafe.AsRef<TBuffer>(in buffer)), length)
+
+                var body = f.Return(f.Call(null,
+                                           f.WellKnownMethod(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan).Construct(TypeParameters[1]),
+                                           f.Call(null,
+                                                  f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T).Construct(ImmutableArray<TypeSymbol>.CastUp(TypeParameters)),
+                                                  f.Call(null,
+                                                         f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T).Construct(TypeParameters[0]),
+                                                         f.Parameter(Parameters[0]))),
+                                           f.Parameter(Parameters[1])));
+
+                // NOTE: we created this block in its most-lowered form, so analysis is unnecessary
+                f.CloseMethod(body);
+            }
+            catch (SyntheticBoundNodeFactory.MissingPredefinedMember ex)
+            {
+                diagnostics.Add(ex.Diagnostic);
+                f.CloseMethod(f.ThrowNull());
+            }
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayAsSpanMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayAsSpanMethod.cs
new file mode 100644
index 0000000000000..67b5bfe39420c
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayAsSpanMethod.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.CodeGen;
+
+namespace Microsoft.CodeAnalysis.CSharp.Symbols
+{
+    internal sealed class SynthesizedInlineArrayAsSpanMethod : SynthesizedGlobalMethodSymbol
+    {
+        internal SynthesizedInlineArrayAsSpanMethod(SourceModuleSymbol containingModule, PrivateImplementationDetails privateImplType, string synthesizedMethodName, NamedTypeSymbol spanType, NamedTypeSymbol intType)
+            : base(containingModule, privateImplType, synthesizedMethodName)
+        {
+            this.SetTypeParameters(ImmutableArray.Create<TypeParameterSymbol>(new SynthesizedSimpleMethodTypeParameterSymbol(this, 0, "TBuffer"), new SynthesizedSimpleMethodTypeParameterSymbol(this, 1, "TElement")));
+            this.SetReturnType(spanType.Construct(TypeParameters[1]));
+            this.SetParameters(ImmutableArray.Create<ParameterSymbol>(SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(TypeParameters[0]), 0, RefKind.Ref, "buffer"),
+                                                                      SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(intType), 1, RefKind.None, "length")));
+        }
+
+        internal override void GenerateMethodBody(TypeCompilationState compilationState, BindingDiagnosticBag diagnostics)
+        {
+            SyntheticBoundNodeFactory f = new SyntheticBoundNodeFactory(this, this.GetNonNullSyntaxNode(), compilationState, diagnostics);
+            f.CurrentFunction = this;
+
+            try
+            {
+                // return MemoryMarshal.CreateSpan<TElement>(ref Unsafe.As<TBuffer, TElement>(ref buffer), length)
+
+                var body = f.Return(f.Call(null,
+                                           f.WellKnownMethod(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan).Construct(TypeParameters[1]),
+                                           f.Call(null,
+                                                  f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T).Construct(ImmutableArray<TypeSymbol>.CastUp(TypeParameters)),
+                                                  f.Parameter(Parameters[0])),
+                                           f.Parameter(Parameters[1])));
+
+                // NOTE: we created this block in its most-lowered form, so analysis is unnecessary
+                f.CloseMethod(body);
+            }
+            catch (SyntheticBoundNodeFactory.MissingPredefinedMember ex)
+            {
+                diagnostics.Add(ex.Diagnostic);
+                f.CloseMethod(f.ThrowNull());
+            }
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayElementRefMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayElementRefMethod.cs
new file mode 100644
index 0000000000000..d73c2e10b382a
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayElementRefMethod.cs
@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.CodeGen;
+
+namespace Microsoft.CodeAnalysis.CSharp.Symbols
+{
+    internal sealed class SynthesizedInlineArrayElementRefMethod : SynthesizedGlobalMethodSymbol
+    {
+        internal SynthesizedInlineArrayElementRefMethod(SourceModuleSymbol containingModule, PrivateImplementationDetails privateImplType, string synthesizedMethodName, NamedTypeSymbol intType)
+            : base(containingModule, privateImplType, synthesizedMethodName)
+        {
+            this.SetTypeParameters(ImmutableArray.Create<TypeParameterSymbol>(new SynthesizedSimpleMethodTypeParameterSymbol(this, 0, "TBuffer"), new SynthesizedSimpleMethodTypeParameterSymbol(this, 1, "TElement")));
+            this.SetReturnType(TypeParameters[1]);
+            this.SetParameters(ImmutableArray.Create<ParameterSymbol>(SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(TypeParameters[0]), 0, RefKind.Ref, "buffer"),
+                                                                      SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(intType), 1, RefKind.None, "index")));
+        }
+
+        public override RefKind RefKind => RefKind.Ref;
+
+        internal override void GenerateMethodBody(TypeCompilationState compilationState, BindingDiagnosticBag diagnostics)
+        {
+            SyntheticBoundNodeFactory f = new SyntheticBoundNodeFactory(this, this.GetNonNullSyntaxNode(), compilationState, diagnostics);
+            f.CurrentFunction = this;
+
+            try
+            {
+                // return ref Unsafe.Add<TElement>(ref Unsafe.As<TBuffer, TElement>(ref buffer), index)
+
+                var body = f.Return(f.Call(null,
+                                           f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T).Construct(TypeParameters[1]),
+                                           f.Call(null,
+                                                  f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T).Construct(ImmutableArray<TypeSymbol>.CastUp(TypeParameters)),
+                                                  f.Parameter(Parameters[0])),
+                                           f.Parameter(Parameters[1])));
+
+                // NOTE: we created this block in its most-lowered form, so analysis is unnecessary
+                f.CloseMethod(body);
+            }
+            catch (SyntheticBoundNodeFactory.MissingPredefinedMember ex)
+            {
+                diagnostics.Add(ex.Diagnostic);
+                f.CloseMethod(f.ThrowNull());
+            }
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayElementRefReadOnlyMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayElementRefReadOnlyMethod.cs
new file mode 100644
index 0000000000000..b3eec39cfd708
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayElementRefReadOnlyMethod.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.CodeGen;
+
+namespace Microsoft.CodeAnalysis.CSharp.Symbols
+{
+    internal sealed class SynthesizedInlineArrayElementRefReadOnlyMethod : SynthesizedGlobalMethodSymbol
+    {
+        internal SynthesizedInlineArrayElementRefReadOnlyMethod(SourceModuleSymbol containingModule, PrivateImplementationDetails privateImplType, string synthesizedMethodName, NamedTypeSymbol intType)
+            : base(containingModule, privateImplType, synthesizedMethodName)
+        {
+            this.SetTypeParameters(ImmutableArray.Create<TypeParameterSymbol>(new SynthesizedSimpleMethodTypeParameterSymbol(this, 0, "TBuffer"), new SynthesizedSimpleMethodTypeParameterSymbol(this, 1, "TElement")));
+            this.SetReturnType(TypeParameters[1]);
+            this.SetParameters(ImmutableArray.Create<ParameterSymbol>(SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(TypeParameters[0]), 0, RefKind.In, "buffer"),
+                                                                      SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(intType), 1, RefKind.None, "index")));
+        }
+
+        public override RefKind RefKind => RefKind.RefReadOnly;
+
+        internal override void GenerateMethodBody(TypeCompilationState compilationState, BindingDiagnosticBag diagnostics)
+        {
+            SyntheticBoundNodeFactory f = new SyntheticBoundNodeFactory(this, this.GetNonNullSyntaxNode(), compilationState, diagnostics);
+            f.CurrentFunction = this;
+
+            try
+            {
+                // return ref Unsafe.Add<TElement>(ref Unsafe.As<TBuffer, TElement>(ref Unsafe.AsRef<TBuffer>(in buffer)), index)
+
+                var body = f.Return(f.Call(null,
+                                           f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T).Construct(TypeParameters[1]),
+                                           f.Call(null,
+                                                  f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T).Construct(ImmutableArray<TypeSymbol>.CastUp(TypeParameters)),
+                                                  f.Call(null,
+                                                         f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T).Construct(TypeParameters[0]),
+                                                         f.Parameter(Parameters[0]))),
+                                           f.Parameter(Parameters[1])));
+
+                // NOTE: we created this block in its most-lowered form, so analysis is unnecessary
+                f.CloseMethod(body);
+            }
+            catch (SyntheticBoundNodeFactory.MissingPredefinedMember ex)
+            {
+                diagnostics.Add(ex.Diagnostic);
+                f.CloseMethod(f.ThrowNull());
+            }
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayFirstElementRefMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayFirstElementRefMethod.cs
new file mode 100644
index 0000000000000..beb599476437e
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayFirstElementRefMethod.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.CodeGen;
+
+namespace Microsoft.CodeAnalysis.CSharp.Symbols
+{
+    internal sealed class SynthesizedInlineArrayFirstElementRefMethod : SynthesizedGlobalMethodSymbol
+    {
+        internal SynthesizedInlineArrayFirstElementRefMethod(SourceModuleSymbol containingModule, PrivateImplementationDetails privateImplType, string synthesizedMethodName)
+            : base(containingModule, privateImplType, synthesizedMethodName)
+        {
+            this.SetTypeParameters(ImmutableArray.Create<TypeParameterSymbol>(new SynthesizedSimpleMethodTypeParameterSymbol(this, 0, "TBuffer"), new SynthesizedSimpleMethodTypeParameterSymbol(this, 1, "TElement")));
+            this.SetReturnType(TypeParameters[1]);
+            this.SetParameters(ImmutableArray.Create<ParameterSymbol>(SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(TypeParameters[0]), 0, RefKind.Ref, "buffer")));
+        }
+
+        public override RefKind RefKind => RefKind.Ref;
+
+        internal override void GenerateMethodBody(TypeCompilationState compilationState, BindingDiagnosticBag diagnostics)
+        {
+            SyntheticBoundNodeFactory f = new SyntheticBoundNodeFactory(this, this.GetNonNullSyntaxNode(), compilationState, diagnostics);
+            f.CurrentFunction = this;
+
+            try
+            {
+                // return ref Unsafe.As<TBuffer, TElement>(ref buffer)
+
+                var body = f.Return(f.Call(null,
+                                           f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T).Construct(ImmutableArray<TypeSymbol>.CastUp(TypeParameters)),
+                                           f.Parameter(Parameters[0])));
+
+                // NOTE: we created this block in its most-lowered form, so analysis is unnecessary
+                f.CloseMethod(body);
+            }
+            catch (SyntheticBoundNodeFactory.MissingPredefinedMember ex)
+            {
+                diagnostics.Add(ex.Diagnostic);
+                f.CloseMethod(f.ThrowNull());
+            }
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayFirstElementRefReadOnlyMethod.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayFirstElementRefReadOnlyMethod.cs
new file mode 100644
index 0000000000000..39519e235e5fe
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedInlineArrayFirstElementRefReadOnlyMethod.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.CodeGen;
+
+namespace Microsoft.CodeAnalysis.CSharp.Symbols
+{
+    internal sealed class SynthesizedInlineArrayFirstElementRefReadOnlyMethod : SynthesizedGlobalMethodSymbol
+    {
+        internal SynthesizedInlineArrayFirstElementRefReadOnlyMethod(SourceModuleSymbol containingModule, PrivateImplementationDetails privateImplType, string synthesizedMethodName)
+            : base(containingModule, privateImplType, synthesizedMethodName)
+        {
+            this.SetTypeParameters(ImmutableArray.Create<TypeParameterSymbol>(new SynthesizedSimpleMethodTypeParameterSymbol(this, 0, "TBuffer"), new SynthesizedSimpleMethodTypeParameterSymbol(this, 1, "TElement")));
+            this.SetReturnType(TypeParameters[1]);
+            this.SetParameters(ImmutableArray.Create<ParameterSymbol>(SynthesizedParameterSymbol.Create(this, TypeWithAnnotations.Create(TypeParameters[0]), 0, RefKind.In, "buffer")));
+        }
+
+        public override RefKind RefKind => RefKind.RefReadOnly;
+
+        internal override void GenerateMethodBody(TypeCompilationState compilationState, BindingDiagnosticBag diagnostics)
+        {
+            SyntheticBoundNodeFactory f = new SyntheticBoundNodeFactory(this, this.GetNonNullSyntaxNode(), compilationState, diagnostics);
+            f.CurrentFunction = this;
+
+            try
+            {
+                // return ref Unsafe.As<TBuffer, TElement>(ref Unsafe.AsRef<TBuffer>(in buffer))
+
+                var body = f.Return(f.Call(null,
+                                           f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T).Construct(ImmutableArray<TypeSymbol>.CastUp(TypeParameters)),
+                                           f.Call(null,
+                                                  f.WellKnownMethod(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T).Construct(TypeParameters[0]),
+                                                  f.Parameter(Parameters[0]))));
+
+                // NOTE: we created this block in its most-lowered form, so analysis is unnecessary
+                f.CloseMethod(body);
+            }
+            catch (SyntheticBoundNodeFactory.MissingPredefinedMember ex)
+            {
+                diagnostics.Add(ex.Diagnostic);
+                f.CloseMethod(f.ThrowNull());
+            }
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedSimpleProgramEntryPointSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedSimpleProgramEntryPointSymbol.cs
index e102925092460..c96e175176598 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedSimpleProgramEntryPointSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Synthesized/SynthesizedSimpleProgramEntryPointSymbol.cs
@@ -26,7 +26,8 @@ internal sealed class SynthesizedSimpleProgramEntryPointSymbol : SourceMemberMet
         private WeakReference<ExecutableCodeBinder>? _weakIgnoreAccessibilityBodyBinder;
 
         internal SynthesizedSimpleProgramEntryPointSymbol(SourceMemberContainerTypeSymbol containingType, SingleTypeDeclaration declaration, BindingDiagnosticBag diagnostics)
-            : base(containingType, syntaxReferenceOpt: declaration.SyntaxReference, declaration.SyntaxReference.GetLocation(), isIterator: declaration.IsIterator)
+            : base(containingType, syntaxReferenceOpt: declaration.SyntaxReference, declaration.SyntaxReference.GetLocation(), isIterator: declaration.IsIterator,
+                   MakeModifiersAndFlags(containingType, declaration))
         {
             Debug.Assert(declaration.SyntaxReference.GetSyntax() is CompilationUnitSyntax);
             _declaration = declaration;
@@ -52,26 +53,35 @@ internal SynthesizedSimpleProgramEntryPointSymbol(SourceMemberContainerTypeSymbo
                     break;
             }
 
-            bool isNullableAnalysisEnabled = IsNullableAnalysisEnabled(compilation, CompilationUnit);
-            this.MakeFlags(
-                MethodKind.Ordinary,
-                RefKind.None,
-                DeclarationModifiers.Static | DeclarationModifiers.Private | (hasAwait ? DeclarationModifiers.Async : DeclarationModifiers.None),
-                returnsVoid: !hasAwait && !hasReturnWithExpression,
-                // Consider the synthesized entrypoint to always have a body (conceptually the top level statements).
-                hasAnyBody: true,
-                isExpressionBodied: false,
-                isExtensionMethod: false,
-                isNullableAnalysisEnabled: isNullableAnalysisEnabled,
-                isVarArg: false,
-                isMetadataVirtualIgnoringModifiers: false);
-
             _parameters = ImmutableArray.Create(SynthesizedParameterSymbol.Create(this,
                               TypeWithAnnotations.Create(
                                   ArrayTypeSymbol.CreateCSharpArray(compilation.Assembly,
                                       TypeWithAnnotations.Create(Binder.GetSpecialType(compilation, SpecialType.System_String, NoLocation.Singleton, diagnostics)))), 0, RefKind.None, "args"));
         }
 
+        private static (DeclarationModifiers, Flags) MakeModifiersAndFlags(SourceMemberContainerTypeSymbol containingType, SingleTypeDeclaration declaration)
+        {
+            bool hasAwait = declaration.HasAwaitExpressions;
+            bool hasReturnWithExpression = declaration.HasReturnWithExpression;
+
+            DeclarationModifiers declarationModifiers = DeclarationModifiers.Static | DeclarationModifiers.Private | (hasAwait ? DeclarationModifiers.Async : DeclarationModifiers.None);
+            CSharpCompilation compilation = containingType.DeclaringCompilation;
+            var compilationUnit = (CompilationUnitSyntax)declaration.SyntaxReference.GetSyntax();
+            bool isNullableAnalysisEnabled = IsNullableAnalysisEnabled(compilation, compilationUnit);
+            Flags flags = MakeFlags(
+                                    MethodKind.Ordinary,
+                                    RefKind.None,
+                                    declarationModifiers,
+                                    returnsVoid: !hasAwait && !hasReturnWithExpression,
+                                    isExpressionBodied: false,
+                                    isExtensionMethod: false,
+                                    isNullableAnalysisEnabled: isNullableAnalysisEnabled,
+                                    isVarArg: false,
+                                    isExplicitInterfaceImplementation: false);
+
+            return (declarationModifiers, flags);
+        }
+
         internal static SynthesizedSimpleProgramEntryPointSymbol? GetSimpleProgramEntryPoint(CSharpCompilation compilation, CompilationUnitSyntax compilationUnit, bool fallbackToMainEntryPoint)
         {
             var type = GetSimpleProgramNamedTypeSymbol(compilation);
diff --git a/src/Compilers/CSharp/Portable/Symbols/SynthesizedNamespaceSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/SynthesizedNamespaceSymbol.cs
index 8d4ce65c6f617..4cd4ce5aa3f26 100644
--- a/src/Compilers/CSharp/Portable/Symbols/SynthesizedNamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/SynthesizedNamespaceSymbol.cs
@@ -67,16 +67,16 @@ public override ImmutableArray<SyntaxReference> DeclaringSyntaxReferences
         public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
             => ImmutableArray<NamedTypeSymbol>.Empty;
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
             => ImmutableArray<NamedTypeSymbol>.Empty;
 
         public override ImmutableArray<Symbol> GetMembers()
             => ImmutableArray<Symbol>.Empty;
 
-        public override ImmutableArray<Symbol> GetMembers(string name)
+        public override ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name)
             => ImmutableArray<Symbol>.Empty;
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/SynthesizedSimpleMethodTypeParameterSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/SynthesizedSimpleMethodTypeParameterSymbol.cs
new file mode 100644
index 0000000000000..f466741206cd9
--- /dev/null
+++ b/src/Compilers/CSharp/Portable/Symbols/SynthesizedSimpleMethodTypeParameterSymbol.cs
@@ -0,0 +1,126 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Roslyn.Utilities;
+using System.Collections.Immutable;
+using System.Diagnostics;
+
+namespace Microsoft.CodeAnalysis.CSharp.Symbols
+{
+    /// <summary>
+    /// A simple method type parameter with no constraints.
+    /// </summary>
+    internal sealed class SynthesizedSimpleMethodTypeParameterSymbol : TypeParameterSymbol
+    {
+        private readonly MethodSymbol _container;
+        private readonly int _ordinal;
+        private readonly string _name;
+
+        public SynthesizedSimpleMethodTypeParameterSymbol(MethodSymbol container, int ordinal, string name)
+        {
+            _container = container;
+            _ordinal = ordinal;
+            _name = name;
+        }
+
+        public override string Name
+        {
+            get { return _name; }
+        }
+
+        public override int Ordinal
+        {
+            get { return _ordinal; }
+        }
+
+        public override TypeParameterKind TypeParameterKind
+        {
+            get { return TypeParameterKind.Method; }
+        }
+
+        public override bool HasConstructorConstraint
+        {
+            get { return false; }
+        }
+
+        public override bool HasReferenceTypeConstraint
+        {
+            get { return false; }
+        }
+
+        public override bool IsReferenceTypeFromConstraintTypes
+        {
+            get { return false; }
+        }
+
+        internal override bool? ReferenceTypeConstraintIsNullable
+        {
+            get { return false; }
+        }
+
+        public override bool HasNotNullConstraint => false;
+
+        internal override bool? IsNotNullable => null;
+
+        public override bool HasValueTypeConstraint
+        {
+            get { return false; }
+        }
+
+        public override bool IsValueTypeFromConstraintTypes
+        {
+            get { return false; }
+        }
+
+        public override bool HasUnmanagedTypeConstraint
+        {
+            get { return false; }
+        }
+
+        public override VarianceKind Variance
+        {
+            get { return VarianceKind.None; }
+        }
+
+        public override Symbol ContainingSymbol
+        {
+            get { return _container; }
+        }
+
+        public override ImmutableArray<Location> Locations
+        {
+            get { throw ExceptionUtilities.Unreachable(); }
+        }
+
+        public override ImmutableArray<SyntaxReference> DeclaringSyntaxReferences
+        {
+            get { throw ExceptionUtilities.Unreachable(); }
+        }
+
+        internal override void EnsureAllConstraintsAreResolved()
+        {
+        }
+
+        internal override ImmutableArray<TypeWithAnnotations> GetConstraintTypes(ConsList<TypeParameterSymbol> inProgress)
+        {
+            return ImmutableArray<TypeWithAnnotations>.Empty;
+        }
+
+        internal override ImmutableArray<NamedTypeSymbol> GetInterfaces(ConsList<TypeParameterSymbol> inProgress)
+        {
+            throw ExceptionUtilities.Unreachable();
+        }
+
+        internal override NamedTypeSymbol GetEffectiveBaseClass(ConsList<TypeParameterSymbol> inProgress)
+        {
+            throw ExceptionUtilities.Unreachable();
+        }
+
+        internal override TypeSymbol GetDeducedBaseType(ConsList<TypeParameterSymbol> inProgress)
+        {
+            throw ExceptionUtilities.Unreachable();
+        }
+    }
+}
+
diff --git a/src/Compilers/CSharp/Portable/Symbols/TypeParameterSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/TypeParameterSymbol.cs
index 72c230053444e..9e8da066a4518 100644
--- a/src/Compilers/CSharp/Portable/Symbols/TypeParameterSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/TypeParameterSymbol.cs
@@ -158,13 +158,13 @@ public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
         }
 
         // Type parameters do not have members
-        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
         // Type parameters do not have members
-        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public sealed override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
@@ -711,5 +711,11 @@ protected sealed override ITypeSymbol CreateITypeSymbol(CodeAnalysis.NullableAnn
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/TypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/TypeSymbol.cs
index 085419b8ddfdb..5faeb42078a9c 100644
--- a/src/Compilers/CSharp/Portable/Symbols/TypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/TypeSymbol.cs
@@ -2466,5 +2466,40 @@ ITypeSymbol ITypeSymbolInternal.GetITypeSymbol()
         internal abstract bool IsRecord { get; }
 
         internal abstract bool IsRecordStruct { get; }
+
+        internal abstract bool HasInlineArrayAttribute(out int length);
+
+#nullable enable
+        internal FieldSymbol? TryGetInlineArrayElementField()
+        {
+            Debug.Assert(HasInlineArrayAttribute(out var length) && length > 0);
+
+            FieldSymbol? elementField = null;
+
+            if (this.TypeKind == TypeKind.Struct)
+            {
+                foreach (FieldSymbol field in ((NamedTypeSymbol)this).OriginalDefinition.GetFieldsToEmit())
+                {
+                    if (!field.IsStatic)
+                    {
+                        if (field.RefKind != RefKind.None || elementField is not null)
+                        {
+                            return null;
+                        }
+                        else
+                        {
+                            elementField = field;
+                        }
+                    }
+                }
+            }
+
+            if (elementField is not null && elementField.ContainingType.IsGenericType)
+            {
+                elementField = elementField.AsMember((NamedTypeSymbol)this);
+            }
+
+            return elementField;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs b/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs
index e716400a60e8b..69bc5a621c81b 100644
--- a/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs
@@ -1366,7 +1366,7 @@ public static bool IsPartial(this TypeSymbol type)
 
         public static bool HasFileLocalTypes(this TypeSymbol type)
         {
-            var foundType = type.VisitType(predicate: (type, _, _) => type is SourceMemberContainerTypeSymbol { IsFileLocal: true }, arg: (object?)null);
+            var foundType = type.VisitType(predicate: (type, _, _) => type is NamedTypeSymbol { IsFileLocal: true }, arg: (object?)null);
             return foundType is not null;
         }
 
diff --git a/src/Compilers/CSharp/Portable/Symbols/UnboundGenericType.cs b/src/Compilers/CSharp/Portable/Symbols/UnboundGenericType.cs
index 4d62bc15cbfa8..dd45b91113b68 100644
--- a/src/Compilers/CSharp/Portable/Symbols/UnboundGenericType.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/UnboundGenericType.cs
@@ -91,6 +91,7 @@ internal override bool MangleName
             }
         }
 
+        internal override bool IsFileLocal => false;
         internal override FileIdentifier? AssociatedFileIdentifier => null;
 
         internal override DiagnosticInfo ErrorInfo
diff --git a/src/Compilers/CSharp/Portable/Symbols/UnsupportedMetadataTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/UnsupportedMetadataTypeSymbol.cs
index 568823bb450e0..8aaaf41029d72 100644
--- a/src/Compilers/CSharp/Portable/Symbols/UnsupportedMetadataTypeSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/UnsupportedMetadataTypeSymbol.cs
@@ -38,6 +38,7 @@ internal override bool MangleName
             }
         }
 
+        internal override bool IsFileLocal => false;
         internal override FileIdentifier? AssociatedFileIdentifier => null;
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Syntax/SyntaxFacts.cs b/src/Compilers/CSharp/Portable/Syntax/SyntaxFacts.cs
index 2723d5a623788..efb0ee84d9c7a 100644
--- a/src/Compilers/CSharp/Portable/Syntax/SyntaxFacts.cs
+++ b/src/Compilers/CSharp/Portable/Syntax/SyntaxFacts.cs
@@ -515,6 +515,21 @@ internal static bool HasAnyBody(this BaseMethodDeclarationSyntax declaration)
             return (declaration.Body ?? (SyntaxNode?)declaration.ExpressionBody) != null;
         }
 
+        internal static bool IsExpressionBodied(this BaseMethodDeclarationSyntax declaration)
+        {
+            return declaration.Body == null && declaration.ExpressionBody != null;
+        }
+
+        internal static bool IsVarArg(this BaseMethodDeclarationSyntax declaration)
+        {
+            return IsVarArg(declaration.ParameterList);
+        }
+
+        internal static bool IsVarArg(this ParameterListSyntax parameterList)
+        {
+            return parameterList.Parameters.Any(static p => p.IsArgList);
+        }
+
         internal static bool IsTopLevelStatement([NotNullWhen(true)] GlobalStatementSyntax? syntax)
         {
             return syntax?.Parent?.IsKind(SyntaxKind.CompilationUnit) == true;
diff --git a/src/Compilers/CSharp/Portable/Syntax/UsingDirectiveSyntax.cs b/src/Compilers/CSharp/Portable/Syntax/UsingDirectiveSyntax.cs
index ee33a5ec50668..3d1d240686025 100644
--- a/src/Compilers/CSharp/Portable/Syntax/UsingDirectiveSyntax.cs
+++ b/src/Compilers/CSharp/Portable/Syntax/UsingDirectiveSyntax.cs
@@ -35,7 +35,7 @@ public partial class SyntaxFactory
     {
         /// <summary>Creates a new UsingDirectiveSyntax instance.</summary>
         public static UsingDirectiveSyntax UsingDirective(SyntaxToken staticKeyword, NameEqualsSyntax? alias, NameSyntax name)
-            => UsingDirective(globalKeyword: default, usingKeyword: default, staticKeyword, unsafeKeyword: default, alias, namespaceOrType: name, semicolonToken: default);
+            => UsingDirective(globalKeyword: default, usingKeyword: Token(SyntaxKind.UsingKeyword), staticKeyword, unsafeKeyword: default, alias, namespaceOrType: name, semicolonToken: Token(SyntaxKind.SemicolonToken));
 
         /// <summary>Creates a new UsingDirectiveSyntax instance.</summary>
         public static UsingDirectiveSyntax UsingDirective(SyntaxToken globalKeyword, SyntaxToken usingKeyword, SyntaxToken staticKeyword, NameEqualsSyntax? alias, NameSyntax name, SyntaxToken semicolonToken)
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf
index 8801471017ef1..36fa524ba700c 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Pouze „using static“ nebo „using alias“ může být „nebezpečný“.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">Atribut AsyncMethodBuilder je u anonymních metod bez explicitního návratového typu zakázaný.</target>
@@ -497,6 +502,11 @@
         <target state="translated">Položka {0} je explicitně implementována více než jednou.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">{0} je již uvedeno v seznamu rozhraní u typu {2} jako {1}.</target>
@@ -592,6 +602,11 @@
         <target state="translated">Strom výrazů nesmí obsahovat výraz indexu od-do (^).</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Strom výrazů nesmí obsahovat převod obslužné rutiny interpolovaného řetězce.</target>
@@ -852,11 +867,136 @@
         <target state="translated">Přístupové objekty init se nedají označit jako jen pro čtení. Místo toho označte jako jen pro čtení {0}.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Vlastnosti instance v rozhraních nemůžou mít inicializátory.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">Metoda UnmanagedCallersOnly {0} nemůže implementovat člena rozhraní {1} v typu {2}.</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Neplatný název algoritmu hash: {0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">{0} není platný název parametru z {1}.</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">Seznam parametrů může obsahovat pouze jedna deklarace částečného typu.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">Omezení new() nejde používat s omezením unmanaged.</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">{0}: Cílový modul runtime nepodporuje v přepisech kovariantní návratové typy. Návratový typ musí být {2}, aby odpovídal přepsanému členu {1}.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">Cílový modul runtime nepodporuje pro člena rozhraní přístupnost na úrovni Protected, Protected internal nebo Private protected.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">Řídící výraz switch je nutné uzavřít do závorek.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">Interpolovaný literál nezpracovaného řetězce nezačíná dostatečným počtem znaků $, aby bylo možné takový počet po sobě jdoucích koncových složených závorek povolit jako obsah.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Nejde použít parametr primárního konstruktoru typu {0} uvnitř člena instance</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">odvozený typ delegáta</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">člen instance v nameof</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">přístup k elementu ukazatele</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">Operátor „&amp;“ by se neměl používat u parametrů nebo místních proměnných v asynchronních metodách.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">Agument CallerArgumentExpressionAttribute nebude mít žádný účinek. Přepisuje ho atribut CallerMemberNameAttribute.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">Parametr {0} se zachytil do stavu nadřazeného typu a jeho hodnota se také předala základnímu konstruktoru. Hodnotu může zachytit i základní třída.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">Použití proměnné v tomto kontextu může vystavit odkazované proměnné mimo rozsah jejich oboru.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">Argument InterpolatedStringHandlerArgument nemá při použití u parametrů lambda žádný účinek a bude se ignorovat v lokalitě volání.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Větve podmíněného operátoru odkazu odkazují na proměnné s nekompatibilními obory deklarací</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">Požadovaný člen {0} by neměl být přiřazen atributem ObsoleteAttribute, pokud není obsahující typ zastaralý nebo jsou zastaralé všechny konstruktory.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
  Parametry kompilátoru Visual C#
 
  - VÝSTUPNÍ SOUBORY -
@@ -8556,7 +8794,7 @@ Blok catch() po bloku catch (System.Exception e) může zachytit výjimky, kter
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">U iterátorů nejde používat nezabezpečené parametry nebo typy yield.</target>
+        <target state="translated">Iterátory nemůžou mít parametry typu ukazatele.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Poskytněte kompilátoru nějaký způsob, jak metody rozlišit. Můžete např
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Asynchronní metody nemůžou mít návratové typy nebo parametry, které nejsou bezpečné.</target>
+        <target state="translated">Asynchronní metody nemůžou mít parametry typu ukazatele.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ Pokud chcete odstranit toto varování, můžete místo toho použít /reference
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'Argument await nejde použít ve výrazu obsahujícím volání do {0}, protože se vrací pomocí odkazu.</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'Argument await nejde použít ve výrazu obsahujícím volání do {0}, protože se vrací pomocí odkazu.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf
index b550c9f5e5d17..670a9b1161bdc 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Nur ein "using static" oder "using alias" kann "unsicher" sein.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">Das AsyncMethodBuilder-Attribut ist für anonyme Methoden ohne expliziten Rückgabetyp unzulässig.</target>
@@ -497,6 +502,11 @@
         <target state="translated">"{0}" ist mehrfach explizit implementiert.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">"{0}" wird in der Schnittstellenliste bereits für den Typ "{2}" als "{1}" aufgeführt.</target>
@@ -592,6 +602,11 @@
         <target state="translated">Eine Ausdrucksbaumstruktur darf keinen vom Ende ausgehenden Indexausdruck ("^") enthalten.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Eine Ausdrucksbaumstruktur darf keine Handler-Konvertierung einer interpolierten Zeichenfolge enthalten.</target>
@@ -852,11 +867,136 @@
         <target state="translated">init-Zugriffsmethoden können nicht als schreibgeschützt markiert werden. Markieren Sie stattdessen "{0}" als schreibgeschützt.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Instanzeigenschaften in Schnittstellen können keine Initialisierer aufweisen.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">Die Methode „UnmanagedCallersOnly“ „{0}“ kann das Schnittstellenelement „{1}“ im Typ „{2}“ nicht implementieren.</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Ungültiger Name für Hashalgorithmus: "{0}"</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">"{0}" ist kein gültiger Parametername von "{1}".</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">Nur eine einzelne partielle Typdeklaration darf eine Parameterliste aufweisen.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">Die new()-Einschränkung kann nicht mit der unmanaged-Einschränkung verwendet werden.</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">{0}: Die Zielruntime unterstützt keine covarianten Rückgabetypen in Überschreibungen. Der Rückgabetyp muss "{2}" sein, um dem überschriebenen Member "{1}" zu entsprechen.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">Die Zugriffsoptionen "protected", "protected internal" oder "private protected" werden von der Zielruntime für einen Member einer Schnittstelle nicht unterstützt.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">Der Ausdruck zur Steuerung von Schaltern muss in Klammern eingeschlossen werden.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">Das interpolierte Rohzeichenfolgenliteral beginnt nicht mit genügend „$“-Zeichen, um so viele aufeinanderfolgende schließende geschweifte Klammern als Inhalt zuzulassen.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Der primäre Konstruktorparameter vom Typ "{0}" innerhalb eines Instanzmembers kann nicht verwendet werden.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">abgeleiteter Delegattyp</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">Instanzmember in "nameof"</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">Zeigerelementzugriff</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">Der Operator '&amp;' sollte nicht für Parameter oder lokale Variablen in asynchronen Methoden verwendet werden.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">Das CallerArgumentExpressionAttribute hat keine Auswirkungen. Es wird von dem CallerMemberNameAttribute überschrieben</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">Der Parameter „{0}“ wird in den Zustand des einschließenden Typs erfasst und sein Wert wird auch an den Basiskonstruktor übergeben. Der Wert kann auch von der Basisklasse erfasst werden.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">Die Verwendung der Variablen in diesem Kontext kann dazu führen, dass referenzierte Variablen außerhalb ihres Deklarationsbereichs verfügbar gemacht werden.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">Das InterpolatedStringHandlerArgument hat bei Anwendung auf Lambdaparameter keine Auswirkungen und wird am Aufrufstandort ignoriert.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Die Branches des bedingten ref-Operators verweisen auf Variablen mit inkompatiblen Deklarationsbereichen.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">Der erforderliche Member "{0}" darf nicht mit "ObsoleteAttribute" attributiert werden, es sei denn, der enthaltende Typ ist veraltet oder alle Konstruktoren sind veraltet.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Visual C#-Compileroptionen
 
                        – AUSGABEDATEIEN –
@@ -5028,7 +5266,7 @@
       </trans-unit>
       <trans-unit id="WRN_NewNotRequired">
         <source>The member '{0}' does not hide an accessible member. The new keyword is not required.</source>
-        <target state="translated">Das Mitglied "{0}" blendet kein verfügbares Mitglied aus. Das neue Schlüsselwort ist nicht erforderlich.</target>
+        <target state="translated">Das Mitglied "{0}" blendet kein verfügbares Mitglied aus. Das Schlüsselwort "neu" ist nicht erforderlich.</target>
         <note />
       </trans-unit>
       <trans-unit id="WRN_NewNotRequired_Title">
@@ -8556,7 +8794,7 @@ Ein catch()-Block nach einem catch (System.Exception e)-Block kann nicht-CLS-Aus
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Iteratoren dürfen keine unsicheren Parameter oder yield-Typen aufweisen.</target>
+        <target state="translated">Iteratoren dürfen keine Zeigertypparameter aufweisen.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Unterstützen Sie den Compiler bei der Unterscheidung zwischen den Methoden. Daz
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Async-Methoden dürfen über keine unsicheren Parameter oder Rückgabetypen verfügen.</target>
+        <target state="translated">Asynchrone Methoden dürfen keine Zeigertypparameter aufweisen.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11589,7 +11827,7 @@ Um die Warnung zu beheben, können Sie stattdessen /reference verwenden (Einbett
       </trans-unit>
       <trans-unit id="ERR_PPLoadFollowsToken">
         <source>Cannot use #load after first token in file</source>
-        <target state="translated">"#Load" kann nicht nach dem ersten Token in der Datei verwendet werden.</target>
+        <target state="translated">"#load" kann nicht nach dem ersten Token in der Datei verwendet werden.</target>
         <note />
       </trans-unit>
       <trans-unit id="CouldNotFindFile">
@@ -11813,8 +12051,8 @@ Um die Warnung zu beheben, können Sie stattdessen /reference verwenden (Einbett
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'"await" kann nicht in einem Ausdruck verwendet werden, der einen Aufruf von "{0}" enthält, weil die Rückgabe als Verweis erfolgt.</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'"await" kann nicht in einem Ausdruck verwendet werden, der einen Aufruf von "{0}" enthält, weil die Rückgabe als Verweis erfolgt.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf
index 4868efac880d9..e5c4620fbe49b 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Solo un ''usando estática'' o ''usando alias'' puede ser ''No seguro''.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">El atributo AsyncMethodBuilder no se permite en métodos anónimos sin un tipo de valor devuelto explícito.</target>
@@ -497,6 +502,11 @@
         <target state="translated">"{0}" está implementado de forma explícita más de una vez.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">"{0}" ya se muestra en la lista de interfaces en el tipo "{2}" como "{1}".</target>
@@ -592,6 +602,11 @@
         <target state="translated">Un árbol de expresión no puede contener una expresión de índice del otro extremo ("^").</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Un árbol de (la) expresión no puede contener una conversión de controlador de cadena interpolada.</target>
@@ -852,11 +867,136 @@
         <target state="translated">Los descriptores de acceso "init" no se pueden marcar como "readonly". Marque en su lugar "{0}" como readOnly.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Las propiedades de la instancia en las interfaces no pueden tener inicializadores.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">El método "UnmanagedCallersOnly" "{0}" no puede implementar el miembro de interfaz "{1}" en el tipo "{2}"</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Nombre de algoritmo hash no válido: "{0}"</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">"{0}" no es un nombre de parámetro válido para "{1}".</target>
@@ -1019,7 +1174,7 @@
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveRequiresSpace">
         <source>The #line span directive requires space before the first parenthesis, before the character offset, and before the file name</source>
-        <target state="translated">La directiva de intervalo de #línea requiere un espacio delante del primer paréntesis, antes del desplazamiento de caracteres y antes del nombre de archivo</target>
+        <target state="translated">La directiva de intervalo de #line requiere un espacio delante del primer paréntesis, antes del desplazamiento de caracteres y antes del nombre de archivo</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_ListPatternRequiresLength">
@@ -1102,6 +1257,11 @@
         <target state="translated">Solo una declaración de tipo parcial puede tener una lista de parámetros</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">La restricción "new()" no se puede utilizar con la restricción "unmanaged"</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">"{0}": el entorno de ejecución de destino no admite los tipos de valores devueltos de covariante en las invalidaciones. El tipo de valor devuelto debe ser "{2}" para que coincida con el miembro "{1}" invalidado.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">El entorno de ejecución de destino no admite la accesibilidad protegida, protegida interna o protegida privada para un miembro de una interfaz.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">La expresión switch aplicable requiere paréntesis.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">El literal de cadena sin formato interpolado no comienza con suficientes caracteres \"$\" para permitir tantos corchetes de cierre consecutivos como contenido.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">No se puede usar el parámetro de constructor principal de tipo '{0}' dentro de un miembro de instancia</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">tipo de delegado inferido</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">miembro de instancia en 'nameof'</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">acceso al elemento de puntero</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">El operador ''&amp;'' no debe usarse en parámetros o variables locales en métodos asincrónicos.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">El atributo CallerArgumentExpressionAttribute no tendrá efecto: lo reemplaza el atributo CallerMemberNameAttribute</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">El parámetro '{0}' se captura en el estado del tipo envolvente y su valor también se pasa al constructor base. La clase base también puede capturar el valor.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">Usar la variable en este contexto puede exponer variables a las que se hace referencia fuera de su ámbito de declaración</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">El argumento InterpolatedStringHandlerArgument no tiene ningún efecto cuando se aplica a parámetros lambda y se omitirá en el sitio de llamada.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Las ramas del operador condicional ref hacen referencia a variables con ámbitos de declaración incompatibles</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">El miembro requerido '{0}' no se debe atribuir con 'ObsoleteAttribute' a menos que el tipo contenedor esté obsoleto o todos los constructores estén obsoletos.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Opciones del compilador de Visual C#
 
                        - ARCHIVOS DE SALIDA -
@@ -8556,7 +8794,7 @@ Un bloque catch() después de un bloque catch (System.Exception e) puede abarcar
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Los iteradores no pueden tener parámetros no seguros o tipos yield</target>
+        <target state="translated">Los iteradores no pueden tener parámetros de tipo de puntero</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Indique al compilador alguna forma de diferenciar los métodos. Por ejemplo, pue
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Los métodos asincrónicos no pueden tener parámetros no seguros o tipos de valor devuelto</target>
+        <target state="translated">Los métodos asincrónicos no pueden tener parámetros de tipo de puntero</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ Para eliminar la advertencia puede usar /reference (establezca la propiedad Embe
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'No se puede usar 'await' en una expresión que contiene una llamada a '{0}' porque devuelve datos por referencia.</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'No se puede usar 'await' en una expresión que contiene una llamada a '{0}' porque devuelve datos por referencia.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf
index c3d6225b203a0..b6b47799f2267 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Seul un 'using static' ou 'using alias' peut être 'unsafe'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">L'attribut AsyncMethodBuilder n'est pas autorisé pour les méthodes anonymes sans type de retour explicite.</target>
@@ -497,6 +502,11 @@
         <target state="translated">'{0}' est implémenté explicitement plusieurs fois.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">'{0}' est déjà listé dans la liste d'interfaces du type '{2}' en tant que '{1}'.</target>
@@ -592,6 +602,11 @@
         <target state="translated">Une arborescence de l'expression ne peut pas contenir d'expression d'index partant de la fin ('^').</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Une arborescence de l’expression ne peut pas contenir une conversion de gestionnaire de chaîne interpolée.</target>
@@ -852,11 +867,136 @@
         <target state="translated">Les accesseurs 'init' ne peuvent pas être marqués 'readonly'. Marquez '{0}' readonly à la place.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Les propriétés d'instance dans les interfaces ne peuvent pas avoir d'initialiseurs.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">La méthode UnmanagedCallersOnly '{0}' ne peut pas implémenter le membre d'interface '{1}' dans le type '{2}'</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Nom d'algorithme de hachage non valide : '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">« {0} » n’est pas un nom de paramètre valide de « {1} ».</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">Seule une déclaration de type partiel d’un seul enregistrement peut avoir une liste de paramètres.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">La contrainte 'new()' ne peut pas être utilisée avec la contrainte 'unmanaged'</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">'{0}' : le runtime cible ne prend pas en charge les types de retour covariants dans les substitutions. Le type de retour doit être '{2}' pour correspondre au membre substitué '{1}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">Le runtime cible ne prend pas en charge l'accessibilité 'protected', 'protected internal' ou 'private protected' d'un membre d'interface.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">Des parenthèses sont obligatoires autour de l'expression régissant switch.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">Le littéral de chaîne brute interpolée ne commence pas par suffisamment de caractères '$' pour autoriser autant d’accolades fermante consécutives comme contenu.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Impossible d'utiliser le paramètre de constructeur principal de type '{0}' dans un membre d'instance</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">type délégué déduit</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">membre d'instance dans 'nameof'</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">accès à l’élément de pointeur</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">L’opérateur '&amp;' ne doit pas être utilisé sur les paramètres ou les variables locales dans les méthodes asynchrones.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">CallerArgumentExpressionAttribute n'aura pas d'effet ; il est remplacé par CallerMemberNameAttribute</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">Paramètre '{0}' est capturé dans l’état du type englobant et sa valeur est également passée au constructeur de base. La valeur peut également être capturée par la classe de base.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">Utiliser la variable dans ce contexte peut exposer des variables de référence en dehors de leur étendue de déclaration</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">InterpolatedStringHandlerArgument n’a aucun effet lorsqu’il est appliqué aux paramètres lambda et qu’il est ignoré sur le site d’appel.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Les branches d'un opérateur conditionnel ref font référence à des variables ayant des étendues de déclaration incompatibles</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">Le membre obligatoire '{0}' ne doit pas être attribué avec 'ObsoleteAttribute', sauf si le type conteneur est obsolète ou si tous les constructeurs sont obsolètes.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Options du compilateur Visual C#
 
                        - FICHIERS DE SORTIE -
@@ -8556,7 +8794,7 @@ Un bloc catch() après un bloc catch (System.Exception e) peut intercepter des e
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Les itérateurs ne peuvent pas avoir de paramètres unsafe ou de types yield</target>
+        <target state="translated">Les itérateurs ne peuvent pas avoir de paramètres de type pointeur</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Permettez au compilateur de différencier les méthodes. Par exemple, vous pouve
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Les méthodes ne peuvent pas avoir de paramètres unsafe ou de types de retour</target>
+        <target state="translated">Les méthodes asynchrones ne peuvent pas avoir de paramètres de type pointeur</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ Pour supprimer l'avertissement, vous pouvez utiliser la commande /reference (dé
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'Impossible d'utiliser 'await' dans une expression contenant un appel à '{0}', car il effectue un retour par référence</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'Impossible d'utiliser 'await' dans une expression contenant un appel à '{0}', car il effectue un retour par référence</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf
index 0929d05995999..f36f41a2d8e5f 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Solo 'using static' o 'using alias' può essere 'unsafe'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">L'attributo AsyncMethodBuilder non è consentito in metodi anonimi senza un tipo restituito esplicito.</target>
@@ -497,6 +502,11 @@
         <target state="translated">'{0}' è implementato più di una volta in modo esplicito.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">'{0}' è già incluso nell'elenco di interfacce nel tipo '{2}' come '{1}'.</target>
@@ -592,6 +602,11 @@
         <target state="translated">Un albero delle espressioni non può contenere un'espressione di indice from end ('^').</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Un albero delle espressioni non può contenere una conversione del gestore di stringhe interpolate.</target>
@@ -852,11 +867,136 @@
         <target state="translated">Non è possibile contrassegnare le funzioni di accesso 'init' come 'readonly'. Contrassegnare '{0}' come readonly.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Le proprietà di istanza nelle interfacce non possono avere inizializzatori.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">Il metodo '{0}' di 'UnmanagedCallersOnly' non può implementare il membro di interfaccia '{1}' nel tipo '{2}'</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Il nome dell'algoritmo hash non è valido: '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">'{0}' non è un nome di parametro valido da '{1}'.</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">Solo una dichiarazione parziale di singolo record può includere un elenco di parametri</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">Non è possibile usare il vincolo 'new()' con il vincolo 'unmanaged'</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">'{0}': il runtime di destinazione non supporta tipi restituiti covarianti negli override. Il tipo restituito deve essere '{2}' in modo da corrispondere al membro '{1}' di cui è stato eseguito l'override</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">Il runtime di destinazione non supporta l'accessibilità 'protected', 'protected internal' o 'private protected' per un membro di un'interfaccia.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">L'espressione che gestisce lo switch deve essere racchiusa tra parentesi.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">Il valore letterale stringa non elaborata interpolato non inizia con un numero di caratteri '$' sufficiente per consentire il contenuto di questo numero di parentesi graffe di chiusura consecutive.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Non è possibile usare il parametro del costruttore primario di tipo '{0}' all'interno di un membro di istanza</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">tipo di delegato dedotto</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">membro di istanza in 'nameof'</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">accesso all'elemento puntatore</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">L'operatore '&amp;' non deve essere usato su parametri o variabili locali in metodi asincroni.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">CallerArgumentExpressionAttribute non avrà alcun effetto. CallerMemberNameAttribute ne eseguirà l'override</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">Il parametro '{0}' viene catturato nello stato del tipo di inclusione e il relativo valore viene passato anche al costruttore di base. Il valore potrebbe essere catturato anche dalla classe di base.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">L'uso di variabili in questo contesto potrebbe esporre le variabili a cui si fa riferimento al di fuori dell'ambito della dichiarazione</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">InterpolatedStringHandlerArgument non ha alcun effetto se viene applicato ai parametri lambda e verrà ignorato nel sito di chiamata.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">I rami dell'operatore condizionale di riferimento fanno riferimento a variabili con ambiti di dichiarazione incompatibili</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">Al membro obbligatorio '{0}' non deve essere attribuito 'ObsoleteAttribute' a meno che il tipo contenitore sia obsoleto o che tutti i costruttori siano obsoleti.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Opzioni del compilatore Visual C#
 
                        - FILE DI OUTPUT -
@@ -8556,7 +8794,7 @@ Un blocco catch() dopo un blocco catch (System.Exception e) può rilevare eccezi
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Gli iteratori non possono avere parametri unsafe o tipi yield</target>
+        <target state="translated">Gli iteratori non possono avere parametri di tipo puntatore</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Impostare il compilatore in modo tale da distinguere i metodi, ad esempio assegn
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">I metodi asincroni non possono avere parametri non sicuri o tipi restituiti</target>
+        <target state="translated">I metodi asincroni non possono avere parametri di tipo puntatore</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ Per rimuovere l'avviso, è invece possibile usare /reference (impostare la propr
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'Non è possibile usare 'await' in un'espressione che contiene una chiamata a '{0}' perché viene restituito per riferimento</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'Non è possibile usare 'await' in un'espressione che contiene una chiamata a '{0}' perché viene restituito per riferimento</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf
index 98abd63f33f19..13187ff4f1530 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf
@@ -287,6 +287,11 @@
         <target state="translated">'unsafe' に設定できるのは、'using static' または 'using エイリアス' のみです。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">AsyncMethodBuilder 属性は、明示的な戻り値の型のない匿名メソッドでは許可されていません。</target>
@@ -497,6 +502,11 @@
         <target state="translated">'{0}' が複数回、明示的に実装されています。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">'{0}' は、型 '{2}' のインターフェイス リストに '{1}' として既に指定されています。</target>
@@ -592,6 +602,11 @@
         <target state="translated">式ツリーに、from-end インデックス ('^') 式を含めることはできません。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">式ツリーには、補間された文字列ハンドラー変換を含めることはできません。</target>
@@ -852,11 +867,136 @@
         <target state="translated">'init' アクセサーを 'readonly' としてマークできません。代わりに '{0}' を readonly としてマークします。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">インターフェイス内のインスタンス プロパティは初期化子を持つことができません。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">'UnmanagedCallersOnly' メソッド '{0}' は、インターフェイス メンバー '{1}' を型 '{2}' で実装できません</target>
@@ -922,6 +1062,21 @@
         <target state="translated">無効なハッシュ アルゴリズム名: '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">'{0}' は、'{1}' からの有効なパラメーター名ではありません。</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">単一の部分型宣言のみがパラメーター リストを持つことができます</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">new()' 制約は 'unmanaged' 制約と一緒には使用できません</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">'{0}': ターゲットのランタイムはオーバーライドで戻り値の型 covariant をサポートしていません。戻り値の型は、オーバーライドされるメンバー '{1}' と一致する '{2}' にする必要があります</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">ターゲット ランタイムは、インターフェイスのメンバーに対して 'protected'、'protected internal'、'private protected' アクセシビリティをサポートしていません。</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">switch を制御する式の周囲にはかっこが必要です。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">補間された生文字列リテラルの先頭に十分な数の '$' 文字がないため、連続する終わり波かっこをコンテンツとして使用できません。</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">インスタンス メンバー内に ref に似た型を持つプライマリ コンストラクター パラメーター '{0}' を使用することはできません</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">推論されたデリゲート型</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">'nameof' のインスタンス メンバー</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">ポインター要素アクセス</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">'&amp;' 演算子は、非同期メソッドのパラメーターまたはローカル変数では使用できません。</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">CallerArgumentExpressionAttribute は効果がなく、CallerMemberNameAttribute によってオーバーライドされます</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">パラメーター '{0}' は外側の型の状態にキャプチャされ、その値も基底コンストラクターに渡されます。この値は、基底クラスでもキャプチャされる可能性があります。</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">このコンテキストでの変数の使用は、参照される変数が宣言のスコープ外に公開される可能性があります</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">ラムダ パラメーターに適用しても InterpolatedStringHandlerArgument は効果がありません。呼び出しサイトでは無視されます。</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">ref 条件演算子のブランチでは、互換性のない宣言スコープを持つ変数を参照します</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">必要なメンバー '{0}' は、包含する型が古い形式であるか、すべてのコンストラクターが古い形式でない限り、属性 'ObsoleteAttribute' が必要ありません。</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Visual C# Compiler のオプション
 
                        - 出力ファイル -
@@ -8556,7 +8794,7 @@ AssemblyInfo.cs ファイルで RuntimeCompatibilityAttribute が false に設
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">反復子には unsafe パラメーターまたは yield 型を指定できません</target>
+        <target state="translated">反復子にポインター型パラメーターを指定することはできません</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ C# では out と ref を区別しますが、CLR では同じと認識します
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">非同期メソッドのパラメーターまたは戻り値の型をアンセーフにすることはできません</target>
+        <target state="translated">非同期メソッドにポインター型パラメーターを指定することはできません</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'参照渡しで返すため、'{0}' の呼び出しが含まれる式では 'await' を使用することができません</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'参照渡しで返すため、'{0}' の呼び出しが含まれる式では 'await' を使用することができません</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf
index 1d73701fc153e..59a6403bbebf5 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf
@@ -287,6 +287,11 @@
         <target state="translated">'using static' 또는 'using alias'만 'unsafe'일 수 있습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">AsyncMethodBuilder 특성은 명시적 반환 형식이 없는 익명 메서드에서 허용되지 않습니다.</target>
@@ -497,6 +502,11 @@
         <target state="translated">'{0}'은(는) 두 번 이상 명시적으로 구현됩니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">'{0}'은(는) '{2}' 형식에 대한 인터페이스 목록에 '{1}'(으)로 이미 나열되어 있습니다.</target>
@@ -592,6 +602,11 @@
         <target state="translated">식 트리에는 내림차순 인덱스('^') 식을 포함할 수 없습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">식 트리에는 보간된 문자열 처리기 변환이 포함될 수 없습니다.</target>
@@ -852,11 +867,136 @@
         <target state="translated">'init' 접근자는 'readonly'로 표시할 수 없습니다. 대신 '{0}' 읽기 전용으로 표시합니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">인터페이스의 인스턴스 속성은 이니셜라이저를 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">'UnmanagedCallersOnly' 메서드 '{0}'은(는) '{2}' 유형의 인터페이스 멤버 '{1}'을(를) 구현할 수 없습니다.</target>
@@ -922,6 +1062,21 @@
         <target state="translated">잘못된 해시 알고리즘 이름: '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">'{0}'은(는) '{1}'의 유효한 매개 변수 이름이 아닙니다.</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">단일 부분 형식 선언만 매개 변수 목록을 가질 수 있습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">new()' 제약 조건은 'unmanaged' 제약 조건과 함께 사용할 수 없습니다.</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">'{0}': 대상 런타임이 재정의에서 공변(covariant) 반환 형식을 지원하지 않습니다. 재정의된 멤버 '{1}'과(와) 일치하려면 '{2}' 반환 형식이어야 합니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">대상 런타임이 인터페이스 멤버의 'protected', 'protected internal' 또는 'private protected' 접근성을 지원하지 않습니다.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">식을 제어하는 switch 주위에 괄호가 필요합니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">보간된 원시 문자열 리터럴을 시작하는 '$' 문자가 부족해 이렇게 많은 연속 닫는 중괄호를 콘텐츠로 사용할 수 없습니다.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">인스턴스 멤버 내에서 '{0}' 형식의 기본 생성자 매개 변수를 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">유추된 대리자 형식</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">'nameof'의 인스턴스 멤버</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">포인터 요소 액세스</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">'&amp;' 연산자는 비동기 메서드의 매개 변수 또는 지역 변수에 사용하면 안 됩니다.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">CallerArgumentExpressionAttribute는 효과가 없습니다. CallerMemberNameAttribute에 의해 재정의됩니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">'{0}' 매개 변수는 둘러싸인 형식의 상태로 캡처되며 해당 값도 기본 생성자에 전달됩니다. 기본 클래스에서도 값을 캡처할 수 있습니다.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">이 컨텍스트에서 변수를 사용하면 선언 범위 외부에서 참조된 변수가 노출될 수 있습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">InterpolatedStringHandlerArgument는 람다 매개 변수에 적용할 때 효과가 없으며 호출 사이트에서 무시됩니다.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">ref 조건부 연산자의 분기는 선언 범위가 호환되지 않는 변수를 참조합니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">필수 구성원 '{0}'은(는) 포함하는 유형이 더 이상 사용되지 않거나 모든 생성자가 사용되지 않는 경우가 아니면 'ObsoleteAttribute'로 특성을 지정해서는 안 됩니다.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Visual C# 컴파일러 옵션
 
                        - 출력 파일 -
@@ -8555,7 +8793,7 @@ catch (System.Exception e) 블록 뒤의 catch() 블록은 RuntimeCompatibilityA
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">반복기에 안전하지 않은 매개 변수 또는 yield 형식을 사용할 수 없습니다.</target>
+        <target state="translated">반복기에는 포인터 형식 매개 변수를 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9898,7 +10136,7 @@ C#에서는 out과 ref를 구분하지만 CLR에서는 동일한 것으로 간
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">비동기 메서드에는 안전하지 않은 매개 변수 또는 반환 형식을 사용할 수 없습니다.</target>
+        <target state="translated">비동기 메서드에는 포인터 형식 매개 변수를 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11812,8 +12050,8 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'await'는 참조로 반환되므로 '{0}'에 대한 호출이 포함된 식에 사용할 수 없습니다.</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'await'는 참조로 반환되므로 '{0}'에 대한 호출이 포함된 식에 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf
index d347b57bcd65c..757e6656463b5 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Tylko element „użycie statyczne” lub „użycie aliasu” może być „niebezpieczne”.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">Atrybut AsyncMethodBuilder jest niedozwolony w metodach anonimowych bez jawnego zwracanego typu.</target>
@@ -497,6 +502,11 @@
         <target state="translated">Element „{0}” jest jawnie zaimplementowany więcej niż raz.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">Element „{0}” znajduje się już na liście interfejsów typu „{2}” jako „{1}”.</target>
@@ -592,6 +602,11 @@
         <target state="translated">Drzewo wyrażeń nie może zawierać wyrażenia „od końca indeksu” („^”).</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Drzewo wyrażenia nie może zawierać konwersji procedury obsługi ciągu interpolowanego.</target>
@@ -852,11 +867,136 @@
         <target state="translated">Metody dostępu „init” nie można oznaczyć jako „tylko do odczytu”. Zamiast tego oznacz jako tylko do odczytu element „{0}”.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Właściwości wystąpienia w interfejsach nie mogą mieć inicjatorów.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">Metoda "UnmanagedCallersOnly" "{0}" nie może implementować składowej interfejsu "{1}" w typie "{2}"</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Nieprawidłowa nazwa algorytmu wyznaczania wartości skrótu: „{0}”</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">„{0}” nie jest prawidłową nazwą parametru z elementu „{1}”.</target>
@@ -1009,7 +1164,7 @@
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveEndLessThanStart">
         <source>The #line directive end position must be greater than or equal to the start position</source>
-        <target state="translated">Pozycja końcowa dyrektywy #wiersza musi być większa lub równa pozycji początkowej</target>
+        <target state="translated">Pozycja końcowa dyrektywy #line musi być większa lub równa pozycji początkowej</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveInvalidValue">
@@ -1102,6 +1257,11 @@
         <target state="translated">Tylko pojedyncza deklaracja typu częściowego może mieć listę parametrów</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">Ograniczenie „new()” nie może być używane z ograniczeniem „unmanaged”</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">„{0}”: docelowe środowisko uruchomieniowe nie obsługuje kowariantnych typów zwracanych w przesłonięciach. Typem zwracanym musi być „{2}”, aby zachować zgodność z przesłoniętą składową „{1}”.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">Docelowe środowisko uruchomieniowe nie obsługuje specyfikatorów dostępu „protected”, „protected internal” i „private protected” dla składowej interfejsu.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">Wymagane są nawiasy wokół wyrażenia sterującego instrukcją switch.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">Interpolowany literał nieprzetworzonego ciągu nie zaczyna się od wystarczającej liczby znaków „$”, aby zezwolić na następującą liczbę kolejnych zamykających nawiasów klamrowych jako zawartość.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Nie można użyć podstawowego parametru konstruktora typu „{0}” wewnątrz składowej wystąpienia</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">Typ delegowania wywnioskowanego</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">składowa wystąpienia w elemencie „nameof”</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">dostęp do elementu wskaźnika</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">Operator „&amp;” nie powinien być używany w parametrach ani zmiennych lokalnych w metodach asynchronicznych.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">Atrybut CallerMemberNameAttribute nie odniesie żadnego skutku; ponieważ jest on zastąpiony przez atrybut CallerFilePathAttribute</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">Parametr '{0}' jest przechwytywane do stanu otaczającego typu, a jego wartość jest również przekazywana do konstruktora podstawowego. Wartość może zostać również przechwycona przez klasę bazową.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">Nie można używać zmiennej w tym kontekście, ponieważ może uwidaczniać odwoływane zmienne poza ich zakresem deklaracji</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">Argument InterpolatedStringHandlerArgument nie odniesie żadnego skutku po zastosowaniu do parametrów lambda i zostanie zignorowany w lokacji wywołania.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Gałęzie operatora warunkowego ref nie mogą przywoływać zmiennych z niezgodnymi zakresami deklaracji</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">Wymagana składowa „{0}” nie powinna mieć atrybutu „ObsoleteAttribute”, chyba że zawierający typ jest przestarzały lub wszystkie konstruktory są przestarzałe.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Opcje kompilatora Visual C#
 
                         - PLIKI WYJŚCIOWE -
@@ -8556,7 +8794,7 @@ Blok catch() po bloku catch (System.Exception e) może przechwytywać wyjątki n
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Iteratory nie mogą mieć niebezpiecznych parametrów ani typów przekazywania.</target>
+        <target state="translated">Iteratory nie mogą mieć parametrów typu wskaźnika</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Musisz umożliwić kompilatorowi rozróżnienie metod. Możesz na przykład nada
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Metody asynchroniczne nie mogą zawierać niezabezpieczonych parametrów ani zwracanych typów.</target>
+        <target state="translated">Metody asynchroniczne nie mogą mieć parametrów typu wskaźnika</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ Aby usunąć ostrzeżenie, możesz zamiast tego użyć opcji /reference (ustaw w
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'Elementu „await” nie można użyć w wyrażeniu zawierającym wywołanie elementu „{0}”, ponieważ zwraca ono wartość przez referencję</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'Elementu „await” nie można użyć w wyrażeniu zawierającym wywołanie elementu „{0}”, ponieważ zwraca ono wartość przez referencję</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf
index dbe78c4e7ffdb..ce1e4fe5ef4b8 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Somente um 'usando estático' ou 'usando alias' pode ser 'inseguro'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">O atributo AsyncMethodBuilder não é permitido em métodos anônimos sem um tipo de retorno explícito.</target>
@@ -497,6 +502,11 @@
         <target state="translated">'{0}' é implementado explicitamente mais de uma vez.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">'{0}' já está listado na lista de interfaces no tipo '{2}' como '{1}'.</target>
@@ -592,6 +602,11 @@
         <target state="translated">Uma árvore de expressão não pode conter uma expressão de índice de front-end ('^').</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Uma árvore de expressão pode não conter uma conversão de manipulador de cadeia de caracteres interpolada.</target>
@@ -852,11 +867,136 @@
         <target state="translated">Os acessadores 'init' não podem ser marcados como 'readonly'. Em vez disso, marque '{0}' como readonly.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">As propriedades da instância nas interfaces não podem ter inicializadores.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">O método 'UnmanagedCallersOnly' '{0}' não pode implementar o membro de interface '{1}' no tipo '{2}'</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Nome de algoritmo de hash inválido: '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">'{0}' não é um nome de parâmetro válido de '{1}'.</target>
@@ -1019,7 +1174,7 @@
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveRequiresSpace">
         <source>The #line span directive requires space before the first parenthesis, before the character offset, and before the file name</source>
-        <target state="translated">A #linha de intervalo requer espaço antes do primeiro parêntese, antes do deslocamento do caractere e antes do nome do arquivo</target>
+        <target state="translated">A #line de intervalo requer espaço antes do primeiro parêntese, antes do deslocamento do caractere e antes do nome do arquivo</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_ListPatternRequiresLength">
@@ -1102,6 +1257,11 @@
         <target state="translated">Apenas uma declaração de tipo parcial simples pode ter uma lista de parâmetros</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">A restrição 'new()' não pode ser usada com a restrição 'unmanaged'</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">'{0}': o runtime de destino não dá suporte a tipos de retorno covariantes em substituições. O tipo de retorno precisa ser '{2}' para corresponder ao membro substituído '{1}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">O runtime de destino não é compatível com a acessibilidade 'protected', 'protected internal' ou 'private protected' para um membro de uma interface.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">É necessário colocar a expressão que rege a switch entre parênteses.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">A literal da cadeia de caracteres bruta interpolada não começa com caracteres “$” suficientes para permitir esse número de chaves de fechamento consecutivas como conteúdo.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Não é possível usar o parâmetro de construtor primário do tipo '{0}' dentro de um membro da instância</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">tipo representante inferido</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">membro da instância em 'nameof'</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">acesso ao elemento de ponteiro</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">O operador '&amp;' não deve ser usado em parâmetros ou variáveis locais em métodos assíncronos.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">O CallerArgumentExpressionAttribute não terá nenhum efeito; ele é substituído pelo CallerMemberNameAttribute</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">O parâmetro "{0}" é capturado no estado do tipo delimitador e seu valor também é passado para o construtor base. O valor também pode ser capturado pela classe base.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">O uso de variável neste contexto pode expor variáveis referenciadas fora de seu escopo de declaração</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">InterpolatedStringHandlerArgument não tem efeito quando aplicado a parâmetros lambda e será ignorado no local de chamada.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">As ramificações do operador condicional ref referem-se a variáveis com escopos de declaração incompatíveis</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">Os membros requeridos '{0}' não devem ser atribuídos com 'ObsoleteAttribute', a menos que o tipo que o contém seja obsoleto ou que todos os construtores estejam obsoletos.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Opções do Compilador do Visual C#
 
                        – ARQUIVOS DE SAÍDA –
@@ -8556,7 +8794,7 @@ Um bloco catch() depois de um bloco catch (System.Exception e) poderá capturar
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Iteradores não podem ter tipos yield nem parâmetros sem segurança</target>
+        <target state="translated">Iteradores não podem ter parâmetros de tipo de ponteiro</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Forneça ao compilador alguma forma de diferenciar os métodos. Por exemplo, voc
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Os métodos assíncronos não podem ter parâmetros ou tipos de retorno sem segurança</target>
+        <target state="translated">Os métodos assíncronos não podem ter parâmetros de tipo de ponteiro</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ Para incorporar informações de tipo de interoperabilidade para os dois assembl
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'await' não pode ser usado em uma expressão contendo uma chamada para '{0}', pois ele é retornado por referência</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'await' não pode ser usado em uma expressão contendo uma chamada para '{0}', pois ele é retornado por referência</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf
index 4a1438454569d..4f255178c8ed0 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Только параметр "using static" или "using alias" может иметь значение "unsafe".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">Атрибут AsyncMethodBuilder запрещен для анонимных методов без явного типа возвращаемого значения.</target>
@@ -497,6 +502,11 @@
         <target state="translated">"{0}" явно реализуется больше одного раза.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">"{0}" уже указан в списке интерфейсов в типе "{2}" в виде "{1}".</target>
@@ -592,6 +602,11 @@
         <target state="translated">Дерево выражений не может содержать выражение индекса, отсчитываемого с конца ("^").</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Дерево выражения не может содержать преобразование обработчика интерполированных строк.</target>
@@ -852,11 +867,136 @@
         <target state="translated">Методы доступа "init" не могут быть помечены как доступные только для чтения. Вместо них пометьте "{0}" как доступные только для чтения.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Свойства экземпляра в интерфейсах не могут иметь инициализаторы.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">Метод UnmanagedCallersOnly "{0}" не может реализовать элемент интерфейса "{1}" в типе "{2}"</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Недопустимое имя хэш-алгоритма: "{0}"</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">"{0}" не является допустимым именем параметра из "{1}".</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">Только отдельное объявление разделяемого типа может содержать список параметров</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">Ограничение "new()" невозможно использовать вместе с ограничением "unmanaged"</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">"{0}": целевая среда выполнения не поддерживает ковариантные возвращаемые типы в переопределениях. Для сопоставления переопределенного элемента "{1}" необходимо использовать возвращаемый тип "{2}".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">Целевая среда выполнения не поддерживает специальные возможности "защищенный", "внутренний защищенный" или "частный защищенный" для члена интерфейса.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">Вокруг главного выражения switch требуются скобки.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">Интерполированный литерал необработанной строки не начинается с достаточного количества символов \"$\", чтобы разрешить использование такого же количества последовательных закрывающих фигурных скобок в качестве содержимого.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Невозможно использовать первичный параметр конструктора типа "{0}" внутри элемента экземпляра</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">выводимый тип делегата</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">элемент экземпляра в "nameof"</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">доступ к элементу указателя</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">Оператор "&amp;" не следует использовать для параметров или локальных переменных в асинхронных методах.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">Класс CallerArgumentExpressionAttribute не подействует, он переопределен классом CallerMemberNameAttribute</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">Параметр "{0}" записан в состоянии включающего типа, а его значение также передается базовому конструктору. Значение также может быть записано базовым классом.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">Использование переменной в этом контексте может представить ссылочные переменные за пределами области их объявления.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">Атрибут InterpolatedStringHandlerArgument не действует при применении к лямбда-параметрам и будет проигнорирован на сайте вызова.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Ветви условного оператора ref ссылаются на переменные с несовместимыми областями объявления.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">У обязательного элемента "{0}" не должно быть атрибута "ObsoleteAttribute", если содержащий тип или все конструкторы не являются устаревшими.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Параметры компилятора Visual C#
 
                        — Выходные файлы -
@@ -8556,7 +8794,7 @@ A catch() block after a catch (System.Exception e) block can catch non-CLS excep
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Итераторы не могут иметь небезопасные параметры или типы yield.</target>
+        <target state="translated">Итераторы не могут использовать параметры типа указателя</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Give the compiler some way to differentiate the methods. For example, you can gi
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">У асинхронных методов не может быть небезопасных параметров или возвращаемых типов.</target>
+        <target state="translated">Асинхронные методы не могут использовать параметры типа указателя</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'await нельзя использовать в выражении, содержащем вызов "{0}", так как он возвращает данные по ссылке</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'await нельзя использовать в выражении, содержащем вызов "{0}", так как он возвращает данные по ссылке</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf
index a8a720f6c5602..3f1816a84bff2 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf
@@ -287,6 +287,11 @@
         <target state="translated">Yalnızca 'using static' veya 'using alias' 'unsafe' olabilir.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">Açık dönüş türü olmadan, anonim yöntemlerde AsyncMethodBuilder özniteliğine izin verilmez.</target>
@@ -497,6 +502,11 @@
         <target state="translated">'{0}' bir defadan fazla açıkça uygulanmış.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">'{0}', '{2}' türünün arabirim listesinde zaten '{1}' olarak listelenmiş.</target>
@@ -592,6 +602,11 @@
         <target state="translated">İfade ağacı, sondan dizin ('^') ifadesi içeremez.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">Bir ifade ağacı, düz metin arasına kod eklenmiş dize işleyicisi dönüşümü içeremez.</target>
@@ -852,11 +867,136 @@
         <target state="translated">'init' erişimcileri 'readonly' olarak işaretlenemez. Bunun yerine '{0}' öğesini salt okunur olarak işaretleyin.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">Arabirimlerdeki örnek özelliklerinin başlatıcıları olamaz.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">'{0}' 'UnmanagedCallersOnly' yöntemi, '{1}' arabirim üyesini '{2}' türünde uygulayamaz</target>
@@ -922,6 +1062,21 @@
         <target state="translated">Geçersiz karma algoritması adı: '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">'{0}', '{1}' kaynağından geçerli bir parametre adı değil.</target>
@@ -1102,6 +1257,11 @@
         <target state="translated">Yalnızca tek bir parçalı tür bildiriminde bir parametre listesi olabilir</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">'new()' kısıtlaması, 'unmanaged' kısıtlamasıyla kullanılamaz</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">'{0}': Hedef çalışma zamanı, geçersiz kılmalarda birlikte değişken dönüş türlerini desteklemiyor. Dönüş türü, geçersiz kılınan '{1}' üyesiyle eşleşmek için '{2}' olmalıdır</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">Hedef çalışma zamanı, bir arabirim üyesi için 'protected', 'protected internal' veya 'private protected' erişilebilirliğini desteklemez.</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">Switch yönetim ifadesinin parantez içine alınması gerekir.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">Düz metin arasına kod ekli ham dize sabit değeri, bu kadar çok ardışık kapatma küme ayracı içerik olarak izin vermek için yeterli '$' karakterle başlamıyor.</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">Bir örnek üye içinde ref benzeri türe sahip '{0}' birincil oluşturucu parametresi kullanılamaz</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">çıkarsanan temsilci türü</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">'nameof' içinde örnek üyesi</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">işaretçi öğesi erişimi</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">'&amp;' işleci, zaman uyumsuz yöntemlerdeki parametrelerde veya yerel değişkenlerde kullanılmamalı.</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">CallerArgumentExpressionAttribute öğesinin etkisi olmaz; CallerMemberNameAttribute tarafından geçersiz kılındı</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">'{0}' parametresi kapsayan türün durumuna yakalandı ve değeri temel oluşturucuya da geçirildi. Değer, temel sınıf tarafından da yakalanamıyor olabilir.</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">Bu bağlamda değişken kullanımı, başvurulan değişkenleri bildirim kapsamının dışında gösterebilir.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">InterpolatedStringHandlerArgument, lambda parametrelerine uygulandığında hiçbir etkiye sahip değildir ve çağrı sitesinde yok sayılır.</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Ref koşullu operatörünün dalları, uyumsuz bildirim kapsamlarına sahip değişkenlere başvurur</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">Gerekli '{0}' üyesine, kapsayan tür veya tüm oluşturucular artık kullanılmadığı sürece 'ObsoleteAttribute' özniteliği atanmamalıdır.</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Visual C# Derleyici Seçenekleri
 
                        - ÇIKIŞ DOSYALARI -
@@ -8556,7 +8794,7 @@ RuntimeCompatibilityAttribute AssemblyInfo.cs dosyasında false olarak ayarlanm
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Yineleyicilerin unsafe parametreleri veya yield türleri olamaz</target>
+        <target state="translated">Yineleyici, işaretçi tür parametreleri içeremez</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Derleyiciye yöntemleri ayrıştırma yolu verin. Örneğin, bunlara farklı adl
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">Zaman uyumsuz yöntemlerin güvenli olmayan parametreleri veya dönüş türleri olamaz</target>
+        <target state="translated">Zaman uyumsuz yöntemler, işaretçi tür parametreleri içeremez</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ Uyarıyı kaldırmak için, /reference kullanabilirsiniz (Birlikte Çalışma T
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'Await' öğesi başvuru ile döndürüldüğünden, '{0}' öğesine yönelik bir çağrı içeren ifadede kullanılamaz</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'Await' öğesi başvuru ile döndürüldüğünden, '{0}' öğesine yönelik bir çağrı içeren ifadede kullanılamaz</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf
index 8c7447ea4748e..3e82fb405a260 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf
@@ -287,6 +287,11 @@
         <target state="translated">只有 “using static” 或 “using alias” 才能为 “unsafe”。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">没有显式返回类型的匿名方法不允许使用 AsyncMethodBuilder 属性。</target>
@@ -497,6 +502,11 @@
         <target state="translated">多次显式实现“{0}”。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">“{0}”已作为“{1}”列入类型“{2}”的接口列表中。</target>
@@ -592,6 +602,11 @@
         <target state="translated">表达式树不能包含 from-end 索引("^")表达式。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">表达式树可能不包含内插字符串处理程序转换。</target>
@@ -852,11 +867,136 @@
         <target state="translated">"init" 访问器不能标记为“只读”。请转而将“{0}”标记为“只读”。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">接口中的实例属性不能具有初始值设定项。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">“UnmanagedCallersOnly”方法“{0}”无法实现类型“{2}”中的接口成员“{1}”</target>
@@ -922,6 +1062,21 @@
         <target state="translated">无效的哈希算法名称:“{0}”</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">“{0}”不是来自“{1}”的有效参数名称。</target>
@@ -1009,7 +1164,7 @@
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveEndLessThanStart">
         <source>The #line directive end position must be greater than or equal to the start position</source>
-        <target state="translated">#Line 指令结束位置必须大于或等于起始位置</target>
+        <target state="translated">#line 指令结束位置必须大于或等于起始位置</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveInvalidValue">
@@ -1102,6 +1257,11 @@
         <target state="translated">只有一个分部类型声明可以拥有参数列表</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">"new()" 约束不能与 "unmanaged" 约束一起使用</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">“{0}”: 目标运行时不支持替代中的协变返回类型。返回类型必须为“{2}”才能匹配替代成员“{1}”</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">目标运行时不支持对接口的成员使用 "protected"、"protected internal" 或 "private protected" 辅助功能。</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">switch governing 表达式的周围需要括号。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">内插原始字符串字面量的开头没有足够的 \"$\" 字符以允许将这么多连续的右大括号作为内容。</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">无法在实例成员中使用类型为 "{0}" 的主构造函数参数</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">推断的委托类型</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">"nameof" 中的实例成员</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">指针元素访问</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">'&amp;' 运算符不应用于异步方法中的参数或局部变量。</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">CallerArgumentExpressionAttribute 将不起任何作用；它由 CallerMemberNameAttribute 替代</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">参数“{0}”捕获到封闭类型状态，其值也传递给基构造函数。该值也可能由基类捕获。</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">在此上下文中使用变量可能会在变量声明范围以外公开所引用的变量</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">应用于 lambda 参数时，InterpolatedStringHandlerArgument 不起任何作用，并将在调用站点被忽略。</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">ref 条件运算符的分支引用具有不兼容声明范围的变量</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">除非包含类型已过时或所有构造函数已过时，否则不应将所需的成员'{0}'归属于 'ObsoleteAttribute'。</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Visual C# 编译器选项
 
                        - 输出文件 -
@@ -8561,7 +8799,7 @@ A catch() block after a catch (System.Exception e) block can catch non-CLS excep
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">迭代器不能有不安全的参数或 yield 类型</target>
+        <target state="translated">迭代器不能具有指针类型参数</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9904,7 +10142,7 @@ Give the compiler some way to differentiate the methods. For example, you can gi
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">异步方法不能具有不安全的参数或返回类型</target>
+        <target state="translated">异步方法不能具有指针类型参数</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11818,8 +12056,8 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'不能在包含对“{0}”的调用的表达式中使用 "await"，因为它通过引用返回</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'不能在包含对“{0}”的调用的表达式中使用 "await"，因为它通过引用返回</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf
index 15a11a719b4da..5f481888cda76 100644
--- a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf
+++ b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf
@@ -287,6 +287,11 @@
         <target state="translated">只有 'using static' 或 'using alias' 可以是 'unsafe'。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadUsingStaticType">
+        <source>'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</source>
+        <target state="new">'{0}' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate, or namespace can be used.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_BuilderAttributeDisallowed">
         <source>The AsyncMethodBuilder attribute is disallowed on anonymous methods without an explicit return type.</source>
         <target state="translated">沒有明確傳回型別的匿名方法上不允許 AsyncMethodBuilder 屬性。</target>
@@ -497,6 +502,11 @@
         <target state="translated">'{0}' 已明確實作多次。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DuplicateInterceptor">
+        <source>The indicated call is intercepted multiple times.</source>
+        <target state="new">The indicated call is intercepted multiple times.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DuplicateInterfaceWithDifferencesInBaseList">
         <source>'{0}' is already listed in the interface list on type '{2}' as '{1}'.</source>
         <target state="translated">'{0}' 已列於類型 '{2}' 的介面清單中，名稱為 '{1}'。</target>
@@ -592,6 +602,11 @@
         <target state="translated">運算式樹狀架構不可包含 from-end index ('^') 運算式。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExpressionTreeContainsInlineArrayOperation">
+        <source>An expression tree may not contain an inline array access or conversion</source>
+        <target state="new">An expression tree may not contain an inline array access or conversion</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_ExpressionTreeContainsInterpolatedStringHandlerConversion">
         <source>An expression tree may not contain an interpolated string handler conversion.</source>
         <target state="translated">運算式樹狀架構不可包含差補字串處理常式轉換。</target>
@@ -852,11 +867,136 @@
         <target state="translated">'init' 存取子不得標記為 'readonly'。改為將 '{0}' 標記為唯讀。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InlineArrayBadIndex">
+        <source>Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</source>
+        <target state="new">Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToReadOnlySpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it may not be passed or returned by reference</source>
+        <target state="new">Cannot convert expression to '{0}' because it may not be passed or returned by reference</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayConversionToSpanNotSupported">
+        <source>Cannot convert expression to '{0}' because it is not an assignable variable</source>
+        <target state="new">Cannot convert expression to '{0}' because it is not an assignable variable</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InlineArrayIndexOutOfRange">
+        <source>Index is outside the bounds of the inline array</source>
+        <target state="new">Index is outside the bounds of the inline array</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InstancePropertyInitializerInInterface">
         <source>Instance properties in interfaces cannot have initializers.</source>
         <target state="translated">介面中的執行個體屬性不可有初始設定式。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotBeGeneric">
+        <source>Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</source>
+        <target state="new">Method '{0}' cannot be used as an interceptor because it or its containing type has type parameters.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotInterceptNameof">
+        <source>A nameof operator cannot be intercepted.</source>
+        <target state="new">A nameof operator cannot be intercepted.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCannotUseUnmanagedCallersOnly">
+        <source>An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</source>
+        <target state="new">An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorCharacterOutOfRange">
+        <source>The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</source>
+        <target state="new">The given line is '{0}' characters long, which is fewer than the provided character number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorFilePathCannotBeNull">
+        <source>Interceptor cannot have a 'null' file path.</source>
+        <target state="new">Interceptor cannot have a 'null' file path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineCharacterMustBePositive">
+        <source>Line and character numbers provided to InterceptsLocationAttribute must be positive.</source>
+        <target state="new">Line and character numbers provided to InterceptsLocationAttribute must be positive.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorLineOutOfRange">
+        <source>The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</source>
+        <target state="new">The given file has '{0}' lines, which is fewer than the provided line number '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMethodMustBeOrdinary">
+        <source>An interceptor method must be an ordinary member method.</source>
+        <target state="new">An interceptor method must be an ordinary member method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustHaveMatchingThisParameter">
+        <source>Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</source>
+        <target state="new">Interceptor must have a 'this' parameter matching parameter '{0}' on '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustNotHaveThisParameter">
+        <source>Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</source>
+        <target state="new">Interceptor must not have a 'this' parameter because '{0}' does not have a 'this' parameter.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorMustReferToStartOfTokenPosition">
+        <source>The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</source>
+        <target state="new">The provided line and character number does not refer to the start of token '{0}'. Did you mean to use line '{1}' and character '{2}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNameNotInvoked">
+        <source>Possible method name '{0}' cannot be intercepted because it is not being invoked.</source>
+        <target state="new">Possible method name '{0}' cannot be intercepted because it is not being invoked.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNonUniquePath">
+        <source>Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</source>
+        <target state="new">Cannot intercept a call in file with path '{0}' because multiple files in the compilation have this path.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorNotAccessible">
+        <source>Cannot intercept call with '{0}' because it is not accessible within '{1}'.</source>
+        <target state="new">Cannot intercept call with '{0}' because it is not accessible within '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilation">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'.</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithCandidate">
+        <source>Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</source>
+        <target state="new">Cannot intercept: compilation does not contain a file with path '{0}'. Did you mean to use path '{1}'?</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPathNotInCompilationWithUnmappedCandidate">
+        <source>Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</source>
+        <target state="new">Cannot intercept: Path '{0}' is unmapped. Expected mapped path '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorPositionBadToken">
+        <source>The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</source>
+        <target state="new">The provided line and character number does not refer to an interceptable method name, but rather to token '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorScopedMismatch">
+        <source>Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</source>
+        <target state="new">Cannot intercept call to '{0}' with '{1}' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorSignatureMismatch">
+        <source>Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</source>
+        <target state="new">Cannot intercept method '{0}' with interceptor '{1}' because the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InterceptorsFeatureNotEnabled">
+        <source>The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</source>
+        <target state="new">The 'interceptors' experimental feature is not enabled. Add '&lt;Features&gt;InterceptorsPreview&lt;/Features&gt;' to your project.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InterfaceImplementedByUnmanagedCallersOnlyMethod">
         <source>'UnmanagedCallersOnly' method '{0}' cannot implement interface member '{1}' in type '{2}'</source>
         <target state="translated">'UnmanagedCallersOnly' 方法 '{0}' 無法在類型 '{2}' 中實作介面成員 '{1}'</target>
@@ -922,6 +1062,21 @@
         <target state="translated">雜湊演算法名稱無效: '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayFields">
+        <source>Inline array struct must declare one and only one instance field which must not be a ref field.</source>
+        <target state="new">Inline array struct must declare one and only one instance field which must not be a ref field.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLayout">
+        <source>Inline array struct must not have explicit layout.</source>
+        <target state="new">Inline array struct must not have explicit layout.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="ERR_InvalidInlineArrayLength">
+        <source>Inline array length must be greater than 0.</source>
+        <target state="new">Inline array length must be greater than 0.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_InvalidInterpolatedStringHandlerArgumentName">
         <source>'{0}' is not a valid parameter name from '{1}'.</source>
         <target state="translated">'{0}' 不是來自 '{1}' 的有效參數名稱。</target>
@@ -1009,12 +1164,12 @@
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveEndLessThanStart">
         <source>The #line directive end position must be greater than or equal to the start position</source>
-        <target state="translated">#Line 指示詞結束位置必須大於或等於開始位置</target>
+        <target state="translated">#line 指示詞結束位置必須大於或等於開始位置</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveInvalidValue">
         <source>The #line directive value is missing or out of range</source>
-        <target state="translated">#Line 指示詞值遺漏或超出範圍</target>
+        <target state="translated">#line 指示詞值遺漏或超出範圍</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_LineSpanDirectiveRequiresSpace">
@@ -1102,6 +1257,11 @@
         <target state="translated">只有單一部分類型宣告可以有參數清單</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_NamedArgumentForInlineArray">
+        <source>An inline array access may not have a named argument specifier</source>
+        <target state="new">An inline array access may not have a named argument specifier</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_NewBoundWithUnmanaged">
         <source>The 'new()' constraint cannot be used with the 'unmanaged' constraint</source>
         <target state="translated">new()' 條件約束不能和 'unmanaged' 條件約束一起使用</target>
@@ -1512,6 +1672,11 @@
         <target state="translated">'{0}': 在覆寫中，目標執行階段不支援 Covariant 傳回型別。傳回型別必須是 '{2}'，才符合覆寫的成員 '{1}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_RuntimeDoesNotSupportInlineArrayTypes">
+        <source>Target runtime doesn't support inline array types.</source>
+        <target state="new">Target runtime doesn't support inline array types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportProtectedAccessForInterfaceMember">
         <source>Target runtime doesn't support 'protected', 'protected internal', or 'private protected' accessibility for a member of an interface.</source>
         <target state="translated">目標執行階段不支援介面成員的 'protected'、'protected internal' 或 'private protected' 存取權。</target>
@@ -1682,6 +1847,11 @@
         <target state="translated">switch 主導的運算式前後必須有括弧。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_TooManyCloseBracesForRawString">
         <source>The interpolated raw string literal does not start with enough '$' characters to allow this many consecutive closing braces as content.</source>
         <target state="translated">差補原始字串常值開頭沒有足夠的 '$' 字元數，因此無法允許這麼多連續的右大括弧做為內容。</target>
@@ -1794,7 +1964,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefAny">
         <source>Cannot use primary constructor parameter of type '{0}' inside an instance member</source>
-        <target state="new">Cannot use primary constructor parameter of type '{0}' inside an instance member</target>
+        <target state="translated">無法使用執行個體成員內類型 '{0}' 的主要建構函式參數</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_UnsupportedPrimaryConstructorParameterCapturingRefLike">
@@ -1927,9 +2097,14 @@
         <target state="translated">推斷委派類型</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_FeatureInlineArrays">
+        <source>inline arrays</source>
+        <target state="new">inline arrays</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_FeatureInstanceMemberInNameof">
         <source>instance member in 'nameof'</source>
-        <target state="new">instance member in 'nameof'</target>
+        <target state="translated">'nameof' 中的執行個體成員</target>
         <note />
       </trans-unit>
       <trans-unit id="IDS_FeatureLambdaAttributes">
@@ -2057,6 +2232,26 @@
         <target state="translated">指標元素存取</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_SK_ARRAY">
+        <source>array</source>
+        <target state="new">array</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_DYNAMIC">
+        <source>dynamic</source>
+        <target state="new">dynamic</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_FUNCTION_POINTER">
+        <source>function pointer</source>
+        <target state="new">function pointer</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="IDS_SK_POINTER">
+        <source>pointer</source>
+        <target state="new">pointer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_AddressOfInAsync">
         <source>The '&amp;' operator should not be used on parameters or local variables in async methods.</source>
         <target state="translated">'&amp;' 運算子不應該用於非同步方法中的參數或區域變數。</target>
@@ -2167,6 +2362,16 @@
         <target state="translated">CallerArgumentExpressionAttribute 將沒有效果; CallerMemberNameAttribute 會覆寫它</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer">
+        <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter '{0}' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_CapturedPrimaryConstructorParameterInFieldInitializer_Title">
+        <source>Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</source>
+        <target state="new">Parameter is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_CapturedPrimaryConstructorParameterPassedToBase">
         <source>Parameter '{0}' is captured into the state of the enclosing type and its value is also passed to the base constructor. The value might be captured by the base class as well.</source>
         <target state="translated">參數 '{0}' 會擷取至包含類型的狀態，且其值也會傳遞給基礎建構函式。值也可能由基礎類別擷取。</target>
@@ -2247,6 +2452,16 @@
         <target state="translated">在此內容中使用變數，可能會將參考的變數公開在其宣告範圍外</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch">
+        <source>Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</source>
+        <target state="new">Intercepting a call to '{0}' with interceptor '{1}', but the signatures do not match.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_InterceptorSignatureMismatch_Title">
+        <source>Signatures of interceptable and interceptor methods do not match.</source>
+        <target state="new">Signatures of interceptable and interceptor methods do not match.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_InterpolatedStringHandlerArgumentAttributeIgnoredOnLambdaParameters">
         <source>InterpolatedStringHandlerArgument has no effect when applied to lambda parameters and will be ignored at the call site.</source>
         <target state="translated">InterpolatedStringHandlerArgument 在套用至 Lambda 參數時沒有效果，將於呼叫網站忽略。</target>
@@ -2297,6 +2512,26 @@
         <target state="translated">Ref 條件運算子的分支參考具有不相容宣告範圍的變數</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor">
+        <source>Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</source>
+        <target state="new">Nullability of reference types in type of parameter '{0}' doesn't match interceptable method '{1}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInParameterTypeOnInterceptor_Title">
+        <source>Nullability of reference types in type of parameter doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in type of parameter doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor">
+        <source>Nullability of reference types in return type doesn't match interceptable method '{0}'.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method '{0}'.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnInterceptor_Title">
+        <source>Nullability of reference types in return type doesn't match interceptable method.</source>
+        <target state="new">Nullability of reference types in return type doesn't match interceptable method.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_ObsoleteMembersShouldNotBeRequired">
         <source>Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.</source>
         <target state="translated">除非包含的類型已過時或所有建構函式已過時，否則必要成員 '{0}' 的屬性不應為 'ObsoleteAttribute'。</target>
@@ -2808,8 +3043,11 @@
 -modulename:&lt;string&gt;          Specify the name of the source module
 -generatedfilesout:&lt;dir&gt;      Place files generated during compilation in the
                               specified directory.
+-reportivts[+|-]                    Output information on all IVTs granted to this
+                              assembly by all dependencies, and annotate foreign assembly
+                              accessibility errors with what assembly they came from.
 </source>
-        <target state="translated">
+        <target state="needs-review-translation">
                              Visual C# 編譯器選項
 
                        - 輸出檔案 -
@@ -8556,7 +8794,7 @@ A catch() block after a catch (System.Exception e) block can catch non-CLS excep
       </trans-unit>
       <trans-unit id="ERR_UnsafeIteratorArgType">
         <source>Iterators cannot have pointer type parameters</source>
-        <target state="needs-review-translation">迭代器不能有 Unsafe 參數或 yield 類型</target>
+        <target state="translated">迭代器不能具有指標型別參數</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadCoClassSig">
@@ -9899,7 +10137,7 @@ Give the compiler some way to differentiate the methods. For example, you can gi
       </trans-unit>
       <trans-unit id="ERR_UnsafeAsyncArgType">
         <source>Async methods cannot have pointer type parameters</source>
-        <target state="needs-review-translation">非同步方法不能有 Unsafe 參數或 return 類型</target>
+        <target state="translated">非同步方法不能具有指標型別參數</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_BadAsyncArgType">
@@ -11813,8 +12051,8 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefReturningCallAndAwait">
-        <source>'await' cannot be used in an expression containing a call to '{0}' because it returns by reference</source>
-        <target state="translated">'await' 不能用於包含呼叫 '{0}' 的運算式，因為其藉傳址方式傳回</target>
+        <source>A reference returned by a call to '{0}' cannot be preserved across 'await' or 'yield' boundary.</source>
+        <target state="needs-review-translation">'await' 不能用於包含呼叫 '{0}' 的運算式，因為其藉傳址方式傳回</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RefConditionalAndAwait">
diff --git a/src/Compilers/CSharp/Test/CommandLine/CommandLineIVTTests.cs b/src/Compilers/CSharp/Test/CommandLine/CommandLineIVTTests.cs
new file mode 100644
index 0000000000000..83fcbb4991c18
--- /dev/null
+++ b/src/Compilers/CSharp/Test/CommandLine/CommandLineIVTTests.cs
@@ -0,0 +1,374 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.CommandLine.UnitTests;
+
+public class CommandLineIVTTests : CommandLineTestBase
+{
+    [Fact]
+    public void InaccessibleBaseType()
+    {
+        var source1 = """
+            namespace N1;
+            internal class A {}
+            """;
+
+        var comp1 = CreateCompilation(source1, options: TestOptions.DebugDll, assemblyName: "N1", targetFramework: TargetFramework.Mscorlib461);
+
+        var dir = Temp.CreateDirectory();
+
+        var source2 = dir.CreateFile("B.cs").WriteAllText("""
+            namespace N2;
+            internal class B : N1.A {}
+            """);
+
+        var sw = new StringWriter();
+
+        var compiler = CreateCSharpCompiler(new[] {
+            "/nologo",
+            "/t:library",
+            "/preferreduilang:en",
+            "/reportivts",
+            source2.Path,
+        }, additionalReferences: new[] { comp1.ToMetadataReference() });
+
+        var errorCode = compiler.Run(sw);
+
+        Assert.Equal(CommonCompiler.Failed, errorCode);
+        var outputFilePath = $"{Path.GetFileName(dir.Path)}{Path.DirectorySeparatorChar}{Path.GetFileName(source2.Path)}";
+        AssertEx.AssertEqualToleratingWhitespaceDifferences($"""
+{outputFilePath}(2,23): error CS0122: 'A' is inaccessible due to its protection level
+{outputFilePath}(2,23): error CS9163: 'A' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'B, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+""", sw.ToString().Trim());
+    }
+
+    [Fact]
+    public void AccessibleBaseType()
+    {
+        var source1 = """
+            [assembly: System.Runtime.CompilerServices.InternalsVisibleToAttribute("B")]
+            namespace N1;
+            internal class A {}
+            """;
+
+        var comp1 = CreateCompilation(source1, options: TestOptions.DebugDll, assemblyName: "N1", targetFramework: TargetFramework.Mscorlib461);
+
+        var dir = Temp.CreateDirectory();
+
+        var source2 = dir.CreateFile("B.cs").WriteAllText("""
+            namespace N2;
+            internal class B : N1.A {}
+            """);
+
+        var sw = new StringWriter();
+
+        var compiler = CreateCSharpCompiler(new[] {
+            "/nologo",
+            "/t:library",
+            "/preferreduilang:en",
+            "/reportivts",
+            source2.Path,
+        }, additionalReferences: new[] { comp1.ToMetadataReference() });
+
+        var errorCode = compiler.Run(sw);
+
+        Assert.Equal(CommonCompiler.Succeeded, errorCode);
+        var outputFilePath = $"{Path.GetFileName(dir.Path)}{Path.DirectorySeparatorChar}{Path.GetFileName(source2.Path)}";
+        AssertEx.AssertEqualToleratingWhitespaceDifferences($"""
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'B, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: True
+  Grants IVTs to:
+    Assembly name: 'B'
+    Public Keys:
+""", sw.ToString().Trim());
+    }
+
+    [Fact]
+    public void InaccessibleGetterSetter()
+    {
+        var source1 = """
+            namespace N1;
+            public class A
+            {
+                internal string Prop { get; set; }
+            }
+            """;
+
+        var comp1 = CreateCompilation(source1, options: TestOptions.DebugDll, assemblyName: "N1", targetFramework: TargetFramework.Mscorlib461);
+
+        var dir = Temp.CreateDirectory();
+
+        var source2 = dir.CreateFile("B.cs").WriteAllText("""
+            var a = new N1.A();
+            _ = a.Prop;
+            a.Prop = "hello";
+            """);
+
+        var sw = new StringWriter();
+
+        var compiler = CreateCSharpCompiler(new[] {
+            "/nologo",
+            "/t:exe",
+            "/preferreduilang:en",
+            "/reportivts",
+            source2.Path,
+        }, additionalReferences: new[] { comp1.ToMetadataReference() });
+
+        var errorCode = compiler.Run(sw);
+
+        Assert.Equal(CommonCompiler.Failed, errorCode);
+        var outputFilePath = $"{Path.GetFileName(dir.Path)}{Path.DirectorySeparatorChar}{Path.GetFileName(source2.Path)}";
+        AssertEx.AssertEqualToleratingWhitespaceDifferences($"""
+{outputFilePath}(2,7): error CS0122: 'A.Prop' is inaccessible due to its protection level
+{outputFilePath}(3,3): error CS0122: 'A.Prop' is inaccessible due to its protection level
+{outputFilePath}(2,7): error CS9163: 'A.Prop' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+{outputFilePath}(3,3): error CS9163: 'A.Prop' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: '?, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+""", sw.ToString().Trim());
+    }
+
+    [Fact]
+    public void InaccessibleImplicitInterfaceImpl()
+    {
+        var source1 = """
+            namespace N1;
+            public interface A
+            {
+                internal void M();
+            }
+            """;
+
+        var comp1 = CreateCompilation(source1, options: TestOptions.DebugDll, assemblyName: "N1", targetFramework: TargetFramework.Mscorlib461);
+
+        var dir = Temp.CreateDirectory();
+
+        var source2 = dir.CreateFile("B.cs").WriteAllText("""
+            namespace N2;
+            public class B : N1.A
+            {
+                public void M() { }
+            }
+            """);
+
+        var sw = new StringWriter();
+
+        var compiler = CreateCSharpCompiler(new[] {
+            "/nologo",
+            "/t:library",
+            "/preferreduilang:en",
+            "/reportivts",
+            source2.Path,
+        }, additionalReferences: new[] { comp1.ToMetadataReference() });
+
+        var errorCode = compiler.Run(sw);
+
+        Assert.Equal(CommonCompiler.Failed, errorCode);
+        var outputFilePath = $"{Path.GetFileName(dir.Path)}{Path.DirectorySeparatorChar}{Path.GetFileName(source2.Path)}";
+        AssertEx.AssertEqualToleratingWhitespaceDifferences($"""
+{outputFilePath}(4,17): error CS9044: 'B' does not implement interface member 'A.M()'. 'B.M()' cannot implicitly implement an inaccessible member.
+{outputFilePath}(4,17): error CS9163: 'A.M()' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'B, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+""", sw.ToString().Trim());
+    }
+
+    [Theory]
+    [InlineData("/reportivts")]
+    [InlineData("/reportivts+")]
+    public void TurnOnLast(string onFlag)
+    {
+        var compiler = CreateCSharpCompiler(new[] {
+            "/nologo",
+            "/reportivts-",
+            onFlag,
+        });
+
+        Assert.True(compiler.Arguments.ReportInternalsVisibleToAttributes);
+    }
+
+    [Theory]
+    [InlineData("/reportivts")]
+    [InlineData("/reportivts+")]
+    public void TurnOffLast(string onFlag)
+    {
+        var compiler = CreateCSharpCompiler(new[] {
+            "/nologo",
+            onFlag,
+            "/reportivts-",
+        });
+
+        Assert.False(compiler.Arguments.ReportInternalsVisibleToAttributes);
+    }
+
+    [Fact]
+    public void BadReportIvtsValue()
+    {
+        var compiler = CreateCSharpCompiler(new[] {
+            "/nologo",
+            "/reportivts:bad",
+        });
+
+        Assert.False(compiler.Arguments.ReportInternalsVisibleToAttributes);
+        compiler.Arguments.Errors.Verify(
+            Diagnostic(ErrorCode.ERR_BadSwitch).WithArguments("/reportivts:bad").WithLocation(1, 1),
+            Diagnostic(ErrorCode.WRN_NoSources).WithLocation(1, 1),
+            Diagnostic(ErrorCode.ERR_OutputNeedsName).WithLocation(1, 1)
+        );
+    }
+}
diff --git a/src/Compilers/CSharp/Test/CommandLine/CommandLineTestBase.cs b/src/Compilers/CSharp/Test/CommandLine/CommandLineTestBase.cs
index 2cca9cad3c7c0..50e51c9e3b42d 100644
--- a/src/Compilers/CSharp/Test/CommandLine/CommandLineTestBase.cs
+++ b/src/Compilers/CSharp/Test/CommandLine/CommandLineTestBase.cs
@@ -53,15 +53,15 @@ internal CSharpCommandLineArguments DefaultParse(IEnumerable<string> args, strin
             return CSharpCommandLineParser.Default.Parse(args, baseDirectory, sdkDirectory, additionalReferenceDirectories);
         }
 
-        internal MockCSharpCompiler CreateCSharpCompiler(string[] args, DiagnosticAnalyzer[]? analyzers = null, ISourceGenerator[]? generators = null, AnalyzerAssemblyLoader? loader = null, GeneratorDriverCache? driverCache = null)
+        internal MockCSharpCompiler CreateCSharpCompiler(string[] args, DiagnosticAnalyzer[]? analyzers = null, ISourceGenerator[]? generators = null, AnalyzerAssemblyLoader? loader = null, GeneratorDriverCache? driverCache = null, MetadataReference[]? additionalReferences = null)
         {
-            return CreateCSharpCompiler(null, WorkingDirectory, args, analyzers, generators, loader, driverCache);
+            return CreateCSharpCompiler(null, WorkingDirectory, args, analyzers, generators, loader, driverCache, additionalReferences);
         }
 
-        internal MockCSharpCompiler CreateCSharpCompiler(string? responseFile, string workingDirectory, string[] args, DiagnosticAnalyzer[]? analyzers = null, ISourceGenerator[]? generators = null, AnalyzerAssemblyLoader? loader = null, GeneratorDriverCache? driverCache = null)
+        internal MockCSharpCompiler CreateCSharpCompiler(string? responseFile, string workingDirectory, string[] args, DiagnosticAnalyzer[]? analyzers = null, ISourceGenerator[]? generators = null, AnalyzerAssemblyLoader? loader = null, GeneratorDriverCache? driverCache = null, MetadataReference[]? additionalReferences = null)
         {
             var buildPaths = RuntimeUtilities.CreateBuildPaths(workingDirectory, sdkDirectory: SdkDirectory);
-            return new MockCSharpCompiler(responseFile, buildPaths, args, analyzers.AsImmutableOrEmpty(), generators.AsImmutableOrEmpty(), loader, driverCache);
+            return new MockCSharpCompiler(responseFile, buildPaths, args, analyzers.AsImmutableOrEmpty(), generators.AsImmutableOrEmpty(), loader, driverCache, additionalReferences.AsImmutableOrEmpty());
         }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncSpillTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncSpillTests.cs
index 1fb7b56912b4e..90af07a96d624 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncSpillTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncSpillTests.cs
@@ -3393,7 +3393,7 @@ public static void Main()
 
             var comp = CreateCompilationWithMscorlib46(source, options: TestOptions.ReleaseExe);
             comp.VerifyEmitDiagnostics(
-                // (18,28): error CS8178: 'await' cannot be used in an expression containing a call to 'C.P.get' because it returns by reference
+                // (18,28): error CS8178: A reference returned by a call to 'C.P.get' cannot be preserved across 'await' or 'yield' boundary.
                 //         Assign(second: ref P, first: await t);
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "P").WithArguments("C.P.get").WithLocation(18, 28)
                 );
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncTests.cs
index 4e88eea1564b5..fa39f561f1e8b 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncTests.cs
@@ -5893,10 +5893,10 @@ public async Task Step(Task<int> t)
 ";
             var expected = new[]
             {
-                // (8,9): error CS8178: 'await' cannot be used in an expression containing a call to 'IntCode.ReadMemory()' because it returns by reference
+                // (8,9): error CS8178: A reference returned by a call to 'IntCode.ReadMemory()' cannot be preserved across 'await' or 'yield' boundary.
                 //         ReadMemory() = await t;
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "ReadMemory()").WithArguments("IntCode.ReadMemory()").WithLocation(8, 9),
-                // (9,9): error CS8178: 'await' cannot be used in an expression containing a call to 'IntCode.ReadMemory()' because it returns by reference
+                // (9,9): error CS8178: A reference returned by a call to 'IntCode.ReadMemory()' cannot be preserved across 'await' or 'yield' boundary.
                 //         ReadMemory() += await t;
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "ReadMemory()").WithArguments("IntCode.ReadMemory()").WithLocation(9, 9)
             };
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenInParametersTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenInParametersTests.cs
index 66dd8a93f88fe..029e2d50442df 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenInParametersTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenInParametersTests.cs
@@ -1539,7 +1539,7 @@ public static void M1(in int arg1, in int arg2, in int arg3)
 
             var comp = CreateCompilationWithMscorlib46(text, new[] { ValueTupleRef, SystemRuntimeFacadeRef }, options: TestOptions.ReleaseExe);
             comp.VerifyEmitDiagnostics(
-                // (14,19): error CS8178: 'await' cannot be used in an expression containing a call to 'Program.RefReturning(ref int)' because it returns by reference
+                // (14,19): error CS8178: A reference returned by a call to 'Program.RefReturning(ref int)' cannot be preserved across 'await' or 'yield' boundary.
                 //             M1(in RefReturning(ref local), await GetT(2), 3);
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "RefReturning(ref local)").WithArguments("Program.RefReturning(ref int)").WithLocation(14, 19)
                 );
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/IndexAndRangeTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/IndexAndRangeTests.cs
index 1210b1997564c..0749e47f7df78 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/IndexAndRangeTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/IndexAndRangeTests.cs
@@ -3359,7 +3359,7 @@ public static void Main()
     }
 }
 ", TestOptions.ReleaseExe);
-            CompileAndVerify(comp, expectedOutput:
+            var verifier = CompileAndVerify(comp, expectedOutput:
 @"
 Get GetIdx Length Slice 1, 2
 Get GetIdx1 GetIdx2 Slice 1, 2
@@ -3378,6 +3378,333 @@ public static void Main()
 Get GetIdx1 GetIdx4 Length Slice 1, 2
 Get GetIdx3 GetIdx2 Length Slice 1, 2
 Get GetIdx3 GetIdx2 Length Slice 1, 2
+");
+            verifier.VerifyMethodBody("SideEffect.Main", @"
+{
+  // Code size      731 (0x2db)
+  .maxstack  4
+  .locals init (System.Range V_0,
+                int V_1,
+                int V_2,
+                int V_3,
+                System.Index V_4,
+                CollectionX V_5,
+                int V_6,
+                System.Index V_7)
+  // sequence point: _ = Get()[GetIdx()];
+  IL_0000:  call       ""CollectionX SideEffect.Get()""
+  IL_0005:  call       ""System.Range SideEffect.GetIdx()""
+  IL_000a:  stloc.0
+  IL_000b:  dup
+  IL_000c:  callvirt   ""int CollectionX.Length.get""
+  IL_0011:  stloc.1
+  IL_0012:  ldloca.s   V_0
+  IL_0014:  call       ""System.Index System.Range.Start.get""
+  IL_0019:  stloc.s    V_4
+  IL_001b:  ldloca.s   V_4
+  IL_001d:  ldloc.1
+  IL_001e:  call       ""int System.Index.GetOffset(int)""
+  IL_0023:  stloc.2
+  IL_0024:  ldloca.s   V_0
+  IL_0026:  call       ""System.Index System.Range.End.get""
+  IL_002b:  stloc.s    V_4
+  IL_002d:  ldloca.s   V_4
+  IL_002f:  ldloc.1
+  IL_0030:  call       ""int System.Index.GetOffset(int)""
+  IL_0035:  ldloc.2
+  IL_0036:  sub
+  IL_0037:  stloc.3
+  IL_0038:  ldloc.2
+  IL_0039:  ldloc.3
+  IL_003a:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_003f:  pop
+  // sequence point: _ = Get()[GetIdx1(1)..GetIdx2(3)];
+  IL_0040:  call       ""CollectionX SideEffect.Get()""
+  IL_0045:  ldc.i4.1
+  IL_0046:  call       ""int SideEffect.GetIdx1(int)""
+  IL_004b:  stloc.3
+  IL_004c:  ldloc.3
+  IL_004d:  ldc.i4.3
+  IL_004e:  call       ""int SideEffect.GetIdx2(int)""
+  IL_0053:  ldloc.3
+  IL_0054:  sub
+  IL_0055:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_005a:  pop
+  // sequence point: _ = Get()[^GetIdx1(3)..GetIdx2(3)];
+  IL_005b:  call       ""CollectionX SideEffect.Get()""
+  IL_0060:  ldc.i4.3
+  IL_0061:  call       ""int SideEffect.GetIdx1(int)""
+  IL_0066:  stloc.3
+  IL_0067:  ldc.i4.3
+  IL_0068:  call       ""int SideEffect.GetIdx2(int)""
+  IL_006d:  stloc.2
+  IL_006e:  dup
+  IL_006f:  callvirt   ""int CollectionX.Length.get""
+  IL_0074:  ldloc.3
+  IL_0075:  sub
+  IL_0076:  stloc.1
+  IL_0077:  ldloc.1
+  IL_0078:  ldloc.2
+  IL_0079:  ldloc.1
+  IL_007a:  sub
+  IL_007b:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_0080:  pop
+  // sequence point: _ = Get()[GetIdx1(1)..^GetIdx2(1)];
+  IL_0081:  call       ""CollectionX SideEffect.Get()""
+  IL_0086:  stloc.s    V_5
+  IL_0088:  ldc.i4.1
+  IL_0089:  call       ""int SideEffect.GetIdx1(int)""
+  IL_008e:  stloc.1
+  IL_008f:  ldc.i4.1
+  IL_0090:  call       ""int SideEffect.GetIdx2(int)""
+  IL_0095:  stloc.2
+  IL_0096:  ldloc.s    V_5
+  IL_0098:  ldloc.1
+  IL_0099:  ldloc.s    V_5
+  IL_009b:  callvirt   ""int CollectionX.Length.get""
+  IL_00a0:  ldloc.2
+  IL_00a1:  sub
+  IL_00a2:  ldloc.1
+  IL_00a3:  sub
+  IL_00a4:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_00a9:  pop
+  // sequence point: _ = Get()[^GetIdx1(3)..^GetIdx2(1)];
+  IL_00aa:  call       ""CollectionX SideEffect.Get()""
+  IL_00af:  ldc.i4.3
+  IL_00b0:  call       ""int SideEffect.GetIdx1(int)""
+  IL_00b5:  stloc.2
+  IL_00b6:  ldc.i4.1
+  IL_00b7:  call       ""int SideEffect.GetIdx2(int)""
+  IL_00bc:  stloc.1
+  IL_00bd:  dup
+  IL_00be:  callvirt   ""int CollectionX.Length.get""
+  IL_00c3:  stloc.3
+  IL_00c4:  ldloc.3
+  IL_00c5:  ldloc.2
+  IL_00c6:  sub
+  IL_00c7:  stloc.s    V_6
+  IL_00c9:  ldloc.s    V_6
+  IL_00cb:  ldloc.3
+  IL_00cc:  ldloc.1
+  IL_00cd:  sub
+  IL_00ce:  ldloc.s    V_6
+  IL_00d0:  sub
+  IL_00d1:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_00d6:  pop
+  // sequence point: _ = Get()[GetIdx3(1)..GetIdx4(3)];
+  IL_00d7:  call       ""CollectionX SideEffect.Get()""
+  IL_00dc:  ldc.i4.1
+  IL_00dd:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_00e2:  call       ""System.Index SideEffect.GetIdx3(System.Index)""
+  IL_00e7:  stloc.s    V_4
+  IL_00e9:  ldc.i4.3
+  IL_00ea:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_00ef:  call       ""System.Index SideEffect.GetIdx4(System.Index)""
+  IL_00f4:  stloc.s    V_7
+  IL_00f6:  dup
+  IL_00f7:  callvirt   ""int CollectionX.Length.get""
+  IL_00fc:  stloc.s    V_6
+  IL_00fe:  ldloca.s   V_4
+  IL_0100:  ldloc.s    V_6
+  IL_0102:  call       ""int System.Index.GetOffset(int)""
+  IL_0107:  stloc.3
+  IL_0108:  ldloc.3
+  IL_0109:  ldloca.s   V_7
+  IL_010b:  ldloc.s    V_6
+  IL_010d:  call       ""int System.Index.GetOffset(int)""
+  IL_0112:  ldloc.3
+  IL_0113:  sub
+  IL_0114:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_0119:  pop
+  // sequence point: _ = Get()[^GetIdx1(3)..];
+  IL_011a:  call       ""CollectionX SideEffect.Get()""
+  IL_011f:  ldc.i4.3
+  IL_0120:  call       ""int SideEffect.GetIdx1(int)""
+  IL_0125:  stloc.3
+  IL_0126:  dup
+  IL_0127:  callvirt   ""int CollectionX.Length.get""
+  IL_012c:  stloc.s    V_6
+  IL_012e:  ldloc.s    V_6
+  IL_0130:  ldloc.3
+  IL_0131:  sub
+  IL_0132:  stloc.1
+  IL_0133:  ldloc.1
+  IL_0134:  ldloc.s    V_6
+  IL_0136:  ldloc.1
+  IL_0137:  sub
+  IL_0138:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_013d:  pop
+  // sequence point: _ = Get()[GetIdx1(1)..];
+  IL_013e:  call       ""CollectionX SideEffect.Get()""
+  IL_0143:  stloc.s    V_5
+  IL_0145:  ldc.i4.1
+  IL_0146:  call       ""int SideEffect.GetIdx1(int)""
+  IL_014b:  stloc.1
+  IL_014c:  ldloc.s    V_5
+  IL_014e:  ldloc.1
+  IL_014f:  ldloc.s    V_5
+  IL_0151:  callvirt   ""int CollectionX.Length.get""
+  IL_0156:  ldloc.1
+  IL_0157:  sub
+  IL_0158:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_015d:  pop
+  // sequence point: _ = Get()[..GetIdx2(3)];
+  IL_015e:  call       ""CollectionX SideEffect.Get()""
+  IL_0163:  ldc.i4.0
+  IL_0164:  ldc.i4.3
+  IL_0165:  call       ""int SideEffect.GetIdx2(int)""
+  IL_016a:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_016f:  pop
+  // sequence point: _ = Get()[..^GetIdx2(1)];
+  IL_0170:  call       ""CollectionX SideEffect.Get()""
+  IL_0175:  stloc.s    V_5
+  IL_0177:  ldc.i4.1
+  IL_0178:  call       ""int SideEffect.GetIdx2(int)""
+  IL_017d:  stloc.1
+  IL_017e:  ldloc.s    V_5
+  IL_0180:  ldc.i4.0
+  IL_0181:  ldloc.s    V_5
+  IL_0183:  callvirt   ""int CollectionX.Length.get""
+  IL_0188:  ldloc.1
+  IL_0189:  sub
+  IL_018a:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_018f:  pop
+  // sequence point: _ = Get()[..];
+  IL_0190:  call       ""CollectionX SideEffect.Get()""
+  IL_0195:  stloc.s    V_5
+  IL_0197:  ldloc.s    V_5
+  IL_0199:  ldc.i4.0
+  IL_019a:  ldloc.s    V_5
+  IL_019c:  callvirt   ""int CollectionX.Length.get""
+  IL_01a1:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_01a6:  pop
+  // sequence point: _ = Get()[GetIdx3(1)..];
+  IL_01a7:  call       ""CollectionX SideEffect.Get()""
+  IL_01ac:  ldc.i4.1
+  IL_01ad:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_01b2:  call       ""System.Index SideEffect.GetIdx3(System.Index)""
+  IL_01b7:  stloc.s    V_7
+  IL_01b9:  dup
+  IL_01ba:  callvirt   ""int CollectionX.Length.get""
+  IL_01bf:  stloc.1
+  IL_01c0:  ldloca.s   V_7
+  IL_01c2:  ldloc.1
+  IL_01c3:  call       ""int System.Index.GetOffset(int)""
+  IL_01c8:  stloc.s    V_6
+  IL_01ca:  ldloc.s    V_6
+  IL_01cc:  ldloc.1
+  IL_01cd:  ldloc.s    V_6
+  IL_01cf:  sub
+  IL_01d0:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_01d5:  pop
+  // sequence point: _ = Get()[..GetIdx4(3)];
+  IL_01d6:  call       ""CollectionX SideEffect.Get()""
+  IL_01db:  stloc.s    V_5
+  IL_01dd:  ldloc.s    V_5
+  IL_01df:  ldc.i4.0
+  IL_01e0:  ldc.i4.3
+  IL_01e1:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_01e6:  call       ""System.Index SideEffect.GetIdx4(System.Index)""
+  IL_01eb:  stloc.s    V_7
+  IL_01ed:  ldloca.s   V_7
+  IL_01ef:  ldloc.s    V_5
+  IL_01f1:  callvirt   ""int CollectionX.Length.get""
+  IL_01f6:  call       ""int System.Index.GetOffset(int)""
+  IL_01fb:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_0200:  pop
+  // sequence point: _ = Get()[^GetIdx1(3)..GetIdx4(3)];
+  IL_0201:  call       ""CollectionX SideEffect.Get()""
+  IL_0206:  ldc.i4.3
+  IL_0207:  call       ""int SideEffect.GetIdx1(int)""
+  IL_020c:  stloc.s    V_6
+  IL_020e:  ldc.i4.3
+  IL_020f:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_0214:  call       ""System.Index SideEffect.GetIdx4(System.Index)""
+  IL_0219:  stloc.s    V_7
+  IL_021b:  dup
+  IL_021c:  callvirt   ""int CollectionX.Length.get""
+  IL_0221:  stloc.1
+  IL_0222:  ldloc.1
+  IL_0223:  ldloc.s    V_6
+  IL_0225:  sub
+  IL_0226:  stloc.3
+  IL_0227:  ldloc.3
+  IL_0228:  ldloca.s   V_7
+  IL_022a:  ldloc.1
+  IL_022b:  call       ""int System.Index.GetOffset(int)""
+  IL_0230:  ldloc.3
+  IL_0231:  sub
+  IL_0232:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_0237:  pop
+  // sequence point: _ = Get()[GetIdx1(1)..GetIdx4(3)];
+  IL_0238:  call       ""CollectionX SideEffect.Get()""
+  IL_023d:  stloc.s    V_5
+  IL_023f:  ldc.i4.1
+  IL_0240:  call       ""int SideEffect.GetIdx1(int)""
+  IL_0245:  stloc.3
+  IL_0246:  ldloc.s    V_5
+  IL_0248:  ldloc.3
+  IL_0249:  ldc.i4.3
+  IL_024a:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_024f:  call       ""System.Index SideEffect.GetIdx4(System.Index)""
+  IL_0254:  stloc.s    V_7
+  IL_0256:  ldloca.s   V_7
+  IL_0258:  ldloc.s    V_5
+  IL_025a:  callvirt   ""int CollectionX.Length.get""
+  IL_025f:  call       ""int System.Index.GetOffset(int)""
+  IL_0264:  ldloc.3
+  IL_0265:  sub
+  IL_0266:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_026b:  pop
+  // sequence point: _ = Get()[GetIdx3(1)..GetIdx2(3)];
+  IL_026c:  call       ""CollectionX SideEffect.Get()""
+  IL_0271:  stloc.s    V_5
+  IL_0273:  ldc.i4.1
+  IL_0274:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_0279:  call       ""System.Index SideEffect.GetIdx3(System.Index)""
+  IL_027e:  stloc.s    V_7
+  IL_0280:  ldc.i4.3
+  IL_0281:  call       ""int SideEffect.GetIdx2(int)""
+  IL_0286:  stloc.3
+  IL_0287:  ldloca.s   V_7
+  IL_0289:  ldloc.s    V_5
+  IL_028b:  callvirt   ""int CollectionX.Length.get""
+  IL_0290:  call       ""int System.Index.GetOffset(int)""
+  IL_0295:  stloc.1
+  IL_0296:  ldloc.s    V_5
+  IL_0298:  ldloc.1
+  IL_0299:  ldloc.3
+  IL_029a:  ldloc.1
+  IL_029b:  sub
+  IL_029c:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_02a1:  pop
+  // sequence point: _ = Get()[GetIdx3(1)..^GetIdx2(1)];
+  IL_02a2:  call       ""CollectionX SideEffect.Get()""
+  IL_02a7:  ldc.i4.1
+  IL_02a8:  call       ""System.Index System.Index.op_Implicit(int)""
+  IL_02ad:  call       ""System.Index SideEffect.GetIdx3(System.Index)""
+  IL_02b2:  stloc.s    V_7
+  IL_02b4:  ldc.i4.1
+  IL_02b5:  call       ""int SideEffect.GetIdx2(int)""
+  IL_02ba:  stloc.1
+  IL_02bb:  dup
+  IL_02bc:  callvirt   ""int CollectionX.Length.get""
+  IL_02c1:  stloc.3
+  IL_02c2:  ldloca.s   V_7
+  IL_02c4:  ldloc.3
+  IL_02c5:  call       ""int System.Index.GetOffset(int)""
+  IL_02ca:  stloc.s    V_6
+  IL_02cc:  ldloc.s    V_6
+  IL_02ce:  ldloc.3
+  IL_02cf:  ldloc.1
+  IL_02d0:  sub
+  IL_02d1:  ldloc.s    V_6
+  IL_02d3:  sub
+  IL_02d4:  callvirt   ""int CollectionX.Slice(int, int)""
+  IL_02d9:  pop
+  // sequence point: }
+  IL_02da:  ret
+}
 ");
         }
 
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/SwitchTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/SwitchTests.cs
index 9e114ce1aec4a..80639c18b5aee 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/SwitchTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/SwitchTests.cs
@@ -2922,7 +2922,7 @@ .locals init (string V_0, //value
   IL_0021:  ldarg.0
   IL_0022:  brfalse    IL_012b
   IL_0027:  ldarg.0
-  IL_0028:  call       ""ComputeStringHash""
+  IL_0028:  call       ""ComputeStringHash(string)""
   IL_002d:  stloc.1
   IL_002e:  ldloc.1
   IL_002f:  ldc.i4     0xc70bfb85
@@ -3367,7 +3367,7 @@ .locals init (string V_0, //value
   IL_0017:  callvirt   ""string string.Remove(int, int)""
   IL_001c:  starg.s    V_0
   IL_001e:  ldarg.0
-  IL_001f:  call       ""ComputeStringHash""
+  IL_001f:  call       ""ComputeStringHash(string)""
   IL_0024:  stloc.1
   IL_0025:  ldloc.1
   IL_0026:  ldc.i4     0xb2f29419
@@ -4039,7 +4039,7 @@ static int M(string s)
 
         private static void VerifySynthesizedStringHashMethod(CompilationVerifier compVerifier, bool expected)
         {
-            compVerifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected);
+            compVerifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected);
 
             if (expected)
             {
@@ -7165,7 +7165,7 @@ public static int M(string s)
   .maxstack  2
   .locals init (uint V_0)
   IL_0000:  ldarg.0
-  IL_0001:  call       ""ComputeStringHash""
+  IL_0001:  call       ""ComputeStringHash(string)""
   IL_0006:  stloc.0
   IL_0007:  ldloc.0
   IL_0008:  ldc.i4     0x6ceb2d06
@@ -7870,7 +7870,7 @@ .locals init (string V_0,
   IL_0017:  ldelem.ref
   IL_0018:  stloc.0
   IL_0019:  ldloc.0
-  IL_001a:  call       ""ComputeStringHash""
+  IL_001a:  call       ""ComputeStringHash(string)""
   IL_001f:  stloc.1
   IL_0020:  ldloc.1
   IL_0021:  ldc.i4     0xc30bf539
@@ -8104,7 +8104,7 @@ .locals init (string V_0,
   IL_0002:  ldelem.ref
   IL_0003:  stloc.0
   IL_0004:  ldloc.0
-  IL_0005:  call       ""ComputeStringHash""
+  IL_0005:  call       ""ComputeStringHash(string)""
   IL_000a:  stloc.1
   IL_000b:  ldloc.1
   IL_000c:  ldc.i4     0xc30bf539
diff --git a/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTest.cs b/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTest.cs
index 018bec4f8190e..05bbbe11fa3d6 100644
--- a/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTest.cs
+++ b/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTest.cs
@@ -26,6 +26,7 @@ internal sealed partial class EditAndContinueTest : IDisposable
         private readonly CSharpCompilationOptions? _options;
         private readonly CSharpParseOptions? _parseOptions;
         private readonly TargetFramework _targetFramework;
+        private readonly Verification _verification;
 
         private readonly List<IDisposable> _disposables = new();
         private readonly List<GenerationInfo> _generations = new();
@@ -33,11 +34,16 @@ internal sealed partial class EditAndContinueTest : IDisposable
 
         private bool _hasVerified;
 
-        public EditAndContinueTest(CSharpCompilationOptions? options = null, CSharpParseOptions? parseOptions = null, TargetFramework targetFramework = TargetFramework.Standard)
+        public EditAndContinueTest(
+            CSharpCompilationOptions? options = null,
+            CSharpParseOptions? parseOptions = null,
+            TargetFramework targetFramework = TargetFramework.Standard,
+            Verification? verification = null)
         {
             _options = options ?? TestOptions.DebugDll;
             _targetFramework = targetFramework;
             _parseOptions = parseOptions ?? TestOptions.Regular.WithNoRefSafetyRulesAttribute();
+            _verification = verification ?? Verification.Passes;
         }
 
         internal EditAndContinueTest AddBaseline(string source, Action<GenerationVerifier> validator)
@@ -60,7 +66,7 @@ internal EditAndContinueTest AddBaseline(SourceWithMarkedNodes source, Action<Ge
                 args: null,
                 manifestResources: null,
                 emitOptions: EmitOptions.Default,
-                peVerify: Verification.Passes,
+                peVerify: _verification,
                 expectedSignatures: null);
 
             var md = ModuleMetadata.CreateFromImage(verifier.EmittedAssemblyData);
@@ -105,6 +111,8 @@ internal EditAndContinueTest AddGeneration(SourceWithMarkedNodes source, Semanti
                 throw new Exception($"Exception during generation #{_generations.Count}. See inner stack trace for details.", ex);
             }
 
+            Assert.Empty(diff.EmitResult.Diagnostics);
+
             // EncVariableSlotAllocator attempted to map from current source to the previous one,
             // but the mapping failed for these nodes. Mark the nodes in sources with node markers <N:x>...</N:x>.
             Assert.Empty(unmappedNodes);
@@ -155,13 +163,18 @@ private ImmutableArray<SemanticEdit> GetSemanticEdits(
 
             return ImmutableArray.CreateRange(edits.Select(e =>
             {
-                var oldSymbol = e.SymbolProvider(oldCompilation);
+                var oldSymbol = e.Kind is SemanticEditKind.Update or SemanticEditKind.Delete ? e.SymbolProvider(oldCompilation) : null;
+
+                // for delete the new symbol is the new containing type
                 var newSymbol = e.NewSymbolProvider(newCompilation);
 
                 Func<SyntaxNode, SyntaxNode?>? syntaxMap;
                 if (e.PreserveLocalVariables)
                 {
                     Assert.Equal(SemanticEditKind.Update, e.Kind);
+                    Debug.Assert(oldSymbol != null);
+                    Debug.Assert(newSymbol != null);
+
                     syntaxMap = syntaxMapFromMarkers ?? EditAndContinueTestBase.GetEquivalentNodesMap(
                         ((Public.MethodSymbol)newSymbol).GetSymbol<MethodSymbol>(), ((Public.MethodSymbol)oldSymbol).GetSymbol<MethodSymbol>());
                 }
diff --git a/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs b/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs
index ceaf874a2740a..6b8ba463a5a0d 100644
--- a/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs
@@ -40,7 +40,7 @@ private static IEnumerable<string> DumpTypeRefs(MetadataReader[] readers)
         }
 
         [Fact]
-        public void Constructor_Delete()
+        public void Constructor_Delete_WithParameterless()
         {
             using var _ = new EditAndContinueTest()
                 .AddBaseline(
@@ -106,6 +106,73 @@ .maxstack  8
                 .Verify();
         }
 
+        [Fact]
+        public void Constructor_Delete()
+        {
+            using var _ = new EditAndContinueTest()
+                .AddBaseline(
+                    source: $$"""
+                        class C
+                        {
+                            public C(int x)
+                            {
+                            }
+                        }
+                        """,
+                    validator: g =>
+                    {
+                        g.VerifyMethodDefNames(".ctor");
+                    })
+
+                .AddGeneration(
+                    source: """
+                        class C
+                        {
+                        }
+                        """,
+                    edits: new[]
+                    {
+                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.FirstOrDefault(c => c.Parameters.Length == 1), newSymbolProvider: c => c.GetMember("C")),
+                    },
+                    validator: g =>
+                    {
+                        // The default constructor is added and the deleted constructor is updated to throw:
+                        g.VerifyMethodDefNames(".ctor", ".ctor");
+
+                        g.VerifyEncLogDefinitions(new[]
+                        {
+                            Row(1, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(2, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(2, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(1, TableIndex.Param, EditAndContinueOperation.Default)
+                        });
+                        g.VerifyEncMapDefinitions(new[]
+                        {
+                            Handle(1, TableIndex.MethodDef),
+                            Handle(2, TableIndex.MethodDef),
+                            Handle(1, TableIndex.Param)
+                        });
+
+                        g.VerifyIL("""
+                            {
+                              // Code size        6 (0x6)
+                              .maxstack  8
+                              IL_0000:  newobj     0x0A000005
+                              IL_0005:  throw
+                            }
+                            {
+                              // Code size        8 (0x8)
+                              .maxstack  8
+                              IL_0000:  ldarg.0
+                              IL_0001:  call       0x0A000006
+                              IL_0006:  nop
+                              IL_0007:  ret
+                            }
+                            """);
+                    })
+                .Verify();
+        }
+
         [Fact]
         public void Diagnostics_Nullable()
         {
@@ -5050,6 +5117,91 @@ void ValidateReplacedType(CompilationDifference diff, MetadataReader[] readers)
             CheckBlobValue(readers, reader3.GetCustomAttribute(reader3.CustomAttributes.First()).Value, new byte[] { 0x01, 0x00, 0x00, 0x00 });
         }
 
+        [Fact]
+        public void ReplaceType_UpdateNestedType()
+        {
+            using var _ = new EditAndContinueTest()
+                .AddBaseline(
+                    source: $$"""
+                        using System;
+                        
+                        class C
+                        {
+                            class D
+                            {
+                                void M()
+                                {
+                                    Console.WriteLine("1");
+                                }
+                            }
+
+                            void N()
+                            {
+                                Console.WriteLine("1");
+                            }
+                        }
+                        """ + MetadataUpdateOriginalTypeAttributeSource,
+                    validator: g =>
+                    {
+                        g.VerifyTypeDefNames("<Module>", "C", "MetadataUpdateOriginalTypeAttribute", "D");
+                        g.VerifyMethodDefNames("N", ".ctor", ".ctor", "get_OriginalType", "M", ".ctor");
+                    })
+
+                .AddGeneration(
+                    source: """
+                        using System;
+
+                        class C
+                        {
+                            class D
+                            {
+                                void M()
+                                {
+                                    Console.WriteLine("2");
+                                }
+                            }
+
+                            void N()
+                            {
+                                Console.WriteLine("2");
+                            }
+                        }
+                        """ + MetadataUpdateOriginalTypeAttributeSource,
+                    edits: new[] {
+                        // Note: Nested type edit needs to be seen first to repro the bug. Real world scenario requires the nested
+                        // class to be in a separate file.
+                        Edit(SemanticEditKind.Update, c => c.GetMember("C.D.M")),
+                        Edit(SemanticEditKind.Replace, c => null, newSymbolProvider: c => c.GetMember("C")),
+                    },
+                    validator: g =>
+                    {
+                        g.VerifyTypeDefNames("C#1");
+                        g.VerifyMethodDefNames("M", "N", ".ctor", ".ctor");
+                        g.VerifyEncLogDefinitions(new[]
+                        {
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(7, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(8, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(4, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(9, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(8, TableIndex.CustomAttribute, EditAndContinueOperation.Default)
+                        });
+                        g.VerifyEncMapDefinitions(new[]
+                        {
+                            Handle(5, TableIndex.TypeDef),
+                            Handle(5, TableIndex.MethodDef),
+                            Handle(7, TableIndex.MethodDef),
+                            Handle(8, TableIndex.MethodDef),
+                            Handle(9, TableIndex.MethodDef),
+                            Handle(8, TableIndex.CustomAttribute)
+                        });
+                    })
+                .Verify();
+        }
+
         [Fact]
         public void EventFields_Attributes()
         {
@@ -14683,7 +14835,7 @@ namespace N
 {
     record R(int X)
     {
-        protected virtual bool PrintMembers(System.Text.StringBuilder builder)
+        protected virtual bool PrintMembers(System.Text.StringBuilder sb) // note the different parameter name
         {
             return true;
         }
@@ -14822,6 +14974,308 @@ record R(int X)
                 "System.Runtime.CompilerServices: {NullableAttribute, NullableContextAttribute}");
         }
 
+        [Fact]
+        public void Records_AddPrimaryConstructor()
+        {
+            using var _ = new EditAndContinueTest(options: TestOptions.DebugDll, targetFramework: TargetFramework.NetStandard20)
+                .AddBaseline(
+                    source: IsExternalInitTypeDefinition + "record R {}",
+                    validator: g =>
+                    {
+                        g.VerifyMethodDefNames(
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            "get_EqualityContract",
+                            "ToString",
+                            "PrintMembers",
+                            "op_Inequality",
+                            "op_Equality",
+                            "GetHashCode",
+                            "Equals",
+                            "Equals",
+                            "<Clone>$",
+                            ".ctor",
+                            ".ctor");
+                    })
+
+                .AddGeneration(
+                    source: IsExternalInitTypeDefinition + "record R(int P) {}",
+                    edits: new[]
+                    {
+                        // The IDE actually also adds Update edits for synthesized methods (PrintMembers, Equals, GetHashCode).
+                        // This test demonstrates that the compiler does not emit them automatically given just the constructor insert.
+                        Edit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("R")),
+                        Edit(SemanticEditKind.Delete, c => c.GetParameterlessConstructor("R"), c => c.GetMember("R"))
+                    },
+                    validator: g =>
+                    {
+                        g.VerifyMethodDefNames(
+                            ".ctor", // inserted primary ctor
+                            ".ctor", // updated parameterless ctor
+                            "get_P",
+                            "set_P",
+                            "Deconstruct");
+
+                        g.VerifyEncLogDefinitions(new[]
+                        {
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddField),
+                            Row(3, TableIndex.Field, EditAndContinueOperation.Default),
+                            Row(15, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(16, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(17, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(18, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(19, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(1, TableIndex.PropertyMap, EditAndContinueOperation.AddProperty),
+                            Row(2, TableIndex.Property, EditAndContinueOperation.Default),
+                            Row(16, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(9, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(18, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(10, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(19, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(11, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(30, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(31, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(32, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(33, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(34, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(2, TableIndex.MethodSemantics, EditAndContinueOperation.Default),
+                            Row(3, TableIndex.MethodSemantics, EditAndContinueOperation.Default)
+                        });
+                    })
+                .Verify();
+        }
+
+        [Fact]
+        public void Records_AddPrimaryConstructorParameter()
+        {
+            using var _ = new EditAndContinueTest(options: TestOptions.DebugDll, targetFramework: TargetFramework.NetLatest, verification: Verification.Skipped)
+                .AddBaseline(
+                    source: IsExternalInitTypeDefinition + "record R(int P, int U) {}",
+                    validator: g =>
+                    {
+                        g.VerifyMethodDefNames(
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            "get_EqualityContract",
+                            "get_P",
+                            "set_P",
+                            "get_U",
+                            "set_U",
+                            "ToString",
+                            "PrintMembers",
+                            "op_Inequality",
+                            "op_Equality",
+                            "GetHashCode",
+                            "Equals",
+                            "Equals",
+                            "<Clone>$",
+                            ".ctor",
+                            "Deconstruct");
+                    })
+
+                .AddGeneration(
+                    source: IsExternalInitTypeDefinition + "record R(int P, int Q, int U) {}",
+                    edits: new[]
+                    {
+                        // The IDE actually also adds Update edits for synthesized methods (PrintMembers, Equals, GetHashCode, copy-constructor) and 
+                        // delete of the old primary constructor.
+                        // This test demonstrates that the compiler does not emit them automatically given just the constructor insert.
+                        // The synthesized auto-properties and Deconstruct method are emitted.
+                        Edit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("R"))
+                    },
+                    validator: g =>
+                    {
+                        g.VerifyMethodDefNames(
+                            ".ctor",
+                            "get_Q",
+                            "set_Q",
+                            "Deconstruct");
+
+                        g.VerifyEncLogDefinitions(new[]
+                        {
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddField),
+                            Row(5, TableIndex.Field, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(21, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(22, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(23, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(24, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(1, TableIndex.PropertyMap, EditAndContinueOperation.AddProperty),
+                            Row(4, TableIndex.Property, EditAndContinueOperation.Default),
+                            Row(21, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(15, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(21, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(16, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(21, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(17, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(23, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(18, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(24, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(19, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(24, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(20, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(24, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(21, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(39, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(40, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(41, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(42, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(43, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(6, TableIndex.MethodSemantics, EditAndContinueOperation.Default),
+                            Row(7, TableIndex.MethodSemantics, EditAndContinueOperation.Default),
+                        });
+
+                        g.VerifyIL("""
+                        {
+                          // Code size       29 (0x1d)
+                          .maxstack  8
+                          IL_0000:  ldarg.0
+                          IL_0001:  ldarg.1
+                          IL_0002:  stfld      0x04000003
+                          IL_0007:  ldarg.0
+                          IL_0008:  ldarg.2
+                          IL_0009:  stfld      0x04000005
+                          IL_000e:  ldarg.0
+                          IL_000f:  ldarg.3
+                          IL_0010:  stfld      0x04000004
+                          IL_0015:  ldarg.0
+                          IL_0016:  call       0x0A000017
+                          IL_001b:  nop
+                          IL_001c:  ret
+                        }
+                        {
+                          // Code size        7 (0x7)
+                          .maxstack  8
+                          IL_0000:  ldarg.0
+                          IL_0001:  ldfld      0x04000005
+                          IL_0006:  ret
+                        }
+                        {
+                          // Code size        8 (0x8)
+                          .maxstack  8
+                          IL_0000:  ldarg.0
+                          IL_0001:  ldarg.1
+                          IL_0002:  stfld      0x04000005
+                          IL_0007:  ret
+                        }
+                        {
+                          // Code size       25 (0x19)
+                          .maxstack  8
+                          IL_0000:  ldarg.1
+                          IL_0001:  ldarg.0
+                          IL_0002:  call       0x06000007
+                          IL_0007:  stind.i4
+                          IL_0008:  ldarg.2
+                          IL_0009:  ldarg.0
+                          IL_000a:  call       0x06000016
+                          IL_000f:  stind.i4
+                          IL_0010:  ldarg.3
+                          IL_0011:  ldarg.0
+                          IL_0012:  call       0x06000009
+                          IL_0017:  stind.i4
+                          IL_0018:  ret
+                        }
+                        """);
+                    })
+                .Verify();
+        }
+
+        [Fact]
+        public void Records_AddProperty_NonPrimary()
+        {
+            using var _ = new EditAndContinueTest(options: TestOptions.DebugDll, targetFramework: TargetFramework.NetStandard20, verification: Verification.Skipped)
+                .AddBaseline(
+                    source: IsExternalInitTypeDefinition + "record R(int P) {}",
+                    validator: g =>
+                    {
+                        g.VerifyMethodDefNames(
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            ".ctor",
+                            "get_EqualityContract",
+                            "get_P",
+                            "set_P",
+                            "ToString",
+                            "PrintMembers",
+                            "op_Inequality",
+                            "op_Equality",
+                            "GetHashCode",
+                            "Equals",
+                            "Equals",
+                            "<Clone>$",
+                            ".ctor",
+                            "Deconstruct");
+                    })
+
+                .AddGeneration(
+                    source: IsExternalInitTypeDefinition + "record R(int P) { int Q { get; init; } }",
+                    edits: new[]
+                    {
+                        // The IDE actually adds Update edits for synthesized methods (PrintMembers, Equals, GetHashCode, copy-constructor).
+                        // This test demonstrates that the compiler does not emit them automatically given just the property insert.
+                        Edit(SemanticEditKind.Insert, c => c.GetMember("R.Q")),
+                    },
+                    validator: g =>
+                    {
+                        g.VerifyMethodDefNames(
+                            "get_Q",
+                            "set_Q");
+
+                        g.VerifyEncLogDefinitions(new[]
+                        {
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddField),
+                            Row(4, TableIndex.Field, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(19, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.TypeDef, EditAndContinueOperation.AddMethod),
+                            Row(20, TableIndex.MethodDef, EditAndContinueOperation.Default),
+                            Row(1, TableIndex.PropertyMap, EditAndContinueOperation.AddProperty),
+                            Row(3, TableIndex.Property, EditAndContinueOperation.Default),
+                            Row(20, TableIndex.MethodDef, EditAndContinueOperation.AddParameter),
+                            Row(12, TableIndex.Param, EditAndContinueOperation.Default),
+                            Row(35, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(36, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(37, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(38, TableIndex.CustomAttribute, EditAndContinueOperation.Default),
+                            Row(4, TableIndex.MethodSemantics, EditAndContinueOperation.Default),
+                            Row(5, TableIndex.MethodSemantics, EditAndContinueOperation.Default)
+                        });
+
+                        g.VerifyIL("""
+                        {
+                          // Code size        7 (0x7)
+                          .maxstack  8
+                          IL_0000:  ldarg.0
+                          IL_0001:  ldfld      0x04000004
+                          IL_0006:  ret
+                        }
+                        {
+                          // Code size        8 (0x8)
+                          .maxstack  8
+                          IL_0000:  ldarg.0
+                          IL_0001:  ldarg.1
+                          IL_0002:  stfld      0x04000004
+                          IL_0007:  ret
+                        }
+                        """);
+                    })
+                .Verify();
+        }
+
         [Fact]
         public void TopLevelStatement_Update()
         {
diff --git a/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests.cs b/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests.cs
index 65bbe3a450166..e751b713b8132 100644
--- a/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests.cs
+++ b/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests.cs
@@ -11329,7 +11329,6 @@ public void AvoidCascadingDiagnosticsOnMissingAttribute()
                       IDiscardPatternOperation (OperationKind.DiscardPattern, Type: null) (Syntax: '_') (InputType: System.Int32, NarrowedType: System.Int32)
                     Value:
                       ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 1) (Syntax: '1')
-
 """;
             var expectedDiagnostics = new[]
             {
@@ -11341,7 +11340,23 @@ public void AvoidCascadingDiagnosticsOnMissingAttribute()
                 Diagnostic(ErrorCode.ERR_SingleTypeNameNotFound, "Inexistent").WithArguments("Inexistent").WithLocation(1, 22)
             };
 
-            VerifyOperationTreeAndDiagnosticsForTest<AttributeSyntax>(source, expectedOperationTree, expectedDiagnostics);
+            var comp = CreateCompilation(source);
+            VerifyOperationTreeAndDiagnosticsForTest<AttributeSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+
+            var tree = comp.SyntaxTrees[0];
+            var model = comp.GetSemanticModel(tree);
+
+            var firstArgument = tree.GetRoot().DescendantNodes().OfType<AttributeArgumentSyntax>().First();
+            Assert.Equal("SomeProperty = 1", firstArgument.ToString());
+            Assert.Equal("System.Int32", model.GetTypeInfo(firstArgument.Expression).Type.ToTestDisplayString());
+
+            var secondArgument = tree.GetRoot().DescendantNodes().OfType<AttributeArgumentSyntax>().Skip(1).First();
+            Assert.Equal("F = null", secondArgument.ToString());
+            Assert.Null(model.GetTypeInfo(secondArgument.Expression).Type);
+
+            var thirdArgument = tree.GetRoot().DescendantNodes().OfType<AttributeArgumentSyntax>().Skip(2).Single();
+            Assert.Equal("G = 0 switch { _ => 1 }", thirdArgument.ToString());
+            Assert.Equal("System.Int32", model.GetTypeInfo(thirdArgument.Expression).Type.ToTestDisplayString());
         }
         #endregion
     }
diff --git a/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests_WellKnownAttributes.cs b/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests_WellKnownAttributes.cs
index ea17f1a3af60b..3bc948b3fb666 100644
--- a/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests_WellKnownAttributes.cs
+++ b/src/Compilers/CSharp/Test/Emit2/Attributes/AttributeTests_WellKnownAttributes.cs
@@ -4748,11 +4748,15 @@ enum E
                         case "B":
                         case "E":
                         case "D":
+#pragma warning disable SYSLIB0050 // Type or member is obsolete
                             Assert.Equal(TypeAttributes.Serializable, row.Attributes & TypeAttributes.Serializable);
+#pragma warning restore SYSLIB0050 // Type or member is obsolete
                             break;
 
                         case "<Module>":
+#pragma warning disable SYSLIB0050 // Type or member is obsolete
                             Assert.Equal((TypeAttributes)0, row.Attributes & TypeAttributes.Serializable);
+#pragma warning restore SYSLIB0050 // Type or member is obsolete
                             break;
 
                         default:
@@ -4770,11 +4774,15 @@ enum E
                         case "e":
                         case "x":
                         case "A":
+#pragma warning disable SYSLIB0050 // Type or member is obsolete
                             Assert.Equal(FieldAttributes.NotSerialized, flags & FieldAttributes.NotSerialized);
+#pragma warning restore SYSLIB0050 // Type or member is obsolete
                             break;
 
                         case "value__":
+#pragma warning disable SYSLIB0050 // Type or member is obsolete
                             Assert.Equal((FieldAttributes)0, flags & FieldAttributes.NotSerialized);
+#pragma warning restore SYSLIB0050 // Type or member is obsolete
                             break;
                     }
                 }
@@ -6493,12 +6501,9 @@ public SomeAttr1(Action x) {}
                 // (31,15): error CS1503: Argument 1: cannot convert from 'method group' to 'string'
                 //     [Obsolete(Method1)]
                 Diagnostic(ErrorCode.ERR_BadArgType, "Method1").WithArguments("1", "method group", "string").WithLocation(31, 15),
-                // (35,16): warning CS0612: 'Test.Method2()' is obsolete
+                // (35,16): error CS0120: An object reference is required for the non-static field, method, or property 'Test.Method2()'
                 //     [SomeAttr1(Method2)]
-                Diagnostic(ErrorCode.WRN_DeprecatedSymbol, "Method2").WithArguments("Test.Method2()").WithLocation(35, 16),
-                // (35,6): error CS0181: Attribute constructor parameter 'x' has type 'Action', which is not a valid attribute parameter type
-                //     [SomeAttr1(Method2)]
-                Diagnostic(ErrorCode.ERR_BadAttributeParamType, "SomeAttr1").WithArguments("x", "System.Action").WithLocation(35, 6),
+                Diagnostic(ErrorCode.ERR_ObjectRequired, "Method2").WithArguments("Test.Method2()").WithLocation(35, 16),
                 // (43,15): error CS0619: 'Test.F7' is obsolete: 'F7 is obsolete'
                 //     [Obsolete(F7, true)]
                 Diagnostic(ErrorCode.ERR_DeprecatedSymbolStr, "F7").WithArguments("Test.F7", "F7 is obsolete").WithLocation(43, 15),
diff --git a/src/Compilers/CSharp/Test/Emit2/CodeGen/CodeGenLengthBasedSwitchTests.cs b/src/Compilers/CSharp/Test/Emit2/CodeGen/CodeGenLengthBasedSwitchTests.cs
index 08c12c9476513..25fb5a3be2348 100644
--- a/src/Compilers/CSharp/Test/Emit2/CodeGen/CodeGenLengthBasedSwitchTests.cs
+++ b/src/Compilers/CSharp/Test/Emit2/CodeGen/CodeGenLengthBasedSwitchTests.cs
@@ -77,7 +77,7 @@ public static string M(string o)
         var comp = CreateCompilation(source);
         comp.VerifyDiagnostics();
         var verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: false);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: false);
         verifier.VerifyIL("C.M", """
 {
   // Code size      584 (0x248)
@@ -267,7 +267,7 @@ .locals init (string V_0,
         comp = CreateCompilation(source, parseOptions: TestOptions.RegularPreview.WithDisableLengthBasedSwitch());
         comp.VerifyDiagnostics();
         verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: true);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: true);
         verifier.VerifyIL("C.M", """
  {
   // Code size      786 (0x312)
@@ -275,7 +275,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x62366ffa
@@ -572,7 +572,7 @@ public static string M({{keyType}} o)
         comp.VerifyDiagnostics();
         var verifier = CompileAndVerify(comp, expectedOutput: "RAN", verify: Verification.Skipped);
         var indexer = useReadonly ? $$"""ref readonly char {{keyType}}.this[int].get""" : $$"""ref char {{keyType}}.this[int].get""";
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: false);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: false);
         verifier.VerifyIL("C.M", $$"""
 {
   // Code size      648 (0x288)
@@ -776,7 +776,7 @@ .locals init (string V_0,
         comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularPreview.WithDisableLengthBasedSwitch());
         comp.VerifyDiagnostics();
         verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        var helper = useReadonly ? "ComputeReadOnlySpanHash" : "ComputeSpanHash";
+        var helper = useReadonly ? "ComputeReadOnlySpanHash(System.ReadOnlySpan<char>)" : "ComputeSpanHash(System.Span<char>)";
         verifier.VerifyMemberInIL(helper, expected: true);
         verifier.VerifyIL("C.M", $$"""
 {
@@ -1108,7 +1108,7 @@ public static string M(object o)
         var comp = CreateCompilation(source);
         comp.VerifyDiagnostics();
         var verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: false);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: false);
         verifier.VerifyIL("C.M", """
 {
   // Code size      272 (0x110)
@@ -1214,7 +1214,7 @@ .locals init (string V_0,
         comp = CreateCompilation(source, parseOptions: TestOptions.RegularPreview.WithDisableLengthBasedSwitch());
         comp.VerifyDiagnostics();
         verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: true);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: true);
         verifier.VerifyIL("C.M", """
 {
   // Code size      335 (0x14f)
@@ -1228,7 +1228,7 @@ .locals init (string V_0,
   IL_0007:  ldloc.1
   IL_0008:  brfalse    IL_0147
   IL_000d:  ldloc.1
-  IL_000e:  call       "ComputeStringHash"
+  IL_000e:  call       "ComputeStringHash(string)"
   IL_0013:  stloc.2
   IL_0014:  ldloc.2
   IL_0015:  ldc.i4     0x749bcf08
@@ -1389,7 +1389,7 @@ public static string M(object o)
         var comp = CreateCompilation(source);
         comp.VerifyDiagnostics();
         var verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: false);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: false);
         verifier.VerifyIL("C.M", """
 {
   // Code size      310 (0x136)
@@ -1571,7 +1571,7 @@ public static string M(string o)
         comp.VerifyEmitDiagnostics();
 
         var verifier = CompileAndVerify(comp);
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: false);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: false);
         verifier.VerifyIL("C.M", """
 {
   // Code size      178 (0xb2)
@@ -2060,7 +2060,7 @@ public static string M(object o)
         var comp = CreateCompilation(source);
         comp.VerifyDiagnostics();
         var verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: false);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: false);
         verifier.VerifyIL("C.M", """
 {
   // Code size      288 (0x120)
@@ -2172,7 +2172,7 @@ .locals init (string V_0,
         comp = CreateCompilation(source, parseOptions: TestOptions.RegularPreview.WithDisableLengthBasedSwitch());
         comp.VerifyDiagnostics();
         verifier = CompileAndVerify(comp, expectedOutput: "RAN");
-        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName, expected: true);
+        verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: true);
         verifier.VerifyIL("C.M", """
 {
   // Code size      357 (0x165)
@@ -2186,7 +2186,7 @@ .locals init (string V_0,
   IL_0007:  ldloc.1
   IL_0008:  brfalse    IL_0110
   IL_000d:  ldloc.1
-  IL_000e:  call       "ComputeStringHash"
+  IL_000e:  call       "ComputeStringHash(string)"
   IL_0013:  stloc.2
   IL_0014:  ldloc.2
   IL_0015:  ldc.i4     0x749bcf08
@@ -2612,7 +2612,7 @@ .locals init (int V_0,
   .maxstack  2
   .locals init (uint V_0)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.0
   IL_0007:  ldloc.0
   IL_0008:  ldc.i4     0xad238cee
@@ -2917,7 +2917,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x87f05176
@@ -4132,7 +4132,7 @@ public static string M(string fileSystemName)
   .maxstack  2
   .locals init (uint V_0)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.0
   IL_0007:  ldloc.0
   IL_0008:  ldc.i4     0x93254270
@@ -7510,7 +7510,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x77c08b8d
@@ -8933,7 +8933,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x8979e177
@@ -9330,7 +9330,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x2607050f
@@ -10091,7 +10091,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x6ccaf138
@@ -11391,7 +11391,7 @@ .locals init (int V_0,
   .maxstack  2
   .locals init (uint V_0)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.0
   IL_0007:  ldloc.0
   IL_0008:  ldc.i4     0xb508d68f
@@ -12396,7 +12396,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x76692b6a
@@ -12857,7 +12857,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x62fa988f
@@ -13334,7 +13334,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x5ef81c51
@@ -13769,7 +13769,7 @@ .maxstack  2
   .locals init (string V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       "ComputeStringHash"
+  IL_0001:  call       "ComputeStringHash(string)"
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x4569f715
diff --git a/src/Compilers/CSharp/Test/Emit2/Diagnostics/DiagnosticAnalyzerTests.cs b/src/Compilers/CSharp/Test/Emit2/Diagnostics/DiagnosticAnalyzerTests.cs
index 530819e1264fb..1e24fc44adfa7 100644
--- a/src/Compilers/CSharp/Test/Emit2/Diagnostics/DiagnosticAnalyzerTests.cs
+++ b/src/Compilers/CSharp/Test/Emit2/Diagnostics/DiagnosticAnalyzerTests.cs
@@ -4131,66 +4131,101 @@ public override bool TryGetGlobalDiagnosticValue(string diagnosticId, Cancellati
 
         [Theory, WorkItem(67257, "https://github.com/dotnet/roslyn/issues/67257")]
         [CombinatorialData]
-        public async Task TestFilterSpanOnContextAsync(bool testSyntaxTreeAction, bool testGetAnalysisResultApi, bool testAnalyzersBasedOverload)
+        public async Task TestFilterSpanOnContextAsync(FilterSpanTestAnalyzer.AnalysisKind analysisKind, bool testGetAnalysisResultApi, bool testAnalyzersBasedOverload)
         {
-            string source = @"
-class B
+            string source1 = @"
+partial class B
 {
     void M()
     {
         int x = 1;
     }
 }";
+            string source2 = @"
+partial class B
+{
+    void M2()
+    {
+        int x2 = 1;
+    }
+}";
+            string additionalText = @"This is an additional file!";
 
-            var compilation = CreateCompilationWithMscorlib45(new[] { source });
+            var compilation = CreateCompilationWithMscorlib45(new[] { source1, source2 });
             var tree = compilation.SyntaxTrees[0];
             var localDeclaration = tree.GetRoot().DescendantNodes().OfType<LocalDeclarationStatementSyntax>().First();
             var semanticModel = compilation.GetSemanticModel(tree);
 
-            var analyzer = new FilterSpanTestAnalyzer(testSyntaxTreeAction);
+            var analyzer = new FilterSpanTestAnalyzer(analysisKind);
             var analyzers = ImmutableArray.Create<DiagnosticAnalyzer>(analyzer);
-            var compilationWithAnalyzers = compilation.WithAnalyzers(analyzers);
+            var additionalTextFile = new TestAdditionalText(additionalText);
+            var analyzerOptions = new AnalyzerOptions(ImmutableArray.Create<AdditionalText>(additionalTextFile));
+            var options = new CompilationWithAnalyzersOptions(analyzerOptions, onAnalyzerException: null, concurrentAnalysis: true, logAnalyzerExecutionTime: true);
+            var compilationWithAnalyzers = compilation.WithAnalyzers(analyzers, options);
 
             // Invoke "GetAnalysisResultAsync" for a sub-span and then
-            // for the entire tree span and verify FilterSpan on the callback context.
+            // for the entire tree span and verify FilterSpan/FilterTree on the callback context.
             Assert.Null(analyzer.CallbackFilterSpan);
-            await verifyCallbackSpanAsync(filterSpan: localDeclaration.Span);
+            Assert.Null(analyzer.CallbackFilterTree);
+            var filterSpan = analysisKind == FilterSpanTestAnalyzer.AnalysisKind.AdditionalFile
+                ? new TextSpan(0, 1)
+                : localDeclaration.Span;
+            await verifyCallbackSpanAsync(filterSpan);
             await verifyCallbackSpanAsync(filterSpan: null);
 
             async Task verifyCallbackSpanAsync(TextSpan? filterSpan)
             {
-                if (testSyntaxTreeAction)
+                switch (analysisKind)
                 {
-                    if (testGetAnalysisResultApi)
-                    {
-                        _ = testAnalyzersBasedOverload
-                            ? await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel.SyntaxTree, filterSpan, analyzers, CancellationToken.None)
-                            : await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel.SyntaxTree, filterSpan, CancellationToken.None);
-                    }
-                    else
-                    {
+                    case FilterSpanTestAnalyzer.AnalysisKind.SyntaxTree:
+                        if (testGetAnalysisResultApi)
+                        {
+                            _ = testAnalyzersBasedOverload
+                                ? await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel.SyntaxTree, filterSpan, analyzers, CancellationToken.None)
+                                : await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel.SyntaxTree, filterSpan, CancellationToken.None);
+                        }
+                        else
+                        {
+                            _ = testAnalyzersBasedOverload
+                                ? await compilationWithAnalyzers.GetAnalyzerSyntaxDiagnosticsAsync(semanticModel.SyntaxTree, filterSpan, analyzers, CancellationToken.None)
+                                : await compilationWithAnalyzers.GetAnalyzerSyntaxDiagnosticsAsync(semanticModel.SyntaxTree, filterSpan, CancellationToken.None);
+                        }
+
+                        break;
+
+                    case FilterSpanTestAnalyzer.AnalysisKind.AdditionalFile:
                         _ = testAnalyzersBasedOverload
-                            ? await compilationWithAnalyzers.GetAnalyzerSyntaxDiagnosticsAsync(semanticModel.SyntaxTree, filterSpan, analyzers, CancellationToken.None)
-                            : await compilationWithAnalyzers.GetAnalyzerSyntaxDiagnosticsAsync(semanticModel.SyntaxTree, filterSpan, CancellationToken.None);
-                    }
+                            ? await compilationWithAnalyzers.GetAnalysisResultAsync(additionalTextFile, filterSpan, analyzers, CancellationToken.None)
+                            : await compilationWithAnalyzers.GetAnalysisResultAsync(additionalTextFile, filterSpan, CancellationToken.None);
+                        break;
+
+                    default:
+                        if (testGetAnalysisResultApi)
+                        {
+                            _ = testAnalyzersBasedOverload
+                                ? await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel, filterSpan, analyzers, CancellationToken.None)
+                                : await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel, filterSpan, CancellationToken.None);
+                        }
+                        else
+                        {
+                            _ = testAnalyzersBasedOverload
+                                ? await compilationWithAnalyzers.GetAnalyzerSemanticDiagnosticsAsync(semanticModel, filterSpan, analyzers, CancellationToken.None)
+                                : await compilationWithAnalyzers.GetAnalyzerSemanticDiagnosticsAsync(semanticModel, filterSpan, CancellationToken.None);
+                        }
+                        break;
+                }
+
+                Assert.Equal(filterSpan, analyzer.CallbackFilterSpan);
+                if (analysisKind == FilterSpanTestAnalyzer.AnalysisKind.AdditionalFile)
+                {
+                    Assert.Equal(additionalTextFile, analyzer.CallbackFilterFile);
+                    Assert.Null(analyzer.CallbackFilterTree);
                 }
                 else
                 {
-                    if (testGetAnalysisResultApi)
-                    {
-                        _ = testAnalyzersBasedOverload
-                            ? await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel, filterSpan, analyzers, CancellationToken.None)
-                            : await compilationWithAnalyzers.GetAnalysisResultAsync(semanticModel, filterSpan, CancellationToken.None);
-                    }
-                    else
-                    {
-                        _ = testAnalyzersBasedOverload
-                            ? await compilationWithAnalyzers.GetAnalyzerSemanticDiagnosticsAsync(semanticModel, filterSpan, analyzers, CancellationToken.None)
-                            : await compilationWithAnalyzers.GetAnalyzerSemanticDiagnosticsAsync(semanticModel, filterSpan, CancellationToken.None);
-                    }
+                    Assert.Equal(tree, analyzer.CallbackFilterTree);
+                    Assert.Null(analyzer.CallbackFilterFile);
                 }
-
-                Assert.Equal(filterSpan, analyzer.CallbackFilterSpan);
             }
         }
     }
diff --git a/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/FlowTestBase.cs b/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/FlowTestBase.cs
index 509f4667042fd..928ebdceec7b5 100644
--- a/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/FlowTestBase.cs
+++ b/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/FlowTestBase.cs
@@ -11,6 +11,7 @@
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
+using Roslyn.Test.Utilities;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests
@@ -88,6 +89,11 @@ protected DataFlowAnalysis CompileAndAnalyzeDataFlowExpression(string program, p
             return CompileAndGetModelAndExpression(program, (model, expression) => model.AnalyzeDataFlow(expression), references);
         }
 
+        protected DataFlowAnalysis CompileAndAnalyzeDataFlowExpression(string program, TargetFramework targetFramework, params MetadataReference[] references)
+        {
+            return CompileAndGetModelAndExpression(program, (model, expression) => model.AnalyzeDataFlow(expression), targetFramework, assertNoDiagnostics: true, references);
+        }
+
         protected DataFlowAnalysis CompileAndAnalyzeDataFlowConstructorInitializer(string program, params MetadataReference[] references)
         {
             return CompileAndGetModelAndConstructorInitializer(program, (model, constructorInitializer) => model.AnalyzeDataFlow(constructorInitializer), references);
@@ -152,7 +158,18 @@ protected T CompileAndGetModelAndPrimaryConstructorInitializer<T>(string program
 
         protected T CompileAndGetModelAndExpression<T>(string program, Func<SemanticModel, ExpressionSyntax, T> analysisDelegate, params MetadataReference[] references)
         {
-            var comp = CreateCompilation(program, parseOptions: TestOptions.RegularPreview, references: references);
+            return CompileAndGetModelAndExpression<T>(program, analysisDelegate, TargetFramework.Standard, assertNoDiagnostics: false, references);
+        }
+
+        protected T CompileAndGetModelAndExpression<T>(string program, Func<SemanticModel, ExpressionSyntax, T> analysisDelegate, TargetFramework targetFramework, bool assertNoDiagnostics, params MetadataReference[] references)
+        {
+            var comp = CreateCompilation(program, parseOptions: TestOptions.RegularPreview, targetFramework: targetFramework, references: references);
+
+            if (assertNoDiagnostics)
+            {
+                comp.VerifyDiagnostics();
+            }
+
             var tree = comp.SyntaxTrees[0];
             var model = comp.GetSemanticModel(tree);
             int start = program.IndexOf(StartString, StringComparison.Ordinal) + StartString.Length;
diff --git a/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/RegionAnalysisTests.cs b/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/RegionAnalysisTests.cs
index 4b6c69654bf6e..ef7278c45caac 100644
--- a/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/RegionAnalysisTests.cs
+++ b/src/Compilers/CSharp/Test/Emit2/FlowAnalysis/RegionAnalysisTests.cs
@@ -12358,5 +12358,1743 @@ static void verify(DataFlowAnalysis analysis)
                 Assert.Equal("z1, z2", GetSymbolNamesJoined(analysis.WrittenOutside));
             }
         }
+
+        private const string InlineArray1Definition =
+@"
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    private int _element0;
+}
+";
+
+        private const string InlineArray2Definition =
+@"
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    private int _element0;
+}
+";
+
+        private const string InlineArray22Definition =
+@"
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer22
+{
+    private Buffer2 _element0;
+}
+" + InlineArray2Definition;
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_010(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer2 x)
+    {
+        /*<bind>*/x[" + index + @"] = 1/*</bind>*/;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+
+            if (isRef)
+            {
+                Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsOut));
+            }
+            else
+            {
+                Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+            }
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+
+            if (isRef)
+            {
+                Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadOutside));
+            }
+            else
+            {
+                Assert.Null(GetSymbolNamesJoined(analysis.ReadOutside));
+            }
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_011([CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(Buffer2 x)
+    {
+        var d =  () => /*<bind>*/x[" + index + @"] = 1/*</bind>*/;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.Captured));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, d", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_020(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer22 x)
+    {
+        /*<bind>*/x[" + index + @"][" + index + @"] = 1/*</bind>*/;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+
+            if (isRef)
+            {
+                Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsOut));
+            }
+            else
+            {
+                Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+            }
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+
+            if (isRef)
+            {
+                Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadOutside));
+            }
+            else
+            {
+                Assert.Null(GetSymbolNamesJoined(analysis.ReadOutside));
+            }
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_030(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer2 x, int i)
+    {
+        /*<bind>*/x[" + index + @"] = 1/*</bind>*/;
+        _ = x[i];
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_040(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer22 x, int i)
+    {
+        /*<bind>*/x[" + index + @"][" + index + @"] = 1/*</bind>*/;
+        _ = x[i][i];
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, i", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_050(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer2 x)
+    {
+        ref int y = ref /*<bind>*/x[" + index + @"]/*</bind>*/;
+        y++;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_051(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer2 x)
+    {
+        ref int y = ref /*<bind>*/x/*</bind>*/[" + index + @"];
+        y++;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_052(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer2 x)
+    {
+        ref int y = ref x[/*<bind>*/" + index + @"/*</bind>*/];
+        y++;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_060(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer22 x)
+    {
+        ref int y = ref /*<bind>*/x[" + index + @"][" + index + @"]/*</bind>*/;
+        y++;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_061(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer22 x)
+    {
+        ref int y = ref /*<bind>*/x[" + index + @"]/*</bind>*/[" + index + @"];
+        y++;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_062(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer22 x)
+    {
+        ref int y = ref /*<bind>*/x/*</bind>*/[" + index + @"][" + index + @"];
+        y++;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_063(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer22 x)
+    {
+        ref int y = ref x[/*<bind>*/" + index + @"/*</bind>*/][" + index + @"];
+        y++;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_064(bool isRef, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + (isRef ? "ref " : "") + @"Buffer22 x)
+    {
+        ref int y = ref x[" + index + @"][/*<bind>*/" + index + @"/*</bind>*/];
+        y++;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_070([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        ref readonly int y = ref /*<bind>*/x[" + index + @"]/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_071([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        ref readonly int y = ref /*<bind>*/x/*</bind>*/[" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_072([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        ref readonly int y = ref x[/*<bind>*/" + index + @"/*</bind>*/];
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_080([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        ref readonly int y = ref /*<bind>*/x[" + index + @"][" + index + @"]/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_081([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        ref readonly int y = ref /*<bind>*/x[" + index + @"]/*</bind>*/[" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_082([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        ref readonly int y = ref /*<bind>*/x/*</bind>*/[" + index + @"][" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_083([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        ref readonly int y = ref x[/*<bind>*/" + index + @"/*</bind>*/][" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_084([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        ref readonly int y = ref x[" + index + @"][/*<bind>*/" + index + @"/*</bind>*/];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_090([CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M()
+    {
+        Buffer2 x;
+        /*<bind>*/x[" + index + @"] = 1/*</bind>*/;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Null(GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_091([CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M()
+    {
+        Buffer2 x = default;
+        /*<bind>*/x[" + index + @"].F += 1/*</bind>*/;
+    }
+}
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    private S _element0;
+}
+
+struct S
+{
+    public int F;
+}
+", TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Fact]
+        public void InlineArrays_100()
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M()
+    {
+        Buffer1 x;
+        /*<bind>*/x[0] = 1/*</bind>*/;
+    }
+}
+" + InlineArray1Definition, TargetFramework.Net80);
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_110([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        int y = /*<bind>*/x[" + index + @"]/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_111([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        int y = /*<bind>*/x/*</bind>*/[" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_112([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        int y = x[/*<bind>*/" + index + @"/*</bind>*/];
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_113([CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(Buffer2 x)
+    {
+        System.Action d = () =>
+        {
+            int y = /*<bind>*/x[" + index + @"]/*</bind>*/;
+            _ = y;
+        };   
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.Captured));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, d, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_120([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        int y = /*<bind>*/x[" + index + @"][" + index + @"]/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_121([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        int y = /*<bind>*/x[" + index + @"]/*</bind>*/[" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_122([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        int y = /*<bind>*/x/*</bind>*/[" + index + @"][" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_123([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        int y = x[/*<bind>*/" + index + @"/*</bind>*/][" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_124([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        int y = x[" + index + @"][/*<bind>*/" + index + @"/*</bind>*/];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_130([CombinatorialValues("ref ", "in ", "")] string refModifier)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        var y = /*<bind>*/x[0..2]/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_131([CombinatorialValues("ref ", "in ", "")] string refModifier)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        var y = /*<bind>*/x/*</bind>*/[0..2];
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_132([CombinatorialValues("ref ", "in ", "")] string refModifier)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        var y = x[/*<bind>*/0..2/*</bind>*/];
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Fact]
+        public void InlineArrays_133()
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(Buffer2 x)
+    {
+        System.Action d = () =>
+        {
+            var y = /*<bind>*/x[0..2]/*</bind>*/;
+            _ = y;
+        };
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.Captured));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, d, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_140([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = /*<bind>*/x[" + index + @"][0..2]/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_141([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = /*<bind>*/x[" + index + @"]/*</bind>*/[0..2];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_142([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = /*<bind>*/x/*</bind>*/[" + index + @"][0..2];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_143([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = x[/*<bind>*/" + index + @"/*</bind>*/][0..2];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_144([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = x[" + index + @"][/*<bind>*/0..2/*</bind>*/];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_150([CombinatorialValues("ref ", "in ", "")] string refModifier, bool readOnly)
+        {
+            if (refModifier == "in " && !readOnly)
+            {
+                return;
+            }
+
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer2 x)
+    {
+        var y = (System." + (readOnly ? "ReadOnly" : "") + @"Span<int>)/*<bind>*/x/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_153(bool readOnly)
+        {
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(Buffer2 x)
+    {
+        System.Action d = () =>
+        {
+            var y = (System." + (readOnly ? "ReadOnly" : "") + @"Span<int>)/*<bind>*/x/*</bind>*/;
+            _ = y;
+        };
+    }
+}
+" + InlineArray2Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.Captured));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, d, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_160([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index, bool readOnly)
+        {
+            if (refModifier == "in " && !readOnly)
+            {
+                return;
+            }
+
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = (System." + (readOnly ? "ReadOnly" : "") + @"Span<int>)/*<bind>*/x[" + index + @"]/*</bind>*/;
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_162([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index, bool readOnly)
+        {
+            if (refModifier == "in " && !readOnly)
+            {
+                return;
+            }
+
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = (System." + (readOnly ? "ReadOnly" : "") + @"Span<int>)/*<bind>*/x/*</bind>*/[" + index + @"];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal(refModifier != "" ? "x, y" : "y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrays_163([CombinatorialValues("ref ", "in ", "")] string refModifier, [CombinatorialValues(0, 1)] int index, bool readOnly)
+        {
+            if (refModifier == "in " && !readOnly)
+            {
+                return;
+            }
+
+            DataFlowAnalysis analysis = CompileAndAnalyzeDataFlowExpression(
+@"
+class B
+{
+    static void M(" + refModifier + @"Buffer22 x)
+    {
+        var y = (System." + (readOnly ? "ReadOnly" : "") + @"Span<int>)x[/*<bind>*/" + index + @"/*</bind>*/];
+        _ = y;
+    }
+}
+" + InlineArray22Definition, TargetFramework.Net80);
+
+            Assert.Null(GetSymbolNamesJoined(analysis.AlwaysAssigned));
+            Assert.Null(GetSymbolNamesJoined(analysis.Captured));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedInside));
+            Assert.Null(GetSymbolNamesJoined(analysis.CapturedOutside));
+            Assert.Null(GetSymbolNamesJoined(analysis.VariablesDeclared));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsIn));
+            Assert.Null(GetSymbolNamesJoined(analysis.DataFlowsOut));
+
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnEntry));
+            Assert.Equal("x", GetSymbolNamesJoined(analysis.DefinitelyAssignedOnExit));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.ReadInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.ReadOutside));
+
+            Assert.Null(GetSymbolNamesJoined(analysis.WrittenInside));
+            Assert.Equal("x, y", GetSymbolNamesJoined(analysis.WrittenOutside));
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Emit2/Microsoft.CodeAnalysis.CSharp.Emit2.UnitTests.csproj b/src/Compilers/CSharp/Test/Emit2/Microsoft.CodeAnalysis.CSharp.Emit2.UnitTests.csproj
index 77ab6cf9f91c5..c03194a17691b 100644
--- a/src/Compilers/CSharp/Test/Emit2/Microsoft.CodeAnalysis.CSharp.Emit2.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/Emit2/Microsoft.CodeAnalysis.CSharp.Emit2.UnitTests.csproj
@@ -4,7 +4,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.CSharp.UnitTests</RootNamespace>
-    <TargetFrameworks>net7.0;net472</TargetFrameworks>
+    <TargetFrameworks>net8.0;net472</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
   <ItemGroup Label="Project References">
@@ -26,6 +26,7 @@
     <PackageReference Include="Microsoft.DiaSymReader" Version="$(MicrosoftDiaSymReaderVersion)" />
     <PackageReference Include="Basic.Reference.Assemblies.Net50" Version="$(BasicReferenceAssembliesNet50Version)" />
     <PackageReference Include="Basic.Reference.Assemblies.Net60" Version="$(BasicReferenceAssembliesNet60Version)" />
+    <PackageReference Include="Basic.Reference.Assemblies.Net80" Version="$(BasicReferenceAssembliesNet80Version)" />
   </ItemGroup>
   <ItemGroup>
   </ItemGroup>
diff --git a/src/Compilers/CSharp/Test/Emit2/Semantics/InlineArrayTests.cs b/src/Compilers/CSharp/Test/Emit2/Semantics/InlineArrayTests.cs
new file mode 100644
index 0000000000000..a238833812d48
--- /dev/null
+++ b/src/Compilers/CSharp/Test/Emit2/Semantics/InlineArrayTests.cs
@@ -0,0 +1,20610 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#nullable disable
+
+using System.Linq;
+using Microsoft.CodeAnalysis.CSharp.Symbols;
+using Microsoft.CodeAnalysis.CSharp.Symbols.Retargeting;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.UnitTests.Semantics
+{
+    public class InlineArrayTests : CompilingTestBase
+    {
+        public const string InlineArrayAttributeDefinition =
+@"
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Struct, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (int length)
+        {
+            Length = length;
+        }
+
+        public int Length { get; }
+    }
+}
+";
+
+        public const string Buffer10Definition =
+@"
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10<T>
+{
+    private T _element0;
+}
+";
+
+        public const string Buffer4Definition =
+@"
+[System.Runtime.CompilerServices.InlineArray(4)]
+public struct Buffer4<T>
+{
+    private T _element0;
+}
+";
+
+        private static Verification VerifyOnMonoOrCoreClr
+        {
+            get
+            {
+                return ExecutionConditionUtil.IsMonoOrCoreClr ? Verification.Passes : Verification.Skipped;
+            }
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void InlineArrayType_00_LayoutAtRuntime()
+        {
+            var src = @"
+var c = new C();
+c.F = new Enclosing.Buffer[2];
+c.F[0][0] = 111;
+c.F[0][1] = 42;
+c.F[0][2] = 43;
+c.F[0][3] = 44;
+c.F[1][0] = 45;
+c.F[1][1] = 46;
+c.F[1][2] = 47;
+c.F[1][3] = 48;
+System.Console.WriteLine(c.F[0][0]);
+System.Console.WriteLine(c.F[0][1]);
+System.Console.WriteLine(c.F[0][2]);
+System.Console.WriteLine(c.F[0][3]);
+System.Console.WriteLine(c.F[1][0]);
+System.Console.WriteLine(c.F[1][1]);
+System.Console.WriteLine(c.F[1][2]);
+System.Console.WriteLine(c.F[1][3]);
+
+class C
+{
+    public Enclosing.Buffer[] F;
+}
+
+public class Enclosing
+{
+    [System.Runtime.CompilerServices.InlineArray(4)]
+    public struct Buffer
+    {
+        private int _element0;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            var output = @"
+111
+42
+43
+44
+45
+46
+47
+48
+";
+            CompileAndVerify(comp, expectedOutput: output).VerifyDiagnostics();
+
+            var t = comp.GetSpecialType(SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute);
+            Assert.Equal(SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute, t.SpecialType);
+            Assert.Equal(t.IsValueType, SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute.IsValueType());
+
+            Assert.True(comp.SupportsRuntimeCapability(RuntimeCapability.InlineArrayTypes));
+
+            var vbComp = CreateVisualBasicCompilation("", referencedAssemblies: TargetFrameworkUtil.GetReferences(TargetFramework.Net80, null));
+            Assert.True(vbComp.SupportsRuntimeCapability(RuntimeCapability.InlineArrayTypes));
+        }
+
+        [Fact]
+        public void InlineArrayType_01_NoAttribute()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.False(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(0, length);
+            }
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void InlineArrayType_02([CombinatorialValues("private", "public", "internal")] string accessibility)
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    " + accessibility + @" int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_03_Generic()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer<T>
+{
+    private T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal("T", buffer.TryGetInlineArrayElementField().Type.ToTestDisplayString());
+
+                var bufferOfInt = buffer.Construct(m.ContainingAssembly.GetSpecialType(SpecialType.System_Int32));
+
+                Assert.True(bufferOfInt.HasInlineArrayAttribute(out length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, bufferOfInt.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_04_MultipleAttributes()
+        {
+            var src = @"
+#pragma warning disable CS0436 // The type 'InlineArrayAttribute' conflicts with the imported type
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+[System.Runtime.CompilerServices.InlineArray(100)]
+struct Buffer
+{
+    private int _element0;
+}
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Struct, AllowMultiple = true)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (int length)
+        {
+            Length = length;
+        }
+
+        public int Length { get; }
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_05_WrongLength()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray(0)]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (4,46): error CS9167: Inline array length must be greater than 0.
+                // [System.Runtime.CompilerServices.InlineArray(0)]
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayLength, "0").WithLocation(4, 46)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 00 00 00 00 00 00
+    )
+
+    .field private int32 _element0
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.False(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(0, length);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_06_WrongLength()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray(-1)]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (4,46): error CS9167: Inline array length must be greater than 0.
+                // [System.Runtime.CompilerServices.InlineArray(-1)]
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayLength, "-1").WithLocation(4, 46)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 ff ff ff ff 00 00
+    )
+
+    .field private int32 _element0
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.False(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(0, length);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_07_WrongLength()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray(-2)]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (4,46): error CS9167: Inline array length must be greater than 0.
+                // [System.Runtime.CompilerServices.InlineArray(-2)]
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayLength, "-2").WithLocation(4, 46)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 fe ff ff ff 00 00
+    )
+
+    .field private int32 _element0
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.False(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(0, length);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_08_MoreThanOneField()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+    private int _element1;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,8): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 8)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+    // Fields
+    .field private int32 _element0
+    .field private int32 _element1
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_09_NoFields()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,8): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 8)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+    .pack 0
+    .size 1
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_10_WithStaticFields()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    public static long A;
+    private int _element0;
+    public static short B;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_11_WithSingleStaticField()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private static int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,8): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 8)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+    .pack 0
+    .size 1
+
+    .field private static int32 _element0
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_12_Class()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+class Buffer
+{
+    private int _element0;
+}
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.All, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (int length)
+        {
+            Length = length;
+        }
+
+        public int Length { get; }
+    }
+}
+";
+            var comp = CreateCompilation(src, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            comp.VerifyDiagnostics(
+                // (2,2): error CS0592: Attribute 'System.Runtime.CompilerServices.InlineArray' is not valid on this declaration type. It is only valid on 'struct' declarations.
+                // [System.Runtime.CompilerServices.InlineArray(10)]
+                Diagnostic(ErrorCode.ERR_AttributeOnBadSymbolType, "System.Runtime.CompilerServices.InlineArray").WithArguments("System.Runtime.CompilerServices.InlineArray", "struct").WithLocation(2, 2)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private auto ansi beforefieldinit Buffer
+    extends [mscorlib]System.Object
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+
+    .field private int32 _element0
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor () cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Object::.ctor()
+        IL_0006: ret
+    }
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.IsClassType());
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_13_Enum()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+enum Buffer
+{
+    _element0
+}
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.All, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (int length)
+        {
+            Length = length;
+        }
+
+        public int Length { get; }
+    }
+}
+";
+            var comp = CreateCompilation(src, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            comp.VerifyDiagnostics(
+                // (2,2): error CS0592: Attribute 'System.Runtime.CompilerServices.InlineArray' is not valid on this declaration type. It is only valid on 'struct' declarations.
+                // [System.Runtime.CompilerServices.InlineArray(10)]
+                Diagnostic(ErrorCode.ERR_AttributeOnBadSymbolType, "System.Runtime.CompilerServices.InlineArray").WithArguments("System.Runtime.CompilerServices.InlineArray", "struct").WithLocation(2, 2)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private auto ansi sealed Buffer
+    extends [mscorlib]System.Enum
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+    // Fields
+    .field public specialname rtspecialname int32 value__
+    .field public static literal valuetype Buffer _element0 = int32(0)
+
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.IsEnumType());
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_14_Delegate()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+delegate void Buffer();
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.All, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (int length)
+        {
+            Length = length;
+        }
+
+        public int Length { get; }
+    }
+}
+";
+            var comp = CreateCompilation(src, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            comp.VerifyDiagnostics(
+                // (2,2): error CS0592: Attribute 'System.Runtime.CompilerServices.InlineArray' is not valid on this declaration type. It is only valid on 'struct' declarations.
+                // [System.Runtime.CompilerServices.InlineArray(10)]
+                Diagnostic(ErrorCode.ERR_AttributeOnBadSymbolType, "System.Runtime.CompilerServices.InlineArray").WithArguments("System.Runtime.CompilerServices.InlineArray", "struct").WithLocation(2, 2)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private auto ansi sealed Buffer
+    extends [mscorlib]System.MulticastDelegate
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            object 'object',
+            native int 'method'
+        ) runtime managed 
+    {
+    }
+
+    .method public hidebysig newslot virtual 
+        instance void Invoke () runtime managed 
+    {
+    }
+
+    .method public hidebysig newslot virtual 
+        instance class [mscorlib]System.IAsyncResult BeginInvoke (
+            class [mscorlib]System.AsyncCallback callback,
+            object 'object'
+        ) runtime managed 
+    {
+    }
+
+    .method public hidebysig newslot virtual 
+        instance void EndInvoke (
+            class [mscorlib]System.IAsyncResult result
+        ) runtime managed 
+    {
+    }
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.IsDelegateType());
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_15_Interface()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+interface Buffer
+{
+    private int _element0;
+}
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.All, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (int length)
+        {
+            Length = length;
+        }
+
+        public int Length { get; }
+    }
+}
+";
+            var comp = CreateCompilation(src, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            comp.VerifyDiagnostics(
+                // (2,2): error CS0592: Attribute 'System.Runtime.CompilerServices.InlineArray' is not valid on this declaration type. It is only valid on 'struct' declarations.
+                // [System.Runtime.CompilerServices.InlineArray(10)]
+                Diagnostic(ErrorCode.ERR_AttributeOnBadSymbolType, "System.Runtime.CompilerServices.InlineArray").WithArguments("System.Runtime.CompilerServices.InlineArray", "struct").WithLocation(2, 2),
+                // (5,17): error CS0525: Interfaces cannot contain instance fields
+                //     private int _element0;
+                Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "_element0").WithLocation(5, 17)
+                );
+
+            var buffer = comp.SourceAssembly.SourceModule.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Null(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_16_RefField()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+ref struct Buffer
+{
+    private ref int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,12): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // ref struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 12)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.IsByRefLikeAttribute::.ctor() = (
+        01 00 00 00
+    )
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+
+    .field private int32& _element0
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_17_RefField()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+ref struct Buffer
+{
+    private ref readonly int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,12): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // ref struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 12)
+                );
+
+            verify(comp);
+
+            var ilSource = @"
+.class private sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.IsByRefLikeAttribute::.ctor() = (
+        01 00 00 00
+    )
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+
+    .field private int32& _element0
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.IsReadOnlyAttribute::.ctor() = (
+        01 00 00 00
+    )
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 ff 7f 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            comp = CreateCompilationWithIL("", ilSource, options: TestOptions.DebugDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            verify(comp);
+
+            void verify(CSharpCompilation comp)
+            {
+                var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Null(buffer.TryGetInlineArrayElementField());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_18_Retargeting()
+        {
+            var src1 = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp1 = CreateCompilation(src1 + InlineArrayAttributeDefinition, targetFramework: TargetFramework.Net50);
+            var comp2 = CreateCompilation("", references: new[] { comp1.ToMetadataReference() }, targetFramework: TargetFramework.Net60);
+
+            var buffer = comp2.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.IsType<RetargetingNamedTypeSymbol>(buffer);
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+        }
+
+        [Fact]
+        public void InlineArrayType_19()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray((short)10)]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_20()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(Length)]
+struct Buffer
+{
+    [System.Obsolete(""yes"")]
+    public const int Length = 10;
+
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics(
+                // (2,46): warning CS0618: 'Buffer.Length' is obsolete: 'yes'
+                // [System.Runtime.CompilerServices.InlineArray(Length)]
+                Diagnostic(ErrorCode.WRN_DeprecatedSymbolStr, "Length").WithArguments("Buffer.Length", "yes").WithLocation(2, 46)
+                );
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_21()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(Length)]
+struct Buffer
+{
+    [System.Obsolete(""yes"", true)]
+    public const int Length = 10;
+
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (2,46): error CS0619: 'Buffer.Length' is obsolete: 'yes'
+                // [System.Runtime.CompilerServices.InlineArray(Length)]
+                Diagnostic(ErrorCode.ERR_DeprecatedSymbolStr, "Length").WithArguments("Buffer.Length", "yes").WithLocation(2, 46)
+                );
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+        }
+
+        [Fact]
+        public void InlineArrayType_22_WrongSignature()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+}
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Struct, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (long length)
+        {
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.False(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(0, length);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_23()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray(Buffer.Length)]
+struct Buffer
+{
+    public const int Length = 10;
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_24()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray(Buffer<int>.Length)]
+struct Buffer<T>
+{
+    public const int Length = 10;
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_25()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+}
+
+[System.Diagnostics.ConditionalAttribute(nameof(C1.Field))]
+class C1 : System.Attribute
+{
+    public Buffer Field = default;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+
+                Assert.Equal("Field", m.GlobalNamespace.GetTypeMember("C1").GetAppliedConditionalSymbols().Single());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_26()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+    public event System.Action E;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,8): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 8)
+                );
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Null(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_27()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+    int E { get; set; }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,8): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 8)
+                );
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Null(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_28()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+record struct Buffer(int p)
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,15): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // record struct Buffer(int p)
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 15)
+                );
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Null(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_29_UseSiteError()
+        {
+            // [System.Runtime.CompilerServices.InlineArray(10)]
+            // public struct Buffer
+            // {
+            //     private modreq(int32) int _element0;
+            // }
+            var ilSource = @"
+.class public sequential ansi sealed beforefieldinit Buffer
+    extends [mscorlib]System.ValueType
+{
+    .custom instance void System.Runtime.CompilerServices.InlineArrayAttribute::.ctor(int32) = (
+        01 00 0a 00 00 00 00 00
+    )
+
+    .field private int32 modreq(int32) _element0
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.InlineArrayAttribute
+    extends [mscorlib]System.Attribute
+{
+    .custom instance void [mscorlib]System.AttributeUsageAttribute::.ctor(valuetype [mscorlib]System.AttributeTargets) = (
+        01 00 08 00 00 00 01 00 54 02 0d 41 6c 6c 6f 77
+        4d 75 6c 74 69 70 6c 65 00
+    )
+
+    .method public hidebysig specialname rtspecialname 
+        instance void .ctor (
+            int32 length
+        ) cil managed 
+    {
+        .maxstack 8
+
+        IL_0000: ldarg.0
+        IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
+        IL_0006: ret
+    }
+}
+";
+
+            var src = @"
+var x = new Buffer();
+x[0] = 111;
+_ = (System.Span<int>)x;
+";
+
+            var comp = CreateCompilationWithIL(src, ilSource, targetFramework: TargetFramework.Net80);
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Equal(SpecialType.System_Int32, buffer.TryGetInlineArrayElementField().Type.SpecialType);
+
+            comp.VerifyDiagnostics(
+                // (3,1): error CS0570: 'Buffer._element0' is not supported by the language
+                // x[0] = 111;
+                Diagnostic(ErrorCode.ERR_BindToBogus, "x[0]").WithArguments("Buffer._element0").WithLocation(3, 1),
+                // (4,5): error CS0570: 'Buffer._element0' is not supported by the language
+                // _ = (System.Span<int>)x;
+                Diagnostic(ErrorCode.ERR_BindToBogus, "(System.Span<int>)x").WithArguments("Buffer._element0").WithLocation(4, 5)
+                );
+        }
+
+        [Fact]
+        public void InlineArrayType_30_UnsupportedElementType()
+        {
+            var src = @"
+unsafe class Program
+{
+    static void Test()
+    {
+        var x = new Buffer();
+        x[0] = null;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+unsafe struct Buffer
+{
+    private void* _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.DebugDll.WithAllowUnsafe(true));
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Equal("System.Void*", buffer.TryGetInlineArrayElementField().Type.ToTestDisplayString());
+
+            comp.VerifyDiagnostics(
+                // (7,9): error CS0306: The type 'void*' may not be used as a type argument
+                //         x[0] = null;
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "x[0]").WithArguments("void*").WithLocation(7, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void InlineArrayType_31_Nested()
+        {
+            var src = @"
+var c = new C();
+c.F[0] = 111;
+System.Console.WriteLine(c.F[0]);
+
+class C
+{
+    public Enclosing.Buffer F;
+}
+
+public class Enclosing
+{
+    [System.Runtime.CompilerServices.InlineArray(10)]
+    public struct Buffer
+    {
+        private int _element0;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, expectedOutput: "111").VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetMember<FieldSymbol>("C.F").Type;
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal("System.Int32 Enclosing.Buffer._element0", buffer.TryGetInlineArrayElementField().ToTestDisplayString());
+            }
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void InlineArrayType_32_Generic()
+        {
+            var src = @"
+var c = new C();
+c.F[0] = 111;
+System.Console.WriteLine(c.F[0]);
+
+class C
+{
+    public Enclosing<int>.Buffer F;
+}
+
+public class Enclosing<T>
+{
+    [System.Runtime.CompilerServices.InlineArray(10)]
+    public struct Buffer
+    {
+        private T _element0;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, expectedOutput: "111").VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetMember<FieldSymbol>("C.F").Type;
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal("System.Int32 Enclosing<System.Int32>.Buffer._element0", buffer.TryGetInlineArrayElementField().ToTestDisplayString());
+            }
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void InlineArrayType_33_Generic()
+        {
+            var src = @"
+var c = new C();
+c.F[0] = 111;
+System.Console.WriteLine(c.F[0]);
+
+class C
+{
+    public Enclosing.Buffer<int> F;
+}
+
+public class Enclosing
+{
+    [System.Runtime.CompilerServices.InlineArray(10)]
+    public struct Buffer<T>
+    {
+        private T _element0;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, expectedOutput: "111").VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetMember<FieldSymbol>("C.F").Type;
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal("System.Int32 Enclosing.Buffer<System.Int32>._element0", buffer.TryGetInlineArrayElementField().ToTestDisplayString());
+            }
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void InlineArrayType_34_Generic()
+        {
+            var src = @"
+var c = new C();
+c.F[0] = 111;
+System.Console.WriteLine(c.F[0]);
+
+class C
+{
+    public Enclosing<int>.Buffer<string> F;
+}
+
+public class Enclosing<T>
+{
+    [System.Runtime.CompilerServices.InlineArray(10)]
+    public struct Buffer<U>
+    {
+        private T _element0;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, expectedOutput: "111").VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetMember<FieldSymbol>("C.F").Type;
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal("System.Int32 Enclosing<System.Int32>.Buffer<System.String>._element0", buffer.TryGetInlineArrayElementField().ToTestDisplayString());
+            }
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void InlineArrayType_35_Generic()
+        {
+            var src = @"
+var c = new C();
+c.F[0] = ""111"";
+System.Console.WriteLine(c.F[0]);
+
+class C
+{
+    public Enclosing<int>.Buffer<string> F;
+}
+
+public class Enclosing<T>
+{
+    [System.Runtime.CompilerServices.InlineArray(10)]
+    public struct Buffer<U>
+    {
+        private U _element0;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify, expectedOutput: "111").VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetMember<FieldSymbol>("C.F").Type;
+
+                Assert.True(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(10, length);
+                Assert.Equal("System.String Enclosing<System.Int32>.Buffer<System.String>._element0", buffer.TryGetInlineArrayElementField().ToTestDisplayString());
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_36_CapturingPrimaryConstructor()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer(int p)
+{
+    private int _element0;
+
+    int M() => p;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (3,8): error CS9169: Inline array struct must declare one and only one instance field which must not be a ref field.
+                // struct Buffer(int p)
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayFields, "Buffer").WithLocation(3, 8)
+                );
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.Null(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_37_StructLayout_Auto()
+        {
+            var src = @"
+using System.Runtime.InteropServices;
+
+[StructLayout(LayoutKind.Auto)]
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyEmitDiagnostics();
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.NotNull(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_38_StructLayout_Sequential()
+        {
+            var src = @"
+using System.Runtime.InteropServices;
+
+[StructLayout(LayoutKind.Sequential)]
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyEmitDiagnostics();
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.NotNull(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_39_StructLayout_Explicit()
+        {
+            var src = @"
+using System.Runtime.InteropServices;
+
+[StructLayout(LayoutKind.Explicit)]
+[System.Runtime.CompilerServices.InlineArray(10)]
+struct Buffer
+{
+    [FieldOffset(10)]
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (6,8): error CS9168: Inline array struct must not have explicit layout.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_InvalidInlineArrayLayout, "Buffer").WithLocation(6, 8)
+                );
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.True(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(10, length);
+            Assert.NotNull(buffer.TryGetInlineArrayElementField());
+        }
+
+        [Fact]
+        public void InlineArrayType_40_WrongSignature()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray]
+struct Buffer
+{
+    private int _element0;
+}
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Struct, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute ()
+        {
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src);
+            CompileAndVerify(comp, symbolValidator: verify, sourceSymbolValidator: verify).VerifyDiagnostics();
+
+            void verify(ModuleSymbol m)
+            {
+                var buffer = m.GlobalNamespace.GetTypeMember("Buffer");
+
+                Assert.False(buffer.HasInlineArrayAttribute(out int length));
+                Assert.Equal(0, length);
+            }
+        }
+
+        [Fact]
+        public void InlineArrayType_41_MissingArgument()
+        {
+            var src = @"
+#pragma warning disable CS0169 // The field 'Buffer._element0' is never used
+
+[System.Runtime.CompilerServices.InlineArray]
+struct Buffer
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (4,2): error CS7036: There is no argument given that corresponds to the required parameter 'length' of 'InlineArrayAttribute.InlineArrayAttribute(int)'
+                // [System.Runtime.CompilerServices.InlineArray]
+                Diagnostic(ErrorCode.ERR_NoCorrespondingArgument, "System.Runtime.CompilerServices.InlineArray").WithArguments("length", "System.Runtime.CompilerServices.InlineArrayAttribute.InlineArrayAttribute(int)").WithLocation(4, 2)
+                );
+
+            var buffer = comp.GlobalNamespace.GetTypeMember("Buffer");
+
+            Assert.False(buffer.HasInlineArrayAttribute(out int length));
+            Assert.Equal(0, length);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void InlineArrayType_42()
+        {
+            var src = @"
+var b = new Buffer();
+System.Console.WriteLine(b[0]);
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer
+{
+    private int _element0 = 111;
+
+    public Buffer()
+    {
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            // No warning CS0414: The field 'Buffer._element0' is assigned but its value is never used
+            CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Access_ArgumentType_01()
+        {
+            var src = @"
+class C
+{
+    public static implicit operator int(C x) => 0;
+    public static implicit operator System.Index(C x) => 0;
+    public static implicit operator System.Range(C x) => 0..;
+}
+
+
+class Program
+{
+    static void Main(Buffer10<int> b, C c)
+    {
+        _ = b[c];
+    }
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics();
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var c = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "c").Single();
+            Assert.Equal("b[c]", c.Parent.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(c);
+
+            Assert.Equal("C", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
+        }
+
+        [Fact]
+        public void Access_ArgumentType_02()
+        {
+            var src = @"
+class C
+{
+    public static implicit operator System.Index(C x) => 0;
+    public static implicit operator System.Range(C x) => 0..;
+}
+
+
+class Program
+{
+    static void Main(Buffer10<int> b, C c)
+    {
+        _ = b[c];
+    }
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics();
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var c = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "c").Single();
+            Assert.Equal("b[c]", c.Parent.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(c);
+
+            Assert.Equal("C", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Index", typeInfo.ConvertedType.ToTestDisplayString());
+        }
+
+        [Fact]
+        public void Access_ArgumentType_03()
+        {
+            var src = @"
+class C
+{
+    public static implicit operator System.Range(C x) => 0..;
+}
+
+
+class Program
+{
+    static void Main(Buffer10<int> b, C c)
+    {
+        _ = b[c];
+    }
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics();
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var c = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "c").Single();
+            Assert.Equal("b[c]", c.Parent.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(c);
+
+            Assert.Equal("C", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Range", typeInfo.ConvertedType.ToTestDisplayString());
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static void M2(C x) => x.F[0] = 111;
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldc.i4.s   111
+  IL_000d:  stind.i4
+  IL_000e:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.RegularNext);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular11);
+            comp.VerifyDiagnostics(
+                // (18,27): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static int M1(C x) => x.F[0];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F[0]").WithArguments("inline arrays").WithLocation(18, 27),
+                // (19,28): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static void M2(C x) => x.F[0] = 111;
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F[0]").WithArguments("inline arrays").WithLocation(19, 28)
+                );
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "F").First();
+            Assert.Equal("x.F[0]", f.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            var symbolInfo = model.GetSymbolInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32> C.F", symbolInfo.Symbol.ToTestDisplayString());
+
+            var access = f.Parent.Parent;
+            typeInfo = model.GetTypeInfo(access);
+
+            Assert.Equal("System.Int32", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
+
+            symbolInfo = model.GetSymbolInfo(access);
+
+            Assert.Null(symbolInfo.Symbol);
+            Assert.Empty(symbolInfo.CandidateSymbols);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(x) = 111;
+        System.Console.Write(x.F[0]);
+    }
+
+    static ref int M2(C x) => ref x.F[0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_03()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+
+    public ref int M2() => ref F[0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(x) = 111;
+        System.Console.Write(x.F[0]);
+    }
+
+    static ref int M2(C x) => ref x.F[0];
+
+    static ref int M3(C x)
+    {
+        ref int y = ref x.F[0];
+        return ref y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (16,35): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static ref int M2(C x) => ref x.F[0];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(16, 35),
+                // (21,20): error CS8157: Cannot return 'y' by reference because it was initialized to a value that cannot be returned by reference
+                //         return ref y;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "y").WithArguments("y").WithLocation(21, 20)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_05()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public ref int M2() => ref F[0];
+
+    public ref int M3()
+    {
+        ref int y = ref F[0];
+        return ref y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (6,32): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public ref int M2() => ref F[0];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(6, 32),
+                // (11,20): error CS8157: Cannot return 'y' by reference because it was initialized to a value that cannot be returned by reference
+                //         return ref y;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "y").WithArguments("y").WithLocation(11, 20)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_06()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x) = 111;
+        System.Console.Write(x.F[0]);
+    }
+
+    static ref int M2(ref C x) => ref x.F[0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_07()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public ref int M2() => ref F[0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_08()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x) = 111;
+        System.Console.Write(x.F[0]);
+    }
+
+    static ref int M2(ref C x)
+    {
+        ref int y = ref x.F[0];
+        return ref y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_09()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public ref int M2()
+    {
+        ref int y = ref F[0];
+        return ref y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_10()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0][0];
+    static void M2(C x) => x.F[0][0] = 111;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_11()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(x) = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+
+    static ref int M2(C x) => ref x.F[0][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_12()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public ref int M2() => ref F[0][0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_13()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(x) = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+
+    static ref int M2(C x) => ref x.F[0][0];
+
+    static ref int M3(C x)
+    {
+        ref int y = ref x.F[0][0];
+        return ref y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (16,35): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static ref int M2(C x) => ref x.F[0][0];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(16, 35),
+                // (21,20): error CS8157: Cannot return 'y' by reference because it was initialized to a value that cannot be returned by reference
+                //         return ref y;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "y").WithArguments("y").WithLocation(21, 20)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_14()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public ref int M2() => ref F[0][0];
+
+    public ref int M3()
+    {
+        ref int y = ref F[0][0];
+        return ref y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (6,32): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public ref int M2() => ref F[0][0];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(6, 32),
+                // (11,20): error CS8157: Cannot return 'y' by reference because it was initialized to a value that cannot be returned by reference
+                //         return ref y;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "y").WithArguments("y").WithLocation(11, 20)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_15()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x) = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+
+    static ref int M2(ref C x) => ref x.F[0][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_16()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public ref int M2() => ref F[0][0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_17()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x) = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+
+    static ref int M2(ref C x)
+    {
+        ref int y = ref x.F[0][0];
+        return ref y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_18()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public ref int M2()
+    {
+        ref int y = ref F[0][0];
+        return ref y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2() = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_19()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        System.Console.Write(' ');
+        System.Console.Write(M3(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+        System.Console.Write(' ');
+        System.Console.Write(M3(x));
+    }
+
+    static int M1(C x) => x.F[1];
+    static void M2(C x) => x.F[1] = 111;
+    static int M3(C x) { var i = 1; return x.F[i]; }
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 0 111 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.1
+  IL_0007:  call       ""InlineArrayElementRef<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ldind.i4
+  IL_000d:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       16 (0x10)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.1
+  IL_0007:  call       ""InlineArrayElementRef<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ldc.i4.s   111
+  IL_000e:  stind.i4
+  IL_000f:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_20()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        System.Console.Write(' ');
+        System.Console.Write(M3(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+        System.Console.Write(' ');
+        System.Console.Write(M3(x));
+    }
+
+    static int M1(C x) => x.F[9];
+    static void M2(C x) => x.F[9] = 111;
+    static int M3(C x) { var i = 9; return x.F[i]; }
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 0 111 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   9
+  IL_0008:  call       ""InlineArrayElementRef<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ldind.i4
+  IL_000e:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       17 (0x11)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   9
+  IL_0008:  call       ""InlineArrayElementRef<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ldc.i4.s   111
+  IL_000f:  stind.i4
+  IL_0010:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_21()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x, 0));
+        System.Console.Write(' ');
+        System.Console.Write(M3(x));
+        M2(x, 0);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x, 0));
+        System.Console.Write(' ');
+        System.Console.Write(M3(x));
+    }
+
+    static int M1(C x, int i) => x.F[i];
+    static void M2(C x, int i) => x.F[i] = 111;
+    static int M3(C x) => x.F[0];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 0 111 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       24 (0x18)
+  .maxstack  2
+  .locals init (System.Span<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldarg.1
+  IL_0011:  call       ""ref int System.Span<int>.this[int].get""
+  IL_0016:  ldind.i4
+  IL_0017:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       26 (0x1a)
+  .maxstack  2
+  .locals init (System.Span<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldarg.1
+  IL_0011:  call       ""ref int System.Span<int>.this[int].get""
+  IL_0016:  ldc.i4.s   111
+  IL_0018:  stind.i4
+  IL_0019:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_01()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => x.F[await FromResult(0)];
+    static async Task M2(C x) => x.F[await FromResult(0)] = 111;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      189 (0xbd)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Span<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0049:  leave.s    IL_00bc
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  ldc.i4.s   10
+    IL_007c:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0081:  stloc.s    V_4
+    IL_0083:  ldloca.s   V_4
+    IL_0085:  ldloc.2
+    IL_0086:  call       ""ref int System.Span<int>.this[int].get""
+    IL_008b:  ldind.i4
+    IL_008c:  stloc.1
+    IL_008d:  leave.s    IL_00a8
+  }
+  catch System.Exception
+  {
+    IL_008f:  stloc.s    V_5
+    IL_0091:  ldarg.0
+    IL_0092:  ldc.i4.s   -2
+    IL_0094:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0099:  ldarg.0
+    IL_009a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_009f:  ldloc.s    V_5
+    IL_00a1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00a6:  leave.s    IL_00bc
+  }
+  IL_00a8:  ldarg.0
+  IL_00a9:  ldc.i4.s   -2
+  IL_00ab:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00b0:  ldarg.0
+  IL_00b1:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00b6:  ldloc.1
+  IL_00b7:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00bc:  ret
+}
+");
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      195 (0xc3)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_2,
+                System.Span<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.2
+    IL_0022:  ldloca.s   V_2
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.2
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0041:  ldloca.s   V_2
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_0049:  leave.s    IL_00c2
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0051:  stloc.2
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0067:  ldloca.s   V_2
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.1
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  ldc.i4.s   10
+    IL_007c:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0081:  stloc.3
+    IL_0082:  ldloca.s   V_3
+    IL_0084:  ldloc.1
+    IL_0085:  call       ""ref int System.Span<int>.this[int].get""
+    IL_008a:  ldc.i4.s   111
+    IL_008c:  stind.i4
+    IL_008d:  ldarg.0
+    IL_008e:  ldnull
+    IL_008f:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0094:  leave.s    IL_00af
+  }
+  catch System.Exception
+  {
+    IL_0096:  stloc.s    V_4
+    IL_0098:  ldarg.0
+    IL_0099:  ldc.i4.s   -2
+    IL_009b:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00a0:  ldarg.0
+    IL_00a1:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00a6:  ldloc.s    V_4
+    IL_00a8:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00ad:  leave.s    IL_00c2
+  }
+  IL_00af:  ldarg.0
+  IL_00b0:  ldc.i4.s   -2
+  IL_00b2:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00b7:  ldarg.0
+  IL_00b8:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00bd:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00c2:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_02()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => x.F[await FromResult(^10)];
+    static async Task M2(C x) => x.F[await FromResult(^10)] = 111;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      204 (0xcc)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Index V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<System.Index> V_3,
+                System.Span<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0052
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.s   10
+    IL_0018:  ldc.i4.1
+    IL_0019:  newobj     ""System.Index..ctor(int, bool)""
+    IL_001e:  call       ""System.Threading.Tasks.Task<System.Index> Program.FromResult<System.Index>(System.Index)""
+    IL_0023:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> System.Threading.Tasks.Task<System.Index>.GetAwaiter()""
+    IL_0028:  stloc.3
+    IL_0029:  ldloca.s   V_3
+    IL_002b:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<System.Index>.IsCompleted.get""
+    IL_0030:  brtrue.s   IL_006e
+    IL_0032:  ldarg.0
+    IL_0033:  ldc.i4.0
+    IL_0034:  dup
+    IL_0035:  stloc.0
+    IL_0036:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_003b:  ldarg.0
+    IL_003c:  ldloc.3
+    IL_003d:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M1>d__1.<>u__1""
+    IL_0042:  ldarg.0
+    IL_0043:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0048:  ldloca.s   V_3
+    IL_004a:  ldarg.0
+    IL_004b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<System.Index>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<System.Index>, ref Program.<M1>d__1)""
+    IL_0050:  leave.s    IL_00cb
+    IL_0052:  ldarg.0
+    IL_0053:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M1>d__1.<>u__1""
+    IL_0058:  stloc.3
+    IL_0059:  ldarg.0
+    IL_005a:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M1>d__1.<>u__1""
+    IL_005f:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<System.Index>""
+    IL_0065:  ldarg.0
+    IL_0066:  ldc.i4.m1
+    IL_0067:  dup
+    IL_0068:  stloc.0
+    IL_0069:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_006e:  ldloca.s   V_3
+    IL_0070:  call       ""System.Index System.Runtime.CompilerServices.TaskAwaiter<System.Index>.GetResult()""
+    IL_0075:  stloc.2
+    IL_0076:  ldarg.0
+    IL_0077:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_007c:  ldflda     ""Buffer10<int> C.F""
+    IL_0081:  ldc.i4.s   10
+    IL_0083:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0088:  stloc.s    V_4
+    IL_008a:  ldloca.s   V_4
+    IL_008c:  ldloca.s   V_2
+    IL_008e:  ldc.i4.s   10
+    IL_0090:  call       ""int System.Index.GetOffset(int)""
+    IL_0095:  call       ""ref int System.Span<int>.this[int].get""
+    IL_009a:  ldind.i4
+    IL_009b:  stloc.1
+    IL_009c:  leave.s    IL_00b7
+  }
+  catch System.Exception
+  {
+    IL_009e:  stloc.s    V_5
+    IL_00a0:  ldarg.0
+    IL_00a1:  ldc.i4.s   -2
+    IL_00a3:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_00a8:  ldarg.0
+    IL_00a9:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_00ae:  ldloc.s    V_5
+    IL_00b0:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00b5:  leave.s    IL_00cb
+  }
+  IL_00b7:  ldarg.0
+  IL_00b8:  ldc.i4.s   -2
+  IL_00ba:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00bf:  ldarg.0
+  IL_00c0:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00c5:  ldloc.1
+  IL_00c6:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00cb:  ret
+}
+");
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      210 (0xd2)
+  .maxstack  3
+  .locals init (int V_0,
+                System.Index V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<System.Index> V_2,
+                System.Span<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0052
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0016:  ldc.i4.s   10
+    IL_0018:  ldc.i4.1
+    IL_0019:  newobj     ""System.Index..ctor(int, bool)""
+    IL_001e:  call       ""System.Threading.Tasks.Task<System.Index> Program.FromResult<System.Index>(System.Index)""
+    IL_0023:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> System.Threading.Tasks.Task<System.Index>.GetAwaiter()""
+    IL_0028:  stloc.2
+    IL_0029:  ldloca.s   V_2
+    IL_002b:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<System.Index>.IsCompleted.get""
+    IL_0030:  brtrue.s   IL_006e
+    IL_0032:  ldarg.0
+    IL_0033:  ldc.i4.0
+    IL_0034:  dup
+    IL_0035:  stloc.0
+    IL_0036:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_003b:  ldarg.0
+    IL_003c:  ldloc.2
+    IL_003d:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__2.<>u__1""
+    IL_0042:  ldarg.0
+    IL_0043:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0048:  ldloca.s   V_2
+    IL_004a:  ldarg.0
+    IL_004b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<System.Index>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<System.Index>, ref Program.<M2>d__2)""
+    IL_0050:  leave.s    IL_00d1
+    IL_0052:  ldarg.0
+    IL_0053:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__2.<>u__1""
+    IL_0058:  stloc.2
+    IL_0059:  ldarg.0
+    IL_005a:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__2.<>u__1""
+    IL_005f:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<System.Index>""
+    IL_0065:  ldarg.0
+    IL_0066:  ldc.i4.m1
+    IL_0067:  dup
+    IL_0068:  stloc.0
+    IL_0069:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_006e:  ldloca.s   V_2
+    IL_0070:  call       ""System.Index System.Runtime.CompilerServices.TaskAwaiter<System.Index>.GetResult()""
+    IL_0075:  stloc.1
+    IL_0076:  ldarg.0
+    IL_0077:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_007c:  ldflda     ""Buffer10<int> C.F""
+    IL_0081:  ldc.i4.s   10
+    IL_0083:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0088:  stloc.3
+    IL_0089:  ldloca.s   V_3
+    IL_008b:  ldloca.s   V_1
+    IL_008d:  ldc.i4.s   10
+    IL_008f:  call       ""int System.Index.GetOffset(int)""
+    IL_0094:  call       ""ref int System.Span<int>.this[int].get""
+    IL_0099:  ldc.i4.s   111
+    IL_009b:  stind.i4
+    IL_009c:  ldarg.0
+    IL_009d:  ldnull
+    IL_009e:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_00a3:  leave.s    IL_00be
+  }
+  catch System.Exception
+  {
+    IL_00a5:  stloc.s    V_4
+    IL_00a7:  ldarg.0
+    IL_00a8:  ldc.i4.s   -2
+    IL_00aa:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00af:  ldarg.0
+    IL_00b0:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00b5:  ldloc.s    V_4
+    IL_00b7:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00bc:  leave.s    IL_00d1
+  }
+  IL_00be:  ldarg.0
+  IL_00bf:  ldc.i4.s   -2
+  IL_00c1:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00c6:  ldarg.0
+  IL_00c7:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00cc:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00d1:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_03()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => x.F[^await FromResult(10)];
+    static async Task M2(C x) => x.F[^await FromResult(10)] = 111;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      193 (0xc1)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Span<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004c
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.s   10
+    IL_0018:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001d:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0022:  stloc.3
+    IL_0023:  ldloca.s   V_3
+    IL_0025:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_002a:  brtrue.s   IL_0068
+    IL_002c:  ldarg.0
+    IL_002d:  ldc.i4.0
+    IL_002e:  dup
+    IL_002f:  stloc.0
+    IL_0030:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0035:  ldarg.0
+    IL_0036:  ldloc.3
+    IL_0037:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003c:  ldarg.0
+    IL_003d:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0042:  ldloca.s   V_3
+    IL_0044:  ldarg.0
+    IL_0045:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_004a:  leave.s    IL_00c0
+    IL_004c:  ldarg.0
+    IL_004d:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0052:  stloc.3
+    IL_0053:  ldarg.0
+    IL_0054:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0059:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005f:  ldarg.0
+    IL_0060:  ldc.i4.m1
+    IL_0061:  dup
+    IL_0062:  stloc.0
+    IL_0063:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0068:  ldloca.s   V_3
+    IL_006a:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006f:  stloc.2
+    IL_0070:  ldarg.0
+    IL_0071:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0076:  ldflda     ""Buffer10<int> C.F""
+    IL_007b:  ldc.i4.s   10
+    IL_007d:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0082:  stloc.s    V_4
+    IL_0084:  ldloca.s   V_4
+    IL_0086:  ldc.i4.s   10
+    IL_0088:  ldloc.2
+    IL_0089:  sub
+    IL_008a:  call       ""ref int System.Span<int>.this[int].get""
+    IL_008f:  ldind.i4
+    IL_0090:  stloc.1
+    IL_0091:  leave.s    IL_00ac
+  }
+  catch System.Exception
+  {
+    IL_0093:  stloc.s    V_5
+    IL_0095:  ldarg.0
+    IL_0096:  ldc.i4.s   -2
+    IL_0098:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_009d:  ldarg.0
+    IL_009e:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_00a3:  ldloc.s    V_5
+    IL_00a5:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00aa:  leave.s    IL_00c0
+  }
+  IL_00ac:  ldarg.0
+  IL_00ad:  ldc.i4.s   -2
+  IL_00af:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00b4:  ldarg.0
+  IL_00b5:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00ba:  ldloc.1
+  IL_00bb:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00c0:  ret
+}
+");
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      199 (0xc7)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_2,
+                System.Span<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004c
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0016:  ldc.i4.s   10
+    IL_0018:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001d:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0022:  stloc.2
+    IL_0023:  ldloca.s   V_2
+    IL_0025:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_002a:  brtrue.s   IL_0068
+    IL_002c:  ldarg.0
+    IL_002d:  ldc.i4.0
+    IL_002e:  dup
+    IL_002f:  stloc.0
+    IL_0030:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0035:  ldarg.0
+    IL_0036:  ldloc.2
+    IL_0037:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_003c:  ldarg.0
+    IL_003d:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0042:  ldloca.s   V_2
+    IL_0044:  ldarg.0
+    IL_0045:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_004a:  leave.s    IL_00c6
+    IL_004c:  ldarg.0
+    IL_004d:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0052:  stloc.2
+    IL_0053:  ldarg.0
+    IL_0054:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0059:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005f:  ldarg.0
+    IL_0060:  ldc.i4.m1
+    IL_0061:  dup
+    IL_0062:  stloc.0
+    IL_0063:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0068:  ldloca.s   V_2
+    IL_006a:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006f:  stloc.1
+    IL_0070:  ldarg.0
+    IL_0071:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0076:  ldflda     ""Buffer10<int> C.F""
+    IL_007b:  ldc.i4.s   10
+    IL_007d:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0082:  stloc.3
+    IL_0083:  ldloca.s   V_3
+    IL_0085:  ldc.i4.s   10
+    IL_0087:  ldloc.1
+    IL_0088:  sub
+    IL_0089:  call       ""ref int System.Span<int>.this[int].get""
+    IL_008e:  ldc.i4.s   111
+    IL_0090:  stind.i4
+    IL_0091:  ldarg.0
+    IL_0092:  ldnull
+    IL_0093:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0098:  leave.s    IL_00b3
+  }
+  catch System.Exception
+  {
+    IL_009a:  stloc.s    V_4
+    IL_009c:  ldarg.0
+    IL_009d:  ldc.i4.s   -2
+    IL_009f:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00a4:  ldarg.0
+    IL_00a5:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00aa:  ldloc.s    V_4
+    IL_00ac:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00b1:  leave.s    IL_00c6
+  }
+  IL_00b3:  ldarg.0
+  IL_00b4:  ldc.i4.s   -2
+  IL_00b6:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00bb:  ldarg.0
+  IL_00bc:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00c1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00c6:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_04()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().Result);
+    }
+
+    static async Task<int> M2() => M3()[await FromResult(0)];
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      183 (0xb7)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.ReadOnlySpan<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004a
+    IL_000a:  ldarg.0
+    IL_000b:  call       ""Buffer10<int> Program.M3()""
+    IL_0010:  stfld      ""Buffer10<int> Program.<M2>d__1.<>7__wrap1""
+    IL_0015:  ldc.i4.0
+    IL_0016:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001b:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0020:  stloc.3
+    IL_0021:  ldloca.s   V_3
+    IL_0023:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0028:  brtrue.s   IL_0066
+    IL_002a:  ldarg.0
+    IL_002b:  ldc.i4.0
+    IL_002c:  dup
+    IL_002d:  stloc.0
+    IL_002e:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_0033:  ldarg.0
+    IL_0034:  ldloc.3
+    IL_0035:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_003a:  ldarg.0
+    IL_003b:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+    IL_0040:  ldloca.s   V_3
+    IL_0042:  ldarg.0
+    IL_0043:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__1)""
+    IL_0048:  leave.s    IL_00b6
+    IL_004a:  ldarg.0
+    IL_004b:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_0050:  stloc.3
+    IL_0051:  ldarg.0
+    IL_0052:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_0057:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005d:  ldarg.0
+    IL_005e:  ldc.i4.m1
+    IL_005f:  dup
+    IL_0060:  stloc.0
+    IL_0061:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_0066:  ldloca.s   V_3
+    IL_0068:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006d:  stloc.2
+    IL_006e:  ldarg.0
+    IL_006f:  ldflda     ""Buffer10<int> Program.<M2>d__1.<>7__wrap1""
+    IL_0074:  ldc.i4.s   10
+    IL_0076:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_007b:  stloc.s    V_4
+    IL_007d:  ldloca.s   V_4
+    IL_007f:  ldloc.2
+    IL_0080:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+    IL_0085:  ldind.i4
+    IL_0086:  stloc.1
+    IL_0087:  leave.s    IL_00a2
+  }
+  catch System.Exception
+  {
+    IL_0089:  stloc.s    V_5
+    IL_008b:  ldarg.0
+    IL_008c:  ldc.i4.s   -2
+    IL_008e:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_0093:  ldarg.0
+    IL_0094:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+    IL_0099:  ldloc.s    V_5
+    IL_009b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00a0:  leave.s    IL_00b6
+  }
+  IL_00a2:  ldarg.0
+  IL_00a3:  ldc.i4.s   -2
+  IL_00a5:  stfld      ""int Program.<M2>d__1.<>1__state""
+  IL_00aa:  ldarg.0
+  IL_00ab:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+  IL_00b0:  ldloc.1
+  IL_00b1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00b6:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_05()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().Result);
+    }
+
+    static async Task<int> M2() => M3()[await FromResult(^10)];
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      198 (0xc6)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Index V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<System.Index> V_3,
+                System.ReadOnlySpan<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0051
+    IL_000a:  ldarg.0
+    IL_000b:  call       ""Buffer10<int> Program.M3()""
+    IL_0010:  stfld      ""Buffer10<int> Program.<M2>d__1.<>7__wrap1""
+    IL_0015:  ldc.i4.s   10
+    IL_0017:  ldc.i4.1
+    IL_0018:  newobj     ""System.Index..ctor(int, bool)""
+    IL_001d:  call       ""System.Threading.Tasks.Task<System.Index> Program.FromResult<System.Index>(System.Index)""
+    IL_0022:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> System.Threading.Tasks.Task<System.Index>.GetAwaiter()""
+    IL_0027:  stloc.3
+    IL_0028:  ldloca.s   V_3
+    IL_002a:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<System.Index>.IsCompleted.get""
+    IL_002f:  brtrue.s   IL_006d
+    IL_0031:  ldarg.0
+    IL_0032:  ldc.i4.0
+    IL_0033:  dup
+    IL_0034:  stloc.0
+    IL_0035:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_003a:  ldarg.0
+    IL_003b:  ldloc.3
+    IL_003c:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__1.<>u__1""
+    IL_0041:  ldarg.0
+    IL_0042:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+    IL_0047:  ldloca.s   V_3
+    IL_0049:  ldarg.0
+    IL_004a:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<System.Index>, Program.<M2>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<System.Index>, ref Program.<M2>d__1)""
+    IL_004f:  leave.s    IL_00c5
+    IL_0051:  ldarg.0
+    IL_0052:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__1.<>u__1""
+    IL_0057:  stloc.3
+    IL_0058:  ldarg.0
+    IL_0059:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__1.<>u__1""
+    IL_005e:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<System.Index>""
+    IL_0064:  ldarg.0
+    IL_0065:  ldc.i4.m1
+    IL_0066:  dup
+    IL_0067:  stloc.0
+    IL_0068:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_006d:  ldloca.s   V_3
+    IL_006f:  call       ""System.Index System.Runtime.CompilerServices.TaskAwaiter<System.Index>.GetResult()""
+    IL_0074:  stloc.2
+    IL_0075:  ldarg.0
+    IL_0076:  ldflda     ""Buffer10<int> Program.<M2>d__1.<>7__wrap1""
+    IL_007b:  ldc.i4.s   10
+    IL_007d:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_0082:  stloc.s    V_4
+    IL_0084:  ldloca.s   V_4
+    IL_0086:  ldloca.s   V_2
+    IL_0088:  ldc.i4.s   10
+    IL_008a:  call       ""int System.Index.GetOffset(int)""
+    IL_008f:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+    IL_0094:  ldind.i4
+    IL_0095:  stloc.1
+    IL_0096:  leave.s    IL_00b1
+  }
+  catch System.Exception
+  {
+    IL_0098:  stloc.s    V_5
+    IL_009a:  ldarg.0
+    IL_009b:  ldc.i4.s   -2
+    IL_009d:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_00a2:  ldarg.0
+    IL_00a3:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+    IL_00a8:  ldloc.s    V_5
+    IL_00aa:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00af:  leave.s    IL_00c5
+  }
+  IL_00b1:  ldarg.0
+  IL_00b2:  ldc.i4.s   -2
+  IL_00b4:  stfld      ""int Program.<M2>d__1.<>1__state""
+  IL_00b9:  ldarg.0
+  IL_00ba:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+  IL_00bf:  ldloc.1
+  IL_00c0:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00c5:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_06()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().Result);
+    }
+
+    static async Task<int> M2() => M3()[^await FromResult(10)];
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      187 (0xbb)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.ReadOnlySpan<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  call       ""Buffer10<int> Program.M3()""
+    IL_0010:  stfld      ""Buffer10<int> Program.<M2>d__1.<>7__wrap1""
+    IL_0015:  ldc.i4.s   10
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__1)""
+    IL_0049:  leave.s    IL_00ba
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldflda     ""Buffer10<int> Program.<M2>d__1.<>7__wrap1""
+    IL_0075:  ldc.i4.s   10
+    IL_0077:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_007c:  stloc.s    V_4
+    IL_007e:  ldloca.s   V_4
+    IL_0080:  ldc.i4.s   10
+    IL_0082:  ldloc.2
+    IL_0083:  sub
+    IL_0084:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+    IL_0089:  ldind.i4
+    IL_008a:  stloc.1
+    IL_008b:  leave.s    IL_00a6
+  }
+  catch System.Exception
+  {
+    IL_008d:  stloc.s    V_5
+    IL_008f:  ldarg.0
+    IL_0090:  ldc.i4.s   -2
+    IL_0092:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_0097:  ldarg.0
+    IL_0098:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+    IL_009d:  ldloc.s    V_5
+    IL_009f:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00a4:  leave.s    IL_00ba
+  }
+  IL_00a6:  ldarg.0
+  IL_00a7:  ldc.i4.s   -2
+  IL_00a9:  stfld      ""int Program.<M2>d__1.<>1__state""
+  IL_00ae:  ldarg.0
+  IL_00af:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M2>d__1.<>t__builder""
+  IL_00b4:  ldloc.1
+  IL_00b5:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00ba:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_07()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => x.F[await FromResult(0)];
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      189 (0xbd)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.ReadOnlySpan<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0049:  leave.s    IL_00bc
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  ldc.i4.s   10
+    IL_007c:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_0081:  stloc.s    V_4
+    IL_0083:  ldloca.s   V_4
+    IL_0085:  ldloc.2
+    IL_0086:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+    IL_008b:  ldind.i4
+    IL_008c:  stloc.1
+    IL_008d:  leave.s    IL_00a8
+  }
+  catch System.Exception
+  {
+    IL_008f:  stloc.s    V_5
+    IL_0091:  ldarg.0
+    IL_0092:  ldc.i4.s   -2
+    IL_0094:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0099:  ldarg.0
+    IL_009a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_009f:  ldloc.s    V_5
+    IL_00a1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00a6:  leave.s    IL_00bc
+  }
+  IL_00a8:  ldarg.0
+  IL_00a9:  ldc.i4.s   -2
+  IL_00ab:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00b0:  ldarg.0
+  IL_00b1:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00b6:  ldloc.1
+  IL_00b7:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00bc:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_08()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static void Main()
+    {
+        var x = new Buffer10<int>[] { default };
+        System.Console.Write(x[0][0]);
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(x[0][0]);
+    }
+
+    static async Task M2(Buffer10<int>[] x) => x[Get01()][Get02()] = await FromResult(111);
+    static int Get01() => 0;
+    static int Get02() => 0;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      249 (0xf9)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_2,
+                System.Span<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0077
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""Buffer10<int>[] Program.<M2>d__1.x""
+    IL_0011:  stfld      ""Buffer10<int>[] Program.<M2>d__1.<>7__wrap2""
+    IL_0016:  ldarg.0
+    IL_0017:  call       ""int Program.Get01()""
+    IL_001c:  stfld      ""int Program.<M2>d__1.<>7__wrap3""
+    IL_0021:  ldarg.0
+    IL_0022:  ldfld      ""Buffer10<int>[] Program.<M2>d__1.<>7__wrap2""
+    IL_0027:  ldarg.0
+    IL_0028:  ldfld      ""int Program.<M2>d__1.<>7__wrap3""
+    IL_002d:  ldelema    ""Buffer10<int>""
+    IL_0032:  pop
+    IL_0033:  ldarg.0
+    IL_0034:  call       ""int Program.Get02()""
+    IL_0039:  stfld      ""int Program.<M2>d__1.<>7__wrap1""
+    IL_003e:  ldc.i4.s   111
+    IL_0040:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_0045:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_004a:  stloc.2
+    IL_004b:  ldloca.s   V_2
+    IL_004d:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0052:  brtrue.s   IL_0093
+    IL_0054:  ldarg.0
+    IL_0055:  ldc.i4.0
+    IL_0056:  dup
+    IL_0057:  stloc.0
+    IL_0058:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_005d:  ldarg.0
+    IL_005e:  ldloc.2
+    IL_005f:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_0064:  ldarg.0
+    IL_0065:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__1.<>t__builder""
+    IL_006a:  ldloca.s   V_2
+    IL_006c:  ldarg.0
+    IL_006d:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__1)""
+    IL_0072:  leave      IL_00f8
+    IL_0077:  ldarg.0
+    IL_0078:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_007d:  stloc.2
+    IL_007e:  ldarg.0
+    IL_007f:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__1.<>u__1""
+    IL_0084:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_008a:  ldarg.0
+    IL_008b:  ldc.i4.m1
+    IL_008c:  dup
+    IL_008d:  stloc.0
+    IL_008e:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_0093:  ldloca.s   V_2
+    IL_0095:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_009a:  stloc.1
+    IL_009b:  ldarg.0
+    IL_009c:  ldfld      ""Buffer10<int>[] Program.<M2>d__1.<>7__wrap2""
+    IL_00a1:  ldarg.0
+    IL_00a2:  ldfld      ""int Program.<M2>d__1.<>7__wrap3""
+    IL_00a7:  ldelema    ""Buffer10<int>""
+    IL_00ac:  ldc.i4.s   10
+    IL_00ae:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_00b3:  stloc.3
+    IL_00b4:  ldloca.s   V_3
+    IL_00b6:  ldarg.0
+    IL_00b7:  ldfld      ""int Program.<M2>d__1.<>7__wrap1""
+    IL_00bc:  call       ""ref int System.Span<int>.this[int].get""
+    IL_00c1:  ldloc.1
+    IL_00c2:  stind.i4
+    IL_00c3:  ldarg.0
+    IL_00c4:  ldnull
+    IL_00c5:  stfld      ""Buffer10<int>[] Program.<M2>d__1.<>7__wrap2""
+    IL_00ca:  leave.s    IL_00e5
+  }
+  catch System.Exception
+  {
+    IL_00cc:  stloc.s    V_4
+    IL_00ce:  ldarg.0
+    IL_00cf:  ldc.i4.s   -2
+    IL_00d1:  stfld      ""int Program.<M2>d__1.<>1__state""
+    IL_00d6:  ldarg.0
+    IL_00d7:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__1.<>t__builder""
+    IL_00dc:  ldloc.s    V_4
+    IL_00de:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00e3:  leave.s    IL_00f8
+  }
+  IL_00e5:  ldarg.0
+  IL_00e6:  ldc.i4.s   -2
+  IL_00e8:  stfld      ""int Program.<M2>d__1.<>1__state""
+  IL_00ed:  ldarg.0
+  IL_00ee:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__1.<>t__builder""
+  IL_00f3:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00f8:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_09()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public readonly Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => GetC(x).F[Get01()][await FromResult(Get02(x))];
+
+    static C GetC(C x) => x;
+    static int Get01() => 0;
+    static int Get02(C c)
+    {
+        System.Runtime.CompilerServices.Unsafe.AsRef(in c.F)[0][0] = 111;
+        return 0;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      240 (0xf0)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.ReadOnlySpan<Buffer10<int>> V_4,
+                System.ReadOnlySpan<int> V_5,
+                System.Exception V_6)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0068
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  call       ""C Program.GetC(C)""
+    IL_0016:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_001b:  ldarg.0
+    IL_001c:  call       ""int Program.Get01()""
+    IL_0021:  stfld      ""int Program.<M1>d__1.<>7__wrap2""
+    IL_0026:  ldarg.0
+    IL_0027:  ldfld      ""C Program.<M1>d__1.x""
+    IL_002c:  call       ""int Program.Get02(C)""
+    IL_0031:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_0036:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_003b:  stloc.3
+    IL_003c:  ldloca.s   V_3
+    IL_003e:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0043:  brtrue.s   IL_0084
+    IL_0045:  ldarg.0
+    IL_0046:  ldc.i4.0
+    IL_0047:  dup
+    IL_0048:  stloc.0
+    IL_0049:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_004e:  ldarg.0
+    IL_004f:  ldloc.3
+    IL_0050:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0055:  ldarg.0
+    IL_0056:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_005b:  ldloca.s   V_3
+    IL_005d:  ldarg.0
+    IL_005e:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0063:  leave      IL_00ef
+    IL_0068:  ldarg.0
+    IL_0069:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_006e:  stloc.3
+    IL_006f:  ldarg.0
+    IL_0070:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0075:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_007b:  ldarg.0
+    IL_007c:  ldc.i4.m1
+    IL_007d:  dup
+    IL_007e:  stloc.0
+    IL_007f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0084:  ldloca.s   V_3
+    IL_0086:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_008b:  stloc.2
+    IL_008c:  ldarg.0
+    IL_008d:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0092:  ldflda     ""Buffer10<Buffer10<int>> C.F""
+    IL_0097:  ldc.i4.s   10
+    IL_0099:  call       ""InlineArrayAsReadOnlySpan<Buffer10<Buffer10<int>>, Buffer10<int>>(in Buffer10<Buffer10<int>>, int)""
+    IL_009e:  stloc.s    V_4
+    IL_00a0:  ldloca.s   V_4
+    IL_00a2:  ldarg.0
+    IL_00a3:  ldfld      ""int Program.<M1>d__1.<>7__wrap2""
+    IL_00a8:  call       ""ref readonly Buffer10<int> System.ReadOnlySpan<Buffer10<int>>.this[int].get""
+    IL_00ad:  ldc.i4.s   10
+    IL_00af:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_00b4:  stloc.s    V_5
+    IL_00b6:  ldloca.s   V_5
+    IL_00b8:  ldloc.2
+    IL_00b9:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+    IL_00be:  ldind.i4
+    IL_00bf:  stloc.1
+    IL_00c0:  leave.s    IL_00db
+  }
+  catch System.Exception
+  {
+    IL_00c2:  stloc.s    V_6
+    IL_00c4:  ldarg.0
+    IL_00c5:  ldc.i4.s   -2
+    IL_00c7:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_00cc:  ldarg.0
+    IL_00cd:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_00d2:  ldloc.s    V_6
+    IL_00d4:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00d9:  leave.s    IL_00ef
+  }
+  IL_00db:  ldarg.0
+  IL_00dc:  ldc.i4.s   -2
+  IL_00de:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00e3:  ldarg.0
+  IL_00e4:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00e9:  ldloc.1
+  IL_00ea:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00ef:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_Await_10()
+        {
+            var src = @"
+using System.Threading.Tasks;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+class C
+{
+    public readonly Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x)
+        => MemoryMarshal.CreateReadOnlySpan(
+                ref Unsafe.As<Buffer10<Buffer10<int>>, Buffer10<int>>(
+                        ref Unsafe.AsRef(in GetC(x).F)),
+                10)
+           [Get01()][await FromResult(Get02(x))];
+
+    static C GetC(C x) => x;
+    static int Get01() => 0;
+    static int Get02(C c)
+    {
+        Unsafe.AsRef(in c.F)[0][0] = 111;
+        return 0;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyEmitDiagnostics(
+                // (24,22): error CS4007: 'await' cannot be used in an expression containing the type 'System.ReadOnlySpan<Buffer10<int>>'
+                //            [Get01()][await FromResult(Get02(x))];
+                Diagnostic(ErrorCode.ERR_ByRefTypeAndAwait, "await FromResult(Get02(x))").WithArguments("System.ReadOnlySpan<Buffer10<int>>").WithLocation(24, 22)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Await_11()
+        {
+            var src = @"
+using System.Threading.Tasks;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+class C
+{
+    public readonly Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x)
+        => MemoryMarshal.CreateReadOnlySpan(
+                ref Unsafe.As<Buffer10<int>, int>(
+                        ref Unsafe.AsRef(in GetC(x).F[Get01()])),
+                10)
+           [await FromResult(Get02(x))];
+
+    static C GetC(C x) => x;
+    static int Get01() => 0;
+    static int Get02(C c)
+    {
+        Unsafe.AsRef(in c.F)[0][0] = 111;
+        return 0;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyEmitDiagnostics(
+                    // (24,13): error CS4007: 'await' cannot be used in an expression containing the type 'System.ReadOnlySpan<int>'
+                    //            [await FromResult(Get02(x))];
+                    Diagnostic(ErrorCode.ERR_ByRefTypeAndAwait, "await FromResult(Get02(x))").WithArguments("System.ReadOnlySpan<int>").WithLocation(24, 13)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Await_12()
+        {
+            var src = @"
+using System.Threading.Tasks;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+class C
+{
+    public readonly Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x)
+        => GetItem(MemoryMarshal.CreateReadOnlySpan(ref Unsafe.As<Buffer10<Buffer10<int>>, Buffer10<int>>(ref Unsafe.AsRef(in GetC(x).F)),10), Get01())[await FromResult(Get02(x))];
+
+    static C GetC(C x) => x;
+    static int Get01() => 0;
+    static int Get02(C c)
+    {
+        System.Runtime.CompilerServices.Unsafe.AsRef(in c.F)[0][0] = 111;
+        return 0;
+    }
+
+    static ref readonly Buffer10<int> GetItem(System.ReadOnlySpan<Buffer10<int>> span, int index) => ref span[index];  
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyEmitDiagnostics(
+                // (20,12): error CS8178: A reference returned by a call to 'Program.GetItem(ReadOnlySpan<Buffer10<int>>, int)' cannot be preserved across 'await' or 'yield' boundary.
+                //         => GetItem(MemoryMarshal.CreateReadOnlySpan(ref Unsafe.As<Buffer10<Buffer10<int>>, Buffer10<int>>(ref Unsafe.AsRef(in GetC(x).F)),10), Get01())[await FromResult(Get02(x))];
+                Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "GetItem(MemoryMarshal.CreateReadOnlySpan(ref Unsafe.As<Buffer10<Buffer10<int>>, Buffer10<int>>(ref Unsafe.AsRef(in GetC(x).F)),10), Get01())").WithArguments("Program.GetItem(System.ReadOnlySpan<Buffer10<int>>, int)").WithLocation(20, 12)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Await_13()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().Result);
+    }
+
+    static async Task<int> M2() => M3()[await FromResult(0)];
+
+    static Buffer10 M3()
+    {
+        var b = new Buffer10();
+        b[0] = 111;
+        return b;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public ref struct Buffer10
+{
+    private int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyEmitDiagnostics(
+                // (11,41): error CS4007: 'await' cannot be used in an expression containing the type 'Buffer10'
+                //     static async Task<int> M2() => M3()[await FromResult(0)];
+                Diagnostic(ErrorCode.ERR_ByRefTypeAndAwait, "await FromResult(0)").WithArguments("Buffer10").WithLocation(11, 41)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_ExpressionTree_01()
+        {
+            var src = @"
+using System.Linq.Expressions;
+
+class Program
+{
+    static Expression<System.Func<int>> M1(Buffer10<int> x) =>
+        () => x[0];
+
+    static Expression<System.Action> M2(Buffer10<int> x) =>
+        () => x[0] = 111;
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (7,15): error CS9170: An expression tree may not contain an inline array access or conversion
+                //         () => x[0];
+                Diagnostic(ErrorCode.ERR_ExpressionTreeContainsInlineArrayOperation, "x[0]").WithLocation(7, 15),
+                // (10,15): error CS0832: An expression tree may not contain an assignment operator
+                //         () => x[0] = 111;
+                Diagnostic(ErrorCode.ERR_ExpressionTreeContainsAssignment, "x[0] = 111").WithLocation(10, 15),
+                // (10,15): error CS9170: An expression tree may not contain an inline array access or conversion
+                //         () => x[0] = 111;
+                Diagnostic(ErrorCode.ERR_ExpressionTreeContainsInlineArrayOperation, "x[0]").WithLocation(10, 15)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_14_GenericMethod()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C<T>
+{
+    public Buffer10<T> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C<int>();
+        System.Console.Write(M1(x).Result);
+        M2(x, 111).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<T> M1<T>(C<T> x) => x.F[await FromResult(^10)];
+    static async Task M2<T>(C<T> x, T y) => x.F[await FromResult(^10)] = y;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1<T>.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      208 (0xd0)
+  .maxstack  3
+  .locals init (int V_0,
+                T V_1,
+                System.Index V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<System.Index> V_3,
+                System.Span<T> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1<T>.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0052
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C<T> Program.<M1>d__1<T>.x""
+    IL_0011:  stfld      ""C<T> Program.<M1>d__1<T>.<>7__wrap1""
+    IL_0016:  ldc.i4.s   10
+    IL_0018:  ldc.i4.1
+    IL_0019:  newobj     ""System.Index..ctor(int, bool)""
+    IL_001e:  call       ""System.Threading.Tasks.Task<System.Index> Program.FromResult<System.Index>(System.Index)""
+    IL_0023:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> System.Threading.Tasks.Task<System.Index>.GetAwaiter()""
+    IL_0028:  stloc.3
+    IL_0029:  ldloca.s   V_3
+    IL_002b:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<System.Index>.IsCompleted.get""
+    IL_0030:  brtrue.s   IL_006e
+    IL_0032:  ldarg.0
+    IL_0033:  ldc.i4.0
+    IL_0034:  dup
+    IL_0035:  stloc.0
+    IL_0036:  stfld      ""int Program.<M1>d__1<T>.<>1__state""
+    IL_003b:  ldarg.0
+    IL_003c:  ldloc.3
+    IL_003d:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M1>d__1<T>.<>u__1""
+    IL_0042:  ldarg.0
+    IL_0043:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<T> Program.<M1>d__1<T>.<>t__builder""
+    IL_0048:  ldloca.s   V_3
+    IL_004a:  ldarg.0
+    IL_004b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<T>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<System.Index>, Program.<M1>d__1<T>>(ref System.Runtime.CompilerServices.TaskAwaiter<System.Index>, ref Program.<M1>d__1<T>)""
+    IL_0050:  leave.s    IL_00cf
+    IL_0052:  ldarg.0
+    IL_0053:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M1>d__1<T>.<>u__1""
+    IL_0058:  stloc.3
+    IL_0059:  ldarg.0
+    IL_005a:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M1>d__1<T>.<>u__1""
+    IL_005f:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<System.Index>""
+    IL_0065:  ldarg.0
+    IL_0066:  ldc.i4.m1
+    IL_0067:  dup
+    IL_0068:  stloc.0
+    IL_0069:  stfld      ""int Program.<M1>d__1<T>.<>1__state""
+    IL_006e:  ldloca.s   V_3
+    IL_0070:  call       ""System.Index System.Runtime.CompilerServices.TaskAwaiter<System.Index>.GetResult()""
+    IL_0075:  stloc.2
+    IL_0076:  ldarg.0
+    IL_0077:  ldfld      ""C<T> Program.<M1>d__1<T>.<>7__wrap1""
+    IL_007c:  ldflda     ""Buffer10<T> C<T>.F""
+    IL_0081:  ldc.i4.s   10
+    IL_0083:  call       ""InlineArrayAsSpan<Buffer10<T>, T>(ref Buffer10<T>, int)""
+    IL_0088:  stloc.s    V_4
+    IL_008a:  ldloca.s   V_4
+    IL_008c:  ldloca.s   V_2
+    IL_008e:  ldc.i4.s   10
+    IL_0090:  call       ""int System.Index.GetOffset(int)""
+    IL_0095:  call       ""ref T System.Span<T>.this[int].get""
+    IL_009a:  ldobj      ""T""
+    IL_009f:  stloc.1
+    IL_00a0:  leave.s    IL_00bb
+  }
+  catch System.Exception
+  {
+    IL_00a2:  stloc.s    V_5
+    IL_00a4:  ldarg.0
+    IL_00a5:  ldc.i4.s   -2
+    IL_00a7:  stfld      ""int Program.<M1>d__1<T>.<>1__state""
+    IL_00ac:  ldarg.0
+    IL_00ad:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<T> Program.<M1>d__1<T>.<>t__builder""
+    IL_00b2:  ldloc.s    V_5
+    IL_00b4:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<T>.SetException(System.Exception)""
+    IL_00b9:  leave.s    IL_00cf
+  }
+  IL_00bb:  ldarg.0
+  IL_00bc:  ldc.i4.s   -2
+  IL_00be:  stfld      ""int Program.<M1>d__1<T>.<>1__state""
+  IL_00c3:  ldarg.0
+  IL_00c4:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<T> Program.<M1>d__1<T>.<>t__builder""
+  IL_00c9:  ldloc.1
+  IL_00ca:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<T>.SetResult(T)""
+  IL_00cf:  ret
+}
+");
+
+            verifier.VerifyIL("Program.<M2>d__2<T>.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      221 (0xdd)
+  .maxstack  3
+  .locals init (int V_0,
+                System.Index V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<System.Index> V_2,
+                System.Span<T> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2<T>.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0055
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C<T> Program.<M2>d__2<T>.x""
+    IL_0011:  stfld      ""C<T> Program.<M2>d__2<T>.<>7__wrap1""
+    IL_0016:  ldc.i4.s   10
+    IL_0018:  ldc.i4.1
+    IL_0019:  newobj     ""System.Index..ctor(int, bool)""
+    IL_001e:  call       ""System.Threading.Tasks.Task<System.Index> Program.FromResult<System.Index>(System.Index)""
+    IL_0023:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> System.Threading.Tasks.Task<System.Index>.GetAwaiter()""
+    IL_0028:  stloc.2
+    IL_0029:  ldloca.s   V_2
+    IL_002b:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<System.Index>.IsCompleted.get""
+    IL_0030:  brtrue.s   IL_0071
+    IL_0032:  ldarg.0
+    IL_0033:  ldc.i4.0
+    IL_0034:  dup
+    IL_0035:  stloc.0
+    IL_0036:  stfld      ""int Program.<M2>d__2<T>.<>1__state""
+    IL_003b:  ldarg.0
+    IL_003c:  ldloc.2
+    IL_003d:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__2<T>.<>u__1""
+    IL_0042:  ldarg.0
+    IL_0043:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2<T>.<>t__builder""
+    IL_0048:  ldloca.s   V_2
+    IL_004a:  ldarg.0
+    IL_004b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<System.Index>, Program.<M2>d__2<T>>(ref System.Runtime.CompilerServices.TaskAwaiter<System.Index>, ref Program.<M2>d__2<T>)""
+    IL_0050:  leave      IL_00dc
+    IL_0055:  ldarg.0
+    IL_0056:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__2<T>.<>u__1""
+    IL_005b:  stloc.2
+    IL_005c:  ldarg.0
+    IL_005d:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<System.Index> Program.<M2>d__2<T>.<>u__1""
+    IL_0062:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<System.Index>""
+    IL_0068:  ldarg.0
+    IL_0069:  ldc.i4.m1
+    IL_006a:  dup
+    IL_006b:  stloc.0
+    IL_006c:  stfld      ""int Program.<M2>d__2<T>.<>1__state""
+    IL_0071:  ldloca.s   V_2
+    IL_0073:  call       ""System.Index System.Runtime.CompilerServices.TaskAwaiter<System.Index>.GetResult()""
+    IL_0078:  stloc.1
+    IL_0079:  ldarg.0
+    IL_007a:  ldfld      ""C<T> Program.<M2>d__2<T>.<>7__wrap1""
+    IL_007f:  ldflda     ""Buffer10<T> C<T>.F""
+    IL_0084:  ldc.i4.s   10
+    IL_0086:  call       ""InlineArrayAsSpan<Buffer10<T>, T>(ref Buffer10<T>, int)""
+    IL_008b:  stloc.3
+    IL_008c:  ldloca.s   V_3
+    IL_008e:  ldloca.s   V_1
+    IL_0090:  ldc.i4.s   10
+    IL_0092:  call       ""int System.Index.GetOffset(int)""
+    IL_0097:  call       ""ref T System.Span<T>.this[int].get""
+    IL_009c:  ldarg.0
+    IL_009d:  ldfld      ""T Program.<M2>d__2<T>.y""
+    IL_00a2:  stobj      ""T""
+    IL_00a7:  ldarg.0
+    IL_00a8:  ldnull
+    IL_00a9:  stfld      ""C<T> Program.<M2>d__2<T>.<>7__wrap1""
+    IL_00ae:  leave.s    IL_00c9
+  }
+  catch System.Exception
+  {
+    IL_00b0:  stloc.s    V_4
+    IL_00b2:  ldarg.0
+    IL_00b3:  ldc.i4.s   -2
+    IL_00b5:  stfld      ""int Program.<M2>d__2<T>.<>1__state""
+    IL_00ba:  ldarg.0
+    IL_00bb:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2<T>.<>t__builder""
+    IL_00c0:  ldloc.s    V_4
+    IL_00c2:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00c7:  leave.s    IL_00dc
+  }
+  IL_00c9:  ldarg.0
+  IL_00ca:  ldc.i4.s   -2
+  IL_00cc:  stfld      ""int Program.<M2>d__2<T>.<>1__state""
+  IL_00d1:  ldarg.0
+  IL_00d2:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2<T>.<>t__builder""
+  IL_00d7:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00dc:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_15()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => GetInt(ref x.F[1], await FromResult(0));
+    static async Task M2(C x) => x.F[1] = await FromResult(111);
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+
+    static int GetInt(ref int x, int y) => x;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      183 (0xb7)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0049:  leave.s    IL_00b6
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  ldc.i4.1
+    IL_007b:  call       ""InlineArrayElementRef<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0080:  ldloc.2
+    IL_0081:  call       ""int Program.GetInt(ref int, int)""
+    IL_0086:  stloc.1
+    IL_0087:  leave.s    IL_00a2
+  }
+  catch System.Exception
+  {
+    IL_0089:  stloc.s    V_4
+    IL_008b:  ldarg.0
+    IL_008c:  ldc.i4.s   -2
+    IL_008e:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0093:  ldarg.0
+    IL_0094:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0099:  ldloc.s    V_4
+    IL_009b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00a0:  leave.s    IL_00b6
+  }
+  IL_00a2:  ldarg.0
+  IL_00a3:  ldc.i4.s   -2
+  IL_00a5:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00aa:  ldarg.0
+  IL_00ab:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00b0:  ldloc.1
+  IL_00b1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00b6:  ret
+}
+");
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      183 (0xb7)
+  .maxstack  3
+  .locals init (int V_0,
+            int V_1,
+            System.Runtime.CompilerServices.TaskAwaiter<int> V_2,
+            System.Exception V_3)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004c
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0016:  ldc.i4.s   111
+    IL_0018:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001d:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0022:  stloc.2
+    IL_0023:  ldloca.s   V_2
+    IL_0025:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_002a:  brtrue.s   IL_0068
+    IL_002c:  ldarg.0
+    IL_002d:  ldc.i4.0
+    IL_002e:  dup
+    IL_002f:  stloc.0
+    IL_0030:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0035:  ldarg.0
+    IL_0036:  ldloc.2
+    IL_0037:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_003c:  ldarg.0
+    IL_003d:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0042:  ldloca.s   V_2
+    IL_0044:  ldarg.0
+    IL_0045:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_004a:  leave.s    IL_00b6
+    IL_004c:  ldarg.0
+    IL_004d:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0052:  stloc.2
+    IL_0053:  ldarg.0
+    IL_0054:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0059:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005f:  ldarg.0
+    IL_0060:  ldc.i4.m1
+    IL_0061:  dup
+    IL_0062:  stloc.0
+    IL_0063:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0068:  ldloca.s   V_2
+    IL_006a:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006f:  stloc.1
+    IL_0070:  ldarg.0
+    IL_0071:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0076:  ldflda     ""Buffer10<int> C.F""
+    IL_007b:  ldc.i4.1
+    IL_007c:  call       ""InlineArrayElementRef<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0081:  ldloc.1
+    IL_0082:  stind.i4
+    IL_0083:  ldarg.0
+    IL_0084:  ldnull
+    IL_0085:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_008a:  leave.s    IL_00a3
+  }
+  catch System.Exception
+  {
+    IL_008c:  stloc.3
+    IL_008d:  ldarg.0
+    IL_008e:  ldc.i4.s   -2
+    IL_0090:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0095:  ldarg.0
+    IL_0096:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_009b:  ldloc.3
+    IL_009c:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00a1:  leave.s    IL_00b6
+  }
+  IL_00a3:  ldarg.0
+  IL_00a4:  ldc.i4.s   -2
+  IL_00a6:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00ab:  ldarg.0
+  IL_00ac:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00b1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00b6:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_16()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F[1] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => GetInt(in x.F[1], await FromResult(0));
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+
+    static int GetInt(in int x, int y) => x;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      183 (0xb7)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0049:  leave.s    IL_00b6
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  ldc.i4.1
+    IL_007b:  call       ""InlineArrayElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_0080:  ldloc.2
+    IL_0081:  call       ""int Program.GetInt(in int, int)""
+    IL_0086:  stloc.1
+    IL_0087:  leave.s    IL_00a2
+  }
+  catch System.Exception
+  {
+    IL_0089:  stloc.s    V_4
+    IL_008b:  ldarg.0
+    IL_008c:  ldc.i4.s   -2
+    IL_008e:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0093:  ldarg.0
+    IL_0094:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0099:  ldloc.s    V_4
+    IL_009b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00a0:  leave.s    IL_00b6
+  }
+  IL_00a2:  ldarg.0
+  IL_00a3:  ldc.i4.s   -2
+  IL_00a5:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00aa:  ldarg.0
+  IL_00ab:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00b0:  ldloc.1
+  IL_00b1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00b6:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_17()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => GetInt(ref x.F[0], await FromResult(0));
+    static async Task M2(C x) => x.F[0] = await FromResult(111);
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+
+    static int GetInt(ref int x, int y) => x;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      182 (0xb6)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0049:  leave.s    IL_00b5
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+    IL_007f:  ldloc.2
+    IL_0080:  call       ""int Program.GetInt(ref int, int)""
+    IL_0085:  stloc.1
+    IL_0086:  leave.s    IL_00a1
+  }
+  catch System.Exception
+  {
+    IL_0088:  stloc.s    V_4
+    IL_008a:  ldarg.0
+    IL_008b:  ldc.i4.s   -2
+    IL_008d:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0092:  ldarg.0
+    IL_0093:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0098:  ldloc.s    V_4
+    IL_009a:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_009f:  leave.s    IL_00b5
+  }
+  IL_00a1:  ldarg.0
+  IL_00a2:  ldc.i4.s   -2
+  IL_00a4:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00a9:  ldarg.0
+  IL_00aa:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00af:  ldloc.1
+  IL_00b0:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00b5:  ret
+}
+");
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      182 (0xb6)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_2,
+                System.Exception V_3)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004c
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0016:  ldc.i4.s   111
+    IL_0018:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001d:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0022:  stloc.2
+    IL_0023:  ldloca.s   V_2
+    IL_0025:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_002a:  brtrue.s   IL_0068
+    IL_002c:  ldarg.0
+    IL_002d:  ldc.i4.0
+    IL_002e:  dup
+    IL_002f:  stloc.0
+    IL_0030:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0035:  ldarg.0
+    IL_0036:  ldloc.2
+    IL_0037:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_003c:  ldarg.0
+    IL_003d:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0042:  ldloca.s   V_2
+    IL_0044:  ldarg.0
+    IL_0045:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_004a:  leave.s    IL_00b5
+    IL_004c:  ldarg.0
+    IL_004d:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0052:  stloc.2
+    IL_0053:  ldarg.0
+    IL_0054:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0059:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005f:  ldarg.0
+    IL_0060:  ldc.i4.m1
+    IL_0061:  dup
+    IL_0062:  stloc.0
+    IL_0063:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0068:  ldloca.s   V_2
+    IL_006a:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006f:  stloc.1
+    IL_0070:  ldarg.0
+    IL_0071:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0076:  ldflda     ""Buffer10<int> C.F""
+    IL_007b:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+    IL_0080:  ldloc.1
+    IL_0081:  stind.i4
+    IL_0082:  ldarg.0
+    IL_0083:  ldnull
+    IL_0084:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0089:  leave.s    IL_00a2
+  }
+  catch System.Exception
+  {
+    IL_008b:  stloc.3
+    IL_008c:  ldarg.0
+    IL_008d:  ldc.i4.s   -2
+    IL_008f:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0094:  ldarg.0
+    IL_0095:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_009a:  ldloc.3
+    IL_009b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00a0:  leave.s    IL_00b5
+  }
+  IL_00a2:  ldarg.0
+  IL_00a3:  ldc.i4.s   -2
+  IL_00a5:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00aa:  ldarg.0
+  IL_00ab:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00b0:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00b5:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Await_18()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => GetInt(in x.F[0], await FromResult(0));
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+
+    static int GetInt(in int x, int y) => x;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      182 (0xb6)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0049:  leave.s    IL_00b5
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+    IL_007f:  ldloc.2
+    IL_0080:  call       ""int Program.GetInt(in int, int)""
+    IL_0085:  stloc.1
+    IL_0086:  leave.s    IL_00a1
+  }
+  catch System.Exception
+  {
+    IL_0088:  stloc.s    V_4
+    IL_008a:  ldarg.0
+    IL_008b:  ldc.i4.s   -2
+    IL_008d:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0092:  ldarg.0
+    IL_0093:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0098:  ldloc.s    V_4
+    IL_009a:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_009f:  leave.s    IL_00b5
+  }
+  IL_00a1:  ldarg.0
+  IL_00a2:  ldc.i4.s   -2
+  IL_00a4:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00a9:  ldarg.0
+  IL_00aa:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00af:  ldloc.1
+  IL_00b0:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00b5:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Index_Variable_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[^10];
+    static void M2(C x) => x.F[^10] = 111;
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldc.i4.s   111
+  IL_000d:  stind.i4
+  IL_000e:  ret
+}
+");
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.RegularNext);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular11);
+            comp.VerifyDiagnostics(
+                // (18,27): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static int M1(C x) => x.F[^10];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F[^10]").WithArguments("inline arrays").WithLocation(18, 27),
+                // (19,28): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static void M2(C x) => x.F[^10] = 111;
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F[^10]").WithArguments("inline arrays").WithLocation(19, 28)
+                );
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "F").First();
+            Assert.Equal("x.F[^10]", f.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            var symbolInfo = model.GetSymbolInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32> C.F", symbolInfo.Symbol.ToTestDisplayString());
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Dynamic_Variable_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static void M2(C x) => x.F[(dynamic)0] = 111;
+    static void M3(int[] x) => x[(dynamic)0] = 111;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            // Dynamic index is always converted to 'int'. This behavior is consistent with specification and
+            // with behavior around regular arrays (see IL for Program.M3 below).
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       95 (0x5f)
+  .maxstack  4
+  .locals init (System.Span<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__2.<>p__0""
+  IL_0015:  brtrue.s   IL_003c
+  IL_0017:  ldc.i4.s   32
+  IL_0019:  ldtoken    ""int""
+  IL_001e:  call       ""System.Type System.Type.GetTypeFromHandle(System.RuntimeTypeHandle)""
+  IL_0023:  ldtoken    ""Program""
+  IL_0028:  call       ""System.Type System.Type.GetTypeFromHandle(System.RuntimeTypeHandle)""
+  IL_002d:  call       ""System.Runtime.CompilerServices.CallSiteBinder Microsoft.CSharp.RuntimeBinder.Binder.Convert(Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, System.Type, System.Type)""
+  IL_0032:  call       ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>>.Create(System.Runtime.CompilerServices.CallSiteBinder)""
+  IL_0037:  stsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__2.<>p__0""
+  IL_003c:  ldsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__2.<>p__0""
+  IL_0041:  ldfld      ""System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int> System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>>.Target""
+  IL_0046:  ldsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__2.<>p__0""
+  IL_004b:  ldc.i4.0
+  IL_004c:  box        ""int""
+  IL_0051:  callvirt   ""int System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>.Invoke(System.Runtime.CompilerServices.CallSite, dynamic)""
+  IL_0056:  call       ""ref int System.Span<int>.this[int].get""
+  IL_005b:  ldc.i4.s   111
+  IL_005d:  stind.i4
+  IL_005e:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M3",
+@"
+{
+  // Code size       75 (0x4b)
+  .maxstack  4
+  IL_0000:  ldarg.0
+  IL_0001:  ldsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__3.<>p__0""
+  IL_0006:  brtrue.s   IL_002d
+  IL_0008:  ldc.i4.s   32
+  IL_000a:  ldtoken    ""int""
+  IL_000f:  call       ""System.Type System.Type.GetTypeFromHandle(System.RuntimeTypeHandle)""
+  IL_0014:  ldtoken    ""Program""
+  IL_0019:  call       ""System.Type System.Type.GetTypeFromHandle(System.RuntimeTypeHandle)""
+  IL_001e:  call       ""System.Runtime.CompilerServices.CallSiteBinder Microsoft.CSharp.RuntimeBinder.Binder.Convert(Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, System.Type, System.Type)""
+  IL_0023:  call       ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>>.Create(System.Runtime.CompilerServices.CallSiteBinder)""
+  IL_0028:  stsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__3.<>p__0""
+  IL_002d:  ldsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__3.<>p__0""
+  IL_0032:  ldfld      ""System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int> System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>>.Target""
+  IL_0037:  ldsfld     ""System.Runtime.CompilerServices.CallSite<System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>> Program.<>o__3.<>p__0""
+  IL_003c:  ldc.i4.0
+  IL_003d:  box        ""int""
+  IL_0042:  callvirt   ""int System.Func<System.Runtime.CompilerServices.CallSite, dynamic, int>.Invoke(System.Runtime.CompilerServices.CallSite, dynamic)""
+  IL_0047:  ldc.i4.s   111
+  IL_0049:  stelem.i4
+  IL_004a:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M2(x).Length);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x) => x.F[..5];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 5 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.RegularNext);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular11);
+            comp.VerifyDiagnostics(
+                // (20,27): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static int M1(C x) => x.F[0];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F[0]").WithArguments("inline arrays").WithLocation(20, 27),
+                // (21,40): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static System.Span<int> M2(C x) => x.F[..5];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F[..5]").WithArguments("inline arrays").WithLocation(21, 40)
+                );
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "F").Last();
+            Assert.Equal("x.F[..5]", f.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            var symbolInfo = model.GetSymbolInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32> C.F", symbolInfo.Symbol.ToTestDisplayString());
+
+            var access = f.Parent.Parent;
+            typeInfo = model.GetTypeInfo(access);
+
+            Assert.Equal("System.Span<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Span<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            symbolInfo = model.GetSymbolInfo(access);
+
+            Assert.Null(symbolInfo.Symbol);
+            Assert.Empty(symbolInfo.CandidateSymbols);
+        }
+
+        [ConditionalTheory(typeof(CoreClrOnly))]
+        [CombinatorialData]
+        public void Slice_Variable_03([CombinatorialValues("..10", "0..", "..^0", "^10..")] string range)
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+
+    public System.Span<int> M2() => F[" + range + @"];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.M2().Length);
+        System.Console.Write(' ');
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "10 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Slice_Variable_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(x)[0] = 111;
+        System.Console.Write(x.F[0]);
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x) => x.F[..5];
+    static System.Span<int> M3(C x)
+    { 
+        System.Span<int> y = x.F[..5];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (17,40): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.Span<int> M2(C x) => x.F[..5];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(17, 40),
+                // (21,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(21, 16)
+                );
+        }
+
+        [Fact]
+        public void Slice_Variable_05()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public System.Span<int> M2() => F[..5];
+
+    public System.Span<int> M3()
+    { 
+        System.Span<int> y = F[..5];
+        return y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (6,37): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.Span<int> M2() => F[..5];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(6, 37),
+                // (11,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(11, 16)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_06()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0] = 111;
+        System.Console.Write(x.F[0]);
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(ref C x) => x.F[..5];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_07()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<int> M2() => F[..5];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_08()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0] = 111;
+        System.Console.Write(x.F[0]);
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(ref C x)
+    {
+        System.Span<int> y = x.F[..5];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_09()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<int> M2()
+    {
+        System.Span<int> y = F[..5];
+        return y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.F[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_10()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x)[0][0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0][0];
+    static System.Span<Buffer10<int>> M2(C x) => x.F[..5][..3];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_12()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public System.Span<Buffer10<int>> M2() => F[..5][..3];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0][0] = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Slice_Variable_13()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(x)[0][0] = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+
+    static int M1(C x) => x.F[0][0];
+    static System.Span<Buffer10<int>> M2(C x) => x.F[..5][..3];
+    static System.Span<Buffer10<int>> M3(C x)
+    { 
+        System.Span<Buffer10<int>> y = x.F[..5][..3];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (17,50): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.Span<Buffer10<int>> M2(C x) => x.F[..5][..3];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(17, 50),
+                // (21,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(21, 16)
+                );
+        }
+
+        [Fact]
+        public void Slice_Variable_14()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public System.Span<Buffer10<int>> M2() => F[..5][..3];
+
+    public System.Span<Buffer10<int>> M3()
+    { 
+        System.Span<Buffer10<int>> y = F[..5][..3];
+        return y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0][0] = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (6,47): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.Span<Buffer10<int>> M2() => F[..5][..3];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(6, 47),
+                // (11,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(11, 16)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_15()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0][0] = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+
+    static int M1(C x) => x.F[0][0];
+    static System.Span<Buffer10<int>> M2(ref C x) => x.F[..5][..3];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_16()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<Buffer10<int>> M2() => F[..5][..3];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0][0] = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_17()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0][0] = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+
+    static int M1(C x) => x.F[0][0];
+    static System.Span<Buffer10<int>> M2(ref C x)
+    {
+        System.Span<Buffer10<int>> y = x.F[..5][..3];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_18()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<Buffer10<int>> M2()
+    {
+        System.Span<Buffer10<int>> y = F[..5][..3];
+        return y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0][0] = 111;
+        System.Console.Write(x.F[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Slice_Variable_19()
+        {
+            var src = @"
+class C
+{
+    void M(Buffer10<char> a1, System.Range i1, System.Span<char> result1)
+    {
+        result1 = a1[i1];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            // Ref safety error is unexpected. Likely an artifact of https://github.com/dotnet/roslyn/issues/68372
+            comp.VerifyDiagnostics(
+                // (6,19): error CS8166: Cannot return a parameter by reference 'a1' because it is not a ref parameter
+                //         result1 = a1[i1];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter, "a1").WithArguments("a1").WithLocation(6, 19)
+                );
+        }
+
+        [Fact]
+        public void Slice_Variable_20()
+        {
+            var src = @"
+class C
+{
+    void M(Buffer10<char> a1, System.Range i1)
+    {
+        System.Span<char> result1;
+        result1 = a1[i1];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            // Ref safety error is unexpected. Likely an artifact of https://github.com/dotnet/roslyn/issues/68372
+            comp.VerifyDiagnostics(
+                // (7,19): error CS8166: Cannot return a parameter by reference 'a1' because it is not a ref parameter
+                //         result1 = a1[i1];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter, "a1").WithArguments("a1").WithLocation(7, 19)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_21()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+
+    public System.Span<int> M2() => F[..0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(x.M2().Length);
+        System.Console.Write(' ');
+        var r = ..0;
+        System.Console.Write(x.F[r].Length);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 0", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.0
+  IL_0007:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_22()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M2(x).Length);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[1];
+    static System.Span<int> M2(C x) => x.F[1..5];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 4 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       24 (0x18)
+  .maxstack  3
+  .locals init (System.Span<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldc.i4.1
+  IL_0011:  ldc.i4.4
+  IL_0012:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+  IL_0017:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_23()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x, 5)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M2(x, 5).Length);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x, int y) => x.F[0..y];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 5 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       24 (0x18)
+  .maxstack  3
+  .locals init (System.Span<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldc.i4.0
+  IL_0011:  ldarg.1
+  IL_0012:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+  IL_0017:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_24()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x, 0)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M2(x, 0).Length);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x, int y) => x.F[y..5];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 5 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       28 (0x1c)
+  .maxstack  4
+  .locals init (int V_0,
+                System.Span<int> V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldarg.1
+  IL_0007:  stloc.0
+  IL_0008:  ldc.i4.s   10
+  IL_000a:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000f:  stloc.1
+  IL_0010:  ldloca.s   V_1
+  IL_0012:  ldloc.0
+  IL_0013:  ldc.i4.5
+  IL_0014:  ldloc.0
+  IL_0015:  sub
+  IL_0016:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+  IL_001b:  ret
+}
+");
+        }
+
+        [ConditionalTheory(typeof(CoreClrOnly))]
+        [CombinatorialData]
+        public void Slice_Variable_25([CombinatorialValues("1..", "^9..")] string range)
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M2(x).Length);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[1];
+    static System.Span<int> M2(C x) => x.F[" + range + @"];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 9 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       25 (0x19)
+  .maxstack  3
+  .locals init (System.Span<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldc.i4.1
+  IL_0011:  ldc.i4.s   9
+  IL_0013:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+  IL_0018:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_26()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x, 0)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M2(x, 0).Length);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x, int y) => x.F[y..];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 10 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       29 (0x1d)
+  .maxstack  4
+  .locals init (int V_0,
+                System.Span<int> V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldarg.1
+  IL_0007:  stloc.0
+  IL_0008:  ldc.i4.s   10
+  IL_000a:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000f:  stloc.1
+  IL_0010:  ldloca.s   V_1
+  IL_0012:  ldloc.0
+  IL_0013:  ldc.i4.s   10
+  IL_0015:  ldloc.0
+  IL_0016:  sub
+  IL_0017:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+  IL_001c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_27()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M2(x).Length);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x) => x.F[..^1];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 9 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+      // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   9
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Slice_Variable_IsRValue()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[..5] = default;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (12,9): error CS0131: The left-hand side of an assignment must be a variable, property or indexer
+                //         x.F[..5] = default;
+                Diagnostic(ErrorCode.ERR_AssgLvalueExpected, "x.F[..5]").WithLocation(12, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Range_Variable_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x, ..5)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x, System.Range y) => GetBuffer(x)[GetRange(y)];
+    static ref Buffer10<int> GetBuffer(C x) => ref x.F;
+    static System.Range GetRange(System.Range y) => y;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       70 (0x46)
+  .maxstack  3
+  .locals init (System.Range V_0,
+                int V_1,
+                int V_2,
+                System.Index V_3,
+                System.Span<int> V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref Buffer10<int> Program.GetBuffer(C)""
+  IL_0006:  ldarg.1
+  IL_0007:  call       ""System.Range Program.GetRange(System.Range)""
+  IL_000c:  stloc.0
+  IL_000d:  ldloca.s   V_0
+  IL_000f:  call       ""System.Index System.Range.Start.get""
+  IL_0014:  stloc.3
+  IL_0015:  ldloca.s   V_3
+  IL_0017:  ldc.i4.s   10
+  IL_0019:  call       ""int System.Index.GetOffset(int)""
+  IL_001e:  stloc.1
+  IL_001f:  ldloca.s   V_0
+  IL_0021:  call       ""System.Index System.Range.End.get""
+  IL_0026:  stloc.3
+  IL_0027:  ldloca.s   V_3
+  IL_0029:  ldc.i4.s   10
+  IL_002b:  call       ""int System.Index.GetOffset(int)""
+  IL_0030:  ldloc.1
+  IL_0031:  sub
+  IL_0032:  stloc.2
+  IL_0033:  ldc.i4.s   10
+  IL_0035:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_003a:  stloc.s    V_4
+  IL_003c:  ldloca.s   V_4
+  IL_003e:  ldloc.1
+  IL_003f:  ldloc.2
+  IL_0040:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+  IL_0045:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Range_Variable_Readonly_01()
+        {
+            var src = @"
+class C
+{
+    readonly public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Runtime.CompilerServices.Unsafe.AsRef(in M2(x, ..5)[0]) = 111;
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.ReadOnlySpan<int> M2(C x, System.Range y) => GetBuffer(x)[GetRange(y)];
+    static ref readonly Buffer10<int> GetBuffer(C x) => ref x.F;
+    static System.Range GetRange(System.Range y) => y;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       70 (0x46)
+  .maxstack  3
+  .locals init (System.Range V_0,
+                int V_1,
+                int V_2,
+                System.Index V_3,
+                System.ReadOnlySpan<int> V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref readonly Buffer10<int> Program.GetBuffer(C)""
+  IL_0006:  ldarg.1
+  IL_0007:  call       ""System.Range Program.GetRange(System.Range)""
+  IL_000c:  stloc.0
+  IL_000d:  ldloca.s   V_0
+  IL_000f:  call       ""System.Index System.Range.Start.get""
+  IL_0014:  stloc.3
+  IL_0015:  ldloca.s   V_3
+  IL_0017:  ldc.i4.s   10
+  IL_0019:  call       ""int System.Index.GetOffset(int)""
+  IL_001e:  stloc.1
+  IL_001f:  ldloca.s   V_0
+  IL_0021:  call       ""System.Index System.Range.End.get""
+  IL_0026:  stloc.3
+  IL_0027:  ldloca.s   V_3
+  IL_0029:  ldc.i4.s   10
+  IL_002b:  call       ""int System.Index.GetOffset(int)""
+  IL_0030:  ldloc.1
+  IL_0031:  sub
+  IL_0032:  stloc.2
+  IL_0033:  ldc.i4.s   10
+  IL_0035:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_003a:  stloc.s    V_4
+  IL_003c:  ldloca.s   V_4
+  IL_003e:  ldloc.1
+  IL_003f:  ldloc.2
+  IL_0040:  call       ""System.ReadOnlySpan<int> System.ReadOnlySpan<int>.Slice(int, int)""
+  IL_0045:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Await_01()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static async Task M2(C x) => x.F[..await FromResult(5)][0] = 111;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      208 (0xd0)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_2,
+                System.Span<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004e
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0016:  ldc.i4.5
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.2
+    IL_0022:  ldloca.s   V_2
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_006a
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.2
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0041:  ldloca.s   V_2
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_0049:  leave      IL_00cf
+    IL_004e:  ldarg.0
+    IL_004f:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0054:  stloc.2
+    IL_0055:  ldarg.0
+    IL_0056:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_005b:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_0061:  ldarg.0
+    IL_0062:  ldc.i4.m1
+    IL_0063:  dup
+    IL_0064:  stloc.0
+    IL_0065:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_006a:  ldloca.s   V_2
+    IL_006c:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_0071:  stloc.1
+    IL_0072:  ldarg.0
+    IL_0073:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0078:  ldflda     ""Buffer10<int> C.F""
+    IL_007d:  ldc.i4.s   10
+    IL_007f:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0084:  stloc.3
+    IL_0085:  ldloca.s   V_3
+    IL_0087:  ldc.i4.0
+    IL_0088:  ldloc.1
+    IL_0089:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+    IL_008e:  stloc.3
+    IL_008f:  ldloca.s   V_3
+    IL_0091:  ldc.i4.0
+    IL_0092:  call       ""ref int System.Span<int>.this[int].get""
+    IL_0097:  ldc.i4.s   111
+    IL_0099:  stind.i4
+    IL_009a:  ldarg.0
+    IL_009b:  ldnull
+    IL_009c:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_00a1:  leave.s    IL_00bc
+  }
+  catch System.Exception
+  {
+    IL_00a3:  stloc.s    V_4
+    IL_00a5:  ldarg.0
+    IL_00a6:  ldc.i4.s   -2
+    IL_00a8:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00ad:  ldarg.0
+    IL_00ae:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00b3:  ldloc.s    V_4
+    IL_00b5:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00ba:  leave.s    IL_00cf
+  }
+  IL_00bc:  ldarg.0
+  IL_00bd:  ldc.i4.s   -2
+  IL_00bf:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00c4:  ldarg.0
+  IL_00c5:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00ca:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00cf:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Await_02()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static async Task M2(C x) => x.F[await FromResult(0)..5][0] = 111;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      226 (0xe2)
+  .maxstack  4
+  .locals init (int V_0,
+                C V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Span<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_005c
+    IL_000a:  ldarg.0
+    IL_000b:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0010:  stloc.1
+    IL_0011:  ldarg.0
+    IL_0012:  ldloc.1
+    IL_0013:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0018:  ldarg.0
+    IL_0019:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_001e:  ldfld      ""Buffer10<int> C.F""
+    IL_0023:  pop
+    IL_0024:  ldc.i4.0
+    IL_0025:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_002a:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_002f:  stloc.3
+    IL_0030:  ldloca.s   V_3
+    IL_0032:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0037:  brtrue.s   IL_0078
+    IL_0039:  ldarg.0
+    IL_003a:  ldc.i4.0
+    IL_003b:  dup
+    IL_003c:  stloc.0
+    IL_003d:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0042:  ldarg.0
+    IL_0043:  ldloc.3
+    IL_0044:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0049:  ldarg.0
+    IL_004a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_004f:  ldloca.s   V_3
+    IL_0051:  ldarg.0
+    IL_0052:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_0057:  leave      IL_00e1
+    IL_005c:  ldarg.0
+    IL_005d:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0062:  stloc.3
+    IL_0063:  ldarg.0
+    IL_0064:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0069:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_006f:  ldarg.0
+    IL_0070:  ldc.i4.m1
+    IL_0071:  dup
+    IL_0072:  stloc.0
+    IL_0073:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0078:  ldloca.s   V_3
+    IL_007a:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_007f:  stloc.2
+    IL_0080:  ldarg.0
+    IL_0081:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0086:  ldflda     ""Buffer10<int> C.F""
+    IL_008b:  ldc.i4.s   10
+    IL_008d:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0092:  stloc.s    V_4
+    IL_0094:  ldloca.s   V_4
+    IL_0096:  ldloc.2
+    IL_0097:  ldc.i4.5
+    IL_0098:  ldloc.2
+    IL_0099:  sub
+    IL_009a:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+    IL_009f:  stloc.s    V_4
+    IL_00a1:  ldloca.s   V_4
+    IL_00a3:  ldc.i4.0
+    IL_00a4:  call       ""ref int System.Span<int>.this[int].get""
+    IL_00a9:  ldc.i4.s   111
+    IL_00ab:  stind.i4
+    IL_00ac:  ldarg.0
+    IL_00ad:  ldnull
+    IL_00ae:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_00b3:  leave.s    IL_00ce
+  }
+  catch System.Exception
+  {
+    IL_00b5:  stloc.s    V_5
+    IL_00b7:  ldarg.0
+    IL_00b8:  ldc.i4.s   -2
+    IL_00ba:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00bf:  ldarg.0
+    IL_00c0:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00c5:  ldloc.s    V_5
+    IL_00c7:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00cc:  leave.s    IL_00e1
+  }
+  IL_00ce:  ldarg.0
+  IL_00cf:  ldc.i4.s   -2
+  IL_00d1:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00d6:  ldarg.0
+  IL_00d7:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00dc:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00e1:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Await_03()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static async Task M2(C x) => x.F[await FromResult(..5)][0] = 111;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      279 (0x117)
+  .maxstack  3
+  .locals init (int V_0,
+                C V_1,
+                System.Range V_2,
+                int V_3,
+                int V_4,
+                System.Runtime.CompilerServices.TaskAwaiter<System.Range> V_5,
+                System.Index V_6,
+                System.Span<int> V_7,
+                System.Exception V_8)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0068
+    IL_000a:  ldarg.0
+    IL_000b:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0010:  stloc.1
+    IL_0011:  ldarg.0
+    IL_0012:  ldloc.1
+    IL_0013:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0018:  ldarg.0
+    IL_0019:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_001e:  ldfld      ""Buffer10<int> C.F""
+    IL_0023:  pop
+    IL_0024:  ldc.i4.5
+    IL_0025:  call       ""System.Index System.Index.op_Implicit(int)""
+    IL_002a:  call       ""System.Range System.Range.EndAt(System.Index)""
+    IL_002f:  call       ""System.Threading.Tasks.Task<System.Range> Program.FromResult<System.Range>(System.Range)""
+    IL_0034:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<System.Range> System.Threading.Tasks.Task<System.Range>.GetAwaiter()""
+    IL_0039:  stloc.s    V_5
+    IL_003b:  ldloca.s   V_5
+    IL_003d:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<System.Range>.IsCompleted.get""
+    IL_0042:  brtrue.s   IL_0085
+    IL_0044:  ldarg.0
+    IL_0045:  ldc.i4.0
+    IL_0046:  dup
+    IL_0047:  stloc.0
+    IL_0048:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_004d:  ldarg.0
+    IL_004e:  ldloc.s    V_5
+    IL_0050:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Range> Program.<M2>d__2.<>u__1""
+    IL_0055:  ldarg.0
+    IL_0056:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_005b:  ldloca.s   V_5
+    IL_005d:  ldarg.0
+    IL_005e:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<System.Range>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<System.Range>, ref Program.<M2>d__2)""
+    IL_0063:  leave      IL_0116
+    IL_0068:  ldarg.0
+    IL_0069:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<System.Range> Program.<M2>d__2.<>u__1""
+    IL_006e:  stloc.s    V_5
+    IL_0070:  ldarg.0
+    IL_0071:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<System.Range> Program.<M2>d__2.<>u__1""
+    IL_0076:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<System.Range>""
+    IL_007c:  ldarg.0
+    IL_007d:  ldc.i4.m1
+    IL_007e:  dup
+    IL_007f:  stloc.0
+    IL_0080:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0085:  ldloca.s   V_5
+    IL_0087:  call       ""System.Range System.Runtime.CompilerServices.TaskAwaiter<System.Range>.GetResult()""
+    IL_008c:  stloc.2
+    IL_008d:  ldloca.s   V_2
+    IL_008f:  call       ""System.Index System.Range.Start.get""
+    IL_0094:  stloc.s    V_6
+    IL_0096:  ldloca.s   V_6
+    IL_0098:  ldc.i4.s   10
+    IL_009a:  call       ""int System.Index.GetOffset(int)""
+    IL_009f:  stloc.3
+    IL_00a0:  ldloca.s   V_2
+    IL_00a2:  call       ""System.Index System.Range.End.get""
+    IL_00a7:  stloc.s    V_6
+    IL_00a9:  ldloca.s   V_6
+    IL_00ab:  ldc.i4.s   10
+    IL_00ad:  call       ""int System.Index.GetOffset(int)""
+    IL_00b2:  ldloc.3
+    IL_00b3:  sub
+    IL_00b4:  stloc.s    V_4
+    IL_00b6:  ldarg.0
+    IL_00b7:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_00bc:  ldflda     ""Buffer10<int> C.F""
+    IL_00c1:  ldc.i4.s   10
+    IL_00c3:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_00c8:  stloc.s    V_7
+    IL_00ca:  ldloca.s   V_7
+    IL_00cc:  ldloc.3
+    IL_00cd:  ldloc.s    V_4
+    IL_00cf:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+    IL_00d4:  stloc.s    V_7
+    IL_00d6:  ldloca.s   V_7
+    IL_00d8:  ldc.i4.0
+    IL_00d9:  call       ""ref int System.Span<int>.this[int].get""
+    IL_00de:  ldc.i4.s   111
+    IL_00e0:  stind.i4
+    IL_00e1:  ldarg.0
+    IL_00e2:  ldnull
+    IL_00e3:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_00e8:  leave.s    IL_0103
+  }
+  catch System.Exception
+  {
+    IL_00ea:  stloc.s    V_8
+    IL_00ec:  ldarg.0
+    IL_00ed:  ldc.i4.s   -2
+    IL_00ef:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00f4:  ldarg.0
+    IL_00f5:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00fa:  ldloc.s    V_8
+    IL_00fc:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_0101:  leave.s    IL_0116
+  }
+  IL_0103:  ldarg.0
+  IL_0104:  ldc.i4.s   -2
+  IL_0106:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_010b:  ldarg.0
+  IL_010c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_0111:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_0116:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Await_04()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static async Task M2(C x) => GetC(x).F[Get01()..Get5()][Get02()] = await FromResult(111);
+    static C GetC(C x) => x;
+    static int Get01() => 0;
+    static int Get5() => 5;
+    static int Get02() => 0;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      279 (0x117)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.Span<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0085
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  call       ""C Program.GetC(C)""
+    IL_0016:  stfld      ""C Program.<M2>d__2.<>7__wrap4""
+    IL_001b:  ldarg.0
+    IL_001c:  ldfld      ""C Program.<M2>d__2.<>7__wrap4""
+    IL_0021:  ldfld      ""Buffer10<int> C.F""
+    IL_0026:  pop
+    IL_0027:  call       ""int Program.Get01()""
+    IL_002c:  stloc.1
+    IL_002d:  ldarg.0
+    IL_002e:  ldloc.1
+    IL_002f:  stfld      ""int Program.<M2>d__2.<>7__wrap1""
+    IL_0034:  ldarg.0
+    IL_0035:  call       ""int Program.Get5()""
+    IL_003a:  ldloc.1
+    IL_003b:  sub
+    IL_003c:  stfld      ""int Program.<M2>d__2.<>7__wrap2""
+    IL_0041:  ldarg.0
+    IL_0042:  call       ""int Program.Get02()""
+    IL_0047:  stfld      ""int Program.<M2>d__2.<>7__wrap3""
+    IL_004c:  ldc.i4.s   111
+    IL_004e:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_0053:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0058:  stloc.3
+    IL_0059:  ldloca.s   V_3
+    IL_005b:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0060:  brtrue.s   IL_00a1
+    IL_0062:  ldarg.0
+    IL_0063:  ldc.i4.0
+    IL_0064:  dup
+    IL_0065:  stloc.0
+    IL_0066:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_006b:  ldarg.0
+    IL_006c:  ldloc.3
+    IL_006d:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0072:  ldarg.0
+    IL_0073:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0078:  ldloca.s   V_3
+    IL_007a:  ldarg.0
+    IL_007b:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_0080:  leave      IL_0116
+    IL_0085:  ldarg.0
+    IL_0086:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_008b:  stloc.3
+    IL_008c:  ldarg.0
+    IL_008d:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0092:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_0098:  ldarg.0
+    IL_0099:  ldc.i4.m1
+    IL_009a:  dup
+    IL_009b:  stloc.0
+    IL_009c:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00a1:  ldloca.s   V_3
+    IL_00a3:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_00a8:  stloc.2
+    IL_00a9:  ldarg.0
+    IL_00aa:  ldfld      ""C Program.<M2>d__2.<>7__wrap4""
+    IL_00af:  ldflda     ""Buffer10<int> C.F""
+    IL_00b4:  ldc.i4.s   10
+    IL_00b6:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_00bb:  stloc.s    V_4
+    IL_00bd:  ldloca.s   V_4
+    IL_00bf:  ldarg.0
+    IL_00c0:  ldfld      ""int Program.<M2>d__2.<>7__wrap1""
+    IL_00c5:  ldarg.0
+    IL_00c6:  ldfld      ""int Program.<M2>d__2.<>7__wrap2""
+    IL_00cb:  call       ""System.Span<int> System.Span<int>.Slice(int, int)""
+    IL_00d0:  stloc.s    V_4
+    IL_00d2:  ldloca.s   V_4
+    IL_00d4:  ldarg.0
+    IL_00d5:  ldfld      ""int Program.<M2>d__2.<>7__wrap3""
+    IL_00da:  call       ""ref int System.Span<int>.this[int].get""
+    IL_00df:  ldloc.2
+    IL_00e0:  stind.i4
+    IL_00e1:  ldarg.0
+    IL_00e2:  ldnull
+    IL_00e3:  stfld      ""C Program.<M2>d__2.<>7__wrap4""
+    IL_00e8:  leave.s    IL_0103
+  }
+  catch System.Exception
+  {
+    IL_00ea:  stloc.s    V_5
+    IL_00ec:  ldarg.0
+    IL_00ed:  ldc.i4.s   -2
+    IL_00ef:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00f4:  ldarg.0
+    IL_00f5:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00fa:  ldloc.s    V_5
+    IL_00fc:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_0101:  leave.s    IL_0116
+  }
+  IL_0103:  ldarg.0
+  IL_0104:  ldc.i4.s   -2
+  IL_0106:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_010b:  ldarg.0
+  IL_010c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_0111:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_0116:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Await_05()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public readonly Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => GetC(x).F[GetRange()][await FromResult(Get01(x))];
+
+    static C GetC(C x) => x;
+    static System.Range GetRange() => 0..5;
+    static int Get01(C c)
+    {
+        System.Runtime.CompilerServices.Unsafe.AsRef(in c.F)[0] = 111;
+        return 0;
+    }
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      310 (0x136)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Range V_2,
+                int V_3,
+                int V_4,
+                int V_5,
+                System.Index V_6,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_7,
+                System.ReadOnlySpan<int> V_8,
+                System.Exception V_9)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse    IL_00ac
+    IL_000d:  ldarg.0
+    IL_000e:  ldarg.0
+    IL_000f:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0014:  call       ""C Program.GetC(C)""
+    IL_0019:  stfld      ""C Program.<M1>d__1.<>7__wrap3""
+    IL_001e:  ldarg.0
+    IL_001f:  ldfld      ""C Program.<M1>d__1.<>7__wrap3""
+    IL_0024:  ldfld      ""Buffer10<int> C.F""
+    IL_0029:  pop
+    IL_002a:  call       ""System.Range Program.GetRange()""
+    IL_002f:  stloc.2
+    IL_0030:  ldloca.s   V_2
+    IL_0032:  call       ""System.Index System.Range.Start.get""
+    IL_0037:  stloc.s    V_6
+    IL_0039:  ldloca.s   V_6
+    IL_003b:  ldc.i4.s   10
+    IL_003d:  call       ""int System.Index.GetOffset(int)""
+    IL_0042:  stloc.3
+    IL_0043:  ldloca.s   V_2
+    IL_0045:  call       ""System.Index System.Range.End.get""
+    IL_004a:  stloc.s    V_6
+    IL_004c:  ldloca.s   V_6
+    IL_004e:  ldc.i4.s   10
+    IL_0050:  call       ""int System.Index.GetOffset(int)""
+    IL_0055:  ldloc.3
+    IL_0056:  sub
+    IL_0057:  stloc.s    V_4
+    IL_0059:  ldarg.0
+    IL_005a:  ldloc.3
+    IL_005b:  stfld      ""int Program.<M1>d__1.<>7__wrap1""
+    IL_0060:  ldarg.0
+    IL_0061:  ldloc.s    V_4
+    IL_0063:  stfld      ""int Program.<M1>d__1.<>7__wrap2""
+    IL_0068:  ldarg.0
+    IL_0069:  ldfld      ""C Program.<M1>d__1.x""
+    IL_006e:  call       ""int Program.Get01(C)""
+    IL_0073:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_0078:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_007d:  stloc.s    V_7
+    IL_007f:  ldloca.s   V_7
+    IL_0081:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0086:  brtrue.s   IL_00c9
+    IL_0088:  ldarg.0
+    IL_0089:  ldc.i4.0
+    IL_008a:  dup
+    IL_008b:  stloc.0
+    IL_008c:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0091:  ldarg.0
+    IL_0092:  ldloc.s    V_7
+    IL_0094:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0099:  ldarg.0
+    IL_009a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_009f:  ldloca.s   V_7
+    IL_00a1:  ldarg.0
+    IL_00a2:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_00a7:  leave      IL_0135
+    IL_00ac:  ldarg.0
+    IL_00ad:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_00b2:  stloc.s    V_7
+    IL_00b4:  ldarg.0
+    IL_00b5:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_00ba:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_00c0:  ldarg.0
+    IL_00c1:  ldc.i4.m1
+    IL_00c2:  dup
+    IL_00c3:  stloc.0
+    IL_00c4:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_00c9:  ldloca.s   V_7
+    IL_00cb:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_00d0:  stloc.s    V_5
+    IL_00d2:  ldarg.0
+    IL_00d3:  ldfld      ""C Program.<M1>d__1.<>7__wrap3""
+    IL_00d8:  ldflda     ""Buffer10<int> C.F""
+    IL_00dd:  ldc.i4.s   10
+    IL_00df:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_00e4:  stloc.s    V_8
+    IL_00e6:  ldloca.s   V_8
+    IL_00e8:  ldarg.0
+    IL_00e9:  ldfld      ""int Program.<M1>d__1.<>7__wrap1""
+    IL_00ee:  ldarg.0
+    IL_00ef:  ldfld      ""int Program.<M1>d__1.<>7__wrap2""
+    IL_00f4:  call       ""System.ReadOnlySpan<int> System.ReadOnlySpan<int>.Slice(int, int)""
+    IL_00f9:  stloc.s    V_8
+    IL_00fb:  ldloca.s   V_8
+    IL_00fd:  ldloc.s    V_5
+    IL_00ff:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+    IL_0104:  ldind.i4
+    IL_0105:  stloc.1
+    IL_0106:  leave.s    IL_0121
+  }
+  catch System.Exception
+  {
+    IL_0108:  stloc.s    V_9
+    IL_010a:  ldarg.0
+    IL_010b:  ldc.i4.s   -2
+    IL_010d:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0112:  ldarg.0
+    IL_0113:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0118:  ldloc.s    V_9
+    IL_011a:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_011f:  leave.s    IL_0135
+  }
+  IL_0121:  ldarg.0
+  IL_0122:  ldc.i4.s   -2
+  IL_0124:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0129:  ldarg.0
+  IL_012a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_012f:  ldloc.1
+  IL_0130:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_0135:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_ObjectInitializer_Int_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().F[0]);
+    }
+
+    static C M2() => new C() { F = {[0] = 111} };
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            // According to the language specification: "an argument_list enclosed in square brackets shall specify arguments for an accessible indexer on the object being initialized"
+            // Buffer10<int> doesn't have an indexer.
+            comp.VerifyDiagnostics(
+                // (14,37): error CS0021: Cannot apply indexing with [] to an expression of type 'Buffer10<int>'
+                //     static C M2() => new C() { F = {[0] = 111} };
+                Diagnostic(ErrorCode.ERR_BadIndexLHS, "[0]").WithArguments("Buffer10<int>").WithLocation(14, 37)
+                );
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<AssignmentExpressionSyntax>().Last().Left;
+            Assert.Equal("[0]", f.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.True(typeInfo.Type.IsErrorType());
+
+            var symbolInfo = model.GetSymbolInfo(f);
+
+            Assert.Null(symbolInfo.Symbol);
+            Assert.Empty(symbolInfo.CandidateSymbols);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ObjectInitializer_Int_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().F[0]);
+    }
+
+    static C M2() => new C() { F = {[0] = 111} };
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10<T>
+{
+    private T _element0;
+
+    public T this[int i]
+    {
+        get => this[i];
+        set => this[i] = value;
+    }
+}
+";
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       20 (0x14)
+  .maxstack  4
+  IL_0000:  newobj     ""C..ctor()""
+  IL_0005:  dup
+  IL_0006:  ldflda     ""Buffer10<int> C.F""
+  IL_000b:  ldc.i4.0
+  IL_000c:  ldc.i4.s   111
+  IL_000e:  call       ""void Buffer10<int>.this[int].set""
+  IL_0013:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_ObjectInitializer_Index_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().F[0]);
+    }
+
+    static C M2() => new C() { F = {[^10] = 111} };
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            // According to the language specification: "an argument_list enclosed in square brackets shall specify arguments for an accessible indexer on the object being initialized"
+            // Buffer10<int> doesn't have an indexer.
+            comp.VerifyDiagnostics(
+                // (14,37): error CS0021: Cannot apply indexing with [] to an expression of type 'Buffer10<int>'
+                //     static C M2() => new C() { F = {[^10] = 111} };
+                Diagnostic(ErrorCode.ERR_BadIndexLHS, "[^10]").WithArguments("Buffer10<int>").WithLocation(14, 37)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_ObjectInitializer_Index_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().F[0]);
+    }
+
+    static C M2() => new C() { F = {[^10] = 111} };
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10<T>
+{
+    private T _element0;
+
+    public T this[int i]
+    {
+        get => this[i];
+        set => this[i] = value;
+    }
+
+    public int Length => 10;
+}
+";
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            // This scenario fails due to https://github.com/dotnet/roslyn/issues/67533
+            comp.VerifyDiagnostics(
+                // (14,37): error CS1913: Member '[^10]' cannot be initialized. It is not a field or property.
+                //     static C M2() => new C() { F = {[^10] = 111} };
+                Diagnostic(ErrorCode.ERR_MemberCannotBeInitialized, "[^10]").WithArguments("[^10]").WithLocation(14, 37)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_ObjectInitializer_Range_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2().F[0]);
+    }
+
+    static C M2() => new C() { F = {[0..1] = 111} };
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            // According to the language specification: "an argument_list enclosed in square brackets shall specify arguments for an accessible indexer on the object being initialized"
+            // Buffer10<int> doesn't have an indexer.
+            comp.VerifyDiagnostics(
+                // (14,37): error CS0021: Cannot apply indexing with [] to an expression of type 'Buffer10<int>'
+                //     static C M2() => new C() { F = {[0..1] = 111} };
+                Diagnostic(ErrorCode.ERR_BadIndexLHS, "[0..1]").WithArguments("Buffer10<int>").WithLocation(14, 37)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ConditionalAccess_Variable()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        c.F[0] = 111;
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C c) => c?.F[0];
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       31 (0x1f)
+  .maxstack  1
+  .locals init (int? V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  brtrue.s   IL_000d
+  IL_0003:  ldloca.s   V_0
+  IL_0005:  initobj    ""int?""
+  IL_000b:  ldloc.0
+  IL_000c:  ret
+  IL_000d:  ldarg.0
+  IL_000e:  ldflda     ""Buffer10<int> C.F""
+  IL_0013:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_0018:  ldind.i4
+  IL_0019:  newobj     ""int?..ctor(int)""
+  IL_001e:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.RegularNext);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular11);
+            comp.VerifyDiagnostics(
+                // (12,9): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         c.F[0] = 111;
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "c.F[0]").WithArguments("inline arrays").WithLocation(12, 9),
+                // (16,30): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static int? M2(C c) => c?.F[0];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, ".F[0]").WithArguments("inline arrays").WithLocation(16, 30)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_ConditionalAccess_Variable()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        c.F[0] = 111;
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C c) => c?.F[..5][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       41 (0x29)
+  .maxstack  2
+  .locals init (int? V_0,
+                System.Span<int> V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  brtrue.s   IL_000d
+  IL_0003:  ldloca.s   V_0
+  IL_0005:  initobj    ""int?""
+  IL_000b:  ldloc.0
+  IL_000c:  ret
+  IL_000d:  ldarg.0
+  IL_000e:  ldflda     ""Buffer10<int> C.F""
+  IL_0013:  ldc.i4.5
+  IL_0014:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_0019:  stloc.1
+  IL_001a:  ldloca.s   V_1
+  IL_001c:  ldc.i4.0
+  IL_001d:  call       ""ref int System.Span<int>.this[int].get""
+  IL_0022:  ldind.i4
+  IL_0023:  newobj     ""int?..ctor(int)""
+  IL_0028:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ConditionalAccess_Value_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int>? F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C c) => c.F?[0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       45 (0x2d)
+  .maxstack  2
+  .locals init (int? V_0,
+                Buffer10<int> V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int>? C.F""
+  IL_0006:  dup
+  IL_0007:  call       ""readonly bool Buffer10<int>?.HasValue.get""
+  IL_000c:  brtrue.s   IL_0019
+  IL_000e:  pop
+  IL_000f:  ldloca.s   V_0
+  IL_0011:  initobj    ""int?""
+  IL_0017:  ldloc.0
+  IL_0018:  ret
+  IL_0019:  call       ""readonly Buffer10<int> Buffer10<int>?.GetValueOrDefault()""
+  IL_001e:  stloc.1
+  IL_001f:  ldloca.s   V_1
+  IL_0021:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_0026:  ldind.i4
+  IL_0027:  newobj     ""int?..ctor(int)""
+  IL_002c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ConditionalAccess_Value_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int>? F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C c) => c.F?[M3(default)];
+
+    static int M3(Buffer10<int> x) => 0;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       69 (0x45)
+  .maxstack  2
+  .locals init (int? V_0,
+                Buffer10<int> V_1,
+                System.ReadOnlySpan<int> V_2,
+                Buffer10<int> V_3)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int>? C.F""
+  IL_0006:  dup
+  IL_0007:  call       ""readonly bool Buffer10<int>?.HasValue.get""
+  IL_000c:  brtrue.s   IL_0019
+  IL_000e:  pop
+  IL_000f:  ldloca.s   V_0
+  IL_0011:  initobj    ""int?""
+  IL_0017:  ldloc.0
+  IL_0018:  ret
+  IL_0019:  call       ""readonly Buffer10<int> Buffer10<int>?.GetValueOrDefault()""
+  IL_001e:  stloc.1
+  IL_001f:  ldloca.s   V_1
+  IL_0021:  ldc.i4.s   10
+  IL_0023:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_0028:  stloc.2
+  IL_0029:  ldloca.s   V_2
+  IL_002b:  ldloca.s   V_3
+  IL_002d:  initobj    ""Buffer10<int>""
+  IL_0033:  ldloc.3
+  IL_0034:  call       ""int Program.M3(Buffer10<int>)""
+  IL_0039:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+  IL_003e:  ldind.i4
+  IL_003f:  newobj     ""int?..ctor(int)""
+  IL_0044:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ConditionalAccess_Value_03()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C? c) => c?.F[0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       46 (0x2e)
+  .maxstack  1
+  .locals init (int? V_0,
+                Buffer10<int> V_1)
+  IL_0000:  ldarga.s   V_0
+  IL_0002:  call       ""readonly bool C?.HasValue.get""
+  IL_0007:  brtrue.s   IL_0013
+  IL_0009:  ldloca.s   V_0
+  IL_000b:  initobj    ""int?""
+  IL_0011:  ldloc.0
+  IL_0012:  ret
+  IL_0013:  ldarga.s   V_0
+  IL_0015:  call       ""readonly C C?.GetValueOrDefault()""
+  IL_001a:  ldfld      ""Buffer10<int> C.F""
+  IL_001f:  stloc.1
+  IL_0020:  ldloca.s   V_1
+  IL_0022:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_0027:  ldind.i4
+  IL_0028:  newobj     ""int?..ctor(int)""
+  IL_002d:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ConditionalAccess_Value_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C? c) => c?.F[M3(default)];
+
+    static int M3(Buffer10<int> x) => 0;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       70 (0x46)
+  .maxstack  2
+  .locals init (int? V_0,
+                Buffer10<int> V_1,
+                System.ReadOnlySpan<int> V_2,
+                Buffer10<int> V_3)
+  IL_0000:  ldarga.s   V_0
+  IL_0002:  call       ""readonly bool C?.HasValue.get""
+  IL_0007:  brtrue.s   IL_0013
+  IL_0009:  ldloca.s   V_0
+  IL_000b:  initobj    ""int?""
+  IL_0011:  ldloc.0
+  IL_0012:  ret
+  IL_0013:  ldarga.s   V_0
+  IL_0015:  call       ""readonly C C?.GetValueOrDefault()""
+  IL_001a:  ldfld      ""Buffer10<int> C.F""
+  IL_001f:  stloc.1
+  IL_0020:  ldloca.s   V_1
+  IL_0022:  ldc.i4.s   10
+  IL_0024:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_0029:  stloc.2
+  IL_002a:  ldloca.s   V_2
+  IL_002c:  ldloca.s   V_3
+  IL_002e:  initobj    ""Buffer10<int>""
+  IL_0034:  ldloc.3
+  IL_0035:  call       ""int Program.M3(Buffer10<int>)""
+  IL_003a:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+  IL_003f:  ldind.i4
+  IL_0040:  newobj     ""int?..ctor(int)""
+  IL_0045:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Slice_ConditionalAccess_Value_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int>? F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C c) => c.F?[..5][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (17,28): error CS8156: An expression cannot be used in this context because it may not be passed or returned by reference
+                //     static int? M2(C c) => c.F?[..5][0];
+                Diagnostic(ErrorCode.ERR_RefReturnLvalueExpected, "c.F?").WithLocation(17, 28)
+                );
+        }
+
+        [Fact]
+        public void Slice_ConditionalAccess_Value_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int>? F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C c) => c.F?[M3(default)..][M3(default)];
+
+    static int M3(Buffer10<int> x) => 0;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (17,28): error CS8156: An expression cannot be used in this context because it may not be passed or returned by reference
+                //     static int? M2(C c) => c.F?[M3(default)..][M3(default)];
+                Diagnostic(ErrorCode.ERR_RefReturnLvalueExpected, "c.F?").WithLocation(17, 28)
+                );
+        }
+
+        [Fact]
+        public void Slice_ConditionalAccess_Value_03()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C? c) => c?.F[..5][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (17,31): error CS8156: An expression cannot be used in this context because it may not be passed or returned by reference
+                //     static int? M2(C? c) => c?.F[..5][0];
+                Diagnostic(ErrorCode.ERR_RefReturnLvalueExpected, ".F").WithLocation(17, 31)
+                );
+        }
+
+        [Fact]
+        public void Slice_ConditionalAccess_Value_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        var c = new C() { F = b };
+        System.Console.Write(M2(c));
+    }
+
+    static int? M2(C? c) => c?.F[M3(default)..][M3(default)];
+
+    static int M3(Buffer10<int> x) => 0;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (17,31): error CS8156: An expression cannot be used in this context because it may not be passed or returned by reference
+                //     static int? M2(C? c) => c?.F[M3(default)..][M3(default)];
+                Diagnostic(ErrorCode.ERR_RefReturnLvalueExpected, ".F").WithLocation(17, 31)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_NotValue()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        _ = Buffer10<int>[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (6,13): error CS0119: 'Buffer10<int>' is a type, which is not valid in the given context
+                //         _ = Buffer10<int>[0];
+                Diagnostic(ErrorCode.ERR_BadSKunknown, "Buffer10<int>").WithArguments("Buffer10<int>", "type").WithLocation(6, 13)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Value_01()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2() => M4(M3()[0], default);
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static int M4(in int x, Buffer10<int> y)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       32 (0x20)
+  .maxstack  2
+  .locals init (Buffer10<int> V_0,
+                int V_1)
+  IL_0000:  call       ""Buffer10<int> Program.M3()""
+  IL_0005:  stloc.0
+  IL_0006:  ldloca.s   V_0
+  IL_0008:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000d:  ldind.i4
+  IL_000e:  stloc.1
+  IL_000f:  ldloca.s   V_1
+  IL_0011:  ldloca.s   V_0
+  IL_0013:  initobj    ""Buffer10<int>""
+  IL_0019:  ldloc.0
+  IL_001a:  call       ""int Program.M4(in int, Buffer10<int>)""
+  IL_001f:  ret
+}
+");
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var m3 = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "M3").Single().Parent;
+            Assert.Equal("M3()[0]", m3.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(m3);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            var symbolInfo = model.GetSymbolInfo(m3);
+
+            Assert.Equal("Buffer10<System.Int32> Program.M3()", symbolInfo.Symbol.ToTestDisplayString());
+
+            var access = m3.Parent;
+            typeInfo = model.GetTypeInfo(access);
+
+            Assert.Equal("System.Int32", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
+
+            symbolInfo = model.GetSymbolInfo(access);
+
+            Assert.Null(symbolInfo.Symbol);
+            Assert.Empty(symbolInfo.CandidateSymbols);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Value_02()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2() => M3()[M4(default)];
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static int M4(Buffer10<int> y)
+    {
+        return 0;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       39 (0x27)
+  .maxstack  2
+  .locals init (Buffer10<int> V_0,
+                System.ReadOnlySpan<int> V_1,
+                Buffer10<int> V_2)
+  IL_0000:  call       ""Buffer10<int> Program.M3()""
+  IL_0005:  stloc.0
+  IL_0006:  ldloca.s   V_0
+  IL_0008:  ldc.i4.s   10
+  IL_000a:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000f:  stloc.1
+  IL_0010:  ldloca.s   V_1
+  IL_0012:  ldloca.s   V_2
+  IL_0014:  initobj    ""Buffer10<int>""
+  IL_001a:  ldloc.2
+  IL_001b:  call       ""int Program.M4(Buffer10<int>)""
+  IL_0020:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+  IL_0025:  ldind.i4
+  IL_0026:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_Value_03()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2()
+    {
+        ref readonly int x = M3()[0];
+        return x;
+    }
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (11,26): error CS8172: Cannot initialize a by-reference variable with a value
+                //         ref readonly int x = M3()[0];
+                Diagnostic(ErrorCode.ERR_InitializeByReferenceVariableWithValue, "x = M3()[0]").WithLocation(11, 26),
+                // (11,30): error CS8156: An expression cannot be used in this context because it may not be passed or returned by reference
+                //         ref readonly int x = M3()[0];
+                Diagnostic(ErrorCode.ERR_RefReturnLvalueExpected, "M3()[0]").WithLocation(11, 30)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Value_04()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2()
+    {
+        return M4(ref M3()[0]);
+    }
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static int M4(ref int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (11,23): error CS1510: A ref or out value must be an assignable variable
+                //         return M4(ref M3()[0]);
+                Diagnostic(ErrorCode.ERR_RefLvalueExpected, "M3()[0]").WithLocation(11, 23)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Value_05()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2()
+    {
+        return M4(in M3()[0]);
+    }
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static int M4(in int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                    // (11,22): error CS8156: An expression cannot be used in this context because it may not be passed or returned by reference
+                    //         return M4(in M3()[0]);
+                    Diagnostic(ErrorCode.ERR_RefReturnLvalueExpected, "M3()[0]").WithLocation(11, 22)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Value_06()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2()
+    {
+        return M4(M3()[0]);
+    }
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static int M4(in int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       23 (0x17)
+  .maxstack  1
+  .locals init (Buffer10<int> V_0,
+                int V_1)
+  IL_0000:  call       ""Buffer10<int> Program.M3()""
+  IL_0005:  stloc.0
+  IL_0006:  ldloca.s   V_0
+  IL_0008:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000d:  ldind.i4
+  IL_000e:  stloc.1
+  IL_000f:  ldloca.s   V_1
+  IL_0011:  call       ""int Program.M4(in int)""
+  IL_0016:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Value_07()
+        {
+            var src = @"
+class Program
+{
+    static System.Span<int> M1()
+    {
+        System.Span<int> x = stackalloc int[2];
+        return M3(x)[0];
+    }
+
+    static System.Span<int> M2()
+    {
+        System.Span<int> x = stackalloc int[2];
+        var y = M3(x)[0];
+        return y;
+    }
+
+    static Buffer10 M3(System.Span<int> x)
+    {
+        throw null;
+    }
+
+    static System.Span<int> M1(System.Span<int> xx)
+    {
+        return M3(xx)[0];
+    }
+
+    static System.Span<int> M2(System.Span<int> xx)
+    {
+        var yy = M3(xx)[0];
+        return yy;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public ref struct Buffer10
+{
+    private System.Span<int> _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (7,16): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //         return M3(x)[0];
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "M3(x)[0]").WithArguments("System.Span<int>").WithLocation(7, 16),
+                // (7,16): error CS8347: Cannot use a result of 'Program.M3(Span<int>)' in this context because it may expose variables referenced by parameter 'x' outside of their declaration scope
+                //         return M3(x)[0];
+                Diagnostic(ErrorCode.ERR_EscapeCall, "M3(x)").WithArguments("Program.M3(System.Span<int>)", "x").WithLocation(7, 16),
+                // (7,19): error CS8352: Cannot use variable 'x' in this context because it may expose referenced variables outside of their declaration scope
+                //         return M3(x)[0];
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "x").WithArguments("x").WithLocation(7, 19),
+                // (13,17): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //         var y = M3(x)[0];
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "M3(x)[0]").WithArguments("System.Span<int>").WithLocation(13, 17),
+                // (14,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(14, 16),
+                // (24,16): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //         return M3(xx)[0];
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "M3(xx)[0]").WithArguments("System.Span<int>").WithLocation(24, 16),
+                // (29,18): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //         var yy = M3(xx)[0];
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "M3(xx)[0]").WithArguments("System.Span<int>").WithLocation(29, 18)
+                );
+        }
+
+        [Fact]
+        public void Slice_NotValue()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        _ = Buffer10<int>[..5];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (6,13): error CS0119: 'Buffer10<int>' is a type, which is not valid in the given context
+                //         _ = Buffer10<int>[..5];
+                Diagnostic(ErrorCode.ERR_BadSKunknown, "Buffer10<int>").WithArguments("Buffer10<int>", "type").WithLocation(6, 13)
+                );
+        }
+
+        [Fact]
+        public void Slice_Value_01()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2() => M4(M3()[..], default);
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static int M4(System.ReadOnlySpan<int> x, Buffer10<int> y)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (9,27): error CS8156: An expression cannot be used in this context because it may not be passed or returned by reference
+                //     static int M2() => M4(M3()[..], default);
+                Diagnostic(ErrorCode.ERR_RefReturnLvalueExpected, "M3()").WithLocation(9, 27)
+                );
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var m3 = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "M3").Single();
+            Assert.Equal("M3()[..]", m3.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(m3.Parent);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            var symbolInfo = model.GetSymbolInfo(m3.Parent);
+
+            Assert.Equal("Buffer10<System.Int32> Program.M3()", symbolInfo.Symbol.ToTestDisplayString());
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_01()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(C c) => c.F[0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_02()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(C c)
+    {
+        ref readonly int x = ref c.F[0];
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_03()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(C c)
+    {
+        return M4(in c.F[0]);
+    }
+
+    static int M4(in int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       17 (0x11)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  call       ""int Program.M4(in int)""
+  IL_0010:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_04()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(C c)
+    {
+        return M4(ref c.F[0]);
+    }
+
+    static int M4(ref int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (23,23): error CS8329: Cannot use method 'this.get' as a ref or out value because it is a readonly variable
+                //         return M4(ref c.F[0]);
+                Diagnostic(ErrorCode.ERR_RefReadonlyNotField, "c.F[0]").WithArguments("method", "this.get").WithLocation(23, 23)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_05()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(C c)
+    {
+        ref readonly int x = ref c.F[0];
+        return ref x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_06()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(C c)
+    {
+        return ref c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_07()
+        {
+            var src = @"
+struct C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(C c)
+    {
+        ref readonly int x = ref c.F[0];
+        return ref x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (24,20): error CS8157: Cannot return 'x' by reference because it was initialized to a value that cannot be returned by reference
+                //         return ref x;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "x").WithArguments("x").WithLocation(24, 20)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_08()
+        {
+            var src = @"
+struct C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(C c)
+    {
+        return ref c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (23,20): error CS8167: Cannot return by reference a member of parameter 'c' because it is not a ref or out parameter
+                //         return ref c.F[0];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "c").WithArguments("c").WithLocation(23, 20)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_09()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly int M2() => F[0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_10()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly int M2()
+    {
+        ref readonly int x = ref F[0];
+        return x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_11()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly int M2()
+    {
+        return M4(in F[0]);
+    }
+
+    static int M4(in int x)
+    {
+        return x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       17 (0x11)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  call       ""int C.M4(in int)""
+  IL_0010:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_12()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly int M2()
+    {
+        return M4(ref F[0]);
+    }
+
+    static int M4(ref int x)
+    {
+        return x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (15,23): error CS8329: Cannot use method 'this.get' as a ref or out value because it is a readonly variable
+                //         return M4(ref F[0]);
+                Diagnostic(ErrorCode.ERR_RefReadonlyNotField, "F[0]").WithArguments("method", "this.get").WithLocation(15, 23)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_13()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly ref readonly int M2()
+    {
+        ref readonly int x = ref F[0];
+        return ref x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (16,20): error CS8157: Cannot return 'x' by reference because it was initialized to a value that cannot be returned by reference
+                //         return ref x;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "x").WithArguments("x").WithLocation(16, 20)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_14()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public readonly ref readonly int M2()
+    {
+        ref readonly int x = ref F[0];
+        return ref x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_15()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly ref readonly int M2()
+    {
+        return ref F[0];
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (15,20): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //         return ref F[0];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(15, 20)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_ReadonlyContext_16()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public readonly ref readonly int M2()
+    {
+        return ref F[0];
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_17()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        c.F[0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (18,9): error CS8331: Cannot assign to method 'this.get' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         c.F[0] = 1;
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField, "c.F[0]").WithArguments("method", "this.get").WithLocation(18, 9)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_ReadonlyContext_18()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    readonly void Main()
+    {
+        F[0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (15,9): error CS8331: Cannot assign to method 'this.get' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         F[0] = 1;
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField, "F[0]").WithArguments("method", "this.get").WithLocation(15, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_ReadonlyContext_01()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[..][0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(C c) => c.F[..5];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_ReadonlyContext_02()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[..][0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(C c)
+    {
+        System.ReadOnlySpan<int> x = c.F[..5];
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_04()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[..][0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(C c)
+    {
+        return M4(c.F[..]);
+    }
+
+    static int M4(System.Span<int> x)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (23,19): error CS1503: Argument 1: cannot convert from 'System.ReadOnlySpan<int>' to 'System.Span<int>'
+                //         return M4(c.F[..]);
+                Diagnostic(ErrorCode.ERR_BadArgType, "c.F[..]").WithArguments("1", "System.ReadOnlySpan<int>", "System.Span<int>").WithLocation(23, 19)
+                );
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_07()
+        {
+            var src = @"
+struct C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[..][0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(C c)
+    {
+        System.ReadOnlySpan<int> x = c.F[..5];
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (24,16): error CS8352: Cannot use variable 'x' in this context because it may expose referenced variables outside of their declaration scope
+                //         return x;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "x").WithArguments("x").WithLocation(24, 16)
+                );
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_08()
+        {
+            var src = @"
+struct C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[..][0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(C c)
+    {
+        return c.F[..5];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (23,16): error CS8167: Cannot return by reference a member of parameter 'c' because it is not a ref or out parameter
+                //         return c.F[..5];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "c").WithArguments("c").WithLocation(23, 16)
+                );
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_09()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly System.ReadOnlySpan<int> M2() => F[..5];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (13,54): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public readonly System.ReadOnlySpan<int> M2() => F[..5];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(13, 54)
+                );
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_10()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly System.ReadOnlySpan<int> M2()
+    {
+        System.ReadOnlySpan<int> x = F[..5];
+        return x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (16,16): error CS8352: Cannot use variable 'x' in this context because it may expose referenced variables outside of their declaration scope
+                //         return x;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "x").WithArguments("x").WithLocation(16, 16)
+                );
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_12()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly int M2()
+    {
+        return M4(F[..]);
+    }
+
+    static int M4(System.Span<int> x)
+    {
+        return x[0];
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2());
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (15,19): error CS1503: Argument 1: cannot convert from 'System.ReadOnlySpan<int>' to 'System.Span<int>'
+                //         return M4(F[..]);
+                Diagnostic(ErrorCode.ERR_BadArgType, "F[..]").WithArguments("1", "System.ReadOnlySpan<int>", "System.Span<int>").WithLocation(15, 19)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_ReadonlyContext_14()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public readonly System.ReadOnlySpan<int> M2()
+    {
+        System.ReadOnlySpan<int> x = F[..5];
+        return x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_ReadonlyContext_16()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public readonly System.ReadOnlySpan<int> M2() => F[..5];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_17()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[..][0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        c.F[..][0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (18,9): error CS8331: Cannot assign to property 'this' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         c.F[..][0] = 1;
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField, "c.F[..][0]").WithArguments("property", "this").WithLocation(18, 9)
+                );
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_18()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    readonly void Main()
+    {
+        F[..][0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (15,9): error CS8331: Cannot assign to property 'this' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         F[..][0] = 1;
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField, "F[..][0]").WithArguments("property", "this").WithLocation(15, 9)
+                );
+        }
+
+        [Fact]
+        public void Slice_ReadonlyContext_IsRValue()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        F[..][0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        c.F[..5] = default;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (18,9): error CS0131: The left-hand side of an assignment must be a variable, property or indexer
+                //         c.F[..5] = default;
+                Diagnostic(ErrorCode.ERR_AssgLvalueExpected, "c.F[..5]").WithLocation(18, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_01()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c) => c.F[0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "F").Last();
+            Assert.Equal("c.F[0]", f.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            var symbolInfo = model.GetSymbolInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32> C.F", symbolInfo.Symbol.ToTestDisplayString());
+
+            var access = f.Parent.Parent;
+            typeInfo = model.GetTypeInfo(access);
+
+            Assert.Equal("System.Int32", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Int32", typeInfo.ConvertedType.ToTestDisplayString());
+
+            symbolInfo = model.GetSymbolInfo(access);
+
+            Assert.Null(symbolInfo.Symbol);
+            Assert.Empty(symbolInfo.CandidateSymbols);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_02()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        ref readonly int x = ref c.F[0];
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_03()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        return M4(in c.F[0]);
+    }
+
+    static int M4(in int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       17 (0x11)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  call       ""int Program.M4(in int)""
+  IL_0010:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_Readonly_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        return M4(ref c.F[0]);
+    }
+
+    static int M4(ref int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (24,23): error CS8329: Cannot use method 'this.get' as a ref or out value because it is a readonly variable
+                //         return M4(ref c.F[0]);
+                Diagnostic(ErrorCode.ERR_RefReadonlyNotField, "c.F[0]").WithArguments("method", "this.get").WithLocation(24, 23)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_05()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(in C c)
+    {
+        ref readonly int x = ref c.F[0];
+        return ref x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_06()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(in C c)
+    {
+        return ref c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_Readonly_07()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        M2(c);
+    }
+
+    static void M2(in C c)
+    {
+        c.F[0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (24,9): error CS8331: Cannot assign to method 'this.get' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         c.F[0] = 1;
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField, "c.F[0]").WithArguments("method", "this.get").WithLocation(24, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_08()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public C()
+    {
+        var b = new Buffer10<Buffer10<int>>();
+        b[0][0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c) => c.F[0][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_09()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public C()
+    {
+        var b = new Buffer10<Buffer10<int>>();
+        b[0][0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        ref readonly int x = ref c.F[0][0];
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_10()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public C()
+    {
+        var b = new Buffer10<Buffer10<int>>();
+        b[0][0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        return M4(in c.F[0][0]);
+    }
+
+    static int M4(in int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_Readonly_11()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public C()
+    {
+        var b = new Buffer10<Buffer10<int>>();
+        b[0][0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        return M4(ref c.F[0][0]);
+    }
+
+    static int M4(ref int x)
+    {
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (24,23): error CS8329: Cannot use method 'this.get' as a ref or out value because it is a readonly variable
+                //         return M4(ref c.F[0][0]);
+                Diagnostic(ErrorCode.ERR_RefReadonlyNotField, "c.F[0][0]").WithArguments("method", "this.get").WithLocation(24, 23)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_12()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public C()
+    {
+        var b = new Buffer10<Buffer10<int>>();
+        b[0][0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(in C c)
+    {
+        ref readonly int x = ref c.F[0][0];
+        return ref x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_13()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public C()
+    {
+        var b = new Buffer10<Buffer10<int>>();
+        b[0][0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static ref readonly int M2(in C c)
+    {
+        return ref c.F[0][0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111").VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void ElementAccess_Variable_Readonly_14()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public C()
+    {
+        var b = new Buffer10<Buffer10<int>>();
+        b[0][0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        M2(c);
+    }
+
+    static void M2(in C c)
+    {
+        c.F[0][0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (24,9): error CS8331: Cannot assign to method 'this.get' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         c.F[0][0] = 1;
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField, "c.F[0][0]").WithArguments("method", "this.get").WithLocation(24, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_19()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        var i = 1;
+        b[i] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c) => c.F[1];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.1
+  IL_0007:  call       ""InlineArrayElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000c:  ldind.i4
+  IL_000d:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_20()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        var i = 9;
+        b[i] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c) => c.F[9];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   9
+  IL_0008:  call       ""InlineArrayElementRefReadOnly<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ldind.i4
+  IL_000e:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Variable_Readonly_21()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        var i = 0;
+        b[i] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c, 0));
+    }
+
+    static int M2(in C c, int i) => c.F[i];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       24 (0x18)
+  .maxstack  2
+  .locals init (System.ReadOnlySpan<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldarg.1
+  IL_0011:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+  IL_0016:  ldind.i4
+  IL_0017:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_Readonly_01()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(in C c) => c.F[..5];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "F").Last();
+            Assert.Equal("c.F[..5]", f.Parent.Parent.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            var symbolInfo = model.GetSymbolInfo(f);
+
+            Assert.Equal("Buffer10<System.Int32> C.F", symbolInfo.Symbol.ToTestDisplayString());
+
+            var access = f.Parent.Parent;
+            typeInfo = model.GetTypeInfo(access);
+
+            Assert.Equal("System.ReadOnlySpan<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.ReadOnlySpan<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            symbolInfo = model.GetSymbolInfo(access);
+
+            Assert.Null(symbolInfo.Symbol);
+            Assert.Empty(symbolInfo.CandidateSymbols);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_Readonly_02()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(in C c)
+    {
+        System.ReadOnlySpan<int> x = c.F[..5];
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Slice_Variable_Readonly_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        return M4(c.F[..]);
+    }
+
+    static int M4(System.Span<int> x)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (24,19): error CS1503: Argument 1: cannot convert from 'System.ReadOnlySpan<int>' to 'System.Span<int>'
+                //         return M4(c.F[..]);
+                Diagnostic(ErrorCode.ERR_BadArgType, "c.F[..]").WithArguments("1", "System.ReadOnlySpan<int>", "System.Span<int>").WithLocation(24, 19)
+                );
+        }
+
+        [Fact]
+        public void Slice_Variable_Readonly_07()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        M2(c);
+    }
+
+    static void M2(in C c)
+    {
+        c.F[..][0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (24,9): error CS8331: Cannot assign to property 'this' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         c.F[..][0] = 1;
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField, "c.F[..][0]").WithArguments("property", "this").WithLocation(24, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Variable_Readonly_08()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c, 5)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(in C c, int y) => c.F[..y];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       24 (0x18)
+  .maxstack  3
+  .locals init (System.ReadOnlySpan<int> V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  stloc.0
+  IL_000e:  ldloca.s   V_0
+  IL_0010:  ldc.i4.0
+  IL_0011:  ldarg.1
+  IL_0012:  call       ""System.ReadOnlySpan<int> System.ReadOnlySpan<int>.Slice(int, int)""
+  IL_0017:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ListPattern()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F = default;
+    public C() {}
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        if (x.F is [0, ..])
+        {}
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (12,20): error CS8985: List patterns may not be used for a value of type 'Buffer10<int>'. No suitable 'Length' or 'Count' property was found.
+                //         if (x.F is [0, ..])
+                Diagnostic(ErrorCode.ERR_ListPatternRequiresLength, "[0, ..]").WithArguments("Buffer10<int>").WithLocation(12, 20),
+                // (12,20): error CS0021: Cannot apply indexing with [] to an expression of type 'Buffer10<int>'
+                //         if (x.F is [0, ..])
+                Diagnostic(ErrorCode.ERR_BadIndexLHS, "[0, ..]").WithArguments("Buffer10<int>").WithLocation(12, 20)
+                );
+        }
+
+        [Fact]
+        public void NoIndex()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F = default;
+    public C() {}
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (12,17): error CS0443: Syntax error; value expected
+                //         _ = x.F[];
+                Diagnostic(ErrorCode.ERR_ValueExpected, "]").WithLocation(12, 17)
+                );
+        }
+
+        [Fact]
+        public void TooManyIndexes()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F = default;
+    public C() {}
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[0, 1];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,13): error CS9172: Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.
+                //         _ = x.F[0, 1];
+                Diagnostic(ErrorCode.ERR_InlineArrayBadIndex, "x.F[0, 1]").WithLocation(12, 13)
+                );
+        }
+
+        [Fact]
+        public void WrongIndexType_01()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F = default;
+    public C() {}
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[""a""];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,13): error CS9172: Elements of an inline array type can be accessed only with a single argument implicitly convertible to 'int', 'System.Index', or 'System.Range'.
+                //         _ = x.F["a"];
+                Diagnostic(ErrorCode.ERR_InlineArrayBadIndex, @"x.F[""a""]").WithLocation(12, 13)
+                );
+        }
+
+        [Fact]
+        public void NamedIndex()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[x: 1];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (11,13): error CS9173: An inline array access may not have a named argument specifier
+                //         _ = x.F[x: 1];
+                Diagnostic(ErrorCode.ERR_NamedArgumentForInlineArray, "x.F[x: 1]").WithLocation(11, 13)
+                );
+        }
+
+        [Fact]
+        public void RefOutInIndex()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x, int y)
+    {
+        _ = x.F[ref y];
+        _ = x.F[in y];
+        _ = x.F[out y];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (11,21): error CS1615: Argument 1 may not be passed with the 'ref' keyword
+                //         _ = x.F[ref y];
+                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "y").WithArguments("1", "ref").WithLocation(11, 21),
+                // (12,20): error CS1615: Argument 1 may not be passed with the 'in' keyword
+                //         _ = x.F[in y];
+                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "y").WithArguments("1", "in").WithLocation(12, 20),
+                // (13,21): error CS1615: Argument 1 may not be passed with the 'out' keyword
+                //         _ = x.F[out y];
+                Diagnostic(ErrorCode.ERR_BadArgExtraRef, "y").WithArguments("1", "out").WithLocation(13, 21)
+                );
+        }
+
+        [Fact]
+        public void AlwaysDefault_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (4,26): warning CS0649: Field 'C.F' is never assigned to, and will always have its default value 
+                //     public Buffer10<int> F;
+                Diagnostic(ErrorCode.WRN_UnassignedInternalField, "F").WithArguments("C.F", "").WithLocation(4, 26)
+                );
+        }
+
+        [Fact]
+        public void AlwaysDefault_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        ref int x = ref c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void AlwaysDefault_03_1()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F1;
+    public int F2;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        ref readonly int x = ref c.F1[0];
+        ref readonly int y = ref c.F2;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void AlwaysDefault_03_2()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F1;
+    public readonly int F2;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        ref readonly int x = ref c.F1[0];
+        ref readonly int y = ref c.F2;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void AlwaysDefault_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F1;
+    public int F2;
+}
+
+class Program
+{
+    static void M(in C c)
+    {
+        ref readonly int x = ref c.F1[0];
+        ref readonly int y = ref c.F2;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void AlwaysDefault_05()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        System.Span<int> x = c.F[..5];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void AlwaysDefault_06_1()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        System.ReadOnlySpan<int> x = c.F[..5];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void AlwaysDefault_06_2()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        System.ReadOnlySpan<int> x = c.F[..5];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (4,35): warning CS0649: Field 'C.F' is never assigned to, and will always have its default value 
+                //     public readonly Buffer10<int> F;
+                Diagnostic(ErrorCode.WRN_UnassignedInternalField, "F").WithArguments("C.F", "").WithLocation(4, 35)
+                );
+        }
+
+        [Fact]
+        public void AlwaysDefault_07()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M(in C c)
+    {
+        System.ReadOnlySpan<int> x = c.F[..5];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (4,26): warning CS0649: Field 'C.F' is never assigned to, and will always have its default value 
+                //     public Buffer10<int> F;
+                Diagnostic(ErrorCode.WRN_UnassignedInternalField, "F").WithArguments("C.F", "").WithLocation(4, 26)
+                );
+        }
+
+        [Fact]
+        public void AlwaysDefault_08()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        System.Span<int> x = c.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void AlwaysDefault_09()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M(C c)
+    {
+        System.ReadOnlySpan<int> x = c.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (4,26): warning CS0649: Field 'C.F' is never assigned to, and will always have its default value 
+                //     public Buffer10<int> F;
+                Diagnostic(ErrorCode.WRN_UnassignedInternalField, "F").WithArguments("C.F", "").WithLocation(4, 26)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_01()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        _ = c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,13): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = c.F[0];
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 13)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_02()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F[0] = 1;
+        _ = c.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (13,13): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = c.F;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(13, 13)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_03()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        F[0] = 1;
+    }
+}
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.F[0]);
+        System.Console.Write(' ');
+        System.Console.Write(c.F[9]);
+
+        System.Console.Write(' ');
+        c.F[9] = 2; 
+        c = new C();
+        System.Console.Write(c.F[0]);
+        System.Console.Write(' ');
+        System.Console.Write(c.F[9]);
+    }
+}
+
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1 0 1 0").VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       26 (0x1a)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  initobj    ""Buffer10<int>""
+  IL_000c:  ldarg.0
+  IL_000d:  ldflda     ""Buffer10<int> C.F""
+  IL_0012:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_0017:  ldc.i4.1
+  IL_0018:  stind.i4
+  IL_0019:  ret
+}
+");
+        }
+
+        [Fact]
+        public void DefiniteAssignment_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F._element0 = 1;
+        _ = c.F;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (13,13): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = c.F;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(13, 13)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_05()
+        {
+            var src = @"
+struct C
+{
+    public Buffer1<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F._element0 = 1;
+        _ = c.F;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void DefiniteAssignment_06()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F = default;
+        _ = c.F;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void DefiniteAssignment_07()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer2<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c = default;
+        _ = c.F;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void DefiniteAssignment_08()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+
+    public C()
+    {
+        F._element0 = 0;
+        F[0] = 1;
+        F[1] = 2;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       52 (0x34)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer2<int> C.F""
+  IL_0006:  initobj    ""Buffer2<int>""
+  IL_000c:  ldarg.0
+  IL_000d:  ldflda     ""Buffer2<int> C.F""
+  IL_0012:  ldc.i4.0
+  IL_0013:  stfld      ""int Buffer2<int>._element0""
+  IL_0018:  ldarg.0
+  IL_0019:  ldflda     ""Buffer2<int> C.F""
+  IL_001e:  call       ""InlineArrayFirstElementRef<Buffer2<int>, int>(ref Buffer2<int>)""
+  IL_0023:  ldc.i4.1
+  IL_0024:  stind.i4
+  IL_0025:  ldarg.0
+  IL_0026:  ldflda     ""Buffer2<int> C.F""
+  IL_002b:  ldc.i4.1
+  IL_002c:  call       ""InlineArrayElementRef<Buffer2<int>, int>(ref Buffer2<int>, int)""
+  IL_0031:  ldc.i4.2
+  IL_0032:  stind.i4
+  IL_0033:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_09()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+
+    public C()
+    {
+        F._element0 = 1;
+        F[1] = 2;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.F[0]);
+        System.Console.Write(' ');
+        System.Console.Write(c.F[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1 2").VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       39 (0x27)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer2<int> C.F""
+  IL_0006:  initobj    ""Buffer2<int>""
+  IL_000c:  ldarg.0
+  IL_000d:  ldflda     ""Buffer2<int> C.F""
+  IL_0012:  ldc.i4.1
+  IL_0013:  stfld      ""int Buffer2<int>._element0""
+  IL_0018:  ldarg.0
+  IL_0019:  ldflda     ""Buffer2<int> C.F""
+  IL_001e:  ldc.i4.1
+  IL_001f:  call       ""InlineArrayElementRef<Buffer2<int>, int>(ref Buffer2<int>, int)""
+  IL_0024:  ldc.i4.2
+  IL_0025:  stind.i4
+  IL_0026:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_10()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+
+    public C()
+    {
+        F._element0 = 1;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.F[0]);
+        System.Console.Write(' ');
+        System.Console.Write(c.F[1]);
+        c.F[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(c.F[1]);
+        System.Console.Write(' ');
+
+        c = new C();
+        System.Console.Write(c.F[0]);
+        System.Console.Write(' ');
+        System.Console.Write(c.F[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1 0 2 1 0").VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       25 (0x19)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer2<int> C.F""
+  IL_0006:  initobj    ""Buffer2<int>""
+  IL_000c:  ldarg.0
+  IL_000d:  ldflda     ""Buffer2<int> C.F""
+  IL_0012:  ldc.i4.1
+  IL_0013:  stfld      ""int Buffer2<int>._element0""
+  IL_0018:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_11()
+        {
+            var src = @"
+struct C
+{
+    public Buffer1<int> F;
+
+    public C()
+    {
+        F._element0 = 1;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.F[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer1<int> C.F""
+  IL_0006:  ldc.i4.1
+  IL_0007:  stfld      ""int Buffer1<int>._element0""
+  IL_000c:  ret
+}
+");
+        }
+
+        [Fact]
+        public void DefiniteAssignment_12()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        _ = c.F[2..5];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,13): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = c.F[2..5];
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 13)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_13()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F[2..5][0] = 1;
+        _ = c.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,9): error CS0170: Use of possibly unassigned field 'F'
+                //         c.F[2..5][0] = 1;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 9)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_14()
+        {
+            var src = @"
+struct C
+{
+    public Buffer1 F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F[0] = 1;
+        _ = c.F;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void DefiniteAssignment_15()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        ref int x = ref c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,25): error CS0170: Use of possibly unassigned field 'F'
+                //         ref int x = ref c.F[0];
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 25)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_16()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        ref readonly int x = ref c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,34): error CS0170: Use of possibly unassigned field 'F'
+                //         ref readonly int x = ref c.F[0];
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 34)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_17()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F[0] = 1;
+        _ = c.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (13,13): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = c.F[0];
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(13, 13)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_18()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer1 F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F[0] = 1;
+        _ = c.F[0];
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    int _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void DefiniteAssignment_19()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        _ = (System.Span<int>)c.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,31): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = (System.Span<int>)c.F;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 31)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_20()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        _ = (System.ReadOnlySpan<int>)c.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,39): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = (System.ReadOnlySpan<int>)c.F;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 39)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_21()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M()
+    {
+        C c;
+        c.F[0] += 1;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (12,9): error CS0170: Use of possibly unassigned field 'F'
+                //         c.F[0] += 1;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.F").WithArguments("F").WithLocation(12, 9)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_22()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer10<S> FF;
+}
+
+public struct S
+{
+    public int F;
+}
+
+class Program
+{
+    static void M1()
+    {
+        C c;
+        c.FF[0].F += 1;
+    }
+
+    static void M2()
+    {
+        C c;
+        _ = c.FF[0].F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (17,9): error CS0170: Use of possibly unassigned field 'F'
+                //         c.FF[0].F += 1;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.FF[0].F").WithArguments("F").WithLocation(17, 9),
+                // (23,13): error CS0170: Use of possibly unassigned field 'F'
+                //         _ = c.FF[0].F;
+                Diagnostic(ErrorCode.ERR_UseDefViolationField, "c.FF[0].F").WithArguments("F").WithLocation(23, 13)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_31()
+        {
+            var src = @"
+class Program
+{
+    static void M()
+    {
+        Buffer10<int> f;
+        _ = f[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (7,13): error CS0165: Use of unassigned local variable 'f'
+                //         _ = f[0];
+                Diagnostic(ErrorCode.ERR_UseDefViolation, "f").WithArguments("f").WithLocation(7, 13)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_32()
+        {
+            var src = @"
+class Program
+{
+    static void M()
+    {
+        Buffer10<int> f;
+        f[0] = 1;
+        _ = f;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (8,13): error CS0165: Use of unassigned local variable 'f'
+                //         _ = f;
+                Diagnostic(ErrorCode.ERR_UseDefViolation, "f").WithArguments("f").WithLocation(8, 13)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_33()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer10();
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+        System.Console.Write(f[9]);
+
+        System.Console.Write(' ');
+        f[9] = 2; 
+        f = new Buffer10();
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+        System.Console.Write(f[9]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10
+{
+    private int _element0;
+
+    public Buffer10()
+    {
+        this[0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1 0 1 0").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer10..ctor",
+@"
+{
+  // Code size       16 (0x10)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer10""
+  IL_0007:  ldarg.0
+  IL_0008:  call       ""InlineArrayFirstElementRef<Buffer10, int>(ref Buffer10)""
+  IL_000d:  ldc.i4.1
+  IL_000e:  stind.i4
+  IL_000f:  ret
+}
+");
+        }
+
+        [Fact]
+        public void DefiniteAssignment_34()
+        {
+            var src = @"
+class Program
+{
+    static void M()
+    {
+        Buffer2<int> f;
+        f._element0 = 1;
+        _ = f;
+
+        Buffer2<int> f2;
+        f2._element0 = 1;
+        f2[0] = 1;
+        f2[1] = 2;
+        _ = f2;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics(
+                // (8,13): error CS0165: Use of unassigned local variable 'f'
+                //         _ = f;
+                Diagnostic(ErrorCode.ERR_UseDefViolation, "f").WithArguments("f").WithLocation(8, 13),
+                // (14,13): error CS0165: Use of unassigned local variable 'f2'
+                //         _ = f2;
+                Diagnostic(ErrorCode.ERR_UseDefViolation, "f2").WithArguments("f2").WithLocation(14, 13)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_35()
+        {
+            var src = @"
+class Program
+{
+    static void M()
+    {
+        Buffer1<int> f;
+        f._element0 = 1;
+        _ = f;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void DefiniteAssignment_36()
+        {
+            var src = @"
+class Program
+{
+    static void M()
+    {
+        Buffer2<int> f;
+        f = default;
+        _ = f;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    public T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void DefiniteAssignment_38()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _element0 = 0;
+        this[0] = 1;
+        this[1] = 2;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       32 (0x20)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.0
+  IL_0009:  stfld      ""int Buffer2._element0""
+  IL_000e:  ldarg.0
+  IL_000f:  call       ""InlineArrayFirstElementRef<Buffer2, int>(ref Buffer2)""
+  IL_0014:  ldc.i4.1
+  IL_0015:  stind.i4
+  IL_0016:  ldarg.0
+  IL_0017:  ldc.i4.1
+  IL_0018:  call       ""InlineArrayElementRef<Buffer2, int>(ref Buffer2, int)""
+  IL_001d:  ldc.i4.2
+  IL_001e:  stind.i4
+  IL_001f:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_39()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer2();
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+        System.Console.Write(f[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _element0 = 1;
+        this[1] = 2;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1 2").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       24 (0x18)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.1
+  IL_0009:  stfld      ""int Buffer2._element0""
+  IL_000e:  ldarg.0
+  IL_000f:  ldc.i4.1
+  IL_0010:  call       ""InlineArrayElementRef<Buffer2, int>(ref Buffer2, int)""
+  IL_0015:  ldc.i4.2
+  IL_0016:  stind.i4
+  IL_0017:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_40()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer2();
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+        System.Console.Write(f[1]);
+        f[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(f[1]);
+        System.Console.Write(' ');
+
+        f = new Buffer2();
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+        System.Console.Write(f[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _element0 = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1 0 2 1 0").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.1
+  IL_0009:  stfld      ""int Buffer2._element0""
+  IL_000e:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_41()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer1();
+        System.Console.Write(f[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    public int _element0;
+
+    public Buffer1()
+    {
+        _element0 = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer1..ctor",
+@"
+{
+  // Code size        8 (0x8)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldc.i4.1
+  IL_0002:  stfld      ""int Buffer1._element0""
+  IL_0007:  ret
+}
+");
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular10);
+            comp.VerifyDiagnostics(
+                // (7,30): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         System.Console.Write(f[0]);
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "f[0]").WithArguments("inline arrays").WithLocation(7, 30)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_42()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer1();
+        System.Console.Write(f[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    int _element0 = 1;
+
+    public Buffer1()
+    {
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer1..ctor",
+@"
+{
+  // Code size        8 (0x8)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldc.i4.1
+  IL_0002:  stfld      ""int Buffer1._element0""
+  IL_0007:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_43()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer1();
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+        f[0] = 1;
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+
+        f = new Buffer1();
+        System.Console.Write(f[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    public int _element0;
+
+    public Buffer1()
+    {
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 1 0").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer1..ctor",
+@"
+{
+  // Code size        8 (0x8)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldc.i4.0
+  IL_0002:  stfld      ""int Buffer1._element0""
+  IL_0007:  ret
+}
+");
+        }
+
+        [Fact]
+        public void DefiniteAssignment_44()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _element0 = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.1
+  IL_0009:  stfld      ""int Buffer2._element0""
+  IL_000e:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular10);
+            comp.VerifyDiagnostics(
+                // (7,12): error CS0177: The out parameter 'this' must be assigned to before control leaves the current method
+                //     public Buffer2()
+                Diagnostic(ErrorCode.ERR_ParamUnassigned, "Buffer2").WithArguments("this").WithLocation(7, 12)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_45()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    int _element0 = 1;
+
+    public Buffer2()
+    {
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.1
+  IL_0009:  stfld      ""int Buffer2._element0""
+  IL_000e:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular10);
+            comp.VerifyDiagnostics(
+                // (7,12): error CS0177: The out parameter 'this' must be assigned to before control leaves the current method
+                //     public Buffer2()
+                Diagnostic(ErrorCode.ERR_ParamUnassigned, "Buffer2").WithArguments("this").WithLocation(7, 12)
+                );
+        }
+
+        [Fact]
+        public void DefiniteAssignment_46()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        this = default;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size        8 (0x8)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular10);
+            comp.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_47()
+        {
+            var src = @"
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _element0 = 1;
+        _ = this[0];
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            var verifier = CompileAndVerify(comp).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       22 (0x16)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.1
+  IL_0009:  stfld      ""int Buffer2._element0""
+  IL_000e:  ldarg.0
+  IL_000f:  call       ""InlineArrayFirstElementRef<Buffer2, int>(ref Buffer2)""
+  IL_0014:  pop
+  IL_0015:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular10);
+            comp.VerifyDiagnostics(
+                // (7,12): error CS0177: The out parameter 'this' must be assigned to before control leaves the current method
+                //     public Buffer2()
+                Diagnostic(ErrorCode.ERR_ParamUnassigned, "Buffer2").WithArguments("this").WithLocation(7, 12),
+                // (10,13): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         _ = this[0];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "this[0]").WithArguments("inline arrays").WithLocation(10, 13),
+                // (10,13): error CS0188: The 'this' object cannot be used before all of its fields have been assigned. Consider updating to language version '11.0' to auto-default the unassigned fields.
+                //         _ = this[0];
+                Diagnostic(ErrorCode.ERR_UseDefViolationThisUnsupportedVersion, "this").WithArguments("11.0").WithLocation(10, 13)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_48()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer1();
+        System.Console.Write(f[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    public int _element0;
+
+    public Buffer1()
+    {
+        _element0 = 1;
+        _ = this[0];
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer1..ctor",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldc.i4.1
+  IL_0002:  stfld      ""int Buffer1._element0""
+  IL_0007:  ldarg.0
+  IL_0008:  call       ""InlineArrayFirstElementRef<Buffer1, int>(ref Buffer1)""
+  IL_000d:  pop
+  IL_000e:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular10);
+            comp.VerifyDiagnostics(
+                // (7,30): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         System.Console.Write(f[0]);
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "f[0]").WithArguments("inline arrays").WithLocation(7, 30),
+                // (19,13): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         _ = this[0];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "this[0]").WithArguments("inline arrays").WithLocation(19, 13)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_49()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer1();
+        System.Console.Write(f[0]);
+
+        f[0] = 1; 
+        System.Console.Write(' ');
+        System.Console.Write(f[0]);
+        System.Console.Write(' ');
+
+        f = new Buffer1();
+        System.Console.Write(f[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    public int _element0;
+
+    public Buffer1()
+    {
+        _ = this[0];
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 1 0").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer1..ctor",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldc.i4.0
+  IL_0002:  stfld      ""int Buffer1._element0""
+  IL_0007:  ldarg.0
+  IL_0008:  call       ""InlineArrayFirstElementRef<Buffer1, int>(ref Buffer1)""
+  IL_000d:  pop
+  IL_000e:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular10);
+            comp.VerifyDiagnostics(
+                // (7,30): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         System.Console.Write(f[0]);
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "f[0]").WithArguments("inline arrays").WithLocation(7, 30),
+                // (9,9): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         f[0] = 1; 
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "f[0]").WithArguments("inline arrays").WithLocation(9, 9),
+                // (11,30): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         System.Console.Write(f[0]);
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "f[0]").WithArguments("inline arrays").WithLocation(11, 30),
+                // (15,30): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         System.Console.Write(f[0]);
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "f[0]").WithArguments("inline arrays").WithLocation(15, 30),
+                // (24,12): error CS0171: Field 'Buffer1._element0' must be fully assigned before control is returned to the caller. Consider updating to language version '11.0' to auto-default the field.
+                //     public Buffer1()
+                Diagnostic(ErrorCode.ERR_UnassignedThisUnsupportedVersion, "Buffer1").WithArguments("Buffer1._element0", "11.0").WithLocation(24, 12),
+                // (26,13): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         _ = this[0];
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "this[0]").WithArguments("inline arrays").WithLocation(26, 13),
+                // (26,13): error CS0188: The 'this' object cannot be used before all of its fields have been assigned. Consider updating to language version '11.0' to auto-default the unassigned fields.
+                //         _ = this[0];
+                Diagnostic(ErrorCode.ERR_UseDefViolationThisUnsupportedVersion, "this").WithArguments("11.0").WithLocation(26, 13)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_50()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer1();
+        System.Console.Write(f[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    public int _element0;
+
+    public Buffer1()
+    {
+        this[0] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer1..ctor",
+@"
+{
+  // Code size        9 (0x9)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""InlineArrayFirstElementRef<Buffer1, int>(ref Buffer1)""
+  IL_0006:  ldc.i4.1
+  IL_0007:  stind.i4
+  IL_0008:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_51()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer1();
+        System.Console.Write(f[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(1)]
+public struct Buffer1
+{
+    public int _element0;
+
+    public Buffer1()
+    {
+        this[^1] = 1;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer1..ctor",
+@"
+{
+  // Code size        9 (0x9)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""InlineArrayFirstElementRef<Buffer1, int>(ref Buffer1)""
+  IL_0006:  ldc.i4.1
+  IL_0007:  stind.i4
+  IL_0008:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_52()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+
+    public C()
+    {
+        _ = F[..];
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.F[1]);
+        c.F[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(c.F[1]);
+        System.Console.Write(' ');
+
+        c = new C();
+        System.Console.Write(c.F[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    private T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 2 0", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       26 (0x1a)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer2<int> C.F""
+  IL_0006:  initobj    ""Buffer2<int>""
+  IL_000c:  ldarg.0
+  IL_000d:  ldflda     ""Buffer2<int> C.F""
+  IL_0012:  ldc.i4.2
+  IL_0013:  call       ""InlineArrayAsSpan<Buffer2<int>, int>(ref Buffer2<int>, int)""
+  IL_0018:  pop
+  IL_0019:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_53()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+
+    public C()
+    {
+        _ = (System.Span<int>)F;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.F[1]);
+        c.F[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(c.F[1]);
+        System.Console.Write(' ');
+
+        c = new C();
+        System.Console.Write(c.F[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    private T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 2 0", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       26 (0x1a)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer2<int> C.F""
+  IL_0006:  initobj    ""Buffer2<int>""
+  IL_000c:  ldarg.0
+  IL_000d:  ldflda     ""Buffer2<int> C.F""
+  IL_0012:  ldc.i4.2
+  IL_0013:  call       ""InlineArrayAsSpan<Buffer2<int>, int>(ref Buffer2<int>, int)""
+  IL_0018:  pop
+  IL_0019:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_54()
+        {
+            var src = @"
+struct C
+{
+    public Buffer2<int> F;
+
+    public C()
+    {
+        _ = (System.ReadOnlySpan<int>)F;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.F[1]);
+        c.F[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(c.F[1]);
+        System.Console.Write(' ');
+
+        c = new C();
+        System.Console.Write(c.F[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2<T>
+{
+    private T _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 2 0", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C..ctor",
+@"
+{
+  // Code size       26 (0x1a)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer2<int> C.F""
+  IL_0006:  initobj    ""Buffer2<int>""
+  IL_000c:  ldarg.0
+  IL_000d:  ldflda     ""Buffer2<int> C.F""
+  IL_0012:  ldc.i4.2
+  IL_0013:  call       ""InlineArrayAsReadOnlySpan<Buffer2<int>, int>(in Buffer2<int>, int)""
+  IL_0018:  pop
+  IL_0019:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_55()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer2();
+        System.Console.Write(f[1]);
+        f[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(f[1]);
+        System.Console.Write(' ');
+
+        f = new Buffer2();
+        System.Console.Write(f[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _ = this[..];
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 2 0", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       16 (0x10)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.2
+  IL_0009:  call       ""InlineArrayAsSpan<Buffer2, int>(ref Buffer2, int)""
+  IL_000e:  pop
+  IL_000f:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_56()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer2();
+        System.Console.Write(f[1]);
+        f[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(f[1]);
+        System.Console.Write(' ');
+
+        f = new Buffer2();
+        System.Console.Write(f[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _ = (System.Span<int>)this;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 2 0", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       16 (0x10)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.2
+  IL_0009:  call       ""InlineArrayAsSpan<Buffer2, int>(ref Buffer2, int)""
+  IL_000e:  pop
+  IL_000f:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void DefiniteAssignment_57()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        var f = new Buffer2();
+        System.Console.Write(f[1]);
+        f[1] = 2;
+
+        System.Console.Write(' ');
+        System.Console.Write(f[1]);
+        System.Console.Write(' ');
+
+        f = new Buffer2();
+        System.Console.Write(f[1]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(2)]
+public struct Buffer2
+{
+    public int _element0;
+
+    public Buffer2()
+    {
+        _ = (System.ReadOnlySpan<int>)this;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 2 0", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Buffer2..ctor",
+@"
+{
+  // Code size       16 (0x10)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  initobj    ""Buffer2""
+  IL_0007:  ldarg.0
+  IL_0008:  ldc.i4.2
+  IL_0009:  call       ""InlineArrayAsReadOnlySpan<Buffer2, int>(in Buffer2, int)""
+  IL_000e:  pop
+  IL_000f:  ret
+}
+");
+        }
+
+        [Fact]
+        public void MissingHelper_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_Start);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_End);
+            comp.MakeMemberMissing(WellKnownMember.System_Index__GetOffset);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__get_Item);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[^10];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_Start);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_End);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__get_Item);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_03()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[^10];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Index__GetOffset);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__get_Item);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,13): error CS0656: Missing compiler required member 'System.Index.GetOffset'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Index", "GetOffset").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateSpan'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Runtime.InteropServices.MemoryMarshal", "CreateSpan").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Span`1.get_Item'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Span`1", "get_Item").WithLocation(11, 13)
+                );
+        }
+
+        [Fact]
+        public void MissingHelper_04()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[..3];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__get_Item);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__get_Item);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_05()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[..3];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Index__GetOffset);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_Start);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_End);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__Slice_Int_Int);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,13): error CS0656: Missing compiler required member 'System.Index.GetOffset'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Index", "GetOffset").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Range.get_Start'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Range", "get_Start").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Range.get_End'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Range", "get_End").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateSpan'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Runtime.InteropServices.MemoryMarshal", "CreateSpan").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Span`1.Slice'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Span`1", "Slice").WithLocation(11, 13)
+                );
+        }
+
+        [Fact]
+        public void MissingHelper_06()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        _ = x.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_Start);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_End);
+            comp.MakeMemberMissing(WellKnownMember.System_Index__GetOffset);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__get_Item);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_07()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        _ = x.F[^10];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_Start);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_End);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__get_Item);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_08()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        _ = x.F[^10];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Index__GetOffset);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__get_Item);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,13): error CS0656: Missing compiler required member 'System.Index.GetOffset'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Index", "GetOffset").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.AsRef'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Runtime.CompilerServices.Unsafe", "AsRef").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.Runtime.InteropServices.MemoryMarshal", "CreateReadOnlySpan").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.ReadOnlySpan`1.get_Item'
+                //         _ = x.F[^10];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[^10]").WithArguments("System.ReadOnlySpan`1", "get_Item").WithLocation(11, 13)
+                );
+        }
+
+        [Fact]
+        public void MissingHelper_09()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        _ = x.F[..3];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__Slice_Int_Int);
+            comp.MakeMemberMissing(WellKnownMember.System_Span_T__get_Item);
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__get_Item);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_10()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        _ = x.F[..3];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Index__GetOffset);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_Start);
+            comp.MakeMemberMissing(WellKnownMember.System_Range__get_End);
+
+            comp.MakeMemberMissing(WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,13): error CS0656: Missing compiler required member 'System.Index.GetOffset'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Index", "GetOffset").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Range.get_Start'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Range", "get_Start").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Range.get_End'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Range", "get_End").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.AsRef'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Runtime.CompilerServices.Unsafe", "AsRef").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.Runtime.InteropServices.MemoryMarshal", "CreateReadOnlySpan").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.ReadOnlySpan`1.Slice'
+                //         _ = x.F[..3];
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F[..3]").WithArguments("System.ReadOnlySpan`1", "Slice").WithLocation(11, 13)
+                );
+        }
+
+        [Fact]
+        public void MissingHelper_11()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = (System.Span<int>)x.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_12()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = (System.ReadOnlySpan<int>)x.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_13()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = (System.Span<int>)x.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateSpan'
+                //         _ = (System.Span<int>)x.F;
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "(System.Span<int>)x.F").WithArguments("System.Runtime.InteropServices.MemoryMarshal", "CreateSpan").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         _ = (System.Span<int>)x.F;
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "(System.Span<int>)x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 13)
+                );
+        }
+
+        [Fact]
+        public void MissingHelper_14()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = (System.ReadOnlySpan<int>)x.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan'
+                //         _ = (System.ReadOnlySpan<int>)x.F;
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "(System.ReadOnlySpan<int>)x.F").WithArguments("System.Runtime.InteropServices.MemoryMarshal", "CreateReadOnlySpan").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.AsRef'
+                //         _ = (System.ReadOnlySpan<int>)x.F;
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "(System.ReadOnlySpan<int>)x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "AsRef").WithLocation(11, 13),
+                // (11,13): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         _ = (System.ReadOnlySpan<int>)x.F;
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "(System.ReadOnlySpan<int>)x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 13)
+                );
+        }
+
+        [Fact]
+        public void MissingHelper_15()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        foreach (var y in x.F)
+        {}
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void MissingHelper_16()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        foreach (var y in x.F)
+        {}
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,27): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.Add'
+                //         foreach (var y in x.F)
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "Add").WithLocation(11, 27),
+                // (11,27): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         foreach (var y in x.F)
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 27)
+                );
+        }
+
+        [Fact]
+        public void MissingHelper_17()
+        {
+            var src = @"#pragma warning disable CS0649 // Field 'C.F' is never assigned to
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        foreach (var y in x.F)
+        {}
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T);
+            comp.MakeMemberMissing(WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T);
+
+            comp.VerifyEmitDiagnostics(
+                // (11,27): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.AsRef'
+                //         foreach (var y in x.F)
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "AsRef").WithLocation(11, 27),
+                // (11,27): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.Add'
+                //         foreach (var y in x.F)
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "Add").WithLocation(11, 27),
+                // (11,27): error CS0656: Missing compiler required member 'System.Runtime.CompilerServices.Unsafe.As'
+                //         foreach (var y in x.F)
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "x.F").WithArguments("System.Runtime.CompilerServices.Unsafe", "As").WithLocation(11, 27)
+                );
+        }
+
+        [Fact]
+        public void PrivateImplementationDetails_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        var i = 0;
+        _ = x.F[i];
+        _ = x.F[..5];
+        _ = (System.Span<int>)x.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All));
+
+            var verifier = CompileAndVerify(comp, verify: Verification.Fails,
+                symbolValidator: m =>
+                {
+                    var t = m.GlobalNamespace.GetTypeMember("<PrivateImplementationDetails>");
+                    AssertEx.Equal("System.Span<TElement> <PrivateImplementationDetails>.InlineArrayAsSpan<TBuffer, TElement>(ref TBuffer buffer, System.Int32 length)",
+                                   t.GetMember(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName).ToTestDisplayString());
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName));
+                }).VerifyDiagnostics();
+
+            verifier.VerifyIL(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName,
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.As<TBuffer, TElement>(ref TBuffer)""
+  IL_0006:  ldarg.1
+  IL_0007:  call       ""System.Span<TElement> System.Runtime.InteropServices.MemoryMarshal.CreateSpan<TElement>(scoped ref TElement, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [Fact]
+        public void PrivateImplementationDetails_02()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        var i = 0;
+        _ = x.F[i];
+        _ = x.F[..5];
+        _ = (System.ReadOnlySpan<int>)x.F;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All));
+
+            var verifier = CompileAndVerify(comp, verify: Verification.Fails,
+                symbolValidator: m =>
+                {
+                    var t = m.GlobalNamespace.GetTypeMember("<PrivateImplementationDetails>");
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName));
+                    AssertEx.Equal("System.ReadOnlySpan<TElement> <PrivateImplementationDetails>.InlineArrayAsReadOnlySpan<TBuffer, TElement>(in TBuffer buffer, System.Int32 length)",
+                                   t.GetMember(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName).ToTestDisplayString());
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName));
+                }).VerifyDiagnostics();
+
+            verifier.VerifyIL(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName,
+@"
+{
+  // Code size       18 (0x12)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref TBuffer System.Runtime.CompilerServices.Unsafe.AsRef<TBuffer>(scoped in TBuffer)""
+  IL_0006:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.As<TBuffer, TElement>(ref TBuffer)""
+  IL_000b:  ldarg.1
+  IL_000c:  call       ""System.ReadOnlySpan<TElement> System.Runtime.InteropServices.MemoryMarshal.CreateReadOnlySpan<TElement>(scoped ref TElement, int)""
+  IL_0011:  ret
+}
+");
+        }
+
+        [Fact]
+        public void PrivateImplementationDetails_03()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[1];
+        foreach (var y in x.F)
+        {}
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All));
+
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr,
+                symbolValidator: m =>
+                {
+                    var t = m.GlobalNamespace.GetTypeMember("<PrivateImplementationDetails>");
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName));
+                    Assert.Equal("ref TElement <PrivateImplementationDetails>.InlineArrayElementRef<TBuffer, TElement>(ref TBuffer buffer, System.Int32 index)",
+                                 t.GetMember(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefName).ToTestDisplayString());
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName));
+                }).VerifyDiagnostics();
+
+            verifier.VerifyIL(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefName,
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.As<TBuffer, TElement>(ref TBuffer)""
+  IL_0006:  ldarg.1
+  IL_0007:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.Add<TElement>(ref TElement, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [Fact]
+        public void PrivateImplementationDetails_04()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        _ = x.F[1];
+        foreach (var y in x.F)
+        {}
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All));
+
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr,
+                symbolValidator: m =>
+                {
+                    var t = m.GlobalNamespace.GetTypeMember("<PrivateImplementationDetails>");
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefName));
+                    Assert.Equal("ref readonly TElement <PrivateImplementationDetails>.InlineArrayElementRefReadOnly<TBuffer, TElement>(in TBuffer buffer, System.Int32 index)",
+                                 t.GetMember(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName).ToTestDisplayString());
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName));
+                }).VerifyDiagnostics();
+
+            verifier.VerifyIL(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName,
+@"
+{
+  // Code size       18 (0x12)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref TBuffer System.Runtime.CompilerServices.Unsafe.AsRef<TBuffer>(scoped in TBuffer)""
+  IL_0006:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.As<TBuffer, TElement>(ref TBuffer)""
+  IL_000b:  ldarg.1
+  IL_000c:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.Add<TElement>(ref TElement, int)""
+  IL_0011:  ret
+}
+");
+        }
+
+        [Fact]
+        public void PrivateImplementationDetails_05()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F = default;
+}
+
+class Program
+{
+    static void M3(C x)
+    {
+        _ = x.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All));
+
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr,
+                symbolValidator: m =>
+                {
+                    var t = m.GlobalNamespace.GetTypeMember("<PrivateImplementationDetails>");
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName));
+                    Assert.Equal("ref TElement <PrivateImplementationDetails>.InlineArrayFirstElementRef<TBuffer, TElement>(ref TBuffer buffer)",
+                                 t.GetMember(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName).ToTestDisplayString());
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName));
+                }).VerifyDiagnostics();
+
+            verifier.VerifyIL(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName,
+@"
+{
+  // Code size        7 (0x7)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.As<TBuffer, TElement>(ref TBuffer)""
+  IL_0006:  ret
+}
+");
+        }
+
+        [Fact]
+        public void PrivateImplementationDetails_06()
+        {
+            var src = @"#pragma warning disable CS0649
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void M3(in C x)
+    {
+        _ = x.F[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All));
+
+            var verifier = CompileAndVerify(comp, verify: VerifyOnMonoOrCoreClr,
+                symbolValidator: m =>
+                {
+                    var t = m.GlobalNamespace.GetTypeMember("<PrivateImplementationDetails>");
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsSpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayAsReadOnlySpanName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayElementRefReadOnlyName));
+                    Assert.Empty(t.GetMembers(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefName));
+                    Assert.Equal("ref readonly TElement <PrivateImplementationDetails>.InlineArrayFirstElementRefReadOnly<TBuffer, TElement>(in TBuffer buffer)",
+                                 t.GetMember(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName).ToTestDisplayString());
+                }).VerifyDiagnostics();
+
+            verifier.VerifyIL(CodeAnalysis.CodeGen.PrivateImplementationDetails.SynthesizedInlineArrayFirstElementRefReadOnlyName,
+@"
+{
+  // Code size       12 (0xc)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""ref TBuffer System.Runtime.CompilerServices.Unsafe.AsRef<TBuffer>(scoped in TBuffer)""
+  IL_0006:  call       ""ref TElement System.Runtime.CompilerServices.Unsafe.As<TBuffer, TElement>(ref TBuffer)""
+  IL_000b:  ret
+}
+");
+        }
+
+        [Fact]
+        public void NullableAnalysis_01()
+        {
+            var src = @"
+#nullable enable
+
+class C<T>
+{
+    public Buffer10<T> F = default;
+}
+
+class Program
+{
+    static void M2(string s1, string? s2)
+    {
+        _ = GetC(s1).F[0].Length;
+        _ = GetC(s2).F[0].Length;
+        _ = GetC(s1).F[..5][0].Length;
+        _ = GetC(s2).F[..5][0].Length;
+    }
+
+    static C<T> GetC<T>(T x)
+    {
+        var c = new C<T>();
+        c.F[0] = x;
+        return c;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (14,13): warning CS8602: Dereference of a possibly null reference.
+                //         _ = GetC(s2).F[0].Length;
+                Diagnostic(ErrorCode.WRN_NullReferenceReceiver, "GetC(s2).F[0]").WithLocation(14, 13),
+                // (16,13): warning CS8602: Dereference of a possibly null reference.
+                //         _ = GetC(s2).F[..5][0].Length;
+                Diagnostic(ErrorCode.WRN_NullReferenceReceiver, "GetC(s2).F[..5][0]").WithLocation(16, 13)
+                );
+        }
+
+        [Fact]
+        public void NullableAnalysis_02()
+        {
+            var src = @"
+#nullable enable
+
+class Program
+{
+    static void M1(Buffer10<string?> b)
+    {
+        System.Span<string> x = b;
+        System.ReadOnlySpan<string> y = b;
+    }
+
+    static void M2(Buffer10<string> b2)
+    {
+        System.Span<string> x = b2;
+        System.ReadOnlySpan<string> y = b2;
+    }
+
+    static void M3(Buffer10<string?> b3)
+    {
+        System.Span<string?> x = b3;
+        System.ReadOnlySpan<string?> y = b3;
+    }
+
+    static void M4(Buffer10<string> b4)
+    {
+        System.Span<string?> x = b4;
+        System.ReadOnlySpan<string?> y = b4;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (8,33): warning CS8619: Nullability of reference types in value of type 'Buffer10<string?>' doesn't match target type 'Span<string>'.
+                //         System.Span<string> x = b;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b").WithArguments("Buffer10<string?>", "System.Span<string>").WithLocation(8, 33),
+                // (9,41): warning CS8619: Nullability of reference types in value of type 'Buffer10<string?>' doesn't match target type 'ReadOnlySpan<string>'.
+                //         System.ReadOnlySpan<string> y = b;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b").WithArguments("Buffer10<string?>", "System.ReadOnlySpan<string>").WithLocation(9, 41),
+                // (26,34): warning CS8619: Nullability of reference types in value of type 'Buffer10<string>' doesn't match target type 'Span<string?>'.
+                //         System.Span<string?> x = b4;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b4").WithArguments("Buffer10<string>", "System.Span<string?>").WithLocation(26, 34),
+                // (27,42): warning CS8619: Nullability of reference types in value of type 'Buffer10<string>' doesn't match target type 'ReadOnlySpan<string?>'.
+                //         System.ReadOnlySpan<string?> y = b4;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b4").WithArguments("Buffer10<string>", "System.ReadOnlySpan<string?>").WithLocation(27, 42)
+                );
+        }
+
+        [Fact]
+        public void NullableAnalysis_03()
+        {
+            var src = @"
+#nullable enable
+
+class Program
+{
+    static void M1(Buffer10<string?[]> b)
+    {
+        System.Span<string[]> x = b;
+        System.ReadOnlySpan<string[]> y = b;
+    }
+
+    static void M2(Buffer10<string[]> b2)
+    {
+        System.Span<string[]> x = b2;
+        System.ReadOnlySpan<string[]> y = b2;
+    }
+
+    static void M3(Buffer10<string?[]> b3)
+    {
+        System.Span<string?[]> x = b3;
+        System.ReadOnlySpan<string?[]> y = b3;
+    }
+
+    static void M4(Buffer10<string[]> b4)
+    {
+        System.Span<string?[]> x = b4;
+        System.ReadOnlySpan<string?[]> y = b4;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (8,35): warning CS8619: Nullability of reference types in value of type 'Buffer10<string?[]>' doesn't match target type 'Span<string[]>'.
+                //         System.Span<string[]> x = b;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b").WithArguments("Buffer10<string?[]>", "System.Span<string[]>").WithLocation(8, 35),
+                // (9,43): warning CS8619: Nullability of reference types in value of type 'Buffer10<string?[]>' doesn't match target type 'ReadOnlySpan<string[]>'.
+                //         System.ReadOnlySpan<string[]> y = b;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b").WithArguments("Buffer10<string?[]>", "System.ReadOnlySpan<string[]>").WithLocation(9, 43),
+                // (26,36): warning CS8619: Nullability of reference types in value of type 'Buffer10<string[]>' doesn't match target type 'Span<string?[]>'.
+                //         System.Span<string?[]> x = b4;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b4").WithArguments("Buffer10<string[]>", "System.Span<string?[]>").WithLocation(26, 36),
+                // (27,44): warning CS8619: Nullability of reference types in value of type 'Buffer10<string[]>' doesn't match target type 'ReadOnlySpan<string?[]>'.
+                //         System.ReadOnlySpan<string?[]> y = b4;
+                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "b4").WithArguments("Buffer10<string[]>", "System.ReadOnlySpan<string?[]>").WithLocation(27, 44)
+                );
+        }
+
+        [Fact]
+        public void NullableAnalysis_04()
+        {
+            var src = @"
+#nullable enable
+
+class C<T>
+{
+    public Buffer10<T> F = default;
+}
+
+class Program
+{
+    static void M2(string s1, string? s2)
+    {
+        foreach(var x in GetC(s1).F)
+            _ = x.Length;
+
+        foreach(var y in GetC(s2).F)
+            _ = y.Length;
+
+        foreach(string a in GetC(s1).F)
+        {}
+
+        foreach(string b in GetC(s2).F)
+        {}
+
+        foreach(string? c in GetC(s1).F)
+        {}
+
+        foreach(string? d in GetC(s2).F)
+        {}
+    }
+
+    static C<T> GetC<T>(T x)
+    {
+        var c = new C<T>();
+        return c;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (17,17): warning CS8602: Dereference of a possibly null reference.
+                //             _ = y.Length;
+                Diagnostic(ErrorCode.WRN_NullReferenceReceiver, "y").WithLocation(17, 17),
+                // (22,24): warning CS8600: Converting null literal or possible null value to non-nullable type.
+                //         foreach(string b in GetC(s2).F)
+                Diagnostic(ErrorCode.WRN_ConvertingNullableToNonNullable, "b").WithLocation(22, 24)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void CompoundAssignment_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = -1;
+        System.Console.Write(M1(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static void M2(C x) => x.F[0] += 111;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "-1 110").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       18 (0x12)
+  .maxstack  3
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  dup
+  IL_000c:  ldind.i4
+  IL_000d:  ldc.i4.s   111
+  IL_000f:  add
+  IL_0010:  stind.i4
+  IL_0011:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x)[0]);
+        M2(x)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M1(x)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M1(C x) => x.F;
+    static System.Span<int> M2(C x) => x.F;
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.RegularNext);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular11);
+            comp.VerifyDiagnostics(
+                // (18,48): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static System.ReadOnlySpan<int> M1(C x) => x.F;
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F").WithArguments("inline arrays").WithLocation(18, 48),
+                // (19,40): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //     static System.Span<int> M2(C x) => x.F;
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x.F").WithArguments("inline arrays").WithLocation(19, 40)
+                );
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "F").ToArray();
+
+            Assert.Equal("=> x.F", f[^2].Parent.Parent.ToString());
+            var typeInfo = model.GetTypeInfo(f[^2]);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.ReadOnlySpan<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+            Assert.Equal(ConversionKind.InlineArray, model.GetConversion(f[^2]).Kind);
+
+            Assert.Equal("=> x.F", f[^1].Parent.Parent.ToString());
+            typeInfo = model.GetTypeInfo(f[^1]);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.Span<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+            Assert.Equal(ConversionKind.InlineArray, model.GetConversion(f[^1]).Kind);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_03()
+        {
+            var src = @"
+class C
+{
+    private Buffer10<int> F;
+
+    public System.ReadOnlySpan<int> M1() => F;
+    public System.Span<int> M2() => F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.M1()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M1",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Conversion_Variable_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static System.Span<int> M2(C x) => x.F;
+    static System.Span<int> M3(C x)
+    { 
+        System.Span<int> y = x.F;
+        return y;
+    }
+
+    static System.ReadOnlySpan<int> M4(C x) => x.F;
+    static System.ReadOnlySpan<int> M5(C x)
+    { 
+        System.ReadOnlySpan<int> y = x.F;
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (9,40): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.Span<int> M2(C x) => x.F;
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(9, 40),
+                // (13,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(13, 16),
+                // (16,48): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.ReadOnlySpan<int> M4(C x) => x.F;
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(16, 48),
+                // (20,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(20, 16)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Variable_05()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public System.Span<int> M2() => F;
+
+    public System.Span<int> M3()
+    { 
+        System.Span<int> y = F;
+        return y;
+    }
+
+    public System.ReadOnlySpan<int> M4() => F;
+
+    public System.ReadOnlySpan<int> M5()
+    { 
+        System.ReadOnlySpan<int> y = F;
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (6,37): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.Span<int> M2() => F;
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(6, 37),
+                // (11,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(11, 16),
+                // (14,45): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.ReadOnlySpan<int> M4() => F;
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(14, 45),
+                // (19,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(19, 16)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_06()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0] = 111;
+        System.Console.Write(M1(ref x)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M1(ref C x) => x.F;
+    static System.Span<int> M2(ref C x) => x.F;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_07()
+        {
+            var src = @"
+struct C
+{
+    private Buffer10<int> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.ReadOnlySpan<int> M1() => F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<int> M2() => F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.M1()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M1",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_08()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0] = 111;
+        System.Console.Write(M1(ref x)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M1(ref C x)
+    {
+        System.ReadOnlySpan<int> y = x.F;
+        return y;
+    }
+
+    static System.Span<int> M2(ref C x)
+    {
+        System.Span<int> y = x.F;
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_09()
+        {
+            var src = @"
+struct C
+{
+    private Buffer10<int> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.ReadOnlySpan<int> M1()
+    {
+        System.ReadOnlySpan<int> y = F;
+        return y;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<int> M2()
+    {
+        System.Span<int> y = F;
+        return y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.M1()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M1",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_10_1()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x)[0]);
+        M2(x)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M1(x)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M1(C x) => x.F[..5][0];
+    static System.Span<int> M2(C x) => x.F[..5][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_10_2()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x)[0][0]);
+        M2(x)[0][0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M1(x)[0][0]);
+    }
+
+    static System.ReadOnlySpan<Buffer10<int>> M1(C x) => ((System.ReadOnlySpan<Buffer10<int>>)x.F)[..3];
+    static System.Span<Buffer10<int>> M2(C x) => ((System.Span<Buffer10<int>>)x.F)[..3];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_12_1()
+        {
+            var src = @"
+class C
+{
+    private Buffer10<Buffer10<int>> F;
+
+    public System.ReadOnlySpan<int> M1() => F[..5][0];
+    public System.Span<int> M2() => F[..5][0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.M1()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_12_2()
+        {
+            var src = @"
+class C
+{
+    private Buffer10<Buffer10<int>> F;
+
+    public System.ReadOnlySpan<Buffer10<int>> M1() => ((System.ReadOnlySpan<Buffer10<int>>)F)[..3];
+    public System.Span<Buffer10<int>> M2() => ((System.Span<Buffer10<int>>)F)[..3];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0][0] = 111;
+        System.Console.Write(x.M1()[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_13_1()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static System.Span<int> M2(C x) => x.F[..5][0];
+    static System.Span<int> M3(C x)
+    { 
+        System.Span<int> y = x.F[..5][0];
+        return y;
+    }
+
+    static System.ReadOnlySpan<int> M4(C x) => x.F[..5][0];
+    static System.ReadOnlySpan<int> M5(C x)
+    { 
+        System.ReadOnlySpan<int> y = x.F[..5][0];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (9,40): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.Span<int> M2(C x) => x.F[..5][0];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(9, 40),
+                // (13,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(13, 16),
+                // (16,48): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.ReadOnlySpan<int> M4(C x) => x.F[..5][0];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(16, 48),
+                // (20,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(20, 16)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Variable_13_2()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static System.Span<Buffer10<int>> M2(C x) => ((System.Span<Buffer10<int>>)x.F)[..3];
+    static System.Span<Buffer10<int>> M3(C x)
+    { 
+        System.Span<Buffer10<int>> y = ((System.Span<Buffer10<int>>)x.F)[..3];
+        return y;
+    }
+
+    static System.ReadOnlySpan<Buffer10<int>> M4(C x) => ((System.ReadOnlySpan<Buffer10<int>>)x.F)[..3];
+    static System.ReadOnlySpan<Buffer10<int>> M5(C x)
+    { 
+        System.ReadOnlySpan<Buffer10<int>> y = ((System.ReadOnlySpan<Buffer10<int>>)x.F)[..3];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (9,79): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.Span<Buffer10<int>> M2(C x) => ((System.Span<Buffer10<int>>)x.F)[..3];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(9, 79),
+                // (13,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(13, 16),
+                // (16,95): error CS8167: Cannot return by reference a member of parameter 'x' because it is not a ref or out parameter
+                //     static System.ReadOnlySpan<Buffer10<int>> M4(C x) => ((System.ReadOnlySpan<Buffer10<int>>)x.F)[..3];
+                Diagnostic(ErrorCode.ERR_RefReturnParameter2, "x").WithArguments("x").WithLocation(16, 95),
+                // (20,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(20, 16)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Variable_14_1()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public System.Span<int> M2() => F[..5][0];
+
+    public System.Span<int> M3()
+    { 
+        System.Span<int> y = F[..5][0];
+        return y;
+    }
+
+    public System.ReadOnlySpan<int> M4() => F[..5][0];
+
+    public System.ReadOnlySpan<int> M5()
+    { 
+        System.ReadOnlySpan<int> y = F[..5][0];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (6,37): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.Span<int> M2() => F[..5][0];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(6, 37),
+                // (11,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(11, 16),
+                // (14,45): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.ReadOnlySpan<int> M4() => F[..5][0];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(14, 45),
+                // (19,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(19, 16)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Variable_14_2()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+
+    public System.Span<Buffer10<int>> M2() => ((System.Span<Buffer10<int>>)F)[..3];
+
+    public System.Span<Buffer10<int>> M3()
+    { 
+        System.Span<Buffer10<int>> y = ((System.Span<Buffer10<int>>)F)[..3];
+        return y;
+    }
+
+    public System.ReadOnlySpan<Buffer10<int>> M4() => ((System.ReadOnlySpan<Buffer10<int>>)F)[..3];
+
+    public System.ReadOnlySpan<Buffer10<int>> M5()
+    { 
+        System.ReadOnlySpan<Buffer10<int>> y = ((System.ReadOnlySpan<Buffer10<int>>)F)[..3];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (6,76): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.Span<Buffer10<int>> M2() => ((System.Span<Buffer10<int>>)F)[..3];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(6, 76),
+                // (11,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(11, 16),
+                // (14,92): error CS8170: Struct members cannot return 'this' or other instance members by reference
+                //     public System.ReadOnlySpan<Buffer10<int>> M4() => ((System.ReadOnlySpan<Buffer10<int>>)F)[..3];
+                Diagnostic(ErrorCode.ERR_RefReturnStructThis, "F").WithLocation(14, 92),
+                // (19,16): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //         return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(19, 16)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_15_1()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0] = 111;
+        System.Console.Write(M1(ref x)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M1(ref C x) => x.F[..5][0];
+    static System.Span<int> M2(ref C x) => x.F[..5][0];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_15_2()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0][0] = 111;
+        System.Console.Write(M1(ref x)[0][0]);
+    }
+
+    static System.ReadOnlySpan<Buffer10<int>> M1(ref C x) => ((System.ReadOnlySpan<Buffer10<int>>)x.F)[..3];
+    static System.Span<Buffer10<int>> M2(ref C x) => ((System.Span<Buffer10<int>>)x.F)[..3];
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_16_1()
+        {
+            var src = @"
+struct C
+{
+    private Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.ReadOnlySpan<int> M1() => F[..5][0];
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<int> M2() => F[..5][0];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.M1()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_16_2()
+        {
+            var src = @"
+struct C
+{
+    private Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.ReadOnlySpan<Buffer10<int>> M1() => ((System.ReadOnlySpan<Buffer10<int>>)F)[..3];
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<Buffer10<int>> M2() => ((System.Span<Buffer10<int>>)F)[..3];
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0][0] = 111;
+        System.Console.Write(x.M1()[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_17_1()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0] = 111;
+        System.Console.Write(M1(ref x)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M1(ref C x)
+    {
+        System.ReadOnlySpan<int> y = x.F[..5][0];
+        return y;
+    }
+
+    static System.Span<int> M2(ref C x)
+    {
+        System.Span<int> y = x.F[..5][0];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_17_2()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<Buffer10<int>> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        M2(ref x)[0][0] = 111;
+        System.Console.Write(M1(ref x)[0][0]);
+    }
+
+    static System.ReadOnlySpan<Buffer10<int>> M1(ref C x)
+    {
+        System.ReadOnlySpan<Buffer10<int>> y = ((System.ReadOnlySpan<Buffer10<int>>)x.F)[..3];
+        return y;
+    }
+
+    static System.Span<Buffer10<int>> M2(ref C x)
+    {
+        System.Span<Buffer10<int>> y = ((System.Span<Buffer10<int>>)x.F)[..3];
+        return y;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_18_1()
+        {
+            var src = @"
+struct C
+{
+    private Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.ReadOnlySpan<int> M1()
+    {
+        System.ReadOnlySpan<int> y = F[..5][0];
+        return y;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<int> M2()
+    {
+        System.Span<int> y = F[..5][0];
+        return y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0] = 111;
+        System.Console.Write(x.M1()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_18_2()
+        {
+            var src = @"
+struct C
+{
+    private Buffer10<Buffer10<int>> F;
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.ReadOnlySpan<Buffer10<int>> M1()
+    {
+        System.ReadOnlySpan<Buffer10<int>> y = ((System.ReadOnlySpan<Buffer10<int>>)F)[..3];
+        return y;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public System.Span<Buffer10<int>> M2()
+    {
+        System.Span<Buffer10<int>> y = ((System.Span<Buffer10<int>>)F)[..3];
+        return y;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.M2()[0][0] = 111;
+        System.Console.Write(x.M1()[0][0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Conversion_Variable_IsRValue()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        ((System.Span<int>)x.F) = default;
+        ((System.ReadOnlySpan<int>)x.F) = default;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (12,10): error CS0131: The left-hand side of an assignment must be a variable, property or indexer
+                //         ((System.Span<int>)x.F) = default;
+                Diagnostic(ErrorCode.ERR_AssgLvalueExpected, "(System.Span<int>)x.F").WithLocation(12, 10),
+                // (13,10): error CS0131: The left-hand side of an assignment must be a variable, property or indexer
+                //         ((System.ReadOnlySpan<int>)x.F) = default;
+                Diagnostic(ErrorCode.ERR_AssgLvalueExpected, "(System.ReadOnlySpan<int>)x.F").WithLocation(13, 10)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_Readonly_01()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(in C c) => c.F;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Variable_Readonly_02()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(in C c)
+    {
+        System.ReadOnlySpan<int> x = c.F;
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Conversion_Variable_Readonly_04()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c));
+    }
+
+    static int M2(in C c)
+    {
+        return M4(c.F);
+    }
+
+    static int M4(System.Span<int> x)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (24,19): error CS9164: Cannot convert expression to 'Span<int>' because it is not an assignable variable
+                //         return M4(c.F);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToSpanNotSupported, "c.F").WithArguments("System.Span<int>").WithLocation(24, 19)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_ReadonlyContext_01()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+
+    public C()
+    {
+        F = new Buffer10<int>();
+        ((System.Span<int>)F)[0] = 111;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(M2(c)[0]);
+    }
+
+    static System.ReadOnlySpan<int> M2(C c) => c.F;
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Conversion_ReadonlyContext_04()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer10<int> F;
+}
+
+class Program
+{
+    static int M2(C c)
+    {
+        return M4(c.F);
+    }
+
+    static int M4(System.Span<int> x)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+
+            comp.VerifyDiagnostics(
+                // (11,19): error CS9164: Cannot convert expression to 'Span<int>' because it is not an assignable variable
+                //         return M4(c.F);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToSpanNotSupported, "c.F").WithArguments("System.Span<int>").WithLocation(11, 19)
+                );
+        }
+
+        [Fact]
+        public void Conversion_ReadonlyContext_12()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    public readonly int M2()
+    {
+        return M4(F);
+    }
+
+    static int M4(System.Span<int> x)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+
+            comp.VerifyDiagnostics(
+                // (15,19): error CS9164: Cannot convert expression to 'Span<int>' because it is not an assignable variable
+                //         return M4(F);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToSpanNotSupported, "F").WithArguments("System.Span<int>").WithLocation(15, 19)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_ReadonlyContext_14()
+        {
+            var src = @"
+struct C
+{
+    public Buffer10<int> F;
+
+    public C()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        F = b;
+    }
+
+    [System.Diagnostics.CodeAnalysis.UnscopedRef]
+    public readonly System.ReadOnlySpan<int> M2()
+    {
+        System.ReadOnlySpan<int> x = F;
+        return x;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var c = new C();
+        System.Console.Write(c.M2()[0]);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("C.M2",
+@"
+{
+  // Code size       14 (0xe)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.s   10
+  IL_0008:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+  IL_000d:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Conversion_Value_01()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2() => M4(M3(), default);
+
+    static Buffer10<int> M3()
+    {
+        var b = new Buffer10<int>();
+        b[0] = 111;
+        return b;
+    }
+
+    static int M4(System.ReadOnlySpan<int> x, Buffer10<int> y)
+    {
+        return x[0];
+    }
+
+    static int M5() => M6(M3(), default);
+
+    static int M6(System.Span<int> x, Buffer10<int> y)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (9,27): error CS9165: Cannot convert expression to 'ReadOnlySpan<int>' because it may not be passed or returned by reference
+                //     static int M2() => M4(M3(), default);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToReadOnlySpanNotSupported, "M3()").WithArguments("System.ReadOnlySpan<int>").WithLocation(9, 27),
+                // (23,27): error CS9164: Cannot convert expression to 'Span<int>' because it is not an assignable variable
+                //     static int M5() => M6(M3(), default);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToSpanNotSupported, "M3()").WithArguments("System.Span<int>").WithLocation(23, 27)
+                );
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var m3 = tree.GetRoot().DescendantNodes().OfType<IdentifierNameSyntax>().Where(m => m.Identifier.ValueText == "M3").First().Parent;
+
+            Assert.Equal("M3()", m3.ToString());
+            var typeInfo = model.GetTypeInfo(m3);
+
+            Assert.Equal("Buffer10<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("System.ReadOnlySpan<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+            Assert.Equal(ConversionKind.InlineArray, model.GetConversion(m3).Kind);
+        }
+
+        [Fact]
+        public void Conversion_Value_02()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2() => M4(M3(), default);
+
+    static Buffer10<int>? M3() => null;
+
+    static int M4(System.ReadOnlySpan<int>? x, Buffer10<int> y)
+    {
+        return 0;
+    }
+
+    static int M5() => M6(M3(), default);
+
+    static int M6(System.Span<int>? x, Buffer10<int> y)
+    {
+        return 0;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (9,27): error CS1503: Argument 1: cannot convert from 'Buffer10<int>?' to 'System.ReadOnlySpan<int>?'
+                //     static int M2() => M4(M3(), default);
+                Diagnostic(ErrorCode.ERR_BadArgType, "M3()").WithArguments("1", "Buffer10<int>?", "System.ReadOnlySpan<int>?").WithLocation(9, 27),
+                // (13,45): error CS0306: The type 'ReadOnlySpan<int>' may not be used as a type argument
+                //     static int M4(System.ReadOnlySpan<int>? x, Buffer10<int> y)
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "x").WithArguments("System.ReadOnlySpan<int>").WithLocation(13, 45),
+                // (18,27): error CS1503: Argument 1: cannot convert from 'Buffer10<int>?' to 'System.Span<int>?'
+                //     static int M5() => M6(M3(), default);
+                Diagnostic(ErrorCode.ERR_BadArgType, "M3()").WithArguments("1", "Buffer10<int>?", "System.Span<int>?").WithLocation(18, 27),
+                // (20,37): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //     static int M6(System.Span<int>? x, Buffer10<int> y)
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "x").WithArguments("System.Span<int>").WithLocation(20, 37)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Value_03()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2() => M4((System.ReadOnlySpan<int>)M3(), default);
+
+    static Buffer10<int>? M3() => null;
+
+    static int M4(System.ReadOnlySpan<int> x, Buffer10<int> y)
+    {
+        return x[0];
+    }
+
+    static int M5() => M6((System.Span<int>)M3(), default);
+
+    static int M6(System.Span<int> x, Buffer10<int> y)
+    {
+        return x[0];
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (9,27): error CS0030: Cannot convert type 'Buffer10<int>?' to 'System.ReadOnlySpan<int>'
+                //     static int M2() => M4((System.ReadOnlySpan<int>)M3(), default);
+                Diagnostic(ErrorCode.ERR_NoExplicitConv, "(System.ReadOnlySpan<int>)M3()").WithArguments("Buffer10<int>?", "System.ReadOnlySpan<int>").WithLocation(9, 27),
+                // (18,27): error CS0030: Cannot convert type 'Buffer10<int>?' to 'System.Span<int>'
+                //     static int M5() => M6((System.Span<int>)M3(), default);
+                Diagnostic(ErrorCode.ERR_NoExplicitConv, "(System.Span<int>)M3()").WithArguments("Buffer10<int>?", "System.Span<int>").WithLocation(18, 27)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Value_04()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(M2());
+    }
+
+    static int M2() => M4(M3(), default);
+
+    static Buffer10<int> M3() => default;
+
+    static int M4(System.ReadOnlySpan<int>? x, Buffer10<int> y)
+    {
+        return 0;
+    }
+
+    static int M5() => M6(M3(), default);
+
+    static int M6(System.Span<int>? x, Buffer10<int> y)
+    {
+        return 0;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            // Once we stop reporting error CS0306: The type 'ReadOnlySpan<int>' may not be used as a type argument
+            // We might decide to allow a conversion from an inline array expression to nullable span types, but this scenario 
+            // should still remain an error in that case because the expression is a value.
+            comp.VerifyDiagnostics(
+                // (9,27): error CS1503: Argument 1: cannot convert from 'Buffer10<int>' to 'System.ReadOnlySpan<int>?'
+                //     static int M2() => M4(M3(), default);
+                Diagnostic(ErrorCode.ERR_BadArgType, "M3()").WithArguments("1", "Buffer10<int>", "System.ReadOnlySpan<int>?").WithLocation(9, 27),
+                // (13,45): error CS0306: The type 'ReadOnlySpan<int>' may not be used as a type argument
+                //     static int M4(System.ReadOnlySpan<int>? x, Buffer10<int> y)
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "x").WithArguments("System.ReadOnlySpan<int>").WithLocation(13, 45),
+                // (18,27): error CS1503: Argument 1: cannot convert from 'Buffer10<int>' to 'System.Span<int>?'
+                //     static int M5() => M6(M3(), default);
+                Diagnostic(ErrorCode.ERR_BadArgType, "M3()").WithArguments("1", "Buffer10<int>", "System.Span<int>?").WithLocation(18, 27),
+                // (20,37): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //     static int M6(System.Span<int>? x, Buffer10<int> y)
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "x").WithArguments("System.Span<int>").WithLocation(20, 37)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Await_01()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x).Result);
+        M2(x).Wait();
+        System.Console.Write(' ');
+        System.Console.Write(M1(x).Result);
+    }
+
+    static async Task<int> M1(C x) => ((System.ReadOnlySpan<int>)x.F)[await FromResult(0)];
+    static async Task M2(C x) => ((System.Span<int>)x.F)[await FromResult(0)] = 111;
+
+    static async Task<T> FromResult<T>(T r)
+    {
+        await Task.Yield();
+        await Task.Delay(2);
+        return await Task.FromResult(r);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<M1>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      189 (0xbd)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                int V_2,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_3,
+                System.ReadOnlySpan<int> V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M1>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M1>d__1.x""
+    IL_0011:  stfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.3
+    IL_0022:  ldloca.s   V_3
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.3
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_0041:  ldloca.s   V_3
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M1>d__1>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M1>d__1)""
+    IL_0049:  leave.s    IL_00bc
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0051:  stloc.3
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M1>d__1.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0067:  ldloca.s   V_3
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.2
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M1>d__1.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  ldc.i4.s   10
+    IL_007c:  call       ""InlineArrayAsReadOnlySpan<Buffer10<int>, int>(in Buffer10<int>, int)""
+    IL_0081:  stloc.s    V_4
+    IL_0083:  ldloca.s   V_4
+    IL_0085:  ldloc.2
+    IL_0086:  call       ""ref readonly int System.ReadOnlySpan<int>.this[int].get""
+    IL_008b:  ldind.i4
+    IL_008c:  stloc.1
+    IL_008d:  leave.s    IL_00a8
+  }
+  catch System.Exception
+  {
+    IL_008f:  stloc.s    V_5
+    IL_0091:  ldarg.0
+    IL_0092:  ldc.i4.s   -2
+    IL_0094:  stfld      ""int Program.<M1>d__1.<>1__state""
+    IL_0099:  ldarg.0
+    IL_009a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+    IL_009f:  ldloc.s    V_5
+    IL_00a1:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetException(System.Exception)""
+    IL_00a6:  leave.s    IL_00bc
+  }
+  IL_00a8:  ldarg.0
+  IL_00a9:  ldc.i4.s   -2
+  IL_00ab:  stfld      ""int Program.<M1>d__1.<>1__state""
+  IL_00b0:  ldarg.0
+  IL_00b1:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int> Program.<M1>d__1.<>t__builder""
+  IL_00b6:  ldloc.1
+  IL_00b7:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<int>.SetResult(int)""
+  IL_00bc:  ret
+}
+");
+
+            verifier.VerifyIL("Program.<M2>d__2.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      195 (0xc3)
+  .maxstack  3
+  .locals init (int V_0,
+                int V_1,
+                System.Runtime.CompilerServices.TaskAwaiter<int> V_2,
+                System.Span<int> V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<M2>d__2.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldarg.0
+    IL_000b:  ldarg.0
+    IL_000c:  ldfld      ""C Program.<M2>d__2.x""
+    IL_0011:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0016:  ldc.i4.0
+    IL_0017:  call       ""System.Threading.Tasks.Task<int> Program.FromResult<int>(int)""
+    IL_001c:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter<int> System.Threading.Tasks.Task<int>.GetAwaiter()""
+    IL_0021:  stloc.2
+    IL_0022:  ldloca.s   V_2
+    IL_0024:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter<int>.IsCompleted.get""
+    IL_0029:  brtrue.s   IL_0067
+    IL_002b:  ldarg.0
+    IL_002c:  ldc.i4.0
+    IL_002d:  dup
+    IL_002e:  stloc.0
+    IL_002f:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0034:  ldarg.0
+    IL_0035:  ldloc.2
+    IL_0036:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_003b:  ldarg.0
+    IL_003c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_0041:  ldloca.s   V_2
+    IL_0043:  ldarg.0
+    IL_0044:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter<int>, Program.<M2>d__2>(ref System.Runtime.CompilerServices.TaskAwaiter<int>, ref Program.<M2>d__2)""
+    IL_0049:  leave.s    IL_00c2
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0051:  stloc.2
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter<int> Program.<M2>d__2.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter<int>""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_0067:  ldloca.s   V_2
+    IL_0069:  call       ""int System.Runtime.CompilerServices.TaskAwaiter<int>.GetResult()""
+    IL_006e:  stloc.1
+    IL_006f:  ldarg.0
+    IL_0070:  ldfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0075:  ldflda     ""Buffer10<int> C.F""
+    IL_007a:  ldc.i4.s   10
+    IL_007c:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+    IL_0081:  stloc.3
+    IL_0082:  ldloca.s   V_3
+    IL_0084:  ldloc.1
+    IL_0085:  call       ""ref int System.Span<int>.this[int].get""
+    IL_008a:  ldc.i4.s   111
+    IL_008c:  stind.i4
+    IL_008d:  ldarg.0
+    IL_008e:  ldnull
+    IL_008f:  stfld      ""C Program.<M2>d__2.<>7__wrap1""
+    IL_0094:  leave.s    IL_00af
+  }
+  catch System.Exception
+  {
+    IL_0096:  stloc.s    V_4
+    IL_0098:  ldarg.0
+    IL_0099:  ldc.i4.s   -2
+    IL_009b:  stfld      ""int Program.<M2>d__2.<>1__state""
+    IL_00a0:  ldarg.0
+    IL_00a1:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+    IL_00a6:  ldloc.s    V_4
+    IL_00a8:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00ad:  leave.s    IL_00c2
+  }
+  IL_00af:  ldarg.0
+  IL_00b0:  ldc.i4.s   -2
+  IL_00b2:  stfld      ""int Program.<M2>d__2.<>1__state""
+  IL_00b7:  ldarg.0
+  IL_00b8:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<M2>d__2.<>t__builder""
+  IL_00bd:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00c2:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Conversion_ExpressionTree_01()
+        {
+            var src = @"
+using System.Linq.Expressions;
+
+class Program
+{
+    static Expression<System.Func<int>> M1(Buffer10<int> x) =>
+        () => ((System.Span<int>)x).Length;
+
+    static Expression<System.Func<int>> M2(Buffer10<int> x) =>
+        () => ((System.ReadOnlySpan<int>)x).Length;
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (7,16): error CS9170: An expression tree may not contain an inline array access or conversion
+                //         () => ((System.Span<int>)x).Length;
+                Diagnostic(ErrorCode.ERR_ExpressionTreeContainsInlineArrayOperation, "(System.Span<int>)x").WithLocation(7, 16),
+                // (10,16): error CS9170: An expression tree may not contain an inline array access or conversion
+                //         () => ((System.ReadOnlySpan<int>)x).Length;
+                Diagnostic(ErrorCode.ERR_ExpressionTreeContainsInlineArrayOperation, "(System.ReadOnlySpan<int>)x").WithLocation(10, 16)
+                );
+        }
+
+        [Fact]
+        public void Conversion_NotFromType_01()
+        {
+            var src = @"
+class Program
+{
+    public static implicit operator Buffer10<int>(Program x) => default;
+
+    static void Main()
+    {
+        var x = new Program();
+
+        _ = (Buffer10<int>)x;
+        _ = (System.Span<int>)x;
+        _ = (System.ReadOnlySpan<int>)x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            comp.VerifyDiagnostics(
+                // (11,13): error CS0030: Cannot convert type 'Program' to 'System.Span<int>'
+                //         _ = (System.Span<int>)x;
+                Diagnostic(ErrorCode.ERR_NoExplicitConv, "(System.Span<int>)x").WithArguments("Program", "System.Span<int>").WithLocation(11, 13),
+                // (12,13): error CS0030: Cannot convert type 'Program' to 'System.ReadOnlySpan<int>'
+                //         _ = (System.ReadOnlySpan<int>)x;
+                Diagnostic(ErrorCode.ERR_NoExplicitConv, "(System.ReadOnlySpan<int>)x").WithArguments("Program", "System.ReadOnlySpan<int>").WithLocation(12, 13)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_NotFromType_02()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        Buffer10 b = default;
+        b[0] = 111;
+        System.Console.Write(((System.ReadOnlySpan<int>)b)[0]);
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10
+{
+    private int _element0;
+
+    public static implicit operator System.ReadOnlySpan<int>(Buffer10 x) => new[] { -111 };
+}
+";
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Standard_01()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.ReadOnlySpan<int> x) => new C() { F = x[0] };
+}
+
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> b = default;
+        b[0] = 111;
+        System.Console.Write(((C)b).F);
+    }
+}
+" + Buffer10Definition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.RegularNext);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular11);
+            comp.VerifyDiagnostics(
+                // (14,9): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         b[0] = 111;
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "b[0]").WithArguments("inline arrays").WithLocation(14, 9),
+                // (15,34): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         System.Console.Write(((C)b).F);
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "b").WithArguments("inline arrays").WithLocation(15, 34)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Standard_02()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.Span<int> x) => new C() { F = x[0] };
+}
+
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> b = default;
+        b[0] = 111;
+        System.Console.Write(((C)b).F);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Conversion_Standard_03()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.ReadOnlySpan<int> x) => new C() { F = x[0] + 1 };
+    public static implicit operator C(System.Span<int> x) => new C() { F = x[0] - 1 };
+}
+
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> b = default;
+        b[0] = 111;
+        System.Console.Write(((C)b).F);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (16,31): error CS0457: Ambiguous user defined conversions 'C.implicit operator C(ReadOnlySpan<int>)' and 'C.implicit operator C(Span<int>)' when converting from 'Buffer10<int>' to 'C'
+                //         System.Console.Write(((C)b).F);
+                Diagnostic(ErrorCode.ERR_AmbigUDConv, "(C)b").WithArguments("C.implicit operator C(System.ReadOnlySpan<int>)", "C.implicit operator C(System.Span<int>)", "Buffer10<int>", "C").WithLocation(16, 31)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Standard_04()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.ReadOnlySpan<int> x) => new C() { F = x[0] + 1 };
+    public static implicit operator C(System.Span<int> x) => new C() { F = x[0] - 1 };
+}
+
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> b = default;
+        b[0] = 111;
+        Test(in b);
+    }
+
+    static void Test(in Buffer10<int> b)
+    {
+        System.Console.Write(((C)b).F);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (21,31): error CS0457: Ambiguous user defined conversions 'C.implicit operator C(ReadOnlySpan<int>)' and 'C.implicit operator C(Span<int>)' when converting from 'Buffer10<int>' to 'C'
+                //         System.Console.Write(((C)b).F);
+                Diagnostic(ErrorCode.ERR_AmbigUDConv, "(C)b").WithArguments("C.implicit operator C(System.ReadOnlySpan<int>)", "C.implicit operator C(System.Span<int>)", "Buffer10<int>", "C").WithLocation(21, 31)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Standard_05()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.Span<int> x) => new C() { F = x[0] - 1 };
+}
+
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> b = default;
+        b[0] = 111;
+        Test(in b);
+    }
+
+    static void Test(in Buffer10<int> b)
+    {
+        System.Console.Write(((C)b).F);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (20,34): error CS9164: Cannot convert expression to 'Span<int>' because it is not an assignable variable
+                //         System.Console.Write(((C)b).F);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToSpanNotSupported, "b").WithArguments("System.Span<int>").WithLocation(20, 34)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Conversion_Standard_06()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.ReadOnlySpan<int> x) => new C() { F = x[0] };
+}
+
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> b = default;
+        b[0] = 111;
+        Test(in b);
+    }
+
+    static void Test(in Buffer10<int> b)
+    {
+        System.Console.Write(((C)b).F);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            CompileAndVerify(comp, expectedOutput: "111", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Conversion_Standard_07()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.ReadOnlySpan<int> x) => new C() { F = x[0] };
+}
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(((C)new Buffer10<int>()).F);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (13,34): error CS9165: Cannot convert expression to 'ReadOnlySpan<int>' because it may not be passed or returned by reference
+                //         System.Console.Write(((C)new Buffer10<int>()).F);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToReadOnlySpanNotSupported, "new Buffer10<int>()").WithArguments("System.ReadOnlySpan<int>").WithLocation(13, 34)
+                );
+        }
+
+        [Fact]
+        public void Conversion_Standard_08()
+        {
+            var src = @"
+class C
+{
+    public int F;
+
+    public static implicit operator C(System.Span<int> x) => new C() { F = x[0] };
+}
+
+class Program
+{
+    static void Main()
+    {
+        System.Console.Write(((C)new Buffer10<int>()).F);
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (13,34): error CS9164: Cannot convert expression to 'Span<int>' because it is not an assignable variable
+                //         System.Console.Write(((C)new Buffer10<int>()).F);
+                Diagnostic(ErrorCode.ERR_InlineArrayConversionToSpanNotSupported, "new Buffer10<int>()").WithArguments("System.Span<int>").WithLocation(13, 34)
+                );
+        }
+
+        [Fact]
+        public void Conversion_ElementTypeMismatch()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> b = default;
+        _ = (System.Span<long>)b;
+        _ = (System.ReadOnlySpan<long>)b;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            comp.VerifyDiagnostics(
+                // (7,13): error CS0030: Cannot convert type 'Buffer10<int>' to 'System.Span<long>'
+                //         _ = (System.Span<long>)b;
+                Diagnostic(ErrorCode.ERR_NoExplicitConv, "(System.Span<long>)b").WithArguments("Buffer10<int>", "System.Span<long>").WithLocation(7, 13),
+                // (8,13): error CS0030: Cannot convert type 'Buffer10<int>' to 'System.ReadOnlySpan<long>'
+                //         _ = (System.ReadOnlySpan<long>)b;
+                Diagnostic(ErrorCode.ERR_NoExplicitConv, "(System.ReadOnlySpan<long>)b").WithArguments("Buffer10<int>", "System.ReadOnlySpan<long>").WithLocation(8, 13)
+                );
+        }
+
+        [Fact]
+        public void AttributeDefaultValueArgument()
+        {
+            var source =
+@"using System;
+ 
+namespace AttributeTest
+{
+    [A(3, X = 6)]
+    public class A : Attribute
+    {
+        public int X;
+        public A(int x, int y = 4, object a = default(A)) { }
+    
+        static void Main()
+        {
+            typeof(A).GetCustomAttributes(false);
+        }
+    }
+}
+";
+            var compilation = CreateCompilation(source);
+
+            var a = compilation.GlobalNamespace.GetMember<MethodSymbol>("AttributeTest.A..ctor");
+            // The following was causing a reentrancy into DefaultSyntaxValue on the same thread,
+            // effectively blocking the thread indefinitely instead of causing a stack overflow.
+            // DefaultSyntaxValue starts binding the syntax, that triggers attribute binding,
+            // that asks for a default value for the same parameter and we are back where we started.
+            Assert.Null(a.Parameters[2].ExplicitDefaultValue);
+            Assert.True(a.Parameters[2].HasExplicitDefaultValue);
+
+            compilation.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void DefaultSyntaxValueReentrancy_01()
+        {
+            var source =
+@"
+#nullable enable
+
+[A(3, X = 6)]
+public struct A
+{
+    public int X;
+
+    public A(int x, System.Span<int> a = default(A)) { }
+}
+";
+            var compilation = CreateCompilation(source, targetFramework: TargetFramework.Net80);
+
+            var a = compilation.GlobalNamespace.GetTypeMember("A").InstanceConstructors.Where(c => !c.IsDefaultValueTypeConstructor()).Single();
+
+            // The following was causing a reentrancy into DefaultSyntaxValue on the same thread,
+            // effectively blocking the thread indefinitely instead of causing a stack overflow.
+            // DefaultSyntaxValue starts binding the syntax, that triggers attribute binding,
+            // that asks for a default value for the same parameter and we are back where we started.
+            Assert.Null(a.Parameters[1].ExplicitDefaultValue);
+            Assert.True(a.Parameters[1].HasExplicitDefaultValue);
+
+            compilation.VerifyDiagnostics(
+                // (4,2): error CS0616: 'A' is not an attribute class
+                // [A(3, X = 6)]
+                Diagnostic(ErrorCode.ERR_NotAnAttributeClass, "A").WithArguments("A").WithLocation(4, 2),
+                // (4,2): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
+                // [A(3, X = 6)]
+                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "A(3, X = 6)").WithLocation(4, 2),
+                // (9,38): error CS1750: A value of type 'A' cannot be used as a default parameter because there are no standard conversions to type 'Span<int>'
+                //     public A(int x, System.Span<int> a = default(A)) { }
+                Diagnostic(ErrorCode.ERR_NoConversionForDefaultParam, "a").WithArguments("A", "System.Span<int>").WithLocation(9, 38)
+                );
+        }
+
+        [Fact]
+        public void DefaultSyntaxValueReentrancy_02()
+        {
+            var source =
+@"
+#nullable enable
+
+[A(3, X = 6)]
+public struct A
+{
+    public int X;
+
+    public A(int x, int a = default(A)[0]) { }
+}
+";
+            var compilation = CreateCompilation(source, targetFramework: TargetFramework.Net80);
+
+            var a = compilation.GlobalNamespace.GetTypeMember("A").InstanceConstructors.Where(c => !c.IsDefaultValueTypeConstructor()).Single();
+
+            // The following was causing a reentrancy into DefaultSyntaxValue on the same thread,
+            // effectively blocking the thread indefinitely instead of causing a stack overflow.
+            // DefaultSyntaxValue starts binding the syntax, that triggers attribute binding,
+            // that asks for a default value for the same parameter and we are back where we started.
+            Assert.Null(a.Parameters[1].ExplicitDefaultValue);
+            Assert.True(a.Parameters[1].HasExplicitDefaultValue);
+
+            compilation.VerifyDiagnostics(
+                // (4,2): error CS0616: 'A' is not an attribute class
+                // [A(3, X = 6)]
+                Diagnostic(ErrorCode.ERR_NotAnAttributeClass, "A").WithArguments("A").WithLocation(4, 2),
+                // (4,2): error CS0182: An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type
+                // [A(3, X = 6)]
+                Diagnostic(ErrorCode.ERR_BadAttributeArgument, "A(3, X = 6)").WithLocation(4, 2),
+                // (9,29): error CS0021: Cannot apply indexing with [] to an expression of type 'A'
+                //     public A(int x, int a = default(A)[0]) { }
+                Diagnostic(ErrorCode.ERR_BadIndexLHS, "default(A)[0]").WithArguments("A").WithLocation(9, 29)
+                );
+        }
+
+        [Fact]
+        public void CycleThroughAttributes_00()
+        {
+            var source =
+@"
+#pragma warning disable CS0169 // The field 'Buffer10._element0' is never used
+
+class C
+{
+    public static Buffer10 F = default;
+}
+ 
+[System.Runtime.CompilerServices.InlineArray(default(Buffer10))]
+public struct Buffer10
+{
+    private int _element0;
+}
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Struct, AllowMultiple = false)]
+    public sealed class InlineArrayAttribute : Attribute
+    {
+        public InlineArrayAttribute (System.Span<int> length)
+        {
+        }
+    }
+}
+";
+
+            var compilation = CreateCompilation(source, targetFramework: TargetFramework.NetCoreApp);
+            compilation.VerifyDiagnostics(
+                // (9,46): error CS1503: Argument 1: cannot convert from 'Buffer10' to 'System.Span<int>'
+                // [System.Runtime.CompilerServices.InlineArray(default(Buffer10))]
+                Diagnostic(ErrorCode.ERR_BadArgType, "default(Buffer10)").WithArguments("1", "Buffer10", "System.Span<int>").WithLocation(9, 46)
+                );
+        }
+
+        [Fact]
+        public void CycleThroughAttributes_01()
+        {
+            var source =
+@"using System;
+ 
+public class A : Attribute
+{
+    public A(System.Span<int> x) {}
+}
+ 
+[A(default(Buffer10))]
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10
+{
+    private int _element0;
+}
+";
+
+            var compilation = CreateCompilation(source, targetFramework: TargetFramework.Net80);
+            compilation.VerifyDiagnostics(
+                // (8,4): error CS1503: Argument 1: cannot convert from 'Buffer10' to 'System.Span<int>'
+                // [A(default(Buffer10))]
+                Diagnostic(ErrorCode.ERR_BadArgType, "default(Buffer10)").WithArguments("1", "Buffer10", "System.Span<int>").WithLocation(8, 4)
+                );
+        }
+
+        [Fact]
+        public void CycleThroughAttributes_02()
+        {
+            var source =
+@"using System;
+ 
+public class A : Attribute
+{
+    public A(int x) {}
+}
+ 
+[A(default(Buffer10)[0])]
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10
+{
+    private int _element0;
+}
+";
+
+            var compilation = CreateCompilation(source, targetFramework: TargetFramework.Net80);
+            compilation.VerifyDiagnostics(
+                // (8,4): error CS0021: Cannot apply indexing with [] to an expression of type 'Buffer10'
+                // [A(default(Buffer10)[0])]
+                Diagnostic(ErrorCode.ERR_BadIndexLHS, "default(Buffer10)[0]").WithArguments("Buffer10").WithLocation(8, 4)
+                );
+        }
+
+        [Fact]
+        public void CycleThroughAttributes_03()
+        {
+            var source =
+@"
+#pragma warning disable CS0169 // The field 'Buffer10._element0' is never used
+
+class C
+{
+    public static Buffer10 F = default;
+}
+ 
+[System.Runtime.CompilerServices.InlineArray(((System.Span<int>)C.F)[0])]
+public struct Buffer10
+{
+    private int _element0;
+}
+";
+
+            var compilation = CreateCompilation(source, targetFramework: TargetFramework.Net80);
+            compilation.VerifyDiagnostics(
+                // (9,47): error CS0030: Cannot convert type 'Buffer10' to 'System.Span<int>'
+                // [System.Runtime.CompilerServices.InlineArray(((System.Span<int>)C.F)[0])]
+                Diagnostic(ErrorCode.ERR_NoExplicitConv, "(System.Span<int>)C.F").WithArguments("Buffer10", "System.Span<int>").WithLocation(9, 47)
+                );
+        }
+
+        [Fact]
+        public void CycleThroughAttributes_04()
+        {
+            var source =
+@"
+#pragma warning disable CS0169 // The field 'Buffer10._element0' is never used
+
+class C
+{
+    public static Buffer10 F = default;
+}
+ 
+[System.Runtime.CompilerServices.InlineArray(C.F[0])]
+public struct Buffer10
+{
+    private int _element0;
+}
+";
+
+            var compilation = CreateCompilation(source, targetFramework: TargetFramework.Net80);
+            compilation.VerifyDiagnostics(
+                // (9,46): error CS0021: Cannot apply indexing with [] to an expression of type 'Buffer10'
+                // [System.Runtime.CompilerServices.InlineArray(C.F[0])]
+                Diagnostic(ErrorCode.ERR_BadIndexLHS, "C.F[0]").WithArguments("Buffer10").WithLocation(9, 46)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_IndexerIsIgnored_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static void M2(C x) => x.F[0] = 111;
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10<T>
+{
+    private T _element0;
+
+    public T this[int i]
+    {
+        get => this[i];
+        set => this[i] = value;
+    }
+}
+";
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldc.i4.s   111
+  IL_000d:  stind.i4
+  IL_000e:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Index_IndexerIsIgnored_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x);
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[^10];
+    static void M2(C x) => x.F[^10] = 111;
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10<T>
+{
+    private T _element0;
+
+    public T this[int i]
+    {
+        get => this[i];
+        set => this[i] = value;
+    }
+
+    public int Length => 10;
+}
+";
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M1",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  1
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldind.i4
+  IL_000c:  ret
+}
+");
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       15 (0xf)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  call       ""InlineArrayFirstElementRef<Buffer10<int>, int>(ref Buffer10<int>)""
+  IL_000b:  ldc.i4.s   111
+  IL_000d:  stind.i4
+  IL_000e:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_SliceMethodIsIgnored_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer10<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        System.Console.Write(M1(x));
+        M2(x)[0] = 111;
+        System.Console.Write(' ');
+        System.Console.Write(M1(x));
+    }
+
+    static int M1(C x) => x.F[0];
+    static System.Span<int> M2(C x) => x.F[..5];
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10<T>
+{
+    private T _element0;
+
+    public T this[int i]
+    {
+        get => this[i];
+        set => this[i] = value;
+    }
+
+    public int Length => 10;
+    public System.Span<int> Slice(int start, int length) => throw null;
+}
+";
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "0 111", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.M2",
+@"
+{
+  // Code size       13 (0xd)
+  .maxstack  2
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer10<int> C.F""
+  IL_0006:  ldc.i4.5
+  IL_0007:  call       ""InlineArrayAsSpan<Buffer10<int>, int>(ref Buffer10<int>, int)""
+  IL_000c:  ret
+}
+");
+        }
+
+        [Fact]
+        public void ElementAccess_Bounds_01()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[-2];
+        _ = f[-1];
+        _ = f[0];
+        _ = f[9];
+        _ = f[10];
+        _ = f[11];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[-2];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-2").WithLocation(6, 15),
+                // (7,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[-1];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(7, 15),
+                // (10,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[10];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "10").WithLocation(10, 15),
+                // (11,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[11];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(11, 15)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Bounds_02()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[(System.Index)(-2)];
+        _ = f[(System.Index)(-1)];
+        _ = f[(System.Index)0];
+        _ = f[(System.Index)9];
+        _ = f[(System.Index)10];
+        _ = f[(System.Index)11];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,30): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[(System.Index)(-2)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-2").WithLocation(6, 30),
+                // (7,30): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[(System.Index)(-1)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(7, 30),
+                // (10,29): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[(System.Index)10];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "10").WithLocation(10, 29),
+                // (11,29): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[(System.Index)11];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(11, 29)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Bounds_03()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[^12];
+        _ = f[^11];
+        _ = f[^10];
+        _ = f[^1];
+        _ = f[^0];
+        _ = f[^-1];
+        _ = f[^int.MinValue];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[^12];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^12").WithLocation(6, 15),
+                // (7,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[^11];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^11").WithLocation(7, 15),
+                // (10,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[^0];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^0").WithLocation(10, 15),
+                // (11,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[^-1];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^-1").WithLocation(11, 15),
+                // (12,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[^int.MinValue];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^int.MinValue").WithLocation(12, 15)
+                );
+        }
+
+        [Fact]
+        public void ElementAccess_Bounds_04()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[new System.Index(-2, false)];
+        _ = f[new System.Index(-1, false)];
+        _ = f[new System.Index(0, false)];
+        _ = f[new System.Index(9, false)];
+        _ = f[new System.Index(10, false)];
+        _ = f[new System.Index(11, false)];
+
+        _ = f[new System.Index(-2)];
+        _ = f[new System.Index(-1)];
+        _ = f[new System.Index(0)];
+        _ = f[new System.Index(9)];
+        _ = f[new System.Index(10)];
+        _ = f[new System.Index(11)];
+
+        _ = f[new System.Index(12, true)];
+        _ = f[new System.Index(11, true)];
+        _ = f[new System.Index(10, true)];
+        _ = f[new System.Index(1, true)];
+        _ = f[new System.Index(0, true)];
+        _ = f[new System.Index(-1, true)];
+        _ = f[new System.Index(int.MinValue, true)];
+
+        _ = f[new System.Index()];
+        _ = f[new System.Index(value: -1)];
+        _ = f[new System.Index(value: -1, fromEnd: false)];
+        _ = f[new System.Index(fromEnd: false, value: -1)];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(-2, false)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-2").WithLocation(6, 32),
+                // (7,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(-1, false)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(7, 32),
+                // (10,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(10, false)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "10").WithLocation(10, 32),
+                // (11,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(11, false)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(11, 32),
+                // (13,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(-2)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-2").WithLocation(13, 32),
+                // (14,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(-1)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(14, 32),
+                // (17,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(10)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "10").WithLocation(17, 32),
+                // (18,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(11)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(18, 32),
+                // (20,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(12, true)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "12").WithLocation(20, 32),
+                // (21,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(11, true)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(21, 32),
+                // (24,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(0, true)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "0").WithLocation(24, 32),
+                // (25,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(-1, true)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(25, 32),
+                // (26,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(int.MinValue, true)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "int.MinValue").WithLocation(26, 32),
+                // (29,39): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(value: -1)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(29, 39),
+                // (30,39): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(value: -1, fromEnd: false)];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(30, 39)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void ElementAccess_Bounds_05()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> f = default;
+        f[0] = 111;
+        f[9] = 999;
+        Test(f, -1);
+        Test(f, 0);
+        Test(f, 9);
+        Test(f, 10);
+    }
+
+    static void Test(Buffer10<int> f, int index)
+    {
+        System.Console.Write(' ');
+
+        try
+        {
+            System.Console.Write(f[index]);
+        }
+        catch (System.IndexOutOfRangeException)
+        {
+            System.Console.Write(""Throw"");
+        }
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            CompileAndVerify(comp, expectedOutput: " Throw 111 999 Throw", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Slice_Bounds_01()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[-2..];
+        _ = f[-1..];
+        _ = f[0..];
+        _ = f[9..];
+        _ = f[10..];
+        _ = f[11..];
+        _ = f[12..];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[-2..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-2").WithLocation(6, 15),
+                // (7,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[-1..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(7, 15),
+                // (11,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[11..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(11, 15),
+                // (12,15): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[12..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "12").WithLocation(12, 15)
+                );
+        }
+
+        [Fact]
+        public void Slice_Bounds_02()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[..-2];
+        _ = f[..-1];
+        _ = f[..0];
+        _ = f[..9];
+        _ = f[..10];
+        _ = f[..11];
+        _ = f[..12];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..-2];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-2").WithLocation(6, 17),
+                // (7,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..-1];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(7, 17),
+                // (11,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..11];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(11, 17),
+                // (12,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..12];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "12").WithLocation(12, 17)
+                );
+        }
+
+        [Fact]
+        public void Slice_Bounds_03()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[new System.Index(-2)..];
+        _ = f[new System.Index(-1)..];
+        _ = f[new System.Index(0)..];
+        _ = f[new System.Index(9)..];
+        _ = f[new System.Index(10)..];
+        _ = f[new System.Index(11)..];
+        _ = f[new System.Index(12)..];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(-2)..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-2").WithLocation(6, 32),
+                // (7,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(-1)..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "-1").WithLocation(7, 32),
+                // (11,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(11)..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "11").WithLocation(11, 32),
+                // (12,32): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[new System.Index(12)..];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "12").WithLocation(12, 32)
+                );
+        }
+
+        [Fact]
+        public void Slice_Bounds_04()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer10<int> f)
+    {
+        _ = f[..^12];
+        _ = f[..^11];
+        _ = f[..^10];
+        _ = f[..^1];
+        _ = f[..^0];
+        _ = f[..^-1];
+        _ = f[..^int.MinValue];
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..^12];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^12").WithLocation(6, 17),
+                // (7,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..^11];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^11").WithLocation(7, 17),
+                // (11,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..^-1];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^-1").WithLocation(11, 17),
+                // (12,17): error CS9166: Index is outside the bounds of the inline array
+                //         _ = f[..^int.MinValue];
+                Diagnostic(ErrorCode.ERR_InlineArrayIndexOutOfRange, "^int.MinValue").WithLocation(12, 17)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Slice_Bounds_05()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        Buffer10<int> f = default;
+        Test(f, 0..10);
+        Test(f, 9..10);
+        Test(f, 9..11);
+        Test(f, 10..10);
+        Test(f, 10..11);
+    }
+
+    static void Test(Buffer10<int> f, System.Range range)
+    {
+        System.Console.Write(' ');
+
+        try
+        {
+            System.Console.Write(f[range].Length);
+        }
+        catch (System.ArgumentOutOfRangeException)
+        {
+            System.Console.Write(""Throw"");
+        }
+    }
+}
+";
+
+            var comp = CreateCompilation(src + Buffer10Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            CompileAndVerify(comp, expectedOutput: " 10 1 Throw 0 Throw", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void ElementAccess_RuntimeSupport()
+        {
+            var src = @"
+var b = new Buffer();
+_ = b[2];
+
+
+[System.Runtime.CompilerServices.InlineArray(3)]
+struct Buffer
+{
+    private int _element0;
+}
+" + InlineArrayAttributeDefinition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net70);
+            comp.VerifyDiagnostics(
+                // (3,5): error CS9171: Target runtime doesn't support inline array types.
+                // _ = b[2];
+                Diagnostic(ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, "b[2]").WithLocation(3, 5),
+                // (7,8): error CS9171: Target runtime doesn't support inline array types.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, "Buffer").WithLocation(7, 8)
+                );
+
+            Assert.False(comp.SupportsRuntimeCapability(RuntimeCapability.InlineArrayTypes));
+
+            var vbComp = CreateVisualBasicCompilation("", referencedAssemblies: TargetFrameworkUtil.GetReferences(TargetFramework.Net70, null));
+            Assert.False(vbComp.SupportsRuntimeCapability(RuntimeCapability.InlineArrayTypes));
+        }
+
+        [Fact]
+        public void Slice_RuntimeSupport()
+        {
+            var src = @"
+var b = new Buffer();
+_ = b[2..];
+
+
+[System.Runtime.CompilerServices.InlineArray(3)]
+struct Buffer
+{
+    private int _element0;
+}
+" + InlineArrayAttributeDefinition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net70);
+            comp.VerifyDiagnostics(
+                // (3,5): error CS9171: Target runtime doesn't support inline array types.
+                // _ = b[2..];
+                Diagnostic(ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, "b[2..]").WithLocation(3, 5),
+                // (7,8): error CS9171: Target runtime doesn't support inline array types.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, "Buffer").WithLocation(7, 8)
+                );
+        }
+
+        [Fact]
+        public void Conversion_RuntimeSupport()
+        {
+            var src = @"
+var b = new Buffer();
+_ = (System.Span<int>)b;
+
+
+[System.Runtime.CompilerServices.InlineArray(3)]
+struct Buffer
+{
+    private int _element0;
+}
+" + InlineArrayAttributeDefinition;
+
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net70);
+            comp.VerifyDiagnostics(
+                // (3,5): error CS9171: Target runtime doesn't support inline array types.
+                // _ = (System.Span<int>)b;
+                Diagnostic(ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, "(System.Span<int>)b").WithLocation(3, 5),
+                // (7,8): error CS9171: Target runtime doesn't support inline array types.
+                // struct Buffer
+                Diagnostic(ErrorCode.ERR_RuntimeDoesNotSupportInlineArrayTypes, "Buffer").WithLocation(7, 8)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_Variable_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+        Test(x);
+        Test(x);
+    }
+
+    static void Test(C x)
+    {
+        foreach (ref int y in x.F)
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+            y *= -1;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 111 112 113 114 -111 -112 -113 -114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.Test",
+@"
+{
+  // Code size       46 (0x2e)
+  .maxstack  3
+  .locals init (Buffer4<int>& V_0,
+                int V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer4<int> C.F""
+  IL_0006:  stloc.0
+  IL_0007:  ldc.i4.0
+  IL_0008:  stloc.1
+  IL_0009:  br.s       IL_0029
+  IL_000b:  ldloc.0
+  IL_000c:  ldloc.1
+  IL_000d:  call       ""InlineArrayElementRef<Buffer4<int>, int>(ref Buffer4<int>, int)""
+  IL_0012:  ldc.i4.s   32
+  IL_0014:  call       ""void System.Console.Write(char)""
+  IL_0019:  dup
+  IL_001a:  ldind.i4
+  IL_001b:  call       ""void System.Console.Write(int)""
+  IL_0020:  dup
+  IL_0021:  ldind.i4
+  IL_0022:  ldc.i4.m1
+  IL_0023:  mul
+  IL_0024:  stind.i4
+  IL_0025:  ldloc.1
+  IL_0026:  ldc.i4.1
+  IL_0027:  add
+  IL_0028:  stloc.1
+  IL_0029:  ldloc.1
+  IL_002a:  ldc.i4.4
+  IL_002b:  blt.s      IL_000b
+  IL_002d:  ret
+}
+");
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<ForEachStatementSyntax>().Single().Expression;
+            Assert.Equal("x.F", f.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.Equal("Buffer4<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer4<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            Assert.True(model.GetConversion(f).IsIdentity);
+
+            var forEachInfo = model.GetForEachStatementInfo((ForEachStatementSyntax)f.Parent);
+
+            Assert.False(forEachInfo.IsAsynchronous);
+            Assert.Equal("System.Span<System.Int32>.Enumerator System.Span<System.Int32>.GetEnumerator()", forEachInfo.GetEnumeratorMethod.ToTestDisplayString());
+            Assert.Equal("System.Boolean System.Span<System.Int32>.Enumerator.MoveNext()", forEachInfo.MoveNextMethod.ToTestDisplayString());
+            Assert.Equal("ref System.Int32 System.Span<System.Int32>.Enumerator.Current { get; }", forEachInfo.CurrentProperty.ToTestDisplayString());
+            Assert.Null(forEachInfo.DisposeMethod);
+            Assert.Equal("System.Int32", forEachInfo.ElementType.ToTestDisplayString());
+            Assert.True(forEachInfo.ElementConversion.IsIdentity);
+            Assert.True(forEachInfo.CurrentConversion.IsIdentity);
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_Variable_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+        Test(x);
+        Test(x);
+    }
+
+    static void Test(C x)
+    {
+        foreach (ref readonly int y in x.F)
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+            System.Runtime.CompilerServices.Unsafe.AsRef(in y) *= -1;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 111 112 113 114 -111 -112 -113 -114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.Test",
+@"
+{
+  // Code size       51 (0x33)
+  .maxstack  3
+  .locals init (Buffer4<int>& V_0,
+                int V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer4<int> C.F""
+  IL_0006:  stloc.0
+  IL_0007:  ldc.i4.0
+  IL_0008:  stloc.1
+  IL_0009:  br.s       IL_002e
+  IL_000b:  ldloc.0
+  IL_000c:  ldloc.1
+  IL_000d:  call       ""InlineArrayElementRef<Buffer4<int>, int>(ref Buffer4<int>, int)""
+  IL_0012:  ldc.i4.s   32
+  IL_0014:  call       ""void System.Console.Write(char)""
+  IL_0019:  dup
+  IL_001a:  ldind.i4
+  IL_001b:  call       ""void System.Console.Write(int)""
+  IL_0020:  call       ""ref int System.Runtime.CompilerServices.Unsafe.AsRef<int>(scoped in int)""
+  IL_0025:  dup
+  IL_0026:  ldind.i4
+  IL_0027:  ldc.i4.m1
+  IL_0028:  mul
+  IL_0029:  stind.i4
+  IL_002a:  ldloc.1
+  IL_002b:  ldc.i4.1
+  IL_002c:  add
+  IL_002d:  stloc.1
+  IL_002e:  ldloc.1
+  IL_002f:  ldc.i4.4
+  IL_0030:  blt.s      IL_000b
+  IL_0032:  ret
+}
+");
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_Variable_03()
+        {
+            var src = @"
+class C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+        Test(x);
+    }
+
+    static void Test(C x)
+    {
+        foreach (var y in x.F)
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 111 112 113 114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.Test",
+@"
+{
+  // Code size       40 (0x28)
+  .maxstack  2
+  .locals init (Buffer4<int>& V_0,
+                int V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer4<int> C.F""
+  IL_0006:  stloc.0
+  IL_0007:  ldc.i4.0
+  IL_0008:  stloc.1
+  IL_0009:  br.s       IL_0023
+  IL_000b:  ldloc.0
+  IL_000c:  ldloc.1
+  IL_000d:  call       ""InlineArrayElementRef<Buffer4<int>, int>(ref Buffer4<int>, int)""
+  IL_0012:  ldind.i4
+  IL_0013:  ldc.i4.s   32
+  IL_0015:  call       ""void System.Console.Write(char)""
+  IL_001a:  call       ""void System.Console.Write(int)""
+  IL_001f:  ldloc.1
+  IL_0020:  ldc.i4.1
+  IL_0021:  add
+  IL_0022:  stloc.1
+  IL_0023:  ldloc.1
+  IL_0024:  ldc.i4.4
+  IL_0025:  blt.s      IL_000b
+  IL_0027:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Foreach_Variable_04()
+        {
+            var src = @"
+class Program
+{
+    static ref int Test1(Buffer4<int> x)
+    {
+        foreach (ref int y in x)
+        {
+            return ref y;
+        }
+
+        throw null;
+    }
+
+    static ref int Test2(ref Buffer4<int> x)
+    {
+        foreach (ref int z in x)
+        {
+            return ref z;
+        }
+
+        throw null;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (8,24): error CS8157: Cannot return 'y' by reference because it was initialized to a value that cannot be returned by reference
+                //             return ref y;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "y").WithArguments("y").WithLocation(8, 24)
+                );
+        }
+
+        [Fact]
+        public void Foreach_Variable_05_MissingSpan()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer4<int> x)
+    {
+        foreach (var y in x)
+        {
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.MakeTypeMissing(WellKnownType.System_Span_T);
+            comp.VerifyDiagnostics(
+                // (6,27): error CS0518: Predefined type 'System.Span`1' is not defined or imported
+                //         foreach (var y in x)
+                Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "x").WithArguments("System.Span`1").WithLocation(6, 27)
+                );
+        }
+
+        [Fact]
+        public void Foreach_Variable_06_LanguageVersion()
+        {
+            var src = @"
+class Program
+{
+    static void Test(Buffer4<int> x)
+    {
+        foreach (var y in x)
+        {
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.RegularNext);
+            comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular11);
+            comp.VerifyDiagnostics(
+                // (6,27): error CS8652: The feature 'inline arrays' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         foreach (var y in x)
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "x").WithArguments("inline arrays").WithLocation(6, 27)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_Variable_ReadOnly_01()
+        {
+            var src = @"
+struct C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+        Test(in x);
+        Test(in x);
+    }
+
+    static void Test(in C x)
+    {
+        foreach (ref readonly int y in x.F)
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+            System.Runtime.CompilerServices.Unsafe.AsRef(in y) *= -1;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 111 112 113 114 -111 -112 -113 -114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.Test",
+@"
+{
+  // Code size       51 (0x33)
+  .maxstack  3
+  .locals init (Buffer4<int>& V_0,
+                int V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer4<int> C.F""
+  IL_0006:  stloc.0
+  IL_0007:  ldc.i4.0
+  IL_0008:  stloc.1
+  IL_0009:  br.s       IL_002e
+  IL_000b:  ldloc.0
+  IL_000c:  ldloc.1
+  IL_000d:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+  IL_0012:  ldc.i4.s   32
+  IL_0014:  call       ""void System.Console.Write(char)""
+  IL_0019:  dup
+  IL_001a:  ldind.i4
+  IL_001b:  call       ""void System.Console.Write(int)""
+  IL_0020:  call       ""ref int System.Runtime.CompilerServices.Unsafe.AsRef<int>(scoped in int)""
+  IL_0025:  dup
+  IL_0026:  ldind.i4
+  IL_0027:  ldc.i4.m1
+  IL_0028:  mul
+  IL_0029:  stind.i4
+  IL_002a:  ldloc.1
+  IL_002b:  ldc.i4.1
+  IL_002c:  add
+  IL_002d:  stloc.1
+  IL_002e:  ldloc.1
+  IL_002f:  ldc.i4.4
+  IL_0030:  blt.s      IL_000b
+  IL_0032:  ret
+}
+");
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var f = tree.GetRoot().DescendantNodes().OfType<ForEachStatementSyntax>().Single().Expression;
+            Assert.Equal("x.F", f.ToString());
+
+            var typeInfo = model.GetTypeInfo(f);
+
+            Assert.Equal("Buffer4<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer4<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            Assert.True(model.GetConversion(f).IsIdentity);
+
+            var forEachInfo = model.GetForEachStatementInfo((ForEachStatementSyntax)f.Parent);
+
+            Assert.False(forEachInfo.IsAsynchronous);
+            Assert.Equal("System.ReadOnlySpan<System.Int32>.Enumerator System.ReadOnlySpan<System.Int32>.GetEnumerator()", forEachInfo.GetEnumeratorMethod.ToTestDisplayString());
+            Assert.Equal("System.Boolean System.ReadOnlySpan<System.Int32>.Enumerator.MoveNext()", forEachInfo.MoveNextMethod.ToTestDisplayString());
+            Assert.Equal("ref readonly modreq(System.Runtime.InteropServices.InAttribute) System.Int32 System.ReadOnlySpan<System.Int32>.Enumerator.Current { get; }", forEachInfo.CurrentProperty.ToTestDisplayString());
+            Assert.Null(forEachInfo.DisposeMethod);
+            Assert.Equal("System.Int32", forEachInfo.ElementType.ToTestDisplayString());
+            Assert.True(forEachInfo.ElementConversion.IsIdentity);
+            Assert.True(forEachInfo.CurrentConversion.IsIdentity);
+        }
+
+        [Fact]
+        public void Foreach_Variable_ReadOnly_02()
+        {
+            var src = @"
+public struct C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Test(in C x)
+    {
+        foreach (ref int y in x.F)
+        {
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (11,31): error CS8332: Cannot assign to a member of variable 'x' or use it as the right hand side of a ref assignment because it is a readonly variable
+                //         foreach (ref int y in x.F)
+                Diagnostic(ErrorCode.ERR_AssignReadonlyNotField2, "x.F").WithArguments("variable", "x").WithLocation(11, 31)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_Variable_ReadOnly_03()
+        {
+            var src = @"
+struct C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+        Test(in x);
+    }
+
+    static void Test(in C x)
+    {
+        foreach (var y in x.F)
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+public struct Buffer4<T>
+{
+    private T _element0;
+
+    public System.Collections.Generic.IEnumerator<T> GetEnumerator()
+    {
+        throw null;
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 111 112 113 114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.Test",
+@"
+{
+  // Code size       40 (0x28)
+  .maxstack  2
+  .locals init (Buffer4<int>& V_0,
+                int V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldflda     ""Buffer4<int> C.F""
+  IL_0006:  stloc.0
+  IL_0007:  ldc.i4.0
+  IL_0008:  stloc.1
+  IL_0009:  br.s       IL_0023
+  IL_000b:  ldloc.0
+  IL_000c:  ldloc.1
+  IL_000d:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+  IL_0012:  ldind.i4
+  IL_0013:  ldc.i4.s   32
+  IL_0015:  call       ""void System.Console.Write(char)""
+  IL_001a:  call       ""void System.Console.Write(int)""
+  IL_001f:  ldloc.1
+  IL_0020:  ldc.i4.1
+  IL_0021:  add
+  IL_0022:  stloc.1
+  IL_0023:  ldloc.1
+  IL_0024:  ldc.i4.4
+  IL_0025:  blt.s      IL_000b
+  IL_0027:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Foreach_Variable_ReadOnly_04()
+        {
+            var src = @"
+class Program
+{
+    static ref readonly int Test1(in Buffer4<int> x)
+    {
+        foreach (ref readonly int y in x)
+        {
+            return ref y;
+        }
+
+        throw null;
+    }
+
+    static ref readonly int Test2()
+    {
+        Buffer4<int> x = default;
+        ref readonly Buffer4<int> xx = ref x;
+        foreach (ref readonly int yy in xx)
+        {
+            return ref yy;
+        }
+
+        throw null;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (20,24): error CS8157: Cannot return 'yy' by reference because it was initialized to a value that cannot be returned by reference
+                //             return ref yy;
+                Diagnostic(ErrorCode.ERR_RefReturnNonreturnableLocal, "yy").WithArguments("yy").WithLocation(20, 24)
+                );
+        }
+
+        [Fact]
+        public void Foreach_Variable_ReadOnly_05_MissingSpan()
+        {
+            var src = @"
+class Program
+{
+    static void Test(in Buffer4<int> x)
+    {
+        foreach (var y in x)
+        {
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.MakeTypeMissing(WellKnownType.System_ReadOnlySpan_T);
+            comp.VerifyDiagnostics(
+                // (6,27): error CS0518: Predefined type 'System.ReadOnlySpan`1' is not defined or imported
+                //         foreach (var y in x)
+                Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "x").WithArguments("System.ReadOnlySpan`1").WithLocation(6, 27)
+                );
+        }
+
+        [Fact]
+        public void Foreach_Value_01()
+        {
+            var src = @"
+class C
+{
+    public Buffer4<int> F = default;
+}
+
+class Program
+{
+    static void Test(C x)
+    {
+        foreach (ref readonly int y in GetBuffer(x))
+        {
+        }
+    }
+
+    static Buffer4<int> GetBuffer(C x) => x.F;
+
+    void Test(System.Collections.Generic.IEnumerable<int> x)
+    {
+        foreach (ref readonly int y in x)
+        {}
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            // The error wording is somewhat confusing because 'ref readonly' doesn't actually require assignability.
+            // However, it looks like the issue isn't inline array specific (see the second error). In other words,
+            // this is a pre-existing condition.
+            comp.VerifyDiagnostics(
+                // (11,40): error CS1510: A ref or out value must be an assignable variable
+                //         foreach (ref readonly int y in GetBuffer(x))
+                Diagnostic(ErrorCode.ERR_RefLvalueExpected, "GetBuffer(x)").WithLocation(11, 40),
+                // (20,40): error CS1510: A ref or out value must be an assignable variable
+                //         foreach (ref readonly int y in x)
+                Diagnostic(ErrorCode.ERR_RefLvalueExpected, "x").WithLocation(20, 40)
+                );
+        }
+
+        [Fact]
+        public void Foreach_Value_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer4<int> F = default;
+}
+
+class Program
+{
+    static void Test(C x)
+    {
+        foreach (ref int y in GetBuffer(x))
+        {
+        }
+    }
+
+    static Buffer4<int> GetBuffer(C x) => x.F;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (11,31): error CS1510: A ref or out value must be an assignable variable
+                //         foreach (ref int y in GetBuffer(x))
+                Diagnostic(ErrorCode.ERR_RefLvalueExpected, "GetBuffer(x)").WithLocation(11, 31)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_Value_03()
+        {
+            var src = @"
+class C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+        Test(x);
+    }
+
+    static void Test(C x)
+    {
+        foreach (var y in GetBuffer(x))
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+            _ = new Buffer4<int>().ToString();
+        }
+    }
+
+    static Buffer4<int> GetBuffer(C x) => x.F;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 111 112 113 114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.Test",
+@"
+{
+  // Code size       64 (0x40)
+  .maxstack  2
+  .locals init (Buffer4<int> V_0,
+                Buffer4<int>& V_1,
+                int V_2,
+                Buffer4<int> V_3)
+  IL_0000:  ldarg.0
+  IL_0001:  call       ""Buffer4<int> Program.GetBuffer(C)""
+  IL_0006:  stloc.0
+  IL_0007:  ldloca.s   V_0
+  IL_0009:  stloc.1
+  IL_000a:  ldc.i4.0
+  IL_000b:  stloc.2
+  IL_000c:  br.s       IL_003b
+  IL_000e:  ldloc.1
+  IL_000f:  ldloc.2
+  IL_0010:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+  IL_0015:  ldind.i4
+  IL_0016:  ldc.i4.s   32
+  IL_0018:  call       ""void System.Console.Write(char)""
+  IL_001d:  call       ""void System.Console.Write(int)""
+  IL_0022:  ldloca.s   V_3
+  IL_0024:  dup
+  IL_0025:  initobj    ""Buffer4<int>""
+  IL_002b:  constrained. ""Buffer4<int>""
+  IL_0031:  callvirt   ""string object.ToString()""
+  IL_0036:  pop
+  IL_0037:  ldloc.2
+  IL_0038:  ldc.i4.1
+  IL_0039:  add
+  IL_003a:  stloc.2
+  IL_003b:  ldloc.2
+  IL_003c:  ldc.i4.4
+  IL_003d:  blt.s      IL_000e
+  IL_003f:  ret
+}
+");
+
+            var tree = comp.SyntaxTrees.First();
+            var model = comp.GetSemanticModel(tree);
+
+            var collection = tree.GetRoot().DescendantNodes().OfType<ForEachStatementSyntax>().Single().Expression;
+            Assert.Equal("GetBuffer(x)", collection.ToString());
+
+            var typeInfo = model.GetTypeInfo(collection);
+
+            Assert.Equal("Buffer4<System.Int32>", typeInfo.Type.ToTestDisplayString());
+            Assert.Equal("Buffer4<System.Int32>", typeInfo.ConvertedType.ToTestDisplayString());
+
+            Assert.True(model.GetConversion(collection).IsIdentity);
+
+            var forEachInfo = model.GetForEachStatementInfo((ForEachStatementSyntax)collection.Parent);
+
+            Assert.False(forEachInfo.IsAsynchronous);
+            Assert.Equal("System.ReadOnlySpan<System.Int32>.Enumerator System.ReadOnlySpan<System.Int32>.GetEnumerator()", forEachInfo.GetEnumeratorMethod.ToTestDisplayString());
+            Assert.Equal("System.Boolean System.ReadOnlySpan<System.Int32>.Enumerator.MoveNext()", forEachInfo.MoveNextMethod.ToTestDisplayString());
+            Assert.Equal("ref readonly modreq(System.Runtime.InteropServices.InAttribute) System.Int32 System.ReadOnlySpan<System.Int32>.Enumerator.Current { get; }", forEachInfo.CurrentProperty.ToTestDisplayString());
+            Assert.Null(forEachInfo.DisposeMethod);
+            Assert.Equal("System.Int32", forEachInfo.ElementType.ToTestDisplayString());
+            Assert.True(forEachInfo.ElementConversion.IsIdentity);
+            Assert.True(forEachInfo.CurrentConversion.IsIdentity);
+        }
+
+        [Fact]
+        public void Foreach_Value_04()
+        {
+            var src = @"
+class Program
+{
+    static ref int Test()
+    {
+        foreach (var y in GetBuffer())
+        {
+            return ref y;
+        }
+
+        throw null;
+    }
+
+    static Buffer4<int> GetBuffer() => default;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (8,24): error CS1657: Cannot use 'y' as a ref or out value because it is a 'foreach iteration variable'
+                //             return ref y;
+                Diagnostic(ErrorCode.ERR_RefReadonlyLocalCause, "y").WithArguments("y", "foreach iteration variable").WithLocation(8, 24)
+                );
+        }
+
+        [Fact]
+        public void Foreach_Value_05()
+        {
+            var src = @"
+class Program
+{
+    static System.Span<int> Test1()
+    {
+        System.Span<int> x = stackalloc int[2];
+        foreach (var y in GetBuffer(x))
+        {
+            return y;
+        }
+
+        throw null;
+    }
+
+    static System.Span<int> Test2(System.Span<int> xx)
+    {
+        foreach (var yy in GetBuffer(xx))
+        {
+            return yy;
+        }
+
+        throw null;
+    }
+
+    static Buffer10 GetBuffer(System.Span<int> x)
+    {
+        throw null;
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+public ref struct Buffer10
+{
+    private System.Span<int> _element0;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (7,27): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //         foreach (var y in GetBuffer(x))
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "GetBuffer(x)").WithArguments("System.Span<int>").WithLocation(7, 27),
+                // (9,20): error CS8352: Cannot use variable 'y' in this context because it may expose referenced variables outside of their declaration scope
+                //             return y;
+                Diagnostic(ErrorCode.ERR_EscapeVariable, "y").WithArguments("y").WithLocation(9, 20),
+                // (17,28): error CS0306: The type 'Span<int>' may not be used as a type argument
+                //         foreach (var yy in GetBuffer(xx))
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "GetBuffer(xx)").WithArguments("System.Span<int>").WithLocation(17, 28)
+                );
+        }
+
+        [Fact]
+        public void AwaitForeach_01()
+        {
+            var src = @"
+class Program
+{
+    public static async void M()
+    {
+        await foreach(var s in GetBuffer())
+        {
+        }
+    }
+
+    static Buffer4<int> GetBuffer() => default;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,32): error CS8415: Asynchronous foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetAsyncEnumerator'. Did you mean 'foreach' rather than 'await foreach'?
+                //         await foreach(var s in GetBuffer())
+                Diagnostic(ErrorCode.ERR_AwaitForEachMissingMemberWrongAsync, "GetBuffer()").WithArguments("Buffer4<int>", "GetAsyncEnumerator").WithLocation(6, 32)
+                );
+        }
+
+        [Fact]
+        public void AwaitForeach_02()
+        {
+            var src = @"
+class Program
+{
+    public static async void M(Buffer4<int> x)
+    {
+        await foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct Span<T>
+    {
+        public Enumerator GetEnumerator() => default;
+
+        public ref struct Enumerator
+        {
+            public ref T Current => throw null;
+
+            public bool MoveNext() => false;
+        }
+
+        public AsyncEnumerator GetAsyncEnumerator(System.Threading.CancellationToken token = default)
+        {
+            throw null;
+        }
+
+        public sealed class AsyncEnumerator
+        {
+            public async System.Threading.Tasks.Task<bool> MoveNextAsync(int ok = 1)
+            {
+                await System.Threading.Tasks.Task.Yield();
+                return false;
+            }
+            public T Current
+            {
+                get => throw null;
+            }
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,32): error CS8415: Asynchronous foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetAsyncEnumerator'. Did you mean 'foreach' rather than 'await foreach'?
+                //         await foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_AwaitForEachMissingMemberWrongAsync, "x").WithArguments("Buffer4<int>", "GetAsyncEnumerator").WithLocation(6, 32)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void AwaitForeach_03()
+        {
+            var src = @"
+struct C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static async System.Threading.Tasks.Task Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+
+        await foreach (var y in x.F)
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+public struct Buffer4<T>
+{
+    private T _element0;
+
+    public AsyncEnumerator GetAsyncEnumerator(System.Threading.CancellationToken token = default)
+    {
+        return new AsyncEnumerator(new[] { this[0], this[1], this[2], this[3] });
+    }
+
+    public sealed class AsyncEnumerator
+    {
+        private readonly System.Collections.IEnumerator _underlying;
+
+        public AsyncEnumerator(T[] buffer)
+        {
+            _underlying = buffer.GetEnumerator();
+        }
+        
+        public async System.Threading.Tasks.Task<bool> MoveNextAsync(int ok = 1)
+        {
+            await System.Threading.Tasks.Task.Yield();
+            return _underlying.MoveNext();
+        }
+        public T Current
+        {
+            get => (T)_underlying.Current;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            CompileAndVerify(comp, expectedOutput: " 111 112 113 114").VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Foreach_Extension_01()
+        {
+            var src = @"
+class Program
+{
+    public static void M(Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct Span<T>
+    {
+    }
+}
+
+static class Ext 
+{
+    public static Enumerator<T> GetEnumerator<T>(this System.Span<T> f) => default;
+
+    public ref struct Enumerator<T>
+    {
+        public ref T Current => throw null;
+
+        public bool MoveNext() => false;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS1061: 'Buffer4<int>' does not contain a definition for 'GetEnumerator' and no accessible extension method 'GetEnumerator' accepting a first argument of type 'Buffer4<int>' could be found (are you missing a using directive or an assembly reference?)
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_NoSuchMemberOrExtension, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26),
+                // (6,26): error CS1579: foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetEnumerator'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_ForEachMissingMember, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26),
+                // (21,62): warning CS0436: The type 'Span<T>' in '' conflicts with the imported type 'Span<T>' in 'System.Runtime, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. Using the type defined in ''.
+                //     public static Enumerator<T> GetEnumerator<T>(this System.Span<T> f) => default;
+                Diagnostic(ErrorCode.WRN_SameFullNameThisAggAgg, "Span<T>").WithArguments("", "System.Span<T>", "System.Runtime, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", "System.Span<T>").WithLocation(21, 62)
+                );
+        }
+
+        [Fact]
+        public void Foreach_RefMismatch_01()
+        {
+            var src = @"
+class Program
+{
+    public static void M(Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct Span<T>
+    {
+
+        public Enumerator GetEnumerator() => default;
+
+        public ref struct Enumerator
+        {
+            public ref readonly T Current => throw null;
+
+            public bool MoveNext() => false;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS1579: foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetEnumerator'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_ForEachMissingMember, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_RefMismatch_02()
+        {
+            var src = @"
+class Program
+{
+    public static void M(Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct Span<T>
+    {
+
+        public Enumerator GetEnumerator() => default;
+
+        public ref struct Enumerator
+        {
+            public T Current => throw null;
+
+            public bool MoveNext() => false;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS1579: foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetEnumerator'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_ForEachMissingMember, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_RefMismatch_03()
+        {
+            var src = @"
+class Program
+{
+    public static void M(in Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct ReadOnlySpan<T>
+    {
+
+        public Enumerator GetEnumerator() => default;
+
+        public ref struct Enumerator
+        {
+            public ref T Current => throw null;
+
+            public bool MoveNext() => false;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS1579: foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetEnumerator'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_ForEachMissingMember, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_RefMismatch_04()
+        {
+            var src = @"
+class Program
+{
+    public static void M(in Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct ReadOnlySpan<T>
+    {
+
+        public Enumerator GetEnumerator() => default;
+
+        public ref struct Enumerator
+        {
+            public T Current => throw null;
+
+            public bool MoveNext() => false;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS1579: foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetEnumerator'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_ForEachMissingMember, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_ElementTypeMismatch_01()
+        {
+            var src = @"
+class Program
+{
+    public static void M(in Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct ReadOnlySpan<T>
+    {
+        public Enumerator GetEnumerator() => default;
+
+        public ref struct Enumerator
+        {
+            public ref readonly object Current => throw null;
+
+            public bool MoveNext() => false;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS1579: foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetEnumerator'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_ForEachMissingMember, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_NotEnumerableSpan_01()
+        {
+            var src = @"
+class Program
+{
+    public static void M(in Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct ReadOnlySpan<T>
+    {
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS1579: foreach statement cannot operate on variables of type 'Buffer4<int>' because 'Buffer4<int>' does not contain a public instance or extension definition for 'GetEnumerator'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_ForEachMissingMember, "x").WithArguments("Buffer4<int>", "GetEnumerator").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_NotEnumerableSpan_02()
+        {
+            var src = @"
+class Program
+{
+    public static void M(in Buffer4<int> x)
+    {
+        foreach(var s in x)
+        {
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct ReadOnlySpan<T>
+    {
+        public Enumerator GetEnumerator() => default;
+
+        public ref struct Enumerator
+        {
+            public bool MoveNext() => false;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS0117: 'ReadOnlySpan<int>.Enumerator' does not contain a definition for 'Current'
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_NoSuchMember, "x").WithArguments("System.ReadOnlySpan<int>.Enumerator", "Current").WithLocation(6, 26),
+                // (6,26): error CS0202: foreach requires that the return type 'ReadOnlySpan<int>.Enumerator' of 'ReadOnlySpan<int>.GetEnumerator()' must have a suitable public 'MoveNext' method and public 'Current' property
+                //         foreach(var s in x)
+                Diagnostic(ErrorCode.ERR_BadGetEnumerator, "x").WithArguments("System.ReadOnlySpan<int>.Enumerator", "System.ReadOnlySpan<int>.GetEnumerator()").WithLocation(6, 26)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_NotEnumerableSpan_03_Fallback()
+        {
+            var src = @"
+struct C
+{
+    public Buffer4<int> F;
+}
+
+class Program
+{
+    static void Main()
+    {
+        var x = new C();
+        x.F[0] = 111;
+        x.F[1] = 112;
+        x.F[2] = 113;
+        x.F[3] = 114;
+        Test(in x);
+    }
+
+    static void Test(in C x)
+    {
+        foreach (var y in x.F)
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+public struct Buffer4<T>
+{
+    private T _element0;
+
+    public System.Collections.Generic.IEnumerator<T> GetEnumerator()
+    {
+        for (int i = 0; i < 4; i++)
+        {
+            yield return this[i];
+        }
+    }
+}
+
+namespace System
+{
+    public readonly ref struct ReadOnlySpan<T>
+    {
+    }
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 111 112 113 114", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.Test",
+@"
+{
+  // Code size       56 (0x38)
+  .maxstack  2
+  .locals init (System.Collections.Generic.IEnumerator<int> V_0,
+                Buffer4<int> V_1)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""Buffer4<int> C.F""
+  IL_0006:  stloc.1
+  IL_0007:  ldloca.s   V_1
+  IL_0009:  call       ""System.Collections.Generic.IEnumerator<int> Buffer4<int>.GetEnumerator()""
+  IL_000e:  stloc.0
+  .try
+  {
+    IL_000f:  br.s       IL_0023
+    IL_0011:  ldloc.0
+    IL_0012:  callvirt   ""int System.Collections.Generic.IEnumerator<int>.Current.get""
+    IL_0017:  ldc.i4.s   32
+    IL_0019:  call       ""void System.Console.Write(char)""
+    IL_001e:  call       ""void System.Console.Write(int)""
+    IL_0023:  ldloc.0
+    IL_0024:  callvirt   ""bool System.Collections.IEnumerator.MoveNext()""
+    IL_0029:  brtrue.s   IL_0011
+    IL_002b:  leave.s    IL_0037
+  }
+  finally
+  {
+    IL_002d:  ldloc.0
+    IL_002e:  brfalse.s  IL_0036
+    IL_0030:  ldloc.0
+    IL_0031:  callvirt   ""void System.IDisposable.Dispose()""
+    IL_0036:  endfinally
+  }
+  IL_0037:  ret
+}
+");
+        }
+
+        [Fact]
+        public void Foreach_UnsupportedElementType()
+        {
+            var src = @"
+class Program
+{
+    public void M()
+    {
+        foreach(var s in GetBuffer())
+        {
+        }
+    }
+
+    static Buffer GetBuffer() => default;
+}
+
+[System.Runtime.CompilerServices.InlineArray(10)]
+unsafe struct Buffer
+{
+    private void* _element0;
+}
+";
+            var comp = CreateCompilation(src, targetFramework: TargetFramework.Net80, options: TestOptions.DebugDll.WithAllowUnsafe(true));
+            comp.VerifyDiagnostics(
+                // (6,26): error CS0306: The type 'void*' may not be used as a type argument
+                //         foreach(var s in GetBuffer())
+                Diagnostic(ErrorCode.ERR_BadTypeArgument, "GetBuffer()").WithArguments("void*").WithLocation(6, 26)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InAsync_01()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static private Buffer4<int> F = default;
+    private static int index = 0;
+
+    static void Main()
+    {
+        Test().Wait();
+    }
+
+    static async Task Test()
+    {
+        await Task.Yield();
+
+        foreach (var y in GetBuffer())
+        {
+            Increment();
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+
+        await Task.Yield();
+    }
+
+    static ref Buffer4<int> GetBuffer()
+    {
+        System.Console.Write(-1);
+        return ref F;
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            F[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      295 (0x127)
+  .maxstack  3
+  .locals init (int V_0,
+                System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter V_1,
+                System.Runtime.CompilerServices.YieldAwaitable V_2,
+                Buffer4<int>& V_3,
+                int V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldloc.0
+    IL_000b:  ldc.i4.1
+    IL_000c:  beq        IL_00d5
+    IL_0011:  call       ""System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()""
+    IL_0016:  stloc.2
+    IL_0017:  ldloca.s   V_2
+    IL_0019:  call       ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()""
+    IL_001e:  stloc.1
+    IL_001f:  ldloca.s   V_1
+    IL_0021:  call       ""bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get""
+    IL_0026:  brtrue.s   IL_0067
+    IL_0028:  ldarg.0
+    IL_0029:  ldc.i4.0
+    IL_002a:  dup
+    IL_002b:  stloc.0
+    IL_002c:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0031:  ldarg.0
+    IL_0032:  ldloc.1
+    IL_0033:  stfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0038:  ldarg.0
+    IL_0039:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_003e:  ldloca.s   V_1
+    IL_0040:  ldarg.0
+    IL_0041:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, ref Program.<Test>d__3)""
+    IL_0046:  leave      IL_0126
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0051:  stloc.1
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0067:  ldloca.s   V_1
+    IL_0069:  call       ""void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()""
+    IL_006e:  call       ""ref Buffer4<int> Program.GetBuffer()""
+    IL_0073:  stloc.3
+    IL_0074:  ldc.i4.0
+    IL_0075:  stloc.s    V_4
+    IL_0077:  br.s       IL_0099
+    IL_0079:  ldloc.3
+    IL_007a:  ldloc.s    V_4
+    IL_007c:  call       ""InlineArrayElementRef<Buffer4<int>, int>(ref Buffer4<int>, int)""
+    IL_0081:  ldind.i4
+    IL_0082:  call       ""void Program.Increment()""
+    IL_0087:  ldc.i4.s   32
+    IL_0089:  call       ""void System.Console.Write(char)""
+    IL_008e:  call       ""void System.Console.Write(int)""
+    IL_0093:  ldloc.s    V_4
+    IL_0095:  ldc.i4.1
+    IL_0096:  add
+    IL_0097:  stloc.s    V_4
+    IL_0099:  ldloc.s    V_4
+    IL_009b:  ldc.i4.4
+    IL_009c:  blt.s      IL_0079
+    IL_009e:  call       ""System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()""
+    IL_00a3:  stloc.2
+    IL_00a4:  ldloca.s   V_2
+    IL_00a6:  call       ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()""
+    IL_00ab:  stloc.1
+    IL_00ac:  ldloca.s   V_1
+    IL_00ae:  call       ""bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get""
+    IL_00b3:  brtrue.s   IL_00f1
+    IL_00b5:  ldarg.0
+    IL_00b6:  ldc.i4.1
+    IL_00b7:  dup
+    IL_00b8:  stloc.0
+    IL_00b9:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00be:  ldarg.0
+    IL_00bf:  ldloc.1
+    IL_00c0:  stfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00c5:  ldarg.0
+    IL_00c6:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_00cb:  ldloca.s   V_1
+    IL_00cd:  ldarg.0
+    IL_00ce:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, ref Program.<Test>d__3)""
+    IL_00d3:  leave.s    IL_0126
+    IL_00d5:  ldarg.0
+    IL_00d6:  ldfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00db:  stloc.1
+    IL_00dc:  ldarg.0
+    IL_00dd:  ldflda     ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00e2:  initobj    ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter""
+    IL_00e8:  ldarg.0
+    IL_00e9:  ldc.i4.m1
+    IL_00ea:  dup
+    IL_00eb:  stloc.0
+    IL_00ec:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00f1:  ldloca.s   V_1
+    IL_00f3:  call       ""void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()""
+    IL_00f8:  leave.s    IL_0113
+  }
+  catch System.Exception
+  {
+    IL_00fa:  stloc.s    V_5
+    IL_00fc:  ldarg.0
+    IL_00fd:  ldc.i4.s   -2
+    IL_00ff:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0104:  ldarg.0
+    IL_0105:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_010a:  ldloc.s    V_5
+    IL_010c:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_0111:  leave.s    IL_0126
+  }
+  IL_0113:  ldarg.0
+  IL_0114:  ldc.i4.s   -2
+  IL_0116:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_011b:  ldarg.0
+  IL_011c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+  IL_0121:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_0126:  ret
+}
+");
+
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InAsync_02()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public Buffer4<int> F = default;
+}
+
+class Program
+{
+    private static C c = new C();
+    private static int index = 0;
+
+    static void Main()
+    {
+        Test(c).Wait();
+    }
+
+    static async Task Test(C x)
+    {
+        foreach (var y in x.F)
+        {
+            Increment();    
+            System.Console.Write(' ');
+            System.Console.Write(y);
+
+            await Task.Yield();
+            await Task.Delay(2);
+        }
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            c.F[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      357 (0x165)
+  .maxstack  3
+  .locals init (int V_0,
+                System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter V_1,
+                System.Runtime.CompilerServices.YieldAwaitable V_2,
+                System.Runtime.CompilerServices.TaskAwaiter V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse    IL_009a
+    IL_000d:  ldloc.0
+    IL_000e:  ldc.i4.1
+    IL_000f:  beq        IL_00f2
+    IL_0014:  ldarg.0
+    IL_0015:  ldarg.0
+    IL_0016:  ldfld      ""C Program.<Test>d__3.x""
+    IL_001b:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_0020:  ldarg.0
+    IL_0021:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_0026:  ldfld      ""Buffer4<int> C.F""
+    IL_002b:  pop
+    IL_002c:  ldarg.0
+    IL_002d:  ldc.i4.0
+    IL_002e:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0033:  br         IL_0123
+    IL_0038:  ldarg.0
+    IL_0039:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_003e:  ldflda     ""Buffer4<int> C.F""
+    IL_0043:  ldarg.0
+    IL_0044:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0049:  call       ""InlineArrayElementRef<Buffer4<int>, int>(ref Buffer4<int>, int)""
+    IL_004e:  ldind.i4
+    IL_004f:  call       ""void Program.Increment()""
+    IL_0054:  ldc.i4.s   32
+    IL_0056:  call       ""void System.Console.Write(char)""
+    IL_005b:  call       ""void System.Console.Write(int)""
+    IL_0060:  call       ""System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()""
+    IL_0065:  stloc.2
+    IL_0066:  ldloca.s   V_2
+    IL_0068:  call       ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()""
+    IL_006d:  stloc.1
+    IL_006e:  ldloca.s   V_1
+    IL_0070:  call       ""bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get""
+    IL_0075:  brtrue.s   IL_00b6
+    IL_0077:  ldarg.0
+    IL_0078:  ldc.i4.0
+    IL_0079:  dup
+    IL_007a:  stloc.0
+    IL_007b:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0080:  ldarg.0
+    IL_0081:  ldloc.1
+    IL_0082:  stfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0087:  ldarg.0
+    IL_0088:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_008d:  ldloca.s   V_1
+    IL_008f:  ldarg.0
+    IL_0090:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, ref Program.<Test>d__3)""
+    IL_0095:  leave      IL_0164
+    IL_009a:  ldarg.0
+    IL_009b:  ldfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00a0:  stloc.1
+    IL_00a1:  ldarg.0
+    IL_00a2:  ldflda     ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00a7:  initobj    ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter""
+    IL_00ad:  ldarg.0
+    IL_00ae:  ldc.i4.m1
+    IL_00af:  dup
+    IL_00b0:  stloc.0
+    IL_00b1:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00b6:  ldloca.s   V_1
+    IL_00b8:  call       ""void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()""
+    IL_00bd:  ldc.i4.2
+    IL_00be:  call       ""System.Threading.Tasks.Task System.Threading.Tasks.Task.Delay(int)""
+    IL_00c3:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter System.Threading.Tasks.Task.GetAwaiter()""
+    IL_00c8:  stloc.3
+    IL_00c9:  ldloca.s   V_3
+    IL_00cb:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter.IsCompleted.get""
+    IL_00d0:  brtrue.s   IL_010e
+    IL_00d2:  ldarg.0
+    IL_00d3:  ldc.i4.1
+    IL_00d4:  dup
+    IL_00d5:  stloc.0
+    IL_00d6:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00db:  ldarg.0
+    IL_00dc:  ldloc.3
+    IL_00dd:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter Program.<Test>d__3.<>u__2""
+    IL_00e2:  ldarg.0
+    IL_00e3:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_00e8:  ldloca.s   V_3
+    IL_00ea:  ldarg.0
+    IL_00eb:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.TaskAwaiter, ref Program.<Test>d__3)""
+    IL_00f0:  leave.s    IL_0164
+    IL_00f2:  ldarg.0
+    IL_00f3:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter Program.<Test>d__3.<>u__2""
+    IL_00f8:  stloc.3
+    IL_00f9:  ldarg.0
+    IL_00fa:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter Program.<Test>d__3.<>u__2""
+    IL_00ff:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter""
+    IL_0105:  ldarg.0
+    IL_0106:  ldc.i4.m1
+    IL_0107:  dup
+    IL_0108:  stloc.0
+    IL_0109:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_010e:  ldloca.s   V_3
+    IL_0110:  call       ""void System.Runtime.CompilerServices.TaskAwaiter.GetResult()""
+    IL_0115:  ldarg.0
+    IL_0116:  ldarg.0
+    IL_0117:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_011c:  ldc.i4.1
+    IL_011d:  add
+    IL_011e:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0123:  ldarg.0
+    IL_0124:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0129:  ldc.i4.4
+    IL_012a:  blt        IL_0038
+    IL_012f:  ldarg.0
+    IL_0130:  ldnull
+    IL_0131:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_0136:  leave.s    IL_0151
+  }
+  catch System.Exception
+  {
+    IL_0138:  stloc.s    V_4
+    IL_013a:  ldarg.0
+    IL_013b:  ldc.i4.s   -2
+    IL_013d:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0142:  ldarg.0
+    IL_0143:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_0148:  ldloc.s    V_4
+    IL_014a:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_014f:  leave.s    IL_0164
+  }
+  IL_0151:  ldarg.0
+  IL_0152:  ldc.i4.s   -2
+  IL_0154:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0159:  ldarg.0
+  IL_015a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+  IL_015f:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_0164:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Foreach_InAsync_03()
+        {
+            var src = @"
+class Program
+{
+    static async void Test()
+    {
+        foreach (ref int y in GetBuffer())
+        {
+        }
+
+        await System.Threading.Tasks.Task.Yield();
+    }
+
+    static ref Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS8177: Async methods cannot have by-reference locals
+                //         foreach (ref int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_BadAsyncLocalType, "y").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_InAsync_04()
+        {
+            var src = @"
+class Program
+{
+    static async void Test()
+    {
+        foreach (int y in GetBuffer())
+        {
+            await System.Threading.Tasks.Task.Yield();
+        }
+    }
+
+    static ref Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyEmitDiagnostics(
+                // (6,9): error CS8178: A reference returned by a call to 'Program.GetBuffer()' cannot be preserved across 'await' or 'yield' boundary.
+                //         foreach (int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait,
+        @"foreach (int y in GetBuffer())
+        {
+            await System.Threading.Tasks.Task.Yield();
+        }").WithArguments("Program.GetBuffer()").WithLocation(6, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InAsync_05()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static private Buffer4<int> F = default;
+    private static int index = 0;
+
+    static void Main()
+    {
+        Test().Wait();
+    }
+
+    static async Task Test()
+    {
+        await Task.Yield();
+
+        foreach (var y in GetBuffer())
+        {
+            Increment();
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+
+        await Task.Yield();
+    }
+
+    static ref readonly Buffer4<int> GetBuffer()
+    {
+        System.Console.Write(-1);
+        return ref F;
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            F[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      295 (0x127)
+  .maxstack  3
+  .locals init (int V_0,
+                System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter V_1,
+                System.Runtime.CompilerServices.YieldAwaitable V_2,
+                Buffer4<int>& V_3,
+                int V_4,
+                System.Exception V_5)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_004b
+    IL_000a:  ldloc.0
+    IL_000b:  ldc.i4.1
+    IL_000c:  beq        IL_00d5
+    IL_0011:  call       ""System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()""
+    IL_0016:  stloc.2
+    IL_0017:  ldloca.s   V_2
+    IL_0019:  call       ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()""
+    IL_001e:  stloc.1
+    IL_001f:  ldloca.s   V_1
+    IL_0021:  call       ""bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get""
+    IL_0026:  brtrue.s   IL_0067
+    IL_0028:  ldarg.0
+    IL_0029:  ldc.i4.0
+    IL_002a:  dup
+    IL_002b:  stloc.0
+    IL_002c:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0031:  ldarg.0
+    IL_0032:  ldloc.1
+    IL_0033:  stfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0038:  ldarg.0
+    IL_0039:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_003e:  ldloca.s   V_1
+    IL_0040:  ldarg.0
+    IL_0041:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, ref Program.<Test>d__3)""
+    IL_0046:  leave      IL_0126
+    IL_004b:  ldarg.0
+    IL_004c:  ldfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0051:  stloc.1
+    IL_0052:  ldarg.0
+    IL_0053:  ldflda     ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0058:  initobj    ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter""
+    IL_005e:  ldarg.0
+    IL_005f:  ldc.i4.m1
+    IL_0060:  dup
+    IL_0061:  stloc.0
+    IL_0062:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0067:  ldloca.s   V_1
+    IL_0069:  call       ""void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()""
+    IL_006e:  call       ""ref readonly Buffer4<int> Program.GetBuffer()""
+    IL_0073:  stloc.3
+    IL_0074:  ldc.i4.0
+    IL_0075:  stloc.s    V_4
+    IL_0077:  br.s       IL_0099
+    IL_0079:  ldloc.3
+    IL_007a:  ldloc.s    V_4
+    IL_007c:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+    IL_0081:  ldind.i4
+    IL_0082:  call       ""void Program.Increment()""
+    IL_0087:  ldc.i4.s   32
+    IL_0089:  call       ""void System.Console.Write(char)""
+    IL_008e:  call       ""void System.Console.Write(int)""
+    IL_0093:  ldloc.s    V_4
+    IL_0095:  ldc.i4.1
+    IL_0096:  add
+    IL_0097:  stloc.s    V_4
+    IL_0099:  ldloc.s    V_4
+    IL_009b:  ldc.i4.4
+    IL_009c:  blt.s      IL_0079
+    IL_009e:  call       ""System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()""
+    IL_00a3:  stloc.2
+    IL_00a4:  ldloca.s   V_2
+    IL_00a6:  call       ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()""
+    IL_00ab:  stloc.1
+    IL_00ac:  ldloca.s   V_1
+    IL_00ae:  call       ""bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get""
+    IL_00b3:  brtrue.s   IL_00f1
+    IL_00b5:  ldarg.0
+    IL_00b6:  ldc.i4.1
+    IL_00b7:  dup
+    IL_00b8:  stloc.0
+    IL_00b9:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00be:  ldarg.0
+    IL_00bf:  ldloc.1
+    IL_00c0:  stfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00c5:  ldarg.0
+    IL_00c6:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_00cb:  ldloca.s   V_1
+    IL_00cd:  ldarg.0
+    IL_00ce:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, ref Program.<Test>d__3)""
+    IL_00d3:  leave.s    IL_0126
+    IL_00d5:  ldarg.0
+    IL_00d6:  ldfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00db:  stloc.1
+    IL_00dc:  ldarg.0
+    IL_00dd:  ldflda     ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00e2:  initobj    ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter""
+    IL_00e8:  ldarg.0
+    IL_00e9:  ldc.i4.m1
+    IL_00ea:  dup
+    IL_00eb:  stloc.0
+    IL_00ec:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00f1:  ldloca.s   V_1
+    IL_00f3:  call       ""void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()""
+    IL_00f8:  leave.s    IL_0113
+  }
+  catch System.Exception
+  {
+    IL_00fa:  stloc.s    V_5
+    IL_00fc:  ldarg.0
+    IL_00fd:  ldc.i4.s   -2
+    IL_00ff:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0104:  ldarg.0
+    IL_0105:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_010a:  ldloc.s    V_5
+    IL_010c:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_0111:  leave.s    IL_0126
+  }
+  IL_0113:  ldarg.0
+  IL_0114:  ldc.i4.s   -2
+  IL_0116:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_011b:  ldarg.0
+  IL_011c:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+  IL_0121:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_0126:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InAsync_06()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class C
+{
+    public readonly Buffer4<int> F = default;
+}
+
+class Program
+{
+    private static C c = new C();
+    private static int index = 0;
+
+    static void Main()
+    {
+        Test(c).Wait();
+    }
+
+    static async Task Test(C x)
+    {
+        foreach (var y in x.F)
+        {
+            Increment();    
+            System.Console.Write(' ');
+            System.Console.Write(y);
+
+            await Task.Yield();
+            await Task.Delay(2);
+        }
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            System.Runtime.CompilerServices.Unsafe.AsRef(in c.F)[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      357 (0x165)
+  .maxstack  3
+  .locals init (int V_0,
+                System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter V_1,
+                System.Runtime.CompilerServices.YieldAwaitable V_2,
+                System.Runtime.CompilerServices.TaskAwaiter V_3,
+                System.Exception V_4)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse    IL_009a
+    IL_000d:  ldloc.0
+    IL_000e:  ldc.i4.1
+    IL_000f:  beq        IL_00f2
+    IL_0014:  ldarg.0
+    IL_0015:  ldarg.0
+    IL_0016:  ldfld      ""C Program.<Test>d__3.x""
+    IL_001b:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_0020:  ldarg.0
+    IL_0021:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_0026:  ldfld      ""Buffer4<int> C.F""
+    IL_002b:  pop
+    IL_002c:  ldarg.0
+    IL_002d:  ldc.i4.0
+    IL_002e:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0033:  br         IL_0123
+    IL_0038:  ldarg.0
+    IL_0039:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_003e:  ldflda     ""Buffer4<int> C.F""
+    IL_0043:  ldarg.0
+    IL_0044:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0049:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+    IL_004e:  ldind.i4
+    IL_004f:  call       ""void Program.Increment()""
+    IL_0054:  ldc.i4.s   32
+    IL_0056:  call       ""void System.Console.Write(char)""
+    IL_005b:  call       ""void System.Console.Write(int)""
+    IL_0060:  call       ""System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()""
+    IL_0065:  stloc.2
+    IL_0066:  ldloca.s   V_2
+    IL_0068:  call       ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()""
+    IL_006d:  stloc.1
+    IL_006e:  ldloca.s   V_1
+    IL_0070:  call       ""bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get""
+    IL_0075:  brtrue.s   IL_00b6
+    IL_0077:  ldarg.0
+    IL_0078:  ldc.i4.0
+    IL_0079:  dup
+    IL_007a:  stloc.0
+    IL_007b:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0080:  ldarg.0
+    IL_0081:  ldloc.1
+    IL_0082:  stfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_0087:  ldarg.0
+    IL_0088:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_008d:  ldloca.s   V_1
+    IL_008f:  ldarg.0
+    IL_0090:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, ref Program.<Test>d__3)""
+    IL_0095:  leave      IL_0164
+    IL_009a:  ldarg.0
+    IL_009b:  ldfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00a0:  stloc.1
+    IL_00a1:  ldarg.0
+    IL_00a2:  ldflda     ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__3.<>u__1""
+    IL_00a7:  initobj    ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter""
+    IL_00ad:  ldarg.0
+    IL_00ae:  ldc.i4.m1
+    IL_00af:  dup
+    IL_00b0:  stloc.0
+    IL_00b1:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00b6:  ldloca.s   V_1
+    IL_00b8:  call       ""void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()""
+    IL_00bd:  ldc.i4.2
+    IL_00be:  call       ""System.Threading.Tasks.Task System.Threading.Tasks.Task.Delay(int)""
+    IL_00c3:  callvirt   ""System.Runtime.CompilerServices.TaskAwaiter System.Threading.Tasks.Task.GetAwaiter()""
+    IL_00c8:  stloc.3
+    IL_00c9:  ldloca.s   V_3
+    IL_00cb:  call       ""bool System.Runtime.CompilerServices.TaskAwaiter.IsCompleted.get""
+    IL_00d0:  brtrue.s   IL_010e
+    IL_00d2:  ldarg.0
+    IL_00d3:  ldc.i4.1
+    IL_00d4:  dup
+    IL_00d5:  stloc.0
+    IL_00d6:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_00db:  ldarg.0
+    IL_00dc:  ldloc.3
+    IL_00dd:  stfld      ""System.Runtime.CompilerServices.TaskAwaiter Program.<Test>d__3.<>u__2""
+    IL_00e2:  ldarg.0
+    IL_00e3:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_00e8:  ldloca.s   V_3
+    IL_00ea:  ldarg.0
+    IL_00eb:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.TaskAwaiter, Program.<Test>d__3>(ref System.Runtime.CompilerServices.TaskAwaiter, ref Program.<Test>d__3)""
+    IL_00f0:  leave.s    IL_0164
+    IL_00f2:  ldarg.0
+    IL_00f3:  ldfld      ""System.Runtime.CompilerServices.TaskAwaiter Program.<Test>d__3.<>u__2""
+    IL_00f8:  stloc.3
+    IL_00f9:  ldarg.0
+    IL_00fa:  ldflda     ""System.Runtime.CompilerServices.TaskAwaiter Program.<Test>d__3.<>u__2""
+    IL_00ff:  initobj    ""System.Runtime.CompilerServices.TaskAwaiter""
+    IL_0105:  ldarg.0
+    IL_0106:  ldc.i4.m1
+    IL_0107:  dup
+    IL_0108:  stloc.0
+    IL_0109:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_010e:  ldloca.s   V_3
+    IL_0110:  call       ""void System.Runtime.CompilerServices.TaskAwaiter.GetResult()""
+    IL_0115:  ldarg.0
+    IL_0116:  ldarg.0
+    IL_0117:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_011c:  ldc.i4.1
+    IL_011d:  add
+    IL_011e:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0123:  ldarg.0
+    IL_0124:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+    IL_0129:  ldc.i4.4
+    IL_012a:  blt        IL_0038
+    IL_012f:  ldarg.0
+    IL_0130:  ldnull
+    IL_0131:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+    IL_0136:  leave.s    IL_0151
+  }
+  catch System.Exception
+  {
+    IL_0138:  stloc.s    V_4
+    IL_013a:  ldarg.0
+    IL_013b:  ldc.i4.s   -2
+    IL_013d:  stfld      ""int Program.<Test>d__3.<>1__state""
+    IL_0142:  ldarg.0
+    IL_0143:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+    IL_0148:  ldloc.s    V_4
+    IL_014a:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_014f:  leave.s    IL_0164
+  }
+  IL_0151:  ldarg.0
+  IL_0152:  ldc.i4.s   -2
+  IL_0154:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0159:  ldarg.0
+  IL_015a:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__3.<>t__builder""
+  IL_015f:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_0164:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Foreach_InAsync_07()
+        {
+            var src = @"
+class Program
+{
+    static async void Test()
+    {
+        foreach (ref readonly int y in GetBuffer())
+        {
+        }
+
+        await System.Threading.Tasks.Task.Yield();
+    }
+
+    static ref readonly Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,35): error CS8177: Async methods cannot have by-reference locals
+                //         foreach (ref readonly int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_BadAsyncLocalType, "y").WithLocation(6, 35)
+                );
+        }
+
+        [Fact]
+        public void Foreach_InAsync_08()
+        {
+            var src = @"
+class Program
+{
+    static async void Test()
+    {
+        foreach (int y in GetBuffer())
+        {
+            await System.Threading.Tasks.Task.Yield();
+        }
+    }
+
+    static ref readonly Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyEmitDiagnostics(
+                // (6,9): error CS8178: A reference returned by a call to 'Program.GetBuffer()' cannot be preserved across 'await' or 'yield' boundary.
+                //         foreach (int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait,
+        @"foreach (int y in GetBuffer())
+        {
+            await System.Threading.Tasks.Task.Yield();
+        }").WithArguments("Program.GetBuffer()").WithLocation(6, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InAsync_09()
+        {
+            var src = @"
+using System.Threading.Tasks;
+
+class Program
+{
+    static void Main()
+    {
+        Test().Wait();
+    }
+
+    static async Task Test()
+    {
+        foreach (var y in GetBuffer())
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+            await System.Threading.Tasks.Task.Yield();
+        }
+    }
+
+    static Buffer4<int> GetBuffer()
+    {
+        Buffer4<int> x = default;
+        x[0] = 111;
+        x[1] = 112;
+        x[2] = 113;
+        x[3] = 114;
+ 
+        System.Console.Write(-1);
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "-1 111 112 113 114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__1.System.Runtime.CompilerServices.IAsyncStateMachine.MoveNext",
+@"
+{
+  // Code size      224 (0xe0)
+  .maxstack  3
+  .locals init (int V_0,
+                System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter V_1,
+                System.Runtime.CompilerServices.YieldAwaitable V_2,
+                System.Exception V_3)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__1.<>1__state""
+  IL_0006:  stloc.0
+  .try
+  {
+    IL_0007:  ldloc.0
+    IL_0008:  brfalse.s  IL_0076
+    IL_000a:  ldarg.0
+    IL_000b:  call       ""Buffer4<int> Program.GetBuffer()""
+    IL_0010:  stfld      ""Buffer4<int> Program.<Test>d__1.<>7__wrap1""
+    IL_0015:  ldarg.0
+    IL_0016:  ldc.i4.0
+    IL_0017:  stfld      ""int Program.<Test>d__1.<>7__wrap2""
+    IL_001c:  br         IL_00a7
+    IL_0021:  ldarg.0
+    IL_0022:  ldflda     ""Buffer4<int> Program.<Test>d__1.<>7__wrap1""
+    IL_0027:  ldarg.0
+    IL_0028:  ldfld      ""int Program.<Test>d__1.<>7__wrap2""
+    IL_002d:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+    IL_0032:  ldind.i4
+    IL_0033:  ldc.i4.s   32
+    IL_0035:  call       ""void System.Console.Write(char)""
+    IL_003a:  call       ""void System.Console.Write(int)""
+    IL_003f:  call       ""System.Runtime.CompilerServices.YieldAwaitable System.Threading.Tasks.Task.Yield()""
+    IL_0044:  stloc.2
+    IL_0045:  ldloca.s   V_2
+    IL_0047:  call       ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter System.Runtime.CompilerServices.YieldAwaitable.GetAwaiter()""
+    IL_004c:  stloc.1
+    IL_004d:  ldloca.s   V_1
+    IL_004f:  call       ""bool System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.IsCompleted.get""
+    IL_0054:  brtrue.s   IL_0092
+    IL_0056:  ldarg.0
+    IL_0057:  ldc.i4.0
+    IL_0058:  dup
+    IL_0059:  stloc.0
+    IL_005a:  stfld      ""int Program.<Test>d__1.<>1__state""
+    IL_005f:  ldarg.0
+    IL_0060:  ldloc.1
+    IL_0061:  stfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__1.<>u__1""
+    IL_0066:  ldarg.0
+    IL_0067:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__1.<>t__builder""
+    IL_006c:  ldloca.s   V_1
+    IL_006e:  ldarg.0
+    IL_006f:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.AwaitUnsafeOnCompleted<System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, Program.<Test>d__1>(ref System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter, ref Program.<Test>d__1)""
+    IL_0074:  leave.s    IL_00df
+    IL_0076:  ldarg.0
+    IL_0077:  ldfld      ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__1.<>u__1""
+    IL_007c:  stloc.1
+    IL_007d:  ldarg.0
+    IL_007e:  ldflda     ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter Program.<Test>d__1.<>u__1""
+    IL_0083:  initobj    ""System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter""
+    IL_0089:  ldarg.0
+    IL_008a:  ldc.i4.m1
+    IL_008b:  dup
+    IL_008c:  stloc.0
+    IL_008d:  stfld      ""int Program.<Test>d__1.<>1__state""
+    IL_0092:  ldloca.s   V_1
+    IL_0094:  call       ""void System.Runtime.CompilerServices.YieldAwaitable.YieldAwaiter.GetResult()""
+    IL_0099:  ldarg.0
+    IL_009a:  ldarg.0
+    IL_009b:  ldfld      ""int Program.<Test>d__1.<>7__wrap2""
+    IL_00a0:  ldc.i4.1
+    IL_00a1:  add
+    IL_00a2:  stfld      ""int Program.<Test>d__1.<>7__wrap2""
+    IL_00a7:  ldarg.0
+    IL_00a8:  ldfld      ""int Program.<Test>d__1.<>7__wrap2""
+    IL_00ad:  ldc.i4.4
+    IL_00ae:  blt        IL_0021
+    IL_00b3:  leave.s    IL_00cc
+  }
+  catch System.Exception
+  {
+    IL_00b5:  stloc.3
+    IL_00b6:  ldarg.0
+    IL_00b7:  ldc.i4.s   -2
+    IL_00b9:  stfld      ""int Program.<Test>d__1.<>1__state""
+    IL_00be:  ldarg.0
+    IL_00bf:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__1.<>t__builder""
+    IL_00c4:  ldloc.3
+    IL_00c5:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetException(System.Exception)""
+    IL_00ca:  leave.s    IL_00df
+  }
+  IL_00cc:  ldarg.0
+  IL_00cd:  ldc.i4.s   -2
+  IL_00cf:  stfld      ""int Program.<Test>d__1.<>1__state""
+  IL_00d4:  ldarg.0
+  IL_00d5:  ldflda     ""System.Runtime.CompilerServices.AsyncTaskMethodBuilder Program.<Test>d__1.<>t__builder""
+  IL_00da:  call       ""void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.SetResult()""
+  IL_00df:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: "-1 111 112 113 114").VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InIterator_01()
+        {
+            var src = @"
+class Program
+{
+    static private Buffer4<int> F = default;
+    private static int index = 0;
+
+    static void Main()
+    {
+        foreach (var a in Test())
+        {}
+    }
+
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        yield return -1;
+
+        foreach (var y in GetBuffer())
+        {
+            Increment();
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+
+        yield return -2;
+    }
+
+    static ref Buffer4<int> GetBuffer()
+    {
+        System.Console.Write(-1);
+        return ref F;
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            F[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Collections.IEnumerator.MoveNext",
+@"
+{
+  // Code size      126 (0x7e)
+  .maxstack  2
+  .locals init (int V_0,
+                Buffer4<int>& V_1,
+                int V_2)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  IL_0007:  ldloc.0
+  IL_0008:  switch    (
+        IL_001b,
+        IL_0032,
+        IL_0075)
+  IL_0019:  ldc.i4.0
+  IL_001a:  ret
+  IL_001b:  ldarg.0
+  IL_001c:  ldc.i4.m1
+  IL_001d:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0022:  ldarg.0
+  IL_0023:  ldc.i4.m1
+  IL_0024:  stfld      ""int Program.<Test>d__3.<>2__current""
+  IL_0029:  ldarg.0
+  IL_002a:  ldc.i4.1
+  IL_002b:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0030:  ldc.i4.1
+  IL_0031:  ret
+  IL_0032:  ldarg.0
+  IL_0033:  ldc.i4.m1
+  IL_0034:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0039:  call       ""ref Buffer4<int> Program.GetBuffer()""
+  IL_003e:  stloc.1
+  IL_003f:  ldc.i4.0
+  IL_0040:  stloc.2
+  IL_0041:  br.s       IL_0060
+  IL_0043:  ldloc.1
+  IL_0044:  ldloc.2
+  IL_0045:  call       ""InlineArrayElementRef<Buffer4<int>, int>(ref Buffer4<int>, int)""
+  IL_004a:  ldind.i4
+  IL_004b:  call       ""void Program.Increment()""
+  IL_0050:  ldc.i4.s   32
+  IL_0052:  call       ""void System.Console.Write(char)""
+  IL_0057:  call       ""void System.Console.Write(int)""
+  IL_005c:  ldloc.2
+  IL_005d:  ldc.i4.1
+  IL_005e:  add
+  IL_005f:  stloc.2
+  IL_0060:  ldloc.2
+  IL_0061:  ldc.i4.4
+  IL_0062:  blt.s      IL_0043
+  IL_0064:  ldarg.0
+  IL_0065:  ldc.i4.s   -2
+  IL_0067:  stfld      ""int Program.<Test>d__3.<>2__current""
+  IL_006c:  ldarg.0
+  IL_006d:  ldc.i4.2
+  IL_006e:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0073:  ldc.i4.1
+  IL_0074:  ret
+  IL_0075:  ldarg.0
+  IL_0076:  ldc.i4.m1
+  IL_0077:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_007c:  ldc.i4.0
+  IL_007d:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InIterator_02()
+        {
+            var src = @"
+class C
+{
+    public Buffer4<int> F = default;
+}
+
+class Program
+{
+    private static C c = new C();
+    private static int index = 0;
+
+    static void Main()
+    {
+        foreach (var a in Test(c))
+        {}
+    }
+
+    static System.Collections.Generic.IEnumerable<int> Test(C x)
+    {
+        foreach (var y in x.F)
+        {
+            Increment();    
+            System.Console.Write(' ');
+            System.Console.Write(y);
+
+            yield return -1;
+        }
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            c.F[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Collections.IEnumerator.MoveNext",
+@"
+{
+  // Code size      151 (0x97)
+  .maxstack  3
+  .locals init (int V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  IL_0007:  ldloc.0
+  IL_0008:  brfalse.s  IL_0010
+  IL_000a:  ldloc.0
+  IL_000b:  ldc.i4.1
+  IL_000c:  beq.s      IL_0070
+  IL_000e:  ldc.i4.0
+  IL_000f:  ret
+  IL_0010:  ldarg.0
+  IL_0011:  ldc.i4.m1
+  IL_0012:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0017:  ldarg.0
+  IL_0018:  ldarg.0
+  IL_0019:  ldfld      ""C Program.<Test>d__3.x""
+  IL_001e:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_0023:  ldarg.0
+  IL_0024:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_0029:  ldfld      ""Buffer4<int> C.F""
+  IL_002e:  pop
+  IL_002f:  ldarg.0
+  IL_0030:  ldc.i4.0
+  IL_0031:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_0036:  br.s       IL_0085
+  IL_0038:  ldarg.0
+  IL_0039:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_003e:  ldflda     ""Buffer4<int> C.F""
+  IL_0043:  ldarg.0
+  IL_0044:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_0049:  call       ""InlineArrayElementRef<Buffer4<int>, int>(ref Buffer4<int>, int)""
+  IL_004e:  ldind.i4
+  IL_004f:  call       ""void Program.Increment()""
+  IL_0054:  ldc.i4.s   32
+  IL_0056:  call       ""void System.Console.Write(char)""
+  IL_005b:  call       ""void System.Console.Write(int)""
+  IL_0060:  ldarg.0
+  IL_0061:  ldc.i4.m1
+  IL_0062:  stfld      ""int Program.<Test>d__3.<>2__current""
+  IL_0067:  ldarg.0
+  IL_0068:  ldc.i4.1
+  IL_0069:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_006e:  ldc.i4.1
+  IL_006f:  ret
+  IL_0070:  ldarg.0
+  IL_0071:  ldc.i4.m1
+  IL_0072:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0077:  ldarg.0
+  IL_0078:  ldarg.0
+  IL_0079:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_007e:  ldc.i4.1
+  IL_007f:  add
+  IL_0080:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_0085:  ldarg.0
+  IL_0086:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_008b:  ldc.i4.4
+  IL_008c:  blt.s      IL_0038
+  IL_008e:  ldarg.0
+  IL_008f:  ldnull
+  IL_0090:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_0095:  ldc.i4.0
+  IL_0096:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Foreach_InIterator_03()
+        {
+            var src = @"
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        foreach (ref int y in GetBuffer())
+        {
+        }
+
+        yield return -1;
+    }
+
+    static ref Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,26): error CS8176: Iterators cannot have by-reference locals
+                //         foreach (ref int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_BadIteratorLocalType, "y").WithLocation(6, 26)
+                );
+        }
+
+        [Fact]
+        public void Foreach_InIterator_04()
+        {
+            var src = @"
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        foreach (int y in GetBuffer())
+        {
+            yield return -1;
+        }
+    }
+
+    static ref Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyEmitDiagnostics(
+                // (6,9): error CS8178: A reference returned by a call to 'Program.GetBuffer()' cannot be preserved across 'await' or 'yield' boundary.
+                //         foreach (int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait,
+        @"foreach (int y in GetBuffer())
+        {
+            yield return -1;
+        }").WithArguments("Program.GetBuffer()").WithLocation(6, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InIterator_05()
+        {
+            var src = @"
+class Program
+{
+    static private Buffer4<int> F = default;
+    private static int index = 0;
+
+    static void Main()
+    {
+        foreach (var a in Test())
+        {}
+    }
+
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        yield return -1;
+
+        foreach (var y in GetBuffer())
+        {
+            Increment();
+            System.Console.Write(' ');
+            System.Console.Write(y);
+        }
+
+        yield return -2;
+    }
+
+    static ref readonly Buffer4<int> GetBuffer()
+    {
+        System.Console.Write(-1);
+        return ref F;
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            F[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Collections.IEnumerator.MoveNext",
+@"
+{
+  // Code size      126 (0x7e)
+  .maxstack  2
+  .locals init (int V_0,
+                Buffer4<int>& V_1,
+                int V_2)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  IL_0007:  ldloc.0
+  IL_0008:  switch    (
+        IL_001b,
+        IL_0032,
+        IL_0075)
+  IL_0019:  ldc.i4.0
+  IL_001a:  ret
+  IL_001b:  ldarg.0
+  IL_001c:  ldc.i4.m1
+  IL_001d:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0022:  ldarg.0
+  IL_0023:  ldc.i4.m1
+  IL_0024:  stfld      ""int Program.<Test>d__3.<>2__current""
+  IL_0029:  ldarg.0
+  IL_002a:  ldc.i4.1
+  IL_002b:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0030:  ldc.i4.1
+  IL_0031:  ret
+  IL_0032:  ldarg.0
+  IL_0033:  ldc.i4.m1
+  IL_0034:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0039:  call       ""ref readonly Buffer4<int> Program.GetBuffer()""
+  IL_003e:  stloc.1
+  IL_003f:  ldc.i4.0
+  IL_0040:  stloc.2
+  IL_0041:  br.s       IL_0060
+  IL_0043:  ldloc.1
+  IL_0044:  ldloc.2
+  IL_0045:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+  IL_004a:  ldind.i4
+  IL_004b:  call       ""void Program.Increment()""
+  IL_0050:  ldc.i4.s   32
+  IL_0052:  call       ""void System.Console.Write(char)""
+  IL_0057:  call       ""void System.Console.Write(int)""
+  IL_005c:  ldloc.2
+  IL_005d:  ldc.i4.1
+  IL_005e:  add
+  IL_005f:  stloc.2
+  IL_0060:  ldloc.2
+  IL_0061:  ldc.i4.4
+  IL_0062:  blt.s      IL_0043
+  IL_0064:  ldarg.0
+  IL_0065:  ldc.i4.s   -2
+  IL_0067:  stfld      ""int Program.<Test>d__3.<>2__current""
+  IL_006c:  ldarg.0
+  IL_006d:  ldc.i4.2
+  IL_006e:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0073:  ldc.i4.1
+  IL_0074:  ret
+  IL_0075:  ldarg.0
+  IL_0076:  ldc.i4.m1
+  IL_0077:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_007c:  ldc.i4.0
+  IL_007d:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: "-1 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InIterator_06()
+        {
+            var src = @"
+class C
+{
+    public readonly Buffer4<int> F = default;
+}
+
+class Program
+{
+    private static C c = new C();
+    private static int index = 0;
+
+    static void Main()
+    {
+        foreach (var a in Test(c))
+        {}
+    }
+
+    static System.Collections.Generic.IEnumerable<int> Test(C x)
+    {
+        foreach (var y in x.F)
+        {
+            Increment();    
+            System.Console.Write(' ');
+            System.Console.Write(y);
+
+            yield return -1;
+        }
+    }
+
+    static void Increment()
+    {
+        index++;
+
+        if (index < 4)
+        {
+            System.Runtime.CompilerServices.Unsafe.AsRef(in c.F)[index] = index;
+        }
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__3.System.Collections.IEnumerator.MoveNext",
+@"
+{
+  // Code size      151 (0x97)
+  .maxstack  3
+  .locals init (int V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0006:  stloc.0
+  IL_0007:  ldloc.0
+  IL_0008:  brfalse.s  IL_0010
+  IL_000a:  ldloc.0
+  IL_000b:  ldc.i4.1
+  IL_000c:  beq.s      IL_0070
+  IL_000e:  ldc.i4.0
+  IL_000f:  ret
+  IL_0010:  ldarg.0
+  IL_0011:  ldc.i4.m1
+  IL_0012:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0017:  ldarg.0
+  IL_0018:  ldarg.0
+  IL_0019:  ldfld      ""C Program.<Test>d__3.x""
+  IL_001e:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_0023:  ldarg.0
+  IL_0024:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_0029:  ldfld      ""Buffer4<int> C.F""
+  IL_002e:  pop
+  IL_002f:  ldarg.0
+  IL_0030:  ldc.i4.0
+  IL_0031:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_0036:  br.s       IL_0085
+  IL_0038:  ldarg.0
+  IL_0039:  ldfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_003e:  ldflda     ""Buffer4<int> C.F""
+  IL_0043:  ldarg.0
+  IL_0044:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_0049:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+  IL_004e:  ldind.i4
+  IL_004f:  call       ""void Program.Increment()""
+  IL_0054:  ldc.i4.s   32
+  IL_0056:  call       ""void System.Console.Write(char)""
+  IL_005b:  call       ""void System.Console.Write(int)""
+  IL_0060:  ldarg.0
+  IL_0061:  ldc.i4.m1
+  IL_0062:  stfld      ""int Program.<Test>d__3.<>2__current""
+  IL_0067:  ldarg.0
+  IL_0068:  ldc.i4.1
+  IL_0069:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_006e:  ldc.i4.1
+  IL_006f:  ret
+  IL_0070:  ldarg.0
+  IL_0071:  ldc.i4.m1
+  IL_0072:  stfld      ""int Program.<Test>d__3.<>1__state""
+  IL_0077:  ldarg.0
+  IL_0078:  ldarg.0
+  IL_0079:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_007e:  ldc.i4.1
+  IL_007f:  add
+  IL_0080:  stfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_0085:  ldarg.0
+  IL_0086:  ldfld      ""int Program.<Test>d__3.<>7__wrap1""
+  IL_008b:  ldc.i4.4
+  IL_008c:  blt.s      IL_0038
+  IL_008e:  ldarg.0
+  IL_008f:  ldnull
+  IL_0090:  stfld      ""C Program.<Test>d__3.<>7__wrap2""
+  IL_0095:  ldc.i4.0
+  IL_0096:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: " 0 1 2 3", verify: Verification.Fails).VerifyDiagnostics();
+        }
+
+        [Fact]
+        public void Foreach_InIterator_07()
+        {
+            var src = @"
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        foreach (ref readonly int y in GetBuffer())
+        {
+        }
+
+        yield return -1;
+    }
+
+    static ref readonly Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+            comp.VerifyDiagnostics(
+                // (6,35): error CS8176: Iterators cannot have by-reference locals
+                //         foreach (ref readonly int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_BadIteratorLocalType, "y").WithLocation(6, 35)
+                );
+        }
+
+        [Fact]
+        public void Foreach_InIterator_08()
+        {
+            var src = @"
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        foreach (int y in GetBuffer())
+        {
+            yield return -1;
+        }
+    }
+
+    static ref readonly Buffer4<int> GetBuffer() => throw null;
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseDll);
+
+            comp.VerifyEmitDiagnostics(
+                // (6,9): error CS8178: A reference returned by a call to 'Program.GetBuffer()' cannot be preserved across 'await' or 'yield' boundary.
+                //         foreach (int y in GetBuffer())
+                Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait,
+        @"foreach (int y in GetBuffer())
+        {
+            yield return -1;
+        }").WithArguments("Program.GetBuffer()").WithLocation(6, 9)
+                );
+        }
+
+        [ConditionalFact(typeof(CoreClrOnly))]
+        public void Foreach_InIterator_09()
+        {
+            var src = @"
+class Program
+{
+    static void Main()
+    {
+        foreach (var a in Test())
+        {}
+    }
+
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        foreach (var y in GetBuffer())
+        {
+            System.Console.Write(' ');
+            System.Console.Write(y);
+            yield return -1;
+        }
+    }
+
+    static Buffer4<int> GetBuffer()
+    {
+        Buffer4<int> x = default;
+        x[0] = 111;
+        x[1] = 112;
+        x[2] = 113;
+        x[3] = 114;
+ 
+        System.Console.Write(-1);
+        return x;
+    }
+}
+";
+            var comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.ReleaseExe);
+            var verifier = CompileAndVerify(comp, expectedOutput: "-1 111 112 113 114").VerifyDiagnostics();
+
+            verifier.VerifyIL("Program.<Test>d__1.System.Collections.IEnumerator.MoveNext",
+@"
+{
+  // Code size      121 (0x79)
+  .maxstack  3
+  .locals init (int V_0)
+  IL_0000:  ldarg.0
+  IL_0001:  ldfld      ""int Program.<Test>d__1.<>1__state""
+  IL_0006:  stloc.0
+  IL_0007:  ldloc.0
+  IL_0008:  brfalse.s  IL_0010
+  IL_000a:  ldloc.0
+  IL_000b:  ldc.i4.1
+  IL_000c:  beq.s      IL_0059
+  IL_000e:  ldc.i4.0
+  IL_000f:  ret
+  IL_0010:  ldarg.0
+  IL_0011:  ldc.i4.m1
+  IL_0012:  stfld      ""int Program.<Test>d__1.<>1__state""
+  IL_0017:  ldarg.0
+  IL_0018:  call       ""Buffer4<int> Program.GetBuffer()""
+  IL_001d:  stfld      ""Buffer4<int> Program.<Test>d__1.<>7__wrap1""
+  IL_0022:  ldarg.0
+  IL_0023:  ldc.i4.0
+  IL_0024:  stfld      ""int Program.<Test>d__1.<>7__wrap2""
+  IL_0029:  br.s       IL_006e
+  IL_002b:  ldarg.0
+  IL_002c:  ldflda     ""Buffer4<int> Program.<Test>d__1.<>7__wrap1""
+  IL_0031:  ldarg.0
+  IL_0032:  ldfld      ""int Program.<Test>d__1.<>7__wrap2""
+  IL_0037:  call       ""InlineArrayElementRefReadOnly<Buffer4<int>, int>(in Buffer4<int>, int)""
+  IL_003c:  ldind.i4
+  IL_003d:  ldc.i4.s   32
+  IL_003f:  call       ""void System.Console.Write(char)""
+  IL_0044:  call       ""void System.Console.Write(int)""
+  IL_0049:  ldarg.0
+  IL_004a:  ldc.i4.m1
+  IL_004b:  stfld      ""int Program.<Test>d__1.<>2__current""
+  IL_0050:  ldarg.0
+  IL_0051:  ldc.i4.1
+  IL_0052:  stfld      ""int Program.<Test>d__1.<>1__state""
+  IL_0057:  ldc.i4.1
+  IL_0058:  ret
+  IL_0059:  ldarg.0
+  IL_005a:  ldc.i4.m1
+  IL_005b:  stfld      ""int Program.<Test>d__1.<>1__state""
+  IL_0060:  ldarg.0
+  IL_0061:  ldarg.0
+  IL_0062:  ldfld      ""int Program.<Test>d__1.<>7__wrap2""
+  IL_0067:  ldc.i4.1
+  IL_0068:  add
+  IL_0069:  stfld      ""int Program.<Test>d__1.<>7__wrap2""
+  IL_006e:  ldarg.0
+  IL_006f:  ldfld      ""int Program.<Test>d__1.<>7__wrap2""
+  IL_0074:  ldc.i4.4
+  IL_0075:  blt.s      IL_002b
+  IL_0077:  ldc.i4.0
+  IL_0078:  ret
+}
+");
+            comp = CreateCompilation(src + Buffer4Definition, targetFramework: TargetFramework.Net80, options: TestOptions.DebugExe);
+            CompileAndVerify(comp, expectedOutput: "-1 111 112 113 114").VerifyDiagnostics();
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests.cs b/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests.cs
index 4f99b0a55c5aa..079528fbe3997 100644
--- a/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests.cs
+++ b/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests.cs
@@ -7684,7 +7684,7 @@ .maxstack  2
   .locals init (int V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       ""ComputeReadOnlySpanHash""
+  IL_0001:  call       ""ComputeReadOnlySpanHash(System.ReadOnlySpan<char>)""
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x75b03721
@@ -8000,7 +8000,7 @@ static int GetResult(ReadOnlySpan<char> chars)
   .maxstack  2
   .locals init (uint V_0)
   IL_0000:  ldarg.0
-  IL_0001:  call       ""ComputeReadOnlySpanHash""
+  IL_0001:  call       ""ComputeReadOnlySpanHash(System.ReadOnlySpan<char>)""
   IL_0006:  stloc.0
   IL_0007:  ldloc.0
   IL_0008:  ldc.i4     0x75b03721
@@ -9282,7 +9282,7 @@ .maxstack  2
   .locals init (int V_0,
                 uint V_1)
   IL_0000:  ldarg.0
-  IL_0001:  call       ""ComputeSpanHash""
+  IL_0001:  call       ""ComputeSpanHash(System.Span<char>)""
   IL_0006:  stloc.1
   IL_0007:  ldloc.1
   IL_0008:  ldc.i4     0x75b03721
@@ -9599,7 +9599,7 @@ static int GetResult(Span<char> chars)
   .maxstack  2
   .locals init (uint V_0)
   IL_0000:  ldarg.0
-  IL_0001:  call       ""ComputeSpanHash""
+  IL_0001:  call       ""ComputeSpanHash(System.Span<char>)""
   IL_0006:  stloc.0
   IL_0007:  ldloc.0
   IL_0008:  ldc.i4     0x75b03721
diff --git a/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests4.cs b/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests4.cs
index fb76806b6e989..adf0656d06fe0 100644
--- a/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests4.cs
+++ b/src/Compilers/CSharp/Test/Emit2/Semantics/PatternMatchingTests4.cs
@@ -2135,7 +2135,7 @@ .locals init (System.ValueTuple<int, int> V_0, //t
     // sequence point: switch { (3, 4) => 1 }
     IL_002e:  nop
     // sequence point: <hidden>
-    IL_002f:  call       ""ThrowInvalidOperationException""
+    IL_002f:  call       ""ThrowInvalidOperationException()""
     IL_0034:  nop
     // sequence point: <hidden>
     IL_0035:  ldc.i4.1
@@ -2277,7 +2277,7 @@ .locals init (System.ValueTuple<int, int> V_0, //t
     // sequence point: switch { (3, 4) => 1 }
     IL_002e:  nop
     // sequence point: <hidden>
-    IL_002f:  call       ""ThrowSwitchExpressionExceptionParameterless""
+    IL_002f:  call       ""ThrowSwitchExpressionExceptionParameterless()""
     IL_0034:  nop
     // sequence point: <hidden>
     IL_0035:  ldc.i4.1
@@ -2471,7 +2471,7 @@ .locals init (int V_0,
     IL_001d:  ldloc.1
     IL_001e:  newobj     ""System.ValueTuple<int, int>..ctor(int, int)""
     IL_0023:  box        ""System.ValueTuple<int, int>""
-    IL_0028:  call       ""ThrowSwitchExpressionException""
+    IL_0028:  call       ""ThrowSwitchExpressionException(object)""
     IL_002d:  nop
     // sequence point: <hidden>
     IL_002e:  ldc.i4.1
diff --git a/src/Compilers/CSharp/Test/Emit2/Semantics/PatternSwitchTests.cs b/src/Compilers/CSharp/Test/Emit2/Semantics/PatternSwitchTests.cs
index e53ff87a55de4..71aa2f13839f5 100644
--- a/src/Compilers/CSharp/Test/Emit2/Semantics/PatternSwitchTests.cs
+++ b/src/Compilers/CSharp/Test/Emit2/Semantics/PatternSwitchTests.cs
@@ -3530,7 +3530,7 @@ public void AssignSwitchToRefReturningMethod()
 
             var comp = CreateCompilation(source, options: TestOptions.DebugExe);
             comp.VerifyEmitDiagnostics(
-                // (2,1): error CS8178: 'await' cannot be used in an expression containing a call to 'Program.<<Main>$>g__GetRef|0_0()' because it returns by reference
+                // (2,1): error CS8178: A reference returned by a call to 'Program.<<Main>$>g__GetRef|0_0()' cannot be preserved across 'await' or 'yield' boundary.
                 // GetRef() = 1 switch { _ => await System.Threading.Tasks.Task.FromResult(1) };
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "GetRef()").WithArguments("Program.<<Main>$>g__GetRef|0_0()").WithLocation(2, 1)
             );
diff --git a/src/Compilers/CSharp/Test/EndToEnd/EndToEndTests.cs b/src/Compilers/CSharp/Test/EndToEnd/EndToEndTests.cs
index 27b99ac19c0b8..e8cf7655b89fa 100644
--- a/src/Compilers/CSharp/Test/EndToEnd/EndToEndTests.cs
+++ b/src/Compilers/CSharp/Test/EndToEnd/EndToEndTests.cs
@@ -12,6 +12,10 @@
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.PooledObjects;
+using System.Linq;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using System.Threading.Tasks;
+using System.Threading;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests.EndToEnd
 {
@@ -318,5 +322,121 @@ static void runTest(int n)
                 });
             }
         }
+
+        [Fact, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1819416")]
+        public void LongInitializerList()
+        {
+            CancellationTokenSource cts = new CancellationTokenSource(TimeSpan.FromSeconds(30));
+            int iterations = 0;
+            try
+            {
+                initializerTest(cts.Token, ref iterations);
+            }
+            catch (Exception e) when (e is OperationCanceledException or TaskCanceledException)
+            {
+                Assert.True(false, $"Test timed out while getting all semantic info for long initializer list. Got to {iterations} iterations.");
+            }
+
+            static void initializerTest(CancellationToken ct, ref int iterationReached)
+            {
+                var sb = new StringBuilder();
+                sb.AppendLine("""
+                    _ = new System.Collections.Generic.Dictionary<string, string>
+                    {
+                    """);
+
+                for (int i = 0; i < 50000; i++)
+                {
+                    sb.AppendLine("""    { "a", "b" },""");
+                }
+
+                sb.AppendLine("};");
+
+                var comp = CreateCompilation(sb.ToString());
+                comp.VerifyEmitDiagnostics();
+
+                var tree = comp.SyntaxTrees[0];
+                var model = comp.GetSemanticModel(tree);
+
+                // If we regress perf here, this test will time out. The original condition here was a O(n^2) algorithm because the syntactic parent of each literal
+                // was being rebound on every call to GetTypeInfo.
+                iterationReached = 0;
+                foreach (var literal in tree.GetRoot().DescendantNodes().OfType<LiteralExpressionSyntax>())
+                {
+                    ct.ThrowIfCancellationRequested();
+                    iterationReached++;
+                    var type = model.GetTypeInfo(literal).Type;
+                    Assert.Equal(SpecialType.System_String, type.SpecialType);
+                }
+            }
+        }
+
+        [Fact]
+        public void Interceptors()
+        {
+            const int numberOfInterceptors = 10000;
+
+            // write a program which has many intercepted calls.
+            // each interceptor is in a different file.
+            var files = ArrayBuilder<(string source, string path)>.GetInstance();
+
+            // Build a top-level-statements main like:
+            //    C.M();
+            //    C.M();
+            //    C.M();
+            //    ...
+            var builder = new StringBuilder();
+            for (int i = 0; i < numberOfInterceptors; i++)
+            {
+                builder.AppendLine("C.M();");
+            }
+
+            files.Add((builder.ToString(), "Program.cs"));
+
+            files.Add(("""
+                class C
+                {
+                    public static void M() => throw null!;
+                }
+
+                namespace System.Runtime.CompilerServices
+                {
+                    public class InterceptsLocationAttribute : Attribute
+                    {
+                        public InterceptsLocationAttribute(string path, int line, int column) { }
+                    }
+                }
+                """, "C.cs"));
+
+            for (int i = 0; i < numberOfInterceptors; i++)
+            {
+                files.Add(($$"""
+                    using System;
+                    using System.Runtime.CompilerServices;
+
+                    class C{{i}}
+                    {
+                        [InterceptsLocation("Program.cs", {{i + 1}}, 3)]
+                        public static void M()
+                        {
+                            Console.WriteLine({{i}});
+                        }
+                    }
+                    """, $"C{i}.cs"));
+            }
+
+            var verifier = CompileAndVerify(files.ToArrayAndFree(), parseOptions: TestOptions.Regular.WithFeature("InterceptorsPreview"), expectedOutput: makeExpectedOutput());
+            verifier.VerifyDiagnostics();
+
+            string makeExpectedOutput()
+            {
+                builder.Clear();
+                for (int i = 0; i < numberOfInterceptors; i++)
+                {
+                    builder.AppendLine($"{i}");
+                }
+                return builder.ToString();
+            }
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IConversionExpression.cs b/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IConversionExpression.cs
index de9023b9f6aac..7d648397969bc 100644
--- a/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IConversionExpression.cs
+++ b/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IConversionExpression.cs
@@ -10,6 +10,7 @@
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.Operations;
 using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests
@@ -3373,6 +3374,36 @@ void M(int i, long l)
             VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(source, expectedFlowGraph, expectedDiagnostics);
         }
 
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ConversionExpression_Implicit_InlineArray()
+        {
+            string source = @"
+class C
+{
+    public void F(Buffer10 arg)
+    {
+        System.ReadOnlySpan<char> /*<bind>*/span = arg/*</bind>*/;
+    }
+}
+";
+
+            string expectedOperationTree = @"
+IVariableDeclaratorOperation (Symbol: System.ReadOnlySpan<System.Char> span) (OperationKind.VariableDeclarator, Type: null) (Syntax: 'span = arg')
+  Initializer:
+    IVariableInitializerOperation (OperationKind.VariableInitializer, Type: null) (Syntax: '= arg')
+      IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.ReadOnlySpan<System.Char>, IsImplicit) (Syntax: 'arg')
+        Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        Operand:
+          IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<VariableDeclaratorSyntax>(comp, expectedOperationTree, expectedDiagnostics,
+                additionalOperationTreeVerifier: new ExpectedSymbolVerifier().Verify);
+        }
+
         #endregion
 
         #region Explicit Conversion
@@ -5215,6 +5246,32 @@ public static void Method()
             Assert.Equal(CodeAnalysis.NullableAnnotation.Annotated, iopTree.Value.Type.NullableAnnotation);
         }
 
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ConversionExpression_Explicit_InlineArray()
+        {
+            string source = @"
+class C
+{
+    public void F(Buffer10 arg)
+    {
+        var a = /*<bind>*/(System.Span<char>)arg/*</bind>*/;
+    }
+}
+";
+
+            string expectedOperationTree = @"
+IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Span<System.Char>) (Syntax: '(System.Span<char>)arg')
+  Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  Operand:
+    IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<CastExpressionSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+        }
+
         #endregion
 
         internal class ExpectedSymbolVerifier
diff --git a/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IForEachLoopStatement.cs b/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IForEachLoopStatement.cs
index c9577fbfe751e..3f46d135d3cf0 100644
--- a/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IForEachLoopStatement.cs
+++ b/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IForEachLoopStatement.cs
@@ -7556,5 +7556,460 @@ public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter
         public System.Threading.Tasks.ValueTask<T> Task => default;
     }
 }";
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ForEach_InlineArray_01()
+        {
+            string source = @"
+class C
+{
+    public void F(Buffer10 arg)
+    {
+        /*<bind>*/foreach (ref char item in arg)
+        {
+            item = '0';
+        }/*</bind>*/
+    }
+}
+";
+
+            string expectedOperationTree = @"
+IForEachLoopOperation (LoopKind.ForEach, Continue Label Id: 0, Exit Label Id: 1) (OperationKind.Loop, Type: null) (Syntax: 'foreach (re ... }')
+  Locals: Local_1: System.Char item
+  LoopControlVariable:
+    IVariableDeclaratorOperation (Symbol: System.Char item) (OperationKind.VariableDeclarator, Type: null) (Syntax: 'char')
+      Initializer:
+        null
+  Collection:
+    IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+  Body:
+    IBlockOperation (1 statements) (OperationKind.Block, Type: null) (Syntax: '{ ... }')
+      IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'item = '0';')
+        Expression:
+          ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Char) (Syntax: 'item = '0'')
+            Left:
+              ILocalReferenceOperation: item (OperationKind.LocalReference, Type: System.Char) (Syntax: 'item')
+            Right:
+              ILiteralOperation (OperationKind.Literal, Type: System.Char, Constant: 0) (Syntax: ''0'')
+  NextVariables(0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<ForEachStatementSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void ForEach_InlineArray_01_Flow()
+        {
+            string source = @"
+class C
+{
+    public void F(Buffer10 arg)
+    /*<bind>*/{
+        foreach (ref char item in arg)
+        {
+            item = '0';
+        }
+    }/*</bind>*/
+}
+";
+
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'arg')
+              Value:
+                IInvocationOperation ( System.Span<System.Char>.Enumerator System.Span<System.Char>.GetEnumerator()) (OperationKind.Invocation, Type: System.Span<System.Char>.Enumerator, IsImplicit) (Syntax: 'arg')
+                  Instance Receiver:
+                    IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Span<System.Char>, IsImplicit) (Syntax: 'arg')
+                      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                        (InlineArray)
+                      Operand:
+                        IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+                  Arguments(0)
+        Next (Regular) Block[B2]
+    Block[B2] - Block
+        Predecessors: [B1] [B3]
+        Statements (0)
+        Jump if False (Regular) to Block[B4]
+            IInvocationOperation ( System.Boolean System.Span<System.Char>.Enumerator.MoveNext()) (OperationKind.Invocation, Type: System.Boolean, IsImplicit) (Syntax: 'arg')
+              Instance Receiver:
+                IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Span<System.Char>.Enumerator, IsImplicit) (Syntax: 'arg')
+              Arguments(0)
+            Leaving: {R1}
+        Next (Regular) Block[B3]
+            Entering: {R2}
+    .locals {R2}
+    {
+        Locals: [System.Char item]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (2)
+                ISimpleAssignmentOperation (IsRef) (OperationKind.SimpleAssignment, Type: null, IsImplicit) (Syntax: 'char')
+                  Left:
+                    ILocalReferenceOperation: item (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Char, IsImplicit) (Syntax: 'char')
+                  Right:
+                    IPropertyReferenceOperation: ref System.Char System.Span<System.Char>.Enumerator.Current { get; } (OperationKind.PropertyReference, Type: System.Char, IsImplicit) (Syntax: 'char')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Span<System.Char>.Enumerator, IsImplicit) (Syntax: 'arg')
+                IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'item = '0';')
+                  Expression:
+                    ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Char) (Syntax: 'item = '0'')
+                      Left:
+                        ILocalReferenceOperation: item (OperationKind.LocalReference, Type: System.Char) (Syntax: 'item')
+                      Right:
+                        ILiteralOperation (OperationKind.Literal, Type: System.Char, Constant: 0) (Syntax: ''0'')
+            Next (Regular) Block[B2]
+                Leaving: {R2}
+    }
+}
+Block[B4] - Exit
+    Predecessors: [B2]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ForEach_InlineArray_02()
+        {
+            string source = @"
+class C
+{
+    public void F(in Buffer10 arg)
+    {
+        /*<bind>*/foreach (ref readonly char item in arg)
+        {
+            System.Console.WriteLine(item);
+        }/*</bind>*/
+    }
+}
+";
+
+            string expectedOperationTree = @"
+IForEachLoopOperation (LoopKind.ForEach, Continue Label Id: 0, Exit Label Id: 1) (OperationKind.Loop, Type: null) (Syntax: 'foreach (re ... }')
+  Locals: Local_1: System.Char item
+  LoopControlVariable:
+    IVariableDeclaratorOperation (Symbol: System.Char item) (OperationKind.VariableDeclarator, Type: null) (Syntax: 'char')
+      Initializer:
+        null
+  Collection:
+    IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+  Body:
+    IBlockOperation (1 statements) (OperationKind.Block, Type: null) (Syntax: '{ ... }')
+      IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'System.Cons ... Line(item);')
+        Expression:
+          IInvocationOperation (void System.Console.WriteLine(System.Char value)) (OperationKind.Invocation, Type: System.Void) (Syntax: 'System.Cons ... eLine(item)')
+            Instance Receiver:
+              null
+            Arguments(1):
+                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: value) (OperationKind.Argument, Type: null) (Syntax: 'item')
+                  ILocalReferenceOperation: item (OperationKind.LocalReference, Type: System.Char) (Syntax: 'item')
+                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  NextVariables(0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<ForEachStatementSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void ForEach_InlineArray_02_Flow()
+        {
+            string source = @"
+class C
+{
+    public void F(in Buffer10 arg)
+    /*<bind>*/{
+        foreach (ref readonly char item in arg)
+        {
+            System.Console.WriteLine(item);
+        }
+    }/*</bind>*/
+}
+";
+
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'arg')
+              Value:
+                IInvocationOperation ( System.ReadOnlySpan<System.Char>.Enumerator System.ReadOnlySpan<System.Char>.GetEnumerator()) (OperationKind.Invocation, Type: System.ReadOnlySpan<System.Char>.Enumerator, IsImplicit) (Syntax: 'arg')
+                  Instance Receiver:
+                    IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.ReadOnlySpan<System.Char>, IsImplicit) (Syntax: 'arg')
+                      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                        (InlineArray)
+                      Operand:
+                        IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+                  Arguments(0)
+        Next (Regular) Block[B2]
+    Block[B2] - Block
+        Predecessors: [B1] [B3]
+        Statements (0)
+        Jump if False (Regular) to Block[B4]
+            IInvocationOperation ( System.Boolean System.ReadOnlySpan<System.Char>.Enumerator.MoveNext()) (OperationKind.Invocation, Type: System.Boolean, IsImplicit) (Syntax: 'arg')
+              Instance Receiver:
+                IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.ReadOnlySpan<System.Char>.Enumerator, IsImplicit) (Syntax: 'arg')
+              Arguments(0)
+            Leaving: {R1}
+        Next (Regular) Block[B3]
+            Entering: {R2}
+    .locals {R2}
+    {
+        Locals: [System.Char item]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (2)
+                ISimpleAssignmentOperation (IsRef) (OperationKind.SimpleAssignment, Type: null, IsImplicit) (Syntax: 'char')
+                  Left:
+                    ILocalReferenceOperation: item (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Char, IsImplicit) (Syntax: 'char')
+                  Right:
+                    IPropertyReferenceOperation: ref readonly modreq(System.Runtime.InteropServices.InAttribute) System.Char System.ReadOnlySpan<System.Char>.Enumerator.Current { get; } (OperationKind.PropertyReference, Type: System.Char, IsImplicit) (Syntax: 'char')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.ReadOnlySpan<System.Char>.Enumerator, IsImplicit) (Syntax: 'arg')
+                IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'System.Cons ... Line(item);')
+                  Expression:
+                    IInvocationOperation (void System.Console.WriteLine(System.Char value)) (OperationKind.Invocation, Type: System.Void) (Syntax: 'System.Cons ... eLine(item)')
+                      Instance Receiver:
+                        null
+                      Arguments(1):
+                          IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: value) (OperationKind.Argument, Type: null) (Syntax: 'item')
+                            ILocalReferenceOperation: item (OperationKind.LocalReference, Type: System.Char) (Syntax: 'item')
+                            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            Next (Regular) Block[B2]
+                Leaving: {R2}
+    }
+}
+Block[B4] - Exit
+    Predecessors: [B2]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ForEach_InlineArray_03()
+        {
+            string source = @"
+class C
+{
+    public void F()
+    {
+        /*<bind>*/foreach (char item in GetBuffer())
+        {
+            System.Console.WriteLine(item);
+        }/*</bind>*/
+    }
+
+    static Buffer10 GetBuffer() => default;
+}
+";
+
+            string expectedOperationTree = @"
+IForEachLoopOperation (LoopKind.ForEach, Continue Label Id: 0, Exit Label Id: 1) (OperationKind.Loop, Type: null) (Syntax: 'foreach (ch ... }')
+  Locals: Local_1: System.Char item
+  LoopControlVariable:
+    IVariableDeclaratorOperation (Symbol: System.Char item) (OperationKind.VariableDeclarator, Type: null) (Syntax: 'char')
+      Initializer:
+        null
+  Collection:
+    IInvocationOperation (Buffer10 C.GetBuffer()) (OperationKind.Invocation, Type: Buffer10) (Syntax: 'GetBuffer()')
+      Instance Receiver:
+        null
+      Arguments(0)
+  Body:
+    IBlockOperation (1 statements) (OperationKind.Block, Type: null) (Syntax: '{ ... }')
+      IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'System.Cons ... Line(item);')
+        Expression:
+          IInvocationOperation (void System.Console.WriteLine(System.Char value)) (OperationKind.Invocation, Type: System.Void) (Syntax: 'System.Cons ... eLine(item)')
+            Instance Receiver:
+              null
+            Arguments(1):
+                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: value) (OperationKind.Argument, Type: null) (Syntax: 'item')
+                  ILocalReferenceOperation: item (OperationKind.LocalReference, Type: System.Char) (Syntax: 'item')
+                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  NextVariables(0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<ForEachStatementSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void ForEach_InlineArray_03_Flow()
+        {
+            string source = @"
+class C
+{
+    public void F(in Buffer10 arg)
+    /*<bind>*/{
+        foreach (char item in GetBuffer())
+        {
+            System.Console.WriteLine(item);
+        }
+    }/*</bind>*/
+
+    static Buffer10 GetBuffer() => default;
+}
+";
+
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0] [1]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (2)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'GetBuffer()')
+              Value:
+                IInvocationOperation (Buffer10 C.GetBuffer()) (OperationKind.Invocation, Type: Buffer10) (Syntax: 'GetBuffer()')
+                  Instance Receiver:
+                    null
+                  Arguments(0)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'GetBuffer()')
+              Value:
+                IInvocationOperation ( System.ReadOnlySpan<System.Char>.Enumerator System.ReadOnlySpan<System.Char>.GetEnumerator()) (OperationKind.Invocation, Type: System.ReadOnlySpan<System.Char>.Enumerator, IsImplicit) (Syntax: 'GetBuffer()')
+                  Instance Receiver:
+                    IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.ReadOnlySpan<System.Char>, IsImplicit) (Syntax: 'GetBuffer()')
+                      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                        (InlineArray)
+                      Operand:
+                        IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: Buffer10, IsImplicit) (Syntax: 'GetBuffer()')
+                  Arguments(0)
+        Next (Regular) Block[B2]
+    Block[B2] - Block
+        Predecessors: [B1] [B3]
+        Statements (0)
+        Jump if False (Regular) to Block[B4]
+            IInvocationOperation ( System.Boolean System.ReadOnlySpan<System.Char>.Enumerator.MoveNext()) (OperationKind.Invocation, Type: System.Boolean, IsImplicit) (Syntax: 'GetBuffer()')
+              Instance Receiver:
+                IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.ReadOnlySpan<System.Char>.Enumerator, IsImplicit) (Syntax: 'GetBuffer()')
+              Arguments(0)
+            Leaving: {R1}
+        Next (Regular) Block[B3]
+            Entering: {R2}
+    .locals {R2}
+    {
+        Locals: [System.Char item]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (2)
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: null, IsImplicit) (Syntax: 'char')
+                  Left:
+                    ILocalReferenceOperation: item (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Char, IsImplicit) (Syntax: 'char')
+                  Right:
+                    IPropertyReferenceOperation: ref readonly modreq(System.Runtime.InteropServices.InAttribute) System.Char System.ReadOnlySpan<System.Char>.Enumerator.Current { get; } (OperationKind.PropertyReference, Type: System.Char, IsImplicit) (Syntax: 'char')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.ReadOnlySpan<System.Char>.Enumerator, IsImplicit) (Syntax: 'GetBuffer()')
+                IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'System.Cons ... Line(item);')
+                  Expression:
+                    IInvocationOperation (void System.Console.WriteLine(System.Char value)) (OperationKind.Invocation, Type: System.Void) (Syntax: 'System.Cons ... eLine(item)')
+                      Instance Receiver:
+                        null
+                      Arguments(1):
+                          IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: value) (OperationKind.Argument, Type: null) (Syntax: 'item')
+                            ILocalReferenceOperation: item (OperationKind.LocalReference, Type: System.Char) (Syntax: 'item')
+                            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            Next (Regular) Block[B2]
+                Leaving: {R2}
+    }
+}
+Block[B4] - Exit
+    Predecessors: [B2]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ForEach_InlineArray_04()
+        {
+            string source = @"
+class C
+{
+    public void F(Buffer10 arg)
+    {
+        /*<bind>*/foreach (char item in (Buffer10)arg)
+        {
+            System.Console.WriteLine(item);
+        }/*</bind>*/
+    }
+}
+";
+
+            string expectedOperationTree = @"
+IForEachLoopOperation (LoopKind.ForEach, Continue Label Id: 0, Exit Label Id: 1) (OperationKind.Loop, Type: null) (Syntax: 'foreach (ch ... }')
+  Locals: Local_1: System.Char item
+  LoopControlVariable:
+    IVariableDeclaratorOperation (Symbol: System.Char item) (OperationKind.VariableDeclarator, Type: null) (Syntax: 'char')
+      Initializer:
+        null
+  Collection:
+    IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: Buffer10) (Syntax: '(Buffer10)arg')
+      Conversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      Operand:
+        IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+  Body:
+    IBlockOperation (1 statements) (OperationKind.Block, Type: null) (Syntax: '{ ... }')
+      IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'System.Cons ... Line(item);')
+        Expression:
+          IInvocationOperation (void System.Console.WriteLine(System.Char value)) (OperationKind.Invocation, Type: System.Void) (Syntax: 'System.Cons ... eLine(item)')
+            Instance Receiver:
+              null
+            Arguments(1):
+                IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: value) (OperationKind.Argument, Type: null) (Syntax: 'item')
+                  ILocalReferenceOperation: item (OperationKind.LocalReference, Type: System.Char) (Syntax: 'item')
+                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  NextVariables(0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + IOperationTests_IInlineArrayAccessOperation.Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<ForEachStatementSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IInlineArrayAccessOperation.cs b/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IInlineArrayAccessOperation.cs
new file mode 100644
index 0000000000000..128cad22a52f0
--- /dev/null
+++ b/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IInlineArrayAccessOperation.cs
@@ -0,0 +1,804 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#nullable disable
+
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.UnitTests
+{
+    public class IOperationTests_IInlineArrayAccessOperation : SemanticModelTestBase
+    {
+        public const string Buffer10Definition =
+@"
+[System.Runtime.CompilerServices.InlineArray(10)]
+public struct Buffer10
+{
+    private char _element0;
+}
+";
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ElementAccess()
+        {
+            string source = @"
+class C
+{
+    public void F(Buffer10 arg, System.Index x)
+    {
+        var a = /*<bind>*/arg[x]/*</bind>*/;
+    }
+}
+";
+
+            string expectedOperationTree = @"
+IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Char) (Syntax: 'arg[x]')
+  Instance:
+    IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+  Argument:
+    IParameterReferenceOperation: x (OperationKind.ParameterReference, Type: System.Index) (Syntax: 'x')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<ElementAccessExpressionSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void ElementAccess_NoControlFlow()
+        {
+            string source = @"
+class C
+{
+    void M(Buffer10 a1, System.Index i1, char result1)
+    /*<bind>*/{
+        result1 = a1[i1];
+    }/*</bind>*/
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+Block[B1] - Block
+    Predecessors: [B0]
+    Statements (1)
+        IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'result1 = a1[i1];')
+          Expression:
+            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Char) (Syntax: 'result1 = a1[i1]')
+              Left:
+                IParameterReferenceOperation: result1 (OperationKind.ParameterReference, Type: System.Char) (Syntax: 'result1')
+              Right:
+                IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Char) (Syntax: 'a1[i1]')
+                  Instance:
+                    IParameterReferenceOperation: a1 (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'a1')
+                  Argument:
+                    IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Index) (Syntax: 'i1')
+    Next (Regular) Block[B2]
+Block[B2] - Exit
+    Predecessors: [B1]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void ElementAccess_ControlFlowInInstance()
+        {
+            string source = @"
+class C
+{
+    void M(Buffer10? a1, Buffer10 a2, System.Index i1, char result)
+    /*<bind>*/{
+        result = (a1 ?? a2)[i1];
+    }/*</bind>*/
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0] [2]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'result')
+              Value:
+                IParameterReferenceOperation: result (OperationKind.ParameterReference, Type: System.Char) (Syntax: 'result')
+        Next (Regular) Block[B2]
+            Entering: {R2}
+    .locals {R2}
+    {
+        CaptureIds: [1]
+        Block[B2] - Block
+            Predecessors: [B1]
+            Statements (1)
+                IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                  Value:
+                    IParameterReferenceOperation: a1 (OperationKind.ParameterReference, Type: Buffer10?) (Syntax: 'a1')
+            Jump if True (Regular) to Block[B4]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'a1')
+                  Operand:
+                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: Buffer10?, IsImplicit) (Syntax: 'a1')
+                Leaving: {R2}
+            Next (Regular) Block[B3]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (1)
+                IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                  Value:
+                    IInvocationOperation ( readonly Buffer10 Buffer10?.GetValueOrDefault()) (OperationKind.Invocation, Type: Buffer10, IsImplicit) (Syntax: 'a1')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: Buffer10?, IsImplicit) (Syntax: 'a1')
+                      Arguments(0)
+            Next (Regular) Block[B5]
+                Leaving: {R2}
+    }
+    Block[B4] - Block
+        Predecessors: [B2]
+        Statements (1)
+            IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a2')
+              Value:
+                IParameterReferenceOperation: a2 (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'a2')
+        Next (Regular) Block[B5]
+    Block[B5] - Block
+        Predecessors: [B3] [B4]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'result = (a1 ?? a2)[i1];')
+              Expression:
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Char) (Syntax: 'result = (a1 ?? a2)[i1]')
+                  Left:
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Char, IsImplicit) (Syntax: 'result')
+                  Right:
+                    IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Char) (Syntax: '(a1 ?? a2)[i1]')
+                      Instance:
+                        IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: Buffer10, IsImplicit) (Syntax: 'a1 ?? a2')
+                      Argument:
+                        IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Index) (Syntax: 'i1')
+        Next (Regular) Block[B6]
+            Leaving: {R1}
+}
+Block[B6] - Exit
+    Predecessors: [B5]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void ElementAccess_ControlFlowInArgument()
+        {
+            string source = @"
+class C
+{
+    void M(Buffer10 a, System.Index? i1, System.Index i2, char result)
+    /*<bind>*/{
+        result = a[i1 ?? i2];
+    }/*</bind>*/
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0] [1] [3]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (2)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'result')
+              Value:
+                IParameterReferenceOperation: result (OperationKind.ParameterReference, Type: System.Char) (Syntax: 'result')
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a')
+              Value:
+                IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'a')
+        Next (Regular) Block[B2]
+            Entering: {R2}
+    .locals {R2}
+    {
+        CaptureIds: [2]
+        Block[B2] - Block
+            Predecessors: [B1]
+            Statements (1)
+                IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Index?) (Syntax: 'i1')
+            Jump if True (Regular) to Block[B4]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'i1')
+                  Operand:
+                    IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: System.Index?, IsImplicit) (Syntax: 'i1')
+                Leaving: {R2}
+            Next (Regular) Block[B3]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (1)
+                IFlowCaptureOperation: 3 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IInvocationOperation ( readonly System.Index System.Index?.GetValueOrDefault()) (OperationKind.Invocation, Type: System.Index, IsImplicit) (Syntax: 'i1')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: System.Index?, IsImplicit) (Syntax: 'i1')
+                      Arguments(0)
+            Next (Regular) Block[B5]
+                Leaving: {R2}
+    }
+    Block[B4] - Block
+        Predecessors: [B2]
+        Statements (1)
+            IFlowCaptureOperation: 3 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i2')
+              Value:
+                IParameterReferenceOperation: i2 (OperationKind.ParameterReference, Type: System.Index) (Syntax: 'i2')
+        Next (Regular) Block[B5]
+    Block[B5] - Block
+        Predecessors: [B3] [B4]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'result = a[i1 ?? i2];')
+              Expression:
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Char) (Syntax: 'result = a[i1 ?? i2]')
+                  Left:
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Char, IsImplicit) (Syntax: 'result')
+                  Right:
+                    IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Char) (Syntax: 'a[i1 ?? i2]')
+                      Instance:
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: Buffer10, IsImplicit) (Syntax: 'a')
+                      Argument:
+                        IFlowCaptureReferenceOperation: 3 (OperationKind.FlowCaptureReference, Type: System.Index, IsImplicit) (Syntax: 'i1 ?? i2')
+        Next (Regular) Block[B6]
+            Leaving: {R1}
+}
+Block[B6] - Exit
+    Predecessors: [B5]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void ElementAccess_ControlFlowInInstanceAndArgument()
+        {
+            string source = @"
+class C
+{
+    void M(Buffer10? a1, Buffer10 a2, System.Index? i1, System.Index i2, char result)
+    /*<bind>*/{
+        result = (a1 ?? a2)[i1 ?? i2];
+    }/*</bind>*/
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0] [2] [4]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'result')
+              Value:
+                IParameterReferenceOperation: result (OperationKind.ParameterReference, Type: System.Char) (Syntax: 'result')
+        Next (Regular) Block[B2]
+            Entering: {R2}
+    .locals {R2}
+    {
+        CaptureIds: [1]
+        Block[B2] - Block
+            Predecessors: [B1]
+            Statements (1)
+                IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                  Value:
+                    IParameterReferenceOperation: a1 (OperationKind.ParameterReference, Type: Buffer10?) (Syntax: 'a1')
+            Jump if True (Regular) to Block[B4]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'a1')
+                  Operand:
+                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: Buffer10?, IsImplicit) (Syntax: 'a1')
+                Leaving: {R2}
+            Next (Regular) Block[B3]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (1)
+                IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                  Value:
+                    IInvocationOperation ( readonly Buffer10 Buffer10?.GetValueOrDefault()) (OperationKind.Invocation, Type: Buffer10, IsImplicit) (Syntax: 'a1')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: Buffer10?, IsImplicit) (Syntax: 'a1')
+                      Arguments(0)
+            Next (Regular) Block[B5]
+                Leaving: {R2}
+                Entering: {R3}
+    }
+    Block[B4] - Block
+        Predecessors: [B2]
+        Statements (1)
+            IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a2')
+              Value:
+                IParameterReferenceOperation: a2 (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'a2')
+        Next (Regular) Block[B5]
+            Entering: {R3}
+    .locals {R3}
+    {
+        CaptureIds: [3]
+        Block[B5] - Block
+            Predecessors: [B3] [B4]
+            Statements (1)
+                IFlowCaptureOperation: 3 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Index?) (Syntax: 'i1')
+            Jump if True (Regular) to Block[B7]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'i1')
+                  Operand:
+                    IFlowCaptureReferenceOperation: 3 (OperationKind.FlowCaptureReference, Type: System.Index?, IsImplicit) (Syntax: 'i1')
+                Leaving: {R3}
+            Next (Regular) Block[B6]
+        Block[B6] - Block
+            Predecessors: [B5]
+            Statements (1)
+                IFlowCaptureOperation: 4 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IInvocationOperation ( readonly System.Index System.Index?.GetValueOrDefault()) (OperationKind.Invocation, Type: System.Index, IsImplicit) (Syntax: 'i1')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 3 (OperationKind.FlowCaptureReference, Type: System.Index?, IsImplicit) (Syntax: 'i1')
+                      Arguments(0)
+            Next (Regular) Block[B8]
+                Leaving: {R3}
+    }
+    Block[B7] - Block
+        Predecessors: [B5]
+        Statements (1)
+            IFlowCaptureOperation: 4 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i2')
+              Value:
+                IParameterReferenceOperation: i2 (OperationKind.ParameterReference, Type: System.Index) (Syntax: 'i2')
+        Next (Regular) Block[B8]
+    Block[B8] - Block
+        Predecessors: [B6] [B7]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'result = (a ... [i1 ?? i2];')
+              Expression:
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Char) (Syntax: 'result = (a ... )[i1 ?? i2]')
+                  Left:
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Char, IsImplicit) (Syntax: 'result')
+                  Right:
+                    IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Char) (Syntax: '(a1 ?? a2)[i1 ?? i2]')
+                      Instance:
+                        IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: Buffer10, IsImplicit) (Syntax: 'a1 ?? a2')
+                      Argument:
+                        IFlowCaptureReferenceOperation: 4 (OperationKind.FlowCaptureReference, Type: System.Index, IsImplicit) (Syntax: 'i1 ?? i2')
+        Next (Regular) Block[B9]
+            Leaving: {R1}
+}
+Block[B9] - Exit
+    Predecessors: [B8]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void Slice()
+        {
+            string source = @"
+class C
+{
+    public void F(Buffer10 arg, System.Range x)
+    {
+        var a = /*<bind>*/arg[x]/*</bind>*/;
+    }
+}
+";
+
+            string expectedOperationTree = @"
+IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Span<System.Char>) (Syntax: 'arg[x]')
+  Instance:
+    IParameterReferenceOperation: arg (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'arg')
+  Argument:
+    IParameterReferenceOperation: x (OperationKind.ParameterReference, Type: System.Range) (Syntax: 'x')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyOperationTreeAndDiagnosticsForTest<ElementAccessExpressionSyntax>(comp, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void Slice_NoControlFlow()
+        {
+            string source = @"
+class C
+{
+    void M(Buffer10 a1, System.Range i1)
+    /*<bind>*/{
+        System.Span<char> result1 = a1[i1];
+    }/*</bind>*/
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    Locals: [System.Span<System.Char> result1]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Span<System.Char>, IsImplicit) (Syntax: 'result1 = a1[i1]')
+              Left:
+                ILocalReferenceOperation: result1 (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Span<System.Char>, IsImplicit) (Syntax: 'result1 = a1[i1]')
+              Right:
+                IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Span<System.Char>) (Syntax: 'a1[i1]')
+                  Instance:
+                    IParameterReferenceOperation: a1 (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'a1')
+                  Argument:
+                    IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Range) (Syntax: 'i1')
+        Next (Regular) Block[B2]
+            Leaving: {R1}
+}
+Block[B2] - Exit
+    Predecessors: [B1]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void Slice_ControlFlowInInstance()
+        {
+            string source = @"
+class C
+{
+    void M(string a1, string a2, System.Range i1, System.Span<char> result)
+    /*<bind>*/{
+        result = GetBuffer(a1 ?? a2)[i1];
+    }/*</bind>*/
+
+    static ref Buffer10 GetBuffer(string s) => throw null;
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0] [2]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'result')
+              Value:
+                IParameterReferenceOperation: result (OperationKind.ParameterReference, Type: System.Span<System.Char>) (Syntax: 'result')
+        Next (Regular) Block[B2]
+            Entering: {R2}
+    .locals {R2}
+    {
+        CaptureIds: [1]
+        Block[B2] - Block
+            Predecessors: [B1]
+            Statements (1)
+                IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                  Value:
+                    IParameterReferenceOperation: a1 (OperationKind.ParameterReference, Type: System.String) (Syntax: 'a1')
+            Jump if True (Regular) to Block[B4]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'a1')
+                  Operand:
+                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.String, IsImplicit) (Syntax: 'a1')
+                Leaving: {R2}
+            Next (Regular) Block[B3]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (1)
+                IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                  Value:
+                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.String, IsImplicit) (Syntax: 'a1')
+            Next (Regular) Block[B5]
+                Leaving: {R2}
+    }
+    Block[B4] - Block
+        Predecessors: [B2]
+        Statements (1)
+            IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a2')
+              Value:
+                IParameterReferenceOperation: a2 (OperationKind.ParameterReference, Type: System.String) (Syntax: 'a2')
+        Next (Regular) Block[B5]
+    Block[B5] - Block
+        Predecessors: [B3] [B4]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'result = Ge ... ?? a2)[i1];')
+              Expression:
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Span<System.Char>) (Syntax: 'result = Ge ...  ?? a2)[i1]')
+                  Left:
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Span<System.Char>, IsImplicit) (Syntax: 'result')
+                  Right:
+                    IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Span<System.Char>) (Syntax: 'GetBuffer(a1 ?? a2)[i1]')
+                      Instance:
+                        IInvocationOperation (ref Buffer10 C.GetBuffer(System.String s)) (OperationKind.Invocation, Type: Buffer10) (Syntax: 'GetBuffer(a1 ?? a2)')
+                          Instance Receiver:
+                            null
+                          Arguments(1):
+                              IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: s) (OperationKind.Argument, Type: null) (Syntax: 'a1 ?? a2')
+                                IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: System.String, IsImplicit) (Syntax: 'a1 ?? a2')
+                                InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                                OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                      Argument:
+                        IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Range) (Syntax: 'i1')
+        Next (Regular) Block[B6]
+            Leaving: {R1}
+}
+Block[B6] - Exit
+    Predecessors: [B5]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void Slice_ControlFlowInArgument()
+        {
+            string source = @"
+class C
+{
+    void M(Buffer10 a, System.Range? i1, System.Range i2)
+    /*<bind>*/{
+        System.Span<char> result = a[i1 ?? i2];
+    }/*</bind>*/
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    Locals: [System.Span<System.Char> result]
+    CaptureIds: [0] [2]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a')
+              Value:
+                IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: Buffer10) (Syntax: 'a')
+        Next (Regular) Block[B2]
+            Entering: {R2}
+    .locals {R2}
+    {
+        CaptureIds: [1]
+        Block[B2] - Block
+            Predecessors: [B1]
+            Statements (1)
+                IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Range?) (Syntax: 'i1')
+            Jump if True (Regular) to Block[B4]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'i1')
+                  Operand:
+                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Range?, IsImplicit) (Syntax: 'i1')
+                Leaving: {R2}
+            Next (Regular) Block[B3]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (1)
+                IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IInvocationOperation ( readonly System.Range System.Range?.GetValueOrDefault()) (OperationKind.Invocation, Type: System.Range, IsImplicit) (Syntax: 'i1')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Range?, IsImplicit) (Syntax: 'i1')
+                      Arguments(0)
+            Next (Regular) Block[B5]
+                Leaving: {R2}
+    }
+    Block[B4] - Block
+        Predecessors: [B2]
+        Statements (1)
+            IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i2')
+              Value:
+                IParameterReferenceOperation: i2 (OperationKind.ParameterReference, Type: System.Range) (Syntax: 'i2')
+        Next (Regular) Block[B5]
+    Block[B5] - Block
+        Predecessors: [B3] [B4]
+        Statements (1)
+            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Span<System.Char>, IsImplicit) (Syntax: 'result = a[i1 ?? i2]')
+              Left:
+                ILocalReferenceOperation: result (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Span<System.Char>, IsImplicit) (Syntax: 'result = a[i1 ?? i2]')
+              Right:
+                IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Span<System.Char>) (Syntax: 'a[i1 ?? i2]')
+                  Instance:
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: Buffer10, IsImplicit) (Syntax: 'a')
+                  Argument:
+                    IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: System.Range, IsImplicit) (Syntax: 'i1 ?? i2')
+        Next (Regular) Block[B6]
+            Leaving: {R1}
+}
+Block[B6] - Exit
+    Predecessors: [B5]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation, CompilerFeature.Dataflow)]
+        [Fact]
+        public void Slice_ControlFlowInInstanceAndArgument()
+        {
+            string source = @"
+class C
+{
+    void M(string a1, string a2, System.Range? i1, System.Range i2, System.Span<char> result)
+    /*<bind>*/{
+        result = GetBuffer(a1 ?? a2)[i1 ?? i2];
+    }/*</bind>*/
+
+    static ref Buffer10 GetBuffer(string s) => throw null;
+}
+";
+            string expectedFlowGraph = @"
+Block[B0] - Entry
+    Statements (0)
+    Next (Regular) Block[B1]
+        Entering: {R1}
+.locals {R1}
+{
+    CaptureIds: [0] [3] [5]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'result')
+              Value:
+                IParameterReferenceOperation: result (OperationKind.ParameterReference, Type: System.Span<System.Char>) (Syntax: 'result')
+        Next (Regular) Block[B2]
+            Entering: {R2} {R3}
+    .locals {R2}
+    {
+        CaptureIds: [2]
+        .locals {R3}
+        {
+            CaptureIds: [1]
+            Block[B2] - Block
+                Predecessors: [B1]
+                Statements (1)
+                    IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                      Value:
+                        IParameterReferenceOperation: a1 (OperationKind.ParameterReference, Type: System.String) (Syntax: 'a1')
+                Jump if True (Regular) to Block[B4]
+                    IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'a1')
+                      Operand:
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.String, IsImplicit) (Syntax: 'a1')
+                    Leaving: {R3}
+                Next (Regular) Block[B3]
+            Block[B3] - Block
+                Predecessors: [B2]
+                Statements (1)
+                    IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a1')
+                      Value:
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.String, IsImplicit) (Syntax: 'a1')
+                Next (Regular) Block[B5]
+                    Leaving: {R3}
+        }
+        Block[B4] - Block
+            Predecessors: [B2]
+            Statements (1)
+                IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'a2')
+                  Value:
+                    IParameterReferenceOperation: a2 (OperationKind.ParameterReference, Type: System.String) (Syntax: 'a2')
+            Next (Regular) Block[B5]
+        Block[B5] - Block
+            Predecessors: [B3] [B4]
+            Statements (1)
+                IFlowCaptureOperation: 3 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'GetBuffer(a1 ?? a2)')
+                  Value:
+                    IInvocationOperation (ref Buffer10 C.GetBuffer(System.String s)) (OperationKind.Invocation, Type: Buffer10) (Syntax: 'GetBuffer(a1 ?? a2)')
+                      Instance Receiver:
+                        null
+                      Arguments(1):
+                          IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: s) (OperationKind.Argument, Type: null) (Syntax: 'a1 ?? a2')
+                            IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: System.String, IsImplicit) (Syntax: 'a1 ?? a2')
+                            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            Next (Regular) Block[B6]
+                Leaving: {R2}
+                Entering: {R4}
+    }
+    .locals {R4}
+    {
+        CaptureIds: [4]
+        Block[B6] - Block
+            Predecessors: [B5]
+            Statements (1)
+                IFlowCaptureOperation: 4 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IParameterReferenceOperation: i1 (OperationKind.ParameterReference, Type: System.Range?) (Syntax: 'i1')
+            Jump if True (Regular) to Block[B8]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'i1')
+                  Operand:
+                    IFlowCaptureReferenceOperation: 4 (OperationKind.FlowCaptureReference, Type: System.Range?, IsImplicit) (Syntax: 'i1')
+                Leaving: {R4}
+            Next (Regular) Block[B7]
+        Block[B7] - Block
+            Predecessors: [B6]
+            Statements (1)
+                IFlowCaptureOperation: 5 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i1')
+                  Value:
+                    IInvocationOperation ( readonly System.Range System.Range?.GetValueOrDefault()) (OperationKind.Invocation, Type: System.Range, IsImplicit) (Syntax: 'i1')
+                      Instance Receiver:
+                        IFlowCaptureReferenceOperation: 4 (OperationKind.FlowCaptureReference, Type: System.Range?, IsImplicit) (Syntax: 'i1')
+                      Arguments(0)
+            Next (Regular) Block[B9]
+                Leaving: {R4}
+    }
+    Block[B8] - Block
+        Predecessors: [B6]
+        Statements (1)
+            IFlowCaptureOperation: 5 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i2')
+              Value:
+                IParameterReferenceOperation: i2 (OperationKind.ParameterReference, Type: System.Range) (Syntax: 'i2')
+        Next (Regular) Block[B9]
+    Block[B9] - Block
+        Predecessors: [B7] [B8]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'result = Ge ... [i1 ?? i2];')
+              Expression:
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Span<System.Char>) (Syntax: 'result = Ge ... )[i1 ?? i2]')
+                  Left:
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Span<System.Char>, IsImplicit) (Syntax: 'result')
+                  Right:
+                    IInlineArrayAccessOperation (OperationKind.InlineArrayAccess, Type: System.Span<System.Char>) (Syntax: 'GetBuffer(a ... )[i1 ?? i2]')
+                      Instance:
+                        IFlowCaptureReferenceOperation: 3 (OperationKind.FlowCaptureReference, Type: Buffer10, IsImplicit) (Syntax: 'GetBuffer(a1 ?? a2)')
+                      Argument:
+                        IFlowCaptureReferenceOperation: 5 (OperationKind.FlowCaptureReference, Type: System.Range, IsImplicit) (Syntax: 'i1 ?? i2')
+        Next (Regular) Block[B10]
+            Leaving: {R1}
+}
+Block[B10] - Exit
+    Predecessors: [B9]
+    Statements (0)
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            var comp = CreateCompilation(source + Buffer10Definition, targetFramework: TargetFramework.Net80);
+            VerifyFlowGraphAndDiagnosticsForTest<BlockSyntax>(comp, expectedFlowGraph, expectedDiagnostics);
+        }
+    }
+}
diff --git a/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj b/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj
index 12ed08f8cdb3c..cccd86ca92bb1 100644
--- a/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj
@@ -18,6 +18,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.CSharp" Version="$(MicrosoftCSharpVersion)" />
     <PackageReference Include="Basic.Reference.Assemblies.Net60" Version="$(BasicReferenceAssembliesNet60Version)" />
+    <PackageReference Include="Basic.Reference.Assemblies.Net80" Version="$(BasicReferenceAssembliesNet80Version)" />
   </ItemGroup>
   <ItemGroup>
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/ArglistTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/ArglistTests.cs
index 45bec5e7d7069..a0f7639367253 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/ArglistTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/ArglistTests.cs
@@ -1659,5 +1659,43 @@ static void Main()
                 options: TestOptions.DebugExe,
                 expectedOutput: "5");
         }
+
+        [ConditionalTheory(typeof(WindowsOnly), Reason = ConditionalSkipReason.RestrictedTypesNeedDesktop)]
+        [CombinatorialData]
+        public void RefModifier([CombinatorialValues("ref", "in")] string modifier)
+        {
+            var source = $$"""
+                class C
+                {
+                    static void M({{modifier}} int x, __arglist) => System.Console.Write(x);
+
+                    static void Main()
+                    {
+                        int x = 111;
+                        M({{modifier}} x, __arglist(x));
+                    }
+                }
+                """;
+            CompileAndVerify(source, expectedOutput: "111", verify: Verification.FailsILVerify).VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(WindowsOnly), Reason = ConditionalSkipReason.RestrictedTypesNeedDesktop)]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68714")]
+        public void InAsRValue()
+        {
+            var source = """
+                class C
+                {
+                    static void M(in int x, __arglist) => System.Console.Write(x);
+
+                    static void Main()
+                    {
+                        int x = 111;
+                        M(x, __arglist(x));
+                    }
+                }
+                """;
+            CompileAndVerify(source, expectedOutput: "111", verify: Verification.FailsILVerify).VerifyDiagnostics();
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/InterceptorsTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/InterceptorsTests.cs
new file mode 100644
index 0000000000000..e29066a3336db
--- /dev/null
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/InterceptorsTests.cs
@@ -0,0 +1,4083 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using Microsoft.CodeAnalysis.CSharp.Symbols;
+using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
+using Microsoft.CodeAnalysis.Emit;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Roslyn.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.UnitTests.Semantics;
+
+public class InterceptorsTests : CSharpTestBase
+{
+    private static readonly (string, string) s_attributesSource = ("""
+        namespace System.Runtime.CompilerServices;
+
+        [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = false)]
+        public sealed class InterceptsLocationAttribute : Attribute
+        {
+            public InterceptsLocationAttribute(string filePath, int line, int character)
+            {
+            }
+        }
+        """, "attributes.cs");
+
+    private static readonly CSharpParseOptions RegularWithInterceptors = TestOptions.Regular.WithFeature("InterceptorsPreview");
+
+    [Fact]
+    public void FeatureFlag()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C.M();
+
+            class C
+            {
+                public static void M() => throw null!;
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 4, 3)]
+                public static void M() => Console.Write(1);
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource });
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(13,6): error CS9137: The 'interceptors' experimental feature is not enabled. Add '<Features>InterceptorsPreview</Features>' to your project.
+            //     [InterceptsLocation("Program.cs", 4, 3)]
+            Diagnostic(ErrorCode.ERR_InterceptorsFeatureNotEnabled, @"InterceptsLocation(""Program.cs"", 4, 3)").WithLocation(13, 6));
+
+        comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: TestOptions.Regular.WithFeature("InterceptorsPreview-experimental"));
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(13,6): error CS9137: The 'interceptors' experimental feature is not enabled. Add '<Features>InterceptorsPreview</Features>' to your project.
+            //     [InterceptsLocation("Program.cs", 4, 3)]
+            Diagnostic(ErrorCode.ERR_InterceptorsFeatureNotEnabled, @"InterceptsLocation(""Program.cs"", 4, 3)").WithLocation(13, 6));
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+
+        verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: TestOptions.Regular.WithFeature("InterceptorsPreview", "false"), expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+
+        verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: TestOptions.Regular.WithFeature("interceptorspreview"), expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+
+    }
+
+    [Fact]
+    public void SelfInterception()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+                public static void Main()
+                {
+                    InterceptableMethod();
+                }
+
+
+                [InterceptsLocation("Program.cs", 8, 9)]
+                public static void InterceptableMethod() { Console.Write(1); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void StaticInterceptable_StaticInterceptor_NoParameters()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod() { Console.Write("interceptable"); }
+
+                public static void Main()
+                {
+                    InterceptableMethod();
+                }
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 11, 9)]
+                public static void Interceptor1() { Console.Write("interceptor 1"); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor 1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void Accessibility_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod() { Console.Write("interceptable"); }
+
+                public static void Main()
+                {
+                    InterceptableMethod();
+                }
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 11, 9)]
+                private static void Interceptor1() { Console.Write("interceptor 1"); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+                // Program.cs(17,6): error CS9155: Cannot intercept because 'D.Interceptor1()' is not accessible within 'C.Main()'.
+                //     [InterceptsLocation("Program.cs", 11, 9)]
+                Diagnostic(ErrorCode.ERR_InterceptorNotAccessible, @"InterceptsLocation(""Program.cs"", 11, 9)").WithArguments("D.Interceptor1()", "C.Main()").WithLocation(17, 6));
+    }
+
+    [Fact]
+    public void Accessibility_02()
+    {
+        // An interceptor declared within a file-local type can intercept a call even if the call site can't normally refer to the file-local type.
+        var source1 = """
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod() { Console.Write("interceptable"); }
+
+                public static void Main()
+                {
+                    InterceptableMethod();
+                }
+            }
+            """;
+
+        var source2 = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            file class D
+            {
+                [InterceptsLocation("Program.cs", 10, 9)]
+                public static void Interceptor1() { Console.Write("interceptor 1"); }
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source1, "Program.cs"), (source2, "Other.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor 1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void FileLocalAttributeDefinitions_01()
+    {
+        // Treat a file-local declaration of InterceptsLocationAttribute as a well-known attribute within the declaring compilation.
+        var source = """
+            using System;
+            using System.Runtime.CompilerServices;
+
+            C.M();
+
+            class C
+            {
+                public static void M() => throw null!;
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 4, 3)]
+                public static void M()
+                {
+                    Console.Write(1);
+                }
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                file class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int character) { }
+                }
+            }
+            """;
+
+        var verifier = CompileAndVerify((source, "Program.cs"), parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    /// <summary>
+    /// File-local InterceptsLocationAttribute from another compilation is not considered to *duplicate* an interception, even if it is inherited.
+    /// See also <see cref="DuplicateLocation_03"/>.
+    /// </summary>
+    [Fact]
+    public void FileLocalAttributeDefinitions_02()
+    {
+        var source1 = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            var c = new C();
+            c.M();
+
+            public class C
+            {
+                public void M() => Console.Write(1);
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                public virtual void Interceptor() => throw null!;
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
+                file sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int character)
+                    {
+                    }
+                }
+            }
+            """;
+
+        // Inherited attribute on 'override void Interceptor' from other compilation doesn't cause a call in this compilation to be intercepted.
+        var source2 = """
+
+
+            // leading blank lines for alignment with the call in the other compilation.
+            var d = new D();
+            d.M();
+
+            class D : C
+            {
+                public override void Interceptor() => throw null!;
+            }
+            """;
+
+        var comp1 = CreateCompilation((source1, "Program.cs"), parseOptions: RegularWithInterceptors);
+        comp1.VerifyEmitDiagnostics();
+
+        var comp2Verifier = CompileAndVerify((source2, "Program.cs"), references: new[] { comp1.ToMetadataReference() }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        comp2Verifier.VerifyDiagnostics();
+
+        comp2Verifier = CompileAndVerify((source2, "Program.cs"), references: new[] { comp1.EmitToImageReference() }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        comp2Verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableExtensionMethod_InterceptorExtensionMethod()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor call site");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableExtensionMethod_InterceptorExtensionMethod_NormalForm()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    InterceptableMethod(c, "call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 9)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor call site");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableInstanceMethod_InterceptorExtensionMethod()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public C InterceptableMethod(string param) { Console.Write("interceptable " + param); return this; }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static C Interceptor1(this C i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor call site");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableInstanceMethod_InterceptorStaticMethod()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public C InterceptableMethod(string param) { Console.Write("interceptable " + param); return this; }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static C Interceptor1(C i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9144: Cannot intercept method 'C.InterceptableMethod(string)' with interceptor 'D.Interceptor1(C, string)' because the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 15, 11)").WithArguments("C.InterceptableMethod(string)", "D.Interceptor1(C, string)").WithLocation(21, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationDuplicatePath()
+    {
+        var source0 = ("""
+            public class D0
+            {
+                public static void M()
+                {
+                    C.InterceptableMethod("a");
+                }
+            }
+            """, "Program.cs");
+
+        var source1 = ("""
+            public class D1
+            {
+                public static void M()
+                {
+                    C.InterceptableMethod("a");
+                }
+            }
+            """, "Program.cs");
+
+        var source2 = ("""
+            using System.Runtime.CompilerServices;
+            using System;
+
+            D0.M();
+            D1.M();
+
+            public class C
+            {
+
+                public static void InterceptableMethod(string param) { Console.Write("interceptable " + param); }
+            }
+
+            public static class Interceptor
+            {
+                [InterceptsLocation("Program.cs", 5, 11)]
+                public static void Interceptor1(string param) { Console.Write("interceptor " + param); }
+            }
+            """, "Interceptor.cs");
+
+        var comp = CreateCompilation(new[] { source0, source1, source2, s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Interceptor.cs(15,25): error CS9152: Cannot intercept a call in file with path 'Program.cs' because multiple files in the compilation have this path.
+            //     [InterceptsLocation("Program.cs", 5, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorNonUniquePath, @"""Program.cs""").WithArguments("Program.cs").WithLocation(15, 25));
+    }
+
+    [Fact]
+    public void DuplicateLocation_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M() { }
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 3, 3)]
+                public static void M1() { }
+
+                [InterceptsLocation("Program.cs", 3, 3)]
+                public static void M2() { }
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(13,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 3, 3)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 3, 3)").WithLocation(13, 6),
+            // Program.cs(16,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 3, 3)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 3, 3)").WithLocation(16, 6));
+    }
+
+    [Fact]
+    public void DuplicateLocation_02()
+    {
+        var source0 = """
+            using System.Runtime.CompilerServices;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M() { }
+            }
+            """;
+
+        var source1 = """
+            using System.Runtime.CompilerServices;
+
+            class D1
+            {
+                [InterceptsLocation("Program.cs", 3, 3)]
+                public static void M1() { }
+            }
+            """;
+
+        var source2 = """
+            using System.Runtime.CompilerServices;
+
+            class D2
+            {
+                [InterceptsLocation("Program.cs", 3, 3)]
+                public static void M1() { }
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source0, "Program.cs"), (source1, "File1.cs"), (source2, "File2.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // File2.cs(5,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 3, 3)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 3, 3)").WithLocation(5, 6),
+            // File1.cs(5,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 3, 3)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 3, 3)").WithLocation(5, 6)
+            );
+    }
+
+    [Fact]
+    public void DuplicateLocation_03()
+    {
+        // InterceptsLocationAttribute is not considered to *duplicate* an interception, even if it is inherited.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            var d = new D();
+            d.M();
+
+            class C
+            {
+
+                public void M() => throw null!;
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                public virtual void Interceptor() => throw null!;
+            }
+
+            class D : C
+            {
+                public override void Interceptor() => Console.Write(1);
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                [AttributeUsage(AttributeTargets.Method)]
+                public sealed class InterceptableAttribute : Attribute { }
+
+                [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
+                public sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int character)
+                    {
+                    }
+                }
+            }
+            """;
+
+        var verifier = CompileAndVerify((source, "Program.cs"), parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void DuplicateLocation_04()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M() { }
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 3, 3)]
+                [InterceptsLocation("Program.cs", 3, 3)]
+                public static void M1() { }
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(13,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 3, 3)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 3, 3)").WithLocation(13, 6),
+            // Program.cs(14,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 3, 3)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 3, 3)").WithLocation(14, 6));
+    }
+
+    [Fact]
+    public void InterceptorVirtual_01()
+    {
+        // Intercept a method call with a call to a virtual method on the same type.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C c = new C();
+            c.M();
+
+            c = new D();
+            c.M();
+
+            class C
+            {
+
+                public void M() => throw null!;
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                [InterceptsLocation("Program.cs", 8, 3)]
+                public virtual void Interceptor() => Console.Write("C");
+            }
+
+            class D : C
+            {
+                public override void Interceptor() => Console.Write("D");
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                [AttributeUsage(AttributeTargets.Method)]
+                public sealed class InterceptableAttribute : Attribute { }
+
+                [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
+                public sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int character)
+                    {
+                    }
+                }
+            }
+            """;
+
+        var verifier = CompileAndVerify((source, "Program.cs"), parseOptions: RegularWithInterceptors, expectedOutput: "CD");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptorVirtual_02()
+    {
+        // Intercept a call with a virtual method call on the base type.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            D d = new D();
+            d.M();
+
+            class C
+            {
+                [InterceptsLocation("Program.cs", 5, 3)]
+                public virtual void Interceptor() => throw null!;
+            }
+
+            class D : C
+            {
+
+                public void M() => throw null!;
+
+                public override void Interceptor() => throw null!;
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                [AttributeUsage(AttributeTargets.Method)]
+                public sealed class InterceptableAttribute : Attribute { }
+
+                [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
+                public sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int character)
+                    {
+                    }
+                }
+            }
+            """;
+
+        var comp = CreateCompilation((source, "Program.cs"), parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(9,6): error CS9148: Interceptor must have a 'this' parameter matching parameter 'D this' on 'D.M()'.
+            //     [InterceptsLocation("Program.cs", 5, 3)]
+            Diagnostic(ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter, @"InterceptsLocation(""Program.cs"", 5, 3)").WithArguments("D this", "D.M()").WithLocation(9, 6));
+    }
+
+    [Fact]
+    public void InterceptorOverride_01()
+    {
+        // Intercept a call with a call to an override method on a derived type.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            D d = new D();
+            d.M();
+
+            class C
+            {
+
+                public void M() => throw null!;
+
+                public virtual void Interceptor() => throw null!;
+            }
+
+            class D : C
+            {
+                [InterceptsLocation("Program.cs", 5, 3)] // 1
+                public override void Interceptor() => throw null!;
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                [AttributeUsage(AttributeTargets.Method)]
+                public sealed class InterceptableAttribute : Attribute { }
+
+                [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
+                public sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int character)
+                    {
+                    }
+                }
+            }
+            """;
+
+        var comp = CreateCompilation((source, "Program.cs"), parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(17,6): error CS9148: Interceptor must have a 'this' parameter matching parameter 'C this' on 'C.M()'.
+            //     [InterceptsLocation("Program.cs", 5, 3)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter, @"InterceptsLocation(""Program.cs"", 5, 3)").WithArguments("C this", "C.M()").WithLocation(17, 6));
+    }
+
+    [Fact]
+    public void InterceptorOverride_02()
+    {
+        // Intercept a call with an override method on the same type.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            D d = new D();
+            d.M();
+
+            class C
+            {
+                public virtual void Interceptor() => throw null!;
+            }
+
+            class D : C
+            {
+
+                public void M() => throw null!;
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                public override void Interceptor() => Console.Write(1);
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                [AttributeUsage(AttributeTargets.Method)]
+                public sealed class InterceptableAttribute : Attribute { }
+
+                [AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
+                public sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int character)
+                    {
+                    }
+                }
+            }
+            """;
+
+        var verifier = CompileAndVerify((source, "Program.cs"), parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void EmitMetadataOnly_01()
+    {
+        // We can emit a ref assembly even though there are duplicate interceptions.
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            class C
+            {
+                public static void Main()
+                {
+                    C.M();
+                }
+
+
+                public static void M() { }
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 7, 11)]
+                public static void M1() { }
+
+                [InterceptsLocation("Program.cs", 7, 11)]
+                public static void M2() { }
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, emitOptions: EmitOptions.Default.WithEmitMetadataOnly(true));
+        verifier.VerifyDiagnostics();
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(16,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 7, 11)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 7, 11)").WithLocation(16, 6),
+            // Program.cs(19,6): error CS9153: The indicated call is intercepted multiple times.
+            //     [InterceptsLocation("Program.cs", 7, 11)]
+            Diagnostic(ErrorCode.ERR_DuplicateInterceptor, @"InterceptsLocation(""Program.cs"", 7, 11)").WithLocation(19, 6));
+    }
+
+    [Fact]
+    public void EmitMetadataOnly_02()
+    {
+        // We can't emit a ref assembly when a problem is found with an InterceptsLocationAttribute in the declaration phase.
+        // Strictly, we should perhaps allow this emit anyway, but it doesn't feel urgent to do so.
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M() { }
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 3, 4)]
+                public static void M1() { }
+
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(EmitOptions.Default.WithEmitMetadataOnly(true),
+            // Program.cs(13,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '('.
+            //     [InterceptsLocation("Program.cs", 3, 4)]
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 3, 4)").WithArguments("(").WithLocation(13, 6));
+    }
+
+    [Fact]
+    public void InterceptsLocationFromMetadata()
+    {
+        // Verify that `[InterceptsLocation]` on a method from metadata does not cause a call in the current compilation to be intercepted.
+        var source0 = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            public class C0
+            {
+
+                public static void InterceptableMethod(string param) { Console.Write("interceptable " + param); }
+
+                static void M0()
+                {
+                    InterceptableMethod("1");
+                }
+            }
+
+            public static class D
+            {
+                [InterceptsLocation("Program.cs", 11, 9)]
+                public static void Interceptor1(string param) { Console.Write("interceptor " + param); }
+            }
+            """;
+        var comp0 = CreateCompilation(new[] { (source0, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp0.VerifyEmitDiagnostics();
+
+        var source1 = """
+
+            using System;
+
+            class C1
+            {
+
+                public static void InterceptableMethod(string param) { Console.Write("interceptable " + param); }
+
+                static void Main()
+                {
+                    InterceptableMethod("1");
+                }
+            }
+            """;
+
+        var comp1 = CompileAndVerify(new[] { (source1, "Program.cs") }, new[] { comp0.ToMetadataReference() }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptable 1");
+        comp1.VerifyDiagnostics();
+
+        comp1 = CompileAndVerify(new[] { (source1, "Program.cs") }, new[] { comp0.EmitToImageReference() }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptable 1");
+        comp1.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableDelegateConversion()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public C InterceptableMethod(string param) { Console.Write("interceptable " + param); return this; }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    var del = c.InterceptableMethod;
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 21)]
+                public static C Interceptor1(this C i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var compilation = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        compilation.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9151: Possible method name 'InterceptableMethod' cannot be intercepted because it is not being invoked.
+            //     [InterceptsLocation("Program.cs", 15, 21)]
+            Diagnostic(ErrorCode.ERR_InterceptorNameNotInvoked, @"InterceptsLocation(""Program.cs"", 15, 21)").WithArguments("InterceptableMethod").WithLocation(21, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptableNameof()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    _ = nameof(Main);
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 7, 13)]
+                public static void Interceptor1(object param) { }
+            }
+            """;
+        var compilation = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        compilation.VerifyEmitDiagnostics(
+            // Program.cs(7,13): error CS9160: A nameof operator cannot be intercepted.
+            //         _ = nameof(Main);
+            Diagnostic(ErrorCode.ERR_InterceptorCannotInterceptNameof, "nameof").WithLocation(7, 13)
+            );
+    }
+
+    [Fact]
+    public void InterceptableNameof_MethodCall()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    _ = nameof(F);
+                }
+
+                private static object F = 1;
+
+
+                public static string nameof(object param) => throw null!;
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 8, 13)]
+                public static string Interceptor1(object param)
+                {
+                    Console.Write(1);
+                    return param.ToString();
+                }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableDoubleUnderscoreReservedIdentifiers()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    M1(__arglist(1, 2, 3));
+
+                    int i = 0;
+                    TypedReference tr = __makeref(i);
+                    ref int ri = ref __refvalue(tr, int);
+                    Type t = __reftype(tr);
+                }
+
+                static void M1(__arglist) { }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 8, 12)] // __arglist
+                [InterceptsLocation("Program.cs", 11, 29)] // __makeref
+                [InterceptsLocation("Program.cs", 12, 26)] // __refvalue
+                [InterceptsLocation("Program.cs", 13, 18)] // __reftype
+                public static void Interceptor1(int x, int y, int z) { }
+            }
+            """;
+        var compilation = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        compilation.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '__arglist'.
+            //     [InterceptsLocation("Program.cs", 8, 12)] // __arglist
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 8, 12)").WithArguments("__arglist").WithLocation(21, 6),
+            // Program.cs(22,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '__makeref'.
+            //     [InterceptsLocation("Program.cs", 11, 29)] // __makeref
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 11, 29)").WithArguments("__makeref").WithLocation(22, 6),
+            // Program.cs(23,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '__refvalue'.
+            //     [InterceptsLocation("Program.cs", 12, 26)] // __refvalue
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 12, 26)").WithArguments("__refvalue").WithLocation(23, 6),
+            // Program.cs(24,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '__reftype'.
+            //     [InterceptsLocation("Program.cs", 13, 18)] // __reftype
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 13, 18)").WithArguments("__reftype").WithLocation(24, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptableDelegateInvocation()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C.M(() => Console.Write(1));
+
+            static class C
+            {
+                public static void M(Action action)
+                {
+                    action();
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 10, 9)]
+                public static void Interceptor1(this Action action) { action(); Console.Write(2); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "12");
+        verifier.VerifyDiagnostics(
+            );
+    }
+
+    [Fact]
+    public void QualifiedNameAtCallSite()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static C InterceptableMethod(C c, string param) { Console.Write("interceptable " + param); return c; }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    C.InterceptableMethod(c, "call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static C Interceptor1(C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor call site");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableStaticMethod_InterceptorExtensionMethod()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static C InterceptableMethod(C c, string param) { Console.Write("interceptable " + param); return c; }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    C.InterceptableMethod(c, "call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor call site");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableExtensionMethod_InterceptorStaticMethod()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            var c = new C();
+            c.InterceptableMethod();
+
+            class C { }
+
+            static class D
+            {
+
+                public static void InterceptableMethod(this C c) => throw null!;
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                public static void Interceptor1(C c) => throw null!;
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(14,6): error CS9148: Interceptor must have a 'this' parameter matching parameter 'C c' on 'D.InterceptableMethod(C)'.
+            //     [InterceptsLocation("Program.cs", 5, 3)]
+            Diagnostic(ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter, @"InterceptsLocation(""Program.cs"", 5, 3)").WithArguments("C c", "D.InterceptableMethod(C)").WithLocation(14, 6));
+    }
+
+    [Fact]
+    public void InterceptableExtensionMethod_InterceptorStaticMethod_NormalForm()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            var c = new C();
+            D.InterceptableMethod(c);
+
+            class C { }
+
+            static class D
+            {
+
+                public static void InterceptableMethod(this C c) => throw null!;
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                public static void Interceptor1(C c) => Console.Write(1);
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableStaticMethod_InterceptorInstanceMethod()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod("call site");
+                }
+            }
+
+            class C
+            {
+
+                public static void InterceptableMethod(string param) { Console.Write("interceptable " + param); }
+
+                [InterceptsLocation("Program.cs", 8, 11)]
+                public void Interceptor1(string param) { Console.Write("interceptor " + param); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(17,6): error CS9149: Interceptor must not have a 'this' parameter because 'C.InterceptableMethod(string)' does not have a 'this' parameter.
+            //     [InterceptsLocation("Program.cs", 8, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorMustNotHaveThisParameter, @"InterceptsLocation(""Program.cs"", 8, 11)").WithArguments("C.InterceptableMethod(string)").WithLocation(17, 6));
+    }
+
+    [Fact]
+    public void ArgumentLabels()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public void InterceptableMethod(string s1, string s2) { Console.Write(s1 + s2); }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod(s2: "World", s1: "Hello ");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor1(this C c, string s1, string s2) { Console.Write("interceptor " + s1 + s2); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor Hello World");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void ParameterNameDifference()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public void InterceptableMethod(string s1) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod(s1: "1");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor1(this C c, string s2) { Console.Write(s2); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void ParameterNamesInDifferentOrder()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public void InterceptableMethod(string s1, string s2) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("1", "2");
+                    c.InterceptableMethod(s2: "4", s1: "3");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                [InterceptsLocation("Program.cs", 16, 11)]
+                public static void Interceptor1(this C c, string s2, string s1) { Console.Write(s2); Console.Write(s1); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1234");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void AttributeArgumentLabels_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public void InterceptableMethod() => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod();
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", character: 11, line: 15)]
+                public static void Interceptor1(this C c) { Console.Write(1); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void AttributeArgumentLabels_02()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            class C
+            {
+
+                public void InterceptableMethod() => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod();
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", character: 1, line: 50)] // 1
+                public static void Interceptor1(this C c) => throw null!;
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyDiagnostics(
+            // Program.cs(20,53): error CS9142: The given file has '22' lines, which is fewer than the provided line number '50'.
+            //     [InterceptsLocation("Program.cs", character: 1, line: 50)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorLineOutOfRange, "line: 50").WithArguments("22", "50").WithLocation(20, 53)
+            );
+    }
+
+    [Fact]
+    public void InterceptableExtensionMethod_InterceptorExtensionMethod_Sequence()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site")
+                        .InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor call siteinterceptable call site");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableFromMetadata()
+    {
+        var source1 = """
+
+            using System;
+
+            public class C
+            {
+
+                public C InterceptableMethod(string param) { Console.Write("interceptable " + param); return this; }
+            }
+            """;
+
+        var source2 = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 9, 11)]
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+            """;
+
+        var comp1 = CreateCompilation(new[] { (source1, "File1.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp1.VerifyEmitDiagnostics();
+
+        var verifier = CompileAndVerify((source2, "Program.cs"), references: new[] { comp1.ToMetadataReference() }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor call site");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptsLocation_BadMethodKind()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            static class Program
+            {
+
+                public static void InterceptableMethod(string param) { }
+
+                public static void Main()
+                {
+                    InterceptableMethod("");
+                    Interceptor1("");
+
+                    var lambda = [InterceptsLocation("Program.cs", 13, 8)] (string param) => { }; // 1
+
+                    [InterceptsLocation("Program.cs", 13, 8)] // 2
+                    static void Interceptor1(string param) { }
+                }
+
+                public static string Prop
+                {
+                    [InterceptsLocation("Program.cs", 13, 8)] // 3
+                    set { }
+                }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyDiagnostics(
+            // Program.cs(13,23): error CS9146: An interceptor method must be an ordinary member method.
+            //         var lambda = [InterceptsLocation("Program.cs", 13, 8)] (string param) => { }; // 1
+            Diagnostic(ErrorCode.ERR_InterceptorMethodMustBeOrdinary, @"InterceptsLocation(""Program.cs"", 13, 8)").WithLocation(13, 23),
+            // Program.cs(15,10): error CS9146: An interceptor method must be an ordinary member method.
+            //         [InterceptsLocation("Program.cs", 13, 8)] // 2
+            Diagnostic(ErrorCode.ERR_InterceptorMethodMustBeOrdinary, @"InterceptsLocation(""Program.cs"", 13, 8)").WithLocation(15, 10),
+            // Program.cs(21,10): error CS9146: An interceptor method must be an ordinary member method.
+            //         [InterceptsLocation("Program.cs", 13, 8)] // 3
+            Diagnostic(ErrorCode.ERR_InterceptorMethodMustBeOrdinary, @"InterceptsLocation(""Program.cs"", 13, 8)").WithLocation(21, 10)
+            );
+    }
+
+    [Fact]
+    public void InterceptorCannotBeGeneric_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1
+            {
+
+                public I1 InterceptableMethod(string param) { Console.Write("interceptable " + param); return this; }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 16, 11)]
+                public static I1 Interceptor1<T>(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+                // Program.cs(22,6): error CS9138: Method 'D.Interceptor1<T>(I1, string)' cannot be used as an interceptor because it or its containing type has type parameters.
+                //     [InterceptsLocation("Program.cs", 16, 11)]
+                Diagnostic(ErrorCode.ERR_InterceptorCannotBeGeneric, @"InterceptsLocation(""Program.cs"", 16, 11)").WithArguments("D.Interceptor1<T>(I1, string)").WithLocation(22, 6));
+    }
+
+    [Fact]
+    public void InterceptorCannotBeGeneric_02()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1
+            {
+
+                public static void InterceptableMethod(string param) { Console.Write("interceptable " + param); }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod("call site");
+                }
+            }
+
+            static class D<T>
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor1(string param) { Console.Write("interceptor " + param); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9138: Method 'D<T>.Interceptor1(string)' cannot be used as an interceptor because it or its containing type has type parameters.
+            //     [InterceptsLocation("Program.cs", 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorCannotBeGeneric, @"InterceptsLocation(""Program.cs"", 15, 11)").WithArguments("D<T>.Interceptor1(string)").WithLocation(21, 6));
+    }
+
+    [Fact]
+    public void InterceptorCannotBeGeneric_03()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1
+            {
+
+                public static void InterceptableMethod(string param) { Console.Write("interceptable " + param); }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod("call site");
+                }
+            }
+
+            static class Outer<T>
+            {
+                static class D
+                {
+                    [InterceptsLocation("Program.cs", 15, 11)]
+                    public static void Interceptor1(string param) { Console.Write("interceptor " + param); }
+                }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(23,10): error CS9138: Method 'Outer<T>.D.Interceptor1(string)' cannot be used as an interceptor because it or its containing type has type parameters.
+            //         [InterceptsLocation("Program.cs", 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorCannotBeGeneric, @"InterceptsLocation(""Program.cs"", 15, 11)").WithArguments("Outer<T>.D.Interceptor1(string)").WithLocation(23, 10)
+            );
+    }
+
+    [Fact]
+    public void InterceptableGeneric_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod<T>(T t) { Console.Write("0"); }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod<string>("1");
+                    C.InterceptableMethod("2");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)]
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor1(string s) { Console.Write(s); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableGeneric_02()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod<T>(T t) { Console.Write("0"); }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod<string>("1");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 30)]
+                [InterceptsLocation("Program.cs", 14, 31)]
+                [InterceptsLocation("Program.cs", 14, 37)]
+                public static void Interceptor1(string s) { Console.Write(s); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(20,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '<'.
+            //     [InterceptsLocation("Program.cs", 14, 30)]
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 14, 30)").WithArguments("<").WithLocation(20, 6),
+            // Program.cs(21,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token 'string'.
+            //     [InterceptsLocation("Program.cs", 14, 31)]
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 14, 31)").WithArguments("string").WithLocation(21, 6),
+            // Program.cs(22,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '>'.
+            //     [InterceptsLocation("Program.cs", 14, 37)]
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 14, 37)").WithArguments(">").WithLocation(22, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptableGeneric_03()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod<T>(T t) where T : class => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod<string>("1");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)]
+                public static void Interceptor1(string s) { Console.Write(s); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptableGeneric_04()
+    {
+        // No interceptor can satisfy a signature like `void InterceptableMethod<T2>(T2 t2)` where `T2` is a method type argument.
+        // We would need to re-examine arity limitations and devise method type argument inference rules for interceptors to make this work.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod<T1>(T1 t) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void M<T2>(T2 t)
+                {
+                    C.InterceptableMethod(t);
+                    C.InterceptableMethod<T2>(t);
+                    C.InterceptableMethod<object>(t);
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)] // 1
+                [InterceptsLocation("Program.cs", 15, 11)] // 2
+                [InterceptsLocation("Program.cs", 16, 11)]
+                public static void Interceptor1(object s) { Console.Write(s); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(22,6): error CS9144: Cannot intercept method 'C.InterceptableMethod<T2>(T2)' with interceptor 'D.Interceptor1(object)' because the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 14, 11)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 14, 11)").WithArguments("C.InterceptableMethod<T2>(T2)", "D.Interceptor1(object)").WithLocation(22, 6),
+            // Program.cs(23,6): error CS9144: Cannot intercept method 'C.InterceptableMethod<T2>(T2)' with interceptor 'D.Interceptor1(object)' because the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 15, 11)] // 2
+            Diagnostic(ErrorCode.ERR_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 15, 11)").WithArguments("C.InterceptableMethod<T2>(T2)", "D.Interceptor1(object)").WithLocation(23, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadAttributeArguments_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 1, "10")]
+                [InterceptsLocation("Program.cs", 1, 1, 9999)]
+                [InterceptsLocation("Program.cs", ERROR, 1)]
+                [InterceptsLocation()]
+                public static void Interceptor1(string param) { Console.Write("interceptor " + param); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(6,42): error CS1503: Argument 3: cannot convert from 'string' to 'int'
+            //     [InterceptsLocation("Program.cs", 1, "10")]
+            Diagnostic(ErrorCode.ERR_BadArgType, @"""10""").WithArguments("3", "string", "int").WithLocation(6, 42),
+            // Program.cs(7,6): error CS1729: 'InterceptsLocationAttribute' does not contain a constructor that takes 4 arguments
+            //     [InterceptsLocation("Program.cs", 1, 1, 9999)]
+            Diagnostic(ErrorCode.ERR_BadCtorArgCount, @"InterceptsLocation(""Program.cs"", 1, 1, 9999)").WithArguments("System.Runtime.CompilerServices.InterceptsLocationAttribute", "4").WithLocation(7, 6),
+            // Program.cs(8,39): error CS0103: The name 'ERROR' does not exist in the current context
+            //     [InterceptsLocation("Program.cs", ERROR, 1)]
+            Diagnostic(ErrorCode.ERR_NameNotInContext, "ERROR").WithArguments("ERROR").WithLocation(8, 39),
+            // Program.cs(9,6): error CS7036: There is no argument given that corresponds to the required parameter 'filePath' of 'InterceptsLocationAttribute.InterceptsLocationAttribute(string, int, int)'
+            //     [InterceptsLocation()]
+            Diagnostic(ErrorCode.ERR_NoCorrespondingArgument, "InterceptsLocation()").WithArguments("filePath", "System.Runtime.CompilerServices.InterceptsLocationAttribute.InterceptsLocationAttribute(string, int, int)").WithLocation(9, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPath_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("BAD", 15, 11)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,25): error CS9139: Cannot intercept: compilation does not contain a file with path 'BAD'.
+            //     [InterceptsLocation("BAD", 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilation, @"""BAD""").WithArguments("BAD").WithLocation(21, 25)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPath_02()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("projects/Program.cs", 15, 11)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "/Users/me/projects/Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // /Users/me/projects/Program.cs(21,25): error CS9140: Cannot intercept: compilation does not contain a file with path 'projects/Program.cs'. Did you mean to use path '/Users/me/projects/Program.cs'?
+            //     [InterceptsLocation("projects/Program.cs", 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilationWithCandidate, @"""projects/Program.cs""").WithArguments("projects/Program.cs", "/Users/me/projects/Program.cs").WithLocation(21, 25)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPath_03()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C { }
+
+            static class Program
+            {
+
+                public static C InterceptableMethod(this C c, string param) { Console.Write("interceptable " + param); return c; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation(null, 15, 11)]
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(20,25): error CS9150: Interceptor cannot have a 'null' file path.
+            //     [InterceptsLocation(null, 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorFilePathCannotBeNull, "null").WithLocation(20, 25)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPath_04()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C { }
+
+            static class Program
+            {
+
+                public static C InterceptableMethod(this C c, string param) { Console.Write("interceptable " + param); return c; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("program.cs", 15, 11)]
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(20,25): error CS9139: Cannot intercept: compilation does not contain a file with path 'program.cs'.
+            //     [InterceptsLocation("program.cs", 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilation, @"""program.cs""").WithArguments("program.cs").WithLocation(20, 25)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 25, 1)]
+                [InterceptsLocation("Program.cs", 26, 1)]
+                [InterceptsLocation("Program.cs", 100, 1)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '}'.
+            //     [InterceptsLocation("Program.cs", 25, 1)]
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 25, 1)").WithArguments("}").WithLocation(21, 6),
+            // Program.cs(22,39): error CS9142: The given file has '25' lines, which is fewer than the provided line number '26'.
+            //     [InterceptsLocation("Program.cs", 26, 1)]
+            Diagnostic(ErrorCode.ERR_InterceptorLineOutOfRange, "26").WithArguments("25", "26").WithLocation(22, 39),
+            // Program.cs(23,39): error CS9142: The given file has '25' lines, which is fewer than the provided line number '100'.
+            //     [InterceptsLocation("Program.cs", 100, 1)]
+            Diagnostic(ErrorCode.ERR_InterceptorLineOutOfRange, "100").WithArguments("25", "100").WithLocation(23, 39)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_02()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 16, 5)]
+                [InterceptsLocation("Program.cs", 16, 6)]
+                [InterceptsLocation("Program.cs", 16, 1000)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9141: The provided line and character number does not refer to an interceptable method name, but rather to token '}'.
+            //     [InterceptsLocation("Program.cs", 16, 5)]
+            Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 16, 5)").WithArguments("}").WithLocation(21, 6),
+            // Program.cs(22,43): error CS9143: The given line is '5' characters long, which is fewer than the provided character number '6'.
+            //     [InterceptsLocation("Program.cs", 16, 6)]
+            Diagnostic(ErrorCode.ERR_InterceptorCharacterOutOfRange, "6").WithArguments("5", "6").WithLocation(22, 43),
+            // Program.cs(23,43): error CS9143: The given line is '5' characters long, which is fewer than the provided character number '1000'.
+            //     [InterceptsLocation("Program.cs", 16, 1000)]
+            Diagnostic(ErrorCode.ERR_InterceptorCharacterOutOfRange, "1000").WithArguments("5", "1000").WithLocation(23, 43)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_03()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 9)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+                // Program.cs(21,6): error CS9141: The provided line and character number does not refer to an interceptable method, but rather to token 'c'.
+                //     [InterceptsLocation("Program.cs", 15, 9)]
+                Diagnostic(ErrorCode.ERR_InterceptorPositionBadToken, @"InterceptsLocation(""Program.cs"", 15, 9)").WithArguments("c").WithLocation(21, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_04()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 13)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9147: The provided line and character number does not refer to the start of token 'InterceptableMethod'. Did you mean to use line '15' and character '11'?
+            //     [InterceptsLocation("Program.cs", 15, 13)]
+            Diagnostic(ErrorCode.ERR_InterceptorMustReferToStartOfTokenPosition, @"InterceptsLocation(""Program.cs"", 15, 13)").WithArguments("InterceptableMethod", "15", "11").WithLocation(21, 6)
+        );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_05()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C { }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.
+                        InterceptableMethod("call site");
+
+                    c.InterceptableMethod    ("call site");
+                }
+
+
+                public static C InterceptableMethod(this C c, string param) { Console.Write("interceptable " + param); return c; }
+
+                [InterceptsLocation("Program.cs", 12, 11)] // intercept spaces before 'InterceptableMethod' token
+                [InterceptsLocation("Program.cs", 14, 33)] // intercept spaces after 'InterceptableMethod' token
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+
+            static class CExt
+            {
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(20,6): error CS9147: The provided line and character number does not refer to the start of token 'InterceptableMethod'. Did you mean to use line '12' and character '13'?
+            //     [InterceptsLocation("Program.cs", 12, 11)] // intercept spaces before 'InterceptableMethod' token
+            Diagnostic(ErrorCode.ERR_InterceptorMustReferToStartOfTokenPosition, @"InterceptsLocation(""Program.cs"", 12, 11)").WithArguments("InterceptableMethod", "12", "13").WithLocation(20, 6),
+            // Program.cs(21,6): error CS9147: The provided line and character number does not refer to the start of token 'InterceptableMethod'. Did you mean to use line '14' and character '11'?
+            //     [InterceptsLocation("Program.cs", 14, 33)] // intercept spaces after 'InterceptableMethod' token
+            Diagnostic(ErrorCode.ERR_InterceptorMustReferToStartOfTokenPosition, @"InterceptsLocation(""Program.cs"", 14, 33)").WithArguments("InterceptableMethod", "14", "11").WithLocation(21, 6)
+        );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_06()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C { }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod/*comment*/("call site");
+                }
+
+
+                public static C InterceptableMethod(this C c, string param) { Console.Write("interceptable " + param); return c; }
+
+                [InterceptsLocation("Program.cs", 11, 31)] // intercept comment after 'InterceptableMethod' token
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+
+            static class CExt
+            {
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(17,6): error CS9147: The provided line and character number does not refer to the start of token 'InterceptableMethod'. Did you mean to use line '11' and character '11'?
+            //     [InterceptsLocation("Program.cs", 11, 31)] // intercept comment after 'InterceptableMethod' token
+            Diagnostic(ErrorCode.ERR_InterceptorMustReferToStartOfTokenPosition, @"InterceptsLocation(""Program.cs"", 11, 31)").WithArguments("InterceptableMethod", "11", "11").WithLocation(17, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_07()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C { }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.
+                        // comment
+                        InterceptableMethod("call site");
+                }
+
+
+                public static C InterceptableMethod(this C c, string param) { Console.Write("interceptable " + param); return c; }
+
+                [InterceptsLocation("Program.cs", 12, 13)] // intercept comment above 'InterceptableMethod' token
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+
+            static class CExt
+            {
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+                // Program.cs(19,6): error CS9147: The provided line and character number does not refer to the start of token 'InterceptableMethod'. Did you mean to use line '13' and character '13'?
+                //     [InterceptsLocation("Program.cs", 12, 13)] // intercept comment above 'InterceptableMethod' token
+                Diagnostic(ErrorCode.ERR_InterceptorMustReferToStartOfTokenPosition, @"InterceptsLocation(""Program.cs"", 12, 13)").WithArguments("InterceptableMethod", "13", "13").WithLocation(19, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptsLocationBadPosition_08()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C { }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+
+
+                public static C InterceptableMethod(this C c, string param) { Console.Write("interceptable " + param); return c; }
+
+                [InterceptsLocation("Program.cs", -1, 1)] // 1
+                [InterceptsLocation("Program.cs", 1, -1)] // 2
+                [InterceptsLocation("Program.cs", -1, -1)] // 3
+                [InterceptsLocation("Program.cs", 0, 1)] // 4
+                [InterceptsLocation("Program.cs", 1, 0)] // 5 
+                [InterceptsLocation("Program.cs", 0, 0)] // 6
+                public static C Interceptor1(this C c, string param) { Console.Write("interceptor " + param); return c; }
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(17,39): error CS9157: Line and character numbers provided to InterceptsLocationAttribute must be positive.
+            //     [InterceptsLocation("Program.cs", -1, 1)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorLineCharacterMustBePositive, "-1").WithLocation(17, 39),
+            // Program.cs(18,42): error CS9157: Line and character numbers provided to InterceptsLocationAttribute must be positive.
+            //     [InterceptsLocation("Program.cs", 1, -1)] // 2
+            Diagnostic(ErrorCode.ERR_InterceptorLineCharacterMustBePositive, "-1").WithLocation(18, 42),
+            // Program.cs(19,39): error CS9157: Line and character numbers provided to InterceptsLocationAttribute must be positive.
+            //     [InterceptsLocation("Program.cs", -1, -1)] // 3
+            Diagnostic(ErrorCode.ERR_InterceptorLineCharacterMustBePositive, "-1").WithLocation(19, 39),
+            // Program.cs(20,39): error CS9157: Line and character numbers provided to InterceptsLocationAttribute must be positive.
+            //     [InterceptsLocation("Program.cs", 0, 1)] // 4
+            Diagnostic(ErrorCode.ERR_InterceptorLineCharacterMustBePositive, "0").WithLocation(20, 39),
+            // Program.cs(21,42): error CS9157: Line and character numbers provided to InterceptsLocationAttribute must be positive.
+            //     [InterceptsLocation("Program.cs", 1, 0)] // 5 
+            Diagnostic(ErrorCode.ERR_InterceptorLineCharacterMustBePositive, "0").WithLocation(21, 42),
+            // Program.cs(22,39): error CS9157: Line and character numbers provided to InterceptsLocationAttribute must be positive.
+            //     [InterceptsLocation("Program.cs", 0, 0)] // 6
+            Diagnostic(ErrorCode.ERR_InterceptorLineCharacterMustBePositive, "0").WithLocation(22, 39)
+            );
+    }
+
+    [Fact]
+    public void SignatureMismatch_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1 { }
+
+            static class Program
+            {
+
+                public static I1 InterceptableMethod(this I1 i1, string param) { Console.Write("interceptable " + param); return i1; }
+
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static I1 Interceptor1(this I1 i1, int param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+                // Program.cs(21,6): error CS9144: Cannot intercept method 'Program.InterceptableMethod(I1, string)' with interceptor 'D.Interceptor1(I1, int)' because the signatures do not match.
+                //     [InterceptsLocation("Program.cs", 15, 11)]
+                Diagnostic(ErrorCode.ERR_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 15, 11)").WithArguments("Program.InterceptableMethod(I1, string)", "D.Interceptor1(I1, int)").WithLocation(21, 6)
+            );
+    }
+
+    [Fact]
+    public void SignatureMismatch_02()
+    {
+        // Instance method receiver type differs from interceptor 'this' parameter type.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            interface I1 { }
+            class C : I1
+            {
+
+                public I1 InterceptableMethod(string param) { Console.Write("interceptable " + param); return this; }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 16, 11)]
+                public static I1 Interceptor1(this I1 i1, string param) { Console.Write("interceptor " + param); return i1; }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(22,6): error CS9148: Interceptor must have a 'this' parameter matching parameter 'C this' on 'C.InterceptableMethod(string)'.
+            //     [InterceptsLocation("Program.cs", 16, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter, @"InterceptsLocation(""Program.cs"", 16, 11)").WithArguments("C this", "C.InterceptableMethod(string)").WithLocation(22, 6)
+            );
+    }
+
+    [Fact]
+    public void SignatureMismatch_03()
+    {
+        // Instance method 'this' parameter ref kind differs from interceptor 'this' parameter ref kind.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            struct S
+            {
+
+                public void InterceptableMethod(string param) { Console.Write("interceptable " + param); }
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var s = new S();
+                    s.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor1(this S s, string param) { Console.Write("interceptor " + param); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9148: Interceptor must have a 'this' parameter matching parameter 'ref S this' on 'S.InterceptableMethod(string)'.
+            //     [InterceptsLocation("Program.cs", 15, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter, @"InterceptsLocation(""Program.cs"", 15, 11)").WithArguments("ref S this", "S.InterceptableMethod(string)").WithLocation(21, 6)
+            );
+    }
+
+    [Fact]
+    public void SignatureMismatch_04()
+    {
+        // Safe nullability difference
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            class C
+            {
+
+                public string? InterceptableMethod(string param) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.InterceptableMethod("call site");
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)]
+                public static string Interceptor1(this C s, string? param) => throw null!;
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, options: WithNullableEnable());
+        comp.VerifyEmitDiagnostics();
+    }
+
+    [Fact]
+    public void SignatureMismatch_05()
+    {
+        // Unsafe nullability difference
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            class C
+            {
+
+                public void Method1(string? param1) => throw null!;
+
+
+                public string Method2() => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.Method1("call site");
+                    _ = c.Method2();
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 17, 11)] // 1
+                public static void Interceptor1(this C s, string param2) => throw null!;
+
+                [InterceptsLocation("Program.cs", 18, 15)] // 2
+                public static string? Interceptor2(this C s) => throw null!;
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, options: WithNullableEnable());
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(24,6): warning CS9159: Nullability of reference types in type of parameter 'param2' doesn't match interceptable method 'C.Method1(string?)'.
+            //     [InterceptsLocation("Program.cs", 17, 11)] // 1
+            Diagnostic(ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor, @"InterceptsLocation(""Program.cs"", 17, 11)").WithArguments("param2", "C.Method1(string?)").WithLocation(24, 6),
+            // Program.cs(27,6): warning CS9158: Nullability of reference types in return type doesn't match interceptable method 'C.Method2()'.
+            //     [InterceptsLocation("Program.cs", 18, 15)] // 2
+            Diagnostic(ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor, @"InterceptsLocation(""Program.cs"", 18, 15)").WithArguments("C.Method2()").WithLocation(27, 6)
+            );
+
+        comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, options: WithNullableDisable());
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(6,31): warning CS8632: The annotation for nullable reference types should only be used in code within a '#nullable' annotations context.
+            //     public void Method1(string? param1) => throw null!;
+            Diagnostic(ErrorCode.WRN_MissingNonNullTypesContextForAnnotation, "?").WithLocation(6, 31),
+            // Program.cs(28,25): warning CS8632: The annotation for nullable reference types should only be used in code within a '#nullable' annotations context.
+            //     public static string? Interceptor2(this C s) => throw null!;
+            Diagnostic(ErrorCode.WRN_MissingNonNullTypesContextForAnnotation, "?").WithLocation(28, 25)
+            );
+    }
+
+    [Fact]
+    public void SignatureMismatch_06()
+    {
+        // 'dynamic' difference
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            class C
+            {
+
+                public void Method1(object param1) => throw null!;
+
+
+                public dynamic Method2() => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.Method1("call site");
+                    _ = c.Method2();
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 17, 11)] // 1
+                public static void Interceptor1(this C s, dynamic param2) => throw null!;
+
+                [InterceptsLocation("Program.cs", 18, 15)] // 2
+                public static object Interceptor2(this C s) => throw null!;
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(24,6): warning CS9154: Intercepting a call to 'C.Method1(object)' with interceptor 'D.Interceptor1(C, dynamic)', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 17, 11)] // 1
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 17, 11)").WithArguments("C.Method1(object)", "D.Interceptor1(C, dynamic)").WithLocation(24, 6),
+            // Program.cs(27,6): warning CS9154: Intercepting a call to 'C.Method2()' with interceptor 'D.Interceptor2(C)', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 18, 15)] // 2
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 18, 15)").WithArguments("C.Method2()", "D.Interceptor2(C)").WithLocation(27, 6)
+            );
+    }
+
+    [Fact]
+    public void SignatureMismatch_07()
+    {
+        // tuple element name difference
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+                public void Method1((string a, string b) param1) => throw null!;
+                public void Method2((string x, string y) param1) => throw null!;
+                public void Method3((string, string) param1) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+
+                    c.Method1(default!);
+                    c.Method2(default!);
+                    c.Method3(default!);
+
+                    c.Method1(default!);
+                    c.Method2(default!);
+                    c.Method3(default!);
+
+                    c.Method1(default!);
+                    c.Method2(default!);
+                    c.Method3(default!);
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 17, 11)]
+                [InterceptsLocation("Program.cs", 18, 11)] // 1
+                [InterceptsLocation("Program.cs", 19, 11)] // 2
+                public static void Interceptor1(this C s, (string a, string b) param2) => Console.Write(1);
+
+                [InterceptsLocation("Program.cs", 21, 11)] // 3
+                [InterceptsLocation("Program.cs", 22, 11)]
+                [InterceptsLocation("Program.cs", 23, 11)] // 4
+                public static void Interceptor2(this C s, (string x, string y) param2) => Console.Write(2);
+
+                [InterceptsLocation("Program.cs", 25, 11)] // 5
+                [InterceptsLocation("Program.cs", 26, 11)] // 6
+                [InterceptsLocation("Program.cs", 27, 11)]
+                public static void Interceptor3(this C s, (string, string) param2) => Console.Write(3);
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "111222333");
+        verifier.VerifyDiagnostics(
+            // Program.cs(34,6): warning CS9154: Intercepting a call to 'C.Method2((string x, string y))' with interceptor 'D.Interceptor1(C, (string a, string b))', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 18, 11)] // 1
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 18, 11)").WithArguments("C.Method2((string x, string y))", "D.Interceptor1(C, (string a, string b))").WithLocation(34, 6),
+            // Program.cs(35,6): warning CS9154: Intercepting a call to 'C.Method3((string, string))' with interceptor 'D.Interceptor1(C, (string a, string b))', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 19, 11)] // 2
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 19, 11)").WithArguments("C.Method3((string, string))", "D.Interceptor1(C, (string a, string b))").WithLocation(35, 6),
+            // Program.cs(38,6): warning CS9154: Intercepting a call to 'C.Method1((string a, string b))' with interceptor 'D.Interceptor2(C, (string x, string y))', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 21, 11)] // 3
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 21, 11)").WithArguments("C.Method1((string a, string b))", "D.Interceptor2(C, (string x, string y))").WithLocation(38, 6),
+            // Program.cs(40,6): warning CS9154: Intercepting a call to 'C.Method3((string, string))' with interceptor 'D.Interceptor2(C, (string x, string y))', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 23, 11)] // 4
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 23, 11)").WithArguments("C.Method3((string, string))", "D.Interceptor2(C, (string x, string y))").WithLocation(40, 6),
+            // Program.cs(43,6): warning CS9154: Intercepting a call to 'C.Method1((string a, string b))' with interceptor 'D.Interceptor3(C, (string, string))', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 25, 11)] // 5
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 25, 11)").WithArguments("C.Method1((string a, string b))", "D.Interceptor3(C, (string, string))").WithLocation(43, 6),
+            // Program.cs(44,6): warning CS9154: Intercepting a call to 'C.Method2((string x, string y))' with interceptor 'D.Interceptor3(C, (string, string))', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 26, 11)] // 6
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 26, 11)").WithArguments("C.Method2((string x, string y))", "D.Interceptor3(C, (string, string))").WithLocation(44, 6)
+            );
+    }
+
+    [Fact]
+    public void SignatureMismatch_08()
+    {
+        // nint/IntPtr difference
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public void Method1(nint param1) => throw null!;
+                public void Method2(IntPtr param1) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    var c = new C();
+                    c.Method1(default!);
+                    c.Method2(default!);
+
+                    c.Method2(default!);
+                    c.Method1(default!);
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 16, 11)] // 1
+                [InterceptsLocation("Program.cs", 17, 11)]
+                public static void Interceptor1(this C s, IntPtr param2) => Console.Write(1);
+
+                [InterceptsLocation("Program.cs", 19, 11)] // 2
+                [InterceptsLocation("Program.cs", 20, 11)]
+                public static void Interceptor2(this C s, nint param2) => Console.Write(2);
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1122");
+        verifier.VerifyDiagnostics(
+            // Program.cs(26,6): warning CS9154: Intercepting a call to 'C.Method1(nint)' with interceptor 'D.Interceptor1(C, IntPtr)', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 16, 11)] // 1
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 16, 11)").WithArguments("C.Method1(nint)", "D.Interceptor1(C, System.IntPtr)").WithLocation(26, 6),
+            // Program.cs(30,6): warning CS9154: Intercepting a call to 'C.Method2(IntPtr)' with interceptor 'D.Interceptor2(C, nint)', but the signatures do not match.
+            //     [InterceptsLocation("Program.cs", 19, 11)] // 2
+            Diagnostic(ErrorCode.WRN_InterceptorSignatureMismatch, @"InterceptsLocation(""Program.cs"", 19, 11)").WithArguments("C.Method2(System.IntPtr)", "D.Interceptor2(C, nint)").WithLocation(30, 6));
+    }
+
+    [Fact]
+    public void ScopedMismatch_01()
+    {
+        // Unsafe 'scoped' difference
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            class C
+            {
+
+                public static ref int InterceptableMethod(scoped ref int value) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    int i = 0;
+                    C.InterceptableMethod(ref i);
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)] // 1
+                public static ref int Interceptor1(ref int value) => throw null!;
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, options: WithNullableEnable());
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(20,6): error CS9156: Cannot intercept call to 'C.InterceptableMethod(scoped ref int)' with 'D.Interceptor1(ref int)' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.
+            //     [InterceptsLocation("Program.cs", 14, 11)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorScopedMismatch, @"InterceptsLocation(""Program.cs"", 14, 11)").WithArguments("C.InterceptableMethod(scoped ref int)", "D.Interceptor1(ref int)").WithLocation(20, 6)
+            );
+    }
+
+    [Fact]
+    public void ScopedMismatch_02()
+    {
+        // safe 'scoped' difference
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static ref int InterceptableMethod(ref int value) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    int i = 0;
+                    _ = C.InterceptableMethod(ref i);
+                }
+            }
+
+            static class D
+            {
+                static int i;
+
+                [InterceptsLocation("Program.cs", 15, 15)]
+                public static ref int Interceptor1(scoped ref int value)
+                {
+                    Console.Write(1);
+                    return ref i;
+                }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void ScopedMismatch_03()
+    {
+        // safe '[UnscopedRef]' difference
+        var source = """
+            using System.Diagnostics.CodeAnalysis;
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static ref int InterceptableMethod([UnscopedRef] out int value) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    _ = C.InterceptableMethod(out int i);
+                }
+            }
+
+            static class D
+            {
+                static int i;
+
+                [InterceptsLocation("Program.cs", 15, 15)]
+                public static ref int Interceptor1(out int value)
+                {
+                    Console.Write(1);
+                    value = 0;
+                    return ref i;
+                }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource, (UnscopedRefAttributeDefinition, "UnscopedRefAttribute.cs") }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void ScopedMismatch_04()
+    {
+        // unsafe '[UnscopedRef]' difference
+        var source = """
+            using System.Diagnostics.CodeAnalysis;
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static ref int InterceptableMethod(out int value) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod(out int i);
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 15, 11)] // 1
+                public static ref int Interceptor1([UnscopedRef] out int value) => throw null!;
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource, (UnscopedRefAttributeDefinition, "UnscopedRefAttribute.cs") }, parseOptions: RegularWithInterceptors, options: WithNullableEnable());
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(21,6): error CS9156: Cannot intercept call to 'C.InterceptableMethod(out int)' with 'D.Interceptor1(out int)' because of a difference in 'scoped' modifiers or '[UnscopedRef]' attributes.
+            //     [InterceptsLocation("Program.cs", 15, 11)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorScopedMismatch, @"InterceptsLocation(""Program.cs"", 15, 11)").WithArguments("C.InterceptableMethod(out int)", "D.Interceptor1(out int)").WithLocation(21, 6)
+            );
+    }
+
+    [Fact]
+    public void ReferenceEquals_01()
+    {
+        // A call to 'object.ReferenceEquals(a, b)' is defined as being equivalent to '(object)a == b'.
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            static class D
+            {
+
+                public static bool Interceptable(object? obj1, object? obj2) => throw null!;
+
+                public static void M0(object? obj1, object? obj2)
+                {
+                    if (obj1 == obj2)
+                       throw null!;
+                }
+
+                public static void M1(object? obj1, object? obj2)
+                {
+                    if (Interceptable(obj1, obj2))
+                       throw null!;
+                }
+
+                public static void M2(object? obj1, object? obj2)
+                {
+                    if (Interceptable(obj1, obj2))
+                       throw null!;
+                }
+            }
+
+            namespace System
+            {
+                public class Object
+                {
+                    [InterceptsLocation("Program.cs", 16, 13)]
+                    public static bool ReferenceEquals(object? obj1, object? obj2) => throw null!;
+
+                    [InterceptsLocation("Program.cs", 22, 13)]
+                    public static bool NotReferenceEquals(object? obj1, object? obj2) => throw null!;
+                }
+
+                public class Void { }
+                public struct Boolean { }
+                public class String { }
+                public class Attribute { }
+                public abstract class Enum { }
+                public enum AttributeTargets { }
+                public class AttributeUsageAttribute : Attribute
+                {
+                    public AttributeUsageAttribute(AttributeTargets targets) { }
+                    public bool AllowMultiple { get; set; }
+                    public bool Inherited { get; set; }
+                }
+                public class Exception { }
+                public abstract class ValueType { }
+                public struct Int32 { }
+                public struct Byte { }
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                public sealed class InterceptableAttribute : Attribute { }
+
+                public sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int column)
+                    {
+                    }
+                }
+            }
+            """;
+        var verifier = CompileAndVerify(CreateEmptyCompilation((source, "Program.cs"), parseOptions: RegularWithInterceptors, options: WithNullableEnable()), verify: Verification.Skipped);
+        verifier.Diagnostics.Where(d => d.Severity == DiagnosticSeverity.Error).Verify();
+
+        var referenceEqualsCallIL = """
+            {
+              // Code size        7 (0x7)
+              .maxstack  2
+              IL_0000:  ldarg.0
+              IL_0001:  ldarg.1
+              IL_0002:  bne.un.s   IL_0006
+              IL_0004:  ldnull
+              IL_0005:  throw
+              IL_0006:  ret
+            }
+            """;
+        verifier.VerifyIL("D.M0", referenceEqualsCallIL);
+        verifier.VerifyIL("D.M1", referenceEqualsCallIL);
+
+        verifier.VerifyIL("D.M2", """
+            {
+              // Code size       12 (0xc)
+              .maxstack  2
+              IL_0000:  ldarg.0
+              IL_0001:  ldarg.1
+              IL_0002:  call       "bool object.NotReferenceEquals(object, object)"
+              IL_0007:  brfalse.s  IL_000b
+              IL_0009:  ldnull
+              IL_000a:  throw
+              IL_000b:  ret
+            }
+            """);
+    }
+
+    [Fact]
+    public void ReferenceEquals_02()
+    {
+        // Intercept a call to object.ReferenceEquals
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            static class D
+            {
+                public static void M0(object? obj1, object? obj2)
+                {
+                    if (object.ReferenceEquals(obj1, obj2))
+                       throw null!;
+                }
+
+                [InterceptsLocation("Program.cs", 7, 20)]
+                public static bool Interceptor(object? obj1, object? obj2)
+                {
+                    return false;
+                }
+            }
+
+            namespace System
+            {
+                public class Object
+                {
+
+                    public static bool ReferenceEquals(object? obj1, object? obj2) => throw null!;
+                }
+
+                public class Void { }
+                public struct Boolean { }
+                public class String { }
+                public class Attribute { }
+                public abstract class Enum { }
+                public enum AttributeTargets { }
+                public class AttributeUsageAttribute : Attribute
+                {
+                    public AttributeUsageAttribute(AttributeTargets targets) { }
+                    public bool AllowMultiple { get; set; }
+                    public bool Inherited { get; set; }
+                }
+                public class Exception { }
+                public abstract class ValueType { }
+                public struct Int32 { }
+                public struct Byte { }
+            }
+
+            namespace System.Runtime.CompilerServices
+            {
+                public sealed class InterceptableAttribute : Attribute { }
+
+                public sealed class InterceptsLocationAttribute : Attribute
+                {
+                    public InterceptsLocationAttribute(string filePath, int line, int column)
+                    {
+                    }
+                }
+            }
+            """;
+        var verifier = CompileAndVerify(CreateEmptyCompilation((source, "Program.cs"), parseOptions: RegularWithInterceptors, options: WithNullableEnable()), verify: Verification.Skipped);
+        verifier.Diagnostics.Where(d => d.Severity == DiagnosticSeverity.Error).Verify();
+
+        verifier.VerifyIL("D.M0", """
+            {
+              // Code size       12 (0xc)
+              .maxstack  2
+              IL_0000:  ldarg.0
+              IL_0001:  ldarg.1
+              IL_0002:  call       "bool D.Interceptor(object, object)"
+              IL_0007:  brfalse.s  IL_000b
+              IL_0009:  ldnull
+              IL_000a:  throw
+              IL_000b:  ret
+            }
+            """);
+    }
+
+    [Fact]
+    public void ParamsMismatch_01()
+    {
+        // Test when interceptable method has 'params' parameter.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod(params int[] value) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod(1, 2, 3);
+                    C.InterceptableMethod(4, 5, 6);
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)]
+                public static void Interceptor1(int[] value)
+                {
+                    foreach (var i in value)
+                        Console.Write(i);
+                }
+
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor2(params int[] value)
+                {
+                    foreach (var i in value)
+                        Console.Write(i);
+                }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "123456");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void ParamsMismatch_02()
+    {
+        // Test when interceptable method lacks 'params' parameter, and interceptor has one, and method is called as if it has one.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod(int[] value) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod(1, 2, 3 ); // 1
+                    C.InterceptableMethod(4, 5, 6); // 2
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)]
+                public static void Interceptor1(int[] value)
+                {
+                    foreach (var i in value)
+                        Console.Write(i);
+                }
+
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor2(params int[] value)
+                {
+                    foreach (var i in value)
+                        Console.Write(i);
+                }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+                // Program.cs(14,11): error CS1501: No overload for method 'InterceptableMethod' takes 3 arguments
+                //         C.InterceptableMethod(1, 2, 3 ); // 1
+                Diagnostic(ErrorCode.ERR_BadArgCount, "InterceptableMethod").WithArguments("InterceptableMethod", "3").WithLocation(14, 11),
+                // Program.cs(15,11): error CS1501: No overload for method 'InterceptableMethod' takes 3 arguments
+                //         C.InterceptableMethod(4, 5, 6); // 2
+                Diagnostic(ErrorCode.ERR_BadArgCount, "InterceptableMethod").WithArguments("InterceptableMethod", "3").WithLocation(15, 11));
+    }
+
+    [Fact]
+    public void ParamsMismatch_03()
+    {
+        // Test when interceptable method lacks 'params' parameter, and interceptor has one, and method is called in normal form.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod(int[] value) => throw null!;
+            }
+
+            static class Program
+            {
+                public static void Main()
+                {
+                    C.InterceptableMethod(new[] { 1, 2, 3 });
+                    C.InterceptableMethod(new[] { 4, 5, 6 });
+                }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 14, 11)]
+                public static void Interceptor1(int[] value)
+                {
+                    foreach (var i in value)
+                        Console.Write(i);
+                }
+
+                [InterceptsLocation("Program.cs", 15, 11)]
+                public static void Interceptor2(params int[] value)
+                {
+                    foreach (var i in value)
+                        Console.Write(i);
+                }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "123456");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterpolatedStringHandler_01()
+    {
+        // Verify that interpolated string-related attributes on an intercepted call use the attributes from the interceptable method.
+        var code = """
+using System;
+using System.Runtime.CompilerServices;
+
+var s = new S1();
+s.M($"");
+
+public struct S1
+{
+    public S1() { }
+    public int Field = 1;
+
+
+    public void M([InterpolatedStringHandlerArgument("")] CustomHandler c)
+    {
+        Console.Write(0);
+    }
+}
+
+public static class S1Ext
+{
+    [InterceptsLocation("Program.cs", 5, 3)]
+    public static void M1(ref this S1 s1, CustomHandler c)
+    {
+        Console.Write(2);
+    }
+}
+
+partial struct CustomHandler
+{
+    public CustomHandler(int literalLength, int formattedCount, S1 s)
+    {
+        Console.Write(1);
+    }
+}
+""";
+        var verifier = CompileAndVerify(
+            new[]
+            {
+                (code, "Program.cs"),
+                (InterpolatedStringHandlerArgumentAttribute, "a.cs"),
+                (GetInterpolatedStringCustomHandlerType("CustomHandler", "partial struct", useBoolReturns: false), "b.cs"),
+                s_attributesSource
+            },
+            parseOptions: RegularWithInterceptors,
+            expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterpolatedStringHandler_02()
+    {
+        // Verify that interpolated string-related attributes are ignored on an interceptor in an intercepted call.
+        var code = """
+using System;
+using System.Runtime.CompilerServices;
+
+var s = new S1();
+s.M($"");
+
+public struct S1
+{
+    public S1() { }
+    public int Field = 1;
+
+
+    public void M(CustomHandler c)
+    {
+        Console.Write(0);
+    }
+}
+
+public static class S1Ext
+{
+    [InterceptsLocation("Program.cs", 5, 3)]
+    public static void M1(ref this S1 s1, [InterpolatedStringHandlerArgument("s1")] CustomHandler c)
+    {
+        Console.Write(1);
+    }
+}
+
+partial struct CustomHandler
+{
+    public CustomHandler(int literalLength, int formattedCount, S1 s)
+    {
+        throw null!; // we don't expect this to be called
+    }
+}
+""";
+        var verifier = CompileAndVerify(
+            new[]
+            {
+                (code, "Program.cs"),
+                (InterpolatedStringHandlerArgumentAttribute, "a.cs"),
+                (GetInterpolatedStringCustomHandlerType("CustomHandler", "partial struct", useBoolReturns: false), "b.cs"),
+                s_attributesSource
+            },
+            parseOptions: RegularWithInterceptors,
+            expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterpolatedStringHandler_03()
+    {
+        // Verify that interpolated string attributes on an interceptor don't cause us to somehow pick a different argument.
+        var code = """
+using System;
+using System.Runtime.CompilerServices;
+
+var s1 = new S1(1);
+var s2 = new S1(2);
+S1.M(s1, s2, $"");
+
+public struct S1
+{
+    public S1(int field) => Field = field;
+    public int Field = 1;
+
+
+    public static void M(S1 s1, S1 s2, [InterpolatedStringHandlerArgument("s1")] CustomHandler c)
+    {
+        Console.Write(0);
+    }
+}
+
+public static class S1Ext
+{
+    [InterceptsLocation("Program.cs", 6, 4)]
+    public static void M1(S1 s2, S1 s3, [InterpolatedStringHandlerArgument("s2")] CustomHandler c)
+    {
+        Console.Write(2);
+    }
+}
+
+partial struct CustomHandler
+{
+    public CustomHandler(int literalLength, int formattedCount, S1 s)
+    {
+        Console.Write(s.Field);
+    }
+}
+""";
+        var verifier = CompileAndVerify(
+            new[]
+            {
+                (code, "Program.cs"),
+                (InterpolatedStringHandlerArgumentAttribute, "a.cs"),
+                (GetInterpolatedStringCustomHandlerType("CustomHandler", "partial struct", useBoolReturns: false), "b.cs"),
+                s_attributesSource
+            },
+            parseOptions: RegularWithInterceptors,
+            expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void LineDirective_01()
+    {
+        // Verify that line directives are not considered when deciding if a particular call is being intercepted.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod() { Console.Write("interceptable"); }
+
+                public static void Main()
+                {
+                    #line 42 "OtherFile.cs"
+                    InterceptableMethod();
+                }
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 12, 9)]
+                public static void Interceptor1() { Console.Write("interceptor 1"); }
+            }
+            """;
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "interceptor 1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void LineDirective_02()
+    {
+        // Verify that line directives are not considered when deciding if a particular call is being intercepted.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+
+                public static void InterceptableMethod() { Console.Write("interceptable"); }
+
+                public static void Main()
+                {
+                    #line 42 "OtherFile.cs"
+                    InterceptableMethod();
+                }
+            }
+
+            class D
+            {
+                [InterceptsLocation("OtherFile.cs", 42, 9)]
+                public static void Interceptor1() { Console.Write("interceptor 1"); }
+            }
+            """;
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // OtherFile.cs(48,25): error CS9139: Cannot intercept: compilation does not contain a file with path 'OtherFile.cs'.
+            //     [InterceptsLocation("OtherFile.cs", 42, 9)]
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilation, @"""OtherFile.cs""").WithArguments("OtherFile.cs").WithLocation(48, 25));
+    }
+
+    [Fact]
+    public void ObsoleteInterceptor()
+    {
+        // Expect no Obsolete diagnostics to be reported
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M() => throw null!;
+            }
+
+            class D
+            {
+                [Obsolete]
+                [InterceptsLocation("Program.cs", 4, 3)]
+                public static void M1() => Console.Write(1);
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void CallerInfo()
+    {
+        // CallerLineNumber, etc. on the interceptor doesn't affect the default arguments passed to an intercepted call.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M(int lineNumber = 1) => throw null!;
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 4, 3)]
+                public static void M1([CallerLineNumber] int lineNumber = 0) => Console.Write(lineNumber);
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void DefaultArguments_01()
+    {
+        // Default parameter values on the interceptor doesn't affect the default arguments passed to an intercepted call.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M(int lineNumber = 1) => throw null!;
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 4, 3)]
+                public static void M1(int lineNumber = 0) => Console.Write(lineNumber);
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void DefaultArguments_02()
+    {
+        // Interceptor cannot add a default argument when original method lacks it.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C.M(); // 1
+
+            class C
+            {
+                public static void M(int lineNumber) => throw null!;
+            }
+
+            class D
+            {
+                [InterceptsLocation("Program.cs", 4, 3)]
+                public static void M1(int lineNumber = 0) => Console.Write(lineNumber);
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(4,3): error CS7036: There is no argument given that corresponds to the required parameter 'lineNumber' of 'C.M(int)'
+            // C.M(); // 1
+            Diagnostic(ErrorCode.ERR_NoCorrespondingArgument, "M").WithArguments("lineNumber", "C.M(int)").WithLocation(4, 3));
+    }
+
+    [Fact]
+    public void InterceptorExtern()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+
+            C.M();
+
+            class C
+            {
+
+                public static void M() => throw null!;
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 3, 3)]
+                public static extern void Interceptor();
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, verify: Verification.Skipped);
+        verifier.VerifyDiagnostics();
+
+        verifier.VerifyIL("<top-level-statements-entry-point>", """
+            {
+              // Code size        6 (0x6)
+              .maxstack  0
+              IL_0000:  call       "void D.Interceptor()"
+              IL_0005:  ret
+            }
+            """);
+    }
+
+    [Fact]
+    public void InterceptorAbstract()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            var d = new D();
+            d.M();
+
+            abstract class C
+            {
+
+                public void M() => throw null!;
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                public abstract void Interceptor();
+            }
+
+            class D : C
+            {
+                public override void Interceptor() => Console.Write(1);
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptorInterface()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            I i = new C();
+            i.M();
+
+            interface I
+            {
+
+                public void M();
+
+                [InterceptsLocation("Program.cs", 5, 3)]
+                void Interceptor();
+            }
+
+            class C : I
+            {
+                public void M() => throw null!;
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors, expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void InterceptGetEnumerator()
+    {
+        var source = """
+            using System.Collections;
+            using System.Runtime.CompilerServices;
+
+            var myEnumerable = new MyEnumerable();
+            foreach (var item in myEnumerable)
+            {
+            }
+
+            class MyEnumerable : IEnumerable
+            {
+                public IEnumerator GetEnumerator() => throw null!;
+            }
+
+            static class MyEnumerableExt
+            {
+                [InterceptsLocation("Program.cs", 5, 22)] // 1
+                public static IEnumerator GetEnumerator1(this MyEnumerable en) => throw null!;
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(16,6): error CS9151: Possible method name 'myEnumerable' cannot be intercepted because it is not being invoked.
+            //     [InterceptsLocation("Program.cs", 5, 22)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorNameNotInvoked, @"InterceptsLocation(""Program.cs"", 5, 22)").WithArguments("myEnumerable").WithLocation(16, 6));
+    }
+
+    [Fact]
+    public void InterceptDispose()
+    {
+        var source = """
+            using System;
+            using System.Runtime.CompilerServices;
+
+            var myDisposable = new MyDisposable();
+            using (myDisposable)
+            {
+            }
+
+            class MyDisposable : IDisposable
+            {
+                public void Dispose() => throw null!;
+            }
+
+            static class MyDisposeExt
+            {
+                [InterceptsLocation("Program.cs", 5, 8)] // 1
+                public static void Dispose1(this MyDisposable md) => throw null!;
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(16,6): error CS9151: Possible method name 'myDisposable' cannot be intercepted because it is not being invoked.
+            //     [InterceptsLocation("Program.cs", 5, 8)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorNameNotInvoked, @"InterceptsLocation(""Program.cs"", 5, 8)").WithArguments("myDisposable").WithLocation(16, 6)
+            );
+    }
+
+    [Fact]
+    public void InterceptDeconstruct()
+    {
+        var source = """
+            using System;
+            using System.Runtime.CompilerServices;
+
+            var myDeconstructable = new MyDeconstructable();
+            var (x, y) = myDeconstructable;
+
+            class MyDeconstructable
+            {
+                public void Deconstruct(out int x, out int y) => throw null!;
+            }
+
+            static class MyDeconstructableExt
+            {
+                [InterceptsLocation("Program.cs", 5, 14)] // 1
+                public static void Deconstruct1(this MyDeconstructable md, out int x, out int y) => throw null!;
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(14,6): error CS9151: Possible method name 'myDeconstructable' cannot be intercepted because it is not being invoked.
+            //     [InterceptsLocation("Program.cs", 5, 14)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorNameNotInvoked, @"InterceptsLocation(""Program.cs"", 5, 14)").WithArguments("myDeconstructable").WithLocation(14, 6)
+            );
+    }
+
+    [Fact]
+    public void PathMapping_01()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C c = new C();
+            c.M();
+
+            class C
+            {
+                public void M() => throw null!;
+
+                [InterceptsLocation("/_/Program.cs", 5, 3)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+        var pathPrefix = PlatformInformation.IsWindows ? """C:\My\Machine\Specific\Path\""" : "/My/Machine/Specific/Path/";
+        var path = pathPrefix + "Program.cs";
+        var pathMap = ImmutableArray.Create(new KeyValuePair<string, string>(pathPrefix, "/_/"));
+
+        var verifier = CompileAndVerify(
+            new[] { (source, path), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            options: TestOptions.DebugExe.WithSourceReferenceResolver(
+                new SourceFileResolver(ImmutableArray<string>.Empty, null, pathMap)),
+            expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void PathMapping_02()
+    {
+        // Attribute uses a physical path, but we expected a mapped path.
+        // Diagnostic can suggest using the mapped path instead.
+        var pathPrefix = PlatformInformation.IsWindows ? @"C:\My\Machine\Specific\Path\" : "/My/Machine/Specific/Path/";
+        var path = pathPrefix + "Program.cs";
+        var source = $$"""
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C c = new C();
+            c.M();
+
+            class C
+            {
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"{{path}}", 5, 3)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+        var pathMap = ImmutableArray.Create(new KeyValuePair<string, string>(pathPrefix, "/_/"));
+
+        var comp = CreateCompilation(
+            new[] { (source, path), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            options: TestOptions.DebugExe.WithSourceReferenceResolver(
+                new SourceFileResolver(ImmutableArray<string>.Empty, null, pathMap)));
+        comp.VerifyEmitDiagnostics(
+                // C:\My\Machine\Specific\Path\Program.cs(11,25): error CS9145: Cannot intercept: Path 'C:\My\Machine\Specific\Path\Program.cs' is unmapped. Expected mapped path '/_/Program.cs'.
+                //     [InterceptsLocation(@"C:\My\Machine\Specific\Path\Program.cs", 5, 3)]
+                Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilationWithUnmappedCandidate, $@"@""{path}""").WithArguments(path, "/_/Program.cs").WithLocation(11, 25)
+            );
+    }
+
+    [Fact]
+    public void PathMapping_03()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C c = new C();
+            c.M();
+
+            class C
+            {
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"\_\Program.cs", 5, 3)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+        var pathPrefix = PlatformInformation.IsWindows ? """C:\My\Machine\Specific\Path\""" : "/My/Machine/Specific/Path/";
+        var path = pathPrefix + "Program.cs";
+        var pathMap = ImmutableArray.Create(new KeyValuePair<string, string>(pathPrefix, "/_/"));
+
+        var comp = CreateCompilation(
+            new[] { (source, path), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            options: TestOptions.DebugExe.WithSourceReferenceResolver(
+                new SourceFileResolver(ImmutableArray<string>.Empty, null, pathMap)));
+        comp.VerifyEmitDiagnostics(
+            // C:\My\Machine\Specific\Path\Program.cs(11,25): error CS9140: Cannot intercept: compilation does not contain a file with path '\_\Program.cs'. Did you mean to use path '/_/Program.cs'?
+            //     [InterceptsLocation(@"\_\Program.cs", 5, 3)]
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilationWithCandidate, @"@""\_\Program.cs""").WithArguments(@"\_\Program.cs", "/_/Program.cs").WithLocation(11, 25));
+    }
+
+    [Fact]
+    public void PathMapping_04()
+    {
+        // Test when unmapped file paths are distinct, but mapped paths are equal.
+        var source1 = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            namespace NS1;
+
+            class C
+            {
+                public static void M0()
+                {
+                    C c = new C();
+                    c.M();
+                }
+
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"/_/Program.cs", 11, 9)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+
+        var source2 = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            namespace NS2;
+
+            class C
+            {
+                public static void M0()
+                {
+                    C c = new C();
+                    c.M();
+                }
+
+                public void M() => throw null!;
+            }
+            """;
+
+        var pathPrefix1 = PlatformInformation.IsWindows ? """C:\My\Machine\Specific\Path1\""" : "/My/Machine/Specific/Path1/";
+        var pathPrefix2 = PlatformInformation.IsWindows ? """C:\My\Machine\Specific\Path2\""" : "/My/Machine/Specific/Path2/";
+        var path1 = pathPrefix1 + "Program.cs";
+        var path2 = pathPrefix2 + "Program.cs";
+        var pathMap = ImmutableArray.Create(
+            new KeyValuePair<string, string>(pathPrefix1, "/_/"),
+            new KeyValuePair<string, string>(pathPrefix2, "/_/")
+            );
+
+        var comp = CreateCompilation(
+            new[] { (source1, path1), (source2, path2), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            options: TestOptions.DebugDll.WithSourceReferenceResolver(
+                new SourceFileResolver(ImmutableArray<string>.Empty, null, pathMap)));
+        comp.VerifyEmitDiagnostics(
+            // C:\My\Machine\Specific\Path1\Program.cs(16,25): error CS9152: Cannot intercept a call in file with path '/_/Program.cs' because multiple files in the compilation have this path.
+            //     [InterceptsLocation(@"/_/Program.cs", 11, 9)]
+            Diagnostic(ErrorCode.ERR_InterceptorNonUniquePath, @"@""/_/Program.cs""").WithArguments("/_/Program.cs").WithLocation(16, 25));
+    }
+
+    [Fact]
+    public void PathMapping_05()
+    {
+        // Pathmap replacement contains backslashes, and attribute path contains backslashes.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C c = new C();
+            c.M();
+
+            class C
+            {
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"\_\Program.cs", 5, 3)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+        var pathPrefix = PlatformInformation.IsWindows ? """C:\My\Machine\Specific\Path\""" : "/My/Machine/Specific/Path/";
+        var path = pathPrefix + "Program.cs";
+        var pathMap = ImmutableArray.Create(new KeyValuePair<string, string>(pathPrefix, @"\_\"));
+
+        var verifier = CompileAndVerify(
+            new[] { (source, path), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            options: TestOptions.DebugExe.WithSourceReferenceResolver(
+                new SourceFileResolver(ImmutableArray<string>.Empty, null, pathMap)),
+            expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void PathMapping_06()
+    {
+        // Pathmap mixes slashes and backslashes, attribute path is normalized to slashes
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C c = new C();
+            c.M();
+
+            class C
+            {
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"/_/Program.cs", 5, 3)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+        var pathPrefix = PlatformInformation.IsWindows ? """C:\My\Machine\Specific\Path\""" : "/My/Machine/Specific/Path/";
+        var path = pathPrefix + "Program.cs";
+        var pathMap = ImmutableArray.Create(new KeyValuePair<string, string>(pathPrefix, @"\_/"));
+
+        var comp = CreateCompilation(
+            new[] { (source, path), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            options: TestOptions.DebugExe.WithSourceReferenceResolver(
+                new SourceFileResolver(ImmutableArray<string>.Empty, null, pathMap)));
+        comp.VerifyEmitDiagnostics(
+            // C:\My\Machine\Specific\Path\Program.cs(11,25): error CS9140: Cannot intercept: compilation does not contain a file with path '/_/Program.cs'. Did you mean to use path '\_/Program.cs'?
+            //     [InterceptsLocation(@"/_/Program.cs", 5, 3)]
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilationWithCandidate, @"@""/_/Program.cs""").WithArguments("/_/Program.cs", @"\_/Program.cs").WithLocation(11, 25));
+    }
+
+    [Fact]
+    public void PathMapping_07()
+    {
+        // Pathmap replacement mixes slashes and backslashes, attribute path matches it
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            C c = new C();
+            c.M();
+
+            class C
+            {
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"\_/Program.cs", 5, 3)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+        var pathPrefix = PlatformInformation.IsWindows ? """C:\My\Machine\Specific\Path\""" : "/My/Machine/Specific/Path/";
+        var path = pathPrefix + "Program.cs";
+        var pathMap = ImmutableArray.Create(new KeyValuePair<string, string>(pathPrefix, @"\_/"));
+
+        var verifier = CompileAndVerify(
+            new[] { (source, path), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            options: TestOptions.DebugExe.WithSourceReferenceResolver(
+                new SourceFileResolver(ImmutableArray<string>.Empty, null, pathMap)),
+            expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void PathNormalization_01()
+    {
+        // No pathmap is present and slashes in the attribute match the FilePath on the syntax tree.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+                public static void Main()
+                {
+                    C c = new C();
+                    c.M();
+                }
+
+                public void M() => throw null!;
+
+                [InterceptsLocation("src/Program.cs", 9, 11)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+
+        var verifier = CompileAndVerify(
+            new[] { (source, "src/Program.cs"), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void PathNormalization_02()
+    {
+        // No pathmap is present and backslashes in the attribute match the FilePath on the syntax tree.
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+                public static void Main()
+                {
+                    C c = new C();
+                    c.M();
+                }
+
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"src\Program.cs", 9, 11)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+
+        var verifier = CompileAndVerify(
+            new[] { (source, @"src\Program.cs"), s_attributesSource },
+            parseOptions: RegularWithInterceptors,
+            expectedOutput: "1");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact]
+    public void PathNormalization_03()
+    {
+        // Relative paths do not have slashes normalized when pathmap is not present
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+                public static void Main()
+                {
+                    C c = new C();
+                    c.M();
+                }
+
+                public void M() => throw null!;
+
+                [InterceptsLocation(@"src/Program.cs", 9, 11)]
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, @"src\Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // src\Program.cs(14,25): error CS9140: Cannot intercept: compilation does not contain a file with path 'src/Program.cs'. Did you mean to use path 'src\Program.cs'?
+            //     [InterceptsLocation(@"src/Program.cs", 9, 11)]
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilationWithCandidate, @"@""src/Program.cs""").WithArguments("src/Program.cs", @"src\Program.cs").WithLocation(14, 25));
+    }
+
+    [Fact]
+    public void PathNormalization_04()
+    {
+        // Absolute paths do not have slashes normalized when no pathmap is present
+        // Note that any such normalization step would be specific to Windows
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System;
+
+            class C
+            {
+                public static void Main()
+                {
+                    C c = new C();
+                    c.M();
+                }
+
+                public void M() => throw null!;
+
+                [InterceptsLocation("C:/src/Program.cs", 9, 11)] // 1
+                public void Interceptor() => Console.Write(1);
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, @"C:\src\Program.cs"), s_attributesSource }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // C:\src\Program.cs(14,25): error CS9140: Cannot intercept: compilation does not contain a file with path 'C:/src/Program.cs'. Did you mean to use path 'C:\src\Program.cs'?
+            //     [InterceptsLocation("C:/src/Program.cs", 9, 11)] // 1
+            Diagnostic(ErrorCode.ERR_InterceptorPathNotInCompilationWithCandidate, @"""C:/src/Program.cs""").WithArguments("C:/src/Program.cs", @"C:\src\Program.cs").WithLocation(14, 25));
+    }
+
+    [Fact]
+    public void InterceptorUnmanagedCallersOnly()
+    {
+        var source = """
+            using System.Runtime.CompilerServices;
+            using System.Runtime.InteropServices;
+            using System;
+
+            C.Interceptable();
+
+            class C
+            {
+                public static void Interceptable() { }
+            }
+
+            static class D
+            {
+                [InterceptsLocation("Program.cs", 5, 3)]
+                [UnmanagedCallersOnly]
+                public static void Interceptor() { }
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source, "Program.cs"), s_attributesSource, (UnmanagedCallersOnlyAttributeDefinition, "UnmanagedCallersOnlyAttribute.cs") }, parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+                // Program.cs(14,6): error CS9161: An interceptor cannot be marked with 'UnmanagedCallersOnlyAttribute'.
+                //     [InterceptsLocation("Program.cs", 5, 3)]
+                Diagnostic(ErrorCode.ERR_InterceptorCannotUseUnmanagedCallersOnly, @"InterceptsLocation(""Program.cs"", 5, 3)").WithLocation(14, 6));
+    }
+}
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs
index c7678cad8de0f..70bc2c9fec4f8 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs
@@ -15782,6 +15782,130 @@ .locals init (string V_0, //s
     );
         }
 
+        [Fact, WorkItem("https://github.com/dotnet/runtime/issues/78991")]
+        public void InterpolatedStringsAddedUnderObjectAddition_AdditionsWithMoreParts_01()
+        {
+            var code = """
+                using System;
+                _ = $"1{Environment.NewLine}" +
+                    $"2{Environment.NewLine}";
+                """;
+
+            var comp = CreateCompilation(new[] { code, GetInterpolatedStringHandlerDefinition(includeSpanOverloads: false, useDefaultParameters: false, useBoolReturns: false) });
+            CompileAndVerify(comp).VerifyIL("<top-level-statements-entry-point>",
+                """
+                {
+                  // Code size       27 (0x1b)
+                  .maxstack  4
+                  IL_0000:  ldstr      "1"
+                  IL_0005:  call       "string System.Environment.NewLine.get"
+                  IL_000a:  ldstr      "2"
+                  IL_000f:  call       "string System.Environment.NewLine.get"
+                  IL_0014:  call       "string string.Concat(string, string, string, string)"
+                  IL_0019:  pop
+                  IL_001a:  ret
+                }
+                """);
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/runtime/issues/78991")]
+        public void InterpolatedStringsAddedUnderObjectAddition_AdditionsWithMoreParts_02()
+        {
+            var code = """
+                using System;
+                _ = $"1{Environment.NewLine}" +
+                    $"2{Environment.NewLine}" +
+                    $"3";
+                """;
+
+            var comp = CreateCompilation(new[] { code, GetInterpolatedStringHandlerDefinition(includeSpanOverloads: false, useDefaultParameters: false, useBoolReturns: false) });
+            CompileAndVerify(comp).VerifyIL("<top-level-statements-entry-point>",
+                """
+                {
+                  // Code size       78 (0x4e)
+                  .maxstack  3
+                  .locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V_0)
+                  IL_0000:  ldloca.s   V_0
+                  IL_0002:  ldc.i4.3
+                  IL_0003:  ldc.i4.2
+                  IL_0004:  call       "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int, int)"
+                  IL_0009:  ldloca.s   V_0
+                  IL_000b:  ldstr      "1"
+                  IL_0010:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
+                  IL_0015:  ldloca.s   V_0
+                  IL_0017:  call       "string System.Environment.NewLine.get"
+                  IL_001c:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted(string)"
+                  IL_0021:  ldloca.s   V_0
+                  IL_0023:  ldstr      "2"
+                  IL_0028:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
+                  IL_002d:  ldloca.s   V_0
+                  IL_002f:  call       "string System.Environment.NewLine.get"
+                  IL_0034:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted(string)"
+                  IL_0039:  ldloca.s   V_0
+                  IL_003b:  ldstr      "3"
+                  IL_0040:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
+                  IL_0045:  ldloca.s   V_0
+                  IL_0047:  call       "string System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.ToStringAndClear()"
+                  IL_004c:  pop
+                  IL_004d:  ret
+                }
+                """);
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/runtime/issues/78991")]
+        public void InterpolatedStringsAddedUnderObjectAddition_AdditionsWithMoreParts_03()
+        {
+            var code = """
+                using System;
+                _ = $"1{Environment.NewLine}" +
+                    $"2{Environment.NewLine}" +
+                    $"3{Environment.NewLine}" +
+                    $"4{Environment.NewLine}";
+                """;
+
+            var comp = CreateCompilation(new[] { code, GetInterpolatedStringHandlerDefinition(includeSpanOverloads: false, useDefaultParameters: false, useBoolReturns: false) });
+            CompileAndVerify(comp).VerifyIL("<top-level-statements-entry-point>",
+                """
+                {
+                  // Code size      114 (0x72)
+                  .maxstack  3
+                  .locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V_0)
+                  IL_0000:  ldloca.s   V_0
+                  IL_0002:  ldc.i4.4
+                  IL_0003:  ldc.i4.4
+                  IL_0004:  call       "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int, int)"
+                  IL_0009:  ldloca.s   V_0
+                  IL_000b:  ldstr      "1"
+                  IL_0010:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
+                  IL_0015:  ldloca.s   V_0
+                  IL_0017:  call       "string System.Environment.NewLine.get"
+                  IL_001c:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted(string)"
+                  IL_0021:  ldloca.s   V_0
+                  IL_0023:  ldstr      "2"
+                  IL_0028:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
+                  IL_002d:  ldloca.s   V_0
+                  IL_002f:  call       "string System.Environment.NewLine.get"
+                  IL_0034:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted(string)"
+                  IL_0039:  ldloca.s   V_0
+                  IL_003b:  ldstr      "3"
+                  IL_0040:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
+                  IL_0045:  ldloca.s   V_0
+                  IL_0047:  call       "string System.Environment.NewLine.get"
+                  IL_004c:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted(string)"
+                  IL_0051:  ldloca.s   V_0
+                  IL_0053:  ldstr      "4"
+                  IL_0058:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
+                  IL_005d:  ldloca.s   V_0
+                  IL_005f:  call       "string System.Environment.NewLine.get"
+                  IL_0064:  call       "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted(string)"
+                  IL_0069:  ldloca.s   V_0
+                  IL_006b:  call       "string System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.ToStringAndClear()"
+                  IL_0070:  pop
+                  IL_0071:  ret
+                }
+                """);
+        }
+
         [Fact]
         public void InterpolatedStringsAddedUnderObjectAddition_DefiniteAssignment()
         {
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/ObjectAndCollectionInitializerTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/ObjectAndCollectionInitializerTests.cs
index 764b90baddebe..02dbd2001b96d 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/ObjectAndCollectionInitializerTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/ObjectAndCollectionInitializerTests.cs
@@ -3780,6 +3780,77 @@ static void Main()
             }
         }
 
+        [Fact]
+        public void GetComplexCollectionInitializerConversionInfo_NoConversion()
+        {
+            var source = """
+                using System.Collections.Generic;
+                _ = new Dictionary<string, string> { { "a", "b" } };
+                """;
+
+            var comp = CreateCompilation(source);
+            comp.VerifyDiagnostics();
+            var syntax = comp.SyntaxTrees[0];
+            var model = comp.GetSemanticModel(syntax);
+            var literals = syntax.GetRoot().DescendantNodes().OfType<LiteralExpressionSyntax>().ToArray();
+            Assert.Equal(2, literals.Length);
+            foreach (var literal in literals)
+            {
+                var conversion = model.GetConversion(literal);
+                Assert.Equal(ConversionKind.Identity, conversion.Kind);
+                var typeInfo = model.GetTypeInfo(literal);
+                Assert.Same(typeInfo.Type, typeInfo.ConvertedType);
+            }
+        }
+
+        [Fact]
+        public void GetComplexCollectionInitializerConversionInfo_ImplicitReferenceConversion()
+        {
+            var source = """
+                using System.Collections.Generic;
+                _ = new Dictionary<object, object> { { "a", "b" } };
+                """;
+
+            var comp = CreateCompilation(source);
+            comp.VerifyDiagnostics();
+            var syntax = comp.SyntaxTrees[0];
+            var model = comp.GetSemanticModel(syntax);
+            var literals = syntax.GetRoot().DescendantNodes().OfType<LiteralExpressionSyntax>().ToArray();
+            Assert.Equal(2, literals.Length);
+            foreach (var literal in literals)
+            {
+                var conversion = model.GetConversion(literal);
+                Assert.Equal(ConversionKind.ImplicitReference, conversion.Kind);
+                var typeInfo = model.GetTypeInfo(literal);
+                Assert.Equal(SpecialType.System_String, typeInfo.Type.SpecialType);
+                Assert.Equal(SpecialType.System_Object, typeInfo.ConvertedType.SpecialType);
+            }
+        }
+
+        [Fact]
+        public void GetComplexCollectionInitializerConversionInfo_ImplicitBoxingConversion()
+        {
+            var source = """
+                using System.Collections.Generic;
+                _ = new Dictionary<object, object> { { 1, 2 } };
+                """;
+
+            var comp = CreateCompilation(source);
+            comp.VerifyDiagnostics();
+            var syntax = comp.SyntaxTrees[0];
+            var model = comp.GetSemanticModel(syntax);
+            var literals = syntax.GetRoot().DescendantNodes().OfType<LiteralExpressionSyntax>().ToArray();
+            Assert.Equal(2, literals.Length);
+            foreach (var literal in literals)
+            {
+                var conversion = model.GetConversion(literal);
+                Assert.Equal(ConversionKind.Boxing, conversion.Kind);
+                var typeInfo = model.GetTypeInfo(literal);
+                Assert.Equal(SpecialType.System_Int32, typeInfo.Type.SpecialType);
+                Assert.Equal(SpecialType.System_Object, typeInfo.ConvertedType.SpecialType);
+            }
+        }
+
         [Fact, WorkItem(1073330, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/1073330")]
         public void NestedIndexerInitializerArray()
         {
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/OverloadResolutionPerfTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/OverloadResolutionPerfTests.cs
index 4ee3a6c1809c4..b70642d750407 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/OverloadResolutionPerfTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/OverloadResolutionPerfTests.cs
@@ -4,9 +4,10 @@
 
 #nullable disable
 
-using Microsoft.CodeAnalysis.CSharp.Symbols;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Roslyn.Test.Utilities;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Text;
 using Xunit;
@@ -780,5 +781,211 @@ public void DefiniteAssignment_ManySwitchCasesAndLabels()
                 //         int tmp2; // unused
                 Diagnostic(ErrorCode.WRN_UnreferencedVar, "tmp2").WithArguments("tmp2").WithLocation(9, 13));
         }
+
+        [ConditionalFact(typeof(IsRelease))]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/67926")]
+        public void ExtensionOverloadsDistinctClasses_01()
+        {
+            const int n = 1000;
+
+            var builder = new StringBuilder();
+            builder.AppendLine(
+                $$"""
+                class Program
+                {
+                    static void Main()
+                    {
+                        var o = new object();
+                        var c = new C1();
+                        o.F(c, c => o.F(c, null));
+                    }
+                }
+                """);
+
+            for (int i = 0; i < n; i++)
+            {
+                builder.AppendLine(
+                    $$"""
+                    class C{{i}} { }
+                    static class E{{i}}
+                    {
+                        public static void F(this object o, C{{i}} c, System.Action<C{{i}}> a) { }
+                    }
+                    """);
+            }
+
+            string source = builder.ToString();
+            var comp = CreateCompilation(source);
+            comp.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsRelease))]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/67926")]
+        public void ExtensionOverloadsDistinctClasses_02()
+        {
+            const int n = 1000;
+
+            var builder = new StringBuilder();
+            builder.AppendLine(
+                $$"""
+                class Program
+                {
+                    static void Main()
+                    {
+                        var o = new object();
+                        o.F(null, c => o.F(c, null));
+                    }
+                }
+                """);
+
+            for (int i = 0; i < n; i++)
+            {
+                builder.AppendLine(
+                    $$"""
+                    class C{{i}} { }
+                    static class E{{i}}
+                    {
+                        public static void F(this object o, C{{i}} c, System.Action<C{{i}}> a) { }
+                    }
+                    """);
+            }
+
+            string source = builder.ToString();
+            var comp = CreateCompilation(source);
+            comp.VerifyDiagnostics(
+                // (6,11): error CS0121: The call is ambiguous between the following methods or properties: 'E0.F(object, C0, Action<C0>)' and 'E1.F(object, C1, Action<C1>)'
+                //         o.F(null, c => o.F(c, null));
+                Diagnostic(ErrorCode.ERR_AmbigCall, "F").WithArguments("E0.F(object, C0, System.Action<C0>)", "E1.F(object, C1, System.Action<C1>)").WithLocation(6, 11));
+        }
+
+        [ConditionalFact(typeof(IsRelease))]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/67926")]
+        public void ExtensionOverloadsDistinctClasses_03()
+        {
+            const int n = 1000;
+
+            var builder = new StringBuilder();
+            builder.AppendLine(
+                $$"""
+                class Program
+                {
+                    static void Main()
+                    {
+                        var o = new object();
+                        var c = new C1();
+                        o.F(c, c => { o.F( });
+                    }
+                }
+                """);
+
+            for (int i = 0; i < n; i++)
+            {
+                builder.AppendLine(
+                    $$"""
+                    class C{{i}} { }
+                    static class E{{i}}
+                    {
+                        public static void F(this object o, C{{i}} c, System.Action<C{{i}}> a) { }
+                    }
+                    """);
+            }
+
+            string source = builder.ToString();
+            var comp = CreateCompilation(source);
+            comp.VerifyDiagnostics(
+                // (7,25): error CS1501: No overload for method 'F' takes 0 arguments
+                //         o.F(c, c => { o.F( });
+                Diagnostic(ErrorCode.ERR_BadArgCount, "F").WithArguments("F", "0").WithLocation(7, 25),
+                // (7,28): error CS1026: ) expected
+                //         o.F(c, c => { o.F( });
+                Diagnostic(ErrorCode.ERR_CloseParenExpected, "}").WithLocation(7, 28),
+                // (7,28): error CS1002: ; expected
+                //         o.F(c, c => { o.F( });
+                Diagnostic(ErrorCode.ERR_SemicolonExpected, "}").WithLocation(7, 28));
+
+            var tree = comp.SyntaxTrees.Single();
+            var model = comp.GetSemanticModel(tree);
+            var expr = tree.GetCompilationUnitRoot().DescendantNodes().OfType<Syntax.InvocationExpressionSyntax>().Last();
+            Assert.Equal("o.F( ", expr.ToString());
+            _ = model.GetTypeInfo(expr);
+        }
+
+        [Fact]
+        public void ExtensionOverloadsDistinctClasses_04()
+        {
+            // public abstract class A
+            // {
+            //     public static void F1(this object obj) { }
+            //     public static void F3(this object obj) { }
+            // }
+            // public abstract class B : A
+            // {
+            //     public static void F2(this object obj) { }
+            //     public static void F3(this object obj) { }
+            // }
+            string sourceA = """
+                .assembly extern mscorlib { .ver 4:0:0:0 .publickeytoken = (B7 7A 5C 56 19 34 E0 89) }
+                .assembly extern System.Core { }
+                .assembly '<<GeneratedFileName>>'
+                {
+                    .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 )
+                }
+                .class public abstract A
+                {
+                  .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 )
+                  .method public hidebysig specialname rtspecialname instance void .ctor() { ret }
+                  .method public static void F1(object o)
+                  {
+                    .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 )
+                    ret
+                  }
+                  .method public static void F3(object o)
+                  {
+                    .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 )
+                    ret
+                  }
+                }
+                .class public abstract B extends A
+                {
+                  .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 )
+                  .method public hidebysig specialname rtspecialname instance void .ctor() { ret }
+                  .method public static void F2(object o)
+                  {
+                    .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 )
+                    ret
+                  }
+                  .method public static void F3(object o)
+                  {
+                    .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 )
+                    ret
+                  }
+                }
+                """;
+            var refA = CompileIL(sourceA, prependDefaultHeader: false);
+
+            // The calls to B.F3(o) and o.F3() should bind to B.F3 and should not be
+            // considered ambiguous with A.F3 because B is derived from A.
+            string sourceB = """
+                class Program
+                {
+                    static void M(object o)
+                    {
+                        B.F1(o);
+                        B.F2(o);
+                        B.F3(o);
+                        o.F1();
+                        o.F2();
+                        o.F3();
+                    }
+                }
+                """;
+            var comp = CreateCompilation(sourceB, references: new[] { refA });
+            comp.VerifyDiagnostics();
+            var tree = comp.SyntaxTrees.Single();
+            var model = comp.GetSemanticModel(tree);
+            var exprs = tree.GetRoot().DescendantNodes().OfType<InvocationExpressionSyntax>().ToImmutableArray();
+            var containingTypes = exprs.SelectAsArray(e => model.GetSymbolInfo(e).Symbol.ContainingSymbol).ToTestDisplayStrings();
+            Assert.Equal(new[] { "A", "B", "B", "A", "B", "B" }, containingTypes);
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/PrimaryConstructorTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/PrimaryConstructorTests.cs
index f8bc08b9e7721..b937b0761e156 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/PrimaryConstructorTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/PrimaryConstructorTests.cs
@@ -11878,7 +11878,11 @@ static void Main()
 ";
             var comp = CreateCompilation(source, options: TestOptions.ReleaseExe);
 
-            var verifier = CompileAndVerify(comp, expectedOutput: @"123123124-1-2-3", verify: Verification.Passes).VerifyDiagnostics();
+            var verifier = CompileAndVerify(comp, expectedOutput: @"123123124-1-2-3", verify: Verification.Passes).VerifyDiagnostics(
+                // (4,21): warning CS9124: Parameter 'int p1' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.
+                //     public int F1 = p1;
+                Diagnostic(ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer, "p1").WithArguments("int p1").WithLocation(4, 21)
+                );
 
             verifier.VerifyIL("C1..ctor(int, int)",
 @"
@@ -15592,6 +15596,237 @@ class C(B b)
             comp.VerifyDiagnostics();
         }
 
+        [Fact]
+        public void ParameterCapturing_155_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(int p1)
+{
+    int F = p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+
+            var expected = new[] {
+                // (4,13): warning CS9124: Parameter 'int p1' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.
+                //     int F = p1;
+                Diagnostic(ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer, "p1").WithArguments("int p1").WithLocation(4, 13)
+                };
+
+            comp.VerifyDiagnostics(expected);
+            comp.VerifyEmitDiagnostics(expected);
+        }
+
+        [Fact]
+        public void ParameterCapturing_156_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(int p1)
+{
+    int F = (int)p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+
+            var expected = new[] {
+                // (4,18): warning CS9124: Parameter 'int p1' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.
+                //     int F = (int)p1;
+                Diagnostic(ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer, "p1").WithArguments("int p1").WithLocation(4, 18)
+                };
+
+            comp.VerifyDiagnostics(expected);
+            comp.VerifyEmitDiagnostics(expected);
+        }
+
+        [Fact]
+        public void ParameterCapturing_157_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(int p1)
+{
+    long F = p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void ParameterCapturing_158_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(int p1)
+{
+    long F = (long)p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+            comp.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        public void ParameterCapturing_159_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(int p1)
+{
+    static int F = p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+
+            var expected = new[] {
+                // (4,20): error CS9105: Cannot use primary constructor parameter 'int p1' in this context.
+                //     static int F = p1;
+                Diagnostic(ErrorCode.ERR_InvalidPrimaryConstructorParameterReference, "p1").WithArguments("int p1").WithLocation(4, 20)
+                };
+
+            comp.VerifyDiagnostics(expected);
+            comp.VerifyEmitDiagnostics(expected);
+        }
+
+        [Fact]
+        public void ParameterCapturing_160_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+ref struct C1([System.Diagnostics.CodeAnalysis.UnscopedRef] ref int p1)
+{
+    ref int F = ref p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll, targetFramework: TargetFramework.NetCoreApp);
+
+            var expected = new[] {
+                // (8,13): error CS9109: Cannot use ref, out, or in primary constructor parameter 'p1' inside an instance member
+                //         _ = p1; 
+                Diagnostic(ErrorCode.ERR_UnsupportedPrimaryConstructorParameterCapturingRef, "p1").WithArguments("p1").WithLocation(8, 13)
+                };
+
+            comp.VerifyDiagnostics(expected);
+            comp.VerifyEmitDiagnostics(expected);
+        }
+
+        [Fact]
+        public void ParameterCapturing_161_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+ref struct C1([System.Diagnostics.CodeAnalysis.UnscopedRef] ref int p1)
+{
+    ref readonly int F = ref p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll, targetFramework: TargetFramework.NetCoreApp);
+
+            var expected = new[] {
+                // (8,13): error CS9109: Cannot use ref, out, or in primary constructor parameter 'p1' inside an instance member
+                //         _ = p1; 
+                Diagnostic(ErrorCode.ERR_UnsupportedPrimaryConstructorParameterCapturingRef, "p1").WithArguments("p1").WithLocation(8, 13)
+                };
+
+            comp.VerifyDiagnostics(expected);
+            comp.VerifyEmitDiagnostics(expected);
+        }
+
+        [Fact]
+        public void ParameterCapturing_162_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(int p1)
+{
+    int F { get; } = p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+
+            var expected = new[] {
+                // (4,22): warning CS9124: Parameter 'int p1' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.
+                //     int F { get; } = p1;
+                Diagnostic(ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer, "p1").WithArguments("int p1").WithLocation(4, 22)
+                };
+
+            comp.VerifyDiagnostics(expected);
+            comp.VerifyEmitDiagnostics(expected);
+        }
+
+        [Fact]
+        public void ParameterCapturing_163_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(System.Action p1)
+{
+    event System.Action F = p1;
+
+    void M()
+    {
+        _ = p1; 
+    }
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+
+            var expected = new[] {
+                // (4,29): warning CS9124: Parameter 'Action p1' is captured into the state of the enclosing type and its value is also used to initialize a field, property, or event.
+                //     event System.Action F = p1;
+                Diagnostic(ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer, "p1").WithArguments("System.Action p1").WithLocation(4, 29)
+                };
+
+            comp.VerifyDiagnostics(expected);
+            comp.VerifyEmitDiagnostics(expected);
+        }
+
+        [Fact]
+        public void ParameterCapturing_164_WRN_CapturedPrimaryConstructorParameterInFieldInitializer()
+        {
+            var source = @"
+class C1(int p1)
+{
+    int F = p1;
+}
+";
+            var comp = CreateCompilation(source, options: TestOptions.ReleaseDll);
+            comp.VerifyEmitDiagnostics();
+        }
+
         [Fact]
         public void CycleDueToIndexerNameAttribute_01()
         {
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/RefLocalsAndReturnsTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/RefLocalsAndReturnsTests.cs
index 105cde5be1a1c..f9e638a969f61 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/RefLocalsAndReturnsTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/RefLocalsAndReturnsTests.cs
@@ -3156,7 +3156,7 @@ async Task TestMethod()
     }
 }";
             CreateCompilationWithMscorlib45(code).VerifyEmitDiagnostics(
-                // (26,19): error CS8178: 'await' cannot be used in an expression containing a call to 'TestClass.Save(int)' because it returns by reference
+                // (26,19): error CS8178: A reference returned by a call to 'TestClass.Save(int)' cannot be preserved across 'await' or 'yield' boundary.
                 //         Write(ref Save(await Task.FromResult(0)), await Task.FromResult(1));
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "Save(await Task.FromResult(0))").WithArguments("TestClass.Save(int)").WithLocation(26, 19)
             );
@@ -4049,10 +4049,10 @@ public async Task<int> Do(int i)
 ";
 
             CreateCompilationWithMscorlib45(text).VerifyEmitDiagnostics(
-                // (32,17): error CS8178: 'await' cannot be used in an expression containing a call to 'S.Instance.get' because it returns by reference
+                // (32,17): error CS8178: A reference returned by a call to 'S.Instance.get' cannot be preserved across 'await' or 'yield' boundary.
                 //         var a = S.Instance.Echo(await Do(i - 1));
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "S.Instance").WithArguments("S.Instance.get").WithLocation(32, 17),
-                // (33,28): error CS8178: 'await' cannot be used in an expression containing a call to 'C.Assign(ref int, int)' because it returns by reference
+                // (33,28): error CS8178: A reference returned by a call to 'C.Assign(ref int, int)' cannot be preserved across 'await' or 'yield' boundary.
                 //         var b = Assign(ref Assign(ref temp, 0), await Do(i - 1));
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "Assign(ref temp, 0)").WithArguments("C.Assign(ref int, int)").WithLocation(33, 28)
                 );
@@ -4100,10 +4100,10 @@ async Task TestMethod()
     }
 }";
             CreateCompilationWithMscorlib45(code).VerifyEmitDiagnostics(
-                // (28,9): error CS8178: 'await' cannot be used in an expression containing a call to 'TestClass.Save(int)' because it returns by reference
+                // (28,9): error CS8178: A reference returned by a call to 'TestClass.Save(int)' cannot be preserved across 'await' or 'yield' boundary.
                 //         Save(1) = await Task.FromResult(0);
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "Save(1)").WithArguments("TestClass.Save(int)").WithLocation(28, 9),
-                // (36,9): error CS8178: 'await' cannot be used in an expression containing a call to 'TestClass.this[int, int].get' because it returns by reference
+                // (36,9): error CS8178: A reference returned by a call to 'TestClass.this[int, int].get' cannot be preserved across 'await' or 'yield' boundary.
                 //         inst[1, 2] = await Task.FromResult(1);
                 Diagnostic(ErrorCode.ERR_RefReturningCallAndAwait, "inst[1, 2]").WithArguments("TestClass.this[int, int].get").WithLocation(36, 9)
             );
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/SwitchTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/SwitchTests.cs
index 4aa59e87ea4cc..27db7808349e5 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/SwitchTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/SwitchTests.cs
@@ -3557,7 +3557,7 @@ .locals init (int V_0,
     IL_008a:  br.s       IL_0097
     IL_008c:  ldloc.1
     IL_008d:  box        ""System.ValueTuple<int, int, int, int, int, int, int, System.ValueTuple<int>>""
-    IL_0092:  call       ""ThrowSwitchExpressionException""
+    IL_0092:  call       ""ThrowSwitchExpressionException(object)""
     IL_0097:  ldloc.0
     IL_0098:  call       ""void System.Console.WriteLine(int)""
     IL_009d:  leave.s    IL_00ac
@@ -3687,7 +3687,7 @@ .locals init (int V_0,
     IL_009f:  br.s       IL_00ac
     IL_00a1:  ldloc.1
     IL_00a2:  box        ""System.ValueTuple<int, int, int, int, int, int, int, System.ValueTuple<int, int>>""
-    IL_00a7:  call       ""ThrowSwitchExpressionException""
+    IL_00a7:  call       ""ThrowSwitchExpressionException(object)""
     IL_00ac:  ldloc.0
     IL_00ad:  call       ""void System.Console.WriteLine(int)""
     IL_00b2:  leave.s    IL_00c1
diff --git a/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests.cs b/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests.cs
index d874c2549f03f..5fff98950f6bf 100644
--- a/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests.cs
@@ -485,7 +485,7 @@ class C { }
             Assert.Equal(2, outputCompilation.SyntaxTrees.Count());
         }
 
-        [ConditionalFact(typeof(MonoOrCoreClrOnly), Reason = "Desktop CLR displays argument exceptions differently")]
+        [ConditionalFact(typeof(IsEnglishLocal))]
         public void Generator_HintName_MustBe_Unique_Across_Outputs()
         {
             var source = @"
@@ -521,7 +521,7 @@ class C { }
             driver.RunGeneratorsAndUpdateCompilation(compilation, out var outputCompilation, out var generatorDiagnostics);
             outputCompilation.VerifyDiagnostics();
             generatorDiagnostics.Verify(
-                Diagnostic("CS8785").WithArguments("PipelineCallbackGenerator", "ArgumentException", "The hintName 'test.cs' of the added source file must be unique within a generator. (Parameter 'hintName')").WithLocation(1, 1)
+                ArgumentExceptionDiagnostic(nameof(PipelineCallbackGenerator), "The hintName 'test.cs' of the added source file must be unique within a generator.", "hintName").WithLocation(1, 1)
                 );
             Assert.Equal(1, outputCompilation.SyntaxTrees.Count());
         }
@@ -758,7 +758,7 @@ class C
             Assert.Same(oldDriver, driver);
         }
 
-        [ConditionalFact(typeof(MonoOrCoreClrOnly), Reason = "Desktop CLR displays argument exceptions differently")]
+        [ConditionalFact(typeof(IsEnglishLocal))]
         public void Adding_A_Source_Text_Without_Encoding_Fails_Generation()
         {
             var source = @"
@@ -776,7 +776,7 @@ class C { }
 
             Assert.Single(outputDiagnostics);
             outputDiagnostics.Verify(
-                Diagnostic("CS" + (int)ErrorCode.WRN_GeneratorFailedDuringGeneration).WithArguments("CallbackGenerator", "ArgumentException", "The SourceText with hintName 'a.cs' must have an explicit encoding set. (Parameter 'source')").WithLocation(1, 1)
+                ArgumentExceptionDiagnostic(nameof(CallbackGenerator), "The SourceText with hintName 'a.cs' must have an explicit encoding set.", "source").WithLocation(1, 1)
                 );
         }
 
@@ -3554,6 +3554,327 @@ class D {  (int, bool) _field; }";
             compilation.VerifyDiagnostics();
         }
 
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_DetachedSyntaxTree_Incremental()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions);
+            compilation.VerifyDiagnostics();
+
+            var generator = new PipelineCallbackGenerator(ctx =>
+            {
+                ctx.RegisterSourceOutput(ctx.CompilationProvider, (ctx, _) =>
+                {
+                    var syntaxTree = CSharpSyntaxTree.ParseText(source, parseOptions, path: "/detached");
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault: true,
+                        warningLevel: 1,
+                        location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 2))));
+                });
+            }).AsSourceGenerator();
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(PipelineCallbackGenerator), "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_DetachedSyntaxTree_Incremental_AdditionalLocations()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions);
+            compilation.VerifyDiagnostics();
+
+            var generator = new PipelineCallbackGenerator(ctx =>
+            {
+                ctx.RegisterSourceOutput(ctx.CompilationProvider, (ctx, comp) =>
+                {
+                    var validSyntaxTree = comp.SyntaxTrees.Single();
+                    var invalidSyntaxTree = CSharpSyntaxTree.ParseText(source, parseOptions, path: "/detached");
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault: true,
+                        warningLevel: 1,
+                        location: Location.Create(validSyntaxTree, TextSpan.FromBounds(0, 2)),
+                        additionalLocations: new[] { Location.Create(invalidSyntaxTree, TextSpan.FromBounds(0, 2)) }));
+                });
+            }).AsSourceGenerator();
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(PipelineCallbackGenerator), "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_DetachedSyntaxTree_Execute()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions);
+            compilation.VerifyDiagnostics();
+
+            var generator = new CallbackGenerator(ctx => { }, ctx =>
+            {
+                var syntaxTree = CSharpSyntaxTree.ParseText(source, parseOptions, path: "/detached");
+                ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                    "TEST0001",
+                    "Test",
+                    "Test diagnostic",
+                    DiagnosticSeverity.Warning,
+                    DiagnosticSeverity.Warning,
+                    isEnabledByDefault: true,
+                    warningLevel: 1,
+                    location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 2))));
+            });
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(CallbackGenerator), "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_DetachedSyntaxTree_Execute_AdditionalLocations()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions);
+            compilation.VerifyDiagnostics();
+
+            var generator = new CallbackGenerator(ctx => { }, ctx =>
+            {
+                var validSyntaxTree = ctx.Compilation.SyntaxTrees.Single();
+                var invalidSyntaxTree = CSharpSyntaxTree.ParseText(source, parseOptions, path: "/detached");
+                ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                    "TEST0001",
+                    "Test",
+                    "Test diagnostic",
+                    DiagnosticSeverity.Warning,
+                    DiagnosticSeverity.Warning,
+                    isEnabledByDefault: true,
+                    warningLevel: 1,
+                    location: Location.Create(validSyntaxTree, TextSpan.FromBounds(0, 2)),
+                    additionalLocations: new[] { Location.Create(invalidSyntaxTree, TextSpan.FromBounds(0, 2)) }));
+            });
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(CallbackGenerator), "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_SpanOutsideRange_Incremental()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions, sourceFileName: "/original");
+            compilation.VerifyDiagnostics();
+
+            var generator = new PipelineCallbackGenerator(ctx =>
+            {
+                ctx.RegisterSourceOutput(ctx.CompilationProvider, (ctx, comp) =>
+                {
+                    var syntaxTree = comp.SyntaxTrees.Single();
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault: true,
+                        warningLevel: 1,
+                        location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 100))));
+                });
+            }).AsSourceGenerator();
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(PipelineCallbackGenerator), "Reported diagnostic 'TEST0001' has a source location '[0..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_SpanOutsideRange_Incremental_AdditionalLocations()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions, sourceFileName: "/original");
+            compilation.VerifyDiagnostics();
+
+            var generator = new PipelineCallbackGenerator(ctx =>
+            {
+                ctx.RegisterSourceOutput(ctx.CompilationProvider, (ctx, comp) =>
+                {
+                    var syntaxTree = comp.SyntaxTrees.Single();
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault: true,
+                        warningLevel: 1,
+                        location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 2)),
+                        additionalLocations: new[] { Location.Create(syntaxTree, TextSpan.FromBounds(0, 100)) }));
+                });
+            }).AsSourceGenerator();
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(PipelineCallbackGenerator), "Reported diagnostic 'TEST0001' has a source location '[0..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_SpanOutsideRange_Execute()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions, sourceFileName: "/original");
+            compilation.VerifyDiagnostics();
+
+            var generator = new CallbackGenerator(ctx => { }, ctx =>
+            {
+                var syntaxTree = ctx.Compilation.SyntaxTrees.Single();
+                ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                    "TEST0001",
+                    "Test",
+                    "Test diagnostic",
+                    DiagnosticSeverity.Warning,
+                    DiagnosticSeverity.Warning,
+                    isEnabledByDefault: true,
+                    warningLevel: 1,
+                    location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 100))));
+            });
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(CallbackGenerator), "Reported diagnostic 'TEST0001' has a source location '[0..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_SpanOutsideRange_Execute_AdditionalLocations()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions, sourceFileName: "/original");
+            compilation.VerifyDiagnostics();
+
+            var generator = new CallbackGenerator(ctx => { }, ctx =>
+            {
+                var syntaxTree = ctx.Compilation.SyntaxTrees.Single();
+                ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                    "TEST0001",
+                    "Test",
+                    "Test diagnostic",
+                    DiagnosticSeverity.Warning,
+                    DiagnosticSeverity.Warning,
+                    isEnabledByDefault: true,
+                    warningLevel: 1,
+                    location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 2)),
+                    additionalLocations: new[] { Location.Create(syntaxTree, TextSpan.FromBounds(0, 100)) }));
+            });
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(CallbackGenerator), "Reported diagnostic 'TEST0001' has a source location '[0..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_SpaceInIdentifier_Incremental()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions);
+            compilation.VerifyDiagnostics();
+
+            var generator = new PipelineCallbackGenerator(ctx =>
+            {
+                ctx.RegisterSourceOutput(ctx.CompilationProvider, (ctx, comp) =>
+                {
+                    var syntaxTree = comp.SyntaxTrees.Single();
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST 0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault: true,
+                        warningLevel: 1,
+                        location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 2))));
+                });
+            }).AsSourceGenerator();
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(PipelineCallbackGenerator), "Reported diagnostic has an ID 'TEST 0001', which is not a valid identifier.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
+        [ConditionalFact(typeof(IsEnglishLocal))]
+        [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")]
+        public void Diagnostic_SpaceInIdentifier_Execute()
+        {
+            var source = "class C {}";
+            var parseOptions = TestOptions.RegularPreview;
+            Compilation compilation = CreateCompilation(source, options: TestOptions.DebugDll, parseOptions: parseOptions);
+            compilation.VerifyDiagnostics();
+
+            var generator = new CallbackGenerator(ctx => { }, ctx =>
+            {
+                var syntaxTree = ctx.Compilation.SyntaxTrees.Single();
+                ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                    "TEST 0001",
+                    "Test",
+                    "Test diagnostic",
+                    DiagnosticSeverity.Warning,
+                    DiagnosticSeverity.Warning,
+                    isEnabledByDefault: true,
+                    warningLevel: 1,
+                    location: Location.Create(syntaxTree, TextSpan.FromBounds(0, 2))));
+            });
+
+            GeneratorDriver driver = CSharpGeneratorDriver.Create(new[] { generator }, parseOptions: parseOptions);
+            driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out compilation, out var diagnostics);
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic(nameof(CallbackGenerator), "Reported diagnostic has an ID 'TEST 0001', which is not a valid identifier.", "diagnostic").WithLocation(1, 1));
+            compilation.VerifyDiagnostics();
+        }
+
         [Fact]
         public void IncrementalGenerator_Add_New_Generator_After_Generation()
         {
@@ -3746,5 +4067,16 @@ static void replace(ref Compilation compilation, CSharpParseOptions parseOptions
                 compilation = compilation.ReplaceSyntaxTree(tree, CSharpSyntaxTree.ParseText(source, parseOptions));
             }
         }
+
+        private static DiagnosticDescription ArgumentExceptionDiagnostic(string generatorName, string message, string parameterName)
+        {
+            return Diagnostic("CS8785").WithArguments(generatorName, nameof(ArgumentException),
+#if NETCOREAPP
+                $"{message} (Parameter '{parameterName}')"
+#else
+                $"{message}{Environment.NewLine}Parameter name: {parameterName}"
+#endif
+                );
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests_Attributes_SimpleName.cs b/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests_Attributes_SimpleName.cs
index eddd65200a21e..d095dc41f9d41 100644
--- a/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests_Attributes_SimpleName.cs
+++ b/src/Compilers/CSharp/Test/Semantic/SourceGeneration/GeneratorDriverTests_Attributes_SimpleName.cs
@@ -1310,13 +1310,25 @@ class C { }
             compilation.SyntaxTrees.First()));
         runResult = driver.GetRunResult().Results[0];
 
-        Assert.False(runResult.TrackedSteps.ContainsKey("result_ForAttribute"));
-        Assert.False(runResult.TrackedSteps.ContainsKey("individualFileGlobalAliases_ForAttribute"));
-        Assert.False(runResult.TrackedSteps.ContainsKey("collectedGlobalAliases_ForAttribute"));
-        Assert.False(runResult.TrackedSteps.ContainsKey("allUpGlobalAliases_ForAttribute"));
+        Assert.Collection(runResult.TrackedSteps["result_ForAttribute"],
+            step =>
+            {
+                Assert.True(step.Outputs.Single().Value is ClassDeclarationSyntax { Identifier.ValueText: "C" });
+                Assert.Equal(IncrementalStepRunReason.Removed, step.Outputs.Single().Reason);
+            });
+
+        Assert.Collection(runResult.TrackedSteps["individualFileGlobalAliases_ForAttribute"],
+            s => Assert.Equal(IncrementalStepRunReason.Modified, s.Outputs.Single().Reason),
+            s => Assert.Equal(IncrementalStepRunReason.Removed, s.Outputs.Single().Reason));
+        Assert.Equal(IncrementalStepRunReason.Modified, runResult.TrackedSteps["collectedGlobalAliases_ForAttribute"].Single().Outputs.Single().Reason);
+        Assert.Equal(IncrementalStepRunReason.Modified, runResult.TrackedSteps["allUpGlobalAliases_ForAttribute"].Single().Outputs.Single().Reason);
 
-        Assert.False(runResult.TrackedSteps.ContainsKey("compilationUnit_ForAttribute"));
-        Assert.False(runResult.TrackedSteps.ContainsKey("compilationUnitAndGlobalAliases_ForAttribute"));
+        Assert.Collection(runResult.TrackedSteps["compilationUnit_ForAttribute"].Single().Outputs,
+            o => Assert.Equal(IncrementalStepRunReason.Modified, o.Reason),
+            o => Assert.Equal(IncrementalStepRunReason.Modified, o.Reason),
+            o => Assert.Equal(IncrementalStepRunReason.Removed, o.Reason));
+        Assert.Equal(IncrementalStepRunReason.Removed, runResult.TrackedSteps["compilationUnitAndGlobalAliases_ForAttribute"].Single().Outputs.Single().Reason);
+        Assert.Equal(IncrementalStepRunReason.Removed, runResult.TrackedSteps["result_ForAttribute"].Single().Outputs.Single().Reason);
     }
 
     [Fact]
diff --git a/src/Compilers/CSharp/Test/Semantic/SourceGeneration/StateTableTests.cs b/src/Compilers/CSharp/Test/Semantic/SourceGeneration/StateTableTests.cs
index bb73064c78ebc..0949c4f74aaad 100644
--- a/src/Compilers/CSharp/Test/Semantic/SourceGeneration/StateTableTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/SourceGeneration/StateTableTests.cs
@@ -82,24 +82,24 @@ public void Node_Builder_Can_Add_Entries_From_Previous_Table()
             var previousTable = builder.ToImmutableAndFree();
 
             builder = previousTable.ToBuilder(stepName: null, false);
-            builder.AddEntries(ImmutableArray.Create(10, 11), EntryState.Added, TimeSpan.Zero, default, EntryState.Added);
+            builder.TryModifyEntries(ImmutableArray.Create(10, 11), EqualityComparer<int>.Default, TimeSpan.Zero, default, EntryState.Modified);
             builder.TryUseCachedEntries(TimeSpan.Zero, default, out var cachedEntries); // ((2, EntryState.Cached), (3, EntryState.Cached))
-            builder.AddEntries(ImmutableArray.Create(20, 21, 22), EntryState.Modified, TimeSpan.Zero, default, EntryState.Modified);
+            builder.TryModifyEntries(ImmutableArray.Create(20, 21, 22), EqualityComparer<int>.Default, TimeSpan.Zero, default, EntryState.Modified);
             bool didRemoveEntries = builder.TryRemoveEntries(TimeSpan.Zero, default, out var removedEntries); //((6, EntryState.Removed))
             var newTable = builder.ToImmutableAndFree();
 
-            var expected = ImmutableArray.Create((10, EntryState.Added, 0), (11, EntryState.Added, 1), (2, EntryState.Cached, 0), (3, EntryState.Cached, 1), (20, EntryState.Modified, 0), (21, EntryState.Modified, 1), (22, EntryState.Modified, 2), (6, EntryState.Removed, 0));
+            var expected = ImmutableArray.Create((10, EntryState.Modified, 0), (11, EntryState.Added, 1), (2, EntryState.Cached, 0), (3, EntryState.Cached, 1), (20, EntryState.Modified, 0), (21, EntryState.Modified, 1), (22, EntryState.Added, 2), (6, EntryState.Removed, 0));
             AssertTableEntries(newTable, expected);
             Assert.Equal(new[] { 2, 3 }, YieldItems(cachedEntries.Items));
             Assert.Equal(1, removedEntries.Count);
             Assert.Equal(6, removedEntries[0]);
             Assert.True(didRemoveEntries);
-        }
 
-        private static IEnumerable<int> YieldItems(OneOrMany<int> items)
-        {
-            foreach (var value in items)
-                yield return value;
+            static IEnumerable<int> YieldItems(OneOrMany<int> items)
+            {
+                foreach (var value in items)
+                    yield return value;
+            }
         }
 
         [Fact]
@@ -1104,6 +1104,217 @@ public void Node_Table_When_Previous_Was_Larger_Multi()
             AssertTableEntries(table.AsCached(), ImmutableArray.Create(("class1", EntryState.Cached, 0), ("class1.1", EntryState.Cached, 1)));
         }
 
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/67123")]
+        public void Node_Table_When_Previous_Was_Smaller()
+        {
+            ImmutableArray<string> values = ImmutableArray.Create("1", "2");
+            var inputNode = new InputNode<string>(_ => values).WithTrackingName("Input");
+
+            var transformNode = new TransformNode<string, string>(inputNode, (a, ct) =>
+            {
+                return a switch
+                {
+                    "1" => ImmutableArray.Create("1.1", "1.2"),
+                    "2" => ImmutableArray.Create("2.1", "2.2"),
+                    _ => ImmutableArray.Create("1.1", "inserted", "1.2")
+                };
+            }, name: "Select");
+
+            var select2 = new TransformNode<string, string>(transformNode, (a, ct) => a, name: "Select2");
+
+            DriverStateTable.Builder dstBuilder = GetBuilder(DriverStateTable.Empty, trackIncrementalGeneratorSteps: false);
+            var table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Added, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Added, 0), ("2.2", EntryState.Added, 0)));
+            Assert.Equal(4, table.AsCached().Count); // [1.1, 1.2, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+
+            // change the input so we can re-run, this time with the extra value inserted
+            values = ImmutableArray.Create("3", "2");
+            dstBuilder = GetBuilder(dstBuilder.ToImmutable(), trackIncrementalGeneratorSteps: false);
+            table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("inserted", EntryState.Modified, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+            Assert.Equal(5, table.AsCached().Count); // [1.1, inserted, 1.2, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("inserted", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/67123")]
+        public void Node_Table_When_Previous_Was_Smaller_InsertedAtStart()
+        {
+            ImmutableArray<string> values = ImmutableArray.Create("1", "2");
+            var inputNode = new InputNode<string>(_ => values).WithTrackingName("Input");
+
+            var transformNode = new TransformNode<string, string>(inputNode, (a, ct) =>
+            {
+                return a switch
+                {
+                    "1" => ImmutableArray.Create("1.1", "1.2"),
+                    "2" => ImmutableArray.Create("2.1", "2.2"),
+                    _ => ImmutableArray.Create("inserted", "1.1", "1.2")
+                };
+            }, name: "Select");
+
+            var select2 = new TransformNode<string, string>(transformNode, (a, ct) => a, name: "Select2");
+
+            DriverStateTable.Builder dstBuilder = GetBuilder(DriverStateTable.Empty, trackIncrementalGeneratorSteps: false);
+            var table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Added, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Added, 0), ("2.2", EntryState.Added, 0)));
+            Assert.Equal(4, table.AsCached().Count); // [1.1, 1.2, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+
+            // change the input so we can re-run, this time with the extra value inserted
+            values = ImmutableArray.Create("3", "2");
+            dstBuilder = GetBuilder(dstBuilder.ToImmutable(), trackIncrementalGeneratorSteps: false);
+            table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("inserted", EntryState.Modified, 0), ("1.1", EntryState.Modified, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+            Assert.Equal(5, table.AsCached().Count); // [inserted, 1.1, 1.2, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("inserted", EntryState.Cached, 0), ("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/67123")]
+        public void Node_Table_When_Previous_Was_Smaller_InsertedAtEnd()
+        {
+            ImmutableArray<string> values = ImmutableArray.Create("1", "2");
+            var inputNode = new InputNode<string>(_ => values).WithTrackingName("Input");
+
+            var transformNode = new TransformNode<string, string>(inputNode, (a, ct) =>
+            {
+                return a switch
+                {
+                    "1" => ImmutableArray.Create("1.1", "1.2"),
+                    "2" => ImmutableArray.Create("2.1", "2.2"),
+                    _ => ImmutableArray.Create("1.1", "1.2", "inserted")
+                };
+            }, name: "Select");
+
+            var select2 = new TransformNode<string, string>(transformNode, (a, ct) => a, name: "Select2");
+
+            DriverStateTable.Builder dstBuilder = GetBuilder(DriverStateTable.Empty, trackIncrementalGeneratorSteps: false);
+            var table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Added, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Added, 0), ("2.2", EntryState.Added, 0)));
+            Assert.Equal(4, table.AsCached().Count); // [1.1, 1.2, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+
+            // change the input so we can re-run, this time with the extra value inserted
+            values = ImmutableArray.Create("3", "2");
+            dstBuilder = GetBuilder(dstBuilder.ToImmutable(), trackIncrementalGeneratorSteps: false);
+            table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("inserted", EntryState.Added, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+            Assert.Equal(5, table.AsCached().Count); // [1.1, 1.2, inserted, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("inserted", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/67123")]
+        public void Node_Table_When_Previous_Was_Smaller_InsertedIntoEndValue()
+        {
+            ImmutableArray<string> values = ImmutableArray.Create("1", "2");
+            var inputNode = new InputNode<string>(_ => values).WithTrackingName("Input");
+
+            var transformNode = new TransformNode<string, string>(inputNode, (a, ct) =>
+            {
+                return a switch
+                {
+                    "1" => ImmutableArray.Create("1.1", "1.2"),
+                    "2" => ImmutableArray.Create("2.1", "2.2"),
+                    _ => ImmutableArray.Create("2.1", "inserted", "2.2")
+                };
+            }, name: "Select");
+
+            var select2 = new TransformNode<string, string>(transformNode, (a, ct) => a, name: "Select2");
+
+            DriverStateTable.Builder dstBuilder = GetBuilder(DriverStateTable.Empty, trackIncrementalGeneratorSteps: false);
+            var table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Added, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Added, 0), ("2.2", EntryState.Added, 0)));
+            Assert.Equal(4, table.AsCached().Count); // [1.1, 1.2, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+
+            // change the input so we can re-run, this time with the extra value inserted
+            values = ImmutableArray.Create("1", "3");
+            dstBuilder = GetBuilder(dstBuilder.ToImmutable(), trackIncrementalGeneratorSteps: false);
+            table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("inserted", EntryState.Modified, 0), ("2.2", EntryState.Added, 0)));
+            Assert.Equal(5, table.AsCached().Count); // [1.1, 1.2, 2.1, inserted, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("inserted", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/67123")]
+        public void Node_Table_When_Previous_Was_Smaller_InsertedIntoMiddleValue()
+        {
+            ImmutableArray<string> values = ImmutableArray.Create("1", "2", "3");
+            var inputNode = new InputNode<string>(_ => values).WithTrackingName("Input");
+
+            var transformNode = new TransformNode<string, string>(inputNode, (a, ct) =>
+            {
+                return a switch
+                {
+                    "1" => ImmutableArray.Create("1.1", "1.2"),
+                    "2" => ImmutableArray.Create("2.1", "2.2"),
+                    "3" => ImmutableArray.Create("3.1", "3.2"),
+                    _ => ImmutableArray.Create("2.1", "inserted", "2.2")
+                };
+            }, name: "Select");
+
+            var select2 = new TransformNode<string, string>(transformNode, (a, ct) => a, name: "Select2");
+
+            DriverStateTable.Builder dstBuilder = GetBuilder(DriverStateTable.Empty, trackIncrementalGeneratorSteps: false);
+            var table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Added, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Added, 0), ("2.2", EntryState.Added, 0), ("3.1", EntryState.Added, 0), ("3.2", EntryState.Added, 0)));
+            Assert.Equal(6, table.AsCached().Count); // [1.1, 1.2, 2.1, 2.2, 3.1, 3.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0), ("3.1", EntryState.Cached, 0), ("3.2", EntryState.Cached, 0)));
+
+            // change the input so we can re-run, this time with the extra value inserted
+            values = ImmutableArray.Create("1", "4", "3");
+            dstBuilder = GetBuilder(dstBuilder.ToImmutable(), trackIncrementalGeneratorSteps: false);
+            table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("inserted", EntryState.Modified, 0), ("2.2", EntryState.Added, 0), ("3.1", EntryState.Cached, 0), ("3.2", EntryState.Cached, 0)));
+            Assert.Equal(7, table.AsCached().Count); // [1.1, 1.2, 2.1, inserted, 2.2, 3.1, 3.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("inserted", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0), ("3.1", EntryState.Cached, 0), ("3.2", EntryState.Cached, 0)));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/67123")]
+        public void Node_Table_When_Previous_Was_Larger_2()
+        {
+            ImmutableArray<string> values = ImmutableArray.Create("1", "2");
+            var inputNode = new InputNode<string>(_ => values).WithTrackingName("Input");
+
+            var transformNode = new TransformNode<string, string>(inputNode, (a, ct) =>
+            {
+                return a switch
+                {
+                    "1" => ImmutableArray.Create("1.1", "1.2"),
+                    "2" => ImmutableArray.Create("2.1", "2.2"),
+                    _ => ImmutableArray.Create("1.1")
+                };
+            }, name: "Select");
+
+            var select2 = new TransformNode<string, string>(transformNode, (a, ct) => a, name: "Select2");
+
+            DriverStateTable.Builder dstBuilder = GetBuilder(DriverStateTable.Empty, trackIncrementalGeneratorSteps: false);
+            var table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Added, 0), ("1.2", EntryState.Added, 0), ("2.1", EntryState.Added, 0), ("2.2", EntryState.Added, 0)));
+            Assert.Equal(4, table.AsCached().Count); // [1.1, 1.2, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+
+            // change the input so we can re-run, this time when we produce less values
+            values = ImmutableArray.Create("3", "2");
+            dstBuilder = GetBuilder(dstBuilder.ToImmutable(), trackIncrementalGeneratorSteps: false);
+            table = dstBuilder.GetLatestStateTableForNode(select2);
+
+            AssertTableEntries(table, ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("1.2", EntryState.Removed, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+            Assert.Equal(3, table.AsCached().Count); // [1.1, 2.1, 2.2]
+            AssertTableEntries(table.AsCached(), ImmutableArray.Create(("1.1", EntryState.Cached, 0), ("2.1", EntryState.Cached, 0), ("2.2", EntryState.Cached, 0)));
+        }
+
         private void AssertTableEntries<T>(NodeStateTable<T> table, IList<(T Item, EntryState State, int OutputIndex)> expected)
         {
             int index = 0;
diff --git a/src/Compilers/CSharp/Test/Symbol/Compilation/UsedAssembliesTests.cs b/src/Compilers/CSharp/Test/Symbol/Compilation/UsedAssembliesTests.cs
index e899c4da8b17f..dff6ce2c6815a 100644
--- a/src/Compilers/CSharp/Test/Symbol/Compilation/UsedAssembliesTests.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Compilation/UsedAssembliesTests.cs
@@ -3732,7 +3732,6 @@ public unsafe static void Main()
 }
 ");
 
-            // Support for `using unsafe static` tracked by https://github.com/dotnet/roslyn/issues/67329
             verifyDiagnostics(comp0Ref, comp1Ref,
 @"
 using static C1<S<C0>*[]>;
@@ -3757,7 +3756,18 @@ public static void Main()
                 //         _ = E1.F1 + 1;
                 Diagnostic(ErrorCode.ERR_UnsafeNeeded, "E1.F1 + 1").WithLocation(7, 13));
 
-            // Support for `using unsafe static` tracked by https://github.com/dotnet/roslyn/issues/67329
+            verifyDiagnostics(comp0Ref, comp1Ref,
+@"
+using static unsafe C1<S<C0>*[]>;
+public class C2
+{
+    public static unsafe void Main()
+    {
+        _ = E1.F1 + 1;
+    }
+}
+");
+
             verifyDiagnostics(comp0Ref, comp1Ref,
 @"
 using static C1<S<C0>*[]>.E1;
@@ -3782,6 +3792,18 @@ public static void Main()
                 //         _ = F1 + 1;
                 Diagnostic(ErrorCode.ERR_UnsafeNeeded, "F1 + 1").WithLocation(7, 13));
 
+            verifyDiagnostics(comp0Ref, comp1Ref,
+@"
+using static unsafe C1<S<C0>*[]>.E1;
+public class C2
+{
+    public static unsafe void Main()
+    {
+        _ = F1 + 1;
+    }
+}
+");
+
             verify(comp0Ref, comp1Ref,
 @"
 using unsafe @alias = C1<S<C0>*[]>.E1;
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/CompilationCreationTests.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/CompilationCreationTests.cs
index f6c6c78d291b8..a16c746ef12fc 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/CompilationCreationTests.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/CompilationCreationTests.cs
@@ -78,8 +78,9 @@ public void CorLibTypes()
             for (int i = 1; i <= (int)SpecialType.Count; i++)
             {
                 NamedTypeSymbol type = c1.GetSpecialType((SpecialType)i);
-                if (i == (int)SpecialType.System_Runtime_CompilerServices_RuntimeFeature ||
-                    i == (int)SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute)
+                if (i is (int)SpecialType.System_Runtime_CompilerServices_RuntimeFeature or
+                         (int)SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute or
+                         (int)SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute)
                 {
                     Assert.True(type.IsErrorType()); // Not available
                 }
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/CorLibrary/CorTypes.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/CorLibrary/CorTypes.cs
index bb7e2ca155ecd..503d43d3e923b 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/CorLibrary/CorTypes.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/CorLibrary/CorTypes.cs
@@ -56,6 +56,7 @@ public void PresentCorLib()
 
             var knownMissingTypes = new HashSet<int>()
             {
+                (int)SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute
             };
 
             for (int i = 1; i <= (int)SpecialType.Count; i++)
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/ExtensionMethodTests.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/ExtensionMethodTests.cs
index 2b5e6d04c03bc..e25babdc31e6d 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/ExtensionMethodTests.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/ExtensionMethodTests.cs
@@ -2745,8 +2745,9 @@ static void Main(string[] args)
             methodSymbol = (MethodSymbol)symbolInfo.Symbol.GetSymbol<MethodSymbol>();
             Assert.False(methodSymbol.IsFromCompilation(compilation));
 
-            // 9341 is resolved as Won't Fix since ThisParameter property is internal.
-            Assert.Throws<InvalidOperationException>(() => methodSymbol.ThisParameter);
+            parameter = methodSymbol.ThisParameter;
+            Assert.Equal(-1, parameter.Ordinal);
+            Assert.Equal(parameter.ContainingSymbol, methodSymbol);
         }
 
         private CompilationVerifier CompileAndVerify(string source, string expectedOutput = null, Action<ModuleSymbol> validator = null,
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/MissingSpecialMember.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/MissingSpecialMember.cs
index f59fea213f982..d4d9daa076fab 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/MissingSpecialMember.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/MissingSpecialMember.cs
@@ -530,8 +530,9 @@ public void AllSpecialTypes()
                 var symbol = comp.GetSpecialType(special);
                 Assert.NotNull(symbol);
 
-                if (special == SpecialType.System_Runtime_CompilerServices_RuntimeFeature ||
-                    special == SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute)
+                if (special is SpecialType.System_Runtime_CompilerServices_RuntimeFeature or
+                               SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute or
+                               SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute)
                 {
                     Assert.Equal(SymbolKind.ErrorType, symbol.Kind); // Not available
                 }
@@ -559,7 +560,8 @@ public void AllSpecialTypeMembers()
                     || special == SpecialMember.System_Runtime_CompilerServices_RuntimeFeature__UnmanagedSignatureCallingConvention
                     || special == SpecialMember.System_Runtime_CompilerServices_RuntimeFeature__NumericIntPtr
                     || special == SpecialMember.System_Runtime_CompilerServices_RuntimeFeature__ByRefFields
-                    || special == SpecialMember.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute__ctor)
+                    || special == SpecialMember.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute__ctor
+                    || special == SpecialMember.System_Runtime_CompilerServices_InlineArrayAttribute__ctor)
                 {
                     Assert.Null(symbol); // Not available
                 }
@@ -633,6 +635,8 @@ public void AllWellKnownTypes()
                     case WellKnownType.System_Runtime_CompilerServices_CompilerFeatureRequiredAttribute:
                     case WellKnownType.System_Diagnostics_CodeAnalysis_UnscopedRefAttribute:
                     case WellKnownType.System_Runtime_CompilerServices_MetadataUpdateOriginalTypeAttribute:
+                    case WellKnownType.System_Runtime_InteropServices_MemoryMarshal:
+                    case WellKnownType.System_Runtime_CompilerServices_Unsafe:
                         // Not yet in the platform.
                         continue;
                     case WellKnownType.Microsoft_CodeAnalysis_Runtime_Instrumentation:
@@ -945,11 +949,13 @@ public void AllWellKnownTypeMembers()
                     case WellKnownMember.System_Span_T__ctor_Array:
                     case WellKnownMember.System_Span_T__get_Item:
                     case WellKnownMember.System_Span_T__get_Length:
+                    case WellKnownMember.System_Span_T__Slice_Int_Int:
                     case WellKnownMember.System_ReadOnlySpan_T__ctor_Pointer:
                     case WellKnownMember.System_ReadOnlySpan_T__ctor_Array:
                     case WellKnownMember.System_ReadOnlySpan_T__ctor_Array_Start_Length:
                     case WellKnownMember.System_ReadOnlySpan_T__get_Item:
                     case WellKnownMember.System_ReadOnlySpan_T__get_Length:
+                    case WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int:
                     case WellKnownMember.System_Index__ctor:
                     case WellKnownMember.System_Index__GetOffset:
                     case WellKnownMember.System_Range__ctor:
@@ -1002,6 +1008,11 @@ public void AllWellKnownTypeMembers()
                     case WellKnownMember.System_Diagnostics_CodeAnalysis_UnscopedRefAttribute__ctor:
                     case WellKnownMember.System_Runtime_CompilerServices_MetadataUpdateOriginalTypeAttribute__ctor:
                     case WellKnownMember.System_Runtime_CompilerServices_RuntimeHelpers__CreateSpanRuntimeFieldHandle:
+                    case WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan:
+                    case WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan:
+                    case WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T:
+                    case WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T:
+                    case WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T:
                         // Not yet in the platform.
                         continue;
                     case WellKnownMember.Microsoft_CodeAnalysis_Runtime_Instrumentation__CreatePayloadForMethodsSpanningSingleFile:
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/MockAssemblySymbol.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/MockAssemblySymbol.cs
index 99dd26d99e887..b6b446e4af80f 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/MockAssemblySymbol.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/MockAssemblySymbol.cs
@@ -85,6 +85,11 @@ internal override IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicK
             throw new NotImplementedException();
         }
 
+        internal override IEnumerable<string> GetInternalsVisibleToAssemblyNames()
+        {
+            throw new NotImplementedException();
+        }
+
         public override ICollection<string> TypeNames
         {
             get
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamedTypeSymbol.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamedTypeSymbol.cs
index cfca66891dc05..7d45236864f30 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamedTypeSymbol.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamedTypeSymbol.cs
@@ -44,7 +44,8 @@ internal override bool MangleName
             }
         }
 
-        internal override FileIdentifier? AssociatedFileIdentifier => null;
+        internal sealed override bool IsFileLocal => false;
+        internal sealed override FileIdentifier? AssociatedFileIdentifier => null;
 
         public override ImmutableArray<TypeParameterSymbol> TypeParameters
         {
@@ -127,17 +128,17 @@ where sym is NamedTypeSymbol
                     select (NamedTypeSymbol)sym).ToArray().AsImmutableOrNull();
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             return (from sym in _children
-                    where sym is NamedTypeSymbol && sym.Name == name && ((NamedTypeSymbol)sym).Arity == arity
+                    where sym is NamedTypeSymbol namedType && sym.Name.AsSpan().SequenceEqual(name.Span) && namedType.Arity == arity
                     select (NamedTypeSymbol)sym).ToArray().AsImmutableOrNull();
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return (from sym in _children
-                    where sym is NamedTypeSymbol && sym.Name == name
+                    where sym is NamedTypeSymbol && sym.Name.AsSpan().SequenceEqual(name.Span)
                     select (NamedTypeSymbol)sym).ToArray().AsImmutableOrNull();
         }
 
@@ -337,5 +338,11 @@ internal override AttributeUsageInfo GetAttributeUsageInfo()
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal sealed override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamespaceSymbol.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamespaceSymbol.cs
index e57da723dc052..47360f090da10 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamespaceSymbol.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/MockNamespaceSymbol.cs
@@ -4,6 +4,7 @@
 
 #nullable disable
 
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
@@ -51,9 +52,9 @@ public override ImmutableArray<Symbol> GetMembers()
             return _children.AsImmutable();
         }
 
-        public override ImmutableArray<Symbol> GetMembers(string name)
+        public override ImmutableArray<Symbol> GetMembers(ReadOnlyMemory<char> name)
         {
-            return _children.Where(ns => (ns.Name == name)).ToArray().AsImmutableOrNull();
+            return _children.Where(ns => ns.Name.AsSpan().SequenceEqual(name.Span)).ToArray().AsImmutableOrNull();
         }
 
         public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
@@ -63,10 +64,10 @@ where c is NamedTypeSymbol
                     select (NamedTypeSymbol)c).ToArray().AsImmutableOrNull();
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             return (from c in _children
-                    where c is NamedTypeSymbol && c.Name == name
+                    where c is NamedTypeSymbol && c.Name.AsSpan().SequenceEqual(name.Span)
                     select (NamedTypeSymbol)c).ToArray().AsImmutableOrNull();
         }
 
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/Source/ClsComplianceTests.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/Source/ClsComplianceTests.cs
index a6474df00408e..d07c9baf2682a 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/Source/ClsComplianceTests.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/Source/ClsComplianceTests.cs
@@ -3165,6 +3165,7 @@ public class C
                     case SpecialType.System_Runtime_CompilerServices_IsVolatile: // static
                     case SpecialType.System_Runtime_CompilerServices_RuntimeFeature: // static and not available
                     case SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute: // not available
+                    case SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute: // not available
                         continue;
                 }
 
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/Source/FileModifierTests.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/Source/FileModifierTests.cs
index 96928b63c0555..97684fbc0b1ce 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/Source/FileModifierTests.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/Source/FileModifierTests.cs
@@ -2020,6 +2020,35 @@ file class C
             Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "Del2").WithArguments("C", "Del2").WithLocation(6, 12));
     }
 
+    [Fact]
+    public void SignatureUsage_06_2()
+    {
+        var source = """
+            file class C<T>
+            {
+            }
+
+            delegate void Del1(C<int> c); // 1
+            delegate C<int> Del2(); // 2
+
+            file delegate void Del3(C<int> c); // ok
+            file delegate C<int> Del4(); // ok
+            """;
+
+        var comp = CreateCompilation(source);
+        comp.VerifyDiagnostics(
+            // (5,15): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'Del1'.
+            // delegate void Del1(C<int> c); // 1
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "Del1").WithArguments("C<int>", "Del1").WithLocation(5, 15),
+            // (6,17): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'Del2'.
+            // delegate C<int> Del2(); // 2
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "Del2").WithArguments("C<int>", "Del2").WithLocation(6, 17));
+
+        var del1 = comp.GetMember<NamedTypeSymbol>("Del1");
+        var cInt = (ConstructedNamedTypeSymbol)del1.DelegateInvokeMethod.Parameters[0].Type;
+        Assert.True(cInt.IsFileLocal);
+    }
+
     [Fact]
     public void SignatureUsage_07()
     {
@@ -2093,6 +2122,73 @@ class D
             Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "M").WithArguments("C", "D").WithLocation(7, 14));
     }
 
+    [Fact]
+    public void SignatureUsage_10()
+    {
+        var source = """
+            #pragma warning disable 67, 169 // unused event, field
+
+            file class C<T> { }
+            file delegate void Del<T>(T input);
+
+            class C1
+            {
+                private C<int> F; // 1
+                private event Del<int> E; // 2
+                private void M1(C<int> input) { } // 3
+                private C<int> M2() => throw null!; // 4
+
+                private C<int> P { get; set; } // 5
+                private C<int> this[int i] => throw null!; // 6
+            }
+
+            file class FC
+            {
+                private C<int> F;
+                private event Del<int> E;
+                private void M1(C<int> input) { }
+                private C<int> M2() => throw null!;
+
+                private C<int> P { get; set; }
+                private C<int> this[int i] => throw null!;
+            }
+            """;
+
+        var comp = CreateCompilation(source);
+        comp.VerifyDiagnostics(
+            // (8,20): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'C1'.
+            //     private C<int> F; // 1
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "F").WithArguments("C<int>", "C1").WithLocation(8, 20),
+            // (9,28): error CS9051: File-local type 'Del<int>' cannot be used in a member signature in non-file-local type 'C1'.
+            //     private event Del<int> E; // 2
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "E").WithArguments("Del<int>", "C1").WithLocation(9, 28),
+            // (10,18): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'C1'.
+            //     private void M1(C<int> input) { } // 3
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "M1").WithArguments("C<int>", "C1").WithLocation(10, 18),
+            // (11,20): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'C1'.
+            //     private C<int> M2() => throw null!; // 4
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "M2").WithArguments("C<int>", "C1").WithLocation(11, 20),
+            // (13,20): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'C1'.
+            //     private C<int> P { get; set; } // 5
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "P").WithArguments("C<int>", "C1").WithLocation(13, 20),
+            // (14,20): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'C1'.
+            //     private C<int> this[int i] => throw null!; // 6
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "this").WithArguments("C<int>", "C1").WithLocation(14, 20));
+
+        verifyConstructedFileType(comp.GetMember<FieldSymbol>("C1.F").Type);
+        verifyConstructedFileType(comp.GetMember<EventSymbol>("C1.E").Type);
+        verifyConstructedFileType(comp.GetMember<MethodSymbol>("C1.M1").Parameters[0].Type);
+        verifyConstructedFileType(comp.GetMember<MethodSymbol>("C1.M2").ReturnType);
+        verifyConstructedFileType(comp.GetMember<PropertySymbol>("C1.P").Type);
+        verifyConstructedFileType(comp.GetMember<PropertySymbol>("C1.this[]").Type);
+
+        void verifyConstructedFileType(TypeSymbol type)
+        {
+            var cInt = (ConstructedNamedTypeSymbol)type;
+            Assert.True(cInt.IsFileLocal);
+        }
+    }
+
     [Fact]
     public void AccessModifiers_01()
     {
@@ -2285,6 +2381,43 @@ partial interface Derived : I2 { }
             Diagnostic(ErrorCode.ERR_FileTypeBase, "Derived").WithArguments("I1", "Derived").WithLocation(3, 19));
     }
 
+    [Fact]
+    public void BaseClause_06()
+    {
+        var source = """
+        file class C<T> { }
+
+        class D : C<int> { } // 1
+        file class E : C<int> { }
+
+        file interface I<T> { }
+
+        class F : I<int> { } // ok
+        file class G : I<int> { }
+
+        interface J : I<int> { } // 2
+        file interface K : I<int> { }
+        """;
+
+        var comp = CreateCompilation((source, "Program.cs"));
+        comp.VerifyEmitDiagnostics(
+            // Program.cs(3,7): error CS9053: File-local type 'C<int>' cannot be used as a base type of non-file-local type 'D'.
+            // class D : C<int>, I<int> { } // 1
+            Diagnostic(ErrorCode.ERR_FileTypeBase, "D").WithArguments("C<int>", "D").WithLocation(3, 7),
+            // Program.cs(11,11): error CS9053: File-local type 'I<int>' cannot be used as a base type of non-file-local type 'J'.
+            // interface J : I<int> { } // 2
+            Diagnostic(ErrorCode.ERR_FileTypeBase, "J").WithArguments("I<int>", "J").WithLocation(11, 11));
+
+        var cInt = (ConstructedNamedTypeSymbol)comp.GetMember<NamedTypeSymbol>("D").BaseTypeNoUseSiteDiagnostics;
+        Assert.True(cInt.IsFileLocal);
+
+        var iInt = (ConstructedNamedTypeSymbol)comp.GetMember<NamedTypeSymbol>("F").InterfacesNoUseSiteDiagnostics()[0];
+        Assert.True(iInt.IsFileLocal);
+
+        iInt = (ConstructedNamedTypeSymbol)comp.GetMember<NamedTypeSymbol>("J").InterfacesNoUseSiteDiagnostics()[0];
+        Assert.True(iInt.IsFileLocal);
+    }
+
     [Fact]
     public void InterfaceImplementation_01()
     {
@@ -2404,6 +2537,67 @@ void I.F() { } // 2, 3
             Diagnostic(ErrorCode.ERR_UnimplementedInterfaceMember, "I").WithArguments("C", "I.F()").WithLocation(5, 19));
     }
 
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void InterfaceImplementation_06()
+    {
+        // Ensure that appropriate error is given for duplicate implementations which have a type difference which is insignificant to the runtime.
+        var source1 = """
+            file interface FI<T>
+            {
+                public T Prop { get; }
+            }
+
+            internal class C : FI<object>
+            {
+                object FI<object>.Prop { get; }
+                dynamic FI<dynamic>.Prop { get; }
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs") }, targetFramework: TargetFramework.Net70);
+        comp.VerifyDiagnostics(
+            // F1.cs(6,16): error CS8646: 'FI<object>.Prop' is explicitly implemented more than once.
+            // internal class C : FI<object>
+            Diagnostic(ErrorCode.ERR_DuplicateExplicitImpl, "C").WithArguments("FI<object>.Prop").WithLocation(6, 16),
+            // F1.cs(9,13): error CS0540: 'C.FI<dynamic>.Prop': containing type does not implement interface 'FI<dynamic>'
+            //     dynamic FI<dynamic>.Prop { get; }
+            Diagnostic(ErrorCode.ERR_ClassDoesntImplementInterface, "FI<dynamic>").WithArguments("C.FI<dynamic>.Prop", "FI<dynamic>").WithLocation(9, 13)
+            );
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void InterfaceImplementation_07()
+    {
+        // Ensure that appropriate error is given for duplicate implementations which have a type difference which is insignificant to the runtime.
+        var source1 = """
+            using System;
+
+            file interface FI<T>
+            {
+                public T Prop { get; }
+            }
+
+            internal class C : FI<nint>, FI<IntPtr>
+            {
+                nint FI<nint>.Prop { get; }
+                IntPtr FI<IntPtr>.Prop { get; }
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs") }, targetFramework: TargetFramework.Net70);
+        comp.VerifyDiagnostics(
+            // F1.cs(8,16): error CS8646: 'FI<nint>.Prop' is explicitly implemented more than once.
+            // internal class C : FI<nint>, FI<IntPtr>
+            Diagnostic(ErrorCode.ERR_DuplicateExplicitImpl, "C").WithArguments("FI<nint>.Prop").WithLocation(8, 16),
+            // F1.cs(8,30): error CS0528: 'FI<nint>' is already listed in interface list
+            // internal class C : FI<nint>, FI<IntPtr>
+            Diagnostic(ErrorCode.ERR_DuplicateInterfaceInBaseList, "FI<IntPtr>").WithArguments("FI<nint>").WithLocation(8, 30),
+            // F1.cs(11,23): error CS0102: The type 'C' already contains a definition for '<F1>F2A62B10769F2595F65CAD631A41E2B54F5D1B3601B00884A41306FA9AD9BACDB__FI<nint>.Prop'
+            //     IntPtr FI<IntPtr>.Prop { get; }
+            Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "Prop").WithArguments("C", "<F1>F2A62B10769F2595F65CAD631A41E2B54F5D1B3601B00884A41306FA9AD9BACDB__FI<nint>.Prop").WithLocation(11, 23)
+            );
+    }
+
     [Fact]
     public void TypeArguments_01()
     {
@@ -2541,6 +2735,54 @@ file class C { }
             Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "C").WithArguments("C", "D2<T>").WithLocation(5, 36));
     }
 
+    [Fact]
+    public void Constraints_05()
+    {
+        var source = """
+            file class C<T> { }
+
+            class D
+            {
+                private void M<T>(T t) where T : C<int> { } // 1
+            }
+
+            file class E
+            {
+                private void M<T>(T t) where T : C<int> { } // ok
+            }
+            """;
+
+        var comp = CreateCompilation(source);
+        comp.VerifyDiagnostics(
+            // (5,38): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'D.M<T>(T)'.
+            //     private void M<T>(T t) where T : C<int> { } // 1
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "C<int>").WithArguments("C<int>", "D.M<T>(T)").WithLocation(5, 38));
+
+        var cInt = (ConstructedNamedTypeSymbol)comp.GetMember<MethodSymbol>("D.M").TypeParameters[0].ConstraintTypesNoUseSiteDiagnostics[0].Type;
+        Assert.True(cInt.IsFileLocal);
+    }
+
+    [Fact]
+    public void Constraints_06()
+    {
+        var source = """
+            file class C<T> { }
+
+            class D<T> where T : C<int> { } // 1
+
+            file class E<T> where T : C<int> { } // ok
+            """;
+
+        var comp = CreateCompilation(source);
+        comp.VerifyDiagnostics(
+            // (3,22): error CS9051: File-local type 'C<int>' cannot be used in a member signature in non-file-local type 'D<T>'.
+            // class D<T> where T : C<int> { } // 1
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "C<int>").WithArguments("C<int>", "D<T>").WithLocation(3, 22));
+
+        var cInt = (ConstructedNamedTypeSymbol)comp.GetMember<NamedTypeSymbol>("D").TypeParameters[0].ConstraintTypesNoUseSiteDiagnostics[0].Type;
+        Assert.True(cInt.IsFileLocal);
+    }
+
     [Fact]
     public void PrimaryConstructor_01()
     {
@@ -2882,6 +3124,41 @@ public static void Main()
                 Diagnostic(ErrorCode.ERR_NameNotInContext, "M").WithArguments("M").WithLocation(5, 9));
     }
 
+    [Fact]
+    public void GlobalUsingStatic_03()
+    {
+        var source = """
+            global using static C<int>;
+
+            file class C<T>
+            {
+                public static void M() { }
+            }
+            """;
+
+        var main = """
+            class Program
+            {
+                public static void Main()
+                {
+                    M();
+                }
+            }
+            """;
+
+        var compilation = CreateCompilation(new[] { (source, "file1.cs"), (main, "file2.cs") });
+        compilation.VerifyDiagnostics(
+            // file1.cs(1,1): hidden CS8019: Unnecessary using directive.
+            // global using static C<int>;
+            Diagnostic(ErrorCode.HDN_UnusedUsingDirective, "global using static C<int>;").WithLocation(1, 1),
+            // file1.cs(1,21): error CS9055: File-local type 'C<int>' cannot be used in a 'global using static' directive.
+            // global using static C<int>;
+            Diagnostic(ErrorCode.ERR_GlobalUsingStaticFileType, "C<int>").WithArguments("C<int>").WithLocation(1, 21),
+            // file2.cs(5,9): error CS0103: The name 'M' does not exist in the current context
+            //         M();
+            Diagnostic(ErrorCode.ERR_NameNotInContext, "M").WithArguments("M").WithLocation(5, 9));
+    }
+
     [Fact]
     public void UsingStatic_01()
     {
@@ -4022,4 +4299,463 @@ partial file class C { }
         var ex = Assert.Throws<ArgumentException>(() => CreateCompilation(new[] { tree, tree }));
         Assert.Equal("trees[1]", ex.ParamName);
     }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_01()
+    {
+        var source0 = """
+            var c = new C();
+            c.Use1();
+            c.Use2();
+            """;
+
+        var source1 = """
+            using System;
+
+            file interface FI
+            {
+                void M();
+            }
+
+            partial class C : FI
+            {
+                void FI.M() { Console.Write(1); }
+
+                public void Use1() { ((FI)this).M(); }
+            }
+            """;
+
+        var source2 = """
+            using System;
+
+            file interface FI
+            {
+                void M();
+            }
+
+            partial class C : FI
+            {
+                void FI.M() { Console.Write(2); }
+
+                public void Use2() { ((FI)this).M(); }
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source0, "F0.cs"), (source1, "F1.cs"), (source2, "F2.cs") }, expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_02()
+    {
+        var source1 = """
+            file interface FI
+            {
+                void M();
+            }
+
+            partial class C : FI
+            {
+                void FI.M() => throw null!;
+            }
+            """;
+
+        // Explicit implementation of 'FI.M()' in 'source1' does not implement 'FI.M()' in 'source2'.
+        var source2 = """
+            file interface FI
+            {
+                void M();
+            }
+
+            partial class C : FI
+            {
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs"), (source2, "F2.cs") });
+        comp.VerifyDiagnostics(
+            // F2.cs(6,19): error CS0535: 'C' does not implement interface member 'FI.M()'
+            // partial class C : FI
+            Diagnostic(ErrorCode.ERR_UnimplementedInterfaceMember, "FI").WithArguments("C", "FI.M()").WithLocation(6, 19));
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_03()
+    {
+        var source1 = """
+            using System.Collections.Generic;
+
+            file interface I
+            {
+                IReadOnlyDictionary<int, string> P { get; }
+            }
+
+            internal partial class C : I
+            {
+                private readonly Dictionary<int, string> _p = new() { { 1, "one" }, { 2, "two" } };
+                IReadOnlyDictionary<int, string> I.P => _p;
+            }
+            """;
+
+        var source2 = """
+            using System.Collections.Generic;
+
+            file interface I
+            {
+                IReadOnlyDictionary<int, string> P { get; }
+            }
+
+            internal partial class C : I
+            {
+                IReadOnlyDictionary<int, string> I.P => _p;
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs"), (source2, "F2.cs") });
+        comp.VerifyDiagnostics();
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_04()
+    {
+        var source1 = """
+            file interface I
+            {
+                int P { get; }
+            }
+
+            internal partial class C : I
+            {
+            }
+            """;
+
+        var source2 = """
+            file interface I
+            {
+                int P { get; }
+            }
+
+            internal partial class C : I
+            {
+                int I.P => 1;
+                int I.P => 2;
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs"), (source2, "F2.cs") });
+        comp.VerifyDiagnostics(
+            // F1.cs(6,24): error CS8646: 'I.P' is explicitly implemented more than once.
+            // internal partial class C : I
+            Diagnostic(ErrorCode.ERR_DuplicateExplicitImpl, "C").WithArguments("I.P").WithLocation(6, 24),
+            // F1.cs(6,28): error CS0535: 'C' does not implement interface member 'I.P'
+            // internal partial class C : I
+            Diagnostic(ErrorCode.ERR_UnimplementedInterfaceMember, "I").WithArguments("C", "I.P").WithLocation(6, 28),
+            // F2.cs(9,11): error CS0102: The type 'C' already contains a definition for '<F2>F141A34209AF0D3C8CA844A7D9A360C895EB14E557F17D27626C519D9BE96AF4A__I.P'
+            //     int I.P => 2;
+            Diagnostic(ErrorCode.ERR_DuplicateNameInClass, "P").WithArguments("C", "<F2>F141A34209AF0D3C8CA844A7D9A360C895EB14E557F17D27626C519D9BE96AF4A__I.P").WithLocation(9, 11));
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_05()
+    {
+        var source0 = """
+            var c = new C();
+            c.Use1();
+            c.Use2();
+            """;
+
+        var source1 = """
+            using System;
+
+            file interface FI
+            {
+                int Bar { get; }
+            }
+
+            internal partial class C : FI
+            {
+                int FI.Bar => 1;
+                public void Use1() => Console.Write(((FI)this).Bar);
+            }
+            """;
+
+        var source2 = """
+            using System;
+
+            file interface FI
+            {
+                int Bar { get; }
+            }
+
+            internal partial class C : FI
+            {
+                int FI.Bar => 2;
+                public void Use2() => Console.Write(((FI)this).Bar);
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source0, "F0.cs"), (source1, "F1.cs"), (source2, "F2.cs") }, expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_06()
+    {
+        var source0 = """
+            var c = new C();
+            c.Use1();
+            c.Use2();
+            """;
+
+        var source1 = """
+            using System;
+
+            file interface FI
+            {
+                event Action E;
+            }
+
+            internal partial class C : FI
+            {
+                event Action FI.E { add { Console.Write(1); } remove { } }
+                public void Use1() => ((FI)this).E += () => { };
+            }
+            """;
+
+        var source2 = """
+            using System;
+
+            file interface FI
+            {
+                event Action E;
+            }
+
+            internal partial class C : FI
+            {
+                event Action FI.E { add { Console.Write(2); } remove { } }
+                public void Use2() => ((FI)this).E += () => { };
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source0, "F0.cs"), (source1, "F1.cs"), (source2, "F2.cs") }, expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_07()
+    {
+        var source0 = """
+            var c = new C();
+            c.Use1();
+            c.Use2();
+            """;
+
+        var source1 = """
+            using System;
+
+            file interface FI
+            {
+                int this[int i] { get; }
+            }
+
+            internal partial class C : FI
+            {
+                int FI.this[int i] => 1;
+                public void Use1() => Console.Write(((FI)this)[0]);
+            }
+            """;
+
+        var source2 = """
+            using System;
+
+            file interface FI
+            {
+                int this[int i] { get; }
+            }
+
+            internal partial class C : FI
+            {
+                int FI.this[int i] => 2;
+                public void Use2() => Console.Write(((FI)this)[0]);
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source0, "F0.cs"), (source1, "F1.cs"), (source2, "F2.cs") }, expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_08()
+    {
+        // Test explicit implementation of a file interface operator in a partial type multiple times across files.
+        // File types can't be used in signatures of non-file types, so this scenario isn't allowed currently,
+        // but we'd like to make sure that redundant/invalid duplicate member name diagnostics aren't given here.
+        var source1 = """
+            file interface FI
+            {
+                static abstract int operator +(FI fi, int i);
+            }
+
+            internal partial class C : FI
+            {
+                static int FI.operator +(FI fi, int i) => throw null!; // 1
+            }
+            """;
+
+        var source2 = """
+            file interface FI
+            {
+                static abstract int operator +(FI fi, int i);
+            }
+
+            internal partial class C : FI
+            {
+                static int FI.operator +(FI fi, int i) => throw null!; // 2
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs"), (source2, "F2.cs") }, targetFramework: TargetFramework.Net70);
+        comp.VerifyDiagnostics(
+            // F2.cs(8,28): error CS9051: File-local type 'FI' cannot be used in a member signature in non-file-local type 'C'.
+            //     static int FI.operator +(FI fi, int i) => throw null!; // 2
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "+").WithArguments("FI", "C").WithLocation(8, 28),
+            // F1.cs(8,28): error CS9051: File-local type 'FI' cannot be used in a member signature in non-file-local type 'C'.
+            //     static int FI.operator +(FI fi, int i) => throw null!; // 1
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "+").WithArguments("FI", "C").WithLocation(8, 28)
+            );
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_09()
+    {
+        // Similar to PartialExplicitImplementation_08, except only one of the files contains duplicate operator implementations.
+        var source1 = """
+            file interface FI
+            {
+                static abstract int operator +(FI fi, int i);
+            }
+
+            internal partial class C : FI // 1, 2
+            {
+            }
+            """;
+
+        var source2 = """
+            file interface FI
+            {
+                static abstract int operator +(FI fi, int i);
+            }
+
+            internal partial class C : FI
+            {
+                static int FI.operator +(FI fi, int i) => throw null!; // 3
+                static int FI.operator +(FI fi, int i) => throw null!; // 4, 5
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs"), (source2, "F2.cs") }, targetFramework: TargetFramework.Net70);
+        comp.VerifyDiagnostics(
+            // F1.cs(6,24): error CS8646: 'FI.operator +(FI, int)' is explicitly implemented more than once.
+            // internal partial class C : FI // 1, 2
+            Diagnostic(ErrorCode.ERR_DuplicateExplicitImpl, "C").WithArguments("FI.operator +(FI, int)").WithLocation(6, 24),
+            // F1.cs(6,28): error CS0535: 'C' does not implement interface member 'FI.operator +(FI, int)'
+            // internal partial class C : FI // 1, 2
+            Diagnostic(ErrorCode.ERR_UnimplementedInterfaceMember, "FI").WithArguments("C", "FI.operator +(FI, int)").WithLocation(6, 28),
+            // F2.cs(8,28): error CS9051: File-local type 'FI' cannot be used in a member signature in non-file-local type 'C'.
+            //     static int FI.operator +(FI fi, int i) => throw null!; // 3
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "+").WithArguments("FI", "C").WithLocation(8, 28),
+            // F2.cs(9,28): error CS9051: File-local type 'FI' cannot be used in a member signature in non-file-local type 'C'.
+            //     static int FI.operator +(FI fi, int i) => throw null!; // 4, 5
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "+").WithArguments("FI", "C").WithLocation(9, 28),
+            // F2.cs(9,28): error CS0111: Type 'C' already defines a member called '<F2>F141A34209AF0D3C8CA844A7D9A360C895EB14E557F17D27626C519D9BE96AF4A__FI.op_Addition' with the same parameter types
+            //     static int FI.operator +(FI fi, int i) => throw null!; // 4, 5
+            Diagnostic(ErrorCode.ERR_MemberAlreadyExists, "+").WithArguments("<F2>F141A34209AF0D3C8CA844A7D9A360C895EB14E557F17D27626C519D9BE96AF4A__FI.op_Addition", "C").WithLocation(9, 28)
+            );
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_10()
+    {
+        // Test explicit implementation of a file interface operator in a partial type.
+        // In another file, implement a member in a type with the same source name, but with member name using the metadata name of the same operator.
+        // File types can't be used in signatures of non-file types, so this scenario isn't allowed currently,
+        // but we'd like to make sure that redundant/invalid duplicate member name diagnostics aren't given here.
+        var source1 = """
+            file interface FI
+            {
+                static abstract int operator +(FI fi, int i);
+            }
+
+            internal partial class C : FI
+            {
+                static int FI.operator +(FI fi, int i) => throw null!;
+            }
+            """;
+
+        var source2 = """
+            file interface FI
+            {
+                static abstract int op_Addition(FI fi, int i);
+            }
+
+            internal partial class C : FI
+            {
+                static int FI.op_Addition(FI fi, int i) => throw null!;
+            }
+            """;
+
+        var comp = CreateCompilation(new[] { (source1, "F1.cs"), (source2, "F2.cs") }, targetFramework: TargetFramework.Net70);
+        comp.VerifyDiagnostics(
+            // F2.cs(8,19): error CS9051: File-local type 'FI' cannot be used in a member signature in non-file-local type 'C'.
+            //     static int FI.op_Addition(FI fi, int i) => throw null!;
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "op_Addition").WithArguments("FI", "C").WithLocation(8, 19),
+            // F1.cs(8,28): error CS9051: File-local type 'FI' cannot be used in a member signature in non-file-local type 'C'.
+            //     static int FI.operator +(FI fi, int i) => throw null!;
+            Diagnostic(ErrorCode.ERR_FileTypeDisallowedInSignature, "+").WithArguments("FI", "C").WithLocation(8, 28)
+            );
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68219")]
+    public void PartialExplicitImplementation_11()
+    {
+        var source0 = """
+            var c = new C();
+            c.Use1();
+            c.Use2();
+
+            interface I<T>
+            {
+                void M();
+            }
+            """;
+
+        var source1 = """
+            using System;
+
+            file interface FI { }
+
+            partial class C : I<FI>
+            {
+                void I<FI>.M() { Console.Write(1); }
+
+                public void Use1() { ((I<FI>)this).M(); }
+            }
+            """;
+
+        var source2 = """
+            using System;
+
+            file interface FI { }
+
+            partial class C : I<FI>
+            {
+                void I<FI>.M() { Console.Write(2); }
+
+                public void Use2() { ((I<FI>)this).M(); }
+            }
+            """;
+
+        var verifier = CompileAndVerify(new[] { (source0, "F0.cs"), (source1, "F1.cs"), (source2, "F2.cs") }, expectedOutput: "12");
+        verifier.VerifyDiagnostics();
+    }
 }
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/Source/UsingAliasTests.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/Source/UsingAliasTests.cs
index d1b4321085c30..a1970eaf42c09 100644
--- a/src/Compilers/CSharp/Test/Symbol/Symbols/Source/UsingAliasTests.cs
+++ b/src/Compilers/CSharp/Test/Symbol/Symbols/Source/UsingAliasTests.cs
@@ -4,6 +4,7 @@
 
 #nullable disable
 
+using System;
 using System.Linq;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
@@ -969,5 +970,98 @@ void M()
                 }
                 """).VerifyDiagnostics();
         }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68546")]
+        public void AliasToArrayReferencedInUsingStatic()
+        {
+            CreateCompilation("""
+                using A = int[];
+
+                namespace N
+                {
+                    using static A;
+                }
+                """).VerifyDiagnostics(
+                    // (5,5): hidden CS8019: Unnecessary using directive.
+                    //     using static A;
+                    Diagnostic(ErrorCode.HDN_UnusedUsingDirective, "using static A;").WithLocation(5, 5),
+                    // (5,18): error CS9137: 'array' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate or namespace can be used.
+                    //     using static A;
+                    Diagnostic(ErrorCode.ERR_BadUsingStaticType, "A").WithArguments("array").WithLocation(5, 18));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68546")]
+        public void AliasToPointerReferencedInUsingStatic()
+        {
+            CreateCompilation("""
+                using unsafe A = int*;
+
+                namespace N
+                {
+                    using static A;
+                }
+                """, options: TestOptions.UnsafeDebugDll).VerifyDiagnostics(
+                    // (5,5): hidden CS8019: Unnecessary using directive.
+                    //     using static A;
+                    Diagnostic(ErrorCode.HDN_UnusedUsingDirective, "using static A;").WithLocation(5, 5),
+                    // (5,18): error CS9137: 'pointer' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate or namespace can be used.
+                    //     using static A;
+                    Diagnostic(ErrorCode.ERR_BadUsingStaticType, "A").WithArguments("pointer").WithLocation(5, 18));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68546")]
+        public void AliasToFunctionPointerReferencedInUsingStatic()
+        {
+            CreateCompilation("""
+                using unsafe A = delegate*<int,int>;
+
+                namespace N
+                {
+                    using static A;
+                }
+                """, options: TestOptions.UnsafeDebugDll).VerifyDiagnostics(
+                    // (5,5): hidden CS8019: Unnecessary using directive.
+                    //     using static A;
+                    Diagnostic(ErrorCode.HDN_UnusedUsingDirective, "using static A;").WithLocation(5, 5),
+                    // (5,18): error CS9137: 'function pointer' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate or namespace can be used.
+                    //     using static A;
+                    Diagnostic(ErrorCode.ERR_BadUsingStaticType, "A").WithArguments("function pointer").WithLocation(5, 18));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68546")]
+        public void AliasToDynamicReferencedInUsingStatic()
+        {
+            CreateCompilation("""
+                using A = dynamic;
+
+                namespace N
+                {
+                    using static A;
+                }
+                """).VerifyDiagnostics(
+                    // (5,5): hidden CS8019: Unnecessary using directive.
+                    //     using static A;
+                    Diagnostic(ErrorCode.HDN_UnusedUsingDirective, "using static A;").WithLocation(5, 5),
+                    // (5,18): error CS9137: 'dynamic' type is not valid for 'using static'. Only a class, struct, interface, enum, delegate or namespace can be used.
+                    //     using static A;
+                    Diagnostic(ErrorCode.ERR_BadUsingStaticType, "A").WithArguments("dynamic").WithLocation(5, 18));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/68546")]
+        public void AliasToTupleReferencedInUsingStatic()
+        {
+            // Allowed, as it's the same as `using A = System.ValueTuple<int, int>;`
+            CreateCompilation("""
+                using A = (int, int);
+
+                namespace N
+                {
+                    using static A;
+                }
+                """).VerifyDiagnostics(
+                    // (5,5): hidden CS8019: Unnecessary using directive.
+                    //     using static A;
+                    Diagnostic(ErrorCode.HDN_UnusedUsingDirective, "using static A;").WithLocation(5, 5));
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs b/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs
index 3eddc361b3951..a74c9a86b9f72 100644
--- a/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs
+++ b/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs
@@ -304,6 +304,10 @@ public void WarningLevel_2()
                         case ErrorCode.WRN_ParamsArrayInLambdaOnly:
                         case ErrorCode.WRN_CapturedPrimaryConstructorParameterPassedToBase:
                         case ErrorCode.WRN_UnreadPrimaryConstructorParameter:
+                        case ErrorCode.WRN_InterceptorSignatureMismatch:
+                        case ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor:
+                        case ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor:
+                        case ErrorCode.WRN_CapturedPrimaryConstructorParameterInFieldInitializer:
                             Assert.Equal(1, ErrorFacts.GetWarningLevel(errorCode));
                             break;
                         case ErrorCode.WRN_MainIgnored:
@@ -2937,6 +2941,17 @@ public void TestIsBuildOnlyDiagnostic()
                     case ErrorCode.ERR_EncUpdateFailedDelegateTypeChanged:
                     case ErrorCode.ERR_CannotBeConvertedToUtf8:
                     case ErrorCode.ERR_FileTypeNonUniquePath:
+                    case ErrorCode.ERR_InterceptorSignatureMismatch:
+                    case ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter:
+                    case ErrorCode.ERR_InterceptorMustNotHaveThisParameter:
+                    case ErrorCode.ERR_DuplicateInterceptor:
+                    case ErrorCode.WRN_InterceptorSignatureMismatch:
+                    case ErrorCode.ERR_InterceptorNotAccessible:
+                    case ErrorCode.ERR_InterceptorScopedMismatch:
+                    case ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor:
+                    case ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor:
+                    case ErrorCode.ERR_InterceptorCannotInterceptNameof:
+                    case ErrorCode.ERR_SymbolDefinedInAssembly:
                         Assert.True(isBuildOnly, $"Check failed for ErrorCode.{errorCode}");
                         break;
 
diff --git a/src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxFactoryTests.cs b/src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxFactoryTests.cs
index 7b014369bfcd8..1b3be501c2706 100644
--- a/src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxFactoryTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxFactoryTests.cs
@@ -27,6 +27,18 @@ public void AlternateVerbatimString()
             Assert.Equal("$@\"", token.ValueText);
         }
 
+        [Fact]
+        public void UsingDirective()
+        {
+            var someValidName = SyntaxFactory.ParseName("System.String");
+            var usingDirective = SyntaxFactory.UsingDirective(SyntaxFactory.Token(SyntaxKind.StaticKeyword), null, someValidName);
+            Assert.NotNull(usingDirective);
+            Assert.Equal(SyntaxKind.StaticKeyword, usingDirective.StaticKeyword.Kind());
+            Assert.Null(usingDirective.Alias);
+            Assert.Equal("System.String", usingDirective.Name.ToFullString());
+            Assert.Equal(SyntaxKind.SemicolonToken, usingDirective.SemicolonToken.Kind());
+        }
+
         [Fact]
         public void SyntaxTree()
         {
diff --git a/src/Compilers/Core/CodeAnalysisTest/CachingLookupTests.cs b/src/Compilers/Core/CodeAnalysisTest/CachingLookupTests.cs
index c29baf8a516c4..f4f090921febb 100644
--- a/src/Compilers/Core/CodeAnalysisTest/CachingLookupTests.cs
+++ b/src/Compilers/Core/CodeAnalysisTest/CachingLookupTests.cs
@@ -35,9 +35,9 @@ private int[] RandomNumbers(int length, int seed)
             return result;
         }
 
-        private HashSet<string> Keys(int[] numbers, bool randomCase, IEqualityComparer<string> comparer)
+        private SegmentedHashSet<string> Keys(int[] numbers, bool randomCase, IEqualityComparer<string> comparer)
         {
-            var keys = new HashSet<string>(comparer);
+            var keys = new SegmentedHashSet<string>(comparer);
             foreach (var n in numbers)
             {
                 keys.Add(GetKey(n, randomCase));
@@ -101,7 +101,7 @@ private void CheckEqualEnumerable<T>(IEnumerable<T> e1, IEnumerable<T> e2)
             }
         }
 
-        private void CompareLookups1(ILookup<string, int> look1, CachingDictionary<string, int> look2, HashSet<string> keys)
+        private void CompareLookups1(ILookup<string, int> look1, CachingDictionary<string, int> look2, SegmentedHashSet<string> keys)
         {
             foreach (string k in keys)
             {
@@ -118,7 +118,7 @@ private void CompareLookups1(ILookup<string, int> look1, CachingDictionary<strin
             }
         }
 
-        private void CompareLookups2(ILookup<string, int> look1, CachingDictionary<string, int> look2, HashSet<string> keys)
+        private void CompareLookups2(ILookup<string, int> look1, CachingDictionary<string, int> look2, SegmentedHashSet<string> keys)
         {
             foreach (string k in look1.Select(g => g.Key))
             {
@@ -133,7 +133,7 @@ private void CompareLookups2(ILookup<string, int> look1, CachingDictionary<strin
             Assert.Equal(look1.Count, look2.Count);
         }
 
-        private void CompareLookups2(CachingDictionary<string, int> look1, ILookup<string, int> look2, HashSet<string> keys)
+        private void CompareLookups2(CachingDictionary<string, int> look1, ILookup<string, int> look2, SegmentedHashSet<string> keys)
         {
             foreach (string k in look1.Keys)
             {
@@ -161,20 +161,20 @@ public void CachingLookupCorrectResults()
 
             var look1 = CreateLookup(numbers, false);
             var look2 = new CachingDictionary<string, int>(
-                s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+                s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                 (c) => Keys(numbers, false, comparer: c), comparer);
             CompareLookups1(look1, look2, Keys(numbers, false, comparer));
 
             look1 = CreateLookup(numbers, false);
             look2 = new CachingDictionary<string, int>(
-                s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+                s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                 (c) => Keys(numbers, false, comparer: c), comparer);
             CompareLookups2(look1, look2, Keys(numbers, false, comparer));
             CompareLookups1(look1, look2, Keys(numbers, false, comparer));
 
             look1 = CreateLookup(numbers, false);
             look2 = new CachingDictionary<string, int>(
-                s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+                s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                 (c) => Keys(numbers, false, comparer: c), comparer);
             CompareLookups2(look2, look1, Keys(numbers, false, comparer));
             CompareLookups1(look1, look2, Keys(numbers, false, comparer));
@@ -193,20 +193,20 @@ public void CachingLookupCaseInsensitive()
 
             var look1 = CreateLookup(numbers, true);
             var look2 = new CachingDictionary<string, int>(
-                s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+                s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                 (c) => Keys(numbers, true, comparer: c), comparer);
             CompareLookups1(look1, look2, Keys(numbers, true, comparer));
 
             look1 = CreateLookup(numbers, true);
             look2 = new CachingDictionary<string, int>(
-                s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+                s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                 (c) => Keys(numbers, true, comparer: c), comparer);
             CompareLookups2(look1, look2, Keys(numbers, true, comparer));
             CompareLookups1(look1, look2, Keys(numbers, true, comparer));
 
             look1 = CreateLookup(numbers, true);
             look2 = new CachingDictionary<string, int>(
-                s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+                s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                 (c) => Keys(numbers, true, comparer: c), comparer);
             CompareLookups2(look2, look1, Keys(numbers, true, comparer));
             CompareLookups1(look1, look2, Keys(numbers, true, comparer));
@@ -224,18 +224,18 @@ public void CachingLookupCaseInsensitiveNoCacheMissingKeys()
             }
 
             var look1 = CreateLookup(numbers, true);
-            var look2 = new CachingDictionary<string, int>(s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+            var look2 = new CachingDictionary<string, int>(s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                                                                         (c) => Keys(numbers, true, comparer: c), comparer);
             CompareLookups1(look1, look2, Keys(numbers, true, comparer));
 
             look1 = CreateLookup(numbers, true);
-            look2 = new CachingDictionary<string, int>(s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+            look2 = new CachingDictionary<string, int>(s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                                                    (c) => Keys(numbers, true, comparer: c), comparer);
             CompareLookups2(look1, look2, Keys(numbers, true, comparer));
             CompareLookups1(look1, look2, Keys(numbers, true, comparer));
 
             look1 = CreateLookup(numbers, true);
-            look2 = new CachingDictionary<string, int>(s => dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>(),
+            look2 = new CachingDictionary<string, int>(s => dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>(),
                                                    (c) => Keys(numbers, true, comparer: c), comparer);
             CompareLookups2(look2, look1, Keys(numbers, true, comparer));
             CompareLookups1(look1, look2, Keys(numbers, true, comparer));
@@ -260,7 +260,7 @@ public void CallExactlyOncePerKey()
             {
                 Assert.False(lookedUp.Contains(s));
                 lookedUp.Add(s);
-                return dict.ContainsKey(s) ? dict[s] : ImmutableArray.Create<int>();
+                return dict.TryGetValue(s, out var value) ? value : ImmutableArray.Create<int>();
             },
                  (c) =>
             {
@@ -313,9 +313,9 @@ ImmutableArray<FullyPopulateRaceHelper> getElementsOfKey(int id)
                 return ImmutableArray.Create<FullyPopulateRaceHelper>(new FullyPopulateRaceHelper());
             }
 
-            HashSet<int> getKeys(IEqualityComparer<int> comparer)
+            SegmentedHashSet<int> getKeys(IEqualityComparer<int> comparer)
             {
-                return new HashSet<int>(new[] { 1 }, comparer);
+                return new SegmentedHashSet<int>(new[] { 1 }, comparer);
             }
 
             FullyPopulateRaceHelper getItem()
@@ -356,9 +356,9 @@ ImmutableArray<FullyPopulateRaceHelper> getElementsOfKey(int id)
                 return ImmutableArray.Create<FullyPopulateRaceHelper>(new FullyPopulateRaceHelper());
             }
 
-            HashSet<int> getKeys(IEqualityComparer<int> comparer)
+            SegmentedHashSet<int> getKeys(IEqualityComparer<int> comparer)
             {
-                return new HashSet<int>(new[] { 1 }, comparer);
+                return new SegmentedHashSet<int>(new[] { 1 }, comparer);
             }
 
             FullyPopulateRaceHelper getItem()
diff --git a/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.Generic.Tests.cs b/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.Generic.Tests.cs
index f859e6145ff77..580da72026389 100644
--- a/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.Generic.Tests.cs
+++ b/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.Generic.Tests.cs
@@ -586,15 +586,15 @@ public void IEnumerable_Generic_Enumerator_Current_ReturnsSameObjectsOnDifferent
             // Ensures that the elements returned from enumeration are exactly the same collection of
             // elements returned from a previous enumeration
             IEnumerable<T> enumerable = GenericIEnumerableFactory(count);
-            Dictionary<T, int> firstValues = new Dictionary<T, int>(count);
-            Dictionary<T, int> secondValues = new Dictionary<T, int>(count);
+            HashSet<T> firstValues = new HashSet<T>(count);
+            HashSet<T> secondValues = new HashSet<T>(count);
             foreach (T item in enumerable)
-                firstValues[item] = firstValues.ContainsKey(item) ? firstValues[item]++ : 1;
+                Assert.True(firstValues.Add(item));
             foreach (T item in enumerable)
-                secondValues[item] = secondValues.ContainsKey(item) ? secondValues[item]++ : 1;
+                Assert.True(secondValues.Add(item));
             Assert.Equal(firstValues.Count, secondValues.Count);
-            foreach (T key in firstValues.Keys)
-                Assert.Equal(firstValues[key], secondValues[key]);
+            foreach (T item in firstValues)
+                Assert.True(secondValues.Contains(item));
         }
 
         [Theory]
diff --git a/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.NonGeneric.Tests.cs b/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.NonGeneric.Tests.cs
index b980dc272ff5c..7117c5156ed86 100644
--- a/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.NonGeneric.Tests.cs
+++ b/src/Compilers/Core/CodeAnalysisTest/Collections/List/IEnumerable.NonGeneric.Tests.cs
@@ -216,15 +216,15 @@ public void IEnumerable_NonGeneric_Enumerator_Current_ReturnsSameObjectsOnDiffer
             // Ensures that the elements returned from enumeration are exactly the same collection of
             // elements returned from a previous enumeration
             IEnumerable enumerable = NonGenericIEnumerableFactory(count);
-            Dictionary<object, int> firstValues = new Dictionary<object, int>(count);
-            Dictionary<object, int> secondValues = new Dictionary<object, int>(count);
+            HashSet<object> firstValues = new HashSet<object>(count);
+            HashSet<object> secondValues = new HashSet<object>(count);
             foreach (object item in enumerable)
-                firstValues[item] = firstValues.ContainsKey(item) ? firstValues[item]++ : 1;
+                Assert.True(firstValues.Add(item));
             foreach (object item in enumerable)
-                secondValues[item] = secondValues.ContainsKey(item) ? secondValues[item]++ : 1;
+                Assert.True(secondValues.Add(item));
             Assert.Equal(firstValues.Count, secondValues.Count);
-            foreach (object key in firstValues.Keys)
-                Assert.Equal(firstValues[key], secondValues[key]);
+            foreach (object item in firstValues)
+                Assert.True(secondValues.Contains(item));
         }
 
         [Theory]
diff --git a/src/Compilers/Core/CodeAnalysisTest/CorLibTypesTests.cs b/src/Compilers/Core/CodeAnalysisTest/CorLibTypesTests.cs
index f827959ab0bc0..dc3497183e8d9 100644
--- a/src/Compilers/Core/CodeAnalysisTest/CorLibTypesTests.cs
+++ b/src/Compilers/Core/CodeAnalysisTest/CorLibTypesTests.cs
@@ -71,6 +71,7 @@ public void SpecialTypeIsValueType()
 
             var knownMissingTypes = new HashSet<SpecialType>()
             {
+                SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute
             };
 
             for (var specialType = SpecialType.None + 1; specialType <= SpecialType.Count; specialType++)
diff --git a/src/Compilers/Core/MSBuildTask/CanonicalError.cs b/src/Compilers/Core/MSBuildTask/CanonicalError.cs
index e00471737bae2..1665fe561adf6 100644
--- a/src/Compilers/Core/MSBuildTask/CanonicalError.cs
+++ b/src/Compilers/Core/MSBuildTask/CanonicalError.cs
@@ -48,7 +48,6 @@ namespace Microsoft.CodeAnalysis.BuildTasks
     ///
     ///          &lt;text&gt; : warning [num]: &lt;msg&gt;
     /// </remarks>
-    /// <owner>JomoF</owner>
     internal static class CanonicalError
     {
         // Defines the main pattern for matching messages.
@@ -141,7 +140,6 @@ internal static class CanonicalError
         /// <summary>
         /// Represents the parts of a decomposed canonical message.
         /// </summary>
-        /// <owner>JomoF</owner>
         internal sealed class Parts
         {
             /// <summary>
@@ -237,7 +235,6 @@ internal Parts()
         /// </summary>
         /// <param name="value"></param>
         /// <returns>'value' converted to int or 0 if it can't be parsed or is negative</returns>
-        /// <owner>LukaszG</owner>
         private static int ConvertToIntWithDefault(string value)
         {
             int result;
@@ -255,7 +252,6 @@ private static int ConvertToIntWithDefault(string value)
         /// Decompose an error or warning message into constituent parts. If the message isn't in the canonical form, return null.
         /// </summary>
         /// <remarks>This method is thread-safe, because the Regex class is thread-safe (per MSDN).</remarks>
-        /// <owner>JomoF</owner>
         /// <param name="message"></param>
         /// <returns>Decomposed canonical message, or null.</returns>
         internal static Parts? Parse(string message)
diff --git a/src/Compilers/Core/MSBuildTask/Csc.cs b/src/Compilers/Core/MSBuildTask/Csc.cs
index 9a7d8cbc51277..ea3fd91183d84 100644
--- a/src/Compilers/Core/MSBuildTask/Csc.cs
+++ b/src/Compilers/Core/MSBuildTask/Csc.cs
@@ -459,7 +459,6 @@ internal static void AddReferencesToCommandLine(
         ///     thing for csc.exe, the IDE compiler cannot support it.  In this situation
         ///     the return value will also be false.
         /// </summary>
-        /// <owner>RGoel</owner>
         private bool InitializeHostCompiler(ICscHostObject cscHostObject)
         {
             bool success;
@@ -659,7 +658,6 @@ private bool InitializeHostCompiler(ICscHostObject cscHostObject)
         ///     NoActionReturnSuccess           Host compiler was already up-to-date, and we're done.
         ///     NoActionReturnFailure           Bad parameters were passed into the task.
         /// </summary>
-        /// <owner>RGoel</owner>
         protected override HostObjectInitializationStatus InitializeHostObject()
         {
             if (HostObject != null)
@@ -746,7 +744,6 @@ protected override HostObjectInitializationStatus InitializeHostObject()
         /// This method will get called during Execute() if a host object has been passed into the Csc
         /// task.  Returns true if the compilation succeeded, otherwise false.  
         /// </summary>
-        /// <owner>RGoel</owner>
         protected override bool CallHostObjectToExecute()
         {
             Debug.Assert(HostObject != null, "We should not be here if the host object has not been set.");
diff --git a/src/Compilers/Core/MSBuildTask/ManagedCompiler.cs b/src/Compilers/Core/MSBuildTask/ManagedCompiler.cs
index dc2b29dd2fb7b..fd7584f390acb 100644
--- a/src/Compilers/Core/MSBuildTask/ManagedCompiler.cs
+++ b/src/Compilers/Core/MSBuildTask/ManagedCompiler.cs
@@ -469,6 +469,12 @@ public string? LangVersion
             get { return (string?)_store[nameof(LangVersion)]; }
         }
 
+        public bool ReportIVTs
+        {
+            set { _store[nameof(ReportIVTs)] = value; }
+            get { return _store.GetOrDefault(nameof(ReportIVTs), false); }
+        }
+
         #endregion
 
         // ToolExe delegates back to ToolName if the override is not
@@ -905,6 +911,8 @@ protected internal virtual void AddResponseFileCommands(CommandLineBuilderExtens
 
             commandLine.AppendPlusOrMinusSwitch("/delaysign", _store, nameof(DelaySign));
 
+            commandLine.AppendWhenTrue("/reportivts", _store, nameof(ReportIVTs));
+
             commandLine.AppendSwitchWithInteger("/filealign:", _store, nameof(FileAlignment));
             commandLine.AppendSwitchIfNotNull("/generatedfilesout:", GeneratedFilesOutputPath);
             commandLine.AppendSwitchIfNotNull("/keycontainer:", KeyContainer);
@@ -1134,7 +1142,6 @@ protected bool HostCompilerSupportsAllParameters
         /// support a particular parameter or variation on a parameter.  So we log a comment,
         /// and set our state so we know not to call the host object to do the actual compilation.
         /// </summary>
-        /// <owner>RGoel</owner>
         protected void CheckHostObjectSupport
             (
             string parameterName,
@@ -1164,7 +1171,6 @@ internal void InitializeHostObjectSupportForNewSwitches(ITaskHost hostObject, re
         /// <summary>
         /// Checks to see whether all of the passed-in references exist on disk before we launch the compiler.
         /// </summary>
-        /// <owner>RGoel</owner>
         protected bool CheckAllReferencesExistOnDisk()
         {
             if (null == References)
diff --git a/src/Compilers/Core/MSBuildTask/Microsoft.CSharp.Core.targets b/src/Compilers/Core/MSBuildTask/Microsoft.CSharp.Core.targets
index 6d33c2c1b256c..6dbee25fc9a56 100644
--- a/src/Compilers/Core/MSBuildTask/Microsoft.CSharp.Core.targets
+++ b/src/Compilers/Core/MSBuildTask/Microsoft.CSharp.Core.targets
@@ -133,6 +133,7 @@
          References="@(ReferencePathWithRefAssemblies)"
          RefOnly="$(ProduceOnlyReferenceAssembly)"
          ReportAnalyzer="$(ReportAnalyzer)"
+         ReportIVTs="$(ReportIVTs)"
          Resources="@(_CoreCompileResourceInputs);@(CompiledLicenseFile)"
          ResponseFiles="$(CompilerResponseFile)"
          RuntimeMetadataVersion="$(RuntimeMetadataVersion)"
@@ -190,4 +191,4 @@
     <CommandLineArgsForDesignTimeEvaluation Condition="'$(ChecksumAlgorithm)' != ''">$(CommandLineArgsForDesignTimeEvaluation) -checksumalgorithm:$(ChecksumAlgorithm)</CommandLineArgsForDesignTimeEvaluation>
     <CommandLineArgsForDesignTimeEvaluation Condition="'$(DefineConstants)' != ''">$(CommandLineArgsForDesignTimeEvaluation) -define:$(DefineConstants)</CommandLineArgsForDesignTimeEvaluation>
   </PropertyGroup>
-</Project>
\ No newline at end of file
+</Project>
diff --git a/src/Compilers/Core/MSBuildTask/Microsoft.VisualBasic.Core.targets b/src/Compilers/Core/MSBuildTask/Microsoft.VisualBasic.Core.targets
index 1f280736a9597..0e6b49ddc15ce 100644
--- a/src/Compilers/Core/MSBuildTask/Microsoft.VisualBasic.Core.targets
+++ b/src/Compilers/Core/MSBuildTask/Microsoft.VisualBasic.Core.targets
@@ -99,6 +99,7 @@
          RefOnly="$(ProduceOnlyReferenceAssembly)"
          RemoveIntegerChecks="$(RemoveIntegerChecks)"
          ReportAnalyzer="$(ReportAnalyzer)"
+         ReportIVTs="$(ReportIVTs)"
          Resources="@(_CoreCompileResourceInputs);@(CompiledLicenseFile)"
          ResponseFiles="$(CompilerResponseFile)"
          RootNamespace="$(RootNamespace)"
diff --git a/src/Compilers/Core/MSBuildTask/Vbc.cs b/src/Compilers/Core/MSBuildTask/Vbc.cs
index 347293d634993..17038b1c24508 100644
--- a/src/Compilers/Core/MSBuildTask/Vbc.cs
+++ b/src/Compilers/Core/MSBuildTask/Vbc.cs
@@ -801,7 +801,6 @@ internal static string? GetDefineConstantsSwitch
         ///     thing for csc.exe, the IDE compiler cannot support it.  In this situation
         ///     the return value will also be false.
         /// </summary>
-        /// <owner>RGoel</owner>
         private bool InitializeHostCompiler(IVbcHostObject vbcHostObject)
         {
             this.HostCompilerSupportsAllParameters = this.UseHostCompilerIfAvailable;
@@ -1012,7 +1011,6 @@ private static bool DeferToICompilerOptionsHostObject(string? langVersion, IVbcH
         ///     NoActionReturnSuccess           Host compiler was already up-to-date, and we're done.
         ///     NoActionReturnFailure           Bad parameters were passed into the task.
         /// </summary>
-        /// <owner>RGoel</owner>
         protected override HostObjectInitializationStatus InitializeHostObject()
         {
             if (this.HostObject != null)
@@ -1099,7 +1097,6 @@ protected override HostObjectInitializationStatus InitializeHostObject()
         /// task.  Returns true if an appropriate host object was found, it was called to do the compile,
         /// and the compile succeeded.  Otherwise, we return false.
         /// </summary>
-        /// <owner>RGoel</owner>
         protected override bool CallHostObjectToExecute()
         {
             Debug.Assert(this.HostObject != null, "We should not be here if the host object has not been set.");
diff --git a/src/Compilers/Core/MSBuildTaskTests/CscTests.cs b/src/Compilers/Core/MSBuildTaskTests/CscTests.cs
index f3a6c128630c2..99c0fc0ed16fa 100644
--- a/src/Compilers/Core/MSBuildTaskTests/CscTests.cs
+++ b/src/Compilers/Core/MSBuildTaskTests/CscTests.cs
@@ -516,5 +516,13 @@ public void UnexpectedExceptionLogsMessage()
             });
             Assert.False(string.IsNullOrEmpty(engine.Log));
         }
+
+        [Fact]
+        public void ReportIVTsSwitch()
+        {
+            var csc = new Csc();
+            csc.ReportIVTs = true;
+            AssertEx.Equal("/reportivts", csc.GenerateResponseFileContents());
+        }
     }
 }
diff --git a/src/Compilers/Core/MSBuildTaskTests/TestUtilities/MSBuildUtil.cs b/src/Compilers/Core/MSBuildTaskTests/TestUtilities/MSBuildUtil.cs
index 17518299a9114..6874e3f667f73 100644
--- a/src/Compilers/Core/MSBuildTaskTests/TestUtilities/MSBuildUtil.cs
+++ b/src/Compilers/Core/MSBuildTaskTests/TestUtilities/MSBuildUtil.cs
@@ -33,7 +33,7 @@ public static ITaskItem CreateTaskItem(string fileName, Dictionary<string, strin
             taskItem.Setup(x => x.GetMetadata(It.IsAny<string>())).Returns<string>(s => s switch
             {
                 "FullPath" => fileName,
-                _ => metadata.ContainsKey(s) ? metadata[s] : string.Empty
+                _ => metadata.TryGetValue(s, out var value) ? value : string.Empty
             });
             return taskItem.Object;
         }
diff --git a/src/Compilers/Core/MSBuildTaskTests/VbcTests.cs b/src/Compilers/Core/MSBuildTaskTests/VbcTests.cs
index f00012c40e0e0..7f3a106a9e01c 100644
--- a/src/Compilers/Core/MSBuildTaskTests/VbcTests.cs
+++ b/src/Compilers/Core/MSBuildTaskTests/VbcTests.cs
@@ -511,5 +511,13 @@ public void UnexpectedExceptionLogsMessage()
             });
             Assert.False(string.IsNullOrEmpty(engine.Log));
         }
+
+        [Fact]
+        public void ReportIVTsSwitch()
+        {
+            var vbc = new Vbc();
+            vbc.ReportIVTs = true;
+            AssertEx.Equal("/optionstrict:custom /reportivts", vbc.GenerateResponseFileContents());
+        }
     }
 }
diff --git a/src/Compilers/Core/Portable/CodeAnalysisResources.resx b/src/Compilers/Core/Portable/CodeAnalysisResources.resx
index ae5e213f97839..f8b9c1b716a7f 100644
--- a/src/Compilers/Core/Portable/CodeAnalysisResources.resx
+++ b/src/Compilers/Core/Portable/CodeAnalysisResources.resx
@@ -759,4 +759,22 @@
   <data name="LineCannotBeGreaterThanEnd" xml:space="preserve">
     <value>The requested line number {0} must be less than the number of lines {1}.</value>
   </data>
-</root>
\ No newline at end of file
+  <data name="InternalsVisibleToHeaderSummary" xml:space="preserve">
+    <value>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</value>
+  </data>
+  <data name="InternalsVisibleToCurrentAssembly" xml:space="preserve">
+    <value>Current assembly: '{0}'</value>
+  </data>
+  <data name="InternalsVisibleToReferencedAssembly" xml:space="preserve">
+    <value>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</value>
+  </data>
+  <data name="InternalsVisibleToReferencedAssemblyDetails" xml:space="preserve">
+    <value>    Assembly name: '{0}'
+    Public Keys:</value>
+  </data>
+  <data name="Nothing" xml:space="preserve">
+    <value>Nothing</value>
+  </data>
+</root>
diff --git a/src/Compilers/Core/Portable/CodeGen/PrivateImplementationDetails.cs b/src/Compilers/Core/Portable/CodeGen/PrivateImplementationDetails.cs
index 4601d4b8daedb..2150191642108 100644
--- a/src/Compilers/Core/Portable/CodeGen/PrivateImplementationDetails.cs
+++ b/src/Compilers/Core/Portable/CodeGen/PrivateImplementationDetails.cs
@@ -38,6 +38,15 @@ internal sealed class PrivateImplementationDetails : DefaultTypeDef, Cci.INamesp
         internal const string SynthesizedThrowSwitchExpressionExceptionParameterlessFunctionName = "ThrowSwitchExpressionExceptionParameterless";
         internal const string SynthesizedThrowInvalidOperationExceptionFunctionName = "ThrowInvalidOperationException";
 
+        internal const string SynthesizedInlineArrayAsSpanName = "InlineArrayAsSpan";
+        internal const string SynthesizedInlineArrayAsReadOnlySpanName = "InlineArrayAsReadOnlySpan";
+
+        internal const string SynthesizedInlineArrayElementRefName = "InlineArrayElementRef";
+        internal const string SynthesizedInlineArrayElementRefReadOnlyName = "InlineArrayElementRefReadOnly";
+
+        internal const string SynthesizedInlineArrayFirstElementRefName = "InlineArrayFirstElementRef";
+        internal const string SynthesizedInlineArrayFirstElementRefReadOnlyName = "InlineArrayFirstElementRefReadOnly";
+
         private readonly CommonPEModuleBuilder _moduleBuilder;       //the module builder
         private readonly Cci.ITypeReference _systemObject;           //base type
         private readonly Cci.ITypeReference _systemValueType;        //base for nested structs
diff --git a/src/Compilers/Core/Portable/Collections/CachingDictionary.cs b/src/Compilers/Core/Portable/Collections/CachingDictionary.cs
index e8ea421d87418..f6219931b80be 100644
--- a/src/Compilers/Core/Portable/Collections/CachingDictionary.cs
+++ b/src/Compilers/Core/Portable/Collections/CachingDictionary.cs
@@ -31,7 +31,7 @@ internal class CachingDictionary<TKey, TElement>
         where TKey : notnull
     {
         private readonly Func<TKey, ImmutableArray<TElement>> _getElementsOfKey;
-        private readonly Func<IEqualityComparer<TKey>, HashSet<TKey>> _getKeys;
+        private readonly Func<IEqualityComparer<TKey>, SegmentedHashSet<TKey>> _getKeys;
         private readonly IEqualityComparer<TKey> _comparer;
 
         // The underlying dictionary. It may be null (indicating that nothing is cached), a ConcurrentDictionary
@@ -54,7 +54,7 @@ internal class CachingDictionary<TKey, TElement>
         /// <param name="comparer">A IEqualityComparer used to compare keys.</param>
         public CachingDictionary(
             Func<TKey, ImmutableArray<TElement>> getElementsOfKey,
-            Func<IEqualityComparer<TKey>, HashSet<TKey>> getKeys,
+            Func<IEqualityComparer<TKey>, SegmentedHashSet<TKey>> getKeys,
             IEqualityComparer<TKey> comparer)
         {
             _getElementsOfKey = getElementsOfKey;
diff --git a/src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs b/src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs
index e1f0fb1d5dbc7..79a0e48f2d9b8 100644
--- a/src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs
+++ b/src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs
@@ -848,52 +848,6 @@ public static int Sum<T>(this ImmutableArray<T> items, Func<T, int> selector)
             return sum;
         }
 
-        internal static Dictionary<K, ImmutableArray<T>> ToDictionary<K, T>(this ImmutableArray<T> items, Func<T, K> keySelector)
-            where K : notnull
-            where T : notnull
-        {
-            if (items.Length == 1)
-            {
-                T value = items[0];
-                return new Dictionary<K, ImmutableArray<T>>(1)
-                {
-                    {  keySelector(value), ImmutableArray.Create(value) },
-                };
-            }
-
-            if (items.Length == 0)
-            {
-                return new Dictionary<K, ImmutableArray<T>>();
-            }
-
-            // bucketize
-            // prevent reallocation. it may not have 'count' entries, but it won't have more. 
-            //
-            // We store a mapping from keys to either a single item (very common in practice as this is used from
-            // callers that maps names to symbols with that name, and most names are unique), or an array builder of items.
-
-            var accumulator = PooledDictionary<K, object>.GetInstance();
-            foreach (var item in items)
-            {
-                var key = keySelector(item);
-                AddToMultiValueDictionaryBuilder(accumulator, key, item);
-            }
-
-            var dictionary = new Dictionary<K, ImmutableArray<T>>(accumulator.Count);
-
-            // freeze
-            foreach (var pair in accumulator)
-            {
-                dictionary.Add(pair.Key, pair.Value is ArrayBuilder<T> arrayBuilder
-                    ? arrayBuilder.ToImmutableAndFree()
-                    : ImmutableArray.Create((T)pair.Value));
-            }
-
-            accumulator.Free();
-
-            return dictionary;
-        }
-
         internal static void AddToMultiValueDictionaryBuilder<K, T>(Dictionary<K, object> accumulator, K key, T item)
             where K : notnull
             where T : notnull
@@ -921,9 +875,9 @@ internal static void AddToMultiValueDictionaryBuilder<K, T>(Dictionary<K, object
             }
         }
 
-        internal static void CreateNameToMembersMap
-            <TNamespaceOrTypeSymbol, TNamedTypeSymbol, TNamespaceSymbol>
-            (Dictionary<string, object> dictionary, Dictionary<string, ImmutableArray<TNamespaceOrTypeSymbol>> result)
+        internal static void CreateNameToMembersMap<TKey, TNamespaceOrTypeSymbol, TNamedTypeSymbol, TNamespaceSymbol>
+            (Dictionary<TKey, object> dictionary, Dictionary<TKey, ImmutableArray<TNamespaceOrTypeSymbol>> result)
+            where TKey : notnull
             where TNamespaceOrTypeSymbol : class
             where TNamedTypeSymbol : class, TNamespaceOrTypeSymbol
             where TNamespaceSymbol : class, TNamespaceOrTypeSymbol
@@ -956,12 +910,13 @@ static ImmutableArray<TNamespaceOrTypeSymbol> createMembers(object value)
             }
         }
 
-        internal static Dictionary<string, ImmutableArray<TNamedTypeSymbol>> GetTypesFromMemberMap<TNamespaceOrTypeSymbol, TNamedTypeSymbol>
-            (Dictionary<string, ImmutableArray<TNamespaceOrTypeSymbol>> map, IEqualityComparer<string> comparer)
+        internal static Dictionary<TKey, ImmutableArray<TNamedTypeSymbol>> GetTypesFromMemberMap<TKey, TNamespaceOrTypeSymbol, TNamedTypeSymbol>
+            (Dictionary<TKey, ImmutableArray<TNamespaceOrTypeSymbol>> map, IEqualityComparer<TKey> comparer)
+            where TKey : notnull
             where TNamespaceOrTypeSymbol : class
             where TNamedTypeSymbol : class, TNamespaceOrTypeSymbol
         {
-            var dictionary = new Dictionary<string, ImmutableArray<TNamedTypeSymbol>>(comparer);
+            var dictionary = new Dictionary<TKey, ImmutableArray<TNamedTypeSymbol>>(comparer);
 
             foreach (var (name, members) in map)
             {
diff --git a/src/Compilers/Core/Portable/CommandLine/CommandLineArguments.cs b/src/Compilers/Core/Portable/CommandLine/CommandLineArguments.cs
index c74595ff8b4bd..cc79c598cd69f 100644
--- a/src/Compilers/Core/Portable/CommandLine/CommandLineArguments.cs
+++ b/src/Compilers/Core/Portable/CommandLine/CommandLineArguments.cs
@@ -181,6 +181,11 @@ public abstract class CommandLineArguments
         /// </value>
         public bool ReportAnalyzer { get; internal set; }
 
+        /// <summary>
+        /// Report additional information related to InternalsVisibleToAttributes for all assemblies the compiler sees in this compilation.
+        /// </summary>
+        public bool ReportInternalsVisibleToAttributes { get; internal set; }
+
         /// <value>
         /// Skip execution of <see cref="DiagnosticAnalyzer"/>s.
         /// </value>
diff --git a/src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs b/src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs
index b24b4feb787d2..00fc2831eea6b 100644
--- a/src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs
+++ b/src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs
@@ -18,6 +18,7 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Emit;
 using Microsoft.CodeAnalysis.PooledObjects;
+using Microsoft.CodeAnalysis.Symbols;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
@@ -599,6 +600,68 @@ private bool ReportDiagnostics(DiagnosticBag diagnostics, TextWriter consoleOutp
         internal bool ReportDiagnostics(IEnumerable<DiagnosticInfo> diagnostics, TextWriter consoleOutput, ErrorLogger? errorLoggerOpt, Compilation? compilation)
             => ReportDiagnostics(diagnostics.Select(info => Diagnostic.Create(info)), consoleOutput, errorLoggerOpt, compilation);
 
+        /// <summary>
+        /// Reports all IVT information for the given compilation and references, to aid in troubleshooting otherwise inexplicable IVT failures.
+        /// </summary>
+        private void ReportIVTInfos(TextWriter consoleOutput, ErrorLogger? errorLogger, Compilation compilation, ImmutableArray<Diagnostic> diagnostics)
+        {
+            // Annotate any bad accesses with what assemblies they came from, if they are from a foreign assembly
+            DiagnoseBadAccesses(consoleOutput, errorLogger, compilation, diagnostics);
+
+            consoleOutput.WriteLine();
+
+            // Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+            consoleOutput.WriteLine(CodeAnalysisResources.InternalsVisibleToHeaderSummary);
+
+            var currentAssembly = compilation.Assembly;
+            var currentAssemblyInternal = compilation.GetSymbolInternal<IAssemblySymbolInternal>(currentAssembly);
+
+            // Current assembly: '{0}'
+            consoleOutput.WriteLine(string.Format(CodeAnalysisResources.InternalsVisibleToCurrentAssembly, currentAssembly.Identity.GetDisplayName(fullKey: true)));
+
+            consoleOutput.WriteLine();
+
+            // Now, go through each of the referenced assemblies and print their IVT information.
+            foreach (var assembly in currentAssembly.Modules.First().ReferencedAssemblySymbols.OrderBy(a => a.Name))
+            {
+                // Assembly reference: '{0}'
+                //   Grants IVT to current assembly: {1}
+                //   Grants IVTs to:
+
+                var assemblyInternal = compilation.GetSymbolInternal<IAssemblySymbolInternal>(assembly);
+                bool grantsIvt = currentAssemblyInternal.AreInternalsVisibleToThisAssembly(assemblyInternal);
+
+                consoleOutput.WriteLine(string.Format(CodeAnalysisResources.InternalsVisibleToReferencedAssembly, assembly.Identity.GetDisplayName(fullKey: true), grantsIvt));
+
+                var enumerable = assemblyInternal.GetInternalsVisibleToAssemblyNames();
+
+                if (enumerable.Any())
+                {
+                    foreach (var simpleName in enumerable.OrderBy<string, string>(n => n))
+                    {
+                        //     Assembly name: '{0}'
+                        //     Public Keys:
+                        consoleOutput.WriteLine(string.Format(CodeAnalysisResources.InternalsVisibleToReferencedAssemblyDetails, simpleName));
+                        foreach (var key in assemblyInternal.GetInternalsVisibleToPublicKeys(simpleName).Select(k => AssemblyIdentity.PublicKeyToString(k)).OrderBy(k => k))
+                        {
+                            consoleOutput.Write("      ");
+                            consoleOutput.WriteLine(key);
+                        }
+                    }
+                }
+                else
+                {
+                    // Nothing
+                    consoleOutput.Write("    ");
+                    consoleOutput.WriteLine(CodeAnalysisResources.Nothing);
+                }
+
+                consoleOutput.WriteLine();
+            }
+        }
+
+        private protected abstract void DiagnoseBadAccesses(TextWriter consoleOutput, ErrorLogger? errorLogger, Compilation compilation, ImmutableArray<Diagnostic> diagnostics);
+
         /// <summary>
         /// Returns true if there are any error diagnostics in the bag which cannot be suppressed and
         /// are guaranteed to break the build.
@@ -913,12 +976,18 @@ private int RunCore(TextWriter consoleOutput, ErrorLogger? errorLogger, Cancella
                 }
             }
 
-            diagnostics.Free();
             if (Arguments.ReportAnalyzer)
             {
                 ReportAnalyzerUtil.Report(consoleOutput, analyzerDriver, driverTimingInfo, Culture, compilation.Options.ConcurrentBuild);
             }
 
+            if (Arguments.ReportInternalsVisibleToAttributes)
+            {
+                ReportIVTInfos(consoleOutput, errorLogger, compilation, diagnostics.ToReadOnly());
+            }
+
+            diagnostics.Free();
+
             return exitCode;
         }
 
diff --git a/src/Compilers/Core/Portable/Compilation/Compilation.cs b/src/Compilers/Core/Portable/Compilation/Compilation.cs
index 8b253b00a3d03..b5b25a1a25414 100644
--- a/src/Compilers/Core/Portable/Compilation/Compilation.cs
+++ b/src/Compilers/Core/Portable/Compilation/Compilation.cs
@@ -875,6 +875,9 @@ public Compilation ReplaceReference(MetadataReference oldReference, MetadataRefe
 
         protected abstract ISymbol? CommonGetAssemblyOrModuleSymbol(MetadataReference reference);
 
+        [return: NotNullIfNotNull(nameof(symbol))]
+        internal abstract TSymbol? GetSymbolInternal<TSymbol>(ISymbol? symbol) where TSymbol : class, ISymbolInternal;
+
         /// <summary>
         /// Gets the <see cref="MetadataReference"/> that corresponds to the assembly symbol.
         /// </summary>
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisResultBuilder.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisResultBuilder.cs
index 259d0c193ad59..a2673decbda91 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisResultBuilder.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisResultBuilder.cs
@@ -220,7 +220,7 @@ public void ApplySuppressionsAndStoreAnalysisResult(AnalysisScope analysisScope,
                             // Already stored analysis result for this analyzer for the analyzed file.
                             continue;
                         }
-                        else if (!analysisScope.FilterSpanOpt.HasValue)
+                        else if (!analysisScope.FilterSpanOpt.HasValue && !analysisScope.OriginalFilterSpan.HasValue)
                         {
                             // We have complete analysis result for this file.
                             // Mark this file as completely analyzed for this analyzer.
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisScope.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisScope.cs
index f3b2b9f847357..d7f251955cd6a 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisScope.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalysisScope.cs
@@ -25,6 +25,28 @@ internal class AnalysisScope
         public SourceOrAdditionalFile? FilterFileOpt { get; }
         public TextSpan? FilterSpanOpt { get; }
 
+        /// <summary>
+        /// Original filter file for the input analysis scope.
+        /// Normally, this is the same as <see cref="FilterFileOpt"/>,
+        /// except for SymbolStart/End action execution where original input
+        /// file/span for diagnostic request can require analyzing other files/spans
+        /// which have partial definitions for the symbol being analyzed.
+        /// This property is used to ensure that SymbolStart action and SymbolEnd
+        /// action both receive this same original filter file.
+        /// </summary>
+        public SourceOrAdditionalFile? OriginalFilterFile { get; }
+
+        /// <summary>
+        /// Original filter span for the input analysis scope.
+        /// Normally, this is the same as <see cref="FilterSpanOpt"/>,
+        /// except for SymbolStart/End action execution where original input
+        /// file/span for diagnostic request can require analyzing other files/spans
+        /// which have partial definitions for the symbol being analyzed.
+        /// This property is used to ensure that SymbolStart action and SymbolEnd
+        /// action both receive this same original filter span.
+        /// </summary>
+        public TextSpan? OriginalFilterSpan { get; }
+
         public ImmutableArray<DiagnosticAnalyzer> Analyzers { get; }
 
         /// <summary>
@@ -88,49 +110,70 @@ private static AnalysisScope Create(Compilation compilation, AnalyzerOptions? an
         {
             var additionalFiles = analyzerOptions?.AdditionalFiles ?? ImmutableArray<AdditionalText>.Empty;
             return new AnalysisScope(compilation.CommonSyntaxTrees, additionalFiles,
-                   analyzers, hasAllAnalyzers, filterFile: null, filterSpanOpt: null, isSyntacticSingleFileAnalysis: false,
+                   analyzers, hasAllAnalyzers, filterFile: null, filterSpanOpt: null,
+                   originalFilterFile: null, originalFilterSpan: null, isSyntacticSingleFileAnalysis: false,
                    concurrentAnalysis: concurrentAnalysis);
         }
 
         public static AnalysisScope Create(ImmutableArray<DiagnosticAnalyzer> analyzers, SourceOrAdditionalFile filterFile, TextSpan? filterSpan, bool isSyntacticSingleFileAnalysis, CompilationWithAnalyzers compilationWithAnalyzers)
+            => Create(analyzers, filterFile, filterSpan, originalFilterFile: filterFile, originalFilterSpan: filterSpan, isSyntacticSingleFileAnalysis, compilationWithAnalyzers);
+
+        public static AnalysisScope Create(ImmutableArray<DiagnosticAnalyzer> analyzers, SourceOrAdditionalFile filterFile, TextSpan? filterSpan, SourceOrAdditionalFile originalFilterFile, TextSpan? originalFilterSpan, bool isSyntacticSingleFileAnalysis, CompilationWithAnalyzers compilationWithAnalyzers)
         {
             var trees = filterFile.SourceTree != null ? ImmutableArray.Create(filterFile.SourceTree) : ImmutableArray<SyntaxTree>.Empty;
             var additionalFiles = filterFile.AdditionalFile != null ? ImmutableArray.Create(filterFile.AdditionalFile) : ImmutableArray<AdditionalText>.Empty;
             var hasAllAnalyzers = ComputeHasAllAnalyzers(analyzers, compilationWithAnalyzers);
             var concurrentAnalysis = compilationWithAnalyzers.AnalysisOptions.ConcurrentAnalysis;
-            return new AnalysisScope(trees, additionalFiles, analyzers, hasAllAnalyzers, filterFile, filterSpan, isSyntacticSingleFileAnalysis, concurrentAnalysis);
+            return new AnalysisScope(trees, additionalFiles, analyzers, hasAllAnalyzers, filterFile, filterSpan, originalFilterFile, originalFilterSpan, isSyntacticSingleFileAnalysis, concurrentAnalysis);
         }
 
-        private AnalysisScope(ImmutableArray<SyntaxTree> trees, ImmutableArray<AdditionalText> additionalFiles, ImmutableArray<DiagnosticAnalyzer> analyzers, bool hasAllAnalyzers, SourceOrAdditionalFile? filterFile, TextSpan? filterSpanOpt, bool isSyntacticSingleFileAnalysis, bool concurrentAnalysis)
+        private AnalysisScope(
+            ImmutableArray<SyntaxTree> trees,
+            ImmutableArray<AdditionalText> additionalFiles,
+            ImmutableArray<DiagnosticAnalyzer> analyzers,
+            bool hasAllAnalyzers,
+            SourceOrAdditionalFile? filterFile,
+            TextSpan? filterSpanOpt,
+            SourceOrAdditionalFile? originalFilterFile,
+            TextSpan? originalFilterSpan,
+            bool isSyntacticSingleFileAnalysis,
+            bool concurrentAnalysis)
         {
-            Debug.Assert(!filterSpanOpt.HasValue || filterFile.HasValue);
             Debug.Assert(!isSyntacticSingleFileAnalysis || filterFile.HasValue);
 
-            if (filterSpanOpt.HasValue)
+            SyntaxTrees = trees;
+            AdditionalFiles = additionalFiles;
+            Analyzers = analyzers;
+            HasAllAnalyzers = hasAllAnalyzers;
+            FilterFileOpt = filterFile;
+            FilterSpanOpt = GetEffectiveFilterSpan(filterSpanOpt, filterFile);
+            OriginalFilterFile = originalFilterFile;
+            OriginalFilterSpan = GetEffectiveFilterSpan(originalFilterSpan, originalFilterFile);
+            IsSyntacticSingleFileAnalysis = isSyntacticSingleFileAnalysis;
+            ConcurrentAnalysis = concurrentAnalysis;
+
+            _lazyAnalyzersSet = new Lazy<ImmutableHashSet<DiagnosticAnalyzer>>(CreateAnalyzersSet);
+        }
+
+        private static TextSpan? GetEffectiveFilterSpan(TextSpan? filterSpan, SourceOrAdditionalFile? filterFile)
+        {
+            Debug.Assert(!filterSpan.HasValue || filterFile.HasValue);
+
+            if (filterSpan.HasValue && filterFile.GetValueOrDefault().SourceTree != null)
             {
                 Debug.Assert(filterFile.HasValue);
-                Debug.Assert(filterFile.GetValueOrDefault().SourceTree != null);
 
                 // PERF: Clear out filter span if the span length is equal to the entire tree span, and the filter span starts at 0.
                 //       We are basically analyzing the entire tree, and clearing out the filter span
                 //       avoids span intersection checks for each symbol/node/operation in the tree
                 //       to determine if it falls in the analysis scope.
-                if (filterSpanOpt.GetValueOrDefault().Start == 0 && filterSpanOpt.GetValueOrDefault().Length == filterFile.GetValueOrDefault().SourceTree!.Length)
+                if (filterSpan.GetValueOrDefault().Start == 0 && filterSpan.GetValueOrDefault().Length == filterFile.GetValueOrDefault().SourceTree!.Length)
                 {
-                    filterSpanOpt = null;
+                    return null;
                 }
             }
 
-            SyntaxTrees = trees;
-            AdditionalFiles = additionalFiles;
-            Analyzers = analyzers;
-            HasAllAnalyzers = hasAllAnalyzers;
-            FilterFileOpt = filterFile;
-            FilterSpanOpt = filterSpanOpt;
-            IsSyntacticSingleFileAnalysis = isSyntacticSingleFileAnalysis;
-            ConcurrentAnalysis = concurrentAnalysis;
-
-            _lazyAnalyzersSet = new Lazy<ImmutableHashSet<DiagnosticAnalyzer>>(CreateAnalyzersSet);
+            return filterSpan;
         }
 
         private ImmutableHashSet<DiagnosticAnalyzer> CreateAnalyzersSet() => Analyzers.ToImmutableHashSet();
@@ -149,7 +192,7 @@ public bool Contains(DiagnosticAnalyzer analyzer)
         public AnalysisScope WithAnalyzers(ImmutableArray<DiagnosticAnalyzer> analyzers, CompilationWithAnalyzers compilationWithAnalyzers)
         {
             var hasAllAnalyzers = ComputeHasAllAnalyzers(analyzers, compilationWithAnalyzers);
-            return new AnalysisScope(SyntaxTrees, AdditionalFiles, analyzers, hasAllAnalyzers, FilterFileOpt, FilterSpanOpt, IsSyntacticSingleFileAnalysis, ConcurrentAnalysis);
+            return new AnalysisScope(SyntaxTrees, AdditionalFiles, analyzers, hasAllAnalyzers, FilterFileOpt, FilterSpanOpt, OriginalFilterFile, OriginalFilterSpan, IsSyntacticSingleFileAnalysis, ConcurrentAnalysis);
         }
 
         private static bool ComputeHasAllAnalyzers(ImmutableArray<DiagnosticAnalyzer> analyzers, CompilationWithAnalyzers compilationWithAnalyzers)
@@ -165,7 +208,7 @@ private static bool ComputeHasAllAnalyzers(ImmutableArray<DiagnosticAnalyzer> an
         }
 
         public AnalysisScope WithFilterSpan(TextSpan? filterSpan)
-            => new AnalysisScope(SyntaxTrees, AdditionalFiles, Analyzers, HasAllAnalyzers, FilterFileOpt, filterSpan, IsSyntacticSingleFileAnalysis, ConcurrentAnalysis);
+            => new AnalysisScope(SyntaxTrees, AdditionalFiles, Analyzers, HasAllAnalyzers, FilterFileOpt, filterSpan, OriginalFilterFile, OriginalFilterSpan, IsSyntacticSingleFileAnalysis, ConcurrentAnalysis);
 
         public static bool ShouldSkipSymbolAnalysis(SymbolDeclaredCompilationEvent symbolEvent)
         {
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs
index 3e70f952c9a66..b89f08033a046 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs
@@ -785,7 +785,7 @@ private void ExecuteAdditionalFileActions(AnalysisScope analysisScope, Cancellat
                     cancellationToken.ThrowIfCancellationRequested();
 
                     // Execute actions for a given analyzer sequentially.
-                    AnalyzerExecutor.ExecuteAdditionalFileActions(additionalFileActions, analyzer, file, cancellationToken);
+                    AnalyzerExecutor.ExecuteAdditionalFileActions(additionalFileActions, analyzer, file, analysisScope.FilterSpanOpt, cancellationToken);
                 }
             }
         }
@@ -1575,10 +1575,10 @@ private async Task ProcessEventAsync(CompilationEvent e, AnalysisScope analysisS
                     return;
             }
 
-            await OnEventProcessedCoreAsync(e, processedAnalyzers, cancellationToken).ConfigureAwait(false);
+            await OnEventProcessedCoreAsync(e, processedAnalyzers, analysisScope, cancellationToken).ConfigureAwait(false);
         }
 
-        private async Task OnEventProcessedCoreAsync(CompilationEvent compilationEvent, ImmutableArray<DiagnosticAnalyzer> processedAnalyzers, CancellationToken cancellationToken)
+        private async Task OnEventProcessedCoreAsync(CompilationEvent compilationEvent, ImmutableArray<DiagnosticAnalyzer> processedAnalyzers, AnalysisScope analysisScope, CancellationToken cancellationToken)
         {
             switch (compilationEvent)
             {
@@ -1627,9 +1627,10 @@ async Task processContainerOnMemberCompletedAsync(INamespaceOrTypeSymbol contain
             {
                 if (containerSymbol != null &&
                     AnalyzerExecutor.TryExecuteSymbolEndActionsForContainer(containerSymbol, processedMemberSymbol,
-                        analyzer, s_getTopmostNodeForAnalysis, IsGeneratedCodeSymbol(containerSymbol, cancellationToken), cancellationToken, out var processedContainerEvent))
+                        analyzer, s_getTopmostNodeForAnalysis, IsGeneratedCodeSymbol(containerSymbol, cancellationToken),
+                        analysisScope.OriginalFilterFile?.SourceTree, analysisScope.OriginalFilterSpan, cancellationToken, out var processedContainerEvent))
                 {
-                    await OnEventProcessedCoreAsync(processedContainerEvent, ImmutableArray.Create(analyzer), cancellationToken).ConfigureAwait(false);
+                    await OnEventProcessedCoreAsync(processedContainerEvent, ImmutableArray.Create(analyzer), analysisScope, cancellationToken).ConfigureAwait(false);
                 }
             }
         }
@@ -1723,7 +1724,7 @@ private void ExecuteSymbolActions(SymbolDeclaredCompilationEvent symbolEvent, An
                 // Invoke symbol analyzers only for source symbols.
                 if ((int)symbol.Kind < actionsByKind.Length)
                 {
-                    AnalyzerExecutor.ExecuteSymbolActions(actionsByKind[(int)symbol.Kind], analyzer, symbolEvent, s_getTopmostNodeForAnalysis, isGeneratedCodeSymbol, cancellationToken);
+                    AnalyzerExecutor.ExecuteSymbolActions(actionsByKind[(int)symbol.Kind], analyzer, symbolEvent, s_getTopmostNodeForAnalysis, isGeneratedCodeSymbol, analysisScope.FilterFileOpt?.SourceTree, analysisScope.FilterSpanOpt, cancellationToken);
                 }
             }
         }
@@ -1763,7 +1764,7 @@ private bool TryExecuteSymbolEndActions(
 
                     var symbolEndActionsForAnalyzer = groupedActions.ToImmutableArrayOrEmpty();
                     if (!symbolEndActionsForAnalyzer.IsEmpty &&
-                        !AnalyzerExecutor.TryExecuteSymbolEndActions(symbolEndActionsForAnalyzer, analyzer, symbolEvent, s_getTopmostNodeForAnalysis, isGeneratedCodeSymbol, cancellationToken))
+                        !AnalyzerExecutor.TryExecuteSymbolEndActions(symbolEndActionsForAnalyzer, analyzer, symbolEvent, s_getTopmostNodeForAnalysis, isGeneratedCodeSymbol, analysisScope.OriginalFilterFile?.SourceTree, analysisScope.OriginalFilterSpan, cancellationToken))
                     {
                         success = false;
                         continue;
@@ -2043,7 +2044,7 @@ private async ValueTask<IGroupedAnalyzerActions> GetPerSymbolAnalyzerActionsAsyn
                     continue;
                 }
 
-                var analyzerActions = await GetPerSymbolAnalyzerActionsAsync(symbol, analyzer, cancellationToken).ConfigureAwait(false);
+                var analyzerActions = await GetPerSymbolAnalyzerActionsAsync(symbol, analyzer, analysisScope.OriginalFilterFile?.SourceTree, analysisScope.OriginalFilterSpan, cancellationToken).ConfigureAwait(false);
                 if (!analyzerActions.IsEmpty)
                 {
                     allActions = allActions.Append(analyzerActions);
@@ -2059,6 +2060,8 @@ private async ValueTask<IGroupedAnalyzerActions> GetPerSymbolAnalyzerActionsAsyn
         private async ValueTask<IGroupedAnalyzerActions> GetPerSymbolAnalyzerActionsAsync(
             ISymbol symbol,
             DiagnosticAnalyzer analyzer,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
             Debug.Assert(AnalyzerActions.SymbolStartActionsCount > 0);
@@ -2073,7 +2076,7 @@ private async ValueTask<IGroupedAnalyzerActions> GetPerSymbolAnalyzerActionsAsyn
             // For member symbols, we do not want to cache as we will not reach this path again.
             if (symbol is not INamespaceOrTypeSymbol namespaceOrType)
             {
-                return await getAllActionsAsync(this, symbol, analyzer, cancellationToken).ConfigureAwait(false);
+                return await getAllActionsAsync(this, symbol, analyzer, filterTree, filterSpan, cancellationToken).ConfigureAwait(false);
             }
 
             if (PerSymbolAnalyzerActionsCache.TryGetValue((namespaceOrType, analyzer), out var actions))
@@ -2081,16 +2084,16 @@ private async ValueTask<IGroupedAnalyzerActions> GetPerSymbolAnalyzerActionsAsyn
                 return actions;
             }
 
-            var allActions = await getAllActionsAsync(this, symbol, analyzer, cancellationToken).ConfigureAwait(false);
+            var allActions = await getAllActionsAsync(this, symbol, analyzer, filterTree, filterSpan, cancellationToken).ConfigureAwait(false);
             return PerSymbolAnalyzerActionsCache.GetOrAdd((namespaceOrType, analyzer), allActions);
 
-            async ValueTask<IGroupedAnalyzerActions> getAllActionsAsync(AnalyzerDriver driver, ISymbol symbol, DiagnosticAnalyzer analyzer, CancellationToken cancellationToken)
+            async ValueTask<IGroupedAnalyzerActions> getAllActionsAsync(AnalyzerDriver driver, ISymbol symbol, DiagnosticAnalyzer analyzer, SyntaxTree? filterTree, TextSpan? filterSpan, CancellationToken cancellationToken)
             {
                 // Compute additional inherited actions for this symbol by running the containing symbol's start actions.
-                var inheritedActions = await getInheritedActionsAsync(driver, symbol, analyzer, cancellationToken).ConfigureAwait(false);
+                var inheritedActions = await getInheritedActionsAsync(driver, symbol, analyzer, filterTree, filterSpan, cancellationToken).ConfigureAwait(false);
 
                 // Execute the symbol start actions for this symbol to compute additional actions for its members.
-                AnalyzerActions myActions = await getSymbolActionsCoreAsync(driver, symbol, analyzer, cancellationToken).ConfigureAwait(false);
+                AnalyzerActions myActions = await getSymbolActionsCoreAsync(driver, symbol, analyzer, filterTree, filterSpan, cancellationToken).ConfigureAwait(false);
                 if (myActions.IsEmpty)
                 {
                     return inheritedActions;
@@ -2100,12 +2103,12 @@ async ValueTask<IGroupedAnalyzerActions> getAllActionsAsync(AnalyzerDriver drive
                 return CreateGroupedActions(analyzer, allActions);
             }
 
-            async ValueTask<IGroupedAnalyzerActions> getInheritedActionsAsync(AnalyzerDriver driver, ISymbol symbol, DiagnosticAnalyzer analyzer, CancellationToken cancellationToken)
+            async ValueTask<IGroupedAnalyzerActions> getInheritedActionsAsync(AnalyzerDriver driver, ISymbol symbol, DiagnosticAnalyzer analyzer, SyntaxTree? filterTree, TextSpan? filterSpan, CancellationToken cancellationToken)
             {
                 if (symbol.ContainingSymbol != null)
                 {
                     // Get container symbol's per-symbol actions, which also forces its start actions to execute.
-                    var containerActions = await driver.GetPerSymbolAnalyzerActionsAsync(symbol.ContainingSymbol, analyzer, cancellationToken).ConfigureAwait(false);
+                    var containerActions = await driver.GetPerSymbolAnalyzerActionsAsync(symbol.ContainingSymbol, analyzer, filterTree, filterSpan, cancellationToken).ConfigureAwait(false);
                     if (!containerActions.IsEmpty)
                     {
                         // Don't inherit actions for nested type and namespace from its containing type and namespace respectively.
@@ -2124,7 +2127,7 @@ async ValueTask<IGroupedAnalyzerActions> getInheritedActionsAsync(AnalyzerDriver
                 return EmptyGroupedActions;
             }
 
-            static async ValueTask<AnalyzerActions> getSymbolActionsCoreAsync(AnalyzerDriver driver, ISymbol symbol, DiagnosticAnalyzer analyzer, CancellationToken cancellationToken)
+            static async ValueTask<AnalyzerActions> getSymbolActionsCoreAsync(AnalyzerDriver driver, ISymbol symbol, DiagnosticAnalyzer analyzer, SyntaxTree? filterTree, TextSpan? filterSpan, CancellationToken cancellationToken)
             {
                 if (!driver.UnsuppressedAnalyzers.Contains(analyzer))
                 {
@@ -2137,7 +2140,7 @@ static async ValueTask<AnalyzerActions> getSymbolActionsCoreAsync(AnalyzerDriver
                     return AnalyzerActions.Empty;
                 }
 
-                return await driver.AnalyzerManager.GetPerSymbolAnalyzerActionsAsync(symbol, isGeneratedCodeSymbol, analyzer, driver.AnalyzerExecutor, cancellationToken).ConfigureAwait(false);
+                return await driver.AnalyzerManager.GetPerSymbolAnalyzerActionsAsync(symbol, isGeneratedCodeSymbol, filterTree, filterSpan, analyzer, driver.AnalyzerExecutor, cancellationToken).ConfigureAwait(false);
             }
         }
 
@@ -2570,7 +2573,7 @@ void executeSyntaxNodeActions(
                     AnalyzerExecutor.ExecuteSyntaxNodeActions(
                         filteredNodesToAnalyze, groupedActionsForAnalyzer.NodeActionsByAnalyzerAndKind,
                         analyzer, semanticModel, _getKind, declarationAnalysisData.TopmostNodeForAnalysis.FullSpan,
-                        symbol, isInGeneratedCode, hasCodeBlockStartOrSymbolStartActions: groupedActionsForAnalyzer.HasCodeBlockStartActions || arePerSymbolActions,
+                        symbol, analysisScope.FilterSpanOpt, isInGeneratedCode, hasCodeBlockStartOrSymbolStartActions: groupedActionsForAnalyzer.HasCodeBlockStartActions || arePerSymbolActions,
                         cancellationToken);
                 }
             }
@@ -2679,7 +2682,7 @@ void executeOperationsActionsByKind(ImmutableArray<IOperation> operationsToAnaly
 
                     AnalyzerExecutor.ExecuteOperationActions(filteredOperationsToAnalyze, operationActionsByKind,
                         analyzer, semanticModel, declarationAnalysisData.TopmostNodeForAnalysis.FullSpan,
-                        symbol, isInGeneratedCode, hasOperationBlockStartOrSymbolStartActions: groupedActionsForAnalyzer.HasOperationBlockStartActions || arePerSymbolActions,
+                        symbol, analysisScope.FilterSpanOpt, isInGeneratedCode, hasOperationBlockStartOrSymbolStartActions: groupedActionsForAnalyzer.HasOperationBlockStartActions || arePerSymbolActions,
                         cancellationToken);
                 }
             }
@@ -2708,7 +2711,7 @@ void executeOperationsBlockActions(ImmutableArray<IOperation> operationBlocksToA
                     AnalyzerExecutor.ExecuteOperationBlockActions(
                         analyzerActions.OperationBlockStartActions, analyzerActions.OperationBlockActions,
                         analyzerActions.OperationBlockEndActions, analyzerActions.Analyzer, declarationAnalysisData.TopmostNodeForAnalysis, symbol,
-                        operationBlocksToAnalyze, operationsToAnalyze, semanticModel, isInGeneratedCode, cancellationToken);
+                        operationBlocksToAnalyze, operationsToAnalyze, semanticModel, analysisScope.FilterSpanOpt, isInGeneratedCode, cancellationToken);
                 }
             }
 
@@ -2736,7 +2739,7 @@ void executeCodeBlockActions(ImmutableArray<SyntaxNode> executableCodeBlocks, IE
                     AnalyzerExecutor.ExecuteCodeBlockActions(
                         analyzerActions.CodeBlockStartActions, analyzerActions.CodeBlockActions,
                         analyzerActions.CodeBlockEndActions, analyzerActions.Analyzer, declarationAnalysisData.TopmostNodeForAnalysis, symbol,
-                        executableCodeBlocks, semanticModel, _getKind, isInGeneratedCode, cancellationToken);
+                        executableCodeBlocks, semanticModel, _getKind, analysisScope.FilterSpanOpt, isInGeneratedCode, cancellationToken);
                 }
             }
 
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs
index c5f9321f2543b..c2e3cad8ebd31 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs
@@ -242,6 +242,8 @@ public void ExecuteSymbolStartActions(
             ImmutableArray<SymbolStartAnalyzerAction> actions,
             HostSymbolStartAnalysisScope symbolScope,
             bool isGeneratedCodeSymbol,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
             if (isGeneratedCodeSymbol && _shouldSkipAnalysisOnGeneratedCode(analyzer) ||
@@ -256,7 +258,7 @@ public void ExecuteSymbolStartActions(
                 cancellationToken.ThrowIfCancellationRequested();
 
                 var context = new AnalyzerSymbolStartAnalysisContext(startAction.Analyzer, symbolScope,
-                    symbol, Compilation, AnalyzerOptions, isGeneratedCodeSymbol, cancellationToken);
+                    symbol, Compilation, AnalyzerOptions, isGeneratedCodeSymbol, filterTree, filterSpan, cancellationToken);
 
                 ExecuteAndCatchIfThrows(
                     startAction.Analyzer,
@@ -349,9 +351,12 @@ public void ExecuteSymbolActions(
             SymbolDeclaredCompilationEvent symbolDeclaredEvent,
             Func<ISymbol, SyntaxReference, Compilation, CancellationToken, SyntaxNode> getTopMostNodeForAnalysis,
             bool isGeneratedCodeSymbol,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
             Debug.Assert(getTopMostNodeForAnalysis != null);
+            Debug.Assert(!filterSpan.HasValue || filterTree != null);
 
             if (isGeneratedCodeSymbol && _shouldSkipAnalysisOnGeneratedCode(analyzer) ||
                 IsAnalyzerSuppressedForSymbol(analyzer, symbolDeclaredEvent.Symbol, cancellationToken))
@@ -374,7 +379,7 @@ public void ExecuteSymbolActions(
                     cancellationToken.ThrowIfCancellationRequested();
 
                     var context = new SymbolAnalysisContext(symbol, Compilation, AnalyzerOptions, addDiagnostic,
-                        isSupportedDiagnostic, isGeneratedCodeSymbol, cancellationToken);
+                        isSupportedDiagnostic, isGeneratedCodeSymbol, filterTree, filterSpan, cancellationToken);
 
                     ExecuteAndCatchIfThrows(
                         symbolAction.Analyzer,
@@ -393,6 +398,7 @@ public void ExecuteSymbolActions(
         /// <param name="processedMemberSymbol">Completed member symbol.</param>
         /// <param name="analyzer">Analyzer whose actions are to be executed.</param>
         /// <param name="getTopMostNodeForAnalysis">Delegate to get topmost declaration node for a symbol declaration reference.</param>
+        /// <param name="filterSpan">Optional filter span for analysis.</param>
         /// <param name="isGeneratedCode">Flag indicating if the containing symbol being analyzed is generated code.</param>
         public bool TryExecuteSymbolEndActionsForContainer(
             INamespaceOrTypeSymbol containingSymbol,
@@ -400,6 +406,8 @@ public bool TryExecuteSymbolEndActionsForContainer(
             DiagnosticAnalyzer analyzer,
             Func<ISymbol, SyntaxReference, Compilation, CancellationToken, SyntaxNode> getTopMostNodeForAnalysis,
             bool isGeneratedCode,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken,
             [NotNullWhen(returnValue: true)] out SymbolDeclaredCompilationEvent? containingSymbolDeclaredEvent)
         {
@@ -411,7 +419,7 @@ public bool TryExecuteSymbolEndActionsForContainer(
 
             ImmutableArray<SymbolEndAnalyzerAction> endActions = containerEndActionsAndEvent.symbolEndActions;
             containingSymbolDeclaredEvent = containerEndActionsAndEvent.symbolDeclaredEvent;
-            ExecuteSymbolEndActionsCore(endActions, analyzer, containingSymbolDeclaredEvent, getTopMostNodeForAnalysis, isGeneratedCode, cancellationToken);
+            ExecuteSymbolEndActionsCore(endActions, analyzer, containingSymbolDeclaredEvent, getTopMostNodeForAnalysis, isGeneratedCode, filterTree, filterSpan, cancellationToken);
             return true;
         }
 
@@ -422,6 +430,7 @@ public bool TryExecuteSymbolEndActionsForContainer(
         /// <param name="analyzer">Analyzer whose actions are to be executed.</param>
         /// <param name="symbolDeclaredEvent">Symbol event to be analyzed.</param>
         /// <param name="getTopMostNodeForAnalysis">Delegate to get topmost declaration node for a symbol declaration reference.</param>
+        /// <param name="filterSpan">Optional filter span for analysis.</param>
         /// <param name="isGeneratedCode">Flag indicating if the symbol being analyzed is generated code.</param>
         /// <param name="cancellationToken">Cancellation token.</param>
         /// <returns>
@@ -434,12 +443,14 @@ public bool TryExecuteSymbolEndActions(
             SymbolDeclaredCompilationEvent symbolDeclaredEvent,
             Func<ISymbol, SyntaxReference, Compilation, CancellationToken, SyntaxNode> getTopMostNodeForAnalysis,
             bool isGeneratedCode,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
             if (!_analyzerManager.TryStartExecuteSymbolEndActions(symbolEndActions, analyzer, symbolDeclaredEvent))
                 return false;
 
-            ExecuteSymbolEndActionsCore(symbolEndActions, analyzer, symbolDeclaredEvent, getTopMostNodeForAnalysis, isGeneratedCode, cancellationToken);
+            ExecuteSymbolEndActionsCore(symbolEndActions, analyzer, symbolDeclaredEvent, getTopMostNodeForAnalysis, isGeneratedCode, filterTree, filterSpan, cancellationToken);
             return true;
         }
 
@@ -449,11 +460,14 @@ private void ExecuteSymbolEndActionsCore(
             SymbolDeclaredCompilationEvent symbolDeclaredEvent,
             Func<ISymbol, SyntaxReference, Compilation, CancellationToken, SyntaxNode> getTopMostNodeForAnalysis,
             bool isGeneratedCode,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
             Debug.Assert(getTopMostNodeForAnalysis != null);
             Debug.Assert(!isGeneratedCode || !_shouldSkipAnalysisOnGeneratedCode(analyzer));
             Debug.Assert(!IsAnalyzerSuppressedForSymbol(analyzer, symbolDeclaredEvent.Symbol, cancellationToken));
+            Debug.Assert(!filterSpan.HasValue || filterTree != null);
 
             var symbol = symbolDeclaredEvent.Symbol;
             var addDiagnostic = GetAddDiagnostic(symbol, symbolDeclaredEvent.DeclaringSyntaxReferences, analyzer, getTopMostNodeForAnalysis, cancellationToken);
@@ -467,7 +481,7 @@ private void ExecuteSymbolEndActionsCore(
                 cancellationToken.ThrowIfCancellationRequested();
 
                 var context = new SymbolAnalysisContext(symbol, Compilation, AnalyzerOptions, addDiagnostic,
-                    isSupportedDiagnostic, isGeneratedCode, cancellationToken);
+                    isSupportedDiagnostic, isGeneratedCode, filterTree, filterSpan, cancellationToken);
 
                 ExecuteAndCatchIfThrows(
                     symbolAction.Analyzer,
@@ -580,11 +594,13 @@ public void ExecuteSyntaxTreeActions(
         /// <param name="additionalFileActions">Actions to be executed.</param>
         /// <param name="analyzer">Analyzer whose actions are to be executed.</param>
         /// <param name="file">Additional file to analyze.</param>
+        /// <param name="filterSpan">Optional filter span within the <paramref name="file"/> for analysis.</param>
         /// <param name="cancellationToken">Cancellation token.</param>
         public void ExecuteAdditionalFileActions(
             ImmutableArray<AdditionalFileAnalyzerAction> additionalFileActions,
             DiagnosticAnalyzer analyzer,
             SourceOrAdditionalFile file,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
             Debug.Assert(file.AdditionalFile != null);
@@ -597,7 +613,7 @@ public void ExecuteAdditionalFileActions(
             {
                 cancellationToken.ThrowIfCancellationRequested();
 
-                var context = new AdditionalFileAnalysisContext(additionalFile, AnalyzerOptions, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, Compilation, cancellationToken);
+                var context = new AdditionalFileAnalysisContext(additionalFile, AnalyzerOptions, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, Compilation, filterSpan, cancellationToken);
 
                 // Catch Exception from action.
                 ExecuteAndCatchIfThrows(
@@ -618,6 +634,7 @@ private void ExecuteSyntaxNodeAction<TLanguageKindEnum>(
             SemanticModel semanticModel,
             Action<Diagnostic> addDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
             where TLanguageKindEnum : struct
@@ -626,7 +643,7 @@ private void ExecuteSyntaxNodeAction<TLanguageKindEnum>(
             Debug.Assert(!IsAnalyzerSuppressedForTree(syntaxNodeAction.Analyzer, node.SyntaxTree, cancellationToken));
 
             var syntaxNodeContext = new SyntaxNodeAnalysisContext(node, containingSymbol, semanticModel, AnalyzerOptions, addDiagnostic,
-                    isSupportedDiagnostic, isGeneratedCode, cancellationToken);
+                    isSupportedDiagnostic, filterSpan, isGeneratedCode, cancellationToken);
 
             ExecuteAndCatchIfThrows(
                 syntaxNodeAction.Analyzer,
@@ -643,6 +660,7 @@ private void ExecuteOperationAction(
             SemanticModel semanticModel,
             Action<Diagnostic> addDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
@@ -650,7 +668,7 @@ private void ExecuteOperationAction(
             Debug.Assert(!IsAnalyzerSuppressedForTree(operationAction.Analyzer, semanticModel.SyntaxTree, cancellationToken));
 
             var operationContext = new OperationAnalysisContext(operation, containingSymbol, semanticModel.Compilation,
-                    AnalyzerOptions, addDiagnostic, isSupportedDiagnostic, GetControlFlowGraph, isGeneratedCode, cancellationToken);
+                    AnalyzerOptions, addDiagnostic, isSupportedDiagnostic, GetControlFlowGraph, filterSpan, isGeneratedCode, cancellationToken);
             ExecuteAndCatchIfThrows(
                 operationAction.Analyzer,
                 data => data.action(data.context),
@@ -672,6 +690,7 @@ public void ExecuteCodeBlockActions<TLanguageKindEnum>(
             ImmutableArray<SyntaxNode> executableCodeBlocks,
             SemanticModel semanticModel,
             Func<SyntaxNode, TLanguageKindEnum> getKind,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
             where TLanguageKindEnum : struct
@@ -692,7 +711,7 @@ public void ExecuteCodeBlockActions<TLanguageKindEnum>(
                             return cb.DescendantNodesAndSelf();
                         }
                     }),
-                semanticModel, getKind, isGeneratedCode, cancellationToken);
+                semanticModel, getKind, filterSpan, isGeneratedCode, cancellationToken);
         }
 
         /// <summary>
@@ -708,13 +727,14 @@ public void ExecuteOperationBlockActions(
             ImmutableArray<IOperation> operationBlocks,
             ImmutableArray<IOperation> operations,
             SemanticModel semanticModel,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
             ExecuteBlockActionsCore<OperationBlockStartAnalyzerAction, OperationBlockAnalyzerAction, OperationAnalyzerAction, IOperation, int>(
                 operationBlockStartActions, operationBlockActions, operationBlockEndActions, analyzer,
                 declaredNode, declaredSymbol, operationBlocks, (blocks) => operations, semanticModel,
-                getKind: null, isGeneratedCode, cancellationToken);
+                getKind: null, filterSpan, isGeneratedCode, cancellationToken);
         }
 
         private void ExecuteBlockActionsCore<TBlockStartAction, TBlockAction, TNodeAction, TNode, TLanguageKindEnum>(
@@ -728,6 +748,7 @@ private void ExecuteBlockActionsCore<TBlockStartAction, TBlockAction, TNodeActio
            Func<ImmutableArray<TNode>, IEnumerable<TNode>> getNodesToAnalyze,
            SemanticModel semanticModel,
            Func<SyntaxNode, TLanguageKindEnum>? getKind,
+           TextSpan? filterSpan,
            bool isGeneratedCode,
            CancellationToken cancellationToken)
            where TLanguageKindEnum : struct
@@ -772,7 +793,7 @@ private void ExecuteBlockActionsCore<TBlockStartAction, TBlockAction, TNodeActio
                     var codeBlockEndActions = blockEndActions as PooledHashSet<CodeBlockAnalyzerAction>;
                     var codeBlockScope = new HostCodeBlockStartAnalysisScope<TLanguageKindEnum>();
                     var blockStartContext = new AnalyzerCodeBlockStartAnalysisContext<TLanguageKindEnum>(startAction.Analyzer,
-                        codeBlockScope, declaredNode, declaredSymbol, semanticModel, AnalyzerOptions, isGeneratedCode, cancellationToken);
+                        codeBlockScope, declaredNode, declaredSymbol, semanticModel, AnalyzerOptions, filterSpan, isGeneratedCode, cancellationToken);
 
                     // Catch Exception from the start action.
                     ExecuteAndCatchIfThrows(
@@ -795,7 +816,7 @@ private void ExecuteBlockActionsCore<TBlockStartAction, TBlockAction, TNodeActio
                         var operationBlockScope = new HostOperationBlockStartAnalysisScope();
                         var operationStartContext = new AnalyzerOperationBlockStartAnalysisContext(startAction.Analyzer,
                             operationBlockScope, operationBlocks, declaredSymbol, semanticModel.Compilation, AnalyzerOptions,
-                            GetControlFlowGraph, isGeneratedCode, cancellationToken);
+                            GetControlFlowGraph, declaredNode.SyntaxTree, filterSpan, isGeneratedCode, cancellationToken);
 
                         // Catch Exception from the start action.
                         ExecuteAndCatchIfThrows(
@@ -824,20 +845,20 @@ private void ExecuteBlockActionsCore<TBlockStartAction, TBlockAction, TNodeActio
 
                     var executableNodeActionsByKind = GetNodeActionsByKind(syntaxNodeActions);
                     var syntaxNodesToAnalyze = (IEnumerable<SyntaxNode>)getNodesToAnalyze(executableBlocks);
-                    ExecuteSyntaxNodeActions(syntaxNodesToAnalyze, executableNodeActionsByKind, analyzer, declaredSymbol, semanticModel, getKind, diagReporter, isSupportedDiagnostic, isGeneratedCode, hasCodeBlockStartOrSymbolStartActions: startActions.Any(), cancellationToken);
+                    ExecuteSyntaxNodeActions(syntaxNodesToAnalyze, executableNodeActionsByKind, analyzer, declaredSymbol, semanticModel, getKind, diagReporter, isSupportedDiagnostic, filterSpan, isGeneratedCode, hasCodeBlockStartOrSymbolStartActions: startActions.Any(), cancellationToken);
                 }
                 else if (operationActions != null)
                 {
                     var operationActionsByKind = GetOperationActionsByKind(operationActions);
                     var operationsToAnalyze = (IEnumerable<IOperation>)getNodesToAnalyze(executableBlocks);
-                    ExecuteOperationActions(operationsToAnalyze, operationActionsByKind, analyzer, declaredSymbol, semanticModel, diagReporter, isSupportedDiagnostic, isGeneratedCode, hasOperationBlockStartOrSymbolStartActions: startActions.Any(), cancellationToken);
+                    ExecuteOperationActions(operationsToAnalyze, operationActionsByKind, analyzer, declaredSymbol, semanticModel, diagReporter, isSupportedDiagnostic, filterSpan, isGeneratedCode, hasOperationBlockStartOrSymbolStartActions: startActions.Any(), cancellationToken);
                 }
             }
 
             executableNodeActions.Free();
 
-            ExecuteBlockActions(blockActions, declaredNode, declaredSymbol, analyzer, semanticModel, operationBlocks, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, isGeneratedCode, cancellationToken);
-            ExecuteBlockActions(blockEndActions, declaredNode, declaredSymbol, analyzer, semanticModel, operationBlocks, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, isGeneratedCode, cancellationToken);
+            ExecuteBlockActions(blockActions, declaredNode, declaredSymbol, analyzer, semanticModel, operationBlocks, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, filterSpan, isGeneratedCode, cancellationToken);
+            ExecuteBlockActions(blockEndActions, declaredNode, declaredSymbol, analyzer, semanticModel, operationBlocks, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, filterSpan, isGeneratedCode, cancellationToken);
 
             diagReporter.Free();
         }
@@ -851,6 +872,7 @@ private void ExecuteBlockActions<TBlockAction>(
             ImmutableArray<IOperation> operationBlocks,
             Action<Diagnostic> addDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
             where TBlockAction : AnalyzerAction
@@ -863,7 +885,8 @@ private void ExecuteBlockActions<TBlockAction>(
                 var codeBlockAction = blockAction as CodeBlockAnalyzerAction;
                 if (codeBlockAction != null)
                 {
-                    var context = new CodeBlockAnalysisContext(declaredNode, declaredSymbol, semanticModel, AnalyzerOptions, addDiagnostic, isSupportedDiagnostic, isGeneratedCode, cancellationToken);
+                    var context = new CodeBlockAnalysisContext(declaredNode, declaredSymbol, semanticModel,
+                        AnalyzerOptions, addDiagnostic, isSupportedDiagnostic, filterSpan, isGeneratedCode, cancellationToken);
 
                     ExecuteAndCatchIfThrows(
                         codeBlockAction.Analyzer,
@@ -878,7 +901,7 @@ private void ExecuteBlockActions<TBlockAction>(
                     if (operationBlockAction != null)
                     {
                         var context = new OperationBlockAnalysisContext(operationBlocks, declaredSymbol, semanticModel.Compilation,
-                            AnalyzerOptions, addDiagnostic, isSupportedDiagnostic, GetControlFlowGraph, isGeneratedCode, cancellationToken);
+                            AnalyzerOptions, addDiagnostic, isSupportedDiagnostic, GetControlFlowGraph, declaredNode.SyntaxTree, filterSpan, isGeneratedCode, cancellationToken);
 
                         ExecuteAndCatchIfThrows(
                             operationBlockAction.Analyzer,
@@ -928,8 +951,9 @@ public void ExecuteSyntaxNodeActions<TLanguageKindEnum>(
            DiagnosticAnalyzer analyzer,
            SemanticModel model,
            Func<SyntaxNode, TLanguageKindEnum> getKind,
-           TextSpan filterSpan,
+           TextSpan spanForContainingTopmostNodeForAnalysis,
            ISymbol declaredSymbol,
+           TextSpan? filterSpan,
            bool isGeneratedCode,
            bool hasCodeBlockStartOrSymbolStartActions,
            CancellationToken cancellationToken)
@@ -941,10 +965,10 @@ public void ExecuteSyntaxNodeActions<TLanguageKindEnum>(
                 return;
             }
 
-            var diagReporter = GetAddSemanticDiagnostic(model.SyntaxTree, filterSpan, analyzer, cancellationToken);
+            var diagReporter = GetAddSemanticDiagnostic(model.SyntaxTree, spanForContainingTopmostNodeForAnalysis, analyzer, cancellationToken);
 
             using var _ = PooledDelegates.GetPooledFunction((d, ct, arg) => arg.self.IsSupportedDiagnostic(arg.analyzer, d, ct), (self: this, analyzer), out Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic);
-            ExecuteSyntaxNodeActions(nodesToAnalyze, nodeActionsByKind, analyzer, declaredSymbol, model, getKind, diagReporter, isSupportedDiagnostic, isGeneratedCode, hasCodeBlockStartOrSymbolStartActions, cancellationToken);
+            ExecuteSyntaxNodeActions(nodesToAnalyze, nodeActionsByKind, analyzer, declaredSymbol, model, getKind, diagReporter, isSupportedDiagnostic, filterSpan, isGeneratedCode, hasCodeBlockStartOrSymbolStartActions, cancellationToken);
             diagReporter.Free();
         }
 
@@ -957,6 +981,7 @@ private void ExecuteSyntaxNodeActions<TLanguageKindEnum>(
             Func<SyntaxNode, TLanguageKindEnum> getKind,
             AnalyzerDiagnosticReporter diagReporter,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             bool hasCodeBlockStartOrSymbolStartActions,
             CancellationToken cancellationToken)
@@ -985,7 +1010,7 @@ private void ExecuteSyntaxNodeActions<TLanguageKindEnum>(
 
                         foreach (var action in actionsForKind)
                         {
-                            ExecuteSyntaxNodeAction(action, node, containingSymbol, model, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, isGeneratedCode, cancellationToken);
+                            ExecuteSyntaxNodeAction(action, node, containingSymbol, model, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, filterSpan, isGeneratedCode, cancellationToken);
                         }
                     }
                 }
@@ -1028,8 +1053,9 @@ public void ExecuteOperationActions(
             ImmutableSegmentedDictionary<OperationKind, ImmutableArray<OperationAnalyzerAction>> operationActionsByKind,
             DiagnosticAnalyzer analyzer,
             SemanticModel model,
-            TextSpan filterSpan,
+            TextSpan spanForContainingOperationBlock,
             ISymbol declaredSymbol,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             bool hasOperationBlockStartOrSymbolStartActions,
             CancellationToken cancellationToken)
@@ -1040,10 +1066,10 @@ public void ExecuteOperationActions(
                 return;
             }
 
-            var diagReporter = GetAddSemanticDiagnostic(model.SyntaxTree, filterSpan, analyzer, cancellationToken);
+            var diagReporter = GetAddSemanticDiagnostic(model.SyntaxTree, spanForContainingOperationBlock, analyzer, cancellationToken);
 
             using var _ = PooledDelegates.GetPooledFunction((d, ct, arg) => arg.self.IsSupportedDiagnostic(arg.analyzer, d, ct), (self: this, analyzer), out Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic);
-            ExecuteOperationActions(operationsToAnalyze, operationActionsByKind, analyzer, declaredSymbol, model, diagReporter, isSupportedDiagnostic, isGeneratedCode, hasOperationBlockStartOrSymbolStartActions, cancellationToken);
+            ExecuteOperationActions(operationsToAnalyze, operationActionsByKind, analyzer, declaredSymbol, model, diagReporter, isSupportedDiagnostic, filterSpan, isGeneratedCode, hasOperationBlockStartOrSymbolStartActions, cancellationToken);
             diagReporter.Free();
         }
 
@@ -1055,6 +1081,7 @@ private void ExecuteOperationActions(
             SemanticModel model,
             AnalyzerDiagnosticReporter diagReporter,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             bool hasOperationBlockStartOrSymbolStartActions,
             CancellationToken cancellationToken)
@@ -1083,7 +1110,7 @@ private void ExecuteOperationActions(
 
                         foreach (var action in actionsForKind)
                         {
-                            ExecuteOperationAction(action, operation, containingSymbol, model, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, isGeneratedCode, cancellationToken);
+                            ExecuteOperationAction(action, operation, containingSymbol, model, diagReporter.AddDiagnosticAction, isSupportedDiagnostic, filterSpan, isGeneratedCode, cancellationToken);
                         }
                     }
                 }
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.AnalyzerExecutionContext.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.AnalyzerExecutionContext.cs
index e589c463aca4c..fe6d59ede2541 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.AnalyzerExecutionContext.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.AnalyzerExecutionContext.cs
@@ -10,6 +10,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Collections;
+using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.Diagnostics
@@ -137,6 +138,8 @@ public void ClearCompilationScopeTask()
             public Task<HostSymbolStartAnalysisScope> GetSymbolAnalysisScopeAsync(
                 ISymbol symbol,
                 bool isGeneratedCodeSymbol,
+                SyntaxTree? filterTree,
+                TextSpan? filterSpan,
                 ImmutableArray<SymbolStartAnalyzerAction> symbolStartActions,
                 AnalyzerExecutor analyzerExecutor,
                 CancellationToken cancellationToken)
@@ -155,7 +158,7 @@ public Task<HostSymbolStartAnalysisScope> GetSymbolAnalysisScopeAsync(
                     HostSymbolStartAnalysisScope getSymbolAnalysisScopeCore()
                     {
                         var symbolAnalysisScope = new HostSymbolStartAnalysisScope();
-                        analyzerExecutor.ExecuteSymbolStartActions(symbol, _analyzer, symbolStartActions, symbolAnalysisScope, isGeneratedCodeSymbol, cancellationToken);
+                        analyzerExecutor.ExecuteSymbolStartActions(symbol, _analyzer, symbolStartActions, symbolAnalysisScope, isGeneratedCodeSymbol, filterTree, filterSpan, cancellationToken);
 
                         var symbolEndActions = symbolAnalysisScope.GetAnalyzerActions(_analyzer);
                         if (symbolEndActions.SymbolEndActionsCount > 0)
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.cs
index d8ed74f140798..bb45a763a45f8 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerManager.cs
@@ -9,6 +9,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.PooledObjects;
+using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.Diagnostics
@@ -90,18 +91,22 @@ private async ValueTask<HostCompilationStartAnalysisScope> GetCompilationAnalysi
         private async Task<HostSymbolStartAnalysisScope> GetSymbolAnalysisScopeAsync(
             ISymbol symbol,
             bool isGeneratedCodeSymbol,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             DiagnosticAnalyzer analyzer,
             ImmutableArray<SymbolStartAnalyzerAction> symbolStartActions,
             AnalyzerExecutor analyzerExecutor,
             CancellationToken cancellationToken)
         {
             var analyzerExecutionContext = GetAnalyzerExecutionContext(analyzer);
-            return await GetSymbolAnalysisScopeCoreAsync(symbol, isGeneratedCodeSymbol, symbolStartActions, analyzerExecutor, analyzerExecutionContext, cancellationToken).ConfigureAwait(false);
+            return await GetSymbolAnalysisScopeCoreAsync(symbol, isGeneratedCodeSymbol, filterTree, filterSpan, symbolStartActions, analyzerExecutor, analyzerExecutionContext, cancellationToken).ConfigureAwait(false);
         }
 
         private async Task<HostSymbolStartAnalysisScope> GetSymbolAnalysisScopeCoreAsync(
             ISymbol symbol,
             bool isGeneratedCodeSymbol,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             ImmutableArray<SymbolStartAnalyzerAction> symbolStartActions,
             AnalyzerExecutor analyzerExecutor,
             AnalyzerExecutionContext analyzerExecutionContext,
@@ -109,7 +114,7 @@ private async Task<HostSymbolStartAnalysisScope> GetSymbolAnalysisScopeCoreAsync
         {
             try
             {
-                return await analyzerExecutionContext.GetSymbolAnalysisScopeAsync(symbol, isGeneratedCodeSymbol, symbolStartActions, analyzerExecutor, cancellationToken).ConfigureAwait(false);
+                return await analyzerExecutionContext.GetSymbolAnalysisScopeAsync(symbol, isGeneratedCodeSymbol, filterTree, filterSpan, symbolStartActions, analyzerExecutor, cancellationToken).ConfigureAwait(false);
             }
             catch (OperationCanceledException)
             {
@@ -118,7 +123,7 @@ private async Task<HostSymbolStartAnalysisScope> GetSymbolAnalysisScopeCoreAsync
                 analyzerExecutionContext.ClearSymbolScopeTask(symbol);
 
                 cancellationToken.ThrowIfCancellationRequested();
-                return await GetSymbolAnalysisScopeCoreAsync(symbol, isGeneratedCodeSymbol, symbolStartActions, analyzerExecutor, analyzerExecutionContext, cancellationToken).ConfigureAwait(false);
+                return await GetSymbolAnalysisScopeCoreAsync(symbol, isGeneratedCodeSymbol, filterTree, filterSpan, symbolStartActions, analyzerExecutor, analyzerExecutionContext, cancellationToken).ConfigureAwait(false);
             }
         }
 
@@ -180,6 +185,8 @@ public async ValueTask<AnalyzerActions> GetAnalyzerActionsAsync(DiagnosticAnalyz
         public async ValueTask<AnalyzerActions> GetPerSymbolAnalyzerActionsAsync(
             ISymbol symbol,
             bool isGeneratedCodeSymbol,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             DiagnosticAnalyzer analyzer,
             AnalyzerExecutor analyzerExecutor,
             CancellationToken cancellationToken)
@@ -190,7 +197,7 @@ public async ValueTask<AnalyzerActions> GetPerSymbolAnalyzerActionsAsync(
                 var filteredSymbolStartActions = getFilteredActionsByKind(analyzerActions.SymbolStartActions);
                 if (filteredSymbolStartActions.Length > 0)
                 {
-                    var symbolScope = await GetSymbolAnalysisScopeAsync(symbol, isGeneratedCodeSymbol, analyzer, filteredSymbolStartActions, analyzerExecutor, cancellationToken).ConfigureAwait(false);
+                    var symbolScope = await GetSymbolAnalysisScopeAsync(symbol, isGeneratedCodeSymbol, filterTree, filterSpan, analyzer, filteredSymbolStartActions, analyzerExecutor, cancellationToken).ConfigureAwait(false);
                     return symbolScope.GetAnalyzerActions(analyzer);
                 }
             }
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/CompilationWithAnalyzers.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/CompilationWithAnalyzers.cs
index 6e2b225962fbc..c7fafa539fbd9 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/CompilationWithAnalyzers.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/CompilationWithAnalyzers.cs
@@ -532,6 +532,40 @@ public async Task<AnalysisResult> GetAnalysisResultAsync(AdditionalText file, Im
             return await GetAnalysisResultCoreAsync(new SourceOrAdditionalFile(file), analyzers, filterSpan: null, cancellationToken).ConfigureAwait(false);
         }
 
+        /// <summary>
+        /// Returns an <see cref="AnalysisResult"/> populated with <see cref="AnalysisResult.AdditionalFileDiagnostics"/> produced by all <see cref="Analyzers"/> from analyzing the given additional <paramref name="file"/>,
+        /// optionally scoped to a <paramref name="filterSpan"/>.
+        /// The given <paramref name="file"/> must be part of <see cref="AnalyzerOptions.AdditionalFiles"/> for the <see cref="AnalysisOptions"/> for this CompilationWithAnalyzers instance.
+        /// Depending on analyzers' behavior, some diagnostics that would be reported for the file by an analysis of the complete compilation can be absent.
+        /// </summary>
+        /// <param name="file">Additional file to analyze.</param>
+        /// <param name="filterSpan">Optional filter span to analyze within the <paramref name="file"/>.</param>
+        /// <param name="cancellationToken">Cancellation token.</param>
+        public async Task<AnalysisResult> GetAnalysisResultAsync(AdditionalText file, TextSpan? filterSpan, CancellationToken cancellationToken)
+        {
+            VerifyAdditionalFile(file);
+
+            return await GetAnalysisResultCoreAsync(new SourceOrAdditionalFile(file), Analyzers, filterSpan, cancellationToken).ConfigureAwait(false);
+        }
+
+        /// <summary>
+        /// Returns an <see cref="AnalysisResult"/> populated with <see cref="AnalysisResult.AdditionalFileDiagnostics"/> produced by given <paramref name="analyzers"/> from analyzing the given additional <paramref name="file"/>,
+        /// optionally scoped to a <paramref name="filterSpan"/>.
+        /// The given <paramref name="file"/> must be part of <see cref="AnalyzerOptions.AdditionalFiles"/> for the <see cref="AnalysisOptions"/> for this CompilationWithAnalyzers instance.
+        /// Depending on analyzers' behavior, some diagnostics that would be reported for the file by an analysis of the complete compilation can be absent.
+        /// </summary>
+        /// <param name="file">Additional file to analyze.</param>
+        /// <param name="filterSpan">Optional filter span to analyze within the <paramref name="file"/>.</param>
+        /// <param name="analyzers">Analyzers whose diagnostics are required. All the given analyzers must be from the analyzers passed into the constructor of <see cref="CompilationWithAnalyzers"/>.</param>
+        /// <param name="cancellationToken">Cancellation token.</param>
+        public async Task<AnalysisResult> GetAnalysisResultAsync(AdditionalText file, TextSpan? filterSpan, ImmutableArray<DiagnosticAnalyzer> analyzers, CancellationToken cancellationToken)
+        {
+            VerifyAdditionalFile(file);
+            VerifyExistingAnalyzersArgument(analyzers);
+
+            return await GetAnalysisResultCoreAsync(new SourceOrAdditionalFile(file), analyzers, filterSpan, cancellationToken).ConfigureAwait(false);
+        }
+
         private async Task<AnalysisResult> GetAnalysisResultCoreAsync(SourceOrAdditionalFile file, ImmutableArray<DiagnosticAnalyzer> analyzers, TextSpan? filterSpan, CancellationToken cancellationToken)
         {
             var analysisScope = AnalysisScope.Create(analyzers, file, filterSpan, isSyntacticSingleFileAnalysis: true, this);
@@ -749,8 +783,7 @@ private async Task ComputeAnalyzerDiagnosticsAsync(AnalysisScope? analysisScope,
                             builder.Add((otherAnalyzersAnalysisScope, compilationEvents));
                         }
 
-                        var tree = analysisScope.FilterFileOpt!.Value.SourceTree!;
-                        processSymbolStartAnalyzers(tree, compilationEvents, symbolStartAnalyzers, compilation,
+                        processSymbolStartAnalyzers(analysisScope.FilterFileOpt!.Value, analysisScope.FilterSpanOpt, compilationEvents, symbolStartAnalyzers, compilation,
                             _analysisResultBuilder, builder, AdditionalFiles, cancellationToken);
                     }
 
@@ -832,7 +865,8 @@ static async Task attachQueueAndProcessAllEventsAsync(
             }
 
             void processSymbolStartAnalyzers(
-                SyntaxTree tree,
+                SourceOrAdditionalFile originalFile,
+                TextSpan? originalSpan,
                 ImmutableArray<CompilationEvent> compilationEventsForTree,
                 ImmutableArray<DiagnosticAnalyzer> symbolStartAnalyzers,
                 Compilation compilation,
@@ -852,6 +886,7 @@ void processSymbolStartAnalyzers(
                 // compilation events generated for each tree.
 
                 var partialTrees = PooledHashSet<SyntaxTree>.GetInstance();
+                var tree = originalFile.SourceTree!;
                 partialTrees.Add(tree);
 
                 try
@@ -895,7 +930,7 @@ bool tryProcessTree(SyntaxTree partialTree, [NotNullWhen(true)] out (AnalysisSco
 
                     var file = new SourceOrAdditionalFile(partialTree);
                     var analysisScope = AnalysisScope.Create(symbolStartAnalyzers, file, filterSpan: null,
-                        isSyntacticSingleFileAnalysis: false, this);
+                        originalFile, originalSpan, isSyntacticSingleFileAnalysis: false, this);
 
                     analysisScope = GetPendingAnalysisScope(analysisScope);
                     if (analysisScope == null)
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticAnalysisContext.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticAnalysisContext.cs
index 3fc8b712b033f..46e549aa6221d 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticAnalysisContext.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticAnalysisContext.cs
@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Threading;
 using Microsoft.CodeAnalysis.FlowAnalysis;
@@ -695,7 +696,14 @@ public readonly struct SemanticModelAnalysisContext
         public CancellationToken CancellationToken { get { return _cancellationToken; } }
 
         /// <summary>
-        /// Optional filter span for which to compute diagnostics.
+        /// Syntax tree for the <see cref="SemanticModel"/> being analyzed.
+        /// </summary>
+        public SyntaxTree FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
         /// </summary>
         public TextSpan? FilterSpan { get; }
 
@@ -723,6 +731,7 @@ internal SemanticModelAnalysisContext(
             _options = options;
             _reportDiagnostic = reportDiagnostic;
             _isSupportedDiagnostic = isSupportedDiagnostic;
+            FilterTree = semanticModel.SyntaxTree;
             FilterSpan = filterSpan;
             IsGeneratedCode = isGeneratedCode;
             _cancellationToken = cancellationToken;
@@ -770,6 +779,20 @@ public readonly struct SymbolAnalysisContext
         /// </summary>
         public AnalyzerOptions Options { get { return _options; } }
 
+        /// <summary>
+        /// Optional filter tree being analyzed.
+        /// <see langword="null"/> if we are analyzing the entire compilation.
+        /// </summary>
+        public SyntaxTree? FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        /// <remarks>This property is guaranteed to be <see langword="null"/> if <see cref="FilterTree"/> is <see langword="null"/>.</remarks>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Token to check for requested cancellation of the analysis.
         /// </summary>
@@ -784,7 +807,7 @@ public readonly struct SymbolAnalysisContext
 
         [Obsolete("Use CompilationWithAnalyzers instead. See https://github.com/dotnet/roslyn/issues/63440 for more details.")]
         public SymbolAnalysisContext(ISymbol symbol, Compilation compilation, AnalyzerOptions options, Action<Diagnostic> reportDiagnostic, Func<Diagnostic, bool> isSupportedDiagnostic, CancellationToken cancellationToken)
-            : this(symbol, compilation, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), isGeneratedCode: false, cancellationToken)
+            : this(symbol, compilation, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), isGeneratedCode: false, filterTree: null, filterSpan: null, cancellationToken)
         {
         }
 
@@ -795,14 +818,20 @@ internal SymbolAnalysisContext(
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
             bool isGeneratedCode,
+            SyntaxTree? filterTree,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
+            Debug.Assert(!filterSpan.HasValue || filterTree != null);
+
             _symbol = symbol;
             _compilation = compilation;
             _options = options;
             _reportDiagnostic = reportDiagnostic;
             _isSupportedDiagnostic = isSupportedDiagnostic;
             IsGeneratedCode = isGeneratedCode;
+            FilterTree = filterTree;
+            FilterSpan = filterSpan;
             _cancellationToken = cancellationToken;
         }
 
@@ -846,6 +875,20 @@ public abstract class SymbolStartAnalysisContext
         /// </summary>
         public bool IsGeneratedCode { get; }
 
+        /// <summary>
+        /// Optional filter tree being analyzed.
+        /// <see langword="null"/> if we are analyzing the entire compilation.
+        /// </summary>
+        public SyntaxTree? FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        /// <remarks>This property is guaranteed to be <see langword="null"/> if <see cref="FilterTree"/> is <see langword="null"/>.</remarks>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Token to check for requested cancellation of the analysis.
         /// </summary>
@@ -853,16 +896,20 @@ public abstract class SymbolStartAnalysisContext
 
         [Obsolete("Use CompilationWithAnalyzers instead. See https://github.com/dotnet/roslyn/issues/63440 for more details.")]
         public SymbolStartAnalysisContext(ISymbol symbol, Compilation compilation, AnalyzerOptions options, CancellationToken cancellationToken)
-            : this(symbol, compilation, options, isGeneratedCode: false, cancellationToken)
+            : this(symbol, compilation, options, isGeneratedCode: false, filterTree: null, filterSpan: null, cancellationToken)
         {
         }
 
-        internal SymbolStartAnalysisContext(ISymbol symbol, Compilation compilation, AnalyzerOptions options, bool isGeneratedCode, CancellationToken cancellationToken)
+        internal SymbolStartAnalysisContext(ISymbol symbol, Compilation compilation, AnalyzerOptions options, bool isGeneratedCode, SyntaxTree? filterTree, TextSpan? filterSpan, CancellationToken cancellationToken)
         {
+            Debug.Assert(!filterSpan.HasValue || filterTree != null);
+
             Symbol = symbol;
             Compilation = compilation;
             Options = options;
             IsGeneratedCode = isGeneratedCode;
+            FilterTree = filterTree;
+            FilterSpan = filterSpan;
             CancellationToken = cancellationToken;
         }
 
@@ -990,6 +1037,18 @@ public abstract class CodeBlockStartAnalysisContext<TLanguageKindEnum> where TLa
         /// </summary>
         public AnalyzerOptions Options { get { return _options; } }
 
+        /// <summary>
+        /// Syntax tree corresponding to the code block being analyzed.
+        /// </summary>
+        public SyntaxTree FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Indicates if the <see cref="CodeBlock"/> is generated code.
         /// </summary>
@@ -1002,7 +1061,7 @@ public abstract class CodeBlockStartAnalysisContext<TLanguageKindEnum> where TLa
 
         [Obsolete("Use CompilationWithAnalyzers instead. See https://github.com/dotnet/roslyn/issues/63440 for more details.")]
         protected CodeBlockStartAnalysisContext(SyntaxNode codeBlock, ISymbol owningSymbol, SemanticModel semanticModel, AnalyzerOptions options, CancellationToken cancellationToken)
-            : this(codeBlock, owningSymbol, semanticModel, options, isGeneratedCode: false, cancellationToken)
+            : this(codeBlock, owningSymbol, semanticModel, options, filterSpan: null, isGeneratedCode: false, cancellationToken)
         {
         }
 
@@ -1011,6 +1070,7 @@ private protected CodeBlockStartAnalysisContext(
             ISymbol owningSymbol,
             SemanticModel semanticModel,
             AnalyzerOptions options,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
@@ -1018,6 +1078,8 @@ private protected CodeBlockStartAnalysisContext(
             _owningSymbol = owningSymbol;
             _semanticModel = semanticModel;
             _options = options;
+            FilterTree = codeBlock.SyntaxTree;
+            FilterSpan = filterSpan;
             IsGeneratedCode = isGeneratedCode;
             _cancellationToken = cancellationToken;
         }
@@ -1085,6 +1147,18 @@ public readonly struct CodeBlockAnalysisContext
         /// </summary>
         public AnalyzerOptions Options { get { return _options; } }
 
+        /// <summary>
+        /// Syntax tree for the code block being analyzed.
+        /// </summary>
+        public SyntaxTree FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Indicates if the <see cref="CodeBlock"/> is generated code.
         /// </summary>
@@ -1097,7 +1171,7 @@ public readonly struct CodeBlockAnalysisContext
 
         [Obsolete("Use CompilationWithAnalyzers instead. See https://github.com/dotnet/roslyn/issues/63440 for more details.")]
         public CodeBlockAnalysisContext(SyntaxNode codeBlock, ISymbol owningSymbol, SemanticModel semanticModel, AnalyzerOptions options, Action<Diagnostic> reportDiagnostic, Func<Diagnostic, bool> isSupportedDiagnostic, CancellationToken cancellationToken)
-            : this(codeBlock, owningSymbol, semanticModel, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), isGeneratedCode: false, cancellationToken)
+            : this(codeBlock, owningSymbol, semanticModel, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), filterSpan: null, isGeneratedCode: false, cancellationToken)
         {
         }
 
@@ -1108,6 +1182,7 @@ internal CodeBlockAnalysisContext(
             AnalyzerOptions options,
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
@@ -1117,6 +1192,8 @@ internal CodeBlockAnalysisContext(
             _options = options;
             _reportDiagnostic = reportDiagnostic;
             _isSupportedDiagnostic = isSupportedDiagnostic;
+            FilterTree = codeBlock.SyntaxTree;
+            FilterSpan = filterSpan;
             IsGeneratedCode = isGeneratedCode;
             _cancellationToken = cancellationToken;
         }
@@ -1180,6 +1257,18 @@ public abstract class OperationBlockStartAnalysisContext
         /// </summary>
         public AnalyzerOptions Options => _options;
 
+        /// <summary>
+        /// Syntax tree for the <see cref="OperationBlocks"/> being analyzed.
+        /// </summary>
+        public SyntaxTree FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Indicates if the <see cref="OperationBlocks"/> is generated code.
         /// </summary>
@@ -1197,7 +1286,8 @@ protected OperationBlockStartAnalysisContext(
             Compilation compilation,
             AnalyzerOptions options,
             CancellationToken cancellationToken)
-            : this(operationBlocks, owningSymbol, compilation, options, getControlFlowGraph: null, isGeneratedCode: false, cancellationToken)
+            : this(operationBlocks, owningSymbol, compilation, options, getControlFlowGraph: null,
+                  filterTree: operationBlocks[0].Syntax.SyntaxTree, filterSpan: null, isGeneratedCode: false, cancellationToken)
         {
         }
 
@@ -1207,6 +1297,8 @@ internal OperationBlockStartAnalysisContext(
             Compilation compilation,
             AnalyzerOptions options,
             Func<IOperation, ControlFlowGraph>? getControlFlowGraph,
+            SyntaxTree filterTree,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
@@ -1215,6 +1307,8 @@ internal OperationBlockStartAnalysisContext(
             _compilation = compilation;
             _options = options;
             _getControlFlowGraph = getControlFlowGraph;
+            FilterTree = filterTree;
+            FilterSpan = filterSpan;
             IsGeneratedCode = isGeneratedCode;
             _cancellationToken = cancellationToken;
         }
@@ -1305,6 +1399,18 @@ public readonly struct OperationBlockAnalysisContext
         /// </summary>
         public AnalyzerOptions Options => _options;
 
+        /// <summary>
+        /// Syntax tree for the <see cref="OperationBlocks"/> being analyzed.
+        /// </summary>
+        public SyntaxTree FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Indicates if the <see cref="OperationBlocks"/> is generated code.
         /// </summary>
@@ -1324,7 +1430,8 @@ public OperationBlockAnalysisContext(
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, bool> isSupportedDiagnostic,
             CancellationToken cancellationToken)
-            : this(operationBlocks, owningSymbol, compilation, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), getControlFlowGraph: null, isGeneratedCode: false, cancellationToken)
+            : this(operationBlocks, owningSymbol, compilation, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), getControlFlowGraph: null,
+                  filterTree: operationBlocks[0].Syntax.SyntaxTree, filterSpan: null, isGeneratedCode: false, cancellationToken)
         {
         }
 
@@ -1336,6 +1443,8 @@ internal OperationBlockAnalysisContext(
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
             Func<IOperation, ControlFlowGraph>? getControlFlowGraph,
+            SyntaxTree filterTree,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
@@ -1346,6 +1455,8 @@ internal OperationBlockAnalysisContext(
             _reportDiagnostic = reportDiagnostic;
             _isSupportedDiagnostic = isSupportedDiagnostic;
             _getControlFlowGraph = getControlFlowGraph;
+            FilterTree = filterTree;
+            FilterSpan = filterSpan;
             IsGeneratedCode = isGeneratedCode;
             _cancellationToken = cancellationToken;
         }
@@ -1407,7 +1518,9 @@ public readonly struct SyntaxTreeAnalysisContext
         public AnalyzerOptions Options => _options;
 
         /// <summary>
-        /// Optional filter span for analysis.
+        /// Optional filter span within the <see cref="Tree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="Tree"/>
+        /// or the entire compilation.
         /// </summary>
         public TextSpan? FilterSpan { get; }
 
@@ -1482,6 +1595,13 @@ public readonly struct AdditionalFileAnalysisContext
         /// </summary>
         public AnalyzerOptions Options { get; }
 
+        /// <summary>
+        /// Optional filter span within the <see cref="AdditionalFile"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="AdditionalFile"/>
+        /// or the entire compilation.
+        /// </summary>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Token to check for requested cancellation of the analysis.
         /// </summary>
@@ -1498,6 +1618,7 @@ internal AdditionalFileAnalysisContext(
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
             Compilation compilation,
+            TextSpan? filterSpan,
             CancellationToken cancellationToken)
         {
             AdditionalFile = additionalFile;
@@ -1505,6 +1626,7 @@ internal AdditionalFileAnalysisContext(
             _reportDiagnostic = reportDiagnostic;
             _isSupportedDiagnostic = isSupportedDiagnostic;
             Compilation = compilation;
+            FilterSpan = filterSpan;
             CancellationToken = cancellationToken;
         }
 
@@ -1562,6 +1684,18 @@ public readonly struct SyntaxNodeAnalysisContext
         /// </summary>
         public AnalyzerOptions Options => _options;
 
+        /// <summary>
+        /// Syntax tree for the <see cref="Node"/> being analyzed.
+        /// </summary>
+        public SyntaxTree FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Indicates if the <see cref="Node"/> is generated code.
         /// </summary>
@@ -1574,13 +1708,13 @@ public readonly struct SyntaxNodeAnalysisContext
 
         [Obsolete("Use CompilationWithAnalyzers instead. See https://github.com/dotnet/roslyn/issues/63440 for more details.")]
         public SyntaxNodeAnalysisContext(SyntaxNode node, ISymbol? containingSymbol, SemanticModel semanticModel, AnalyzerOptions options, Action<Diagnostic> reportDiagnostic, Func<Diagnostic, bool> isSupportedDiagnostic, CancellationToken cancellationToken)
-            : this(node, containingSymbol, semanticModel, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), isGeneratedCode: false, cancellationToken)
+            : this(node, containingSymbol, semanticModel, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), filterSpan: null, isGeneratedCode: false, cancellationToken)
         {
         }
 
         [Obsolete("Use CompilationWithAnalyzers instead. See https://github.com/dotnet/roslyn/issues/63440 for more details.")]
         public SyntaxNodeAnalysisContext(SyntaxNode node, SemanticModel semanticModel, AnalyzerOptions options, Action<Diagnostic> reportDiagnostic, Func<Diagnostic, bool> isSupportedDiagnostic, CancellationToken cancellationToken)
-           : this(node, null, semanticModel, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), isGeneratedCode: false, cancellationToken)
+           : this(node, null, semanticModel, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), filterSpan: null, isGeneratedCode: false, cancellationToken)
         {
         }
 
@@ -1591,6 +1725,7 @@ internal SyntaxNodeAnalysisContext(
             AnalyzerOptions options,
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
@@ -1600,6 +1735,8 @@ internal SyntaxNodeAnalysisContext(
             _options = options;
             _reportDiagnostic = reportDiagnostic;
             _isSupportedDiagnostic = isSupportedDiagnostic;
+            FilterTree = node.SyntaxTree;
+            FilterSpan = filterSpan;
             IsGeneratedCode = isGeneratedCode;
             _cancellationToken = cancellationToken;
         }
@@ -1653,6 +1790,18 @@ public readonly struct OperationAnalysisContext
         /// </summary>
         public AnalyzerOptions Options => _options;
 
+        /// <summary>
+        /// Syntax tree for the <see cref="Operation"/> being analyzed.
+        /// </summary>
+        public SyntaxTree FilterTree { get; }
+
+        /// <summary>
+        /// Optional filter span within the <see cref="FilterTree"/> for which to compute diagnostics.
+        /// <see langword="null"/> if we are analyzing the entire <see cref="FilterTree"/>
+        /// or the entire compilation.
+        /// </summary>
+        public TextSpan? FilterSpan { get; }
+
         /// <summary>
         /// Indicates if the <see cref="Operation"/> is generated code.
         /// </summary>
@@ -1672,7 +1821,7 @@ public OperationAnalysisContext(
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, bool> isSupportedDiagnostic,
             CancellationToken cancellationToken)
-            : this(operation, containingSymbol, compilation, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), getControlFlowGraph: null, isGeneratedCode: false, cancellationToken)
+            : this(operation, containingSymbol, compilation, options, reportDiagnostic, isSupportedDiagnostic: (d, _) => isSupportedDiagnostic(d), getControlFlowGraph: null, filterSpan: null, isGeneratedCode: false, cancellationToken)
         {
         }
 
@@ -1684,6 +1833,7 @@ internal OperationAnalysisContext(
             Action<Diagnostic> reportDiagnostic,
             Func<Diagnostic, CancellationToken, bool> isSupportedDiagnostic,
             Func<IOperation, ControlFlowGraph>? getControlFlowGraph,
+            TextSpan? filterSpan,
             bool isGeneratedCode,
             CancellationToken cancellationToken)
         {
@@ -1694,6 +1844,8 @@ internal OperationAnalysisContext(
             _reportDiagnostic = reportDiagnostic;
             _isSupportedDiagnostic = isSupportedDiagnostic;
             _getControlFlowGraph = getControlFlowGraph;
+            FilterTree = operation.Syntax.SyntaxTree;
+            FilterSpan = filterSpan;
             IsGeneratedCode = isGeneratedCode;
             _cancellationToken = cancellationToken;
         }
diff --git a/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticStartAnalysisScope.cs b/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticStartAnalysisScope.cs
index e1d484806c696..caeffdd96c0bf 100644
--- a/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticStartAnalysisScope.cs
+++ b/src/Compilers/Core/Portable/DiagnosticAnalyzer/DiagnosticStartAnalysisScope.cs
@@ -10,6 +10,7 @@
 using System.Threading;
 using Microsoft.CodeAnalysis.FlowAnalysis;
 using Microsoft.CodeAnalysis.PooledObjects;
+using Microsoft.CodeAnalysis.Text;
 
 namespace Microsoft.CodeAnalysis.Diagnostics
 {
@@ -232,8 +233,10 @@ internal AnalyzerSymbolStartAnalysisContext(DiagnosticAnalyzer analyzer,
                                                        Compilation compilation,
                                                        AnalyzerOptions options,
                                                        bool isGeneratedCode,
+                                                       SyntaxTree? filterTree,
+                                                       TextSpan? filterSpan,
                                                        CancellationToken cancellationToken)
-            : base(owningSymbol, compilation, options, isGeneratedCode, cancellationToken)
+            : base(owningSymbol, compilation, options, isGeneratedCode, filterTree, filterSpan, cancellationToken)
         {
             _analyzer = analyzer;
             _scope = scope;
@@ -296,9 +299,10 @@ internal AnalyzerCodeBlockStartAnalysisContext(DiagnosticAnalyzer analyzer,
                                                        ISymbol owningSymbol,
                                                        SemanticModel semanticModel,
                                                        AnalyzerOptions options,
+                                                       TextSpan? filterSpan,
                                                        bool isGeneratedCode,
                                                        CancellationToken cancellationToken)
-            : base(codeBlock, owningSymbol, semanticModel, options, isGeneratedCode, cancellationToken)
+            : base(codeBlock, owningSymbol, semanticModel, options, filterSpan, isGeneratedCode, cancellationToken)
         {
             _analyzer = analyzer;
             _scope = scope;
@@ -332,9 +336,11 @@ internal AnalyzerOperationBlockStartAnalysisContext(DiagnosticAnalyzer analyzer,
                                                             Compilation compilation,
                                                             AnalyzerOptions options,
                                                             Func<IOperation, ControlFlowGraph> getControlFlowGraph,
+                                                            SyntaxTree filterTree,
+                                                            TextSpan? filterSpan,
                                                             bool isGeneratedCode,
                                                             CancellationToken cancellationToken)
-            : base(operationBlocks, owningSymbol, compilation, options, getControlFlowGraph, isGeneratedCode, cancellationToken)
+            : base(operationBlocks, owningSymbol, compilation, options, getControlFlowGraph, filterTree, filterSpan, isGeneratedCode, cancellationToken)
         {
             _analyzer = analyzer;
             _scope = scope;
@@ -573,6 +579,8 @@ public void RegisterSymbolAction(DiagnosticAnalyzer analyzer, Action<SymbolAnaly
                                     context.ReportDiagnostic,
                                     context.IsSupportedDiagnostic,
                                     context.IsGeneratedCode,
+                                    context.FilterTree,
+                                    context.FilterSpan,
                                     context.CancellationToken));
                             }
                         }
diff --git a/src/Compilers/Core/Portable/Emit/EditAndContinue/SymbolChanges.cs b/src/Compilers/Core/Portable/Emit/EditAndContinue/SymbolChanges.cs
index 62af09ad4622e..1a4c0ae63fe6b 100644
--- a/src/Compilers/Core/Portable/Emit/EditAndContinue/SymbolChanges.cs
+++ b/src/Compilers/Core/Portable/Emit/EditAndContinue/SymbolChanges.cs
@@ -494,7 +494,18 @@ private static void CalculateChanges(IEnumerable<SemanticEdit> edits, out IReadO
                 }
 
                 AddContainingTypesAndNamespaces(changesBuilder, member);
-                changesBuilder.Add(member, change);
+
+                // If we saw an edit for a symbol that is a nested type of this symbol, we might already have a dictionary entry
+                // for it, flagging that it contains changes. If so we "upgrade" the change to the real one.
+                if (changesBuilder.TryGetValue(member, out var existingChange) && existingChange == SymbolChange.ContainsChanges)
+                {
+                    Debug.Assert(member is INamedTypeSymbol);
+                    changesBuilder[member] = change;
+                }
+                else
+                {
+                    changesBuilder.Add(member, change);
+                }
             }
 
             changes = changesBuilder;
diff --git a/src/Compilers/Core/Portable/Generated/OperationKind.Generated.cs b/src/Compilers/Core/Portable/Generated/OperationKind.Generated.cs
index 5a68010063f9e..59b18510edc27 100644
--- a/src/Compilers/Core/Portable/Generated/OperationKind.Generated.cs
+++ b/src/Compilers/Core/Portable/Generated/OperationKind.Generated.cs
@@ -279,5 +279,7 @@ public enum OperationKind
         Utf8String = 0x7c,
         /// <summary>Indicates an <see cref="IAttributeOperation"/>.</summary>
         Attribute = 0x7d,
+        /// <summary>Indicates an <see cref="IInlineArrayAccessOperation"/>.</summary>
+        InlineArrayAccess = 0x7e,
     }
 }
diff --git a/src/Compilers/Core/Portable/Generated/Operations.Generated.cs b/src/Compilers/Core/Portable/Generated/Operations.Generated.cs
index 249b1af87b2e4..4f8ee2280daba 100644
--- a/src/Compilers/Core/Portable/Generated/Operations.Generated.cs
+++ b/src/Compilers/Core/Portable/Generated/Operations.Generated.cs
@@ -3620,6 +3620,32 @@ public interface IAttributeOperation : IOperation
         /// </summary>
         IOperation Operation { get; }
     }
+    /// <summary>
+    /// Represents an element reference or a slice operation over an inline array type.
+    /// <para>
+    ///   Current usage:
+    ///   (1) C# inline array access.
+    /// </para>
+    /// </summary>
+    /// <remarks>
+    /// <para>This node is associated with the following operation kinds:</para>
+    /// <list type="bullet">
+    /// <item><description><see cref="OperationKind.InlineArrayAccess"/></description></item>
+    /// </list>
+    /// <para>This interface is reserved for implementation by its associated APIs. We reserve the right to
+    /// change it in the future.</para>
+    /// </remarks>
+    public interface IInlineArrayAccessOperation : IOperation
+    {
+        /// <summary>
+        /// Instance of the inline array type to be accessed.
+        /// </summary>
+        IOperation Instance { get; }
+        /// <summary>
+        /// System.Int32, System.Index or System.Range value.
+        /// </summary>
+        IOperation Argument { get; }
+    }
     #endregion
 
     #region Implementations
@@ -10230,6 +10256,69 @@ internal override (bool hasNext, int nextSlot, int nextIndex) MoveNextReversed(i
         public override void Accept(OperationVisitor visitor) => visitor.VisitAttribute(this);
         public override TResult? Accept<TArgument, TResult>(OperationVisitor<TArgument, TResult> visitor, TArgument argument) where TResult : default => visitor.VisitAttribute(this, argument);
     }
+    internal sealed partial class InlineArrayAccessOperation : Operation, IInlineArrayAccessOperation
+    {
+        internal InlineArrayAccessOperation(IOperation instance, IOperation argument, SemanticModel? semanticModel, SyntaxNode syntax, ITypeSymbol? type, bool isImplicit)
+            : base(semanticModel, syntax, isImplicit)
+        {
+            Instance = SetParentOperation(instance, this);
+            Argument = SetParentOperation(argument, this);
+            Type = type;
+        }
+        public IOperation Instance { get; }
+        public IOperation Argument { get; }
+        internal override int ChildOperationsCount =>
+            (Instance is null ? 0 : 1) +
+            (Argument is null ? 0 : 1);
+        internal override IOperation GetCurrent(int slot, int index)
+            => slot switch
+            {
+                0 when Instance != null
+                    => Instance,
+                1 when Argument != null
+                    => Argument,
+                _ => throw ExceptionUtilities.UnexpectedValue((slot, index)),
+            };
+        internal override (bool hasNext, int nextSlot, int nextIndex) MoveNext(int previousSlot, int previousIndex)
+        {
+            switch (previousSlot)
+            {
+                case -1:
+                    if (Instance != null) return (true, 0, 0);
+                    else goto case 0;
+                case 0:
+                    if (Argument != null) return (true, 1, 0);
+                    else goto case 1;
+                case 1:
+                case 2:
+                    return (false, 2, 0);
+                default:
+                    throw ExceptionUtilities.UnexpectedValue((previousSlot, previousIndex));
+            }
+        }
+        internal override (bool hasNext, int nextSlot, int nextIndex) MoveNextReversed(int previousSlot, int previousIndex)
+        {
+            switch (previousSlot)
+            {
+                case int.MaxValue:
+                    if (Argument != null) return (true, 1, 0);
+                    else goto case 1;
+                case 1:
+                    if (Instance != null) return (true, 0, 0);
+                    else goto case 0;
+                case 0:
+                case -1:
+                    return (false, -1, 0);
+                default:
+                    throw ExceptionUtilities.UnexpectedValue((previousSlot, previousIndex));
+            }
+        }
+        public override ITypeSymbol? Type { get; }
+        internal override ConstantValue? OperationConstantValue => null;
+        public override OperationKind Kind => OperationKind.InlineArrayAccess;
+        public override void Accept(OperationVisitor visitor) => visitor.VisitInlineArrayAccess(this);
+        public override TResult? Accept<TArgument, TResult>(OperationVisitor<TArgument, TResult> visitor, TArgument argument) where TResult : default => visitor.VisitInlineArrayAccess(this, argument);
+    }
     #endregion
     #region Cloner
     internal sealed partial class OperationCloner : OperationVisitor<object?, IOperation>
@@ -10838,6 +10927,11 @@ public override IOperation VisitAttribute(IAttributeOperation operation, object?
             var internalOperation = (AttributeOperation)operation;
             return new AttributeOperation(Visit(internalOperation.Operation), internalOperation.OwningSemanticModel, internalOperation.Syntax, internalOperation.IsImplicit);
         }
+        public override IOperation VisitInlineArrayAccess(IInlineArrayAccessOperation operation, object? argument)
+        {
+            var internalOperation = (InlineArrayAccessOperation)operation;
+            return new InlineArrayAccessOperation(Visit(internalOperation.Instance), Visit(internalOperation.Argument), internalOperation.OwningSemanticModel, internalOperation.Syntax, internalOperation.Type, internalOperation.IsImplicit);
+        }
     }
     #endregion
     
@@ -10977,6 +11071,7 @@ internal virtual void VisitNoneOperation(IOperation operation) { /* no-op */ }
         public virtual void VisitImplicitIndexerReference(IImplicitIndexerReferenceOperation operation) => DefaultVisit(operation);
         public virtual void VisitUtf8String(IUtf8StringOperation operation) => DefaultVisit(operation);
         public virtual void VisitAttribute(IAttributeOperation operation) => DefaultVisit(operation);
+        public virtual void VisitInlineArrayAccess(IInlineArrayAccessOperation operation) => DefaultVisit(operation);
     }
     public abstract partial class OperationVisitor<TArgument, TResult>
     {
@@ -11113,6 +11208,7 @@ public abstract partial class OperationVisitor<TArgument, TResult>
         public virtual TResult? VisitImplicitIndexerReference(IImplicitIndexerReferenceOperation operation, TArgument argument) => DefaultVisit(operation, argument);
         public virtual TResult? VisitUtf8String(IUtf8StringOperation operation, TArgument argument) => DefaultVisit(operation, argument);
         public virtual TResult? VisitAttribute(IAttributeOperation operation, TArgument argument) => DefaultVisit(operation, argument);
+        public virtual TResult? VisitInlineArrayAccess(IInlineArrayAccessOperation operation, TArgument argument) => DefaultVisit(operation, argument);
     }
     #endregion
 }
diff --git a/src/Compilers/Core/Portable/InternalUtilities/ConcurrentDictionaryExtensions.cs b/src/Compilers/Core/Portable/InternalUtilities/ConcurrentDictionaryExtensions.cs
index 061b7394c93f3..900003e99ea6d 100644
--- a/src/Compilers/Core/Portable/InternalUtilities/ConcurrentDictionaryExtensions.cs
+++ b/src/Compilers/Core/Portable/InternalUtilities/ConcurrentDictionaryExtensions.cs
@@ -38,5 +38,25 @@ public static TValue GetOrAdd<TKey, TArg, TValue>(this ConcurrentDictionary<TKey
             return dictionary.GetOrAdd(key, boundFunction);
 #endif
         }
+
+        // original signature:
+        // public TValue ConcurrentDictionary<TKey, TValue>.AddOrUpdate<TArg>(TKey key, Func<TKey,TArg,TValue> addValueFactory, Func<TKey,TValue,TArg,TValue> updateValueFactory, TArg factoryArgument);
+        public static TValue AddOrUpdate<TKey, TValue, TArg>(
+            this ConcurrentDictionary<TKey, TValue> dictionary,
+            TKey key,
+            Func<TKey, TArg, TValue> addValueFactory,
+            Func<TKey, TValue, TArg, TValue> updateValueFactory,
+            TArg factoryArgument)
+            where TKey : notnull
+        {
+#if NETCOREAPP
+            return dictionary.AddOrUpdate(key, addValueFactory, updateValueFactory, factoryArgument);
+#else
+            using var _a = PooledDelegates.GetPooledFunction(addValueFactory, factoryArgument, out var pooledAddValueFactory);
+            using var _b = PooledDelegates.GetPooledFunction(updateValueFactory, factoryArgument, out var pooledUpdateValueFactory);
+            return dictionary.AddOrUpdate(key, pooledAddValueFactory, pooledUpdateValueFactory);
+#endif
+        }
+
     }
 }
diff --git a/src/Compilers/Core/Portable/InternalUtilities/EmptyComparer.cs b/src/Compilers/Core/Portable/InternalUtilities/EmptyComparer.cs
index 93b8e0e912fa6..71e3a791ee95b 100644
--- a/src/Compilers/Core/Portable/InternalUtilities/EmptyComparer.cs
+++ b/src/Compilers/Core/Portable/InternalUtilities/EmptyComparer.cs
@@ -21,10 +21,7 @@ private EmptyComparer()
         }
 
         bool IEqualityComparer<object>.Equals(object? a, object? b)
-        {
-            Debug.Assert(false, "Are we using empty comparer with nonempty dictionary?");
-            return false;
-        }
+            => throw ExceptionUtilities.Unreachable();
 
         int IEqualityComparer<object>.GetHashCode(object s)
         {
diff --git a/src/Compilers/Core/Portable/InternalUtilities/ReadOnlyMemoryOfCharComparer.cs b/src/Compilers/Core/Portable/InternalUtilities/ReadOnlyMemoryOfCharComparer.cs
new file mode 100644
index 0000000000000..8c6fa879e3218
--- /dev/null
+++ b/src/Compilers/Core/Portable/InternalUtilities/ReadOnlyMemoryOfCharComparer.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#nullable disable
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis
+{
+    internal sealed class ReadOnlyMemoryOfCharComparer : IEqualityComparer<ReadOnlyMemory<char>>
+    {
+        public static readonly ReadOnlyMemoryOfCharComparer Instance = new ReadOnlyMemoryOfCharComparer();
+
+        private ReadOnlyMemoryOfCharComparer()
+        {
+        }
+
+        public static bool Equals(ReadOnlySpan<char> x, ReadOnlyMemory<char> y)
+            => x.SequenceEqual(y.Span);
+
+        public bool Equals(ReadOnlyMemory<char> x, ReadOnlyMemory<char> y)
+            => x.Span.SequenceEqual(y.Span);
+
+        public int GetHashCode(ReadOnlyMemory<char> obj)
+        {
+#if NET
+            return string.GetHashCode(obj.Span);
+#else
+            return Hash.GetFNVHashCode(obj.Span);
+#endif
+        }
+    }
+
+    /// <summary>
+    /// Very cheap trivial comparer that never matches the keys,
+    /// should only be used in empty dictionaries.
+    /// </summary>
+    internal sealed class EmptyReadOnlyMemoryOfCharComparer : IEqualityComparer<ReadOnlyMemory<char>>
+    {
+        public static readonly EmptyReadOnlyMemoryOfCharComparer Instance = new EmptyReadOnlyMemoryOfCharComparer();
+
+        private EmptyReadOnlyMemoryOfCharComparer()
+        {
+        }
+
+        public bool Equals(ReadOnlyMemory<char> a, ReadOnlyMemory<char> b)
+            => throw ExceptionUtilities.Unreachable();
+
+        public int GetHashCode(ReadOnlyMemory<char> s)
+        {
+            // dictionary will call this often
+            return 0;
+        }
+    }
+}
diff --git a/src/Compilers/Core/Portable/MetadataReader/MetadataHelpers.cs b/src/Compilers/Core/Portable/MetadataReader/MetadataHelpers.cs
index d39b39bc002ef..c940072347ad8 100644
--- a/src/Compilers/Core/Portable/MetadataReader/MetadataHelpers.cs
+++ b/src/Compilers/Core/Portable/MetadataReader/MetadataHelpers.cs
@@ -480,10 +480,10 @@ internal static string ComposeAritySuffixedMetadataName(string name, int arity,
         internal static int InferTypeArityFromMetadataName(string emittedTypeName)
         {
             int suffixStartsAt;
-            return InferTypeArityFromMetadataName(emittedTypeName, out suffixStartsAt);
+            return InferTypeArityFromMetadataName(emittedTypeName.AsSpan(), out suffixStartsAt);
         }
 
-        private static short InferTypeArityFromMetadataName(string emittedTypeName, out int suffixStartsAt)
+        private static short InferTypeArityFromMetadataName(ReadOnlySpan<char> emittedTypeName, out int suffixStartsAt)
         {
             Debug.Assert(emittedTypeName != null, "NULL actual name unexpected!!!");
             int emittedTypeNameLength = emittedTypeName.Length;
@@ -505,28 +505,56 @@ private static short InferTypeArityFromMetadataName(string emittedTypeName, out
                 return 0;
             }
 
-            // Given a name corresponding to <unmangledName>`<arity>,
-            // extract the arity.
-            string stringRepresentingArity = emittedTypeName.Substring(indexOfManglingChar);
-
-            int arity;
-            bool nonNumericCharFound = !int.TryParse(stringRepresentingArity, NumberStyles.None, CultureInfo.InvariantCulture, out arity);
-
-            if (nonNumericCharFound || arity < 0 || arity > short.MaxValue ||
-                stringRepresentingArity != arity.ToString())
+            // Given a name corresponding to <unmangledName>`<arity>, extract the arity.
+            if (tryScanArity(emittedTypeName[indexOfManglingChar..]) is not short arity)
             {
                 suffixStartsAt = -1;
                 return 0;
             }
 
             suffixStartsAt = indexOfManglingChar - 1;
-            return (short)arity;
+            return arity;
+
+            static short? tryScanArity(ReadOnlySpan<char> aritySpan)
+            {
+                // Arity must have at least one character and must not have leading zeroes.
+                // Also, in order to fit into short.MaxValue (32767), it must be at most 5 characters long. 
+                if (aritySpan is { Length: >= 1 and <= 5 } and not ['0', ..])
+                {
+                    int intArity = 0;
+                    foreach (char digit in aritySpan)
+                    {
+                        // Accepting integral decimal digits only
+                        if (digit is < '0' or > '9')
+                            return null;
+
+                        intArity = intArity * 10 + (digit - '0');
+                    }
+
+                    Debug.Assert(intArity > 0);
+
+                    if (intArity <= short.MaxValue)
+                        return (short)intArity;
+                }
+
+                return null;
+            }
         }
 
         internal static string InferTypeArityAndUnmangleMetadataName(string emittedTypeName, out short arity)
+        {
+            var emittedTypeNameMemory = emittedTypeName.AsMemory();
+            var resultMemory = InferTypeArityAndUnmangleMetadataName(emittedTypeNameMemory, out arity);
+            var resultString = resultMemory.ToString();
+
+            Debug.Assert(!resultMemory.Equals(emittedTypeNameMemory) || ReferenceEquals(resultString, emittedTypeName), "If the name was not mangled, we should get the original string instance back.");
+            return resultString;
+        }
+
+        internal static ReadOnlyMemory<char> InferTypeArityAndUnmangleMetadataName(ReadOnlyMemory<char> emittedTypeName, out short arity)
         {
             int suffixStartsAt;
-            arity = InferTypeArityFromMetadataName(emittedTypeName, out suffixStartsAt);
+            arity = InferTypeArityFromMetadataName(emittedTypeName.Span, out suffixStartsAt);
 
             if (arity == 0)
             {
@@ -535,7 +563,7 @@ internal static string InferTypeArityAndUnmangleMetadataName(string emittedTypeN
             }
 
             Debug.Assert(suffixStartsAt > 0 && suffixStartsAt < emittedTypeName.Length - 1);
-            return emittedTypeName.Substring(0, suffixStartsAt);
+            return emittedTypeName[..suffixStartsAt];
         }
 
         internal static string UnmangleMetadataNameForArity(string emittedTypeName, int arity)
@@ -543,10 +571,10 @@ internal static string UnmangleMetadataNameForArity(string emittedTypeName, int
             Debug.Assert(arity > 0);
 
             int suffixStartsAt;
-            if (arity == InferTypeArityFromMetadataName(emittedTypeName, out suffixStartsAt))
+            if (arity == InferTypeArityFromMetadataName(emittedTypeName.AsSpan(), out suffixStartsAt))
             {
                 Debug.Assert(suffixStartsAt > 0 && suffixStartsAt < emittedTypeName.Length - 1);
-                return emittedTypeName.Substring(0, suffixStartsAt);
+                return emittedTypeName[..suffixStartsAt];
             }
 
             return emittedTypeName;
@@ -556,22 +584,30 @@ internal static string UnmangleMetadataNameForArity(string emittedTypeName, int
         /// An ImmutableArray representing the single string "System"
         /// </summary>
         private static readonly ImmutableArray<string> s_splitQualifiedNameSystem = ImmutableArray.Create(SystemString);
+        private static readonly ImmutableArray<ReadOnlyMemory<char>> s_splitQualifiedNameSystemMemory = ImmutableArray.Create(SystemString.AsMemory());
+
+        internal static ImmutableArray<string> SplitQualifiedName(string name)
+            => SplitQualifiedNameWorker(name.AsMemory(), s_splitQualifiedNameSystem, static memory => memory.ToString());
+
+        internal static ImmutableArray<ReadOnlyMemory<char>> SplitQualifiedName(ReadOnlyMemory<char> name)
+            => SplitQualifiedNameWorker(name, s_splitQualifiedNameSystemMemory, static memory => memory);
 
-        internal static ImmutableArray<string> SplitQualifiedName(
-              string name)
+        internal static ImmutableArray<T> SplitQualifiedNameWorker<T>(
+            ReadOnlyMemory<char> nameMemory, ImmutableArray<T> splitSystemString, Func<ReadOnlyMemory<char>, T> convert)
         {
-            Debug.Assert(name != null);
+            Debug.Assert(!nameMemory.Equals(default(ReadOnlyMemory<char>)));
 
-            if (name.Length == 0)
+            if (nameMemory.Length == 0)
             {
-                return ImmutableArray<string>.Empty;
+                return ImmutableArray<T>.Empty;
             }
 
             // PERF: Avoid String.Split because of the allocations. Also, we can special-case
             // for "System" if it is the first or only part.
 
             int dots = 0;
-            foreach (char ch in name)
+            var nameSpan = nameMemory.Span;
+            foreach (char ch in nameSpan)
             {
                 if (ch == DotDelimiter)
                 {
@@ -581,24 +617,24 @@ internal static ImmutableArray<string> SplitQualifiedName(
 
             if (dots == 0)
             {
-                return name == SystemString ? s_splitQualifiedNameSystem : ImmutableArray.Create(name);
+                return nameMemory.Span.SequenceEqual(SystemString.AsSpan()) ? splitSystemString : ImmutableArray.Create(convert(nameMemory));
             }
 
-            var result = ArrayBuilder<string>.GetInstance(dots + 1);
+            var result = ArrayBuilder<T>.GetInstance(dots + 1);
 
             int start = 0;
             for (int i = 0; dots > 0; i++)
             {
-                if (name[i] == DotDelimiter)
+                if (nameSpan[i] == DotDelimiter)
                 {
                     int len = i - start;
-                    if (len == 6 && start == 0 && name.StartsWith(SystemString, StringComparison.Ordinal))
+                    if (len == 6 && start == 0 && nameSpan.StartsWith(SystemString.AsSpan(), StringComparison.Ordinal))
                     {
-                        result.Add(SystemString);
+                        result.Add(convert(SystemString.AsMemory()));
                     }
                     else
                     {
-                        result.Add(name.Substring(start, len));
+                        result.Add(convert(nameMemory.Slice(start, len)));
                     }
 
                     dots--;
@@ -606,7 +642,7 @@ internal static ImmutableArray<string> SplitQualifiedName(
                 }
             }
 
-            result.Add(name.Substring(start));
+            result.Add(convert(nameMemory[start..]));
 
             return result.ToImmutableAndFree();
         }
@@ -614,6 +650,15 @@ internal static ImmutableArray<string> SplitQualifiedName(
         internal static string SplitQualifiedName(
             string pstrName,
             out string qualifier)
+        {
+            ReadOnlyMemory<char> nameMemory = SplitQualifiedName(pstrName, out ReadOnlyMemory<char> qualifierMemory);
+            qualifier = qualifierMemory.ToString();
+            return nameMemory.ToString();
+        }
+
+        internal static ReadOnlyMemory<char> SplitQualifiedName(
+            string pstrName,
+            out ReadOnlyMemory<char> qualifier)
         {
             Debug.Assert(pstrName != null);
 
@@ -647,20 +692,20 @@ internal static string SplitQualifiedName(
 
             if (delimiter < 0)
             {
-                qualifier = string.Empty;
-                return pstrName;
+                qualifier = string.Empty.AsMemory();
+                return pstrName.AsMemory();
             }
 
             if (delimiter == 6 && pstrName.StartsWith(SystemString, StringComparison.Ordinal))
             {
-                qualifier = SystemString;
+                qualifier = SystemString.AsMemory();
             }
             else
             {
-                qualifier = pstrName.Substring(0, delimiter);
+                qualifier = pstrName.AsMemory()[..delimiter];
             }
 
-            return pstrName.Substring(delimiter + 1);
+            return pstrName.AsMemory()[(delimiter + 1)..];
         }
 
         internal static string BuildQualifiedName(
diff --git a/src/Compilers/Core/Portable/MetadataReader/MetadataTypeName.cs b/src/Compilers/Core/Portable/MetadataReader/MetadataTypeName.cs
index 2a64ff7926820..7021eef56177b 100644
--- a/src/Compilers/Core/Portable/MetadataReader/MetadataTypeName.cs
+++ b/src/Compilers/Core/Portable/MetadataReader/MetadataTypeName.cs
@@ -5,6 +5,7 @@
 #nullable disable
 
 using System;
+using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
 using Roslyn.Utilities;
@@ -30,16 +31,30 @@ internal partial struct MetadataTypeName
         /// </summary>
         private string _namespaceName;
 
+        /// <summary>
+        /// <see cref="ReadOnlyMemory{T}"/> version of <see cref="_namespaceName"/>.  Preferred when possible to avoid
+        /// the copy of the portion of <see cref="_fullName"/> used for <see cref="_namespaceName"/>.
+        /// </summary>
+        private ReadOnlyMemory<char> _namespaceNameMemory;
+
         /// <summary>
         /// Name of the type without namespace prefix, but possibly with generic arity mangling present.
         /// </summary>
         private string _typeName;
 
+        /// <summary>
+        /// <see cref="ReadOnlyMemory{T}"/> version of <see cref="_typeName"/>.  Preferred when possible to avoid
+        /// the copy of the portion of <see cref="_fullName"/> used for <see cref="_typeName"/>.
+        /// </summary>
+        private ReadOnlyMemory<char> _typeNameMemory;
+
         /// <summary>
         /// Name of the type without namespace prefix and without generic arity mangling.
         /// </summary>
         private string _unmangledTypeName;
 
+        private ReadOnlyMemory<char> _unmangledTypeNameMemory;
+
         /// <summary>
         /// Arity of the type inferred based on the name mangling. It doesn't have to match the actual
         /// arity of the type.
@@ -68,6 +83,12 @@ internal partial struct MetadataTypeName
         /// </summary>
         private ImmutableArray<string> _namespaceSegments;
 
+        /// <summary>
+        /// <see cref="ReadOnlyMemory{T}"/> version of <see cref="_namespaceSegments"/>.  Preferred when possible to
+        /// avoid the copies of the portions of <see cref="_fullName"/> used for <see cref="_namespaceSegments"/>.
+        /// </summary>
+        private ImmutableArray<ReadOnlyMemory<char>> _namespaceSegmentsMemory;
+
         public static MetadataTypeName FromFullName(string fullName, bool useCLSCompliantNameArityEncoding = false, int forcedArity = -1)
         {
             Debug.Assert(fullName != null);
@@ -81,12 +102,16 @@ public static MetadataTypeName FromFullName(string fullName, bool useCLSComplian
 
             name._fullName = fullName;
             name._namespaceName = null;
+            name._namespaceNameMemory = default;
             name._typeName = null;
+            name._typeNameMemory = default;
             name._unmangledTypeName = null;
+            name._unmangledTypeNameMemory = default;
             name._inferredArity = -1;
             name._useCLSCompliantNameArityEncoding = useCLSCompliantNameArityEncoding;
             name._forcedArity = (short)forcedArity;
             name._namespaceSegments = default(ImmutableArray<string>);
+            name._namespaceSegmentsMemory = default;
 
             return name;
         }
@@ -109,12 +134,16 @@ public static MetadataTypeName FromNamespaceAndTypeName(
 
             name._fullName = null;
             name._namespaceName = namespaceName;
+            name._namespaceNameMemory = namespaceName.AsMemory();
             name._typeName = typeName;
+            name._typeNameMemory = typeName.AsMemory();
             name._unmangledTypeName = null;
+            name._unmangledTypeNameMemory = default;
             name._inferredArity = -1;
             name._useCLSCompliantNameArityEncoding = useCLSCompliantNameArityEncoding;
             name._forcedArity = (short)forcedArity;
             name._namespaceSegments = default(ImmutableArray<string>);
+            name._namespaceSegmentsMemory = default;
 
             return name;
         }
@@ -133,12 +162,16 @@ public static MetadataTypeName FromTypeName(string typeName, bool useCLSComplian
 
             name._fullName = typeName;
             name._namespaceName = string.Empty;
+            name._namespaceNameMemory = string.Empty.AsMemory();
             name._typeName = typeName;
+            name._typeNameMemory = typeName.AsMemory();
             name._unmangledTypeName = null;
+            name._unmangledTypeNameMemory = default;
             name._inferredArity = -1;
             name._useCLSCompliantNameArityEncoding = useCLSCompliantNameArityEncoding;
             name._forcedArity = (short)forcedArity;
             name._namespaceSegments = ImmutableArray<string>.Empty;
+            name._namespaceSegmentsMemory = ImmutableArray<ReadOnlyMemory<char>>.Empty;
 
             return name;
         }
@@ -161,37 +194,58 @@ public string FullName
             }
         }
 
+        /// <inheritdoc cref="NamespaceName"/>
+        public ReadOnlyMemory<char> NamespaceNameMemory
+        {
+            get
+            {
+                if (_namespaceNameMemory.Equals(default(ReadOnlyMemory<char>)))
+                {
+                    Debug.Assert(_fullName != null);
+                    _typeNameMemory = MetadataHelpers.SplitQualifiedName(_fullName, out _namespaceNameMemory);
+                }
+
+                return _namespaceNameMemory;
+            }
+        }
+
         /// <summary>
         /// Namespace name for top level types, empty string for nested types.
         /// </summary>
-        public string NamespaceName
+        public string NamespaceName => _namespaceName ??= NamespaceNameMemory.ToString();
+
+        /// <inheritdoc cref="TypeName"/>
+        public ReadOnlyMemory<char> TypeNameMemory
         {
             get
             {
-                if (_namespaceName == null)
+                if (_typeNameMemory.Equals(default(ReadOnlyMemory<char>)))
                 {
                     Debug.Assert(_fullName != null);
-                    _typeName = MetadataHelpers.SplitQualifiedName(_fullName, out _namespaceName);
+                    _typeNameMemory = MetadataHelpers.SplitQualifiedName(_fullName, out _namespaceNameMemory);
                 }
 
-                return _namespaceName;
+                return _typeNameMemory;
             }
         }
 
         /// <summary>
         /// Name of the type without namespace prefix, but possibly with generic arity mangling present.
         /// </summary>
-        public string TypeName
+        public string TypeName => _typeName ??= TypeNameMemory.ToString();
+
+        /// <inheritdoc cref="UnmangledTypeName"/>
+        public ReadOnlyMemory<char> UnmangledTypeNameMemory
         {
             get
             {
-                if (_typeName == null)
+                if (_unmangledTypeNameMemory.Equals(default(ReadOnlyMemory<char>)))
                 {
-                    Debug.Assert(_fullName != null);
-                    _typeName = MetadataHelpers.SplitQualifiedName(_fullName, out _namespaceName);
+                    Debug.Assert(_inferredArity == -1);
+                    _unmangledTypeNameMemory = MetadataHelpers.InferTypeArityAndUnmangleMetadataName(TypeNameMemory, out _inferredArity);
                 }
 
-                return _typeName;
+                return _unmangledTypeNameMemory;
             }
         }
 
@@ -202,11 +256,11 @@ public string UnmangledTypeName
         {
             get
             {
-                if (_unmangledTypeName == null)
-                {
-                    Debug.Assert(_inferredArity == -1);
-                    _unmangledTypeName = MetadataHelpers.InferTypeArityAndUnmangleMetadataName(TypeName, out _inferredArity);
-                }
+                // Common case optimization.  If the type name is not generic, then point directly at TypeName
+                // instead of allocating a new string.
+                _unmangledTypeName ??= UnmangledTypeNameMemory.Equals(TypeNameMemory)
+                    ? TypeName
+                    : UnmangledTypeNameMemory.ToString();
 
                 return _unmangledTypeName;
             }
@@ -222,8 +276,9 @@ public int InferredArity
             {
                 if (_inferredArity == -1)
                 {
+                    Debug.Assert(_unmangledTypeNameMemory.Equals(default(ReadOnlyMemory<char>)));
                     Debug.Assert(_unmangledTypeName == null);
-                    _unmangledTypeName = MetadataHelpers.InferTypeArityAndUnmangleMetadataName(TypeName, out _inferredArity);
+                    _unmangledTypeNameMemory = MetadataHelpers.InferTypeArityAndUnmangleMetadataName(TypeNameMemory, out _inferredArity);
                 }
 
                 return _inferredArity;
@@ -269,6 +324,20 @@ public readonly int ForcedArity
             }
         }
 
+        /// <inheritdoc cref="NamespaceSegments"/>
+        public ImmutableArray<ReadOnlyMemory<char>> NamespaceSegmentsMemory
+        {
+            get
+            {
+                if (_namespaceSegmentsMemory.IsDefault)
+                {
+                    _namespaceSegmentsMemory = MetadataHelpers.SplitQualifiedName(NamespaceNameMemory);
+                }
+
+                return _namespaceSegmentsMemory;
+            }
+        }
+
         /// <summary>
         /// Individual parts of qualified namespace name.
         /// </summary>
@@ -278,7 +347,7 @@ public ImmutableArray<string> NamespaceSegments
             {
                 if (_namespaceSegments.IsDefault)
                 {
-                    _namespaceSegments = MetadataHelpers.SplitQualifiedName(NamespaceName);
+                    _namespaceSegments = NamespaceSegmentsMemory.SelectAsArray(static s => s.ToString());
                 }
 
                 return _namespaceSegments;
diff --git a/src/Compilers/Core/Portable/MetadataReader/PEAssembly.cs b/src/Compilers/Core/Portable/MetadataReader/PEAssembly.cs
index 04af11a9dee76..c7a69ed3db968 100644
--- a/src/Compilers/Core/Portable/MetadataReader/PEAssembly.cs
+++ b/src/Compilers/Core/Portable/MetadataReader/PEAssembly.cs
@@ -159,8 +159,7 @@ private Dictionary<string, List<ImmutableArray<byte>>> BuildInternalsVisibleToMa
 
         internal IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicKeys(string simpleName)
         {
-            if (_lazyInternalsVisibleToMap == null)
-                Interlocked.CompareExchange(ref _lazyInternalsVisibleToMap, BuildInternalsVisibleToMap(), null);
+            EnsureInternalsVisibleToMapInitialized();
 
             List<ImmutableArray<byte>> result;
 
@@ -169,6 +168,19 @@ internal IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicKeys(strin
             return result ?? SpecializedCollections.EmptyEnumerable<ImmutableArray<byte>>();
         }
 
+        internal IEnumerable<string> GetInternalsVisibleToAssemblyNames()
+        {
+            EnsureInternalsVisibleToMapInitialized();
+
+            return _lazyInternalsVisibleToMap.Keys;
+        }
+
+        private void EnsureInternalsVisibleToMapInitialized()
+        {
+            if (_lazyInternalsVisibleToMap == null)
+                Interlocked.CompareExchange(ref _lazyInternalsVisibleToMap, BuildInternalsVisibleToMap(), null);
+        }
+
         internal bool DeclaresTheObjectClass
         {
             get
diff --git a/src/Compilers/Core/Portable/MetadataReader/PEModule.cs b/src/Compilers/Core/Portable/MetadataReader/PEModule.cs
index 478a6c3f80911..eb4cef10960c6 100644
--- a/src/Compilers/Core/Portable/MetadataReader/PEModule.cs
+++ b/src/Compilers/Core/Portable/MetadataReader/PEModule.cs
@@ -1113,6 +1113,23 @@ internal bool HasRefSafetyRulesAttribute(EntityHandle token, out int version, ou
             return false;
         }
 
+        internal bool HasInlineArrayAttribute(TypeDefinitionHandle token, out int length)
+        {
+            AttributeInfo info = FindTargetAttribute(token, AttributeDescription.InlineArrayAttribute);
+            if (info.HasValue)
+            {
+                Debug.Assert(info.SignatureIndex == 0);
+                if (TryExtractValueFromAttribute(info.Handle, out int value, s_attributeIntValueExtractor))
+                {
+                    length = value;
+                    return true;
+                }
+            }
+
+            length = 0;
+            return false;
+        }
+
         internal bool HasTupleElementNamesAttribute(EntityHandle token, out ImmutableArray<string> tupleElementNames)
         {
             var info = FindTargetAttribute(token, AttributeDescription.TupleElementNamesAttribute);
diff --git a/src/Compilers/Core/Portable/Operations/ControlFlowGraphBuilder.cs b/src/Compilers/Core/Portable/Operations/ControlFlowGraphBuilder.cs
index 8a4ab396e0b1e..ec0424d548a78 100644
--- a/src/Compilers/Core/Portable/Operations/ControlFlowGraphBuilder.cs
+++ b/src/Compilers/Core/Portable/Operations/ControlFlowGraphBuilder.cs
@@ -2132,6 +2132,17 @@ public override IOperation VisitImplicitIndexerReference(IImplicitIndexerReferen
                 operation.Syntax, operation.Type, IsImplicit(operation));
         }
 
+        public override IOperation? VisitInlineArrayAccess(IInlineArrayAccessOperation operation, int? captureIdForResult)
+        {
+            EvalStackFrame frame = PushStackFrame();
+            PushOperand(VisitRequired(operation.Instance));
+            IOperation argument = VisitRequired(operation.Argument);
+            IOperation instance = PopOperand();
+            PopStackFrame(frame);
+            return new InlineArrayAccessOperation(instance, argument, semanticModel: null,
+                operation.Syntax, operation.Type, IsImplicit(operation));
+        }
+
         private static bool IsConditional(IBinaryOperation operation)
         {
             switch (operation.OperatorKind)
@@ -4493,9 +4504,25 @@ IOperation getEnumerator()
 
                 if (info?.GetEnumeratorMethod != null)
                 {
+                    IOperation? collection = info.GetEnumeratorMethod.IsStatic ? null : Visit(operation.Collection);
+
+                    if (collection is not null && info.InlineArrayConversion is { } inlineArrayConversion)
+                    {
+                        if (info.CollectionIsInlineArrayValue)
+                        {
+                            // We cannot convert a value to a span, need to make a local copy and convert that.
+                            int localCopyCaptureId = GetNextCaptureId(enumeratorCaptureRegion);
+                            AddStatement(new FlowCaptureOperation(localCopyCaptureId, operation.Collection.Syntax, collection));
+
+                            collection = new FlowCaptureReferenceOperation(localCopyCaptureId, operation.Collection.Syntax, collection.Type, constantValue: null);
+                        }
+
+                        collection = applyConversion(inlineArrayConversion, collection, info.GetEnumeratorMethod.ContainingType);
+                    }
+
                     IOperation invocation = makeInvocation(operation.Collection.Syntax,
                                                            info.GetEnumeratorMethod,
-                                                           info.GetEnumeratorMethod.IsStatic ? null : Visit(operation.Collection),
+                                                           collection,
                                                            info.GetEnumeratorArguments);
 
                     int enumeratorCaptureId = GetNextCaptureId(enumeratorCaptureRegion);
diff --git a/src/Compilers/Core/Portable/Operations/Loops/ForEachLoopOperationInfo.cs b/src/Compilers/Core/Portable/Operations/Loops/ForEachLoopOperationInfo.cs
index f3b6fb3d19722..2d9898330ff74 100644
--- a/src/Compilers/Core/Portable/Operations/Loops/ForEachLoopOperationInfo.cs
+++ b/src/Compilers/Core/Portable/Operations/Loops/ForEachLoopOperationInfo.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
+using System.Diagnostics;
 
 namespace Microsoft.CodeAnalysis.Operations
 {
@@ -18,6 +19,8 @@ internal class ForEachLoopOperationInfo
         public readonly IMethodSymbol MoveNextMethod;
 
         public readonly bool IsAsynchronous;
+        public readonly IConvertibleConversion? InlineArrayConversion;
+        public readonly bool CollectionIsInlineArrayValue;
         public readonly bool NeedsDispose;
         public readonly bool KnownToImplementIDisposable;
         public readonly IMethodSymbol? PatternDisposeMethod;
@@ -43,6 +46,8 @@ public ForEachLoopOperationInfo(
             IPropertySymbol currentProperty,
             IMethodSymbol moveNextMethod,
             bool isAsynchronous,
+            IConvertibleConversion? inlineArrayConversion,
+            bool collectionIsInlineArrayValue,
             bool needsDispose,
             bool knownToImplementIDisposable,
             IMethodSymbol? patternDisposeMethod,
@@ -53,11 +58,15 @@ public ForEachLoopOperationInfo(
             ImmutableArray<IArgumentOperation> currentArguments = default,
             ImmutableArray<IArgumentOperation> disposeArguments = default)
         {
+            Debug.Assert(!collectionIsInlineArrayValue || inlineArrayConversion is { });
+
             ElementType = elementType;
             GetEnumeratorMethod = getEnumeratorMethod;
             CurrentProperty = currentProperty;
             MoveNextMethod = moveNextMethod;
             IsAsynchronous = isAsynchronous;
+            InlineArrayConversion = inlineArrayConversion;
+            CollectionIsInlineArrayValue = collectionIsInlineArrayValue;
             KnownToImplementIDisposable = knownToImplementIDisposable;
             NeedsDispose = needsDispose;
             PatternDisposeMethod = patternDisposeMethod;
diff --git a/src/Compilers/Core/Portable/Operations/OperationInterfaces.xml b/src/Compilers/Core/Portable/Operations/OperationInterfaces.xml
index 3dea22c6f4959..a33680234b008 100644
--- a/src/Compilers/Core/Portable/Operations/OperationInterfaces.xml
+++ b/src/Compilers/Core/Portable/Operations/OperationInterfaces.xml
@@ -3366,4 +3366,25 @@
       </Comments>
     </Property>
   </Node>
+  <Node Name="IInlineArrayAccessOperation" Base="IOperation" ChildrenOrder="Instance,Argument" HasType="true">
+    <Comments>
+      <summary>
+        Represents an element reference or a slice operation over an inline array type.
+        <para>
+          Current usage:
+          (1) C# inline array access.
+        </para>
+      </summary>
+    </Comments>
+    <Property Name="Instance" Type="IOperation">
+      <Comments>
+        <summary>Instance of the inline array type to be accessed.</summary>
+      </Comments>
+    </Property>
+    <Property Name="Argument" Type="IOperation">
+      <Comments>
+        <summary>System.Int32, System.Index or System.Range value.</summary>
+      </Comments>
+    </Property>
+  </Node>
 </Tree>
diff --git a/src/Compilers/Core/Portable/PEWriter/MetadataWriter.cs b/src/Compilers/Core/Portable/PEWriter/MetadataWriter.cs
index 569d329a3c2ca..2c6c096f04f26 100644
--- a/src/Compilers/Core/Portable/PEWriter/MetadataWriter.cs
+++ b/src/Compilers/Core/Portable/PEWriter/MetadataWriter.cs
@@ -4,6 +4,10 @@
 
 #nullable disable
 
+// We're not actually doing formatter-based serialization in this file.
+// We're simply propagating along the attributes of symbols we are emitting to metadata.
+#pragma warning disable SYSLIB0050 // 'FieldAttributes.NotSerialized' is obsolete: 'Formatter-based serialization is obsolete and should not be used.'
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
diff --git a/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt b/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt
index 6135880dd7fc0..2a7e194459c46 100644
--- a/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt
+++ b/src/Compilers/Core/Portable/PublicAPI.Unshipped.txt
@@ -1,17 +1,48 @@
 *REMOVED*static Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode>.implicit operator Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode!>(Microsoft.CodeAnalysis.SeparatedSyntaxList<Microsoft.CodeAnalysis.SyntaxNode!> nodes) -> Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode!>
 *REMOVED*static Microsoft.CodeAnalysis.SyntaxList<TNode>.implicit operator Microsoft.CodeAnalysis.SyntaxList<TNode!>(Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.SyntaxNode!> nodes) -> Microsoft.CodeAnalysis.SyntaxList<TNode!>
+Microsoft.CodeAnalysis.CommandLineArguments.ReportInternalsVisibleToAttributes.get -> bool
 Microsoft.CodeAnalysis.Diagnostics.AdditionalTextValueProvider<TValue>
 Microsoft.CodeAnalysis.Diagnostics.AdditionalTextValueProvider<TValue>.AdditionalTextValueProvider(System.Func<Microsoft.CodeAnalysis.AdditionalText!, TValue>! computeValue, System.Collections.Generic.IEqualityComparer<Microsoft.CodeAnalysis.AdditionalText!>? additionalTextComparer = null) -> void
 Microsoft.CodeAnalysis.Diagnostics.AnalysisContext.TryGetValue<TValue>(Microsoft.CodeAnalysis.AdditionalText! text, Microsoft.CodeAnalysis.Diagnostics.AdditionalTextValueProvider<TValue>! valueProvider, out TValue value) -> bool
+Microsoft.CodeAnalysis.Diagnostics.CodeBlockAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree!
+Microsoft.CodeAnalysis.Diagnostics.CodeBlockStartAnalysisContext<TLanguageKindEnum>.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree!
 Microsoft.CodeAnalysis.Diagnostics.CompilationAnalysisContext.TryGetValue<TValue>(Microsoft.CodeAnalysis.AdditionalText! text, Microsoft.CodeAnalysis.Diagnostics.AdditionalTextValueProvider<TValue>! valueProvider, out TValue value) -> bool
 Microsoft.CodeAnalysis.Diagnostics.CompilationStartAnalysisContext.TryGetValue<TValue>(Microsoft.CodeAnalysis.AdditionalText! text, Microsoft.CodeAnalysis.Diagnostics.AdditionalTextValueProvider<TValue>! valueProvider, out TValue value) -> bool
+Microsoft.CodeAnalysis.Diagnostics.AdditionalFileAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.CodeBlockAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.CodeBlockStartAnalysisContext<TLanguageKindEnum>.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetAnalysisResultAsync(Microsoft.CodeAnalysis.AdditionalText! file, Microsoft.CodeAnalysis.Text.TextSpan? filterSpan, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzer!> analyzers, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<Microsoft.CodeAnalysis.Diagnostics.AnalysisResult!>!
+Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetAnalysisResultAsync(Microsoft.CodeAnalysis.AdditionalText! file, Microsoft.CodeAnalysis.Text.TextSpan? filterSpan, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<Microsoft.CodeAnalysis.Diagnostics.AnalysisResult!>!
 Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetAnalysisResultAsync(Microsoft.CodeAnalysis.SyntaxTree! tree, Microsoft.CodeAnalysis.Text.TextSpan? filterSpan, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzer!> analyzers, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<Microsoft.CodeAnalysis.Diagnostics.AnalysisResult!>!
 Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetAnalysisResultAsync(Microsoft.CodeAnalysis.SyntaxTree! tree, Microsoft.CodeAnalysis.Text.TextSpan? filterSpan, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<Microsoft.CodeAnalysis.Diagnostics.AnalysisResult!>!
 Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetAnalyzerSyntaxDiagnosticsAsync(Microsoft.CodeAnalysis.SyntaxTree! tree, Microsoft.CodeAnalysis.Text.TextSpan? filterSpan, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Diagnostics.DiagnosticAnalyzer!> analyzers, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Diagnostic!>>!
 Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.GetAnalyzerSyntaxDiagnosticsAsync(Microsoft.CodeAnalysis.SyntaxTree! tree, Microsoft.CodeAnalysis.Text.TextSpan? filterSpan, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Diagnostic!>>!
+Microsoft.CodeAnalysis.Diagnostics.OperationAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.OperationAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree!
+Microsoft.CodeAnalysis.Diagnostics.OperationBlockAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.OperationBlockAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree!
+Microsoft.CodeAnalysis.Diagnostics.OperationBlockStartAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.OperationBlockStartAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree!
 Microsoft.CodeAnalysis.Diagnostics.SemanticModelAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.SemanticModelAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree!
+Microsoft.CodeAnalysis.Diagnostics.SymbolAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.SymbolAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree?
+Microsoft.CodeAnalysis.Diagnostics.SymbolStartAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.SymbolStartAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree?
+Microsoft.CodeAnalysis.Diagnostics.SyntaxNodeAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
+Microsoft.CodeAnalysis.Diagnostics.SyntaxNodeAnalysisContext.FilterTree.get -> Microsoft.CodeAnalysis.SyntaxTree!
 Microsoft.CodeAnalysis.Diagnostics.SyntaxTreeAnalysisContext.FilterSpan.get -> Microsoft.CodeAnalysis.Text.TextSpan?
 static Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode>.explicit operator Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode!>(Microsoft.CodeAnalysis.SeparatedSyntaxList<Microsoft.CodeAnalysis.SyntaxNode!> nodes) -> Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode!>
 static Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode>.op_Implicit(Microsoft.CodeAnalysis.SeparatedSyntaxList<Microsoft.CodeAnalysis.SyntaxNode!> nodes) -> Microsoft.CodeAnalysis.SeparatedSyntaxList<TNode!>
 static Microsoft.CodeAnalysis.SyntaxList<TNode>.explicit operator Microsoft.CodeAnalysis.SyntaxList<TNode!>(Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.SyntaxNode!> nodes) -> Microsoft.CodeAnalysis.SyntaxList<TNode!>
 static Microsoft.CodeAnalysis.SyntaxList<TNode>.op_Implicit(Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.SyntaxNode!> nodes) -> Microsoft.CodeAnalysis.SyntaxList<TNode!>
+Microsoft.CodeAnalysis.OperationKind.InlineArrayAccess = 126 -> Microsoft.CodeAnalysis.OperationKind
+Microsoft.CodeAnalysis.Operations.IInlineArrayAccessOperation
+Microsoft.CodeAnalysis.Operations.IInlineArrayAccessOperation.Argument.get -> Microsoft.CodeAnalysis.IOperation!
+Microsoft.CodeAnalysis.Operations.IInlineArrayAccessOperation.Instance.get -> Microsoft.CodeAnalysis.IOperation!
+Microsoft.CodeAnalysis.RuntimeCapability.InlineArrayTypes = 7 -> Microsoft.CodeAnalysis.RuntimeCapability
+*REMOVED*Microsoft.CodeAnalysis.SpecialType.Count = 45 -> Microsoft.CodeAnalysis.SpecialType
+Microsoft.CodeAnalysis.SpecialType.Count = 46 -> Microsoft.CodeAnalysis.SpecialType
+Microsoft.CodeAnalysis.SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute = 46 -> Microsoft.CodeAnalysis.SpecialType
+virtual Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitInlineArrayAccess(Microsoft.CodeAnalysis.Operations.IInlineArrayAccessOperation! operation) -> void
+virtual Microsoft.CodeAnalysis.Operations.OperationVisitor<TArgument, TResult>.VisitInlineArrayAccess(Microsoft.CodeAnalysis.Operations.IInlineArrayAccessOperation! operation, TArgument argument) -> TResult?
diff --git a/src/Compilers/Core/Portable/RuntimeCapability.cs b/src/Compilers/Core/Portable/RuntimeCapability.cs
index fe9145189449b..b1502cff4867c 100644
--- a/src/Compilers/Core/Portable/RuntimeCapability.cs
+++ b/src/Compilers/Core/Portable/RuntimeCapability.cs
@@ -39,5 +39,10 @@ public enum RuntimeCapability
         /// Indicates that this version of runtime supports virtual static members of interfaces.
         /// </summary>
         VirtualStaticsInInterfaces = 6,
+
+        /// <summary>
+        /// Indicates that this version of runtime supports inline array types.
+        /// </summary>
+        InlineArrayTypes = 7
     }
 }
diff --git a/src/Compilers/Core/Portable/SourceGeneration/GeneratorContexts.cs b/src/Compilers/Core/Portable/SourceGeneration/GeneratorContexts.cs
index 086a349862546..0d3894f4756c6 100644
--- a/src/Compilers/Core/Portable/SourceGeneration/GeneratorContexts.cs
+++ b/src/Compilers/Core/Portable/SourceGeneration/GeneratorContexts.cs
@@ -98,7 +98,15 @@ internal GeneratorExecutionContext(Compilation compilation, ParseOptions parseOp
         /// <remarks>
         /// The severity of the diagnostic may cause the compilation to fail, depending on the <see cref="Compilation"/> settings.
         /// </remarks>
-        public void ReportDiagnostic(Diagnostic diagnostic) => _diagnostics.Add(diagnostic);
+        /// <exception cref="ArgumentException">
+        /// <paramref name="diagnostic"/> is located in a syntax tree which is not part of the compilation,
+        /// its location span is outside of the given file, or its identifier is not valid.
+        /// </exception>
+        public void ReportDiagnostic(Diagnostic diagnostic)
+        {
+            DiagnosticAnalysisContextHelpers.VerifyArguments(diagnostic, Compilation, isSupportedDiagnostic: static (_, _) => true, CancellationToken);
+            _diagnostics.Add(diagnostic);
+        }
 
         internal (ImmutableArray<GeneratedSourceText> sources, ImmutableArray<Diagnostic> diagnostics) ToImmutableAndFree()
             => (_additionalSources.ToImmutableAndFree(), _diagnostics.ToReadOnlyAndFree());
diff --git a/src/Compilers/Core/Portable/SourceGeneration/IncrementalContexts.cs b/src/Compilers/Core/Portable/SourceGeneration/IncrementalContexts.cs
index 23bc75b4cd32e..b671e126fac3a 100644
--- a/src/Compilers/Core/Portable/SourceGeneration/IncrementalContexts.cs
+++ b/src/Compilers/Core/Portable/SourceGeneration/IncrementalContexts.cs
@@ -126,12 +126,14 @@ public readonly struct SourceProductionContext
     {
         internal readonly AdditionalSourcesCollection Sources;
         internal readonly DiagnosticBag Diagnostics;
+        internal readonly Compilation Compilation;
 
-        internal SourceProductionContext(AdditionalSourcesCollection sources, DiagnosticBag diagnostics, CancellationToken cancellationToken)
+        internal SourceProductionContext(AdditionalSourcesCollection sources, DiagnosticBag diagnostics, Compilation compilation, CancellationToken cancellationToken)
         {
             CancellationToken = cancellationToken;
             Sources = sources;
             Diagnostics = diagnostics;
+            Compilation = compilation;
         }
 
         public CancellationToken CancellationToken { get; }
@@ -160,7 +162,15 @@ internal SourceProductionContext(AdditionalSourcesCollection sources, Diagnostic
         /// <remarks>
         /// The severity of the diagnostic may cause the compilation to fail, depending on the <see cref="Compilation"/> settings.
         /// </remarks>
-        public void ReportDiagnostic(Diagnostic diagnostic) => Diagnostics.Add(diagnostic);
+        /// <exception cref="ArgumentException">
+        /// <paramref name="diagnostic"/> is located in a syntax tree which is not part of the compilation,
+        /// its location span is outside of the given file, or its identifier is not valid.
+        /// </exception>
+        public void ReportDiagnostic(Diagnostic diagnostic)
+        {
+            DiagnosticAnalysisContextHelpers.VerifyArguments(diagnostic, Compilation, isSupportedDiagnostic: static (_, _) => true, CancellationToken);
+            Diagnostics.Add(diagnostic);
+        }
     }
 
     // https://github.com/dotnet/roslyn/issues/53608 right now we only support generating source + diagnostics, but actively want to support generation of other things
diff --git a/src/Compilers/Core/Portable/SourceGeneration/Nodes/NodeStateTable.cs b/src/Compilers/Core/Portable/SourceGeneration/Nodes/NodeStateTable.cs
index 20822a5f7261d..a092f06a910cf 100644
--- a/src/Compilers/Core/Portable/SourceGeneration/Nodes/NodeStateTable.cs
+++ b/src/Compilers/Core/Portable/SourceGeneration/Nodes/NodeStateTable.cs
@@ -154,6 +154,9 @@ public NodeStateTable<T> CreateCachedTableWithUpdatedSteps<TInput>(NodeStateTabl
             return builder.ToImmutableAndFree();
         }
 
+        /// <remarks>
+        /// The builder is <b>not</b> threadsafe.
+        /// </remarks>
         public sealed class Builder
         {
             private readonly ArrayBuilder<TableEntry> _states;
@@ -163,6 +166,8 @@ public sealed class Builder
             private readonly IEqualityComparer<T> _equalityComparer;
             private readonly ArrayBuilder<IncrementalGeneratorRunStep>? _steps;
 
+            private int _insertedCount = 0;
+
             [MemberNotNullWhen(true, nameof(_steps))]
             public bool TrackIncrementalSteps => _steps is not null;
 
@@ -196,7 +201,7 @@ internal Builder(
 
             public bool TryRemoveEntries(TimeSpan elapsedTime, ImmutableArray<(IncrementalGeneratorRunStep InputStep, int OutputIndex)> stepInputs)
             {
-                if (_previous._states.Length <= _states.Count)
+                if (!TryGetPreviousEntry(out var previousEntry))
                 {
                     // The previous table had less node executions than this one, so we don't have any entries from a previous corresponding node execution to remove.
                     return false;
@@ -204,7 +209,7 @@ public bool TryRemoveEntries(TimeSpan elapsedTime, ImmutableArray<(IncrementalGe
 
                 // Mark the corresponding entries to this node execution in the previous table as removed.
                 // Since they are removed due to their input having been removed, we won't have to keep placeholders for them.
-                var previousEntries = _previous._states[_states.Count].AsRemovedDueToInputRemoval();
+                var previousEntries = previousEntry.AsRemovedDueToInputRemoval();
                 _states.Add(previousEntries);
                 RecordStepInfoForLastEntry(elapsedTime, stepInputs, EntryState.Removed);
                 return true;
@@ -224,13 +229,12 @@ public bool TryRemoveEntries(TimeSpan elapsedTime, ImmutableArray<(IncrementalGe
 
             public bool TryUseCachedEntries(TimeSpan elapsedTime, ImmutableArray<(IncrementalGeneratorRunStep InputStep, int OutputIndex)> stepInputs)
             {
-                if (_previous._states.Length <= _states.Count)
+                if (!TryGetPreviousEntry(out var previousEntries))
                 {
                     // The previous table had less node executions than this one, so we don't have any entries from a previous corresponding node execution to copy as cached.
                     return false;
                 }
 
-                var previousEntries = _previous._states[_states.Count];
                 Debug.Assert(previousEntries.IsCached);
 
                 _states.Add(previousEntries);
@@ -252,14 +256,20 @@ internal bool TryUseCachedEntries(TimeSpan elapsedTime, ImmutableArray<(Incremen
 
             public bool TryModifyEntry(T value, IEqualityComparer<T> comparer, TimeSpan elapsedTime, ImmutableArray<(IncrementalGeneratorRunStep InputStep, int OutputIndex)> stepInputs, EntryState overallInputState)
             {
-                if (_previous._states.Length <= _states.Count)
+                if (!TryGetPreviousEntry(out var previousEntry))
                 {
                     // The previous table had less node executions than this one, so we don't have any entries from a previous corresponding node execution to try to modify.
                     return false;
                 }
 
-                Debug.Assert(_previous._states[_states.Count].Count == 1);
-                var (chosen, state, _) = GetModifiedItemAndState(_previous._states[_states.Count].GetItem(0), value, comparer);
+                if (previousEntry.Count == 0)
+                {
+                    // it's possible that the previous execution removed this item, but we left in an empty entry as a placeholder. In which case, we can't modify it
+                    return false;
+                }
+
+                Debug.Assert(previousEntry.Count == 1);
+                var (chosen, state, _) = GetModifiedItemAndState(previousEntry.GetItem(0), value, comparer);
                 _states.Add(new TableEntry(OneOrMany.Create(chosen), state));
                 RecordStepInfoForLastEntry(elapsedTime, stepInputs, overallInputState);
                 return true;
@@ -267,11 +277,6 @@ public bool TryModifyEntry(T value, IEqualityComparer<T> comparer, TimeSpan elap
 
             public bool TryModifyEntries(ImmutableArray<T> outputs, IEqualityComparer<T> comparer, TimeSpan elapsedTime, ImmutableArray<(IncrementalGeneratorRunStep InputStep, int OutputIndex)> stepInputs, EntryState overallInputState)
             {
-                if (_previous._states.Length <= _states.Count)
-                {
-                    return false;
-                }
-
                 // Semantics:
                 // For each item in the row, we compare with the new matching new value.
                 // - Cached when the same
@@ -279,7 +284,10 @@ public bool TryModifyEntries(ImmutableArray<T> outputs, IEqualityComparer<T> com
                 // - Removed when old item position > outputs.length
                 // - Added when new item position < previousTable.length
 
-                var previousEntry = _previous._states[_states.Count];
+                if (!TryGetPreviousEntry(out var previousEntry))
+                {
+                    return false;
+                }
 
                 // when both entries have no items, we can short circuit
                 if (previousEntry.Count == 0 && outputs.Length == 0)
@@ -374,6 +382,7 @@ public bool TryModifyEntries(ImmutableArray<T> outputs, IEqualityComparer<T> com
             public void AddEntry(T value, EntryState state, TimeSpan elapsedTime, ImmutableArray<(IncrementalGeneratorRunStep InputStep, int OutputIndex)> stepInputs, EntryState overallInputState)
             {
                 _states.Add(new TableEntry(OneOrMany.Create(value), state));
+                _insertedCount += state == EntryState.Added ? 1 : 0;
                 RecordStepInfoForLastEntry(elapsedTime, stepInputs, overallInputState);
             }
 
@@ -381,10 +390,22 @@ public TableEntry AddEntries(ImmutableArray<T> values, EntryState state, TimeSpa
             {
                 var tableEntry = new TableEntry(OneOrMany.Create(values), state);
                 _states.Add(tableEntry);
+                _insertedCount += state == EntryState.Added ? 1 : 0;
                 RecordStepInfoForLastEntry(elapsedTime, stepInputs, overallInputState);
                 return tableEntry;
             }
 
+            private bool TryGetPreviousEntry(out TableEntry previousEntry)
+            {
+                // When indexing into the previous table we need to subtract the number of entries that have been explicitly added
+                // to the current table, as they didn't exist in the previous one.
+                var previousTableEntryIndex = _states.Count - _insertedCount;
+
+                var canUsePrevious = _previous._states.Length > previousTableEntryIndex;
+                previousEntry = canUsePrevious ? _previous._states[previousTableEntryIndex] : default;
+                return canUsePrevious;
+            }
+
             private void RecordStepInfoForLastEntry(TimeSpan elapsedTime, ImmutableArray<(IncrementalGeneratorRunStep InputStep, int OutputIndex)> stepInputs, EntryState overallInputState)
             {
                 Debug.Assert(stepInputs.IsDefault == !TrackIncrementalSteps);
diff --git a/src/Compilers/Core/Portable/SourceGeneration/Nodes/SourceOutputNode.cs b/src/Compilers/Core/Portable/SourceGeneration/Nodes/SourceOutputNode.cs
index 0e924eb337626..011ea258a2fe1 100644
--- a/src/Compilers/Core/Portable/SourceGeneration/Nodes/SourceOutputNode.cs
+++ b/src/Compilers/Core/Portable/SourceGeneration/Nodes/SourceOutputNode.cs
@@ -58,21 +58,20 @@ public NodeStateTable<TOutput> UpdateStateTable(DriverStateTable.Builder graphSt
                 }
                 else if (entry.State != EntryState.Cached || !nodeTable.TryUseCachedEntries(TimeSpan.Zero, inputs))
                 {
-                    // we don't currently handle modified any differently than added at the output
-                    // we just run the action and mark the new source as added. In theory we could compare
-                    // the diagnostics and sources produced and compare them, to see if they are any different 
-                    // than before.
-
                     var sourcesBuilder = new AdditionalSourcesCollection(_sourceExtension);
                     var diagnostics = DiagnosticBag.GetInstance();
 
-                    SourceProductionContext context = new SourceProductionContext(sourcesBuilder, diagnostics, cancellationToken);
+                    SourceProductionContext context = new SourceProductionContext(sourcesBuilder, diagnostics, graphState.Compilation, cancellationToken);
                     try
                     {
                         var stopwatch = SharedStopwatch.StartNew();
                         _action(context, entry.Item, cancellationToken);
                         var sourcesAndDiagnostics = (sourcesBuilder.ToImmutable(), diagnostics.ToReadOnly());
-                        nodeTable.AddEntry(sourcesAndDiagnostics, EntryState.Added, stopwatch.Elapsed, inputs, EntryState.Added);
+
+                        if (entry.State != EntryState.Modified || !nodeTable.TryModifyEntry(sourcesAndDiagnostics, EqualityComparer<TOutput>.Default, stopwatch.Elapsed, inputs, entry.State))
+                        {
+                            nodeTable.AddEntry(sourcesAndDiagnostics, EntryState.Added, stopwatch.Elapsed, inputs, EntryState.Added);
+                        }
                     }
                     finally
                     {
diff --git a/src/Compilers/Core/Portable/SpecialMember.cs b/src/Compilers/Core/Portable/SpecialMember.cs
index 70ce904483e6b..a8142967d08a7 100644
--- a/src/Compilers/Core/Portable/SpecialMember.cs
+++ b/src/Compilers/Core/Portable/SpecialMember.cs
@@ -156,6 +156,7 @@ internal enum SpecialMember
         System_Runtime_CompilerServices_RuntimeFeature__ByRefFields,
 
         System_Runtime_CompilerServices_PreserveBaseOverridesAttribute__ctor,
+        System_Runtime_CompilerServices_InlineArrayAttribute__ctor,
 
         Count
     }
diff --git a/src/Compilers/Core/Portable/SpecialMembers.cs b/src/Compilers/Core/Portable/SpecialMembers.cs
index 447eb68838110..6c2fc7905353e 100644
--- a/src/Compilers/Core/Portable/SpecialMembers.cs
+++ b/src/Compilers/Core/Portable/SpecialMembers.cs
@@ -1044,6 +1044,14 @@ static SpecialMembers()
                 0,                                                                                                          // Arity
                     0,                                                                                                      // Method Signature
                     (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Void, // Return Type
+
+                // System_Runtime_CompilerServices_InlineArrayAttribute__ctor
+                (byte)MemberFlags.Constructor,                                                                              // Flags
+                (byte)SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute,                                     // DeclaringTypeId
+                0,                                                                                                          // Arity
+                    1,                                                                                                      // Method Signature
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Void, // Return Type
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
             };
 
             string[] allNames = new string[(int)SpecialMember.Count]
@@ -1173,8 +1181,9 @@ static SpecialMembers()
                 "CovariantReturnsOfClasses",                // System_Runtime_CompilerServices_RuntimeFeature__CovariantReturnsOfClasses
                 "VirtualStaticsInInterfaces",               // System_Runtime_CompilerServices_RuntimeFeature__VirtualStaticsInInterfaces
                 "NumericIntPtr",                            // System_Runtime_CompilerServices_RuntimeFeature__NumericIntPtr
-                "ByRefFields",                // System_Runtime_CompilerServices_RuntimeFeature__ByRefFields
+                "ByRefFields",                              // System_Runtime_CompilerServices_RuntimeFeature__ByRefFields
                 ".ctor",                                    // System_Runtime_CompilerServices_PreserveBaseOverridesAttribute__ctor
+                ".ctor",                                    // System_Runtime_CompilerServices_InlineArrayAttribute__ctor
             };
 
             s_descriptors = MemberDescriptor.InitializeFromStream(new System.IO.MemoryStream(initializationBytes, writable: false), allNames);
diff --git a/src/Compilers/Core/Portable/SpecialType.cs b/src/Compilers/Core/Portable/SpecialType.cs
index c1695c57132da..66e5b3eb9d84d 100644
--- a/src/Compilers/Core/Portable/SpecialType.cs
+++ b/src/Compilers/Core/Portable/SpecialType.cs
@@ -258,9 +258,14 @@ public enum SpecialType : sbyte
         /// </summary>
         System_Runtime_CompilerServices_PreserveBaseOverridesAttribute = 45,
 
+        /// <summary>
+        /// An attribute that is placed on an inline array type.
+        /// </summary>
+        System_Runtime_CompilerServices_InlineArrayAttribute = 46,
+
         /// <summary>
         /// Count of special types. This is not a count of enum members.
         /// </summary>
-        Count = System_Runtime_CompilerServices_PreserveBaseOverridesAttribute
+        Count = System_Runtime_CompilerServices_InlineArrayAttribute
     }
 }
diff --git a/src/Compilers/Core/Portable/SpecialTypes.cs b/src/Compilers/Core/Portable/SpecialTypes.cs
index 4641a4e72bd5b..163237fbfd8f3 100644
--- a/src/Compilers/Core/Portable/SpecialTypes.cs
+++ b/src/Compilers/Core/Portable/SpecialTypes.cs
@@ -16,7 +16,7 @@ internal static class SpecialTypes
         /// that we could use ids to index into the array
         /// </summary>
         /// <remarks></remarks>
-        private static readonly string?[] s_emittedNames = new string?[]
+        private static readonly string?[] s_emittedNames = new string?[(int)SpecialType.Count + 1]
         {
             // The following things should be in sync:
             // 1) SpecialType enum
@@ -69,6 +69,7 @@ internal static class SpecialTypes
             "System.AsyncCallback",
             "System.Runtime.CompilerServices.RuntimeFeature",
             "System.Runtime.CompilerServices.PreserveBaseOverridesAttribute",
+            "System.Runtime.CompilerServices.InlineArrayAttribute",
         };
 
         private static readonly Dictionary<string, SpecialType> s_nameToTypeIdMap;
diff --git a/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayCompilerInternalOptions.cs b/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayCompilerInternalOptions.cs
index eea505665d8d8..b7ecd7c4f9f6b 100644
--- a/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayCompilerInternalOptions.cs
+++ b/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayCompilerInternalOptions.cs
@@ -73,5 +73,12 @@ internal enum SymbolDisplayCompilerInternalOptions
         /// (i.e., not as part of a method, delegate, or indexer).
         /// </summary>
         ExcludeParameterNameIfStandalone = 1 << 9,
+
+        /// <summary>
+        /// Display `&lt;File&gt;F&lt;sha256-hex-string&gt;_MyType` instead of `MyType`.
+        /// Differs from <see cref="IncludeContainingFileForFileTypes"/> because it guarantees that
+        /// the prefix will be unique for all files which are permitted to declare file-local types.
+        /// </summary>
+        IncludeFileLocalTypesPrefix = 1 << 10,
     }
 }
diff --git a/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayFormat.cs b/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayFormat.cs
index 7ff86cd4e5360..fef71e511e6ce 100644
--- a/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayFormat.cs
+++ b/src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayFormat.cs
@@ -269,7 +269,7 @@ public class SymbolDisplayFormat
                 typeQualificationStyle: SymbolDisplayTypeQualificationStyle.NameAndContainingTypesAndNamespaces,
                 genericsOptions: SymbolDisplayGenericsOptions.IncludeTypeParameters,
                 miscellaneousOptions: SymbolDisplayMiscellaneousOptions.EscapeKeywordIdentifiers,
-                compilerInternalOptions: SymbolDisplayCompilerInternalOptions.ReverseArrayRankSpecifiers);
+                compilerInternalOptions: SymbolDisplayCompilerInternalOptions.ReverseArrayRankSpecifiers | SymbolDisplayCompilerInternalOptions.IncludeFileLocalTypesPrefix);
 
         /// <summary>
         /// Determines how the global namespace is displayed.
diff --git a/src/Compilers/Core/Portable/Symbols/Attributes/AttributeDescription.cs b/src/Compilers/Core/Portable/Symbols/Attributes/AttributeDescription.cs
index 59fe257f622ad..d842b536c6a4c 100644
--- a/src/Compilers/Core/Portable/Symbols/Attributes/AttributeDescription.cs
+++ b/src/Compilers/Core/Portable/Symbols/Attributes/AttributeDescription.cs
@@ -179,6 +179,8 @@ static AttributeDescription()
         private static readonly byte[] s_signature_HasThis_Void_Type_Type_Type_Type = new byte[] { (byte)SignatureAttributes.Instance, 4, Void, TypeHandle, (byte)TypeHandleTarget.SystemType, TypeHandle, (byte)TypeHandleTarget.SystemType, TypeHandle, (byte)TypeHandleTarget.SystemType, TypeHandle, (byte)TypeHandleTarget.SystemType };
         private static readonly byte[] s_signature_HasThis_Void_Type_Int32 = new byte[] { (byte)SignatureAttributes.Instance, 2, Void, TypeHandle, (byte)TypeHandleTarget.SystemType, Int32 };
 
+        private static readonly byte[] s_signature_HasThis_Void_String_Int32_Int32 = new byte[] { (byte)SignatureAttributes.Instance, 3, Void, String, Int32, Int32 };
+
         private static readonly byte[] s_signature_HasThis_Void_SzArray_Boolean = new byte[] { (byte)SignatureAttributes.Instance, 1, Void, SzArray, Boolean };
         private static readonly byte[] s_signature_HasThis_Void_SzArray_Byte = new byte[] { (byte)SignatureAttributes.Instance, 1, Void, SzArray, Byte };
         private static readonly byte[] s_signature_HasThis_Void_SzArray_String = new byte[] { (byte)SignatureAttributes.Instance, 1, Void, SzArray, String };
@@ -194,6 +196,7 @@ static AttributeDescription()
         private static readonly byte[][] s_signatures_HasThis_Void_String_Only = { s_signature_HasThis_Void_String };
         private static readonly byte[][] s_signatures_HasThis_Void_Type_Only = { s_signature_HasThis_Void_Type };
         private static readonly byte[][] s_signatures_HasThis_Void_Boolean_Only = { s_signature_HasThis_Void_Boolean };
+        private static readonly byte[][] s_signatures_HasThis_Void_Int32_Only = { s_signature_HasThis_Void_Int32 };
 
         private static readonly byte[][] s_signaturesOfTypeIdentifierAttribute = { s_signature_HasThis_Void, s_signature_HasThis_Void_String_String };
         private static readonly byte[][] s_signaturesOfAttributeUsage = { s_signature_HasThis_Void_AttributeTargets };
@@ -218,10 +221,10 @@ static AttributeDescription()
 
         private static readonly byte[][] s_signaturesOfDefaultCharSetAttribute = { s_signature_HasThis_Void_CharSet };
 
-        private static readonly byte[][] s_signaturesOfFieldOffsetAttribute = { s_signature_HasThis_Void_Int32 };
         private static readonly byte[][] s_signaturesOfMemberNotNullAttribute = { s_signature_HasThis_Void_String, s_signature_HasThis_Void_SzArray_String };
         private static readonly byte[][] s_signaturesOfMemberNotNullWhenAttribute = { s_signature_HasThis_Void_Boolean_String, s_signature_HasThis_Void_Boolean_SzArray_String };
         private static readonly byte[][] s_signaturesOfFixedBufferAttribute = { s_signature_HasThis_Void_Type_Int32 };
+        private static readonly byte[][] s_signaturesOfInterceptsLocationAttribute = { s_signature_HasThis_Void_String_Int32_Int32 };
         private static readonly byte[][] s_signaturesOfPrincipalPermissionAttribute = { s_signature_HasThis_Void_SecurityAction };
         private static readonly byte[][] s_signaturesOfPermissionSetAttribute = { s_signature_HasThis_Void_SecurityAction };
 
@@ -313,7 +316,6 @@ static AttributeDescription()
 
         private static readonly byte[][] s_signaturesOfMyGroupCollectionAttribute = { s_signature_HasThis_Void_String_String_String_String };
         private static readonly byte[][] s_signaturesOfComEventInterfaceAttribute = { s_signature_HasThis_Void_Type_Type };
-        private static readonly byte[][] s_signaturesOfLCIDConversionAttribute = { s_signature_HasThis_Void_Int32 };
         private static readonly byte[][] s_signaturesOfUnmanagedFunctionPointerAttribute = { s_signature_HasThis_Void_CallingConvention };
         private static readonly byte[][] s_signaturesOfPrimaryInteropAssemblyAttribute = { s_signature_HasThis_Void_Int32_Int32 };
         private static readonly byte[][] s_signaturesOfAssemblyAlgorithmIdAttribute =
@@ -333,7 +335,6 @@ static AttributeDescription()
         private static readonly byte[][] s_signaturesOfNullableAttribute = { s_signature_HasThis_Void_Byte, s_signature_HasThis_Void_SzArray_Byte };
         private static readonly byte[][] s_signaturesOfNullableContextAttribute = { s_signature_HasThis_Void_Byte };
         private static readonly byte[][] s_signaturesOfNativeIntegerAttribute = { s_signature_HasThis_Void, s_signature_HasThis_Void_SzArray_Boolean };
-        private static readonly byte[][] s_signaturesOfRefSafetyRulesAttribute = { s_signature_HasThis_Void_Int32 };
         private static readonly byte[][] s_signaturesOfInterpolatedStringArgumentAttribute = { s_signature_HasThis_Void_String, s_signature_HasThis_Void_SzArray_String };
 
         // early decoded attributes:
@@ -382,8 +383,9 @@ static AttributeDescription()
         internal static readonly AttributeDescription SerializableAttribute = new AttributeDescription("System", "SerializableAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription NonSerializedAttribute = new AttributeDescription("System", "NonSerializedAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription StructLayoutAttribute = new AttributeDescription("System.Runtime.InteropServices", "StructLayoutAttribute", s_signaturesOfStructLayoutAttribute);
-        internal static readonly AttributeDescription FieldOffsetAttribute = new AttributeDescription("System.Runtime.InteropServices", "FieldOffsetAttribute", s_signaturesOfFieldOffsetAttribute);
+        internal static readonly AttributeDescription FieldOffsetAttribute = new AttributeDescription("System.Runtime.InteropServices", "FieldOffsetAttribute", s_signatures_HasThis_Void_Int32_Only);
         internal static readonly AttributeDescription FixedBufferAttribute = new AttributeDescription("System.Runtime.CompilerServices", "FixedBufferAttribute", s_signaturesOfFixedBufferAttribute);
+        internal static readonly AttributeDescription InterceptsLocationAttribute = new AttributeDescription("System.Runtime.CompilerServices", "InterceptsLocationAttribute", s_signaturesOfInterceptsLocationAttribute);
         internal static readonly AttributeDescription AllowNullAttribute = new AttributeDescription("System.Diagnostics.CodeAnalysis", "AllowNullAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription DisallowNullAttribute = new AttributeDescription("System.Diagnostics.CodeAnalysis", "DisallowNullAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription MaybeNullAttribute = new AttributeDescription("System.Diagnostics.CodeAnalysis", "MaybeNullAttribute", s_signatures_HasThis_Void_Only);
@@ -419,7 +421,7 @@ static AttributeDescription()
         internal static readonly AttributeDescription ClassInterfaceAttribute = new AttributeDescription("System.Runtime.InteropServices", "ClassInterfaceAttribute", s_signaturesOfClassInterfaceAttribute);
         internal static readonly AttributeDescription ComSourceInterfacesAttribute = new AttributeDescription("System.Runtime.InteropServices", "ComSourceInterfacesAttribute", s_signaturesOfComSourceInterfacesAttribute);
         internal static readonly AttributeDescription ComVisibleAttribute = new AttributeDescription("System.Runtime.InteropServices", "ComVisibleAttribute", s_signatures_HasThis_Void_Boolean_Only);
-        internal static readonly AttributeDescription DispIdAttribute = new AttributeDescription("System.Runtime.InteropServices", "DispIdAttribute", new byte[][] { s_signature_HasThis_Void_Int32 });
+        internal static readonly AttributeDescription DispIdAttribute = new AttributeDescription("System.Runtime.InteropServices", "DispIdAttribute", s_signatures_HasThis_Void_Int32_Only);
         internal static readonly AttributeDescription TypeLibVersionAttribute = new AttributeDescription("System.Runtime.InteropServices", "TypeLibVersionAttribute", s_signaturesOfTypeLibVersionAttribute);
         internal static readonly AttributeDescription ComCompatibleVersionAttribute = new AttributeDescription("System.Runtime.InteropServices", "ComCompatibleVersionAttribute", s_signaturesOfComCompatibleVersionAttribute);
         internal static readonly AttributeDescription InterfaceTypeAttribute = new AttributeDescription("System.Runtime.InteropServices", "InterfaceTypeAttribute", s_signaturesOfInterfaceTypeAttribute);
@@ -453,7 +455,7 @@ static AttributeDescription()
         internal static readonly AttributeDescription ComEventInterfaceAttribute = new AttributeDescription("System.Runtime.InteropServices", "ComEventInterfaceAttribute", s_signaturesOfComEventInterfaceAttribute);
         internal static readonly AttributeDescription BestFitMappingAttribute = new AttributeDescription("System.Runtime.InteropServices", "BestFitMappingAttribute", s_signatures_HasThis_Void_Boolean_Only);
         internal static readonly AttributeDescription FlagsAttribute = new AttributeDescription("System", "FlagsAttribute", s_signatures_HasThis_Void_Only);
-        internal static readonly AttributeDescription LCIDConversionAttribute = new AttributeDescription("System.Runtime.InteropServices", "LCIDConversionAttribute", s_signaturesOfLCIDConversionAttribute);
+        internal static readonly AttributeDescription LCIDConversionAttribute = new AttributeDescription("System.Runtime.InteropServices", "LCIDConversionAttribute", s_signatures_HasThis_Void_Int32_Only);
         internal static readonly AttributeDescription UnmanagedFunctionPointerAttribute = new AttributeDescription("System.Runtime.InteropServices", "UnmanagedFunctionPointerAttribute", s_signaturesOfUnmanagedFunctionPointerAttribute);
         internal static readonly AttributeDescription PrimaryInteropAssemblyAttribute = new AttributeDescription("System.Runtime.InteropServices", "PrimaryInteropAssemblyAttribute", s_signaturesOfPrimaryInteropAssemblyAttribute);
         internal static readonly AttributeDescription ImportedFromTypeLibAttribute = new AttributeDescription("System.Runtime.InteropServices", "ImportedFromTypeLibAttribute", s_signatures_HasThis_Void_String_Only);
@@ -470,7 +472,7 @@ static AttributeDescription()
         internal static readonly AttributeDescription SkipLocalsInitAttribute = new AttributeDescription("System.Runtime.CompilerServices", "SkipLocalsInitAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription NativeIntegerAttribute = new AttributeDescription("System.Runtime.CompilerServices", "NativeIntegerAttribute", s_signaturesOfNativeIntegerAttribute);
         internal static readonly AttributeDescription ScopedRefAttribute = new AttributeDescription("System.Runtime.CompilerServices", "ScopedRefAttribute", s_signatures_HasThis_Void_Only);
-        internal static readonly AttributeDescription RefSafetyRulesAttribute = new AttributeDescription("System.Runtime.CompilerServices", "RefSafetyRulesAttribute", s_signaturesOfRefSafetyRulesAttribute);
+        internal static readonly AttributeDescription RefSafetyRulesAttribute = new AttributeDescription("System.Runtime.CompilerServices", "RefSafetyRulesAttribute", s_signatures_HasThis_Void_Int32_Only);
         internal static readonly AttributeDescription ModuleInitializerAttribute = new AttributeDescription("System.Runtime.CompilerServices", "ModuleInitializerAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription UnmanagedCallersOnlyAttribute = new AttributeDescription("System.Runtime.InteropServices", "UnmanagedCallersOnlyAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription InterpolatedStringHandlerAttribute = new AttributeDescription("System.Runtime.CompilerServices", "InterpolatedStringHandlerAttribute", s_signatures_HasThis_Void_Only);
@@ -479,5 +481,6 @@ static AttributeDescription()
         internal static readonly AttributeDescription SetsRequiredMembersAttribute = new AttributeDescription("System.Diagnostics.CodeAnalysis", "SetsRequiredMembersAttribute", s_signatures_HasThis_Void_Only);
         internal static readonly AttributeDescription CompilerFeatureRequiredAttribute = new AttributeDescription("System.Runtime.CompilerServices", "CompilerFeatureRequiredAttribute", s_signatures_HasThis_Void_String_Only);
         internal static readonly AttributeDescription UnscopedRefAttribute = new AttributeDescription("System.Diagnostics.CodeAnalysis", "UnscopedRefAttribute", s_signatures_HasThis_Void_Only);
+        internal static readonly AttributeDescription InlineArrayAttribute = new AttributeDescription("System.Runtime.CompilerServices", "InlineArrayAttribute", s_signatures_HasThis_Void_Int32_Only);
     }
 }
diff --git a/src/Compilers/Core/Portable/Symbols/IAssemblySymbolInternal.cs b/src/Compilers/Core/Portable/Symbols/IAssemblySymbolInternal.cs
index bd8fbd6b948e5..d0d87a97b1987 100644
--- a/src/Compilers/Core/Portable/Symbols/IAssemblySymbolInternal.cs
+++ b/src/Compilers/Core/Portable/Symbols/IAssemblySymbolInternal.cs
@@ -3,6 +3,8 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
 
 namespace Microsoft.CodeAnalysis.Symbols
 {
@@ -16,5 +18,11 @@ internal interface IAssemblySymbolInternal : ISymbolInternal
         AssemblyIdentity Identity { get; }
 
         IAssemblySymbolInternal CorLibrary { get; }
+
+        IEnumerable<ImmutableArray<byte>> GetInternalsVisibleToPublicKeys(string simpleName);
+
+        IEnumerable<string> GetInternalsVisibleToAssemblyNames();
+
+        bool AreInternalsVisibleToThisAssembly(IAssemblySymbolInternal? otherAssembly);
     }
 }
diff --git a/src/Compilers/Core/Portable/WellKnownMember.cs b/src/Compilers/Core/Portable/WellKnownMember.cs
index 41044055c3e48..286e7f459fbdf 100644
--- a/src/Compilers/Core/Portable/WellKnownMember.cs
+++ b/src/Compilers/Core/Portable/WellKnownMember.cs
@@ -123,6 +123,9 @@ internal enum WellKnownMember
         System_Runtime_InteropServices_LCIDConversionAttribute__ctor,
         System_Runtime_InteropServices_UnmanagedFunctionPointerAttribute__ctor,
 
+        System_Runtime_InteropServices_MemoryMarshal__CreateSpan,
+        System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan,
+
         System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T__AddEventHandler,
         System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T__GetOrCreateEventRegistrationTokenTable,
         System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T__InvocationList,
@@ -155,6 +158,10 @@ internal enum WellKnownMember
         System_Runtime_CompilerServices_RuntimeHelpers__GetSubArray_T,
         System_Runtime_CompilerServices_RuntimeHelpers__EnsureSufficientExecutionStack,
 
+        System_Runtime_CompilerServices_Unsafe__Add_T,
+        System_Runtime_CompilerServices_Unsafe__As_T,
+        System_Runtime_CompilerServices_Unsafe__AsRef_T,
+
         System_Runtime_ExceptionServices_ExceptionDispatchInfo__Capture,
         System_Runtime_ExceptionServices_ExceptionDispatchInfo__Throw,
 
@@ -482,12 +489,14 @@ internal enum WellKnownMember
         System_Span_T__ctor_Array,
         System_Span_T__get_Item,
         System_Span_T__get_Length,
+        System_Span_T__Slice_Int_Int,
 
         System_ReadOnlySpan_T__ctor_Pointer,
         System_ReadOnlySpan_T__ctor_Array,
         System_ReadOnlySpan_T__ctor_Array_Start_Length,
         System_ReadOnlySpan_T__get_Item,
         System_ReadOnlySpan_T__get_Length,
+        System_ReadOnlySpan_T__Slice_Int_Int,
 
         System_Runtime_CompilerServices_IsUnmanagedAttribute__ctor,
 
diff --git a/src/Compilers/Core/Portable/WellKnownMembers.cs b/src/Compilers/Core/Portable/WellKnownMembers.cs
index ddf5322bf8999..d0d59d8edba6b 100644
--- a/src/Compilers/Core/Portable/WellKnownMembers.cs
+++ b/src/Compilers/Core/Portable/WellKnownMembers.cs
@@ -798,6 +798,30 @@ static WellKnownMembers()
                     (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Void, // Return Type
                     (byte)SignatureTypeCode.TypeHandle, (byte)WellKnownType.System_Runtime_InteropServices_CallingConvention,
 
+                // System_Runtime_InteropServices_MemoryMarshal__CreateSpan
+                (byte)(MemberFlags.Method | MemberFlags.Static),                                                            // Flags
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Runtime_InteropServices_MemoryMarshal - WellKnownType.ExtSentinel), // DeclaringTypeId
+                1,                                                                                                          // Arity
+                    2,                                                                                                      // Method Signature
+                    (byte)SignatureTypeCode.GenericTypeInstance,
+                        (byte)SignatureTypeCode.TypeHandle, (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Span_T - WellKnownType.ExtSentinel),  // Return Type
+                        1,
+                        (byte)SignatureTypeCode.GenericMethodParameter, 0,
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 0,
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
+
+                // System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan
+                (byte)(MemberFlags.Method | MemberFlags.Static),                                                            // Flags
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Runtime_InteropServices_MemoryMarshal - WellKnownType.ExtSentinel), // DeclaringTypeId
+                1,                                                                                                          // Arity
+                    2,                                                                                                      // Method Signature
+                    (byte)SignatureTypeCode.GenericTypeInstance,
+                        (byte)SignatureTypeCode.TypeHandle, (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_ReadOnlySpan_T - WellKnownType.ExtSentinel),  // Return Type
+                        1,
+                        (byte)SignatureTypeCode.GenericMethodParameter, 0,
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 0,
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
+
                 // System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T__AddEventHandler
                 (byte)MemberFlags.Method,                                                                                   // Flags
                 (byte)WellKnownType.System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T,            // DeclaringTypeId
@@ -1050,6 +1074,31 @@ static WellKnownMembers()
                     0,                                                                                                      // Method Signature
                     (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Void, // Return Type
 
+                // System_Runtime_CompilerServices_Unsafe__Add_T
+                (byte)(MemberFlags.Method | MemberFlags.Static),                                                            // Flags
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Runtime_CompilerServices_Unsafe - WellKnownType.ExtSentinel), // DeclaringTypeId
+                1,                                                                                                          // Arity
+                    2,                                                                                                      // Method Signature
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 0,                 // Return type
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 0,
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
+
+                // System_Runtime_CompilerServices_Unsafe__As_T
+                (byte)(MemberFlags.Method | MemberFlags.Static),                                                            // Flags
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Runtime_CompilerServices_Unsafe - WellKnownType.ExtSentinel), // DeclaringTypeId
+                2,                                                                                                          // Arity
+                    1,                                                                                                      // Method Signature
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 1,                 // Return type
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 0,
+
+                // System_Runtime_CompilerServices_Unsafe__AsRef_T
+                (byte)(MemberFlags.Method | MemberFlags.Static),                                                            // Flags
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Runtime_CompilerServices_Unsafe - WellKnownType.ExtSentinel), // DeclaringTypeId
+                1,                                                                                                          // Arity
+                    1,                                                                                                      // Method Signature
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 0,                 // Return type
+                    (byte)SignatureTypeCode.ByReference, (byte)SignatureTypeCode.GenericMethodParameter, 0,
+
                 // System_Runtime_ExceptionServices_ExceptionDispatchInfo__Capture
                 (byte)(MemberFlags.Method | MemberFlags.Static),                                                            // Flags
                 (byte)WellKnownType.System_Runtime_ExceptionServices_ExceptionDispatchInfo,                                 // DeclaringTypeId
@@ -2623,19 +2672,19 @@ static WellKnownMembers()
 
                 // System_ValueTuple_T3__Item1
                 (byte)MemberFlags.Field,                                                                                    // Flags
-                (byte)WellKnownType.System_ValueTuple_T3,                                                                   // DeclaringTypeId
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_ValueTuple_T3 - WellKnownType.ExtSentinel),    // DeclaringTypeId
                 0,                                                                                                          // Arity
                     (byte)SignatureTypeCode.GenericTypeParameter, 0,                                                        // Field Signature
 
                 // System_ValueTuple_T3__Item2
                 (byte)MemberFlags.Field,                                                                                    // Flags
-                (byte)WellKnownType.System_ValueTuple_T3,                                                                   // DeclaringTypeId
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_ValueTuple_T3 - WellKnownType.ExtSentinel),    // DeclaringTypeId
                 0,                                                                                                          // Arity
                     (byte)SignatureTypeCode.GenericTypeParameter, 1,                                                        // Field Signature
 
                 // System_ValueTuple_T3__Item3
                 (byte)MemberFlags.Field,                                                                                    // Flags
-                (byte)WellKnownType.System_ValueTuple_T3,                                                                   // DeclaringTypeId
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_ValueTuple_T3 - WellKnownType.ExtSentinel),    // DeclaringTypeId
                 0,                                                                                                          // Arity
                     (byte)SignatureTypeCode.GenericTypeParameter, 2,                                                        // Field Signature
 
@@ -2838,7 +2887,7 @@ static WellKnownMembers()
 
                 // System_ValueTuple_T3__ctor
                 (byte)MemberFlags.Constructor,                                                                              // Flags
-                (byte)WellKnownType.System_ValueTuple_T3,                                                                   // DeclaringTypeId
+                (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_ValueTuple_T3 - WellKnownType.ExtSentinel),    // DeclaringTypeId
                 0,                                                                                                          // Arity
                     3,                                                                                                      // Method Signature
                     (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Void, // Return Type
@@ -3344,6 +3393,18 @@ static WellKnownMembers()
                     0,                                                                                                                                          // Method Signature
                     (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32, // Return Type
 
+                 // System_Span_T__Slice_Int_Int
+                 (byte)(MemberFlags.Method),                                                                                                                    // Flags
+                 (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Span_T - WellKnownType.ExtSentinel),                                              // DeclaringTypeId
+                 0,                                                                                                                                             // Arity
+                    2,                                                                                                                                          // Method Signature
+                    (byte)SignatureTypeCode.GenericTypeInstance, (byte)SignatureTypeCode.TypeHandle,
+                    (byte)WellKnownType.ExtSentinel, (WellKnownType.System_Span_T - WellKnownType.ExtSentinel),
+                    1,
+                    (byte)SignatureTypeCode.GenericTypeParameter, (byte)0,              // Return Type
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
+
                  // System_ReadOnlySpan_T__ctor_Pointer
                  (byte)(MemberFlags.Constructor),                                                                                                               // Flags
                  (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_ReadOnlySpan_T - WellKnownType.ExtSentinel),                                      // DeclaringTypeId
@@ -3386,7 +3447,19 @@ static WellKnownMembers()
                     0,                                                                                                                                          // Method Signature
                     (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32, // Return Type
 
-                // System_Runtime_CompilerServices_IsUnmanagedAttribute__ctor
+                 // System_ReadOnlySpan_T__Slice_Int_Int
+                 (byte)(MemberFlags.Method),                                                                                                                    // Flags
+                 (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_ReadOnlySpan_T - WellKnownType.ExtSentinel),                                      // DeclaringTypeId
+                 0,                                                                                                                                             // Arity
+                    2,                                                                                                                                          // Method Signature
+                    (byte)SignatureTypeCode.GenericTypeInstance, (byte)SignatureTypeCode.TypeHandle,
+                    (byte)WellKnownType.ExtSentinel, (WellKnownType.System_ReadOnlySpan_T - WellKnownType.ExtSentinel),
+                    1,
+                    (byte)SignatureTypeCode.GenericTypeParameter, (byte)0,              // Return Type
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
+                    (byte)SignatureTypeCode.TypeHandle, (byte)SpecialType.System_Int32,
+
+                 // System_Runtime_CompilerServices_IsUnmanagedAttribute__ctor
                  (byte)(MemberFlags.Constructor),                                                                                                               // Flags
                  (byte)WellKnownType.ExtSentinel, (byte)(WellKnownType.System_Runtime_CompilerServices_IsUnmanagedAttribute - WellKnownType.ExtSentinel),       // DeclaringTypeId
                  0,                                                                                                                                             // Arity
@@ -4091,6 +4164,8 @@ static WellKnownMembers()
                 ".ctor",                                    // System_Runtime_InteropServices_DefaultParameterValueAttribute__ctor
                 ".ctor",                                    // System_Runtime_InteropServices_LCIDConversionAttribute__ctor
                 ".ctor",                                    // System_Runtime_InteropServices_UnmanagedFunctionPointerAttribute__ctor
+                "CreateSpan",                               // System_Runtime_InteropServices_MemoryMarshal__CreateSpan,
+                "CreateReadOnlySpan",                       // System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan,
                 "AddEventHandler",                          // System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T__AddEventHandler
                 "GetOrCreateEventRegistrationTokenTable",   // System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T__GetOrCreateEventRegistrationTokenTable
                 "InvocationList",                           // System_Runtime_InteropServices_WindowsRuntime_EventRegistrationTokenTable_T__InvocationList
@@ -4119,6 +4194,9 @@ static WellKnownMembers()
                 "get_OffsetToStringData",                   // System_Runtime_CompilerServices_RuntimeHelpers__get_OffsetToStringData
                 "GetSubArray",                              // System_Runtime_CompilerServices_RuntimeHelpers__GetSubArray_T
                 "EnsureSufficientExecutionStack",           // System_Runtime_CompilerServices_RuntimeHelpers__EnsureSufficientExecutionStack
+                "Add",                                      // System_Runtime_CompilerServices_Unsafe__Add_T
+                "As",                                       // System_Runtime_CompilerServices_Unsafe__As_T,
+                "AsRef",                                    // System_Runtime_CompilerServices_Unsafe__AsRef_T,
                 "Capture",                                  // System_Runtime_ExceptionServices_ExceptionDispatchInfo__Capture
                 "Throw",                                    // System_Runtime_ExceptionServices_ExceptionDispatchInfo__Throw
                 ".ctor",                                    // System_Security_UnverifiableCodeAttribute__ctor
@@ -4402,11 +4480,13 @@ static WellKnownMembers()
                 ".ctor",                                    // System_Span_T__ctor_Array
                 "get_Item",                                 // System_Span_T__get_Item
                 "get_Length",                               // System_Span_T__get_Length
+                "Slice",                                    // System_Span_T__Slice_Int_Int
                 ".ctor",                                    // System_ReadOnlySpan_T__ctor_Pointer
                 ".ctor",                                    // System_ReadOnlySpan_T__ctor_Array
                 ".ctor",                                    // System_ReadOnlySpan_T__ctor_Array_Start_Length
                 "get_Item",                                 // System_ReadOnlySpan_T__get_Item
                 "get_Length",                               // System_ReadOnlySpan_T__get_Length
+                "Slice",                                    // System_ReadOnlySpan_T__Slice_Int_Int
                 ".ctor",                                    // System_Runtime_CompilerServices_IsUnmanagedAttribute__ctor
 
                 "Fix",                                      // Microsoft_VisualBasic_Conversion__FixSingle
diff --git a/src/Compilers/Core/Portable/WellKnownTypes.cs b/src/Compilers/Core/Portable/WellKnownTypes.cs
index 25eaebfc06e49..230d1733e3ff6 100644
--- a/src/Compilers/Core/Portable/WellKnownTypes.cs
+++ b/src/Compilers/Core/Portable/WellKnownTypes.cs
@@ -252,10 +252,10 @@ internal enum WellKnownType
         System_ValueTuple,
         System_ValueTuple_T1,
         System_ValueTuple_T2,
-        System_ValueTuple_T3,
 
         ExtSentinel, // Not a real type, just a marker for types above 255 and strictly below 512
 
+        System_ValueTuple_T3,
         System_ValueTuple_T4,
         System_ValueTuple_T5,
         System_ValueTuple_T6,
@@ -311,6 +311,7 @@ internal enum WellKnownType
 
         System_Runtime_CompilerServices_IsExternalInit,
         System_Runtime_InteropServices_OutAttribute,
+        System_Runtime_InteropServices_MemoryMarshal,
 
         System_Text_StringBuilder,
 
@@ -329,6 +330,7 @@ internal enum WellKnownType
 
         System_MissingMethodException,
         System_Runtime_CompilerServices_MetadataUpdateOriginalTypeAttribute,
+        System_Runtime_CompilerServices_Unsafe,
 
         NextAvailable,
         // Remember to update the AllWellKnownTypes tests when making changes here
@@ -575,10 +577,10 @@ internal static class WellKnownTypes
             "System.ValueTuple",
             "System.ValueTuple`1",
             "System.ValueTuple`2",
-            "System.ValueTuple`3",
 
             "", // extension marker
 
+            "System.ValueTuple`3",
             "System.ValueTuple`4",
             "System.ValueTuple`5",
             "System.ValueTuple`6",
@@ -635,6 +637,7 @@ internal static class WellKnownTypes
             "System.Runtime.CompilerServices.NativeIntegerAttribute",
             "System.Runtime.CompilerServices.IsExternalInit",
             "System.Runtime.InteropServices.OutAttribute",
+            "System.Runtime.InteropServices.MemoryMarshal",
 
             "System.Text.StringBuilder",
             "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler",
@@ -649,6 +652,7 @@ internal static class WellKnownTypes
             "System.Diagnostics.CodeAnalysis.UnscopedRefAttribute",
             "System.MissingMethodException",
             "System.Runtime.CompilerServices.MetadataUpdateOriginalTypeAttribute",
+            "System.Runtime.CompilerServices.Unsafe",
         };
 
         private static readonly Dictionary<string, WellKnownType> s_nameToTypeIdMap = new Dictionary<string, WellKnownType>((int)Count);
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.cs.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.cs.xlf
index 2a40d2bfc714b..122f6f9117328 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.cs.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.cs.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">Hodnota end nesmí být menší než hodnota start. start={0} end={1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">{0} hintName přidaného zdrojového souboru musí být v rámci generátoru jedinečná.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">Další soubor nepatří do základního CompilationWithAnalyzers.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">Požadované číslo řádku {0} musí být menší než počet řádků {1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">Daná operace má nadřazenou položku, která není null.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">Daná operace má sémantický model null.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Chyba analyzátoru</target>
+        <target state="translated">Chyba analyzátoru</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">Analyzátor {0} způsobil výjimku typu {1} se zprávou {2}.
+        <target state="translated">Analyzátor {0} způsobil výjimku typu {1} se zprávou {2}.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.de.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.de.xlf
index 65520c80622bc..932b86129feb2 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.de.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.de.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">"Ende" darf nicht kleiner sein als "Start". start='{0}' end='{1}'.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">Der hintName "{0}" der hinzugefügten Quelldatei muss innerhalb eines Generators eindeutig sein.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">Die zusätzliche Datei gehört nicht zur zugrunde liegenden "CompilationWithAnalyzers".</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">Die angeforderte Zeilennummer {0} muss kleiner als die Anzahl der Zeilen {1} sein.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">Die angegebene Operation weist ein übergeordnetes Element ungleich NULL auf.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">Die angegebene Operation weist ein NULL-Semantikmodell auf.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Analysefehler</target>
+        <target state="translated">Analysefehler</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">Die Analyse "{0}" hat eine Ausnahme vom Typ "{1}" mit der Meldung "{2}" ausgelöst.
+        <target state="translated">Die Analyse "{0}" hat eine Ausnahme vom Typ "{1}" mit der Meldung "{2}" ausgelöst.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.es.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.es.xlf
index 4711109ba73c4..d0fcff254f458 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.es.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.es.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">'fin' no debe ser menor que 'inicio'. inicio='{0}' fin='{1}'.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">El elemento hintName "{0}"del archivo de código fuente agregado debe ser único dentro de un generador.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">El archivo adicional no pertenece al elemento "CompilationWithAnalyzers" subyacente.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">El número de línea solicitado {0} debe ser menor que el número de líneas {1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">La operación dada tiene un elemento primario no nulo.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">La operación dada tiene un modelo semántico nulo.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Error del analizador</target>
+        <target state="translated">Error del analizador</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">El analizador "{0}" produjo una excepción de tipo "{1}" con el mensaje "{2}".
+        <target state="translated">El analizador "{0}" produjo una excepción de tipo "{1}" con el mensaje "{2}".
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.fr.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.fr.xlf
index ffb5684cd82d4..075a848760b63 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.fr.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.fr.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">'end' ne doit pas être inférieur à 'start'. start='{0}'end='{1}'.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">Le hintName « {0} »du fichier source ajouté doit être unique dans un générateur.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">Le fichier supplémentaire n'appartient pas au 'CompilationWithAnalyzers' sous-jacent.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">Le numéro de ligne demandé {0} doit être inférieur au nombre de lignes {1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">L'opération donnée a un parent non-null.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">L'opération donnée a un modèle sémantique Null.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Échec de l'analyseur</target>
+        <target state="translated">Échec de l'analyseur</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">L'analyseur '{0}' a levé une exception de type '{1}' avec le message '{2}'.
+        <target state="translated">L'analyseur '{0}' a levé une exception de type '{1}' avec le message '{2}'.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.it.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.it.xlf
index 56479c8127f66..7fffec42d4664 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.it.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.it.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">il valore di 'end' non deve essere minore di quello di 'start'. start='{0}' end='{1}'.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">L'elemento hintName '{0}' del file di origine aggiunto deve essere univoco all'interno di un generatore.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">Il file aggiuntivo non appartiene all'oggetto 'CompilationWithAnalyzers' sottostante.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">Il numero di riga richiesto {0} deve essere minore del numero di righe {1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">L'operazione specificata contiene un elemento padre non Null.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">L'operazione specificata contiene un modello semantico Null.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Errore dell'analizzatore</target>
+        <target state="translated">Errore dell'analizzatore</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">L'analizzatore '{0}' ha generato un'eccezione di tipo '{1}'. Messaggio: '{2}'.
+        <target state="translated">L'analizzatore '{0}' ha generato un'eccezione di tipo '{1}'. Messaggio: '{2}'.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ja.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ja.xlf
index 08f6e053eb8c2..57c88b7815298 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ja.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ja.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">'end' は 'start' より小さくすることはできません。start='{0}' end='{1}'。</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">追加されたソース ファイルの hintName '{0}' は、ジェネレーター内で一意である必要があります。</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">追加ファイルは、基になる 'CompilationWithAnalyzers' に属していません。</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">要求された行番号 {0} は、行数 {1} より小さくする必要があります。</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">指定した操作の親が null 以外です。</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">指定した操作のセマンティック モデルが null です。</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">アナライザー エラー</target>
+        <target state="translated">アナライザー エラー</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">アナライザー '{0}' が型 '{1}' の例外をメッセージ '{2}' 付きでスローしました。
+        <target state="translated">アナライザー '{0}' が型 '{1}' の例外をメッセージ '{2}' 付きでスローしました。
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ko.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ko.xlf
index e34b77c6512c3..ad8af0718adcd 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ko.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ko.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">'end'는 'start'보다 작을 수 없습니다. start='{0}' end='{1}'</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">추가된 원본 파일의 hintName ‘{0}’은(는) 생성기 내에서 고유해야 합니다.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">추가 파일이 기본 'CompilationWithAnalyzers'에 속하지 않습니다.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">요청한 줄 번호 {0}은(는) {1} 줄 수보다 작아야 합니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">지정한 작업에 null이 아닌 부모가 있습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">지정한 작업에 null 의미 체계 모델이 있습니다.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">분석기 오류</target>
+        <target state="translated">분석기 오류</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">분석기 '{0}'에서 '{2}' 메시지와 함께 '{1}' 형식의 예외를 throw했습니다.
+        <target state="translated">분석기 '{0}'에서 '{2}' 메시지와 함께 '{1}' 형식의 예외를 throw했습니다.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pl.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pl.xlf
index d140cd61713e4..1995382796e74 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pl.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pl.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">Wartość „end” nie może być mniejsza niż wartość „start”. start=„{0}” end=„{1}”.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">Element hintName „{0}” dodanego pliku źródłowego musi być unikatowy w generatorze.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">Dodatkowy plik nie należy do źródłowego elementu „CompilationWithAnalyzers”.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">Żądany numer wiersza {0} musi być mniejszy niż liczba wierszy {1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">Dana operacja ma element nadrzędny inny niż null.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">Dana operacja ma model semantyczny o wartości null.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Błąd analizatora</target>
+        <target state="translated">Błąd analizatora</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">Analizator „{0}” zgłosił wyjątek typu „{1}” z komunikatem „{2}”.
+        <target state="translated">Analizator „{0}” zgłosił wyjątek typu „{1}” z komunikatem „{2}”.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pt-BR.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pt-BR.xlf
index f6cc5b3bd4e33..115e066d479ec 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pt-BR.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.pt-BR.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">'end' não deve ser menor que 'start'. start='{0}' end='{1}'.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">O hintName '{0}' do arquivo de origem adicionado precisa ser exclusivo em um gerador.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">O arquivo adicional não pertence ao 'CompilationWithAnalyzers' subjacente.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">O número de linha solicitado {0} deve ser menor que o número de linhas {1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">A operação especificada tem um pai não nulo.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">A operação fornecida tem um modelo não semântico.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Falha no Analisador</target>
+        <target state="translated">Falha no Analisador</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">O analisador '{0}' gerou uma exceção do tipo '{1}' com a mensagem '{2}'.
+        <target state="translated">O analisador '{0}' gerou uma exceção do tipo '{1}' com a mensagem '{2}'.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ru.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ru.xlf
index de5d45c9c7e89..64e4d16e6a1ef 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ru.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.ru.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">Значение "end" не должно быть меньше, чем "start". start="{0}", end="{1}".</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">HintName "{0}" добавленного исходного файла должно быть уникальным в пределах генератора.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">Дополнительный файл не принадлежит базовому элементу "CompilationWithAnalyzers".</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">Номер запрашиваемой строки {0} должен быть меньше числа строк {1}.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">Заданная операция имеет родительский элемент, отличный от NULL.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">Заданная операция имеет семантическую модель со значением NULL.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Сбой анализатора</target>
+        <target state="translated">Сбой анализатора</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">Анализатор "{0}" создал исключение типа "{1}" с сообщением "{2}".
+        <target state="translated">Анализатор "{0}" создал исключение типа "{1}" с сообщением "{2}".
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.tr.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.tr.xlf
index 9592f0b8157c6..61505c951b17f 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.tr.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.tr.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">'bitiş', 'başlangıç' değerinden küçük olmamalıdır. başla='{0}' bitiş='{1}'.</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">Eklenen kaynak dosyanın '{0}' hintName'i bir oluşturucu içinde benzersiz olmalıdır.</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">Ek dosya, temel alınan 'CompilationWithAnalyzers' öğesine ait değil.</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">İstenen satır numarası {0}, {1} satır sayısından az olmalıdır.</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">Belirtilen işlemin null olmayan bir üst öğesi var.</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">Belirtilen işlemin null bir anlam modeli var.</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">Çözümleyici Hatası</target>
+        <target state="translated">Çözümleyici Hatası</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">'{0}' çözümleyicisi '{2}' iletisiyle '{1}' türünde bir özel durum oluşturdu.
+        <target state="translated">'{0}' çözümleyicisi '{2}' iletisiyle '{1}' türünde bir özel durum oluşturdu.
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hans.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hans.xlf
index 6aa8a00ed2ac4..41262f0612074 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hans.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hans.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">"end" 不得小于 "start"。start="{0}" end="{1}"。</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">添加的源文件的 hintName“{0}”在生成器中必须唯一。</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">其他文件不属于基础 "CompilationWithAnalyzers"。</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">请求的行号 {0} 必须小于 {1} 的行数。</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">给定操作具有一个非 null 父级。</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">给定操作具有一个 null 语义模型。</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">分析器故障</target>
+        <target state="translated">分析器故障</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">分析器“{0}”引发类型为“{1}”的异常，并显示消息“{2}”。
+        <target state="translated">分析器“{0}”引发类型为“{1}”的异常，并显示消息“{2}”。
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hant.xlf b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hant.xlf
index e9cecf339431b..95fe8ffac91c2 100644
--- a/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hant.xlf
+++ b/src/Compilers/Core/Portable/xlf/CodeAnalysisResources.zh-Hant.xlf
@@ -66,7 +66,7 @@
       </trans-unit>
       <trans-unit id="EndMustNotBeLessThanStart">
         <source>'end' must not be less than 'start'. start='{0}' end='{1}'.</source>
-        <target state="new">'end' must not be less than 'start'. start='{0}' end='{1}'.</target>
+        <target state="translated">'end' 不可小於 'start'。start='{0}' end='{1}'。</target>
         <note />
       </trans-unit>
       <trans-unit id="GeneratorNameColumnHeader">
@@ -99,6 +99,32 @@
         <target state="translated">新增來源檔案的 hintName '{0}' 在產生器中必須是唯一的。</target>
         <note>{0}: the provided hintname</note>
       </trans-unit>
+      <trans-unit id="InternalsVisibleToCurrentAssembly">
+        <source>Current assembly: '{0}'</source>
+        <target state="new">Current assembly: '{0}'</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToHeaderSummary">
+        <source>Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</source>
+        <target state="new">Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssembly">
+        <source>Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</source>
+        <target state="new">Assembly reference: '{0}'
+  Grants IVT to current assembly: {1}
+  Grants IVTs to:</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="InternalsVisibleToReferencedAssemblyDetails">
+        <source>    Assembly name: '{0}'
+    Public Keys:</source>
+        <target state="new">    Assembly name: '{0}'
+    Public Keys:</target>
+        <note />
+      </trans-unit>
       <trans-unit id="InvalidAdditionalFile">
         <source>Additional file doesn't belong to the underlying 'CompilationWithAnalyzers'.</source>
         <target state="translated">其他檔案不屬於基礎 'CompilationWithAnalyzers'。</target>
@@ -131,7 +157,7 @@
       </trans-unit>
       <trans-unit id="LineCannotBeGreaterThanEnd">
         <source>The requested line number {0} must be less than the number of lines {1}.</source>
-        <target state="new">The requested line number {0} must be less than the number of lines {1}.</target>
+        <target state="translated">要求的行號 {0} 必須小於 {1} 的行數。</target>
         <note />
       </trans-unit>
       <trans-unit id="MethodSymbolExpected">
@@ -154,6 +180,11 @@
         <target state="translated">指定的作業有非 null 的父代。</target>
         <note />
       </trans-unit>
+      <trans-unit id="Nothing">
+        <source>Nothing</source>
+        <target state="new">Nothing</target>
+        <note />
+      </trans-unit>
       <trans-unit id="OperationHasNullSemanticModel">
         <source>Given operation has a null semantic model.</source>
         <target state="translated">指定的作業有 null 的語意模型。</target>
@@ -696,13 +727,13 @@
       </trans-unit>
       <trans-unit id="CompilerAnalyzerFailure">
         <source>Analyzer Failure</source>
-        <target state="needs-review-translation">分析器失敗</target>
+        <target state="translated">分析器失敗</target>
         <note />
       </trans-unit>
       <trans-unit id="CompilerAnalyzerThrows">
         <source>Analyzer '{0}' threw an exception of type '{1}' with message '{2}'.
 {3}</source>
-        <target state="needs-review-translation">分析器 '{0}' 擲回了類型為 '{1}' 的例外狀況。訊息: '{2}'。
+        <target state="translated">分析器 '{0}' 擲回了類型為 '{1}' 的例外狀況。訊息: '{2}'。
 {3}</target>
         <note>{0}: Analyzer name
 {1}: Type name
diff --git a/src/Compilers/Server/VBCSCompiler/AnalyzerConsistencyChecker.cs b/src/Compilers/Server/VBCSCompiler/AnalyzerConsistencyChecker.cs
index 243509d75a2a2..996ec0a7109a4 100644
--- a/src/Compilers/Server/VBCSCompiler/AnalyzerConsistencyChecker.cs
+++ b/src/Compilers/Server/VBCSCompiler/AnalyzerConsistencyChecker.cs
@@ -33,15 +33,16 @@ public static bool Check(
             [NotNullWhen(false)]
             out List<string>? errorMessages)
         {
+            errorMessages = null;
             try
             {
-                logger?.Log("Begin Analyzer Consistency Check");
+                logger?.Log($"Begin Analyzer Consistency Check for {baseDirectory}");
                 return CheckCore(baseDirectory, analyzerReferences, loader, logger, out errorMessages);
             }
             catch (Exception e)
             {
                 logger?.LogException(e, "Analyzer Consistency Check");
-                errorMessages = new List<string>();
+                errorMessages ??= new List<string>();
                 errorMessages.Add(e.Message);
                 return false;
             }
@@ -119,9 +120,10 @@ private static bool CheckCore(
                 var loadedAssemblyMvid = loadedAssembly.ManifestModule.ModuleVersionId;
                 if (resolvedPathMvid != loadedAssemblyMvid)
                 {
-                    var message = $"analyzer assembly '{resolvedPath}' has MVID '{resolvedPathMvid}' but loaded assembly '{loadedAssembly.FullName}' has MVID '{loadedAssemblyMvid}'";
+                    var message = $"analyzer assembly '{resolvedPath}' has MVID '{resolvedPathMvid}' but loaded assembly '{loadedAssembly.Location}' has MVID '{loadedAssemblyMvid}'";
                     errorMessages ??= new List<string>();
                     errorMessages.Add(message);
+                    logger.LogError(message);
                 }
             }
 
diff --git a/src/Compilers/Test/Core/Compilation/ControlFlowGraphVerifier.cs b/src/Compilers/Test/Core/Compilation/ControlFlowGraphVerifier.cs
index c856f7ae044e7..f797b39ff939c 100644
--- a/src/Compilers/Test/Core/Compilation/ControlFlowGraphVerifier.cs
+++ b/src/Compilers/Test/Core/Compilation/ControlFlowGraphVerifier.cs
@@ -2007,6 +2007,7 @@ propertyReference.Parent is ISimpleAssignmentOperation simpleAssignment &&
                 case OperationKind.ListPattern:
                 case OperationKind.ImplicitIndexerReference:
                 case OperationKind.Attribute:
+                case OperationKind.InlineArrayAccess:
                     return true;
             }
 
diff --git a/src/Compilers/Test/Core/Compilation/OperationTreeVerifier.cs b/src/Compilers/Test/Core/Compilation/OperationTreeVerifier.cs
index 74eb88a55cf08..4fe5121f25fbd 100644
--- a/src/Compilers/Test/Core/Compilation/OperationTreeVerifier.cs
+++ b/src/Compilers/Test/Core/Compilation/OperationTreeVerifier.cs
@@ -279,12 +279,12 @@ private void LogType(ITypeSymbol type, string header = "Type")
 
         private uint GetLabelId(ILabelSymbol symbol)
         {
-            if (_labelIdMap.ContainsKey(symbol))
+            if (_labelIdMap.TryGetValue(symbol, out var id))
             {
-                return _labelIdMap[symbol];
+                return id;
             }
 
-            var id = _currentLabelId++;
+            id = _currentLabelId++;
             _labelIdMap[symbol] = id;
             return id;
         }
@@ -958,6 +958,15 @@ public override void VisitImplicitIndexerReference(IImplicitIndexerReferenceOper
             Unindent();
         }
 
+        public override void VisitInlineArrayAccess(IInlineArrayAccessOperation operation)
+        {
+            LogString(nameof(IInlineArrayAccessOperation));
+            LogCommonPropertiesAndNewLine(operation);
+
+            Visit(operation.Instance, "Instance");
+            Visit(operation.Argument, "Argument");
+        }
+
         internal override void VisitPointerIndirectionReference(IPointerIndirectionReferenceOperation operation)
         {
             LogString(nameof(IPointerIndirectionReferenceOperation));
diff --git a/src/Compilers/Test/Core/Compilation/TestOperationVisitor.cs b/src/Compilers/Test/Core/Compilation/TestOperationVisitor.cs
index 72080aa86cdff..92ebd30b50aab 100644
--- a/src/Compilers/Test/Core/Compilation/TestOperationVisitor.cs
+++ b/src/Compilers/Test/Core/Compilation/TestOperationVisitor.cs
@@ -598,6 +598,12 @@ public override void VisitImplicitIndexerReference(IImplicitIndexerReferenceOper
             Assert.NotNull(operation.IndexerSymbol);
         }
 
+        public override void VisitInlineArrayAccess(IInlineArrayAccessOperation operation)
+        {
+            Assert.Equal(OperationKind.InlineArrayAccess, operation.Kind);
+            AssertEx.Equal(new[] { operation.Instance, operation.Argument }, operation.ChildOperations);
+        }
+
         internal override void VisitPointerIndirectionReference(IPointerIndirectionReferenceOperation operation)
         {
             Assert.Equal(OperationKind.None, operation.Kind);
diff --git a/src/Compilers/Test/Core/Diagnostics/CommonDiagnosticAnalyzers.cs b/src/Compilers/Test/Core/Diagnostics/CommonDiagnosticAnalyzers.cs
index 5657021e3786d..a4fd22342e99f 100644
--- a/src/Compilers/Test/Core/Diagnostics/CommonDiagnosticAnalyzers.cs
+++ b/src/Compilers/Test/Core/Diagnostics/CommonDiagnosticAnalyzers.cs
@@ -2948,6 +2948,21 @@ private void AnalyzeCompilation(CompilationStartAnalysisContext context)
         [DiagnosticAnalyzer(LanguageNames.CSharp)]
         public sealed class FilterSpanTestAnalyzer : DiagnosticAnalyzer
         {
+            public enum AnalysisKind
+            {
+                SyntaxTree,
+                AdditionalFile,
+                SemanticModel,
+                Symbol,
+                SymbolStart,
+                Operation,
+                OperationBlockStart,
+                OperationBlock,
+                SyntaxNode,
+                CodeBlockStart,
+                CodeBlock,
+            }
+
             private static readonly DiagnosticDescriptor s_descriptor = new DiagnosticDescriptor(
                     "ID0001",
                     "Title",
@@ -2956,26 +2971,140 @@ public sealed class FilterSpanTestAnalyzer : DiagnosticAnalyzer
                     defaultSeverity: DiagnosticSeverity.Warning,
                     isEnabledByDefault: true);
 
-            private readonly bool _testSyntaxTreeAction;
+            private readonly AnalysisKind _analysisKind;
 
-            public FilterSpanTestAnalyzer(bool testSyntaxTreeAction)
+            public FilterSpanTestAnalyzer(AnalysisKind analysisKind)
             {
-                _testSyntaxTreeAction = testSyntaxTreeAction;
+                _analysisKind = analysisKind;
             }
 
             public TextSpan? CallbackFilterSpan { get; private set; }
+            public SyntaxTree CallbackFilterTree { get; private set; }
+            public AdditionalText CallbackFilterFile { get; private set; }
 
             public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(s_descriptor);
 
             public override void Initialize(AnalysisContext context)
             {
-                if (_testSyntaxTreeAction)
-                {
-                    context.RegisterSyntaxTreeAction(context => CallbackFilterSpan = context.FilterSpan);
-                }
-                else
+                switch (_analysisKind)
                 {
-                    context.RegisterSemanticModelAction(context => CallbackFilterSpan = context.FilterSpan);
+                    case AnalysisKind.SyntaxTree:
+                        context.RegisterSyntaxTreeAction(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterTree = context.Tree;
+                        });
+                        break;
+
+                    case AnalysisKind.AdditionalFile:
+                        context.RegisterAdditionalFileAction(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterFile = context.AdditionalFile;
+                        });
+                        break;
+
+                    case AnalysisKind.SemanticModel:
+                        context.RegisterSemanticModelAction(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterTree = context.FilterTree;
+                        });
+                        break;
+
+                    case AnalysisKind.Symbol:
+                        context.RegisterSymbolAction(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterTree = context.FilterTree;
+                        }, SymbolKind.NamedType);
+                        break;
+
+                    case AnalysisKind.SymbolStart:
+                        context.RegisterSymbolStartAction(startContext =>
+                        {
+                            CallbackFilterSpan = startContext.FilterSpan;
+                            CallbackFilterTree = startContext.FilterTree;
+
+                            startContext.RegisterSymbolEndAction(endContext =>
+                            {
+                                if (startContext.FilterTree != endContext.FilterTree)
+                                    throw new InvalidOperationException("Mismatched FilterTree");
+
+                                if (startContext.FilterSpan != endContext.FilterSpan)
+                                    throw new InvalidOperationException("Mismatched FilterSpan");
+                            });
+                        }, SymbolKind.NamedType);
+                        break;
+
+                    case AnalysisKind.Operation:
+                        context.RegisterOperationAction(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterTree = context.FilterTree;
+                        }, OperationKind.VariableDeclarationGroup);
+                        break;
+
+                    case AnalysisKind.OperationBlockStart:
+                        context.RegisterOperationBlockStartAction(startContext =>
+                        {
+                            CallbackFilterSpan = startContext.FilterSpan;
+                            CallbackFilterTree = startContext.FilterTree;
+
+                            startContext.RegisterOperationBlockEndAction(endContext =>
+                            {
+                                if (startContext.FilterTree != endContext.FilterTree)
+                                    throw new InvalidOperationException("Mismatched FilterTree");
+
+                                if (startContext.FilterSpan != endContext.FilterSpan)
+                                    throw new InvalidOperationException("Mismatched FilterSpan");
+                            });
+                        });
+                        break;
+
+                    case AnalysisKind.OperationBlock:
+                        context.RegisterOperationBlockAction(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterTree = context.FilterTree;
+                        });
+                        break;
+
+                    case AnalysisKind.SyntaxNode:
+                        context.RegisterSyntaxNodeAction<SyntaxKind>(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterTree = context.FilterTree;
+                        }, SyntaxKind.LocalDeclarationStatement);
+                        break;
+
+                    case AnalysisKind.CodeBlockStart:
+                        context.RegisterCodeBlockStartAction<SyntaxKind>(startContext =>
+                        {
+                            CallbackFilterSpan = startContext.FilterSpan;
+                            CallbackFilterTree = startContext.FilterTree;
+
+                            startContext.RegisterCodeBlockEndAction(endContext =>
+                            {
+                                if (startContext.FilterTree != endContext.FilterTree)
+                                    throw new InvalidOperationException("Mismatched FilterTree");
+
+                                if (startContext.FilterSpan != endContext.FilterSpan)
+                                    throw new InvalidOperationException("Mismatched FilterSpan");
+                            });
+                        });
+                        break;
+
+                    case AnalysisKind.CodeBlock:
+                        context.RegisterCodeBlockAction(context =>
+                        {
+                            CallbackFilterSpan = context.FilterSpan;
+                            CallbackFilterTree = context.FilterTree;
+                        });
+                        break;
+
+                    default:
+                        throw ExceptionUtilities.UnexpectedValue(_analysisKind);
                 }
             }
         }
diff --git a/src/Compilers/Test/Core/Diagnostics/DiagnosticExtensions.cs b/src/Compilers/Test/Core/Diagnostics/DiagnosticExtensions.cs
index 75b0e0e80653f..586f49034d22c 100644
--- a/src/Compilers/Test/Core/Diagnostics/DiagnosticExtensions.cs
+++ b/src/Compilers/Test/Core/Diagnostics/DiagnosticExtensions.cs
@@ -363,7 +363,7 @@ public static ImmutableArray<Diagnostic> GetEmitDiagnostics<TCompilation>(
             IEnumerable<ResourceDescription> manifestResources = null)
             where TCompilation : Compilation
         {
-            var pdbStream = MonoHelpers.IsRunningOnMono() ? null : new MemoryStream();
+            var pdbStream = MonoHelpers.IsRunningOnMono() || options?.EmitMetadataOnly == true ? null : new MemoryStream();
             return c.Emit(new MemoryStream(), pdbStream: pdbStream, options: options, manifestResources: manifestResources).Diagnostics;
         }
 
diff --git a/src/Compilers/Test/Core/Microsoft.CodeAnalysis.Test.Utilities.csproj b/src/Compilers/Test/Core/Microsoft.CodeAnalysis.Test.Utilities.csproj
index 9268709e34723..a248cee8236e1 100644
--- a/src/Compilers/Test/Core/Microsoft.CodeAnalysis.Test.Utilities.csproj
+++ b/src/Compilers/Test/Core/Microsoft.CodeAnalysis.Test.Utilities.csproj
@@ -6,6 +6,9 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <TargetFrameworks>net6.0;net7.0;net472</TargetFrameworks>
     <IsShipping>false</IsShipping>
+    <IsPackable>true</IsPackable>
+    <PackageId>Microsoft.CodeAnalysis.Test.Utilities</PackageId>
+    <PackageDescription>This is an internal package for testing. Not meant for external or production uses. The API can and will break at our discretion.</PackageDescription>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\Compilers\Test\Resources\Core\Microsoft.CodeAnalysis.Compiler.Test.Resources.csproj" />
diff --git a/src/Compilers/Test/Core/TargetFrameworkUtil.cs b/src/Compilers/Test/Core/TargetFrameworkUtil.cs
index 1b40128102417..6f9ea4264263a 100644
--- a/src/Compilers/Test/Core/TargetFrameworkUtil.cs
+++ b/src/Compilers/Test/Core/TargetFrameworkUtil.cs
@@ -90,7 +90,8 @@ public enum TargetFramework
 
         Net50,
         Net60,
-        Net70
+        Net70,
+        Net80
     }
 
     /// <summary>
@@ -206,6 +207,7 @@ static TargetFrameworkUtil()
             TargetFramework.Net50 => ImmutableArray.CreateRange<MetadataReference>(LoadDynamicReferences("Net50")),
             TargetFramework.Net60 => ImmutableArray.CreateRange<MetadataReference>(LoadDynamicReferences("Net60")),
             TargetFramework.NetCoreApp or TargetFramework.Net70 => ImmutableArray.CreateRange<MetadataReference>(Net70.All),
+            TargetFramework.Net80 => ImmutableArray.CreateRange<MetadataReference>(LoadDynamicReferences("Net80")),
             TargetFramework.NetFramework => NetFramework.References,
             TargetFramework.NetLatest => NetLatest,
             TargetFramework.Standard => StandardReferences,
@@ -322,6 +324,11 @@ private static ImmutableArray<PortableExecutableReference> LoadDynamicReferences
 
                 var type = assembly.GetType(assemblyName, throwOnError: true);
                 var prop = type.GetProperty("All", BindingFlags.Public | BindingFlags.Static);
+                if (prop is null)
+                {
+                    type = assembly.GetType(assemblyName + "+References", throwOnError: true);
+                    prop = type.GetProperty("All", BindingFlags.Public | BindingFlags.Static);
+                }
                 var obj = prop.GetGetMethod()!.Invoke(obj: null, parameters: null);
                 references = ((IEnumerable<PortableExecutableReference>)obj).ToImmutableArray();
 
diff --git a/src/Compilers/Test/Resources/Core/Microsoft.CodeAnalysis.Compiler.Test.Resources.csproj b/src/Compilers/Test/Resources/Core/Microsoft.CodeAnalysis.Compiler.Test.Resources.csproj
index 28bb8dc578b26..edd55502f536d 100644
--- a/src/Compilers/Test/Resources/Core/Microsoft.CodeAnalysis.Compiler.Test.Resources.csproj
+++ b/src/Compilers/Test/Resources/Core/Microsoft.CodeAnalysis.Compiler.Test.Resources.csproj
@@ -7,6 +7,10 @@
     <RootNamespace></RootNamespace>
     <EnableDefaultItems>false</EnableDefaultItems>
     <IsShipping>false</IsShipping>
+    <IsPackable>true</IsPackable>
+    <PackageId>Microsoft.CodeAnalysis.Compiler.Test.Resources</PackageId>
+    <PackageDescription>This is an internal package for testing. Not meant for external or production uses. The API can and will break at our discretion.</PackageDescription>
+    <NoWarn>NU5100,NU5106,CS1591</NoWarn>
   </PropertyGroup>
   <ItemGroup Label="Project References">
     <ProjectReference Include="..\..\..\Core\Portable\Microsoft.CodeAnalysis.csproj" />
@@ -385,4 +389,4 @@
   <ItemGroup>
     <EmbeddedResource Include="SymbolsTests\nativeCOFFResources.obj" />
   </ItemGroup>
-</Project>
\ No newline at end of file
+</Project>
diff --git a/src/Compilers/Test/Utilities/CSharp/Extensions.cs b/src/Compilers/Test/Utilities/CSharp/Extensions.cs
index 3cc47f6453cd7..b0ab8df743ef2 100644
--- a/src/Compilers/Test/Utilities/CSharp/Extensions.cs
+++ b/src/Compilers/Test/Utilities/CSharp/Extensions.cs
@@ -163,25 +163,62 @@ private static ImmutableArray<string> SplitMemberName(string name)
         }
 
         public static Symbol GetMember(this CSharpCompilation compilation, string qualifiedName)
+            => compilation.GlobalNamespace.GetMember(qualifiedName);
+
+        public static ISymbol GetMember(this Compilation compilation, string qualifiedName)
+            => compilation.GlobalNamespace.GetMember(qualifiedName);
+
+        public static T GetMember<T>(this CSharpCompilation compilation, string qualifiedName) where T : Symbol
+            => (T)compilation.GlobalNamespace.GetMember(qualifiedName);
+
+        public static T GetMember<T>(this Compilation compilation, string qualifiedName) where T : ISymbol
+            => (T)compilation.GlobalNamespace.GetMember(qualifiedName);
+
+        public static IMethodSymbol GetCopyConstructor(this Compilation compilation, string qualifiedTypeName)
+        {
+            var type = compilation.GetMember<INamedTypeSymbol>(qualifiedTypeName);
+            if (!type.IsRecord)
+            {
+                throw new InvalidOperationException("Only records have copy-constructor");
+            }
+
+            return type.InstanceConstructors.Single(c => c.Parameters is [{ Type: var parameterType }] && parameterType.Equals(type, SymbolEqualityComparer.Default));
+        }
+
+        public static IMethodSymbol GetPrimaryConstructor(this Compilation compilation, string qualifiedTypeName)
         {
-            return compilation.GlobalNamespace.GetMember(qualifiedName);
+            var type = compilation.GetMember<INamedTypeSymbol>(qualifiedTypeName);
+            return type.InstanceConstructors.Single(c => c.DeclaringSyntaxReferences.Any(r => r.GetSyntax() is TypeDeclarationSyntax));
         }
 
-        public static ISymbol GetMember(this Compilation compilation, string qualifiedName)
+        public static IMethodSymbol GetParameterlessConstructor(this Compilation compilation, string qualifiedTypeName)
         {
-            return compilation.GlobalNamespace.GetMember(qualifiedName);
+            var type = compilation.GetMember<INamedTypeSymbol>(qualifiedTypeName);
+            return type.InstanceConstructors.Single(c => c.Parameters is []);
         }
 
-        public static T GetMember<T>(this CSharpCompilation compilation, string qualifiedName) where T : Symbol
+        public static IMethodSymbol GetSpecializedEqualsOverload(this Compilation compilation, string qualifiedTypeName)
         {
-            return (T)compilation.GlobalNamespace.GetMember(qualifiedName);
+            var type = compilation.GetMember<INamedTypeSymbol>(qualifiedTypeName);
+            return type.GetMembers("Equals").OfType<IMethodSymbol>().Single(m => m.Parameters is [{ Type: var parameterType }] && parameterType.Equals(type, SymbolEqualityComparer.Default));
         }
 
-        public static T GetMember<T>(this Compilation compilation, string qualifiedName) where T : ISymbol
+        public static IMethodSymbol GetPrimaryDeconstructor(this Compilation compilation, string qualifiedTypeName)
         {
-            return (T)compilation.GlobalNamespace.GetMember(qualifiedName);
+            var primaryConstructor = compilation.GetPrimaryConstructor(qualifiedTypeName);
+            if (!primaryConstructor.ContainingType.IsRecord)
+            {
+                throw new InvalidOperationException("Only records have primary deconstructor");
+            }
+
+            return primaryConstructor.ContainingType.GetMembers("Deconstruct").OfType<IMethodSymbol>().Single(
+                m => m.Parameters.Length == primaryConstructor.Parameters.Length &&
+                     m.Parameters.All(p => p.RefKind == RefKind.Out && p.Type.Equals(primaryConstructor.Parameters[p.Ordinal].Type, SymbolEqualityComparer.Default)));
         }
 
+        public static ImmutableArray<T> GetMembers<T>(this Compilation compilation, string qualifiedName) where T : ISymbol
+            => GetMembers(compilation, qualifiedName).SelectAsArray(s => (T)s.ISymbol);
+
         public static ImmutableArray<Symbol> GetMembers(this Compilation compilation, string qualifiedName)
         {
             NamespaceOrTypeSymbol lastContainer;
diff --git a/src/Compilers/Test/Utilities/CSharp/MockCSharpCompiler.cs b/src/Compilers/Test/Utilities/CSharp/MockCSharpCompiler.cs
index c3f96361f8499..ea1e65d98cf30 100644
--- a/src/Compilers/Test/Utilities/CSharp/MockCSharpCompiler.cs
+++ b/src/Compilers/Test/Utilities/CSharp/MockCSharpCompiler.cs
@@ -18,19 +18,21 @@ internal class MockCSharpCompiler : CSharpCompiler
     {
         private readonly ImmutableArray<DiagnosticAnalyzer> _analyzers;
         private readonly ImmutableArray<ISourceGenerator> _generators;
+        private readonly ImmutableArray<MetadataReference> _additionalReferences;
         internal Compilation Compilation;
         internal AnalyzerOptions AnalyzerOptions;
 
-        public MockCSharpCompiler(string responseFile, string workingDirectory, string[] args, ImmutableArray<DiagnosticAnalyzer> analyzers = default, ImmutableArray<ISourceGenerator> generators = default, AnalyzerAssemblyLoader loader = null)
-            : this(responseFile, CreateBuildPaths(workingDirectory), args, analyzers, generators, loader)
+        public MockCSharpCompiler(string responseFile, string workingDirectory, string[] args, ImmutableArray<DiagnosticAnalyzer> analyzers = default, ImmutableArray<ISourceGenerator> generators = default, AnalyzerAssemblyLoader loader = null, ImmutableArray<MetadataReference> additionalReferences = default)
+            : this(responseFile, CreateBuildPaths(workingDirectory), args, analyzers, generators, loader, additionalReferences: additionalReferences)
         {
         }
 
-        public MockCSharpCompiler(string responseFile, BuildPaths buildPaths, string[] args, ImmutableArray<DiagnosticAnalyzer> analyzers = default, ImmutableArray<ISourceGenerator> generators = default, AnalyzerAssemblyLoader loader = null, GeneratorDriverCache driverCache = null)
+        public MockCSharpCompiler(string responseFile, BuildPaths buildPaths, string[] args, ImmutableArray<DiagnosticAnalyzer> analyzers = default, ImmutableArray<ISourceGenerator> generators = default, AnalyzerAssemblyLoader loader = null, GeneratorDriverCache driverCache = null, ImmutableArray<MetadataReference> additionalReferences = default)
             : base(CSharpCommandLineParser.Default, responseFile, args, buildPaths, Environment.GetEnvironmentVariable("LIB"), loader ?? new DefaultAnalyzerAssemblyLoader(), driverCache)
         {
             _analyzers = analyzers.NullToEmpty();
             _generators = generators.NullToEmpty();
+            _additionalReferences = additionalReferences.NullToEmpty();
         }
 
         private static BuildPaths CreateBuildPaths(string workingDirectory, string sdkDirectory = null) => RuntimeUtilities.CreateBuildPaths(workingDirectory, sdkDirectory);
@@ -78,6 +80,12 @@ public override Compilation CreateCompilation(
             AnalyzerConfigOptionsResult globalDiagnosticOptionsOpt)
         {
             Compilation = base.CreateCompilation(consoleOutput, touchedFilesLogger, errorLogger, syntaxDiagOptionsOpt, globalDiagnosticOptionsOpt);
+
+            if (!_additionalReferences.IsEmpty)
+            {
+                Compilation = Compilation.AddReferences(_additionalReferences);
+            }
+
             return Compilation;
         }
 
diff --git a/src/Compilers/Test/Utilities/VisualBasic/MockSymbols.vb b/src/Compilers/Test/Utilities/VisualBasic/MockSymbols.vb
index 03c4231d9650d..28cdd322f7cec 100644
--- a/src/Compilers/Test/Utilities/VisualBasic/MockSymbols.vb
+++ b/src/Compilers/Test/Utilities/VisualBasic/MockSymbols.vb
@@ -824,6 +824,10 @@ Friend Class MockAssemblySymbol
         Throw New NotImplementedException()
     End Function
 
+    Friend Overrides Function GetInternalsVisibleToAssemblyNames() As IEnumerable(Of String)
+        Throw New NotImplementedException()
+    End Function
+
     Friend Overrides Function AreInternalsVisibleToThisAssembly(potentialGiverOfAccess As AssemblySymbol) As Boolean
         Throw New NotImplementedException()
     End Function
diff --git a/src/Compilers/Test/Utilities/VisualBasic/MockVisualBasicCompiler.vb b/src/Compilers/Test/Utilities/VisualBasic/MockVisualBasicCompiler.vb
index ca19b3c1f814c..1d23d1e75f9f1 100644
--- a/src/Compilers/Test/Utilities/VisualBasic/MockVisualBasicCompiler.vb
+++ b/src/Compilers/Test/Utilities/VisualBasic/MockVisualBasicCompiler.vb
@@ -13,6 +13,7 @@ Friend Class MockVisualBasicCompiler
 
     Private ReadOnly _analyzers As ImmutableArray(Of DiagnosticAnalyzer)
     Private ReadOnly _generators As ImmutableArray(Of ISourceGenerator)
+    Private ReadOnly _additionalReferences As ImmutableArray(Of MetadataReference)
     Public Compilation As Compilation
     Public AnalyzerOptions As AnalyzerOptions
 
@@ -28,15 +29,16 @@ Friend Class MockVisualBasicCompiler
         MyClass.New(responseFile, buildPaths, args, If(analyzer Is Nothing, Nothing, {analyzer}))
     End Sub
 
-    Public Sub New(responseFile As String, workingDirectory As String, args As String(), Optional analyzers As DiagnosticAnalyzer() = Nothing, Optional generators As ISourceGenerator() = Nothing)
-        MyClass.New(responseFile, CreateBuildPaths(workingDirectory, Path.GetTempPath()), args, analyzers, generators)
+    Public Sub New(responseFile As String, workingDirectory As String, args As String(), Optional analyzers As DiagnosticAnalyzer() = Nothing, Optional generators As ISourceGenerator() = Nothing, Optional additionalReferences As MetadataReference() = Nothing)
+        MyClass.New(responseFile, CreateBuildPaths(workingDirectory, Path.GetTempPath()), args, analyzers, generators, additionalReferences)
     End Sub
 
-    Public Sub New(responseFile As String, buildPaths As BuildPaths, args As String(), Optional analyzers As DiagnosticAnalyzer() = Nothing, Optional generators As ISourceGenerator() = Nothing)
+    Public Sub New(responseFile As String, buildPaths As BuildPaths, args As String(), Optional analyzers As DiagnosticAnalyzer() = Nothing, Optional generators As ISourceGenerator() = Nothing, Optional additionalReferences As MetadataReference() = Nothing)
         MyBase.New(VisualBasicCommandLineParser.Default, responseFile, args, buildPaths, Environment.GetEnvironmentVariable("LIB"), New DefaultAnalyzerAssemblyLoader())
 
         _analyzers = analyzers.AsImmutableOrEmpty()
         _generators = generators.AsImmutableOrEmpty()
+        _additionalReferences = additionalReferences.AsImmutableOrEmpty()
     End Sub
 
     Private Shared Function CreateBuildPaths(workingDirectory As String, tempDirectory As String) As BuildPaths
@@ -67,6 +69,11 @@ Friend Class MockVisualBasicCompiler
 
     Public Overrides Function CreateCompilation(consoleOutput As TextWriter, touchedFilesLogger As TouchedFileLogger, errorLogger As ErrorLogger, syntaxTreeDiagnosticOptionsOpt As ImmutableArray(Of AnalyzerConfigOptionsResult), globalConfigOptions As AnalyzerConfigOptionsResult) As Compilation
         Compilation = MyBase.CreateCompilation(consoleOutput, touchedFilesLogger, errorLogger, syntaxTreeDiagnosticOptionsOpt, globalConfigOptions)
+
+        If Not _additionalReferences.IsEmpty Then
+            Compilation = Compilation.AddReferences(_additionalReferences)
+        End If
+
         Return Compilation
     End Function
 
diff --git a/src/Compilers/Test/Utilities/VisualBasic/ParserTestUtilities.vb b/src/Compilers/Test/Utilities/VisualBasic/ParserTestUtilities.vb
index 822a2315edbda..005330a70f15c 100644
--- a/src/Compilers/Test/Utilities/VisualBasic/ParserTestUtilities.vb
+++ b/src/Compilers/Test/Utilities/VisualBasic/ParserTestUtilities.vb
@@ -1025,16 +1025,19 @@ Public Module VerificationHelpers
 
         Public Sub IncrementTypeCounter(Node As VisualBasicSyntaxNode, NodeKey As String)
             _Items.Add(Node)
-            If _Dict.ContainsKey(NodeKey) Then
-                _Dict(NodeKey) = _Dict(NodeKey) + 1 'Increment Count
+
+            Dim count As Integer = Nothing
+            If _Dict.TryGetValue(NodeKey, count) Then
+                _Dict(NodeKey) = count + 1 'Increment Count
             Else
                 _Dict.Add(NodeKey, 1) ' New Item
             End If
         End Sub
 
         Public Function GetCount(Node As String) As Integer
-            If _Dict.ContainsKey(Node) Then
-                Return _Dict(Node)
+            Dim count As Integer = Nothing
+            If _Dict.TryGetValue(Node, count) Then
+                Return count
             Else
                 Return 0
             End If
diff --git a/src/Compilers/VisualBasic/Portable/Binding/Binder_Attributes.vb b/src/Compilers/VisualBasic/Portable/Binding/Binder_Attributes.vb
index fa54ad39218b9..3ca2e0be870a5 100644
--- a/src/Compilers/VisualBasic/Portable/Binding/Binder_Attributes.vb
+++ b/src/Compilers/VisualBasic/Portable/Binding/Binder_Attributes.vb
@@ -481,10 +481,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                             End If
 
                             If Not IsAccessible(setMethod, useSiteInfo) Then
-                                ReportDiagnostic(diagnostics, identifierName, ERRID.ERR_InaccessibleMember3,
+                                ReportDiagnostic(diagnostics, identifierName, New BadSymbolDiagnostic(propertySym,
+                                                   ERRID.ERR_InaccessibleMember3,
                                                    propertySym.ContainingSymbol,
                                                    propertySym,
-                                                   AccessCheck.GetAccessibilityForErrorMessage(setMethod, Me.Compilation.Assembly))
+                                                   AccessCheck.GetAccessibilityForErrorMessage(setMethod, Me.Compilation.Assembly)))
                                 hasErrors = True
                             End If
 
diff --git a/src/Compilers/VisualBasic/Portable/Binding/Binder_ObjectInitializer.vb b/src/Compilers/VisualBasic/Portable/Binding/Binder_ObjectInitializer.vb
index 04e5f17926272..4cc611dbbfcec 100644
--- a/src/Compilers/VisualBasic/Portable/Binding/Binder_ObjectInitializer.vb
+++ b/src/Compilers/VisualBasic/Portable/Binding/Binder_ObjectInitializer.vb
@@ -260,7 +260,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
 
                                 If isInAccessible Then
                                     ' CoClass is inaccessible
-                                    diagInfo = ErrorFactory.ErrorInfo(ERRID.ERR_InAccessibleCoClass3, coClass, type0, coClass.DeclaredAccessibility.ToDiagnosticString())
+                                    diagInfo = New BadSymbolDiagnostic(coClass, ERRID.ERR_InAccessibleCoClass3, coClass, type0, coClass.DeclaredAccessibility.ToDiagnosticString())
                                     Exit Select
                                 End If
 
diff --git a/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCommandLineParser.vb b/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCommandLineParser.vb
index deaa76737dd10..1911ad1aab92f 100644
--- a/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCommandLineParser.vb
+++ b/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCommandLineParser.vb
@@ -168,6 +168,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Dim sourceLink As String = Nothing
             Dim ruleSetPath As String = Nothing
             Dim generatedFilesOutputDirectory As String = Nothing
+            Dim reportIvts As Boolean = False
 
             ' Process ruleset files first so that diagnostic severity settings specified on the command line via
             ' /nowarn and /warnaserror can override diagnostic severity settings specified in the ruleset file.
@@ -424,6 +425,24 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                         libPaths.AddRange(ParseSeparatedPaths(value))
                         Continue For
 
+                    Case "reportivts", "reportivts+"
+                        If value IsNot Nothing Then
+                            AddDiagnostic(diagnostics, ERRID.ERR_SwitchNeedsBool, "reportivts")
+                            Continue For
+                        End If
+
+                        reportIvts = True
+                        Continue For
+
+                    Case "reportivts-"
+                        If value IsNot Nothing Then
+                            AddDiagnostic(diagnostics, ERRID.ERR_SwitchNeedsBool, "reportivts")
+                            Continue For
+                        End If
+
+                        reportIvts = False
+                        Continue For
+
 #If DEBUG Then
                     Case "attachdebugger"
                         Debugger.Launch()
@@ -1504,7 +1523,8 @@ lVbRuntimePlus:
                 .ReportAnalyzer = reportAnalyzer,
                 .SkipAnalyzers = skipAnalyzers,
                 .EmbeddedFiles = embeddedFiles.AsImmutable(),
-                .GeneratedFilesOutputDirectory = generatedFilesOutputDirectory
+                .GeneratedFilesOutputDirectory = generatedFilesOutputDirectory,
+                .ReportInternalsVisibleToAttributes = reportIVTs
             }
         End Function
 
diff --git a/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCompiler.vb b/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCompiler.vb
index 4408df3c1dc4a..4cd8e1ca1b010 100644
--- a/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCompiler.vb
+++ b/src/Compilers/VisualBasic/Portable/CommandLine/VisualBasicCompiler.vb
@@ -301,5 +301,30 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Return VisualBasicGeneratorDriver.Create(generators, additionalTexts, DirectCast(parseOptions, VisualBasicParseOptions), analyzerConfigOptionsProvider)
         End Function
 
+        Private Protected Overrides Sub DiagnoseBadAccesses(consoleOutput As TextWriter, errorLogger As ErrorLogger, compilation As Compilation, diagnostics As ImmutableArray(Of Diagnostic))
+            Dim newDiagnostics = DiagnosticBag.GetInstance()
+
+            For Each diag In diagnostics
+                Dim symbol As Symbol
+                Select Case diag.Code
+                    Case ERRID.ERR_InaccessibleSymbol2,
+                         ERRID.ERR_InaccessibleMember3,
+                         ERRID.ERR_InAccessibleCoClass3,
+                         ERRID.ERR_CannotOverrideInAccessibleMember,
+                         ERRID.ERR_InaccessibleReturnTypeOfMember2
+
+                        Dim symbolDiagnostic = DirectCast(DirectCast(diag, DiagnosticWithInfo).Info, BadSymbolDiagnostic)
+                        symbol = symbolDiagnostic.BadSymbol
+
+                    Case Else
+                        Continue For
+                End Select
+
+                newDiagnostics.Add(New VBDiagnostic(ErrorFactory.ErrorInfo(ERRID.ERR_SymbolDefinedInAssembly, symbol, symbol.ContainingAssembly), diag.Location))
+            Next
+
+            ReportDiagnostics(newDiagnostics.ToReadOnlyAndFree(), consoleOutput, errorLogger, compilation)
+        End Sub
+
     End Class
 End Namespace
diff --git a/src/Compilers/VisualBasic/Portable/Compilation/VisualBasicCompilation.vb b/src/Compilers/VisualBasic/Portable/Compilation/VisualBasicCompilation.vb
index 4c5ec2d9b7d82..036703faf8579 100644
--- a/src/Compilers/VisualBasic/Portable/Compilation/VisualBasicCompilation.vb
+++ b/src/Compilers/VisualBasic/Portable/Compilation/VisualBasicCompilation.vb
@@ -1326,6 +1326,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             End If
         End Function
 
+        Friend Overrides Function GetSymbolInternal(Of TSymbol As {Class, ISymbolInternal})(symbol As ISymbol) As TSymbol
+            Return DirectCast(symbol, TSymbol)
+        End Function
+
         ''' <summary>
         ''' Gets the <see cref="MetadataReference"/> that corresponds to the assembly symbol.
         ''' </summary>
diff --git a/src/Compilers/VisualBasic/Portable/Errors/ErrorFacts.vb b/src/Compilers/VisualBasic/Portable/Errors/ErrorFacts.vb
index bc8058d5ed9da..c11ef619b2bec 100644
--- a/src/Compilers/VisualBasic/Portable/Errors/ErrorFacts.vb
+++ b/src/Compilers/VisualBasic/Portable/Errors/ErrorFacts.vb
@@ -18,7 +18,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Select Case code
                 Case ERRID.ERR_TypeRefResolutionError3,
                      ERRID.ERR_MissingRuntimeHelper,
-                     ERRID.ERR_CannotGotoNonScopeBlocksWithClosure
+                     ERRID.ERR_CannotGotoNonScopeBlocksWithClosure,
+                     ERRID.ERR_SymbolDefinedInAssembly
                     ' Update src\EditorFeatures\VisualBasic\LanguageServer\VisualBasicLspBuildOnlyDiagnostics.vb
                     ' whenever new values are added here.
                     Return True
diff --git a/src/Compilers/VisualBasic/Portable/Errors/Errors.vb b/src/Compilers/VisualBasic/Portable/Errors/Errors.vb
index 688f1f13592f6..d440070420d43 100644
--- a/src/Compilers/VisualBasic/Portable/Errors/Errors.vb
+++ b/src/Compilers/VisualBasic/Portable/Errors/Errors.vb
@@ -1774,8 +1774,9 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         ERR_DoNotUseRequiredMember = 37325
 
         ERR_UnsupportedRefReturningCallInWithStatement = 37326
+        ERR_SymbolDefinedInAssembly = 37327
 
-        ERR_NextAvailable = 37327
+        ERR_NextAvailable = 37328
 
         '// WARNINGS BEGIN HERE
         WRN_UseOfObsoleteSymbol2 = 40000
diff --git a/src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory.vb b/src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory.vb
index 4c9978ca71b3f..274ad11340d8a 100644
--- a/src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory.vb
+++ b/src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory.vb
@@ -1206,6 +1206,8 @@ Namespace Microsoft.CodeAnalysis.Operations
                                                      statementInfo.CurrentProperty,
                                                      statementInfo.MoveNextMethod,
                                                      isAsynchronous:=False,
+                                                     inlineArrayConversion:=Nothing,
+                                                     collectionIsInlineArrayValue:=False,
                                                      boundForEachStatement.EnumeratorInfo.NeedToDispose,
                                                      knownToImplementIDisposable:=boundForEachStatement.EnumeratorInfo.NeedToDispose AndAlso
                                                                                   boundForEachStatement.EnumeratorInfo.IsOrInheritsFromOrImplementsIDisposable,
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/AssemblySymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/AssemblySymbol.vb
index be87b24886d00..09e42621e0c18 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/AssemblySymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/AssemblySymbol.vb
@@ -351,6 +351,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                     Return Me.RuntimeSupportsUnmanagedSignatureCallingConvention
                 Case RuntimeCapability.VirtualStaticsInInterfaces
                     Return Me.RuntimeSupportsVirtualStaticsInInterfaces
+                Case RuntimeCapability.InlineArrayTypes
+                    Return Me.RuntimeSupportsInlineArrayTypes
             End Select
 
             Return False
@@ -406,6 +408,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             End Get
         End Property
 
+        Private ReadOnly Property RuntimeSupportsInlineArrayTypes As Boolean
+            Get
+                ' Keep in sync with C#'s AssemblySymbol.RuntimeSupportsInlineArrayTypes
+                Return GetSpecialTypeMember(SpecialMember.System_Runtime_CompilerServices_InlineArrayAttribute__ctor) IsNot Nothing
+            End Get
+        End Property
+
         Private Function RuntimeSupportsFeature(feature As SpecialMember) As Boolean
             Debug.Assert(SpecialMembers.GetDescriptor(feature).DeclaringTypeId = SpecialType.System_Runtime_CompilerServices_RuntimeFeature)
 
@@ -458,6 +467,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
         ''' <remarks></remarks>
         Friend MustOverride Function GetInternalsVisibleToPublicKeys(simpleName As String) As IEnumerable(Of ImmutableArray(Of Byte))
 
+        Friend MustOverride Function GetInternalsVisibleToAssemblyNames() As IEnumerable(Of String)
+
         Friend MustOverride Function AreInternalsVisibleToThisAssembly(other As AssemblySymbol) As Boolean
 
         ''' <summary>
@@ -785,6 +796,18 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             Return visitor.VisitAssembly(Me)
         End Function
 
+        Private Function IAssemblySymbolInternal_GetInternalsVisibleToPublicKeys(simpleName As String) As IEnumerable(Of ImmutableArray(Of Byte)) Implements IAssemblySymbolInternal.GetInternalsVisibleToPublicKeys
+            Return GetInternalsVisibleToPublicKeys(simpleName)
+        End Function
+
+        Private Function IAssemblySymbolInternal_GetInternalsVisibleToAssemblyNames() As IEnumerable(Of String) Implements IAssemblySymbolInternal.GetInternalsVisibleToAssemblyNames
+            Return GetInternalsVisibleToAssemblyNames()
+        End Function
+
+        Private Function IAssemblySymbolInternal_AreInternalsVisibleToThisAssembly(other As IAssemblySymbolInternal) As Boolean Implements IAssemblySymbolInternal.AreInternalsVisibleToThisAssembly
+            Return AreInternalsVisibleToThisAssembly(DirectCast(other, AssemblySymbol))
+        End Function
+
 #End Region
 
     End Class
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/MergedNamespaceSymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/MergedNamespaceSymbol.vb
index 32a7004d629ba..930a49dda99cf 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/MergedNamespaceSymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/MergedNamespaceSymbol.vb
@@ -235,8 +235,15 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
         ''' Method that is called from the CachingLookup to get all child names. Looks
         ''' in all constituent namespaces.
         ''' </summary>
-        Private Function SlowGetChildNames(comparer As IEqualityComparer(Of String)) As HashSet(Of String)
-            Dim childNames As New HashSet(Of String)(comparer)
+        Private Function SlowGetChildNames(comparer As IEqualityComparer(Of String)) As SegmentedHashSet(Of String)
+            ' compute an upper bound for the final capacity of the set we'll return, to reduce heap churn
+            Dim childCount As Integer = 0
+
+            For Each nsSym As NamespaceSymbol In _namespacesToMerge
+                childCount += nsSym.GetMembersUnordered().Length
+            Next
+
+            Dim childNames As New SegmentedHashSet(Of String)(childCount, comparer)
 
             For Each nsSym As NamespaceSymbol In _namespacesToMerge
                 For Each childSym As NamespaceOrTypeSymbol In nsSym.GetMembersUnordered()
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEAssemblySymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEAssemblySymbol.vb
index 5a6aa1fc5cdd8..9306bafa7931c 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEAssemblySymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEAssemblySymbol.vb
@@ -122,6 +122,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Metadata.PE
             Return Assembly.GetInternalsVisibleToPublicKeys(simpleName)
         End Function
 
+        Friend Overrides Function GetInternalsVisibleToAssemblyNames() As IEnumerable(Of String)
+            Return Assembly.GetInternalsVisibleToAssemblyNames()
+        End Function
+
         Public Overloads Overrides Function GetAttributes() As ImmutableArray(Of VisualBasicAttributeData)
             If _lazyCustomAttributes.IsDefault Then
                 PrimaryModule.LoadCustomAttributes(Me.Assembly.Handle, _lazyCustomAttributes)
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEFieldSymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEFieldSymbol.vb
index 45e323c4448d9..08d6707ef54b7 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEFieldSymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PEFieldSymbol.vb
@@ -206,7 +206,9 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Metadata.PE
 
         Friend Overrides ReadOnly Property IsNotSerialized As Boolean
             Get
+#Disable Warning SYSLIB0050 ' 'TypeAttributes.Serializable' is obsolete
                 Return (_flags And FieldAttributes.NotSerialized) <> 0
+#Enable Warning SYSLIB0050
             End Get
         End Property
 
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.vb
index 18cd55d9a2149..a7d23650814bc 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.vb
@@ -220,7 +220,9 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Metadata.PE
 
         Public Overrides ReadOnly Property IsSerializable As Boolean
             Get
+#Disable Warning SYSLIB0050 ' 'TypeAttributes.Serializable' is obsolete
                 Return (_flags And TypeAttributes.Serializable) <> 0
+#Enable Warning SYSLIB0050
             End Get
         End Property
 
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/MissingAssemblySymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/MissingAssemblySymbol.vb
index 65975f9bd2063..c6a1d7d5a4936 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/MissingAssemblySymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/MissingAssemblySymbol.vb
@@ -120,6 +120,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             Return SpecializedCollections.EmptyEnumerable(Of ImmutableArray(Of Byte))()
         End Function
 
+        Friend Overrides Function GetInternalsVisibleToAssemblyNames() As IEnumerable(Of String)
+            Return SpecializedCollections.EmptyEnumerable(Of String)()
+        End Function
+
         Public Overrides ReadOnly Property TypeNames As ICollection(Of String)
             Get
                 Return SpecializedCollections.EmptyCollection(Of String)()
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.vb
index d74fa93184cee..00d063d90fb91 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Retargeting/RetargetingAssemblySymbol.vb
@@ -222,6 +222,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Retargeting
             Return _underlyingAssembly.GetInternalsVisibleToPublicKeys(simpleName)
         End Function
 
+        Friend Overrides Function GetInternalsVisibleToAssemblyNames() As IEnumerable(Of String)
+            Return _underlyingAssembly.GetInternalsVisibleToAssemblyNames()
+        End Function
+
         Friend Overrides Function AreInternalsVisibleToThisAssembly(potentialGiverOfAccess As AssemblySymbol) As Boolean
             Return _underlyingAssembly.AreInternalsVisibleToThisAssembly(potentialGiverOfAccess)
         End Function
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Source/OverrideHidingHelper.vb b/src/Compilers/VisualBasic/Portable/Symbols/Source/OverrideHidingHelper.vb
index 054cbc1e36c10..65b5d02fe85e3 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Source/OverrideHidingHelper.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Source/OverrideHidingHelper.vb
@@ -1000,7 +1000,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                                                overridingMember As Symbol,
                                                overriddenMember As Symbol,
                                                diagnostics As BindingDiagnosticBag)
-            diagnostics.Add(New VBDiagnostic(ErrorFactory.ErrorInfo(id, overridingMember, overriddenMember),
+            diagnostics.Add(New VBDiagnostic(New BadSymbolDiagnostic(overriddenMember, id, overridingMember, overriddenMember),
                                             overridingMember.Locations(0)))
         End Sub
 
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceAssemblySymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceAssemblySymbol.vb
index af0e3ed39ad7e..7e522d31b6a95 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceAssemblySymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceAssemblySymbol.vb
@@ -903,6 +903,16 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             Return If(result IsNot Nothing, result.Keys, SpecializedCollections.EmptyEnumerable(Of ImmutableArray(Of Byte))())
         End Function
 
+        Friend Overrides Function GetInternalsVisibleToAssemblyNames() As IEnumerable(Of String)
+            EnsureAttributesAreBound()
+
+            If _lazyInternalsVisibleToMap Is Nothing Then
+                Return SpecializedCollections.EmptyEnumerable(Of String)()
+            End If
+
+            Return _lazyInternalsVisibleToMap.Keys
+        End Function
+
         Friend ReadOnly Property DeclaresTheObjectClass As Boolean
             Get
                 If Me.CorLibrary IsNot Me Then
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceNamespaceSymbol.vb b/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceNamespaceSymbol.vb
index 4f303cc874116..1ef132bb7bb5b 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceNamespaceSymbol.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Source/SourceNamespaceSymbol.vb
@@ -153,7 +153,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             ' Is that what we want?
 
             Dim result As New Dictionary(Of String, ImmutableArray(Of NamespaceOrTypeSymbol))(builder.Count, IdentifierComparison.Comparer)
-            ImmutableArrayExtensions.CreateNameToMembersMap(Of NamespaceOrTypeSymbol, NamedTypeSymbol, NamespaceSymbol)(builder, result)
+            ImmutableArrayExtensions.CreateNameToMembersMap(Of String, NamespaceOrTypeSymbol, NamedTypeSymbol, NamespaceSymbol)(builder, result)
             Return result
         End Function
 
@@ -188,7 +188,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
                 ' NOTE: type of the array, see comments in MakeNameToMembersMap() for details
                 Interlocked.CompareExchange(
                     _nameToTypeMembersMap,
-                    ImmutableArrayExtensions.GetTypesFromMemberMap(Of NamespaceOrTypeSymbol, NamedTypeSymbol)(Me.GetNameToMembersMap(), CaseInsensitiveComparison.Comparer),
+                    ImmutableArrayExtensions.GetTypesFromMemberMap(Of String, NamespaceOrTypeSymbol, NamedTypeSymbol)(
+                        Me.GetNameToMembersMap(), CaseInsensitiveComparison.Comparer),
                     comparand:=Nothing)
             End If
 
diff --git a/src/Compilers/VisualBasic/Portable/VBResources.resx b/src/Compilers/VisualBasic/Portable/VBResources.resx
index df15b37941e1d..1cd00e68a5770 100644
--- a/src/Compilers/VisualBasic/Portable/VBResources.resx
+++ b/src/Compilers/VisualBasic/Portable/VBResources.resx
@@ -5224,6 +5224,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -5688,4 +5691,7 @@
   <data name="ERR_UnsupportedRefReturningCallInWithStatement" xml:space="preserve">
     <value>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</value>
   </data>
-</root>
\ No newline at end of file
+  <data name="ERR_SymbolDefinedInAssembly" xml:space="preserve">
+    <value>'{0}' is defined in assembly '{1}'.</value>
+  </data>
+</root>
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.cs.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.cs.xlf
index 7a29f5096722b..396de0fb06ed0 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.cs.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.cs.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Z {0} nelze dědit, protože obsahuje požadované členy.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">Atribut System.Runtime.CompilerServices.RequiredMemberAttribute je vyhrazen pouze pro použití kompilátoru.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">{2} nemůže splňovat omezení New u parametru {1} v obecném typu nebo metodě {0}, protože {2} má požadované členy.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">V inicializátoru objektu nebo argumentech atributu musí být nastaven požadovaný člen {0}.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">Seznam požadovaných členů pro {0} má chybný formát a nelze ho interpretovat.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Události sdílených proměnných WithEvents se nedají zpracovat metodami v jiném typu.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} {1} nemůže implementovat rozhraní {3}, protože obsahuje sdílené abstraktní nebo virtuální {2}.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Volání metody nebo vlastnosti, které vrací odkaz, nelze použít jako výraz příkazu With v asynchronní nebo iterační metodě, nebo v případě, že je odkazováno implicitně ve výrazu lambda.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Možnosti kompilátoru jazyka Visual Basic
+        <target state="needs-review-translation">                  Možnosti kompilátoru jazyka Visual Basic
 
                                   - VÝSTUPNÍ SOUBOR -
 -out:&lt;file&gt;                       Určuje název výstupního souboru.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.de.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.de.xlf
index feee6da3898bb..91aeb95c7d6e5 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.de.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.de.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Von "{0}" kann nicht geerbt werden, da er über erforderliche Member verfügt.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">"System.Runtime.CompilerServices.RequiredMemberAttribute" ist nur für die Compilerverwendung reserviert.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">"{2}" kann die "New"-Einschränkung für Parameter "{1}" im generischen Typ oder in der generischen Methode "{0}" nicht erfüllen, da "{2}" erforderliche Member aufweist.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">Das erforderliche Mitglied "{0}" muss im Objektinitialisierer oder in den Attributargumenten festgelegt werden.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">Die erforderliche Mitgliederliste für '{0}' ist falsch formatiert und kann nicht interpretiert werden.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Ereignisse freigegebener WithEvents-Variablen können nicht von Methoden in einem anderen Typ behandelt werden.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} "{1}" kann die Schnittstelle "{3}" nicht implementieren, da sie freigegebene abstrakte oder virtuelle "{2}" enthält.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Ein Aufruf einer Methode oder Eigenschaft, die als Verweis zurückgegeben wird, kann nicht als With-Anweisungsausdruck in einer Async- oder Iteratormethode verwendet werden oder wenn implizit in einem Lambda-Ausdruck darauf verwiesen wird.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Visual Basic Compiler-Optionen
+        <target state="needs-review-translation">                  Visual Basic Compiler-Optionen
 
                                   – AUSGABEDATEI –
 -out:&lt;file&gt;                       Gibt den Namen der Ausgabedatei an.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.es.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.es.xlf
index 4ade6e7ff9a21..17f9ecbba1a42 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.es.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.es.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">No se puede heredar de '{0}' porque tiene miembros necesarios.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute' está reservado solo para uso del compilador.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}' no puede satisfacer la restricción 'New' en el parámetro '{1}' en el tipo o método genérico '{0}' porque '{2}' tiene miembros necesarios.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">El miembro requerido '{0}' debe establecerse en el inicializador de objeto o en los argumentos de atributo.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">La lista de miembros necesarios para '{0}' tiene un formato incorrecto y no se puede interpretar.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Los métodos no pueden controlar los eventos de variables WithEvents compartidas en un tipo distinto.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}' no puede implementar la interfaz '{3}' porque contiene abstracto compartido o '{2}' virtual.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Una llamada a un método o propiedad que devuelve por referencia no se puede usar como expresión de instrucción 'With' en un método asincrónico o iterador, o si se hace referencia implícitamente en una expresión lambda.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Opciones del compilador de Visual Basic
+        <target state="needs-review-translation">                  Opciones del compilador de Visual Basic
 
                                   - ARCHIVO DE SALIDA -
 -out:&lt;file&gt;                       Especifica el nombre del archivo de salida.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.fr.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.fr.xlf
index 86a76b0f9ff55..fc0e05e171acf 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.fr.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.fr.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Impossible d'hériter de '{0}' car il a requis des membres.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute' est réservé à l'usage du compilateur uniquement.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}' ne peut pas satisfaire la contrainte 'Nouveau' sur le paramètre '{1}' dans le type ou la méthode générique '{0}' car '{2}' a des membres requis.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">Le membre requis '{0}' doit être défini dans l'initialiseur d'objet ou les arguments d'attribut.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">La liste des membres requis pour «{0}» est incorrecte et ne peut pas être interprétée.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Les événements des variables WithEvents partagées ne peuvent pas être pris en charge par des méthodes dans un autre type.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}' ne peut pas mettre en œuvre l'interface '{3}' car elle contient des données abstraites ou virtuelles partagées '{2}'.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Un appel à une méthode ou une propriété qui retourne par référence ne peut pas être utilisé comme expression d'instruction 'With' dans une méthode asynchrone ou itérateur, ou s'il est référencé implicitement dans un lambda.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Options du compilateur Visual Basic 
+        <target state="needs-review-translation">                  Options du compilateur Visual Basic 
 
                                   - FICHIER DE SORTIE -
 -out:&lt;file&gt;                       Spécifie le nom du fichier de sortie.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.it.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.it.xlf
index 6af1dfc0688d9..cc16a36786264 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.it.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.it.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Non è possibile ereditare da '{0}' perché contiene membri obbligatori.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute' è riservato solo all’uso del compilatore.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}' non può soddisfare il vincolo 'New' nel parametro '{1}' nel tipo generico o nel metodo '{0}' perché '{2}' contiene membri obbligatori.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">Il membro obbligatorio '{0}' deve essere impostato nell'inizializzatore di oggetto o negli argomenti dell'attributo.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">L'elenco dei membri obbligatori per '{0}' non è valido e non può essere interpretato.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Gli eventi di variabili WithEvents condivise non possono essere gestiti da metodi in un tipo diverso.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}' non può implementare l'interfaccia '{3}' perché contiene '{2}' condiviso astratto o virtuale.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Una chiamata a un metodo o a una proprietà che restituisce un riferimento non può essere usata come espressione 'With' in un metodo asincrono o iteratore, o se implicitamente di riferimento in un’espressione lambda.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Opzioni del compilatore Visual Basic
+        <target state="needs-review-translation">                  Opzioni del compilatore Visual Basic
 
                                   - FILE DI OUTPUT -
 -out:&lt;file&gt;                       Consente di specificare il nome del file di output.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.ja.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.ja.xlf
index bb417ed37ac05..dcfb5070567c9 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.ja.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.ja.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">必要なメンバーがあるため、'{0}' から継承できません。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute' は、コンパイラでのみ使用するために予約されています。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}' は、ジェネリック型またはメソッド '{0}' のパラメーター '{1}' の 'New' 制約を満たすことはできません。これは、'{2}' に必要なメンバーが含まれているためです。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">必要なメンバー '{0}' は、オブジェクト初期化子または属性引数に設定する必要があります。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">'{0}' に必要なメンバーの一覧の形式が正しくないため、解釈できません。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">共有された WithEvents 変数のイベントを、別の種類のメソッドで処理することはできません。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}' には、共有された抽象または仮想 '{2}' が含まれているため、インターフェイス '{3}' を実装できません。</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">参照によって返されるメソッドまたはプロパティの呼び出しは、非同期メソッドまたは反復子メソッドで 'With' ステートメント式として、またはラムダで暗黙的に参照される場合は使用できません。</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Visual Basic コンパイラ オプション
+        <target state="needs-review-translation">                  Visual Basic コンパイラ オプション
 
                                  - 出力ファイル -
 -out:&lt;file&gt;                       出力ファイル名を指定します。
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.ko.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.ko.xlf
index 3e4f00bbe1ff2..3056d1303c8ec 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.ko.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.ko.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">필요한 멤버가 있어 '{0}'에서 상속할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute'는 컴파일러 용도로만 예약되어 있습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}'에 필수 멤버가 있으므로 '{2}'은(는) 제네릭 형식 또는 메서드 '{0}'의 '{1}' 매개 변수에 대한 'New' 제약 조건을 충족할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">필수 멤버 '{0}'은(는) 개체 이니셜라이저 또는 특성 인수에서 설정해야 합니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">'{0}'에 대한 필수 구성원 목록 형식이 잘못되어 해석할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">공유 WithEvents 변수의 이벤트는 다른 형식의 메서드에서 처리할 수 없습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}'은(는) 공유 추상 또는 가상 '{2}'이(가) 포함되어 있으므로 '{3}' 인터페이스를 구현할 수 없습니다.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">참조로 반환하는 메서드 또는 속성에 대한 호출은 비동기 메서드나 반복기 메서드에서 또는 람다에서 암시적으로 참조되는 경우 'With' 문 식으로 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Visual Basic 컴파일러 옵션
+        <target state="needs-review-translation">                  Visual Basic 컴파일러 옵션
 
                                   - 출력 파일 -
 -out:&lt;file&gt; 출력 파일 이름을 지정합니다.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.pl.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.pl.xlf
index f69022e9347b4..b97ad41e8f726 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.pl.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.pl.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Nie można dziedziczyć z elementu „{0}”, ponieważ zawiera wymagane elementy członkowskie.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">Element „System.Runtime.CompilerServices.RequiredMemberAttribute” jest zarezerwowany tylko do użycia przez kompilator.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">„{2}” nie może spełnić ograniczenia „New” dla parametru „{1}” w typie ogólnym lub metodzie „{0}”, ponieważ „{2}” ma wymagane elementy członkowskie.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">Wymagana składowa „{0}” musi być ustawiona w inicjatorze obiektu lub argumentach atrybutów.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">Lista wymaganych składowych dla „{0}” jest źle sformułowana i nie można jej zinterpretować.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Zdarzenia udostępnionych zmiennych WithEvents nie mogą zostać obsłużone przez metody w innym typie.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0}„{1}” nie może zaimplementować interfejsu „{3}”, ponieważ zawiera udostępnioną abstrakcyjną lub wirtualną „{2}”.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Wywołanie metody lub właściwości zwracanej przez odwołanie nie może być używane jako wyrażenie instrukcji „With” w metodzie asynchronicznej lub iteratora albo w przypadku niejawnego odwołania w wyrażeniu lambda.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Opcje kompilatora Visual Basic
+        <target state="needs-review-translation">                  Opcje kompilatora Visual Basic
 
                                   - PLIK WYJŚCIOWY -
 -out:&lt;file&gt;                       Określa nazwę pliku wyjściowego.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.pt-BR.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.pt-BR.xlf
index 66cfe9000aa27..cb2741748d5a0 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.pt-BR.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.pt-BR.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Não é possível herdar de '{0}' porque ele tem membros necessários.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute' está reservado somente para uso do compilador.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}' não pode satisfazer a restrição 'New' no parâmetro '{1}' no tipo genérico ou método '{0}' porque '{2}' tem membros requeridos.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">O membro necessário '{0}' deve ser definido no inicializador de objeto ou argumentos de atributo.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">A lista de membros requeridos '{0}' está malformada e não pode ser interpretada.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Os eventos das variáveis WithEvents compartilhadas não podem ser manipulados por métodos em um tipo diferente.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}' não é possível implementar a interface '{3}' porque ela contém um abstrato compartilhado ou virtual '{2}'.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Uma chamada a um método ou propriedade retornada por referência não pode ser usada como expressão de instrução 'With' em um método assíncrono ou iterador, ou se referenciada implicitamente em um lambda.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Opções do compilador do Visual Basic
+        <target state="needs-review-translation">                  Opções do compilador do Visual Basic
 
                                   - ARQUIVO DE SAÍDA -
 -out:&lt;file&gt;                       Especifica o nome do arquivo de saída.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.ru.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.ru.xlf
index f5878abdb22ac..871b39582ff7c 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.ru.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.ru.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Не удалось наследование от "{0}", так как в нем есть обязательные элементы.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">"System.Runtime.CompilerServices.RequiredMemberAttribute" зарезервирован только для использования компилятором.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">"{2}" не соответствует ограничению "New" параметра "{1}" в универсальном типе или методе "{0}", поскольку у "{2}" есть обязательные элементы.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">Обязательный элемент "{0}" должен быть установлен в инициализаторе объекта или аргументах атрибута.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">Неправильный формат списка обязательных элементов для "{0}", его не удается интерпретировать.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">События общих переменных WithEvents не могут обрабатывать методы другого типа.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} "{1}" не может реализовать интерфейс "{3}", поскольку он содержит общий абстрактный или виртуальный элемент "{2}".</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Вызов метода или свойства, возвращаемого по ссылке, нельзя использовать в качестве выражения оператора With в асинхронном методе или методе итератора, а также при неявной ссылке в лямбда-выражении.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Параметры компилятора Visual Basic
+        <target state="needs-review-translation">                  Параметры компилятора Visual Basic
 
                                   - ВЫХОДНОЙ ФАЙЛ -
 -out: &lt;файл&gt;                       Задает имя выходного файла.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.tr.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.tr.xlf
index 7a9a49a28e56b..73ad24c10a4ba 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.tr.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.tr.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">Gerekli üyelere sahip olduğu için '{0}' öğesinden devralınamaz.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute' yalnızca derleyici kullanımı için ayrılmıştır.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}' gerekli üyelere sahip olduğundan '{2}', '{0}' genel türünde veya metodunda bulunan '{1}' parametresindeki 'new()' kısıtlamasını karşılayamıyor.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">Gerekli '{0}' üyesi nesne başlatıcısında veya öznitelik bağımsız değişkeninde ayarlanmış olmalıdır.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">'{0}' için gerekli üye listesi hatalı biçimlendirilmiş ve yorumlanamıyor.</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">Paylaşılan WithEvents değişkenlerinin olayları farklı türdeki metotlar tarafından işlenemez.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}', paylaşılan soyut veya sanal '{2}' içerdiğinden '{3}' arabirimini uygulayamıyor.</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">Başvuruya göre dönen bir yönteme veya özelliğe yapılan çağrı, bir zaman uyumsuz veya yineleyici yöntemde veya bir lambda'da dolaylı olarak başvuruluyorsa 'With' deyimi olarak kullanılamaz.</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Visual Basic Derleyicisi Seçenekleri
+        <target state="needs-review-translation">                  Visual Basic Derleyicisi Seçenekleri
 
                                   - ÇIKIŞ DOSYASI -
 -out:&lt;file&gt;                       Çıkış dosyası adını belirtir.
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hans.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hans.xlf
index 9a49644116afa..231d12d51b710 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hans.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hans.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">无法从 "{0}" 继承，因为它具有必需的成员。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">"System.Runtime.CompilerServices.RequiredMemberAttribute" 仅供编译器使用。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">"{2}" 无法满足泛型类型或方法 "{1}" 中参数 "{0}" 的 "New" 约束，因为 "{2}" 具有必需的成员。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">必须在对象初始值设定项或属性构参数中设置所需的成员 "{0}"。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">'{0}' 所需的成员列表格式不正确，无法解释。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">共享 WithEvents 变量的事件不能由其他类型的方法处理。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}'无法实现接口 '{3}' ，因为它包含共享抽象或虚拟'{2}'。</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">对通过引用返回的方法或属性的调用不能用作异步或迭代器方法中的 "With" 语句表达式，或者在 lambda 中隐式引用。</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Visual Basic 编译器选项
+        <target state="needs-review-translation">                  Visual Basic 编译器选项
 
                                  - 输出文件 -
 -out:&lt;file&gt;                       指定输出文件名。
diff --git a/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hant.xlf b/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hant.xlf
index 6efb5f5f0b29b..adf9a673ac1f6 100644
--- a/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hant.xlf
+++ b/src/Compilers/VisualBasic/Portable/xlf/VBResources.zh-Hant.xlf
@@ -19,7 +19,7 @@
       </trans-unit>
       <trans-unit id="ERR_CannotInheritFromTypeWithRequiredMembers">
         <source>Cannot inherit from '{0}' because it has required members.</source>
-        <target state="new">Cannot inherit from '{0}' because it has required members.</target>
+        <target state="translated">'{0}' 具有必要的成員，因此無法從其繼承。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_CommentsAfterLineContinuationNotAvailable1">
@@ -39,7 +39,7 @@
       </trans-unit>
       <trans-unit id="ERR_DoNotUseRequiredMember">
         <source>'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</source>
-        <target state="new">'System.Runtime.CompilerServices.RequiredMemberAttribute' is reserved for compiler usage only.</target>
+        <target state="translated">'System.Runtime.CompilerServices.RequiredMemberAttribute' 僅保留給編譯器使用。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_MultipleAnalyzerConfigsInSameDir">
@@ -49,7 +49,7 @@
       </trans-unit>
       <trans-unit id="ERR_NewConstraintCannotHaveRequiredMembers">
         <source>'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</source>
-        <target state="new">'{2}' cannot satisfy the 'New' constraint on parameter '{1}' in the generic type or or method '{0}' because '{2}' has required members.</target>
+        <target state="translated">'{2}' 無法滿足泛型型別或方法 '{0}' 中參數 '{1}' 的 'New' 限制式，因為 '{2}' 具有必要的成員。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_OverridingInitOnlyProperty">
@@ -69,12 +69,12 @@
       </trans-unit>
       <trans-unit id="ERR_RequiredMemberMustBeSet">
         <source>Required member '{0}' must be set in the object initializer or attribute arguments.</source>
-        <target state="new">Required member '{0}' must be set in the object initializer or attribute arguments.</target>
+        <target state="translated">必要成員 '{0}' 必須在物件初始設定式或屬性引數中進行設定。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RequiredMembersInvalid">
         <source>The required members list for '{0}' is malformed and cannot be interpreted.</source>
-        <target state="new">The required members list for '{0}' is malformed and cannot be interpreted.</target>
+        <target state="translated">'{0}' 的必要成員清單格式錯誤，無法解譯。</target>
         <note />
       </trans-unit>
       <trans-unit id="ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation">
@@ -92,6 +92,11 @@
         <target state="translated">無法使用其他類型的方法，處理共用 WithEvents 變數的事件。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_SymbolDefinedInAssembly">
+        <source>'{0}' is defined in assembly '{1}'.</source>
+        <target state="new">'{0}' is defined in assembly '{1}'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_UnimplementedSharedMember">
         <source>{0} '{1}' cannot implement interface '{3}' because it contains shared abstract or virtual '{2}'.</source>
         <target state="translated">{0} '{1}' 無法實作介面 '{3}' 因為其包含共用摘要或虛擬效果 '{2}'。</target>
@@ -109,7 +114,7 @@
       </trans-unit>
       <trans-unit id="ERR_UnsupportedRefReturningCallInWithStatement">
         <source>A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</source>
-        <target state="new">A call to a method or property that returns by reference may not be used as 'With' statement expression in an async or iterator method, or if referenced implicitly in a lambda.</target>
+        <target state="translated">針對會藉傳址傳回的方法或屬性所進行的呼叫，不可在 Async 或 Iterator 方法中作為 'With' 陳述式運算式使用，也不可在 Lambda 中隱含參考。</target>
         <note />
       </trans-unit>
       <trans-unit id="FEATURE_CallerArgumentExpression">
@@ -287,6 +292,9 @@
                                   AnyCPU32BitPreferred or anycpu (default).
 -preferreduilang                  Specify the preferred output language name.
 -nosdkpath                        Disable searching the default SDK path for standard library assemblies.
+-reportivts[+|-]                  Output information on all IVTs granted to this
+                                  assembly by all dependencies, and annotate foreign assembly
+                                  accessibility errors with what assembly they came from.
 -sdkpath:&lt;path&gt;                   Location of the .NET Framework SDK directory
                                   (mscorlib.dll).
 -subsystemversion:&lt;version&gt;       Specify subsystem version of the output PE.
@@ -299,7 +307,7 @@
 -vbruntime:&lt;file&gt;                 Compile with the alternate Visual Basic
                                   runtime in &lt;file&gt;.
 </source>
-        <target state="translated">                  Visual Basic 編譯器選項
+        <target state="needs-review-translation">                  Visual Basic 編譯器選項
 
                                  - OUTPUT FILE -
 -out:&lt;file&gt;                       指定輸出檔案名稱。
diff --git a/src/Compilers/VisualBasic/Test/CommandLine/CommandLineIVTTests.vb b/src/Compilers/VisualBasic/Test/CommandLine/CommandLineIVTTests.vb
new file mode 100644
index 0000000000000..cd64e32787a7b
--- /dev/null
+++ b/src/Compilers/VisualBasic/Test/CommandLine/CommandLineIVTTests.vb
@@ -0,0 +1,596 @@
+' Licensed to the .NET Foundation under one or more agreements.
+' The .NET Foundation licenses this file to you under the MIT license.
+' See the LICENSE file in the project root for more information.
+
+Imports System.IO
+Imports Microsoft.CodeAnalysis.VisualBasic.UnitTests
+Imports Roslyn.Test.Utilities
+Imports Xunit
+
+Namespace Microsoft.CodeAnalysis.VisualBasic.CommandLine.UnitTests
+    Public Class CommandLineIVTTests
+        Inherits BasicTestBase
+
+        <Fact>
+        Public Sub InaccessibleBaseType()
+            Dim source1 = "
+Namespace N1
+    Friend Class A
+    End Class
+End Namespace"
+
+            Dim comp1 = CreateCompilation(source1, assemblyName:="N1", targetFramework:=TargetFramework.Mscorlib461)
+
+            Dim dir = Temp.CreateDirectory()
+            Dim source2 = dir.CreateFile("B.vb").WriteAllText("
+Class B
+    Inherits N1.A
+End Class")
+
+            Dim sw = New StringWriter()
+
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                dir.Path,
+                {
+                "/nologo",
+                "/t:library",
+                "/preferreduilang:en",
+                "/reportivts",
+                source2.Path
+                }, additionalReferences:={comp1.ToMetadataReference()})
+
+            Dim errorCode = compiler.Run(sw)
+
+            Assert.Equal(1, errorCode)
+
+            AssertEx.AssertEqualToleratingWhitespaceDifferences($"
+{source2.Path}(3) : error BC30389: 'N1.A' is not accessible in this context because it is 'Friend'.
+    Inherits N1.A
+             ~~~~
+{source2.Path}(3) : error BC37327: 'A' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+    Inherits N1.A
+             ~~~~
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'B, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'Microsoft.VisualBasic, Version=10.0.0.0, Culture=neutral, PublicKey=002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'System, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'System.Net.Http'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293
+    Assembly name: 'System.Net.Http.WebRequest'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293", sw.ToString())
+        End Sub
+
+        <Fact>
+        Public Sub InaccessibleMember()
+            Dim source1 = "
+Namespace N1
+    Public Class A
+        Friend Sub M()
+        End Sub
+    End Class
+End Namespace"
+
+            Dim comp1 = CreateCompilation(source1, assemblyName:="N1", targetFramework:=TargetFramework.Mscorlib461)
+
+            Dim dir = Temp.CreateDirectory()
+            Dim source2 = dir.CreateFile("B.vb").WriteAllText("
+Class B
+    Inherits N1.A
+    Public Sub S()
+        MyBase.M()
+    End Sub
+End Class")
+
+            Dim sw = New StringWriter()
+
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                dir.Path,
+                {
+                "/nologo",
+                "/t:library",
+                "/preferreduilang:en",
+                "/reportivts",
+                source2.Path
+                }, additionalReferences:={comp1.ToMetadataReference()})
+
+            Dim errorCode = compiler.Run(sw)
+
+            Assert.Equal(1, errorCode)
+
+            AssertEx.AssertEqualToleratingWhitespaceDifferences($"
+{source2.Path}(5) : error BC30390: 'A.Friend Sub M()' is not accessible in this context because it is 'Friend'.
+        MyBase.M()
+        ~~~~~~~~  
+{source2.Path}(5) : error BC37327: 'Friend Sub M()' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+        MyBase.M()
+        ~~~~~~~~  
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'B, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'Microsoft.VisualBasic, Version=10.0.0.0, Culture=neutral, PublicKey=002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'System, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'System.Net.Http'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293
+    Assembly name: 'System.Net.Http.WebRequest'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293", sw.ToString())
+        End Sub
+
+        <Fact>
+        Public Sub InaccessibleMemberOverride()
+            Dim source1 = "
+Namespace N1
+    Public Class A
+        Friend Overridable Sub M()
+        End Sub
+    End Class
+End Namespace"
+
+            Dim comp1 = CreateCompilation(source1, assemblyName:="N1", targetFramework:=TargetFramework.Mscorlib461)
+
+            Dim dir = Temp.CreateDirectory()
+            Dim source2 = dir.CreateFile("B.vb").WriteAllText("
+Class B
+    Inherits N1.A
+
+    Friend Overrides Sub M()
+    End Sub
+End Class")
+
+            Dim sw = New StringWriter()
+
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                dir.Path,
+                {
+                "/nologo",
+                "/t:library",
+                "/preferreduilang:en",
+                "/reportivts",
+                source2.Path
+                }, additionalReferences:={comp1.ToMetadataReference()})
+
+            Dim errorCode = compiler.Run(sw)
+
+            Assert.Equal(1, errorCode)
+
+            AssertEx.AssertEqualToleratingWhitespaceDifferences($"
+{source2.Path}(5) : error BC31417: 'Friend Overrides Sub M()' cannot override 'Friend Overridable Sub M()' because it is not accessible in this context.
+    Friend Overrides Sub M()
+                         ~  
+{source2.Path}(5) : error BC37327: 'Friend Overridable Sub M()' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+    Friend Overrides Sub M()
+                         ~ 
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'B, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'Microsoft.VisualBasic, Version=10.0.0.0, Culture=neutral, PublicKey=002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'System, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'System.Net.Http'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293
+    Assembly name: 'System.Net.Http.WebRequest'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293", sw.ToString())
+        End Sub
+
+        <Fact>
+        Public Sub InaccessibleCoClass()
+            Dim source1 = "
+Imports System.Runtime.InteropServices
+<Assembly: ImportedFromTypeLib(""NoPIANew1-PIA2.dll"")>
+<Assembly: Guid(""f9c2d51d-4f44-45f0-9eda-c9d599b58257"")>
+Public Class Class1
+    <Guid(""bd60d4b3-f50b-478b-8ef2-e777df99d810"")> _
+    <ComImport()> _
+    <InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)> _
+    <CoClass(GetType(FooImpl))> _
+    Public Interface IFoo
+    End Interface
+    <Guid(""c9dcf748-b634-4504-a7ce-348cf7c61891"")> _
+    Friend Class FooImpl
+    End Class
+End Class
+"
+
+            Dim comp1 = CreateCompilation(source1, assemblyName:="N1", targetFramework:=TargetFramework.Mscorlib461)
+
+            Dim dir = Temp.CreateDirectory()
+            Dim source2 = dir.CreateFile("B.vb").WriteAllText("
+Public Module Module1
+    Public Sub Main()
+        Dim i1 As New Class1.IFoo(1)
+        Dim i2 = New Class1.IFoo(Nothing)
+    End Sub
+End Module
+")
+
+            Dim sw = New StringWriter()
+
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                dir.Path,
+                {
+                "/nologo",
+                "/t:library",
+                "/preferreduilang:en",
+                "/reportivts",
+                source2.Path
+                }, additionalReferences:={comp1.ToMetadataReference()})
+
+            Dim errorCode = compiler.Run(sw)
+
+            Assert.Equal(1, errorCode)
+
+            AssertEx.AssertEqualToleratingWhitespaceDifferences($"
+{source2.Path}(4) : error BC31109: Implementing class 'Class1.FooImpl' for interface 'Class1.IFoo' is not accessible in this context because it is 'Friend'.
+        Dim i1 As New Class1.IFoo(1)
+                  ~~~~~~~~~~~~~~~~~~
+{source2.Path}(5) : error BC31109: Implementing class 'Class1.FooImpl' for interface 'Class1.IFoo' is not accessible in this context because it is 'Friend'.
+        Dim i2 = New Class1.IFoo(Nothing)
+                 ~~~~~~~~~~~~~~~~~~~~~~~~
+{source2.Path}(4) : error BC37327: 'Class1.FooImpl' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+        Dim i1 As New Class1.IFoo(1)
+                  ~~~~~~~~~~~~~~~~~~
+{source2.Path}(5) : error BC37327: 'Class1.FooImpl' is defined in assembly 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+        Dim i2 = New Class1.IFoo(Nothing)
+                 ~~~~~~~~~~~~~~~~~~~~~~~~
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'B, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'Microsoft.VisualBasic, Version=10.0.0.0, Culture=neutral, PublicKey=002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'System, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'System.Net.Http'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293
+    Assembly name: 'System.Net.Http.WebRequest'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293", sw.ToString())
+        End Sub
+
+        <Fact>
+        Public Sub InaccessibleReturnTypeOfMember()
+            Dim source1 = "
+<assembly: System.Runtime.CompilerServices.InternalsVisibleTo(""N2"")>
+Namespace N1
+    Friend Class A
+    End Class
+End Namespace"
+
+            Dim comp1 = CreateCompilation(source1, assemblyName:="N1", targetFramework:=TargetFramework.Mscorlib461)
+
+            Dim source2 = "
+<assembly: System.Runtime.CompilerServices.InternalsVisibleTo(""C"")>
+Namespace N2
+    Friend Class B
+        Friend Function M() As N1.A
+            Return Nothing
+        End Function
+    End Class
+End Namespace"
+
+            Dim comp2 = CreateCompilation(source2, assemblyName:="N2", references:={comp1.ToMetadataReference()}, targetFramework:=TargetFramework.Mscorlib461)
+
+            Dim dir = Temp.CreateDirectory()
+            Dim source3 = dir.CreateFile("C.vb").WriteAllText("
+Class C
+    Sub S()
+        Dim b as New N2.B()
+        b.M()
+    End Sub
+End Class")
+
+            Dim sw = New StringWriter()
+
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                dir.Path,
+                {
+                "/nologo",
+                "/t:library",
+                "/preferreduilang:en",
+                "/reportivts",
+                source3.Path
+                }, additionalReferences:={comp1.ToMetadataReference(), comp2.ToMetadataReference()})
+
+            Dim errorCode = compiler.Run(sw)
+
+            Assert.Equal(1, errorCode)
+
+            AssertEx.AssertEqualToleratingWhitespaceDifferences($"
+{source3.Path}(5) : error BC36666: 'Friend Function N2.B.M() As N1.A' is not accessible in this context because the return type is not accessible.
+        b.M()
+        ~~~~~
+{source3.Path}(5) : error BC37327: 'Friend Function M() As A' is defined in assembly 'N2, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.
+        b.M()
+        ~~~~~
+
+Printing 'InternalsVisibleToAttribute' information for the current compilation and all referenced assemblies.
+Current assembly: 'C, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+
+Assembly reference: 'Microsoft.VisualBasic, Version=10.0.0.0, Culture=neutral, PublicKey=002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Nothing
+
+Assembly reference: 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'PresentationCore'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'PresentationFramework'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+    Assembly name: 'System'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Core'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Numerics'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Reflection.Context'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'System.Runtime.WindowsRuntime.UI.Xaml'
+    Public Keys:
+      00000000000000000400000000000000
+    Assembly name: 'WindowsBase'
+    Public Keys:
+      0024000004800000940000000602000000240000525341310004000001000100b5fc90e7027f67871e773a8fde8938c81dd402ba65b9201d60593e96c492651e889cc13f1415ebb53fac1131ae0bd333c5ee6021672d9718ea31a8aebd0da0072f25d87dba6fc90ffd598ed4da35e44c398c454307e8e33b8426143daec9f596836f97c8f74750e5975c64e2189f45def46b2a2b1247adc3652bf5c308055da9
+
+Assembly reference: 'N1, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'N2'
+    Public Keys:
+
+Assembly reference: 'N2, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
+  Grants IVT to current assembly: True
+  Grants IVTs to:
+    Assembly name: 'C'
+    Public Keys:
+
+Assembly reference: 'System, Version=4.0.0.0, Culture=neutral, PublicKey=00000000000000000400000000000000'
+  Grants IVT to current assembly: False
+  Grants IVTs to:
+    Assembly name: 'System.Net.Http'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293
+    Assembly name: 'System.Net.Http.WebRequest'
+    Public Keys:
+      002400000480000094000000060200000024000052534131000400000100010007d1fa57c4aed9f0a32e84aa0faefd0de9e8fd6aec8f87fb03766c834c99921eb23be79ad9d5dcc1dd9ad236132102900b723cf980957fc4e177108fc607774f29e8320e92ea05ece4e821c0a5efe8f1645c4c0c93c1ab99285d622caa652c1dfad63d745d6f2de5f17e5eaf0fc4963d261c8a12436518206dc093344d5ad293", sw.ToString())
+        End Sub
+
+        <Theory>
+        <InlineData("/reportivts")>
+        <InlineData("/reportivts+")>
+        Public Sub TurnOnLast(onFlag As String)
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                DirectCast(Nothing, String),
+                {
+                "/nologo",
+                "/reportivts-",
+                onFlag
+                })
+
+            Assert.True(compiler.Arguments.ReportInternalsVisibleToAttributes)
+        End Sub
+
+        <Theory>
+        <InlineData("/reportivts")>
+        <InlineData("/reportivts+")>
+        Public Sub TurnOffLast(onFlag As String)
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                DirectCast(Nothing, String),
+                {
+                "/nologo",
+                onFlag,
+                "/reportivts-"
+                })
+
+            Assert.False(compiler.Arguments.ReportInternalsVisibleToAttributes)
+        End Sub
+
+        <Fact>
+        Public Sub BadReportIvtsValue()
+            Dim compiler = New MockVisualBasicCompiler(
+                Nothing,
+                DirectCast(Nothing, String),
+                {
+                "/nologo",
+                "/reportivts:bad"
+                })
+
+            Assert.False(compiler.Arguments.ReportInternalsVisibleToAttributes)
+            compiler.Arguments.Errors.Verify(
+                Diagnostic(ERRID.ERR_SwitchNeedsBool).WithArguments("reportivts").WithLocation(1, 1),
+                Diagnostic(ERRID.ERR_NoSources).WithLocation(1, 1))
+        End Sub
+    End Class
+End Namespace
diff --git a/src/Compilers/VisualBasic/Test/Semantic/Diagnostics/DiagnosticTests.vb b/src/Compilers/VisualBasic/Test/Semantic/Diagnostics/DiagnosticTests.vb
index f6dc72e795929..1e797c4ceec51 100644
--- a/src/Compilers/VisualBasic/Test/Semantic/Diagnostics/DiagnosticTests.vb
+++ b/src/Compilers/VisualBasic/Test/Semantic/Diagnostics/DiagnosticTests.vb
@@ -150,7 +150,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests
                 Select Case err
                     Case ERRID.ERR_TypeRefResolutionError3,
                          ERRID.ERR_MissingRuntimeHelper,
-                         ERRID.ERR_CannotGotoNonScopeBlocksWithClosure
+                         ERRID.ERR_CannotGotoNonScopeBlocksWithClosure,
+                         ERRID.ERR_SymbolDefinedInAssembly
                         Assert.True(isBuildOnly, $"Check failed for ERRID.{err}")
                     Case Else
                         Assert.False(isBuildOnly, $"Check failed for ERRID.{err}")
diff --git a/src/Compilers/VisualBasic/Test/Semantic/SourceGeneration/GeneratorDriverTests.vb b/src/Compilers/VisualBasic/Test/Semantic/SourceGeneration/GeneratorDriverTests.vb
index b644e80a31583..763c4d8541c39 100644
--- a/src/Compilers/VisualBasic/Test/Semantic/SourceGeneration/GeneratorDriverTests.vb
+++ b/src/Compilers/VisualBasic/Test/Semantic/SourceGeneration/GeneratorDriverTests.vb
@@ -6,6 +6,7 @@ Imports System.Collections.Immutable
 Imports Microsoft.CodeAnalysis.Test.Utilities
 Imports Microsoft.CodeAnalysis.Text
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
+Imports Roslyn.Test.Utilities
 Imports Roslyn.Test.Utilities.TestGenerators
 
 Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests
@@ -295,6 +296,317 @@ End Class",
                                           Diagnostic("GEN001", "ano").WithLocation(5, 6))
         End Sub
 
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_DetachedSyntaxTree_Incremental()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions)
+
+            Dim generator = New PipelineCallbackGenerator(
+                Sub(ctx)
+                    ctx.RegisterSourceOutput(ctx.CompilationProvider,
+                        Sub(ctx2, comp)
+                            Dim syntaxTree = VisualBasicSyntaxTree.ParseText(comp.SyntaxTrees.Single().GetText(), parseOptions, path:="/detached")
+                            ctx2.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                                "TEST0001",
+                                "Test",
+                                "Test diagnostic",
+                                DiagnosticSeverity.Warning,
+                                DiagnosticSeverity.Warning,
+                                isEnabledByDefault:=True,
+                                warningLevel:=1,
+                                location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 4))))
+                        End Sub)
+                End Sub).AsSourceGenerator()
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, Diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("PipelineCallbackGenerator", "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_DetachedSyntaxTree_Incremental_AdditionalLocations()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions)
+
+            Dim generator = New PipelineCallbackGenerator(
+                Sub(ctx)
+                    ctx.RegisterSourceOutput(ctx.CompilationProvider,
+                        Sub(ctx2, comp)
+                            Dim validSyntaxTree = comp.SyntaxTrees.Single()
+                            Dim invalidSyntaxTree = VisualBasicSyntaxTree.ParseText(validSyntaxTree.GetText(), parseOptions, path:="/detached")
+                            ctx2.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                                "TEST0001",
+                                "Test",
+                                "Test diagnostic",
+                                DiagnosticSeverity.Warning,
+                                DiagnosticSeverity.Warning,
+                                isEnabledByDefault:=True,
+                                warningLevel:=1,
+                                location:=Location.Create(validSyntaxTree, TextSpan.FromBounds(2, 4)),
+                                additionalLocations:={Location.Create(invalidSyntaxTree, TextSpan.FromBounds(2, 4))}))
+                        End Sub)
+                End Sub).AsSourceGenerator()
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("PipelineCallbackGenerator", "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_DetachedSyntaxTree_Execute()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions)
+
+            Dim generator As ISourceGenerator = New CallbackGenerator(
+                Sub(ctx)
+                End Sub,
+                Sub(ctx)
+                    Dim syntaxTree = VisualBasicSyntaxTree.ParseText(ctx.Compilation.SyntaxTrees.Single().GetText(), parseOptions, path:="/detached")
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault:=True,
+                        warningLevel:=1,
+                        location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 4))))
+                End Sub)
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("CallbackGenerator", "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_DetachedSyntaxTree_Execute_AdditionalLocations()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions)
+
+            Dim generator As ISourceGenerator = New CallbackGenerator(
+                Sub(ctx)
+                End Sub,
+                Sub(ctx)
+                    Dim validSyntaxTree = ctx.Compilation.SyntaxTrees.Single()
+                    Dim invalidSyntaxTree = VisualBasicSyntaxTree.ParseText(validSyntaxTree.GetText(), parseOptions, path:="/detached")
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault:=True,
+                        warningLevel:=1,
+                        location:=Location.Create(validSyntaxTree, TextSpan.FromBounds(2, 4)),
+                        additionalLocations:={Location.Create(invalidSyntaxTree, TextSpan.FromBounds(2, 4))}))
+                End Sub)
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("CallbackGenerator", "Reported diagnostic 'TEST0001' has a source location in file '/detached', which is not part of the compilation being analyzed.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_SpanOutsideRange_Incremental()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions, sourcePath:="/original")
+
+            Dim generator = New PipelineCallbackGenerator(
+                Sub(ctx)
+                    ctx.RegisterSourceOutput(ctx.CompilationProvider,
+                        Sub(ctx2, comp)
+                            Dim syntaxTree = comp.SyntaxTrees.Single()
+                            ctx2.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                                "TEST0001",
+                                "Test",
+                                "Test diagnostic",
+                                DiagnosticSeverity.Warning,
+                                DiagnosticSeverity.Warning,
+                                isEnabledByDefault:=True,
+                                warningLevel:=1,
+                                location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 100))))
+                        End Sub)
+                End Sub).AsSourceGenerator()
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("PipelineCallbackGenerator", "Reported diagnostic 'TEST0001' has a source location '[2..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_SpanOutsideRange_Incremental_AdditionalLocations()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions, sourcePath:="/original")
+
+            Dim generator = New PipelineCallbackGenerator(
+                Sub(ctx)
+                    ctx.RegisterSourceOutput(ctx.CompilationProvider,
+                        Sub(ctx2, comp)
+                            Dim syntaxTree = comp.SyntaxTrees.Single()
+                            ctx2.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                                "TEST0001",
+                                "Test",
+                                "Test diagnostic",
+                                DiagnosticSeverity.Warning,
+                                DiagnosticSeverity.Warning,
+                                isEnabledByDefault:=True,
+                                warningLevel:=1,
+                                location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 4)),
+                                additionalLocations:={Location.Create(syntaxTree, TextSpan.FromBounds(2, 100))}))
+                        End Sub)
+                End Sub).AsSourceGenerator()
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("PipelineCallbackGenerator", "Reported diagnostic 'TEST0001' has a source location '[2..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_SpanOutsideRange_Execute()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions, sourcePath:="/original")
+
+            Dim generator As ISourceGenerator = New CallbackGenerator(
+                Sub(ctx)
+                End Sub,
+                Sub(ctx)
+                    Dim syntaxTree = ctx.Compilation.SyntaxTrees.Single()
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault:=True,
+                        warningLevel:=1,
+                        location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 100))))
+                End Sub)
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("CallbackGenerator", "Reported diagnostic 'TEST0001' has a source location '[2..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_SpanOutsideRange_Execute_AdditionalLocations()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions, sourcePath:="/original")
+
+            Dim generator As ISourceGenerator = New CallbackGenerator(
+                Sub(ctx)
+                End Sub,
+                Sub(ctx)
+                    Dim syntaxTree = ctx.Compilation.SyntaxTrees.Single()
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault:=True,
+                        warningLevel:=1,
+                        location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 4)),
+                        additionalLocations:={Location.Create(syntaxTree, TextSpan.FromBounds(2, 100))}))
+                End Sub)
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("CallbackGenerator", "Reported diagnostic 'TEST0001' has a source location '[2..100)' in file '/original', which is outside of the given file.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_SpaceInIdentifier_Incremental()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions)
+
+            Dim generator = New PipelineCallbackGenerator(
+                Sub(ctx)
+                    ctx.RegisterSourceOutput(ctx.CompilationProvider,
+                        Sub(ctx2, comp)
+                            Dim syntaxTree = comp.SyntaxTrees.Single()
+                            ctx2.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                                "TEST 0001",
+                                "Test",
+                                "Test diagnostic",
+                                DiagnosticSeverity.Warning,
+                                DiagnosticSeverity.Warning,
+                                isEnabledByDefault:=True,
+                                warningLevel:=1,
+                                location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 4))))
+                        End Sub)
+                End Sub).AsSourceGenerator()
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("PipelineCallbackGenerator", "Reported diagnostic has an ID 'TEST 0001', which is not a valid identifier.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
+        <ConditionalFact(GetType(IsEnglishLocal))>
+        <WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1805836")>
+        Public Sub Diagnostic_SpaceInIdentifier_Execute()
+            Dim parseOptions = TestOptions.Regular
+            Dim compilation As Compilation = GetCompilation(parseOptions)
+
+            Dim generator As ISourceGenerator = New CallbackGenerator(
+                Sub(ctx)
+                End Sub,
+                Sub(ctx)
+                    Dim syntaxTree = ctx.Compilation.SyntaxTrees.Single()
+                    ctx.ReportDiagnostic(CodeAnalysis.Diagnostic.Create(
+                        "TEST 0001",
+                        "Test",
+                        "Test diagnostic",
+                        DiagnosticSeverity.Warning,
+                        DiagnosticSeverity.Warning,
+                        isEnabledByDefault:=True,
+                        warningLevel:=1,
+                        location:=Location.Create(syntaxTree, TextSpan.FromBounds(2, 4))))
+                End Sub)
+
+            Dim driver As GeneratorDriver = VisualBasicGeneratorDriver.Create(ImmutableArray.Create(generator), parseOptions:=parseOptions)
+            Dim diagnostics As ImmutableArray(Of Diagnostic) = Nothing
+            driver.RunGeneratorsAndUpdateCompilation(compilation, compilation, diagnostics)
+            diagnostics.Verify(
+                ArgumentExceptionDiagnostic("CallbackGenerator", "Reported diagnostic has an ID 'TEST 0001', which is not a valid identifier.", "diagnostic").WithLocation(1, 1))
+            compilation.VerifyDiagnostics()
+        End Sub
+
         <Fact>
         Public Sub Enable_Incremental_Generators()
 
@@ -333,7 +645,7 @@ End Class",
             Assert.False(testGenerator._sourceExecuted)
         End Sub
 
-        Shared Function GetCompilation(parseOptions As VisualBasicParseOptions, Optional source As String = "") As Compilation
+        Shared Function GetCompilation(parseOptions As VisualBasicParseOptions, Optional source As String = "", Optional sourcePath As String = "") As Compilation
             If (String.IsNullOrWhiteSpace(source)) Then
                 source = "
 Public Class C
@@ -341,7 +653,7 @@ End Class
 "
             End If
 
-            Dim compilation As Compilation = CreateCompilation(source, options:=TestOptions.DebugDll, parseOptions:=parseOptions)
+            Dim compilation As Compilation = CreateCompilation(BasicTestSource.Parse(source, sourcePath, parseOptions), options:=TestOptions.DebugDll)
             compilation.VerifyDiagnostics()
             Assert.Single(compilation.SyntaxTrees)
 
@@ -423,6 +735,15 @@ End Class
             outputCompilation.VerifyDiagnostics()
             diagnostics.Verify(expected)
         End Sub
+
+        Shared Function ArgumentExceptionDiagnostic(generatorName As String, message As String, parameterName As String) As DiagnosticDescription
+#If NETCOREAPP Then
+            Dim fullMessage = $"{message} (Parameter '{parameterName}')"
+#Else
+            Dim fullMessage = $"{message}{Environment.NewLine}Parameter name: {parameterName}"
+#End If
+            Return Diagnostic("BC42502").WithArguments(generatorName, NameOf(ArgumentException), fullMessage)
+        End Function
     End Class
 
     <Generator(LanguageNames.VisualBasic)>
diff --git a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CompilationCreationTests.vb b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CompilationCreationTests.vb
index ca30b5c4a849b..5bba005131b8d 100644
--- a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CompilationCreationTests.vb
+++ b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CompilationCreationTests.vb
@@ -94,8 +94,9 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests
             For i As Integer = 1 To SpecialType.Count Step 1
                 Dim type As NamedTypeSymbol = c1.Assembly.GetSpecialType(CType(i, SpecialType))
 
-                If i = SpecialType.System_Runtime_CompilerServices_RuntimeFeature Or
-                   i = SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute Then
+                If i = SpecialType.System_Runtime_CompilerServices_RuntimeFeature OrElse
+                   i = SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute OrElse
+                   i = SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute Then
                     Assert.Equal(type.Kind, SymbolKind.ErrorType) ' Not available
                 Else
                     Assert.NotEqual(type.Kind, SymbolKind.ErrorType)
diff --git a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CorLibrary/CorTypes.vb b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CorLibrary/CorTypes.vb
index cfe4417a749b1..9b22b84b668ec 100644
--- a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CorLibrary/CorTypes.vb
+++ b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/CorLibrary/CorTypes.vb
@@ -38,7 +38,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests.Symbols.CorLibrary
             Dim assemblies = MetadataTestHelpers.GetSymbolsForReferences({NetCoreApp.SystemRuntime})
             Dim msCorLibRef As MetadataOrSourceAssemblySymbol = DirectCast(assemblies(0), MetadataOrSourceAssemblySymbol)
 
-            Dim knownMissingTypes As HashSet(Of Integer) = New HashSet(Of Integer)
+            Dim knownMissingTypes As HashSet(Of Integer) = New HashSet(Of Integer) From {SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute}
 
             For i As Integer = 1 To SpecialType.Count
                 Dim t = msCorLibRef.GetSpecialType(CType(i, SpecialType))
diff --git a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/WellKnownTypeValidationTests.vb b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/WellKnownTypeValidationTests.vb
index 9a21cce528e3f..0d9a24f095f3a 100644
--- a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/WellKnownTypeValidationTests.vb
+++ b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/WellKnownTypeValidationTests.vb
@@ -455,7 +455,8 @@ End Namespace
                 Assert.NotNull(symbol)
 
                 If special = SpecialType.System_Runtime_CompilerServices_RuntimeFeature OrElse
-                   special = SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute Then
+                   special = SpecialType.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute OrElse
+                   special = SpecialType.System_Runtime_CompilerServices_InlineArrayAttribute Then
                     Assert.Equal(SymbolKind.ErrorType, symbol.Kind) ' Not available
                 Else
                     Assert.NotEqual(SymbolKind.ErrorType, symbol.Kind)
@@ -489,7 +490,8 @@ End Namespace
                    special = SpecialMember.System_Runtime_CompilerServices_RuntimeFeature__VirtualStaticsInInterfaces OrElse
                    special = SpecialMember.System_Runtime_CompilerServices_RuntimeFeature__NumericIntPtr OrElse
                    special = SpecialMember.System_Runtime_CompilerServices_RuntimeFeature__ByRefFields OrElse
-                   special = SpecialMember.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute__ctor Then
+                   special = SpecialMember.System_Runtime_CompilerServices_PreserveBaseOverridesAttribute__ctor OrElse
+                   special = SpecialMember.System_Runtime_CompilerServices_InlineArrayAttribute__ctor Then
                     Assert.Null(symbol) ' Not available
                 Else
                     Assert.NotNull(symbol)
@@ -555,7 +557,9 @@ End Namespace
                          WellKnownType.System_Runtime_CompilerServices_RefSafetyRulesAttribute,
                          WellKnownType.System_Diagnostics_CodeAnalysis_UnscopedRefAttribute,
                          WellKnownType.System_MemoryExtensions,
-                         WellKnownType.System_Runtime_CompilerServices_MetadataUpdateOriginalTypeAttribute
+                         WellKnownType.System_Runtime_CompilerServices_MetadataUpdateOriginalTypeAttribute,
+                         WellKnownType.System_Runtime_InteropServices_MemoryMarshal,
+                         WellKnownType.System_Runtime_CompilerServices_Unsafe
                         ' Not available on all platforms.
                         Continue For
                     Case WellKnownType.ExtSentinel
@@ -630,7 +634,9 @@ End Namespace
                          WellKnownType.System_Runtime_CompilerServices_ScopedRefAttribute,
                          WellKnownType.System_Runtime_CompilerServices_RefSafetyRulesAttribute,
                          WellKnownType.System_Diagnostics_CodeAnalysis_UnscopedRefAttribute,
-                         WellKnownType.System_Runtime_CompilerServices_MetadataUpdateOriginalTypeAttribute
+                         WellKnownType.System_Runtime_CompilerServices_MetadataUpdateOriginalTypeAttribute,
+                         WellKnownType.System_Runtime_InteropServices_MemoryMarshal,
+                         WellKnownType.System_Runtime_CompilerServices_Unsafe
                         ' Not available on all platforms.
                         Continue For
                     Case WellKnownType.ExtSentinel
@@ -685,11 +691,13 @@ End Namespace
                          WellKnownMember.System_Span_T__ctor_Array,
                          WellKnownMember.System_Span_T__get_Item,
                          WellKnownMember.System_Span_T__get_Length,
+                         WellKnownMember.System_Span_T__Slice_Int_Int,
                          WellKnownMember.System_ReadOnlySpan_T__ctor_Pointer,
                          WellKnownMember.System_ReadOnlySpan_T__ctor_Array,
                          WellKnownMember.System_ReadOnlySpan_T__ctor_Array_Start_Length,
                          WellKnownMember.System_ReadOnlySpan_T__get_Item,
                          WellKnownMember.System_ReadOnlySpan_T__get_Length,
+                         WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int,
                          WellKnownMember.System_Runtime_CompilerServices_AsyncIteratorStateMachineAttribute__ctor,
                          WellKnownMember.System_IAsyncDisposable__DisposeAsync,
                          WellKnownMember.System_Collections_Generic_IAsyncEnumerable_T__GetAsyncEnumerator,
@@ -784,7 +792,12 @@ End Namespace
                          WellKnownMember.System_Runtime_CompilerServices_ITuple__get_Item,
                          WellKnownMember.System_Runtime_CompilerServices_ITuple__get_Length,
                          WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctor,
-                         WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctorObject
+                         WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctorObject,
+                         WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan,
+                         WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan,
+                         WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T,
+                         WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T,
+                         WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T
                         ' Not always available.
                         Continue For
                 End Select
@@ -874,11 +887,13 @@ End Namespace
                          WellKnownMember.System_Span_T__ctor_Array,
                          WellKnownMember.System_Span_T__get_Item,
                          WellKnownMember.System_Span_T__get_Length,
+                         WellKnownMember.System_Span_T__Slice_Int_Int,
                          WellKnownMember.System_ReadOnlySpan_T__ctor_Pointer,
                          WellKnownMember.System_ReadOnlySpan_T__ctor_Array,
                          WellKnownMember.System_ReadOnlySpan_T__ctor_Array_Start_Length,
                          WellKnownMember.System_ReadOnlySpan_T__get_Item,
                          WellKnownMember.System_ReadOnlySpan_T__get_Length,
+                         WellKnownMember.System_ReadOnlySpan_T__Slice_Int_Int,
                          WellKnownMember.System_Runtime_CompilerServices_AsyncIteratorStateMachineAttribute__ctor,
                          WellKnownMember.System_IAsyncDisposable__DisposeAsync,
                          WellKnownMember.System_Collections_Generic_IAsyncEnumerable_T__GetAsyncEnumerator,
@@ -973,7 +988,12 @@ End Namespace
                          WellKnownMember.System_Runtime_CompilerServices_ITuple__get_Item,
                          WellKnownMember.System_Runtime_CompilerServices_ITuple__get_Length,
                          WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctor,
-                         WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctorObject
+                         WellKnownMember.System_Runtime_CompilerServices_SwitchExpressionException__ctorObject,
+                         WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateReadOnlySpan,
+                         WellKnownMember.System_Runtime_InteropServices_MemoryMarshal__CreateSpan,
+                         WellKnownMember.System_Runtime_CompilerServices_Unsafe__Add_T,
+                         WellKnownMember.System_Runtime_CompilerServices_Unsafe__As_T,
+                         WellKnownMember.System_Runtime_CompilerServices_Unsafe__AsRef_T
                         ' Not always available.
                         Continue For
                 End Select
diff --git a/src/Dependencies/Collections/Microsoft.CodeAnalysis.Collections.Package.csproj b/src/Dependencies/Collections/Microsoft.CodeAnalysis.Collections.Package.csproj
index 216dfaf096c8a..c5f9ed8fc7590 100644
--- a/src/Dependencies/Collections/Microsoft.CodeAnalysis.Collections.Package.csproj
+++ b/src/Dependencies/Collections/Microsoft.CodeAnalysis.Collections.Package.csproj
@@ -9,6 +9,9 @@
     <GenerateDependencyFile>false</GenerateDependencyFile>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
 
+    <!-- System.Collections.Immutable 7.0.0 does not support netcoreapp3.1 -->
+    <SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>
+
     <!-- NuGet -->
     <IsPackable>true</IsPackable>
     <IsSourcePackage>true</IsSourcePackage>
diff --git a/src/Dependencies/PooledObjects/ArrayBuilder.cs b/src/Dependencies/PooledObjects/ArrayBuilder.cs
index dc4622a580a73..2879d24088a4c 100644
--- a/src/Dependencies/PooledObjects/ArrayBuilder.cs
+++ b/src/Dependencies/PooledObjects/ArrayBuilder.cs
@@ -590,6 +590,8 @@ public void ZeroInit(int count)
 
         public void AddMany(T item, int count)
         {
+            EnsureCapacity(Count + count);
+
             for (var i = 0; i < count; i++)
             {
                 Add(item);
diff --git a/src/EditorFeatures/CSharp/DocumentationComments/XmlTagCompletionCommandHandler.cs b/src/EditorFeatures/CSharp/DocumentationComments/XmlTagCompletionCommandHandler.cs
index ae9b03b9c0a54..10948b8a028f8 100644
--- a/src/EditorFeatures/CSharp/DocumentationComments/XmlTagCompletionCommandHandler.cs
+++ b/src/EditorFeatures/CSharp/DocumentationComments/XmlTagCompletionCommandHandler.cs
@@ -96,7 +96,7 @@ private static bool HasFollowingEndTagTrivia(XmlElementSyntax parentElement, Syn
             return false;
         }
 
-        private bool HasUnmatchedIdenticalParent(XmlElementStartTagSyntax parentStartTag)
+        private static bool HasUnmatchedIdenticalParent(XmlElementStartTagSyntax parentStartTag)
         {
             if (parentStartTag.Parent?.Parent is XmlElementSyntax grandParentElement)
             {
diff --git a/src/EditorFeatures/CSharp/LanguageServer/CSharpLspBuildOnlyDiagnostics.cs b/src/EditorFeatures/CSharp/LanguageServer/CSharpLspBuildOnlyDiagnostics.cs
index a2cea39d04673..37871cfc1b13b 100644
--- a/src/EditorFeatures/CSharp/LanguageServer/CSharpLspBuildOnlyDiagnostics.cs
+++ b/src/EditorFeatures/CSharp/LanguageServer/CSharpLspBuildOnlyDiagnostics.cs
@@ -43,7 +43,18 @@ namespace Microsoft.CodeAnalysis.CSharp.LanguageServer
         "CS1969", // ErrorCode.ERR_DynamicRequiredTypesMissing:
         "CS8984", // ErrorCode.ERR_EncUpdateFailedDelegateTypeChanged:
         "CS9026", // ErrorCode.ERR_CannotBeConvertedToUtf8:
-        "CS9068" // ErrorCode.ERR_FileTypeNonUniquePath:
+        "CS9068", // ErrorCode.ERR_FileTypeNonUniquePath:
+        "CS9144", // ErrorCode.ERR_InterceptorSignatureMismatch
+        "CS9148", // ErrorCode.ERR_InterceptorMustHaveMatchingThisParameter
+        "CS9149", // ErrorCode.ERR_InterceptorMustNotHaveThisParameter
+        "CS9153", // ErrorCode.ERR_DuplicateInterceptor
+        "CS9154", // ErrorCode.WRN_InterceptorSignatureMismatch,
+        "CS9155", // ErrorCode.ERR_InterceptorNotAccessible
+        "CS9156", // ErrorCode.ERR_InterceptorScopedMismatch
+        "CS9158", // ErrorCode.WRN_NullabilityMismatchInReturnTypeOnInterceptor
+        "CS9159", // ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor
+        "CS9160", // ErrorCode.ERR_InterceptorCannotInterceptNameof
+        "CS9163"  // ErrorCode.ERR_SymbolDefinedInAssembly
         )]
     internal sealed class CSharpLspBuildOnlyDiagnostics : ILspBuildOnlyDiagnostics
     {
diff --git a/src/EditorFeatures/CSharpTest/Classification/SemanticClassifierTests.cs b/src/EditorFeatures/CSharpTest/Classification/SemanticClassifierTests.cs
index 9abfce0a992f4..7b6cb9880f526 100644
--- a/src/EditorFeatures/CSharpTest/Classification/SemanticClassifierTests.cs
+++ b/src/EditorFeatures/CSharpTest/Classification/SemanticClassifierTests.cs
@@ -4023,6 +4023,7 @@ void Goo()
         }
 
         [Theory, CombinatorialData]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68534")]
         public async Task TestJson1(TestHost testHost)
         {
             await TestAsync(
@@ -4043,10 +4044,12 @@ void Goo()
 Json.PropertyName("'goo'"),
 Json.Punctuation(":"),
 Json.Number("0"),
+Json.Punctuation(","),
 Json.PropertyName("bar"),
 Json.Punctuation(":"),
 Json.Operator("-"),
 Json.Keyword("Infinity"),
+Json.Punctuation(","),
 Json.PropertyName(@"""""baz"""""),
 Json.Punctuation(":"),
 Json.Keyword("true"),
@@ -4090,6 +4093,7 @@ void Goo()
         }
 
         [Theory, CombinatorialData]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68534")]
         public async Task TestMultiLineJson1(TestHost testHost)
         {
             await TestAsync(
@@ -4120,13 +4124,16 @@ void Goo()
 Json.PropertyName("'goo'"),
 Json.Punctuation(":"),
 Json.Number("0"),
+Json.Punctuation(","),
 Json.PropertyName("bar"),
 Json.Punctuation(":"),
 Json.Operator("-"),
 Json.Keyword("Infinity"),
+Json.Punctuation(","),
 Json.PropertyName(@"""""baz"""""),
 Json.Punctuation(":"),
 Json.Keyword("true"),
+Json.Punctuation(","),
 Json.PropertyName("0"),
 Json.Punctuation(":"),
 Json.Keyword("null"),
diff --git a/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/AbstractCSharpConditionalBlockSnippetCompletionProviderTests.cs b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/AbstractCSharpConditionalBlockSnippetCompletionProviderTests.cs
index 125dc206fc836..7757ec11ccecc 100644
--- a/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/AbstractCSharpConditionalBlockSnippetCompletionProviderTests.cs
+++ b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/AbstractCSharpConditionalBlockSnippetCompletionProviderTests.cs
@@ -467,5 +467,118 @@ void M(bool arg)
 
             await VerifyItemIsAbsentAsync(markupBeforeCommit, ItemToCommit);
         }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        [InlineData("#region test")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(bool arg)
+                    {
+                        {{trivia}}
+                        arg.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(bool arg)
+                    {
+                        {{trivia}}
+                        {{ItemToCommit}} (arg)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(bool arg)
+                    {
+                {{trivia}}
+                        arg.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(bool arg)
+                    {
+                {{trivia}}
+                        {{ItemToCommit}} (arg)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                true.$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                {{trivia}}
+                {{ItemToCommit}} (true)
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#region test")]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                true.$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+
+                {{trivia}}
+                {{ItemToCommit}} (true)
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
     }
 }
diff --git a/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForEachSnippetCompletionProviderTests.cs b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForEachSnippetCompletionProviderTests.cs
index 0d2dfbbbf638a..c41b1408ae25e 100644
--- a/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForEachSnippetCompletionProviderTests.cs
+++ b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForEachSnippetCompletionProviderTests.cs
@@ -315,5 +315,118 @@ void M(List<int> list)
 
             await VerifyItemIsAbsentAsync(markupBeforeCommit, ItemToCommit);
         }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        [InlineData("#region test")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(int[] arr)
+                    {
+                        {{trivia}}
+                        arr.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(int[] arr)
+                    {
+                        {{trivia}}
+                        foreach (var item in arr)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(int[] arr)
+                    {
+                {{trivia}}
+                        arr.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(int[] arr)
+                    {
+                {{trivia}}
+                        foreach (var item in arr)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                (new int[10]).$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                {{trivia}}
+                foreach (var item in new int[10])
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#region test")]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                (new int[10]).$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+
+                {{trivia}}
+                foreach (var item in new int[10])
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
     }
 }
diff --git a/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForSnippetCompletionProviderTests.cs b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForSnippetCompletionProviderTests.cs
new file mode 100644
index 0000000000000..22aeb80ce85a4
--- /dev/null
+++ b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForSnippetCompletionProviderTests.cs
@@ -0,0 +1,524 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.Completion.CompletionProviders.Snippets
+{
+    [Trait(Traits.Feature, Traits.Features.Completion)]
+    public class CSharpForSnippetCompletionProviderTests : AbstractCSharpSnippetCompletionProviderTests
+    {
+        protected override string ItemToCommit => "for";
+
+        [WpfFact]
+        public async Task InsertForSnippetInMethodTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        for (int i = 0; i < length; i++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForSnippetInMethodUsedIncrementorTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i;
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i;
+                        for (int j = 0; j < length; j++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForSnippetInMethodUsedIncrementorsTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i, j, k;
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i, j, k;
+                        for (int i1 = 0; i1 < length; i1++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForSnippetInGlobalContextTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                $$
+                """, ItemToCommit, """
+                for (int i = 0; i < length; i++)
+                {
+                    $$
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForSnippetInConstructorTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public Program()
+                    {
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public Program()
+                    {
+                        for (int i = 0; i < length; i++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForSnippetInLocalFunctionTest()
+        {
+            // TODO: fix this test when bug with simplifier failing to find correct node is fixed
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        void LocalFunction()
+                        {
+                            $$
+                        }
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        void LocalFunction()
+                        {
+                            for (global::System.Int32 i = 0; i < length; i++)
+                            {
+                                $$
+                            }
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForSnippetInAnonymousFunctionTest()
+        {
+            // TODO: fix this test when bug with simplifier failing to find correct node is fixed
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = delegate()
+                        {
+                            $$
+                        };
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = delegate()
+                        {
+                            for (global::System.Int32 i = 0; i < length; i++)
+                            {
+                                $$
+                            }
+                        };
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForSnippetInParenthesizedLambdaExpressionTest()
+        {
+            // TODO: fix this test when bug with simplifier failing to find correct node is fixed
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = () =>
+                        {
+                            $$
+                        };
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = () =>
+                        {
+                            for (global::System.Int32 i = 0; i < length; i++)
+                            {
+                                $$
+                            }
+                        };
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task ProduceVarWithSpecificCodeStyleTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                <Workspace>
+                    <Project Language="C#" AssemblyName="Assembly1" CommonReferences="true">
+                    <Document FilePath="/0/Test0.cs">class Program
+                {
+                    public void Method()
+                    {
+                        $$
+                    }
+                }</Document>
+                <AnalyzerConfigDocument FilePath="/.editorconfig">
+                root = true
+
+                [*]
+                # IDE0008: Use explicit type
+                csharp_style_var_for_built_in_types = true
+                    </AnalyzerConfigDocument>
+                    </Project>
+                </Workspace>
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        for (var i = 0; i < length; i++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfTheory]
+        [InlineData("byte")]
+        [InlineData("sbyte")]
+        [InlineData("short")]
+        [InlineData("ushort")]
+        [InlineData("int")]
+        [InlineData("uint")]
+        [InlineData("long")]
+        [InlineData("ulong")]
+        [InlineData("nint")]
+        [InlineData("nuint")]
+        public async Task InsertInlineForSnippetInMethodTest(string inlineExpressionType)
+        {
+            await VerifyCustomCommitProviderAsync($$"""
+                class Program
+                {
+                    public void Method({{inlineExpressionType}} l)
+                    {
+                        l.$$
+                    }
+                }
+                """, ItemToCommit, $$"""
+                class Program
+                {
+                    public void Method({{inlineExpressionType}} l)
+                    {
+                        for ({{inlineExpressionType}} i = 0; i < l; i++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfTheory]
+        [InlineData("byte")]
+        [InlineData("sbyte")]
+        [InlineData("short")]
+        [InlineData("ushort")]
+        [InlineData("int")]
+        [InlineData("uint")]
+        [InlineData("long")]
+        [InlineData("ulong")]
+        [InlineData("nint")]
+        [InlineData("nuint")]
+        public async Task InsertInlineForSnippetInGlobalContextTest(string inlineExpressionType)
+        {
+            await VerifyCustomCommitProviderAsync($$"""
+                {{inlineExpressionType}} l;
+                l.$$
+                """, ItemToCommit, $$"""
+                {{inlineExpressionType}} l;
+                for ({{inlineExpressionType}} i = 0; i < l; i++)
+                {
+                    $$
+                }
+                """);
+        }
+
+        [WpfTheory]
+        [InlineData("string")]
+        [InlineData("System.DateTime")]
+        [InlineData("System.Action")]
+        public async Task NoInlineForSnippetForIncorrectTypeInMethodTest(string inlineExpressionType)
+        {
+            var markup = $$"""
+                class Program
+                {
+                    public void Method({{inlineExpressionType}} l)
+                    {
+                        l.$$
+                    }
+                }
+                """;
+
+            await VerifyItemIsAbsentAsync(markup, ItemToCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("string")]
+        [InlineData("System.DateTime")]
+        [InlineData("System.Action")]
+        public async Task NoInlineForSnippetForIncorrectTypeInGlobalContextTest(string inlineExpressionType)
+        {
+            var markup = $$"""
+                {{inlineExpressionType}} l;
+                l.$$
+                """;
+
+            await VerifyItemIsAbsentAsync(markup, ItemToCommit);
+        }
+
+        [WpfFact]
+        public async Task ProduceVarWithSpecificCodeStyleForInlineSnippetTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                <Workspace>
+                    <Project Language="C#" AssemblyName="Assembly1" CommonReferences="true">
+                    <Document FilePath="/0/Test0.cs">class Program
+                {
+                    public void Method(int l)
+                    {
+                        l.$$
+                    }
+                }</Document>
+                <AnalyzerConfigDocument FilePath="/.editorconfig">
+                root = true
+
+                [*]
+                # IDE0008: Use explicit type
+                csharp_style_var_for_built_in_types = true
+                    </AnalyzerConfigDocument>
+                    </Project>
+                </Workspace>
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method(int l)
+                    {
+                        for (var i = 0; i < l; i++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task NoInlineForSnippetNotDirectlyExpressionStatementTest()
+        {
+            var markup = """
+                class Program
+                {
+                    public void Method(int l)
+                    {
+                        System.Console.WriteLine(l.$$);
+                    }
+                }
+                """;
+
+            await VerifyItemIsAbsentAsync(markup, ItemToCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        [InlineData("#region test")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                        {{trivia}}
+                        len.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                        {{trivia}}
+                        for (int i = 0; i < len; i++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                {{trivia}}
+                        len.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                {{trivia}}
+                        for (int i = 0; i < len; i++)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                10.$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                {{trivia}}
+                for (int i = 0; i < 10; i++)
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#region test")]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                10.$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+
+                {{trivia}}
+                for (int i = 0; i < 10; i++)
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+    }
+}
diff --git a/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForrSnippetCompletionProviderTests.cs b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForrSnippetCompletionProviderTests.cs
new file mode 100644
index 0000000000000..aa209c5593913
--- /dev/null
+++ b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpForrSnippetCompletionProviderTests.cs
@@ -0,0 +1,526 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.Completion.CompletionProviders.Snippets
+{
+    [Trait(Traits.Feature, Traits.Features.Completion)]
+    public class CSharpForrSnippetCompletionProviderTests : AbstractCSharpSnippetCompletionProviderTests
+    {
+        protected override string ItemToCommit => "forr";
+
+        [WpfFact]
+        public async Task InsertForrSnippetInMethodTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        for (int i = length - 1; i >= 0; i--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForrSnippetInMethodUsedIncrementorTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i;
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i;
+                        for (int j = length - 1; j >= 0; j--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForrSnippetInMethodUsedIncrementorsTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i, j, k;
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        int i, j, k;
+                        for (int i1 = length - 1; i1 >= 0; i1--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForrSnippetInGlobalContextTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                $$
+                """, ItemToCommit, """
+                for (int i = length - 1; i >= 0; i--)
+                {
+                    $$
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForrSnippetInConstructorTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public Program()
+                    {
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public Program()
+                    {
+                        for (int i = length - 1; i >= 0; i--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForrSnippetInLocalFunctionTest()
+        {
+            // TODO: fix this test when bug with simplifier failing to find correct node is fixed
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        void LocalFunction()
+                        {
+                            $$
+                        }
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        void LocalFunction()
+                        {
+                            for (global::System.Int32 i = (length) - (1); i >= 0; i--)
+                            {
+                                $$
+                            }
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForrSnippetInAnonymousFunctionTest()
+        {
+            // TODO: fix this test when bug with simplifier failing to find correct node is fixed
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = delegate()
+                        {
+                            $$
+                        };
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = delegate()
+                        {
+                            for (global::System.Int32 i = (length) - (1); i >= 0; i--)
+                            {
+                                $$
+                            }
+                        };
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertForrSnippetInParenthesizedLambdaExpressionTest()
+        {
+            // TODO: fix this test when bug with simplifier failing to find correct node is fixed
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = () =>
+                        {
+                            $$
+                        };
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = () =>
+                        {
+                            for (global::System.Int32 i = (length) - (1); i >= 0; i--)
+                            {
+                                $$
+                            }
+                        };
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task TryToProduceVarWithSpecificCodeStyleTest()
+        {
+            // In non-inline reversed for snippet type of expression `length - 1` is unknown,
+            // so it cannot be simplified to `var`. Therefore having explicit `int` type here is expected
+            await VerifyCustomCommitProviderAsync("""
+                <Workspace>
+                    <Project Language="C#" AssemblyName="Assembly1" CommonReferences="true">
+                    <Document FilePath="/0/Test0.cs">class Program
+                {
+                    public void Method()
+                    {
+                        $$
+                    }
+                }</Document>
+                <AnalyzerConfigDocument FilePath="/.editorconfig">
+                root = true
+
+                [*]
+                # IDE0008: Use explicit type
+                csharp_style_var_for_built_in_types = true
+                    </AnalyzerConfigDocument>
+                    </Project>
+                </Workspace>
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        for (int i = length - 1; i >= 0; i--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfTheory]
+        [InlineData("byte")]
+        [InlineData("sbyte")]
+        [InlineData("short")]
+        [InlineData("ushort")]
+        [InlineData("int")]
+        [InlineData("uint")]
+        [InlineData("long")]
+        [InlineData("ulong")]
+        [InlineData("nint")]
+        [InlineData("nuint")]
+        public async Task InsertInlineForrSnippetInMethodTest(string inlineExpressionType)
+        {
+            await VerifyCustomCommitProviderAsync($$"""
+                class Program
+                {
+                    public void Method({{inlineExpressionType}} l)
+                    {
+                        l.$$
+                    }
+                }
+                """, ItemToCommit, $$"""
+                class Program
+                {
+                    public void Method({{inlineExpressionType}} l)
+                    {
+                        for ({{inlineExpressionType}} i = l - 1; i >= 0; i--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfTheory]
+        [InlineData("byte")]
+        [InlineData("sbyte")]
+        [InlineData("short")]
+        [InlineData("ushort")]
+        [InlineData("int")]
+        [InlineData("uint")]
+        [InlineData("long")]
+        [InlineData("ulong")]
+        [InlineData("nint")]
+        [InlineData("nuint")]
+        public async Task InsertInlineForrSnippetInGlobalContextTest(string inlineExpressionType)
+        {
+            await VerifyCustomCommitProviderAsync($$"""
+                {{inlineExpressionType}} l;
+                l.$$
+                """, ItemToCommit, $$"""
+                {{inlineExpressionType}} l;
+                for ({{inlineExpressionType}} i = l - 1; i >= 0; i--)
+                {
+                    $$
+                }
+                """);
+        }
+
+        [WpfTheory]
+        [InlineData("string")]
+        [InlineData("System.DateTime")]
+        [InlineData("System.Action")]
+        public async Task NoInlineForrSnippetForIncorrectTypeInMethodTest(string inlineExpressionType)
+        {
+            var markup = $$"""
+                class Program
+                {
+                    public void Method({{inlineExpressionType}} l)
+                    {
+                        l.$$
+                    }
+                }
+                """;
+
+            await VerifyItemIsAbsentAsync(markup, ItemToCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("string")]
+        [InlineData("System.DateTime")]
+        [InlineData("System.Action")]
+        public async Task NoInlineForrSnippetForIncorrectTypeInGlobalContextTest(string inlineExpressionType)
+        {
+            var markup = $$"""
+                {{inlineExpressionType}} l;
+                l.$$
+                """;
+
+            await VerifyItemIsAbsentAsync(markup, ItemToCommit);
+        }
+
+        [WpfFact]
+        public async Task ProduceVarWithSpecificCodeStyleForInlineSnippetTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                <Workspace>
+                    <Project Language="C#" AssemblyName="Assembly1" CommonReferences="true">
+                    <Document FilePath="/0/Test0.cs">class Program
+                {
+                    public void Method(int l)
+                    {
+                        l.$$
+                    }
+                }</Document>
+                <AnalyzerConfigDocument FilePath="/.editorconfig">
+                root = true
+
+                [*]
+                # IDE0008: Use explicit type
+                csharp_style_var_for_built_in_types = true
+                    </AnalyzerConfigDocument>
+                    </Project>
+                </Workspace>
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method(int l)
+                    {
+                        for (var i = l - 1; i >= 0; i--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task NoInlineForrSnippetNotDirectlyExpressionStatementTest()
+        {
+            var markup = """
+                class Program
+                {
+                    public void Method(int l)
+                    {
+                        System.Console.WriteLine(l.$$);
+                    }
+                }
+                """;
+
+            await VerifyItemIsAbsentAsync(markup, ItemToCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        [InlineData("#region test")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                        {{trivia}}
+                        len.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                        {{trivia}}
+                        for (int i = len - 1; i >= 0; i--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInMethodTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                {{trivia}}
+                        len.$$
+                    }
+                }
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                class Program
+                {
+                    void M(int len)
+                    {
+                {{trivia}}
+                        for (int i = len - 1; i >= 0; i--)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("// comment")]
+        [InlineData("/* comment */")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest1(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                10.$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+                {{trivia}}
+                for (int i = 10 - 1; i >= 0; i--)
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+
+        [WpfTheory]
+        [InlineData("#region test")]
+        [InlineData("#if true")]
+        [InlineData("#pragma warning disable CS0108")]
+        [InlineData("#nullable enable")]
+        public async Task CorrectlyDealWithLeadingTriviaInInlineSnippetInGlobalStatementTest2(string trivia)
+        {
+            var markupBeforeCommit = $$"""
+                {{trivia}}
+                10.$$
+                """;
+
+            var expectedCodeAfterCommit = $$"""
+
+                {{trivia}}
+                for (int i = 10 - 1; i >= 0; i--)
+                {
+                    $$
+                }
+                """;
+
+            await VerifyCustomCommitProviderAsync(markupBeforeCommit, ItemToCommit, expectedCodeAfterCommit);
+        }
+    }
+}
diff --git a/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpLockSnippetCompletionProviderTests.cs b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpLockSnippetCompletionProviderTests.cs
new file mode 100644
index 0000000000000..8c21573746acd
--- /dev/null
+++ b/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/Snippets/CSharpLockSnippetCompletionProviderTests.cs
@@ -0,0 +1,204 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Roslyn.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.Completion.CompletionProviders.Snippets
+{
+    [Trait(Traits.Feature, Traits.Features.Completion)]
+    public class CSharpLockSnippetCompletionProviderTests : AbstractCSharpSnippetCompletionProviderTests
+    {
+        protected override string ItemToCommit => "lock";
+
+        [WpfFact]
+        public async Task InsertLockSnippetInMethodTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        lock (this)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertLockSnippetInGlobalContextTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                $$
+                """, ItemToCommit, """
+                lock (this)
+                {
+                    $$
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task NoLockSnippetInBlockNamespaceTest()
+        {
+            await VerifyItemIsAbsentAsync("""
+                namespace Namespace
+                {
+                    $$
+                }
+                """, ItemToCommit);
+        }
+
+        [WpfFact]
+        public async Task NoLockSnippetInFileScopedNamespaceTest()
+        {
+            await VerifyItemIsAbsentAsync("""
+                namespace Namespace;
+                $$
+                """, ItemToCommit);
+        }
+
+        [WpfFact]
+        public async Task InsertLockSnippetInConstructorTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public Program()
+                    {
+                        $$
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public Program()
+                    {
+                        lock (this)
+                        {
+                            $$
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task NoLockSnippetInTypeBodyTest()
+        {
+            await VerifyItemIsAbsentAsync("""
+                class Program
+                {
+                    $$
+                }
+                """, ItemToCommit);
+        }
+
+        [WpfFact]
+        public async Task InsertLockSnippetInLocalFunctionTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        void LocalFunction()
+                        {
+                            $$
+                        }
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        void LocalFunction()
+                        {
+                            lock (this)
+                            {
+                                $$
+                            }
+                        }
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertLockSnippetInAnonymousFunctionTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = delegate()
+                        {
+                            $$
+                        };
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = delegate()
+                        {
+                            lock (this)
+                            {
+                                $$
+                            }
+                        };
+                    }
+                }
+                """);
+        }
+
+        [WpfFact]
+        public async Task InsertLockSnippetInParenthesizedLambdaExpressionTest()
+        {
+            await VerifyCustomCommitProviderAsync("""
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = () =>
+                        {
+                            $$
+                        };
+                    }
+                }
+                """, ItemToCommit, """
+                class Program
+                {
+                    public void Method()
+                    {
+                        var action = () =>
+                        {
+                            lock (this)
+                            {
+                                $$
+                            }
+                        };
+                    }
+                }
+                """);
+        }
+    }
+}
diff --git a/src/EditorFeatures/CSharpTest/EditAndContinue/ActiveStatementTests.cs b/src/EditorFeatures/CSharpTest/EditAndContinue/ActiveStatementTests.cs
index d4dafe9cc9597..e2517fb943aa8 100644
--- a/src/EditorFeatures/CSharpTest/EditAndContinue/ActiveStatementTests.cs
+++ b/src/EditorFeatures/CSharpTest/EditAndContinue/ActiveStatementTests.cs
@@ -4224,6 +4224,210 @@ static unsafe void Main(string[] args)
                 Diagnostic(RudeEditKind.UpdateAroundActiveStatement, "foreach (var a in G(a => a))", CSharpFeaturesResources.foreach_statement));
         }
 
+        [Fact]
+        public void ForEach_Update_Collection_01()
+        {
+            var src1 = @"
+class C
+{
+    static void Main()
+    {
+        var aa = new int[4];
+        var bb = new int[4];
+        
+        foreach (var a in aa)
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+        }
+    }
+}
+";
+            var src2 = @"
+class C
+{
+    static void Main()
+    {
+        var aa = new int[4];
+        var bb = new int[4];
+        
+        foreach (var a in bb)
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+        }
+    }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+            var active = GetActiveStatements(src1, src2);
+
+            edits.VerifySemanticDiagnostics(active,
+                Diagnostic(RudeEditKind.UpdateAroundActiveStatement, "foreach (var a in bb)", CSharpFeaturesResources.foreach_statement));
+        }
+
+        [Fact]
+        public void ForEach_Update_Collection_02()
+        {
+            var src1 = @"
+class C
+{
+    static void Main()
+    {
+        Buffer4 aa = default;
+        Buffer4 bb = default;
+        
+        foreach (var a in aa)
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+        }
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+struct Buffer4
+{
+    private int _f;
+}
+";
+            var src2 = @"
+class C
+{
+    static void Main()
+    {
+        Buffer4 aa = default;
+        Buffer4 bb = default;
+        
+        foreach (var a in bb)
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+        }
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+struct Buffer4
+{
+    private int _f;
+}
+";
+            var edits = GetTopEdits(src1, src2);
+            var active = GetActiveStatements(src1, src2);
+
+            edits.VerifySemanticDiagnostics(active,
+                Diagnostic(RudeEditKind.UpdateAroundActiveStatement, "foreach (var a in bb)", CSharpFeaturesResources.foreach_statement));
+        }
+
+        [Fact]
+        public void ForEach_Update_Collection_03()
+        {
+            var src1 = @"
+class C
+{
+    public readonly Buffer4 F = default;
+}
+
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test(C x, C z)
+    {
+        foreach (var y in x.F)
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+            yield return -1;
+        }
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+struct Buffer4
+{
+    private int _f;
+}
+";
+            var src2 = @"
+class C
+{
+    public readonly Buffer4 F = default;
+}
+
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test(C x, C z)
+    {
+        foreach (var y in z.F)
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+            yield return -1;
+        }
+    }
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+struct Buffer4
+{
+    private int _f;
+}
+";
+            var edits = GetTopEdits(src1, src2);
+            var active = GetActiveStatements(src1, src2);
+
+            edits.VerifySemanticDiagnostics(active,
+                Diagnostic(RudeEditKind.UpdateAroundActiveStatement, "foreach (var y in z.F)", CSharpFeaturesResources.foreach_statement));
+        }
+
+        [Fact]
+        public void ForEach_Update_Collection_04()
+        {
+            var src1 = @"
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        foreach (var y in GetBuffer1())
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+            yield return -1;
+        }
+    }
+
+    static Buffer4 GetBuffer1() => default;
+    static Buffer4 GetBuffer2() => default;
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+struct Buffer4
+{
+    private int _f;
+}
+";
+            var src2 = @"
+class Program
+{
+    static System.Collections.Generic.IEnumerable<int> Test()
+    {
+        foreach (var y in GetBuffer2())
+        {
+            <AS:0>Console.WriteLine(1);</AS:0>
+            yield return -1;
+        }
+    }
+
+    static Buffer4 GetBuffer1() => default;
+    static Buffer4 GetBuffer2() => default;
+}
+
+[System.Runtime.CompilerServices.InlineArray(4)]
+struct Buffer4
+{
+    private int _f;
+}
+";
+            var edits = GetTopEdits(src1, src2);
+            var active = GetActiveStatements(src1, src2);
+
+            edits.VerifySemanticDiagnostics(active,
+                Diagnostic(RudeEditKind.UpdateAroundActiveStatement, "foreach (var y in GetBuffer2())", CSharpFeaturesResources.foreach_statement));
+        }
+
         [Fact]
         public void ForEach_Update_Nullable()
         {
diff --git a/src/EditorFeatures/CSharpTest/EditAndContinue/Helpers/EditingTestBase.cs b/src/EditorFeatures/CSharpTest/EditAndContinue/Helpers/EditingTestBase.cs
index 30da268821528..1d1a47d5fae6c 100644
--- a/src/EditorFeatures/CSharpTest/EditAndContinue/Helpers/EditingTestBase.cs
+++ b/src/EditorFeatures/CSharpTest/EditAndContinue/Helpers/EditingTestBase.cs
@@ -45,6 +45,14 @@ internal enum MethodKind
         public static string GetResource(string keyword, string symbolDisplayName)
             => string.Format(FeaturesResources.member_kind_and_name, TryGetResource(keyword) ?? throw ExceptionUtilities.UnexpectedValue(keyword), symbolDisplayName);
 
+        public static string GetResource(string keyword, string symbolDisplayName, string containerKeyword, string containerDisplayName)
+            => string.Format(
+                FeaturesResources.symbol_kind_and_name_of_member_kind_and_name,
+                TryGetResource(keyword) ?? throw ExceptionUtilities.UnexpectedValue(keyword),
+                symbolDisplayName,
+                TryGetResource(containerKeyword) ?? throw ExceptionUtilities.UnexpectedValue(containerKeyword),
+                containerDisplayName);
+
         public static string GetResource(string keyword)
             => TryGetResource(keyword) ?? throw ExceptionUtilities.UnexpectedValue(keyword);
 
@@ -63,6 +71,8 @@ public static string GetResource(string keyword)
                 "field" => FeaturesResources.field,
                 "method" => FeaturesResources.method,
                 "property" => FeaturesResources.property_,
+                "property getter" => CSharpFeaturesResources.property_getter,
+                "property setter" => CSharpFeaturesResources.property_setter,
                 "auto-property" => FeaturesResources.auto_property,
                 "indexer" => CSharpFeaturesResources.indexer,
                 "indexer getter" => CSharpFeaturesResources.indexer_getter,
diff --git a/src/EditorFeatures/CSharpTest/EditAndContinue/StatementEditingTests.cs b/src/EditorFeatures/CSharpTest/EditAndContinue/StatementEditingTests.cs
index aceec048675f9..d0ee06b0bbf0b 100644
--- a/src/EditorFeatures/CSharpTest/EditAndContinue/StatementEditingTests.cs
+++ b/src/EditorFeatures/CSharpTest/EditAndContinue/StatementEditingTests.cs
@@ -2097,18 +2097,6 @@ public void Lambdas_InLambda_ChangeOnlyInLambdaBody()
             edits.VerifyEdits();
         }
 
-        [Fact]
-        public void Lambdas_Update_ParameterRefness_NoBodyChange()
-        {
-            var src1 = @"F((ref int a) => a = 1);";
-            var src2 = @"F((out int a) => a = 1);";
-
-            var edits = GetMethodEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [ref int a]@5 -> [out int a]@5");
-        }
-
         [Fact]
         public void Lambdas_Insert_First_Static()
         {
@@ -3045,38 +3033,15 @@ void F()
         }
 
         [Fact]
-        public void Lambdas_Update_CeaseCapture_This()
+        public void Lambdas_Update_ParameterRefness_NoBodyChange()
         {
-            var src1 = @"
-using System;
-
-class C
-{
-    int x = 1;
-
-    void F()
-    {
-        var f = new Func<int, int>(a => a + x);
-    }
-}
-";
-            var src2 = @"
-using System;
+            var src1 = @"F((ref int a) => a = 1);";
+            var src2 = @"F((out int a) => a = 1);";
 
-class C
-{
-    int x;
-   
-    void F()
-    {
-        var f = new Func<int, int>(a => a);
-    }
-}
-";
-            var edits = GetTopEdits(src1, src2);
+            var edits = GetMethodEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "this"));
+            edits.VerifyEdits(
+                "Update [ref int a]@5 -> [out int a]@5");
         }
 
         [Fact]
@@ -3557,7 +3522,7 @@ void F()
         }
 
         [Fact]
-        public void Lambdas_Signature_MatchingErrorType()
+        public void Lambdas_Update_Signature_MatchingErrorType()
         {
             var src1 = @"
 using System;
@@ -3596,7 +3561,7 @@ void F()
         }
 
         [Fact]
-        public void Lambdas_Signature_NonMatchingErrorType()
+        public void Lambdas_Update_Signature_NonMatchingErrorType()
         {
             var src1 = @"
 using System;
@@ -3971,6 +3936,41 @@ void F(int x1)
             edits.VerifySemanticDiagnostics();
         }
 
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_This()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    int x = 1;
+
+    void F()
+    {
+        var f = new Func<int, int>(a => a + x);
+    }
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    int x;
+   
+    void F()
+    {
+        var f = new Func<int, int>(a => a);
+    }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "this"));
+        }
+
         [Fact]
         public void Lambdas_Update_CeaseCapture_Closure1()
         {
@@ -4013,8 +4013,8 @@ void F()
                 Diagnostic(RudeEditKind.NotAccessingCapturedVariableInLambda, "a2", "y", CSharpFeaturesResources.lambda));
         }
 
-        [Fact]
-        public void Lambdas_Update_CeaseCapture_IndexerParameter1()
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
+        public void Lambdas_Update_CeaseCapture_IndexerParameter_WithExpressionBody()
         {
             var src1 = @"
 using System;
@@ -4035,18 +4035,76 @@ class C
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a1", "a1"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a1", "a1"));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
+        public void Lambdas_Update_CeaseCapture_IndexerParameter_WithExpressionBody_LambdaBlock()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    int this[int a] => new Func<int>(() => { return a + 1; })();
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    int this[int a] => new Func<int>(() => { return 2; })();   // not capturing a anymore
+}";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [int this[int a] => new Func<int>(() => { return a + 1; })();]@35 -> [int this[int a] => new Func<int>(() => { return 2; })();]@35",
+                "Update [=> new Func<int>(() => { return a + 1; })()]@51 -> [=> new Func<int>(() => { return 2; })()]@51");
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a", "a"));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
+        public void Lambdas_Update_CeaseCapture_IndexerParameter_WithExpressionBody_Delegate()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    int this[int a] => new Func<int>(delegate { return a + 1; })();
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    int this[int a] => new Func<int>(delegate { return 2; })();   // not capturing a anymore
+}";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [int this[int a] => new Func<int>(delegate { return a + 1; })();]@35 -> [int this[int a] => new Func<int>(delegate { return 2; })();]@35",
+                "Update [=> new Func<int>(delegate { return a + 1; })()]@51 -> [=> new Func<int>(delegate { return 2; })()]@51");
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a", "a"));
         }
 
         [Fact]
-        public void Lambdas_Update_CeaseCapture_IndexerParameter2()
+        public void Lambdas_Update_CeaseCapture_IndexerParameter_WithExpressionBody_Getter()
         {
             var src1 = @"
 using System;
 
 class C
 {
-    Func<int, int> this[int a1, int a2] { get { return new Func<int, int>(a3 => a1 + a2); } }
+    Func<int, int> this[int a1, int a2] { get => new(a3 => a1 + a2); }
 }
 ";
             var src2 = @"
@@ -4060,11 +4118,68 @@ class C
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a1", "a1"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a1", "a1"));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
+        public void Lambdas_Update_CeaseCapture_IndexerParameter_WithExpressionBody_Partial()
+        {
+            var srcA1 = @"
+partial class C
+{
+}";
+            var srcB1 = @"
+partial class C
+{
+    int this[int a] => new System.Func<int>(() => a + 1);
+}";
+
+            var srcA2 = @"
+partial class C
+{
+    int this[int a] => new System.Func<int>(() => 2); // no capture
+}";
+            var srcB2 = @"
+partial class C
+{
+}";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(diagnostics: new[] { Diagnostic(RudeEditKind.NotCapturingVariable, "int a", "a") }),
+                    DocumentResults(),
+                });
         }
 
         [Fact]
-        public void Lambdas_Update_CeaseCapture_MethodParameter1()
+        public void Lambdas_Update_CeaseCapture_IndexerParameter_ParameterDelete()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> this[int a1, int a2] { get { return new Func<int, int>(a3 => a1 + a2); } }
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> this[int a2] { get { return new Func<int, int>(a3 => a2); } }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "get", "a1"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_MethodParameter()
         {
             var src1 = @"
 using System;
@@ -4091,11 +4206,11 @@ void F(int a1, int a2)
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a2", "a2"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a2", "a2"));
         }
 
-        [Fact]
-        public void Lambdas_Update_CeaseCapture_MethodParameter2()
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
+        public void Lambdas_Update_CeaseCapture_MethodParameter_WithExpressionBody()
         {
             var src1 = @"
 using System;
@@ -4116,7 +4231,110 @@ class C
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a2", "a2"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a2", "a2"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_MethodParameter_ParameterDelete()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1 + a2);
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1) => new Func<int, int>(a3 => a1);
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "a2"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_MethodParameter_ParameterTypeChange()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1 + a2);
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(byte a1) => new Func<int, int>(a3 => a1);
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingCapturedVariableType, "a1", "a1", "int"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "a2"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_MethodParameter_LocalToParameter()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1) { int a2 = 1; return new Func<int, int>(a3 => a1 + a2); }
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1, int a2) { return new Func<int, int>(a3 => a1 + a2); }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"),
+                Diagnostic(RudeEditKind.DeletingCapturedVariable, "{", "a2"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_MethodParameter_ParameterToLocal()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1, int a2) { return new Func<int, int>(a3 => a1 + a2); }
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1) { int a2 = 1; return new Func<int, int>(a3 => a1 + a2); }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "a2"));
         }
 
         [Fact]
@@ -4131,7 +4349,11 @@ void F()
     {
         var f1 = new Func<int, int, int>((a1, a2) => 
         {
-            var f2 = new Func<int, int>(a3 => a1 + a2);
+            var f2 = new Func<int, int>(a3 => 
+            {
+                var f3 = new Func<int, int>(a4 => a1 + a2 + a3);
+                return 1;
+            });
             return a1;
         });
     }
@@ -4146,7 +4368,11 @@ void F()
     {
         var f1 = new Func<int, int, int>((a1, a2) => 
         {
-            var f2 = new Func<int, int>(a3 => a2);
+            var f2 = new Func<int, int>(a3 => 
+            {
+                var f3 = new Func<int, int>(a4 => a2);
+                return 1;
+            });
             return a1;
         });
     }
@@ -4155,7 +4381,8 @@ void F()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a1", "a1"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a1", "a1"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a3", "a3"));
         }
 
         [Fact, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems?id=234448")]
@@ -4290,6 +4517,123 @@ event Action D
                 Diagnostic(RudeEditKind.NotCapturingVariable, "remove", "value"));
         }
 
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        public void Lambdas_Update_CeaseCapture_ConstructorInitializer_This()
+        {
+            var src1 = "class C { C(int x) : this(() => x) {} C(Func<int> f) {} }";
+            var src2 = "class C { C(int x) : this(() => 1) {} C(Func<int> f) {} }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int x", "x"));
+        }
+
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        public void Lambdas_Update_CeaseCapture_ConstructorInitializer_Base()
+        {
+            var src1 = "class C : B { C(int x) : base(() => x) {} } class B { public B(Func<int> f) {} }";
+            var src2 = "class C : B { C(int x) : base(() => 1) {} } class B { public B(Func<int> f) {} }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int x", "x"));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Lambdas_Update_CeaseCapture_PrimaryParameter_InPrimaryConstructor_First(
+            [CombinatorialValues("class", "struct", "record", "record struct")] string keyword)
+        {
+            var src1 = keyword + " C(int x, int y) { System.Func<int> z = () => x; }";
+            var src2 = keyword + " C(int x, int y) { System.Func<int> z = () => 1; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int x", "x"));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Lambdas_Update_CeaseCapture_PrimaryParameter_InPrimaryConstructor_Second(
+            [CombinatorialValues("class", "struct", "record", "record struct")] string keyword)
+        {
+            var src1 = keyword + " C(int x, int y) { System.Func<int> z = () => x + y; }";
+            var src2 = keyword + " C(int x, int y) { System.Func<int> z = () => x; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int y", "y"));
+        }
+
+        [Theory(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        [CombinatorialData]
+        public void Lambdas_Update_CeaseCapture_PrimaryParameter_InPrimaryConstructor_BaseInitializer(
+            [CombinatorialValues("class", "struct", "record")] string keyword)
+        {
+            var src1 = keyword + " C(int x, int y) : B(() => x);";
+            var src2 = keyword + " C(int x, int y) : B(() => 1);";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "x", "x"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_PrimaryParameter_Method_First()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => 1; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "M", "x"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_PrimaryParameter_Method_Second()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => x + y; }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.M"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_PrimaryParameter_Method_ThisToPrimaryCapture()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => this.M()(); }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.M"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Lambdas_Update_CeaseCapture_PrimaryParameter_Method_PrimaryToThisCapture()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => this.M()(); }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.M"), preserveLocalVariables: true));
+        }
+
         [Fact]
         public void Lambdas_Update_DeleteCapture1()
         {
@@ -4381,6 +4725,31 @@ class C
                 Diagnostic(RudeEditKind.CapturingVariable, "a1", "a1"));
         }
 
+        [Fact]
+        public void Lambdas_Update_Capturing_IndexerGetterParameter_ParameterInsert()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> this[int a1] => new(a3 => a1);
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> this[int a1, int a2] => new(a3 => a1 + a2);
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"));
+        }
+
         [Fact]
         public void Lambdas_Update_Capturing_IndexerSetterParameter1()
         {
@@ -4524,10 +4893,60 @@ void F(int a1, int a2)
 
 class C
 {
-    void F(int a1, int a2)
-    {
-        var f2 = new Func<int, int>(a3 => a1 + a2);
-    }
+    void F(int a1, int a2)
+    {
+        var f2 = new Func<int, int>(a3 => a1 + a2);
+    }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_Capturing_MethodParameter2()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1);
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1 + a2);
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_Capturing_MethodParameter_ParameterInsert()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1) => new Func<int, int>(a3 => a1);
+}
+";
+            var src2 = @"
+using System;
+
+class C
+{
+    Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1 + a2);
 }
 ";
             var edits = GetTopEdits(src1, src2);
@@ -4537,22 +4956,32 @@ void F(int a1, int a2)
         }
 
         [Fact]
-        public void Lambdas_Update_Capturing_MethodParameter2()
+        public void Lambdas_Update_Capturing_MethodParameter_ParameterInsert_Partial()
         {
             var src1 = @"
 using System;
 
-class C
+partial class C
 {
-    Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1);
+    public partial Func<int, int> F(int a1);
+}
+
+partial class C
+{
+    public partial Func<int, int> F(int a1) => new Func<int, int>(a3 => a1);
 }
 ";
             var src2 = @"
 using System;
 
-class C
+partial class C
 {
-    Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1 + a2);
+    public partial Func<int, int> F(int a1, int a2);
+}
+
+partial class C
+{
+    public partial Func<int, int> F(int a1, int a2) => new Func<int, int>(a3 => a1 + a2);
 }
 ";
             var edits = GetTopEdits(src1, src2);
@@ -4600,6 +5029,123 @@ void F()
                 Diagnostic(RudeEditKind.CapturingVariable, "a1", "a1"));
         }
 
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        public void Lambdas_Update_Capturing_ConstructorInitializer_This()
+        {
+            var src1 = "class C { C(int x) : this(() => 1) {} C(Func<int> f) {} }";
+            var src2 = "class C { C(int x) : this(() => x) {} C(Func<int> f) {} }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "x", "x"));
+        }
+
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        public void Lambdas_Update_Capturing_ConstructorInitializer_Base()
+        {
+            var src1 = "class C : B { C(int x) : base(() => 1) {} } class B { public B(Func<int> f) {} }";
+            var src2 = "class C : B { C(int x) : base(() => x) {} } class B { public B(Func<int> f) {} }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "x", "x"));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Lambdas_Update_Capturing_PrimaryParameter_InPrimaryConstructor_First(
+            [CombinatorialValues("class", "struct", "record", "record struct")] string keyword)
+        {
+            var src1 = keyword + " C(int x, int y) { System.Func<int> z = () => 1; }";
+            var src2 = keyword + " C(int x, int y) { System.Func<int> z = () => x; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "x", "x"));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Lambdas_Update_Capturing_PrimaryParameter_InPrimaryConstructor_Second(
+            [CombinatorialValues("class", "struct", "record", "record struct")] string keyword)
+        {
+            var src1 = keyword + " C(int x, int y) { System.Func<int> z = () => x; }";
+            var src2 = keyword + " C(int x, int y) { System.Func<int> z = () => x + y; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "y", "y"));
+        }
+
+        [Theory(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        [CombinatorialData]
+        public void Lambdas_Update_Capturing_PrimaryParameter_InPrimaryConstructor_BaseInitializer(
+            [CombinatorialValues("class", "struct", "record")] string keyword)
+        {
+            var src1 = keyword + " C(int x, int y) : B(() => 1);";
+            var src2 = keyword + " C(int x, int y) : B(() => x);";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "x", "x"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_Capturing_PrimaryParameter_Method_First()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => 1; }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "x", "x"));
+        }
+
+        [Fact]
+        public void Lambdas_Update_Capturing_PrimaryParameter_Method_Second()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => x + y; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.M"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Lambdas_Update_Capturing_PrimaryParameter_Method_ThisToPrimaryCapture()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => this.M()(); }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.M"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Lambdas_Update_Capturing_PrimaryParameter_Method_PrimaryToThisCapture()
+        {
+            var src1 = "class C(int x, int y) { System.Func<int> M() => () => x; }";
+            var src2 = "class C(int x, int y) { System.Func<int> M() => () => this.M()(); }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.M"), preserveLocalVariables: true));
+        }
+
         [Fact]
         public void Lambdas_Update_StaticToThisOnly1()
         {
@@ -5143,15 +5689,14 @@ void F()
         }
 
         [Fact]
-        public void Lambdas_RenameCapturedLocal()
+        public void Lambdas_CapturedLocal_Rename()
         {
             var src1 = @"
 using System;
-using System.Diagnostics;
 
-class Program
+class C
 {
-    static void Main()
+    static void F()
     {
         int x = 1;
         Func<int> f = () => x;
@@ -5159,11 +5704,10 @@ static void Main()
 }";
             var src2 = @"
 using System;
-using System.Diagnostics;
 
-class Program
+class C
 {
-    static void Main()
+    static void F()
     {
         int X = 1;
         Func<int> f = () => X;
@@ -5177,7 +5721,100 @@ static void Main()
         }
 
         [Fact]
-        public void Lambdas_RenameCapturedParameter()
+        public void Lambdas_CapturedLocal_ChangeType()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    static void F()
+    {
+        int x = 1;
+        Func<int> f = () => x;
+    }
+}";
+            var src2 = @"
+using System;
+
+class C
+{
+    static void F()
+    {
+        byte x = 1;
+        Func<int> f = () => x;
+    }
+}";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingCapturedVariableType, "x", "x", "int"));
+        }
+
+        [Fact]
+        public void Lambdas_CapturedParameter_Rename()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    static void F(int x)
+    {
+        Func<int> f = () => x;
+    }
+}";
+            var src2 = @"
+using System;
+
+class C
+{
+    static void F(int X)
+    {
+        Func<int> f = () => X;
+    }
+}";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.RenamingCapturedVariable, "X", "x", "X"));
+        }
+
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68708")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68708")]
+        public void Lambdas_CapturedParameter_ChangeType()
+        {
+            var src1 = @"
+using System;
+
+class C
+{
+    static void F(int x)
+    {
+        Func<int> f = () => x;
+    }
+}";
+            var src2 = @"
+using System;
+
+class C
+{
+    static void F(byte x)
+    {
+        Func<int> f = () => x;
+    }
+}";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingCapturedVariableType, "x", "x", "int"));
+        }
+
+        [Fact]
+        public void Lambdas_ReorderCapturedParameters()
         {
             var src1 = @"
 using System;
@@ -5185,9 +5822,9 @@ public void Lambdas_RenameCapturedParameter()
 
 class Program
 {
-    static void Main(int x)
+    static void Main(int x, int y)
     {
-        Func<int> f = () => x;
+        Func<int> f = () => x + y;
     }
 }";
             var src2 = @"
@@ -5196,9 +5833,9 @@ static void Main(int x)
 
 class Program
 {
-    static void Main(int X)
+    static void Main(int y, int x)
     {
-        Func<int> f = () => X;
+        Func<int> f = () => x + y;
     }
 }";
 
@@ -6688,7 +7325,7 @@ class C
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a1", "a1"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a1", "a1"));
         }
 
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/21499")]
@@ -6719,7 +7356,7 @@ void F(int a1, int a2)
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a2", "a2"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a2", "a2"));
         }
 
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/21499")]
@@ -6758,7 +7395,7 @@ int f1(int a1, int a2)
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "int f1(int a1, int a2)\r\n        {\r\n            int f2(int a3) => a2;\r\n            return a1;\r\n        };\r\n  ", "a1"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "int a1", "a1"));
         }
 
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/21499")]
@@ -7506,37 +8143,32 @@ static void Main()
         public void LocalFunctions_RenameCapturedParameter()
         {
             var src1 = @"
-        using System;
-        using System.Diagnostics;
+using System;
+using System.Diagnostics;
 
-        class Program
-        {
-            static void Main(int x)
-            {
-                int f() => x;
-            }
-        }";
+class Program
+{
+    static void Main(int x)
+    {
+        int f() => x;
+    }
+}";
             var src2 = @"
-        using System;
-        using System.Diagnostics;
+using System;
+using System.Diagnostics;
 
-        class Program
-        {
-            static void Main(int X)
-            {
-                int f() => X;
-            }
-        }";
+class Program
+{
+    static void Main(int X)
+    {
+        int f() => X;
+    }
+}";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemantics(
-                ActiveStatementsDescription.Empty,
-                new[]
-                {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("Program.Main"), preserveLocalVariables: true)
-                },
-                capabilities: EditAndContinueTestHelpers.Net6RuntimeCapabilities);
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.RenamingCapturedVariable, "X", "x", "X"));
         }
 
         [Fact]
@@ -11814,27 +12446,71 @@ public void WithExpression_PropertyValueReorder()
         #region Top Level Statements
 
         [Fact]
-        public void TopLevelStatement_CaptureArgs()
+        public void TopLevelStatement_Capture_Args()
         {
             var src1 = @"
 using System;
 
-var x = new Func<string>(() => ""Hello"");
-
-Console.WriteLine(x());
+var x = new Func<string[]>(() => null);
 ";
             var src2 = @"
 using System;
 
-var x = new Func<string>(() => ""Hello"" + args[0]);
+var x = new Func<string[]>(() => args);
+";
+            var edits = GetTopEdits(src1, src2);
+
+            // TODO: allow creating a new leaf closure: https://github.com/dotnet/roslyn/issues/54672
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "var x = new Func<string[]>(() => args);", "args"));
+        }
+
+        [Fact]
+        public void TopLevelStatement_CeaseCapture_Args()
+        {
+            var src1 = @"
+using System;
+
+var x = new Func<string[]>(() => args);
+";
+            var src2 = @"
+using System;
 
-Console.WriteLine(x());
+var x = new Func<string[]>(() => null);
 ";
             var edits = GetTopEdits(src1, src2);
 
             // TODO: allow creating a new leaf closure: https://github.com/dotnet/roslyn/issues/54672
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.CapturingVariable, "using System;\r\n\r\nvar x = new Func<string>(() => \"Hello\" + args[0]);\r\n\r\nConsole.WriteLine(x());\r\n", "args"));
+                Diagnostic(RudeEditKind.NotCapturingVariable, "var x = new Func<string[]>(() => null);", "args"));
+        }
+
+        [Fact]
+        public void TopLevelStatement_CeaseCapture_Args_Closure()
+        {
+            var src1 = @"
+using System;
+
+var f1 = new Func<int, int>(a1 => 
+{
+    var f2 = new Func<int, int>(a2 => args.Length + a2);
+    return a1;
+});
+";
+            var src2 = @"
+using System;
+
+var f1 = new Func<int, int>(a1 => 
+{
+    var f2 = new Func<int, int>(a2 => a2);
+    return a1 + args.Length;
+});
+";
+            var edits = GetTopEdits(src1, src2);
+
+            // y is no longer captured in f2
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotAccessingCapturedVariableInLambda, "a2", "args", CSharpFeaturesResources.lambda));
         }
 
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/21499")]
diff --git a/src/EditorFeatures/CSharpTest/EditAndContinue/TopLevelEditingTests.cs b/src/EditorFeatures/CSharpTest/EditAndContinue/TopLevelEditingTests.cs
index 308d5ecf2643e..73c8f0fdf9c52 100644
--- a/src/EditorFeatures/CSharpTest/EditAndContinue/TopLevelEditingTests.cs
+++ b/src/EditorFeatures/CSharpTest/EditAndContinue/TopLevelEditingTests.cs
@@ -5,6 +5,7 @@
 #nullable disable
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
@@ -22,6 +23,9 @@ namespace Microsoft.CodeAnalysis.CSharp.EditAndContinue.UnitTests
     [UseExportProvider]
     public class TopLevelEditingTests : EditingTestBase
     {
+        private static readonly string s_attributeSource = @"
+[System.AttributeUsage(System.AttributeTargets.All)]class A : System.Attribute { }
+";
         #region Usings
 
         [Fact]
@@ -1414,7 +1418,7 @@ public void Struct_NoModifiers_IntoType_Insert()
         }
 
         [Fact]
-        public void Type_BaseType_Add_Unchanged()
+        public void Type_BaseType_Insert_Unchanged()
         {
             var src1 = "class C { }";
             var src2 = "class C : object { }";
@@ -1422,13 +1426,13 @@ public void Type_BaseType_Add_Unchanged()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [class C { }]@0 -> [class C : object { }]@0");
+                "Insert [: object]@8");
 
             edits.VerifySemantics();
         }
 
         [Fact]
-        public void Type_BaseType_Add_Changed()
+        public void Type_BaseType_Insert_Changed()
         {
             var src1 = "class C { }";
             var src2 = "class C : D { }";
@@ -1436,7 +1440,39 @@ public void Type_BaseType_Add_Changed()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [class C { }]@0 -> [class C : D { }]@0");
+                "Insert [: D]@8");
+
+            edits.VerifySemanticDiagnostics(
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "D", FeaturesResources.class_));
+        }
+
+        [Fact]
+        public void Type_BaseType_Insert_WithPrimaryInitializer()
+        {
+            var src1 = "class C() { }";
+            var src2 = "class C() : D() { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Insert [: D()]@10",
+                "Insert [D()]@12");
+
+            edits.VerifySemanticDiagnostics(
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "D()", FeaturesResources.class_));
+        }
+
+        [Fact]
+        public void Type_BaseType_Delete_WithPrimaryInitializer()
+        {
+            var src1 = "class C() : D() { }";
+            var src2 = "class C() { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Delete [: D()]@10",
+                "Delete [D()]@12");
 
             edits.VerifySemanticDiagnostics(
                  Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "class C", FeaturesResources.class_));
@@ -1471,7 +1507,7 @@ public void Type_BaseType_Update_RuntimeTypeChanged(string oldType, string newTy
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "class C", FeaturesResources.class_));
+                Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "System.Collections.Generic.List<" + newType + ">", FeaturesResources.class_));
         }
 
         [Fact]
@@ -1494,10 +1530,10 @@ public void Type_BaseInterface_Add()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [class C { }]@0 -> [class C : IDisposable { }]@0");
+                "Insert [: IDisposable]@8");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "class C", FeaturesResources.class_));
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "IDisposable", FeaturesResources.class_));
         }
 
         [Fact]
@@ -1530,10 +1566,10 @@ public void Type_BaseInterface_Reorder()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [class C : IGoo, IBar { }]@0 -> [class C : IBar, IGoo { }]@0");
+                "Update [: IGoo, IBar]@8 -> [: IBar, IGoo]@8");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "class C", FeaturesResources.class_));
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "IBar, IGoo", FeaturesResources.class_));
         }
 
         [Theory]
@@ -1563,7 +1599,7 @@ public void Type_BaseInterface_Update_RuntimeTypeChanged(string oldType, string
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "class C", FeaturesResources.class_));
+                Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "System.Collections.Generic.IEnumerable<" + newType + ">", FeaturesResources.class_));
         }
 
         [Fact]
@@ -1870,6 +1906,7 @@ public class SubClass : BaseClass, IConflict
 
     string IConflict.Get() => String.Empty;
 }]@219",
+                "Insert [: BaseClass, IConflict]@241",
                 "Insert [public override string Get() => string.Empty;]@272",
                 "Insert [string IConflict.Get() => String.Empty;]@325",
                 "Insert [()]@298",
@@ -2542,7 +2579,7 @@ class C
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.P").GetMethod),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.P").SetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true),
                         })
                 });
         }
@@ -2584,7 +2621,7 @@ partial class C
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.P").GetMethod),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.P").SetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true),
                         })
                 });
         }
@@ -2626,7 +2663,7 @@ class C
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.P").GetMethod),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.P").SetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true),
                         }),
 
                     DocumentResults()
@@ -2727,23 +2764,6 @@ public void Type_Move_MultiFile()
 
         #region Records
 
-        [Fact]
-        public void Record_Partial_MovePrimaryConstructor()
-        {
-            var src1 = @"
-partial record C { }
-partial record C(int X);";
-            var src2 = @"
-partial record C(int X);
-partial record C { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemantics();
-
-            edits.VerifySemanticDiagnostics();
-        }
-
         [Fact]
         public void Record_Name_Update()
         {
@@ -2846,7 +2866,7 @@ public void Record_NoModifiers_IntoType_Insert()
         }
 
         [Fact]
-        public void Record_BaseTypeUpdate1()
+        public void Record_BaseType_Update1()
         {
             var src1 = "record C { }";
             var src2 = "record C : D { }";
@@ -2854,14 +2874,14 @@ public void Record_BaseTypeUpdate1()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [record C { }]@0 -> [record C : D { }]@0");
+                "Insert [: D]@9");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "record C", CSharpFeaturesResources.record_));
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "D", CSharpFeaturesResources.record_));
         }
 
         [Fact]
-        public void Record_BaseTypeUpdate2()
+        public void Record_BaseType_Update2()
         {
             var src1 = "record C : D1 { }";
             var src2 = "record C : D2 { }";
@@ -2869,14 +2889,14 @@ public void Record_BaseTypeUpdate2()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [record C : D1 { }]@0 -> [record C : D2 { }]@0");
+                "Update [: D1]@9 -> [: D2]@9");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "record C", CSharpFeaturesResources.record_));
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "D2", CSharpFeaturesResources.record_));
         }
 
         [Fact]
-        public void Record_BaseInterfaceUpdate1()
+        public void Record_BaseInterface_Update1()
         {
             var src1 = "record C { }";
             var src2 = "record C : IDisposable { }";
@@ -2884,14 +2904,14 @@ public void Record_BaseInterfaceUpdate1()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [record C { }]@0 -> [record C : IDisposable { }]@0");
+                "Insert [: IDisposable]@9");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "record C", CSharpFeaturesResources.record_));
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "IDisposable", CSharpFeaturesResources.record_));
         }
 
         [Fact]
-        public void Record_BaseInterfaceUpdate2()
+        public void Record_BaseInterface_Update2()
         {
             var src1 = "record C : IGoo, IBar { }";
             var src2 = "record C : IGoo { }";
@@ -2899,14 +2919,14 @@ public void Record_BaseInterfaceUpdate2()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [record C : IGoo, IBar { }]@0 -> [record C : IGoo { }]@0");
+                "Update [: IGoo, IBar]@9 -> [: IGoo]@9");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "record C", CSharpFeaturesResources.record_));
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "IGoo", CSharpFeaturesResources.record_));
         }
 
         [Fact]
-        public void Record_BaseInterfaceUpdate3()
+        public void Record_BaseInterface_Update3()
         {
             var src1 = "record C : IGoo, IBar { }";
             var src2 = "record C : IBar, IGoo { }";
@@ -2914,14 +2934,14 @@ public void Record_BaseInterfaceUpdate3()
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [record C : IGoo, IBar { }]@0 -> [record C : IBar, IGoo { }]@0");
+                "Update [: IGoo, IBar]@9 -> [: IBar, IGoo]@9");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "record C", CSharpFeaturesResources.record_));
+                 Diagnostic(RudeEditKind.BaseTypeOrInterfaceUpdate, "IBar, IGoo", CSharpFeaturesResources.record_));
         }
 
         [Fact]
-        public void RecordInsert_AbstractVirtualOverride()
+        public void Record_Method_Insert_AbstractVirtualOverride()
         {
             var src1 = "";
             var src2 = @"
@@ -2937,380 +2957,312 @@ public override void H() {}
                 capabilities: EditAndContinueCapabilities.NewTypeDefinition);
         }
 
-        [Fact]
-        public void Record_ImplementSynthesized_ParameterlessConstructor()
+        [Theory]
+        [InlineData("Equals", "public virtual bool Equals(C rhs) => true;", "C rhs")]
+        [InlineData("PrintMembers", "protected virtual bool PrintMembers(System.Text.StringBuilder sb) => true;", "System.Text.StringBuilder sb")]
+        [InlineData("Deconstruct", "public void Deconstruct(out int Y) { Y = 1; }", "out int Y")]
+        [InlineData(".ctor", "protected C(C other) {}", "C other")]
+        public void Record_Method_Insert_ReplacingSynthesizedWithCustom_ParameterNameChanges(string methodName, string methodImpl, string parameterDecl)
         {
-            var src1 = "record C { }";
-            var src2 = @"
-record C
-{
-    public C()
-    {
-    }
-}";
+            var src1 = "record C(int X) { }";
+            var src2 = "record C(int X) { " + methodImpl + " }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.First(c => c.ToString() == "C.C()"), preserveLocalVariables: true));
+            edits.VerifySemanticDiagnostics(
+                new[]
+                {
+                    Diagnostic(RudeEditKind.RenamingNotSupportedByRuntime, parameterDecl, FeaturesResources.parameter),
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
 
-            edits.VerifySemanticDiagnostics();
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => methodName switch { ".ctor" => c.GetCopyConstructor("C"), "Equals" => c.GetSpecializedEqualsOverload("C"), _ => c.GetMember("C." + methodName) }),
+                },
+                capabilities: EditAndContinueCapabilities.UpdateParameters);
         }
 
         [Fact]
-        public void RecordStruct_ImplementSynthesized_ParameterlessConstructor()
+        public void Record_Method_Insert_ReplacingSynthesizedWithCustom_SemanticError()
         {
-            var src1 = "record struct C { }";
-            var src2 = @"
-record struct C
+            var src1 = "record C { }";
+            var src2 = @"record C
 {
-    public C()
-    {
-    }
+protected virtual bool PrintMembers(System.Text.StringBuilder sb) => false;
+protected virtual bool PrintMembers(System.Text.StringBuilder sb) => false;
 }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.First(c => c.ToString() == "C.C()"), preserveLocalVariables: true));
+            edits.VerifySemanticDiagnostics(
+                new[]
+                {
+                    Diagnostic(RudeEditKind.RenamingNotSupportedByRuntime, "System.Text.StringBuilder sb", GetResource("parameter")),
+                    Diagnostic(RudeEditKind.RenamingNotSupportedByRuntime, "System.Text.StringBuilder sb", GetResource("parameter"))
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
 
-            edits.VerifySemanticDiagnostics();
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMembers("C.PrintMembers").First().ISymbol),
+                },
+                capabilities: EditAndContinueCapabilities.UpdateParameters | EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
-        [Fact]
-        public void Record_ImplementSynthesized_PrintMembers()
+        [Theory]
+        [InlineData("ToString", "public override string ToString() => null;")]
+        [InlineData("GetHashCode", "public override int GetHashCode() => 1;")]
+        [InlineData("Equals", "public virtual bool Equals(C other) => true;")]
+        [InlineData("PrintMembers", "protected virtual bool PrintMembers(System.Text.StringBuilder builder) => true;")]
+        [InlineData("Deconstruct", "public void Deconstruct(out int X) { X = 1; }")]
+        [InlineData(".ctor", "protected C(C original) {}")]
+        public void Record_Method_Insert_ReplacingSynthesizedWithCustom(string methodName, string methodImpl)
         {
-            var src1 = "record C { }";
-            var src2 = @"
-record C
-{
-    protected virtual bool PrintMembers(System.Text.StringBuilder builder)
-    {
-        return true;
-    }
-}";
+            var src1 = "record C(int X) { }";
+            var src2 = "record C(int X) { " + methodImpl + " }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")));
-
-            edits.VerifySemanticDiagnostics();
+                SemanticEdit(SemanticEditKind.Update, c => methodName switch { ".ctor" => c.GetCopyConstructor("C"), "Equals" => c.GetSpecializedEqualsOverload("C"), _ => c.GetMember("C." + methodName) }));
         }
 
-        [Fact]
-        public void RecordStruct_ImplementSynthesized_PrintMembers()
-        {
-            var src1 = "record struct C { }";
-            var src2 = @"
-record struct C
-{
-    private readonly bool PrintMembers(System.Text.StringBuilder builder)
-    {
-        return true;
-    }
-}";
+        [Theory]
+        [InlineData("ToString", "public override string ToString() => null;")]
+        [InlineData("GetHashCode", "public override int GetHashCode() => 1;")]
+        [InlineData("Equals", "public virtual bool Equals(C other) => true;")]
+        [InlineData("PrintMembers", "protected virtual bool PrintMembers(System.Text.StringBuilder builder) => true;")]
+        [InlineData("Deconstruct", "public void Deconstruct(out int X) { X = 1; }")]
+        [InlineData(".ctor", "protected C(C original) {}")]
+        public void Record_Method_Delete_ReplacingCustomWithSynthesized(string methodName, string methodImpl)
+        {
+            var src1 = "record C(int X) { " + methodImpl + " }";
+            var src2 = "record C(int X) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")));
+                SemanticEdit(SemanticEditKind.Update, c => methodName switch { ".ctor" => c.GetCopyConstructor("C"), "Equals" => c.GetSpecializedEqualsOverload("C"), _ => c.GetMember("C." + methodName) }));
 
             edits.VerifySemanticDiagnostics();
         }
 
-        [Fact]
-        public void Record_ImplementSynthesized_WrongParameterName()
+        [Theory]
+        [InlineData("Equals", "public virtual bool Equals(C rhs) => true;", "Equals(C other)", "other")]
+        [InlineData("PrintMembers", "protected virtual bool PrintMembers(System.Text.StringBuilder sb) => true;", "PrintMembers(StringBuilder builder)", "builder")]
+        [InlineData("Deconstruct", "public void Deconstruct(out int Y) { Y = 1; }", "Deconstruct(out int X)", "X")]
+        [InlineData(".ctor", "protected C(C other) {}", "C(C original)", "original")]
+        public void Record_Method_Delete_ReplacingSynthesizedWithCustom_ParameterNameChanges(string methodName, string methodImpl, string methodDisplay, string parameterDisplay)
         {
-            var src1 = "record C { }";
-            var src2 = @"
-record C
-{
-    protected virtual bool PrintMembers(System.Text.StringBuilder sb)
-    {
-        return false;
-    }
-
-    public virtual bool Equals(C rhs)
-    {
-        return false;
-    }
-
-    protected C(C other)
-    {
-    }
-}";
+            var src1 = "record C(int X) { " + methodImpl + " }";
+            var src2 = "record C(int X) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
                 new[]
                 {
-                    Diagnostic(RudeEditKind.ExplicitRecordMethodParameterNamesMustMatch, "protected virtual bool PrintMembers(System.Text.StringBuilder sb)", "PrintMembers(System.Text.StringBuilder builder)"),
-                    Diagnostic(RudeEditKind.RenamingNotSupportedByRuntime, "System.Text.StringBuilder sb", FeaturesResources.parameter),
-                    Diagnostic(RudeEditKind.ExplicitRecordMethodParameterNamesMustMatch, "public virtual bool Equals(C rhs)", "Equals(C other)"),
-                    Diagnostic(RudeEditKind.RenamingNotSupportedByRuntime, "C rhs", FeaturesResources.parameter),
-                    Diagnostic(RudeEditKind.ExplicitRecordMethodParameterNamesMustMatch, "protected C(C other)", "C(C original)")
+                    Diagnostic(
+                        RudeEditKind.RenamingNotSupportedByRuntime,
+                        "record C",
+                        GetResource("parameter", parameterDisplay, methodName switch { ".ctor" => "constructor", _ => "method" }, methodDisplay)),
                 },
                 capabilities: EditAndContinueCapabilities.Baseline);
 
             edits.VerifySemantics(
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters.FirstOrDefault()?.Type.ToDisplayString() == "C"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters.Length == 0), preserveLocalVariables: true),
+                    SemanticEdit(SemanticEditKind.Update, c => methodName switch { ".ctor" => c.GetCopyConstructor("C"), "Equals" => c.GetSpecializedEqualsOverload("C"), _ => c.GetMember("C." + methodName) }),
                 },
                 capabilities: EditAndContinueCapabilities.UpdateParameters);
         }
 
         [Fact]
-        public void Record_ImplementSynthesized_ToString()
+        public void Record_Field_Insert()
         {
-            var src1 = "record C { }";
-            var src2 = @"
-record C
-{
-    public override string ToString()
-    {
-        return ""R"";
-    }
-}";
+            var src1 = "record C(int X) { }";
+            var src2 = "record C(int X) { private int _y; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.ToString")));
-
-            edits.VerifySemanticDiagnostics();
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._y")),
+                },
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
         }
 
         [Fact]
-        public void Record_UnImplementSynthesized_ToString()
+        public void Record_Field_Insert_WithExplicitMembers()
         {
             var src1 = @"
-record C
+record C(int X)
 {
-    public override string ToString()
+    public C(C other)
     {
-        return ""R"";
     }
 }";
-            var src2 = "record C { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.ToString")));
-
-            edits.VerifySemanticDiagnostics();
-        }
-
-        [Fact]
-        public void Record_AddProperty_Primary()
-        {
-            var src1 = "record C(int X);";
-            var src2 = "record C(int X, int Y);";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Insert, "int Y", FeaturesResources.parameter));
-        }
-
-        [Fact]
-        public void Record_UnimplementSynthesized_ParameterlessConstructor()
-        {
-            var src1 = @"
-record C
+            var src2 = @"
+record C(int X)
 {
-    public C()
+    private int _y;
+    
+    public C(C other)
     {
     }
 }";
-            var src2 = "record C { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.First(c => c.ToString() == "C.C()"), preserveLocalVariables: true));
-
-            edits.VerifySemanticDiagnostics();
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._y")),
+                },
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
         }
 
         [Fact]
-        public void RecordStruct_UnimplementSynthesized_ParameterlessConstructor()
+        public void Record_Field_Insert_WithInitializer()
         {
-            var src1 = @"
-record struct C
-{
-    public C()
-    {
-    }
-}";
-            var src2 = "record struct C { }";
+            var src1 = "record C(int X) { }";
+            var src2 = "record C(int X) { private int _y = 1; }";
+            var syntaxMap = GetSyntaxMap(src1, src2);
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.First(c => c.ToString() == "C.C()"), preserveLocalVariables: true));
-
-            edits.VerifySemanticDiagnostics();
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._y")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true)
+                },
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
         }
 
         [Fact]
-        public void Record_AddProperty_NotPrimary()
+        public void Record_Field_Insert_WithExistingInitializer()
         {
-            var src1 = "record C(int X);";
-            var src2 = @"
-record C(int X)
-{
-    public int Y { get; set; }
-}";
+            var src1 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; }";
+            var src2 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; private int _z; }";
 
             var edits = GetTopEdits(src1, src2);
+            var syntaxMap = GetSyntaxMap(src1, src2);
 
             edits.VerifySemantics(
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._z")),
                 },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
         }
 
         [Fact]
-        public void Record_AddProperty_NotPrimary_WithConstructor()
+        public void Record_Field_Insert_WithInitializerAndExistingInitializer()
         {
-            var src1 = @"
-record C(int X)
-{
-    public C(string fromAString)
-    {
-    }
-}";
-            var src2 = @"
-record C(int X)
-{
-    public int Y { get; set; }
-
-    public C(string fromAString)
-    {
-    }
-}";
+            var src1 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; }";
+            var src2 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; private int _z = 1; }";
 
             var edits = GetTopEdits(src1, src2);
+            var syntaxMap = GetSyntaxMap(src1, src2);
 
             edits.VerifySemantics(
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._z")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), syntaxMap[0]),
                 },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
         }
 
         [Fact]
-        public void Record_AddProperty_NotPrimary_WithExplicitMembers()
+        public void Record_Field_Delete()
         {
-            var src1 = @"
-record C(int X)
-{
-    protected virtual bool PrintMembers(System.Text.StringBuilder builder)
-    {
-        return false;
-    }
-
-    public override int GetHashCode()
-    {
-        return 0;
-    }
+            var src1 = "record C(int X) { private int _y; }";
+            var src2 = "record C(int X) { }";
 
-    public virtual bool Equals(C other)
-    {
-        return false;
-    }
+            var edits = GetTopEdits(src1, src2);
 
-    public C(C original)
-    {
-    }
-}";
-            var src2 = @"
-record C(int X)
-{
-    public int Y { get; set; }
+            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.Delete, "record C", DeletedSymbolDisplay(FeaturesResources.field, "_y")));
+        }
 
-    protected virtual bool PrintMembers(System.Text.StringBuilder builder)
-    {
-        return false;
-    }
+        [Fact]
+        public void Record_Property_Update_Initializer_NotPrimary()
+        {
+            var src1 = "record C { int X { get; } = 0; }";
+            var src2 = "record C { int X { get; } = 1; }";
 
-    public override int GetHashCode()
-    {
-        return 0;
-    }
+            var edits = GetTopEdits(src1, src2);
 
-    public virtual bool Equals(C other)
-    {
-        return false;
-    }
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters.Length == 0), preserveLocalVariables: true));
+        }
 
-    public C(C original)
-    {
-    }
-}";
+        [Fact]
+        public void Record_Property_Update_Initializer_Primary()
+        {
+            var src1 = "record C(int X) { int X { get; } = 0; }";
+            var src2 = "record C(int X) { int X { get; } = 1; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                new[]
-                {
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true)
-                },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true));
         }
 
-        [Fact]
-        public void Record_AddProperty_NotPrimary_WithInitializer()
+        [Theory]
+        [InlineData("set")]
+        [InlineData("init")]
+        public void Record_Property_Delete_Writable(string setter)
         {
-            var src1 = "record C(int X);";
-            var src2 = @"
-record C(int X)
-{
-    public int Y { get; set; } = 1;
-}";
+            var src1 = "record C(int X) { public int P { get; " + setter + "; } }";
+            var src2 = "record C(int X) { }";
 
             var edits = GetTopEdits(src1, src2);
-            var syntaxMap = GetSyntaxMap(src1, src2);
 
             edits.VerifySemantics(
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_P"), deletedSymbolContainerProvider: c => c.GetMember("C"))
                 },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
-        [Fact]
-        public void Record_AddField()
+        [Theory]
+        [InlineData("get;")]
+        [InlineData("get => 1;")]
+        public void Record_Property_Delete_ReadOnly(string getter)
         {
-            var src1 = "record C(int X) { }";
-            var src2 = "record C(int X) { private int _y; }";
+            var src1 = "record C(int X) { public int P { " + getter + " } }";
+            var src2 = "record C(int X) { }";
 
             var edits = GetTopEdits(src1, src2);
 
@@ -3318,76 +3270,75 @@ public void Record_AddField()
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._y")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
                 },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
+        [Theory]
+        [InlineData("get;")]
+        [InlineData("get => 1;")]
+        public void Record_Property_Delete_ReadOnly_ReplacingCustomWithSynthesized(string getter)
+        {
+            var src1 = "record C(int X) { public int X { " + getter + " } }";
+            var src2 = "record C(int X);";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics();
         }
 
         [Fact]
-        public void Record_AddField_WithExplicitMembers()
+        public void Record_Property_Delete_WriteOnly()
         {
-            var src1 = @"
-record C(int X)
-{
-    public C(C other)
-    {
-    }
-}";
-            var src2 = @"
-record C(int X)
-{
-    private int _y;
-    
-    public C(C other)
-    {
-    }
-}";
+            var src1 = "record C(int X) { public int P { set { } } }";
+            var src2 = "record C(int X) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._y")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true)
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
                 },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void Record_AddField_WithInitializer()
+        public void Record_Property_Delete_Static()
         {
-            var src1 = "record C(int X) { }";
-            var src2 = "record C(int X) { private int _y = 1; }";
-            var syntaxMap = GetSyntaxMap(src1, src2);
+            var src1 = "record C(int X) { public static int P { get; set; } }";
+            var src2 = "record C(int X) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._y")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
                 },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void Record_AddField_WithExistingInitializer()
+        public void Record_Property_Delete_WithInitializer()
         {
-            var src1 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; }";
-            var src2 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; private int _z; }";
+            var src1 = @"
+record C(int X)
+{
+    public int Y { get; set; } = 1;
+
+    public C(bool b) : this(1) { }
+}";
+            var src2 = @"
+record C(int X)
+{
+    public C(bool b) : this(1) { }
+}";
 
             var edits = GetTopEdits(src1, src2);
             var syntaxMap = GetSyntaxMap(src1, src2);
@@ -3396,261 +3347,436 @@ public void Record_AddField_WithExistingInitializer()
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._z")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), syntaxMap[0]),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true),
                 },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
-        [Fact]
-        public void Record_AddField_WithInitializerAndExistingInitializer()
+        [Theory]
+        [InlineData("")]
+        [InlineData(" = 1;")]
+        [InlineData(" = X;")]
+        public void Record_Property_Delete_ReplacingCustomWithSynthesized_Auto(string initializer)
         {
-            var src1 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; }";
-            var src2 = "record C(int X) { private int _y = <N:0.0>1</N:0.0>; private int _z = 1; }";
+            var src1 = "record C(int X) { public int X { get; init; }" + initializer + " }";
+            var src2 = "record C(int X);";
 
             var edits = GetTopEdits(src1, src2);
-            var syntaxMap = GetSyntaxMap(src1, src2);
 
             edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_X")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_X")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Theory]
+        [InlineData("")]
+        [InlineData(" = 1;")]
+        [InlineData(" = X;")]
+        public void Record_Property_Delete_ReplacingCustomWithSynthesized_Auto_Partial(string initializer)
+        {
+            var srcA1 = "partial record C(int X);";
+            var srcB1 = "partial record C { public int X { get; init; }" + initializer + " }";
+
+            var srcA2 = "partial record C(int X);";
+            var srcB2 = "partial record C;";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C._z")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), syntaxMap[0]),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
-                },
-                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
+                    DocumentResults(),
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_X")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_X")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), partialType: "C", preserveLocalVariables: true)
+                        })
+                });
         }
 
-        [Fact]
-        public void Record_DeleteField()
+        [Theory]
+        [InlineData("get => 4; init => throw null;")]
+        [InlineData("get { return 4; } init { }")]
+        public void Record_Property_Delete_ReplacingCustomWithSynthesized_WithBody(string body)
         {
-            var src1 = "record C(int X) { private int _y; }";
-            var src2 = "record C(int X) { }";
+            var src1 = "record C(int X) { public int X { " + body + " } }";
+            var src2 = "record C(int X);";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.Delete, "record C", DeletedSymbolDisplay(FeaturesResources.field, "_y")));
+            // The property changes from custom property to field-backed auto-prop.
+            // Methods using backing field must be updated, unless they are explicitly declared.
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+
+            edits.VerifySemanticDiagnostics();
         }
 
-        [Fact]
-        public void Record_DeleteProperty_Primary()
+        [Theory]
+        [InlineData("PrintMembers", "protected virtual bool PrintMembers(System.Text.StringBuilder builder) => true;")]
+        [InlineData("GetHashCode", "public override int GetHashCode() => 1;")]
+        [InlineData(".ctor", "protected C(C original) {}")]
+        public void Record_Property_Delete_ReplacingCustomWithSynthesized_WithBodyAndMethod(string methodName, string methodImpl)
         {
-            var src1 = "record C(int X, int Y) { }";
-            var src2 = "record C(int X) { }";
+            var src1 = "record C(int X) { " + methodImpl + " public int X { get => 4; init => throw null; } }";
+            var src2 = "record C(int X) { " + methodImpl + " }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.Delete, "record C", DeletedSymbolDisplay(FeaturesResources.parameter, "int Y")));
+            // The property changes from custom property to field-backed auto-prop.
+            // Methods using backing field must be updated, unless they are explicitly declared.
+
+            var expectedEdits = new List<SemanticEditDescription>();
+
+            if (methodName != "PrintMembers")
+            {
+                expectedEdits.Add(SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")));
+            }
+
+            expectedEdits.Add(SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")));
+
+            if (methodName != "GetHashCode")
+            {
+                expectedEdits.Add(SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")));
+            }
+
+            if (methodName != ".ctor")
+            {
+                expectedEdits.Add(SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")));
+            }
+
+            expectedEdits.Add(SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod));
+            expectedEdits.Add(SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod));
+            expectedEdits.Add(SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+
+            edits.VerifySemantics(expectedEdits.ToArray());
+        }
+
+        [Theory]
+        [InlineData("get => 4; init => throw null;")]
+        [InlineData("get { return 4; } init { }")]
+        public void Record_Property_Delete_ReplacingCustomWithSynthesized_WithBody_Partial(string body)
+        {
+            var srcA1 = "partial record C(int X);";
+            var srcB1 = "partial record C { public int X { " + body + " } }";
+
+            var srcA2 = "partial record C(int X);";
+            var srcB2 = "partial record C;";
+
+            // The property changes from custom property to field-backed auto-prop.
+            // Methods using backing field must be updated, unless they are explicitly declared.
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(),
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), partialType : "C", preserveLocalVariables: true),
+                        })
+                });
         }
 
         [Fact]
-        public void Record_DeleteProperty_NotPrimary()
+        public void Record_Property_Delete_ReplacingCustomWithSynthesized_WithAttribute()
         {
-            var src1 = "record C(int X) { public int P { get; set; } }";
-            var src2 = "record C(int X) { }";
+            var src1 = "record C([property: System.Obsolete]int P) { public int P { get; init; } = P; }";
+            var src2 = "record C([property: System.Obsolete]int P) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
-                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true),
                 },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "int P", GetResource("property")) },
                 capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void Record_ImplementSynthesized_Property()
+        public void Record_Property_Delete_ReplacingCustomWithSynthesized_WithAttributeOnAccessor()
         {
-            var src1 = "record C(int X);";
-            var src2 = @"
-record C(int X)
-{
-    public int X { get; init; }
-}";
+            var src1 = "record C(int P) { public int P { get; [System.Obsolete] init; } = P; }";
+            var src2 = "record C(int P) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true));
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true),
+                },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
 
-            edits.VerifySemanticDiagnostics();
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "record C", GetResource("property setter", "P.init")) },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
-        [Fact]
-        public void Record_ImplementSynthesized_Property_WithBody()
+        [Theory]
+        [InlineData("get; set;")]
+        [InlineData("get; init;")]
+        [InlineData("get {} set {}")]
+        [InlineData("get;")]
+        public void Record_Property_Insert(string accessors)
         {
             var src1 = "record C(int X);";
-            var src2 = @"
-record C(int X)
-{
-    public int X
-    {
-        get
-        {
-            return 4;
-        }
-        init
-        {
-            throw null;
-        }
-    }
-}";
+            var src2 = "record C(int X) { public int Y { " + accessors + " } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C")));
-
-            edits.VerifySemanticDiagnostics();
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                },
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void Record_ImplementSynthesized_Property_WithExpressionBody()
+        public void Record_Property_Insert_WriteOnly()
         {
             var src1 = "record C(int X);";
-            var src2 = @"
-record C(int X)
-{
-    public int X { get => 4; init => throw null; }
-}";
+            var src2 = "record C(int X) { public int Y { set { } } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C")));
-
-            edits.VerifySemanticDiagnostics();
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y"))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void Record_ImplementSynthesized_Property_InitToSet()
+        public void Record_Property_Insert_Static()
         {
             var src1 = "record C(int X);";
+            var src2 = "record C(int X) { public static int Y { get; set; } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y"))
+                },
+                capabilities: EditAndContinueCapabilities.AddStaticFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Record_Property_Insert_WithInitializer()
+        {
+            var src1 = @"
+record C(int X)
+{
+    public C(bool b) : this(1) { }
+}";
             var src2 = @"
 record C(int X)
 {
-    public int X { get; set; }
+    public int Y { get; set; } = 1;
+
+    public C(bool b) : this(1) { }
 }";
 
             var edits = GetTopEdits(src1, src2);
+            var syntaxMap = GetSyntaxMap(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ImplementRecordParameterWithSet, "public int X", "X"));
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true),
+                },
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void Record_ImplementSynthesized_Property_MakeReadOnly()
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_WithSetter()
         {
             var src1 = "record C(int X);";
-            var src2 = @"
-record C(int X)
-{
-    public int X { get; }
-}";
+            var src2 = "record C(int X) { public int X { get; set; } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ImplementRecordParameterAsReadOnly, "public int X", "X"));
+                Diagnostic(RudeEditKind.AccessorKindUpdate, "set", GetResource("property setter")));
         }
 
         [Fact]
-        public void Record_UnImplementSynthesized_Property()
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_ReadOnly()
         {
-            var src1 = @"
-record C(int X)
-{
-    public int X { get; init; }
-}";
-            var src2 = "record C(int X);";
+            var src1 = "record C(int X);";
+            var src2 = "record C(int X) { public int X { get; } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true));
-
-            edits.VerifySemanticDiagnostics();
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_X"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_X")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true),
+                });
         }
 
         [Fact]
-        public void Record_UnImplementSynthesized_Property_WithExpressionBody()
+        public void Record_Property_Insert_NotPrimary_WithExplicitMembers()
         {
             var src1 = @"
 record C(int X)
 {
-    public int X { get => 4; init => throw null; }
+    protected virtual bool PrintMembers(System.Text.StringBuilder builder)
+    {
+        return false;
+    }
+
+    public override int GetHashCode()
+    {
+        return 0;
+    }
+
+    public virtual bool Equals(C other)
+    {
+        return false;
+    }
+
+    public C(C original)
+    {
+    }
+}";
+            var src2 = @"
+record C(int X)
+{
+    public int Y { get; set; }
+
+    protected virtual bool PrintMembers(System.Text.StringBuilder builder)
+    {
+        return false;
+    }
+
+    public override int GetHashCode()
+    {
+        return 0;
+    }
+
+    public virtual bool Equals(C other)
+    {
+        return false;
+    }
+
+    public C(C original)
+    {
+    }
 }";
-            var src2 = "record C(int X);";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C")));
-
-            edits.VerifySemanticDiagnostics();
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                },
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
-        [Fact]
-        public void Record_UnImplementSynthesized_Property_WithBody()
+        [Theory]
+        [InlineData("")]
+        [InlineData(" = 1;")]
+        [InlineData(" = X;")]
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_Auto(string initializer)
         {
-            var src1 = @"
-record C(int X)
-{
-    public int X { get { return 4; } init { } }
-}";
-            var src2 = "record C(int X);";
+            var src1 = "record C(int X);";
+            var src2 = "record C(int X) { public int X { get; init; } " + initializer + " }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
                 SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
                 SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C")));
+                SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_X")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_X")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
 
             edits.VerifySemanticDiagnostics();
         }
 
-        [Fact]
-        public void Record_ImplementSynthesized_Property_Partial()
+        [Theory]
+        [InlineData("")]
+        [InlineData(" = 1;")]
+        [InlineData(" = X;")]
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_Auto_Partial(string initializer)
         {
-            var srcA1 = @"partial record C(int X);";
-            var srcB1 = @"partial record C;";
-            var srcA2 = @"partial record C(int X);";
-            var srcB2 = @"
-partial record C
-{
-    public int X { get; init; }
-}";
+            var srcA1 = "partial record C(int X);";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C(int X);";
+            var srcB2 = "partial record C { public int X { get; init; }" + initializer + " }";
 
             EditAndContinueValidation.VerifySemantics(
                 new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
@@ -3660,57 +3786,49 @@ partial record C
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_X")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_X")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         })
                 });
         }
 
-        [Fact]
-        public void Record_UnImplementSynthesized_Property_Partial()
+        [Theory]
+        [InlineData("get => 4; init => throw null;")]
+        [InlineData("get { return 4; } init { }")]
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_WithBody(string body)
         {
-            var srcA1 = @"partial record C(int X);";
-            var srcB1 = @"
-partial record C
-{
-    public int X { get; init; }
-}";
-            var srcA2 = @"partial record C(int X);";
-            var srcB2 = @"partial record C;";
+            var src1 = "record C(int X);";
+            var src2 = "record C(int X) { public int X { " + body + " } }";
 
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
-                new[]
-                {
-                    DocumentResults(),
-                    DocumentResults(
-                        semanticEdits: new[]
-                        {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), partialType: "C", preserveLocalVariables: true)
-                        })
-                });
-        }
+            var edits = GetTopEdits(src1, src2);
 
-        [Fact]
-        public void Record_ImplementSynthesized_Property_Partial_WithBody()
-        {
-            var srcA1 = @"partial record C(int X);";
-            var srcB1 = @"partial record C;";
-            var srcA2 = @"partial record C(int X);";
-            var srcB2 = @"
-partial record C
-{
-    public int X
-    {
-        get
-        {
-            return 4;
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+
+            edits.VerifySemanticDiagnostics();
         }
-        init
+
+        [Theory]
+        [InlineData("get => 4; init => throw null;")]
+        [InlineData("get { return 4; } init { }")]
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_WithBody_Partial(string body)
         {
-            throw null;
-        }
-    }
-}";
+            var srcA1 = "partial record C(int X);";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C(int X);";
+            var srcB2 = "partial record C { public int X { " + body + " } }";
 
             EditAndContinueValidation.VerifySemantics(
                 new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
@@ -3721,78 +3839,79 @@ public int X
                         semanticEdits: new[]
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), partialType : "C", preserveLocalVariables: true),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         })
                 });
         }
 
         [Fact]
-        public void Record_UnImplementSynthesized_Property_Partial_WithBody()
-        {
-            var srcA1 = @"partial record C(int X);";
-            var srcB1 = @"
-partial record C
-{
-    public int X
-    {
-        get
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_WithAttribute()
         {
-            return 4;
+            var src1 = "record C([property: System.Obsolete]int P) { }";
+            var src2 = "record C([property: System.Obsolete]int P) { public int P { get; init; } = P; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true),
+                },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "public int P", GetResource("property")) },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
-        init
+
+        [Fact]
+        public void Record_Property_Insert_ReplacingSynthesizedWithCustom_WithAttributeOnAccessor()
         {
-            throw null;
-        }
-    }
-}";
-            var srcA2 = @"partial record C(int X);";
-            var srcB2 = @"partial record C;";
+            var src1 = "record C(int P) { }";
+            var src2 = "record C(int P) { public int P { get; [System.Obsolete] init; } = P; }";
 
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
                 new[]
                 {
-                    DocumentResults(),
-                    DocumentResults(
-                        semanticEdits: new[]
-                        {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMembers("Equals").OfType<IMethodSymbol>().First(m => SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType))),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").GetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.X").SetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), partialType : "C", preserveLocalVariables: true),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "C"))
-                        })
-                });
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true),
+                },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "init", GetResource("property setter")) },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void Record_MoveProperty_Partial()
+        public void Record_Property_DeleteInsert()
         {
-            var srcA1 = @"
-partial record C(int X)
-{
-    public int Y { get; init; }
-}";
-            var srcB1 = @"
-partial record C;
-";
-
-            var srcA2 = @"
-partial record C(int X);
-";
+            var srcA1 = "partial record C(int X) { public int Y { get; init; } }";
+            var srcB1 = "partial record C;";
 
-            var srcB2 = @"
-partial record C
-{
-    public int Y { get; init; }
-}";
+            var srcA2 = "partial record C(int X);";
+            var srcB2 = "partial record C { public int Y { get; init; } }";
 
             EditAndContinueValidation.VerifySemantics(
                 new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
@@ -3808,117 +3927,36 @@ partial record C
                 });
         }
 
+        #endregion
+
+        #region Enums
+
         [Fact]
-        public void Record_UnImplementSynthesized_Property_WithInitializer()
+        public void Enum_NoModifiers_Insert()
         {
-            var src1 = @"
-record C(int X)
-{
-    public int X { get; init; } = 1;
-}";
-            var src2 = "record C(int X);";
+            var src1 = "";
+            var src2 = "enum C { A }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true));
-
-            edits.VerifySemanticDiagnostics();
+            edits.VerifySemanticDiagnostics(
+                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
         }
 
         [Fact]
-        public void Record_UnImplementSynthesized_Property_WithInitializerMatchingCompilerGenerated()
+        public void Enum_NoModifiers_IntoNamespace_Insert()
         {
-            var src1 = @"
-record C(int X)
-{
-    public int X { get; init; } = X;
-}";
-            var src2 = "record C(int X);";
+            var src1 = "namespace N { }";
+            var src2 = "namespace N { enum C { } }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true));
-
-            edits.VerifySemanticDiagnostics();
+            edits.VerifySemanticDiagnostics(
+                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
         }
 
         [Fact]
-        public void Record_Property_Delete_NotPrimary()
-        {
-            var src1 = @"
-record C(int X)
-{
-    public int Y { get; init; }
-}";
-            var src2 = "record C(int X);";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemantics(
-                new[]
-                {
-                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
-                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
-                },
-                capabilities: EditAndContinueCapabilities.Baseline);
-        }
-
-        [Fact]
-        public void Record_PropertyInitializer_Update_NotPrimary()
-        {
-            var src1 = "record C { int X { get; } = 0; }";
-            var src2 = "record C { int X { get; } = 1; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters.Length == 0), preserveLocalVariables: true));
-        }
-
-        [Fact]
-        public void Record_PropertyInitializer_Update_Primary()
-        {
-            var src1 = "record C(int X) { int X { get; } = 0; }";
-            var src2 = "record C(int X) { int X { get; } = 1; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(c => c.Parameters[0].Type.ToDisplayString() == "int"), preserveLocalVariables: true));
-        }
-
-        #endregion
-
-        #region Enums
-
-        [Fact]
-        public void Enum_NoModifiers_Insert()
-        {
-            var src1 = "";
-            var src2 = "enum C { A }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
-        }
-
-        [Fact]
-        public void Enum_NoModifiers_IntoNamespace_Insert()
-        {
-            var src1 = "namespace N { }";
-            var src2 = "namespace N { enum C { } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
-        }
-
-        [Fact]
-        public void Enum_NoModifiers_IntoType_Insert()
+        public void Enum_NoModifiers_IntoType_Insert()
         {
             var src1 = "struct N { }";
             var src2 = "struct N { enum C { } }";
@@ -4045,10 +4083,10 @@ public void Enum_BaseType_Add()
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits("Update [enum Color { Red = 1, Blue = 2, }]@0 -> [enum Color : ushort { Red = 1, Blue = 2, }]@0");
+            edits.VerifyEdits("Insert [: ushort]@11");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.EnumUnderlyingTypeUpdate, "enum Color", FeaturesResources.enum_));
+                 Diagnostic(RudeEditKind.EnumUnderlyingTypeUpdate, "ushort", FeaturesResources.enum_));
         }
 
         [Fact]
@@ -4059,7 +4097,7 @@ public void Enum_BaseType_Add_Unchanged()
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits("Update [enum Color { Red = 1, Blue = 2, }]@0 -> [enum Color : int { Red = 1, Blue = 2, }]@0");
+            edits.VerifyEdits("Insert [: int]@11");
 
             edits.VerifySemantics();
         }
@@ -4072,10 +4110,10 @@ public void Enum_BaseType_Update()
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits("Update [enum Color : ushort { Red = 1, Blue = 2, }]@0 -> [enum Color : long { Red = 1, Blue = 2, }]@0");
+            edits.VerifyEdits("Update [: ushort]@11 -> [: long]@11");
 
             edits.VerifySemanticDiagnostics(
-                 Diagnostic(RudeEditKind.EnumUnderlyingTypeUpdate, "enum Color", FeaturesResources.enum_));
+                 Diagnostic(RudeEditKind.EnumUnderlyingTypeUpdate, "long", FeaturesResources.enum_));
         }
 
         [Fact]
@@ -4086,7 +4124,7 @@ public void Enum_BaseType_Delete_Unchanged()
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits("Update [enum Color : int { Red = 1, Blue = 2, }]@0 -> [enum Color { Red = 1, Blue = 2, }]@0");
+            edits.VerifyEdits("Delete [: int]@11");
 
             edits.VerifySemantics();
         }
@@ -4099,7 +4137,7 @@ public void Enum_BaseType_Delete_Changed()
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits("Update [enum Color : ushort { Red = 1, Blue = 2, }]@0 -> [enum Color { Red = 1, Blue = 2, }]@0");
+            edits.VerifyEdits("Delete [: ushort]@11");
 
             edits.VerifySemanticDiagnostics(
                  Diagnostic(RudeEditKind.EnumUnderlyingTypeUpdate, "enum Color", FeaturesResources.enum_));
@@ -4576,7 +4614,7 @@ public void Delegate_Parameter_Rename()
                 "Update [int a]@22 -> [int b]@22");
 
             edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.RenamingNotSupportedByRuntime, "int b", FeaturesResources.parameter) },
+                new[] { Diagnostic(RudeEditKind.RenamingNotSupportedByRuntime, "int b", GetResource("parameter", "int b")) },
                 capabilities: EditAndContinueCapabilities.Baseline);
 
             edits.VerifySemantics(
@@ -4600,25 +4638,7 @@ public void Delegate_Parameter_Update()
                 "Update [int a]@22 -> [byte a]@22");
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.TypeUpdate, "byte a", FeaturesResources.parameter));
-        }
-
-        [Fact]
-        public void Delegate_Parameter_AddAttribute_NotSupportedByRuntime()
-        {
-            var attribute = "public class AAttribute : System.Attribute { }\n\n";
-
-            var src1 = attribute + "public delegate int D(int a);";
-            var src2 = attribute + "public delegate int D([A]int a);";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [int a]@70 -> [[A]int a]@70");
-
-            edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "int a", FeaturesResources.parameter) },
-                capabilities: EditAndContinueCapabilities.Baseline);
+                Diagnostic(RudeEditKind.TypeUpdate, "byte a", GetResource("parameter", "byte a")));
         }
 
         [Fact]
@@ -4642,6 +4662,10 @@ public void Delegate_Parameter_AddAttribute()
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("D.BeginInvoke"))
                 },
                 capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "int a", GetResource("parameter", "int a")) },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
@@ -4870,7 +4894,7 @@ public void Delegate_ReadOnlyRef_Parameter_Update()
                 "Update [int b]@22 -> [in int b]@22");
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ModifiersUpdate, "in int b", FeaturesResources.parameter));
+                Diagnostic(RudeEditKind.ModifiersUpdate, "in int b", GetResource("parameter", "in int b")));
         }
 
         [Fact]
@@ -4908,6 +4932,87 @@ public void Delegate_ReadOnlyRef_ReturnType_Update()
 
         #region Nested Types
 
+        [Fact]
+        public void NestedType_Replace_WithUpdateInNestedType_Partial_DifferentDocument()
+        {
+            var srcA1 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]partial class C { int N() => 1; }";
+            var srcB1 = "partial class C { class D { int M() => 1; } }";
+            var srcA2 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]partial class C { int N() => 2; }";
+            var srcB2 = "partial class C { class D { int M() => 2; } }";
+
+            var editsA = GetTopEdits(srcA1, srcA2);
+            var editsB = GetTopEdits(srcB1, srcB2);
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { editsA, editsB },
+                new[]
+                {
+                    DocumentResults(semanticEdits: new[]
+                    {
+                        SemanticEdit(SemanticEditKind.Replace, c => c.GetMember("C"), partialType: "C")
+                    }),
+                    DocumentResults(semanticEdits: new[]
+                    {
+                        SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.D.M"))
+                    })
+                },
+                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
+        }
+
+        [Fact]
+        public void NestedType_Replace_WithUpdateInNestedType_Partial_SameDocument()
+        {
+            var src1 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]partial class C { int N() => 1; } partial class C { class D { int M() => 1; } }";
+            var src2 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]partial class C { int N() => 2; } partial class C { class D { int M() => 2; } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            EditAndContinueValidation.VerifySemantics(
+                edits,
+                semanticEdits: new[]
+                {
+                    SemanticEdit(SemanticEditKind.Replace, c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.D.M"))
+                },
+                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
+        }
+
+        [Fact]
+        public void NestedType_Replace_WithUpdateInNestedType()
+        {
+            var src1 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]class C { int N() => 1; class D { int M() => 1; } }";
+            var src2 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]class C { int N() => 2; class D { int M() => 2; } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            EditAndContinueValidation.VerifySemantics(
+                edits,
+                semanticEdits: new[]
+                {
+                    SemanticEdit(SemanticEditKind.Replace, c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.D.M"))
+                },
+                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
+        }
+
+        [Fact]
+        public void NestedType_Update_WithUpdateInNestedType()
+        {
+            var src1 = @"[System.Obsolete(""A"")]class C { int N() => 1; class D { int M() => 1; } }";
+            var src2 = @"[System.Obsolete(""B"")]class C { int N() => 1; class D { int M() => 2; } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            EditAndContinueValidation.VerifySemantics(
+                edits,
+                semanticEdits: new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.D.M"))
+                },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+        }
+
         [Fact]
         public void NestedType_Move_Sideways()
         {
@@ -5511,7 +5616,7 @@ public void NestedDelegateInPartialType_InsertDeleteAndChangeOptionalParameterVa
                     DocumentResults(
                         diagnostics: new[]
                         {
-                            Diagnostic(RudeEditKind.InitializerUpdate, "int x = 2", FeaturesResources.parameter)
+                            Diagnostic(RudeEditKind.InitializerUpdate, "int x = 2", GetResource("parameter", "int x"))
                         }),
 
                     DocumentResults()
@@ -6802,7 +6907,7 @@ public void PartialMember_DeleteInsert_AddFieldInitializer()
                     DocumentResults(),
                     DocumentResults(semanticEdits: new[]
                     {
-                        SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                        SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                     })
                 });
         }
@@ -6823,7 +6928,7 @@ public void PartialMember_DeleteInsert_RemoveFieldInitializer()
                     DocumentResults(),
                     DocumentResults(semanticEdits: new[]
                     {
-                        SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                        SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                     })
                 });
         }
@@ -7263,34 +7368,6 @@ class C
                 new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Main"), preserveLocalVariables: false) });
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
-        public void MethodWithExpressionBody_Update_LiftedParameter()
-        {
-            var src1 = @"
-using System;
-
-class C
-{
-    int M(int a) => new Func<int>(() => a + 1)();
-}
-";
-            var src2 = @"
-using System;
-
-class C
-{
-    int M(int a) => new Func<int>(() => 2)();   // not capturing a anymore
-}";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [int M(int a) => new Func<int>(() => a + 1)();]@35 -> [int M(int a) => new Func<int>(() => 2)();]@35");
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a", "a"));
-        }
-
         [Fact]
         public void MethodWithExpressionBody_ToBlockBody()
         {
@@ -8082,7 +8159,7 @@ static void Main()
                 capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
 
             edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "static void Main()", DeletedSymbolDisplay(FeaturesResources.parameter, "string[] args")) },
+                new[] { Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "static void Main()", GetResource("parameter", "args", "method", "Main(string[] args)")) },
                 capabilities: EditAndContinueCapabilities.Baseline);
         }
 
@@ -8116,8 +8193,8 @@ void M(int a)
             edits.VerifySemanticDiagnostics(
                 new[]
                 {
-                    Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "void M(int a)", DeletedSymbolDisplay(FeaturesResources.parameter, "int b")),
-                    Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "void M(int a)", DeletedSymbolDisplay(FeaturesResources.parameter, "int c"))
+                    Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "void M(int a)", GetResource("parameter", "b", "method", "M(int a, int b, int c)")),
+                    Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "void M(int a)", GetResource("parameter", "c", "method", "M(int a, int b, int c)"))
                 },
                 capabilities: EditAndContinueCapabilities.Baseline);
         }
@@ -10032,36 +10109,16 @@ public void Operator_Delete()
 
         #endregion
 
-        #region Constructor, Destructor
+        #region Constructor
 
         [Fact]
         public void Constructor_Parameter_AddAttribute()
         {
-            var src1 = @"
-class C
-{
-    private int x = 1;
-
-    public C(int a)
-    {
-    }
-}";
-            var src2 = @"
-class C
-{
-    private int x = 2;
-
-    public C([System.Obsolete]int a)
-    {
-    }
-}";
+            var src1 = "class C { public C(int a) { } }";
+            var src2 = "class C { public C([System.Obsolete]int a) { } }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits(
-                "Update [x = 1]@30 -> [x = 2]@30",
-                "Update [int a]@53 -> [[System.Obsolete]int a]@53");
-
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
                 new[]
@@ -10072,413 +10129,1628 @@ public C([System.Obsolete]int a)
         }
 
         [Fact]
-        public void Constructor_ChangeParameterType()
+        public void Constructor_Parameter_AddAttribute_Primary()
         {
-            var src1 = @"
-class C
-{
-    public C(bool x)
-    {
-    }
-}";
-            var src2 = @"
-class C
-{
-    public C(int x)
-    {
-    }
-}";
+            var src1 = "class C(int a);";
+            var src2 = "class C([System.Obsolete] int a);";
+
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMembers("C..ctor").FirstOrDefault(m => m.GetParameterTypes().Any(t => t.SpecialType == SpecialType.System_Boolean))?.ISymbol, deletedSymbolContainerProvider: c => c.GetMember("C")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMembers("C..ctor").FirstOrDefault(m => m.GetParameterTypes().Any(t => t.SpecialType == SpecialType.System_Int32))?.ISymbol)
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C..ctor"))
                 },
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
-
-            edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.ChangingTypeNotSupportedByRuntime, "int x", FeaturesResources.parameter) },
-                capabilities: EditAndContinueCapabilities.Baseline);
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/2068")]
-        public void Constructor_ExternModifier_Add()
+        [Theory]
+        [InlineData("")]
+        [InlineData("param:")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68458")]
+        public void Constructor_Parameter_AddAttribute_Record(string target)
         {
-            var src1 = "class C { }";
-            var src2 = "class C { public extern C(); }";
+            var src1 = "record C(int P);" + s_attributeSource;
+            var src2 = "record C([" + target + "A]int P);" + s_attributeSource;
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits(
-                "Insert [public extern C();]@10",
-                "Insert [()]@25");
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+        }
+
+        [Theory]
+        [InlineData("class")]
+        [InlineData("struct")]
+        [InlineData("record")]
+        [InlineData("record struct")]
+        public void Constructor_Parameter_DefaultValue_Primary(string keyword)
+        {
+            var src1 = keyword + " C(int X = 1) : D {  }";
+            var src2 = keyword + " C(int X = 2) : D {  }";
+
+            var edits = GetTopEdits(src1, src2);
 
-            // This can be allowed as the compiler generates an empty constructor, but it's not worth the complexity.
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ModifiersUpdate, "public extern C()", FeaturesResources.constructor));
+                Diagnostic(RudeEditKind.InitializerUpdate, "int X = 2", GetResource("parameter")));
         }
 
-        [Fact]
-        public void ConstructorInitializer_Update1()
+        [Theory(Skip = "https://github.com/dotnet/roslyn/issues/68458")]
+        [InlineData("field")]
+        [InlineData("property")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68458")]
+        public void Constructor_Parameter_AddAttribute_Record_NonParamTargets(string target)
         {
-            var src1 = @"
-class C
-{
-    public C(int a) : base(a) { }
-}";
-            var src2 = @"
-class C
-{
-    public C(int a) : base(a + 1) { }
-}";
-            var edits = GetTopEdits(src1, src2);
+            var src1 = "record C(int P);" + s_attributeSource;
+            var src2 = "record C([" + target + ": A]int P);" + s_attributeSource;
 
-            edits.VerifyEdits(
-                "Update [public C(int a) : base(a) { }]@18 -> [public C(int a) : base(a + 1) { }]@18");
+            var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics();
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.P")),
+                },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
         }
 
         [Fact]
-        public void ConstructorInitializer_Update2()
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68458")]
+        public void Constructor_Parameter_AddAttribute_Record_ReplacingSynthesizedWithCustomProperty()
         {
-            var src1 = @"
-class C<T>
-{
-    public C(int a) : base(a) { }
-}";
-            var src2 = @"
-class C<T>
-{
-    public C(int a) { }
-}";
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [public C(int a) : base(a) { }]@21 -> [public C(int a) { }]@21");
+            var src1 = "record C(int P) { }" + s_attributeSource;
+            var src2 = "record C([property: A][field: A][param: A]int P) { public int P { get; init; } }" + s_attributeSource;
 
-            edits.VerifySemanticDiagnostics(
-                new[]
-                {
-                    Diagnostic(RudeEditKind.UpdatingGenericNotSupportedByRuntime, "public C(int a)", GetResource("constructor"))
-                },
-                capabilities: EditAndContinueCapabilities.Baseline);
+            var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
+                    // TOOD: Should include update of P: https://github.com/dotnet/roslyn/issues/68458
                 },
-                capabilities: EditAndContinueCapabilities.Baseline | EditAndContinueCapabilities.GenericUpdateMethod);
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
         }
 
         [Fact]
-        public void ConstructorInitializer_Update3()
+        public void Constructor_Parameter_AddAttribute_Record_ReplacingCustomPropertyWithSynthesized()
         {
-            var src1 = @"
-class C
-{
-    public C(int a) { }
-}";
-            var src2 = @"
-class C
-{
-    public C(int a) : base(a) { }
-}";
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [public C(int a) { }]@18 -> [public C(int a) : base(a) { }]@18");
+            var src1 = "record C(int P) { public int P { get; init; } }" + s_attributeSource;
+            var src2 = "record C([property: A][field: A][param: A]int P) {} " + s_attributeSource;
 
-            edits.VerifySemanticDiagnostics();
-        }
-
-        [Fact]
-        public void ConstructorInitializer_Update4()
-        {
-            var src1 = @"
-class C<T>
-{
-    public C(int a) : base(a) { }
-}";
-            var src2 = @"
-class C<T>
-{
-    public C(int a) : base(a + 1) { }
-}";
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits(
-                "Update [public C(int a) : base(a) { }]@21 -> [public C(int a) : base(a + 1) { }]@21");
-
-            edits.VerifySemanticDiagnostics(
-                new[]
-                {
-                    Diagnostic(RudeEditKind.UpdatingGenericNotSupportedByRuntime, "public C(int a)", GetResource("constructor"))
-                },
-                capabilities: EditAndContinueCapabilities.Baseline);
-
             edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
                 },
-                capabilities: EditAndContinueCapabilities.Baseline | EditAndContinueCapabilities.GenericUpdateMethod);
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
         }
 
-        [Fact, WorkItem("http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/743552")]
-        public void ConstructorUpdate_AddParameter()
+        [Fact]
+        public void Constructor_Parameter_ChangeType()
         {
-            var src1 = @"
-class C
-{
-    public C(int a) { }
-}";
-            var src2 = @"
-class C
-{
-    public C(int a, int b) { }
-}";
+            var src1 = "class C { public C(bool x) { } }";
+            var src2 = "class C { public C(int x) { } }";
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits(
-                "Update [(int a)]@26 -> [(int a, int b)]@26",
-                "Insert [int b]@34");
-
             edits.VerifySemantics(
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMembers("C..ctor").FirstOrDefault(m => m.GetParameterCount() == 1)?.ISymbol, deletedSymbolContainerProvider: c => c.GetMember("C")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMembers("C..ctor").FirstOrDefault(m => m.GetParameterCount() == 2)?.ISymbol)
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single())
                 },
                 capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
 
             edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.InsertNotSupportedByRuntime, "int b", FeaturesResources.parameter) },
+                new[] { Diagnostic(RudeEditKind.ChangingTypeNotSupportedByRuntime, "int x", FeaturesResources.parameter) },
                 capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void DestructorDelete()
+        public void Constructor_Parameter_ChangeType_Primary()
         {
-            var src1 = @"class B { ~B() { } }";
-            var src2 = @"class B { }";
-
-            var expectedEdit1 = @"Delete [~B() { }]@10";
-
+            var src1 = @"class C(bool x);";
+            var src2 = @"class C(int x);";
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits(expectedEdit1);
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C"))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, "class B", DeletedSymbolDisplay(CSharpFeaturesResources.destructor, "~B()")));
+                new[] { Diagnostic(RudeEditKind.ChangingTypeNotSupportedByRuntime, "int x", FeaturesResources.parameter) },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void DestructorDelete_InsertConstructor()
+        public void Constructor_Parameter_ChangeType_Primary_PartialMove()
         {
-            var src1 = @"class B { ~B() { } }";
-            var src2 = @"class B { B() { } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Insert [B() { }]@10",
-                "Insert [()]@11",
-                "Delete [~B() { }]@10");
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, "B()", FeaturesResources.constructor),
-                Diagnostic(RudeEditKind.Delete, "class B", DeletedSymbolDisplay(CSharpFeaturesResources.destructor, "~B()")));
-        }
+            var srcA1 = "partial class C(bool a);";
+            var srcB1 = "partial class C;";
 
-        [Fact, WorkItem("http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/789577")]
-        public void ConstructorUpdate_AnonymousTypeInFieldInitializer()
-        {
-            var src1 = "class C { int a = F(new { A = 1, B = 2 }); C() { x = 1; } }";
-            var src2 = "class C { int a = F(new { A = 1, B = 2 }); C() { x = 2; } }";
+            var srcA2 = "partial class C;";
+            var srcB2 = "partial class C(int a);";
 
-            var edits = GetTopEdits(src1, src2);
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                        }),
 
-            edits.VerifySemanticDiagnostics();
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C"))
+                        }),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void Constructor_Delete()
+        public void Constructor_Parameter_ChangeType_Record()
         {
-            var src1 = "class C { public C(int x) { } }";
-            var src2 = "class C { }";
-
+            var src1 = @"record C(bool x);";
+            var src2 = @"record C(int x);";
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                new[] { SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.FirstOrDefault(c => c.Parameters.Length == 1), deletedSymbolContainerProvider: c => c.GetMember("C")) },
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_x"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMembers<IMethodSymbol>("C.set_x").FirstOrDefault(p => p.Parameters is [{ Type.SpecialType: SpecialType.System_Boolean }]), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.x")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingTypeNotSupportedByRuntime, "int x", FeaturesResources.parameter) },
                 capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void Constructor_Static_Delete()
+        public void Constructor_Parameter_ChangeType_ReplacingClassWithRecord()
         {
-            var src1 = "class C { static C() { } }";
-            var src2 = "class C { }";
-
+            var src1 = @"class C(bool x);";
+            var src2 = @"record C(int x);";
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, "class C", DeletedSymbolDisplay(FeaturesResources.static_constructor, "C()")));
+                new[]
+                {
+                    Diagnostic(RudeEditKind.TypeKindUpdate, "record C")
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void Constructor_Static_Delete_Reloadable()
+        public void Constructor_Parameter_Delete()
         {
-            var src1 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]class C { static C() { } }";
-            var src2 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]class C { }";
+            var src1 = "class C { C(int x, int y) { } }";
+            var src2 = "class C { C(int x) { } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                new[] { SemanticEdit(SemanticEditKind.Replace, c => c.GetMember("C")) },
-                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single()),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void Constructor_Static_Insert()
+        public void Constructor_Parameter_Delete_Primary()
         {
-            var src1 = "class C { }";
-            var src2 = "class C { static C() { } }";
+            var src1 = "class C(int x, int y) { }";
+            var src2 = "class C(int x) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                new[] { SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").StaticConstructors.Single()) },
-                EditAndContinueCapabilities.AddMethodToExistingType);
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void InstanceCtorDelete_Public()
+        public void Constructor_Parameter_Delete_Primary_Record()
         {
-            var src1 = "class C { public C() { } }";
-            var src2 = "class C { }";
+            var src1 = "record C(int X, int Y) { }";
+            var src2 = "record C(int X) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true));
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
-        [Theory]
-        [InlineData("")]
-        [InlineData("private")]
-        [InlineData("protected")]
-        [InlineData("internal")]
-        [InlineData("private protected")]
-        [InlineData("protected internal")]
-        public void InstanceCtorDelete_NonPublic(string accessibility)
+        [Fact]
+        public void Constructor_Parameter_Delete_Primary_Record_ReplacingSynthesizedWithCustomProperty()
         {
-            var src1 = "class C { [System.Obsolete] " + accessibility + " C() { } }";
-            var src2 = "class C { }";
+            var src1 = "record C(int X, int Y) { }";
+            var src2 = "record C(int X) { public int Y { get; init; } }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
+            edits.VerifySemantics(
                 new[]
                 {
-                    Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "class C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()")),
-                    Diagnostic(RudeEditKind.ChangingAccessibility, "class C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()"))
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_Y")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_Y")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
                 },
-                capabilities: EditAndContinueCapabilities.Baseline);
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void InstanceCtorDelete_Public_PartialWithInitializerUpdate()
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomProperty_WithUpdate()
         {
-            var srcA1 = "partial class C { public C() { } }";
-            var srcB1 = "partial class C { int x = 1; }";
+            var src1 = "record C(int X, int Y) {           public int Y { get; init; } }";
+            var src2 = "record C(int X       ) { [Obsolete]public int Y { get; init; } }";
 
-            var srcA2 = "partial class C { }";
-            var srcB2 = "partial class C { int x = 2; }";
+            var edits = GetTopEdits(src1, src2);
 
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+            edits.VerifySemantics(
                 new[]
                 {
-                    DocumentResults(
-                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true) }),
-
-                    DocumentResults(
-                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true) })
-                });
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType | EditAndContinueCapabilities.ChangeCustomAttributes);
         }
 
         [Fact]
-        public void InstanceCtorInsert_Public_Implicit()
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomProperty_WithAccessorUpdate()
         {
-            var src1 = "class C { }";
-            var src2 = "class C { public C() { } }";
+            var src1 = "record C(int X, int Y) { public int Y { get => new System.Func<int>(<N:0.0>() => 1</N:0.0>).Invoke(); init { } } }";
+            var src2 = "record C(int X       ) { public int Y { get => new System.Func<int>(<N:0.0>() => 2</N:0.0>).Invoke(); init { } } }";
 
             var edits = GetTopEdits(src1, src2);
+            var syntaxMap = GetSyntaxMap(src1, src2);
 
             edits.VerifySemantics(
-                ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_Y"), syntaxMap: syntaxMap[0]),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void InstanceCtorInsert_Partial_Public_Implicit()
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomField_WithUpdate()
         {
-            var srcA1 = "partial class C { }";
-            var srcB1 = "partial class C { }";
+            var src1 = "record C(int X, int Y) {           public int Y; }";
+            var src2 = "record C(int X       ) { [Obsolete]public int Y; }";
 
-            var srcA2 = "partial class C { }";
-            var srcB2 = "partial class C { public C() { } }";
+            var edits = GetTopEdits(src1, src2);
 
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+            edits.VerifySemantics(
                 new[]
                 {
-                    // no change in document A
-                    DocumentResults(),
-
-                    DocumentResults(
-                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true) }),
-                });
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType | EditAndContinueCapabilities.ChangeCustomAttributes);
         }
 
         [Fact]
-        public void InstanceCtorInsert_Public_NoImplicit()
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomPropertyDelete()
         {
-            var src1 = "class C { public C(int a) { } }";
-            var src2 = "class C { public C(int a) { } public C() { } }";
+            var src1 = "record C(int X, int Y) { public int Y { get => 0; init {} } }";
+            var src2 = "record C(int X       ) { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                semanticEdits: new[]
+                new[]
                 {
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters.IsEmpty))
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
                 },
                 capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void InstanceCtorInsert_Partial_Public_NoImplicit()
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomDeconstructor_NoUpdate()
         {
-            var srcA1 = "partial class C { }";
-            var srcB1 = "partial class C { public C(int a) { } }";
+            var src1 = "record C(int X, int Y) { public void Deconstruct(out int X) => X = 1; }";
+            var src2 = "record C(int X       ) { public void Deconstruct(out int X) => X = 1; }";
 
-            var srcA2 = "partial class C { public C() { } }";
-            var srcB2 = "partial class C { public C(int a) { } }";
+            var edits = GetTopEdits(src1, src2);
 
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomDeconstructor_Update()
+        {
+            var src1 = "record C(int X, int Y) { public void Deconstruct(out int X) => X = 1; }";
+            var src2 = "record C(int X       ) { public void Deconstruct(out int X) => X = 2; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMembers<IMethodSymbol>("C.Deconstruct").Single(m => m.Parameters is [_])),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomDeconstructor_Insert()
+        {
+            var src1 = "record C(int X, int Y) { }";
+            var src2 = "record C(int X       ) { public void Deconstruct(out int X) => X = 1; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Delete_Primary_Record_WithCustomDeconstructor_Delete()
+        {
+            var src1 = "record C(int X, int Y) { public void Deconstruct(out int X, out int Y) => X = Y = 1; }";
+            var src2 = "record C(int X       ) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_Y"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact, WorkItem("http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/743552")]
+        public void Constructor_Parameter_Insert()
+        {
+            var src1 = "class C { public C(int a) { } }";
+            var src2 = "class C { public C(int a, int b) { } }";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [(int a)]@18 -> [(int a, int b)]@18",
+                "Insert [int b]@26");
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single())
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.InsertNotSupportedByRuntime, "int b", FeaturesResources.parameter) },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_Primary()
+        {
+            var src1 = "class C(int a) { }";
+            var src2 = "class C(int a, int b) { }";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [(int a)]@7 -> [(int a, int b)]@7",
+                "Insert [int b]@15");
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C"))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.InsertNotSupportedByRuntime, "int b", FeaturesResources.parameter) },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_Primary_Record()
+        {
+            var src1 = "record C(int X) { }";
+            var src2 = "record C(int X, int Y, int Z, int U) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Z")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.U")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_In()
+        {
+            var src1 = "class C { C() => throw null; }";
+            var src2 = "class C { C(in int b) => throw null; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Insert [in int b]@12");
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetParameterlessConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single())
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.InsertNotSupportedByRuntime, "in int b", FeaturesResources.parameter) },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_Primary_Record_WithCustomDeconstructor_NoUpdate1()
+        {
+            var src1 = "record C(int X       ) { public void Deconstruct(out int X) => X = 1; }";
+            var src2 = "record C(int X, int Y) { public void Deconstruct(out int X) => X = 1; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_Primary_Record_WithCustomDeconstructor_NoUpdate2()
+        {
+            var src1 = "record C(int X       ) { public void Deconstruct(out int X, out int Y) => X = Y = 1; }";
+            var src2 = "record C(int X, int Y) { public void Deconstruct(out int X, out int Y) => X = Y = 1; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_Primary_Record_WithCustomDeconstructor_Update()
+        {
+            var src1 = "record C(int X       ) { public void Deconstruct(out int X, out int Y) => X = Y = 1; }";
+            var src2 = "record C(int X, int Y) { public void Deconstruct(out int X, out int Y) => X = Y = 2; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMembers<IMethodSymbol>("C.Deconstruct").Single(m => m.Parameters is [_, _])),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_Primary_Record_WithCustomDeconstructor_Insert()
+        {
+            var src1 = "record C(int X       ) { }";
+            var src2 = "record C(int X, int Y) { public void Deconstruct(out int X, out int Y) => X = Y = 1; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Insert_Primary_Record_WithCustomDeconstructor_Delete()
+        {
+            var src1 = "record C(int X       ) { public void Deconstruct(out int X) => X = 1; }";
+            var src2 = "record C(int X, int Y) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.Y")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_Update_In()
+        {
+            var src1 = "class Test { Test(int b) => throw null; }";
+            var src2 = "class Test { Test(in int b) => throw null; }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [int b]@18 -> [in int b]@18");
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ModifiersUpdate, "in int b", FeaturesResources.parameter));
+        }
+
+        [Theory]
+        [InlineData("class")]
+        [InlineData("struct")]
+        [InlineData("record")]
+        [InlineData("record struct")]
+        public void Constructor_Parameter_DeleteInsert_Primary(string keyword)
+        {
+            var srcA1 = "partial " + keyword + " C(int P);";
+            var srcB1 = "partial " + keyword + " C;";
+
+            var srcA2 = "partial " + keyword + " C;";
+            var srcB2 = "partial " + keyword + " C(int P);";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), partialType: "C", preserveLocalVariables: true)
+                        }),
+                });
+        }
+
+        [Theory]
+        [InlineData("class")]
+        [InlineData("struct")]
+        public void Constructor_Parameter_DeleteInsert_ReplacingPrimaryWithNonPrimary(string keyword)
+        {
+            var srcA1 = "partial " + keyword + " C(int a);";
+            var srcB1 = "partial " + keyword + " C;";
+
+            var srcA2 = "partial " + keyword + " C;";
+            var srcB2 = "partial " + keyword + " C { public C(int a) { } }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "a"}]), partialType: "C", preserveLocalVariables: true)
+                        }),
+                });
+        }
+
+        [Fact]
+        public void Constructor_Parameter_DeleteInsert_ReplacingPrimaryWithNonPrimary_Record()
+        {
+            var srcA1 = "partial record C(int P);";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C;";
+            var srcB2 = "partial record C { public int P { get; init; } public C(int P) { } public void Deconstruct(out int P) { P = this.P; } }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Deconstruct")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "P"}]), partialType: "C", preserveLocalVariables: true),
+                        }),
+                });
+        }
+
+        [Fact]
+        public void Constructor_Parameter_DeleteInsert_ReplacingNonPrimaryWithPrimary_Record()
+        {
+            var srcA1 = "partial record C { public int P { get; init; } public C(int P) { } public void Deconstruct(out int P) { P = this.P; } }";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C;";
+            var srcB2 = "partial record C(int P);";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "P" }]), partialType: "C", preserveLocalVariables: true),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Deconstruct")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                        }),
+                });
+        }
+
+        [Fact]
+        public void Constructor_Parameter_DeleteInsert_ReplacingNonPrimaryWithPrimary_WithExplicitPropertyAdded_Record()
+        {
+            var srcA1 = "partial record C        { public int P { get; init; } public C(int P) { } public void Deconstruct(out int P) { P = this.P; } }";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C;";
+            var srcB2 = "partial record C(int P) { public int P { get; init; } }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.get_P")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.set_P")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "P" }]), partialType: "C", preserveLocalVariables: true),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Deconstruct")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                        }),
+                });
+        }
+
+        [Fact]
+        public void Constructor_Parameter_DeleteInsert_ReplacingNonPrimaryWithPrimary_WithExplicitFieldAdded_Record()
+        {
+            var srcA1 = "partial record C { public int P { get; init; } public C(int P) { } public void Deconstruct(out int P) { P = this.P; } }";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C;";
+            var srcB2 = "partial record C(int P) { public int P; }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                            SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                        }),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                            SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.P")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.Parameters is [{ Name: "P" }]), partialType: "C", preserveLocalVariables: true),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.Deconstruct")),
+                        }),
+                },
+                capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Parameter_DeleteInsert_SwappingNonPrimaryWithPrimary_Record()
+        {
+            var srcA1 = "partial record C(int P) { public C() : this(1) { } }";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C;";
+            var srcB2 = "partial record C() { public C(int P) : this() { } }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.Parameters is [{ Name: "P" }])),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.Parameters is []), partialType: "C", preserveLocalVariables: true),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C"))
+                        }),
+                });
+        }
+
+        [Fact]
+        public void Constructor_Parameter_DeleteInsert_ReplacingPropertyWithField_Record()
+        {
+            var srcA1 = "partial record C(int P) { public int P { get; init; } }";
+            var srcB1 = "partial record C;";
+
+            var srcA2 = "partial record C;";
+            var srcB2 = "partial record C(int P) { public int P; }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                            SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_P"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                        }),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                            SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.P")),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), partialType: "C", preserveLocalVariables: true),
+                        }),
+                }, capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Theory(Skip = "https://github.com/dotnet/roslyn/issues/68458")]
+        [CombinatorialData]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68458")]
+        public void Constructor_Instance_Update_Primary_Attributes(
+            [CombinatorialValues("class", "struct", "record", "record struct")] string keyword)
+        {
+            var src1 = keyword + " C() { }";
+            var src2 = "[method: System.Obsolete] " + keyword + " C() { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Constructor_Instance_Update_Initializer_Update()
+        {
+            var src1 = @"
+class C
+{
+    public C(int a) : base(a) { }
+}";
+            var src2 = @"
+class C
+{
+    public C(int a) : base(a + 1) { }
+}";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [public C(int a) : base(a) { }]@18 -> [public C(int a) : base(a + 1) { }]@18");
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Constructor_Instance_Update_Initializer_Update_Generic()
+        {
+            var src1 = @"
+class C<T>
+{
+    public C(int a) : base(a) { }
+}";
+            var src2 = @"
+class C<T>
+{
+    public C(int a) : base(a + 1) { }
+}";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [public C(int a) : base(a) { }]@21 -> [public C(int a) : base(a + 1) { }]@21");
+
+            edits.VerifySemanticDiagnostics(
+                new[]
+                {
+                    Diagnostic(RudeEditKind.UpdatingGenericNotSupportedByRuntime, "public C(int a)", GetResource("constructor"))
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                },
+                capabilities: EditAndContinueCapabilities.Baseline | EditAndContinueCapabilities.GenericUpdateMethod);
+        }
+
+        [Theory]
+        [InlineData("class")]
+        [InlineData("record")]
+        public void Constructor_Instance_Update_Initializer_Update_Primary(string keyword)
+        {
+            var src1 = keyword + " C(int a) : D(a);";
+            var src2 = keyword + " C(int a) : D(a + 1);";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Theory]
+        [InlineData("class")]
+        [InlineData("record")]
+        public void Constructor_Instance_Update_Initializer_Update_Primary_WithInterface(string keyword)
+        {
+            var src1 = keyword + " C(int a) : D(a), I;";
+            var src2 = keyword + " C(int a) : D(a + 1), I;";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Constructor_Instance_Update_Initializer_Delete()
+        {
+            var src1 = @"
+class C<T>
+{
+    public C(int a) : base(a) { }
+}";
+            var src2 = @"
+class C<T>
+{
+    public C(int a) { }
+}";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [public C(int a) : base(a) { }]@21 -> [public C(int a) { }]@21");
+
+            edits.VerifySemanticDiagnostics(
+                new[]
+                {
+                    Diagnostic(RudeEditKind.UpdatingGenericNotSupportedByRuntime, "public C(int a)", GetResource("constructor"))
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                },
+                capabilities: EditAndContinueCapabilities.Baseline | EditAndContinueCapabilities.GenericUpdateMethod);
+        }
+
+        [Theory]
+        [InlineData("class ")]
+        [InlineData("record")]
+        public void Constructor_Instance_Update_Initializer_Delete_Primary(string keyword)
+        {
+            var src1 = keyword + " C(int a) : D(a);";
+            var src2 = keyword + " C(int a) : D;";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [: D(a)]@16 -> [: D]@16",
+                "Delete [D(a)]@18");
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Constructor_Instance_Update_Initializer_Insert()
+        {
+            var src1 = @"
+class C
+{
+    public C(int a) { }
+}";
+            var src2 = @"
+class C
+{
+    public C(int a) : base(a) { }
+}";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [public C(int a) { }]@18 -> [public C(int a) : base(a) { }]@18");
+
+            edits.VerifySemanticDiagnostics();
+        }
+
+        [Theory]
+        [InlineData("class ")]
+        [InlineData("record")]
+        public void Constructor_Instance_Update_Initializer_Insert_Primary(string keyword)
+        {
+            var src1 = keyword + " C(int a) : D;";
+            var src2 = keyword + " C(int a) : D(a);";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [: D]@16 -> [: D(a)]@16",
+                "Insert [D(a)]@18");
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        public void Constructor_Instance_Update_Initializer_StackAlloc()
+        {
+            var src1 = "class C { C() : this(stackalloc int[1]) {} C(Span<int> span) {} }";
+            var src2 = "class C { C() : this(stackalloc int[2]) {} C(Span<int> span) {} }";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.StackAllocUpdate, "stackalloc", FeaturesResources.constructor));
+        }
+
+        [Fact]
+        public void Constructor_Instance_Update_AnonymousTypeInFieldInitializer()
+        {
+            var src1 = "class C { int a = F(new { A = 1, B = 2 }); C() { x = 1; } }";
+            var src2 = "class C { int a = F(new { A = 1, B = 2 }); C() { x = 2; } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Theory]
+        [InlineData("class ")]
+        [InlineData("record")]
+        public void Constructor_Instance_Update_AnonymousTypeInFieldInitializer_Primary(string keyword)
+        {
+            var src1 = keyword + " C() : D(1) { int a = F(new { A = 1, B = 2 }); }";
+            var src2 = keyword + " C() : D(2) { int a = F(new { A = 1, B = 2 }); }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Update [D(1)]@13 -> [D(2)]@13");
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
+        public void Constructor_Instance_Update_BlockBodyToExpressionBody()
+        {
+            var src1 = @"
+public class C
+{
+    private int _value;
+
+    public C(int value) { _value = value; }
+}
+";
+            var src2 = @"
+public class C
+{
+    private int _value;
+
+    public C(int value) => _value = value;
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits("Update [public C(int value) { _value = value; }]@52 -> [public C(int value) => _value = value;]@52");
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                });
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
+        public void Constructor_Instance_Update_BlockBodyToExpressionBody_WithInitializer()
+        {
+            var src1 = @"
+public class B { B(int value) {} }
+public class C : B
+{
+    private int _value;
+    public C(int value) : base(value) { _value = value; }
+}
+";
+            var src2 = @"
+public class B { B(int value) {} }
+public class C : B
+{
+    private int _value;
+    public C(int value) : base(value) => _value = value;
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits("Update [public C(int value) : base(value) { _value = value; }]@90 -> [public C(int value) : base(value) => _value = value;]@90");
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                });
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
+        public void Constructor_Instance_Update_ExpressionBodyToBlockBody()
+        {
+            var src1 = @"
+public class C
+{
+    private int _value;
+
+    public C(int value) => _value = value;
+}
+";
+            var src2 = @"
+public class C
+{
+    private int _value;
+
+    public C(int value) { _value = value; }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(@"Update [public C(int value) => _value = value;]@52 -> [public C(int value) { _value = value; }]@52");
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                });
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
+        public void Constructor_Instance_Update_ExpressionBodyToBlockBody_WithInitializer()
+        {
+            var src1 = @"
+public class B { B(int value) {} }
+public class C : B
+{
+    private int _value;
+    public C(int value) : base(value) => _value = value;
+}
+";
+            var src2 = @"
+public class B { B(int value) {} }
+public class C : B
+{
+    private int _value;
+    public C(int value) : base(value) { _value = value; }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(@"Update [public C(int value) : base(value) => _value = value;]@90 -> [public C(int value) : base(value) { _value = value; }]@90");
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                });
+        }
+
+        [Fact]
+        public void Constructor_Instance_Update_SemanticError_Partial()
+        {
+            var src1 = @"
+partial class C
+{
+    partial void C(int x);
+}
+
+partial class C
+{
+    partial void C(int x)
+    {
+        System.Console.WriteLine(1);
+    }
+}
+";
+            var src2 = @"
+partial class C
+{
+    partial void C(int x);
+}
+
+partial class C
+{
+    partial void C(int x)
+    {
+        System.Console.WriteLine(2);
+    }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IMethodSymbol>("C").PartialImplementationPart));
+        }
+
+        [Fact]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/2068")]
+        public void Constructor_Instance_Update_Modifier_Extern_Add()
+        {
+            var src1 = "class C { }";
+            var src2 = "class C { public extern C(); }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            // This can be allowed as the compiler generates an empty constructor, but it's not worth the complexity.
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ModifiersUpdate, "public extern C()", GetResource("constructor")));
+        }
+
+        [Theory]
+        [InlineData("struct")]
+        [InlineData("record struct")]
+        public void Constructor_Instance_Insert_Struct(string keyword)
+        {
+            var src1 = keyword + " C { }";
+            var src2 = keyword + " C { public C(int X) {} }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "X" }]))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Insert_Struct_Primary()
+        {
+            var src1 = "struct C { }";
+            var src2 = "struct C(int X) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "X" }]))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Insert_Struct_Primary_Record()
+        {
+            var src1 = "record struct C { }";
+            var src2 = "record struct C(int X) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Theory]
+        [InlineData("class")]
+        [InlineData("record class")]
+        public void Constructor_Instance_Insert_ReplacingDefault_Class(string keyword)
+        {
+            var src1 = keyword + " C { }";
+            var src2 = keyword + " C { public C(int X) {} }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "X"}])),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetParameterlessConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Insert_ReplacingDefault_Class_Primary()
+        {
+            var src1 = "class C { }";
+            var src2 = "class C(int X) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetParameterlessConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Insert_ReplacingDefault_Class_Primary_Record()
+        {
+            var src1 = "record C { }";
+            var src2 = "record C(int X) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetPrimaryDeconstructor("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetParameterlessConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C"))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_UpdatingImplicit(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("public", "protected")] string accessibility)
+        {
+            if (accessibility == "protected")
+                keyword = "abstract " + keyword;
+
+            var src1 = keyword + " C { }";
+            var src2 = keyword + " C { [System.Obsolete] " + accessibility + " C() { } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_UpdatingImplicit_Partial(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("public", "protected")] string accessibility)
+        {
+            if (accessibility == "protected")
+                keyword = "abstract " + keyword;
+
+            var srcA1 = "partial " + keyword + " C { }";
+            var srcB1 = "partial " + keyword + " C { }";
+
+            var srcA2 = "partial " + keyword + " C { }";
+            var srcB2 = "partial " + keyword + " C { " + accessibility + " C() { } }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    // no change in document A
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true) }),
+                });
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_AddingParameterless(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("public", "internal", "private", "protected", "private protected", "internal protected")] string accessibility)
+        {
+            var src1 = keyword + " C { C(int a) { } }";
+            var src2 = keyword + " C { C(int a) { } " + accessibility + " C() : this(1) { } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[] { SemanticEdit(SemanticEditKind.Insert, c => c.GetParameterlessConstructor("C")) },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_AddingParameterless_Primary(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("public", "internal", "private", "protected", "private protected", "internal protected")] string accessibility)
+        {
+            var src1 = keyword + " C(int a) { }";
+            var src2 = keyword + " C(int a) { " + accessibility + " C() : this(1) { } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[] { SemanticEdit(SemanticEditKind.Insert, c => c.GetParameterlessConstructor("C")) },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_AddingParameterless_Partial(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("public", "internal", "private", "protected", "private protected", "internal protected")] string accessibility)
+        {
+            var srcA1 = "partial " + keyword + " C { }";
+            var srcB1 = "partial " + keyword + " C { public C(int a) { } }";
+
+            var srcA2 = "partial " + keyword + " C { " + accessibility + " C() { } }";
+            var srcB2 = "partial " + keyword + " C { public C(int a) { } }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Insert, c => c.GetParameterlessConstructor("C"))
+                        }),
+
+                    // no change in document B
+                    DocumentResults(),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_AddingParameterless_Partial_Primary(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("public", "internal", "private", "protected", "private protected", "internal protected")] string accessibility)
+        {
+            var srcA1 = "partial " + keyword + " C { }";
+            var srcB1 = "partial " + keyword + " C(int a) { }";
+
+            var srcA2 = "partial " + keyword + " C { " + accessibility + " C() { } }";
+            var srcB2 = "partial " + keyword + " C(int a) { }";
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
                 new[]
                 {
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters.IsEmpty))
+                            SemanticEdit(SemanticEditKind.Insert, c => c.GetParameterlessConstructor("C"))
                         }),
 
                     // no change in document B
@@ -10487,157 +11759,487 @@ public void InstanceCtorInsert_Partial_Public_NoImplicit()
                 capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_ReplacingSynthesizedWithCustom_ChangingAccessibilty(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("", "private", "protected", "internal", "private protected", "internal protected")] string accessibility)
+        {
+            var src1 = keyword + " C { }";
+            var src2 = keyword + " C { " + accessibility + " C() { } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                new[]
+                {
+                    Diagnostic(RudeEditKind.ChangingAccessibility, (accessibility + " C()").Trim(), GetResource("constructor"))
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Insert_ReplacingSynthesizedWithCustom_ChangingAccessibilty_AbstractType(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("", "private", "public", "internal", "private protected", "internal protected")] string accessibility)
+        {
+            var src1 = "abstract " + keyword + " C { }";
+            var src2 = "abstract " + keyword + " C { " + accessibility + " C() { } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                new[]
+                {
+                    Diagnostic(RudeEditKind.ChangingAccessibility, (accessibility + " C()").Trim(), FeaturesResources.constructor)
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
         [Fact]
-        public void InstanceCtorInsert_Private_Implicit1()
+        public void Constructor_Instance_Insert_ReplacingSynthesizedWithCustom_Primary()
         {
             var src1 = "class C { }";
-            var src2 = "class C { private C() { } }";
+            var src2 = "class C() { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true));
+        }
+
+        [Fact]
+        public void Constructor_Instance_Insert_ReplacingSynthesizedWithCustom_Primary_Record()
+        {
+            var src1 = "record C { }";
+            var src2 = "record C() { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")));
+        }
+
+        [Theory]
+        [InlineData("struct")]
+        [InlineData("record struct")]
+        public void Constructor_Instance_Delete_Struct(string keyword)
+        {
+            var src1 = keyword + " C { public C(int X) {} }";
+            var src2 = keyword + " C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "X" }]), deletedSymbolContainerProvider: c => c.GetMember("C"))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Delete_Struct_Primary()
+        {
+            var src1 = "struct C(int X) { }";
+            var src2 = "struct C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "X" }]), deletedSymbolContainerProvider: c => c.GetMember("C"))
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Delete_Struct_Primary_Record()
+        {
+            var src1 = "record struct C(int X) { }";
+            var src2 = "record struct C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Theory]
+        [InlineData("class")]
+        [InlineData("record class")]
+        public void Constructor_Instance_Delete_ReplacingWithDefault_Class(string keyword)
+        {
+            var src1 = keyword + " C { public C(int X) {} }";
+            var src2 = keyword + " C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    // The compiler emits default constructor automatically
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "X"}]), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Delete_ReplacingWithDefault_Class_Primary()
+        {
+            var src1 = "class C(int X) { }";
+            var src2 = "class C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    // The compiler emits default constructor automatically
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Delete_ReplacingWithDefault_Class_Primary_Record()
+        {
+            var src1 = "record C(int X) { }";
+            var src2 = "record C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[]
+                {
+                    // The compiler emits default constructor automatically
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Delete_SemanticError()
+        {
+            var src1 = "class C { D() {} }";
+            var src2 = "class C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            // The compiler interprets D() as a constructor declaration.
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingAccessibility, "class C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()")));
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_UpdatingImplicit(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("public", "protected")] string accessibility)
+        {
+            if (accessibility == "protected")
+                keyword = "abstract " + keyword;
+
+            var src1 = keyword + " C { [System.Obsolete] " + accessibility + " C() { } }";
+            var src2 = keyword + " C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Delete_Parameterless()
+        {
+            var src1 = @"
+class C
+{
+    private int a = 10;
+    private int b;
+
+    public C() { b = 3; }
+}
+";
+            var src2 = @"
+class C
+{
+    private int a = 10;
+    private int b;
+}
+";
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifyEdits(
+                "Delete [public C() { b = 3; }]@65",
+                "Delete [()]@73");
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true)
+                });
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_WithParameters([CombinatorialValues("record", "class")] string keyword)
+        {
+            var src1 = keyword + " C { public C(int x) { } }";
+            var src2 = keyword + " C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[] { SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "x" }]), deletedSymbolContainerProvider: c => c.GetMember("C")) },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_Primary_WithParameters([CombinatorialValues("record", "class")] string keyword)
+        {
+            var src1 = keyword + " C(int a) { public C(bool b) { } }";
+            var src2 = keyword + " C(int a) { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[] { SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is [{ Name: "b" }]), deletedSymbolContainerProvider: c => c.GetMember("C")) },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
+
+        [Fact]
+        public void Constructor_Instance_Delete_Primary_Class()
+        {
+            var src1 = "class C(int a) { }";
+            var src2 = "class C { }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, "private C()", FeaturesResources.constructor));
+            edits.VerifySemantics(
+                new[] { SemanticEdit(SemanticEditKind.Delete, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.FirstOrDefault(c => c.Parameters.Length == 1), deletedSymbolContainerProvider: c => c.GetMember("C")) },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void InstanceCtorInsert_Private_Implicit2()
+        public void Constructor_Instance_Delete_Primary_Record()
         {
-            var src1 = "class C { }";
-            var src2 = "class C { C() { } }";
+            var src1 = "record C(int a) { }";
+            var src2 = "record C { }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, "C()", FeaturesResources.constructor));
+            edits.VerifySemantics(
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetPrimaryDeconstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")),
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void InstanceCtorInsert_Protected_PublicImplicit()
+        public void Constructor_Instance_Delete_Public_PartialWithInitializerUpdate()
         {
-            var src1 = "class C { }";
-            var src2 = "class C { protected C() { } }";
+            var srcA1 = "partial class C { public C() { } }";
+            var srcB1 = "partial class C { int x = 1; }";
 
-            var edits = GetTopEdits(src1, src2);
+            var srcA2 = "partial class C { }";
+            var srcB2 = "partial class C { int x = 2; }";
 
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, "protected C()", FeaturesResources.constructor));
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+                new[]
+                {
+                    DocumentResults(
+                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true) }),
+
+                    DocumentResults(
+                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true) })
+                });
         }
 
-        [Fact]
-        public void InstanceCtorInsert_Internal_PublicImplicit()
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_ReplacingCustomWithSynthesized(
+            [CombinatorialValues("record", "class")] string keyword)
         {
-            var src1 = "class C { }";
-            var src2 = "class C { internal C() { } }";
+            var src1 = keyword + " C { public C() { } }";
+            var src2 = keyword + " C { }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, "internal C()", FeaturesResources.constructor));
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(c => c.Parameters is []), preserveLocalVariables: true));
         }
 
-        [Fact]
-        public void InstanceCtorInsert_Internal_ProtectedImplicit()
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_ReplacingCustomWithSynthesized_ChangingAccessibility(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("", "private", "protected", "internal", "private protected", "internal protected")] string accessibility)
         {
-            var src1 = "abstract class C { }";
-            var src2 = "abstract class C { internal C() { } }";
+            var src1 = keyword + " C { " + accessibility + " C() { } }";
+            var src2 = keyword + " C { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, "internal C()", FeaturesResources.constructor));
+                new[]
+                {
+                    Diagnostic(RudeEditKind.ChangingAccessibility, keyword + " C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()"))
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
-        [Fact]
-        public void InstanceCtorUpdate_ProtectedImplicit()
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_ReplacingCustomWithSynthesized_AbstractType(
+            [CombinatorialValues("record", "class")] string keyword)
         {
-            var src1 = "abstract class C { }";
-            var src2 = "abstract class C { protected C() { } }";
+            var src1 = "abstract " + keyword + " C { protected C() { } }";
+            var src2 = "abstract " + keyword + " C { }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true));
+                SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true));
         }
 
-        [Fact]
-        public void InstanceCtorInsert_Private_NoImplicit()
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_ReplacingCustomWithSynthesized_AbstractType_ChangingAccessibility(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("", "private", "public", "internal", "private protected", "internal protected")] string accessibility)
         {
-            var src1 = "class C { public C(int a) { } }";
-            var src2 = "class C { public C(int a) { } private C() { } }";
+            var src1 = "abstract " + keyword + " C { " + accessibility + " C() { } }";
+            var src2 = "abstract " + keyword + " C { }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemantics(
+            edits.VerifySemanticDiagnostics(
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C")
-                        .InstanceConstructors.Single(ctor => ctor.DeclaredAccessibility == Accessibility.Private))
+                    Diagnostic(RudeEditKind.ChangingAccessibility, "abstract " + keyword + " C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()"))
                 },
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
         [Fact]
-        public void InstanceCtorInsert_Internal_NoImplicit()
+        public void Constructor_Instance_Delete_Primary_ReplacingWithSynthesized()
         {
-            var src1 = "class C { public C(int a) { } }";
-            var src2 = "class C { public C(int a) { } internal C() { } }";
+            var src1 = "class C() { }";
+            var src2 = "class C { }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true));
         }
 
         [Fact]
-        public void InstanceCtorInsert_Protected_NoImplicit()
+        public void Constructor_Instance_Delete_Primary_ReplacingWithSynthesized_Record()
         {
-            var src1 = "class C { public C(int a) { } }";
-            var src2 = "class C { public C(int a) { } protected C() { } }";
+            var src1 = "record C() { }";
+            var src2 = "record C { }";
 
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.PrintMembers")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetSpecializedEqualsOverload("C")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.GetHashCode")),
+                SemanticEdit(SemanticEditKind.Update, c => c.GetCopyConstructor("C")));
         }
 
-        [Fact]
-        public void InstanceCtorInsert_InternalProtected_NoImplicit()
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_Primary_ReplacingWithRegular(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("", "private", "protected", "internal", "private protected", "internal protected")] string accessibility)
         {
-            var src1 = "class C { public C(int a) { } }";
-            var src2 = "class C { public C(int a) { } internal protected C() { } }";
+            var src1 = keyword + " C() { }";
+            var src2 = keyword + " C { " + accessibility + " C() { } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
+                new[]
+                {
+                    Diagnostic(RudeEditKind.ChangingAccessibility, (accessibility + " C()").Trim(), GetResource("constructor"))
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
         }
 
-        [Fact]
-        public void StaticCtor_Partial_DeleteInsert()
+        [Theory]
+        [CombinatorialData]
+        public void Constructor_Instance_Delete_Primary_ReplacingWithRegular_AbstractType(
+            [CombinatorialValues("record", "class")] string keyword,
+            [CombinatorialValues("", "private", "public", "internal", "private protected", "internal protected")] string accessibility)
         {
-            var srcA1 = "partial class C { static C() { } }";
-            var srcB1 = "partial class C {  }";
+            var src1 = "abstract " + keyword + " C() { }";
+            var src2 = "abstract " + keyword + " C { " + accessibility + " C() { } }";
 
-            var srcA2 = "partial class C { }";
-            var srcB2 = "partial class C { static C() { } }";
+            var edits = GetTopEdits(src1, src2);
 
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
+            edits.VerifySemanticDiagnostics(
                 new[]
                 {
-                    // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
-                    DocumentResults(),
+                    Diagnostic(RudeEditKind.ChangingAccessibility, (accessibility + " C()").Trim(), GetResource("constructor"))
+                },
+                capabilities: EditAndContinueCapabilities.Baseline);
+        }
 
-                    DocumentResults(
-                        semanticEdits: new[]
-                        {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").StaticConstructors.Single(), partialType: "C", preserveLocalVariables: true)
-                        }),
-                });
+        [Theory]
+        [InlineData("record")]
+        [InlineData("class")]
+        public void Constructor_Instance_InsertDelete_Primary_Partial(string keyword)
+        {
+            var src1 = $$"""
+    partial {{keyword}} C { }
+    partial {{keyword}} C(int X);
+    """;
+            var src2 = $$"""
+    partial {{keyword}} C(int X) { }
+    partial {{keyword}} C;
+    """;
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                SemanticEdit(SemanticEditKind.Update, c => c.GetPrimaryConstructor("C"), preserveLocalVariables: true));
         }
 
         [Fact]
-        public void InstanceCtor_Partial_DeletePrivateInsertPrivate()
+        public void Constructor_Instance_Partial_DeletePrivateInsertPrivate()
         {
             var srcA1 = "partial class C { C() { } }";
             var srcB1 = "partial class C {  }";
@@ -10655,13 +12257,13 @@ public void InstanceCtor_Partial_DeletePrivateInsertPrivate()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                 });
         }
 
         [Fact]
-        public void InstanceCtor_Partial_DeletePublicInsertPublic()
+        public void Constructor_Instance_Partial_DeletePublicInsertPublic()
         {
             var srcA1 = "partial class C { public C() { } }";
             var srcB1 = "partial class C { }";
@@ -10679,13 +12281,13 @@ public void InstanceCtor_Partial_DeletePublicInsertPublic()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                 });
         }
 
         [Fact]
-        public void InstanceCtor_Partial_DeletePrivateInsertPublic()
+        public void Constructor_Instance_Partial_DeletePrivateInsertPublic()
         {
             var srcA1 = "partial class C { C() { } }";
             var srcB1 = "partial class C { }";
@@ -10707,31 +12309,7 @@ public void InstanceCtor_Partial_DeletePrivateInsertPublic()
         }
 
         [Fact]
-        public void StaticCtor_Partial_InsertDelete()
-        {
-            var srcA1 = "partial class C { }";
-            var srcB1 = "partial class C { static C() { } }";
-
-            var srcA2 = "partial class C { static C() { } }";
-            var srcB2 = "partial class C { }";
-
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
-                new[]
-                {
-                    DocumentResults(
-                        semanticEdits: new[]
-                        {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").StaticConstructors.Single(), partialType: "C", preserveLocalVariables: true)
-                        }),
-
-                    // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
-                    DocumentResults(),
-                });
-        }
-
-        [Fact]
-        public void InstanceCtor_Partial_InsertPublicDeletePublic()
+        public void Constructor_Instance_Partial_InsertPublicDeletePublic()
         {
             var srcA1 = "partial class C { }";
             var srcB1 = "partial class C { public C() { } }";
@@ -10746,7 +12324,7 @@ public void InstanceCtor_Partial_InsertPublicDeletePublic()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
 
                     // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
@@ -10755,7 +12333,7 @@ public void InstanceCtor_Partial_InsertPublicDeletePublic()
         }
 
         [Fact]
-        public void InstanceCtor_Partial_InsertPrivateDeletePrivate()
+        public void Constructor_Instance_Partial_InsertPrivateDeletePrivate()
         {
             var srcA1 = "partial class C { }";
             var srcB1 = "partial class C { private C() { } }";
@@ -10770,7 +12348,7 @@ public void InstanceCtor_Partial_InsertPrivateDeletePrivate()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
 
                     // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
@@ -10779,7 +12357,7 @@ public void InstanceCtor_Partial_InsertPrivateDeletePrivate()
         }
 
         [Fact]
-        public void InstanceCtor_Partial_DeleteInternalInsertInternal()
+        public void Constructor_Instance_Partial_DeleteInternalInsertInternal()
         {
             var srcA1 = "partial class C { }";
             var srcB1 = "partial class C { internal C() { } }";
@@ -10794,7 +12372,7 @@ public void InstanceCtor_Partial_DeleteInternalInsertInternal()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
 
                     // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
@@ -10803,7 +12381,7 @@ public void InstanceCtor_Partial_DeleteInternalInsertInternal()
         }
 
         [Fact]
-        public void InstanceCtor_Partial_InsertInternalDeleteInternal_WithBody()
+        public void Constructor_Instance_Partial_InsertInternalDeleteInternal_WithBody()
         {
             var srcA1 = "partial class C { }";
             var srcB1 = "partial class C { internal C() { } }";
@@ -10818,7 +12396,7 @@ public void InstanceCtor_Partial_InsertInternalDeleteInternal_WithBody()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
 
                     // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
@@ -10827,7 +12405,7 @@ public void InstanceCtor_Partial_InsertInternalDeleteInternal_WithBody()
         }
 
         [Fact]
-        public void InstanceCtor_Partial_InsertPublicDeletePrivate()
+        public void Constructor_Instance_Partial_InsertPublicDeletePrivate()
         {
             var srcA1 = "partial class C { }";
             var srcB1 = "partial class C { private C() { } }";
@@ -10848,7 +12426,7 @@ public void InstanceCtor_Partial_InsertPublicDeletePrivate()
         }
 
         [Fact]
-        public void InstanceCtor_Partial_InsertInternalDeletePrivate()
+        public void Constructor_Instance_Partial_InsertInternalDeletePrivate()
         {
             var srcA1 = "partial class C { }";
             var srcB1 = "partial class C { private C() { } }";
@@ -10868,7 +12446,7 @@ public void InstanceCtor_Partial_InsertInternalDeletePrivate()
         }
 
         [Fact]
-        public void InstanceCtor_Partial_Update_LambdaInInitializer1()
+        public void Constructor_Instance_Partial_Update_LambdaInInitializer1()
         {
             var src1 = @"
 using System;
@@ -10919,7 +12497,7 @@ public C()
         }
 
         [Fact]
-        public void InstanceCtor_Partial_Update_LambdaInInitializer_Trivia1()
+        public void Constructor_Instance_Partial_Update_LambdaInInitializer_Trivia1()
         {
             var src1 = @"
 using System;
@@ -10964,7 +12542,7 @@ partial class C
         }
 
         [Fact]
-        public void InstanceCtor_Partial_Update_LambdaInInitializer_ExplicitInterfaceImpl1()
+        public void Constructor_Instance_Partial_Update_LambdaInInitializer_ExplicitInterfaceImpl1()
         {
             var src1 = @"
 using System;
@@ -11022,8 +12600,8 @@ public C()
                 new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(), syntaxMap[0]) });
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/2504")]
-        public void InstanceCtor_Partial_Insert_Parameterless_LambdaInInitializer1()
+        [Fact]
+        public void Constructor_Instance_Partial_Insert_Parameterless_LambdaInInitializer1()
         {
             var src1 = @"
 using System;
@@ -11062,19 +12640,15 @@ partial class C
 ";
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.InsertConstructorToTypeWithInitializersWithLambdas, "public C()"));
-
-            // TODO: 
-            //var syntaxMap = GetSyntaxMap(src1, src2);
+            var syntaxMap = GetSyntaxMap(src1, src2);
 
-            //edits.VerifySemantics(
-            //    ActiveStatementsDescription.Empty,
-            //    new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(), syntaxMap[0]) });
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(), syntaxMap[0]) });
         }
 
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/2504")]
-        public void InstanceCtor_Partial_Insert_WithParameters_LambdaInInitializer1()
+        public void Constructor_Instance_Partial_Insert_WithParameters_LambdaInInitializer1()
         {
             var src1 = @"
 using System;
@@ -11124,7 +12698,7 @@ partial class C
         }
 
         [Fact]
-        public void InstanceCtor_Partial_Explicit_Update()
+        public void Constructor_Instance_Partial_Explicit_Update()
         {
             var srcA1 = @"
 using System;
@@ -11188,7 +12762,7 @@ partial class C
         }
 
         [Fact]
-        public void InstanceCtor_Partial_Explicit_Update_SemanticError()
+        public void Constructor_Instance_Partial_Explicit_Update_SemanticError()
         {
             var srcA1 = @"
 using System;
@@ -11242,7 +12816,7 @@ partial class C
         }
 
         [Fact]
-        public void InstanceCtor_Partial_Implicit_Update()
+        public void Constructor_Instance_Partial_Implicit_Update()
         {
             var srcA1 = "partial class C { int F = 1; }";
             var srcB1 = "partial class C { int G = 1; }";
@@ -11257,74 +12831,16 @@ public void InstanceCtor_Partial_Implicit_Update()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                 });
         }
 
-        [Fact]
-        public void ParameterlessConstructor_SemanticError_Delete1()
-        {
-            var src1 = @"
-class C
-{
-    D() {}
-}
-";
-            var src2 = @"
-class C
-{
-}
-";
-            var edits = GetTopEdits(src1, src2);
-
-            // The compiler interprets D() as a constructor declaration.
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, "class C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()")));
-        }
-
-        [Fact]
-        public void Constructor_SemanticError_Partial()
-        {
-            var src1 = @"
-partial class C
-{
-    partial void C(int x);
-}
-
-partial class C
-{
-    partial void C(int x)
-    {
-        System.Console.WriteLine(1);
-    }
-}
-";
-            var src2 = @"
-partial class C
-{
-    partial void C(int x);
-}
-
-partial class C
-{
-    partial void C(int x)
-    {
-        System.Console.WriteLine(2);
-    }
-}
-";
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemantics(
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IMethodSymbol>("C").PartialImplementationPart));
-        }
-
         [Fact]
         public void PartialDeclaration_Delete()
         {
@@ -11339,13 +12855,13 @@ public void PartialDeclaration_Delete()
                 new[]
                 {
                     DocumentResults(
-                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true) }),
+                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true) }),
 
                     DocumentResults(
                         semanticEdits: new[]
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IMethodSymbol>("F")),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                 });
         }
@@ -11367,11 +12883,11 @@ public void PartialDeclaration_Insert()
                         semanticEdits: new[]
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IMethodSymbol>("F")),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
 
                     DocumentResults(
-                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true) }),
+                        semanticEdits: new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true) }),
                 });
         }
 
@@ -11405,15 +12921,13 @@ public void PartialDeclaration_Insert_Reloadable()
         [Theory]
         [InlineData("class ")]
         [InlineData("struct")]
-        public void Constructor_DeleteParameterless(string typeKind)
+        public void Constructor_Insert_Parameterless(string typeKind)
         {
             var src1 = @"
 " + typeKind + @" C
 {
     private int a = 10;
     private int b;
-
-    public C() { b = 3; }
 }
 ";
             var src2 = @"
@@ -11421,175 +12935,158 @@ public void Constructor_DeleteParameterless(string typeKind)
 {
     private int a = 10;
     private int b;
+
+    public C() { b = 3; }
 }
 ";
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits("Delete [public C() { b = 3; }]@66", "Delete [()]@74");
+            edits.VerifyEdits("Insert [public C() { b = 3; }]@66", "Insert [()]@74");
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true)
                 });
         }
 
-        [Theory]
-        [InlineData("class ")]
-        [InlineData("struct")]
-        public void Constructor_InsertParameterless(string typeKind)
+        [Fact]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/2068")]
+        public void Constructor_Static_Update_Modifier_Extern_Add()
         {
-            var src1 = @"
-" + typeKind + @" C
-{
-    private int a = 10;
-    private int b;
-}
-";
-            var src2 = @"
-" + typeKind + @" C
-{
-    private int a = 10;
-    private int b;
+            var src1 = "class C { }";
+            var src2 = "class C { static extern C(); }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            // This can be allowed as the compiler generates an empty constructor, but it's not worth the complexity.
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.InsertExtern, "static extern C()", GetResource("static constructor")));
+        }
+
+        [Fact]
+        public void Constructor_Static_Delete()
+        {
+            var src1 = "class C { static C() { } }";
+            var src2 = "class C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.Delete, "class C", DeletedSymbolDisplay(FeaturesResources.static_constructor, "C()")));
+        }
+
+        [Fact]
+        public void Constructor_Static_Delete_Reloadable()
+        {
+            var src1 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]class C { static C() { } }";
+            var src2 = ReloadableAttributeSrc + "[CreateNewOnMetadataUpdate]class C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                new[] { SemanticEdit(SemanticEditKind.Replace, c => c.GetMember("C")) },
+                capabilities: EditAndContinueCapabilities.NewTypeDefinition);
+        }
+
+        [Fact]
+        public void Constructor_Static_Insert()
+        {
+            var src1 = "class C { }";
+            var src2 = "class C { static C() { } }";
 
-    public C() { b = 3; }
-}
-";
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits("Insert [public C() { b = 3; }]@66", "Insert [()]@74");
-
             edits.VerifySemantics(
-                ActiveStatementsDescription.Empty,
-                new[]
-                {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
-                });
+                new[] { SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").StaticConstructors.Single()) },
+                EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
-        public void Constructor_BlockBodyToExpressionBody()
+        [Fact]
+        public void Constructor_Static_Partial_DeleteInsert()
         {
-            var src1 = @"
-public class C
-{
-    private int _value;
-
-    public C(int value) { _value = value; }
-}
-";
-            var src2 = @"
-public class C
-{
-    private int _value;
-
-    public C(int value) => _value = value;
-}
-";
-            var edits = GetTopEdits(src1, src2);
+            var srcA1 = "partial class C { static C() { } }";
+            var srcB1 = "partial class C {  }";
 
-            edits.VerifyEdits("Update [public C(int value) { _value = value; }]@52 -> [public C(int value) => _value = value;]@52");
+            var srcA2 = "partial class C { }";
+            var srcB2 = "partial class C { static C() { } }";
 
-            edits.VerifySemantics(
-                ActiveStatementsDescription.Empty,
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
+                    DocumentResults(),
+
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").StaticConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                        }),
                 });
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
-        public void ConstructorWithInitializer_BlockBodyToExpressionBody()
+        [Fact]
+        public void Constructor_Static_Partial_InsertDelete()
         {
-            var src1 = @"
-public class B { B(int value) {} }
-public class C : B
-{
-    private int _value;
-    public C(int value) : base(value) { _value = value; }
-}
-";
-            var src2 = @"
-public class B { B(int value) {} }
-public class C : B
-{
-    private int _value;
-    public C(int value) : base(value) => _value = value;
-}
-";
-            var edits = GetTopEdits(src1, src2);
+            var srcA1 = "partial class C { }";
+            var srcB1 = "partial class C { static C() { } }";
 
-            edits.VerifyEdits("Update [public C(int value) : base(value) { _value = value; }]@90 -> [public C(int value) : base(value) => _value = value;]@90");
+            var srcA2 = "partial class C { static C() { } }";
+            var srcB2 = "partial class C { }";
 
-            edits.VerifySemantics(
-                ActiveStatementsDescription.Empty,
+            EditAndContinueValidation.VerifySemantics(
+                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").StaticConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                        }),
+
+                    // delete of the constructor in partial part will be represented as a semantic update in the other document where it was inserted back
+                    DocumentResults(),
                 });
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
-        public void Constructor_ExpressionBodyToBlockBody()
+        #endregion
+
+        #region Destructors
+
+        [Fact]
+        public void DestructorDelete()
         {
-            var src1 = @"
-public class C
-{
-    private int _value;
+            var src1 = @"class B { ~B() { } }";
+            var src2 = @"class B { }";
 
-    public C(int value) => _value = value;
-}
-";
-            var src2 = @"
-public class C
-{
-    private int _value;
+            var expectedEdit1 = @"Delete [~B() { }]@10";
 
-    public C(int value) { _value = value; }
-}
-";
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits(@"Update [public C(int value) => _value = value;]@52 -> [public C(int value) { _value = value; }]@52");
+            edits.VerifyEdits(expectedEdit1);
 
-            edits.VerifySemantics(
-                ActiveStatementsDescription.Empty,
-                new[]
-                {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
-                });
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.Delete, "class B", DeletedSymbolDisplay(CSharpFeaturesResources.destructor, "~B()")));
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
-        public void ConstructorWithInitializer_ExpressionBodyToBlockBody()
+        [Fact]
+        public void DestructorDelete_InsertConstructor()
         {
-            var src1 = @"
-public class B { B(int value) {} }
-public class C : B
-{
-    private int _value;
-    public C(int value) : base(value) => _value = value;
-}
-";
-            var src2 = @"
-public class B { B(int value) {} }
-public class C : B
-{
-    private int _value;
-    public C(int value) : base(value) { _value = value; }
-}
-";
+            var src1 = @"class B { ~B() { } }";
+            var src2 = @"class B { B() { } }";
+
             var edits = GetTopEdits(src1, src2);
 
-            edits.VerifyEdits(@"Update [public C(int value) : base(value) => _value = value;]@90 -> [public C(int value) : base(value) { _value = value; }]@90");
+            edits.VerifyEdits(
+                "Insert [B() { }]@10",
+                "Insert [()]@11",
+                "Delete [~B() { }]@10");
 
-            edits.VerifySemantics(
-                ActiveStatementsDescription.Empty,
-                new[]
-                {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
-                });
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingAccessibility, "B()", FeaturesResources.constructor),
+                Diagnostic(RudeEditKind.Delete, "class B", DeletedSymbolDisplay(CSharpFeaturesResources.destructor, "~B()")));
         }
 
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
@@ -11646,100 +13143,40 @@ public class C
                 });
         }
 
-        [Fact]
-        public void Constructor_ReadOnlyRef_Parameter_InsertWhole()
-        {
-            var src1 = "class Test { }";
-            var src2 = "class Test { Test(in int b) => throw null; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Insert [Test(in int b) => throw null;]@13",
-                "Insert [(in int b)]@17",
-                "Insert [in int b]@18");
-
-            edits.VerifySemanticDiagnostics(
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
-        }
-
-        [Fact]
-        public void Constructor_ReadOnlyRef_Parameter_InsertParameter()
-        {
-            var src1 = "class Test { Test() => throw null; }";
-            var src2 = "class Test { Test(in int b) => throw null; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Insert [in int b]@18");
-
-            edits.VerifySemantics(
-                new[]
-                {
-                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMembers("Test..ctor").FirstOrDefault(m => m.GetParameterCount() == 0)?.ISymbol, deletedSymbolContainerProvider: c => c.GetMember("Test")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMembers("Test..ctor").FirstOrDefault(m => m.GetParameterCount() == 1)?.ISymbol)
-                },
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
-
-            edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.InsertNotSupportedByRuntime, "in int b", FeaturesResources.parameter) },
-                capabilities: EditAndContinueCapabilities.Baseline);
-        }
-
-        [Fact]
-        public void Constructor_ReadOnlyRef_Parameter_Update()
-        {
-            var src1 = "class Test { Test(int b) => throw null; }";
-            var src2 = "class Test { Test(in int b) => throw null; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [int b]@18 -> [in int b]@18");
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ModifiersUpdate, "in int b", FeaturesResources.parameter));
-        }
-
         #endregion
 
         #region Fields and Properties with Initializers
 
-        [Theory]
-        [InlineData("class ")]
-        [InlineData("struct")]
-        public void FieldInitializer_Update1(string typeKind)
+        [Fact]
+        public void FieldInitializer_Update1()
         {
-            var src1 = typeKind + " C { int a = 0; }";
-            var src2 = typeKind + " C { int a = 1; }";
+            var src1 = "class C { int a = 0; }";
+            var src2 = "class C { int a = 1; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [a = 0]@15 -> [a = 1]@15");
+                "Update [a = 0]@14 -> [a = 1]@14");
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
-        [Theory]
-        [InlineData("class ")]
-        [InlineData("struct")]
-        public void PropertyInitializer_Update1(string typeKind)
+        [Fact]
+        public void PropertyInitializer_Update1()
         {
-            var src1 = typeKind + " C { int a { get; } = 0; }";
-            var src2 = typeKind + " C { int a { get; } = 1; }";
+            var src1 = "class C { int a { get; } = 0; }";
+            var src2 = "class C { int a { get; } = 1; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [int a { get; } = 0;]@11 -> [int a { get; } = 1;]@11");
+                "Update [int a { get; } = 0;]@10 -> [int a { get; } = 1;]@10");
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
@@ -11777,7 +13214,8 @@ public void PropertyInitializer_Update2()
         public void PropertyInitializer_InsertDelete()
         {
             var srcA1 = "partial class C { }";
-            var srcB1 = "partial class C { int a { get; } = 0; }";
+            var srcB1 = "partial class C { int a { get; } = 1; }";
+
             var srcA2 = "partial class C { int a { get { return 1; } } }";
             var srcB2 = "partial class C { }";
 
@@ -11791,7 +13229,7 @@ public void PropertyInitializer_InsertDelete()
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.a").GetMethod),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(), partialType: "C", preserveLocalVariables: true)
                         }),
-                    DocumentResults()
+                    DocumentResults(),
                 });
         }
 
@@ -11808,7 +13246,7 @@ public void FieldInitializer_Update3()
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
@@ -11828,6 +13266,39 @@ public void PropertyInitializer_Update3()
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<IPropertySymbol>("C.a").GetMethod),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true)
+                });
+        }
+
+        [Fact]
+        public void FieldInitializer_Delete()
+        {
+            var src1 = "class C { int a = 1; }";
+            var src2 = "class C { }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.Delete, "class C", DeletedSymbolDisplay(FeaturesResources.field, "a")));
+        }
+
+        [Theory]
+        [InlineData("")]
+        [InlineData("public C() { }")]
+        [InlineData("public C(int x) { }")]
+        public void PropertyInitializer_Delete(string ctor)
+        {
+            var src1 = "class C { " + ctor + " int a { get; set; } = 1; }";
+            var src2 = "class C { " + ctor + " }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.get_a"), deletedSymbolContainerProvider: c => c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.set_a"), deletedSymbolContainerProvider: c => c.GetMember("C")),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
                 });
         }
@@ -11863,67 +13334,59 @@ public void PropertyInitializerUpdate_StaticCtorUpdate1()
                 new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").StaticConstructors.Single(), preserveLocalVariables: true) });
         }
 
-        [Theory]
-        [InlineData("class ")]
-        [InlineData("struct")]
-        public void FieldInitializerUpdate_InstanceCtorUpdate_Private(string typeKind)
+        [Fact]
+        public void FieldInitializerUpdate_InstanceCtorUpdate_Private()
         {
-            var src1 = typeKind + " C { int a; [System.Obsolete]C() { } }";
-            var src2 = typeKind + " C { int a = 0; }";
+            var src1 = "class C { int a; [System.Obsolete]C() { } }";
+            var src2 = "class C { int a = 0; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
                 new[]
                 {
-                    Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, $"{typeKind} C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()")),
-                    Diagnostic(RudeEditKind.ChangingAccessibility, $"{typeKind} C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()"))
+                    Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, $"class C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()")),
+                    Diagnostic(RudeEditKind.ChangingAccessibility, $"class C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()"))
                 },
                 capabilities: EditAndContinueCapabilities.Baseline);
         }
 
-        [Theory]
-        [InlineData("class ")]
-        [InlineData("struct")]
-        public void PropertyInitializerUpdate_InstanceCtorUpdate_Private(string typeKind)
+        [Fact]
+        public void PropertyInitializerUpdate_InstanceCtorUpdate_Private()
         {
-            var src1 = typeKind + " C { int a { get; } = 1; C() { } }";
-            var src2 = typeKind + " C { int a { get; } = 2; }";
+            var src1 = "class C { int a { get; } = 1; C() { } }";
+            var src2 = "class C { int a { get; } = 2; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.ChangingAccessibility, $"{typeKind} C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()")));
+                Diagnostic(RudeEditKind.ChangingAccessibility, $"class C", DeletedSymbolDisplay(FeaturesResources.constructor, "C()")));
         }
 
-        [Theory]
-        [InlineData("class ")]
-        [InlineData("struct")]
-        public void FieldInitializerUpdate_InstanceCtorUpdate_Public(string typeKind)
+        [Fact]
+        public void FieldInitializerUpdate_InstanceCtorUpdate_Public()
         {
-            var src1 = typeKind + " C { int a; public C() { } }";
-            var src2 = typeKind + " C { int a = 0; }";
+            var src1 = "class C { int a; public C() { } }";
+            var src2 = "class C { int a = 0; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
-        [Theory]
-        [InlineData("class ")]
-        [InlineData("struct")]
-        public void PropertyInitializerUpdate_InstanceCtorUpdate_Public(string typeKind)
+        [Fact]
+        public void PropertyInitializerUpdate_InstanceCtorUpdate_Public()
         {
-            var src1 = typeKind + " C { int a { get; } = 1; public C() { } }";
-            var src2 = typeKind + " C { int a { get; } = 2; }";
+            var src1 = "class C { int a { get; } = 1; public C() { } }";
+            var src2 = "class C { int a { get; } = 2; }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
@@ -11970,7 +13433,7 @@ public void FieldInitializerUpdate_InstanceCtorUpdate2(string typeKind)
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Theory]
@@ -11985,7 +13448,7 @@ public void PropertyInitializerUpdate_InstanceCtorUpdate2(string typeKind)
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
@@ -12001,7 +13464,7 @@ public void FieldInitializerUpdate_InstanceCtorUpdate3()
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
@@ -12014,7 +13477,7 @@ public void PropertyInitializerUpdate_InstanceCtorUpdate3()
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
@@ -12030,39 +13493,39 @@ public void FieldInitializerUpdate_InstanceCtorUpdate4()
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
-        public void FieldInitializerUpdate_InstanceCtorUpdate5()
+        public void FieldInitializerUpdate_InstanceCtorUpdate_Class()
         {
-            var src1 = "class C { int a;     private C(int a) { }    private C(bool a) { } }";
-            var src2 = "class C { int a = 0; private C(int a) { } private C(bool a) { } }";
+            var src1 = "class C { int a;     private C(int a) { } private C(bool a) : this() { } private C() : this(1) { } private C(string a) : base() { } }";
+            var src2 = "class C { int a = 1; private C(int a) { } private C(bool a) : this() { } private C() : this(1) { } private C(string a) : base() { } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [a]@14 -> [a = 0]@14");
+                "Update [a]@14 -> [a = 1]@14");
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C(int)"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C(bool)"), preserveLocalVariables: true),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C(string)"), preserveLocalVariables: true),
                 });
         }
 
         [Fact]
-        public void FieldInitializerUpdate_Struct_InstanceCtorUpdate5()
+        public void FieldInitializerUpdate_InstanceCtorUpdate_Struct()
         {
-            var src1 = "struct C { int a;     private C(int a) { } private C(bool a) { } }";
-            var src2 = "struct C { int a = 0; private C(int a) { } private C(bool a) { } }";
+            var src1 = "struct C { int a;     private C(int a) { } private C(bool a) : this() { } private C(char a) : this(1) { } }";
+            var src2 = "struct C { int a = 1; private C(int a) { } private C(bool a) : this() { } private C(char a) : this(1) { } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifyEdits(
-                "Update [a]@15 -> [a = 0]@15");
+                "Update [a]@15 -> [a = 1]@15");
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
@@ -12070,7 +13533,6 @@ public void FieldInitializerUpdate_Struct_InstanceCtorUpdate5()
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C(int)"), preserveLocalVariables: true),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C(bool)"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C()"), preserveLocalVariables: true),
                 });
         }
 
@@ -12105,7 +13567,6 @@ public void PropertyInitializerUpdate_Struct_InstanceCtorUpdate5()
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C(int)"), preserveLocalVariables: true),
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C(bool)"), preserveLocalVariables: true),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(m => m.ToString() == "C.C()"), preserveLocalVariables: true),
                 });
         }
 
@@ -12165,7 +13626,7 @@ public void FieldInitializerUpdate_StaticCtorInsertExplicit()
         [Theory]
         [InlineData("class ")]
         [InlineData("struct")]
-        public void FieldInitializerUpdate_InstanceCtorInsertExplicit(string typeKind)
+        public void FieldInitializerUpdate_Constructor_Instance_InsertExplicit(string typeKind)
         {
             var src1 = typeKind + " C { int a; }";
             var src2 = typeKind + " C { int a = 0; public C() { } }";
@@ -12174,13 +13635,13 @@ public void FieldInitializerUpdate_InstanceCtorInsertExplicit(string typeKind)
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Theory]
         [InlineData("class ")]
         [InlineData("struct")]
-        public void PropertyInitializerUpdate_InstanceCtorInsertExplicit(string typeKind)
+        public void PropertyInitializerUpdate_Constructor_Instance_InsertExplicit(string typeKind)
         {
             var src1 = typeKind + " C { int a { get; } = 1; }";
             var src2 = typeKind + " C { int a { get; } = 2; public C() { } }";
@@ -12189,7 +13650,7 @@ public void PropertyInitializerUpdate_InstanceCtorInsertExplicit(string typeKind
 
             edits.VerifySemantics(
                 ActiveStatementsDescription.Empty,
-                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true) });
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true) });
         }
 
         [Fact]
@@ -12214,7 +13675,7 @@ public void FieldInitializerUpdate_GenericType()
             edits.VerifySemantics(
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true)
                 },
                 capabilities: EditAndContinueCapabilities.Baseline | EditAndContinueCapabilities.GenericUpdateMethod);
         }
@@ -12238,7 +13699,7 @@ public void PropertyInitializerUpdate_GenericType()
             edits.VerifySemantics(
                 new[]
                 {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true)
                 },
                 capabilities: EditAndContinueCapabilities.GenericUpdateMethod);
         }
@@ -12258,6 +13719,19 @@ public void FieldInitializerUpdate_StackAllocInConstructor()
                 Diagnostic(RudeEditKind.StackAllocUpdate, "stackalloc", FeaturesResources.constructor));
         }
 
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68731")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68731")]
+        public void FieldInitializerUpdate_StackAllocInConstructor_Initializer()
+        {
+            var src1 = "class C { int a = 1; C() : this(stackalloc int[1]) { } C(Span<int>) { } }";
+            var src2 = "class C { int a = 2; C() : this(stackalloc int[1]) { } C(Span<int>) { } }";
+
+            var edits = GetTopEdits(src1, src2);
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.StackAllocUpdate, "stackalloc", FeaturesResources.constructor));
+        }
+
         [Fact(Skip = "https://github.com/dotnet/roslyn/issues/67307")]
         [WorkItem("https://github.com/dotnet/roslyn/issues/67307")]
         public void FieldInitializerUpdate_StackAllocInOtherInitializer()
@@ -13178,6 +14652,87 @@ public C(bool b)
                 });
         }
 
+        [Theory]
+        [InlineData("")]
+        [InlineData(" : base()")]
+        public void FieldInitializerUpdate_Lambdas_ReplacingCustomWithSynthesized_ConstructorWithMemberInitializers(string initializer)
+        {
+            var src1 = $$"""
+using System;
+
+class C : B
+{
+    static int F(Func<int, int> x) => 1;
+
+    int A = F(<N:0.0>a => a + 1</N:0.0>);
+
+    public C() {{initializer}}
+    {
+    }
+}
+""";
+            var src2 = @"
+using System;
+
+class C : B
+{
+    static int F(Func<int, int> x) => 1;
+
+    int A = F(<N:0.0>a => a + 1</N:0.0>);
+}
+";
+            var edits = GetTopEdits(src1, src2);
+            var syntaxMap = GetSyntaxMap(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(), syntaxMap[0])
+                });
+        }
+
+        [Theory]
+        [CombinatorialData]
+        public void FieldInitializerUpdate_Lambdas_ReplacingCustomWithSynthesized_ConstructorWithMemberInitializers_Primary(
+            [CombinatorialValues("", "()")] string initializer, bool isInsert)
+        {
+            var src1 = $$"""
+using System;
+
+class C() : B{{initializer}}
+{
+    static int F(Func<int, int> x) => 1;
+
+    int A = F(<N:0.0>a => a + 1</N:0.0>);
+}
+""";
+            var src2 = @"
+using System;
+
+class C : B
+{
+    static int F(Func<int, int> x) => 1;
+
+    int A = F(<N:0.0>a => a + 1</N:0.0>);
+}
+";
+            if (isInsert)
+            {
+                (src1, src2) = (src2, src1);
+            }
+
+            var edits = GetTopEdits(src1, src2);
+            var syntaxMap = GetSyntaxMap(src1, src2);
+
+            edits.VerifySemantics(
+                ActiveStatementsDescription.Empty,
+                new[]
+                {
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single(), syntaxMap[0])
+                });
+        }
+
         [Fact]
         public void FieldInitializerUpdate_Lambdas_PartialDeclarationDelete_SingleDocument()
         {
@@ -13221,7 +14776,7 @@ partial class C
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember("F")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), syntaxMap[0]),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), syntaxMap[0]),
                 });
         }
 
@@ -13296,7 +14851,7 @@ public C() { }
 
             edits.VerifySemantics(
                 SemanticEdit(SemanticEditKind.Update, c => ((IPropertySymbol)c.GetMember<INamedTypeSymbol>("C").GetMembers("P").First()).GetMethod),
-                SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true));
+                SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true));
         }
 
         [Fact]
@@ -13316,7 +14871,7 @@ public void Field_Partial_DeleteInsert_InitializerRemoval()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                 });
         }
@@ -13338,7 +14893,7 @@ public void Field_Partial_DeleteInsert_InitializerUpdate()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                 });
         }
@@ -13528,7 +15083,7 @@ public void Field_Insert()
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.a")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true)
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true)
                 },
                 capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType);
         }
@@ -13889,7 +15444,8 @@ class C
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Insert, c => c.GetMember("C.B")),
-                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single())
+                    SemanticEdit(SemanticEditKind.Insert, c => c.GetMember<INamedTypeSymbol>("C").Constructors.Single()),
+                    SemanticEdit(SemanticEditKind.Delete, c => c.GetParameterlessConstructor("C"), deletedSymbolContainerProvider: c => c.GetMember("C")),
                 },
                 capabilities: EditAndContinueCapabilities.AddInstanceFieldToExistingType | EditAndContinueCapabilities.AddMethodToExistingType);
         }
@@ -13995,7 +15551,7 @@ class C
                 new[]
                 {
                     SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.a")),
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), preserveLocalVariables: true),
+                    SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), preserveLocalVariables: true),
                 },
                 capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
         }
@@ -14018,7 +15574,7 @@ public void Field_Attribute_DeleteInsertUpdate_WithInitializer()
                         semanticEdits: new[]
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.a"), preserveLocalVariables: true),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
                 },
                 capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
@@ -14280,7 +15836,7 @@ public void Field_Event_Partial_InsertDelete()
                     DocumentResults(
                         semanticEdits: new[]
                         {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
 
                     DocumentResults(),
@@ -14860,61 +16416,42 @@ public void PropertyTypeUpdate_WithBodies()
         }
 
         [Fact]
-        public void PropertyUpdate_AddAttribute()
+        public void Property_Update_AddAttribute()
         {
             var src1 = "class C { int P { get; set; } }";
             var src2 = "class C { [System.Obsolete]int P { get; set; } }";
 
             var edits = GetTopEdits(src1, src2);
 
+            edits.VerifySemantics(
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.P")) },
+                capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+
             edits.VerifySemanticDiagnostics(
                 new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "int P", FeaturesResources.property_) },
                 capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
-        [Fact]
-        public void PropertyUpdate_AddAttribute_SupportedByRuntime()
+        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/68458")]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/68458")]
+        public void Property_Update_AddAttribute_FieldTarget()
         {
             var src1 = "class C { int P { get; set; } }";
-            var src2 = "class C { [System.Obsolete]int P { get; set; } }";
+            var src2 = "class C { [field: System.Obsolete]int P { get; set; } }";
 
             var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemantics(
-                new[] {
-                    SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.P"))
-                },
+                new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember("C.P")) },
                 capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
-        }
-
-        [Fact]
-        public void PropertyAccessorUpdate_AddAttribute()
-        {
-            var src1 = "class C { int P { get; set; } }";
-            var src2 = "class C { int P { [System.Obsolete]get; set; } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "get", CSharpFeaturesResources.property_getter) },
-                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
-        }
-
-        [Fact]
-        public void PropertyAccessorUpdate_AddAttribute2()
-        {
-            var src1 = "class C { int P { get; set; } }";
-            var src2 = "class C { int P { get; [System.Obsolete]set; } }";
-
-            var edits = GetTopEdits(src1, src2);
 
             edits.VerifySemanticDiagnostics(
-                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "set", CSharpFeaturesResources.property_setter) },
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "int P", FeaturesResources.property_) },
                 capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void PropertyAccessorUpdate_AddAttribute_SupportedByRuntime()
+        public void PropertyAccessorUpdate_AddAttribute()
         {
             var src1 = "class C { int P { get; set; } }";
             var src2 = "class C { int P { [System.Obsolete]get; set; } }";
@@ -14924,10 +16461,14 @@ public void PropertyAccessorUpdate_AddAttribute_SupportedByRuntime()
             edits.VerifySemantics(
                 new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("P").GetMethod) },
                 capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "get", CSharpFeaturesResources.property_getter) },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
-        public void PropertyAccessorUpdate_AddAttribute_SupportedByRuntime2()
+        public void PropertyAccessorUpdate_AddAttribute2()
         {
             var src1 = "class C { int P { get; set; } }";
             var src2 = "class C { int P { get; [System.Obsolete]set; } }";
@@ -14937,6 +16478,10 @@ public void PropertyAccessorUpdate_AddAttribute_SupportedByRuntime2()
             edits.VerifySemantics(
                 new[] { SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("P").SetMethod) },
                 capabilities: EditAndContinueCapabilities.ChangeCustomAttributes);
+
+            edits.VerifySemanticDiagnostics(
+                new[] { Diagnostic(RudeEditKind.ChangingAttributesNotSupportedByRuntime, "set", CSharpFeaturesResources.property_setter) },
+                capabilities: EditAndContinueCapabilities.AddMethodToExistingType);
         }
 
         [Fact]
@@ -15485,7 +17030,7 @@ public void Property_AutoWithInitializer_Partial_InsertDelete()
                         {
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("P").GetMethod),
                             SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("P").SetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").InstanceConstructors.Single(), partialType: "C", preserveLocalVariables: true)
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetParameterlessConstructor("C"), partialType: "C", preserveLocalVariables: true)
                         }),
 
                     DocumentResults(),
@@ -15689,122 +17234,6 @@ public void IndexerWithExpressionBody_Update()
             });
         }
 
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
-        public void IndexerWithExpressionBody_Update_LiftedParameter()
-        {
-            var src1 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(() => a + 1)() + 10;
-}
-";
-            var src2 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(() => 2)() + 11;   // not capturing a anymore
-}";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [int this[int a] => new Func<int>(() => a + 1)() + 10;]@35 -> [int this[int a] => new Func<int>(() => 2)() + 11;]@35",
-                "Update [=> new Func<int>(() => a + 1)() + 10]@51 -> [=> new Func<int>(() => 2)() + 11]@51");
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a", "a"));
-        }
-
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
-        public void IndexerWithExpressionBody_Update_LiftedParameter_2()
-        {
-            var src1 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(() => a + 1)();
-}
-";
-            var src2 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(() => 2)();   // not capturing a anymore
-}";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [int this[int a] => new Func<int>(() => a + 1)();]@35 -> [int this[int a] => new Func<int>(() => 2)();]@35",
-                "Update [=> new Func<int>(() => a + 1)()]@51 -> [=> new Func<int>(() => 2)()]@51");
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a", "a"));
-        }
-
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
-        public void IndexerWithExpressionBody_Update_LiftedParameter_3()
-        {
-            var src1 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(() => { return a + 1; })();
-}
-";
-            var src2 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(() => { return 2; })();   // not capturing a anymore
-}";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [int this[int a] => new Func<int>(() => { return a + 1; })();]@35 -> [int this[int a] => new Func<int>(() => { return 2; })();]@35",
-                "Update [=> new Func<int>(() => { return a + 1; })()]@51 -> [=> new Func<int>(() => { return 2; })()]@51");
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a", "a"));
-        }
-
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
-        public void IndexerWithExpressionBody_Update_LiftedParameter_4()
-        {
-            var src1 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(delegate { return a + 1; })();
-}
-";
-            var src2 = @"
-using System;
-
-class C
-{
-    int this[int a] => new Func<int>(delegate { return 2; })();   // not capturing a anymore
-}";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifyEdits(
-                "Update [int this[int a] => new Func<int>(delegate { return a + 1; })();]@35 -> [int this[int a] => new Func<int>(delegate { return 2; })();]@35",
-                "Update [=> new Func<int>(delegate { return a + 1; })()]@51 -> [=> new Func<int>(delegate { return 2; })()]@51");
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a", "a"));
-        }
-
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/17681")]
         public void Indexer_ExpressionBodyToBlockBody()
         {
@@ -16464,58 +17893,26 @@ public void IndexerInit_Partial_InsertDelete()
         }
 
         [Fact]
-        public void AutoIndexer_Partial_InsertDelete()
-        {
-            var srcA1 = "partial class C { }";
-            var srcB1 = "partial class C { int this[int x] { get; set; } }";
-
-            var srcA2 = "partial class C { int this[int x] { get; set; } }";
-            var srcB2 = "partial class C { }";
-
-            // Accessors need to be updated even though they do not have an explicit body. 
-            // There is still a sequence point generated for them whose location needs to be updated.
-            EditAndContinueValidation.VerifySemantics(
-                new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
-                new[]
-                {
-                    DocumentResults(
-                        semanticEdits: new[]
-                        {
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("this[]").GetMethod),
-                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("this[]").SetMethod),
-                        }),
-                    DocumentResults(),
-                });
-        }
-
-        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/51297")]
-        public void IndexerWithExpressionBody_Partial_InsertDeleteUpdate_LiftedParameter()
-        {
-            var srcA1 = @"
-partial class C
-{
-}";
-            var srcB1 = @"
-partial class C
-{
-    int this[int a] => new System.Func<int>(() => a + 1);
-}";
+        public void AutoIndexer_Partial_InsertDelete()
+        {
+            var srcA1 = "partial class C { }";
+            var srcB1 = "partial class C { int this[int x] { get; set; } }";
 
-            var srcA2 = @"
-partial class C
-{
-    int this[int a] => new System.Func<int>(() => 2); // no capture
-}";
-            var srcB2 = @"
-partial class C
-{
-}";
+            var srcA2 = "partial class C { int this[int x] { get; set; } }";
+            var srcB2 = "partial class C { }";
 
+            // Accessors need to be updated even though they do not have an explicit body. 
+            // There is still a sequence point generated for them whose location needs to be updated.
             EditAndContinueValidation.VerifySemantics(
                 new[] { GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2) },
                 new[]
                 {
-                    DocumentResults(diagnostics: new[] { Diagnostic(RudeEditKind.NotCapturingVariable, "a", "a") }),
+                    DocumentResults(
+                        semanticEdits: new[]
+                        {
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("this[]").GetMethod),
+                            SemanticEdit(SemanticEditKind.Update, c => c.GetMember<INamedTypeSymbol>("C").GetMember<IPropertySymbol>("this[]").SetMethod),
+                        }),
                     DocumentResults(),
                 });
         }
@@ -19081,328 +20478,5 @@ public void TopLevelStatements_Reorder()
         }
 
         #endregion
-
-        #region Primary Constructors
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_01([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C() { void M() { } }";
-            var src2 = keyword + " C() { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, keyword + " C", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_02([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C() { }";
-            var src2 = keyword + " C() { void M() { } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Insert, "void M()", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_03([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C() { void M() { } }";
-            var src2 = keyword + " C() { void M() { ToString(); } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "void M()", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_04([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int a) { }";
-            var src2 = keyword + " C(int a, int b) { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Insert, "int b", FeaturesResources.parameter));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_05([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int a, int b) { }";
-            var src2 = keyword + " C(int a) { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, keyword + " C", FeaturesResources.parameter));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_06([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C { }";
-            var src2 = keyword + " C() { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics();
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_07([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C() { }";
-            var src2 = keyword + " C { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics();
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_08([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C() { }";
-            var src2 = keyword + " C(int b) { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Insert, "int b", FeaturesResources.parameter));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_09([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int b) { }";
-            var src2 = keyword + " C() { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, keyword + " C", FeaturesResources.parameter));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_10([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C { }";
-            var src2 = keyword + " C(int b) { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Insert, "int b", FeaturesResources.parameter));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_11([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int b) { }";
-            var src2 = keyword + " C { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, keyword + " C", FeaturesResources.parameter));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_12([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = "partial " + keyword + " C(); partial " + keyword + " C { void M() { } }";
-            var src2 = "partial " + keyword + " C(); partial " + keyword + " C { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, "partial " + keyword + " C", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_13([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = "partial " + keyword + " C(); partial " + keyword + " C { }";
-            var src2 = "partial " + keyword + " C(); partial " + keyword + " C { void M() { } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Insert, "void M()", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_14([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = "partial " + keyword + " C(); partial " + keyword + " C { void M() { } }";
-            var src2 = "partial " + keyword + " C(); partial " + keyword + " C { void M() { ToString(); } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "void M()", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_15([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = "partial " + keyword + " C(); partial " + keyword + " C { void M() { } }";
-            var src2 = "partial " + keyword + " C {} partial " + keyword + " C { void M() { ToString(); } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "void M()", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_16([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = "partial " + keyword + " C {} partial " + keyword + " C { void M() { } }";
-            var src2 = "partial " + keyword + " C(); partial " + keyword + " C { void M() { ToString(); } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "void M()", FeaturesResources.method));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_17([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int a) { }";
-            var src2 = keyword + " C(long a) { }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "long a", FeaturesResources.parameter));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_18([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int x, int y) { void M() { x++; } System.Func<int> z = () => y; }";
-            var src2 = keyword + " C(int x, int y) { void M() { x++; } System.Func<int> z = () => x + y; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "z = () => x + y", FeaturesResources.field));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_19([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int x, int y) { void M() { x++; } System.Func<int> z = () => x + y; }";
-            var src2 = keyword + " C(int x, int y) { void M() { x++; } System.Func<int> z = () => y; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "z = () => y", FeaturesResources.field));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_20([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int x) { void M() { x++; } }";
-            var src2 = keyword + " C(int x) { void M() { x++; } System.Func<int> z = () => x; }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Insert, "z = () => x", FeaturesResources.field));
-        }
-
-        [Theory]
-        [CombinatorialData]
-        public void PrimaryConstructors_21([CombinatorialValues("class", "struct")] string keyword)
-        {
-            var src1 = keyword + " C(int x) { void M() { x++; } System.Func<int> z = () => x; }";
-            var src2 = keyword + " C(int x) { void M() { x++; } }";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Delete, keyword + " C", FeaturesResources.field));
-        }
-
-        [Fact]
-        public void PrimaryConstructors_22()
-        {
-            var src1 = "class C2(int x, int y) : C1(() => y) { void M() { x++; } } class C1(System.Func<int> x);";
-            var src2 = "class C2(int x, int y) : C1(() => x + y) { void M() { x++; } } class C1(System.Func<int> x);";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "class C2", FeaturesResources.class_));
-        }
-
-        [Fact]
-        public void PrimaryConstructors_23()
-        {
-            var src1 = "class C2(int x, int y) : C1(() => x + y) { void M() { x++; } } class C1(System.Func<int> x);";
-            var src2 = "class C2(int x, int y) : C1(() => y) { void M() { x++; } } class C1(System.Func<int> x);";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "class C2", FeaturesResources.class_));
-        }
-
-        [Fact]
-        public void PrimaryConstructors_24()
-        {
-            var src1 = "class C2(int x) : C1(null) { void M() { x++; } } class C1(System.Func<int> x);";
-            var src2 = "class C2(int x) : C1(() => x) { void M() { x++; } } class C1(System.Func<int> x);";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "class C2", FeaturesResources.class_));
-        }
-
-        [Fact]
-        public void PrimaryConstructors_25()
-        {
-            var src1 = "class C2(int x) : C1(() => x) { void M() { x++; } } class C1(System.Func<int> x);";
-            var src2 = "class C2(int x) : C1(null) { void M() { x++; } } class C1(System.Func<int> x);";
-
-            var edits = GetTopEdits(src1, src2);
-
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.Update, "class C2", FeaturesResources.class_));
-        }
-
-        #endregion
     }
 }
diff --git a/src/EditorFeatures/CSharpTest/Structure/BlockSyntaxStructureTests.cs b/src/EditorFeatures/CSharpTest/Structure/BlockSyntaxStructureTests.cs
index 4eedd273d383a..182c4f5560fc6 100644
--- a/src/EditorFeatures/CSharpTest/Structure/BlockSyntaxStructureTests.cs
+++ b/src/EditorFeatures/CSharpTest/Structure/BlockSyntaxStructureTests.cs
@@ -286,6 +286,27 @@ await VerifyBlockSpansAsync(code,
                 Region("textspan", "hint", CSharpStructureHelpers.Ellipsis, autoCollapse: false));
         }
 
+        [Fact]
+        public async Task TestElseClause2()
+        {
+            const string code = @"
+class C
+{
+    void M()
+    {
+        {|primaryhint:if (true){|primarytextspan:
+        {
+        }|}|}
+        {|hint:else{|textspan:
+        {$$
+        }|}|}
+    }
+}";
+
+            await VerifyBlockSpansAsync(code,
+                Region("textspan", "hint", "primaryhint", "primarytextspan", CSharpStructureHelpers.Ellipsis, autoCollapse: false));
+        }
+
         [Fact]
         public async Task TestIfElse1()
         {
diff --git a/src/EditorFeatures/Core.Wpf/Peek/PeekableItemFactory.cs b/src/EditorFeatures/Core.Wpf/Peek/PeekableItemFactory.cs
index 5fa5d2e5e210d..d275f78d275f5 100644
--- a/src/EditorFeatures/Core.Wpf/Peek/PeekableItemFactory.cs
+++ b/src/EditorFeatures/Core.Wpf/Peek/PeekableItemFactory.cs
@@ -61,7 +61,7 @@ public async Task<IEnumerable<IPeekableItem>> GetPeekableItemsAsync(
 
             var solution = project.Solution;
             symbol = await SymbolFinder.FindSourceDefinitionAsync(symbol, solution, cancellationToken).ConfigureAwait(false) ?? symbol;
-            symbol = await GoToDefinitionHelpers.TryGetPreferredSymbolAsync(solution, symbol, cancellationToken).ConfigureAwait(false);
+            symbol = await GoToDefinitionFeatureHelpers.TryGetPreferredSymbolAsync(solution, symbol, cancellationToken).ConfigureAwait(false);
             if (symbol is null)
                 return ImmutableArray<IPeekableItem>.Empty;
 
diff --git a/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActions/SuggestedAction.cs b/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActions/SuggestedAction.cs
index 9d3834fa67932..6b2ff81043acd 100644
--- a/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActions/SuggestedAction.cs
+++ b/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActions/SuggestedAction.cs
@@ -17,6 +17,7 @@
 using Microsoft.CodeAnalysis.Extensions;
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.Shared.Utilities;
+using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.Core.Imaging;
 using Microsoft.VisualStudio.Imaging.Interop;
@@ -112,6 +113,8 @@ private async Task InvokeAsync()
         {
             try
             {
+                using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.SuggestedAction_Application_Summary, $"Total");
+
                 using var token = SourceProvider.OperationListener.BeginAsyncOperation($"{nameof(SuggestedAction)}.{nameof(Invoke)}");
                 using var context = SourceProvider.UIThreadOperationExecutor.BeginExecute(
                     EditorFeaturesResources.Execute_Suggested_Action, CodeAction.Title, allowCancellation: true, showProgress: true);
diff --git a/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource.cs b/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource.cs
index 40e2bd4688400..885ccbc2995fd 100644
--- a/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource.cs
+++ b/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource.cs
@@ -4,9 +4,7 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -20,8 +18,6 @@
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.CodeAnalysis.Text;
-using Microsoft.CodeAnalysis.Text.Shared.Extensions;
-using Microsoft.CodeAnalysis.UnifiedSuggestions;
 using Microsoft.VisualStudio.Language.Intellisense;
 using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Editor;
diff --git a/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource_Async.cs b/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource_Async.cs
index fee59d8d3620c..c7e8bf0d93c7f 100644
--- a/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource_Async.cs
+++ b/src/EditorFeatures/Core.Wpf/Suggestions/SuggestedActionsSource_Async.cs
@@ -20,6 +20,7 @@
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Remote;
+using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.CodeAnalysis.Text.Shared.Extensions;
 using Microsoft.CodeAnalysis.UnifiedSuggestions;
@@ -102,79 +103,95 @@ private async Task GetSuggestedActionsWorkerAsync(
                     // items should be pushed higher up, and less important items shouldn't take up that much space.
                     var currentActionCount = 0;
 
-                    var pendingActionSets = new MultiDictionary<CodeActionRequestPriority, SuggestedActionSet>();
+                    using var _ = PooledDictionary<CodeActionRequestPriority, ArrayBuilder<SuggestedActionSet>>.GetInstance(out var pendingActionSets);
 
-                    // Keep track of the diagnostic analyzers that have been deprioritized across calls to the
-                    // diagnostic engine.  We'll run them once we get around to the low-priority bucket.  We want to
-                    // keep track of this *across* calls to each priority. So we create this set outside of the loop and
-                    // then pass it continuously from one priority group to the next.
-                    var lowPriorityAnalyzers = new ConcurrentSet<DiagnosticAnalyzer>();
-
-                    // Collectors are in priority order.  So just walk them from highest to lowest.
-                    foreach (var collector in collectors)
+                    try
                     {
-                        if (TryGetPriority(collector.Priority) is CodeActionRequestPriority priority)
+                        // Keep track of the diagnostic analyzers that have been deprioritized across calls to the
+                        // diagnostic engine.  We'll run them once we get around to the low-priority bucket.  We want to
+                        // keep track of this *across* calls to each priority. So we create this set outside of the loop and
+                        // then pass it continuously from one priority group to the next.
+                        var lowPriorityAnalyzers = new ConcurrentSet<DiagnosticAnalyzer>();
+
+                        using var _2 = TelemetryLogging.LogBlockTimeAggregated(FunctionId.SuggestedAction_Summary, $"Total");
+
+                        // Collectors are in priority order.  So just walk them from highest to lowest.
+                        foreach (var collector in collectors)
                         {
-                            var allSets = GetCodeFixesAndRefactoringsAsync(
-                                state, requestedActionCategories, document,
-                                range, selection,
-                                addOperationScope: _ => null,
-                                new SuggestedActionPriorityProvider(priority, lowPriorityAnalyzers),
-                                currentActionCount, cancellationToken).WithCancellation(cancellationToken).ConfigureAwait(false);
-
-                            await foreach (var set in allSets)
+                            if (TryGetPriority(collector.Priority) is CodeActionRequestPriority priority)
                             {
-                                // Determine the corresponding lightbulb priority class corresponding to the priority
-                                // group the set says it wants to be in.
-                                var actualSetPriority = set.Priority switch
-                                {
-                                    SuggestedActionSetPriority.None => CodeActionRequestPriority.Lowest,
-                                    SuggestedActionSetPriority.Low => CodeActionRequestPriority.Low,
-                                    SuggestedActionSetPriority.Medium => CodeActionRequestPriority.Normal,
-                                    SuggestedActionSetPriority.High => CodeActionRequestPriority.High,
-                                    _ => throw ExceptionUtilities.UnexpectedValue(set.Priority),
-                                };
-
-                                // if the actual priority class is lower than the one we're currently in, then hold onto
-                                // this set for later, and place it in that priority group once we get there.
-                                if (actualSetPriority < priority)
+                                using var _3 = TelemetryLogging.LogBlockTimeAggregated(FunctionId.SuggestedAction_Summary, $"Total.Pri{(int)priority}");
+
+                                var allSets = GetCodeFixesAndRefactoringsAsync(
+                                    state, requestedActionCategories, document,
+                                    range, selection,
+                                    addOperationScope: _ => null,
+                                    new SuggestedActionPriorityProvider(priority, lowPriorityAnalyzers),
+                                    currentActionCount, cancellationToken).WithCancellation(cancellationToken).ConfigureAwait(false);
+
+                                await foreach (var set in allSets)
                                 {
-                                    pendingActionSets.Add(actualSetPriority, set);
+                                    // Determine the corresponding lightbulb priority class corresponding to the priority
+                                    // group the set says it wants to be in.
+                                    var actualSetPriority = set.Priority switch
+                                    {
+                                        SuggestedActionSetPriority.None => CodeActionRequestPriority.Lowest,
+                                        SuggestedActionSetPriority.Low => CodeActionRequestPriority.Low,
+                                        SuggestedActionSetPriority.Medium => CodeActionRequestPriority.Normal,
+                                        SuggestedActionSetPriority.High => CodeActionRequestPriority.High,
+                                        _ => throw ExceptionUtilities.UnexpectedValue(set.Priority),
+                                    };
+
+                                    // if the actual priority class is lower than the one we're currently in, then hold onto
+                                    // this set for later, and place it in that priority group once we get there.
+                                    if (actualSetPriority < priority)
+                                    {
+                                        var builder = pendingActionSets.GetOrAdd(actualSetPriority, _ => ArrayBuilder<SuggestedActionSet>.GetInstance());
+                                        builder.Add(set);
+                                    }
+                                    else
+                                    {
+                                        currentActionCount += set.Actions.Count();
+                                        collector.Add(set);
+                                    }
                                 }
-                                else
+
+                                // We're finishing up with a particular priority group, and we're about to go to a priority
+                                // group one lower than what we have (hence `priority - 1`).  Take any pending items in the
+                                // group we're *about* to go into and add them at the end of this group.
+                                //
+                                // For example, if we're in the high group, and we have an pending items in the normal
+                                // bucket, then add them at the end of the high group.  The reason for this is that we
+                                // already have computed the items and we don't want to force them to have to wait for all
+                                // the processing in their own group to show up.  i.e. imagine if we added at the start of
+                                // the next group.  They'd be in the same location in the lightbulb as when we add at the
+                                // end of the current group, but they'd show up only when that group totally finished,
+                                // instead of right now.
+                                //
+                                // This is critical given that the lower pri groups are often much lower (which is why they
+                                // they choose to be in that class).  We don't want a fast item computed by a higher pri
+                                // provider to still have to wait on those slow items.
+                                if (pendingActionSets.TryGetValue(priority - 1, out var setBuilder))
                                 {
-                                    currentActionCount += set.Actions.Count();
-                                    collector.Add(set);
+                                    foreach (var set in setBuilder)
+                                    {
+                                        currentActionCount += set.Actions.Count();
+                                        collector.Add(set);
+                                    }
                                 }
                             }
 
-                            // We're finishing up with a particular priority group, and we're about to go to a priority
-                            // group one lower than what we have (hence `priority - 1`).  Take any pending items in the
-                            // group we're *about* to go into and add them at the end of this group.
-                            //
-                            // For example, if we're in the high group, and we have an pending items in the normal
-                            // bucket, then add them at the end of the high group.  The reason for this is that we
-                            // already have computed the items and we don't want to force them to have to wait for all
-                            // the processing in their own group to show up.  i.e. imagine if we added at the start of
-                            // the next group.  They'd be in the same location in the lightbulb as when we add at the
-                            // end of the current group, but they'd show up only when that group totally finished,
-                            // instead of right now.
-                            //
-                            // This is critical given that the lower pri groups are often much lower (which is why they
-                            // they choose to be in that class).  We don't want a fast item computed by a higher pri
-                            // provider to still have to wait on those slow items.
-                            foreach (var set in pendingActionSets[priority - 1])
-                            {
-                                currentActionCount += set.Actions.Count();
-                                collector.Add(set);
-                            }
+                            // Ensure we always complete the collector even if we didn't add any items to it.
+                            // This ensures that we unblock the UI from displaying all the results for that
+                            // priority class.
+                            collector.Complete();
+                            completedCollectors.Add(collector);
                         }
-
-                        // Ensure we always complete the collector even if we didn't add any items to it.
-                        // This ensures that we unblock the UI from displaying all the results for that
-                        // priority class.
-                        collector.Complete();
-                        completedCollectors.Add(collector);
+                    }
+                    finally
+                    {
+                        foreach (var (_, builder) in pendingActionSets)
+                            builder.Free();
                     }
                 }
             }
@@ -214,48 +231,52 @@ private async IAsyncEnumerable<SuggestedActionSet> GetCodeFixesAndRefactoringsAs
 
                 yield break;
 
-                Task<ImmutableArray<UnifiedSuggestedActionSet>> GetCodeFixesAsync()
+                async Task<ImmutableArray<UnifiedSuggestedActionSet>> GetCodeFixesAsync()
                 {
+                    using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.SuggestedAction_Summary, $"Total.Pri{(int)priorityProvider.Priority}.{nameof(GetCodeFixesAsync)}");
+
                     if (owner._codeFixService == null ||
                         !supportsFeatureService.SupportsCodeFixes(target.SubjectBuffer) ||
                         !requestedActionCategories.Contains(PredefinedSuggestedActionCategoryNames.CodeFix))
                     {
-                        return SpecializedTasks.EmptyImmutableArray<UnifiedSuggestedActionSet>();
+                        return ImmutableArray<UnifiedSuggestedActionSet>.Empty;
                     }
 
-                    return UnifiedSuggestedActionsSource.GetFilterAndOrderCodeFixesAsync(
+                    return await UnifiedSuggestedActionsSource.GetFilterAndOrderCodeFixesAsync(
                         workspace, owner._codeFixService, document, range.Span.ToTextSpan(),
-                        priorityProvider, options, addOperationScope, cancellationToken).AsTask();
+                        priorityProvider, options, addOperationScope, cancellationToken).ConfigureAwait(false);
                 }
 
-                Task<ImmutableArray<UnifiedSuggestedActionSet>> GetRefactoringsAsync()
+                async Task<ImmutableArray<UnifiedSuggestedActionSet>> GetRefactoringsAsync()
                 {
+                    using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.SuggestedAction_Summary, $"Total.Pri{(int)priorityProvider.Priority}.{nameof(GetRefactoringsAsync)}");
+
                     if (!selection.HasValue)
                     {
                         // this is here to fail test and see why it is failed.
                         Trace.WriteLine("given range is not current");
-                        return SpecializedTasks.EmptyImmutableArray<UnifiedSuggestedActionSet>();
+                        return ImmutableArray<UnifiedSuggestedActionSet>.Empty;
                     }
 
                     if (!this.GlobalOptions.GetOption(EditorComponentOnOffOptions.CodeRefactorings) ||
                         owner._codeRefactoringService == null ||
                         !supportsFeatureService.SupportsRefactorings(subjectBuffer))
                     {
-                        return SpecializedTasks.EmptyImmutableArray<UnifiedSuggestedActionSet>();
+                        return ImmutableArray<UnifiedSuggestedActionSet>.Empty;
                     }
 
                     // 'CodeActionRequestPriority.Lowest' is reserved for suppression/configuration code fixes.
                     // No code refactoring should have this request priority.
                     if (priorityProvider.Priority == CodeActionRequestPriority.Lowest)
-                        return SpecializedTasks.EmptyImmutableArray<UnifiedSuggestedActionSet>();
+                        return ImmutableArray<UnifiedSuggestedActionSet>.Empty;
 
                     // If we are computing refactorings outside the 'Refactoring' context, i.e. for example, from the lightbulb under a squiggle or selection,
                     // then we want to filter out refactorings outside the selection span.
                     var filterOutsideSelection = !requestedActionCategories.Contains(PredefinedSuggestedActionCategoryNames.Refactoring);
 
-                    return UnifiedSuggestedActionsSource.GetFilterAndOrderCodeRefactoringsAsync(
+                    return await UnifiedSuggestedActionsSource.GetFilterAndOrderCodeRefactoringsAsync(
                         workspace, owner._codeRefactoringService, document, selection.Value, priorityProvider.Priority, options,
-                        addOperationScope, filterOutsideSelection, cancellationToken);
+                        addOperationScope, filterOutsideSelection, cancellationToken).ConfigureAwait(false);
                 }
 
                 [return: NotNullIfNotNull(nameof(unifiedSuggestedActionSet))]
diff --git a/src/EditorFeatures/Core/CodeDefinitionWindow/DefinitionContextTracker.cs b/src/EditorFeatures/Core/CodeDefinitionWindow/DefinitionContextTracker.cs
index abe65bdde88ef..42e07c40d24f0 100644
--- a/src/EditorFeatures/Core/CodeDefinitionWindow/DefinitionContextTracker.cs
+++ b/src/EditorFeatures/Core/CodeDefinitionWindow/DefinitionContextTracker.cs
@@ -11,7 +11,6 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Editor;
-using Microsoft.CodeAnalysis.Editor.Shared.Options;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.ErrorReporting;
 using Microsoft.CodeAnalysis.FindSymbols;
@@ -127,7 +126,7 @@ private async Task UpdateForCaretPositionAsync(SnapshotPoint pointInRoslynSnapsh
         {
             try
             {
-                await _asyncListener.Delay(TimeSpan.FromMilliseconds(250), cancellationToken).ConfigureAwait(false);
+                await _asyncListener.Delay(DelayTimeSpan.Short, cancellationToken).ConfigureAwait(false);
 
                 // If it's not open, don't do anything, since if we are going to show locations in metadata that might
                 // be expensive. This doesn't cause a functional issue, since opening the window clears whatever was previously there
diff --git a/src/EditorFeatures/Core/Diagnostics/AbstractDiagnosticsAdornmentTaggerProvider.RoslynErrorTag.cs b/src/EditorFeatures/Core/Diagnostics/AbstractDiagnosticsAdornmentTaggerProvider.RoslynErrorTag.cs
index ed42d35805c08..3e0e5de2054a3 100644
--- a/src/EditorFeatures/Core/Diagnostics/AbstractDiagnosticsAdornmentTaggerProvider.RoslynErrorTag.cs
+++ b/src/EditorFeatures/Core/Diagnostics/AbstractDiagnosticsAdornmentTaggerProvider.RoslynErrorTag.cs
@@ -57,7 +57,7 @@ public bool Equals(RoslynErrorTag? other)
             {
                 return other != null &&
                     this.ErrorType == other.ErrorType &&
-                    this._data.GetValidHelpLinkUri() == other._data.GetValidHelpLinkUri() &&
+                    this._data.HelpLink == other._data.HelpLink &&
                     this._data.Id == other._data.Id &&
                     this._data.Message == other._data.Message;
             }
diff --git a/src/EditorFeatures/Core/EditAndContinue/EditAndContinueLanguageService.cs b/src/EditorFeatures/Core/EditAndContinue/EditAndContinueLanguageService.cs
index c326e8496d0a8..a6924a4b892b1 100644
--- a/src/EditorFeatures/Core/EditAndContinue/EditAndContinueLanguageService.cs
+++ b/src/EditorFeatures/Core/EditAndContinue/EditAndContinueLanguageService.cs
@@ -36,6 +36,7 @@ public NoSessionException()
         }
 
         private readonly PdbMatchingSourceTextProvider _sourceTextProvider;
+        private readonly IDiagnosticsRefresher _diagnosticRefresher;
         private readonly Lazy<IManagedHotReloadService> _debuggerService;
         private readonly IDiagnosticAnalyzerService _diagnosticService;
         private readonly EditAndContinueDiagnosticUpdateSource _diagnosticUpdateSource;
@@ -63,13 +64,15 @@ public EditAndContinueLanguageService(
             Lazy<IManagedHotReloadService> debuggerService,
             IDiagnosticAnalyzerService diagnosticService,
             EditAndContinueDiagnosticUpdateSource diagnosticUpdateSource,
-            PdbMatchingSourceTextProvider sourceTextProvider)
+            PdbMatchingSourceTextProvider sourceTextProvider,
+            IDiagnosticsRefresher diagnosticRefresher)
         {
             WorkspaceProvider = workspaceProvider;
             _debuggerService = debuggerService;
             _diagnosticService = diagnosticService;
             _diagnosticUpdateSource = diagnosticUpdateSource;
             _sourceTextProvider = sourceTextProvider;
+            _diagnosticRefresher = diagnosticRefresher;
         }
 
         public void SetFileLoggingDirectory(string? logDirectory)
@@ -160,6 +163,8 @@ public async ValueTask EnterBreakStateAsync(CancellationToken cancellationToken)
             try
             {
                 await session.BreakStateOrCapabilitiesChangedAsync(_diagnosticService, _diagnosticUpdateSource, inBreakState: true, cancellationToken).ConfigureAwait(false);
+
+                _diagnosticRefresher.RequestWorkspaceRefresh();
             }
             catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
             {
@@ -188,6 +193,8 @@ public async ValueTask ExitBreakStateAsync(CancellationToken cancellationToken)
             try
             {
                 await session.BreakStateOrCapabilitiesChangedAsync(_diagnosticService, _diagnosticUpdateSource, inBreakState: false, cancellationToken).ConfigureAwait(false);
+
+                _diagnosticRefresher.RequestWorkspaceRefresh();
                 GetActiveStatementTrackingService().EndTracking();
             }
             catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
@@ -207,6 +214,8 @@ public async ValueTask OnCapabilitiesChangedAsync(CancellationToken cancellation
             try
             {
                 await GetDebuggingSession().BreakStateOrCapabilitiesChangedAsync(_diagnosticService, _diagnosticUpdateSource, inBreakState: null, cancellationToken).ConfigureAwait(false);
+
+                _diagnosticRefresher.RequestWorkspaceRefresh();
             }
             catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
             {
@@ -271,6 +280,8 @@ public async ValueTask EndSessionAsync(CancellationToken cancellationToken)
                 {
                     var solution = GetCurrentCompileTimeSolution();
                     await GetDebuggingSession().EndDebuggingSessionAsync(solution, _diagnosticUpdateSource, _diagnosticService, cancellationToken).ConfigureAwait(false);
+
+                    _diagnosticRefresher.RequestWorkspaceRefresh();
                 }
                 catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
                 {
@@ -345,6 +356,8 @@ public async ValueTask<ManagedHotReloadUpdates> GetUpdatesAsync(CancellationToke
                 _pendingUpdatedDesignTimeSolution = designTimeSolution;
             }
 
+            _diagnosticRefresher.RequestWorkspaceRefresh();
+
             var diagnostics = await EmitSolutionUpdateResults.GetHotReloadDiagnosticsAsync(solution, diagnosticData, rudeEdits, syntaxError, moduleUpdates.Status, cancellationToken).ConfigureAwait(false);
             return new ManagedHotReloadUpdates(moduleUpdates.Updates.FromContract(), diagnostics.FromContract());
         }
diff --git a/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptBlockStructureService.cs b/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptBlockStructureService.cs
index 941da3d4923c1..9498dd02b30d6 100644
--- a/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptBlockStructureService.cs
+++ b/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptBlockStructureService.cs
@@ -31,7 +31,7 @@ public override async Task<BlockStructure> GetBlockStructureAsync(Document docum
             var blockStructure = await _impl.GetBlockStructureAsync(document, cancellationToken).ConfigureAwait(false);
 
             return new BlockStructure(blockStructure.Spans.SelectAsArray(
-                x => new BlockSpan(x.Type, x.IsCollapsible, x.TextSpan, x.HintSpan, x.BannerText, x.AutoCollapse, x.IsDefaultCollapsed)));
+                x => new BlockSpan(x.Type!, x.IsCollapsible, x.TextSpan, x.HintSpan, primarySpans: null, x.BannerText, x.AutoCollapse, x.IsDefaultCollapsed)));
         }
     }
 }
diff --git a/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptPullDiagnosticHandlerProvider.cs b/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptPullDiagnosticHandlerProvider.cs
index 42a154aefbd1d..ec2b2cecb080e 100644
--- a/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptPullDiagnosticHandlerProvider.cs
+++ b/src/EditorFeatures/Core/ExternalAccess/VSTypeScript/VSTypeScriptPullDiagnosticHandlerProvider.cs
@@ -3,16 +3,12 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections.Immutable;
 using System.Composition;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.EditAndContinue;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.LanguageServer;
-using Microsoft.CodeAnalysis.LanguageServer.Handler;
 using Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics;
 using Microsoft.CodeAnalysis.Options;
-using Microsoft.VisualStudio.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.VSTypeScript;
 
@@ -23,8 +19,8 @@ internal class VSTypeScriptDocumentPullDiagnosticHandlerFactory : DocumentPullDi
     [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
     public VSTypeScriptDocumentPullDiagnosticHandlerFactory(
         IDiagnosticAnalyzerService analyzerService,
-        EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
-        IGlobalOptionService globalOptions) : base(analyzerService, editAndContinueDiagnosticUpdateSource, globalOptions)
+        IDiagnosticsRefresher diagnosticsRefresher,
+        IGlobalOptionService globalOptions) : base(analyzerService, diagnosticsRefresher, globalOptions)
     {
     }
 }
@@ -36,8 +32,8 @@ internal class VSTypeScriptWorkspacePullDiagnosticHandler : WorkspacePullDiagnos
     [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
     public VSTypeScriptWorkspacePullDiagnosticHandler(
         IDiagnosticAnalyzerService analyzerService,
-        EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
-        IGlobalOptionService globalOptions) : base(analyzerService, editAndContinueDiagnosticUpdateSource, globalOptions)
+        IDiagnosticsRefresher diagnosticsRefresher,
+        IGlobalOptionService globalOptions) : base(analyzerService, diagnosticsRefresher, globalOptions)
     {
     }
 }
diff --git a/src/EditorFeatures/Core/GoToDefinition/AbstractGoToDefinitionService.cs b/src/EditorFeatures/Core/GoToDefinition/AbstractGoToDefinitionService.cs
index 03371cd64a531..36b09ed55ad80 100644
--- a/src/EditorFeatures/Core/GoToDefinition/AbstractGoToDefinitionService.cs
+++ b/src/EditorFeatures/Core/GoToDefinition/AbstractGoToDefinitionService.cs
@@ -125,7 +125,7 @@ protected AbstractAsyncGoToDefinitionService(
             using var _ = ArrayBuilder<DefinitionItem>.GetInstance(out var builder);
             foreach (var impl in interfaceImpls)
             {
-                builder.AddRange(await GoToDefinitionHelpers.GetDefinitionsAsync(
+                builder.AddRange(await GoToDefinitionFeatureHelpers.GetDefinitionsAsync(
                     impl, solution, thirdPartyNavigationAllowed: false, cancellationToken).ConfigureAwait(false));
             }
 
diff --git a/src/EditorFeatures/Core/GoToDefinition/GoToDefinitionHelpers.cs b/src/EditorFeatures/Core/GoToDefinition/GoToDefinitionHelpers.cs
index 2588d9f5f93da..f68c0858d2ac6 100644
--- a/src/EditorFeatures/Core/GoToDefinition/GoToDefinitionHelpers.cs
+++ b/src/EditorFeatures/Core/GoToDefinition/GoToDefinitionHelpers.cs
@@ -3,109 +3,18 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Diagnostics.CodeAnalysis;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Editor.Host;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
-using Microsoft.CodeAnalysis.FindSymbols;
 using Microsoft.CodeAnalysis.FindUsages;
 using Microsoft.CodeAnalysis.Navigation;
-using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Extensions;
-using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.GoToDefinition
 {
     internal static class GoToDefinitionHelpers
     {
-        public static async Task<ImmutableArray<DefinitionItem>> GetDefinitionsAsync(
-            ISymbol? symbol,
-            Solution solution,
-            bool thirdPartyNavigationAllowed,
-            CancellationToken cancellationToken)
-        {
-            symbol = await TryGetPreferredSymbolAsync(solution, symbol, cancellationToken).ConfigureAwait(false);
-            if (symbol is null)
-                return ImmutableArray.Create<DefinitionItem>();
-
-            using var _ = ArrayBuilder<DefinitionItem>.GetInstance(out var definitions);
-
-            // Going to a symbol may end up actually showing the symbol in the Find-Usages window.
-            // This happens when there is more than one location for the symbol (i.e. for partial
-            // symbols) and we don't know the best place to take you to.
-            //
-            // The FindUsages window supports showing the classified text for an item.  It does this
-            // in two ways.  Either the item can pass along its classified text (and the window will
-            // defer to that), or the item will have no classified text, and the window will compute
-            // it in the BG.
-            //
-            // Passing along the classified information is valuable for OOP scenarios where we want
-            // all that expensive computation done on the OOP side and not in the VS side.
-            //
-            // However, Go To Definition is all in-process, and is also synchronous.  So we do not
-            // want to fetch the classifications here.  It slows down the command and leads to a
-            // measurable delay in our perf tests.
-            //
-            // So, if we only have a single location to go to, this does no unnecessary work.  And,
-            // if we do have multiple locations to show, it will just be done in the BG, unblocking
-            // this command thread so it can return the user faster.
-            var definitionItem = symbol.ToNonClassifiedDefinitionItem(solution, includeHiddenLocations: true);
-
-            if (thirdPartyNavigationAllowed)
-            {
-                var factory = solution.Services.GetService<IDefinitionsAndReferencesFactory>();
-                if (factory != null)
-                {
-                    var thirdPartyItem = await factory.GetThirdPartyDefinitionItemAsync(solution, definitionItem, cancellationToken).ConfigureAwait(false);
-                    definitions.AddIfNotNull(thirdPartyItem);
-                }
-            }
-
-            definitions.Add(definitionItem);
-            return definitions.ToImmutable();
-        }
-
-        public static async Task<ISymbol?> TryGetPreferredSymbolAsync(
-            Solution solution, ISymbol? symbol, CancellationToken cancellationToken)
-        {
-            // VB global import aliases have a synthesized SyntaxTree.
-            // We can't go to the definition of the alias, so use the target type.
-
-            var alias = symbol as IAliasSymbol;
-            if (alias != null)
-            {
-                if (alias.Target is INamespaceSymbol ns && ns.IsGlobalNamespace)
-                    return null;
-            }
-
-            // VB global import aliases have a synthesized SyntaxTree.
-            // We can't go to the definition of the alias, so use the target type.
-
-            if (alias != null)
-            {
-                var sourceLocations = NavigableItemFactory.GetPreferredSourceLocations(
-                    solution, symbol, cancellationToken);
-
-                if (sourceLocations.All(l => solution.GetDocument(l.SourceTree) == null))
-                    symbol = alias.Target;
-            }
-
-            var definition = await SymbolFinder.FindSourceDefinitionAsync(symbol, solution, cancellationToken).ConfigureAwait(false);
-            cancellationToken.ThrowIfCancellationRequested();
-
-            symbol = definition ?? symbol;
-
-            // If it is a partial method declaration with no body, choose to go to the implementation
-            // that has a method body.
-            if (symbol is IMethodSymbol method)
-                symbol = method.PartialImplementationPart ?? symbol;
-
-            return symbol;
-        }
-
         public static async Task<bool> TryNavigateToLocationAsync(
             ISymbol symbol,
             Solution solution,
@@ -131,7 +40,8 @@ public static async Task<bool> TryNavigateToLocationAsync(
             var title = string.Format(EditorFeaturesResources._0_declarations,
                 FindUsagesHelpers.GetDisplayName(symbol));
 
-            var definitions = await GetDefinitionsAsync(symbol, solution, thirdPartyNavigationAllowed, cancellationToken).ConfigureAwait(false);
+            var definitions = await GoToDefinitionFeatureHelpers.GetDefinitionsAsync(
+                symbol, solution, thirdPartyNavigationAllowed, cancellationToken).ConfigureAwait(false);
 
             return await streamingPresenter.GetStreamingLocationAsync(
                 threadingContext, solution.Workspace, title, definitions, cancellationToken).ConfigureAwait(false);
diff --git a/src/EditorFeatures/Core/InlineRename/InlineRenameSession.OpenTextBufferManager.cs b/src/EditorFeatures/Core/InlineRename/InlineRenameSession.OpenTextBufferManager.cs
index f31ec0970eeef..2d1393f7765ca 100644
--- a/src/EditorFeatures/Core/InlineRename/InlineRenameSession.OpenTextBufferManager.cs
+++ b/src/EditorFeatures/Core/InlineRename/InlineRenameSession.OpenTextBufferManager.cs
@@ -453,9 +453,8 @@ internal void ApplyConflictResolutionEdits(IInlineRenameReplacementInfo conflict
 
                         // Show merge conflicts comments as unresolvable conflicts, and do not
                         // show any other rename-related spans that overlap a merge conflict comment.
-                        var mergeConflictComments = mergeResult.MergeConflictCommentSpans.ContainsKey(document.Id)
-                            ? mergeResult.MergeConflictCommentSpans[document.Id]
-                            : SpecializedCollections.EmptyEnumerable<TextSpan>();
+                        mergeResult.MergeConflictCommentSpans.TryGetValue(document.Id, out var mergeConflictComments);
+                        mergeConflictComments ??= SpecializedCollections.EmptyEnumerable<TextSpan>();
 
                         foreach (var conflict in mergeConflictComments)
                         {
@@ -737,8 +736,8 @@ public void Dispose()
                 private SnapshotPoint GetNewEndpoint(TextSpan span)
                 {
                     var snapshot = _openTextBufferManager._subjectBuffer.CurrentSnapshot;
-                    var endPoint = _openTextBufferManager._referenceSpanToLinkedRenameSpanMap.ContainsKey(span)
-                        ? _openTextBufferManager._referenceSpanToLinkedRenameSpanMap[span].TrackingSpan.GetEndPoint(snapshot)
+                    var endPoint = _openTextBufferManager._referenceSpanToLinkedRenameSpanMap.TryGetValue(span, out var renameTrackingSpan)
+                        ? renameTrackingSpan.TrackingSpan.GetEndPoint(snapshot)
                         : _openTextBufferManager._referenceSpanToLinkedRenameSpanMap.First(kvp => kvp.Key.OverlapsWith(span)).Value.TrackingSpan.GetEndPoint(snapshot);
                     return _openTextBufferManager.ActiveTextView.BufferGraph.MapUpToBuffer(endPoint, PointTrackingMode.Positive, PositionAffinity.Successor, _openTextBufferManager.ActiveTextView.TextBuffer).Value;
                 }
diff --git a/src/EditorFeatures/Core/InlineRename/InlineRenameSession.cs b/src/EditorFeatures/Core/InlineRename/InlineRenameSession.cs
index f99a6d22fa9e2..cb71c4bad36f6 100644
--- a/src/EditorFeatures/Core/InlineRename/InlineRenameSession.cs
+++ b/src/EditorFeatures/Core/InlineRename/InlineRenameSession.cs
@@ -659,6 +659,11 @@ private async Task DismissUIAndRollbackEditsAndEndRenameSessionAsync(
             bool previewChanges,
             Func<Task> finalCommitAction = null)
         {
+            // Note: this entire sequence of steps is not cancellable.  We must perform it all to get back to a correct
+            // state for all the editors the user is interacting with.
+            var cancellationToken = CancellationToken.None;
+            await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
+
             if (_dismissed)
             {
                 return;
@@ -666,11 +671,6 @@ private async Task DismissUIAndRollbackEditsAndEndRenameSessionAsync(
 
             _dismissed = true;
 
-            // Note: this entire sequence of steps is not cancellable.  We must perform it all to get back to a correct
-            // state for all the editors the user is interacting with.
-            var cancellationToken = CancellationToken.None;
-            await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
-
             // Remove all our adornments and restore all buffer texts to their initial state.
             DismissUIAndRollbackEdits();
 
@@ -816,7 +816,7 @@ private async Task CommitCoreAsync(IUIThreadOperationContext operationContext, b
             var eventName = previewChanges ? FunctionId.Rename_CommitCoreWithPreview : FunctionId.Rename_CommitCore;
             using (Logger.LogBlock(eventName, KeyValueLogMessage.Create(LogType.UserAction), cancellationToken))
             {
-                var info = await _conflictResolutionTask.JoinAsync(cancellationToken).ConfigureAwait(false);
+                var info = await _conflictResolutionTask.JoinAsync(cancellationToken).ConfigureAwait(true);
                 var newSolution = info.NewSolution;
 
                 if (previewChanges)
diff --git a/src/EditorFeatures/Core/LanguageServer/AlwaysActivateInProcLanguageClient.cs b/src/EditorFeatures/Core/LanguageServer/AlwaysActivateInProcLanguageClient.cs
index f0c154c74c18c..f2cf2461aad62 100644
--- a/src/EditorFeatures/Core/LanguageServer/AlwaysActivateInProcLanguageClient.cs
+++ b/src/EditorFeatures/Core/LanguageServer/AlwaysActivateInProcLanguageClient.cs
@@ -127,8 +127,8 @@ public override ServerCapabilities GetCapabilities(ClientCapabilities clientCapa
                     Range = true,
                     Legend = new SemanticTokensLegend
                     {
-                        TokenTypes = SemanticTokensSchema.GetSchema(clientCapabilities).AllTokenTypes.ToArray(),
-                        TokenModifiers = new string[] { SemanticTokenModifiers.Static }
+                        TokenTypes = SemanticTokensSchema.GetSchema(clientCapabilities.HasVisualStudioLspCapability()).AllTokenTypes.ToArray(),
+                        TokenModifiers = SemanticTokensSchema.TokenModifiers
                     }
                 };
             }
diff --git a/src/EditorFeatures/Core/LanguageServer/EditorLspCompletionResultCreationService.cs b/src/EditorFeatures/Core/LanguageServer/EditorLspCompletionResultCreationService.cs
index 9201b9f990db1..24dcd042d685e 100644
--- a/src/EditorFeatures/Core/LanguageServer/EditorLspCompletionResultCreationService.cs
+++ b/src/EditorFeatures/Core/LanguageServer/EditorLspCompletionResultCreationService.cs
@@ -20,7 +20,7 @@
 namespace Microsoft.CodeAnalysis.LanguageServer
 {
     [ExportWorkspaceService(typeof(ILspCompletionResultCreationService), ServiceLayer.Editor), Shared]
-    internal sealed class EditorLspCompletionResultCreationService : ILspCompletionResultCreationService
+    internal sealed class EditorLspCompletionResultCreationService : AbstractLspCompletionResultCreationService
     {
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
@@ -28,17 +28,20 @@ public EditorLspCompletionResultCreationService()
         {
         }
 
-        public async Task<LSP.CompletionItem> CreateAsync(
+        protected override async Task<LSP.CompletionItem> CreateItemAndPopulateTextEditAsync(
             Document document,
             SourceText documentText,
             bool snippetsSupported,
             bool itemDefaultsSupported,
             TextSpan defaultSpan,
+            string typedText,
             CompletionItem item,
+            CompletionService completionService,
             CancellationToken cancellationToken)
         {
             var lspItem = new LSP.VSInternalCompletionItem
             {
+                Label = item.GetEntireDisplayText(),
                 Icon = new ImageElement(item.Tags.GetFirstGlyph().GetImageId())
             };
 
@@ -55,37 +58,43 @@ public EditorLspCompletionResultCreationService()
             }
             else
             {
-                await DefaultLspCompletionResultCreationService.PopulateTextEditAsync(
-                    document, documentText, itemDefaultsSupported, defaultSpan, item, lspItem, cancellationToken).ConfigureAwait(false);
+                await GetChangeAndPopulateSimpleTextEditAsync(
+                    document,
+                    documentText,
+                    itemDefaultsSupported,
+                    defaultSpan,
+                    item,
+                    lspItem,
+                    completionService,
+                    cancellationToken).ConfigureAwait(false);
             }
 
             return lspItem;
         }
 
-        public async Task<LSP.CompletionItem> ResolveAsync(
-            LSP.CompletionItem completionItem,
-            CompletionItem selectedItem,
+        public override async Task<LSP.CompletionItem> ResolveAsync(
+            LSP.CompletionItem lspItem,
+            CompletionItem roslynItem,
+            LSP.TextDocumentIdentifier textDocumentIdentifier,
             Document document,
-            LSP.ClientCapabilities clientCapabilities,
+            CompletionCapabilityHelper capabilityHelper,
             CompletionService completionService,
             CompletionOptions completionOptions,
             SymbolDescriptionOptions symbolDescriptionOptions,
             CancellationToken cancellationToken)
         {
-            var description = await completionService.GetDescriptionAsync(document, selectedItem, completionOptions, symbolDescriptionOptions, cancellationToken).ConfigureAwait(false)!;
+            var description = await completionService.GetDescriptionAsync(document, roslynItem, completionOptions, symbolDescriptionOptions, cancellationToken).ConfigureAwait(false)!;
             if (description != null)
             {
-                var supportsVSExtensions = clientCapabilities.HasVisualStudioLspCapability();
-                if (supportsVSExtensions)
+                if (capabilityHelper.SupportVSInternalClientCapabilities)
                 {
-                    var vsCompletionItem = (LSP.VSInternalCompletionItem)completionItem;
+                    var vsCompletionItem = (LSP.VSInternalCompletionItem)lspItem;
                     vsCompletionItem.Description = new ClassifiedTextElement(description.TaggedParts
                         .Select(tp => new ClassifiedTextRun(tp.Tag.ToClassificationTypeName(), tp.Text)));
                 }
                 else
                 {
-                    var clientSupportsMarkdown = clientCapabilities.TextDocument?.Completion?.CompletionItem?.DocumentationFormat?.Contains(LSP.MarkupKind.Markdown) == true;
-                    completionItem.Documentation = ProtocolConversions.GetDocumentationMarkupContent(description.TaggedParts, document, clientSupportsMarkdown);
+                    lspItem.Documentation = ProtocolConversions.GetDocumentationMarkupContent(description.TaggedParts, document, capabilityHelper.SupportsMarkdownDocumentation);
                 }
             }
 
@@ -94,64 +103,19 @@ await DefaultLspCompletionResultCreationService.PopulateTextEditAsync(
             // the LSP spec, but is currently supported by the VS client anyway. Once the VS client
             // adheres to the spec, this logic will need to change and VS will need to provide
             // official support for TextEdit resolution in some form.
-            if (selectedItem.IsComplexTextEdit)
+            if (roslynItem.IsComplexTextEdit)
             {
-                Contract.ThrowIfTrue(completionItem.InsertText != null);
-                Contract.ThrowIfTrue(completionItem.TextEdit != null);
-
-                var snippetsSupported = clientCapabilities?.TextDocument?.Completion?.CompletionItem?.SnippetSupport ?? false;
-
-                completionItem.TextEdit = await GenerateTextEditAsync(
-                    document, completionService, selectedItem, snippetsSupported, cancellationToken).ConfigureAwait(false);
-            }
-
-            return completionItem;
-        }
-
-        // Internal for testing
-        internal static async Task<LSP.TextEdit> GenerateTextEditAsync(
-            Document document,
-            CompletionService completionService,
-            CompletionItem selectedItem,
-            bool snippetsSupported,
-            CancellationToken cancellationToken)
-        {
-            var documentText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
-
-            var completionChange = await completionService.GetChangeAsync(
-                document, selectedItem, cancellationToken: cancellationToken).ConfigureAwait(false);
-            var completionChangeSpan = completionChange.TextChange.Span;
-            var newText = completionChange.TextChange.NewText;
-            Contract.ThrowIfNull(newText);
+                Contract.ThrowIfTrue(lspItem.InsertText != null);
+                Contract.ThrowIfTrue(lspItem.TextEdit != null);
 
-            // If snippets are supported, that means we can move the caret (represented by $0) to
-            // a new location.
-            if (snippetsSupported)
-            {
-                var caretPosition = completionChange.NewPosition;
-                if (caretPosition.HasValue)
-                {
-                    // caretPosition is the absolute position of the caret in the document.
-                    // We want the position relative to the start of the snippet.
-                    var relativeCaretPosition = caretPosition.Value - completionChangeSpan.Start;
+                var sourceText = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
+                var (edit, _, _) = await GenerateComplexTextEditAsync(
+                    document, completionService, roslynItem, capabilityHelper.SupportSnippets, insertNewPositionPlaceholder: true, cancellationToken).ConfigureAwait(false);
 
-                    // The caret could technically be placed outside the bounds of the text
-                    // being inserted. This situation is currently unsupported in LSP, so in
-                    // these cases we won't move the caret.
-                    if (relativeCaretPosition >= 0 && relativeCaretPosition <= newText.Length)
-                    {
-                        newText = newText.Insert(relativeCaretPosition, "$0");
-                    }
-                }
+                lspItem.TextEdit = edit;
             }
 
-            var textEdit = new LSP.TextEdit()
-            {
-                NewText = newText,
-                Range = ProtocolConversions.TextSpanToRange(completionChangeSpan, documentText),
-            };
-
-            return textEdit;
+            return lspItem;
         }
     }
 }
diff --git a/src/EditorFeatures/Core/LanguageServer/RazorInProcLanguageClient.cs b/src/EditorFeatures/Core/LanguageServer/RazorInProcLanguageClient.cs
index a8f1a071fa071..6c091cbf551ba 100644
--- a/src/EditorFeatures/Core/LanguageServer/RazorInProcLanguageClient.cs
+++ b/src/EditorFeatures/Core/LanguageServer/RazorInProcLanguageClient.cs
@@ -77,6 +77,7 @@ public override ServerCapabilities GetCapabilities(ClientCapabilities clientCapa
             if (capabilities is VSInternalServerCapabilities vsServerCapabilities)
             {
                 vsServerCapabilities.SupportsDiagnosticRequests = true;
+                vsServerCapabilities.SpellCheckingProvider = true;
 
                 var regexExpression = string.Join("|", InlineCompletionsHandler.BuiltInSnippets);
                 var regex = new Regex(regexExpression, RegexOptions.Compiled | RegexOptions.Singleline, TimeSpan.FromSeconds(1));
diff --git a/src/EditorFeatures/Core/Microsoft.CodeAnalysis.EditorFeatures.csproj b/src/EditorFeatures/Core/Microsoft.CodeAnalysis.EditorFeatures.csproj
index e0becfd7c0a5a..111fb9d55aa3a 100644
--- a/src/EditorFeatures/Core/Microsoft.CodeAnalysis.EditorFeatures.csproj
+++ b/src/EditorFeatures/Core/Microsoft.CodeAnalysis.EditorFeatures.csproj
@@ -36,6 +36,7 @@
     <PackageReference Include="Microsoft.VisualStudio.Language" Version="$(MicrosoftVisualStudioLanguageVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.LanguageServer.Client" Version="$(MicrosoftVisualStudioLanguageServerClientVersion)" PrivateAssets="all" />
     <PackageReference Include="Microsoft.ServiceHub.Client" Version="$(MicrosoftServiceHubClientVersion)" />
+    <PackageReference Include="Microsoft.ServiceHub.Framework" Version="$(MicrosoftServiceHubFrameworkVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Validation" Version="$(MicrosoftVisualStudioValidationVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Debugger.Contracts" Version="$(MicrosoftVisualStudioDebuggerContractsVersion)" />
     <PackageReference Include="StreamJsonRpc" Version="$(StreamJsonRpcVersion)" />
diff --git a/src/EditorFeatures/Core/NavigationBar/NavigationBarController_ModelComputation.cs b/src/EditorFeatures/Core/NavigationBar/NavigationBarController_ModelComputation.cs
index ed03a513b68c4..c24e57a8153bc 100644
--- a/src/EditorFeatures/Core/NavigationBar/NavigationBarController_ModelComputation.cs
+++ b/src/EditorFeatures/Core/NavigationBar/NavigationBarController_ModelComputation.cs
@@ -65,8 +65,14 @@ internal partial class NavigationBarController
                 // If these are navbars for a file that isn't even visible, then avoid doing any unnecessary computation
                 // work until far in the future (or if visibility changes).  This ensures our non-visible docs do settle
                 // once enough time has passed, while greatly reducing their impact on the system.
+                //
+                // Use NoThrow as this is a high source of cancellation exceptions.  This avoids the exception and instead
+                // bails gracefully by checking below.
                 await _visibilityTracker.DelayWhileNonVisibleAsync(
-                    _threadingContext, _subjectBuffer, DelayTimeSpan.NonFocus, cancellationToken).ConfigureAwait(false);
+                    _threadingContext, _asyncListener, _subjectBuffer, DelayTimeSpan.NonFocus, cancellationToken).NoThrowAwaitable(false);
+
+                if (cancellationToken.IsCancellationRequested)
+                    return null;
 
                 using (Logger.LogBlock(FunctionId.NavigationBar_ComputeModelAsync, cancellationToken))
                 {
diff --git a/src/EditorFeatures/Core/Shared/Extensions/ITextViewExtensions.cs b/src/EditorFeatures/Core/Shared/Extensions/ITextViewExtensions.cs
index b4fd8bae9af11..5ff5954c1721a 100644
--- a/src/EditorFeatures/Core/Shared/Extensions/ITextViewExtensions.cs
+++ b/src/EditorFeatures/Core/Shared/Extensions/ITextViewExtensions.cs
@@ -362,8 +362,8 @@ public static bool TryGetSurfaceBufferSpan(
             var visibleEnd = visibleSpansInBuffer.Last().End;
 
             var snapshot = subjectBuffer.CurrentSnapshot;
-            var startLine = visibleStart.GetContainingLine().LineNumber;
-            var endLine = visibleEnd.GetContainingLine().LineNumber;
+            var startLine = visibleStart.GetContainingLineNumber();
+            var endLine = visibleEnd.GetContainingLineNumber();
 
             startLine = Math.Max(startLine - extraLines, 0);
             endLine = Math.Min(endLine + extraLines, snapshot.LineCount - 1);
diff --git a/src/EditorFeatures/Core/Shared/Extensions/SnapshotPointExtensions.cs b/src/EditorFeatures/Core/Shared/Extensions/SnapshotPointExtensions.cs
index 37eb559c2882a..e6a95c92b0510 100644
--- a/src/EditorFeatures/Core/Shared/Extensions/SnapshotPointExtensions.cs
+++ b/src/EditorFeatures/Core/Shared/Extensions/SnapshotPointExtensions.cs
@@ -13,7 +13,7 @@ public static void GetLineAndCharacter(this SnapshotPoint point, out int lineNum
             => point.Snapshot.GetLineAndCharacter(point.Position, out lineNumber, out characterIndex);
 
         public static int GetContainingLineNumber(this SnapshotPoint point)
-            => point.GetContainingLine().LineNumber;
+            => point.GetContainingLineNumber();
 
         public static ITrackingPoint CreateTrackingPoint(this SnapshotPoint point, PointTrackingMode trackingMode)
             => point.Snapshot.CreateTrackingPoint(point, trackingMode);
diff --git a/src/EditorFeatures/Core/Shared/Tagging/EventSources/TaggerEventSources.WorkspaceChangedEventSource.cs b/src/EditorFeatures/Core/Shared/Tagging/EventSources/TaggerEventSources.WorkspaceChangedEventSource.cs
index e00a949d931f0..a070bffead4ee 100644
--- a/src/EditorFeatures/Core/Shared/Tagging/EventSources/TaggerEventSources.WorkspaceChangedEventSource.cs
+++ b/src/EditorFeatures/Core/Shared/Tagging/EventSources/TaggerEventSources.WorkspaceChangedEventSource.cs
@@ -2,9 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.VisualStudio.Text;
 using Roslyn.Utilities;
@@ -25,7 +23,7 @@ public WorkspaceChangedEventSource(
                 // That will ensure that even if we get a flurry of workspace events that we
                 // only process a tag change once.
                 _asyncDelay = new AsyncBatchingWorkQueue(
-                    TimeSpan.FromMilliseconds(250),
+                    DelayTimeSpan.Short,
                     processBatchAsync: cancellationToken =>
                     {
                         RaiseChanged();
diff --git a/src/EditorFeatures/Core/Structure/AbstractStructureTaggerProvider.cs b/src/EditorFeatures/Core/Structure/AbstractStructureTaggerProvider.cs
index a4c618a78107c..de7f59e0d5c84 100644
--- a/src/EditorFeatures/Core/Structure/AbstractStructureTaggerProvider.cs
+++ b/src/EditorFeatures/Core/Structure/AbstractStructureTaggerProvider.cs
@@ -39,8 +39,8 @@ namespace Microsoft.CodeAnalysis.Editor.Implementation.Structure
     /// editor doesn't know about all the regions in the file, then it wouldn't be able to
     /// persist them to the SUO file to persist this data across sessions.
     /// </summary>
-    internal abstract partial class AbstractStructureTaggerProvider :
-        AsynchronousTaggerProvider<IStructureTag>
+#pragma warning disable CS0618 // Type or member is obsolete
+    internal abstract partial class AbstractStructureTaggerProvider : AsynchronousTaggerProvider<IStructureTag2>
     {
         private const string RegionDirective = "#region";
         private const string UsingDirective = "using";
@@ -178,7 +178,7 @@ protected sealed override ITaggerEventSource CreateEventSource(ITextView? textVi
         }
 
         protected sealed override async Task ProduceTagsAsync(
-            TaggerContext<IStructureTag> context, DocumentSnapshotSpan documentSnapshotSpan, int? caretPosition, CancellationToken cancellationToken)
+            TaggerContext<IStructureTag2> context, DocumentSnapshotSpan documentSnapshotSpan, int? caretPosition, CancellationToken cancellationToken)
         {
             try
             {
@@ -209,7 +209,7 @@ protected sealed override async Task ProduceTagsAsync(
         }
 
         private void ProcessSpans(
-            TaggerContext<IStructureTag> context,
+            TaggerContext<IStructureTag2> context,
             SnapshotSpan snapshotSpan,
             BlockStructureService outliningService,
             ImmutableArray<BlockSpan> spans)
@@ -220,11 +220,11 @@ private void ProcessSpans(
             foreach (var span in spans)
             {
                 var tag = new StructureTag(this, span, snapshot);
-                context.AddTag(new TagSpan<IStructureTag>(span.TextSpan.ToSnapshotSpan(snapshot), tag));
+                context.AddTag(new TagSpan<IStructureTag2>(span.TextSpan.ToSnapshotSpan(snapshot), tag));
             }
         }
 
-        protected override bool TagEquals(IStructureTag tag1, IStructureTag tag2)
+        protected override bool TagEquals(IStructureTag2 tag1, IStructureTag2 tag2)
         {
             Contract.ThrowIfFalse(tag1 is StructureTag);
             Contract.ThrowIfFalse(tag2 is StructureTag);
@@ -364,4 +364,5 @@ private ITextBuffer CreateElisionBufferWithoutIndentation(
 
         #endregion
     }
+#pragma warning restore CS0618 // Type or member is obsolete
 }
diff --git a/src/EditorFeatures/Core/Structure/StructureTag.cs b/src/EditorFeatures/Core/Structure/StructureTag.cs
index 3140ef2bd0c89..0492cb714bd02 100644
--- a/src/EditorFeatures/Core/Structure/StructureTag.cs
+++ b/src/EditorFeatures/Core/Structure/StructureTag.cs
@@ -4,6 +4,7 @@
 
 using System;
 using Microsoft.CodeAnalysis.Structure;
+using Microsoft.CodeAnalysis.Text;
 using Microsoft.CodeAnalysis.Text.Shared.Extensions;
 using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Adornments;
@@ -12,10 +13,30 @@
 
 namespace Microsoft.CodeAnalysis.Editor.Implementation.Structure
 {
-    internal sealed class StructureTag : IStructureTag, IEquatable<StructureTag>
+#pragma warning disable CS0618 // Type or member is obsolete
+    internal sealed class StructureTag : IStructureTag2, IEquatable<StructureTag>
+#pragma warning restore CS0618 // Type or member is obsolete
     {
         private readonly AbstractStructureTaggerProvider _tagProvider;
 
+        /// <summary>
+        /// The contents of the buffer to show if we mouse over the collapsed indicator.
+        /// </summary>
+        public readonly Span CollapsedHintFormSpan;
+
+        public readonly string CollapsedText;
+
+        public ITextSnapshot Snapshot { get; }
+        public Span? OutliningSpan { get; }
+        public Span? HeaderSpan { get; }
+        public Span? PrimaryHeaderSpan { get; }
+        public Span? GuideLineSpan => null;
+        public int? GuideLineHorizontalAnchorPoint => null;
+        public string Type { get; }
+        public bool IsCollapsible { get; }
+        public bool IsDefaultCollapsed { get; }
+        public bool IsImplementation { get; }
+
         public StructureTag(AbstractStructureTaggerProvider tagProvider, BlockSpan blockSpan, ITextSnapshot snapshot)
         {
             Snapshot = snapshot;
@@ -24,43 +45,33 @@ public StructureTag(AbstractStructureTaggerProvider tagProvider, BlockSpan block
             IsCollapsible = blockSpan.IsCollapsible;
             IsDefaultCollapsed = blockSpan.IsDefaultCollapsed;
             IsImplementation = blockSpan.AutoCollapse;
+            HeaderSpan = DetermineHeaderSpan(blockSpan.TextSpan, blockSpan.HintSpan, snapshot);
+            PrimaryHeaderSpan = blockSpan.PrimarySpans is { } primarySpans
+                ? DetermineHeaderSpan(primarySpans.textSpan, primarySpans.hintSpan, snapshot)
+                : null;
+
+            CollapsedText = blockSpan.BannerText;
+            CollapsedHintFormSpan = blockSpan.HintSpan.ToSpan();
+            _tagProvider = tagProvider;
+        }
 
-            if (blockSpan.HintSpan.Start < blockSpan.TextSpan.Start)
+        private static Span DetermineHeaderSpan(TextSpan textSpan, TextSpan hintSpan, ITextSnapshot snapshot)
+        {
+            if (hintSpan.Start < textSpan.Start)
             {
                 // The HeaderSpan is what is used for drawing the guidelines and also what is shown if
                 // you mouse over a guideline. We will use the text from the hint start to the collapsing
                 // start; in the case this spans mutiple lines the editor will clip it for us and suffix an
                 // ellipsis at the end.
-                HeaderSpan = Span.FromBounds(blockSpan.HintSpan.Start, blockSpan.TextSpan.Start);
+                return Span.FromBounds(hintSpan.Start, textSpan.Start);
             }
             else
             {
-                var hintLine = snapshot.GetLineFromPosition(blockSpan.HintSpan.Start);
-                HeaderSpan = AbstractStructureTaggerProvider.TrimLeadingWhitespace(hintLine.Extent);
+                var hintLine = snapshot.GetLineFromPosition(hintSpan.Start);
+                return AbstractStructureTaggerProvider.TrimLeadingWhitespace(hintLine.Extent);
             }
-
-            CollapsedText = blockSpan.BannerText;
-            CollapsedHintFormSpan = blockSpan.HintSpan.ToSpan();
-            _tagProvider = tagProvider;
         }
 
-        /// <summary>
-        /// The contents of the buffer to show if we mouse over the collapsed indicator.
-        /// </summary>
-        public readonly Span CollapsedHintFormSpan;
-
-        public readonly string CollapsedText;
-
-        public ITextSnapshot Snapshot { get; }
-        public Span? OutliningSpan { get; }
-        public Span? HeaderSpan { get; }
-        public Span? GuideLineSpan => null;
-        public int? GuideLineHorizontalAnchorPoint => null;
-        public string Type { get; }
-        public bool IsCollapsible { get; }
-        public bool IsDefaultCollapsed { get; }
-        public bool IsImplementation { get; }
-
         // Editor uses this here:
         // https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_git/VS-Platform?path=/src/Editor/Text/Impl/Structure/StructureSpanningTree/StructureSpanningTree.cs&version=GBmain&line=308&lineEnd=309&lineStartColumn=1&lineEndColumn=1&lineStyle=plain&_a=contents
         public override int GetHashCode()
@@ -70,7 +81,8 @@ public override int GetHashCode()
                Hash.Combine(this.IsDefaultCollapsed,
                Hash.Combine(this.IsImplementation,
                Hash.Combine(this.OutliningSpan.GetHashCode(),
-               Hash.Combine(this.HeaderSpan.GetHashCode(), this.GuideLineSpan.GetHashCode())))))));
+               Hash.Combine(this.HeaderSpan.GetHashCode(),
+               Hash.Combine(this.PrimaryHeaderSpan.GetHashCode(), this.GuideLineSpan.GetHashCode()))))))));
 
         public override bool Equals(object? obj)
             => Equals(obj as StructureTag);
@@ -85,6 +97,7 @@ public bool Equals(StructureTag? other)
                 this.IsImplementation == other.IsImplementation &&
                 _tagProvider.SpanEquals(this.Snapshot, this.OutliningSpan, other.Snapshot, other.OutliningSpan) &&
                 _tagProvider.SpanEquals(this.Snapshot, this.HeaderSpan, other.Snapshot, other.HeaderSpan) &&
+                _tagProvider.SpanEquals(this.Snapshot, this.PrimaryHeaderSpan, other.Snapshot, other.PrimaryHeaderSpan) &&
                 _tagProvider.SpanEquals(this.Snapshot, this.GuideLineSpan, other.Snapshot, other.GuideLineSpan);
         }
 
diff --git a/src/EditorFeatures/Core/Tagging/AbstractAsynchronousTaggerProvider.TagSource_ProduceTags.cs b/src/EditorFeatures/Core/Tagging/AbstractAsynchronousTaggerProvider.TagSource_ProduceTags.cs
index 16da65e2c6390..e72a42d00dee8 100644
--- a/src/EditorFeatures/Core/Tagging/AbstractAsynchronousTaggerProvider.TagSource_ProduceTags.cs
+++ b/src/EditorFeatures/Core/Tagging/AbstractAsynchronousTaggerProvider.TagSource_ProduceTags.cs
@@ -204,8 +204,13 @@ private async Task RecomputeTagsAsync(bool highPriority, CancellationToken cance
                 // possible.
                 if (!highPriority)
                 {
+                    // Use NoThrow as this is a high source of cancellation exceptions.  This avoids the exception and instead
+                    // bails gracefully by checking below.
                     await _visibilityTracker.DelayWhileNonVisibleAsync(
-                        _dataSource.ThreadingContext, _subjectBuffer, DelayTimeSpan.NonFocus, cancellationToken).ConfigureAwait(true);
+                        _dataSource.ThreadingContext, _dataSource.AsyncListener, _subjectBuffer, DelayTimeSpan.NonFocus, cancellationToken).NoThrowAwaitable(captureContext: true);
+
+                    if (cancellationToken.IsCancellationRequested)
+                        return;
                 }
 
                 await _dataSource.ThreadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
diff --git a/src/EditorFeatures/Core/Workspaces/ITextBufferVisibilityTracker.cs b/src/EditorFeatures/Core/Workspaces/ITextBufferVisibilityTracker.cs
index 61ec60395630c..2b4098c123adb 100644
--- a/src/EditorFeatures/Core/Workspaces/ITextBufferVisibilityTracker.cs
+++ b/src/EditorFeatures/Core/Workspaces/ITextBufferVisibilityTracker.cs
@@ -6,8 +6,10 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Editor;
+using Microsoft.VisualStudio.Threading;
 
 namespace Microsoft.CodeAnalysis.Workspaces
 {
@@ -37,40 +39,68 @@ internal interface ITextBufferVisibilityTracker
     internal static class ITextBufferVisibilityTrackerExtensions
     {
         /// <summary>
-        /// Waits the specified amount of time while the specified <paramref name="subjectBuffer"/> is not visible.  If any
-        /// document visibility changes happen, the delay will cancel.
+        /// Waits the specified amount of time while the specified <paramref name="subjectBuffer"/> is not visible.  If
+        /// any document visibility changes happen, the delay will cancel.
         /// </summary>
-        public static async Task DelayWhileNonVisibleAsync(
+        public static Task DelayWhileNonVisibleAsync(
             this ITextBufferVisibilityTracker? service,
             IThreadingContext threadingContext,
+            IAsynchronousOperationListener listener,
             ITextBuffer subjectBuffer,
             TimeSpan timeSpan,
             CancellationToken cancellationToken)
         {
             // Only add a delay if we have access to a service that will tell us when the buffer become visible or not.
             if (service is null)
-                return;
+                return Task.CompletedTask;
 
-            await threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
-            if (service.IsVisible(subjectBuffer))
-                return;
+            // Because cancellation is both expensive, and a super common thing to occur while we're delaying the caller
+            // until visibility, we special case the implementation here and transition to the canceled state
+            // explicitly, rather than throwing a cancellation exception.
 
-            // ensure we listen for visibility changes before checking.  That way we don't have a race where we check
-            // something see it is not visible, but then do not hear about its visibility change because we've hooked up
-            // our event after that happens.
-            var visibilityChangedTaskSource = new TaskCompletionSource<bool>();
-            var callback = void () => visibilityChangedTaskSource.TrySetResult(true);
-            service.RegisterForVisibilityChanges(subjectBuffer, callback);
+            var delayTask = DelayWhileNonVisibleWorkerAsync();
 
-            try
-            {
-                // Listen to when the active document changed so that we startup work on a document once it becomes visible.
-                var delayTask = Task.Delay(timeSpan, cancellationToken);
-                await Task.WhenAny(delayTask, visibilityChangedTaskSource.Task).ConfigureAwait(true);
-            }
-            finally
+            // it's very reasonable for the delay-task to complete synchronously (we've already been canceled, or the
+            // buffer is already visible.  So fast path that out.
+            if (delayTask.IsCompleted)
+                return delayTask;
+
+            var taskOfTask = delayTask.ContinueWith(
+                // Convert a successfully completed task when we were canceled to a canceled task.  Otherwise, return
+                // the faulted or non-canceled task as is.
+                task => task.Status == TaskStatus.RanToCompletion && cancellationToken.IsCancellationRequested ? Task.FromCanceled(cancellationToken) : task,
+                CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default);
+            return taskOfTask.Unwrap();
+
+            // Normal delay logic, except that this does not throw in the event of cancellation, but instead returns
+            // gracefully.  The above task continuation logic then ensures we return a canceled task without needing
+            // exceptions.
+            async Task DelayWhileNonVisibleWorkerAsync()
             {
-                service.UnregisterForVisibilityChanges(subjectBuffer, callback);
+                if (cancellationToken.IsCancellationRequested)
+                    return;
+
+                await threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
+                if (service.IsVisible(subjectBuffer))
+                    return;
+
+                // ensure we listen for visibility changes before checking.  That way we don't have a race where we check
+                // something see it is not visible, but then do not hear about its visibility change because we've hooked up
+                // our event after that happens.
+                var visibilityChangedTaskSource = new TaskCompletionSource<bool>();
+                var callback = void () => visibilityChangedTaskSource.TrySetResult(true);
+                service.RegisterForVisibilityChanges(subjectBuffer, callback);
+
+                try
+                {
+                    // Listen to when the active document changed so that we startup work on a document once it becomes visible.
+                    var delayTask = listener.Delay(timeSpan, cancellationToken);
+                    await Task.WhenAny(delayTask, visibilityChangedTaskSource.Task).NoThrowAwaitable(captureContext: true);
+                }
+                finally
+                {
+                    service.UnregisterForVisibilityChanges(subjectBuffer, callback);
+                }
             }
         }
     }
diff --git a/src/EditorFeatures/DiagnosticsTestUtilities/Diagnostics/AbstractDiagnosticProviderBasedUserDiagnosticTest.cs b/src/EditorFeatures/DiagnosticsTestUtilities/Diagnostics/AbstractDiagnosticProviderBasedUserDiagnosticTest.cs
index e20d435f61587..b449767cc787e 100644
--- a/src/EditorFeatures/DiagnosticsTestUtilities/Diagnostics/AbstractDiagnosticProviderBasedUserDiagnosticTest.cs
+++ b/src/EditorFeatures/DiagnosticsTestUtilities/Diagnostics/AbstractDiagnosticProviderBasedUserDiagnosticTest.cs
@@ -249,12 +249,6 @@ private static void AssertNoAnalyzerExceptionDiagnostics(IEnumerable<Diagnostic>
         // This enables porting the tests for the ported analyzer in CodeStyle layer.
         #region CodeFixProvider Helpers
 
-        // https://github.com/dotnet/roslyn/issues/43056 blocks porting the fixer to CodeStyle layer.
-        protected static CodeFixProvider GetMakeLocalFunctionStaticCodeFixProvider() => new MakeLocalFunctionStaticCodeFixProvider();
-
-        // https://github.com/dotnet/roslyn/issues/43056 blocks porting the fixer to CodeStyle layer.
-        protected static CodeFixProvider GetCSharpUseLocalFunctionCodeFixProvider() => new CSharpUseLocalFunctionCodeFixProvider();
-
         // https://github.com/dotnet/roslyn/issues/43091 blocks porting the fixer to CodeStyle layer.
         protected static CodeFixProvider GetCSharpUseAutoPropertyCodeFixProvider() => new CSharpUseAutoPropertyCodeFixProvider();
 
diff --git a/src/EditorFeatures/Test/Diagnostics/DiagnosticAnalyzerServiceTests.cs b/src/EditorFeatures/Test/Diagnostics/DiagnosticAnalyzerServiceTests.cs
index c6eaba9bfc174..2cce6bb22ccde 100644
--- a/src/EditorFeatures/Test/Diagnostics/DiagnosticAnalyzerServiceTests.cs
+++ b/src/EditorFeatures/Test/Diagnostics/DiagnosticAnalyzerServiceTests.cs
@@ -1086,7 +1086,7 @@ internal async Task TestOnlyRequiredAnalyzerExecutedDuringDiagnosticComputation(
 
         [Theory, WorkItem(67257, "https://github.com/dotnet/roslyn/issues/67257")]
         [CombinatorialData]
-        public async Task TestFilterSpanOnContextAsync(bool testSyntaxTreeAction)
+        public async Task TestFilterSpanOnContextAsync(FilterSpanTestAnalyzer.AnalysisKind kind)
         {
             var source = @"
 class B
@@ -1096,36 +1096,61 @@ void M()
         int x = 1;
     }
 }";
+            var additionalText = @"This is an additional file!";
+
             using var workspace = TestWorkspace.CreateCSharp(source);
+            var project = workspace.CurrentSolution.Projects.Single();
+            project = project.AddAdditionalDocument("additional.txt", additionalText).Project;
 
-            var analyzer = new FilterSpanTestAnalyzer(testSyntaxTreeAction);
+            var analyzer = new FilterSpanTestAnalyzer(kind);
             var analyzerId = analyzer.GetAnalyzerId();
             var analyzerIdsToRequestDiagnostics = new[] { analyzerId };
             var analyzerReference = new AnalyzerImageReference(ImmutableArray.Create<DiagnosticAnalyzer>(analyzer));
-            workspace.TryApplyChanges(workspace.CurrentSolution.WithAnalyzerReferences(new[] { analyzerReference }));
+            project = project.AddAnalyzerReference(analyzerReference);
 
-            var project = workspace.CurrentSolution.Projects.Single();
+            workspace.TryApplyChanges(project.Solution);
+
+            project = workspace.CurrentSolution.Projects.Single();
             var ideAnalyzerOptions = IdeAnalyzerOptions.GetDefault(project.Services);
             var document = project.Documents.Single();
+            var additionalDocument = project.AdditionalDocuments.Single();
 
             var root = await document.GetRequiredSyntaxRootAsync(CancellationToken.None);
             var localDeclaration = root.DescendantNodes().OfType<CodeAnalysis.CSharp.Syntax.LocalDeclarationStatementSyntax>().First();
-
+            var filterSpan = kind == FilterSpanTestAnalyzer.AnalysisKind.AdditionalFile
+                ? new TextSpan(0, 1)
+                : localDeclaration.Span;
             // Invoke "GetDiagnosticsAsync" for a sub-span and then
-            // for the entire document span and verify FilterSpan on the callback context.
+            // for the entire document span and verify FilterSpan/FilterTree on the callback context.
             Assert.Null(analyzer.CallbackFilterSpan);
-            await VerifyCallbackSpanAsync(filterSpan: localDeclaration.Span);
+            Assert.Null(analyzer.CallbackFilterTree);
+            await VerifyCallbackSpanAsync(filterSpan);
             await VerifyCallbackSpanAsync(filterSpan: null);
 
             async Task VerifyCallbackSpanAsync(TextSpan? filterSpan)
             {
-                var analysisKind = testSyntaxTreeAction ? AnalysisKind.Syntax : AnalysisKind.Semantic;
+                var analysisKind = kind is FilterSpanTestAnalyzer.AnalysisKind.SyntaxTree or FilterSpanTestAnalyzer.AnalysisKind.AdditionalFile
+                    ? AnalysisKind.Syntax
+                    : AnalysisKind.Semantic;
+                var documentToAnalyze = kind == FilterSpanTestAnalyzer.AnalysisKind.AdditionalFile ? additionalDocument : document;
                 _ = await DiagnosticComputer.GetDiagnosticsAsync(
-                    document, project, Checksum.Null, ideAnalyzerOptions, filterSpan, analyzerIdsToRequestDiagnostics,
+                    documentToAnalyze, project, Checksum.Null, ideAnalyzerOptions, filterSpan, analyzerIdsToRequestDiagnostics,
                     analysisKind, new DiagnosticAnalyzerInfoCache(), workspace.Services,
                     isExplicit: false, reportSuppressedDiagnostics: false, logPerformanceInfo: false, getTelemetryInfo: false,
                     CancellationToken.None);
                 Assert.Equal(filterSpan, analyzer.CallbackFilterSpan);
+                if (kind == FilterSpanTestAnalyzer.AnalysisKind.AdditionalFile)
+                {
+                    var expectedText = additionalDocument.GetTextSynchronously(CancellationToken.None).ToString();
+                    var actualText = analyzer.CallbackFilterFile.GetText().ToString();
+                    Assert.Equal(expectedText, actualText);
+                    Assert.Null(analyzer.CallbackFilterTree);
+                }
+                else
+                {
+                    Assert.Equal(root.SyntaxTree, analyzer.CallbackFilterTree);
+                    Assert.Null(analyzer.CallbackFilterFile);
+                }
             }
         }
 
diff --git a/src/EditorFeatures/Test/Structure/StructureTaggerTests.cs b/src/EditorFeatures/Test/Structure/StructureTaggerTests.cs
index fd154f1d832c4..053e48ff8eead 100644
--- a/src/EditorFeatures/Test/Structure/StructureTaggerTests.cs
+++ b/src/EditorFeatures/Test/Structure/StructureTaggerTests.cs
@@ -325,7 +325,8 @@ End Sub
             hints.Do(v => v.TextView_TestOnly.Close());
         }
 
-        private static async Task<List<IStructureTag>> GetTagsFromWorkspaceAsync(TestWorkspace workspace)
+#pragma warning disable CS0618 // Type or member is obsolete
+        private static async Task<List<IStructureTag2>> GetTagsFromWorkspaceAsync(TestWorkspace workspace)
         {
             var hostdoc = workspace.Documents.First();
             var view = hostdoc.GetTextView();
@@ -333,11 +334,12 @@ private static async Task<List<IStructureTag>> GetTagsFromWorkspaceAsync(TestWor
             var provider = workspace.ExportProvider.GetExportedValue<AbstractStructureTaggerProvider>();
 
             var document = workspace.CurrentSolution.GetDocument(hostdoc.Id);
-            var context = new TaggerContext<IStructureTag>(document, view.TextSnapshot);
+            var context = new TaggerContext<IStructureTag2>(document, view.TextSnapshot);
             await provider.GetTestAccessor().ProduceTagsAsync(context);
 
             return context.TagSpans.Select(x => x.Tag).OrderBy(t => t.OutliningSpan.Value.Start).ToList();
         }
+#pragma warning restore CS0618 // Type or member is obsolete
 
         private static string GetHeaderText(IStructureTag namespaceTag)
         {
diff --git a/src/EditorFeatures/Test2/Expansion/AbstractExpansionTest.vb b/src/EditorFeatures/Test2/Expansion/AbstractExpansionTest.vb
index 8a42ca5f2a5aa..33f0a9b5328df 100644
--- a/src/EditorFeatures/Test2/Expansion/AbstractExpansionTest.vb
+++ b/src/EditorFeatures/Test2/Expansion/AbstractExpansionTest.vb
@@ -2,6 +2,7 @@
 ' The .NET Foundation licenses this file to you under the MIT license.
 ' See the LICENSE file in the project root for more information.
 
+Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis
 Imports Microsoft.CodeAnalysis.CodeActions
@@ -10,6 +11,7 @@ Imports Microsoft.CodeAnalysis.Editor.UnitTests.Extensions
 Imports Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
 Imports Microsoft.CodeAnalysis.Formatting
 Imports Microsoft.CodeAnalysis.Simplification
+Imports Microsoft.CodeAnalysis.Text
 Imports Roslyn.Utilities
 
 Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Expansion
@@ -30,13 +32,14 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Expansion
 
                 Dim cleanupOptions = CodeCleanupOptions.GetDefault(document.Project.Services)
 
-                If hostDocument.AnnotatedSpans.ContainsKey("Expand") Then
-                    For Each span In hostDocument.AnnotatedSpans("Expand")
+                Dim spans As ImmutableArray(Of TextSpan) = Nothing
+                If hostDocument.AnnotatedSpans.TryGetValue("Expand", spans) Then
+                    For Each span In spans
                         Dim node = GetExpressionSyntaxWithSameSpan(root.FindToken(span.Start).Parent, span.End)
                         root = root.ReplaceNode(node, Await Simplifier.ExpandAsync(node, document, expandInsideNode:=Nothing, expandParameter:=expandParameter))
                     Next
-                ElseIf hostDocument.AnnotatedSpans.ContainsKey("ExpandAndSimplify") Then
-                    For Each span In hostDocument.AnnotatedSpans("ExpandAndSimplify")
+                ElseIf hostDocument.AnnotatedSpans.TryGetValue("ExpandAndSimplify", spans) Then
+                    For Each span In spans
                         Dim node = GetExpressionSyntaxWithSameSpan(root.FindToken(span.Start).Parent, span.End)
                         root = root.ReplaceNode(node, Await Simplifier.ExpandAsync(node, document, expandInsideNode:=Nothing, expandParameter:=expandParameter))
                         document = document.WithSyntaxRoot(root)
diff --git a/src/EditorFeatures/Test2/FindReferences/FindReferencesTests.vb b/src/EditorFeatures/Test2/FindReferences/FindReferencesTests.vb
index 64eff519bf0d2..d663b93c29e23 100644
--- a/src/EditorFeatures/Test2/FindReferences/FindReferencesTests.vb
+++ b/src/EditorFeatures/Test2/FindReferences/FindReferencesTests.vb
@@ -312,8 +312,8 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.FindReferences
                     Dim documentsWithAnnotatedSpans = workspace.Documents.Where(Function(d) d.AnnotatedSpans.Any())
                     Assert.Equal(Of String)(documentsWithAnnotatedSpans.Select(Function(d) GetFilePathAndProjectLabel(d)).Order(), actualDefinitions.Keys.Order())
                     For Each doc In documentsWithAnnotatedSpans
-
-                        Dim expected = If(doc.AnnotatedSpans.ContainsKey(DefinitionKey), doc.AnnotatedSpans(DefinitionKey), ImmutableArray(Of TextSpan).Empty).Order()
+                        Dim spans As ImmutableArray(Of TextSpan) = Nothing
+                        Dim expected = If(doc.AnnotatedSpans.TryGetValue(DefinitionKey, spans), spans, ImmutableArray(Of TextSpan).Empty).Order()
                         Dim actual = actualDefinitions(GetFilePathAndProjectLabel(doc)).Order()
 
                         If Not TextSpansMatch(expected, actual) Then
diff --git a/src/EditorFeatures/Test2/LanguageServices/SyntaxFactsServiceTests.vb b/src/EditorFeatures/Test2/LanguageServices/SyntaxFactsServiceTests.vb
index 1cf54f514ae46..ae3a18150a93e 100644
--- a/src/EditorFeatures/Test2/LanguageServices/SyntaxFactsServiceTests.vb
+++ b/src/EditorFeatures/Test2/LanguageServices/SyntaxFactsServiceTests.vb
@@ -2,6 +2,7 @@
 ' The .NET Foundation licenses this file to you under the MIT license.
 ' See the LICENSE file in the project root for more information.
 
+Imports System.Collections.Immutable
 Imports System.Threading
 Imports System.Threading.Tasks
 Imports Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
@@ -212,7 +213,8 @@ $$End Class
                 Dim node = root.FindNode(New TextSpan(cursorPosition, 0))
                 Dim syntaxFactsService = document.GetLanguageService(Of ISyntaxFactsService)()
 
-                Dim expected = If(cursorDocument.AnnotatedSpans.ContainsKey("MemberBodySpan"), cursorDocument.AnnotatedSpans!MemberBodySpan.Single(), Nothing)
+                Dim spans As ImmutableArray(Of TextSpan) = Nothing
+                Dim expected = If(cursorDocument.AnnotatedSpans.TryGetValue("MemberBodySpan", spans), spans.Single(), Nothing)
                 Dim actual = syntaxFactsService.GetMemberBodySpanForSpeculativeBinding(node)
 
                 Assert.Equal(expected, actual)
diff --git a/src/EditorFeatures/Test2/Rename/RenameCommandHandlerTests.vb b/src/EditorFeatures/Test2/Rename/RenameCommandHandlerTests.vb
index 621939435d6f3..13805677ce6fb 100644
--- a/src/EditorFeatures/Test2/Rename/RenameCommandHandlerTests.vb
+++ b/src/EditorFeatures/Test2/Rename/RenameCommandHandlerTests.vb
@@ -255,7 +255,7 @@ End Class
                                               Sub() AssertEx.Fail("Tab should not have been passed to the editor."),
                                               Utilities.TestCommandExecutionContext.Create())
 
-                Assert.Equal(3, view.Caret.Position.BufferPosition.GetContainingLine().LineNumber)
+                Assert.Equal(3, view.Caret.Position.BufferPosition.GetContainingLineNumber())
 
                 session.Cancel()
             End Using
diff --git a/src/EditorFeatures/Test2/Rename/RenameEngineResult.vb b/src/EditorFeatures/Test2/Rename/RenameEngineResult.vb
index 07f6f3229da64..728c44a52c70c 100644
--- a/src/EditorFeatures/Test2/Rename/RenameEngineResult.vb
+++ b/src/EditorFeatures/Test2/Rename/RenameEngineResult.vb
@@ -2,6 +2,7 @@
 ' The .NET Foundation licenses this file to you under the MIT license.
 ' See the LICENSE file in the project root for more information.
 
+Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis
 Imports Microsoft.CodeAnalysis.CodeActions
@@ -12,6 +13,7 @@ Imports Microsoft.CodeAnalysis.Options
 Imports Microsoft.CodeAnalysis.Remote.Testing
 Imports Microsoft.CodeAnalysis.Rename
 Imports Microsoft.CodeAnalysis.Rename.ConflictEngine
+Imports Microsoft.CodeAnalysis.Text
 Imports Microsoft.VisualStudio.Text
 Imports Xunit.Abstractions
 Imports Xunit.Sdk
@@ -197,10 +199,11 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Rename
             For Each document In _workspace.Documents
                 Dim annotatedSpans = document.AnnotatedSpans
 
-                If annotatedSpans.ContainsKey(label) Then
+                Dim spans As ImmutableArray(Of TextSpan) = Nothing
+                If annotatedSpans.TryGetValue(label, spans) Then
                     Dim syntaxTree = _workspace.CurrentSolution.GetDocument(document.Id).GetSyntaxTreeAsync().Result
 
-                    For Each span In annotatedSpans(label)
+                    For Each span In spans
                         locations.Add(syntaxTree.GetLocation(span))
                     Next
                 End If
diff --git a/src/EditorFeatures/TestUtilities/EditAndContinue/EditAndContinueTestHelpers.cs b/src/EditorFeatures/TestUtilities/EditAndContinue/EditAndContinueTestHelpers.cs
index 80b46faac9fed..e7e1fb90f9763 100644
--- a/src/EditorFeatures/TestUtilities/EditAndContinue/EditAndContinueTestHelpers.cs
+++ b/src/EditorFeatures/TestUtilities/EditAndContinue/EditAndContinueTestHelpers.cs
@@ -294,58 +294,72 @@ private static void VerifySemanticEdits(
 
                 Assert.Equal(editKind, actualSemanticEdit.Kind);
 
-                var expectedOldSymbol = (editKind is SemanticEditKind.Update or SemanticEditKind.Delete) ? expectedSemanticEdit.SymbolProvider(oldCompilation) : null;
-                var expectedNewSymbol = expectedSemanticEdit.SymbolProvider(newCompilation);
                 var symbolKey = actualSemanticEdit.Symbol;
+                ISymbol? expectedOldSymbol = null, expectedNewSymbol = null;
 
-                if (editKind == SemanticEditKind.Update)
+                switch (editKind)
                 {
-                    Assert.Equal(expectedOldSymbol, symbolKey.Resolve(oldCompilation, ignoreAssemblyKey: true).Symbol);
-                    Assert.Equal(expectedNewSymbol, symbolKey.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol);
-                }
-                else if (editKind == SemanticEditKind.Delete)
-                {
-                    // Symbol key will happily resolve to a definition part that has no implementation, so we validate that
-                    // differently
-                    if (expectedOldSymbol is IMethodSymbol { IsPartialDefinition: true } &&
-                       symbolKey.Resolve(oldCompilation, ignoreAssemblyKey: true).Symbol is IMethodSymbol resolvedMethod)
-                    {
-                        Assert.Equal(expectedOldSymbol, resolvedMethod.PartialDefinitionPart);
-                        Assert.Equal(null, resolvedMethod.PartialImplementationPart);
-                    }
-                    else
-                    {
+                    case SemanticEditKind.Update:
+                        expectedOldSymbol = expectedSemanticEdit.SymbolProvider(oldCompilation);
+                        expectedNewSymbol = expectedSemanticEdit.SymbolProvider(newCompilation);
+
                         Assert.Equal(expectedOldSymbol, symbolKey.Resolve(oldCompilation, ignoreAssemblyKey: true).Symbol);
+                        Assert.Equal(expectedNewSymbol, symbolKey.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol);
+                        break;
+
+                    case SemanticEditKind.Delete:
+                        expectedOldSymbol = expectedSemanticEdit.SymbolProvider(oldCompilation);
 
-                        // When we're deleting a symbol, and have a deleted symbol container, it means the symbol wasn't really deleted,
-                        // but rather had its signature changed in some way. Some of those ways, like changing the return type, are not
-                        // represented in the symbol key, so the check below would fail, so we skip it.
-                        if (expectedSemanticEdit.DeletedSymbolContainerProvider is null)
+                        // Symbol key will happily resolve to a definition part that has no implementation, so we validate that
+                        // differently
+                        if (expectedOldSymbol is IMethodSymbol { IsPartialDefinition: true } &&
+                            symbolKey.Resolve(oldCompilation, ignoreAssemblyKey: true).Symbol is IMethodSymbol resolvedMethod)
                         {
-                            Assert.Equal(null, symbolKey.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol);
+                            Assert.Equal(expectedOldSymbol, resolvedMethod.PartialDefinitionPart);
+                            Assert.Equal(null, resolvedMethod.PartialImplementationPart);
+                        }
+                        else
+                        {
+                            Assert.Equal(expectedOldSymbol, symbolKey.Resolve(oldCompilation, ignoreAssemblyKey: true).Symbol);
+
+                            // When we're deleting a symbol, and have a deleted symbol container, it means the symbol wasn't really deleted,
+                            // but rather had its signature changed in some way. Some of those ways, like changing the return type, are not
+                            // represented in the symbol key, so the check below would fail, so we skip it.
+                            if (expectedSemanticEdit.DeletedSymbolContainerProvider is null)
+                            {
+                                Assert.Equal(null, symbolKey.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol);
+                            }
                         }
-                    }
 
-                    var deletedSymbolContainer = actualSemanticEdit.DeletedSymbolContainer?.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol;
-                    Assert.Equal(deletedSymbolContainer, expectedSemanticEdit.DeletedSymbolContainerProvider?.Invoke(newCompilation));
-                }
-                else if (editKind is SemanticEditKind.Insert or SemanticEditKind.Replace)
-                {
-                    Assert.Equal(expectedNewSymbol, symbolKey.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol);
-                }
-                else
-                {
-                    Assert.False(true, "Only Update, Delete, Insert or Replace allowed");
+                        var deletedSymbolContainer = actualSemanticEdit.DeletedSymbolContainer?.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol;
+                        AssertEx.AreEqual(
+                            deletedSymbolContainer,
+                            expectedSemanticEdit.DeletedSymbolContainerProvider?.Invoke(newCompilation),
+                            message: $"{message}, {editKind}({expectedNewSymbol ?? expectedOldSymbol}): Incorrect deleted container");
+
+                        break;
+
+                    case SemanticEditKind.Insert or SemanticEditKind.Replace:
+                        expectedNewSymbol = expectedSemanticEdit.SymbolProvider(newCompilation);
+                        Assert.Equal(expectedNewSymbol, symbolKey.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol);
+                        break;
+
+                    default:
+                        throw ExceptionUtilities.UnexpectedValue(editKind);
                 }
 
                 // Partial types must match:
-                Assert.Equal(
+                AssertEx.AreEqual(
                     expectedSemanticEdit.PartialType?.Invoke(newCompilation),
-                    actualSemanticEdit.PartialType?.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol);
+                    actualSemanticEdit.PartialType?.Resolve(newCompilation, ignoreAssemblyKey: true).Symbol,
+                    message: $"{message}, {editKind}({expectedNewSymbol ?? expectedOldSymbol}): Partial types do not match");
 
                 // Edit is expected to have a syntax map:
                 var actualSyntaxMap = actualSemanticEdit.SyntaxMap;
-                Assert.Equal(expectedSemanticEdit.HasSyntaxMap, actualSyntaxMap != null);
+                AssertEx.AreEqual(
+                    expectedSemanticEdit.HasSyntaxMap,
+                    actualSyntaxMap != null,
+                    message: $"{message}, {editKind}({expectedNewSymbol ?? expectedOldSymbol}): Incorrect syntax map");
 
                 // If expected map is specified validate its mappings with the actual one:
                 var expectedSyntaxMap = expectedSemanticEdit.SyntaxMap;
diff --git a/src/EditorFeatures/TestUtilities/LanguageServer/AbstractLanguageServerProtocolTests.cs b/src/EditorFeatures/TestUtilities/LanguageServer/AbstractLanguageServerProtocolTests.cs
index 1d50704a26538..728205e782d45 100644
--- a/src/EditorFeatures/TestUtilities/LanguageServer/AbstractLanguageServerProtocolTests.cs
+++ b/src/EditorFeatures/TestUtilities/LanguageServer/AbstractLanguageServerProtocolTests.cs
@@ -21,6 +21,7 @@
 using Microsoft.CodeAnalysis.LanguageServer;
 using Microsoft.CodeAnalysis.LanguageServer.Handler;
 using Microsoft.CodeAnalysis.LanguageServer.Handler.CodeActions;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.Completion;
 using Microsoft.CodeAnalysis.LanguageServer.UnitTests;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -49,7 +50,11 @@ protected AbstractLanguageServerProtocolTests(ITestOutputHelper? testOutputHelpe
             TestOutputLspLogger = testOutputHelper != null ? new TestOutputLspLogger(testOutputHelper) : NoOpLspLogger.Instance;
         }
 
-        private static readonly TestComposition s_composition = EditorTestCompositions.LanguageServerProtocolEditorFeatures
+        protected static readonly TestComposition EditorFeaturesLspComposition = EditorTestCompositions.LanguageServerProtocolEditorFeatures
+            .AddParts(typeof(TestDocumentTrackingService))
+            .AddParts(typeof(TestWorkspaceRegistrationService));
+
+        protected static readonly TestComposition FeaturesLspComposition = EditorTestCompositions.LanguageServerProtocol
             .AddParts(typeof(TestDocumentTrackingService))
             .AddParts(typeof(TestWorkspaceRegistrationService));
 
@@ -102,7 +107,7 @@ protected class OrderLocations : Comparer<LSP.Location>
             public override int Compare(LSP.Location x, LSP.Location y) => CompareLocations(x, y);
         }
 
-        protected virtual TestComposition Composition => s_composition;
+        protected virtual TestComposition Composition => EditorFeaturesLspComposition;
 
         private protected virtual TestAnalyzerReferenceByLanguage CreateTestAnalyzersReference()
             => new(DiagnosticExtensions.GetCompilerDiagnosticAnalyzersMap());
@@ -244,11 +249,12 @@ protected static LSP.CompletionParams CreateCompletionParams(
             bool preselect = false,
             ImmutableArray<char>? commitCharacters = null,
             LSP.TextEdit? textEdit = null,
-            string? insertText = null,
+            string? textEditText = null,
             string? sortText = null,
             string? filterText = null,
             long resultId = 0,
-            bool vsResolveTextEditOnCommit = false)
+            bool vsResolveTextEditOnCommit = false,
+            LSP.CompletionItemLabelDetails? labelDetails = null)
         {
             var position = await document.GetPositionFromLinePositionAsync(
                 ProtocolConversions.PositionToLinePosition(request.Position), CancellationToken.None).ConfigureAwait(false);
@@ -258,7 +264,7 @@ protected static LSP.CompletionParams CreateCompletionParams(
             var item = new LSP.VSInternalCompletionItem()
             {
                 TextEdit = textEdit,
-                InsertText = insertText,
+                TextEditText = textEditText,
                 FilterText = filterText,
                 Label = label,
                 SortText = sortText,
@@ -269,7 +275,8 @@ protected static LSP.CompletionParams CreateCompletionParams(
                     ResultId = resultId,
                 }),
                 Preselect = preselect,
-                VsResolveTextEditOnCommit = vsResolveTextEditOnCommit
+                VsResolveTextEditOnCommit = vsResolveTextEditOnCommit,
+                LabelDetails = labelDetails
             };
 
             if (tags != null)
@@ -307,12 +314,12 @@ private protected Task<TestLspServer> CreateTestLspServerAsync(string[] markups,
         private protected Task<TestLspServer> CreateVisualBasicTestLspServerAsync(string markup, bool mutatingLspWorkspace, InitializationOptions? initializationOptions = null)
             => CreateTestLspServerAsync(new string[] { markup }, LanguageNames.VisualBasic, mutatingLspWorkspace, initializationOptions);
 
-        private Task<TestLspServer> CreateTestLspServerAsync(
-            string[] markups, string languageName, bool mutatingLspWorkspace, InitializationOptions? initializationOptions)
+        private protected Task<TestLspServer> CreateTestLspServerAsync(
+            string[] markups, string languageName, bool mutatingLspWorkspace, InitializationOptions? initializationOptions, List<Type>? excludedTypes = null, List<Type>? extraExportedTypes = null)
         {
             var lspOptions = initializationOptions ?? new InitializationOptions();
 
-            var workspace = CreateWorkspace(lspOptions, workspaceKind: null, mutatingLspWorkspace);
+            var workspace = CreateWorkspace(lspOptions, workspaceKind: null, mutatingLspWorkspace, excludedTypes, extraExportedTypes);
 
             workspace.InitializeDocuments(TestWorkspace.CreateWorkspaceElement(languageName, files: markups, sourceGeneratedFiles: lspOptions.SourceGeneratedMarkups), openDocuments: false);
 
@@ -372,10 +379,18 @@ private protected async Task<TestLspServer> CreateXmlTestLspServerAsync(
         }
 
         internal TestWorkspace CreateWorkspace(
-            InitializationOptions? options, string? workspaceKind, bool mutatingLspWorkspace)
+            InitializationOptions? options, string? workspaceKind, bool mutatingLspWorkspace, List<Type>? excludedTypes = null, List<Type>? extraExportedTypes = null)
         {
+            var composition = Composition;
+
+            if (excludedTypes is not null)
+                composition = composition.AddExcludedPartTypes(excludedTypes);
+
+            if (extraExportedTypes is not null)
+                composition = composition.AddParts(extraExportedTypes);
+
             var workspace = new TestWorkspace(
-                Composition, workspaceKind, configurationOptions: new WorkspaceConfigurationOptions(EnableOpeningSourceGeneratedFiles: true), supportsLspMutation: mutatingLspWorkspace);
+                composition, workspaceKind, configurationOptions: new WorkspaceConfigurationOptions(EnableOpeningSourceGeneratedFiles: true), supportsLspMutation: mutatingLspWorkspace);
             options?.OptionUpdater?.Invoke(workspace.GetService<IGlobalOptionService>());
 
             workspace.GetService<LspWorkspaceRegistrationService>().Register(workspace);
@@ -452,6 +467,16 @@ static LSP.Location ConvertTextSpanWithTextToLocation(TextSpan span, SourceText
             }
         }
 
+        protected static LSP.Location GetLocationPlusOne(LSP.Location originalLocation)
+        {
+            var newPosition = new LSP.Position { Character = originalLocation.Range.Start.Character + 1, Line = originalLocation.Range.Start.Line };
+            return new LSP.Location
+            {
+                Uri = originalLocation.Uri,
+                Range = new LSP.Range { Start = newPosition, End = newPosition }
+            };
+        }
+
         private static string GetDocumentFilePathFromName(string documentName)
             => "C:\\" + documentName;
 
diff --git a/src/EditorFeatures/TestUtilities/Microsoft.CodeAnalysis.EditorFeatures.Test.Utilities.csproj b/src/EditorFeatures/TestUtilities/Microsoft.CodeAnalysis.EditorFeatures.Test.Utilities.csproj
index b577be56210d8..681918d94ad00 100644
--- a/src/EditorFeatures/TestUtilities/Microsoft.CodeAnalysis.EditorFeatures.Test.Utilities.csproj
+++ b/src/EditorFeatures/TestUtilities/Microsoft.CodeAnalysis.EditorFeatures.Test.Utilities.csproj
@@ -35,6 +35,7 @@
     <PackageReference Include="SQLitePCLRaw.bundle_green" Version="$(SQLitePCLRawbundle_greenVersion)" />
     <PackageReference Include="StreamJsonRpc" Version="$(StreamJsonRpcVersion)" />
     <PackageReference Include="Microsoft.ServiceHub.Client" Version="$(MicrosoftServiceHubClientVersion)" />
+    <PackageReference Include="Microsoft.ServiceHub.Framework" Version="$(MicrosoftServiceHubFrameworkVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Editor" Version="$(MicrosoftVisualStudioEditorVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Platform.VSEditor" Version="$(MicrosoftVisualStudioPlatformVSEditorVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.ComponentModelHost" Version="$(MicrosoftVisualStudioComponentModelHostVersion)" />
diff --git a/src/EditorFeatures/TestUtilities/QuickInfo/ToolTipAssert.cs b/src/EditorFeatures/TestUtilities/QuickInfo/ToolTipAssert.cs
index 9d7d81393bea8..330de55321e16 100644
--- a/src/EditorFeatures/TestUtilities/QuickInfo/ToolTipAssert.cs
+++ b/src/EditorFeatures/TestUtilities/QuickInfo/ToolTipAssert.cs
@@ -18,7 +18,7 @@ namespace Microsoft.CodeAnalysis.Test.Utilities.QuickInfo
 {
     public static class ToolTipAssert
     {
-        public static void EqualContent(object expected, object actual)
+        public static void EqualContent(object expected, object? actual)
         {
             try
             {
@@ -26,25 +26,25 @@ public static void EqualContent(object expected, object actual)
 
                 if (expected is ContainerElement containerElement)
                 {
-                    EqualContainerElement(containerElement, (ContainerElement)actual);
+                    EqualContainerElement(containerElement, (ContainerElement)actual!);
                     return;
                 }
 
                 if (expected is ImageElement imageElement)
                 {
-                    EqualImageElement(imageElement, (ImageElement)actual);
+                    EqualImageElement(imageElement, (ImageElement)actual!);
                     return;
                 }
 
                 if (expected is ClassifiedTextElement classifiedTextElement)
                 {
-                    EqualClassifiedTextElement(classifiedTextElement, (ClassifiedTextElement)actual);
+                    EqualClassifiedTextElement(classifiedTextElement, (ClassifiedTextElement)actual!);
                     return;
                 }
 
                 if (expected is ClassifiedTextRun classifiedTextRun)
                 {
-                    EqualClassifiedTextRun(classifiedTextRun, (ClassifiedTextRun)actual);
+                    EqualClassifiedTextRun(classifiedTextRun, (ClassifiedTextRun)actual!);
                     return;
                 }
 
@@ -53,7 +53,7 @@ public static void EqualContent(object expected, object actual)
             catch (Exception)
             {
                 var renderedExpected = ContainerToString(expected);
-                var renderedActual = ContainerToString(actual);
+                var renderedActual = ContainerToString(actual!);
                 AssertEx.EqualOrDiff(renderedExpected, renderedActual);
 
                 // This is not expected to be hit, but it will be hit if the difference cannot be detected within the diff
diff --git a/src/EditorFeatures/TestUtilities/Structure/AbstractSyntaxStructureProviderTests.cs b/src/EditorFeatures/TestUtilities/Structure/AbstractSyntaxStructureProviderTests.cs
index b7b16fd8d516b..71da0061609b9 100644
--- a/src/EditorFeatures/TestUtilities/Structure/AbstractSyntaxStructureProviderTests.cs
+++ b/src/EditorFeatures/TestUtilities/Structure/AbstractSyntaxStructureProviderTests.cs
@@ -2,17 +2,17 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Structure;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.Editor.UnitTests.Structure
@@ -44,12 +44,12 @@ private protected async Task VerifyBlockSpansAsync(string markupCode, BlockStruc
             using var workspace = TestWorkspace.Create(WorkspaceKind, LanguageName, compilationOptions: null, parseOptions: null, content: markupCode);
 
             var hostDocument = workspace.Documents.Single();
-            Assert.True(hostDocument.CursorPosition.HasValue, "Test must specify a position.");
+            Contract.ThrowIfNull(hostDocument.CursorPosition);
             var position = hostDocument.CursorPosition.Value;
 
             var expectedRegions = expectedRegionData.Select(data => CreateBlockSpan(data, hostDocument.AnnotatedSpans)).ToArray();
 
-            var document = workspace.CurrentSolution.GetDocument(hostDocument.Id);
+            var document = workspace.CurrentSolution.GetRequiredDocument(hostDocument.Id);
             var actualRegions = await GetBlockSpansAsync(document, options, position);
 
             Assert.True(expectedRegions.Length == actualRegions.Length, $"Expected {expectedRegions.Length} regions but there were {actualRegions.Length}");
@@ -65,27 +65,30 @@ protected async Task VerifyNoBlockSpansAsync(string markupCode)
             using var workspace = TestWorkspace.Create(WorkspaceKind, LanguageName, compilationOptions: null, parseOptions: null, content: markupCode);
 
             var hostDocument = workspace.Documents.Single();
-            Assert.True(hostDocument.CursorPosition.HasValue, "Test must specify a position.");
+            Contract.ThrowIfNull(hostDocument.CursorPosition);
             var position = hostDocument.CursorPosition.Value;
 
-            var document = workspace.CurrentSolution.GetDocument(hostDocument.Id);
+            var document = workspace.CurrentSolution.GetRequiredDocument(hostDocument.Id);
             var options = GetDefaultOptions();
             var actualRegions = await GetBlockSpansAsync(document, options, position);
 
             Assert.True(actualRegions.Length == 0, $"Expected no regions but found {actualRegions.Length}.");
         }
 
+        protected static RegionData Region(string textSpanName, string hintSpanName, string primaryTextSpanName, string primaryHintSpanName, string bannerText, bool autoCollapse, bool isDefaultCollapsed = false)
+            => new RegionData(textSpanName, hintSpanName, primaryTextSpanName, primaryHintSpanName, bannerText, autoCollapse, isDefaultCollapsed);
+
         protected static RegionData Region(string textSpanName, string hintSpanName, string bannerText, bool autoCollapse, bool isDefaultCollapsed = false)
-            => new RegionData(textSpanName, hintSpanName, bannerText, autoCollapse, isDefaultCollapsed);
+            => new RegionData(textSpanName, hintSpanName, primaryTextSpanName: null, primaryHintSpanName: null, bannerText, autoCollapse, isDefaultCollapsed);
 
         protected static RegionData Region(string textSpanName, string bannerText, bool autoCollapse, bool isDefaultCollapsed = false)
-            => new RegionData(textSpanName, textSpanName, bannerText, autoCollapse, isDefaultCollapsed);
+            => new RegionData(textSpanName, textSpanName, primaryTextSpanName: null, primaryHintSpanName: null, bannerText, autoCollapse, isDefaultCollapsed);
 
         private static BlockSpan CreateBlockSpan(
             RegionData regionData,
             IDictionary<string, ImmutableArray<TextSpan>> spans)
         {
-            var (textSpanName, hintSpanName, bannerText, autoCollapse, isDefaultCollapsed) = regionData;
+            var (textSpanName, hintSpanName, primaryTextSpanName, primaryHintSpanName, bannerText, autoCollapse, isDefaultCollapsed) = regionData;
 
             Assert.True(spans.ContainsKey(textSpanName) && spans[textSpanName].Length == 1, $"Test did not specify '{textSpanName}' span.");
             Assert.True(spans.ContainsKey(hintSpanName) && spans[hintSpanName].Length == 1, $"Test did not specify '{hintSpanName}' span.");
@@ -93,9 +96,25 @@ private static BlockSpan CreateBlockSpan(
             var textSpan = spans[textSpanName][0];
             var hintSpan = spans[hintSpanName][0];
 
-            return new BlockSpan(isCollapsible: true,
+            TextSpan? primaryTextSpan = null, primaryHintSpan = null;
+            if (primaryTextSpanName != null || primaryHintSpanName != null)
+            {
+                Contract.ThrowIfNull(primaryTextSpanName);
+                Contract.ThrowIfNull(primaryHintSpanName);
+                Assert.True(spans.ContainsKey(primaryTextSpanName) && spans[primaryTextSpanName].Length == 1, $"Test did not specify '{primaryTextSpanName}' span.");
+                Assert.True(spans.ContainsKey(primaryHintSpanName) && spans[primaryHintSpanName].Length == 1, $"Test did not specify '{primaryHintSpanName}' span.");
+
+                primaryTextSpan = spans[primaryTextSpanName][0];
+                primaryHintSpan = spans[primaryHintSpanName][0];
+            }
+
+            return new BlockSpan(
+                isCollapsible: true,
                 textSpan: textSpan,
                 hintSpan: hintSpan,
+                primarySpans: primaryTextSpan is null || primaryHintSpan is null
+                    ? null
+                    : (primaryTextSpan.Value, primaryHintSpan.Value),
                 type: BlockTypes.Nonstructural,
                 bannerText: bannerText,
                 autoCollapse: autoCollapse,
@@ -118,17 +137,21 @@ public readonly struct RegionData
     {
         public readonly string TextSpanName;
         public readonly string HintSpanName;
+        public readonly string? PrimaryTextSpanName;
+        public readonly string? PrimaryHintSpanName;
         public readonly string BannerText;
         public readonly bool AutoCollapse;
         public readonly bool IsDefaultCollapsed;
 
-        public RegionData(string textSpanName, string hintSpanName, string bannerText, bool autoCollapse, bool isDefaultCollapsed)
+        public RegionData(string textSpanName, string hintSpanName, string? primaryTextSpanName, string? primaryHintSpanName, string bannerText, bool autoCollapse, bool isDefaultCollapsed)
         {
-            this.TextSpanName = textSpanName;
-            this.HintSpanName = hintSpanName;
-            this.BannerText = bannerText;
-            this.AutoCollapse = autoCollapse;
-            this.IsDefaultCollapsed = isDefaultCollapsed;
+            TextSpanName = textSpanName;
+            HintSpanName = hintSpanName;
+            PrimaryTextSpanName = primaryTextSpanName;
+            PrimaryHintSpanName = primaryHintSpanName;
+            BannerText = bannerText;
+            AutoCollapse = autoCollapse;
+            IsDefaultCollapsed = isDefaultCollapsed;
         }
 
         public override bool Equals(object obj)
@@ -152,10 +175,19 @@ public override int GetHashCode()
             return hashCode;
         }
 
-        public void Deconstruct(out string textSpanName, out string hintSpanName, out string bannerText, out bool autoCollapse, out bool isDefaultCollapsed)
+        public void Deconstruct(
+            out string textSpanName,
+            out string hintSpanName,
+            out string? primaryTextSpanName,
+            out string? primaryHintSpanName,
+            out string bannerText,
+            out bool autoCollapse,
+            out bool isDefaultCollapsed)
         {
             textSpanName = this.TextSpanName;
             hintSpanName = this.HintSpanName;
+            primaryTextSpanName = PrimaryTextSpanName;
+            primaryHintSpanName = PrimaryHintSpanName;
             bannerText = this.BannerText;
             autoCollapse = this.AutoCollapse;
             isDefaultCollapsed = this.IsDefaultCollapsed;
diff --git a/src/EditorFeatures/TestUtilities/StubLocalRegistry.cs b/src/EditorFeatures/TestUtilities/StubLocalRegistry.cs
new file mode 100644
index 0000000000000..1da13ce4e0941
--- /dev/null
+++ b/src/EditorFeatures/TestUtilities/StubLocalRegistry.cs
@@ -0,0 +1,105 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices.ComTypes;
+using Microsoft.VisualStudio;
+using Microsoft.VisualStudio.Shell.Interop;
+
+namespace Microsoft.CodeAnalysis.Editor.UnitTests;
+
+internal sealed class StubLocalRegistry : ILocalRegistry5, ILocalRegistry4, ILocalRegistry3
+{
+    int ILocalRegistry.CreateInstance(Guid clsid, object punkOuter, ref Guid riid, uint dwFlags, out IntPtr ppvObj)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry.GetTypeLibOfClsid(Guid clsid, out ITypeLib pptLib)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry.GetClassObjectOfClsid(ref Guid clsid, uint dwFlags, IntPtr lpReserved, ref Guid riid, out IntPtr ppvClassObject)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry2.CreateInstance(Guid clsid, object punkOuter, ref Guid riid, uint dwFlags, out IntPtr ppvObj)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry2.GetTypeLibOfClsid(Guid clsid, out ITypeLib pptLib)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry2.GetClassObjectOfClsid(ref Guid clsid, uint dwFlags, IntPtr lpReserved, ref Guid riid, IntPtr ppvClassObject)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry2.GetLocalRegistryRoot(out string pbstrRoot)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry3.CreateInstance(Guid clsid, object punkOuter, ref Guid riid, uint dwFlags, out IntPtr ppvObj)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry3.GetTypeLibOfClsid(Guid clsid, out ITypeLib pptLib)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry3.GetClassObjectOfClsid(ref Guid clsid, uint dwFlags, IntPtr lpReserved, ref Guid riid, IntPtr ppvClassObject)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry3.GetLocalRegistryRoot(out string pbstrRoot)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry3.CreateManagedInstance(string codeBase, string assemblyName, string typeName, ref Guid riid, out IntPtr ppvObj)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry3.GetClassObjectOfManagedClass(string codeBase, string assemblyName, string typeName, ref Guid riid, out IntPtr ppvClassObject)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry4.RegisterClassObject(ref Guid rclsid, out uint pdwCookie)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry4.RevokeClassObject(uint dwCookie)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry4.RegisterInterface(ref Guid riid)
+    {
+        throw new NotImplementedException();
+    }
+
+    int ILocalRegistry4.GetLocalRegistryRootEx(uint dwRegType, out uint pdwRegRootHandle, out string pbstrRoot)
+    {
+        pdwRegRootHandle = unchecked((uint)__VsLocalRegistryRootHandle.RegHandle_CurrentUser);
+        pbstrRoot = "Software\\Microsoft\\VisualStudio\\17.0_Test";
+        return VSConstants.S_OK;
+    }
+
+    int ILocalRegistry5.CreateAggregatedManagedInstance(string codeBase, string AssemblyName, string TypeName, IntPtr pUnkOuter, ref Guid riid, out IntPtr ppvObj)
+    {
+        throw new NotImplementedException();
+    }
+}
diff --git a/src/EditorFeatures/TestUtilities/StubSettingsManagerHost.cs b/src/EditorFeatures/TestUtilities/StubSettingsManagerHost.cs
new file mode 100644
index 0000000000000..de4f0a5eb0dcc
--- /dev/null
+++ b/src/EditorFeatures/TestUtilities/StubSettingsManagerHost.cs
@@ -0,0 +1,183 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.ComponentModel;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.PlatformUI;
+using Microsoft.VisualStudio.Settings;
+using Microsoft.VisualStudio.Settings.Telemetry;
+
+namespace Microsoft.CodeAnalysis.Editor.UnitTests;
+
+internal sealed class StubSettingsManagerHost : ISettingsManagerHost5
+{
+    Task ISettingsManagerHost.AppInitCompletionTask => throw new NotImplementedException();
+
+    ISettingNameTranslator? ISettingsManagerHost.NameTranslator => null;
+
+    IStringStorage ISettingsManagerHost.PrivateStorage { get; } = new StringStorage();
+
+    ISettingsLogger? ISettingsManagerHost.Logger => null;
+
+    string ISettingsManagerHost.CollectionName => throw new NotImplementedException();
+
+    string? ISettingsManagerHost.TelemetrySettings => null;
+
+    string ISettingsManagerHost.AppDir { get; } = Path.GetRandomFileName();
+
+    IRemoteDefaultsStore? ISettingsManagerHost3.RemoteDefaultsStore => null;
+
+    string ISettingsManagerHost4.DurableHostIdentity => "roslyn-CI";
+
+    IStoreUpdateLogger? ISettingsManagerHost4.StoreUpdateLogger => null;
+
+    bool ISettingsManagerHost4.IsRoamingEnabledByDefault => false;
+
+    bool ISettingsManagerHost5.IsRoamingAndSharingAllowed => false;
+
+    event EventHandler<IdleStateChangedEventArgs> ISettingsManagerHost.IdleStateChanged
+    {
+        add
+        {
+            throw new NotImplementedException();
+        }
+
+        remove
+        {
+            throw new NotImplementedException();
+        }
+    }
+
+    event AsyncEventHandler ISettingsManagerHost.HostShuttingDown
+    {
+        add
+        {
+            throw new NotImplementedException();
+        }
+
+        remove
+        {
+            throw new NotImplementedException();
+        }
+    }
+
+    bool ISettingsManagerHost.IsSharedOrRoamedSetting(string settingName)
+    {
+        // Don't roam settings in tests
+        return false;
+    }
+
+    Task<string> ISettingsManagerHost2.GetTelemetrySettingsAsync()
+    {
+        throw new NotImplementedException();
+    }
+
+    Task<Stream> ISettingsManagerHost5.GetServiceStreamAsync(string serviceMoniker, CancellationToken cancellationToken)
+    {
+        throw new NotImplementedException();
+    }
+
+    private sealed class StringStorage : IStringStorage, IAsyncStringStorage
+    {
+        private ImmutableDictionary<string, VersionedString> _values = ImmutableDictionary<string, VersionedString>.Empty;
+        private PropertyChangedEventHandler? _propertyChanged;
+        private PropertyChangedAsyncEventHandler? _propertyChangedAsync;
+
+        event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged
+        {
+            add => _propertyChanged += value;
+            remove => _propertyChanged -= value;
+        }
+
+        event PropertyChangedAsyncEventHandler IStringStorage.PropertyChangedAsync
+        {
+            add => _propertyChangedAsync += value;
+            remove => _propertyChangedAsync -= value;
+        }
+
+        event PropertyChangedAsyncEventHandler IAsyncStringStorage.PropertyChangedAsync
+        {
+            add => ((IStringStorage)this).PropertyChangedAsync += value;
+            remove => ((IStringStorage)this).PropertyChangedAsync -= value;
+        }
+
+        event StoreUpdatedEventHandler IAsyncStringStorage.StoreUpdated
+        {
+            add
+            {
+                throw new NotImplementedException();
+            }
+
+            remove
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        private async Task FireChangeEventAsync(string name)
+        {
+            _propertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
+            await (_propertyChangedAsync?.RaiseEventAsync(this, new PropertyChangedEventArgs(name)) ?? Task.CompletedTask);
+        }
+
+        Task IStringStorage.ClearAsync(CancellationToken cancellationToken)
+        {
+            throw new NotImplementedException();
+        }
+
+        Task IAsyncStringStorage.ClearAsync(CancellationToken cancellationToken)
+            => ((IStringStorage)this).ClearAsync(cancellationToken);
+
+        async Task IStringStorage.DeleteIfExistsAsync(string name, CancellationToken cancellationToken)
+        {
+            if (ImmutableInterlocked.TryRemove(ref _values, name, out _))
+            {
+                await FireChangeEventAsync(name);
+            }
+        }
+
+        Task IAsyncStringStorage.DeleteIfExistsAsync(string name, CancellationToken cancellationToken)
+            => ((IStringStorage)this).DeleteIfExistsAsync(name, cancellationToken);
+
+        StringWithMachineLocalFlag? IStringStorage.Get(string name)
+        {
+            return _values.GetValueOrDefault(name);
+        }
+
+        Task<IEnumerable<NamedVersionedString>> IAsyncStringStorage.GetAllSinceVersionAsync(int modifiedAfterRevision, CancellationToken cancellationToken)
+        {
+            throw new NotImplementedException();
+        }
+
+        Task<VersionedString?> IAsyncStringStorage.GetAsync(string name, CancellationToken cancellationToken)
+        {
+            return Task.FromResult(_values.GetValueOrDefault(name));
+        }
+
+        Task<string> IAsyncStringStorage.GetStoreIdentityAsync(CancellationToken cancellationToken)
+        {
+            throw new NotImplementedException();
+        }
+
+        string[] IStringStorage.NamesStartingWith(string prefix)
+        {
+            throw new NotImplementedException();
+        }
+
+        Task IStringStorage.SetAsync(string name, StringWithMachineLocalFlag value, Action onBeforePropertyChanged, CancellationToken cancellationToken)
+        {
+            throw new NotImplementedException();
+        }
+
+        Task<ServiceUploadResult> IAsyncStringStorage.SetAsync(NamedVersionedString value, CancellationToken cancellationToken)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}
diff --git a/src/EditorFeatures/TestUtilities/StubVsServiceExporter`1.cs b/src/EditorFeatures/TestUtilities/StubVsServiceExporter`1.cs
new file mode 100644
index 0000000000000..22eff35430d1a
--- /dev/null
+++ b/src/EditorFeatures/TestUtilities/StubVsServiceExporter`1.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.ComponentModel.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.VisualStudio;
+using Microsoft.VisualStudio.Shell;
+using Microsoft.VisualStudio.Shell.Interop;
+using Microsoft.VisualStudio.Threading;
+
+namespace Microsoft.CodeAnalysis.Editor.UnitTests;
+
+[Export(typeof(IVsService<>))]
+[PartCreationPolicy(CreationPolicy.NonShared)]
+[PartNotDiscoverable]
+internal class StubVsServiceExporter<T> : StubVsServiceExporter<T, T>
+    where T : class
+{
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public StubVsServiceExporter(
+        [Import(typeof(SAsyncServiceProvider))] IAsyncServiceProvider2 asyncServiceProvider,
+        JoinableTaskContext joinableTaskContext)
+        : base(asyncServiceProvider, joinableTaskContext)
+    {
+    }
+}
diff --git a/src/EditorFeatures/TestUtilities/StubVsServiceExporter`2.cs b/src/EditorFeatures/TestUtilities/StubVsServiceExporter`2.cs
new file mode 100644
index 0000000000000..a5bd41a9f6ed0
--- /dev/null
+++ b/src/EditorFeatures/TestUtilities/StubVsServiceExporter`2.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.ComponentModel.Composition;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.VisualStudio;
+using Microsoft.VisualStudio.Shell;
+using Microsoft.VisualStudio.Shell.Interop;
+using Microsoft.VisualStudio.Threading;
+
+// Import Roslyn.Utilities with an alias to avoid conflicts with AsyncLazy<T>. This implementation relies on
+// AsyncLazy<T> from vs-threading, and not the one from Roslyn.
+using RoslynUtilities = Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.Editor.UnitTests;
+
+[Export(typeof(IVsService<,>))]
+[PartCreationPolicy(CreationPolicy.NonShared)]
+[PartNotDiscoverable]
+internal class StubVsServiceExporter<TService, TInterface> : IVsService<TService, TInterface>
+    where TService : class
+    where TInterface : class
+{
+    private readonly AsyncLazy<TInterface> _serviceGetter;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public StubVsServiceExporter(
+        [Import(typeof(SAsyncServiceProvider))] IAsyncServiceProvider2 asyncServiceProvider,
+        JoinableTaskContext joinableTaskContext)
+    {
+        _serviceGetter = new AsyncLazy<TInterface>(() => asyncServiceProvider.GetServiceAsync<TService, TInterface>(joinableTaskContext.Factory, throwOnFailure: true)!, joinableTaskContext.Factory);
+    }
+
+    /// <inheritdoc />
+    public Task<TInterface> GetValueAsync(CancellationToken cancellationToken)
+        => _serviceGetter.GetValueAsync(cancellationToken);
+
+    /// <inheritdoc />
+    public Task<TInterface?> GetValueOrNullAsync(CancellationToken cancellationToken)
+    {
+        var value = GetValueAsync(cancellationToken);
+        if (value.IsCompleted)
+        {
+            return TransformResult(value);
+        }
+
+        return value.ContinueWith(
+            static t => TransformResult(t),
+            CancellationToken.None, // token is already passed to antecedent, and this is a tiny sync continuation, so no need to make it also cancelable.
+            TaskContinuationOptions.ExecuteSynchronously,
+            TaskScheduler.Default).Unwrap();
+
+        static Task<TInterface?> TransformResult(Task<TInterface> task)
+        {
+            Debug.Assert(task.IsCompleted);
+            if (task.Status == TaskStatus.Faulted)
+            {
+                // Our caller never wants exceptions, so return a cached null value
+                return RoslynUtilities::SpecializedTasks.Null<TInterface>();
+            }
+            else
+            {
+                // Whether this is cancelled or ran to completion, we return the value as-is
+                return RoslynUtilities::SpecializedTasks.AsNullable(task);
+            }
+        }
+    }
+}
diff --git a/src/EditorFeatures/TestUtilities/Workspaces/TestHostDocument.cs b/src/EditorFeatures/TestUtilities/Workspaces/TestHostDocument.cs
index c719b70842226..72861a39c9654 100644
--- a/src/EditorFeatures/TestUtilities/Workspaces/TestHostDocument.cs
+++ b/src/EditorFeatures/TestUtilities/Workspaces/TestHostDocument.cs
@@ -138,9 +138,9 @@ internal TestHostDocument(
             _documentServiceProvider = documentServiceProvider;
             _roles = roles.IsDefault ? s_defaultRoles : roles;
 
-            if (spans.ContainsKey(string.Empty))
+            if (spans.TryGetValue(string.Empty, out var textSpans))
             {
-                this.SelectedSpans = spans[string.Empty];
+                this.SelectedSpans = textSpans;
             }
 
             foreach (var namedSpanList in spans.Where(s => s.Key != string.Empty))
diff --git a/src/EditorFeatures/TestUtilities/Workspaces/TestWorkspace.cs b/src/EditorFeatures/TestUtilities/Workspaces/TestWorkspace.cs
index f163ee7f4503a..2f14fb3e71fd8 100644
--- a/src/EditorFeatures/TestUtilities/Workspaces/TestWorkspace.cs
+++ b/src/EditorFeatures/TestUtilities/Workspaces/TestWorkspace.cs
@@ -457,8 +457,8 @@ public TestHostDocument CreateProjectionBufferDocument(
             // Add in mapped spans from each of the base documents
             foreach (var document in baseDocuments)
             {
-                mappedSpans[string.Empty] = mappedSpans.ContainsKey(string.Empty)
-                    ? mappedSpans[string.Empty]
+                mappedSpans[string.Empty] = mappedSpans.TryGetValue(string.Empty, out var emptyTextSpans)
+                    ? emptyTextSpans
                     : ImmutableArray<TextSpan>.Empty;
                 foreach (var span in document.SelectedSpans)
                 {
@@ -473,9 +473,7 @@ public TestHostDocument CreateProjectionBufferDocument(
 
                 foreach (var (key, spans) in document.AnnotatedSpans)
                 {
-                    mappedSpans[key] = mappedSpans.ContainsKey(key)
-                        ? mappedSpans[key]
-                        : ImmutableArray<TextSpan>.Empty;
+                    mappedSpans[key] = mappedSpans.TryGetValue(key, out var textSpans) ? textSpans : ImmutableArray<TextSpan>.Empty;
 
                     foreach (var span in spans)
                     {
diff --git a/src/EditorFeatures/TestUtilities2/Intellisense/MockCompletionPresenterProvider.vb b/src/EditorFeatures/TestUtilities2/Intellisense/MockCompletionPresenterProvider.vb
index cc52445075dbe..bd1a6850a55c2 100644
--- a/src/EditorFeatures/TestUtilities2/Intellisense/MockCompletionPresenterProvider.vb
+++ b/src/EditorFeatures/TestUtilities2/Intellisense/MockCompletionPresenterProvider.vb
@@ -34,11 +34,13 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.IntelliSense
         End Property
 
         Public Function GetOrCreate(textView As ITextView) As ICompletionPresenter Implements ICompletionPresenterProvider.GetOrCreate
-            If Not _presenters.ContainsKey(textView) Then
-                _presenters(textView) = New MockCompletionPresenter(textView)
+            Dim presenter As ICompletionPresenter = Nothing
+            If Not _presenters.TryGetValue(textView, presenter) Then
+                presenter = New MockCompletionPresenter(textView)
+                _presenters(textView) = presenter
             End If
 
-            Return _presenters(textView)
+            Return presenter
         End Function
     End Class
 End Namespace
diff --git a/src/EditorFeatures/VisualBasic/DocumentationComments/XmlTagCompletionCommandHandler.vb b/src/EditorFeatures/VisualBasic/DocumentationComments/XmlTagCompletionCommandHandler.vb
index 39d73171a55f8..2f603a42a91dc 100644
--- a/src/EditorFeatures/VisualBasic/DocumentationComments/XmlTagCompletionCommandHandler.vb
+++ b/src/EditorFeatures/VisualBasic/DocumentationComments/XmlTagCompletionCommandHandler.vb
@@ -59,7 +59,7 @@ Namespace Microsoft.CodeAnalysis.Editor.VisualBasic.DocumentationComments
             End If
         End Sub
 
-        Private Function HasUnmatchedIdenticalParentStart(element As XmlElementSyntax, expectedName As String) As Boolean
+        Private Shared Function HasUnmatchedIdenticalParentStart(element As XmlElementSyntax, expectedName As String) As Boolean
             If element Is Nothing Then
                 Return False
             End If
diff --git a/src/EditorFeatures/VisualBasic/LanguageServer/VisualBasicLspBuildOnlyDiagnostics.vb b/src/EditorFeatures/VisualBasic/LanguageServer/VisualBasicLspBuildOnlyDiagnostics.vb
index 2281db5faf018..9e2b56191937b 100644
--- a/src/EditorFeatures/VisualBasic/LanguageServer/VisualBasicLspBuildOnlyDiagnostics.vb
+++ b/src/EditorFeatures/VisualBasic/LanguageServer/VisualBasicLspBuildOnlyDiagnostics.vb
@@ -12,7 +12,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.LanguageServer
     <LspBuildOnlyDiagnostics(
         "BC31091", ' ERRID.ERR_TypeRefResolutionError3,
         "BC35000", ' ERRID.ERR_MissingRuntimeHelper,
-        "BC36597" ' ERRID.ERR_CannotGotoNonScopeBlocksWithClosure
+        "BC36597", ' ERRID.ERR_CannotGotoNonScopeBlocksWithClosure
+        "BC37327"  ' ERRID.ERR_SymbolDefinedInAssembly
     )>
     Friend NotInheritable Class VisualBasicLspBuildOnlyDiagnostics
         Implements ILspBuildOnlyDiagnostics
diff --git a/src/EditorFeatures/VisualBasic/LineCommit/CommitBufferManager.vb b/src/EditorFeatures/VisualBasic/LineCommit/CommitBufferManager.vb
index e6cdbf64e5006..1665f2a0db09d 100644
--- a/src/EditorFeatures/VisualBasic/LineCommit/CommitBufferManager.vb
+++ b/src/EditorFeatures/VisualBasic/LineCommit/CommitBufferManager.vb
@@ -222,7 +222,7 @@ Namespace Microsoft.CodeAnalysis.Editor.VisualBasic.LineCommit
 
         Public Shared Function IsMovementBetweenStatements(oldPoint As SnapshotPoint, newPoint As SnapshotPoint, cancellationToken As CancellationToken) As Boolean
             ' If they are the same line, then definitely no
-            If oldPoint.GetContainingLine().LineNumber = newPoint.GetContainingLine().LineNumber Then
+            If oldPoint.GetContainingLineNumber() = newPoint.GetContainingLineNumber() Then
                 Return False
             End If
 
diff --git a/src/EditorFeatures/VisualBasicTest/EditAndContinue/Helpers/EditingTestBase.vb b/src/EditorFeatures/VisualBasicTest/EditAndContinue/Helpers/EditingTestBase.vb
index 4cb3be3c9c655..fd9c57598bb8a 100644
--- a/src/EditorFeatures/VisualBasicTest/EditAndContinue/Helpers/EditingTestBase.vb
+++ b/src/EditorFeatures/VisualBasicTest/EditAndContinue/Helpers/EditingTestBase.vb
@@ -49,6 +49,25 @@ End Namespace
             Return String.Format(FeaturesResources.member_kind_and_name, resource, symbolDisplayName)
         End Function
 
+        Public Shared Function GetResource(keyword As String, symbolDisplayName As String, containerKeyword As String, containerDisplayName As String) As String
+            Dim keywordResource = TryGetResource(keyword)
+            If keywordResource Is Nothing Then
+                Throw ExceptionUtilities.UnexpectedValue(keyword)
+            End If
+
+            Dim containerResource = TryGetResource(containerKeyword)
+            If containerResource Is Nothing Then
+                Throw ExceptionUtilities.UnexpectedValue(containerKeyword)
+            End If
+
+            Return String.Format(
+                FeaturesResources.symbol_kind_and_name_of_member_kind_and_name,
+                keywordResource,
+                symbolDisplayName,
+                containerResource,
+                containerDisplayName)
+        End Function
+
         Public Shared Function GetResource(keyword As String) As String
             Dim result = TryGetResource(keyword)
             If result Is Nothing Then
diff --git a/src/EditorFeatures/VisualBasicTest/EditAndContinue/LineEditTests.vb b/src/EditorFeatures/VisualBasicTest/EditAndContinue/LineEditTests.vb
index aa8ebdd0372c2..9ca248ca6da54 100644
--- a/src/EditorFeatures/VisualBasicTest/EditAndContinue/LineEditTests.vb
+++ b/src/EditorFeatures/VisualBasicTest/EditAndContinue/LineEditTests.vb
@@ -465,14 +465,14 @@ End Class"
         Public Sub Constructor_Recompile2()
             Dim src1 =
 "Class C
-    Shared Sub New()
+    Sub New()
         MyBase.New()
     End Sub
 End Class"
 
             Dim src2 =
 "Class C
-    Shared Sub _
+    Sub _
                 New()
         MyBase.New()
     End Sub
@@ -481,7 +481,7 @@ End Class"
             Dim edits = GetTopEdits(src1, src2)
             edits.VerifyLineEdits(
                 Array.Empty(Of SequencePointUpdates),
-                {SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").SharedConstructors.Single())})
+                {SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").InstanceConstructors.Single())})
         End Sub
 
 #End Region
diff --git a/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementEditingTests.vb b/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementEditingTests.vb
index ae1e0c8b45db7..c19cea32359bf 100644
--- a/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementEditingTests.vb
+++ b/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementEditingTests.vb
@@ -1247,35 +1247,6 @@ End Class"
                 Diagnostic(RudeEditKind.DeleteLambdaWithMultiScopeCapture, "x3", VBFeaturesResources.Lambda, "Me", "x3"))
         End Sub
 
-        <Fact>
-        Public Sub Lambdas_Update_CeaseCapture_This()
-            Dim src1 = "
-Imports System
-
-Class C
-    Dim x As Integer = 1
-
-    Sub F()
-        Dim f = New Func(Of Integer, Integer)(Function(a) a + x)
-    End Sub
-End Class
-"
-            Dim src2 = "
-Imports System
-
-Class C
-    Dim x As Integer
-
-    Sub F()
-        Dim f = New Func(Of Integer, Integer)(Function(a) a)
-    End Sub
-End Class
-"
-            Dim edits = GetTopEdits(src1, src2)
-            edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "Me"))
-        End Sub
-
         <Fact, WorkItem("https://github.com/dotnet/roslyn/issues/1290")>
         Public Sub Lambdas_Update_Signature1()
             Dim src1 = "
@@ -1999,6 +1970,35 @@ End Class
             edits.VerifySemanticDiagnostics()
         End Sub
 
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_This()
+            Dim src1 = "
+Imports System
+
+Class C
+    Dim x As Integer = 1
+
+    Sub F()
+        Dim f = New Func(Of Integer, Integer)(Function(a) a + x)
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+
+Class C
+    Dim x As Integer
+
+    Sub F()
+        Dim f = New Func(Of Integer, Integer)(Function(a) a)
+    End Sub
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "Me"))
+        End Sub
+
         <Fact>
         Public Sub Lambdas_Update_CeaseCapture_Closure1()
             Dim src1 = "
@@ -2059,11 +2059,142 @@ End Class
 "
             Dim edits = GetTopEdits(src1, src2)
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a1", "a1"))
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a1 As Integer", "a1"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_IndexerParameter_Delete()
+            Dim src1 = "
+Imports System
+Class C
+    Readonly Property Item(a1 As Integer, a2 As Integer) As Func(Of Integer, Integer)
+        Get
+            Return New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+        End Get
+    End Property
+End Class
+"
+            Dim src2 = "
+Imports System
+Class C
+    Readonly Property Item(a2 As Integer) As Func(Of Integer, Integer)
+        Get
+            Return New Func(Of Integer, Integer)(Function(a3) a2)
+        End Get
+    End Property
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "Get", "a1"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_IndexerParameter_Setter_WithExplicitValue()
+            Dim src1 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set(Value As Integer)
+            Dim f = Function() a1 + a2 + Value
+        End Set
+    End Property
+End Class
+"
+            Dim src2 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set(Value As Integer)
+            Dim f = Function() a1
+        End Set
+    End Property
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a2 As Integer", "a2"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "Value As Integer", "Value"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_IndexerParameter_Setter_WithImplicitValue()
+            Dim src1 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set
+            Dim f = Function() a1 + a2 + Value
+        End Set
+    End Property
+End Class
+"
+            Dim src2 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set
+            Dim f = Function() a1
+        End Set
+    End Property
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a2 As Integer", "a2"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "Set", "Value"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_IndexerParameter_Setter_WithImplicitToExplicitValue()
+            Dim src1 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set
+            Dim f = Function() a1 + a2 + Value
+        End Set
+    End Property
+End Class
+"
+            Dim src2 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set(Value As Integer)
+            Dim f = Function() a1
+        End Set
+    End Property
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a2 As Integer", "a2"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "Set", "Value"))
         End Sub
 
         <Fact>
-        Public Sub Lambdas_Update_CeaseCapture_MethodParameter1()
+        Public Sub Lambdas_Update_CeaseCapture_IndexerParameter_Setter_WithExplicitToImplicitValue()
+            Dim src1 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set(Value As Integer)
+            Dim f = Function() a1 + a2 + Value
+        End Set
+    End Property
+End Class
+"
+            Dim src2 = "
+Class C
+    WriteOnly Property Item(a1 As Integer, a2 As Integer) As Integer
+        Set
+            Dim f = Function() a1
+        End Set
+    End Property
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a2 As Integer", "a2"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "Set", "Value"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_MethodParameter()
             Dim src1 = "
 Imports System
 Class C
@@ -2082,7 +2213,104 @@ End Class
 "
             Dim edits = GetTopEdits(src1, src2)
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a2", "a2"))
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a2 As Integer", "a2"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_MethodParameter_ParameterDelete()
+            Dim src1 = "
+Imports System
+Class C
+    Sub F(a1 As Integer, a2 As Integer)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+Class C
+    Sub F(a1 As Integer)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1)
+    End Sub
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "a2"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_MethodParameter_ParameterTypeChange()
+            Dim src1 = "
+Imports System
+Class C
+    Sub F(a1 As Integer, a2 As Integer)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+Class C
+    Sub F(a1 As Byte)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1)
+    End Sub
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingCapturedVariableType, "a1", "a1", "Integer"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "a2"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_MethodParameter_LocalToParameter()
+            Dim src1 = "
+Imports System
+Class C
+    Sub F(a1 As Integer)
+        Dim a2 As Integer
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+Class C
+    Sub F(a1 As Integer, a2 As Integer)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"),
+                Diagnostic(RudeEditKind.DeletingCapturedVariable, "Sub F(a1 As Integer, a2 As Integer)", "a2"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_CeaseCapture_MethodParameter_ParameterToLocal()
+            Dim src1 = "
+Imports System
+Class C
+    Sub F(a1 As Integer, a2 As Integer)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+Class C
+    Sub F(a1 As Integer)
+        Dim a2 As Integer
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"),
+                Diagnostic(RudeEditKind.NotCapturingVariable, "F", "a2"))
         End Sub
 
         <Fact, WorkItem("https://github.com/dotnet/roslyn/issues/1290")>
@@ -2219,7 +2447,7 @@ Class C
 End Class
 "
             Dim edits = GetTopEdits(src1, src2)
-            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.NotCapturingVariable, "Value", "Value"))
+            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.NotCapturingVariable, "Value As Integer", "Value"))
         End Sub
 
         <Fact, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems?id=234448")>
@@ -2258,7 +2486,7 @@ Class C
 End Class
 "
             Dim edits = GetTopEdits(src1, src2)
-            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.NotCapturingVariable, "Value", "Value"))
+            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.NotCapturingVariable, "Value As Action", "Value"))
         End Sub
 
         <Fact, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems?id=234448")>
@@ -2297,7 +2525,7 @@ Class C
 End Class
 "
             Dim edits = GetTopEdits(src1, src2)
-            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.NotCapturingVariable, "Value", "Value"))
+            edits.VerifySemanticDiagnostics(Diagnostic(RudeEditKind.NotCapturingVariable, "Value As Action", "Value"))
         End Sub
 
         <Fact>
@@ -2359,6 +2587,34 @@ End Class
                 Diagnostic(RudeEditKind.CapturingVariable, "a1", "a1"))
         End Sub
 
+        <Fact>
+        Public Sub Lambdas_Update_Capturing_IndexerGetterParameter_ParameterInsert()
+            Dim src1 = "
+Imports System
+Class C
+    Readonly Property Item(a1 As Integer) As Func(Of Integer, Integer)
+        Get
+            Return New Func(Of Integer, Integer)(Function(a3) a1)
+        End Get
+    End Property
+End Class
+"
+            Dim src2 = "
+Imports System
+Class C
+    Readonly Property Item(a1 As Integer, a2 As Integer) As Func(Of Integer, Integer)
+        Get
+            Return New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+        End Get
+    End Property
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"))
+        End Sub
+
         <Fact>
         Public Sub Lambdas_Update_Capturing_IndexerSetterParameter1()
             Dim src1 = "
@@ -2598,6 +2854,64 @@ End Class
                 Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"))
         End Sub
 
+        <Fact>
+        Public Sub Lambdas_Update_Capturing_MethodParameter_ParameterInsert()
+            Dim src1 = "
+Imports System
+Class C
+    Sub F(a1 As Integer)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1)
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+Class C
+    Sub F(a1 As Integer, a2 As Integer)
+        Dim f2 = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_Update_Capturing_MethodParameter_ParameterInsert_Partial()
+            Dim src1 = "
+Imports System
+
+Partial Public Class C
+    Partial Private Sub F(a1 As Integer)
+    End Sub    
+End Class
+
+Partial Public Class C
+    Private Sub F(a1 As Integer)
+        Dim x = New Func(Of Integer, Integer)(Function(a3) a1)
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+
+Partial Public Class C
+    Partial Private Sub F(a1 As Integer, a2 As Integer)
+    End Sub    
+End Class
+
+Partial Public Class C
+    Private Sub F(a1 As Integer, a2 As Integer)
+        Dim x = New Func(Of Integer, Integer)(Function(a3) a1 + a2)
+    End Sub
+End Class
+"
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.CapturingVariable, "a2", "a2"))
+        End Sub
+
         <Fact>
         Public Sub Lambdas_Update_Capturing_LambdaParameter1()
             Dim src1 = "
@@ -3056,13 +3370,11 @@ End Class
         End Sub
 
         <Fact>
-        Public Sub Lambdas_RenameCapturedLocal1()
+        Public Sub Lambdas_CapturedLocal_Rename_CaseChange()
             Dim src1 = "
 Imports System
-Imports System.Diagnostics
 
 Class Program
-
     Shared Sub Main()
         Dim x As Integer = 1
         Dim f As Func(Of Integer) = Function() x
@@ -3071,10 +3383,8 @@ End Class
 "
             Dim src2 = "
 Imports System
-Imports System.Diagnostics
 
 Class Program
-
     Shared Sub Main()
         Dim X As Integer = 1
         Dim f As Func(Of Integer) = Function() X
@@ -3089,13 +3399,11 @@ End Class
         End Sub
 
         <Fact>
-        Public Sub Lambdas_RenameCapturedLocal2()
+        Public Sub Lambdas_CapturedLocal_Rename()
             Dim src1 = "
 Imports System
-Imports System.Diagnostics
 
 Class Program
-
     Shared Sub Main()
         Dim x As Integer = 1
         Dim f As Func(Of Integer) = Function() x
@@ -3104,10 +3412,8 @@ End Class
 "
             Dim src2 = "
 Imports System
-Imports System.Diagnostics
 
 Class Program
-
     Shared Sub Main()
         Dim y As Integer = 1
         Dim f As Func(Of Integer) = Function() y
@@ -3120,6 +3426,87 @@ End Class
                 Diagnostic(RudeEditKind.RenamingCapturedVariable, "y", "x", "y"))
         End Sub
 
+        <Fact>
+        Public Sub Lambdas_CapturedLocal_ChangeType()
+            Dim src1 = "
+Imports System
+
+Class Program
+    Shared Sub Main()
+        Dim x As Integer = 1
+        Dim f As Func(Of Integer) = Function() x
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+
+Class Program
+    Shared Sub Main()
+        Dim x As Byte = 1
+        Dim f As Func(Of Integer) = Function() x
+    End Sub
+End Class
+"
+
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingCapturedVariableType, "x", "x", "Integer"))
+        End Sub
+
+        <Fact>
+        Public Sub Lambdas_CapturedParameter_Rename()
+            Dim src1 = "
+Imports System
+
+Class Program
+    Shared Sub Main(x As Integer)
+        Dim f As Func(Of Integer) = Function() x
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+
+Class Program
+    Shared Sub Main(y As Integer)
+        Dim f As Func(Of Integer) = Function() y
+    End Sub
+End Class
+"
+
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.RenamingCapturedVariable, "y", "x", "y"))
+        End Sub
+
+        <Fact(Skip:="https://github.com/dotnet/roslyn/issues/68708")>
+        <WorkItem("https://github.com/dotnet/roslyn/issues/68708")>
+        Public Sub Lambdas_CapturedParameter_ChangeType()
+            Dim src1 = "
+Imports System
+
+Class Program
+    Shared Sub Main(x As Integer)
+        Dim f As Func(Of Integer) = Function() x
+    End Sub
+End Class
+"
+            Dim src2 = "
+Imports System
+
+Class Program
+    Shared Sub Main(x As Byte)
+        Dim f As Func(Of Integer) = Function() x
+    End Sub
+End Class
+"
+
+            Dim edits = GetTopEdits(src1, src2)
+            edits.VerifySemanticDiagnostics(
+                Diagnostic(RudeEditKind.ChangingCapturedVariableType, "x", "x", "Integer"))
+        End Sub
+
         <Fact>
         Public Sub Lambdas_Signature_MatchingErrorType()
             Dim src1 = "
diff --git a/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementMatchingTests.vb b/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementMatchingTests.vb
index 4e4a559fc5682..c2630a45c041c 100644
--- a/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementMatchingTests.vb
+++ b/src/EditorFeatures/VisualBasicTest/EditAndContinue/StatementMatchingTests.vb
@@ -569,7 +569,6 @@ Do : Dim a = 14, b = 15, c = 16 : Console.WriteLine(a + b + c) : Loop
             Dim src1 = "Dim result = From q in {0} Aggregate b In Q(Function() 1) Join c In Q(Function() 3) On c Equals b Skip Q(Function() 5) Select b Into Count()" & vbLf
             Dim src2 = "Dim result = From q in {0} Aggregate b In Q(Function() 2) Join c In Q(Function() 4) On c Equals b Skip Q(Function() 6) Select b Into Count()" & vbLf
 
-            ' TODO
             Dim match = GetMethodMatches(src1, src2)
             Dim actual = ToMatchingPairs(match)
 
@@ -588,6 +587,7 @@ Do : Dim a = 14, b = 15, c = 16 : Console.WriteLine(a + b + c) : Loop
                 {"b", "b"},
                 {"Function() 1", "Function() 2"},
                 {"Function()", "Function()"},
+                {"()", "()"},
                 {"Join c In Q(Function() 3) On c Equals b", "Join c In Q(Function() 4) On c Equals b"},
                 {"c In Q(Function() 3)", "c In Q(Function() 4)"},
                 {"c", "c"},
@@ -867,10 +867,19 @@ Do : Dim a = 14, b = 15, c = 16 : Console.WriteLine(a + b + c) : Loop
                 {"F(Function(a) Function(b) Function(c) d)", "F(Function(a) Function(b) Function(c) d)"},
                 {"Function(a) Function(b) Function(c) d", "Function(a) Function(b) Function(c) d"},
                 {"Function(a)", "Function(a)"},
+                {"(a)", "(a)"},
+                {"a", "a"},
+                {"a", "a"},
                 {"Function(b) Function(c) d", "Function(b) Function(c) d"},
                 {"Function(b)", "Function(b)"},
+                {"(b)", "(b)"},
+                {"b", "b"},
+                {"b", "b"},
                 {"Function(c) d", "Function(c) d"},
                 {"Function(c)", "Function(c)"},
+                {"(c)", "(c)"},
+                {"c", "c"},
+                {"c", "c"},
                 {"End Sub", "End Sub"}
             }
 
@@ -891,10 +900,19 @@ Do : Dim a = 14, b = 15, c = 16 : Console.WriteLine(a + b + c) : Loop
                 {"F(Function(a) Function(b) Function(c) d)", "F(Function(a) G(Function(b) H(Function(c) d)))"},
                 {"Function(a) Function(b) Function(c) d", "Function(a) G(Function(b) H(Function(c) d))"},
                 {"Function(a)", "Function(a)"},
+                {"(a)", "(a)"},
+                {"a", "a"},
+                {"a", "a"},
                 {"Function(b) Function(c) d", "Function(b) H(Function(c) d)"},
                 {"Function(b)", "Function(b)"},
+                {"(b)", "(b)"},
+                {"b", "b"},
+                {"b", "b"},
                 {"Function(c) d", "Function(c) d"},
                 {"Function(c)", "Function(c)"},
+                {"(c)", "(c)"},
+                {"c", "c"},
+                {"c", "c"},
                 {"End Sub", "End Sub"}
             }
 
@@ -934,22 +952,42 @@ F(Sub(a)
                 {"Sub(a)     F(Function(c) d)     F(Sub(u, v)         F(Function(w) Function(c)  d )         F(Function(p) p)       End Sub)   End Sub",
                  "Sub(a)     F(Function(c) d + 1)     F(Sub(u, v)         F(Function(w) Function(c) d  +  1)         F(Function(p) p*2)       End Sub)   End Sub"},
                 {"Sub(a)", "Sub(a)"},
+                {"(a)", "(a)"},
+                {"a", "a"},
+                {"a", "a"},
                 {"F(Function(c) d)", "F(Function(c) d + 1)"},
                 {"Function(c) d", "Function(c) d + 1"},
                 {"Function(c)", "Function(c)"},
+                {"(c)", "(c)"},
+                {"c", "c"},
+                {"c", "c"},
                 {"F(Sub(u, v)         F(Function(w) Function(c)  d )         F(Function(p) p)       End Sub)",
                  "F(Sub(u, v)         F(Function(w) Function(c) d  +  1)         F(Function(p) p*2)       End Sub)"},
                 {"Sub(u, v)         F(Function(w) Function(c)  d )         F(Function(p) p)       End Sub",
                  "Sub(u, v)         F(Function(w) Function(c) d  +  1)         F(Function(p) p*2)       End Sub"},
                 {"Sub(u, v)", "Sub(u, v)"},
+                {"(u, v)", "(u, v)"},
+                {"u", "u"},
+                {"u", "u"},
+                {"v", "v"},
+                {"v", "v"},
                 {"F(Function(w) Function(c)  d )", "F(Function(w) Function(c) d  +  1)"},
                 {"Function(w) Function(c)  d", "Function(w) Function(c) d  +  1"},
                 {"Function(w)", "Function(w)"},
+                {"(w)", "(w)"},
+                {"w", "w"},
+                {"w", "w"},
                 {"Function(c)  d", "Function(c) d  +  1"},
                 {"Function(c)", "Function(c)"},
+                {"(c)", "(c)"},
+                {"c", "c"},
+                {"c", "c"},
                 {"F(Function(p) p)", "F(Function(p) p*2)"},
                 {"Function(p) p", "Function(p) p*2"},
                 {"Function(p)", "Function(p)"},
+                {"(p)", "(p)"},
+                {"p", "p"},
+                {"p", "p"},
                 {"End Sub", "End Sub"},
                 {"End Sub", "End Sub"},
                 {"End Sub", "End Sub"}
@@ -1134,16 +1172,28 @@ Dim q = From a In seq1
                 {"F(Function(u) u) Equals G(Function(s) s)", "F(Function(u) u + 1) Equals G(Function(s) s + 3)"},
                 {"Function(u) u", "Function(u) u + 1"},
                 {"Function(u)", "Function(u)"},
+                {"(u)", "(u)"},
+                {"u", "u"},
+                {"u", "u"},
                 {"Function(s) s", "Function(s) s + 3"},
                 {"Function(s)", "Function(s)"},
+                {"(s)", "(s)"},
+                {"s", "s"},
+                {"s", "s"},
                 {"Join l In seq3 On F(Function(v) v) Equals G(Function(t) t)", "Join l In seq3 On F(Function(vv) vv + 2) Equals G(Function(tt) tt + 4)"},
                 {"l In seq3", "l In seq3"},
                 {"l", "l"},
                 {"F(Function(v) v) Equals G(Function(t) t)", "F(Function(vv) vv + 2) Equals G(Function(tt) tt + 4)"},
                 {"Function(v) v", "Function(vv) vv + 2"},
                 {"Function(v)", "Function(vv)"},
+                {"(v)", "(vv)"},
+                {"v", "vv"},
+                {"v", "vv"},
                 {"Function(t) t", "Function(tt) tt + 4"},
                 {"Function(t)", "Function(tt)"},
+                {"(t)", "(tt)"},
+                {"t", "tt"},
+                {"t", "tt"},
                 {"Select a", "Select a + 1"},
                 {"a", "a + 1"},
                 {"End Sub", "End Sub"}
@@ -1172,20 +1222,36 @@ Dim q = From a In seq1
                 {"c", "c"},
                 {"Function() d", "Function() d + 1"},
                 {"Function()", "Function()"},
+                {"()", "()"},
                 {"Function(e1) Function(e2) (e1 - e2) Equals Function(f1) Function(f2) (f1 - f2)", "Function(e1) Function(e2) (e1 + e2) Equals Function(f1) Function(f2) (f1 + f2)"},
                 {"Function(e1) Function(e2) (e1 - e2)", "Function(e1) Function(e2) (e1 + e2)"},
                 {"Function(e1)", "Function(e1)"},
+                {"(e1)", "(e1)"},
+                {"e1", "e1"},
+                {"e1", "e1"},
                 {"Function(e2) (e1 - e2)", "Function(e2) (e1 + e2)"},
                 {"Function(e2)", "Function(e2)"},
+                {"(e2)", "(e2)"},
+                {"e2", "e2"},
+                {"e2", "e2"},
                 {"Function(f1) Function(f2) (f1 - f2)", "Function(f1) Function(f2) (f1 + f2)"},
                 {"Function(f1)", "Function(f1)"},
+                {"(f1)", "(f1)"},
+                {"f1", "f1"},
+                {"f1", "f1"},
                 {"Function(f2) (f1 - f2)", "Function(f2) (f1 + f2)"},
                 {"Function(f2)", "Function(f2)"},
+                {"(f2)", "(f2)"},
+                {"f2", "f2"},
+                {"f2", "f2"},
                 {"g", "g"},
                 {"h", "h"},
                 {"Sum(Function(f) f + 1)", "Sum(Function(f) f + 2)"},
                 {"Function(f) f + 1", "Function(f) f + 2"},
                 {"Function(f)", "Function(f)"},
+                {"(f)", "(f)"},
+                {"f", "f"},
+                {"f", "f"},
                 {"Select g", "Select g"},
                 {"g", "g"},
                 {"End Sub", "End Sub"}
diff --git a/src/EditorFeatures/VisualBasicTest/EditAndContinue/TopLevelEditingTests.vb b/src/EditorFeatures/VisualBasicTest/EditAndContinue/TopLevelEditingTests.vb
index 9824d09d8e328..b8665b2bd2c88 100644
--- a/src/EditorFeatures/VisualBasicTest/EditAndContinue/TopLevelEditingTests.vb
+++ b/src/EditorFeatures/VisualBasicTest/EditAndContinue/TopLevelEditingTests.vb
@@ -3915,7 +3915,11 @@ End Class
             EditAndContinueValidation.VerifySemantics(
                 {GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2)},
                 {
-                    DocumentResults(),
+                    DocumentResults(
+                        semanticEdits:=
+                        {
+                            SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").InstanceConstructors.Single(), partialType:="C", preserveLocalVariables:=True)
+                        }),
                     DocumentResults(
                         semanticEdits:=
                         {
@@ -4198,7 +4202,10 @@ End Class"
             EditAndContinueValidation.VerifySemantics(
                 {GetTopEdits(srcA1, srcA2), GetTopEdits(srcB1, srcB2)},
                 {
-                    DocumentResults(),
+                    DocumentResults(semanticEdits:=
+                    {
+                        SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").InstanceConstructors.Single(), partialType:="C", preserveLocalVariables:=True)
+                    }),
                     DocumentResults(semanticEdits:=
                     {
                         SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").InstanceConstructors.Single(), partialType:="C", preserveLocalVariables:=True)
@@ -6620,7 +6627,7 @@ End Class
 Partial Class C
     ReadOnly Property B As Integer = F(<N:0.1>Function(a) a + 1</N:0.1>)
 
-    Sub New()      ' new ctor
+    Sub New(x As Integer)      ' new ctor
         F(Function(c) c + 1)
     End Sub
 End Class
@@ -6630,7 +6637,7 @@ End Class
             Dim syntaxMap = GetSyntaxMap(src1, src2)
 
             edits.VerifySemanticDiagnostics(
-                {Diagnostic(RudeEditKind.InsertConstructorToTypeWithInitializersWithLambdas, "Sub New()")})
+                {Diagnostic(RudeEditKind.InsertConstructorToTypeWithInitializersWithLambdas, "Sub New(x As Integer)")})
         End Sub
 
         <Fact, WorkItem("https://github.com/dotnet/roslyn/issues/2504")>
@@ -7965,7 +7972,8 @@ End Class
                 ActiveStatementsDescription.Empty,
                 {
                     SemanticEdit(SemanticEditKind.Insert, Function(c) c.GetMember("C.B")),
-                    SemanticEdit(SemanticEditKind.Insert, Function(c) c.GetMember(Of NamedTypeSymbol)("C").Constructors.Single())
+                    SemanticEdit(SemanticEditKind.Insert, Function(c) c.GetMember(Of NamedTypeSymbol)("C").Constructors.Single()),
+                    SemanticEdit(SemanticEditKind.Delete, Function(c) c.GetMember(Of NamedTypeSymbol)("C").Constructors.Single(), deletedSymbolContainerProvider:=Function(c) c.GetMember("C"))
                 },
                 capabilities:=EditAndContinueCapabilities.AddMethodToExistingType Or EditAndContinueCapabilities.AddInstanceFieldToExistingType)
         End Sub
@@ -8433,7 +8441,8 @@ End Class
                 {
                     DocumentResults(
                         semanticEdits:={SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").InstanceConstructors.Single(), partialType:="C", preserveLocalVariables:=True)}),
-                    DocumentResults()
+                    DocumentResults(
+                        semanticEdits:={SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").InstanceConstructors.Single(), partialType:="C", preserveLocalVariables:=True)})
                 })
         End Sub
 
@@ -8469,7 +8478,7 @@ End Class
             Dim edits = GetTopEdits(src1, src2)
 
             edits.VerifySemanticDiagnostics(
-                Diagnostic(RudeEditKind.NotCapturingVariable, "a", "a"))
+                Diagnostic(RudeEditKind.NotCapturingVariable, "a As Integer", "a"))
         End Sub
 #End Region
 
@@ -9512,7 +9521,8 @@ End Class
                 semanticEdits:=
                 {
                     SemanticEdit(SemanticEditKind.Delete, Function(c) c.GetMember("C.get_a"), deletedSymbolContainerProvider:=Function(c) c.GetMember("C")),
-                    SemanticEdit(SemanticEditKind.Delete, Function(c) c.GetMember("C.set_a"), deletedSymbolContainerProvider:=Function(c) c.GetMember("C"))
+                    SemanticEdit(SemanticEditKind.Delete, Function(c) c.GetMember("C.set_a"), deletedSymbolContainerProvider:=Function(c) c.GetMember("C")),
+                    SemanticEdit(SemanticEditKind.Update, Function(c) c.GetMember(Of NamedTypeSymbol)("C").InstanceConstructors.Single(), preserveLocalVariables:=True)
                 })
         End Sub
 
@@ -10966,7 +10976,7 @@ End Class
                 capabilities:=EditAndContinueCapabilities.AddMethodToExistingType)
 
             edits.VerifySemanticDiagnostics(
-                {Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "Public Sub M()", DeletedSymbolDisplay(FeaturesResources.parameter, "a As Integer"))},
+                {Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "Public Sub M()", GetResource("parameter", "a", "method", "M(a As Integer)"))},
                 capabilities:=EditAndContinueCapabilities.Baseline)
         End Sub
 
@@ -10990,7 +11000,7 @@ End Class
                 capabilities:=EditAndContinueCapabilities.AddMethodToExistingType)
 
             edits.VerifySemanticDiagnostics(
-                {Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "Public Sub M(b As Integer)", DeletedSymbolDisplay(FeaturesResources.parameter, "a As Integer"))},
+                {Diagnostic(RudeEditKind.DeleteNotSupportedByRuntime, "Public Sub M(b As Integer)", GetResource("parameter", "a", "method", "M(a As Integer, b As Integer)"))},
                 capabilities:=EditAndContinueCapabilities.Baseline)
         End Sub
 
diff --git a/src/EditorFeatures/VisualBasicTest/ImplementInterface/ImplementInterfaceCommandHandlerTests.vb b/src/EditorFeatures/VisualBasicTest/ImplementInterface/ImplementInterfaceCommandHandlerTests.vb
index c649777af1543..0a105a3769b82 100644
--- a/src/EditorFeatures/VisualBasicTest/ImplementInterface/ImplementInterfaceCommandHandlerTests.vb
+++ b/src/EditorFeatures/VisualBasicTest/ImplementInterface/ImplementInterfaceCommandHandlerTests.vb
@@ -462,7 +462,7 @@ End Class
                  End Sub,
                  Sub(expected, actual, view)
                      AssertEx.AssertEqualToleratingWhitespaceDifferences(expected, actual)
-                     Assert.Equal(4, view.Caret.Position.BufferPosition.GetContainingLine().LineNumber)
+                     Assert.Equal(4, view.Caret.Position.BufferPosition.GetContainingLineNumber())
                      Assert.Equal(4, view.Caret.Position.VirtualSpaces)
                  End Sub)
         End Sub
diff --git a/src/EditorFeatures/VisualBasicTest/LineCommit/CommitOnEnterTests.vb b/src/EditorFeatures/VisualBasicTest/LineCommit/CommitOnEnterTests.vb
index 4f76935b25c2f..d2eb16148c21f 100644
--- a/src/EditorFeatures/VisualBasicTest/LineCommit/CommitOnEnterTests.vb
+++ b/src/EditorFeatures/VisualBasicTest/LineCommit/CommitOnEnterTests.vb
@@ -253,7 +253,7 @@ rem Hello World$$|]
                 testData.CommandHandler.ExecuteCommand(New ReturnKeyCommandArgs(testData.View, testData.Buffer), Sub() testData.EditorOperations.InsertNewLine(), TestCommandExecutionContext.Create())
                 testData.UndoHistory.Undo(count:=1)
 
-                Assert.Equal(0, testData.View.Caret.Position.BufferPosition.GetContainingLine().LineNumber)
+                Assert.Equal(0, testData.View.Caret.Position.BufferPosition.GetContainingLineNumber())
             End Using
         End Sub
 
@@ -342,14 +342,14 @@ End Module
 
         Private Shared Sub AssertCommitsStatement(test As XElement, expectCommit As Boolean, Optional usedSemantics As Boolean = True)
             Using testData = CommitTestData.Create(test)
-                Dim lineNumber = testData.View.Caret.Position.BufferPosition.GetContainingLine().LineNumber
+                Dim lineNumber = testData.View.Caret.Position.BufferPosition.GetContainingLineNumber()
                 testData.CommandHandler.ExecuteCommand(New ReturnKeyCommandArgs(testData.View, testData.Buffer), Sub() testData.EditorOperations.InsertNewLine(), TestCommandExecutionContext.Create())
                 testData.AssertHadCommit(expectCommit)
                 If expectCommit Then
                     testData.AssertUsedSemantics(usedSemantics)
                 End If
 
-                Assert.Equal(lineNumber + 1, testData.View.Caret.Position.BufferPosition.GetContainingLine().LineNumber)
+                Assert.Equal(lineNumber + 1, testData.View.Caret.Position.BufferPosition.GetContainingLineNumber())
             End Using
         End Sub
     End Class
diff --git a/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CompilationContext.cs b/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CompilationContext.cs
index ca7708a3d1e5d..1ef4d60de348f 100644
--- a/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CompilationContext.cs
+++ b/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CompilationContext.cs
@@ -1714,11 +1714,11 @@ private static void GetDisplayClassVariables(
                         continue;
                 }
 
-                if (displayClassVariablesBuilder.ContainsKey(variableName))
+                if (displayClassVariablesBuilder.TryGetValue(variableName, out var displayClassVariable))
                 {
                     // Only expecting duplicates for async state machine
                     // fields (that should be at the top-level).
-                    Debug.Assert(displayClassVariablesBuilder[variableName].DisplayClassFields.Count() == 1);
+                    Debug.Assert(displayClassVariable.DisplayClassFields.Count() == 1);
 
                     if (!instance.Fields.Any())
                     {
diff --git a/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/Symbols/EENamedTypeSymbol.cs b/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/Symbols/EENamedTypeSymbol.cs
index 2bd6c9a780ad0..43190f16253bf 100644
--- a/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/Symbols/EENamedTypeSymbol.cs
+++ b/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/Symbols/EENamedTypeSymbol.cs
@@ -159,6 +159,7 @@ internal override bool MangleName
             get { return false; }
         }
 
+        internal override bool IsFileLocal => false;
         internal override FileIdentifier? AssociatedFileIdentifier => null;
 
         public override IEnumerable<string> MemberNames
@@ -186,12 +187,12 @@ public override ImmutableArray<NamedTypeSymbol> GetTypeMembers()
             return ImmutableArray<NamedTypeSymbol>.Empty;
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name)
         {
             throw ExceptionUtilities.Unreachable();
         }
 
-        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(string name, int arity)
+        public override ImmutableArray<NamedTypeSymbol> GetTypeMembers(ReadOnlyMemory<char> name, int arity)
         {
             throw ExceptionUtilities.Unreachable();
         }
@@ -372,5 +373,11 @@ internal static void VerifyTypeParameters(Symbol container, ImmutableArray<TypeP
         {
             return SpecializedCollections.EmptyEnumerable<(MethodSymbol Body, MethodSymbol Implemented)>();
         }
+
+        internal override bool HasInlineArrayAttribute(out int length)
+        {
+            length = 0;
+            return false;
+        }
     }
 }
diff --git a/src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/CompilationContext.vb b/src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/CompilationContext.vb
index 2c4caa29b6e80..b2f78dba09954 100644
--- a/src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/CompilationContext.vb
+++ b/src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/CompilationContext.vb
@@ -1288,10 +1288,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
                     variableKind = DisplayClassVariableKind.Parameter
                 End If
 
-                If displayClassVariablesBuilder.ContainsKey(variableName) Then
+                Dim displayClassVariable As DisplayClassVariable = Nothing
+                If displayClassVariablesBuilder.TryGetValue(variableName, displayClassVariable) Then
                     ' Only expecting duplicates for async state machine
                     ' fields (that should be at the top-level).
-                    Debug.Assert(displayClassVariablesBuilder(variableName).DisplayClassFields.Count() = 1)
+                    Debug.Assert(displayClassVariable.DisplayClassFields.Count() = 1)
 
                     If Not instance.Fields.Any() Then
                         ' Prefer parameters over locals.
diff --git a/src/Features/CSharp/Portable/AddImport/CSharpAddImportFeatureService.cs b/src/Features/CSharp/Portable/AddImport/CSharpAddImportFeatureService.cs
index 418fb61d5aa9c..662166820a676 100644
--- a/src/Features/CSharp/Portable/AddImport/CSharpAddImportFeatureService.cs
+++ b/src/Features/CSharp/Portable/AddImport/CSharpAddImportFeatureService.cs
@@ -349,7 +349,7 @@ protected override async Task<Document> AddImportAsync(
             return document.WithSyntaxRoot(newRoot);
         }
 
-        private async Task<CompilationUnitSyntax> AddImportWorkerAsync(
+        private static async Task<CompilationUnitSyntax> AddImportWorkerAsync(
             Document document, CompilationUnitSyntax root, SyntaxNode contextNode, INamespaceOrTypeSymbol namespaceOrTypeSymbol,
             AddImportPlacementOptions options, CancellationToken cancellationToken)
         {
@@ -403,7 +403,7 @@ protected override async Task<Document> AddImportAsync(
             return document.WithSyntaxRoot(newRoot);
         }
 
-        private NameSyntax CreateNameSyntax(IReadOnlyList<string> namespaceParts, int index)
+        private static NameSyntax CreateNameSyntax(IReadOnlyList<string> namespaceParts, int index)
         {
             var part = namespaceParts[index];
             if (SyntaxFacts.GetKeywordKind(part) != SyntaxKind.None)
@@ -433,7 +433,7 @@ private static (ExternAliasDirectiveSyntax, bool hasExistingImport) GetExternAli
                     hasExistingExtern);
         }
 
-        private (UsingDirectiveSyntax, bool hasExistingImport) GetUsingDirective(
+        private static (UsingDirectiveSyntax, bool hasExistingImport) GetUsingDirective(
             Document document,
             AddImportPlacementOptions options,
             INamespaceOrTypeSymbol namespaceOrTypeSymbol,
@@ -537,7 +537,7 @@ private static bool ConflictsWithExistingMember(
             return false;
         }
 
-        private NameSyntax AddOrReplaceAlias(
+        private static NameSyntax AddOrReplaceAlias(
             NameSyntax nameSyntax, IdentifierNameSyntax alias)
         {
             if (nameSyntax is SimpleNameSyntax simpleName)
diff --git a/src/Features/CSharp/Portable/CSharpFeaturesResources.resx b/src/Features/CSharp/Portable/CSharpFeaturesResources.resx
index acfc531f47412..be9fc97d0afcc 100644
--- a/src/Features/CSharp/Portable/CSharpFeaturesResources.resx
+++ b/src/Features/CSharp/Portable/CSharpFeaturesResources.resx
@@ -591,4 +591,12 @@
   <data name="init_only_property" xml:space="preserve">
     <value>init-only property</value>
   </data>
+  <data name="for_loop" xml:space="preserve">
+    <value>for loop</value>
+    <comment>{Locked="for"} "for" is a C# keyword and should not be localized.</comment>
+  </data>
+  <data name="reversed_for_loop" xml:space="preserve">
+    <value>reversed for loop</value>
+    <comment>{Locked="for"} "for" is a C# keyword and should not be localized.</comment>
+  </data>
 </root>
\ No newline at end of file
diff --git a/src/Features/CSharp/Portable/Completion/CompletionProviders/SnippetCompletionProvider.cs b/src/Features/CSharp/Portable/Completion/CompletionProviders/SnippetCompletionProvider.cs
index 823f7090a9e19..4d84864f5a687 100644
--- a/src/Features/CSharp/Portable/Completion/CompletionProviders/SnippetCompletionProvider.cs
+++ b/src/Features/CSharp/Portable/Completion/CompletionProviders/SnippetCompletionProvider.cs
@@ -33,7 +33,7 @@ internal sealed class SnippetCompletionProvider : LSPCompletionProvider
     {
         private static readonly HashSet<string> s_snippetsWithReplacements = new()
         {
-            "class", "cw", "ctor", "else", "enum", "foreach", "if", "interface", "prop", "propg", "struct", "while"
+            "class", "cw", "ctor", "else", "enum", "for", "forr", "foreach", "if", "interface", "lock", "prop", "propg", "struct", "while"
         };
 
         internal override bool IsSnippetProvider => true;
diff --git a/src/Features/CSharp/Portable/Completion/CompletionProviders/XmlDocCommentCompletionProvider.cs b/src/Features/CSharp/Portable/Completion/CompletionProviders/XmlDocCommentCompletionProvider.cs
index 149fb1fc4f75c..e4c58f1f25596 100644
--- a/src/Features/CSharp/Portable/Completion/CompletionProviders/XmlDocCommentCompletionProvider.cs
+++ b/src/Features/CSharp/Portable/Completion/CompletionProviders/XmlDocCommentCompletionProvider.cs
@@ -225,7 +225,7 @@ SyntaxKind.XmlNameAttribute or
             return elementName != null;
         }
 
-        private (string? name, SyntaxList<XmlAttributeSyntax> attributes) GetElementNameAndAttributes(SyntaxNode node)
+        private static (string? name, SyntaxList<XmlAttributeSyntax> attributes) GetElementNameAndAttributes(SyntaxNode node)
         {
             XmlNameSyntax? nameSyntax;
             SyntaxList<XmlAttributeSyntax> attributes;
diff --git a/src/Features/CSharp/Portable/Diagnostics/Analyzers/CSharpSimplifyTypeNamesDiagnosticAnalyzer.cs b/src/Features/CSharp/Portable/Diagnostics/Analyzers/CSharpSimplifyTypeNamesDiagnosticAnalyzer.cs
index 887a65f451b42..1a88eb0939004 100644
--- a/src/Features/CSharp/Portable/Diagnostics/Analyzers/CSharpSimplifyTypeNamesDiagnosticAnalyzer.cs
+++ b/src/Features/CSharp/Portable/Diagnostics/Analyzers/CSharpSimplifyTypeNamesDiagnosticAnalyzer.cs
@@ -3,6 +3,8 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Linq;
 using System.Threading;
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
@@ -47,14 +49,16 @@ SyntaxKind.DelegateDeclaration or
                 SyntaxKind.EnumDeclaration;
         }
 
-        protected override ImmutableArray<Diagnostic> AnalyzeCodeBlock(CodeBlockAnalysisContext context)
+        protected override ImmutableArray<Diagnostic> AnalyzeCodeBlock(CodeBlockAnalysisContext context, SyntaxNode root)
         {
+            Debug.Assert(context.CodeBlock.DescendantNodesAndSelf().Contains(root));
+
             var semanticModel = context.SemanticModel;
             var cancellationToken = context.CancellationToken;
 
             var options = context.GetCSharpAnalyzerOptions().GetSimplifierOptions();
             using var simplifier = new TypeSyntaxSimplifierWalker(this, semanticModel, options, ignoredSpans: null, cancellationToken);
-            simplifier.Visit(context.CodeBlock);
+            simplifier.Visit(root);
             return simplifier.Diagnostics;
         }
 
diff --git a/src/Features/CSharp/Portable/EditAndContinue/CSharpEditAndContinueAnalyzer.cs b/src/Features/CSharp/Portable/EditAndContinue/CSharpEditAndContinueAnalyzer.cs
index 773981c207f3b..42f10c576ff2d 100644
--- a/src/Features/CSharp/Portable/EditAndContinue/CSharpEditAndContinueAnalyzer.cs
+++ b/src/Features/CSharp/Portable/EditAndContinue/CSharpEditAndContinueAnalyzer.cs
@@ -564,6 +564,19 @@ protected override IEnumerable<SyntaxNode> GetLambdaBodyExpressionsAndStatements
         protected override Match<SyntaxNode> ComputeTopLevelMatch(SyntaxNode oldCompilationUnit, SyntaxNode newCompilationUnit)
             => SyntaxComparer.TopLevel.ComputeMatch(oldCompilationUnit, newCompilationUnit);
 
+        protected override BidirectionalMap<SyntaxNode>? ComputeParameterMap(SyntaxNode oldDeclaration, SyntaxNode newDeclaration)
+            => GetDeclarationParameterList(oldDeclaration) is { } oldParameterList && GetDeclarationParameterList(newDeclaration) is { } newParameterList ?
+                BidirectionalMap<SyntaxNode>.FromMatch(SyntaxComparer.TopLevel.ComputeMatch(oldParameterList, newParameterList)) : null;
+
+        private static SyntaxNode? GetDeclarationParameterList(SyntaxNode declaration)
+            => declaration switch
+            {
+                ParameterListSyntax parameterList => parameterList,
+                AccessorDeclarationSyntax { Parent.Parent: IndexerDeclarationSyntax { ParameterList: var list } } => list,
+                ArrowExpressionClauseSyntax { Parent: { } memberDecl } => GetDeclarationParameterList(memberDecl),
+                _ => declaration.GetParameterList()
+            };
+
         protected override Match<SyntaxNode> ComputeTopLevelDeclarationMatch(SyntaxNode oldDeclaration, SyntaxNode newDeclaration)
         {
             Contract.ThrowIfNull(oldDeclaration.Parent);
@@ -661,79 +674,6 @@ private static IEnumerable<SyntaxNode> GetChildNodes(SyntaxNode root, SyntaxNode
             }
         }
 
-        internal override void ReportDeclarationInsertDeleteRudeEdits(ArrayBuilder<RudeEditDiagnostic> diagnostics, SyntaxNode oldNode, SyntaxNode newNode, ISymbol oldSymbol, ISymbol newSymbol, EditAndContinueCapabilitiesGrantor capabilities, CancellationToken cancellationToken)
-        {
-            // Global statements have a declaring syntax reference to the compilation unit itself, which we can just ignore
-            // for the purposes of declaration rude edits
-            if (oldNode.IsKind(SyntaxKind.CompilationUnit) || newNode.IsKind(SyntaxKind.CompilationUnit))
-            {
-                return;
-            }
-
-            // Compiler generated methods of records have a declaring syntax reference to the record declaration itself
-            // but their explicitly implemented counterparts reference the actual member. Compiler generated properties
-            // of records reference the parameter that names them.
-            //
-            // Since there is no useful "old" syntax node for these members, we can't compute declaration or body edits
-            // using the standard tree comparison code.
-            //
-            // Based on this, we can detect a new explicit implementation of a record member by checking if the
-            // declaration kind has changed. If it hasn't changed, then our standard code will handle it.
-            if (oldNode.RawKind == newNode.RawKind)
-            {
-                base.ReportDeclarationInsertDeleteRudeEdits(diagnostics, oldNode, newNode, oldSymbol, newSymbol, capabilities, cancellationToken);
-                return;
-            }
-
-            // When explicitly implementing a property that is represented by a positional parameter
-            // what looks like an edit could actually be a rude delete, or something else
-            if (oldNode is ParameterSyntax &&
-                newNode is PropertyDeclarationSyntax property)
-            {
-                if (property.AccessorList!.Accessors.Count == 1)
-                {
-                    // Explicitly implementing a property with only one accessor is a delete of the init accessor, so a rude edit.
-                    // Not implementing the get accessor would be a compile error
-
-                    diagnostics.Add(new RudeEditDiagnostic(
-                        RudeEditKind.ImplementRecordParameterAsReadOnly,
-                        GetDiagnosticSpan(newNode, EditKind.Delete),
-                        oldNode,
-                        new[] { property.Identifier.ToString() }));
-                }
-                else if (property.AccessorList.Accessors.Any(a => a.IsKind(SyntaxKind.SetAccessorDeclaration)))
-                {
-                    // The compiler implements the properties with an init accessor so explicitly implementing
-                    // it with a set accessor is a rude accessor change edit
-
-                    diagnostics.Add(new RudeEditDiagnostic(
-                        RudeEditKind.ImplementRecordParameterWithSet,
-                        GetDiagnosticSpan(newNode, EditKind.Delete),
-                        oldNode,
-                        new[] { property.Identifier.ToString() }));
-                }
-            }
-            else if (oldNode is RecordDeclarationSyntax &&
-                     newNode is MethodDeclarationSyntax &&
-                     !oldSymbol.GetParameters().Select(p => p.Name).SequenceEqual(newSymbol.GetParameters().Select(p => p.Name)) &&
-                     !capabilities.Grant(EditAndContinueCapabilities.UpdateParameters))
-            {
-                // Explicitly implemented methods must have parameter names that match the compiler generated versions
-                // exactly if the runtime doesn't support updating parameters, otherwise the debugger would show incorrect
-                // parameter names.
-                // We don't need to worry about parameter types, because if they were different then we wouldn't get here
-                // as this wouldn't be the explicit implementation of a known method.
-                // We don't need to worry about access modifiers because the symbol matching still works, and most of the
-                // time changing access modifiers for these known methods is a compile error anyway.
-
-                diagnostics.Add(new RudeEditDiagnostic(
-                    RudeEditKind.ExplicitRecordMethodParameterNamesMustMatch,
-                    GetDiagnosticSpan(newNode, EditKind.Update),
-                    oldNode,
-                    new[] { oldSymbol.ToDisplayString(SymbolDisplayFormats.NameFormat) }));
-            }
-        }
-
         protected override bool TryMatchActiveStatement(
             SyntaxNode oldStatement,
             int statementPart,
@@ -786,15 +726,20 @@ protected override bool IsCompilationUnitWithGlobalStatements(SyntaxNode node)
         protected override bool IsGlobalStatement(SyntaxNode node)
             => node.IsKind(SyntaxKind.GlobalStatement);
 
-        protected override TextSpan GetGlobalStatementDiagnosticSpan(SyntaxNode node)
+        protected override TextSpan GetGlobalStatementDiagnosticSpan(SyntaxNode node, EditKind editKind)
         {
             if (node is CompilationUnitSyntax unit)
             {
                 // When deleting something from a compilation unit we just report diagnostics for the last global statement
-                return unit.Members.OfType<GlobalStatementSyntax>().LastOrDefault()?.Span ?? default;
+                if (editKind == EditKind.Delete)
+                {
+                    return unit.Members.OfType<GlobalStatementSyntax>().LastOrDefault()?.Span ?? default;
+                }
+
+                return unit.Members.OfType<GlobalStatementSyntax>().FirstOrDefault()?.Span ?? default;
             }
 
-            return GetDiagnosticSpan(node, EditKind.Delete);
+            return GetDiagnosticSpan(node, editKind);
         }
 
         protected override IEnumerable<SyntaxNode> GetTopLevelTypeDeclarations(SyntaxNode compilationUnit)
@@ -1162,12 +1107,21 @@ internal override bool HasBackingField(SyntaxNode propertyOrIndexerDeclaration)
 
         internal override bool TryGetAssociatedMemberDeclaration(SyntaxNode node, EditKind editKind, [NotNullWhen(true)] out SyntaxNode? declaration)
         {
-            if (node.Kind() is SyntaxKind.Parameter or SyntaxKind.TypeParameter)
+            if (node is (kind: SyntaxKind.Parameter))
             {
-                Contract.ThrowIfFalse(node.Parent is (kind:
-                    SyntaxKind.ParameterList or
-                    SyntaxKind.TypeParameterList or
-                    SyntaxKind.BracketedParameterList));
+                Contract.ThrowIfFalse(node.Parent is (kind: SyntaxKind.ParameterList or SyntaxKind.BracketedParameterList));
+
+                // ParameterList represents the primary constructor:
+                declaration = node.Parent.Parent is TypeDeclarationSyntax ? node.Parent : node.Parent.Parent;
+                Contract.ThrowIfNull(declaration);
+
+                return true;
+            }
+
+            if (node is (kind: SyntaxKind.TypeParameter))
+            {
+                Contract.ThrowIfFalse(node.Parent is (kind: SyntaxKind.TypeParameterList));
+
                 declaration = node.Parent.Parent!;
                 return true;
             }
@@ -1190,46 +1144,53 @@ SyntaxKind.IndexerDeclaration or
         internal override bool IsDeclarationWithInitializer(SyntaxNode declaration)
             => declaration is VariableDeclaratorSyntax { Initializer: not null } or PropertyDeclarationSyntax { Initializer: not null };
 
-        internal override bool IsRecordPrimaryConstructorParameter(SyntaxNode declaration)
-            => declaration is ParameterSyntax { Parent: ParameterListSyntax { Parent: RecordDeclarationSyntax } };
+        internal override bool IsPrimaryConstructorDeclaration(SyntaxNode declaration)
+            => declaration.Parent is TypeDeclarationSyntax { ParameterList: var parameterList } && parameterList == declaration;
 
-        private static bool IsPropertyDeclarationMatchingPrimaryConstructorParameter(SyntaxNode declaration, INamedTypeSymbol newContainingType)
+        internal override bool IsConstructorWithMemberInitializers(ISymbol symbol, CancellationToken cancellationToken)
         {
-            if (newContainingType.IsRecord &&
-                declaration is PropertyDeclarationSyntax { Identifier.ValueText: var name })
+            if (symbol is not IMethodSymbol { MethodKind: MethodKind.Constructor or MethodKind.StaticConstructor } method)
             {
-                // We need to use symbol information to find the primary constructor, because it could be in another file if the type is partial
-                foreach (var reference in newContainingType.DeclaringSyntaxReferences)
-                {
-                    // Since users can define as many constructors as they like, going back to syntax to find the parameter list
-                    // in the record declaration is the simplest way to check if there is a matching parameter
-                    if (reference.GetSyntax() is RecordDeclarationSyntax record &&
-                        record.ParameterList is not null &&
-                        record.ParameterList.Parameters.Any(p => p.Identifier.ValueText.Equals(name)))
-                    {
-                        return true;
-                    }
-                }
+                return false;
             }
 
-            return false;
-        }
-
-        internal override bool IsPropertyAccessorDeclarationMatchingPrimaryConstructorParameter(SyntaxNode declaration, INamedTypeSymbol newContainingType, out bool isFirstAccessor)
-        {
-            isFirstAccessor = false;
-            if (declaration is AccessorDeclarationSyntax { Parent: AccessorListSyntax { Parent: PropertyDeclarationSyntax property } list } &&
-                IsPropertyDeclarationMatchingPrimaryConstructorParameter(property, newContainingType))
+            // static constructor has initializers:
+            if (method.IsStatic)
             {
-                isFirstAccessor = list.Accessors[0] == declaration;
                 return true;
             }
 
-            return false;
-        }
+            // If primary constructor is present then no other constructor has member initializers:
+            if (GetPrimaryConstructor(method.ContainingType, cancellationToken) is { } primaryConstructor)
+            {
+                return symbol == primaryConstructor;
+            }
 
-        internal override bool IsConstructorWithMemberInitializers(SyntaxNode constructorDeclaration)
-            => constructorDeclaration is ConstructorDeclarationSyntax ctor && (ctor.Initializer == null || ctor.Initializer.IsKind(SyntaxKind.BaseConstructorInitializer));
+            // Copy-constructor of a record does not have member initializers:
+            if (method.ContainingType.IsRecord && method.IsCopyConstructor())
+            {
+                return false;
+            }
+
+            // Default constructor has initializers unless the type is a struct.
+            // Struct with member initializers is required to have an explicit constructor.
+            if (method.IsImplicitlyDeclared)
+            {
+                return method.ContainingType.TypeKind != TypeKind.Struct;
+            }
+
+            var ctorInitializer = ((ConstructorDeclarationSyntax)symbol.DeclaringSyntaxReferences[0].GetSyntax(cancellationToken)).Initializer;
+            if (method.ContainingType.TypeKind == TypeKind.Struct)
+            {
+                // constructor of a struct with implicit or this() initializer has member initializers:
+                return ctorInitializer is null or { ThisOrBaseKeyword: (kind: SyntaxKind.ThisKeyword), ArgumentList.Arguments: [] };
+            }
+            else
+            {
+                // constructor of a class with implicit or base initializer has member initializers:
+                return ctorInitializer is null or (kind: SyntaxKind.BaseConstructorInitializer);
+            }
+        }
 
         internal override bool IsPartial(INamedTypeSymbol type)
         {
@@ -1238,8 +1199,26 @@ internal override bool IsPartial(INamedTypeSymbol type)
                 || ((BaseTypeDeclarationSyntax)syntaxRefs.Single().GetSyntax()).Modifiers.Any(SyntaxKind.PartialKeyword);
         }
 
-        protected override SyntaxNode GetSymbolDeclarationSyntax(SyntaxReference reference, CancellationToken cancellationToken)
-            => reference.GetSyntax(cancellationToken);
+        protected override SyntaxNode GetSymbolDeclarationSyntax(ISymbol symbol, Func<ImmutableArray<SyntaxReference>, SyntaxReference> selector, CancellationToken cancellationToken)
+        {
+            var syntax = selector(symbol.DeclaringSyntaxReferences).GetSyntax(cancellationToken);
+
+            // Use the parameter list to represent primary constructor declaration.
+            return symbol.Kind == SymbolKind.Method && syntax is TypeDeclarationSyntax { ParameterList: { } parameterList } ? parameterList : syntax;
+        }
+
+        protected override ISymbol? GetDeclaredSymbol(SemanticModel model, SyntaxNode declaration, CancellationToken cancellationToken)
+        {
+            if (IsPrimaryConstructorDeclaration(declaration))
+            {
+                Contract.ThrowIfNull(declaration.Parent);
+                var recordType = (INamedTypeSymbol?)model.GetDeclaredSymbol(declaration.Parent, cancellationToken);
+                Contract.ThrowIfNull(recordType);
+                return recordType.InstanceConstructors.Single(ctor => ctor.DeclaringSyntaxReferences is [var syntaxRef] && syntaxRef.GetSyntax(cancellationToken) == declaration.Parent);
+            }
+
+            return model.GetDeclaredSymbol(declaration, cancellationToken);
+        }
 
         protected override OneOrMany<(ISymbol? oldSymbol, ISymbol? newSymbol, EditKind editKind)> GetSymbolEdits(
             EditKind editKind,
@@ -1354,12 +1333,12 @@ static bool DiffersInReadOnlyModifier(SyntaxTokenList oldModifiers, SyntaxTokenL
                     {
                         if (oldVariables.Count == 1 && newVariables.Count == 1)
                         {
-                            return OneOrMany.Create((oldModel.GetDeclaredSymbol(oldVariables[0], cancellationToken), newModel.GetDeclaredSymbol(newVariables[0], cancellationToken), EditKind.Update));
+                            return OneOrMany.Create((GetDeclaredSymbol(oldModel, oldVariables[0], cancellationToken), GetDeclaredSymbol(newModel, newVariables[0], cancellationToken), EditKind.Update));
                         }
 
                         var result = from oldVariable in oldVariables
                                      join newVariable in newVariables on oldVariable.Identifier.Text equals newVariable.Identifier.Text
-                                     select (oldModel.GetDeclaredSymbol(oldVariable, cancellationToken), newModel.GetDeclaredSymbol(newVariable, cancellationToken), EditKind.Update);
+                                     select (GetDeclaredSymbol(oldModel, oldVariable, cancellationToken), GetDeclaredSymbol(newModel, newVariable, cancellationToken), EditKind.Update);
 
                         return OneOrMany.Create(result.ToImmutableArray());
                     }
@@ -1405,6 +1384,13 @@ join newVariable in newVariables on oldVariable.Identifier.Text equals newVariab
                         return OneOrMany.Create(ImmutableArray.Create((oldSymbol, newSymbol, EditKind.Update)));
                     }
 
+                    // Inserting/deleting a primary constructor base initializer/base list is an update of the constructor/type,
+                    // not a delete/insert of the constructor/type itself:
+                    if (node is (kind: SyntaxKind.PrimaryConstructorBaseType or SyntaxKind.BaseList))
+                    {
+                        return OneOrMany.Create(ImmutableArray.Create((oldSymbol, newSymbol, EditKind.Update)));
+                    }
+
                     break;
 
                 case EditKind.Move:
@@ -1425,7 +1411,7 @@ join newVariable in newVariables on oldVariable.Identifier.Text equals newVariab
                 OneOrMany<(ISymbol?, ISymbol?, EditKind)>.Empty : new OneOrMany<(ISymbol?, ISymbol?, EditKind)>((oldSymbol, newSymbol, editKind));
         }
 
-        private static ISymbol? GetSymbolForEdit(
+        private ISymbol? GetSymbolForEdit(
             SyntaxNode node,
             SemanticModel model,
             CancellationToken cancellationToken)
@@ -1448,7 +1434,18 @@ join newVariable in newVariables on oldVariable.Identifier.Text equals newVariab
                 return model.GetEnclosingSymbol(node.SpanStart, cancellationToken);
             }
 
-            var symbol = model.GetDeclaredSymbol(node, cancellationToken);
+            if (node is PrimaryConstructorBaseTypeSyntax primaryCtorBase)
+            {
+                return model.GetEnclosingSymbol(primaryCtorBase.ArgumentList.SpanStart, cancellationToken);
+            }
+
+            if (node.IsKind(SyntaxKind.BaseList))
+            {
+                Contract.ThrowIfNull(node.Parent);
+                node = node.Parent;
+            }
+
+            var symbol = GetDeclaredSymbol(model, node, cancellationToken);
 
             // TODO: this is incorrect (https://github.com/dotnet/roslyn/issues/54800)
             // Ignore partial method definition parts.
@@ -1623,6 +1620,10 @@ private static bool GroupBySignatureComparer(ImmutableArray<IParameterSymbol> ol
                     return GetDiagnosticSpan(typeDeclaration.Modifiers, typeDeclaration.Keyword,
                         typeDeclaration.TypeParameterList ?? (SyntaxNodeOrToken)typeDeclaration.Identifier);
 
+                case SyntaxKind.BaseList:
+                    var baseList = (BaseListSyntax)node;
+                    return baseList.Types.Span;
+
                 case SyntaxKind.EnumDeclaration:
                     var enumDeclaration = (EnumDeclarationSyntax)node;
                     return GetDiagnosticSpan(enumDeclaration.Modifiers, enumDeclaration.EnumKeyword, enumDeclaration.Identifier);
@@ -1716,10 +1717,8 @@ private static bool GroupBySignatureComparer(ImmutableArray<IParameterSymbol> ol
                     var startNode = parameter.Type ?? (SyntaxNode)parameter;
                     return GetDiagnosticSpan(parameter.Modifiers, startNode, parameter);
 
+                case SyntaxKind.PrimaryConstructorBaseType:
                 case SyntaxKind.AttributeList:
-                    var attributeList = (AttributeListSyntax)node;
-                    return attributeList.Span;
-
                 case SyntaxKind.Attribute:
                     return node.Span;
 
@@ -2088,6 +2087,9 @@ internal override string GetDisplayName(IMethodSymbol symbol)
                 case SyntaxKind.Parameter:
                     return FeaturesResources.parameter;
 
+                case SyntaxKind.ParameterList:
+                    return node.Parent is TypeDeclarationSyntax ? FeaturesResources.constructor : null;
+
                 case SyntaxKind.AttributeList:
                     return FeaturesResources.attribute;
 
@@ -3071,60 +3073,5 @@ private static bool DeclareSameIdentifiers(SyntaxToken[] oldVariables, SyntaxTok
         }
 
         #endregion
-
-        protected override bool IsRudeEditDueToPrimaryConstructor(ISymbol symbol, CancellationToken cancellationToken)
-        {
-            switch (symbol.Kind)
-            {
-                case SymbolKind.NamedType:
-                    {
-                        return IsTypeWithPrimaryConstructor(symbol, cancellationToken);
-                    }
-
-                case SymbolKind.Parameter:
-                    {
-                        var container = symbol.ContainingSymbol;
-
-                        if (container is IMethodSymbol { IsImplicitlyDeclared: false, MethodKind: MethodKind.Constructor })
-                        {
-                            foreach (var syntaxReference in container.DeclaringSyntaxReferences)
-                            {
-                                if (syntaxReference.GetSyntax(cancellationToken) is
-                                    ClassDeclarationSyntax { ParameterList: not null } or
-                                    StructDeclarationSyntax { ParameterList: not null })
-                                {
-                                    return true;
-                                }
-                            }
-                        }
-                    }
-                    break;
-
-                default:
-                    {
-                        return IsTypeWithPrimaryConstructor(symbol.ContainingSymbol, cancellationToken);
-                    }
-            }
-
-            return false;
-
-            static bool IsTypeWithPrimaryConstructor(ISymbol container, CancellationToken cancellationToken)
-            {
-                if (container is { Kind: SymbolKind.NamedType, IsImplicitlyDeclared: false })
-                {
-                    foreach (var syntaxReference in container.DeclaringSyntaxReferences)
-                    {
-                        if (syntaxReference.GetSyntax(cancellationToken) is
-                            ClassDeclarationSyntax { ParameterList: not null } or
-                            StructDeclarationSyntax { ParameterList: not null })
-                        {
-                            return true;
-                        }
-                    }
-                }
-
-                return false;
-            }
-        }
     }
 }
diff --git a/src/Features/CSharp/Portable/EditAndContinue/SyntaxComparer.cs b/src/Features/CSharp/Portable/EditAndContinue/SyntaxComparer.cs
index 3691538e5f7f5..b4b89e2b19ed0 100644
--- a/src/Features/CSharp/Portable/EditAndContinue/SyntaxComparer.cs
+++ b/src/Features/CSharp/Portable/EditAndContinue/SyntaxComparer.cs
@@ -43,12 +43,14 @@ protected override bool IsLambdaBodyStatementOrExpression(SyntaxNode node)
 
         #region Labels
 
-        // Assumptions:
-        // - Each listed label corresponds to one or more syntax kinds.
-        // - Nodes with same labels might produce Update edits, nodes with different labels don't. 
-        // - If IsTiedToParent(label) is true for a label then all its possible parent labels must precede the label.
-        //   (i.e. both MethodDeclaration and TypeDeclaration must precede TypeParameter label).
-        // - All descendants of a node whose kind is listed here will be ignored regardless of their labels
+        /// <summary>
+        /// Assumptions:
+        /// - Each listed label corresponds to one or more syntax kinds.
+        /// - Nodes with same labels might produce Update edits, nodes with different labels don't. 
+        /// - If <see cref="TiedToAncestor(Label)"/> is true for a label then all its possible parent labels must precede the label.
+        ///   (i.e. both MethodDeclaration and TypeDeclaration must precede TypeParameter label).
+        /// - All descendants of a node whose kind is listed here will be ignored regardless of their labels
+        /// </summary>
         internal enum Label
         {
             // Top level syntax kinds
@@ -62,6 +64,8 @@ internal enum Label
 
             TypeDeclaration,
             EnumDeclaration,
+            BaseList,                          // tied to parent
+            PrimaryConstructorBase,            // tied to parent
             DelegateDeclaration,
 
             FieldDeclaration,                  // tied to parent
@@ -185,6 +189,7 @@ private static int TiedToAncestor(Label label)
                 case Label.IndexerDeclaration:
                 case Label.EventDeclaration:
                 case Label.EnumMemberDeclaration:
+                case Label.BaseList:
                 case Label.AccessorDeclaration:
                 case Label.AccessorList:
                 case Label.TypeParameterList:
@@ -592,6 +597,14 @@ private static Label ClassifyTopSyntax(SyntaxKind kind, SyntaxNode? node, out bo
                 case SyntaxKind.RecordStructDeclaration:
                     return Label.TypeDeclaration;
 
+                case SyntaxKind.BaseList:
+                    return Label.BaseList;
+
+                case SyntaxKind.PrimaryConstructorBaseType:
+                    // For top syntax, primary constructor base initializer is a leaf node
+                    isLeaf = true;
+                    return Label.PrimaryConstructorBase;
+
                 case SyntaxKind.MethodDeclaration:
                     return Label.MethodDeclaration;
 
diff --git a/src/Features/CSharp/Portable/ExtractMethod/CSharpMethodExtractor.TriviaResult.cs b/src/Features/CSharp/Portable/ExtractMethod/CSharpMethodExtractor.TriviaResult.cs
index a6835c9cfbcc4..3307d5c465c1c 100644
--- a/src/Features/CSharp/Portable/ExtractMethod/CSharpMethodExtractor.TriviaResult.cs
+++ b/src/Features/CSharp/Portable/ExtractMethod/CSharpMethodExtractor.TriviaResult.cs
@@ -118,10 +118,10 @@ private IEnumerable<SyntaxTrivia> TriviaResolver(
                     }
                 }
 
-                var previousTriviaPair = triviaMap.ContainsKey(tokenPair.PreviousToken) ? triviaMap[tokenPair.PreviousToken] : default;
-                var nextTriviaPair = triviaMap.ContainsKey(tokenPair.NextToken) ? triviaMap[tokenPair.NextToken] : default;
-
+                triviaMap.TryGetValue(tokenPair.PreviousToken, out var previousTriviaPair);
                 var trailingTrivia = previousTriviaPair.TrailingTrivia ?? SpecializedCollections.EmptyEnumerable<SyntaxTrivia>();
+
+                triviaMap.TryGetValue(tokenPair.NextToken, out var nextTriviaPair);
                 var leadingTrivia = nextTriviaPair.LeadingTrivia ?? SpecializedCollections.EmptyEnumerable<SyntaxTrivia>();
 
                 var list = trailingTrivia.Concat(leadingTrivia);
diff --git a/src/Features/CSharp/Portable/GenerateConstructorFromMembers/CSharpGenerateConstructorFromMembersCodeRefactoringProvider.cs b/src/Features/CSharp/Portable/GenerateConstructorFromMembers/CSharpGenerateConstructorFromMembersCodeRefactoringProvider.cs
index a4f9ee7e72cb2..24b47f87f3057 100644
--- a/src/Features/CSharp/Portable/GenerateConstructorFromMembers/CSharpGenerateConstructorFromMembersCodeRefactoringProvider.cs
+++ b/src/Features/CSharp/Portable/GenerateConstructorFromMembers/CSharpGenerateConstructorFromMembersCodeRefactoringProvider.cs
@@ -76,7 +76,7 @@ protected override async ValueTask<bool> PrefersThrowExpressionAsync(Document do
             return property.ContainingType.GetMembers(accessedMemberName).FirstOrDefault() as IFieldSymbol;
         }
 
-        private string? GetAccessedMemberName(SyntaxNode? body)
+        private static string? GetAccessedMemberName(SyntaxNode? body)
         {
             // Finally found a name.
             if (body is IdentifierNameSyntax identifierName)
diff --git a/src/Features/CSharp/Portable/GenerateType/CSharpGenerateTypeService.cs b/src/Features/CSharp/Portable/GenerateType/CSharpGenerateTypeService.cs
index 1aa1394bbc529..8d56e0e6ea34c 100644
--- a/src/Features/CSharp/Portable/GenerateType/CSharpGenerateTypeService.cs
+++ b/src/Features/CSharp/Portable/GenerateType/CSharpGenerateTypeService.cs
@@ -641,7 +641,7 @@ private static bool IdentifierMatches(int indexDone, List<string> namespaceConta
             return true;
         }
 
-        private void GetNamespaceContainers(NameSyntax name, List<string> namespaceContainers)
+        private static void GetNamespaceContainers(NameSyntax name, List<string> namespaceContainers)
         {
             if (name is QualifiedNameSyntax qualifiedName)
             {
diff --git a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/LoopHighlighter.cs b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/LoopHighlighter.cs
index c4883fd4d444d..f60cda400ed8f 100644
--- a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/LoopHighlighter.cs
+++ b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/LoopHighlighter.cs
@@ -70,7 +70,7 @@ private static void HighlightWhileStatement(WhileStatementSyntax statement, List
         /// <summary>
         /// Finds all breaks and continues that are a child of this node, and adds the appropriate spans to the spans list.
         /// </summary>
-        private void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans,
+        private static void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans,
             bool highlightBreaks, bool highlightContinues)
         {
             Debug.Assert(highlightBreaks || highlightContinues);
diff --git a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/ReturnStatementHighlighter.cs b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/ReturnStatementHighlighter.cs
index 343aebba09a6f..bdd9461ebc55d 100644
--- a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/ReturnStatementHighlighter.cs
+++ b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/ReturnStatementHighlighter.cs
@@ -45,7 +45,7 @@ protected override void AddHighlights(
         /// <summary>
         /// Finds all returns that are children of this node, and adds the appropriate spans to the spans list.
         /// </summary>
-        private void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans)
+        private static void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans)
         {
             switch (node)
             {
diff --git a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/SwitchStatementHighlighter.cs b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/SwitchStatementHighlighter.cs
index efae2dac368bb..268906ae4f13e 100644
--- a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/SwitchStatementHighlighter.cs
+++ b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/SwitchStatementHighlighter.cs
@@ -47,7 +47,7 @@ protected override void AddHighlights(
         /// Finds all breaks and continues that are a child of this node, and adds the appropriate spans to the spans
         /// list.
         /// </summary>
-        private void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans,
+        private static void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans,
             bool highlightBreaks, bool highlightGotos)
         {
             Debug.Assert(highlightBreaks || highlightGotos);
diff --git a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/YieldStatementHighlighter.cs b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/YieldStatementHighlighter.cs
index 44de85bb372fa..1b44b35bd79cc 100644
--- a/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/YieldStatementHighlighter.cs
+++ b/src/Features/CSharp/Portable/Highlighting/KeywordHighlighters/YieldStatementHighlighter.cs
@@ -45,7 +45,7 @@ protected override void AddHighlights(
         /// <summary>
         /// Finds all returns that are children of this node, and adds the appropriate spans to the spans list.
         /// </summary>
-        private void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans)
+        private static void HighlightRelatedKeywords(SyntaxNode node, List<TextSpan> spans)
         {
             switch (node)
             {
diff --git a/src/Features/CSharp/Portable/ReverseForStatement/CSharpReverseForStatementCodeRefactoringProvider.cs b/src/Features/CSharp/Portable/ReverseForStatement/CSharpReverseForStatementCodeRefactoringProvider.cs
index 462a7c529f8e1..a1b78c1b98a4a 100644
--- a/src/Features/CSharp/Portable/ReverseForStatement/CSharpReverseForStatementCodeRefactoringProvider.cs
+++ b/src/Features/CSharp/Portable/ReverseForStatement/CSharpReverseForStatementCodeRefactoringProvider.cs
@@ -258,7 +258,7 @@ private static bool IsVariableReference(VariableDeclaratorSyntax variable, Expre
             => expr.WalkDownParentheses() is IdentifierNameSyntax identifier &&
                identifier.Identifier.ValueText == variable.Identifier.ValueText;
 
-        private async Task<Document> ReverseForStatementAsync(
+        private static async Task<Document> ReverseForStatementAsync(
             Document document, ForStatementSyntax forStatement, CancellationToken cancellationToken)
         {
             var variable = forStatement.Declaration!.Variables[0];
@@ -302,7 +302,7 @@ private async Task<Document> ReverseForStatementAsync(
             return document.WithSyntaxRoot(editor.GetChangedRoot());
         }
 
-        private ExpressionSyntax Reduce(ExpressionSyntax expr)
+        private static ExpressionSyntax Reduce(ExpressionSyntax expr)
         {
             expr = expr.WalkDownParentheses();
 
diff --git a/src/Features/CSharp/Portable/Snippets/AbstractCSharpAutoPropertySnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/AbstractCSharpAutoPropertySnippetProvider.cs
index 6d049ae145974..ac51a2caa5625 100644
--- a/src/Features/CSharp/Portable/Snippets/AbstractCSharpAutoPropertySnippetProvider.cs
+++ b/src/Features/CSharp/Portable/Snippets/AbstractCSharpAutoPropertySnippetProvider.cs
@@ -82,8 +82,8 @@ protected override ImmutableArray<SnippetPlaceholder> GetPlaceHolderLocationsLis
             var identifier = propertyDeclaration.Identifier;
             var type = propertyDeclaration.Type;
 
-            arrayBuilder.Add(new SnippetPlaceholder(identifier: type.ToString(), placeholderPositions: ImmutableArray.Create(type.SpanStart)));
-            arrayBuilder.Add(new SnippetPlaceholder(identifier: identifier.ValueText, placeholderPositions: ImmutableArray.Create(identifier.SpanStart)));
+            arrayBuilder.Add(new SnippetPlaceholder(type.ToString(), type.SpanStart));
+            arrayBuilder.Add(new SnippetPlaceholder(identifier.ValueText, identifier.SpanStart));
             return arrayBuilder.ToImmutableArray();
         }
 
diff --git a/src/Features/CSharp/Portable/Snippets/AbstractCSharpForLoopSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/AbstractCSharpForLoopSnippetProvider.cs
new file mode 100644
index 0000000000000..1226d4518427d
--- /dev/null
+++ b/src/Features/CSharp/Portable/Snippets/AbstractCSharpForLoopSnippetProvider.cs
@@ -0,0 +1,137 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CSharp.Extensions;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.PooledObjects;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Shared.Extensions.ContextQuery;
+using Microsoft.CodeAnalysis.Shared.Utilities;
+using Microsoft.CodeAnalysis.Snippets;
+using Microsoft.CodeAnalysis.Snippets.SnippetProviders;
+using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.CSharp.Snippets
+{
+    internal abstract class AbstractCSharpForLoopSnippetProvider : AbstractForLoopSnippetProvider
+    {
+        private static readonly string[] s_iteratorBaseNames = new[] { "i", "j", "k" };
+
+        protected abstract SyntaxKind ConditionKind { get; }
+
+        protected abstract SyntaxKind IncrementorKind { get; }
+
+        protected abstract ExpressionSyntax GenerateInitializerValue(SyntaxGenerator generator, SyntaxNode? inlineExpression);
+
+        protected abstract ExpressionSyntax GenerateRightSideOfCondition(SyntaxGenerator generator, SyntaxNode? inlineExpression);
+
+        protected abstract void AddSpecificPlaceholders(MultiDictionary<string, int> placeholderBuilder, ExpressionSyntax initializer, ExpressionSyntax rightOfCondition);
+
+        protected override SyntaxNode GenerateStatement(SyntaxGenerator generator, SyntaxContext syntaxContext, SyntaxNode? inlineExpression)
+        {
+            var semanticModel = syntaxContext.SemanticModel;
+            var compilation = semanticModel.Compilation;
+
+            var iteratorName = NameGenerator.GenerateUniqueName(s_iteratorBaseNames, n => semanticModel.LookupSymbols(syntaxContext.Position, name: n).IsEmpty);
+            var iteratorVariable = generator.Identifier(iteratorName);
+            var indexVariable = (ExpressionSyntax)generator.IdentifierName(iteratorName);
+
+            TypeSyntax? iteratorTypeSyntax = null;
+
+            if (inlineExpression is null)
+            {
+                iteratorTypeSyntax = compilation.GetSpecialType(SpecialType.System_Int32).GenerateTypeSyntax();
+            }
+            else
+            {
+                var inlineExpressionType = semanticModel.GetTypeInfo(inlineExpression).Type;
+                Debug.Assert(inlineExpressionType is not null && (inlineExpressionType.IsIntegralType() || inlineExpressionType.IsNativeIntegerType));
+                iteratorTypeSyntax = inlineExpressionType.GenerateTypeSyntax();
+            }
+
+            inlineExpression = inlineExpression?.WithoutLeadingTrivia();
+
+            var variableDeclaration = SyntaxFactory.VariableDeclaration(
+                iteratorTypeSyntax,
+                variables: SyntaxFactory.SingletonSeparatedList(
+                    SyntaxFactory.VariableDeclarator(iteratorVariable,
+                        argumentList: null,
+                        SyntaxFactory.EqualsValueClause(GenerateInitializerValue(generator, inlineExpression)))))
+                .NormalizeWhitespace();
+
+            return SyntaxFactory.ForStatement(
+                variableDeclaration,
+                SyntaxFactory.SeparatedList<ExpressionSyntax>(),
+                SyntaxFactory.BinaryExpression(ConditionKind, indexVariable, GenerateRightSideOfCondition(generator, inlineExpression)),
+                SyntaxFactory.SingletonSeparatedList<ExpressionSyntax>(
+                    SyntaxFactory.PostfixUnaryExpression(IncrementorKind, indexVariable)),
+                SyntaxFactory.Block());
+        }
+
+        protected override ImmutableArray<SnippetPlaceholder> GetPlaceHolderLocationsList(SyntaxNode node, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
+        {
+            using var _ = ArrayBuilder<SnippetPlaceholder>.GetInstance(out var arrayBuilder);
+            var placeholderBuilder = new MultiDictionary<string, int>();
+            GetPartsOfForStatement(node, out var declaration, out var condition, out var incrementor, out var _);
+
+            var variableDeclarator = ((VariableDeclarationSyntax)declaration!).Variables.Single();
+            var declaratorIdentifier = variableDeclarator.Identifier;
+            placeholderBuilder.Add(declaratorIdentifier.ValueText, declaratorIdentifier.SpanStart);
+
+            var conditionExpression = (BinaryExpressionSyntax)condition!;
+            var left = conditionExpression.Left;
+            placeholderBuilder.Add(left.ToString(), left.SpanStart);
+
+            AddSpecificPlaceholders(placeholderBuilder, variableDeclarator.Initializer!.Value, conditionExpression.Right);
+
+            var operand = ((PostfixUnaryExpressionSyntax)incrementor!).Operand;
+            placeholderBuilder.Add(operand.ToString(), operand.SpanStart);
+
+            foreach (var (key, value) in placeholderBuilder)
+            {
+                arrayBuilder.Add(new(key, value.ToImmutableArray()));
+            }
+
+            return arrayBuilder.ToImmutableArray();
+        }
+
+        protected override int GetTargetCaretPosition(ISyntaxFactsService syntaxFacts, SyntaxNode caretTarget, SourceText sourceText)
+        {
+            GetPartsOfForStatement(caretTarget, out _, out _, out _, out var statement);
+            var blockStatement = (BlockSyntax)statement!;
+
+            var triviaSpan = blockStatement.CloseBraceToken.LeadingTrivia.Span;
+            var line = sourceText.Lines.GetLineFromPosition(triviaSpan.Start);
+            // Getting the location at the end of the line before the newline.
+            return line.Span.End;
+        }
+
+        protected override Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
+        {
+            return СSharpSnippetIndentationHelpers.AddBlockIndentationToDocumentAsync<ForStatementSyntax>(
+                document,
+                FindSnippetAnnotation,
+                static s => (BlockSyntax)s.Statement,
+                cancellationToken);
+        }
+
+        private static void GetPartsOfForStatement(SyntaxNode node, out SyntaxNode? declaration, out SyntaxNode? condition, out SyntaxNode? incrementor, out SyntaxNode? statement)
+        {
+            var forStatement = (ForStatementSyntax)node;
+            declaration = forStatement.Declaration;
+            condition = forStatement.Condition;
+            incrementor = forStatement.Incrementors.Single();
+            statement = forStatement.Statement;
+        }
+    }
+}
diff --git a/src/Features/CSharp/Portable/Snippets/AbstractCSharpTypeSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/AbstractCSharpTypeSnippetProvider.cs
index bd11b769965c2..e16374aa5f808 100644
--- a/src/Features/CSharp/Portable/Snippets/AbstractCSharpTypeSnippetProvider.cs
+++ b/src/Features/CSharp/Portable/Snippets/AbstractCSharpTypeSnippetProvider.cs
@@ -12,7 +12,6 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Utilities;
 using Microsoft.CodeAnalysis.Formatting;
-using Microsoft.CodeAnalysis.Indentation;
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Extensions.ContextQuery;
@@ -65,43 +64,27 @@ protected override int GetTargetCaretPosition(ISyntaxFactsService syntaxFacts, S
             return line.Span.End;
         }
 
-        private static string GetIndentation(Document document, BaseTypeDeclarationSyntax typeDeclaration, SyntaxFormattingOptions syntaxFormattingOptions, CancellationToken cancellationToken)
-        {
-            var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
-            var openBraceLine = parsedDocument.Text.Lines.GetLineFromPosition(typeDeclaration.OpenBraceToken.SpanStart).LineNumber;
-
-            var indentationOptions = new IndentationOptions(syntaxFormattingOptions);
-            var newLine = indentationOptions.FormattingOptions.NewLine;
-
-            var indentationService = parsedDocument.LanguageServices.GetRequiredService<IIndentationService>();
-            var indentation = indentationService.GetIndentation(parsedDocument, openBraceLine + 1, indentationOptions, cancellationToken);
-
-            // Adding the offset calculated with one tab so that it is indented once past the line containing the opening brace
-            var newIndentation = new IndentationResult(indentation.BasePosition, indentation.Offset + syntaxFormattingOptions.TabSize);
-            return newIndentation.GetIndentationString(parsedDocument.Text, syntaxFormattingOptions.UseTabs, syntaxFormattingOptions.TabSize) + newLine;
-        }
-
         protected override SyntaxNode? FindAddedSnippetSyntaxNode(SyntaxNode root, int position, Func<SyntaxNode?, bool> isCorrectContainer)
         {
             var node = root.FindNode(TextSpan.FromBounds(position, position));
             return node.GetAncestorOrThis<BaseTypeDeclarationSyntax>();
         }
 
-        protected override async Task<Document> AddIndentationToDocumentAsync(Document document, int position, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
+        protected override async Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
         {
             var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var snippet = root.GetAnnotatedNodes(_findSnippetAnnotation).FirstOrDefault();
+            var snippet = root.GetAnnotatedNodes(FindSnippetAnnotation).FirstOrDefault();
 
             if (snippet is not BaseTypeDeclarationSyntax originalTypeDeclaration)
                 return document;
 
             var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
-            var indentationString = GetIndentation(document, originalTypeDeclaration, syntaxFormattingOptions, cancellationToken);
+            var indentationString = СSharpSnippetIndentationHelpers.GetBlockLikeIndentationString(document, originalTypeDeclaration.OpenBraceToken.SpanStart, syntaxFormattingOptions, cancellationToken);
 
             var newTypeDeclaration = originalTypeDeclaration.WithCloseBraceToken(
                 originalTypeDeclaration.CloseBraceToken.WithPrependedLeadingTrivia(SyntaxFactory.SyntaxTrivia(SyntaxKind.WhitespaceTrivia, indentationString)));
 
-            var newRoot = root.ReplaceNode(originalTypeDeclaration, newTypeDeclaration.WithAdditionalAnnotations(_cursorAnnotation, _findSnippetAnnotation));
+            var newRoot = root.ReplaceNode(originalTypeDeclaration, newTypeDeclaration.WithAdditionalAnnotations(CursorAnnotation, FindSnippetAnnotation));
             return document.WithSyntaxRoot(newRoot);
         }
 
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpConstructorSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpConstructorSnippetProvider.cs
index 92e1401e81191..79a9caa399db2 100644
--- a/src/Features/CSharp/Portable/Snippets/CSharpConstructorSnippetProvider.cs
+++ b/src/Features/CSharp/Portable/Snippets/CSharpConstructorSnippetProvider.cs
@@ -3,17 +3,13 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections.Immutable;
 using System.Composition;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Utilities;
-using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.CodeAnalysis.Indentation;
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Extensions.ContextQuery;
@@ -59,39 +55,13 @@ protected override int GetTargetCaretPosition(ISyntaxFactsService syntaxFacts, S
             return line.Span.End;
         }
 
-        private static string GetIndentation(Document document, ConstructorDeclarationSyntax constructorDeclaration, SyntaxFormattingOptions syntaxFormattingOptions, CancellationToken cancellationToken)
+        protected override Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
         {
-            var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
-            var openBraceLine = parsedDocument.Text.Lines.GetLineFromPosition(constructorDeclaration.Body!.SpanStart).LineNumber;
-
-            var indentationOptions = new IndentationOptions(syntaxFormattingOptions);
-            var newLine = indentationOptions.FormattingOptions.NewLine;
-
-            var indentationService = parsedDocument.LanguageServices.GetRequiredService<IIndentationService>();
-            var indentation = indentationService.GetIndentation(parsedDocument, openBraceLine + 1, indentationOptions, cancellationToken);
-
-            // Adding the offset calculated with one tab so that it is indented once past the line containing the opening brace
-            var newIndentation = new IndentationResult(indentation.BasePosition, indentation.Offset + syntaxFormattingOptions.TabSize);
-            return newIndentation.GetIndentationString(parsedDocument.Text, syntaxFormattingOptions.UseTabs, syntaxFormattingOptions.TabSize) + newLine;
-        }
-
-        protected override async Task<Document> AddIndentationToDocumentAsync(Document document, int position, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
-        {
-            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var snippet = root.GetAnnotatedNodes(_findSnippetAnnotation).FirstOrDefault();
-
-            if (snippet is not ConstructorDeclarationSyntax constructorDeclaration)
-                return document;
-
-            var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
-            var indentationString = GetIndentation(document, constructorDeclaration, syntaxFormattingOptions, cancellationToken);
-
-            var blockStatement = constructorDeclaration.Body;
-            blockStatement = blockStatement!.WithCloseBraceToken(blockStatement.CloseBraceToken.WithPrependedLeadingTrivia(SyntaxFactory.SyntaxTrivia(SyntaxKind.WhitespaceTrivia, indentationString)));
-            var newConstructorDeclaration = constructorDeclaration.ReplaceNode(constructorDeclaration.Body!, blockStatement);
-
-            var newRoot = root.ReplaceNode(constructorDeclaration, newConstructorDeclaration);
-            return document.WithSyntaxRoot(newRoot);
+            return СSharpSnippetIndentationHelpers.AddBlockIndentationToDocumentAsync<ConstructorDeclarationSyntax>(
+                document,
+                FindSnippetAnnotation,
+                static d => d.Body!,
+                cancellationToken);
         }
     }
 }
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpElseSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpElseSnippetProvider.cs
index a4610a4d4e42d..1a50776566f85 100644
--- a/src/Features/CSharp/Portable/Snippets/CSharpElseSnippetProvider.cs
+++ b/src/Features/CSharp/Portable/Snippets/CSharpElseSnippetProvider.cs
@@ -4,14 +4,11 @@
 
 using System;
 using System.Composition;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.CodeAnalysis.Indentation;
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Extensions.ContextQuery;
@@ -79,39 +76,13 @@ protected override int GetTargetCaretPosition(ISyntaxFactsService syntaxFacts, S
             return line.Span.End;
         }
 
-        private static string GetIndentationString(Document document, ElseClauseSyntax elseClauseSyntax, SyntaxFormattingOptions syntaxFormattingOptions, CancellationToken cancellationToken)
+        protected override Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
         {
-            var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
-            var openBraceLine = parsedDocument.Text.Lines.GetLineFromPosition(elseClauseSyntax.Statement.SpanStart).LineNumber;
-
-            var indentationOptions = new IndentationOptions(syntaxFormattingOptions);
-            var newLine = indentationOptions.FormattingOptions.NewLine;
-
-            var indentationService = parsedDocument.LanguageServices.GetRequiredService<IIndentationService>();
-            var indentation = indentationService.GetIndentation(parsedDocument, openBraceLine + 1, indentationOptions, cancellationToken);
-
-            // Adding the offset calculated with one tab so that it is indented once past the line containing the opening brace
-            var newIndentation = new IndentationResult(indentation.BasePosition, indentation.Offset + syntaxFormattingOptions.TabSize);
-            return newIndentation.GetIndentationString(parsedDocument.Text, syntaxFormattingOptions.UseTabs, syntaxFormattingOptions.TabSize) + newLine;
-        }
-
-        protected override async Task<Document> AddIndentationToDocumentAsync(Document document, int position, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
-        {
-            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var snippet = root.GetAnnotatedNodes(_findSnippetAnnotation).FirstOrDefault();
-
-            if (snippet is not ElseClauseSyntax elseClauseSyntax)
-                return document;
-
-            var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
-            var indentationString = GetIndentationString(document, elseClauseSyntax, syntaxFormattingOptions, cancellationToken);
-
-            var blockStatement = (BlockSyntax)elseClauseSyntax.Statement;
-            blockStatement = blockStatement.WithCloseBraceToken(blockStatement.CloseBraceToken.WithPrependedLeadingTrivia(SyntaxFactory.SyntaxTrivia(SyntaxKind.WhitespaceTrivia, indentationString)));
-            var newElseClauseSyntax = elseClauseSyntax.ReplaceNode(elseClauseSyntax.Statement, blockStatement);
-
-            var newRoot = root.ReplaceNode(elseClauseSyntax, newElseClauseSyntax);
-            return document.WithSyntaxRoot(newRoot);
+            return СSharpSnippetIndentationHelpers.AddBlockIndentationToDocumentAsync<ElseClauseSyntax>(
+                document,
+                FindSnippetAnnotation,
+                static c => (BlockSyntax)c.Statement,
+                cancellationToken);
         }
     }
 }
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpForEachLoopSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpForEachLoopSnippetProvider.cs
index 368a25c4b881a..968a3274e2cf8 100644
--- a/src/Features/CSharp/Portable/Snippets/CSharpForEachLoopSnippetProvider.cs
+++ b/src/Features/CSharp/Portable/Snippets/CSharpForEachLoopSnippetProvider.cs
@@ -10,9 +10,7 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Editing;
-using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.CodeAnalysis.Indentation;
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -54,7 +52,7 @@ protected override SyntaxNode GenerateStatement(SyntaxGenerator generator, Synta
             var itemString = NameGenerator.GenerateUniqueName(
                 "item", name => semanticModel.LookupSymbols(position, name: name).IsEmpty);
 
-            return SyntaxFactory.ForEachStatement(varIdentifier, itemString, collectionIdentifier, SyntaxFactory.Block()).NormalizeWhitespace();
+            return SyntaxFactory.ForEachStatement(varIdentifier, itemString, collectionIdentifier.WithoutLeadingTrivia(), SyntaxFactory.Block()).NormalizeWhitespace();
         }
 
         /// <summary>
@@ -65,48 +63,22 @@ protected override ImmutableArray<SnippetPlaceholder> GetPlaceHolderLocationsLis
         {
             using var _ = ArrayBuilder<SnippetPlaceholder>.GetInstance(out var arrayBuilder);
             GetPartsOfForEachStatement(node, out var identifier, out var expression, out var _1);
-            arrayBuilder.Add(new SnippetPlaceholder(identifier.ToString(), ImmutableArray.Create(identifier.SpanStart)));
+            arrayBuilder.Add(new SnippetPlaceholder(identifier.ToString(), identifier.SpanStart));
 
             if (!ConstructedFromInlineExpression)
-                arrayBuilder.Add(new SnippetPlaceholder(expression.ToString(), ImmutableArray.Create(expression.SpanStart)));
+                arrayBuilder.Add(new SnippetPlaceholder(expression.ToString(), expression.SpanStart));
 
             return arrayBuilder.ToImmutableArray();
 
         }
 
-        private static string GetIndentation(Document document, ForEachStatementSyntax foreachStatement, SyntaxFormattingOptions syntaxFormattingOptions, CancellationToken cancellationToken)
+        protected override Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
         {
-            var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
-            var openBraceLine = parsedDocument.Text.Lines.GetLineFromPosition(foreachStatement.Statement.SpanStart).LineNumber;
-
-            var indentationOptions = new IndentationOptions(syntaxFormattingOptions);
-            var newLine = indentationOptions.FormattingOptions.NewLine;
-
-            var indentationService = parsedDocument.LanguageServices.GetRequiredService<IIndentationService>();
-            var indentation = indentationService.GetIndentation(parsedDocument, openBraceLine + 1, indentationOptions, cancellationToken);
-
-            // Adding the offset calculated with one tab so that it is indented once past the line containing the opening brace
-            var newIndentation = new IndentationResult(indentation.BasePosition, indentation.Offset + syntaxFormattingOptions.TabSize);
-            return newIndentation.GetIndentationString(parsedDocument.Text, syntaxFormattingOptions.UseTabs, syntaxFormattingOptions.TabSize) + newLine;
-        }
-
-        protected override async Task<Document> AddIndentationToDocumentAsync(Document document, int position, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
-        {
-            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var snippet = root.GetAnnotatedNodes(_findSnippetAnnotation).FirstOrDefault();
-
-            if (snippet is not ForEachStatementSyntax foreachStatement)
-                return document;
-
-            var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
-            var indentationString = GetIndentation(document, foreachStatement, syntaxFormattingOptions, cancellationToken);
-
-            var blockStatement = (BlockSyntax)foreachStatement.Statement;
-            blockStatement = blockStatement.WithCloseBraceToken(blockStatement.CloseBraceToken.WithPrependedLeadingTrivia(SyntaxFactory.SyntaxTrivia(SyntaxKind.WhitespaceTrivia, indentationString)));
-            var newForEachStatement = foreachStatement.ReplaceNode(foreachStatement.Statement, blockStatement);
-
-            var newRoot = root.ReplaceNode(foreachStatement, newForEachStatement);
-            return document.WithSyntaxRoot(newRoot);
+            return СSharpSnippetIndentationHelpers.AddBlockIndentationToDocumentAsync<ForEachStatementSyntax>(
+                document,
+                FindSnippetAnnotation,
+                static s => (BlockSyntax)s.Statement,
+                cancellationToken);
         }
 
         /// <summary>
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpForLoopSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpForLoopSnippetProvider.cs
new file mode 100644
index 0000000000000..a5415bb032349
--- /dev/null
+++ b/src/Features/CSharp/Portable/Snippets/CSharpForLoopSnippetProvider.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Snippets;
+using Microsoft.CodeAnalysis.Snippets.SnippetProviders;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.CSharp.Snippets
+{
+    [ExportSnippetProvider(nameof(ISnippetProvider), LanguageNames.CSharp), Shared]
+    internal sealed class CSharpForLoopSnippetProvider : AbstractCSharpForLoopSnippetProvider
+    {
+        public override string Identifier => "for";
+
+        public override string Description => CSharpFeaturesResources.for_loop;
+
+        protected override SyntaxKind ConditionKind => SyntaxKind.LessThanExpression;
+
+        protected override SyntaxKind IncrementorKind => SyntaxKind.PostIncrementExpression;
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public CSharpForLoopSnippetProvider()
+        {
+        }
+
+        protected override ExpressionSyntax GenerateInitializerValue(SyntaxGenerator generator, SyntaxNode? inlineExpression)
+            => (ExpressionSyntax)generator.LiteralExpression(0);
+
+        protected override ExpressionSyntax GenerateRightSideOfCondition(SyntaxGenerator generator, SyntaxNode? inlineExpression)
+            => (ExpressionSyntax)(inlineExpression ?? generator.IdentifierName("length"));
+
+        protected override void AddSpecificPlaceholders(MultiDictionary<string, int> placeholderBuilder, ExpressionSyntax initializer, ExpressionSyntax rightOfCondition)
+        {
+            if (!ConstructedFromInlineExpression)
+                placeholderBuilder.Add(rightOfCondition.ToString(), rightOfCondition.SpanStart);
+        }
+    }
+}
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpIfSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpIfSnippetProvider.cs
index ef305f70fe655..af1bff44f31af 100644
--- a/src/Features/CSharp/Portable/Snippets/CSharpIfSnippetProvider.cs
+++ b/src/Features/CSharp/Portable/Snippets/CSharpIfSnippetProvider.cs
@@ -4,15 +4,11 @@
 
 using System;
 using System.Composition;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.CodeAnalysis.Indentation;
 using Microsoft.CodeAnalysis.LanguageService;
-using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Snippets;
 using Microsoft.CodeAnalysis.Snippets.SnippetProviders;
 using Microsoft.CodeAnalysis.Text;
@@ -45,39 +41,13 @@ protected override SyntaxNode GetCondition(SyntaxNode node)
             return ifStatement.Condition;
         }
 
-        private static string GetIndentation(Document document, IfStatementSyntax ifStatementSyntax, SyntaxFormattingOptions syntaxFormattingOptions, CancellationToken cancellationToken)
+        protected override Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
         {
-            var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
-            var openBraceLine = parsedDocument.Text.Lines.GetLineFromPosition(ifStatementSyntax.Statement.SpanStart).LineNumber;
-
-            var indentationOptions = new IndentationOptions(syntaxFormattingOptions);
-            var newLine = indentationOptions.FormattingOptions.NewLine;
-
-            var indentationService = parsedDocument.LanguageServices.GetRequiredService<IIndentationService>();
-            var indentation = indentationService.GetIndentation(parsedDocument, openBraceLine + 1, indentationOptions, cancellationToken);
-
-            // Adding the offset calculated with one tab so that it is indented once past the line containing the opening brace
-            var newIndentation = new IndentationResult(indentation.BasePosition, indentation.Offset + syntaxFormattingOptions.TabSize);
-            return newIndentation.GetIndentationString(parsedDocument.Text, syntaxFormattingOptions.UseTabs, syntaxFormattingOptions.TabSize) + newLine;
-        }
-
-        protected override async Task<Document> AddIndentationToDocumentAsync(Document document, int position, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
-        {
-            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var snippet = root.GetAnnotatedNodes(_findSnippetAnnotation).FirstOrDefault();
-
-            if (snippet is not IfStatementSyntax ifStatementSyntax)
-                return document;
-
-            var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
-            var indentationString = GetIndentation(document, ifStatementSyntax, syntaxFormattingOptions, cancellationToken);
-
-            var blockStatement = (BlockSyntax)ifStatementSyntax.Statement;
-            blockStatement = blockStatement.WithCloseBraceToken(blockStatement.CloseBraceToken.WithPrependedLeadingTrivia(SyntaxFactory.SyntaxTrivia(SyntaxKind.WhitespaceTrivia, indentationString)));
-            var newIfStatementSyntax = ifStatementSyntax.ReplaceNode(ifStatementSyntax.Statement, blockStatement);
-
-            var newRoot = root.ReplaceNode(ifStatementSyntax, newIfStatementSyntax);
-            return document.WithSyntaxRoot(newRoot);
+            return СSharpSnippetIndentationHelpers.AddBlockIndentationToDocumentAsync<IfStatementSyntax>(
+                document,
+                FindSnippetAnnotation,
+                static s => (BlockSyntax)s.Statement,
+                cancellationToken);
         }
     }
 }
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpLockSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpLockSnippetProvider.cs
new file mode 100644
index 0000000000000..2c5559462d85d
--- /dev/null
+++ b/src/Features/CSharp/Portable/Snippets/CSharpLockSnippetProvider.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.Snippets;
+using Microsoft.CodeAnalysis.Snippets.SnippetProviders;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.CodeAnalysis.CSharp.Snippets
+{
+    [ExportSnippetProvider(nameof(ISnippetProvider), LanguageNames.CSharp), Shared]
+    internal sealed class CSharpLockSnippetProvider : AbstractLockSnippetProvider
+    {
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public CSharpLockSnippetProvider()
+        {
+        }
+
+        public override string Identifier => "lock";
+
+        public override string Description => CSharpFeaturesResources.lock_statement;
+
+        protected override ImmutableArray<SnippetPlaceholder> GetPlaceHolderLocationsList(SyntaxNode node, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
+        {
+            var lockStatement = (LockStatementSyntax)node;
+            var expression = lockStatement.Expression;
+            return ImmutableArray.Create(new SnippetPlaceholder(expression.ToString(), expression.SpanStart));
+        }
+
+        protected override int GetTargetCaretPosition(ISyntaxFactsService syntaxFacts, SyntaxNode caretTarget, SourceText sourceText)
+        {
+            var lockStatement = (LockStatementSyntax)caretTarget;
+            var blockStatement = (BlockSyntax)lockStatement.Statement;
+
+            var triviaSpan = blockStatement.CloseBraceToken.LeadingTrivia.Span;
+            var line = sourceText.Lines.GetLineFromPosition(triviaSpan.Start);
+            // Getting the location at the end of the line before the newline.
+            return line.Span.End;
+        }
+
+        protected override Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
+        {
+            return СSharpSnippetIndentationHelpers.AddBlockIndentationToDocumentAsync<LockStatementSyntax>(
+                document,
+                FindSnippetAnnotation,
+                static s => (BlockSyntax)s.Statement,
+                cancellationToken);
+        }
+    }
+}
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpReversedForLoopSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpReversedForLoopSnippetProvider.cs
new file mode 100644
index 0000000000000..fa09075801971
--- /dev/null
+++ b/src/Features/CSharp/Portable/Snippets/CSharpReversedForLoopSnippetProvider.cs
@@ -0,0 +1,52 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Snippets;
+using Microsoft.CodeAnalysis.Snippets.SnippetProviders;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.CSharp.Snippets
+{
+    [ExportSnippetProvider(nameof(ISnippetProvider), LanguageNames.CSharp), Shared]
+    internal sealed class CSharpReversedForLoopSnippetProvider : AbstractCSharpForLoopSnippetProvider
+    {
+        public override string Identifier => "forr";
+
+        public override string Description => CSharpFeaturesResources.reversed_for_loop;
+
+        protected override SyntaxKind ConditionKind => SyntaxKind.GreaterThanOrEqualExpression;
+
+        protected override SyntaxKind IncrementorKind => SyntaxKind.PostDecrementExpression;
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public CSharpReversedForLoopSnippetProvider()
+        {
+        }
+
+        protected override ExpressionSyntax GenerateInitializerValue(SyntaxGenerator generator, SyntaxNode? inlineExpression)
+        {
+            var subtractFrom = inlineExpression?.WithoutLeadingTrivia() ?? generator.IdentifierName("length");
+            return (ExpressionSyntax)generator.SubtractExpression(subtractFrom, generator.LiteralExpression(1));
+        }
+
+        protected override ExpressionSyntax GenerateRightSideOfCondition(SyntaxGenerator generator, SyntaxNode? inlineExpression)
+            => (ExpressionSyntax)generator.LiteralExpression(0);
+
+        protected override void AddSpecificPlaceholders(MultiDictionary<string, int> placeholderBuilder, ExpressionSyntax initializer, ExpressionSyntax rightOfCondition)
+        {
+            if (!ConstructedFromInlineExpression)
+            {
+                var binaryInitializer = (BinaryExpressionSyntax)initializer;
+                var left = binaryInitializer.Left;
+                placeholderBuilder.Add(left.ToString(), left.SpanStart);
+            }
+        }
+    }
+}
diff --git a/src/Features/CSharp/Portable/Snippets/CSharpWhileLoopSnippetProvider.cs b/src/Features/CSharp/Portable/Snippets/CSharpWhileLoopSnippetProvider.cs
index 6763c259e0aab..9437d9e75e460 100644
--- a/src/Features/CSharp/Portable/Snippets/CSharpWhileLoopSnippetProvider.cs
+++ b/src/Features/CSharp/Portable/Snippets/CSharpWhileLoopSnippetProvider.cs
@@ -4,15 +4,11 @@
 
 using System;
 using System.Composition;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.CodeAnalysis.Indentation;
 using Microsoft.CodeAnalysis.LanguageService;
-using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Snippets;
 using Microsoft.CodeAnalysis.Snippets.SnippetProviders;
 using Microsoft.CodeAnalysis.Text;
@@ -45,39 +41,13 @@ protected override SyntaxNode GetCondition(SyntaxNode node)
             return whileStatement.Condition;
         }
 
-        private static string GetIndentation(Document document, WhileStatementSyntax whileStatementSyntax, SyntaxFormattingOptions syntaxFormattingOptions, CancellationToken cancellationToken)
+        protected override Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
         {
-            var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
-            var openBraceLine = parsedDocument.Text.Lines.GetLineFromPosition(whileStatementSyntax.Statement.SpanStart).LineNumber;
-
-            var indentationOptions = new IndentationOptions(syntaxFormattingOptions);
-            var newLine = indentationOptions.FormattingOptions.NewLine;
-
-            var indentationService = parsedDocument.LanguageServices.GetRequiredService<IIndentationService>();
-            var indentation = indentationService.GetIndentation(parsedDocument, openBraceLine + 1, indentationOptions, cancellationToken);
-
-            // Adding the offset calculated with one tab so that it is indented once past the line containing the opening brace
-            var newIndentation = new IndentationResult(indentation.BasePosition, indentation.Offset + syntaxFormattingOptions.TabSize);
-            return newIndentation.GetIndentationString(parsedDocument.Text, syntaxFormattingOptions.UseTabs, syntaxFormattingOptions.TabSize) + newLine;
-        }
-
-        protected override async Task<Document> AddIndentationToDocumentAsync(Document document, int position, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
-        {
-            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var snippet = root.GetAnnotatedNodes(_findSnippetAnnotation).FirstOrDefault();
-
-            if (snippet is not WhileStatementSyntax whileStatementSyntax)
-                return document;
-
-            var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
-            var indentationString = GetIndentation(document, whileStatementSyntax, syntaxFormattingOptions, cancellationToken);
-
-            var blockStatement = (BlockSyntax)whileStatementSyntax.Statement;
-            blockStatement = blockStatement.WithCloseBraceToken(blockStatement.CloseBraceToken.WithPrependedLeadingTrivia(SyntaxFactory.SyntaxTrivia(SyntaxKind.WhitespaceTrivia, indentationString)));
-            var newWhileStatementSyntax = whileStatementSyntax.ReplaceNode(whileStatementSyntax.Statement, blockStatement);
-
-            var newRoot = root.ReplaceNode(whileStatementSyntax, newWhileStatementSyntax);
-            return document.WithSyntaxRoot(newRoot);
+            return СSharpSnippetIndentationHelpers.AddBlockIndentationToDocumentAsync<WhileStatementSyntax>(
+                document,
+                FindSnippetAnnotation,
+                static s => (BlockSyntax)s.Statement,
+                cancellationToken);
         }
     }
 }
diff --git "a/src/Features/CSharp/Portable/Snippets/\320\241SharpSnippetIndentationHelpers.cs" "b/src/Features/CSharp/Portable/Snippets/\320\241SharpSnippetIndentationHelpers.cs"
new file mode 100644
index 0000000000000..c6a52fc2d612c
--- /dev/null
+++ "b/src/Features/CSharp/Portable/Snippets/\320\241SharpSnippetIndentationHelpers.cs"
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Formatting;
+using Microsoft.CodeAnalysis.Indentation;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+
+namespace Microsoft.CodeAnalysis.CSharp.Snippets;
+
+internal static class СSharpSnippetIndentationHelpers
+{
+    public static string GetBlockLikeIndentationString(Document document, int startPositionOfOpenCurlyBrace, SyntaxFormattingOptions syntaxFormattingOptions, CancellationToken cancellationToken)
+    {
+        var parsedDocument = ParsedDocument.CreateSynchronously(document, cancellationToken);
+        var openBraceLine = parsedDocument.Text.Lines.GetLineFromPosition(startPositionOfOpenCurlyBrace).LineNumber;
+
+        var indentationOptions = new IndentationOptions(syntaxFormattingOptions);
+        var newLine = indentationOptions.FormattingOptions.NewLine;
+
+        var indentationService = parsedDocument.LanguageServices.GetRequiredService<IIndentationService>();
+        var indentation = indentationService.GetIndentation(parsedDocument, openBraceLine + 1, indentationOptions, cancellationToken);
+
+        // Adding the offset calculated with one tab so that it is indented once past the line containing the opening brace
+        var newIndentation = new IndentationResult(indentation.BasePosition, indentation.Offset + syntaxFormattingOptions.TabSize);
+        return newIndentation.GetIndentationString(parsedDocument.Text, syntaxFormattingOptions.UseTabs, syntaxFormattingOptions.TabSize) + newLine;
+    }
+
+    public static async Task<Document> AddBlockIndentationToDocumentAsync<TTargetNode>(Document document, SyntaxAnnotation findSnippetAnnotation, Func<TTargetNode, BlockSyntax> getBlock, CancellationToken cancellationToken)
+        where TTargetNode : SyntaxNode
+    {
+        var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+        var snippetNode = root.GetAnnotatedNodes(findSnippetAnnotation).FirstOrDefault();
+
+        if (snippetNode is not TTargetNode targetStatement)
+            return document;
+
+        var block = getBlock(targetStatement);
+
+        var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
+        var indentationString = GetBlockLikeIndentationString(document, block.SpanStart, syntaxFormattingOptions, cancellationToken);
+
+        var updatedBlock = block.WithCloseBraceToken(block.CloseBraceToken.WithPrependedLeadingTrivia(SyntaxFactory.SyntaxTrivia(SyntaxKind.WhitespaceTrivia, indentationString)));
+        var updatedTargetStatement = targetStatement.ReplaceNode(block, updatedBlock);
+
+        var newRoot = root.ReplaceNode(targetStatement, updatedTargetStatement);
+        return document.WithSyntaxRoot(newRoot);
+    }
+}
diff --git a/src/Features/CSharp/Portable/Structure/Providers/BlockSyntaxStructureProvider.cs b/src/Features/CSharp/Portable/Structure/Providers/BlockSyntaxStructureProvider.cs
index 3fd19d90d02b7..51560ef434d19 100644
--- a/src/Features/CSharp/Portable/Structure/Providers/BlockSyntaxStructureProvider.cs
+++ b/src/Features/CSharp/Portable/Structure/Providers/BlockSyntaxStructureProvider.cs
@@ -2,19 +2,20 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
+using System;
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Collections;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Structure;
 using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.Structure
 {
-    internal class BlockSyntaxStructureProvider : AbstractSyntaxNodeStructureProvider<BlockSyntax>
+    internal sealed class BlockSyntaxStructureProvider : AbstractSyntaxNodeStructureProvider<BlockSyntax>
     {
         protected override void CollectBlockSpans(
             SyntaxToken previousToken,
@@ -23,7 +24,8 @@ protected override void CollectBlockSpans(
             BlockStructureOptions options,
             CancellationToken cancellationToken)
         {
-            var parentKind = node.Parent.Kind();
+            var parent = node.GetRequiredParent();
+            var parentKind = parent.Kind();
 
             // For most types of statements, just consider the block 'attached' to the 
             // parent node.  That means we'll show the parent node header when doing 
@@ -31,18 +33,23 @@ protected override void CollectBlockSpans(
             //
             // This also works nicely as the close brace for these constructs will always
             // align with the start of these statements.
-            if (IsNonBlockStatement(node.Parent) ||
-                parentKind == SyntaxKind.ElseClause)
+            if (parentKind == SyntaxKind.ElseClause ||
+                IsNonBlockStatement(parent))
             {
-                var type = GetType(node.Parent);
+                var type = GetType(parent);
                 if (type != null)
                 {
                     spans.Add(new BlockSpan(
                         isCollapsible: true,
                         textSpan: GetTextSpan(node),
                         hintSpan: GetHintSpan(node),
+                        // For an 'else' block, add information about the corresponding if-block so it shows up properly
+                        // in 'sticky scroll'.
+                        primarySpans: parent is ElseClauseSyntax { Parent: IfStatementSyntax { Statement: BlockSyntax trueBlock } }
+                            ? (GetTextSpan(trueBlock), GetHintSpan(trueBlock))
+                            : null,
                         type: type,
-                        autoCollapse: parentKind == SyntaxKind.LocalFunctionStatement && node.Parent.IsParentKind(SyntaxKind.GlobalStatement)));
+                        autoCollapse: parentKind == SyntaxKind.LocalFunctionStatement && parent.IsParentKind(SyntaxKind.GlobalStatement)));
                 }
             }
 
@@ -66,25 +73,27 @@ protected override void CollectBlockSpans(
             // spanof the block alone, without consideration for the case clause.
             if (parentKind is SyntaxKind.Block or SyntaxKind.SwitchSection)
             {
-                var type = GetType(node.Parent);
-
-                spans.Add(new BlockSpan(
-                    isCollapsible: true,
-                    textSpan: node.Span,
-                    hintSpan: node.Span,
-                    type: type));
+                var type = GetType(parent);
+                if (type != null)
+                {
+                    spans.Add(new BlockSpan(
+                        isCollapsible: true,
+                        textSpan: node.Span,
+                        hintSpan: node.Span,
+                        type: type));
+                }
             }
         }
 
         private static bool IsNonBlockStatement(SyntaxNode node)
-            => node is StatementSyntax && !node.IsKind(SyntaxKind.Block);
+            => node is StatementSyntax(kind: not SyntaxKind.Block);
 
         private static TextSpan GetHintSpan(BlockSyntax node)
         {
-            var parent = node.Parent;
+            var parent = node.GetRequiredParent();
             if (parent.IsKind(SyntaxKind.IfStatement) && parent.IsParentKind(SyntaxKind.ElseClause))
             {
-                parent = parent.Parent;
+                parent = parent.GetRequiredParent();
             }
 
             var start = parent.Span.Start;
@@ -124,36 +133,39 @@ private static int GetEnd(BlockSyntax node)
             {
                 // For all other constructs, we collapse up to the end of the parent
                 // construct.
-                return node.Parent.Span.End;
+                return node.GetRequiredParent().Span.End;
             }
         }
 
-        private static string GetType(SyntaxNode parent)
+        private static string? GetType(SyntaxNode? parent)
         {
-            switch (parent.Kind())
+            if (parent != null)
             {
-                case SyntaxKind.ForStatement: return BlockTypes.Loop;
-                case SyntaxKind.ForEachStatement: return BlockTypes.Loop;
-                case SyntaxKind.ForEachVariableStatement: return BlockTypes.Loop;
-                case SyntaxKind.WhileStatement: return BlockTypes.Loop;
-                case SyntaxKind.DoStatement: return BlockTypes.Loop;
+                switch (parent.Kind())
+                {
+                    case SyntaxKind.ForStatement: return BlockTypes.Loop;
+                    case SyntaxKind.ForEachStatement: return BlockTypes.Loop;
+                    case SyntaxKind.ForEachVariableStatement: return BlockTypes.Loop;
+                    case SyntaxKind.WhileStatement: return BlockTypes.Loop;
+                    case SyntaxKind.DoStatement: return BlockTypes.Loop;
 
-                case SyntaxKind.TryStatement: return BlockTypes.Statement;
-                case SyntaxKind.CatchClause: return BlockTypes.Statement;
-                case SyntaxKind.FinallyClause: return BlockTypes.Statement;
+                    case SyntaxKind.TryStatement: return BlockTypes.Statement;
+                    case SyntaxKind.CatchClause: return BlockTypes.Statement;
+                    case SyntaxKind.FinallyClause: return BlockTypes.Statement;
 
-                case SyntaxKind.UnsafeStatement: return BlockTypes.Statement;
-                case SyntaxKind.FixedStatement: return BlockTypes.Statement;
-                case SyntaxKind.LockStatement: return BlockTypes.Statement;
-                case SyntaxKind.UsingStatement: return BlockTypes.Statement;
+                    case SyntaxKind.UnsafeStatement: return BlockTypes.Statement;
+                    case SyntaxKind.FixedStatement: return BlockTypes.Statement;
+                    case SyntaxKind.LockStatement: return BlockTypes.Statement;
+                    case SyntaxKind.UsingStatement: return BlockTypes.Statement;
 
-                case SyntaxKind.IfStatement: return BlockTypes.Conditional;
-                case SyntaxKind.ElseClause: return BlockTypes.Conditional;
-                case SyntaxKind.SwitchSection: return BlockTypes.Conditional;
+                    case SyntaxKind.IfStatement: return BlockTypes.Conditional;
+                    case SyntaxKind.ElseClause: return BlockTypes.Conditional;
+                    case SyntaxKind.SwitchSection: return BlockTypes.Conditional;
 
-                case SyntaxKind.Block: return BlockTypes.Statement;
+                    case SyntaxKind.Block: return BlockTypes.Statement;
 
-                case SyntaxKind.LocalFunctionStatement: return BlockTypes.Statement;
+                    case SyntaxKind.LocalFunctionStatement: return BlockTypes.Statement;
+                }
             }
 
             return null;
diff --git a/src/Features/CSharp/Portable/Structure/Providers/StringLiteralExpressionStructureProvider.cs b/src/Features/CSharp/Portable/Structure/Providers/StringLiteralExpressionStructureProvider.cs
index b7c8cafa4d5d3..78b65b2fda29a 100644
--- a/src/Features/CSharp/Portable/Structure/Providers/StringLiteralExpressionStructureProvider.cs
+++ b/src/Features/CSharp/Portable/Structure/Providers/StringLiteralExpressionStructureProvider.cs
@@ -6,6 +6,7 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Shared.Collections;
 using Microsoft.CodeAnalysis.Structure;
+using Microsoft.CodeAnalysis.Text;
 
 namespace Microsoft.CodeAnalysis.CSharp.Structure
 {
@@ -19,7 +20,8 @@ protected override void CollectBlockSpans(
             CancellationToken cancellationToken)
         {
             if (node.IsKind(SyntaxKind.StringLiteralExpression) &&
-                !node.ContainsDiagnostics)
+                !node.ContainsDiagnostics &&
+                CouldBeMultiLine())
             {
                 spans.Add(new BlockSpan(
                     isCollapsible: true,
@@ -29,6 +31,24 @@ protected override void CollectBlockSpans(
                     autoCollapse: true,
                     isDefaultCollapsed: false));
             }
+
+            return;
+
+            bool CouldBeMultiLine()
+            {
+                if (node.Token.Kind() is SyntaxKind.MultiLineRawStringLiteralToken or SyntaxKind.Utf8MultiLineRawStringLiteralToken)
+                    return true;
+
+                if (node.Token.IsVerbatimStringLiteral())
+                {
+                    var span = node.Span;
+                    var sourceText = node.SyntaxTree.GetText(cancellationToken);
+                    return sourceText.Lines.GetLineFromPosition(span.Start).LineNumber !=
+                           sourceText.Lines.GetLineFromPosition(span.End).LineNumber;
+                }
+
+                return false;
+            }
         }
     }
 }
diff --git a/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameCodeFixProvider.cs b/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameCodeFixProvider.cs
index a7dd21ee9eb62..78c044ded4e59 100644
--- a/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameCodeFixProvider.cs
+++ b/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameCodeFixProvider.cs
@@ -59,7 +59,7 @@ protected override async Task FixAllAsync(
             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
             var expressionTypeOpt = semanticModel.Compilation.ExpressionOfTType();
 
-            var (matches, localName) = CSharpIsAndCastCheckWithoutNameDiagnosticAnalyzer.Instance.AnalyzeExpression(
+            var (matches, localName) = CSharpIsAndCastCheckWithoutNameDiagnosticAnalyzer.AnalyzeExpression(
                 semanticModel, isExpression, expressionTypeOpt, cancellationToken);
 
             var updatedSemanticModel = CSharpIsAndCastCheckWithoutNameDiagnosticAnalyzer.ReplaceMatches(
diff --git a/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameDiagnosticAnalyzer.cs b/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameDiagnosticAnalyzer.cs
index 61928e4f57f3f..a4632fb4f1998 100644
--- a/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameDiagnosticAnalyzer.cs
+++ b/src/Features/CSharp/Portable/UsePatternMatching/CSharpIsAndCastCheckWithoutNameDiagnosticAnalyzer.cs
@@ -105,7 +105,7 @@ private void SyntaxNodeAction(
                     ImmutableDictionary<string, string?>.Empty));
         }
 
-        public (HashSet<CastExpressionSyntax>, string localName) AnalyzeExpression(
+        public static (HashSet<CastExpressionSyntax>, string localName) AnalyzeExpression(
             SemanticModel semanticModel,
             BinaryExpressionSyntax isExpression,
             INamedTypeSymbol? expressionType,
@@ -244,7 +244,7 @@ public static SemanticModel ReplaceMatches(
             return null;
         }
 
-        private void AddMatches(
+        private static void AddMatches(
             SyntaxNode node, ExpressionSyntax expr, TypeSyntax type, HashSet<CastExpressionSyntax> matches)
         {
             // Don't bother recursing down nodes that are before the type in the is-expression.
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.cs.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.cs.xlf
index 385157b2f241f..85e749d9a3d14 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.cs.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.cs.xlf
@@ -247,6 +247,11 @@
         <target state="translated">externí alias</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">vlastnost jenom pro inicializaci</target>
@@ -412,6 +417,11 @@
         <target state="translated">struktura záznamu</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">příkaz switch</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.de.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.de.xlf
index f04c9c227d9e6..09937ddae62ad 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.de.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.de.xlf
@@ -247,6 +247,11 @@
         <target state="translated">externer Alias</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">„init-only“-Eigenschaft</target>
@@ -412,6 +417,11 @@
         <target state="translated">Datensatzstruktur</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">switch-Anweisung</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.es.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.es.xlf
index 660a58a11d9e1..94ddb4b9e940c 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.es.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.es.xlf
@@ -247,6 +247,11 @@
         <target state="translated">alias externo</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">propiedad de solo inicialización</target>
@@ -412,6 +417,11 @@
         <target state="translated">registro de estructuras</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">instrucción switch</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.fr.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.fr.xlf
index c13a02f6383c9..bfaba63a0f9d4 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.fr.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.fr.xlf
@@ -247,6 +247,11 @@
         <target state="translated">alias externe</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">propriété init-only</target>
@@ -412,6 +417,11 @@
         <target state="translated">struct d’enregistrement</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">instruction switch</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.it.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.it.xlf
index 166db0f0edef7..ba44b03a12483 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.it.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.it.xlf
@@ -247,6 +247,11 @@
         <target state="translated">alias extern</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">proprietà di sola inizializzazione</target>
@@ -412,6 +417,11 @@
         <target state="translated">struct di record</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">istruzione switch</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ja.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ja.xlf
index 7418e02273253..531f56af2d0cb 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ja.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ja.xlf
@@ -247,6 +247,11 @@
         <target state="translated">extern エイリアス</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">init 専用プロパティ</target>
@@ -412,6 +417,11 @@
         <target state="translated">レコード構造体</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">switch ステートメント</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ko.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ko.xlf
index 06925c6a22ef5..98706cad9626c 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ko.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ko.xlf
@@ -247,6 +247,11 @@
         <target state="translated">extern 별칭</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">init 전용 속성</target>
@@ -412,6 +417,11 @@
         <target state="translated">레코드 구조체</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">switch 문</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pl.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pl.xlf
index 1529d599d29e1..f052cd4a3db8a 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pl.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pl.xlf
@@ -247,6 +247,11 @@
         <target state="translated">alias zewnętrzny</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">właściwość tylko do inicjowania</target>
@@ -412,6 +417,11 @@
         <target state="translated">struktura rekordów</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">instrukcja switch</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pt-BR.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pt-BR.xlf
index 0325f0c2836c4..db92aca013615 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pt-BR.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pt-BR.xlf
@@ -247,6 +247,11 @@
         <target state="translated">alias externo</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">propriedade somente inicialização</target>
@@ -412,6 +417,11 @@
         <target state="translated">registrar struct</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">instrução switch</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ru.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ru.xlf
index e339d31eed7b4..95019a11d6117 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ru.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ru.xlf
@@ -247,6 +247,11 @@
         <target state="translated">внешний псевдоним</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">свойство, предназначенное только для инициализации</target>
@@ -412,6 +417,11 @@
         <target state="translated">структура записей</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">оператор switch</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.tr.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.tr.xlf
index 5a896df056266..166796a70c428 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.tr.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.tr.xlf
@@ -247,6 +247,11 @@
         <target state="translated">dış diğer ad</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">yalnızca init özelliği</target>
@@ -412,6 +417,11 @@
         <target state="translated">kayıt yapısı</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">switch deyimi</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hans.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hans.xlf
index 482b3867c62a1..8deec222a637b 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hans.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hans.xlf
@@ -247,6 +247,11 @@
         <target state="translated">外部别名</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">init-only 属性</target>
@@ -412,6 +417,11 @@
         <target state="translated">记录结构</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">switch 语句</target>
diff --git a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hant.xlf b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hant.xlf
index 99f6ee8fb74a4..45c686d1d697a 100644
--- a/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hant.xlf
+++ b/src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hant.xlf
@@ -247,6 +247,11 @@
         <target state="translated">外部別名</target>
         <note />
       </trans-unit>
+      <trans-unit id="for_loop">
+        <source>for loop</source>
+        <target state="new">for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="init_only_property">
         <source>init-only property</source>
         <target state="translated">init-only 屬性</target>
@@ -412,6 +417,11 @@
         <target state="translated">記錄結構</target>
         <note />
       </trans-unit>
+      <trans-unit id="reversed_for_loop">
+        <source>reversed for loop</source>
+        <target state="new">reversed for loop</target>
+        <note>{Locked="for"} "for" is a C# keyword and should not be localized.</note>
+      </trans-unit>
       <trans-unit id="switch_statement">
         <source>switch statement</source>
         <target state="translated">switch 陳述式</target>
diff --git a/src/Features/Core/Portable/CodeRefactorings/CodeRefactoringService.cs b/src/Features/Core/Portable/CodeRefactorings/CodeRefactoringService.cs
index fd484b78cc17f..73a6e5c65b6fd 100644
--- a/src/Features/Core/Portable/CodeRefactorings/CodeRefactoringService.cs
+++ b/src/Features/Core/Portable/CodeRefactorings/CodeRefactoringService.cs
@@ -17,6 +17,7 @@
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Utilities;
+using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
@@ -122,6 +123,7 @@ public async Task<ImmutableArray<CodeRefactoring>> GetRefactoringsAsync(
             Func<string, IDisposable?> addOperationScope,
             CancellationToken cancellationToken)
         {
+            using (TelemetryLogging.LogBlockTimeAggregated(FunctionId.CodeRefactoring_Summary, $"Pri{(int)priority}"))
             using (Logger.LogBlock(FunctionId.Refactoring_CodeRefactoringService_GetRefactoringsAsync, cancellationToken))
             {
                 var extensionManager = document.Project.Solution.Services.GetRequiredService<IExtensionManager>();
@@ -132,16 +134,23 @@ public async Task<ImmutableArray<CodeRefactoring>> GetRefactoringsAsync(
                     if (priority != CodeActionRequestPriority.None && priority != provider.RequestPriority)
                         continue;
 
-                    tasks.Add(Task.Run(() =>
+                    tasks.Add(Task.Run(async () =>
                         {
+                            // Log an individual telemetry event for slow code refactoring computations to
+                            // allow targeted trace notifications for further investigation. 500 ms seemed like
+                            // a good value so as to not be too noisy, but if fired, indicates a potential
+                            // area requiring investigation.
+                            const int CodeRefactoringTelemetryDelay = 500;
+
                             var providerName = provider.GetType().Name;
                             RefactoringToMetadataMap.TryGetValue(provider, out var providerMetadata);
 
                             using (addOperationScope(providerName))
                             using (RoslynEventSource.LogInformationalBlock(FunctionId.Refactoring_CodeRefactoringService_GetRefactoringsAsync, providerName, cancellationToken))
+                            using (TelemetryLogging.LogBlockTime(FunctionId.CodeRefactoring_Delay, $"{providerName}", CodeRefactoringTelemetryDelay))
                             {
-                                return GetRefactoringFromProviderAsync(document, state, provider, providerMetadata,
-                                    extensionManager, options, cancellationToken);
+                                return await GetRefactoringFromProviderAsync(document, state, provider, providerMetadata,
+                                    extensionManager, options, cancellationToken).ConfigureAwait(false);
                             }
                         },
                         cancellationToken));
diff --git a/src/Features/Core/Portable/Common/DelayTimeSpan.cs b/src/Features/Core/Portable/Common/DelayTimeSpan.cs
index 59d9aa6100664..6a255f7fab847 100644
--- a/src/Features/Core/Portable/Common/DelayTimeSpan.cs
+++ b/src/Features/Core/Portable/Common/DelayTimeSpan.cs
@@ -8,10 +8,29 @@ namespace Microsoft.CodeAnalysis
 {
     internal static class DelayTimeSpan
     {
+        /// <summary>
+        /// 50 milliseconds.
+        /// </summary>
         public static readonly TimeSpan NearImmediate = TimeSpan.FromMilliseconds(50);
+
+        /// <summary>
+        /// 250 milliseconds.
+        /// </summary>
         public static readonly TimeSpan Short = TimeSpan.FromMilliseconds(250);
+
+        /// <summary>
+        /// 500 milliseconds.
+        /// </summary>
         public static readonly TimeSpan Medium = TimeSpan.FromMilliseconds(500);
+
+        /// <summary>
+        /// 1.5 seconds.
+        /// </summary>
         public static readonly TimeSpan Idle = TimeSpan.FromMilliseconds(1500);
+
+        /// <summary>
+        /// 3 seconds.
+        /// </summary>
         public static readonly TimeSpan NonFocus = TimeSpan.FromMilliseconds(3000);
     }
 }
diff --git a/src/Features/Core/Portable/Common/FeaturesSessionTelemetry.cs b/src/Features/Core/Portable/Common/FeaturesSessionTelemetry.cs
new file mode 100644
index 0000000000000..19fc302749750
--- /dev/null
+++ b/src/Features/Core/Portable/Common/FeaturesSessionTelemetry.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.ChangeSignature;
+using Microsoft.CodeAnalysis.Completion.Log;
+using Microsoft.CodeAnalysis.Logging;
+
+namespace Microsoft.CodeAnalysis.Common
+{
+    internal static class FeaturesSessionTelemetry
+    {
+        public static void Report()
+        {
+            CompletionProvidersLogger.ReportTelemetry();
+            SolutionLogger.ReportTelemetry();
+            ChangeSignatureLogger.ReportTelemetry();
+        }
+    }
+}
diff --git a/src/Features/Core/Portable/Completion/CommonCompletionUtilities.cs b/src/Features/Core/Portable/Completion/CommonCompletionUtilities.cs
index 0fc8cf2356e43..e1f49251a2acf 100644
--- a/src/Features/Core/Portable/Completion/CommonCompletionUtilities.cs
+++ b/src/Features/Core/Portable/Completion/CommonCompletionUtilities.cs
@@ -115,13 +115,13 @@ public static async Task<CompletionDescription> CreateDescriptionAsync(
             // TODO(cyrusn): Figure out a way to cancel this.
             var sections = await symbolDisplayService.ToDescriptionGroupsAsync(semanticModel, position, ImmutableArray.Create(symbol), options, cancellationToken).ConfigureAwait(false);
 
-            if (!sections.ContainsKey(SymbolDescriptionGroups.MainDescription))
+            if (!sections.TryGetValue(SymbolDescriptionGroups.MainDescription, out var mainDescriptionTexts))
             {
                 return CompletionDescription.Empty;
             }
 
             var textContentBuilder = new List<TaggedText>();
-            textContentBuilder.AddRange(sections[SymbolDescriptionGroups.MainDescription]);
+            textContentBuilder.AddRange(mainDescriptionTexts);
 
             switch (symbol.Kind)
             {
diff --git a/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/AbstractImportCompletionProvider.cs b/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/AbstractImportCompletionProvider.cs
index 7313c14f91517..41550239a3510 100644
--- a/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/AbstractImportCompletionProvider.cs
+++ b/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/AbstractImportCompletionProvider.cs
@@ -202,10 +202,11 @@ public override async Task<CompletionChange> GetChangeAsync(
 
             async Task<bool> ShouldCompleteWithFullyQualifyTypeName()
             {
+                if (ImportCompletionItem.ShouldAlwaysAddMissingImport(completionItem))
+                    return false;
+
                 if (!IsAddingImportsSupported(document))
-                {
                     return true;
-                }
 
                 // We might need to qualify unimported types to use them in an import directive, because they only affect members of the containing
                 // import container (e.g. namespace/class/etc. declarations).
diff --git a/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/ImportCompletionItem.cs b/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/ImportCompletionItem.cs
index 93c01e94aae3a..c9ac87149b582 100644
--- a/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/ImportCompletionItem.cs
+++ b/src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/ImportCompletionItem.cs
@@ -17,14 +17,15 @@ internal static class ImportCompletionItem
     {
         // Note the additional space as prefix to the System namespace,
         // to make sure items from System.* get sorted ahead.
-        private const string OtherNamespaceSortTextFormat = "{0} {1}";
-        private const string SystemNamespaceSortTextFormat = "{0}  {1}";
+        private const string OtherNamespaceSortTextFormat = "~{0} {1}";
+        private const string SystemNamespaceSortTextFormat = "~{0}  {1}";
 
         private const string TypeAritySuffixName = nameof(TypeAritySuffixName);
         private const string AttributeFullName = nameof(AttributeFullName);
         private const string MethodKey = nameof(MethodKey);
         private const string ReceiverKey = nameof(ReceiverKey);
         private const string OverloadCountKey = nameof(OverloadCountKey);
+        private const string AlwaysAddMissingImportKey = nameof(AlwaysAddMissingImportKey);
 
         public static CompletionItem Create(
             string name,
@@ -209,5 +210,9 @@ private static (ISymbol? symbol, int overloadCount) GetSymbolAndOverloadCount(Co
 
             return (compilation.GetTypeByMetadataName(fullyQualifiedName), 0);
         }
+
+        public static CompletionItem MarkItemToAlwaysAddMissingImport(CompletionItem item) => item.WithProperties(item.Properties.Add(AlwaysAddMissingImportKey, AlwaysAddMissingImportKey));
+
+        public static bool ShouldAlwaysAddMissingImport(CompletionItem item) => item.Properties.ContainsKey(AlwaysAddMissingImportKey);
     }
 }
diff --git a/src/Features/Core/Portable/Contracts/Client/ISolutionSnapshotProvider.cs b/src/Features/Core/Portable/Contracts/Client/ISolutionSnapshotProvider.cs
new file mode 100644
index 0000000000000..cdcdb86d3c14a
--- /dev/null
+++ b/src/Features/Core/Portable/Contracts/Client/ISolutionSnapshotProvider.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.CodeAnalysis.Contracts.Client;
+
+[DataContract]
+internal readonly record struct SolutionSnapshotId([property: DataMember] int Id);
+
+// brokered service implemented by the client
+internal interface ISolutionSnapshotProvider
+{
+    ValueTask<SolutionSnapshotId> RegisterSolutionSnapshotAsync(CancellationToken cancellationToken);
+}
diff --git a/src/Features/Core/Portable/ConvertForEachToFor/AbstractConvertForEachToForCodeRefactoringProvider.cs b/src/Features/Core/Portable/ConvertForEachToFor/AbstractConvertForEachToForCodeRefactoringProvider.cs
index 5e242ce2dec1e..878469e80c31d 100644
--- a/src/Features/Core/Portable/ConvertForEachToFor/AbstractConvertForEachToForCodeRefactoringProvider.cs
+++ b/src/Features/Core/Portable/ConvertForEachToFor/AbstractConvertForEachToForCodeRefactoringProvider.cs
@@ -384,7 +384,7 @@ private static bool CheckRequireCollectionStatement(IOperation operation)
             }
         }
 
-        private IOperation RemoveImplicitConversion(IOperation collection)
+        private static IOperation RemoveImplicitConversion(IOperation collection)
         {
             return (collection is IConversionOperation conversion && conversion.IsImplicit)
                 ? RemoveImplicitConversion(conversion.Operand) : collection;
diff --git a/src/Features/Core/Portable/ConvertToInterpolatedString/AbstractConvertConcatenationToInterpolatedStringRefactoringProvider.cs b/src/Features/Core/Portable/ConvertToInterpolatedString/AbstractConvertConcatenationToInterpolatedStringRefactoringProvider.cs
index e75ee2d2674e6..c3816d1bf719f 100644
--- a/src/Features/Core/Portable/ConvertToInterpolatedString/AbstractConvertConcatenationToInterpolatedStringRefactoringProvider.cs
+++ b/src/Features/Core/Portable/ConvertToInterpolatedString/AbstractConvertConcatenationToInterpolatedStringRefactoringProvider.cs
@@ -218,7 +218,7 @@ private static SyntaxNode ConcatenateTextToTextNode(SyntaxGenerator generator, S
 
         protected abstract string GetTextWithoutQuotes(string text, bool isVerbatimStringLiteral, bool isCharacterLiteral);
 
-        private void CollectPiecesDown(
+        private static void CollectPiecesDown(
             ISyntaxFactsService syntaxFacts,
             ArrayBuilder<SyntaxNode> pieces,
             SyntaxNode node,
diff --git a/src/Features/Core/Portable/Diagnostics/IDiagnosticsRefresher.cs b/src/Features/Core/Portable/Diagnostics/IDiagnosticsRefresher.cs
new file mode 100644
index 0000000000000..bd1b413174aa7
--- /dev/null
+++ b/src/Features/Core/Portable/Diagnostics/IDiagnosticsRefresher.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CodeAnalysis.Diagnostics;
+
+/// <summary>
+/// Used to send request for diagnostic pull to the client.
+/// </summary>
+internal interface IDiagnosticsRefresher
+{
+    /// <summary>
+    /// Requests workspace diagnostics refresh.
+    /// Any component that maintains state whose change may affect reported diagnostics should call <see cref="RequestWorkspaceRefresh"/> whenever that state changes.
+    /// Any component that reports diagnostics based on the value of a global option should also call <see cref="RequestWorkspaceRefresh"/> whenever the option value changes.
+    /// </summary>
+    void RequestWorkspaceRefresh();
+
+    /// <summary>
+    /// Current version of global state that may affect diagnostics. Incremented on every refresh.
+    /// Used to determine whether any global state that might affect workspace diagnostics has changed.
+    /// </summary>
+    int GlobalStateVersion { get; }
+}
diff --git a/src/Features/Core/Portable/DocumentationComments/AbstractDocumentationCommentSnippetService.cs b/src/Features/Core/Portable/DocumentationComments/AbstractDocumentationCommentSnippetService.cs
index ca42b299f8a77..199920bab8338 100644
--- a/src/Features/Core/Portable/DocumentationComments/AbstractDocumentationCommentSnippetService.cs
+++ b/src/Features/Core/Portable/DocumentationComments/AbstractDocumentationCommentSnippetService.cs
@@ -43,7 +43,8 @@ internal abstract class AbstractDocumentationCommentSnippetService<TDocumentatio
             SourceText text,
             int position,
             in DocumentationCommentOptions options,
-            CancellationToken cancellationToken)
+            CancellationToken cancellationToken,
+            bool addIndentation = true)
         {
             if (!options.AutoXmlDocCommentGeneration)
             {
@@ -59,7 +60,10 @@ internal abstract class AbstractDocumentationCommentSnippetService<TDocumentatio
                 return null;
             }
 
-            var lines = GetDocumentationCommentLines(token, text, options, out _, out var caretOffset, out var spanToReplaceLength);
+            var lines = addIndentation
+                ? GetDocumentationCommentLines(token, text, options, out _, out var caretOffset, out var spanToReplaceLength)
+                : GetDocumentationCommentLinesNoIndentation(token, text, options, out caretOffset, out spanToReplaceLength);
+
             if (lines == null)
             {
                 return null;
@@ -80,12 +84,59 @@ internal abstract class AbstractDocumentationCommentSnippetService<TDocumentatio
         private List<string>? GetDocumentationCommentLines(SyntaxToken token, SourceText text, in DocumentationCommentOptions options, out string? indentText, out int caretOffset, out int spanToReplaceLength)
         {
             indentText = null;
+
+            var lines = GetDocumentationStubLines(token, text, options, out caretOffset, out spanToReplaceLength, out var existingCommentText);
+            if (lines is null)
+            {
+                return lines;
+            }
+
+            var documentationComment = token.GetAncestor<TDocumentationComment>();
+            var line = text.Lines.GetLineFromPosition(documentationComment!.FullSpan.Start);
+            if (line.IsEmptyOrWhitespace())
+            {
+                return null;
+            }
+
+            // Add indents
+            var lineOffset = line.GetColumnOfFirstNonWhitespaceCharacterOrEndOfLine(options.TabSize);
+            indentText = lineOffset.CreateIndentationString(options.UseTabs, options.TabSize);
+
+            IndentLines(lines, indentText);
+
+            // We always want the caret text to be on the second line, with one space after the doc comment XML
+            // GetDocumentationCommentStubLines ensures that space is always there
+            caretOffset = lines[0].Length + indentText.Length + ExteriorTriviaText.Length + 1;
+            spanToReplaceLength = existingCommentText!.Length;
+
+            return lines;
+        }
+
+        private List<string>? GetDocumentationCommentLinesNoIndentation(SyntaxToken token, SourceText text, in DocumentationCommentOptions options, out int caretOffset, out int spanToReplaceLength)
+        {
+            var lines = GetDocumentationStubLines(token, text, options, out caretOffset, out spanToReplaceLength, out var existingCommentText);
+            if (lines is null)
+            {
+                return lines;
+            }
+
+            // We always want the caret text to be on the second line, with one space after the doc comment XML
+            // GetDocumentationCommentStubLines ensures that space is always there
+            caretOffset = lines[0].Length + ExteriorTriviaText.Length + 1;
+            spanToReplaceLength = existingCommentText!.Length;
+
+            return lines;
+        }
+
+        private List<string>? GetDocumentationStubLines(SyntaxToken token, SourceText text, in DocumentationCommentOptions options, out int caretOffset, out int spanToReplaceLength, out string? existingCommentText)
+        {
             caretOffset = 0;
             spanToReplaceLength = 0;
+            existingCommentText = null;
 
             var documentationComment = token.GetAncestor<TDocumentationComment>();
 
-            if (documentationComment == null || !IsSingleExteriorTrivia(documentationComment, out var existingCommentText))
+            if (documentationComment == null || !IsSingleExteriorTrivia(documentationComment, out existingCommentText))
             {
                 return null;
             }
@@ -112,17 +163,6 @@ internal abstract class AbstractDocumentationCommentSnippetService<TDocumentatio
             // Shave off initial three slashes
             lines[0] = lines[0][3..];
 
-            // Add indents
-            var lineOffset = line.GetColumnOfFirstNonWhitespaceCharacterOrEndOfLine(options.TabSize);
-            indentText = lineOffset.CreateIndentationString(options.UseTabs, options.TabSize);
-
-            IndentLines(lines, indentText);
-
-            // We always want the caret text to be on the second line, with one space after the doc comment XML
-            // GetDocumentationCommentStubLines ensures that space is always there
-            caretOffset = lines[0].Length + indentText.Length + ExteriorTriviaText.Length + 1;
-            spanToReplaceLength = existingCommentText.Length;
-
             return lines;
         }
 
diff --git a/src/Features/Core/Portable/DocumentationComments/IDocumentationCommentSnippetService.cs b/src/Features/Core/Portable/DocumentationComments/IDocumentationCommentSnippetService.cs
index b0739ec668496..a38e9f57b7374 100644
--- a/src/Features/Core/Portable/DocumentationComments/IDocumentationCommentSnippetService.cs
+++ b/src/Features/Core/Portable/DocumentationComments/IDocumentationCommentSnippetService.cs
@@ -20,7 +20,8 @@ internal interface IDocumentationCommentSnippetService : ILanguageService
             SourceText text,
             int position,
             in DocumentationCommentOptions options,
-            CancellationToken cancellationToken);
+            CancellationToken cancellationToken,
+            bool addIndentation = true);
 
         DocumentationCommentSnippet? GetDocumentationCommentSnippetOnCommandInvoke(
             SyntaxTree syntaxTree,
diff --git a/src/Features/Core/Portable/EditAndContinue/AbstractEditAndContinueAnalyzer.cs b/src/Features/Core/Portable/EditAndContinue/AbstractEditAndContinueAnalyzer.cs
index 64e70365c4875..d872ad42c77c4 100644
--- a/src/Features/Core/Portable/EditAndContinue/AbstractEditAndContinueAnalyzer.cs
+++ b/src/Features/Core/Portable/EditAndContinue/AbstractEditAndContinueAnalyzer.cs
@@ -211,6 +211,7 @@ private SyntaxNode FindStatement(SyntaxNode declarationBody, TextSpan span, out
         protected abstract bool AreEquivalentLambdaBodies(SyntaxNode oldLambda, SyntaxNode oldLambdaBody, SyntaxNode newLambda, SyntaxNode newLambdaBody);
 
         protected abstract Match<SyntaxNode> ComputeTopLevelMatch(SyntaxNode oldCompilationUnit, SyntaxNode newCompilationUnit);
+        protected abstract BidirectionalMap<SyntaxNode>? ComputeParameterMap(SyntaxNode oldDeclaration, SyntaxNode newDeclaration);
         protected abstract Match<SyntaxNode> ComputeBodyMatchImpl(SyntaxNode oldBody, SyntaxNode newBody, IEnumerable<KeyValuePair<SyntaxNode, SyntaxNode>>? knownMatches);
         protected abstract Match<SyntaxNode> ComputeTopLevelDeclarationMatch(SyntaxNode oldDeclaration, SyntaxNode newDeclaration);
         protected abstract IEnumerable<SequenceEdit> GetSyntaxSequenceEdits(ImmutableArray<SyntaxNode> oldNodes, ImmutableArray<SyntaxNode> newNodes);
@@ -260,7 +261,7 @@ protected abstract bool TryMatchActiveStatement(
         protected abstract bool IsNamespaceDeclaration(SyntaxNode node);
         protected abstract bool IsCompilationUnitWithGlobalStatements(SyntaxNode node);
         protected abstract bool IsGlobalStatement(SyntaxNode node);
-        protected abstract TextSpan GetGlobalStatementDiagnosticSpan(SyntaxNode node);
+        protected abstract TextSpan GetGlobalStatementDiagnosticSpan(SyntaxNode node, EditKind editKind);
 
         /// <summary>
         /// Returns all top-level type declarations (non-nested) for a given compilation unit node.
@@ -322,6 +323,25 @@ protected virtual TextSpan GetBodyDiagnosticSpan(SyntaxNode node, EditKind editK
         internal abstract TextSpan GetLambdaParameterDiagnosticSpan(SyntaxNode lambda, int ordinal);
 
         // display names:
+
+        internal string GetDisplayKindAndName(ISymbol symbol, string? displayName = null, bool fullyQualify = false)
+        {
+            displayName ??= GetDisplayName(symbol);
+            var format = fullyQualify ? s_fullyQualifiedMemberDisplayFormat : s_unqualifiedMemberDisplayFormat;
+
+            return (symbol is IParameterSymbol { ContainingType: not { TypeKind: TypeKind.Delegate } })
+                ? string.Format(
+                    FeaturesResources.symbol_kind_and_name_of_member_kind_and_name,
+                    displayName,
+                    symbol.Name,
+                    GetDisplayName(symbol.ContainingSymbol),
+                    symbol.ContainingSymbol.ToDisplayString(format))
+                : string.Format(
+                    FeaturesResources.member_kind_and_name,
+                    displayName,
+                    symbol.ToDisplayString(format));
+        }
+
         internal string GetDisplayName(SyntaxNode node, EditKind editKind = EditKind.Update)
           => TryGetDisplayName(node, editKind) ?? throw ExceptionUtilities.UnexpectedValue(node.GetType().Name);
 
@@ -464,7 +484,7 @@ protected virtual string GetSuspensionPointDisplayName(SyntaxNode node, EditKind
         /// <summary>
         /// Returns the declaration of 
         /// - a property, indexer or event declaration whose accessor is the specified <paramref name="node"/>,
-        /// - a method, an indexer or a type (delegate) if the <paramref name="node"/> is a parameter,
+        /// - a method, an indexer, a type (delegate), or primary constructor parameter list if the <paramref name="node"/> is a parameter,
         /// - a method or an type if the <paramref name="node"/> is a type parameter.
         /// </summary>
         internal abstract bool TryGetAssociatedMemberDeclaration(SyntaxNode node, EditKind editKind, [NotNullWhen(true)] out SyntaxNode? declaration);
@@ -478,19 +498,19 @@ protected virtual string GetSuspensionPointDisplayName(SyntaxNode node, EditKind
         internal abstract bool IsDeclarationWithInitializer(SyntaxNode declaration);
 
         /// <summary>
-        /// Return true if the declaration is a parameter that is part of a records primary constructor.
+        /// True if <paramref name="declaration"/> is a declaration node of a primary constructor (i.e. parameter list of a type declaration).
         /// </summary>
-        internal abstract bool IsRecordPrimaryConstructorParameter(SyntaxNode declaration);
-
-        /// <summary>
-        /// Return true if the declaration is a property accessor for a property that represents one of the parameters in a records primary constructor.
-        /// </summary>
-        internal abstract bool IsPropertyAccessorDeclarationMatchingPrimaryConstructorParameter(SyntaxNode declaration, INamedTypeSymbol newContainingType, out bool isFirstAccessor);
+        /// <remarks>
+        /// <see cref="ISymbol.DeclaringSyntaxReferences"/> of a primary constructor returns the type declaration syntax.
+        /// This is inconvenient for EnC analysis since it doesn't allow us to distinguish declaration of the type from the constructor.
+        /// E.g. delete/insert of a primary constructor is not the same as delete/insert of the entire type declaration.
+        /// </remarks>
+        internal abstract bool IsPrimaryConstructorDeclaration(SyntaxNode declaration);
 
         /// <summary>
-        /// Return true if the declaration is a constructor declaration to which field/property initializers are emitted. 
+        /// Return true if <paramref name="symbol"/> is a constructor to which field/property initializers are emitted. 
         /// </summary>
-        internal abstract bool IsConstructorWithMemberInitializers(SyntaxNode declaration);
+        internal abstract bool IsConstructorWithMemberInitializers(ISymbol symbol, CancellationToken cancellationToken);
 
         internal abstract bool IsPartial(INamedTypeSymbol type);
 
@@ -729,29 +749,6 @@ private void ReportTopLevelSyntacticRudeEdits(ArrayBuilder<RudeEditDiagnostic> d
             }
         }
 
-        /// <summary>
-        /// Reports rude edits for a symbol that's been deleted in one location and inserted in another and the edit was not classified as
-        /// <see cref="EditKind.Move"/> or <see cref="EditKind.Reorder"/>.
-        /// The scenarios include moving a type declaration from one file to another and moving a member of a partial type from one partial declaration to another.
-        /// </summary>
-        internal virtual void ReportDeclarationInsertDeleteRudeEdits(ArrayBuilder<RudeEditDiagnostic> diagnostics, SyntaxNode oldNode, SyntaxNode newNode, ISymbol oldSymbol, ISymbol newSymbol, EditAndContinueCapabilitiesGrantor capabilities, CancellationToken cancellationToken)
-        {
-            // When a method is moved to a different declaration and its parameters are changed at the same time
-            // the new method symbol key will not resolve to the old one since the parameters are different.
-            // As a result we will report separate delete and insert rude edits.
-            //
-            // For delegates, however, the symbol key will resolve to the old type so we need to report
-            // rude edits here.
-            if (oldSymbol is INamedTypeSymbol { DelegateInvokeMethod: not null and var oldDelegateInvoke } &&
-                newSymbol is INamedTypeSymbol { DelegateInvokeMethod: not null and var newDelegateInvoke })
-            {
-                if (!ParameterTypesEquivalent(oldDelegateInvoke.Parameters, newDelegateInvoke.Parameters, exact: false))
-                {
-                    ReportUpdateRudeEdit(diagnostics, RudeEditKind.ChangingParameterTypes, newSymbol, newNode, cancellationToken);
-                }
-            }
-        }
-
         internal Dictionary<SyntaxNode, EditKind> BuildEditMap(EditScript<SyntaxNode> editScript)
         {
             var map = new Dictionary<SyntaxNode, EditKind>(editScript.Edits.Length);
@@ -1070,9 +1067,11 @@ private void AnalyzeChangedMemberBody(
                     oldModel,
                     oldMember,
                     oldBody,
+                    oldDeclaration,
                     newModel,
-                    newBody,
                     newMember,
+                    newBody,
+                    newDeclaration,
                     bodyMatch,
                     lazyActiveOrMatchedLambdas,
                     map,
@@ -1095,7 +1094,7 @@ private void AnalyzeChangedMemberBody(
                 if (!activeNodes.IsEmpty() ||
                     newStateMachineInfo.HasSuspensionPoints ||
                     newBodyHasLambdas ||
-                    IsConstructorWithMemberInitializers(newDeclaration) ||
+                    IsConstructorWithMemberInitializers(newMember, cancellationToken) ||
                     IsDeclarationWithInitializer(oldDeclaration) ||
                     IsDeclarationWithInitializer(newDeclaration))
                 {
@@ -2367,28 +2366,32 @@ protected static bool MemberSignaturesEquivalent(
             }
         }
 
-        private readonly struct ConstructorEdit
+        /// <summary>
+        /// Aggregates information needed to emit updates of constructors that contain member initialization.
+        /// </summary>
+        private sealed class MemberInitializationUpdates
         {
             public readonly INamedTypeSymbol OldType;
 
             /// <summary>
             /// Contains syntax maps for all changed data member initializers or constructor declarations (of constructors emitting initializers)
-            /// in the currently analyzed document. The key is the declaration of the member.
+            /// in the currently analyzed document. The key is the new declaration of the member.
             /// </summary>
             public readonly Dictionary<SyntaxNode, Func<SyntaxNode, SyntaxNode?>?> ChangedDeclarations;
 
-            public ConstructorEdit(INamedTypeSymbol oldType)
+            /// <summary>
+            /// True if a member initializer has been deleted
+            /// (<see cref="ChangedDeclarations"/> only contains syntax nodes of new declarations, which are not available for deleted members).
+            /// </summary>
+            public bool HasDeletedMemberInitializer;
+
+            public MemberInitializationUpdates(INamedTypeSymbol oldType)
             {
                 OldType = oldType;
                 ChangedDeclarations = new Dictionary<SyntaxNode, Func<SyntaxNode, SyntaxNode?>?>();
             }
         }
 
-        protected virtual bool IsRudeEditDueToPrimaryConstructor(ISymbol symbol, CancellationToken cancellationToken)
-        {
-            return false;
-        }
-
         private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
             EditScript<SyntaxNode> editScript,
             IReadOnlyDictionary<SyntaxNode, EditKind> editMap,
@@ -2414,8 +2417,8 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
             }
 
             // { new type -> constructor update }
-            PooledDictionary<INamedTypeSymbol, ConstructorEdit>? instanceConstructorEdits = null;
-            PooledDictionary<INamedTypeSymbol, ConstructorEdit>? staticConstructorEdits = null;
+            PooledDictionary<INamedTypeSymbol, MemberInitializationUpdates>? instanceConstructorEdits = null;
+            PooledDictionary<INamedTypeSymbol, MemberInitializationUpdates>? staticConstructorEdits = null;
 
             using var _1 = PooledHashSet<ISymbol>.GetInstance(out var processedSymbols);
             using var _2 = ArrayBuilder<SemanticEditInfo>.GetInstance(out var semanticEdits);
@@ -2469,7 +2472,7 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                     !SymbolsEquivalent(oldSymbol.ContainingNamespace, newSymbol.ContainingNamespace))
                                 {
                                     // pick the first declaration in the new file that contains the namespace change:
-                                    var newTypeDeclaration = GetSymbolDeclarationSyntax(newSymbol.DeclaringSyntaxReferences.First(r => r.SyntaxTree == edit.NewNode!.SyntaxTree), cancellationToken);
+                                    var newTypeDeclaration = GetSymbolDeclarationSyntax(newSymbol, refs => refs.First(r => r.SyntaxTree == edit.NewNode!.SyntaxTree), cancellationToken);
 
                                     diagnostics.Add(new RudeEditDiagnostic(
                                         RudeEditKind.ChangingNamespace,
@@ -2498,11 +2501,11 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                         // Treat the edit as Insert/Delete. This may happen e.g. when all C# global statements are removed, the first one is added or they are moved to another file.
                         if (syntacticEditKind == EditKind.Update)
                         {
-                            if (oldSymbol == null || oldDeclaration != null && oldDeclaration.SyntaxTree != oldModel?.SyntaxTree)
+                            if (oldSymbol == null || oldDeclaration == null || oldDeclaration != null && oldDeclaration.SyntaxTree != oldModel?.SyntaxTree)
                             {
                                 syntacticEditKind = EditKind.Insert;
                             }
-                            else if (newSymbol == null || newDeclaration != null && newDeclaration.SyntaxTree != newModel.SyntaxTree)
+                            else if (newSymbol == null || newDeclaration == null || newDeclaration != null && newDeclaration.SyntaxTree != newModel.SyntaxTree)
                             {
                                 syntacticEditKind = EditKind.Delete;
                             }
@@ -2587,14 +2590,6 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                     Contract.ThrowIfNull(oldSymbol);
                                     Contract.ThrowIfNull(oldDeclaration);
 
-                                    if (IsRudeEditDueToPrimaryConstructor(oldSymbol, cancellationToken))
-                                    {
-                                        // https://github.com/dotnet/roslyn/issues/67108: Disable edits for now
-                                        diagnostics.Add(new RudeEditDiagnostic(RudeEditKind.Delete, GetDeletedNodeDiagnosticSpan(editScript.Match.Matches, oldDeclaration),
-                                                                               oldDeclaration, new[] { GetDisplayName(oldDeclaration, EditKind.Delete) }));
-                                        continue;
-                                    }
-
                                     var activeStatementIndices = GetOverlappingActiveStatements(oldDeclaration, oldActiveStatements);
                                     var hasActiveStatement = activeStatementIndices.Any();
 
@@ -2619,7 +2614,7 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                     editKind = SemanticEditKind.Delete;
 
                                     // Check if the declaration has been moved from one document to another.
-                                    if (newSymbol != null && !(newSymbol is IMethodSymbol newMethod && newMethod.IsPartialDefinition))
+                                    if (newSymbol is { } and not IMethodSymbol { IsPartialDefinition: true })
                                     {
                                         // Symbol has actually not been deleted but rather moved to another document, another partial type declaration
                                         // or replaced with an implicitly generated one (e.g. parameterless constructor, auto-generated record methods, etc.)
@@ -2637,46 +2632,40 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                             continue;
                                         }
 
-                                        if (!newSymbol.IsImplicitlyDeclared)
+                                        // Ignore the delete if there is going to be an insert corresponding to the new symbol that will create an update edit.
+                                        if (HasInsertMatchingDelete(newSymbol, oldCompilation, cancellationToken))
                                         {
-                                            // Ignore the delete. The new symbol is explicitly declared and thus there will be an insert edit that will issue a semantic update.
-                                            // Note that this could also be the case for deleting properties of records, but they will be handled when we see
-                                            // their accessors below.
                                             continue;
                                         }
 
-                                        if (IsPropertyAccessorDeclarationMatchingPrimaryConstructorParameter(oldDeclaration, newSymbol.ContainingType, out var isFirst))
+                                        if (IsDeclarationWithInitializer(oldDeclaration))
                                         {
-                                            // Defer a constructor edit to cover the property initializer changing
-                                            DeferConstructorEdit(oldSymbol.ContainingType, newSymbol.ContainingType, newDeclaration: null, syntaxMap, oldSymbol.IsStatic, ref instanceConstructorEdits, ref staticConstructorEdits);
-
-                                            // If there was no body deleted then we are done since the compiler generated property also has no body
-                                            if (TryGetDeclarationBody(oldDeclaration) is null)
-                                            {
-                                                continue;
-                                            }
-
-                                            // If there was a body, then the backing field of the property will be affected so we
-                                            // need to issue edits for the synthezied members.
-                                            // We only need to do this once though.
-                                            if (isFirst)
-                                            {
-                                                AddEditsForSynthesizedRecordMembers(newCompilation, newSymbol.ContainingType, semanticEdits, cancellationToken);
-                                            }
+                                            // Note initializer deletion.
+                                            DeferConstructorEdit(oldSymbol.ContainingType, newSymbol.ContainingType, newDeclaration: null, syntaxMap, oldSymbol.IsStatic, isMemberWithDeletedInitializer: true);
                                         }
 
-                                        // If a constructor is deleted and replaced by an implicit one the update needs to aggregate updates to all data member initializers,
-                                        // or if a property is deleted that is part of a records primary constructor, which is effectivelly moving from an explicit to implicit
-                                        // initializer.
-                                        if (IsConstructorWithMemberInitializers(oldDeclaration))
+                                        if (IsConstructorWithMemberInitializers(oldSymbol, cancellationToken))
                                         {
+                                            // If a constructor is deleted and replaced by an implicit one the update needs to aggregate updates (syntax maps) of all data member initializers.
+                                            DeferConstructorEdit(oldSymbol.ContainingType, newSymbol.ContainingType, newDeclaration: null, syntaxMap, oldSymbol.IsStatic, isMemberWithDeletedInitializer: false);
+
                                             processedSymbols.Remove(oldSymbol);
-                                            DeferConstructorEdit(oldSymbol.ContainingType, newSymbol.ContainingType, newDeclaration: null, syntaxMap, oldSymbol.IsStatic, ref instanceConstructorEdits, ref staticConstructorEdits);
                                             continue;
                                         }
 
+                                        if (oldSymbol.ContainingType.IsRecord &&
+                                            newSymbol.ContainingType.IsRecord &&
+                                            newSymbol is IPropertySymbol newProperty &&
+                                            IsPrimaryConstructorParameterMatchingSymbol(newSymbol, cancellationToken))
+                                        {
+                                            AnalyzeRecordPropertyReplacement((IPropertySymbol)oldSymbol, newProperty, isDeleteEdit: true);
+                                            editKind = SemanticEditKind.Update;
+                                            break;
+                                        }
+
                                         // there is no insert edit for an implicit declaration, therefore we need to issue an update:
                                         editKind = SemanticEditKind.Update;
+                                        break;
                                     }
                                     else
                                     {
@@ -2707,9 +2696,9 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                             }
 
                                             // We allow deleting parameters, by issuing delete and insert edits for the old and new method
-                                            if (oldSymbol is IParameterSymbol)
+                                            if (oldSymbol is IParameterSymbol oldParameter)
                                             {
-                                                if (TryAddParameterInsertOrDeleteEdits(semanticEdits, oldSymbol.ContainingSymbol, newModel, capabilities, syntaxMap, editScript, processedSymbols, cancellationToken, out var notSupportedByRuntime))
+                                                if (TryAddParameterInsertOrDeleteEdits(semanticEdits, oldParameter, oldModel, newModel, capabilities, syntaxMap, editScript, processedSymbols, cancellationToken, out var notSupportedByRuntime))
                                                 {
                                                     continue;
                                                 }
@@ -2724,8 +2713,8 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                         {
                                             // Check if the symbol being deleted is a member of a type that's also being deleted.
                                             // If so, skip the member deletion and only report the containing symbol deletion.
-                                            var containingSymbolKey = SymbolKey.Create(oldSymbol.ContainingType, cancellationToken);
-                                            var newContainingSymbol = containingSymbolKey.Resolve(newCompilation, ignoreAssemblyKey: true, cancellationToken).Symbol;
+                                            var containingTypeKey = SymbolKey.Create(oldSymbol.ContainingType, cancellationToken);
+                                            var newContainingSymbol = containingTypeKey.Resolve(newCompilation, ignoreAssemblyKey: true, cancellationToken).Symbol;
                                             if (newContainingSymbol == null)
                                             {
                                                 continue;
@@ -2733,7 +2722,42 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
 
                                             if (!hasActiveStatement && AllowsDeletion(oldSymbol))
                                             {
-                                                AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Delete, oldSymbol, containingSymbolKey, syntaxMap, partialType: null, processedSymbols, cancellationToken);
+                                                var newContainingType = (INamedTypeSymbol)newContainingSymbol;
+
+                                                // If a property or field is deleted from a record the synthesized members may change
+                                                // (PrintMembers print all properties and fields, Equals and GHC compare all data members, etc.)
+                                                if (SymbolPresenceAffectsSynthesizedRecordMembers(oldSymbol))
+                                                {
+                                                    // If the deleted member has been replaced by another member (of a different kind, otherwise newSymbol would be non-null) of the same name
+                                                    // we should not update record members as they will be updated by an insertion edit of the other member.
+                                                    // An insert edit must exist for the other member, otherwise we would have two members in the old type of the same name but different kind (field/property).
+                                                    var newMatchingSymbol = newContainingType.GetMembers(oldSymbol.Name).FirstOrDefault(m => m is IPropertySymbol or IFieldSymbol);
+                                                    if (newMatchingSymbol is null)
+                                                    {
+                                                        AddSynthesizedRecordMethodUpdatesForPropertyChange(semanticEdits, newCompilation, newContainingType, cancellationToken);
+                                                    }
+                                                }
+
+                                                if (IsDeclarationWithInitializer(oldDeclaration))
+                                                {
+                                                    DeferConstructorEdit(oldSymbol.ContainingType, newContainingType, oldDeclaration, syntaxMap, oldSymbol.IsStatic, isMemberWithDeletedInitializer: true);
+                                                }
+
+                                                AddDeleteEditsForMemberAndAccessors(semanticEdits, oldSymbol, containingTypeKey, syntaxMap, partialType: null, cancellationToken);
+
+                                                // Note: Delete of a constructor does not need to be deferred since it does not affect other constructors.
+                                                // We do need to handle deletion of a primary record constructor though.
+                                                if (oldSymbol.ContainingType.IsRecord && IsPrimaryConstructor(oldSymbol, cancellationToken))
+                                                {
+                                                    var oldPrimaryConstructor = (IMethodSymbol)oldSymbol;
+
+                                                    // Deconstructor delete:
+                                                    AddDeconstructorEdits(semanticEdits, oldPrimaryConstructor, otherConstructor: null, containingTypeKey, oldCompilation, newCompilation, syntaxMap: null, processedSymbols, isParameterDelete: true, cancellationToken);
+
+                                                    // Synthesized method updates:
+                                                    AddSynthesizedRecordMethodUpdatesForPropertyChange(semanticEdits, newCompilation, newContainingType, cancellationToken);
+                                                }
+
                                                 continue;
                                             }
                                         }
@@ -2744,33 +2768,18 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                             rudeEditKind,
                                             diagnosticSpan,
                                             oldDeclaration,
-                                            new[]
-                                            {
-                                                string.Format(FeaturesResources.member_kind_and_name,
-                                                    GetDisplayName(oldDeclaration, EditKind.Delete),
-                                                    oldSymbol.ToDisplayString(diagnosticSpan.IsEmpty ? s_fullyQualifiedMemberDisplayFormat : s_unqualifiedMemberDisplayFormat))
-                                            }));
+                                            new[] { GetDisplayKindAndName(oldSymbol, GetDisplayName(oldDeclaration, EditKind.Delete), fullyQualify: diagnosticSpan.IsEmpty) }));
 
                                         continue;
                                     }
                                 }
 
-                                break;
-
                             case EditKind.Insert:
                                 {
                                     Contract.ThrowIfNull(newModel);
                                     Contract.ThrowIfNull(newSymbol);
                                     Contract.ThrowIfNull(newDeclaration);
 
-                                    if (IsRudeEditDueToPrimaryConstructor(newSymbol, cancellationToken))
-                                    {
-                                        // https://github.com/dotnet/roslyn/issues/67108: Disable edits for now
-                                        diagnostics.Add(new RudeEditDiagnostic(RudeEditKind.Insert, GetDiagnosticSpan(newDeclaration, EditKind.Insert),
-                                                                               newDeclaration, new[] { GetDisplayName(newDeclaration, EditKind.Insert) }));
-                                        continue;
-                                    }
-
                                     syntaxMap = null;
 
                                     editKind = SemanticEditKind.Insert;
@@ -2780,53 +2789,46 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                     // Check if the declaration has been moved from one document to another.
                                     if (oldSymbol != null)
                                     {
+                                        editKind = SemanticEditKind.Update;
+
                                         // Symbol has actually not been inserted but rather moved between documents or partial type declarations,
                                         // or is replacing an implicitly generated one (e.g. parameterless constructor, auto-generated record methods, etc.)
                                         oldContainingType = oldSymbol.ContainingType;
 
-                                        if (oldSymbol.IsImplicitlyDeclared)
+                                        if (oldSymbol is IPropertySymbol { ContainingType.IsRecord: true, GetMethod.IsImplicitlyDeclared: true, SetMethod.IsImplicitlyDeclared: true } oldRecordProperty &&
+                                            IsPrimaryConstructorParameterMatchingSymbol(oldSymbol, cancellationToken))
                                         {
-                                            // If a user explicitly implements a member of a record then we want to issue an update, not an insert.
-                                            if (oldSymbol.DeclaringSyntaxReferences.Length == 1)
-                                            {
-                                                Contract.ThrowIfNull(oldDeclaration);
-                                                ReportDeclarationInsertDeleteRudeEdits(diagnostics, oldDeclaration, newDeclaration, oldSymbol, newSymbol, capabilities, cancellationToken);
-
-                                                if (IsPropertyAccessorDeclarationMatchingPrimaryConstructorParameter(newDeclaration, newContainingType, out var isFirst))
-                                                {
-                                                    // If there is no body declared we can skip it entirely because for a property accessor
-                                                    // it matches what the compiler would have previously implicitly implemented.
-                                                    if (TryGetDeclarationBody(newDeclaration) is null)
-                                                    {
-                                                        continue;
-                                                    }
-
-                                                    // If there was a body, then the backing field of the property will be affected so we
-                                                    // need to issue edits for the synthezied members. Only need to do it once.
-                                                    if (isFirst)
-                                                    {
-                                                        AddEditsForSynthesizedRecordMembers(newCompilation, newContainingType, semanticEdits, cancellationToken);
-                                                    }
-                                                }
+                                            AnalyzeRecordPropertyReplacement(oldRecordProperty, (IPropertySymbol)newSymbol, isDeleteEdit: false);
+                                            break;
+                                        }
 
-                                                editKind = SemanticEditKind.Update;
+                                        // When a method is moved to a different declaration and its parameters are changed at the same time
+                                        // the new method symbol key will not resolve to the old one since the parameters are different.
+                                        // As a result we will report separate delete and insert rude edits.
+                                        //
+                                        // For delegates, however, the symbol key will resolve to the old type so we need to report
+                                        // rude edits here.
+                                        if (oldSymbol is INamedTypeSymbol { DelegateInvokeMethod: not null and var oldDelegateInvoke } &&
+                                            newSymbol is INamedTypeSymbol { DelegateInvokeMethod: not null and var newDelegateInvoke })
+                                        {
+                                            if (!ParameterTypesEquivalent(oldDelegateInvoke.Parameters, newDelegateInvoke.Parameters, exact: false))
+                                            {
+                                                ReportUpdateRudeEdit(diagnostics, RudeEditKind.ChangingParameterTypes, newSymbol, newDeclaration, cancellationToken);
                                             }
                                         }
-                                        else if (oldSymbol.DeclaringSyntaxReferences.Length == 1 && newSymbol.DeclaringSyntaxReferences.Length == 1)
+
+                                        if (oldSymbol.DeclaringSyntaxReferences.Length == 1 && newSymbol.DeclaringSyntaxReferences.Length == 1)
                                         {
                                             Contract.ThrowIfNull(oldDeclaration);
 
                                             // Handles partial methods and explicitly implemented properties that implement positional parameters of records
 
+                                            // TODO: update, should this require declaring syntax refs? https://github.com/dotnet/roslyn/issues/68738
                                             // We ignore partial method definition parts when processing edits (GetSymbolForEdit).
                                             // The only declaration in compilation without syntax errors that can have multiple declaring references is a type declaration.
                                             // We can therefore ignore any symbols that have more than one declaration.
                                             ReportTypeLayoutUpdateRudeEdits(diagnostics, newSymbol, newDeclaration, newModel, ref lazyLayoutAttribute);
 
-                                            // Compare the old declaration syntax of the symbol with its new declaration and report rude edits
-                                            // if it changed in any way that's not allowed.
-                                            ReportDeclarationInsertDeleteRudeEdits(diagnostics, oldDeclaration, newDeclaration, oldSymbol, newSymbol, capabilities, cancellationToken);
-
                                             var oldBody = TryGetDeclarationBody(oldDeclaration);
                                             if (oldBody != null)
                                             {
@@ -2860,11 +2862,10 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
 
                                             // If a constructor changes from including initializers to not including initializers
                                             // we don't need to aggregate syntax map from all initializers for the constructor update semantic edit.
-                                            var isNewConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newDeclaration);
+                                            var isNewConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newSymbol, cancellationToken);
                                             var isDeclarationWithInitializer = IsDeclarationWithInitializer(oldDeclaration) || IsDeclarationWithInitializer(newDeclaration);
-                                            var isRecordPrimaryConstructorParameter = IsRecordPrimaryConstructorParameter(oldDeclaration);
 
-                                            if (isNewConstructorWithMemberInitializers || isDeclarationWithInitializer || isRecordPrimaryConstructorParameter)
+                                            if (isNewConstructorWithMemberInitializers || isDeclarationWithInitializer)
                                             {
                                                 if (isNewConstructorWithMemberInitializers)
                                                 {
@@ -2876,25 +2877,21 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                                     AnalyzeSymbolUpdate(oldSymbol, newSymbol, edit.NewNode, newCompilation, editScript.Match, capabilities, diagnostics, semanticEdits, syntaxMap, processedSymbols, cancellationToken);
                                                 }
 
-                                                DeferConstructorEdit(oldSymbol.ContainingType, newContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic, ref instanceConstructorEdits, ref staticConstructorEdits);
+                                                DeferConstructorEdit(oldSymbol.ContainingType, newContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic,
+                                                    isMemberWithDeletedInitializer: IsDeclarationWithInitializer(oldDeclaration) && !IsDeclarationWithInitializer(newDeclaration));
 
                                                 // Don't add a separate semantic edit.
                                                 // Updates of data members with initializers and constructors that emit initializers will be aggregated and added later.
                                                 continue;
                                             }
-
-                                            editKind = SemanticEditKind.Update;
-                                        }
-                                        else
-                                        {
-                                            editKind = SemanticEditKind.Update;
                                         }
                                     }
                                     else if (TryGetAssociatedMemberDeclaration(newDeclaration, EditKind.Insert, out var newAssociatedMemberDeclaration) &&
                                              HasEdit(editMap, newAssociatedMemberDeclaration, EditKind.Insert))
                                     {
-                                        // If the symbol is an accessor and the containing property/indexer/event declaration has also been inserted skip
+                                        // If the symbol is an accessor and the containing property/indexer/event declaration has also been inserted
                                         // the insert of the accessor as it will be inserted by the property/indexer/event.
+                                        // Similarly for (type) parameters and their containing symbol.
                                         continue;
                                     }
                                     else if (newSymbol is ITypeParameterSymbol)
@@ -2907,9 +2904,9 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
 
                                         continue;
                                     }
-                                    else if (newSymbol is IParameterSymbol)
+                                    else if (newSymbol is IParameterSymbol newParameter)
                                     {
-                                        if (!TryAddParameterInsertOrDeleteEdits(semanticEdits, newSymbol.ContainingSymbol, oldModel, capabilities, syntaxMap, editScript, processedSymbols, cancellationToken, out var notSupportedByRuntime))
+                                        if (!TryAddParameterInsertOrDeleteEdits(semanticEdits, newParameter, newModel, oldModel, capabilities, syntaxMap, editScript, processedSymbols, cancellationToken, out var notSupportedByRuntime))
                                         {
                                             diagnostics.Add(new RudeEditDiagnostic(
                                                notSupportedByRuntime ? RudeEditKind.InsertNotSupportedByRuntime : RudeEditKind.Insert,
@@ -2951,13 +2948,11 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                         // We could compare the exact order of the members but the scenario is unlikely to occur.
                                         ReportTypeLayoutUpdateRudeEdits(diagnostics, newSymbol, newDeclaration, newModel, ref lazyLayoutAttribute);
 
-                                        // If a property or field is added to a record then the implicit constructors change,
-                                        // and we need to mark a number of other synthesized members as having changed.
-                                        if (newSymbol is IPropertySymbol or IFieldSymbol && newContainingType.IsRecord)
+                                        // If a property or field is inserted into a record the synthesized members may change
+                                        // (PrintMembers print all properties and fields, Equals and GHC compare all data members, etc.)
+                                        if (SymbolPresenceAffectsSynthesizedRecordMembers(newSymbol))
                                         {
-                                            DeferConstructorEdit(oldContainingType, newContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic, ref instanceConstructorEdits, ref staticConstructorEdits);
-
-                                            AddEditsForSynthesizedRecordMembers(newCompilation, newContainingType, semanticEdits, cancellationToken);
+                                            AddSynthesizedRecordMethodUpdatesForPropertyChange(semanticEdits, newCompilation, newContainingType, cancellationToken);
                                         }
                                     }
                                     else
@@ -2979,7 +2974,7 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                         ReportInsertedMemberSymbolRudeEdits(diagnostics, newSymbol, newDeclaration, insertingIntoExistingContainingType: false);
                                     }
 
-                                    var isConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newDeclaration);
+                                    var isConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newSymbol, cancellationToken);
                                     if (isConstructorWithMemberInitializers || IsDeclarationWithInitializer(newDeclaration))
                                     {
                                         Contract.ThrowIfNull(newContainingType);
@@ -2996,7 +2991,7 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                             break;
                                         }
 
-                                        DeferConstructorEdit(oldContainingType, newContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic, ref instanceConstructorEdits, ref staticConstructorEdits);
+                                        DeferConstructorEdit(oldContainingType, newContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic, isMemberWithDeletedInitializer: false);
 
                                         if (isConstructorWithMemberInitializers)
                                         {
@@ -3036,15 +3031,6 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                     Contract.ThrowIfNull(oldDeclaration);
                                     Contract.ThrowIfNull(newDeclaration);
 
-                                    if (IsRudeEditDueToPrimaryConstructor(oldSymbol, cancellationToken) ||
-                                        IsRudeEditDueToPrimaryConstructor(newSymbol, cancellationToken))
-                                    {
-                                        // https://github.com/dotnet/roslyn/issues/67108: Disable edits for now
-                                        diagnostics.Add(new RudeEditDiagnostic(RudeEditKind.Update, GetDiagnosticSpan(newDeclaration, EditKind.Update),
-                                                                               newDeclaration, new[] { GetDisplayName(newDeclaration, EditKind.Update) }));
-                                        continue;
-                                    }
-
                                     var oldBody = TryGetDeclarationBody(oldDeclaration);
                                     if (oldBody != null)
                                     {
@@ -3072,7 +3058,7 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
 
                                     // If a constructor changes from including initializers to not including initializers
                                     // we don't need to aggregate syntax map from all initializers for the constructor update semantic edit.
-                                    var isConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newDeclaration);
+                                    var isConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newSymbol, cancellationToken);
                                     var isDeclarationWithInitializer = IsDeclarationWithInitializer(oldDeclaration) || IsDeclarationWithInitializer(newDeclaration);
 
                                     if (isConstructorWithMemberInitializers || isDeclarationWithInitializer)
@@ -3087,7 +3073,8 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                             AnalyzeSymbolUpdate(oldSymbol, newSymbol, edit.NewNode, newCompilation, editScript.Match, capabilities, diagnostics, semanticEdits, syntaxMap, processedSymbols, cancellationToken);
                                         }
 
-                                        DeferConstructorEdit(oldSymbol.ContainingType, newSymbol.ContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic, ref instanceConstructorEdits, ref staticConstructorEdits);
+                                        DeferConstructorEdit(oldSymbol.ContainingType, newSymbol.ContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic,
+                                            isMemberWithDeletedInitializer: IsDeclarationWithInitializer(oldDeclaration) && !IsDeclarationWithInitializer(newDeclaration));
 
                                         // Don't add a separate semantic edit.
                                         // Updates of data members with initializers and constructors that emit initializers will be aggregated and added later.
@@ -3101,6 +3088,40 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                 throw ExceptionUtilities.UnexpectedValue(edit.Kind);
                         }
 
+                        void AnalyzeRecordPropertyReplacement(IPropertySymbol oldProperty, IPropertySymbol newProperty, bool isDeleteEdit)
+                        {
+                            Debug.Assert(newDeclaration != null);
+                            Debug.Assert(oldProperty.ContainingType.IsRecord);
+                            Debug.Assert(newProperty.ContainingType.IsRecord);
+
+                            // The synthesized auto-property is `T P { get; init; } = P`.
+                            // If the initializer is different from `P` the primary constructor needs to be updated.
+                            // Note: we update the constructor regardless of the initializer exact shape, but we could check for it.
+                            DeferConstructorEdit(oldProperty.ContainingType, newProperty.ContainingType, newDeclaration: null, syntaxMap, oldProperty.IsStatic, isMemberWithDeletedInitializer: true);
+
+                            var (customProperty, synthesizedProperty) = isDeleteEdit ? (oldProperty, newProperty) : (newProperty, oldProperty);
+
+                            // new property is synthesized
+                            Debug.Assert(synthesizedProperty.SetMethod is { IsInitOnly: true });
+
+                            if (customProperty.SetMethod == null)
+                            {
+                                // Custom read-only property replaced with synthesized auto-property
+                                if (isDeleteEdit)
+                                {
+                                    AddInsertEditsForMemberAndAccessors(semanticEdits, synthesizedProperty.SetMethod, syntaxMap, partialType: null, processedSymbols, cancellationToken);
+                                }
+                                else
+                                {
+                                    AddDeleteEditsForMemberAndAccessors(semanticEdits, synthesizedProperty.SetMethod, SymbolKey.Create(oldProperty.ContainingType, cancellationToken), syntaxMap, partialType: null, cancellationToken);
+                                }
+                            }
+
+                            // The synthesized property replacing the deleted one will be an auto-property.
+                            // If the accessor had body or the property changed accessibility then synthesized record members might be affected.
+                            AddSynthesizedRecordMethodUpdatesForPropertyChange(semanticEdits, newCompilation, newProperty.ContainingType, cancellationToken);
+                        }
+
                         Contract.ThrowIfFalse(editKind is SemanticEditKind.Update or SemanticEditKind.Insert);
 
                         if (editKind == SemanticEditKind.Update)
@@ -3169,8 +3190,8 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                 {
                                     var containingSymbolKey = SymbolKey.Create(oldSymbol.ContainingType, cancellationToken);
 
-                                    AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Delete, oldSymbol, containingSymbolKey, syntaxMap, partialType: null, processedSymbols, cancellationToken);
-                                    AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Insert, newSymbol, containingSymbolKey: null, syntaxMap,
+                                    AddDeleteEditsForMemberAndAccessors(semanticEdits, oldSymbol, containingSymbolKey, syntaxMap, partialType: null, cancellationToken);
+                                    AddInsertEditsForMemberAndAccessors(semanticEdits, newSymbol, syntaxMap,
                                         partialType: IsPartialEdit(oldSymbol, newSymbol, editScript.Match.OldRoot.SyntaxTree, editScript.Match.NewRoot.SyntaxTree) ? symbolKey : null, processedSymbols,
                                         cancellationToken);
                                 }
@@ -3243,10 +3264,10 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                         var syntaxMap = isActiveMember ? CreateSyntaxMapForEquivalentNodes(oldDeclaration, newDeclaration) : null;
 
                         // only trivia changed:
-                        Contract.ThrowIfFalse(IsConstructorWithMemberInitializers(oldDeclaration) == IsConstructorWithMemberInitializers(newDeclaration));
-                        Contract.ThrowIfFalse(IsDeclarationWithInitializer(oldDeclaration) == IsDeclarationWithInitializer(newDeclaration));
+                        Debug.Assert(IsConstructorWithMemberInitializers(oldSymbol, cancellationToken) == IsConstructorWithMemberInitializers(newSymbol, cancellationToken));
+                        Debug.Assert(IsDeclarationWithInitializer(oldDeclaration) == IsDeclarationWithInitializer(newDeclaration));
 
-                        var isConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newDeclaration);
+                        var isConstructorWithMemberInitializers = IsConstructorWithMemberInitializers(newSymbol, cancellationToken);
                         var isDeclarationWithInitializer = IsDeclarationWithInitializer(newDeclaration);
 
                         if (isConstructorWithMemberInitializers || isDeclarationWithInitializer)
@@ -3259,7 +3280,7 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                                 processedSymbols.Remove(newSymbol);
                             }
 
-                            DeferConstructorEdit(oldContainingType, newContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic, ref instanceConstructorEdits, ref staticConstructorEdits);
+                            DeferConstructorEdit(oldContainingType, newContainingType, newDeclaration, syntaxMap, newSymbol.IsStatic, isMemberWithDeletedInitializer: false);
 
                             // Don't add a separate semantic edit.
                             // Updates of data members with initializers and constructors that emit initializers will be aggregated and added later.
@@ -3310,6 +3331,40 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
                         diagnostics,
                         cancellationToken);
                 }
+
+                // Called when a body of a constructor or an initializer of a member is updated or inserted.
+                // newDeclaration is the declaration node of an updated/inserted constructor or a member with an initializer,
+                // or null if the constructor or member has been deleted.
+                void DeferConstructorEdit(
+                    INamedTypeSymbol oldType,
+                    INamedTypeSymbol newType,
+                    SyntaxNode? newDeclaration,
+                    Func<SyntaxNode, SyntaxNode?>? syntaxMap,
+                    bool isStatic,
+                    bool isMemberWithDeletedInitializer)
+                {
+                    Dictionary<INamedTypeSymbol, MemberInitializationUpdates> constructorEdits;
+                    if (isStatic)
+                    {
+                        constructorEdits = staticConstructorEdits ??= PooledDictionary<INamedTypeSymbol, MemberInitializationUpdates>.GetInstance();
+                    }
+                    else
+                    {
+                        constructorEdits = instanceConstructorEdits ??= PooledDictionary<INamedTypeSymbol, MemberInitializationUpdates>.GetInstance();
+                    }
+
+                    if (!constructorEdits.TryGetValue(newType, out var constructorEdit))
+                    {
+                        constructorEdits.Add(newType, constructorEdit = new MemberInitializationUpdates(oldType));
+                    }
+
+                    if (newDeclaration != null && !constructorEdit.ChangedDeclarations.ContainsKey(newDeclaration))
+                    {
+                        constructorEdit.ChangedDeclarations.Add(newDeclaration, syntaxMap);
+                    }
+
+                    constructorEdit.HasDeletedMemberInitializer |= isMemberWithDeletedInitializer;
+                }
             }
             catch (Exception e) when (FatalError.ReportAndPropagateUnlessCanceled(e, cancellationToken))
             {
@@ -3331,91 +3386,218 @@ private async Task<ImmutableArray<SemanticEditInfo>> AnalyzeSemanticsAsync(
             {
                 return (
                     (oldSymbol != null && oldSymbol.DeclaringSyntaxReferences.Length == 1) ?
-                        GetSymbolDeclarationSyntax(oldSymbol.DeclaringSyntaxReferences.Single(), cancellationToken) : oldNode,
+                        GetSymbolDeclarationSyntax(oldSymbol, cancellationToken) : oldNode,
                     (newSymbol != null && newSymbol.DeclaringSyntaxReferences.Length == 1) ?
-                        GetSymbolDeclarationSyntax(newSymbol.DeclaringSyntaxReferences.Single(), cancellationToken) : newNode);
+                        GetSymbolDeclarationSyntax(newSymbol, cancellationToken) : newNode);
             }
         }
 
         /// <summary>
-        /// Adds a delete and insert edit for the old and new symbols that have had a parameter inserted or deleted
+        /// Adds a delete and insert edit for the old and new symbols that have had a parameter inserted or deleted.
+        /// Not used if the symbol containing deleted/inserted parameters was itself deleted/inserted.
         /// </summary>
-        /// <param name="containingSymbol">The symbol that contains the parameter that has been added or deleted (either IMethodSymbol or IPropertySymbol)</param>
-        /// <param name="otherModel">The semantic model from the old compilation, for parameter inserts, or new compilation, for deletes</param>
+        /// <param name="parameterSymbol">The parameter that has been added or deleted</param>
+        /// <param name="otherModel">The semantic model from the compilation without the <paramref name="parameterSymbol"/> (i.e the old compilation for insert, or new compilation for deletes)</param>
         /// <param name="notSupportedByRuntime">Whether the edit should be rejected because the runtime doesn't support inserting new methods. Otherwise a normal rude edit is appropriate.</param>
         /// <returns>Returns whether semantic edits were added, or if not then a rude edit should be created</returns>
-        private bool TryAddParameterInsertOrDeleteEdits(ArrayBuilder<SemanticEditInfo> semanticEdits, ISymbol containingSymbol, SemanticModel? otherModel, EditAndContinueCapabilitiesGrantor capabilities, Func<SyntaxNode, SyntaxNode?>? syntaxMap, EditScript<SyntaxNode> editScript, HashSet<ISymbol> processedSymbols, CancellationToken cancellationToken, out bool notSupportedByRuntime)
+        private bool TryAddParameterInsertOrDeleteEdits(
+            ArrayBuilder<SemanticEditInfo> semanticEdits,
+            IParameterSymbol parameterSymbol,
+            SemanticModel model,
+            SemanticModel? otherModel,
+            EditAndContinueCapabilitiesGrantor capabilities,
+            Func<SyntaxNode, SyntaxNode?>? syntaxMap,
+            EditScript<SyntaxNode> editScript,
+            HashSet<ISymbol> processedSymbols,
+            CancellationToken cancellationToken,
+            out bool notSupportedByRuntime)
         {
-            Debug.Assert(containingSymbol is IPropertySymbol or IMethodSymbol);
+            var member = parameterSymbol.ContainingSymbol;
+            Debug.Assert(member is IPropertySymbol or IMethodSymbol);
 
             notSupportedByRuntime = false;
 
             // Since we're inserting (or deleting) a parameter node, oldSymbol (or newSymbol) would have been null,
-            // and a symbolkey won't map to the other compilation because the parameters are different, so we have to go back to the edit map
+            // and a symbol key won't map to the other compilation because the parameters are different, so we have to go back to the edit map
             // to find the declaration that contains the parameter, and its partner, and then its symbol, so we need to be sure we can get
             // to syntax, and have a semantic model to get back to symbols.
             if (otherModel is null ||
-                containingSymbol.DeclaringSyntaxReferences.Length != 1)
+                member.DeclaringSyntaxReferences.Length != 1)
             {
                 return false;
             }
 
             // We can ignore parameter inserts and deletes for partial method definitions, as we'll report them on the implementation.
             // We return true here so no rude edit is raised.
-            if (containingSymbol is IMethodSymbol { IsPartialDefinition: true })
+            if (member is IMethodSymbol { IsPartialDefinition: true })
             {
                 return true;
             }
 
             // We don't support delegate parameters
-            if (containingSymbol.ContainingType.IsDelegateType())
+            if (member.ContainingType.IsDelegateType())
             {
                 return false;
             }
 
             // Find the node that matches this declaration
-            SyntaxNode otherContainingNode;
-            var containingNode = containingSymbol.DeclaringSyntaxReferences[0].GetSyntax(cancellationToken);
-            if (editScript.Match.TryGetOldNode(containingNode, out var oldNode))
+            SyntaxNode otherContainingDeclaration;
+            bool isParameterDelete;
+            var containingDeclaration = GetSymbolDeclarationSyntax(member, cancellationToken);
+            if (editScript.Match.TryGetOldNode(containingDeclaration, out var oldNode))
             {
-                otherContainingNode = oldNode;
+                otherContainingDeclaration = oldNode;
+                isParameterDelete = false;
             }
-            else if (editScript.Match.TryGetNewNode(containingNode, out var newNode))
+            else if (editScript.Match.TryGetNewNode(containingDeclaration, out var newNode))
             {
-                otherContainingNode = newNode;
+                otherContainingDeclaration = newNode;
+                isParameterDelete = true;
             }
             else
             {
                 return false;
             }
 
-            var otherContainingSymbol = otherModel.GetDeclaredSymbol(otherContainingNode, cancellationToken);
-            if (otherContainingSymbol is null || !AllowsDeletion(otherContainingSymbol))
+            // Member from the other compilation that does not have the parameter and matches the member that does.
+            var otherMember = GetRequiredDeclaredSymbol(otherModel, otherContainingDeclaration, cancellationToken);
+            Debug.Assert(otherMember is IPropertySymbol or IMethodSymbol);
+
+            if (!AllowsDeletion(otherMember))
             {
                 return false;
             }
 
             // Now we can work out which is the old and which is the new, depending on which map we found
             // the match in
-            var oldSymbol = (otherContainingNode == oldNode) ? otherContainingSymbol : containingSymbol;
-            var newSymbol = (otherContainingNode == oldNode) ? containingSymbol : otherContainingSymbol;
+            var (oldContainingSymbol, newContainingSymbol) = isParameterDelete ? (member, otherMember) : (otherMember, member);
 
-            if (!CanRenameOrChangeSignature(oldSymbol, newSymbol, capabilities, cancellationToken))
+            if (!CanRenameOrChangeSignature(oldContainingSymbol, newContainingSymbol, capabilities, cancellationToken))
             {
                 notSupportedByRuntime = true;
                 return false;
             }
 
-            var containingSymbolKey = SymbolKey.Create(oldSymbol.ContainingType, cancellationToken);
+            var containingTypeKey = SymbolKey.Create(oldContainingSymbol.ContainingType, cancellationToken);
+            AddSynthesizedMemberEditsForParameterChange(semanticEdits, parameterSymbol, otherMember, containingTypeKey, model, otherModel, syntaxMap, processedSymbols, isParameterDelete, cancellationToken);
 
-            AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Delete, oldSymbol, containingSymbolKey, syntaxMap, partialType: null, processedSymbols, cancellationToken);
+            AddDeleteAndInsertEditsForMemberAndAccessors(semanticEdits, oldContainingSymbol, newContainingSymbol, containingTypeKey, syntaxMap, processedSymbols, cancellationToken);
+            return true;
+        }
 
-            var symbolKey = SymbolKey.Create(newSymbol, cancellationToken);
-            AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Insert, newSymbol, containingSymbolKey: null, syntaxMap,
-                partialType: IsPartialEdit(oldSymbol, newSymbol, editScript.Match.OldRoot.SyntaxTree, editScript.Match.NewRoot.SyntaxTree) ? symbolKey : null, processedSymbols,
-                cancellationToken);
+        /// <summary>
+        /// Adds edits of synthesized members that may be affected by a <paramref name="parameterSymbol"/> change.
+        /// </summary>
+        /// <param name="otherMember">Is the member in the other compilation corresponding to the member whose <paramref name="parameterSymbol"/> is being changed.</param>
+        private void AddSynthesizedMemberEditsForParameterChange(
+            ArrayBuilder<SemanticEditInfo> semanticEdits,
+            IParameterSymbol parameterSymbol,
+            ISymbol otherMember,
+            SymbolKey containingTypeKey,
+            SemanticModel model,
+            SemanticModel otherModel,
+            Func<SyntaxNode, SyntaxNode?>? syntaxMap,
+            HashSet<ISymbol> processedSymbols,
+            bool isParameterDelete,
+            CancellationToken cancellationToken)
+        {
+            var member = parameterSymbol.ContainingSymbol;
+            Debug.Assert(member is IPropertySymbol or IMethodSymbol);
 
-            return true;
+            if (!member.ContainingType.IsRecord ||
+                !otherMember.ContainingType.IsRecord ||
+                !IsPrimaryConstructor(member, cancellationToken) ||
+                !IsPrimaryConstructor(otherMember, cancellationToken))
+            {
+                return;
+            }
+
+            // Parameter deleted from or inserted into a primary constructor of a record type.
+            //
+            // Note that although the compiler emits auto-properties and deconstructor automatically
+            // given just an insert or udpate edit of the primary constructor, it will not emit the necessary deletes.
+            // We could only add delete edits and avoid adding updates and inserts. It would make the code somewhat simpler
+            // but also asymetric (delete vs insert). Adding inserts and updates to the edits explicitly also avoids
+            // dependency on the compiler implementation details.
+            var primaryConstructor = (IMethodSymbol)member;
+            var otherPrimaryConstructor = (IMethodSymbol)otherMember;
+
+            // Delete/insert/update synthesized properties and their accessors.
+
+            // If deleting a parameter from or inserting a parameter to primary constructor of a record
+            // that does not have a corresponding synthesized property (has a custom property of field)
+            // has no effect on the property.
+
+            var synthesizedProperty = GetPropertySynthesizedForRecordPrimaryConstructorParameter(parameterSymbol);
+            if (synthesizedProperty != null)
+            {
+                var otherMembersOfParameterName = otherMember.ContainingType.GetMembers(parameterSymbol.Name);
+                if (otherMembersOfParameterName.Any(static m => m is IPropertySymbol))
+                {
+                    // Replace a synthesized auto-property with a custom implementation:
+                    AddUpdateEditsForMemberAndAccessors(semanticEdits, synthesizedProperty, syntaxMap, partialType: null, cancellationToken);
+                }
+                else if (isParameterDelete)
+                {
+                    // Delete synthesized property:
+                    AddDeleteEditsForMemberAndAccessors(semanticEdits, synthesizedProperty, deletedSymbolContainer: containingTypeKey, syntaxMap, partialType: null, cancellationToken);
+                }
+                else
+                {
+                    // Insert synthesized property:
+                    AddInsertEditsForMemberAndAccessors(semanticEdits, synthesizedProperty, syntaxMap, partialType: null, processedSymbols, cancellationToken);
+                }
+            }
+
+            // Deconstructor - we can add deconstructor edit for each changed parameter, they will get deduplicated.
+            AddDeconstructorEdits(semanticEdits, primaryConstructor, otherPrimaryConstructor, containingTypeKey, model.Compilation, otherModel.Compilation, syntaxMap, processedSymbols, isParameterDelete, cancellationToken);
+
+            // Synthesized method updates - we can add edits for each changed parameter, they will get deduplicated.
+            AddSynthesizedRecordMethodUpdatesForPropertyChange(semanticEdits, otherModel.Compilation, primaryConstructor.ContainingType, cancellationToken);
+        }
+
+        /// <summary>
+        /// Adds edits deleting/inserting deconstructor no longer matching <paramref name="constructor"/> of a record
+        /// and inserting/deleting deconstructor the one that maches its signature.
+        /// </summary>
+        private void AddDeconstructorEdits(
+            ArrayBuilder<SemanticEditInfo> semanticEdits,
+            IMethodSymbol? constructor,
+            IMethodSymbol? otherConstructor,
+            SymbolKey containingTypeKey,
+            Compilation compilation,
+            Compilation otherCompilation,
+            Func<SyntaxNode, SyntaxNode?>? syntaxMap,
+            HashSet<ISymbol> processedSymbols,
+            bool isParameterDelete,
+            CancellationToken cancellationToken)
+        {
+            AddEdits(constructor, otherCompilation, isParameterDelete);
+            AddEdits(otherConstructor, compilation, !isParameterDelete);
+
+            void AddEdits(IMethodSymbol? constructor, Compilation otherCompilation, bool isDelete)
+            {
+                if (constructor != null &&
+                    IsPrimaryConstructor(constructor, cancellationToken) &&
+                    constructor.GetMatchingDeconstructor() is { IsImplicitlyDeclared: true } deconstructor)
+                {
+                    if (SymbolKey.Create(deconstructor, cancellationToken).Resolve(otherCompilation, ignoreAssemblyKey: true, cancellationToken).Symbol != null)
+                    {
+                        // Update for transition from synthesized to declared deconstructor
+                        AddUpdateEditsForMemberAndAccessors(semanticEdits, deconstructor, syntaxMap, partialType: null, cancellationToken);
+                    }
+                    else if (isDelete)
+                    {
+                        // Delete synthesized deconstructor:
+                        AddDeleteEditsForMemberAndAccessors(semanticEdits, deconstructor, deletedSymbolContainer: containingTypeKey, syntaxMap, partialType: null, cancellationToken);
+                    }
+                    else
+                    {
+                        // Insert synthesized deconstructor:
+                        AddInsertEditsForMemberAndAccessors(semanticEdits, deconstructor, syntaxMap, partialType: null, processedSymbols, cancellationToken);
+                    }
+                }
+            }
         }
 
         /// <summary>
@@ -3460,82 +3642,155 @@ MethodKind.PropertyGet or
         }
 
         /// <summary>
-        /// Add semantic edits for the specified symbol, or the associated members of the specified symbol,
-        /// for example, edits for each accessor if a property symbol is passed in.
+        /// Add <see cref="SemanticEditKind.Update"/> edit for the specified symbol and its accessors.
         /// </summary>
-        private static void AddMemberOrAssociatedMemberSemanticEdits(ArrayBuilder<SemanticEditInfo> semanticEdits, SemanticEditKind editKind, ISymbol symbol, SymbolKey? containingSymbolKey, Func<SyntaxNode, SyntaxNode?>? syntaxMap, SymbolKey? partialType, HashSet<ISymbol>? processedSymbols, CancellationToken cancellationToken)
+        private static void AddUpdateEditsForMemberAndAccessors(
+            ArrayBuilder<SemanticEditInfo> semanticEdits, ISymbol symbol, Func<SyntaxNode, SyntaxNode?>? syntaxMap, SymbolKey? partialType, CancellationToken cancellationToken)
         {
-            Debug.Assert(symbol is IMethodSymbol or IPropertySymbol or IEventSymbol);
-
-            // We store the containing symbol in NewSymbol of the edit for later use.
-            if (symbol is IMethodSymbol)
+            switch (symbol)
             {
-                AddEdit(symbol);
+                case IMethodSymbol:
+                    AddUpdate(symbol);
+                    break;
+
+                case IPropertySymbol propertySymbol:
+                    AddUpdate(propertySymbol);
+                    AddUpdate(propertySymbol.GetMethod);
+                    AddUpdate(propertySymbol.SetMethod);
+                    break;
+
+                case IEventSymbol eventSymbol:
+                    AddUpdate(eventSymbol);
+                    AddUpdate(eventSymbol.AddMethod);
+                    AddUpdate(eventSymbol.RemoveMethod);
+                    AddUpdate(eventSymbol.RaiseMethod);
+                    break;
+
+                default:
+                    throw ExceptionUtilities.UnexpectedValue(symbol.Kind);
             }
-            else if (symbol is IPropertySymbol propertySymbol)
-            {
-                if (editKind == SemanticEditKind.Delete)
-                {
-                    // When deleting a property, we delete the get and set method individually, because we actually just update them
-                    // to be throwing
-                    AddEdit(propertySymbol.GetMethod);
-                    AddEdit(propertySymbol.SetMethod);
-                }
-                else
-                {
-                    Contract.ThrowIfNull(processedSymbols);
 
-                    // When inserting a new property as part of a property change however, we need to insert the entire property, so
-                    // that the field, property and method semantics metadata tables can all be updated if/as necessary
-                    AddEdit(propertySymbol);
-                    if (propertySymbol.GetMethod is not null)
-                    {
-                        processedSymbols.Add(propertySymbol.GetMethod);
-                    }
+            void AddUpdate(ISymbol? symbol)
+            {
+                if (symbol is null)
+                    return;
 
-                    if (propertySymbol.SetMethod is not null)
-                    {
-                        processedSymbols.Add(propertySymbol.SetMethod);
-                    }
-                }
+                var symbolKey = SymbolKey.Create(symbol, cancellationToken);
+                semanticEdits.Add(new SemanticEditInfo(SemanticEditKind.Update, symbolKey, syntaxMap, syntaxMapTree: null, partialType, deletedSymbolContainer: null));
             }
-            else if (symbol is IEventSymbol eventSymbol)
+        }
+
+        /// <summary>
+        /// Add <see cref="SemanticEditKind.Delete"/> edit for the specified symbol and its accessors.
+        /// </summary>
+        private static void AddDeleteEditsForMemberAndAccessors(
+            ArrayBuilder<SemanticEditInfo> semanticEdits, ISymbol oldSymbol, SymbolKey deletedSymbolContainer, Func<SyntaxNode, SyntaxNode?>? syntaxMap, SymbolKey? partialType, CancellationToken cancellationToken)
+        {
+            switch (oldSymbol)
             {
-                if (editKind == SemanticEditKind.Delete)
-                {
-                    AddEdit(eventSymbol.AddMethod);
-                    AddEdit(eventSymbol.RemoveMethod);
-                    AddEdit(eventSymbol.RaiseMethod);
-                }
-                else
-                {
-                    Contract.ThrowIfNull(processedSymbols);
+                case IMethodSymbol:
+                    AddDelete(oldSymbol);
+                    break;
 
-                    AddEdit(eventSymbol);
-                    if (eventSymbol.AddMethod is not null)
-                    {
-                        processedSymbols.Add(eventSymbol.AddMethod);
-                    }
+                case IPropertySymbol propertySymbol:
+                    // Delete accessors individually, because we actually just update them to be throwing.
+                    AddDelete(propertySymbol.GetMethod);
+                    AddDelete(propertySymbol.SetMethod);
+                    break;
 
-                    if (eventSymbol.RemoveMethod is not null)
-                    {
-                        processedSymbols.Add(eventSymbol.RemoveMethod);
-                    }
+                case IEventSymbol eventSymbol:
+                    // Delete accessors individually, because we actually just update them to be throwing.
+                    AddDelete(eventSymbol.AddMethod);
+                    AddDelete(eventSymbol.RemoveMethod);
+                    AddDelete(eventSymbol.RaiseMethod);
+                    break;
 
-                    if (eventSymbol.RaiseMethod is not null)
-                    {
-                        processedSymbols.Add(eventSymbol.RaiseMethod);
-                    }
-                }
+                default:
+                    throw ExceptionUtilities.UnexpectedValue(oldSymbol.Kind);
             }
 
-            void AddEdit(ISymbol? symbol)
+            void AddDelete(ISymbol? symbol)
             {
                 if (symbol is null)
                     return;
 
                 var symbolKey = SymbolKey.Create(symbol, cancellationToken);
-                semanticEdits.Add(new SemanticEditInfo(editKind, symbolKey, syntaxMap, syntaxMapTree: null, partialType, deletedSymbolContainer: containingSymbolKey));
+                semanticEdits.Add(new SemanticEditInfo(SemanticEditKind.Delete, symbolKey, syntaxMap, syntaxMapTree: null, partialType, deletedSymbolContainer: deletedSymbolContainer));
+            }
+        }
+
+        /// <summary>
+        /// Add <see cref="SemanticEditKind.Insert"/> edit for the specified symbol and its accessors.
+        /// </summary>
+        private static void AddInsertEditsForMemberAndAccessors(
+            ArrayBuilder<SemanticEditInfo> semanticEdits, ISymbol newSymbol, Func<SyntaxNode, SyntaxNode?>? syntaxMap, SymbolKey? partialType, HashSet<ISymbol> processedSymbols, CancellationToken cancellationToken)
+        {
+            switch (newSymbol)
+            {
+                case IMethodSymbol:
+                    AddInsert(newSymbol);
+                    break;
+
+                case IPropertySymbol propertySymbol:
+                    // When inserting a new property, we need to insert the entire property, so
+                    // that the backing field (if any), property and method semantics metadata tables can all be updated if/as necessary.
+                    AddInsert(propertySymbol);
+
+                    // Mark processed to suppress adding update edits of the accessors based on syntactic edits:
+                    MarkProcessed(propertySymbol.GetMethod);
+                    MarkProcessed(propertySymbol.SetMethod);
+                    break;
+
+                case IEventSymbol eventSymbol:
+                    // When inserting a new event we need to insert the entire event, so
+                    // pevent and method semantics metadata tables can all be updated if/as necessary.
+                    AddInsert(eventSymbol);
+
+                    // Mark processed to suppress adding update edits of the accessors based on syntactic edits:
+                    MarkProcessed(eventSymbol.AddMethod);
+                    MarkProcessed(eventSymbol.RemoveMethod);
+                    MarkProcessed(eventSymbol.RaiseMethod);
+                    break;
+
+                default:
+                    throw ExceptionUtilities.UnexpectedValue(newSymbol.Kind);
+            }
+
+            void AddInsert(ISymbol symbol)
+            {
+                var symbolKey = SymbolKey.Create(symbol, cancellationToken);
+                semanticEdits.Add(new SemanticEditInfo(SemanticEditKind.Insert, symbolKey, syntaxMap, syntaxMapTree: null, partialType));
+            }
+
+            void MarkProcessed(ISymbol? symbol)
+            {
+                if (symbol != null)
+                {
+                    processedSymbols.Add(symbol);
+                }
+            }
+        }
+
+        private static void AddDeleteAndInsertEditsForMemberAndAccessors(
+            ArrayBuilder<SemanticEditInfo> semanticEdits,
+            ISymbol? oldSymbol,
+            ISymbol? newSymbol,
+            SymbolKey containingSymbolKey,
+            Func<SyntaxNode, SyntaxNode?>? syntaxMap,
+            HashSet<ISymbol> processedSymbols,
+            CancellationToken cancellationToken)
+        {
+            Debug.Assert(oldSymbol is not INamedTypeSymbol);
+            Debug.Assert(newSymbol is not INamedTypeSymbol);
+
+            if (oldSymbol != null)
+            {
+                AddDeleteEditsForMemberAndAccessors(semanticEdits, oldSymbol, containingSymbolKey, syntaxMap, partialType: null, cancellationToken);
+            }
+
+            if (newSymbol != null)
+            {
+                AddInsertEditsForMemberAndAccessors(semanticEdits, newSymbol, syntaxMap, partialType: null, processedSymbols, cancellationToken);
             }
         }
 
@@ -3560,9 +3815,7 @@ void AddEdit(ISymbol? symbol)
             var oldRoot = oldModel.SyntaxTree.GetRoot(cancellationToken);
             foreach (var oldTypeDeclaration in GetTopLevelTypeDeclarations(oldRoot))
             {
-                var oldType = (INamedTypeSymbol?)oldModel.GetDeclaredSymbol(oldTypeDeclaration, cancellationToken);
-                Contract.ThrowIfNull(oldType);
-
+                var oldType = (INamedTypeSymbol)GetRequiredDeclaredSymbol(oldModel, oldTypeDeclaration, cancellationToken);
                 if (!processedTypes.Add(oldType))
                 {
                     continue;
@@ -3593,9 +3846,7 @@ void AddEdit(ISymbol? symbol)
             var newRoot = newModel.SyntaxTree.GetRoot(cancellationToken);
             foreach (var newTypeDeclaration in GetTopLevelTypeDeclarations(newRoot))
             {
-                var newType = (INamedTypeSymbol?)newModel.GetDeclaredSymbol(newTypeDeclaration, cancellationToken);
-                Contract.ThrowIfNull(newType);
-
+                var newType = (INamedTypeSymbol)GetRequiredDeclaredSymbol(newModel, newTypeDeclaration, cancellationToken);
                 if (!processedTypes.Add(newType))
                 {
                     continue;
@@ -4234,7 +4485,7 @@ private void AnalyzeSymbolUpdate(
             ArrayBuilder<RudeEditDiagnostic> diagnostics,
             ArrayBuilder<SemanticEditInfo> semanticEdits,
             Func<SyntaxNode, SyntaxNode?>? syntaxMap,
-            HashSet<ISymbol>? processedSymbols,
+            HashSet<ISymbol> processedSymbols,
             CancellationToken cancellationToken)
         {
             // TODO: fails in VB on delegate parameter https://github.com/dotnet/roslyn/issues/53337
@@ -4253,31 +4504,32 @@ private void AnalyzeSymbolUpdate(
                 // In VB, when the type of a custom event changes, the parameters on the add and remove handlers also change
                 // but we can ignore them because we have already done what we need to the event declaration itself.
                 if (newSymbol.ContainingSymbol is IMethodSymbol { AssociatedSymbol: IEventSymbol associatedSymbol } &&
-                    processedSymbols?.Contains(associatedSymbol) == true)
+                    processedSymbols.Contains(associatedSymbol))
                 {
                     return;
                 }
 
-                AddParameterUpdateSemanticEdit(semanticEdits, (IParameterSymbol)oldSymbol, (IParameterSymbol)newSymbol, syntaxMap, reportDeleteAndInsertEdits: hasParameterTypeChange, processedSymbols, cancellationToken);
+                AddParameterUpdateSemanticEdit(semanticEdits, (IParameterSymbol)oldSymbol, (IParameterSymbol)newSymbol, newCompilation, syntaxMap, reportDeleteAndInsertEdits: hasParameterTypeChange, processedSymbols, cancellationToken);
             }
             else if (hasReturnTypeChange)
             {
                 var containingSymbolKey = SymbolKey.Create(oldSymbol.ContainingSymbol, cancellationToken);
-                AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Delete, oldSymbol, containingSymbolKey, syntaxMap, partialType: null, processedSymbols, cancellationToken);
-                AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Insert, newSymbol, containingSymbolKey: null, syntaxMap, partialType: null, processedSymbols, cancellationToken);
+                AddDeleteAndInsertEditsForMemberAndAccessors(semanticEdits, oldSymbol, newSymbol, containingSymbolKey, syntaxMap, processedSymbols, cancellationToken);
             }
             else if (hasAttributeChange || hasReturnTypeAttributeChange)
             {
-                AddCustomAttributeSemanticEdits(semanticEdits, oldSymbol, newSymbol, topMatch, syntaxMap, hasAttributeChange, hasReturnTypeAttributeChange, cancellationToken);
+                AddCustomAttributeSemanticEdits(semanticEdits, oldSymbol, newSymbol, newCompilation, topMatch, syntaxMap, processedSymbols, hasAttributeChange, hasReturnTypeAttributeChange, cancellationToken);
             }
         }
 
-        private static void AddCustomAttributeSemanticEdits(
+        private void AddCustomAttributeSemanticEdits(
             ArrayBuilder<SemanticEditInfo> semanticEdits,
             ISymbol oldSymbol,
             ISymbol newSymbol,
+            Compilation newCompilation,
             Match<SyntaxNode> topMatch,
             Func<SyntaxNode, SyntaxNode?>? syntaxMap,
+            HashSet<ISymbol> processedSymbols,
             bool hasAttributeChange,
             bool hasReturnTypeAttributeChange,
             CancellationToken cancellationToken)
@@ -4315,28 +4567,59 @@ private static void AddCustomAttributeSemanticEdits(
             }
             else if (newSymbol is IParameterSymbol newParameterSymbol)
             {
-                AddParameterUpdateSemanticEdit(semanticEdits, (IParameterSymbol)oldSymbol, newParameterSymbol, syntaxMap, reportDeleteAndInsertEdits: false, processedSymbols: null, cancellationToken);
+                AddParameterUpdateSemanticEdit(semanticEdits, (IParameterSymbol)oldSymbol, newParameterSymbol, newCompilation, syntaxMap, reportDeleteAndInsertEdits: false, processedSymbols, cancellationToken);
             }
         }
 
-        private static void AddParameterUpdateSemanticEdit(ArrayBuilder<SemanticEditInfo> semanticEdits, IParameterSymbol oldParameterSymbol, IParameterSymbol newParameterSymbol, Func<SyntaxNode, SyntaxNode?>? syntaxMap, bool reportDeleteAndInsertEdits, HashSet<ISymbol>? processedSymbols, CancellationToken cancellationToken)
+        private void AddParameterUpdateSemanticEdit(
+            ArrayBuilder<SemanticEditInfo> semanticEdits,
+            IParameterSymbol oldParameterSymbol,
+            IParameterSymbol newParameterSymbol,
+            Compilation newCompilation,
+            Func<SyntaxNode, SyntaxNode?>? syntaxMap,
+            bool reportDeleteAndInsertEdits,
+            HashSet<ISymbol> processedSymbols,
+            CancellationToken cancellationToken)
         {
-            var newContainingSymbol = newParameterSymbol.ContainingSymbol;
+            var newContainingMember = newParameterSymbol.ContainingSymbol;
 
             if (reportDeleteAndInsertEdits)
             {
-                var oldContainingSymbol = oldParameterSymbol.ContainingSymbol;
-                var containingSymbolKey = SymbolKey.Create(oldContainingSymbol.ContainingSymbol, cancellationToken);
-                AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Delete, oldContainingSymbol, containingSymbolKey, syntaxMap, partialType: null, processedSymbols, cancellationToken);
-                AddMemberOrAssociatedMemberSemanticEdits(semanticEdits, SemanticEditKind.Insert, newContainingSymbol, containingSymbolKey: null, syntaxMap, partialType: null, processedSymbols, cancellationToken);
+                var oldContainingMember = oldParameterSymbol.ContainingSymbol;
+                var containingSymbolKey = SymbolKey.Create(oldContainingMember.ContainingSymbol, cancellationToken);
+
+                AddDeleteAndInsertEditsForMemberAndAccessors(semanticEdits, oldContainingMember, newContainingMember, containingSymbolKey, syntaxMap, processedSymbols, cancellationToken);
+
+                // If primary constructor was replaced with non-primary (or vice versa) we wouldn't be processing a parameter update,
+                // but rather a delete and insert of the constructor symbol.
+                Debug.Assert(IsPrimaryConstructor(oldContainingMember, cancellationToken) == IsPrimaryConstructor(newContainingMember, cancellationToken));
+
+                if (oldContainingMember.ContainingType.IsRecord && newContainingMember.ContainingType.IsRecord && IsPrimaryConstructor(oldContainingMember, cancellationToken))
+                {
+                    var oldPrimaryConstructor = (IMethodSymbol)oldContainingMember;
+                    var newPrimaryConstructor = (IMethodSymbol)newContainingMember;
+
+                    // add delete and insert edits of synthesized properties:
+                    var oldSynthesizedProperty = GetPropertySynthesizedForRecordPrimaryConstructorParameter(oldParameterSymbol);
+                    var newSynthesizedProperty = GetPropertySynthesizedForRecordPrimaryConstructorParameter(newParameterSymbol);
+                    AddDeleteAndInsertEditsForMemberAndAccessors(semanticEdits, oldSynthesizedProperty, newSynthesizedProperty, containingSymbolKey, syntaxMap, processedSymbols, cancellationToken);
+
+                    // add delete and insert edits of synthesized deconstructor:
+                    var oldSynthesizedDeconstructor = oldPrimaryConstructor.GetMatchingDeconstructor();
+                    var newSynthesizedDeconstructor = newPrimaryConstructor.GetMatchingDeconstructor();
+                    AddDeleteAndInsertEditsForMemberAndAccessors(semanticEdits, oldSynthesizedDeconstructor, newSynthesizedDeconstructor, containingSymbolKey, syntaxMap, processedSymbols, cancellationToken);
+
+                    // add updates of synthesized methods:
+                    AddSynthesizedRecordMethodUpdatesForPropertyChange(semanticEdits, newCompilation, newContainingMember.ContainingType, cancellationToken);
+                }
             }
             else
             {
-                semanticEdits.Add(new SemanticEditInfo(SemanticEditKind.Update, SymbolKey.Create(newContainingSymbol, cancellationToken), syntaxMap, syntaxMapTree: null, partialType: null));
+                semanticEdits.Add(new SemanticEditInfo(SemanticEditKind.Update, SymbolKey.Create(newContainingMember, cancellationToken), syntaxMap, syntaxMapTree: null, partialType: null));
             }
 
             // attributes applied on parameters of a delegate are applied to both Invoke and BeginInvoke methods
-            if (newContainingSymbol.ContainingSymbol is INamedTypeSymbol { TypeKind: TypeKind.Delegate } newContainingDelegateType)
+            if (newContainingMember.ContainingType is INamedTypeSymbol { TypeKind: TypeKind.Delegate } newContainingDelegateType)
             {
                 Debug.Assert(reportDeleteAndInsertEdits == false);
                 AddDelegateBeginInvokeEdit(semanticEdits, newContainingDelegateType, syntaxMap, cancellationToken);
@@ -4568,7 +4851,7 @@ private bool CanAddNewMemberToExistingType(ISymbol newSymbol, EditAndContinueCap
                 requiredCapabilities |= EditAndContinueCapabilities.AddMethodToExistingType;
             }
 
-            if (newSymbol is IFieldSymbol || newSymbol is IPropertySymbol { DeclaringSyntaxReferences: [var syntaxRef] } && HasBackingField(syntaxRef.GetSyntax(cancellationToken)))
+            if (newSymbol is IFieldSymbol || newSymbol is IPropertySymbol { DeclaringSyntaxReferences: [_] } && HasBackingField(GetSymbolDeclarationSyntax(newSymbol, cancellationToken)))
             {
                 requiredCapabilities |= newSymbol.IsStatic ? EditAndContinueCapabilities.AddStaticFieldToExistingType : EditAndContinueCapabilities.AddInstanceFieldToExistingType;
             }
@@ -4592,58 +4875,66 @@ private static bool CanUpdateMemberBody(ISymbol oldSymbol, ISymbol newSymbol, Ed
             return true;
         }
 
-        private static void AddEditsForSynthesizedRecordMembers(Compilation compilation, INamedTypeSymbol recordType, ArrayBuilder<SemanticEditInfo> semanticEdits, CancellationToken cancellationToken)
+        /// <summary>
+        /// Adds edits for synthesized record members.
+        /// </summary>
+        private static void AddSynthesizedRecordMethodUpdatesForPropertyChange(
+            ArrayBuilder<SemanticEditInfo> semanticEdits,
+            Compilation compilation,
+            INamedTypeSymbol recordType,
+            CancellationToken cancellationToken)
         {
-            foreach (var member in GetRecordUpdatedSynthesizedMembers(compilation, recordType))
+            Debug.Assert(recordType.IsRecord);
+
+            foreach (var member in GetRecordUpdatedSynthesizedMethods(compilation, recordType))
             {
                 var symbolKey = SymbolKey.Create(member, cancellationToken);
                 semanticEdits.Add(new SemanticEditInfo(SemanticEditKind.Update, symbolKey, syntaxMap: null, syntaxMapTree: null, partialType: null));
             }
         }
 
-        private static IEnumerable<ISymbol> GetRecordUpdatedSynthesizedMembers(Compilation compilation, INamedTypeSymbol record)
+        private static IEnumerable<ISymbol> GetRecordUpdatedSynthesizedMethods(Compilation compilation, INamedTypeSymbol record)
         {
+            Debug.Assert(record.IsRecord);
+
             // All methods that are updated have well known names, and calling GetMembers(string) is
             // faster than enumerating.
 
-            // When a new field or property is added the PrintMembers, Equals(R) and GetHashCode() methods are updated
-            // We don't need to worry about Deconstruct because it only changes when a new positional parameter
-            // is added, and those are rude edits (due to adding a constructor parameter).
-            // We don't need to worry about the constructors as they are reported elsewhere.
-            // We have to use SingleOrDefault and check IsImplicitlyDeclared because the user can provide their
-            // own implementation of these methods, and edits to them are handled by normal processing.
+            // When a new field or property is added methods PrintMembers, Equals, GetHashCode and the copy-constructor may be updated.
+            // Some updates might not be strictly necessary but for simplicity we update all that are not explicitly declared.
+
+            // The primary constructor is deferred since it needs to be aggregated with initializer updates.
+
             var result = record.GetMembers(WellKnownMemberNames.PrintMembersMethodName)
-                .OfType<IMethodSymbol>()
-                .SingleOrDefault(m =>
-                    m.IsImplicitlyDeclared &&
-                    m.Parameters.Length == 1 &&
-                    SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, compilation.GetTypeByMetadataName(typeof(StringBuilder).FullName!)) &&
-                    SymbolEqualityComparer.Default.Equals(m.ReturnType, compilation.GetTypeByMetadataName(typeof(bool).FullName!)));
+                .FirstOrDefault(static (m, compilation) => m is IMethodSymbol { IsImplicitlyDeclared: true } method && HasPrintMembersSignature(method, compilation), compilation);
             if (result is not null)
             {
                 yield return result;
             }
 
             result = record.GetMembers(WellKnownMemberNames.ObjectEquals)
-                .OfType<IMethodSymbol>()
-                .SingleOrDefault(m =>
-                    m.IsImplicitlyDeclared &&
-                    m.Parameters.Length == 1 &&
-                    SymbolEqualityComparer.Default.Equals(m.Parameters[0].Type, m.ContainingType));
+                .FirstOrDefault(static m => m is IMethodSymbol { IsImplicitlyDeclared: true } method && HasIEquatableEqualsSignature(method));
             if (result is not null)
             {
                 yield return result;
             }
 
             result = record.GetMembers(WellKnownMemberNames.ObjectGetHashCode)
-               .OfType<IMethodSymbol>()
-               .SingleOrDefault(m =>
-                    m.IsImplicitlyDeclared &&
-                    m.Parameters.Length == 0);
+                .FirstOrDefault(static m => m is IMethodSymbol { IsImplicitlyDeclared: true } method && HasGetHashCodeSignature(method));
             if (result is not null)
             {
                 yield return result;
             }
+
+            // copy constructor
+            if (record.TypeKind == TypeKind.Class)
+            {
+                result = record.InstanceConstructors.SingleOrDefault(m => m.IsImplicitlyDeclared && m.IsCopyConstructor());
+                if (result is not null)
+                {
+                    yield return result;
+                }
+            }
         }
 
         private void ReportDeletedMemberRudeEdit(
@@ -4658,10 +4949,7 @@ private void ReportDeletedMemberRudeEdit(
             diagnostics.Add(new RudeEditDiagnostic(
                 rudeEditKind,
                 GetDiagnosticSpan(newNode, EditKind.Delete),
-                arguments: new[]
-                {
-                    string.Format(FeaturesResources.member_kind_and_name, GetDisplayName(oldSymbol), oldSymbol.ToDisplayString(s_unqualifiedMemberDisplayFormat))
-                }));
+                arguments: new[] { GetDisplayKindAndName(oldSymbol, fullyQualify: false) }));
         }
 
         private void ReportUpdateRudeEdit(ArrayBuilder<RudeEditDiagnostic> diagnostics, RudeEditKind rudeEdit, SyntaxNode newNode)
@@ -4676,7 +4964,7 @@ private void ReportUpdateRudeEdit(ArrayBuilder<RudeEditDiagnostic> diagnostics,
         private void ReportUpdateRudeEdit(ArrayBuilder<RudeEditDiagnostic> diagnostics, RudeEditKind rudeEdit, ISymbol newSymbol, SyntaxNode? newNode, CancellationToken cancellationToken)
         {
             var node = newNode ?? GetRudeEditDiagnosticNode(newSymbol, cancellationToken);
-            var span = (rudeEdit == RudeEditKind.ChangeImplicitMainReturnType) ? GetGlobalStatementDiagnosticSpan(node) : GetDiagnosticSpan(node, EditKind.Update);
+            var span = (rudeEdit == RudeEditKind.ChangeImplicitMainReturnType) ? GetGlobalStatementDiagnosticSpan(node, EditKind.Delete) : GetDiagnosticSpan(node, EditKind.Update);
 
             var arguments = rudeEdit switch
             {
@@ -4689,7 +4977,14 @@ RudeEditKind.GenericMethodUpdate or
                 RudeEditKind.ChangingReloadableTypeNotSupportedByRuntime
                     => new[] { CreateNewOnMetadataUpdateAttributeName },
 
-                _ => new[] { GetDisplayName(newSymbol) }
+                _ => new[]
+                {
+                    // Include member name if it is implicitly declared, otherwise it might not be obvious which member is being referred to.
+                    // TODO: newSymbol.ContainingSymbol.IsImplicitlyDeclared should not be needed https://github.com/dotnet/roslyn/issues/68510
+                    newSymbol.IsImplicitlyDeclared || newSymbol.ContainingSymbol is { IsImplicitlyDeclared: true, Kind: not SymbolKind.Namespace }
+                        ? GetDisplayKindAndName(newSymbol, fullyQualify: false)
+                        : GetDisplayName(newSymbol)
+                }
             };
 
             diagnostics.Add(new RudeEditDiagnostic(rudeEdit, span, node, arguments));
@@ -4707,14 +5002,15 @@ private void ReportUpdateRudeEdit(ArrayBuilder<RudeEditDiagnostic> diagnostics,
             }
         }
 
-        private static SyntaxNode GetRudeEditDiagnosticNode(ISymbol symbol, CancellationToken cancellationToken)
+        private SyntaxNode GetRudeEditDiagnosticNode(ISymbol symbol, CancellationToken cancellationToken)
         {
             var container = symbol;
             while (container != null)
             {
-                if (container.DeclaringSyntaxReferences.Length > 0)
+                // TODO: only one condition should be sufficient https://github.com/dotnet/roslyn/issues/68510
+                if (container.DeclaringSyntaxReferences.Length > 0 && !container.IsImplicitlyDeclared)
                 {
-                    return container.DeclaringSyntaxReferences[0].GetSyntax(cancellationToken);
+                    return GetSymbolDeclarationSyntax(container, cancellationToken);
                 }
 
                 container = container.ContainingSymbol;
@@ -4723,7 +5019,7 @@ private static SyntaxNode GetRudeEditDiagnosticNode(ISymbol symbol, Cancellation
             throw ExceptionUtilities.Unreachable();
         }
 
-        private static SyntaxNode GetDeleteRudeEditDiagnosticNode(ISymbol oldSymbol, Compilation newCompilation, CancellationToken cancellationToken)
+        private SyntaxNode GetDeleteRudeEditDiagnosticNode(ISymbol oldSymbol, Compilation newCompilation, CancellationToken cancellationToken)
         {
             var oldContainer = oldSymbol.ContainingSymbol;
             while (oldContainer != null)
@@ -4893,46 +5189,13 @@ private static bool HasExplicitOrSequentialLayout(
 
         #region Constructors and Initializers
 
-        /// <summary>
-        /// Called when a body of a constructor or an initializer of a member is updated or inserted.
-        /// </summary>
-        private static void DeferConstructorEdit(
-            INamedTypeSymbol oldType,
-            INamedTypeSymbol newType,
-            SyntaxNode? newDeclaration,
-            Func<SyntaxNode, SyntaxNode?>? syntaxMap,
-            bool isStatic,
-            ref PooledDictionary<INamedTypeSymbol, ConstructorEdit>? instanceConstructorEdits,
-            ref PooledDictionary<INamedTypeSymbol, ConstructorEdit>? staticConstructorEdits)
-        {
-            Dictionary<INamedTypeSymbol, ConstructorEdit> constructorEdits;
-            if (isStatic)
-            {
-                constructorEdits = staticConstructorEdits ??= PooledDictionary<INamedTypeSymbol, ConstructorEdit>.GetInstance();
-            }
-            else
-            {
-                constructorEdits = instanceConstructorEdits ??= PooledDictionary<INamedTypeSymbol, ConstructorEdit>.GetInstance();
-            }
-
-            if (!constructorEdits.TryGetValue(newType, out var constructorEdit))
-            {
-                constructorEdits.Add(newType, constructorEdit = new ConstructorEdit(oldType));
-            }
-
-            if (newDeclaration != null && !constructorEdit.ChangedDeclarations.ContainsKey(newDeclaration))
-            {
-                constructorEdit.ChangedDeclarations.Add(newDeclaration, syntaxMap);
-            }
-        }
-
         private void AddConstructorEdits(
-            IReadOnlyDictionary<INamedTypeSymbol, ConstructorEdit> updatedTypes,
+            IReadOnlyDictionary<INamedTypeSymbol, MemberInitializationUpdates> updatedTypes,
             Match<SyntaxNode> topMatch,
             SemanticModel? oldModel,
             Compilation oldCompilation,
             Compilation newCompilation,
-            Roslyn.Utilities.IReadOnlySet<ISymbol> processedSymbols,
+            HashSet<ISymbol> processedSymbols,
             EditAndContinueCapabilitiesGrantor capabilities,
             bool isStatic,
             [Out] ArrayBuilder<SemanticEditInfo> semanticEdits,
@@ -4946,8 +5209,10 @@ private void AddConstructorEdits(
             {
                 var oldType = updatesInCurrentDocument.OldType;
 
-                var anyInitializerUpdatesInCurrentDocument = updatesInCurrentDocument.ChangedDeclarations.Keys.Any(IsDeclarationWithInitializer);
+                var anyInitializerUpdatesInCurrentDocument = updatesInCurrentDocument.ChangedDeclarations.Keys.Any(IsDeclarationWithInitializer) || updatesInCurrentDocument.HasDeletedMemberInitializer;
                 var isPartialEdit = IsPartialEdit(oldType, newType, oldSyntaxTree, newSyntaxTree);
+                var typeKey = SymbolKey.Create(newType, cancellationToken);
+                var partialType = isPartialEdit ? typeKey : (SymbolKey?)null;
 
                 // Create a syntax map that aggregates syntax maps of the constructor body and all initializers in this document.
                 // Use syntax maps stored in update.ChangedDeclarations and fallback to 1:1 map for unchanged members.
@@ -4970,33 +5235,36 @@ private void AddConstructorEdits(
                         continue;
                     }
 
+                    if (newType.TypeKind != oldType.TypeKind || oldType.IsRecord != newType.IsRecord)
+                    {
+                        // rude edit has been reported when changing type kinds
+                        continue;
+                    }
+
+                    // Constructor that doesn't contain initializers had a corresponding semantic edit produced previously 
+                    // or was not edited. In either case we should not produce a semantic edit for it.
+                    if (!IsConstructorWithMemberInitializers(newCtor, cancellationToken))
+                    {
+                        continue;
+                    }
+
                     var newCtorKey = SymbolKey.Create(newCtor, cancellationToken);
 
                     var syntaxMapToUse = aggregateSyntaxMap;
 
                     SyntaxNode? newDeclaration = null;
-                    ISymbol? oldCtor;
+                    IMethodSymbol? oldCtor;
                     if (!newCtor.IsImplicitlyDeclared)
                     {
                         // Constructors have to have a single declaration syntax, they can't be partial
-                        newDeclaration = GetSymbolDeclarationSyntax(newCtor.DeclaringSyntaxReferences.Single(), cancellationToken);
-
-                        // Implicit record constructors are represented by the record declaration itself.
-                        var isPrimaryRecordConstructor = IsRecordDeclaration(newDeclaration);
-
-                        // Constructor that doesn't contain initializers had a corresponding semantic edit produced previously 
-                        // or was not edited. In either case we should not produce a semantic edit for it.
-                        if (!isPrimaryRecordConstructor && !IsConstructorWithMemberInitializers(newDeclaration))
-                        {
-                            continue;
-                        }
+                        newDeclaration = GetSymbolDeclarationSyntax(newCtor, cancellationToken);
 
                         // If no initializer updates were made in the type we only need to produce semantic edits for constructors
                         // whose body has been updated, otherwise we need to produce edits for all constructors that include initializers.
                         // If changes were made to initializers or constructors of a partial type in another document they will be merged
                         // when aggregating semantic edits from all changed documents. Rude edits resulting from those changes, if any, will
                         // be reported in the document they were made in.
-                        if (!isPrimaryRecordConstructor && !anyInitializerUpdatesInCurrentDocument && !updatesInCurrentDocument.ChangedDeclarations.ContainsKey(newDeclaration))
+                        if (!anyInitializerUpdatesInCurrentDocument && !updatesInCurrentDocument.ChangedDeclarations.ContainsKey(newDeclaration))
                         {
                             continue;
                         }
@@ -5004,14 +5272,14 @@ private void AddConstructorEdits(
                         // To avoid costly SymbolKey resolution we first try to match the constructor in the current document
                         // and special case parameter-less constructor.
 
-                        // In the case of records, newDeclaration will point to the record declaration, take the slow path.
-                        if (!isPrimaryRecordConstructor && topMatch.TryGetOldNode(newDeclaration, out var oldDeclaration))
+                        if (topMatch.TryGetOldNode(newDeclaration, out var oldDeclaration))
                         {
                             Contract.ThrowIfNull(oldModel);
-                            oldCtor = oldModel.GetDeclaredSymbol(oldDeclaration, cancellationToken);
-                            Contract.ThrowIfFalse(oldCtor is IMethodSymbol { MethodKind: MethodKind.Constructor or MethodKind.StaticConstructor });
+
+                            oldCtor = (IMethodSymbol)GetRequiredDeclaredSymbol(oldModel, oldDeclaration, cancellationToken);
+                            Contract.ThrowIfFalse(oldCtor is { MethodKind: MethodKind.Constructor or MethodKind.StaticConstructor });
                         }
-                        else if (!isPrimaryRecordConstructor && newCtor.Parameters.Length == 0)
+                        else if (newCtor.Parameters.Length == 0)
                         {
                             oldCtor = TryGetParameterlessConstructor(oldType, isStatic);
                         }
@@ -5022,7 +5290,7 @@ private void AddConstructorEdits(
                             // There may be semantic errors in the compilation that result in multiple candidates.
                             // Pick the first candidate.
 
-                            oldCtor = resolution.Symbol;
+                            oldCtor = (IMethodSymbol?)resolution.Symbol;
                         }
 
                         if (oldCtor == null && HasMemberInitializerContainingLambda(oldType, isStatic, ref lazyOldTypeHasMemberInitializerContainingLambda, cancellationToken))
@@ -5035,88 +5303,55 @@ private void AddConstructorEdits(
 
                         // Report an error if the updated constructor's declaration is in the current document 
                         // and its body edit is disallowed (e.g. contains stackalloc).
-                        if (oldCtor != null && newDeclaration.SyntaxTree == newSyntaxTree && anyInitializerUpdatesInCurrentDocument && !isPrimaryRecordConstructor)
+                        if (oldCtor != null && newDeclaration.SyntaxTree == newSyntaxTree && anyInitializerUpdatesInCurrentDocument)
                         {
-                            // attribute rude edit to one of the modified members
-                            var firstSpan = updatesInCurrentDocument.ChangedDeclarations.Keys.Where(IsDeclarationWithInitializer).Aggregate(
-                                (min: int.MaxValue, span: default(TextSpan)),
-                                (accumulate, node) => (node.SpanStart < accumulate.min) ? (node.SpanStart, node.Span) : accumulate).span;
-
                             var newBody = TryGetDeclarationBody(newDeclaration);
 
-                            Contract.ThrowIfNull(newBody);
-                            Contract.ThrowIfTrue(firstSpan.IsEmpty);
-                            ReportMemberOrLambdaBodyUpdateRudeEditsImpl(diagnostics, newDeclaration, newBody, firstSpan);
-                        }
+                            // If the declaration represents a primary constructor the body will be null.
+                            if (newBody != null)
+                            {
+                                // attribute rude edit to one of the modified members
+                                var firstSpan = updatesInCurrentDocument.ChangedDeclarations.Keys.Where(IsDeclarationWithInitializer).Aggregate(
+                                    (min: int.MaxValue, span: default(TextSpan)),
+                                    (accumulate, node) => (node.SpanStart < accumulate.min) ? (node.SpanStart, node.Span) : accumulate).span;
 
-                        // When explicitly implementing the copy constructor of a record the parameter name if the runtime doesn't support
-                        // updating parameters, otherwise the debugger would show the incorrect name in the autos/locals/watch window
-                        if (oldCtor != null &&
-                            !isPrimaryRecordConstructor &&
-                            oldCtor.DeclaringSyntaxReferences.Length == 0 &&
-                            newCtor.Parameters.Length == 1 &&
-                            newType.IsRecord &&
-                            oldCtor.GetParameters().First().Name != newCtor.GetParameters().First().Name &&
-                            !capabilities.Grant(EditAndContinueCapabilities.UpdateParameters))
-                        {
-                            diagnostics.Add(new RudeEditDiagnostic(
-                                RudeEditKind.ExplicitRecordMethodParameterNamesMustMatch,
-                                GetDiagnosticSpan(newDeclaration, EditKind.Update),
-                                arguments: new[] { oldCtor.ToDisplayString(SymbolDisplayFormats.NameFormat) }));
+                                // span may be empty if the only edits are deletes of members with initializers
+                                if (firstSpan.IsEmpty)
+                                {
+                                    Debug.Assert(updatesInCurrentDocument.HasDeletedMemberInitializer);
+                                    firstSpan = newDeclaration.Span;
+                                }
 
-                            continue;
+                                ReportMemberOrLambdaBodyUpdateRudeEditsImpl(diagnostics, newDeclaration, newBody, firstSpan);
+                            }
                         }
                     }
                     else
                     {
-                        if (newCtor.Parameters.Length == 1)
-                        {
-                            // New constructor is implicitly declared with a parameter, so its the copy constructor of a record
-                            Debug.Assert(oldType.IsRecord);
-                            Debug.Assert(newType.IsRecord);
-
-                            // We only need an edit for this if the number of properties or fields on the record has changed. Changes to
-                            // initializers, or whether the property is part of the primary constructor, will still come through this code
-                            // path because they need an edit to the other constructor, but not the copy construcor.
-                            if (oldType.GetMembers().OfType<IPropertySymbol>().Count() == newType.GetMembers().OfType<IPropertySymbol>().Count() &&
-                                oldType.GetMembers().OfType<IFieldSymbol>().Count() == newType.GetMembers().OfType<IFieldSymbol>().Count())
-                            {
-                                continue;
-                            }
+                        // New constructor contains initializers and is implicitly declared so it must be parameterless.
+                        Debug.Assert(newCtor.Parameters.IsEmpty);
 
-                            oldCtor = oldType.InstanceConstructors.Single(c => c.Parameters.Length == 1 && SymbolEqualityComparer.Default.Equals(c.Parameters[0].Type, c.ContainingType));
-                            // The copy constructor does not have a syntax map
-                            syntaxMapToUse = null;
-                            // Since there is no syntax map, we don't need to handle anything special to merge them for partial types.
-                            // The easiest way to do this is just to pretend this isn't a partial edit.
-                            isPartialEdit = false;
-                        }
-                        else
+                        oldCtor = TryGetParameterlessConstructor(oldType, isStatic);
+
+                        // Skip update if both old and new are implicitly declared and no initializer updates were made in current document.
+                        // If changes were made to initializers or constructors of a partial type in another document they will be merged
+                        // when aggregating semantic edits from all changed documents.
+                        if (!anyInitializerUpdatesInCurrentDocument && oldCtor is { IsImplicitlyDeclared: true })
                         {
-                            // New constructor is implicitly declared so it must be parameterless.
-                            //
-                            // Instance constructor:
-                            //   Its presence indicates there are no other instance constructors in the new type and therefore
-                            //   there must be a single parameterless instance constructor in the old type (constructors with parameters can't be removed).
-                            //
-                            // Static constructor:
-                            //    Static constructor is always parameterless and not implicitly generated if there are no static initializers.
-                            oldCtor = TryGetParameterlessConstructor(oldType, isStatic);
+                            continue;
                         }
-
-                        Contract.ThrowIfFalse(isStatic || oldCtor != null);
                     }
 
                     if (oldCtor != null)
                     {
-                        AnalyzeSymbolUpdate(oldCtor, newCtor, newDeclaration, newCompilation, topMatch, capabilities, diagnostics, semanticEdits, syntaxMapToUse, processedSymbols: null, cancellationToken);
+                        AnalyzeSymbolUpdate(oldCtor, newCtor, newDeclaration, newCompilation, topMatch, capabilities, diagnostics, semanticEdits, syntaxMapToUse, processedSymbols, cancellationToken);
 
                         semanticEdits.Add(new SemanticEditInfo(
                             SemanticEditKind.Update,
                             newCtorKey,
                             syntaxMapToUse,
                             syntaxMapTree: isPartialEdit ? newSyntaxTree : null,
-                            partialType: isPartialEdit ? SymbolKey.Create(newType, cancellationToken) : null));
+                            partialType: partialType));
                     }
                     else
                     {
@@ -5127,6 +5362,41 @@ private void AddConstructorEdits(
                             syntaxMapTree: null,
                             partialType: null));
                     }
+
+                    // primary record constructor updated to non-primary and vice versa:
+                    if (newType.IsRecord)
+                    {
+                        var oldCtorIsPrimary = oldCtor != null && IsPrimaryConstructor(oldCtor, cancellationToken);
+                        var newCtorIsPrimary = IsPrimaryConstructor(newCtor, cancellationToken);
+
+                        if (oldCtorIsPrimary != newCtorIsPrimary)
+                        {
+                            // Deconstructor:
+                            AddDeconstructorEdits(semanticEdits, oldCtor, newCtor, typeKey, oldCompilation, newCompilation, syntaxMap: null, processedSymbols, isParameterDelete: newCtorIsPrimary, cancellationToken);
+
+                            // Synthesized method updates:
+                            AddSynthesizedRecordMethodUpdatesForPropertyChange(semanticEdits, newCompilation, newCtor.ContainingType, cancellationToken);
+                        }
+                    }
+                }
+
+                if (!isStatic && oldType.TypeKind == TypeKind.Class && newType.TypeKind == TypeKind.Class)
+                {
+                    // Adding the first instance constructor with parameters suppresses synthesized default constructor.
+                    if (oldType.HasSynthesizedDefaultConstructor() && !newType.HasSynthesizedDefaultConstructor())
+                    {
+                        semanticEdits.Add(new SemanticEditInfo(
+                            SemanticEditKind.Delete,
+                            SymbolKey.Create(oldType.InstanceConstructors.Single(c => c.Parameters is []), cancellationToken),
+                            syntaxMap: null,
+                            syntaxMapTree: null,
+                            partialType: partialType,
+                            deletedSymbolContainer: typeKey));
+                    }
+
+                    // Removing the last instance constructor with parameters inserts synthesized default constructor.
+                    // We don't need to add an explicit semantic edit for synthesized members though since the compiler
+                    // emits them automatically.
                 }
             }
         }
@@ -5149,7 +5419,7 @@ private bool HasMemberInitializerContainingLambda(INamedTypeSymbol type, bool is
                     (member.Kind == SymbolKind.Field || member.Kind == SymbolKind.Property) &&
                     member.DeclaringSyntaxReferences.Length > 0) // skip generated fields (e.g. VB auto-property backing fields)
                 {
-                    var syntax = GetSymbolDeclarationSyntax(member.DeclaringSyntaxReferences.Single(), cancellationToken);
+                    var syntax = GetSymbolDeclarationSyntax(member, cancellationToken);
                     if (IsDeclarationWithInitializer(syntax) && ContainsLambda(syntax))
                     {
                         return true;
@@ -5160,7 +5430,7 @@ private bool HasMemberInitializerContainingLambda(INamedTypeSymbol type, bool is
             return false;
         }
 
-        private static ISymbol? TryGetParameterlessConstructor(INamedTypeSymbol type, bool isStatic)
+        private static IMethodSymbol? TryGetParameterlessConstructor(INamedTypeSymbol type, bool isStatic)
         {
             var oldCtors = isStatic ? type.StaticConstructors : type.InstanceConstructors;
             if (isStatic)
@@ -5192,9 +5462,11 @@ private void ReportLambdaAndClosureRudeEdits(
             SemanticModel oldModel,
             ISymbol oldMember,
             SyntaxNode oldMemberBody,
+            SyntaxNode oldDeclaration,
             SemanticModel newModel,
-            SyntaxNode newMemberBody,
             ISymbol newMember,
+            SyntaxNode newMemberBody,
+            SyntaxNode newDeclaration,
             Match<SyntaxNode> memberBodyMatch,
             IReadOnlyDictionary<SyntaxNode, LambdaInfo>? matchedLambdas,
             BidirectionalMap<SyntaxNode> map,
@@ -5329,9 +5601,12 @@ select clausesByQuery.First())
 
             CalculateCapturedVariablesMaps(
                 oldCaptures,
+                oldMember,
+                oldDeclaration,
                 oldMemberBody,
                 newCaptures,
                 newMember,
+                newDeclaration,
                 newMemberBody,
                 map,
                 reverseCapturesMap,
@@ -5621,7 +5896,7 @@ private void ReportMultiScopeCaptures(
                         }
                         else
                         {
-                            errorSpan = newCaptures[reverseCapturesMap.IndexOf(i)].Locations.Single().SourceSpan;
+                            errorSpan = GetSymbolLocationSpan(newCaptures[reverseCapturesMap.IndexOf(i)], cancellationToken);
                             rudeEdit = RudeEditKind.DeleteLambdaWithMultiScopeCapture;
                         }
 
@@ -5672,51 +5947,85 @@ private static void BuildIndex<TKey>(Dictionary<TKey, int> index, ImmutableArray
         }
 
         /// <summary>
-        /// Returns node that represents a declaration of the symbol whose <paramref name="reference"/> is passed in.
+        /// Returns node that represents a declaration of the symbol.
         /// </summary>
-        protected abstract SyntaxNode GetSymbolDeclarationSyntax(SyntaxReference reference, CancellationToken cancellationToken);
+        protected abstract SyntaxNode GetSymbolDeclarationSyntax(ISymbol symbol, Func<ImmutableArray<SyntaxReference>, SyntaxReference> selector, CancellationToken cancellationToken);
+
+        protected SyntaxNode GetSymbolDeclarationSyntax(ISymbol symbol, CancellationToken cancellationToken)
+            => GetSymbolDeclarationSyntax(symbol, selector: System.Linq.ImmutableArrayExtensions.First, cancellationToken);
 
-        private static TextSpan GetThisParameterDiagnosticSpan(ISymbol member)
-            => member.Locations.First().SourceSpan;
+        protected abstract ISymbol? GetDeclaredSymbol(SemanticModel model, SyntaxNode declaration, CancellationToken cancellationToken);
+
+        protected ISymbol GetRequiredDeclaredSymbol(SemanticModel model, SyntaxNode declaration, CancellationToken cancellationToken)
+        {
+            var symbol = GetDeclaredSymbol(model, declaration, cancellationToken);
+            Contract.ThrowIfNull(symbol);
+            return symbol;
+        }
 
-        private static TextSpan GetVariableDiagnosticSpan(ISymbol local)
+        private TextSpan GetSymbolLocationSpan(ISymbol symbol, CancellationToken cancellationToken)
         {
             // Note that in VB implicit value parameter in property setter doesn't have a location.
             // In C# its location is the location of the setter.
             // See https://github.com/dotnet/roslyn/issues/14273
-            return local.Locations.FirstOrDefault()?.SourceSpan ?? local.ContainingSymbol.Locations.First().SourceSpan;
+            return IsGlobalMain(symbol) ? GetGlobalStatementDiagnosticSpan(GetSymbolDeclarationSyntax(symbol, cancellationToken), EditKind.Update) :
+                   symbol is IParameterSymbol && IsGlobalMain(symbol.ContainingSymbol) ? GetGlobalStatementDiagnosticSpan(GetSymbolDeclarationSyntax(symbol.ContainingSymbol, cancellationToken), EditKind.Update) :
+                   symbol.Locations.FirstOrDefault()?.SourceSpan ?? symbol.ContainingSymbol.Locations.First().SourceSpan;
         }
 
-        private static (SyntaxNode? Node, int Ordinal) GetParameterKey(IParameterSymbol parameter, CancellationToken cancellationToken)
+        private CapturedParameterKey GetParameterKey(IParameterSymbol parameter, CancellationToken cancellationToken)
         {
-            var containingLambda = parameter.ContainingSymbol as IMethodSymbol;
-            if (containingLambda?.MethodKind is MethodKind.LambdaMethod or MethodKind.LocalFunction)
+            Debug.Assert(!parameter.IsThis);
+
+            if (parameter.IsImplicitValueParameter())
             {
-                var oldContainingLambdaSyntax = containingLambda.DeclaringSyntaxReferences.Single().GetSyntax(cancellationToken);
-                return (oldContainingLambdaSyntax, parameter.Ordinal);
+                return new CapturedParameterKey(ParameterKind.Value);
             }
-            else
+
+            if (IsGlobalMain(parameter.ContainingSymbol))
             {
-                return (Node: null, parameter.Ordinal);
+                return new CapturedParameterKey(ParameterKind.TopLevelMainArgs);
             }
-        }
 
-        private static bool TryMapParameter((SyntaxNode? Node, int Ordinal) parameterKey, IReadOnlyDictionary<SyntaxNode, SyntaxNode> map, out (SyntaxNode? Node, int Ordinal) mappedParameterKey)
-        {
-            var containingLambdaSyntax = parameterKey.Node;
+            var lambda = parameter.ContainingSymbol is IMethodSymbol { MethodKind: MethodKind.LambdaMethod or MethodKind.LocalFunction } containingLambda ?
+                GetSymbolDeclarationSyntax(containingLambda, cancellationToken) : null;
 
-            if (containingLambdaSyntax == null)
+            // Indexer parameters in the getter/setter are implicitly declared.
+            // We need to find the corresponding parameter of the indexer itself.
+            if (parameter is { IsImplicitlyDeclared: true, ContainingSymbol: IMethodSymbol { AssociatedSymbol: { } associatedSymbol } })
             {
-                // method parameter: no syntax, same ordinal (can't change since method signatures must match)
-                mappedParameterKey = parameterKey;
-                return true;
+                parameter = associatedSymbol.GetParameters().Single(p => p.Name == parameter.Name);
             }
 
-            if (map.TryGetValue(containingLambdaSyntax, out var mappedContainingLambdaSyntax))
+            return new CapturedParameterKey(ParameterKind.Explicit, GetSymbolDeclarationSyntax(parameter, cancellationToken), lambda);
+        }
+
+        private static bool TryMapParameter(
+            CapturedParameterKey parameterKey,
+            IReadOnlyDictionary<SyntaxNode, SyntaxNode>? parameterMap,
+            IReadOnlyDictionary<SyntaxNode, SyntaxNode> bodyMap,
+            out CapturedParameterKey mappedParameterKey)
+        {
+            if (parameterKey.ContainingLambda == null)
             {
-                // parameter of an existing lambda: same ordinal (can't change since lambda signatures must match), 
-                mappedParameterKey = (mappedContainingLambdaSyntax, parameterKey.Ordinal);
-                return true;
+                // method or primary constructor parameter:
+                SyntaxNode? mappedParameter = null;
+                if (parameterKey.Syntax == null || parameterMap?.TryGetValue(parameterKey.Syntax, out mappedParameter) == true)
+                {
+                    mappedParameterKey = parameterKey with { Syntax = mappedParameter };
+                    return true;
+                }
+            }
+            else if (bodyMap.TryGetValue(parameterKey.ContainingLambda, out var mappedContainingLambdaSyntax))
+            {
+                // lambda or local function parameter:
+                Debug.Assert(parameterKey.Syntax != null);
+
+                if (bodyMap.TryGetValue(parameterKey.Syntax, out var mappedParameter))
+                {
+                    mappedParameterKey = parameterKey with { Syntax = mappedParameter, ContainingLambda = mappedContainingLambdaSyntax };
+                    return true;
+                }
             }
 
             // no mapping
@@ -5724,13 +6033,25 @@ private static bool TryMapParameter((SyntaxNode? Node, int Ordinal) parameterKey
             return false;
         }
 
+        private enum ParameterKind
+        {
+            Explicit,
+            Value,
+            TopLevelMainArgs
+        }
+
+        private readonly record struct CapturedParameterKey(ParameterKind Kind, SyntaxNode? Syntax = null, SyntaxNode? ContainingLambda = null);
+
         private void CalculateCapturedVariablesMaps(
             ImmutableArray<ISymbol> oldCaptures,
+            ISymbol oldMember,
+            SyntaxNode oldDeclaration,
             SyntaxNode oldMemberBody,
             ImmutableArray<ISymbol> newCaptures,
             ISymbol newMember,
+            SyntaxNode newDeclaration,
             SyntaxNode newMemberBody,
-            BidirectionalMap<SyntaxNode> map,
+            BidirectionalMap<SyntaxNode> bodyMap,
             [Out] ArrayBuilder<int> reverseCapturesMap,                  // {new capture index -> old capture index}
             [Out] ArrayBuilder<SyntaxNode?> newCapturesToClosureScopes,  // {new capture index -> new closure scope}
             [Out] ArrayBuilder<SyntaxNode?> oldCapturesToClosureScopes,  // {old capture index -> old closure scope}
@@ -5740,6 +6061,21 @@ private void CalculateCapturedVariablesMaps(
         {
             hasErrors = false;
 
+            var parameterMap = ComputeParameterMap(oldDeclaration, newDeclaration);
+
+            var oldEncompassingPrimaryConstructor = GetEncompassingPrimaryConstructor(oldDeclaration, oldMember, cancellationToken);
+            var newEncompassingPrimaryConstructor = GetEncompassingPrimaryConstructor(newDeclaration, newMember, cancellationToken);
+            if (oldEncompassingPrimaryConstructor != null && newEncompassingPrimaryConstructor != null)
+            {
+                var primaryParameterMap = ComputeParameterMap(
+                    GetSymbolDeclarationSyntax(oldEncompassingPrimaryConstructor, cancellationToken),
+                    GetSymbolDeclarationSyntax(newEncompassingPrimaryConstructor, cancellationToken));
+
+                Contract.ThrowIfNull(primaryParameterMap);
+
+                parameterMap = (parameterMap != null) ? parameterMap.Value.With(primaryParameterMap.Value) : primaryParameterMap;
+            }
+
             // Validate that all variables that are/were captured in the new/old body were captured in 
             // the old/new one and their type and scope haven't changed. 
             //
@@ -5769,20 +6105,31 @@ private void CalculateCapturedVariablesMaps(
             //   the closure tree of the previous version and then map 
             //   closure scopes in the new version to the previous ones, keeping empty closures around.
 
-            using var _1 = PooledDictionary<SyntaxNode, int>.GetInstance(out var oldLocalCapturesBySyntax);
-            using var _2 = PooledDictionary<(SyntaxNode? Node, int Ordinal), int>.GetInstance(out var oldParameterCapturesByLambdaAndOrdinal);
+            using var _1 = PooledDictionary<SyntaxNode, int>.GetInstance(out var oldLocalCaptures);
+            using var _2 = PooledDictionary<CapturedParameterKey, int>.GetInstance(out var oldParameterCaptures);
+
+            IParameterSymbol? oldCapturedThisParameter = null;
+            IParameterSymbol? newCapturedThisParameter = null;
 
             for (var i = 0; i < oldCaptures.Length; i++)
             {
                 var oldCapture = oldCaptures[i];
 
-                if (oldCapture.Kind == SymbolKind.Parameter)
+                if (oldCapture is IParameterSymbol oldParameterCapture)
                 {
-                    oldParameterCapturesByLambdaAndOrdinal.Add(GetParameterKey((IParameterSymbol)oldCapture, cancellationToken), i);
+                    // Primary constructor parameter is accessed via "this" from non-primary constructor.
+                    if (oldParameterCapture.IsThis || oldEncompassingPrimaryConstructor is null && IsPrimaryConstructor(oldCapture.ContainingSymbol, cancellationToken))
+                    {
+                        oldCapturedThisParameter ??= oldParameterCapture;
+                    }
+                    else
+                    {
+                        oldParameterCaptures.Add(GetParameterKey(oldParameterCapture, cancellationToken), i);
+                    }
                 }
                 else
                 {
-                    oldLocalCapturesBySyntax.Add(oldCapture.DeclaringSyntaxReferences.Single().GetSyntax(cancellationToken), i);
+                    oldLocalCaptures.Add(GetSymbolDeclarationSyntax(oldCapture, cancellationToken), i);
                 }
             }
 
@@ -5791,18 +6138,23 @@ private void CalculateCapturedVariablesMaps(
                 var newCapture = newCaptures[newCaptureIndex];
                 int oldCaptureIndex;
 
-                if (newCapture.Kind == SymbolKind.Parameter)
+                if (newCapture is IParameterSymbol newParameterCapture)
                 {
-                    var newParameterCapture = (IParameterSymbol)newCapture;
+                    if (newParameterCapture.IsThis || newEncompassingPrimaryConstructor is null && IsPrimaryConstructor(newCapture.ContainingSymbol, cancellationToken))
+                    {
+                        newCapturedThisParameter ??= newParameterCapture;
+                        continue;
+                    }
+
                     var newParameterKey = GetParameterKey(newParameterCapture, cancellationToken);
-                    if (!TryMapParameter(newParameterKey, map.Reverse, out var oldParameterKey) ||
-                        !oldParameterCapturesByLambdaAndOrdinal.TryGetValue(oldParameterKey, out oldCaptureIndex))
+                    if (!TryMapParameter(newParameterKey, parameterMap?.Reverse, bodyMap.Reverse, out var oldParameterKey) ||
+                        !oldParameterCaptures.TryGetValue(oldParameterKey, out oldCaptureIndex))
                     {
                         // parameter has not been captured prior the edit:
                         diagnostics.Add(new RudeEditDiagnostic(
                             RudeEditKind.CapturingVariable,
-                            GetVariableDiagnosticSpan(newCapture),
-                            null,
+                            GetSymbolLocationSpan(newCapture, cancellationToken),
+                            node: null,
                             new[] { newCapture.Name }));
 
                         hasErrors = true;
@@ -5811,20 +6163,20 @@ private void CalculateCapturedVariablesMaps(
 
                     // Remove the old parameter capture so that at the end we can use this hashset 
                     // to identify old captures that don't have a corresponding capture in the new version:
-                    oldParameterCapturesByLambdaAndOrdinal.Remove(oldParameterKey);
+                    oldParameterCaptures.Remove(oldParameterKey);
                 }
                 else
                 {
-                    var newCaptureSyntax = newCapture.DeclaringSyntaxReferences.Single().GetSyntax(cancellationToken);
+                    var newCaptureSyntax = GetSymbolDeclarationSyntax(newCapture, cancellationToken);
 
                     // variable doesn't exists in the old method or has not been captured prior the edit:
-                    if (!map.Reverse.TryGetValue(newCaptureSyntax, out var mappedOldSyntax) ||
-                        !oldLocalCapturesBySyntax.TryGetValue(mappedOldSyntax, out oldCaptureIndex))
+                    if (!bodyMap.Reverse.TryGetValue(newCaptureSyntax, out var mappedOldSyntax) ||
+                        !oldLocalCaptures.TryGetValue(mappedOldSyntax, out oldCaptureIndex))
                     {
                         diagnostics.Add(new RudeEditDiagnostic(
                             RudeEditKind.CapturingVariable,
-                            newCapture.Locations.First().SourceSpan,
-                            null,
+                            GetSymbolLocationSpan(newCapture, cancellationToken),
+                            node: null,
                             new[] { newCapture.Name }));
 
                         hasErrors = true;
@@ -5833,22 +6185,14 @@ private void CalculateCapturedVariablesMaps(
 
                     // Remove the old capture so that at the end we can use this hashset 
                     // to identify old captures that don't have a corresponding capture in the new version:
-                    oldLocalCapturesBySyntax.Remove(mappedOldSyntax);
+                    oldLocalCaptures.Remove(mappedOldSyntax);
                 }
 
                 reverseCapturesMap[newCaptureIndex] = oldCaptureIndex;
 
-                // the type and scope of parameters can't change
-                if (newCapture.Kind == SymbolKind.Parameter)
-                {
-                    continue;
-                }
-
                 var oldCapture = oldCaptures[oldCaptureIndex];
 
-                // Parameter capture can't be changed to local capture and vice versa
-                // because parameters can't be introduced or deleted during EnC 
-                // (we checked above for changes in lambda signatures).
+                // If new parameter/local capture and does not have a corresponding old parameter/local capture a rude edit is reported above.
                 // Also range variables can't be mapped to other variables since they have 
                 // different kinds of declarator syntax nodes.
                 Debug.Assert(oldCapture.Kind == newCapture.Kind);
@@ -5872,7 +6216,7 @@ private void CalculateCapturedVariablesMaps(
                 {
                     diagnostics.Add(new RudeEditDiagnostic(
                         RudeEditKind.RenamingCapturedVariable,
-                        newCapture.Locations.First().SourceSpan,
+                        GetSymbolLocationSpan(newCapture, cancellationToken),
                         null,
                         new[] { oldCapture.Name, newCapture.Name }));
 
@@ -5881,95 +6225,105 @@ private void CalculateCapturedVariablesMaps(
                 }
 
                 // type check
-                var oldTypeOpt = GetType(oldCapture);
-                var newTypeOpt = GetType(newCapture);
+                var oldType = GetType(oldCapture);
+                var newType = GetType(newCapture);
 
-                if (!TypesEquivalent(oldTypeOpt, newTypeOpt, exact: false))
+                if (!TypesEquivalent(oldType, newType, exact: false))
                 {
                     diagnostics.Add(new RudeEditDiagnostic(
                         RudeEditKind.ChangingCapturedVariableType,
-                        GetVariableDiagnosticSpan(newCapture),
-                        null,
-                        new[] { newCapture.Name, oldTypeOpt.ToDisplayString(ErrorDisplayFormat) }));
+                        GetSymbolLocationSpan(newCapture, cancellationToken),
+                        node: null,
+                        new[] { newCapture.Name, oldType.ToDisplayString(ErrorDisplayFormat) }));
 
                     hasErrors = true;
                     continue;
                 }
 
-                // scope check:
-                var oldScopeOpt = GetCapturedVariableScope(oldCapture, oldMemberBody, cancellationToken);
-                var newScopeOpt = GetCapturedVariableScope(newCapture, newMemberBody, cancellationToken);
-                if (!AreEquivalentClosureScopes(oldScopeOpt, newScopeOpt, map.Reverse))
+                // scope check for local variables (parameters can't change scope):
+                if (oldCapture.Kind != SymbolKind.Parameter)
                 {
-                    diagnostics.Add(new RudeEditDiagnostic(
-                        RudeEditKind.ChangingCapturedVariableScope,
-                        GetVariableDiagnosticSpan(newCapture),
-                        null,
-                        new[] { newCapture.Name }));
+                    var oldScope = GetCapturedVariableScope(oldCapture, oldMemberBody, cancellationToken);
+                    var newScope = GetCapturedVariableScope(newCapture, newMemberBody, cancellationToken);
+                    if (!AreEquivalentClosureScopes(oldScope, newScope, bodyMap.Reverse))
+                    {
+                        diagnostics.Add(new RudeEditDiagnostic(
+                            RudeEditKind.ChangingCapturedVariableScope,
+                            GetSymbolLocationSpan(newCapture, cancellationToken),
+                            node: null,
+                            new[] { newCapture.Name }));
 
-                    hasErrors = true;
-                    continue;
+                        hasErrors = true;
+                        continue;
+                    }
+
+                    newCapturesToClosureScopes[newCaptureIndex] = newScope;
+                    oldCapturesToClosureScopes[oldCaptureIndex] = oldScope;
+                }
+            }
+
+            if (oldCapturedThisParameter is null != newCapturedThisParameter is null)
+            {
+                if (oldCapturedThisParameter is null)
+                {
+                    Contract.ThrowIfNull(newCapturedThisParameter);
+
+                    diagnostics.Add(new RudeEditDiagnostic(
+                        RudeEditKind.CapturingVariable,
+                        GetSymbolLocationSpan(newCapturedThisParameter, cancellationToken),
+                        node: null,
+                        new[] { newCapturedThisParameter.Name }));
+                }
+                else
+                {
+                    diagnostics.Add(new RudeEditDiagnostic(
+                        RudeEditKind.NotCapturingVariable,
+                        GetSymbolLocationSpan(newMember, cancellationToken),
+                        node: null,
+                        new[] { oldCapturedThisParameter.Name }));
                 }
 
-                newCapturesToClosureScopes[newCaptureIndex] = newScopeOpt;
-                oldCapturesToClosureScopes[oldCaptureIndex] = oldScopeOpt;
+                hasErrors = true;
             }
 
-            // What's left in oldCapturesBySyntax are captured variables in the previous version
+            // What's left in old*Captures are captured variables in the previous version
             // that have no corresponding captured variables in the new version. 
             // Report a rude edit for all such variables.
 
-            if (oldParameterCapturesByLambdaAndOrdinal.Count > 0)
+            if (oldParameterCaptures.Count > 0)
             {
-                // syntax-less parameters are not included:
-                var newMemberParametersWithSyntax = newMember.GetParameters();
-
                 // uncaptured parameters:
-                foreach (var ((oldContainingLambdaSyntax, ordinal), oldCaptureIndex) in oldParameterCapturesByLambdaAndOrdinal)
+                foreach (var ((oldParameterKind, oldParameterSyntax, oldContainingLambdaSyntax), oldCaptureIndex) in oldParameterCaptures)
                 {
-                    var oldCapture = oldCaptures[oldCaptureIndex];
-
-                    TextSpan span;
-                    if (ordinal < 0)
-                    {
-                        // this parameter:
-                        span = GetThisParameterDiagnosticSpan(newMember);
-                    }
-                    else if (oldContainingLambdaSyntax != null)
-                    {
-                        // lambda:
-                        span = GetLambdaParameterDiagnosticSpan(oldContainingLambdaSyntax, ordinal);
-                    }
-                    else if (oldCapture.IsImplicitValueParameter())
-                    {
-                        // value parameter of a property/indexer setter, event adder/remover:
-                        span = newMember.Locations.First().SourceSpan;
-                    }
-                    else
-                    {
-                        // method or property:
-                        span = GetVariableDiagnosticSpan(newMemberParametersWithSyntax[ordinal]);
-                    }
-
                     diagnostics.Add(new RudeEditDiagnostic(
                         RudeEditKind.NotCapturingVariable,
-                        span,
-                        null,
-                        new[] { oldCapture.Name }));
+                        oldParameterKind switch
+                        {
+                            ParameterKind.Explicit =>
+                                // Try to map the parameter from old to new syntax using either the member parameter map or the body map (for lambda parameters).
+                                // If the parameter doesn't exist in the new source show the error at the containing lambda or member location.
+                                parameterMap?.Forward.TryGetValue(oldParameterSyntax!, out var newParameterSyntax) == true ? GetDiagnosticSpan(newParameterSyntax, EditKind.Update) :
+                                bodyMap.Forward.TryGetValue(oldParameterSyntax!, out newParameterSyntax) ? GetDiagnosticSpan(newParameterSyntax, EditKind.Update) :
+                                oldContainingLambdaSyntax != null && bodyMap.Forward.TryGetValue(oldContainingLambdaSyntax, out var newContainingLambdaSyntax) ? GetDiagnosticSpan(newContainingLambdaSyntax, EditKind.Update) :
+                                GetSymbolLocationSpan(newMember, cancellationToken),
+                            _ => GetSymbolLocationSpan(newMember, cancellationToken),
+                        },
+                        node: null,
+                        new[] { oldCaptures[oldCaptureIndex].Name }));
                 }
 
                 hasErrors = true;
             }
 
-            if (oldLocalCapturesBySyntax.Count > 0)
+            if (oldLocalCaptures.Count > 0)
             {
                 // uncaptured or deleted variables:
-                foreach (var entry in oldLocalCapturesBySyntax)
+                foreach (var entry in oldLocalCaptures)
                 {
                     var oldCaptureNode = entry.Key;
                     var oldCaptureIndex = entry.Value;
                     var name = oldCaptures[oldCaptureIndex].Name;
-                    if (map.Forward.TryGetValue(oldCaptureNode, out var newCaptureNode))
+                    if (bodyMap.Forward.TryGetValue(oldCaptureNode, out var newCaptureNode))
                     {
                         diagnostics.Add(new RudeEditDiagnostic(
                             RudeEditKind.NotCapturingVariable,
@@ -5981,7 +6335,7 @@ private void CalculateCapturedVariablesMaps(
                     {
                         diagnostics.Add(new RudeEditDiagnostic(
                             RudeEditKind.DeletingCapturedVariable,
-                            GetDeletedNodeDiagnosticSpan(map.Forward, oldCaptureNode),
+                            GetDeletedNodeDiagnosticSpan(bodyMap.Forward, oldCaptureNode),
                             null,
                             new[] { name }));
                     }
@@ -6078,9 +6432,9 @@ private SyntaxNode GetCapturedVariableScope(ISymbol localOrParameter, SyntaxNode
                 var member = localOrParameter.ContainingSymbol;
 
                 // lambda parameters and C# constructor parameters are lifted to their own scope:
-                if ((member as IMethodSymbol)?.MethodKind == MethodKind.AnonymousFunction || HasParameterClosureScope(member))
+                if (member is IMethodSymbol { MethodKind: MethodKind.AnonymousFunction } || HasParameterClosureScope(member))
                 {
-                    var result = localOrParameter.DeclaringSyntaxReferences.Single().GetSyntax(cancellationToken);
+                    var result = GetSymbolDeclarationSyntax(localOrParameter, cancellationToken);
                     Debug.Assert(IsLambda(result));
                     return result;
                 }
@@ -6088,7 +6442,7 @@ private SyntaxNode GetCapturedVariableScope(ISymbol localOrParameter, SyntaxNode
                 return memberBody;
             }
 
-            var node = localOrParameter.DeclaringSyntaxReferences.Single().GetSyntax(cancellationToken);
+            var node = GetSymbolDeclarationSyntax(localOrParameter, cancellationToken);
             while (true)
             {
                 RoslynDebug.Assert(node is object);
@@ -6255,6 +6609,98 @@ private bool InGenericLocalContext(SyntaxNode node, SyntaxNode containingMemberB
             return false;
         }
 
+        public IMethodSymbol? GetPrimaryConstructor(INamedTypeSymbol typeSymbol, CancellationToken cancellationToken)
+            => typeSymbol.InstanceConstructors.FirstOrDefault(IsPrimaryConstructor, cancellationToken);
+
+        // TODO: should be compiler API: https://github.com/dotnet/roslyn/issues/53092
+        public bool IsPrimaryConstructor(ISymbol symbol, CancellationToken cancellationToken)
+            => symbol is IMethodSymbol { IsStatic: false, MethodKind: MethodKind.Constructor, DeclaringSyntaxReferences: [_] } && IsPrimaryConstructorDeclaration(GetSymbolDeclarationSyntax(symbol, cancellationToken));
+
+        /// <summary>
+        /// True if <paramref name="symbol"/> is a property or a field whose name matches one of the primary constructor parameter names.
+        /// TODO: should be compiler API: https://github.com/dotnet/roslyn/issues/54286
+        /// </summary>
+        public bool IsPrimaryConstructorParameterMatchingSymbol(ISymbol symbol, CancellationToken cancellationToken)
+            => symbol is { IsStatic: false } and (IPropertySymbol or IFieldSymbol) &&
+                GetPrimaryConstructor(symbol.ContainingType, cancellationToken) is { } primaryCtor &&
+                primaryCtor.Parameters.Any(static (parameter, name) => parameter.Name == name, symbol.Name);
+
+        /// <summary>
+        /// Primary constructor that the <paramref name="symbol"/> participates in (if any),
+        /// i.e. the <paramref name="symbol"/> itself if it is a primary constructor,
+        /// or the primary constructor the member initializer of <paramref name="symbol"/> contributes to.
+        /// </summary>
+        public IMethodSymbol? GetEncompassingPrimaryConstructor(SyntaxNode declaration, ISymbol symbol, CancellationToken cancellationToken)
+            => IsPrimaryConstructorDeclaration(declaration) ? (IMethodSymbol)symbol :
+               IsDeclarationWithInitializer(declaration) ? symbol.ContainingType.InstanceConstructors.FirstOrDefault(IsPrimaryConstructor, cancellationToken) :
+               null;
+
+        private static IPropertySymbol? GetPropertySynthesizedForRecordPrimaryConstructorParameter(IParameterSymbol parameter)
+            => (IPropertySymbol?)parameter.ContainingType.GetMembers(parameter.Name)
+                .FirstOrDefault(static m => m is IPropertySymbol { IsImplicitlyDeclared: false, GetMethod.IsImplicitlyDeclared: true, SetMethod.IsImplicitlyDeclared: true });
+
+        private static bool SymbolPresenceAffectsSynthesizedRecordMembers(ISymbol symbol)
+            => symbol is (IPropertySymbol { GetMethod: not null } or IFieldSymbol) and { IsStatic: false, ContainingType.IsRecord: true };
+
+        /// <summary>
+        /// True if a syntactic delete edit of an old symbol has a matching syntactic insert edit.
+        /// 
+        /// The old symbol has to be explicitly declared, otherwise it couldn't have been deleted via syntactic delete edit.
+        /// </summary>
+        private bool HasInsertMatchingDelete(ISymbol newSymbol, Compilation oldCompilation, CancellationToken cancellationToken)
+        {
+            if (!newSymbol.IsSynthesized())
+            {
+                return true;
+            }
+
+            // new symbol is synthesized - check if there is an insert of another symbol that triggers the synthesis
+
+            // Primary deconstructor is synthesized based on presence of primary constructor:
+            if (newSymbol is IMethodSymbol { IsStatic: false, ContainingType.IsRecord: true, ReturnsVoid: true, Name: WellKnownMemberNames.DeconstructMethodName } method &&
+                GetPrimaryConstructor(newSymbol.ContainingType, cancellationToken) is { } newPrimaryConstructor &&
+                method.HasDeconstructorSignature(newPrimaryConstructor))
+            {
+                var oldConstructor = SymbolKey.Create(newPrimaryConstructor, cancellationToken).Resolve(oldCompilation, ignoreAssemblyKey: true, cancellationToken).Symbol;
+
+                // An insert exists if the new primary constructor is explicitly declared and
+                // the old one doesn't exist, is synthesized, or is not a primary constructor parameter.
+                return !newPrimaryConstructor.IsSynthesized() &&
+                    (oldConstructor == null || oldConstructor.IsSynthesized() || !IsPrimaryConstructor(oldConstructor, cancellationToken));
+            }
+
+            // Primary property is synthesized based on presence of primary constructor parameter:
+            if (newSymbol is IPropertySymbol { IsStatic: false, ContainingType.IsRecord: true } &&
+                GetPrimaryConstructor(newSymbol.ContainingType, cancellationToken)?.Parameters.FirstOrDefault(
+                    static (parameter, name) => parameter.Name == name, newSymbol.Name) is { } newPrimaryParameter)
+            {
+                var oldParameter = SymbolKey.Create(newPrimaryParameter, cancellationToken).Resolve(oldCompilation, ignoreAssemblyKey: true, cancellationToken).Symbol;
+
+                // An insert exists if the new primary parameter is explicitly declared and
+                // the old one doesn't exist, is synthesized, or is not a primary constructor parameter.
+                return !newPrimaryParameter.IsSynthesized() &&
+                    (oldParameter == null || oldParameter.IsSynthesized() || !IsPrimaryConstructor(oldParameter.ContainingSymbol, cancellationToken));
+            }
+
+            // Accessor of a property is synthesized based on presence of the property:
+            if (newSymbol is IMethodSymbol { AssociatedSymbol: IPropertySymbol { } newProperty })
+            {
+                // An insert exists if an insert exists for the new property
+                return HasInsertMatchingDelete(newProperty, oldCompilation, cancellationToken);
+            }
+
+            return false;
+        }
+
+        private static bool HasPrintMembersSignature(IMethodSymbol method, Compilation compilation)
+            => method.Parameters is [var parameter] && SymbolEqualityComparer.Default.Equals(parameter.Type, compilation.GetTypeByMetadataName(typeof(StringBuilder).FullName!));
+
+        private static bool HasIEquatableEqualsSignature(IMethodSymbol method)
+            => method.Parameters is [var parameter] && SymbolEqualityComparer.Default.Equals(parameter.Type, method.ContainingType);
+
+        private static bool HasGetHashCodeSignature(IMethodSymbol method)
+            => method.Parameters is [];
+
         #endregion
 
         #region Testing
diff --git a/src/Features/Core/Portable/EditAndContinue/ActiveStatementsMap.cs b/src/Features/Core/Portable/EditAndContinue/ActiveStatementsMap.cs
index 2c7db324cce73..5ec846bdd527f 100644
--- a/src/Features/Core/Portable/EditAndContinue/ActiveStatementsMap.cs
+++ b/src/Features/Core/Portable/EditAndContinue/ActiveStatementsMap.cs
@@ -115,6 +115,12 @@ public static ActiveStatementsMap Create(
                 }
             }
 
+            // TODO: Remove. Workaround for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1830914.
+            if (EditAndContinueMethodDebugInfoReader.IgnoreCaseWhenComparingDocumentNames)
+            {
+                byDocumentPath = byDocumentPath.WithComparers(keyComparer: StringComparer.OrdinalIgnoreCase);
+            }
+
             return new ActiveStatementsMap(byDocumentPath, byInstruction.ToImmutableDictionary());
         }
 
@@ -190,7 +196,7 @@ void AddStatement(LinePositionSpan unmappedLineSpan, ActiveStatement activeState
             {
                 // Protect against stale/invalid active statement spans read from the PDB.
                 // Also guard against active statements unmapped to multiple locations in the unmapped file
-                // (when multiple #line map to the same span that overlaps with the active statement).
+                // (when multiple #line directives map to the same span that overlaps with the active statement).
                 if (TryGetTextSpan(oldText.Lines, unmappedLineSpan, out var unmappedSpan) &&
                     oldRoot.FullSpan.Contains(unmappedSpan.Start) &&
                     mappedStatements.Add(activeStatement))
diff --git a/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticDescriptors.cs b/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticDescriptors.cs
index 3a78223f022f6..aed9bd94ab3ae 100644
--- a/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticDescriptors.cs
+++ b/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticDescriptors.cs
@@ -133,9 +133,6 @@ void AddGeneralDiagnostic(EditAndContinueErrorCode code, string resourceName, Di
             AddRudeEdit(RudeEditKind.MemberBodyInternalError, nameof(FeaturesResources.Modifying_body_of_0_requires_restarting_the_application_due_to_internal_error_1));
             AddRudeEdit(RudeEditKind.MemberBodyTooBig, nameof(FeaturesResources.Modifying_body_of_0_requires_restarting_the_application_because_the_body_has_too_many_statements));
             AddRudeEdit(RudeEditKind.SourceFileTooBig, nameof(FeaturesResources.Modifying_source_file_0_requires_restarting_the_application_because_the_file_is_too_big));
-            AddRudeEdit(RudeEditKind.ImplementRecordParameterAsReadOnly, nameof(FeaturesResources.Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application));
-            AddRudeEdit(RudeEditKind.ImplementRecordParameterWithSet, nameof(FeaturesResources.Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application));
-            AddRudeEdit(RudeEditKind.ExplicitRecordMethodParameterNamesMustMatch, nameof(FeaturesResources.Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0));
             AddRudeEdit(RudeEditKind.NotSupportedByRuntime, nameof(FeaturesResources.Applying_source_changes_while_the_application_is_running_is_not_supported_by_the_runtime));
             AddRudeEdit(RudeEditKind.MakeMethodAsyncNotSupportedByRuntime, nameof(FeaturesResources.Making_a_method_asynchronous_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime));
             AddRudeEdit(RudeEditKind.MakeMethodIteratorNotSupportedByRuntime, nameof(FeaturesResources.Making_a_method_an_iterator_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime));
diff --git a/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticUpdateSource.cs b/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticUpdateSource.cs
index 0eb7971e96537..171565b249eb2 100644
--- a/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticUpdateSource.cs
+++ b/src/Features/Core/Portable/EditAndContinue/EditAndContinueDiagnosticUpdateSource.cs
@@ -104,7 +104,7 @@ public void ReportDiagnostics(Workspace workspace, Solution solution, ImmutableA
 
             if (documentDiagnostics.Length > 0)
             {
-                foreach (var (documentId, diagnosticData) in documentDiagnostics.ToDictionary(static data => data.DocumentId!))
+                foreach (var (documentId, diagnosticData) in documentDiagnostics.GroupBy(static data => data.DocumentId!))
                 {
                     var diagnosticGroupId = (this, documentId);
 
@@ -114,13 +114,13 @@ public void ReportDiagnostics(Workspace workspace, Solution solution, ImmutableA
                         solution,
                         documentId.ProjectId,
                         documentId: documentId,
-                        diagnostics: diagnosticData));
+                        diagnostics: diagnosticData.ToImmutableArray()));
                 }
             }
 
             if (projectDiagnostics.Length > 0)
             {
-                foreach (var (projectId, diagnosticData) in projectDiagnostics.ToDictionary(static data => data.ProjectId!))
+                foreach (var (projectId, diagnosticData) in projectDiagnostics.GroupBy(static data => data.ProjectId!))
                 {
                     var diagnosticGroupId = (this, projectId);
 
@@ -130,7 +130,7 @@ public void ReportDiagnostics(Workspace workspace, Solution solution, ImmutableA
                         solution,
                         projectId,
                         documentId: null,
-                        diagnostics: diagnosticData));
+                        diagnostics: diagnosticData.ToImmutableArray()));
                 }
             }
 
diff --git a/src/Features/Core/Portable/EditAndContinue/EditAndContinueMethodDebugInfoReader.cs b/src/Features/Core/Portable/EditAndContinue/EditAndContinueMethodDebugInfoReader.cs
index cbc870e77d4dc..e00e5809257a8 100644
--- a/src/Features/Core/Portable/EditAndContinue/EditAndContinueMethodDebugInfoReader.cs
+++ b/src/Features/Core/Portable/EditAndContinue/EditAndContinueMethodDebugInfoReader.cs
@@ -24,6 +24,9 @@ namespace Microsoft.CodeAnalysis.EditAndContinue
     /// </summary>
     internal abstract class EditAndContinueMethodDebugInfoReader
     {
+        // TODO: Remove, the path should match exactly. Workaround for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1830914.
+        internal static bool IgnoreCaseWhenComparingDocumentNames;
+
         public abstract bool IsPortable { get; }
         public abstract EditAndContinueMethodDebugInformation GetDebugInfo(MethodDefinitionHandle methodHandle);
         public abstract StandaloneSignatureHandle GetLocalSignature(MethodDefinitionHandle methodHandle);
@@ -157,7 +160,8 @@ public override bool TryGetDocumentChecksum(string documentPath, out ImmutableAr
                 foreach (var documentHandle in _pdbReader.Documents)
                 {
                     var document = _pdbReader.GetDocument(documentHandle);
-                    if (_pdbReader.StringComparer.Equals(document.Name, documentPath))
+
+                    if (_pdbReader.StringComparer.Equals(document.Name, documentPath, IgnoreCaseWhenComparingDocumentNames))
                     {
                         checksum = _pdbReader.GetBlobContent(document.Hash);
                         algorithmId = _pdbReader.GetGuid(document.HashAlgorithm);
diff --git a/src/Features/Core/Portable/EditAndContinue/EditSession.cs b/src/Features/Core/Portable/EditAndContinue/EditSession.cs
index 163abd3857ab9..eb73bbadd8283 100644
--- a/src/Features/Core/Portable/EditAndContinue/EditSession.cs
+++ b/src/Features/Core/Portable/EditAndContinue/EditSession.cs
@@ -990,6 +990,18 @@ async ValueTask LogDocumentChangesAsync(int? generation, CancellationToken cance
                     // project must support compilations since it supports EnC
                     Contract.ThrowIfNull(newCompilation);
 
+                    // The compiler only uses this predicate to determine if CS7101: "Member 'X' added during the current debug session
+                    // can only be accessed from within its declaring assembly 'Lib'" should be reported. 
+                    // Prior to .NET 8 Preview 4 the runtime failed to apply such edits.
+                    // This was fixed in Preview 4 along with support for generics. If we see a generic capability we can disable reporting
+                    // this compiler error. Otherwise, we leave the check as is in order to detect at least some runtime failures on .NET Framework.
+                    // Note that the analysis in the compiler detecting the circumstances under which the runtime fails
+                    // to apply the change has both false positives (flagged generic updates that shouldn't be flagged) and negatives
+                    // (didn't flag cases like https://github.com/dotnet/roslyn/issues/68293).
+                    var capabilities = await Capabilities.GetValueAsync(cancellationToken).ConfigureAwait(false);
+                    var isAddedSymbolPredicate = capabilities.HasFlag(EditAndContinueCapabilities.GenericAddMethodToExistingType) ?
+                        static _ => false : (Func<ISymbol, bool>)projectChanges.AddedSymbols.Contains;
+
                     EmitDifferenceResult emitResult;
 
                     // The lock protects underlying baseline readers from being disposed while emitting delta.
@@ -1001,7 +1013,7 @@ async ValueTask LogDocumentChangesAsync(int? generation, CancellationToken cance
                         emitResult = newCompilation.EmitDifference(
                             projectBaseline.EmitBaseline,
                             projectChanges.SemanticEdits,
-                            projectChanges.AddedSymbols.Contains,
+                            isAddedSymbolPredicate,
                             metadataStream,
                             ilStream,
                             pdbStream,
@@ -1176,8 +1188,9 @@ internal static void GetActiveStatementAndExceptionRegionSpans(
                     // Adds a region with specified PDB spans.
                     void AddNonRemappableRegion(SourceFileSpan oldSpan, SourceFileSpan newSpan, bool isExceptionRegion)
                     {
-                        // it is a rude edit to change the path of the region span:
-                        Debug.Assert(oldSpan.Path == newSpan.Path);
+                        // TODO: Remove comparer, the path should match exactly. Workaround for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1830914.
+                        Debug.Assert(string.Equals(oldSpan.Path, newSpan.Path,
+                            EditAndContinueMethodDebugInfoReader.IgnoreCaseWhenComparingDocumentNames ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal));
 
                         // The up-to-date flag is copied when new active statement is created from the corresponding old one.
                         Debug.Assert(oldActiveStatement.IsMethodUpToDate == newActiveStatement.IsMethodUpToDate);
diff --git a/src/Features/Core/Portable/EditAndContinue/RudeEditKind.cs b/src/Features/Core/Portable/EditAndContinue/RudeEditKind.cs
index 56b6fad495d43..d1acac4458f14 100644
--- a/src/Features/Core/Portable/EditAndContinue/RudeEditKind.cs
+++ b/src/Features/Core/Portable/EditAndContinue/RudeEditKind.cs
@@ -118,11 +118,11 @@ internal enum RudeEditKind : ushort
         MemberBodyTooBig = 90,
         // InsertIntoGenericType = 91,
 
-        ImplementRecordParameterAsReadOnly = 92,
-        ImplementRecordParameterWithSet = 93,
+        //ImplementRecordParameterAsReadOnly = 92,
+        //ImplementRecordParameterWithSet = 93,
         //AddRecordPositionalParameter = 94,
         //DeleteRecordPositionalParameter = 95,
-        ExplicitRecordMethodParameterNamesMustMatch = 96,
+        //ExplicitRecordMethodParameterNamesMustMatch = 96,
         NotSupportedByRuntime = 97,
         MakeMethodAsyncNotSupportedByRuntime = 98,
         MakeMethodIteratorNotSupportedByRuntime = 99,
diff --git a/src/Features/Core/Portable/EditAndContinue/SolutionSnapshotRegistry.cs b/src/Features/Core/Portable/EditAndContinue/SolutionSnapshotRegistry.cs
new file mode 100644
index 0000000000000..c3527f1137a37
--- /dev/null
+++ b/src/Features/Core/Portable/EditAndContinue/SolutionSnapshotRegistry.cs
@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Composition;
+using System.Threading;
+using Microsoft.CodeAnalysis.Contracts.Client;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.EditAndContinue;
+
+internal interface ISolutionSnapshotRegistry
+{
+    SolutionSnapshotId RegisterSolutionSnapshot(Solution solution);
+}
+
+[Shared]
+[Export(typeof(SolutionSnapshotRegistry))]
+[Export(typeof(ISolutionSnapshotRegistry))]
+internal sealed class SolutionSnapshotRegistry : ISolutionSnapshotRegistry
+{
+    private static int s_solutionSnapshotId;
+
+    // lock on access
+    private readonly Dictionary<SolutionSnapshotId, Solution> _pendingSolutionSnapshots = new();
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public SolutionSnapshotRegistry()
+    {
+    }
+
+    /// <summary>
+    /// Called from LSP server.
+    /// </summary>
+    public SolutionSnapshotId RegisterSolutionSnapshot(Solution solution)
+    {
+        var id = new SolutionSnapshotId(Interlocked.Increment(ref s_solutionSnapshotId));
+
+        lock (_pendingSolutionSnapshots)
+        {
+            _pendingSolutionSnapshots.Add(id, solution);
+        }
+
+        return id;
+    }
+
+    public Solution GetRegisteredSolutionSnapshot(SolutionSnapshotId id)
+    {
+        lock (_pendingSolutionSnapshots)
+        {
+            Contract.ThrowIfFalse(_pendingSolutionSnapshots.TryGetValue(id, out var solution));
+            Contract.ThrowIfFalse(_pendingSolutionSnapshots.Remove(id));
+            return solution;
+        }
+    }
+
+    public void Clear()
+    {
+        lock (_pendingSolutionSnapshots)
+        {
+            _pendingSolutionSnapshots.Clear();
+        }
+    }
+}
diff --git a/src/Features/Core/Portable/EditAndContinue/Utilities/BidirectionalMap.cs b/src/Features/Core/Portable/EditAndContinue/Utilities/BidirectionalMap.cs
index d7995889d9c8c..cd57435749889 100644
--- a/src/Features/Core/Portable/EditAndContinue/Utilities/BidirectionalMap.cs
+++ b/src/Features/Core/Portable/EditAndContinue/Utilities/BidirectionalMap.cs
@@ -2,42 +2,55 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
 using System.Collections.Generic;
 using Microsoft.CodeAnalysis.Differencing;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.EditAndContinue
 {
     internal readonly struct BidirectionalMap<T>
+        where T : notnull
     {
         public readonly IReadOnlyDictionary<T, T> Forward;
         public readonly IReadOnlyDictionary<T, T> Reverse;
 
         public BidirectionalMap(IReadOnlyDictionary<T, T> forward, IReadOnlyDictionary<T, T> reverse)
         {
+            Contract.ThrowIfFalse(forward.Count == reverse.Count);
             Forward = forward;
             Reverse = reverse;
         }
 
-        public BidirectionalMap(IEnumerable<KeyValuePair<T, T>> entries)
+        public BidirectionalMap<T> With(BidirectionalMap<T> map)
         {
-            var map = new Dictionary<T, T>();
-            var reverseMap = new Dictionary<T, T>();
+            if (map.Forward.Count == 0)
+            {
+                return this;
+            }
 
-            foreach (var entry in entries)
+            var count = Forward.Count + map.Forward.Count;
+            var forward = new Dictionary<T, T>(count);
+            var reverse = new Dictionary<T, T>(count);
+
+            foreach (var entry in Forward)
             {
-                map.Add(entry.Key, entry.Value);
-                reverseMap.Add(entry.Value, entry.Key);
+                forward.Add(entry.Key, entry.Value);
+                reverse.Add(entry.Value, entry.Key);
             }
 
-            Forward = map;
-            Reverse = reverseMap;
+            foreach (var entry in map.Forward)
+            {
+                forward.Add(entry.Key, entry.Value);
+                reverse.Add(entry.Value, entry.Key);
+            }
+
+            return new BidirectionalMap<T>(forward, reverse);
         }
 
+        public BidirectionalMap<T> WithMatch(Match<T> match)
+            => With(BidirectionalMap<T>.FromMatch(match));
+
         public static BidirectionalMap<T> FromMatch(Match<T> match)
             => new(match.Matches, match.ReverseMatches);
-
-        public bool IsDefaultOrEmpty => Forward == null || Forward.Count == 0;
     }
 }
diff --git a/src/Features/Core/Portable/EditAndContinue/Utilities/Extensions.cs b/src/Features/Core/Portable/EditAndContinue/Utilities/Extensions.cs
index 33d5e330ac14f..4b0c2bd53c749 100644
--- a/src/Features/Core/Portable/EditAndContinue/Utilities/Extensions.cs
+++ b/src/Features/Core/Portable/EditAndContinue/Utilities/Extensions.cs
@@ -4,8 +4,9 @@
 
 using System;
 using System.Collections.Immutable;
-using Microsoft.CodeAnalysis.Diagnostics;
+using System.Linq;
 using Microsoft.CodeAnalysis.Contracts.EditAndContinue;
+using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
@@ -139,13 +140,39 @@ public static ManagedHotReloadDiagnostic ToHotReloadDiagnostic(this DiagnosticDa
             return new(
                 data.Id,
                 data.Message ?? FeaturesResources.Unknown_error_occurred,
-                updateStatus == ModuleUpdateStatus.RestartRequired ?
-                    ManagedHotReloadDiagnosticSeverity.RestartRequired :
-                    (data.Severity == DiagnosticSeverity.Error) ?
-                        ManagedHotReloadDiagnosticSeverity.Error :
-                        ManagedHotReloadDiagnosticSeverity.Warning,
+                updateStatus == ModuleUpdateStatus.RestartRequired
+                    ? ManagedHotReloadDiagnosticSeverity.RestartRequired
+                    : (data.Severity == DiagnosticSeverity.Error)
+                        ? ManagedHotReloadDiagnosticSeverity.Error
+                        : ManagedHotReloadDiagnosticSeverity.Warning,
                 fileSpan.Path ?? "",
                 fileSpan.Span.ToSourceSpan());
         }
+
+        public static bool IsSynthesized(this ISymbol symbol)
+            => symbol.IsImplicitlyDeclared || symbol.IsSynthesizedAutoProperty();
+
+        public static bool IsSynthesizedAutoProperty(this ISymbol property)
+            => property is IPropertySymbol { GetMethod.IsImplicitlyDeclared: true, SetMethod.IsImplicitlyDeclared: true };
+
+        public static bool HasSynthesizedDefaultConstructor(this INamedTypeSymbol type)
+            => !type.InstanceConstructors.Any(static c => !(c.Parameters is [] || c.ContainingType.IsRecord && c.IsCopyConstructor()));
+
+        public static bool IsCopyConstructor(this ISymbol symbol)
+            => symbol is IMethodSymbol { Parameters: [var parameter] } && SymbolEqualityComparer.Default.Equals(parameter.Type, symbol.ContainingType);
+
+        public static bool HasDeconstructorSignature(this IMethodSymbol method, IMethodSymbol constructor)
+            => method.Parameters.Length > 0 &&
+               method.Parameters.Length == constructor.Parameters.Length &&
+               method.Parameters.All(
+                   static (param, constructor) => param.RefKind == RefKind.Out && param.Type.Equals(constructor.Parameters[param.Ordinal].Type, SymbolEqualityComparer.Default),
+                   constructor);
+
+        /// <summary>
+        /// Returns a deconstructor that matches the parameters of the given <paramref name="constructor"/>, or null if there is none.
+        /// </summary>
+        public static IMethodSymbol? GetMatchingDeconstructor(this IMethodSymbol constructor)
+            => (IMethodSymbol?)constructor.ContainingType.GetMembers(WellKnownMemberNames.DeconstructMethodName).FirstOrDefault(
+                static (symbol, constructor) => symbol is IMethodSymbol method && HasDeconstructorSignature(method, constructor), constructor);
     }
 }
diff --git a/src/Features/Core/Portable/EmbeddedLanguages/EmbeddedLanguageDetector.cs b/src/Features/Core/Portable/EmbeddedLanguages/EmbeddedLanguageDetector.cs
index 1332919b04e0d..2c2900dedd684 100644
--- a/src/Features/Core/Portable/EmbeddedLanguages/EmbeddedLanguageDetector.cs
+++ b/src/Features/Core/Portable/EmbeddedLanguages/EmbeddedLanguageDetector.cs
@@ -364,7 +364,7 @@ private bool IsMatchingStringSyntaxAttribute(
             return true;
         }
 
-        private string? GetNameOfType(SyntaxNode? typeNode, ISyntaxFacts syntaxFacts)
+        private static string? GetNameOfType(SyntaxNode? typeNode, ISyntaxFacts syntaxFacts)
         {
             if (syntaxFacts.IsQualifiedName(typeNode))
             {
diff --git a/src/Features/Core/Portable/EmbeddedLanguages/Json/LanguageServices/JsonClassifier.cs b/src/Features/Core/Portable/EmbeddedLanguages/Json/LanguageServices/JsonClassifier.cs
index 8ae6ca955f550..6bc12323657da 100644
--- a/src/Features/Core/Portable/EmbeddedLanguages/Json/LanguageServices/JsonClassifier.cs
+++ b/src/Features/Core/Portable/EmbeddedLanguages/Json/LanguageServices/JsonClassifier.cs
@@ -80,16 +80,26 @@ private static void AddClassifications(JsonNode node, Visitor visitor, EmbeddedL
                 }
                 else
                 {
-                    AddTriviaClassifications(child.Token, context);
+                    AddTokenClassifications(child.Token, context);
                 }
             }
         }
 
-        private static void AddTriviaClassifications(JsonToken token, EmbeddedLanguageClassificationContext context)
+        private static void AddTokenClassifications(JsonToken token, EmbeddedLanguageClassificationContext context)
         {
             foreach (var trivia in token.LeadingTrivia)
                 AddTriviaClassifications(trivia, context);
 
+            if (!token.IsMissing)
+            {
+                switch (token.Kind)
+                {
+                    case JsonKind.CommaToken:
+                        context.AddClassification(ClassificationTypeNames.JsonPunctuation, token.GetSpan());
+                        break;
+                }
+            }
+
             foreach (var trivia in token.TrailingTrivia)
                 AddTriviaClassifications(trivia, context);
         }
@@ -187,7 +197,9 @@ public void Visit(JsonTextNode node)
 
             public void Visit(JsonCommaValueNode node)
             {
-                AddClassification(node.CommaToken, ClassificationTypeNames.JsonPunctuation);
+                // Already handled when we recurse in AddTokenClassifications.  Specifically, commas show up both as
+                // nodes (with tokens in them) in error recovery scenarios, and also just as tokens in a separated list.
+                // So, to handle both, we just handle the token case in AddTokenClassifications.
             }
         }
     }
diff --git a/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexDocumentHighlighter.cs b/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexDocumentHighlighter.cs
index e0810d43b0a6e..c648fc8fca5b4 100644
--- a/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexDocumentHighlighter.cs
+++ b/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexDocumentHighlighter.cs
@@ -47,7 +47,7 @@ public ImmutableArray<DocumentHighlights> GetDocumentHighlights(
                 : ImmutableArray.Create(new DocumentHighlights(document, GetHighlights(tree, position)));
         }
 
-        private ImmutableArray<HighlightSpan> GetHighlights(RegexTree tree, int positionInDocument)
+        private static ImmutableArray<HighlightSpan> GetHighlights(RegexTree tree, int positionInDocument)
         {
             var referencesOnTheRight = GetReferences(tree, positionInDocument);
             if (!referencesOnTheRight.IsEmpty)
@@ -66,7 +66,7 @@ private ImmutableArray<HighlightSpan> GetHighlights(RegexTree tree, int position
             return referencesOnTheLeft;
         }
 
-        private ImmutableArray<HighlightSpan> GetReferences(RegexTree tree, int position)
+        private static ImmutableArray<HighlightSpan> GetReferences(RegexTree tree, int position)
         {
             var virtualChar = tree.Text.Find(position);
             if (virtualChar == null)
@@ -76,7 +76,7 @@ private ImmutableArray<HighlightSpan> GetReferences(RegexTree tree, int position
             return FindReferenceHighlights(tree, ch);
         }
 
-        private ImmutableArray<HighlightSpan> FindReferenceHighlights(RegexTree tree, VirtualChar ch)
+        private static ImmutableArray<HighlightSpan> FindReferenceHighlights(RegexTree tree, VirtualChar ch)
         {
             var node = FindReferenceNode(tree.Root, ch);
             if (node == null)
@@ -123,7 +123,7 @@ private static RegexToken GetCaptureToken(RegexEscapeNode node)
                 _ => throw new InvalidOperationException(),
             };
 
-        private RegexEscapeNode? FindReferenceNode(RegexNode node, VirtualChar virtualChar)
+        private static RegexEscapeNode? FindReferenceNode(RegexNode node, VirtualChar virtualChar)
         {
             if (node.Kind is RegexKind.BackreferenceEscape or
                 RegexKind.CaptureEscape or
diff --git a/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexEmbeddedCompletionProvider.cs b/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexEmbeddedCompletionProvider.cs
index 5107234a1498c..623f361b59434 100644
--- a/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexEmbeddedCompletionProvider.cs
+++ b/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/LanguageServices/RegexEmbeddedCompletionProvider.cs
@@ -126,7 +126,7 @@ not CompletionTriggerKind.InvokeAndCommitIfUnique and
             context.IsExclusive = true;
         }
 
-        private void ProvideCompletions(EmbeddedCompletionContext context)
+        private static void ProvideCompletions(EmbeddedCompletionContext context)
         {
             // First, act as if the user just inserted the previous character.  This will cause us
             // to complete down to the set of relevant items based on that character. If we get
@@ -163,7 +163,7 @@ private void ProvideCompletions(EmbeddedCompletionContext context)
         /// Produces completions using the previous character to determine which set of
         /// regex items to show.
         /// </summary>
-        private void ProvideCompletionsBasedOffOfPrecedingCharacter(EmbeddedCompletionContext context)
+        private static void ProvideCompletionsBasedOffOfPrecedingCharacter(EmbeddedCompletionContext context)
         {
             var previousVirtualCharOpt = context.Tree.Text.Find(context.Position - 1);
             if (previousVirtualCharOpt == null)
@@ -247,7 +247,7 @@ private static void ProvideTopLevelCompletions(EmbeddedCompletionContext context
             context.AddIfMissing("#", Regex_end_of_line_comment_short, Regex_end_of_line_comment_long, parentOpt: null);
         }
 
-        private void ProvideOpenBraceCompletions(
+        private static void ProvideOpenBraceCompletions(
             EmbeddedCompletionContext context, RegexTree tree, VirtualChar previousVirtualChar)
         {
             // we only provide completions after `{` if the user wrote `\p{`.  In that case
@@ -392,7 +392,7 @@ private static void ProvideBackslashCompletions(
             context.AddIfMissing(@"\W", Regex_non_word_character_short, Regex_non_word_character_long, parentOpt);
         }
 
-        private (RegexNode parent, RegexToken Token)? FindToken(
+        private static (RegexNode parent, RegexToken Token)? FindToken(
             RegexNode parent, VirtualChar ch)
         {
             foreach (var child in parent)
diff --git a/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/RegexParser.cs b/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/RegexParser.cs
index a40e2094d3409..1dd81ba74df48 100644
--- a/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/RegexParser.cs
+++ b/src/Features/Core/Portable/EmbeddedLanguages/RegularExpressions/RegexParser.cs
@@ -1322,7 +1322,7 @@ private void ParseCharacterClassComponents(ArrayBuilder<RegexExpressionNode> com
         private static bool IsEscapedMinus([NotNullWhen(true)] RegexNode? node)
             => node is RegexSimpleEscapeNode simple && IsTextChar(simple.TypeToken, '-');
 
-        private readonly bool TryGetRangeComponentValue(RegexExpressionNode component, out int ch)
+        private static bool TryGetRangeComponentValue(RegexExpressionNode component, out int ch)
         {
             // Don't bother examining the component if it has any errors already.  This also means
             // we don't have to worry about running into invalid escape sequences and the like.
@@ -1335,7 +1335,7 @@ private readonly bool TryGetRangeComponentValue(RegexExpressionNode component, o
             return false;
         }
 
-        private readonly bool TryGetRangeComponentValueWorker(RegexNode component, out int ch)
+        private static bool TryGetRangeComponentValueWorker(RegexNode component, out int ch)
         {
             switch (component.Kind)
             {
diff --git a/src/Features/Core/Portable/ExtractMethod/AbstractSyntaxTriviaService.Result.cs b/src/Features/Core/Portable/ExtractMethod/AbstractSyntaxTriviaService.Result.cs
index 5bf523ab97b96..aa999109e91cb 100644
--- a/src/Features/Core/Portable/ExtractMethod/AbstractSyntaxTriviaService.Result.cs
+++ b/src/Features/Core/Portable/ExtractMethod/AbstractSyntaxTriviaService.Result.cs
@@ -273,10 +273,10 @@ private static IEnumerable<SyntaxTrivia> ResolveTrivia(
                 PreviousNextTokenPair tokenPair,
                 Dictionary<SyntaxToken, LeadingTrailingTriviaPair> triviaMap)
             {
-                var previousTriviaPair = triviaMap.ContainsKey(tokenPair.PreviousToken) ? triviaMap[tokenPair.PreviousToken] : default;
-                var nextTriviaPair = triviaMap.ContainsKey(tokenPair.NextToken) ? triviaMap[tokenPair.NextToken] : default;
-
+                triviaMap.TryGetValue(tokenPair.PreviousToken, out var previousTriviaPair);
                 var trailingTrivia = previousTriviaPair.TrailingTrivia ?? SpecializedCollections.EmptyEnumerable<SyntaxTrivia>();
+
+                triviaMap.TryGetValue(tokenPair.NextToken, out var nextTriviaPair);
                 var leadingTrivia = nextTriviaPair.LeadingTrivia ?? SpecializedCollections.EmptyEnumerable<SyntaxTrivia>();
 
                 return tokenPair.PreviousToken.TrailingTrivia.Concat(trailingTrivia).Concat(leadingTrivia).Concat(tokenPair.NextToken.LeadingTrivia);
diff --git a/src/Features/Core/Portable/ExtractMethod/MethodExtractor.Analyzer.cs b/src/Features/Core/Portable/ExtractMethod/MethodExtractor.Analyzer.cs
index 3782d4ad4888c..a153c3781af76 100644
--- a/src/Features/Core/Portable/ExtractMethod/MethodExtractor.Analyzer.cs
+++ b/src/Features/Core/Portable/ExtractMethod/MethodExtractor.Analyzer.cs
@@ -811,7 +811,7 @@ private IEnumerable<ITypeParameterSymbol> GetMethodTypeParametersInConstraintLis
                 return sortedMap.Values.ToList();
             }
 
-            private void AppendTypeParametersInConstraintsUsedByConstructedTypeWithItsOwnConstraints(SortedDictionary<int, ITypeParameterSymbol> sortedMap)
+            private static void AppendTypeParametersInConstraintsUsedByConstructedTypeWithItsOwnConstraints(SortedDictionary<int, ITypeParameterSymbol> sortedMap)
             {
                 var visited = new HashSet<ITypeSymbol>();
                 var candidates = SpecializedCollections.EmptyEnumerable<ITypeParameterSymbol>();
@@ -838,7 +838,7 @@ private void AppendTypeParametersInConstraintsUsedByConstructedTypeWithItsOwnCon
                 }
             }
 
-            private IEnumerable<ITypeParameterSymbol> AppendTypeParametersInConstraintsUsedByConstructedTypeWithItsOwnConstraints(
+            private static IEnumerable<ITypeParameterSymbol> AppendTypeParametersInConstraintsUsedByConstructedTypeWithItsOwnConstraints(
                 ITypeSymbol type, HashSet<ITypeSymbol> visited)
             {
                 if (visited.Contains(type))
diff --git a/src/Features/Core/Portable/FeaturesResources.resx b/src/Features/Core/Portable/FeaturesResources.resx
index 1137eac7109a1..f396160d91fb1 100644
--- a/src/Features/Core/Portable/FeaturesResources.resx
+++ b/src/Features/Core/Portable/FeaturesResources.resx
@@ -2709,6 +2709,10 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
     <value>{0} '{1}'</value>
     <comment>e.g. "method 'M'"</comment>
   </data>
+  <data name="symbol_kind_and_name_of_member_kind_and_name" xml:space="preserve">
+    <value>{0} '{1}' of {2} '{3}'</value>
+    <comment>e.g. "parameter 'T param' of method 'M'"</comment>
+  </data>
   <data name="code" xml:space="preserve">
     <value>code</value>
   </data>
@@ -2730,15 +2734,6 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
   <data name="and_update_call_sites_directly" xml:space="preserve">
     <value>and update call sites directly</value>
   </data>
-  <data name="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application" xml:space="preserve">
-    <value>Implementing a record positional parameter '{0}' as read only requires restarting the application,</value>
-  </data>
-  <data name="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application" xml:space="preserve">
-    <value>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</value>
-  </data>
-  <data name="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0" xml:space="preserve">
-    <value>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</value>
-  </data>
   <data name="Convert_to_record_struct" xml:space="preserve">
     <value>Convert to record struct</value>
   </data>
diff --git a/src/Features/Core/Portable/GoToDefinition/AbstractFindDefinitionService.cs b/src/Features/Core/Portable/GoToDefinition/AbstractFindDefinitionService.cs
index 7102992b46fb2..718ec2b6edf67 100644
--- a/src/Features/Core/Portable/GoToDefinition/AbstractFindDefinitionService.cs
+++ b/src/Features/Core/Portable/GoToDefinition/AbstractFindDefinitionService.cs
@@ -20,11 +20,13 @@ public async Task<ImmutableArray<INavigableItem>> FindDefinitionsAsync(
             var symbolService = document.GetRequiredLanguageService<IGoToDefinitionSymbolService>();
             var (symbol, project, _) = await symbolService.GetSymbolProjectAndBoundSpanAsync(document, position, includeType: true, cancellationToken).ConfigureAwait(false);
 
-            symbol = await SymbolFinder.FindSourceDefinitionAsync(symbol, project.Solution, cancellationToken).ConfigureAwait(false) ?? symbol;
+            var solution = project.Solution;
+            symbol = await SymbolFinder.FindSourceDefinitionAsync(symbol, solution, cancellationToken).ConfigureAwait(false) ?? symbol;
+            symbol = await GoToDefinitionFeatureHelpers.TryGetPreferredSymbolAsync(solution, symbol, cancellationToken).ConfigureAwait(false);
 
             // Try to compute source definitions from symbol.
             return symbol != null
-                ? NavigableItemFactory.GetItemsFromPreferredSourceLocations(project.Solution, symbol, displayTaggedParts: FindUsagesHelpers.GetDisplayParts(symbol), cancellationToken: cancellationToken)
+                ? NavigableItemFactory.GetItemsFromPreferredSourceLocations(solution, symbol, displayTaggedParts: FindUsagesHelpers.GetDisplayParts(symbol), cancellationToken: cancellationToken)
                 : ImmutableArray<INavigableItem>.Empty;
         }
     }
diff --git a/src/Features/Core/Portable/GoToDefinition/GoToDefinitionFeatureHelpers.cs b/src/Features/Core/Portable/GoToDefinition/GoToDefinitionFeatureHelpers.cs
new file mode 100644
index 0000000000000..1faec1dee9074
--- /dev/null
+++ b/src/Features/Core/Portable/GoToDefinition/GoToDefinitionFeatureHelpers.cs
@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.FindSymbols;
+using Microsoft.CodeAnalysis.FindUsages;
+using Microsoft.CodeAnalysis.Navigation;
+using Microsoft.CodeAnalysis.PooledObjects;
+
+namespace Microsoft.CodeAnalysis.GoToDefinition
+{
+    internal static class GoToDefinitionFeatureHelpers
+    {
+        public static async Task<ISymbol?> TryGetPreferredSymbolAsync(
+            Solution solution, ISymbol? symbol, CancellationToken cancellationToken)
+        {
+            // VB global import aliases have a synthesized SyntaxTree.
+            // We can't go to the definition of the alias, so use the target type.
+
+            var alias = symbol as IAliasSymbol;
+            if (alias != null)
+            {
+                if (alias.Target is INamespaceSymbol ns && ns.IsGlobalNamespace)
+                    return null;
+            }
+
+            // VB global import aliases have a synthesized SyntaxTree.
+            // We can't go to the definition of the alias, so use the target type.
+
+            if (alias != null)
+            {
+                var sourceLocations = NavigableItemFactory.GetPreferredSourceLocations(
+                    solution, symbol, cancellationToken);
+
+                if (sourceLocations.All(l => solution.GetDocument(l.SourceTree) == null))
+                    symbol = alias.Target;
+            }
+
+            var definition = await SymbolFinder.FindSourceDefinitionAsync(symbol, solution, cancellationToken).ConfigureAwait(false);
+            cancellationToken.ThrowIfCancellationRequested();
+
+            symbol = definition ?? symbol;
+
+            // If it is a partial method declaration with no body, choose to go to the implementation
+            // that has a method body.
+            if (symbol is IMethodSymbol method)
+                symbol = method.PartialImplementationPart ?? symbol;
+
+            return symbol;
+        }
+
+        public static async Task<ImmutableArray<DefinitionItem>> GetDefinitionsAsync(
+            ISymbol? symbol,
+            Solution solution,
+            bool thirdPartyNavigationAllowed,
+            CancellationToken cancellationToken)
+        {
+            symbol = await TryGetPreferredSymbolAsync(solution, symbol, cancellationToken).ConfigureAwait(false);
+            if (symbol is null)
+                return ImmutableArray.Create<DefinitionItem>();
+
+            using var _ = ArrayBuilder<DefinitionItem>.GetInstance(out var definitions);
+
+            // Going to a symbol may end up actually showing the symbol in the Find-Usages window.
+            // This happens when there is more than one location for the symbol (i.e. for partial
+            // symbols) and we don't know the best place to take you to.
+            //
+            // The FindUsages window supports showing the classified text for an item.  It does this
+            // in two ways.  Either the item can pass along its classified text (and the window will
+            // defer to that), or the item will have no classified text, and the window will compute
+            // it in the BG.
+            //
+            // Passing along the classified information is valuable for OOP scenarios where we want
+            // all that expensive computation done on the OOP side and not in the VS side.
+            //
+            // However, Go To Definition is all in-process, and is also synchronous.  So we do not
+            // want to fetch the classifications here.  It slows down the command and leads to a
+            // measurable delay in our perf tests.
+            //
+            // So, if we only have a single location to go to, this does no unnecessary work.  And,
+            // if we do have multiple locations to show, it will just be done in the BG, unblocking
+            // this command thread so it can return the user faster.
+            var definitionItem = symbol.ToNonClassifiedDefinitionItem(solution, includeHiddenLocations: true);
+
+            if (thirdPartyNavigationAllowed)
+            {
+                var factory = solution.Services.GetService<IDefinitionsAndReferencesFactory>();
+                if (factory != null)
+                {
+                    var thirdPartyItem = await factory.GetThirdPartyDefinitionItemAsync(solution, definitionItem, cancellationToken).ConfigureAwait(false);
+                    definitions.AddIfNotNull(thirdPartyItem);
+                }
+            }
+
+            definitions.Add(definitionItem);
+            return definitions.ToImmutable();
+        }
+    }
+}
diff --git a/src/Features/Core/Portable/InlineHints/AbstractInlineTypeHintsService.cs b/src/Features/Core/Portable/InlineHints/AbstractInlineTypeHintsService.cs
index edef347eed529..5ad4bfd290940 100644
--- a/src/Features/Core/Portable/InlineHints/AbstractInlineTypeHintsService.cs
+++ b/src/Features/Core/Portable/InlineHints/AbstractInlineTypeHintsService.cs
@@ -89,7 +89,7 @@ public async Task<ImmutableArray<InlineHint>> GetInlineHintsAsync(
             return result.ToImmutable();
         }
 
-        private void AddParts(
+        private static void AddParts(
             IStructuralTypeDisplayService anonymousTypeService,
             ArrayBuilder<SymbolDisplayPart> finalParts,
             ImmutableArray<SymbolDisplayPart> parts,
diff --git a/src/Features/Core/Portable/Microsoft.CodeAnalysis.Features.csproj b/src/Features/Core/Portable/Microsoft.CodeAnalysis.Features.csproj
index 3b57a428d8359..b20aa6906b3f6 100644
--- a/src/Features/Core/Portable/Microsoft.CodeAnalysis.Features.csproj
+++ b/src/Features/Core/Portable/Microsoft.CodeAnalysis.Features.csproj
@@ -27,6 +27,7 @@
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.EditorFeatures.Wpf" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.InteractiveEditorFeatures" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.InteractiveFeatures" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.Protocol" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.Protocol.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.Debugger" />
@@ -44,6 +45,13 @@
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServerIndexFormat.Generator.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.Remote.ServiceHub" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.Remote.Workspaces" />
+
+    <!--
+      Only allow C# DevKit to use types from Contracts namespace. The contracts should not introduce breaking changes between versions,
+      because the versions of C# DevKit and C# Extension might not be aligned.
+    -->
+    <RestrictedInternalsVisibleTo Include="Microsoft.VisualStudio.LanguageServices.DevKit" Namespace="Microsoft.CodeAnalysis.Contracts" />
+
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.Orchestrator" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.UnitTesting.SourceBasedTestDiscovery" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.UnitTesting.SourceBasedTestDiscovery.Core" Partner="UnitTesting" Key="$(UnitTestingKey)" />
@@ -119,6 +127,7 @@
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.AspNetCore" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.Razor" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.Razor.UnitTests" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" />
   </ItemGroup>
   <ItemGroup>
     <Compile Remove="SymbolSearch\Windows\**\*.cs" Condition="'$(DotNetBuildFromSource)' == 'true'" />
diff --git a/src/Features/Core/Portable/Snippets/SnippetPlaceholder.cs b/src/Features/Core/Portable/Snippets/SnippetPlaceholder.cs
index a60fd6401d9cc..1ad7506b7ea92 100644
--- a/src/Features/Core/Portable/Snippets/SnippetPlaceholder.cs
+++ b/src/Features/Core/Portable/Snippets/SnippetPlaceholder.cs
@@ -32,13 +32,21 @@ internal readonly struct SnippetPlaceholder
         /// </summary>
         public SnippetPlaceholder(string identifier, ImmutableArray<int> placeholderPositions)
         {
-            if (identifier.Length == 0)
+            if (string.IsNullOrEmpty(identifier))
             {
-                throw new ArgumentException($"{nameof(identifier)} must not be an empty string.");
+                throw new ArgumentException($"{nameof(identifier)} must not be an null or empty.");
             }
 
             Identifier = identifier;
             PlaceHolderPositions = placeholderPositions;
         }
+
+        /// <summary>
+        /// Initialize a placeholder with a single position
+        /// </summary>
+        public SnippetPlaceholder(string identifier, int placeholderPosition)
+            : this(identifier, ImmutableArray.Create(placeholderPosition))
+        {
+        }
     }
 }
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractConditionalBlockSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractConditionalBlockSnippetProvider.cs
index 69b70a95426ef..8a1c9fda6c2f4 100644
--- a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractConditionalBlockSnippetProvider.cs
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractConditionalBlockSnippetProvider.cs
@@ -24,7 +24,7 @@ protected override ImmutableArray<SnippetPlaceholder> GetPlaceHolderLocationsLis
                 return ImmutableArray<SnippetPlaceholder>.Empty;
 
             var condition = GetCondition(node);
-            var placeholder = new SnippetPlaceholder(identifier: condition.ToString(), placeholderPositions: ImmutableArray.Create(condition.SpanStart));
+            var placeholder = new SnippetPlaceholder(condition.ToString(), condition.SpanStart);
 
             return ImmutableArray.Create(placeholder);
         }
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractForLoopSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractForLoopSnippetProvider.cs
new file mode 100644
index 0000000000000..5d4cfb5126915
--- /dev/null
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractForLoopSnippetProvider.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+
+namespace Microsoft.CodeAnalysis.Snippets.SnippetProviders
+{
+    internal abstract class AbstractForLoopSnippetProvider : AbstractInlineStatementSnippetProvider
+    {
+        protected override bool IsValidAccessingType(ITypeSymbol type)
+            => type.IsIntegralType() || type.IsNativeIntegerType;
+
+        protected override Func<SyntaxNode?, bool> GetSnippetContainerFunction(ISyntaxFacts syntaxFacts)
+            => syntaxFacts.IsForStatement;
+    }
+}
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractIfSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractIfSnippetProvider.cs
index e2b1e19efb246..49b9ad7dd3a32 100644
--- a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractIfSnippetProvider.cs
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractIfSnippetProvider.cs
@@ -22,6 +22,6 @@ internal abstract class AbstractIfSnippetProvider : AbstractConditionalBlockSnip
         protected override Func<SyntaxNode?, bool> GetSnippetContainerFunction(ISyntaxFacts syntaxFacts) => syntaxFacts.IsIfStatement;
 
         protected override SyntaxNode GenerateStatement(SyntaxGenerator generator, SyntaxContext syntaxContext, SyntaxNode? inlineExpression)
-            => generator.IfStatement(inlineExpression ?? generator.TrueLiteralExpression(), Array.Empty<SyntaxNode>());
+            => generator.IfStatement(inlineExpression?.WithoutLeadingTrivia() ?? generator.TrueLiteralExpression(), Array.Empty<SyntaxNode>());
     }
 }
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractInlineStatementSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractInlineStatementSnippetProvider.cs
index 7db4bb7e9a2aa..135c6fda23b63 100644
--- a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractInlineStatementSnippetProvider.cs
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractInlineStatementSnippetProvider.cs
@@ -29,7 +29,7 @@ internal abstract class AbstractInlineStatementSnippetProvider : AbstractStateme
         /// <summary>
         /// Generate statement node
         /// </summary>
-        /// <param name="inlineExpression">Right-hand side of a member access expression.<see langword="null"/> if snippet is executed in normal statement context</param>
+        /// <param name="inlineExpression">Right-hand side of a member access expression. <see langword="null"/> if snippet is executed in normal statement context</param>
         protected abstract SyntaxNode GenerateStatement(SyntaxGenerator generator, SyntaxContext syntaxContext, SyntaxNode? inlineExpression);
 
         /// <summary>
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractLockSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractLockSnippetProvider.cs
new file mode 100644
index 0000000000000..620f9324209f8
--- /dev/null
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractLockSnippetProvider.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.Snippets.SnippetProviders
+{
+    internal abstract class AbstractLockSnippetProvider : AbstractStatementSnippetProvider
+    {
+        protected override Task<TextChange> GenerateSnippetTextChangeAsync(Document document, int position, CancellationToken cancellationToken)
+        {
+            var generator = SyntaxGenerator.GetGenerator(document);
+            var statement = generator.LockStatement(generator.ThisExpression(), SpecializedCollections.EmptyEnumerable<SyntaxNode>());
+            return Task.FromResult(new TextChange(TextSpan.FromBounds(position, position), statement.NormalizeWhitespace().ToFullString()));
+        }
+
+        protected override Func<SyntaxNode?, bool> GetSnippetContainerFunction(ISyntaxFacts syntaxFacts)
+            => syntaxFacts.IsLockStatement;
+    }
+}
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractSnippetProvider.cs
index afa1c91ce5ccc..057af4a95b833 100644
--- a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractSnippetProvider.cs
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractSnippetProvider.cs
@@ -27,8 +27,8 @@ internal abstract class AbstractSnippetProvider : ISnippetProvider
 
         public virtual ImmutableArray<string> AdditionalFilterTexts => ImmutableArray<string>.Empty;
 
-        protected readonly SyntaxAnnotation _cursorAnnotation = new();
-        protected readonly SyntaxAnnotation _findSnippetAnnotation = new();
+        protected readonly SyntaxAnnotation CursorAnnotation = new();
+        protected readonly SyntaxAnnotation FindSnippetAnnotation = new();
 
         /// <summary>
         /// Implemented by each SnippetProvider to determine if that particular position is a valid
@@ -103,11 +103,11 @@ public async Task<SnippetChange> GetSnippetAsync(Document document, int position
             var reformattedDocument = await CleanupDocumentAsync(formatAnnotatedSnippetDocument, cancellationToken).ConfigureAwait(false);
 
             // Finds the added snippet and adds indentation where necessary (braces).
-            var documentWithIndentation = await AddIndentationToDocumentAsync(reformattedDocument, position, syntaxFacts, cancellationToken).ConfigureAwait(false);
+            var documentWithIndentation = await AddIndentationToDocumentAsync(reformattedDocument, cancellationToken).ConfigureAwait(false);
 
             var reformattedRoot = await documentWithIndentation.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var caretTarget = reformattedRoot.GetAnnotatedNodes(_cursorAnnotation).FirstOrDefault();
-            var mainChangeNode = reformattedRoot.GetAnnotatedNodes(_findSnippetAnnotation).FirstOrDefault();
+            var caretTarget = reformattedRoot.GetAnnotatedNodes(CursorAnnotation).FirstOrDefault();
+            var mainChangeNode = reformattedRoot.GetAnnotatedNodes(FindSnippetAnnotation).FirstOrDefault();
 
             Contract.ThrowIfNull(caretTarget);
             Contract.ThrowIfNull(mainChangeNode);
@@ -165,12 +165,12 @@ private async Task<Document> CleanupDocumentAsync(
                 var syntaxFormattingOptions = await document.GetSyntaxFormattingOptionsAsync(fallbackOptions: null, cancellationToken).ConfigureAwait(false);
 
                 document = await ImportAdder.AddImportsFromSymbolAnnotationAsync(
-                    document, _findSnippetAnnotation, addImportPlacementOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
+                    document, FindSnippetAnnotation, addImportPlacementOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
 
-                document = await Simplifier.ReduceAsync(document, _findSnippetAnnotation, simplifierOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
+                document = await Simplifier.ReduceAsync(document, FindSnippetAnnotation, simplifierOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
 
                 // format any node with explicit formatter annotation
-                document = await Formatter.FormatAsync(document, _findSnippetAnnotation, syntaxFormattingOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
+                document = await Formatter.FormatAsync(document, FindSnippetAnnotation, syntaxFormattingOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
 
                 // format any elastic whitespace
                 document = await Formatter.FormatAsync(document, SyntaxAnnotation.ElasticAnnotation, syntaxFormattingOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
@@ -216,7 +216,7 @@ private static async Task<Document> GetDocumentWithSnippetAsync(Document documen
 
         private async Task<Document> AddFormatAnnotationAsync(Document document, int position, CancellationToken cancellationToken)
         {
-            var annotatedSnippetRoot = await AnnotateNodesToReformatAsync(document, _findSnippetAnnotation, _cursorAnnotation, position, cancellationToken).ConfigureAwait(false);
+            var annotatedSnippetRoot = await AnnotateNodesToReformatAsync(document, FindSnippetAnnotation, CursorAnnotation, position, cancellationToken).ConfigureAwait(false);
             document = document.WithSyntaxRoot(annotatedSnippetRoot);
             return document;
         }
@@ -253,7 +253,7 @@ protected virtual async Task<SyntaxNode> AnnotateNodesToReformatAsync(Document d
         /// The SyntaxGenerator does not insert this space for us nor does the LSP Snippet Expander.
         /// We need to manually add that spacing to snippets containing blocks.
         /// </summary>
-        protected virtual async Task<Document> AddIndentationToDocumentAsync(Document document, int position, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
+        protected virtual async Task<Document> AddIndentationToDocumentAsync(Document document, CancellationToken cancellationToken)
         {
             return await Task.FromResult(document).ConfigureAwait(false);
         }
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractTypeSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractTypeSnippetProvider.cs
index 0bb2aba0d745c..d461f39c41791 100644
--- a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractTypeSnippetProvider.cs
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractTypeSnippetProvider.cs
@@ -32,7 +32,7 @@ protected override ImmutableArray<SnippetPlaceholder> GetPlaceHolderLocationsLis
         {
             using var _ = ArrayBuilder<SnippetPlaceholder>.GetInstance(out var arrayBuilder);
             GetTypeDeclarationIdentifier(node, out var identifier);
-            arrayBuilder.Add(new SnippetPlaceholder(identifier: identifier.ValueText, placeholderPositions: ImmutableArray.Create(identifier.SpanStart)));
+            arrayBuilder.Add(new SnippetPlaceholder(identifier.ValueText, identifier.SpanStart));
 
             return arrayBuilder.ToImmutableArray();
         }
diff --git a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractWhileLoopSnippetProvider.cs b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractWhileLoopSnippetProvider.cs
index e5d7622549934..5d8f32897c4cb 100644
--- a/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractWhileLoopSnippetProvider.cs
+++ b/src/Features/Core/Portable/Snippets/SnippetProviders/AbstractWhileLoopSnippetProvider.cs
@@ -18,6 +18,6 @@ internal abstract class AbstractWhileLoopSnippetProvider : AbstractConditionalBl
         protected override Func<SyntaxNode?, bool> GetSnippetContainerFunction(ISyntaxFacts syntaxFacts) => syntaxFacts.IsWhileStatement;
 
         protected override SyntaxNode GenerateStatement(SyntaxGenerator generator, SyntaxContext syntaxContext, SyntaxNode? inlineExpression)
-            => generator.WhileStatement(inlineExpression ?? generator.TrueLiteralExpression(), Array.Empty<SyntaxNode>());
+            => generator.WhileStatement(inlineExpression?.WithoutLeadingTrivia() ?? generator.TrueLiteralExpression(), Array.Empty<SyntaxNode>());
     }
 }
diff --git a/src/Features/Core/Portable/SolutionCrawler/SolutionCrawlerLogger.cs b/src/Features/Core/Portable/SolutionCrawler/SolutionCrawlerLogger.cs
index 28082a32b9946..1e042c18c0edf 100644
--- a/src/Features/Core/Portable/SolutionCrawler/SolutionCrawlerLogger.cs
+++ b/src/Features/Core/Portable/SolutionCrawler/SolutionCrawlerLogger.cs
@@ -106,7 +106,7 @@ private static void LogAnalyzersWorker(
             {
                 m[Id] = correlationId;
                 m[AnalyzerCount] = reordered.Length;
-            }));
+            }, LogLevel.Debug));
 
             foreach (var analyzer in reordered)
             {
@@ -114,7 +114,7 @@ private static void LogAnalyzersWorker(
                 {
                     m[Id] = correlationId;
                     m[Analyzer] = analyzer.ToString();
-                }));
+                }, LogLevel.Debug));
             }
         }
 
diff --git a/src/Features/Core/Portable/Structure/BlockSpan.cs b/src/Features/Core/Portable/Structure/BlockSpan.cs
index df5e006d79bfc..c8e9613ca97e7 100644
--- a/src/Features/Core/Portable/Structure/BlockSpan.cs
+++ b/src/Features/Core/Portable/Structure/BlockSpan.cs
@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
 using Microsoft.CodeAnalysis.Text;
 
 namespace Microsoft.CodeAnalysis.Structure
@@ -27,6 +25,25 @@ internal readonly struct BlockSpan
         /// </summary>
         public TextSpan HintSpan { get; }
 
+        /// <summary>
+        /// Gets the optional span of the primary header of the code block represented by this tag. For example, in the
+        /// following snippet of code:
+        /// <code>
+        ///     if (condition1)
+        ///     {
+        ///         //something;
+        ///     }
+        ///     else
+        ///     {
+        ///         // something else;
+        ///     }
+        /// </code>
+        /// The primary span representing "else" statement block would be the same as the <see cref="TextSpan"/> of
+        /// block span for the  "if" block. This allows structure visualizing features to provide more useful context
+        /// when visualizing "else" structure blocks.
+        /// </summary>
+        public (TextSpan textSpan, TextSpan hintSpan)? PrimarySpans { get; }
+
         /// <summary>
         /// The text to display inside the collapsed region.
         /// </summary>
@@ -49,16 +66,24 @@ internal readonly struct BlockSpan
 
         public BlockSpan(
             string type, bool isCollapsible, TextSpan textSpan, string bannerText = Ellipses, bool autoCollapse = false, bool isDefaultCollapsed = false)
-            : this(type, isCollapsible, textSpan, textSpan, bannerText, autoCollapse, isDefaultCollapsed)
+            : this(type, isCollapsible, textSpan, textSpan, primarySpans: null, bannerText, autoCollapse, isDefaultCollapsed)
         {
         }
 
         public BlockSpan(
-            string type, bool isCollapsible, TextSpan textSpan, TextSpan hintSpan, string bannerText = Ellipses, bool autoCollapse = false, bool isDefaultCollapsed = false)
+            string type,
+            bool isCollapsible,
+            TextSpan textSpan,
+            TextSpan hintSpan,
+            (TextSpan textSpan, TextSpan hintSpan)? primarySpans = null,
+            string bannerText = Ellipses,
+            bool autoCollapse = false,
+            bool isDefaultCollapsed = false)
         {
             TextSpan = textSpan;
-            BannerText = bannerText;
             HintSpan = hintSpan;
+            PrimarySpans = primarySpans;
+            BannerText = bannerText;
             AutoCollapse = autoCollapse;
             IsDefaultCollapsed = isDefaultCollapsed;
             IsCollapsible = isCollapsible;
@@ -82,6 +107,7 @@ internal BlockSpan With(
             Optional<bool> isCollapsible = default,
             Optional<TextSpan> textSpan = default,
             Optional<TextSpan> hintSpan = default,
+            Optional<(TextSpan textSpan, TextSpan hintSpan)> primarySpans = default,
             Optional<string> type = default,
             Optional<string> bannerText = default,
             Optional<bool> autoCollapse = default,
@@ -90,13 +116,14 @@ internal BlockSpan With(
             var newIsCollapsible = isCollapsible.HasValue ? isCollapsible.Value : IsCollapsible;
             var newTextSpan = textSpan.HasValue ? textSpan.Value : TextSpan;
             var newHintSpan = hintSpan.HasValue ? hintSpan.Value : HintSpan;
+            var newPrimarySpans = primarySpans.HasValue ? primarySpans.Value : PrimarySpans;
             var newType = type.HasValue ? type.Value : Type;
             var newBannerText = bannerText.HasValue ? bannerText.Value : BannerText;
             var newAutoCollapse = autoCollapse.HasValue ? autoCollapse.Value : AutoCollapse;
             var newIsDefaultCollapsed = isDefaultCollapsed.HasValue ? isDefaultCollapsed.Value : IsDefaultCollapsed;
 
             return new BlockSpan(
-                newType, newIsCollapsible, newTextSpan, newHintSpan, newBannerText, newAutoCollapse, newIsDefaultCollapsed);
+                newType, newIsCollapsible, newTextSpan, newHintSpan, newPrimarySpans, newBannerText, newAutoCollapse, newIsDefaultCollapsed);
         }
     }
 }
diff --git a/src/Features/Core/Portable/Structure/BlockStructureContext.cs b/src/Features/Core/Portable/Structure/BlockStructureContext.cs
index 1a7315d8ef50f..2a5998057a64e 100644
--- a/src/Features/Core/Portable/Structure/BlockStructureContext.cs
+++ b/src/Features/Core/Portable/Structure/BlockStructureContext.cs
@@ -2,20 +2,22 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Immutable;
 using System.Threading;
+using Microsoft.CodeAnalysis.PooledObjects;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.Structure
 {
-    internal sealed class BlockStructureContext
+    [NonCopyable]
+    internal readonly struct BlockStructureContext : IDisposable
     {
-        private readonly ImmutableArray<BlockSpan>.Builder _spans = ImmutableArray.CreateBuilder<BlockSpan>();
+        public readonly ArrayBuilder<BlockSpan> Spans = ArrayBuilder<BlockSpan>.GetInstance();
 
-        public SyntaxTree SyntaxTree { get; }
-        public BlockStructureOptions Options { get; }
-        public CancellationToken CancellationToken { get; }
-
-        internal ImmutableArray<BlockSpan> Spans => _spans.ToImmutable();
+        public readonly SyntaxTree SyntaxTree;
+        public readonly BlockStructureOptions Options;
+        public readonly CancellationToken CancellationToken;
 
         public BlockStructureContext(SyntaxTree syntaxTree, BlockStructureOptions options, CancellationToken cancellationToken)
         {
@@ -24,7 +26,7 @@ public BlockStructureContext(SyntaxTree syntaxTree, BlockStructureOptions option
             CancellationToken = cancellationToken;
         }
 
-        public void AddBlockSpan(BlockSpan span)
-            => _spans.Add(span);
+        public void Dispose()
+            => Spans.Free();
     }
 }
diff --git a/src/Features/Core/Portable/Structure/BlockStructureProvider.cs b/src/Features/Core/Portable/Structure/BlockStructureProvider.cs
index 05aea7498fd13..961167ecfc59d 100644
--- a/src/Features/Core/Portable/Structure/BlockStructureProvider.cs
+++ b/src/Features/Core/Portable/Structure/BlockStructureProvider.cs
@@ -6,6 +6,6 @@ namespace Microsoft.CodeAnalysis.Structure
 {
     internal abstract class BlockStructureProvider
     {
-        public abstract void ProvideBlockStructure(BlockStructureContext context);
+        public abstract void ProvideBlockStructure(in BlockStructureContext context);
     }
 }
diff --git a/src/Features/Core/Portable/Structure/BlockStructureServiceWithProviders.cs b/src/Features/Core/Portable/Structure/BlockStructureServiceWithProviders.cs
index 7d0547a108f51..e560295d67091 100644
--- a/src/Features/Core/Portable/Structure/BlockStructureServiceWithProviders.cs
+++ b/src/Features/Core/Portable/Structure/BlockStructureServiceWithProviders.cs
@@ -50,8 +50,7 @@ public override async Task<BlockStructure> GetBlockStructureAsync(
             CancellationToken cancellationToken)
         {
             var syntaxTree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
-            var context = CreateContext(syntaxTree, options, cancellationToken);
-
+            using var context = CreateContext(syntaxTree, options, cancellationToken);
             return GetBlockStructure(context, _providers);
         }
 
@@ -64,7 +63,7 @@ private static BlockStructureContext CreateContext(
         }
 
         private static BlockStructure GetBlockStructure(
-            BlockStructureContext context,
+            in BlockStructureContext context,
             ImmutableArray<BlockStructureProvider> providers)
         {
             foreach (var provider in providers)
@@ -73,16 +72,13 @@ private static BlockStructure GetBlockStructure(
             return CreateBlockStructure(context);
         }
 
-        private static BlockStructure CreateBlockStructure(BlockStructureContext context)
+        private static BlockStructure CreateBlockStructure(in BlockStructureContext context)
         {
-            using var _ = ArrayBuilder<BlockSpan>.GetInstance(out var updatedSpans);
+            using var _ = ArrayBuilder<BlockSpan>.GetInstance(context.Spans.Count, out var updatedSpans);
             foreach (var span in context.Spans)
-            {
-                var updatedSpan = UpdateBlockSpan(span, context.Options);
-                updatedSpans.Add(updatedSpan);
-            }
+                updatedSpans.Add(UpdateBlockSpan(span, context.Options));
 
-            return new BlockStructure(updatedSpans.ToImmutable());
+            return new BlockStructure(updatedSpans.ToImmutableAndClear());
         }
 
         private static BlockSpan UpdateBlockSpan(BlockSpan blockSpan, in BlockStructureOptions options)
diff --git a/src/Features/Core/Portable/Structure/Syntax/AbstractBlockStructureProvider.cs b/src/Features/Core/Portable/Structure/Syntax/AbstractBlockStructureProvider.cs
index dfa577a0ba675..60d0f6d771fe5 100644
--- a/src/Features/Core/Portable/Structure/Syntax/AbstractBlockStructureProvider.cs
+++ b/src/Features/Core/Portable/Structure/Syntax/AbstractBlockStructureProvider.cs
@@ -2,8 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
 using System;
 using System.Collections.Immutable;
 using System.Threading.Tasks;
@@ -30,7 +28,7 @@ protected AbstractBlockStructureProvider(
             _triviaProviderMap = defaultTriviaOutlinerMap;
         }
 
-        public override void ProvideBlockStructure(BlockStructureContext context)
+        public override void ProvideBlockStructure(in BlockStructureContext context)
         {
             try
             {
@@ -39,8 +37,9 @@ public override void ProvideBlockStructure(BlockStructureContext context)
                 BlockSpanCollector.CollectBlockSpans(
                     syntaxRoot, context.Options, _nodeProviderMap, _triviaProviderMap, ref spans.AsRef(), context.CancellationToken);
 
+                context.Spans.EnsureCapacity(context.Spans.Count + spans.Count);
                 foreach (var span in spans)
-                    context.AddBlockSpan(span);
+                    context.Spans.Add(span);
             }
             catch (Exception e) when (FatalError.ReportAndPropagateUnlessCanceled(e))
             {
diff --git a/src/Features/Core/Portable/SymbolSearch/Windows/SymbolSearchUpdateEngine.cs b/src/Features/Core/Portable/SymbolSearch/Windows/SymbolSearchUpdateEngine.cs
index 4a99e8afd5ce4..94ee6fbfe34bd 100644
--- a/src/Features/Core/Portable/SymbolSearch/Windows/SymbolSearchUpdateEngine.cs
+++ b/src/Features/Core/Portable/SymbolSearch/Windows/SymbolSearchUpdateEngine.cs
@@ -201,7 +201,7 @@ where IsType(symbol) && !IsType(symbol.Parent())
                 select symbol);
         }
 
-        private PackageWithTypeResult CreateResult(AddReferenceDatabase database, Symbol type)
+        private static PackageWithTypeResult CreateResult(AddReferenceDatabase database, Symbol type)
         {
             var nameParts = ArrayBuilder<string>.GetInstance();
             GetFullName(nameParts, type.FullName.Parent);
@@ -261,7 +261,7 @@ private static bool TryGetRankingSymbolForPackage(Symbol package, out Symbol ran
         private static bool IsType(Symbol symbol)
             => symbol.Type.IsType();
 
-        private void GetFullName(ArrayBuilder<string> nameParts, Path8 path)
+        private static void GetFullName(ArrayBuilder<string> nameParts, Path8 path)
         {
             if (!path.IsEmpty)
             {
diff --git a/src/Features/Core/Portable/SyncNamespaces/AbstractSyncNamespacesService.cs b/src/Features/Core/Portable/SyncNamespaces/AbstractSyncNamespacesService.cs
index f2e1c1a414cea..57a14d585c15b 100644
--- a/src/Features/Core/Portable/SyncNamespaces/AbstractSyncNamespacesService.cs
+++ b/src/Features/Core/Portable/SyncNamespaces/AbstractSyncNamespacesService.cs
@@ -173,8 +173,8 @@ public override async Task<IEnumerable<Diagnostic>> GetDocumentDiagnosticsAsync(
 
             public override Task<IEnumerable<Diagnostic>> GetProjectDiagnosticsAsync(Project project, CancellationToken cancellationToken)
             {
-                return _diagnosticsByProject.ContainsKey(project)
-                    ? Task.FromResult<IEnumerable<Diagnostic>>(_diagnosticsByProject[project])
+                return _diagnosticsByProject.TryGetValue(project, out var diagnostics)
+                    ? Task.FromResult<IEnumerable<Diagnostic>>(diagnostics)
                     : EmptyDiagnosticResult;
             }
         }
diff --git a/src/Features/Core/Portable/UseAutoProperty/AbstractUseAutoPropertyCodeFixProvider.cs b/src/Features/Core/Portable/UseAutoProperty/AbstractUseAutoPropertyCodeFixProvider.cs
index 87b7af95eb498..cad221ec00cd3 100644
--- a/src/Features/Core/Portable/UseAutoProperty/AbstractUseAutoPropertyCodeFixProvider.cs
+++ b/src/Features/Core/Portable/UseAutoProperty/AbstractUseAutoPropertyCodeFixProvider.cs
@@ -267,13 +267,14 @@ private static bool CanEditDocument(
             HashSet<DocumentId> linkedDocuments,
             Dictionary<DocumentId, bool> canEdit)
         {
-            if (!canEdit.ContainsKey(documentId))
+            if (!canEdit.TryGetValue(documentId, out var canEditDocument))
             {
                 var document = solution.GetDocument(documentId);
-                canEdit[documentId] = document != null && !linkedDocuments.Contains(document.Id);
+                canEditDocument = document != null && !linkedDocuments.Contains(document.Id);
+                canEdit[documentId] = canEditDocument;
             }
 
-            return canEdit[documentId];
+            return canEditDocument;
         }
 
         private async Task<SyntaxNode> FormatAsync(SyntaxNode newRoot, Document document, CodeCleanupOptionsProvider fallbackOptions, CancellationToken cancellationToken)
diff --git a/src/Features/Core/Portable/Wrapping/AbstractCodeActionComputer.cs b/src/Features/Core/Portable/Wrapping/AbstractCodeActionComputer.cs
index 822324aa2458d..5602423a1d5cc 100644
--- a/src/Features/Core/Portable/Wrapping/AbstractCodeActionComputer.cs
+++ b/src/Features/Core/Portable/Wrapping/AbstractCodeActionComputer.cs
@@ -17,7 +17,6 @@
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
-using static Microsoft.CodeAnalysis.CodeActions.CodeAction;
 
 namespace Microsoft.CodeAnalysis.Wrapping
 {
@@ -88,9 +87,8 @@ protected string GetSmartIndentationAfter(SyntaxNodeOrToken nodeOrToken)
             protected string GetIndentationAfter(SyntaxNodeOrToken nodeOrToken, FormattingOptions2.IndentStyle indentStyle)
             {
                 var newLine = Options.FormattingOptions.NewLine;
-                var newSourceText = OriginalSourceText.WithChanges(new TextChange(new TextSpan(nodeOrToken.Span.End, 0), newLine));
-                newSourceText = newSourceText.WithChanges(
-                    new TextChange(TextSpan.FromBounds(nodeOrToken.Span.End + newLine.Length, newSourceText.Length), ""));
+                var newSourceText = OriginalSourceText.WithChanges(
+                    new TextChange(TextSpan.FromBounds(nodeOrToken.Span.End, OriginalSourceText.Length), newLine));
 
                 var newDocument = OriginalDocument.WithText(newSourceText);
 
diff --git a/src/Features/Core/Portable/Wrapping/SeparatedSyntaxList/SeparatedSyntaxListCodeActionComputer.cs b/src/Features/Core/Portable/Wrapping/SeparatedSyntaxList/SeparatedSyntaxListCodeActionComputer.cs
index 52b856e0096cf..1d6679ae7954f 100644
--- a/src/Features/Core/Portable/Wrapping/SeparatedSyntaxList/SeparatedSyntaxListCodeActionComputer.cs
+++ b/src/Features/Core/Portable/Wrapping/SeparatedSyntaxList/SeparatedSyntaxListCodeActionComputer.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -45,7 +46,7 @@ private class SeparatedSyntaxListCodeActionComputer : AbstractCodeActionComputer
             ///         ^
             ///         |
             /// </summary>
-            private readonly SyntaxTrivia _singleIndentationTrivia;
+            private readonly Lazy<SyntaxTrivia> _singleIndentationTrivia;
 
             /// <summary>
             /// Indentation to use when placing brace.  e.g.:
@@ -54,7 +55,7 @@ private class SeparatedSyntaxListCodeActionComputer : AbstractCodeActionComputer
             ///     ^
             ///     |
             /// </summary>
-            private readonly SyntaxTrivia _braceIndentationTrivia;
+            private readonly Lazy<SyntaxTrivia> _braceIndentationTrivia;
 
             /// <summary>
             /// Whether or not we should move the open brace of this separated list to a new line.  Many separated lists
@@ -89,15 +90,15 @@ public SeparatedSyntaxListCodeActionComputer(
                 var generator = SyntaxGenerator.GetGenerator(OriginalDocument);
 
                 _afterOpenTokenIndentationTrivia = generator.Whitespace(GetAfterOpenTokenIdentation());
-                _singleIndentationTrivia = generator.Whitespace(GetSingleIdentation());
-                _braceIndentationTrivia = generator.Whitespace(GetBraceTokenIndentation());
+                _singleIndentationTrivia = new Lazy<SyntaxTrivia>(() => generator.Whitespace(GetSingleIdentation()));
+                _braceIndentationTrivia = new Lazy<SyntaxTrivia>(() => generator.Whitespace(GetBraceTokenIndentation()));
             }
 
             private void AddTextChangeBetweenOpenAndFirstItem(
                 WrappingStyle wrappingStyle, ArrayBuilder<Edit> result)
             {
                 result.Add(wrappingStyle == WrappingStyle.WrapFirst_IndentRest
-                    ? Edit.UpdateBetween(_listSyntax.GetFirstToken(), NewLineTrivia, _singleIndentationTrivia, _listItems[0])
+                    ? Edit.UpdateBetween(_listSyntax.GetFirstToken(), NewLineTrivia, _singleIndentationTrivia.Value, _listItems[0])
                     : Edit.DeleteBetween(_listSyntax.GetFirstToken(), _listItems[0]));
             }
 
@@ -124,7 +125,7 @@ private SyntaxTrivia GetIndentationTrivia(WrappingStyle wrappingStyle)
             {
                 return wrappingStyle == WrappingStyle.UnwrapFirst_AlignRest
                     ? _afterOpenTokenIndentationTrivia
-                    : _singleIndentationTrivia;
+                    : _singleIndentationTrivia.Value;
             }
 
             private string GetBraceTokenIndentation()
@@ -270,7 +271,7 @@ private ImmutableArray<Edit> GetWrapLongLinesEdits(
                 using var _ = ArrayBuilder<Edit>.GetInstance(out var result);
 
                 if (_shouldMoveOpenBraceToNewLine)
-                    result.Add(Edit.UpdateBetween(_listSyntax.GetFirstToken().GetPreviousToken(), NewLineTrivia, _braceIndentationTrivia, _listSyntax.GetFirstToken()));
+                    result.Add(Edit.UpdateBetween(_listSyntax.GetFirstToken().GetPreviousToken(), NewLineTrivia, _braceIndentationTrivia.Value, _listSyntax.GetFirstToken()));
 
                 AddTextChangeBetweenOpenAndFirstItem(wrappingStyle, result);
 
@@ -317,7 +318,7 @@ private ImmutableArray<Edit> GetWrapLongLinesEdits(
 
                 if (this.Wrapper.ShouldMoveCloseBraceToNewLine)
                 {
-                    result.Add(Edit.UpdateBetween(itemsAndSeparators.Last(), NewLineTrivia, _braceIndentationTrivia, _listSyntax.GetLastToken()));
+                    result.Add(Edit.UpdateBetween(itemsAndSeparators.Last(), NewLineTrivia, _braceIndentationTrivia.Value, _listSyntax.GetLastToken()));
                 }
                 else
                 {
@@ -396,7 +397,7 @@ private ImmutableArray<Edit> GetWrapEachEdits(
                 using var _ = ArrayBuilder<Edit>.GetInstance(out var result);
 
                 if (_shouldMoveOpenBraceToNewLine)
-                    result.Add(Edit.UpdateBetween(_listSyntax.GetFirstToken().GetPreviousToken(), NewLineTrivia, _braceIndentationTrivia, _listSyntax.GetFirstToken()));
+                    result.Add(Edit.UpdateBetween(_listSyntax.GetFirstToken().GetPreviousToken(), NewLineTrivia, _braceIndentationTrivia.Value, _listSyntax.GetFirstToken()));
 
                 AddTextChangeBetweenOpenAndFirstItem(wrappingStyle, result);
 
@@ -419,7 +420,7 @@ private ImmutableArray<Edit> GetWrapEachEdits(
 
                 if (_shouldMoveCloseBraceToNewLine)
                 {
-                    result.Add(Edit.UpdateBetween(itemsAndSeparators.Last(), NewLineTrivia, _braceIndentationTrivia, _listSyntax.GetLastToken()));
+                    result.Add(Edit.UpdateBetween(itemsAndSeparators.Last(), NewLineTrivia, _braceIndentationTrivia.Value, _listSyntax.GetLastToken()));
                 }
                 else
                 {
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.cs.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.cs.xlf
index 618b03f18a1dc..63d8023f73ddf 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.cs.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.cs.xlf
@@ -700,11 +700,6 @@ Ujistěte se, že specifikátor tt použijete pro jazyky, pro které je nezbytn
         <target state="translated">Příklady:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Explicitně implementované metody záznamů musí mít názvy parametrů, které odpovídají kompilátorem vygenerovanému ekvivalentu {0}.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Extrahovat základní třídu...</target>
@@ -920,16 +915,6 @@ Ujistěte se, že specifikátor tt použijete pro jazyky, pro které je nezbytn
         <target state="translated">Implementovat přes {0}</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">Implementace parametru pozičního záznamu {0} jako jen pro čtení vyžaduje restartování aplikace.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Implementace parametru pozičního záznamu {0} s přístupovým objektem set vyžaduje restartování aplikace.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Neúplné uvození znaků \p{X}</target>
@@ -2807,7 +2792,7 @@ Pozitivní kontrolní výrazy zpětného vyhledávání s nulovou délkou se obv
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Aktualizace {0} v rámci obecného typu nebo metody vyžaduje restartování aplikace, protože není podporována modulem runtime.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Pozitivní kontrolní výrazy zpětného vyhledávání s nulovou délkou se obv
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Aktualizace asnyc nebo iterátoru vyžaduje restartování aplikace, protože tuto akci modul runtime nepodporuje.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Když se tento specifikátor standardního formátu použije, operace formátov
         <target state="translated">'Symbol nemůže být obor názvů.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">oddělovač času</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.de.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.de.xlf
index ccf30680f7fb9..2b9c1435b0ca2 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.de.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.de.xlf
@@ -700,11 +700,6 @@ Stellen Sie sicher, dass Sie den Bezeichner "tt" für Sprachen verwenden, für d
         <target state="translated">Beispiele:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Explizit implementierte Methoden von Datensätzen müssen Parameternamen aufweisen, die mit dem vom Compiler generierten Äquivalent "{0}" übereinstimmen.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Basisklasse extrahieren...</target>
@@ -920,16 +915,6 @@ Stellen Sie sicher, dass Sie den Bezeichner "tt" für Sprachen verwenden, für d
         <target state="translated">Über "{0}" implementieren</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">Das Implementieren eines Positionsparameters „{0}“ als schreibgeschützt erfordert einen Neustart der Anwendung,</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Das Implementieren eines Datensatz-Positionsparameters „{0}“ mit einer festgelegten Zugriffsmethode erfordert einen Neustart der Anwendung.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Unvollständiges \p{X}-Escapezeichen.</target>
@@ -2807,7 +2792,7 @@ Positive Lookbehindassertionen mit Nullbreite werden normalerweise am Anfang reg
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Das Aktualisieren {0} innerhalb des generischen Typs oder der generischen Methode erfordert einen Neustart der Anwendung, da es von der Laufzeit nicht unterstützt wird.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Positive Lookbehindassertionen mit Nullbreite werden normalerweise am Anfang reg
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Das Aktualisieren asynchron oder als Iterator erfordert einen Neustart der Anwendung, da es von der Laufzeit nicht unterstützt wird.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Bei Verwendung dieses Standardformatbezeichners wird zur Formatierung oder Analy
         <target state="translated">'"symbol" kann kein Namespace sein.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">Zeittrennzeichen</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.es.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.es.xlf
index b1cf85449f9fa..7d7d2c6dc689c 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.es.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.es.xlf
@@ -700,11 +700,6 @@ Asegúrese de usar el especificador "tt" para los idiomas para los que es necesa
         <target state="translated">Ejemplos:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Los métodos de registros implementados explícitamente deben tener nombres de parámetro que coincidan con el equivalente generado por el programa "{0}"</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Extraer clase base...</target>
@@ -920,16 +915,6 @@ Asegúrese de usar el especificador "tt" para los idiomas para los que es necesa
         <target state="translated">Implementar a través de "{0}"</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">Para implementar un parámetro posicional de registro "{0}" como solo lectura se requiere reiniciar la aplicación.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Para implementar un parámetro posicional de registro "{0}" con un descriptor de acceso set se requiere reiniciar la aplicación.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Escape de carácter incompleto \p{X}</target>
@@ -2807,7 +2792,7 @@ Las aserciones de búsqueda retrasada (lookbehind) positivas de ancho cero se us
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">La actualización de {0} dentro de un tipo o método genérico requiere reiniciar la aplicación porque no es compatible con el tiempo de ejecución.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Las aserciones de búsqueda retrasada (lookbehind) positivas de ancho cero se us
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">La actualización asincrónica o del iterador requiere reiniciar la aplicación porque no es compatible con el tiempo de ejecución.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Cuando se usa este especificador de formato estándar, la operación de formato
         <target state="translated">'símbolo' no puede ser un espacio de nombres.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">separador de la hora</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.fr.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.fr.xlf
index 391fb91300d67..69d1aab0ec0c0 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.fr.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.fr.xlf
@@ -700,11 +700,6 @@ Veillez à utiliser le spécificateur "tt" pour les langues où il est nécessai
         <target state="translated">Exemples :</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Les méthodes d'enregistrement implémentées explicitement doivent avoir des noms de paramètres qui correspondent à l'équivalent « {0} » généré par le compilateur.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Extraire la classe de base...</target>
@@ -920,16 +915,6 @@ Veillez à utiliser le spécificateur "tt" pour les langues où il est nécessai
         <target state="translated">Implémenter via '{0}'</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">L’implémentation d’un paramètre positionnel « {0} » en lecture seule requiert le redémarrage de l’application,</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">L’implémentation d’un paramètre positionnel d’enregistrement « {0} » avec un accesseur set requiert le redémarrage de l’application.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Caractère d'échappement \p{X} incomplet</target>
@@ -2807,7 +2792,7 @@ Les assertions arrière positives de largeur nulle sont généralement utilisée
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">La mise à jour de {0} au sein d'un type ou d'une méthode générique nécessite le redémarrage de l'application car elle n'est pas prise en charge par le runtime.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Les assertions arrière positives de largeur nulle sont généralement utilisée
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">La mise à jour de l'asynchrone ou de l'itérateur nécessite le redémarrage de l'application car elle n'est pas prise en charge par le runtime.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Quand ce spécificateur de format standard est utilisé, l'opération qui consis
         <target state="translated">'symbol' ne peut pas être un espace de noms.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">séparateur d'heure</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.it.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.it.xlf
index 77092efad4ec7..c546cc7432dfb 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.it.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.it.xlf
@@ -700,11 +700,6 @@ Assicurarsi di usare l'identificatore "tt" per le lingue per le quali è necessa
         <target state="translated">Esempi:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">I metodi dei record implementati in modo esplicito devono avere nomi di parametro corrispondenti all'equivalente generato dal compilatore '{0}'</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Estrai classe di base...</target>
@@ -920,16 +915,6 @@ Assicurarsi di usare l'identificatore "tt" per le lingue per le quali è necessa
         <target state="translated">Implementa tramite '{0}'</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">Se si implementa un parametro posizionale di record '{0}' come di sola lettura, è necessario riavviare l'applicazione.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Se si implementa un parametro posizionale di record '{0}' con una funzione di accesso set, è necessario riavviare l'applicazione.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Sequenza di caratteri di escape \p{X} incompleta</target>
@@ -2807,7 +2792,7 @@ Le asserzioni lookbehind positive di larghezza zero vengono usate in genere all'
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">L'aggiornamento di {0} all'interno del tipo o del metodo generico richiede il riavvio dell'applicazione perché non è supportato dal runtime.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Le asserzioni lookbehind positive di larghezza zero vengono usate in genere all'
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">L'aggiornamento asincrono o iteratore richiede il riavvio dell'applicazione perché non è supportato dal runtime.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Quando si usa questo identificatore di formato standard, la formattazione o l'op
         <target state="translated">'L'elemento 'symbol' non può essere uno spazio dei nomi.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">Separatore di ora</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.ja.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.ja.xlf
index 69f149b7c7d76..af9f866e11cad 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.ja.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.ja.xlf
@@ -700,11 +700,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">例:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">明示的に実装されたレコードのメソッドには、コンパイラ生成と同等の '{0}' と一致するパラメーター名が必要です</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">基底クラスの抽出...</target>
@@ -920,16 +915,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">'{0}' を通じて実装します</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">レコードの位置パラメーター '{0}' を読み取り専用として実装するには、アプリケーションを再起動する必要があります。</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">set アクセサーを含むレコード位置パラメーター '{0}' を実装するには、アプリケーションを再起動する必要があります。</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">不完全な \p{X} 文字エスケープです</target>
@@ -2807,7 +2792,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">ランタイムでサポートされていないため、ジェネリック型またはメソッド内で {0} を更新するには、アプリケーションを再起動する必要があります。</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">ランタイムでサポートされていないため、非同期または反復子を更新するには、アプリケーションを再起動する必要があります。</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ When this standard format specifier is used, the formatting or parsing operation
         <target state="translated">'symbol' は名前空間にすることはできません。</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">時刻の区切り記号</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.ko.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.ko.xlf
index 2775ed8c368e9..fe6541815205d 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.ko.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.ko.xlf
@@ -700,11 +700,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">예:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">명시적으로 구현된 레코드 메서드에는 컴파일러에서 생성된 것과 일치하는 매개 변수 이름 '{0}'이 있어야 합니다.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">기본 클래스 추출...</target>
@@ -920,16 +915,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">'{0}'을(를) 통해 구현</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">레코드 위치 매개 변수 '{0}'을(를) 구현하려면 읽기 전용으로 애플리케이션을 다시 시작해야 합니다.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">설정된 접근자를 사용하여 레코드 위치 매개 변수 '{0}'를 구현하려면 응용 프로그램을 다시 시작해야 합니다.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">불완전한 \p{X} 문자 이스케이프</target>
@@ -2807,7 +2792,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">런타임에서 지원하지 않기 때문에 제네릭 형식 또는 메서드 내에서 {0}을(를) 업데이트하려면 애플리케이션을 다시 시작해야 합니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">런타임에서 지원하지 않기 때문에 비동기 또는 반복기를 업데이트하려면 애플리케이션을 다시 시작해야 합니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ When this standard format specifier is used, the formatting or parsing operation
         <target state="translated">'기호'는 네임스페이스일 수 없습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">시간 구분 기호</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.pl.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.pl.xlf
index a0cc6e1a217f4..bde33325f74e4 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.pl.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.pl.xlf
@@ -700,11 +700,6 @@ Pamiętaj, aby nie używać specyfikatora „tt” dla wszystkich języków, w k
         <target state="translated">Przykłady:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Jawnie zaimplementowane metody rekordów muszą mieć nazwy parametrów pasujące do wygenerowanego odpowiednika kompilatora "{0}"</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Wyodrębnij klasę bazową...</target>
@@ -920,16 +915,6 @@ Pamiętaj, aby nie używać specyfikatora „tt” dla wszystkich języków, w k
         <target state="translated">Implementuj za pomocą elementu „{0}”</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">Wdrożenie parametru pozycyjnyego rekordu „{0}" jako tylko do odczytu wymaga ponownego uruchomienia aplikacji</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Wdrożenie parametru pozycyjnego rekordu "{0}" za pomocą ustawionej metody dostępu wymaga ponownego uruchomienia aplikacji.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Niekompletna sekwencja ucieczki znaku \p{X}</target>
@@ -2807,7 +2792,7 @@ Pozytywne asercje wsteczne o zerowej szerokości są zwykle używane na początk
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Aktualizacja {0} w ramach typu ogólnego lub metody wymaga ponownego uruchomienia aplikacji, ponieważ nie jest obsługiwana przez środowisko uruchomieniowe.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Pozytywne asercje wsteczne o zerowej szerokości są zwykle używane na początk
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Aktualizacja asynchroniczna lub iteratora wymaga ponownego uruchomienia aplikacji, ponieważ nie jest obsługiwana przez środowisko uruchomieniowe.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Gdy jest używany ten standardowy specyfikator formatu, operacja formatowania lu
         <target state="translated">'Element „symbol” nie może być przestrzenią nazw.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">separator godziny</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.pt-BR.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.pt-BR.xlf
index d4afac1c24cd9..0b46a6238ef19 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.pt-BR.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.pt-BR.xlf
@@ -700,11 +700,6 @@ Verifique se o especificador "tt" foi usado para idiomas para os quais é necess
         <target state="translated">Exemplos:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Métodos explicitamente implementados de registros devem ter nomes de parâmetro que correspondem ao compilador gerado '{0}' equivalente</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Extrair a classe base...</target>
@@ -920,16 +915,6 @@ Verifique se o especificador "tt" foi usado para idiomas para os quais é necess
         <target state="translated">Implementar por meio de '{0}'</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">Implementar um parâmetro posicional de registro '{0}' como somente leitura requer reiniciar o aplicativo,</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Implementar um parâmetro posicional de registro '{0}' com um acessador set requer a reinicialização do aplicativo.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Escape de caractere incompleto \p{X}</target>
@@ -2807,7 +2792,7 @@ As declarações de lookbehind positivas de largura zero normalmente são usadas
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">A atualização {0} no tipo ou método genérico requer a reinicialização do aplicativo porque não há suporte para o runtime.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ As declarações de lookbehind positivas de largura zero normalmente são usadas
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">A atualização assíncrona ou iterador requer a reinicialização do aplicativo porque não há suporte para o runtime.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Quando esse especificador de formato padrão é usado, a operação de análise
         <target state="translated">"símbolo" não pode ser um namespace.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">separador de hora</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.ru.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.ru.xlf
index 90a8e079155bb..6331e409a1c78 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.ru.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.ru.xlf
@@ -700,11 +700,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">Примеры:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Явно реализованные методы записей должны иметь имена параметров, соответствующие компилятору, созданному эквивалентом '{0}'</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Извлечь базовый класс...</target>
@@ -920,16 +915,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">Реализовать через "{0}"</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">Для реализации позиционного параметра записи "{0}" в режиме только для чтения требуется перезапустить приложение.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Для реализации позиционного параметра записи "{0}" с заданным методом доступа требуется перезапустить приложение.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Незавершенная escape-последовательность \p{X}</target>
@@ -2807,7 +2792,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Обновление {0} в универсальном типе или методе требует перезапуска приложения, поскольку это не поддерживается средой выполнения.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Обновление асинхронного режима или итератора требует перезапуска приложения, так как это не поддерживается средой выполнения.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ When this standard format specifier is used, the formatting or parsing operation
         <target state="translated">'"символ" не может быть пространством имен.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">разделитель компонентов времени</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.tr.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.tr.xlf
index a890064d01044..6f5a4ac3bbb2f 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.tr.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.tr.xlf
@@ -700,11 +700,6 @@ AM ve PM arasındaki farkın korunmasının gerekli olduğu diller için "tt" be
         <target state="translated">Örnekler:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">Açık olarak uygulanan kayıt yöntemlerinin derleyici tarafından oluşturulan '{0}' eşdeğeri ile eşleşen parametre adlarına sahip olması gerekir</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">Temel sınıfı ayıkla...</target>
@@ -920,16 +915,6 @@ AM ve PM arasındaki farkın korunmasının gerekli olduğu diller için "tt" be
         <target state="translated">'{0}' aracılığıyla uygula</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">'{0}' kayıt konum parametresinin salt okunur olarak uygulanması, uygulamanın yeniden başlatılmasını gerektirir.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">Küme erişimcisi ile '{0}' kayıt konum parametresi uygulamak, uygulamanın yeniden başlatılmasını gerektirir.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">Tamamlanmamış \p{X} karakter kaçış</target>
@@ -2807,7 +2792,7 @@ Sıfır genişlikli pozitif geri yönlü onaylamalar genellikle normal ifadeleri
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Genel tür veya yöntem içinde {0} güncellemesi, çalışma zamanı tarafından desteklenmediğinden uygulamanın yeniden başlatılmasını gerektirir.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Sıfır genişlikli pozitif geri yönlü onaylamalar genellikle normal ifadeleri
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">Zaman uyumsuz veya yineleyicinin güncellenmesi, çalışma zamanı tarafından desteklenmediğinden uygulamanın yeniden başlatılmasını gerektirir.</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ Bu standart biçim belirticisi kullanıldığında, biçimlendirme veya ayrışt
         <target state="translated">'symbol' bir ad alanı olamaz.</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">zaman ayırıcısı</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hans.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hans.xlf
index f20d3350000a9..66018aa5c62b5 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hans.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hans.xlf
@@ -700,11 +700,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">示例:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">记录的显示实施方法参数名必须匹配编辑器生成的等效“{0}”</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">提取基类...</target>
@@ -920,16 +915,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">通过“{0}”实现</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">将记录位置参数“{0}”实现为只读需要重启应用程序，</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">实现带有集取值函数的记录位置参数“{0}”需要重新启动应用程序。</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">\p{X} 字符转义不完整</target>
@@ -2807,7 +2792,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">在泛型类型或方法中更新 {0} 需要重新启动应用程序，因为它不受运行时支持。</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">更新异步或迭代器需要重新启动应用程序，因为它不受运行时支持。</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ When this standard format specifier is used, the formatting or parsing operation
         <target state="translated">'“symbol” 不能为命名空间。</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">时间分隔符</target>
diff --git a/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hant.xlf b/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hant.xlf
index 5120a7b6c0e3e..87ac0571a17fe 100644
--- a/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hant.xlf
+++ b/src/Features/Core/Portable/xlf/FeaturesResources.zh-Hant.xlf
@@ -700,11 +700,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">範例:</target>
         <note>Plural form when we have multiple examples to show.</note>
       </trans-unit>
-      <trans-unit id="Explicitly_implemented_methods_of_records_must_have_parameter_names_that_match_the_compiler_generated_equivalent_0">
-        <source>Explicitly implemented methods of records must have parameter names that match the compiler generated equivalent '{0}'</source>
-        <target state="translated">記錄的明確實作方法，必須有參數名稱符合編譯器產生的相等 '{0}'</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Extract_base_class">
         <source>Extract base class...</source>
         <target state="translated">擷取基底類別...</target>
@@ -920,16 +915,6 @@ Make sure to use the "tt" specifier for languages for which it's necessary to ma
         <target state="translated">透過 '{0}' 實作</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_as_read_only_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' as read only requires restarting the application,</source>
-        <target state="translated">實作記錄位置參數 '{0}' 作爲唯讀需要重新啟動應用程式，</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implementing_a_record_positional_parameter_0_with_a_set_accessor_requires_restarting_the_application">
-        <source>Implementing a record positional parameter '{0}' with a set accessor requires restarting the application.</source>
-        <target state="translated">使用集合存取子實作記錄位置參數 '{0}' 需要重新啟動應用程式。</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Incomplete_character_escape">
         <source>Incomplete \p{X} character escape</source>
         <target state="translated">不完整的 \p{X} 字元逸出</target>
@@ -2807,7 +2792,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_0_within_generic_type_or_method_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating {0} within generic type or method requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">更新泛型型別或方法中的 {0} 需要重新啟動應用程式，因為更新作業不受執行階段支援。</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_a_0_around_an_active_statement_requires_restarting_the_application">
@@ -2832,7 +2817,7 @@ Zero-width positive lookbehind assertions are typically used at the beginning of
       </trans-unit>
       <trans-unit id="Updating_async_or_iterator_requires_restarting_the_application_because_is_not_supported_by_the_runtime">
         <source>Updating async or iterator requires restarting the application because is not supported by the runtime.</source>
-        <target state="new">Updating async or iterator requires restarting the application because is not supported by the runtime.</target>
+        <target state="translated">更新 Async 或 Iterator 需要重新啟動應用程式，因為更新作業不受執行階段支援。</target>
         <note />
       </trans-unit>
       <trans-unit id="Updating_reloadable_type_marked_by_0_attribute_or_its_member_requires_restarting_the_application_because_it_is_not_supported_by_the_runtime">
@@ -4335,6 +4320,11 @@ When this standard format specifier is used, the formatting or parsing operation
         <target state="translated">'symbol' 不可為命名空間。</target>
         <note />
       </trans-unit>
+      <trans-unit id="symbol_kind_and_name_of_member_kind_and_name">
+        <source>{0} '{1}' of {2} '{3}'</source>
+        <target state="new">{0} '{1}' of {2} '{3}'</target>
+        <note>e.g. "parameter 'T param' of method 'M'"</note>
+      </trans-unit>
       <trans-unit id="time_separator">
         <source>time separator</source>
         <target state="translated">時間分隔符號</target>
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/LspFileChangeWatcherTests.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/LspFileChangeWatcherTests.cs
new file mode 100644
index 0000000000000..56b21809f6b2b
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/LspFileChangeWatcherTests.cs
@@ -0,0 +1,146 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Concurrent;
+using Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.FileWatching;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using StreamJsonRpc;
+using Xunit.Abstractions;
+using FileSystemWatcher = Microsoft.VisualStudio.LanguageServer.Protocol.FileSystemWatcher;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+public class LspFileChangeWatcherTests : AbstractLanguageServerHostTests
+{
+    private readonly ClientCapabilities _clientCapabilitiesWithFileWatcherSupport = new ClientCapabilities
+    {
+        Workspace = new WorkspaceClientCapabilities
+        {
+            DidChangeWatchedFiles = new DynamicRegistrationSetting { DynamicRegistration = true }
+        }
+    };
+
+    public LspFileChangeWatcherTests(ITestOutputHelper testOutputHelper) : base(testOutputHelper)
+    {
+    }
+
+    [Fact]
+    public async Task LspFileWatcherNotSupportedWithoutClientSupport()
+    {
+        await using var testLspServer = await TestLspServer.CreateAsync(new ClientCapabilities(), TestOutputLogger);
+
+        Assert.False(LspFileChangeWatcher.SupportsLanguageServerHost(testLspServer.LanguageServerHost));
+    }
+
+    [Fact]
+    public async Task LspFileWatcherSupportedWithClientSupport()
+    {
+        await using var testLspServer = await TestLspServer.CreateAsync(_clientCapabilitiesWithFileWatcherSupport, TestOutputLogger);
+
+        Assert.True(LspFileChangeWatcher.SupportsLanguageServerHost(testLspServer.LanguageServerHost));
+    }
+
+    [Fact]
+    public async Task CreatingDirectoryWatchRequestsDirectoryWatch()
+    {
+        AsynchronousOperationListenerProvider.Enable(enable: true);
+
+        await using var testLspServer = await TestLspServer.CreateAsync(_clientCapabilitiesWithFileWatcherSupport, TestOutputLogger);
+        var lspFileChangeWatcher = new LspFileChangeWatcher(
+            testLspServer.LanguageServerHost,
+            testLspServer.ExportProvider.GetExportedValue<IAsynchronousOperationListenerProvider>());
+
+        var dynamicCapabilitiesRpcTarget = new DynamicCapabilitiesRpcTarget();
+        testLspServer.AddClientLocalRpcTarget(dynamicCapabilitiesRpcTarget);
+
+        using var tempRoot = new TempRoot();
+        var tempDirectory = tempRoot.CreateDirectory();
+
+        // Try creating a context and ensure we created the registration
+        var context = lspFileChangeWatcher.CreateContext(new ProjectSystem.WatchedDirectory(tempDirectory.Path, extensionFilter: null));
+        await WaitForFileWatcherAsync(testLspServer);
+
+        var watcher = GetSingleFileWatcher(dynamicCapabilitiesRpcTarget);
+
+        Assert.Equal(tempDirectory.Path + Path.DirectorySeparatorChar, watcher.GlobPattern.BaseUri.LocalPath);
+        Assert.Equal("**/*", watcher.GlobPattern.Pattern);
+
+        // Get rid of the registration and it should be gone again
+        context.Dispose();
+        await WaitForFileWatcherAsync(testLspServer);
+        Assert.Empty(dynamicCapabilitiesRpcTarget.Registrations);
+    }
+
+    [Fact]
+    public async Task CreatingFileWatchRequestsFileWatch()
+    {
+        AsynchronousOperationListenerProvider.Enable(enable: true);
+
+        await using var testLspServer = await TestLspServer.CreateAsync(_clientCapabilitiesWithFileWatcherSupport, TestOutputLogger);
+        var lspFileChangeWatcher = new LspFileChangeWatcher(
+            testLspServer.LanguageServerHost,
+            testLspServer.ExportProvider.GetExportedValue<IAsynchronousOperationListenerProvider>());
+
+        var dynamicCapabilitiesRpcTarget = new DynamicCapabilitiesRpcTarget();
+        testLspServer.AddClientLocalRpcTarget(dynamicCapabilitiesRpcTarget);
+
+        using var tempRoot = new TempRoot();
+        var tempDirectory = tempRoot.CreateDirectory();
+
+        // Try creating a single file watch and ensure we created the registration
+        var context = lspFileChangeWatcher.CreateContext();
+        var watchedFile = context.EnqueueWatchingFile("Z:\\SingleFile.txt");
+        await WaitForFileWatcherAsync(testLspServer);
+
+        var watcher = GetSingleFileWatcher(dynamicCapabilitiesRpcTarget);
+
+        Assert.Equal("Z:\\", watcher.GlobPattern.BaseUri.LocalPath);
+        Assert.Equal("SingleFile.txt", watcher.GlobPattern.Pattern);
+
+        // Get rid of the registration and it should be gone again
+        watchedFile.Dispose();
+        await WaitForFileWatcherAsync(testLspServer);
+        Assert.Empty(dynamicCapabilitiesRpcTarget.Registrations);
+    }
+
+    private static async Task WaitForFileWatcherAsync(TestLspServer testLspServer)
+    {
+        await testLspServer.ExportProvider.GetExportedValue<AsynchronousOperationListenerProvider>().GetWaiter(FeatureAttribute.Workspace).ExpeditedWaitAsync();
+    }
+
+    private static FileSystemWatcher GetSingleFileWatcher(DynamicCapabilitiesRpcTarget dynamicCapabilities)
+    {
+        var registrationJson = Assert.IsType<JObject>(Assert.Single(dynamicCapabilities.Registrations).Value.RegisterOptions);
+        var registration = registrationJson.ToObject<DidChangeWatchedFilesRegistrationOptions>()!;
+
+        return Assert.Single(registration.Watchers);
+    }
+
+    private sealed class DynamicCapabilitiesRpcTarget
+    {
+        public readonly ConcurrentDictionary<string, Registration> Registrations = new();
+
+        [JsonRpcMethod("client/registerCapability", UseSingleObjectParameterDeserialization = true)]
+        public Task RegisterCapabilityAsync(RegistrationParams registrationParams, CancellationToken _)
+        {
+            foreach (var registration in registrationParams.Registrations)
+                Assert.True(Registrations.TryAdd(registration.Id, registration));
+
+            return Task.CompletedTask;
+        }
+
+        [JsonRpcMethod("client/unregisterCapability", UseSingleObjectParameterDeserialization = true)]
+        public Task UnregisterCapabilityAsync(UnregistrationParamsWithMisspelling unregistrationParams, CancellationToken _)
+        {
+            foreach (var unregistration in unregistrationParams.Unregistrations)
+                Assert.True(Registrations.TryRemove(unregistration.Id, out var _));
+
+            return Task.CompletedTask;
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Microsoft.CodeAnalysis.LanguageServer.UnitTests.csproj b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Microsoft.CodeAnalysis.LanguageServer.UnitTests.csproj
new file mode 100644
index 0000000000000..e6b567e3e8067
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Microsoft.CodeAnalysis.LanguageServer.UnitTests.csproj
@@ -0,0 +1,38 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <RoslynProjectType>UnitTest</RoslynProjectType>
+
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Nerdbank.Streams" Version="$(NerdbankStreamsVersion)" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\Compilers\Test\Core\Microsoft.CodeAnalysis.Test.Utilities.csproj" />
+    <ProjectReference Include="..\Microsoft.CodeAnalysis.LanguageServer\Microsoft.CodeAnalysis.LanguageServer.csproj"/>
+
+    <ProjectReference Include="..\..\..\VisualStudio\DevKit\Impl\Microsoft.VisualStudio.LanguageServices.DevKit.csproj"
+                      ReferenceOutputAssembly="false"
+                      Private="false" />
+  </ItemGroup>
+
+  <!--
+    Copy files contained in the NPM package to a DevKit subdirectory to emulate deployment of the DevKit extension in VS Code.
+  -->
+  <Target Name="_CopyDevKitExtensionFiles" AfterTargets="ResolveProjectReferences">
+    <MSBuild Projects="..\..\..\VisualStudio\DevKit\Impl\Microsoft.VisualStudio.LanguageServices.DevKit.csproj"
+             Targets="CollectNpmInputs">
+      <Output TaskParameter="TargetOutputs" ItemName="_DevKitExtensionFile"/>
+    </MSBuild>
+
+    <ItemGroup>
+      <Content Include="@(_DevKitExtensionFile)" Link="DevKit\%(_DevKitExtensionFile.Filename)%(_DevKitExtensionFile.Extension)" CopyToOutputDirectory="PreserveNewest" />
+    </ItemGroup>
+  </Target>
+</Project>
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/ServerInitializationTests.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/ServerInitializationTests.cs
new file mode 100644
index 0000000000000..817edcb942d2e
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/ServerInitializationTests.cs
@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Xunit.Abstractions;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+public class ServerInitializationTests : AbstractLanguageServerHostTests
+{
+    public ServerInitializationTests(ITestOutputHelper testOutputHelper) : base(testOutputHelper)
+    {
+    }
+
+    [Fact]
+    public async Task TestServerHandlesTextSyncRequestsAsync()
+    {
+        await using var server = await CreateLanguageServerAsync();
+        var document = new VersionedTextDocumentIdentifier { Uri = new Uri(@"C:\file.cs") };
+        var response = await server.ExecuteRequestAsync<DidOpenTextDocumentParams, object>(Methods.TextDocumentDidOpenName, new DidOpenTextDocumentParams
+        {
+            TextDocument = new TextDocumentItem
+            {
+                Uri = document.Uri,
+                Text = "Write"
+            }
+        }, CancellationToken.None);
+
+        // These are notifications so we should get a null response (but no exceptions).
+        Assert.Null(response);
+
+        response = await server.ExecuteRequestAsync<DidChangeTextDocumentParams, object>(Methods.TextDocumentDidChangeName, new DidChangeTextDocumentParams
+        {
+            TextDocument = document,
+            ContentChanges = new[]
+            {
+               new TextDocumentContentChangeEvent
+               {
+                   Range = new VisualStudio.LanguageServer.Protocol.Range { Start = new Position(0, 0), End = new Position(0, 0) },
+                   Text = "Console."
+               }
+            }
+        }, CancellationToken.None);
+
+        // These are notifications so we should get a null response (but no exceptions).
+        Assert.Null(response);
+
+        response = await server.ExecuteRequestAsync<DidCloseTextDocumentParams, object>(Methods.TextDocumentDidCloseName, new DidCloseTextDocumentParams
+        {
+            TextDocument = document
+        }, CancellationToken.None);
+
+        // These are notifications so we should get a null response (but no exceptions).
+        Assert.Null(response);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/TelemetryReporterTests.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/TelemetryReporterTests.cs
new file mode 100644
index 0000000000000..eb2918237c5f4
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/TelemetryReporterTests.cs
@@ -0,0 +1,56 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.Contracts.Telemetry;
+using Microsoft.Extensions.Logging;
+using Roslyn.Utilities;
+using Xunit.Abstractions;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+public sealed class TelemetryReporterTests : AbstractLanguageServerHostTests
+{
+    public TelemetryReporterTests(ITestOutputHelper testOutputHelper)
+        : base(testOutputHelper)
+    {
+    }
+
+    private async Task<ITelemetryReporter> CreateReporterAsync()
+    {
+        var exportProvider = await LanguageServerTestComposition.CreateExportProviderAsync(TestOutputLogger.Factory, includeDevKitComponents: true);
+
+        var reporter = exportProvider.GetExport<ITelemetryReporter>().Value;
+        Assert.NotNull(reporter);
+
+        // Do not set default session in tests to enable test isolation:
+        reporter.InitializeSession("off", "test-session", isDefaultSession: false);
+
+        return reporter;
+    }
+
+    private static string GetEventName(string name) => $"test/event/{name}";
+
+    [Fact]
+    public async Task TestFault()
+    {
+        var service = await CreateReporterAsync();
+        service.ReportFault(GetEventName(nameof(TestFault)), "test description", logLevel: 2, forceDump: false, processId: 0, new Exception());
+    }
+
+    [Fact]
+    public async Task TestBlockLogging()
+    {
+        var service = await CreateReporterAsync();
+        service.LogBlockStart(GetEventName(nameof(TestBlockLogging)), kind: 0, blockId: 0);
+        service.LogBlockEnd(blockId: 0, ImmutableDictionary<string, object?>.Empty, CancellationToken.None);
+    }
+
+    [Fact]
+    public async Task TestLog()
+    {
+        var service = await CreateReporterAsync();
+        service.Log(GetEventName(nameof(TestLog)), ImmutableDictionary<string, object?>.Empty);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/AbstractLanguageServerHostTests.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/AbstractLanguageServerHostTests.cs
new file mode 100644
index 0000000000000..0d0e52c99dc8e
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/AbstractLanguageServerHostTests.cs
@@ -0,0 +1,95 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.Composition;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Nerdbank.Streams;
+using Roslyn.Utilities;
+using StreamJsonRpc;
+using Xunit.Abstractions;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+public abstract class AbstractLanguageServerHostTests
+{
+    protected TestOutputLogger TestOutputLogger { get; }
+
+    protected AbstractLanguageServerHostTests(ITestOutputHelper testOutputHelper)
+    {
+        TestOutputLogger = new TestOutputLogger(testOutputHelper);
+    }
+
+    protected Task<TestLspServer> CreateLanguageServerAsync(bool includeDevKitComponents = true)
+    {
+        return TestLspServer.CreateAsync(new ClientCapabilities(), TestOutputLogger, includeDevKitComponents);
+    }
+
+    protected sealed class TestLspServer : IAsyncDisposable
+    {
+        private readonly Task _languageServerHostCompletionTask;
+        private readonly JsonRpc _clientRpc;
+
+        public static async Task<TestLspServer> CreateAsync(ClientCapabilities clientCapabilities, TestOutputLogger logger, bool includeDevKitComponents = true)
+        {
+            var exportProvider = await LanguageServerTestComposition.CreateExportProviderAsync(logger.Factory, includeDevKitComponents);
+            var testLspServer = new TestLspServer(exportProvider, logger);
+            var initializeResponse = await testLspServer.ExecuteRequestAsync<InitializeParams, InitializeResult>(Methods.InitializeName, new InitializeParams { Capabilities = clientCapabilities }, CancellationToken.None);
+            Assert.NotNull(initializeResponse?.Capabilities);
+
+            await testLspServer.ExecuteRequestAsync<InitializedParams, object>(Methods.InitializedName, new InitializedParams(), CancellationToken.None);
+
+            return testLspServer;
+        }
+
+        internal LanguageServerHost LanguageServerHost { get; }
+        public ExportProvider ExportProvider { get; }
+
+        private TestLspServer(ExportProvider exportProvider, ILogger logger)
+        {
+            var (clientStream, serverStream) = FullDuplexStream.CreatePair();
+            LanguageServerHost = new LanguageServerHost(serverStream, serverStream, exportProvider, logger);
+
+            _clientRpc = new JsonRpc(new HeaderDelimitedMessageHandler(clientStream, clientStream, new JsonMessageFormatter()))
+            {
+                AllowModificationWhileListening = true,
+                ExceptionStrategy = ExceptionProcessing.ISerializable,
+            };
+
+            _clientRpc.StartListening();
+
+            // This task completes when the server shuts down.  We store it so that we can wait for completion
+            // when we dispose of the test server.
+            LanguageServerHost.Start();
+
+            _languageServerHostCompletionTask = LanguageServerHost.WaitForExitAsync();
+            ExportProvider = exportProvider;
+        }
+
+        public async Task<TResponseType?> ExecuteRequestAsync<TRequestType, TResponseType>(string methodName, TRequestType request, CancellationToken cancellationToken) where TRequestType : class
+        {
+            var result = await _clientRpc.InvokeWithParameterObjectAsync<TResponseType>(methodName, request, cancellationToken: cancellationToken);
+            return result;
+        }
+
+        public void AddClientLocalRpcTarget(object target)
+        {
+            _clientRpc.AddLocalRpcTarget(target);
+        }
+
+        public async ValueTask DisposeAsync()
+        {
+            await _clientRpc.InvokeAsync(Methods.ShutdownName);
+            await _clientRpc.NotifyAsync(Methods.ExitName);
+
+            // The language server host task should complete once shutdown and exit are called.
+#pragma warning disable VSTHRD003 // Avoid awaiting foreign Tasks
+            await _languageServerHostCompletionTask;
+#pragma warning restore VSTHRD003 // Avoid awaiting foreign Tasks
+
+            _clientRpc.Dispose();
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/BrokeredServiceProxy.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/BrokeredServiceProxy.cs
new file mode 100644
index 0000000000000..bff88eebd4630
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/BrokeredServiceProxy.cs
@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Nerdbank.Streams;
+using StreamJsonRpc;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+/// <summary>
+/// A wrapper which takes a service but actually sends calls to it through JsonRpc to ensure we can actually use the service across a wire.
+/// </summary>
+internal sealed class BrokeredServiceProxy<T> : IAsyncDisposable where T : class
+{
+    /// <summary>
+    /// A task that cane awaited to assert the rest of the fields in this class being assigned and non-null.
+    /// </summary>
+    private readonly Task _createConnectionTask;
+
+    private JsonRpc? _serverRpc;
+    private JsonRpc? _clientRpc;
+    private T? _clientFactoryProxy;
+
+    public BrokeredServiceProxy(T service)
+    {
+        var (serverStream, clientStream) = FullDuplexStream.CreatePair();
+
+        var serverTask = Task.Run(async () =>
+        {
+            var serverMultiplexingStream = await MultiplexingStream.CreateAsync(serverStream);
+            var serverChannel = await serverMultiplexingStream.AcceptChannelAsync("");
+
+            var serverFormatter = new MessagePackFormatter() { MultiplexingStream = serverMultiplexingStream };
+            _serverRpc = new JsonRpc(new LengthHeaderMessageHandler(serverChannel, serverFormatter));
+
+            _serverRpc.AddLocalRpcTarget(service, options: null);
+            _serverRpc.StartListening();
+        });
+
+        var clientTask = Task.Run(async () =>
+        {
+            var clientMultiplexingStream = await MultiplexingStream.CreateAsync(clientStream);
+            var clientChannel = await clientMultiplexingStream.OfferChannelAsync("");
+
+            var clientFormatter = new MessagePackFormatter() { MultiplexingStream = clientMultiplexingStream };
+            _clientRpc = new JsonRpc(new LengthHeaderMessageHandler(clientChannel, clientFormatter));
+
+            _clientFactoryProxy = _clientRpc.Attach<T>();
+            _clientRpc.StartListening();
+        });
+
+        _createConnectionTask = Task.WhenAll(serverTask, clientTask);
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        await _createConnectionTask;
+
+        _serverRpc!.Dispose();
+        _clientRpc!.Dispose();
+    }
+
+    public async Task<T> GetServiceAsync()
+    {
+        await _createConnectionTask;
+        return _clientFactoryProxy!;
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/LanguageServerTestComposition.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/LanguageServerTestComposition.cs
new file mode 100644
index 0000000000000..9d108c49ae614
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/LanguageServerTestComposition.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.Composition;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+internal sealed class LanguageServerTestComposition
+{
+    /// <summary>
+    /// Build places DevKit files to this subdirectory.
+    /// </summary>
+    private const string DevKitExtensionSubdirectory = "DevKit";
+
+    private const string DevKitAssemblyFileName = "Microsoft.VisualStudio.LanguageServices.DevKit.dll";
+
+    private static string GetDevKitExtensionPath()
+        => Path.Combine(AppContext.BaseDirectory, DevKitExtensionSubdirectory, DevKitAssemblyFileName);
+
+    public static Task<ExportProvider> CreateExportProviderAsync(ILoggerFactory loggerFactory, bool includeDevKitComponents)
+        => ExportProviderBuilder.CreateExportProviderAsync(extensionAssemblyPaths: includeDevKitComponents ? new[] { GetDevKitExtensionPath() } : Array.Empty<string>(), sharedDependenciesPath: null, loggerFactory);
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/TestLoggerProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/TestLoggerProvider.cs
new file mode 100644
index 0000000000000..3ebda77fd10db
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/TestLoggerProvider.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+internal class TestLoggerProvider : ILoggerProvider
+{
+    private readonly ILogger _testLogger;
+    public TestLoggerProvider(ILogger testLogger)
+    {
+        _testLogger = testLogger;
+    }
+
+    public ILogger CreateLogger(string categoryName)
+    {
+        return _testLogger;
+    }
+
+    public void Dispose()
+    {
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/TestOutputLogger.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/TestOutputLogger.cs
new file mode 100644
index 0000000000000..f26d1f89b9ee6
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/TestOutputLogger.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Extensions.Logging;
+using Xunit.Abstractions;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+public class TestOutputLogger : ILogger
+{
+    private readonly ITestOutputHelper _testOutputHelper;
+    public readonly ILoggerFactory Factory;
+
+    public TestOutputLogger(ITestOutputHelper testOutputHelper)
+    {
+        _testOutputHelper = testOutputHelper;
+        Factory = new LoggerFactory(new[] { new TestLoggerProvider(this) });
+    }
+
+    public IDisposable BeginScope<TState>(TState state)
+    {
+        return new NoOpDisposable();
+    }
+
+    public bool IsEnabled(LogLevel logLevel)
+    {
+        return true;
+    }
+
+    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
+    {
+        _testOutputHelper.WriteLine($"[{DateTime.UtcNow:hh:mm:ss.fff}][{logLevel}]{formatter(state, exception)}");
+    }
+
+    private sealed class NoOpDisposable : IDisposable
+    {
+        public void Dispose()
+        {
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/Usings.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/Usings.cs
new file mode 100644
index 0000000000000..349f347431670
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Utilities/Usings.cs
@@ -0,0 +1,5 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+global using Xunit;
\ No newline at end of file
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/WorkspaceProjectFactoryServiceTests.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/WorkspaceProjectFactoryServiceTests.cs
new file mode 100644
index 0000000000000..e575d0879e230
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/WorkspaceProjectFactoryServiceTests.cs
@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+using Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+using Microsoft.CodeAnalysis.LanguageServer.Logging;
+using Microsoft.CodeAnalysis.Remote.ProjectSystem;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests;
+
+public class WorkspaceProjectFactoryServiceTests
+{
+    [Fact]
+    public async Task CreateProjectAndBatch()
+    {
+        using var exportProvider = await LanguageServerTestComposition.CreateExportProviderAsync(new LoggerFactory(), includeDevKitComponents: false);
+        await exportProvider.GetExportedValue<ServiceBrokerFactory>().CreateAsync();
+
+        var workspaceFactory = exportProvider.GetExportedValue<LanguageServerWorkspaceFactory>();
+        var workspaceProjectFactoryServiceInstance = (WorkspaceProjectFactoryService)exportProvider
+            .GetExportedValues<IExportedBrokeredService>()
+            .Single(service => service.Descriptor == WorkspaceProjectFactoryServiceDescriptor.ServiceDescriptor);
+
+        await using var brokeredServiceFactory = new BrokeredServiceProxy<IWorkspaceProjectFactoryService>(
+            workspaceProjectFactoryServiceInstance);
+
+        var workspaceProjectFactoryService = await brokeredServiceFactory.GetServiceAsync();
+        using var workspaceProject = await workspaceProjectFactoryService.CreateAndAddProjectAsync(
+            new WorkspaceProjectCreationInfo(LanguageNames.CSharp, "DisplayName", FilePath: null, new Dictionary<string, string>()),
+            CancellationToken.None);
+
+        using var batch = await workspaceProject.StartBatchAsync(CancellationToken.None);
+
+        var sourceFilePath = MakeAbsolutePath("SourceFile.cs");
+        var additionalFilePath = MakeAbsolutePath("AdditionalFile.txt");
+
+        await workspaceProject.AddSourceFilesAsync(new[] { new SourceFileInfo(sourceFilePath, Array.Empty<string>()) }, CancellationToken.None);
+        await workspaceProject.AddAdditionalFilesAsync(new[] { additionalFilePath }, CancellationToken.None);
+        await batch.ApplyAsync(CancellationToken.None);
+
+        // Verify it actually did something; we won't exclusively test each method since those are tested at lower layers
+        var project = workspaceFactory.Workspace.CurrentSolution.Projects.Single();
+        Assert.Equal(sourceFilePath, project.Documents.Single().FilePath);
+        Assert.Equal(additionalFilePath, project.AdditionalDocuments.Single().FilePath);
+    }
+
+    private static string MakeAbsolutePath(string relativePath)
+    {
+        if (OperatingSystem.IsWindows())
+            return Path.Combine("Z:\\", relativePath);
+        else
+            return Path.Combine("//", relativePath);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/.editorconfig b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/.editorconfig
new file mode 100644
index 0000000000000..e4c1e2f7a4fc5
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/.editorconfig
@@ -0,0 +1,10 @@
+[*.cs]
+
+# CA2007: Consider calling ConfigureAwait on the awaited task
+dotnet_diagnostic.CA2007.severity = none
+
+# CA2007: Do not directly await a Task
+dotnet_diagnostic.CA2007.severity = none
+
+# VSTHRD003: Avoid awaiting foreign Tasks
+dotnet_diagnostic.VSTHRD003.severity = none
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceBridgeProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceBridgeProvider.cs
new file mode 100644
index 0000000000000..eb420c2bc0f9a
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceBridgeProvider.cs
@@ -0,0 +1,78 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using System.Composition;
+using System.Diagnostics;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services;
+using Microsoft.Extensions.Logging;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using Microsoft.VisualStudio.Utilities.ServiceBroker;
+using Nerdbank.Streams;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+
+[Export, Shared]
+internal class BrokeredServiceBridgeProvider
+{
+    private const string ServiceBrokerChannelName = "serviceBroker";
+
+    private readonly ILogger _logger;
+    private readonly TraceSource _brokeredServiceTraceSource;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public BrokeredServiceBridgeProvider(ILoggerFactory loggerFactory, BrokeredServiceTraceListener brokeredServiceTraceListener)
+    {
+        _logger = loggerFactory.CreateLogger<BrokeredServiceBridgeProvider>();
+        _brokeredServiceTraceSource = brokeredServiceTraceListener.Source;
+    }
+
+    /// <summary>
+    /// Creates the brokered service bridge to the remote process.
+    /// We expose the services from our container to the remote and consume services
+    /// from the remote by proffering them into our container.
+    /// </summary>
+    /// <param name="brokeredServicePipeName">the pipe name we use for the connection.</param>
+    /// <param name="container">our local container.</param>
+    /// <param name="cancellationToken">a cancellation token.</param>
+    /// <returns>a task that represents the lifetime of the bridge.  It will complete when the bridge closes.</returns>
+    public async Task SetupBrokeredServicesBridgeAsync(string brokeredServicePipeName, BrokeredServiceContainer container, CancellationToken cancellationToken)
+    {
+        _logger.LogDebug("Setting up brokered service bridge");
+        using var bridgeStream = await ServerFactory.ConnectAsync(brokeredServicePipeName, cancellationToken);
+        using var bridgeMxStream = await MultiplexingStream.CreateAsync(bridgeStream, cancellationToken);
+
+        // Wait until the connection ends (so we don't dispose of the stream before it ends).
+        await Task.WhenAll(ProfferServicesToRemoteAsync(), ConsumeServicesFromRemoteAsync());
+
+        async Task ProfferServicesToRemoteAsync()
+        {
+            using var profferedServiceBrokerChannel = await bridgeMxStream.OfferChannelAsync(ServiceBrokerChannelName, cancellationToken);
+            var serviceBroker = container.GetLimitedAccessServiceBroker(ServiceAudience.Local, ImmutableDictionary<string, string>.Empty, ClientCredentialsPolicy.RequestOverridesDefault);
+            using IpcRelayServiceBroker relayServiceBroker = new(serviceBroker);
+
+            FrameworkServices.RemoteServiceBroker
+                .WithTraceSource(_brokeredServiceTraceSource)
+                .ConstructRpc(relayServiceBroker, profferedServiceBrokerChannel);
+
+            await relayServiceBroker.Completion;
+        }
+
+        async Task ConsumeServicesFromRemoteAsync()
+        {
+            using var consumingServiceBrokerChannel = await bridgeMxStream.AcceptChannelAsync(ServiceBrokerChannelName, cancellationToken);
+            var remoteClient = FrameworkServices.RemoteServiceBroker
+                .WithTraceSource(_brokeredServiceTraceSource)
+                .ConstructRpc<IRemoteServiceBroker>(consumingServiceBrokerChannel);
+
+            using (container.ProfferRemoteBroker(remoteClient, bridgeMxStream, ServiceSource.OtherProcessOnSameMachine, Descriptors.RemoteServicesToRegister.Keys.ToImmutableHashSet()))
+            {
+                await consumingServiceBrokerChannel.Completion;
+            }
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceContainer.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceContainer.cs
new file mode 100644
index 0000000000000..e06bdafc0bb43
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceContainer.cs
@@ -0,0 +1,78 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using System.Diagnostics;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.ServiceHub.Framework.Services;
+using Microsoft.VisualStudio.Composition;
+using Microsoft.VisualStudio.Threading;
+using Microsoft.VisualStudio.Utilities.ServiceBroker;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+internal class BrokeredServiceContainer : GlobalBrokeredServiceContainer
+{
+    public BrokeredServiceContainer(TraceSource traceSource)
+        : base(ImmutableDictionary<ServiceMoniker, ServiceRegistration>.Empty, isClientOfExclusiveServer: false, joinableTaskFactory: null, traceSource)
+    {
+    }
+
+    public override IReadOnlyDictionary<string, string> LocalUserCredentials
+        => ImmutableDictionary<string, string>.Empty;
+
+    /// <inheritdoc cref="GlobalBrokeredServiceContainer.RegisterServices(IReadOnlyDictionary{ServiceMoniker, ServiceRegistration})"/>
+    internal new void RegisterServices(IReadOnlyDictionary<ServiceMoniker, ServiceRegistration> services)
+        => base.RegisterServices(services);
+
+    /// <inheritdoc cref="GlobalBrokeredServiceContainer.UnregisterServices(IEnumerable{ServiceMoniker})"/>
+    internal new void UnregisterServices(IEnumerable<ServiceMoniker> services)
+        => base.UnregisterServices(services);
+
+    internal ImmutableDictionary<ServiceMoniker, ServiceRegistration> GetRegisteredServices()
+        => RegisteredServices;
+
+    internal static async Task<BrokeredServiceContainer> CreateAsync(ExportProvider exportProvider, CancellationToken cancellationToken)
+    {
+        var traceListener = exportProvider.GetExportedValue<BrokeredServiceTraceListener>();
+        var container = new BrokeredServiceContainer(traceListener.Source);
+
+        container.ProfferIntrinsicService(
+            FrameworkServices.Authorization,
+            new ServiceRegistration(VisualStudio.Shell.ServiceBroker.ServiceAudience.Local, null, allowGuestClients: true),
+            (moniker, options, serviceBroker, cancellationToken) => new(new NoOpAuthorizationService()));
+
+        var mefServiceBroker = exportProvider.GetExportedValue<MefServiceBrokerOfExportedServices>();
+        mefServiceBroker.SetContainer(container);
+
+        // Register local mef services.
+        await mefServiceBroker.RegisterAndProfferServicesAsync(cancellationToken);
+
+        // Register the desired remote services
+        container.RegisterServices(Descriptors.RemoteServicesToRegister);
+
+        return container;
+    }
+
+    private class NoOpAuthorizationService : IAuthorizationService
+    {
+        public event EventHandler? CredentialsChanged;
+
+        public event EventHandler? AuthorizationChanged;
+
+        public ValueTask<bool> CheckAuthorizationAsync(ProtectedOperation operation, CancellationToken cancellationToken = default)
+        {
+            return new(true);
+        }
+
+        public ValueTask<IReadOnlyDictionary<string, string>> GetCredentialsAsync(CancellationToken cancellationToken = default)
+        {
+            return new(ImmutableDictionary<string, string>.Empty);
+        }
+
+        protected virtual void OnCredentialsChanged(EventArgs args) => this.CredentialsChanged?.Invoke(this, args);
+
+        protected virtual void OnAuthorizationChanged(EventArgs args) => this.AuthorizationChanged?.Invoke(this, args);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceTraceListener.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceTraceListener.cs
new file mode 100644
index 0000000000000..5dbabf32c5dc0
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/BrokeredServiceTraceListener.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using System.Diagnostics;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+
+[Export, Shared]
+internal class BrokeredServiceTraceListener : TraceListener
+{
+    private readonly ILogger _logger;
+
+    public TraceSource Source { get; }
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public BrokeredServiceTraceListener(ILoggerFactory loggerFactory)
+    {
+        _logger = loggerFactory.CreateLogger(nameof(BrokeredServiceTraceListener));
+        Source = new TraceSource("ServiceBroker", SourceLevels.All);
+        Source.Listeners.Add(this);
+    }
+
+    public override void Write(string? message)
+    {
+        _logger.LogDebug(message);
+    }
+
+    public override void WriteLine(string? message)
+    {
+        _logger.LogDebug(message);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/MefServiceBrokerOfExportedServices.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/MefServiceBrokerOfExportedServices.cs
new file mode 100644
index 0000000000000..2e6436f80af37
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/MefServiceBrokerOfExportedServices.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using Microsoft.VisualStudio.Utilities.ServiceBroker;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+
+[Export, Shared]
+internal class MefServiceBrokerOfExportedServices : ServiceBrokerOfExportedServices
+{
+    private Task<GlobalBrokeredServiceContainer>? _containerTask;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public MefServiceBrokerOfExportedServices()
+    {
+    }
+
+    public void SetContainer(GlobalBrokeredServiceContainer container)
+    {
+        _containerTask = Task.FromResult(container);
+    }
+
+    protected override Task<GlobalBrokeredServiceContainer> GetBrokeredServiceContainerAsync(CancellationToken cancellationToken)
+    {
+        Contract.ThrowIfNull(_containerTask, $"{nameof(SetContainer)} should have already been called.");
+        return _containerTask;
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/ServiceBrokerConnectHandler.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/ServiceBrokerConnectHandler.cs
new file mode 100644
index 0000000000000..ea8dc39c00e83
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/ServiceBrokerConnectHandler.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Composition;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler;
+using Microsoft.CommonLanguageServerProtocol.Framework;
+using Microsoft.VisualStudio.Text.Editor.Commanding.Commands;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+
+[ExportCSharpVisualBasicStatelessLspService(typeof(ServiceBrokerConnectHandler)), Shared]
+[Method("serviceBroker/connect")]
+internal class ServiceBrokerConnectHandler : ILspServiceNotificationHandler<ServiceBrokerConnectHandler.NotificationParams>
+{
+    private readonly ServiceBrokerFactory _serviceBrokerFactory;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ServiceBrokerConnectHandler(ServiceBrokerFactory serviceBrokerFactory)
+    {
+        _serviceBrokerFactory = serviceBrokerFactory;
+    }
+
+    public bool MutatesSolutionState => false;
+
+    public bool RequiresLSPSolution => false;
+
+    Task INotificationHandler<NotificationParams, RequestContext>.HandleNotificationAsync(NotificationParams request, RequestContext requestContext, CancellationToken cancellationToken)
+    {
+        return _serviceBrokerFactory.CreateAndConnectAsync(request.PipeName);
+    }
+
+    [DataContract]
+    private class NotificationParams
+    {
+        [DataMember(Name = "pipeName")]
+        public required string PipeName { get; set; }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/ServiceBrokerFactory.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/ServiceBrokerFactory.cs
new file mode 100644
index 0000000000000..001b513aeb641
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/ServiceBrokerFactory.cs
@@ -0,0 +1,94 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel.Composition;
+using System.ComponentModel.Composition.Hosting;
+using System.Diagnostics.CodeAnalysis;
+using System.Threading;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.HelloWorld;
+using Microsoft.CodeAnalysis.LanguageServer.StarredSuggestions;
+using Microsoft.Extensions.Logging;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Composition;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using Roslyn.Utilities;
+using ExportProvider = Microsoft.VisualStudio.Composition.ExportProvider;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+
+/// <summary>
+/// Exports an <see cref="IServiceBroker"/> for convenient and potentially cross-IDE importing by other features.
+/// </summary>
+/// <remarks>
+/// Each import site gets its own <see cref="IServiceBroker"/> instance to match the behavior of calling <see cref="IBrokeredServiceContainer.GetFullAccessServiceBroker"/>
+/// which returns a private instance for everyone.
+/// This is observable to callers in a few ways, including that they only get the <see cref="IServiceBroker.AvailabilityChanged"/> events
+/// based on their own service queries.
+/// MEF will dispose of each instance as its lifetime comes to an end.
+/// </remarks>
+#pragma warning disable RS0030 // This is intentionally using System.ComponentModel.Composition for compatibility with MEF service broker.
+[Export]
+internal class ServiceBrokerFactory
+{
+    private BrokeredServiceContainer? _container;
+    private readonly ExportProvider _exportProvider;
+    private Task _bridgeCompletionTask;
+    private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ServiceBrokerFactory(ExportProvider exportProvider)
+    {
+        _exportProvider = exportProvider;
+        _bridgeCompletionTask = Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Returns a full-access service broker, but will throw if we haven't yet connected to the Dev Kit broker.
+    /// </summary>
+    [Export(typeof(SVsFullAccessServiceBroker))]
+    public IServiceBroker FullAccessServiceBroker => this.GetRequiredServiceBrokerContainer().GetFullAccessServiceBroker();
+
+    /// <summary>
+    /// Returns a full-access service broker, but will return null if we haven't yet connected to the Dev Kit broker.
+    /// </summary>
+    public IServiceBroker? TryGetFullAccessServiceBroker() => _container?.GetFullAccessServiceBroker();
+
+    public BrokeredServiceContainer GetRequiredServiceBrokerContainer()
+    {
+        Contract.ThrowIfNull(_container);
+        return _container;
+    }
+
+    /// <summary>
+    /// Creates a service broker instance without connecting via a pipe to another process.
+    /// </summary>
+    public async Task CreateAsync()
+    {
+        Contract.ThrowIfFalse(_container == null, "We should only create one container.");
+
+        _container = await BrokeredServiceContainer.CreateAsync(_exportProvider, _cancellationTokenSource.Token);
+    }
+
+    public async Task CreateAndConnectAsync(string brokeredServicePipeName)
+    {
+        await CreateAsync();
+
+        var bridgeProvider = _exportProvider.GetExportedValue<BrokeredServiceBridgeProvider>();
+        _bridgeCompletionTask = bridgeProvider.SetupBrokeredServicesBridgeAsync(brokeredServicePipeName, _container!, _cancellationTokenSource.Token);
+
+        await _exportProvider.GetExportedValue<RemoteHelloWorldProvider>().SayHelloToRemoteServerAsync(_cancellationTokenSource.Token);
+    }
+
+    public Task ShutdownAndWaitForCompletionAsync()
+    {
+        _cancellationTokenSource.Cancel();
+
+        // Return the task we created when we created the bridge; if we never started it in the first place, we'll just return the
+        // completed task set in the constructor, so the waiter no-ops.
+        return _bridgeCompletionTask;
+    }
+}
+#pragma warning restore RS0030 // Do not used banned APIs
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/BrokeredServiceBridgeManifest/BrokeredServiceBridgeManifestService.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/BrokeredServiceBridgeManifest/BrokeredServiceBridgeManifestService.cs
new file mode 100644
index 0000000000000..e98dd47d2f94e
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/BrokeredServiceBridgeManifest/BrokeredServiceBridgeManifestService.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using System.ComponentModel.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.Extensions.Logging;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.BrokeredServiceBridgeManifest;
+
+#pragma warning disable RS0030 // This is intentionally using System.ComponentModel.Composition for compatibility with MEF service broker.
+[ExportBrokeredService(MonikerName, MonikerVersion, Audience = ServiceAudience.Local)]
+internal class BrokeredServiceBridgeManifest : IBrokeredServiceBridgeManifest, IExportedBrokeredService
+{
+    internal const string MonikerName = "Microsoft.VisualStudio.Server.IBrokeredServiceBridgeManifest";
+    internal const string MonikerVersion = "0.1";
+    private static readonly ServiceMoniker s_serviceMoniker = new ServiceMoniker(MonikerName, new Version(MonikerVersion));
+    private static readonly ServiceRpcDescriptor s_serviceDescriptor = new ServiceJsonRpcDescriptor(
+        s_serviceMoniker,
+        ServiceJsonRpcDescriptor.Formatters.UTF8,
+        ServiceJsonRpcDescriptor.MessageDelimiters.HttpLikeHeaders);
+
+    private readonly ServiceBrokerFactory _serviceBrokerFactory;
+    private readonly ILogger _logger;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public BrokeredServiceBridgeManifest(ServiceBrokerFactory serviceBrokerFactory, ILoggerFactory loggerFactory)
+    {
+        _serviceBrokerFactory = serviceBrokerFactory;
+        _logger = loggerFactory.CreateLogger<BrokeredServiceBridgeManifest>();
+    }
+
+    public ServiceRpcDescriptor Descriptor => s_serviceDescriptor;
+
+    /// <summary>
+    /// Returns a subset of services registered to Microsoft.VisualStudio.Code.Server container that are proferred by the Language Server process.
+    /// </summary>
+    public ValueTask<IReadOnlyCollection<ServiceMoniker>> GetAvailableServicesAsync(CancellationToken cancellationToken)
+    {
+        var services = (IReadOnlyCollection<ServiceMoniker>)_serviceBrokerFactory.GetRequiredServiceBrokerContainer().GetRegisteredServices()
+            .Select(s => s.Key)
+            .Where(s => s.Name.StartsWith("Microsoft.CodeAnalysis.LanguageServer.", StringComparison.Ordinal) ||
+                        s.Name.StartsWith("Microsoft.VisualStudio.LanguageServer.", StringComparison.Ordinal) ||
+                        s.Name.StartsWith("Microsoft.VisualStudio.LanguageServices.", StringComparison.Ordinal))
+            .ToImmutableArray();
+        _logger.LogDebug($"Proffered services: {string.Join(',', services.Select(s => s.ToString()))}");
+        return ValueTask.FromResult(services);
+    }
+
+    public Task InitializeAsync(CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+}
+#pragma warning restore RS0030 // Do not used banned APIs
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/BrokeredServiceBridgeManifest/IBrokeredServiceBridgeManifest.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/BrokeredServiceBridgeManifest/IBrokeredServiceBridgeManifest.cs
new file mode 100644
index 0000000000000..8b4df206e01d9
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/BrokeredServiceBridgeManifest/IBrokeredServiceBridgeManifest.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Utilities.ServiceBroker;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.BrokeredServiceBridgeManifest;
+
+/// <summary>
+/// Defines a service to be used by the remote party to determine which services from this container
+/// it should add to its container.  This is useful in the case where the remote party connects to other processes
+/// that proffer the same services as we do (e.g. intrinsic services).
+/// Both are proffered as <see cref="ServiceSource.OtherProcessOnSameMachine"/> and therefore conflict.
+/// </summary>
+internal interface IBrokeredServiceBridgeManifest
+{
+    /// <summary>
+    /// Returns services that the container wishes to expose across the bridge.
+    /// </summary>
+    /// <param name="cancellationToken"></param>
+    /// <returns></returns>
+    ValueTask<IReadOnlyCollection<ServiceMoniker>> GetAvailableServicesAsync(CancellationToken cancellationToken);
+}
+
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Definitions/IProjectInitializationStatusService.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Definitions/IProjectInitializationStatusService.cs
new file mode 100644
index 0000000000000..5b86a2e9c2d4e
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Definitions/IProjectInitializationStatusService.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using StreamJsonRpc;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.Definitions;
+/// <summary>
+/// Copied from https://devdiv.visualstudio.com/DevDiv/_git/CPS?path=/src/Microsoft.VisualStudio.ProjectSystem.Server/BrokerServices/IProjectInitializationStatusService.cs
+/// </summary>
+internal interface IProjectInitializationStatusService
+{
+    [JsonRpcMethod("subscribeInitializationCompletion")]
+    ValueTask<IDisposable> SubscribeInitializationCompletionAsync(IObserver<ProjectInitializationCompletionState> observer, CancellationToken cancellationToken);
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Definitions/ProjectInitializationCompleteState.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Definitions/ProjectInitializationCompleteState.cs
new file mode 100644
index 0000000000000..19f1de709f297
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Definitions/ProjectInitializationCompleteState.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Threading.Tasks;
+using Newtonsoft.Json;
+using System.Xml.Linq;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.Definitions;
+/// <summary>
+/// Copied from https://devdiv.visualstudio.com/DevDiv/_git/CPS?path=/src/Microsoft.VisualStudio.ProjectSystem.Server/ProjectInitializationCompletionState.cs
+/// </summary>
+[DataContract]
+internal class ProjectInitializationCompletionState
+{
+    [DataMember(IsRequired = true, EmitDefaultValue = false, Name = "environmentStateVersion")]
+    public int EnvironmentStateVersion { get; set; }
+
+    [DataMember(IsRequired = false, EmitDefaultValue = true, Name = "projectsLoadedCount")]
+    public int ProjectsLoadedCount { get; set; }
+
+    [DataMember(IsRequired = false, EmitDefaultValue = true, Name = "projectsFailedCount")]
+    public int ProjectsFailedCount { get; set; }
+
+    [DataMember(IsRequired = true, EmitDefaultValue = false, Name = "stateUpdateVersion")]
+    public int StateUpdateVersion { get; set; }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Descriptors.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Descriptors.cs
new file mode 100644
index 0000000000000..fb58b144cb38f
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/Descriptors.cs
@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.BrokeredServices;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.HelloWorld;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using Microsoft.VisualStudio.Utilities.ServiceBroker;
+using Nerdbank.Streams;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services;
+
+internal class Descriptors
+{
+    // Descriptors for remote services.
+    // If adding services here, make sure to update RemoteServicesToRegister.
+
+    public static readonly ServiceRpcDescriptor RemoteHelloWorldService = CreateDescriptor(new("helloServiceHubDotNetHost", new Version("0.1")));
+    public static readonly ServiceRpcDescriptor RemoteModelService = CreateDescriptor(new("vs-intellicode-base-models", new Version("0.1")));
+
+    /// <summary>
+    /// See https://devdiv.visualstudio.com/DevDiv/_git/CPS?path=/src/Microsoft.VisualStudio.ProjectSystem.Server/BrokerServices/ProjectInitializationStatusServiceDescriptor.cs
+    /// </summary>
+    public static readonly ServiceRpcDescriptor RemoteProjectInitializationStatusService = new ServiceJsonRpcDescriptor(
+        new("Microsoft.VisualStudio.ProjectSystem.ProjectInitializationStatusService", new Version(0, 1)),
+        clientInterface: null,
+        ServiceJsonRpcDescriptor.Formatters.MessagePack,
+        ServiceJsonRpcDescriptor.MessageDelimiters.BigEndianInt32LengthHeader,
+        new MultiplexingStream.Options { ProtocolMajorVersion = 3 });
+
+    // Descriptors for local services.
+
+    public static readonly ServiceRpcDescriptor LocalHelloWorldService = CreateDescriptor(new(HelloWorldService.MonikerName, new Version(HelloWorldService.MonikerVersion)));
+
+    /// <summary>
+    /// The set of remote services that we register to our container.
+    /// </summary>
+    /// <remarks>
+    /// Note that while today we only support static registration of services in the remote process it would be possible to implement dynamic registration
+    /// if we read the remote brokered service manifest.
+    /// </remarks>
+    public static ImmutableDictionary<ServiceMoniker, ServiceRegistration> RemoteServicesToRegister = new Dictionary<ServiceMoniker, ServiceRegistration>
+    {
+        { RemoteHelloWorldService.Moniker, new ServiceRegistration(ServiceAudience.Local, null, allowGuestClients: false) },
+        { RemoteModelService.Moniker, new ServiceRegistration(ServiceAudience.Local, null, allowGuestClients: false) },
+        { RemoteProjectInitializationStatusService.Moniker, new ServiceRegistration(ServiceAudience.Local, null, allowGuestClients: false) },
+        { BrokeredServiceDescriptors.SolutionSnapshotProvider.Moniker, new ServiceRegistration(ServiceAudience.Local, null, allowGuestClients: false) },
+        { BrokeredServiceDescriptors.DebuggerManagedHotReloadService.Moniker, new ServiceRegistration(ServiceAudience.Local, null, allowGuestClients: false) },
+    }.ToImmutableDictionary();
+
+    public static ServiceJsonRpcDescriptor CreateDescriptor(ServiceMoniker serviceMoniker) => new(
+        serviceMoniker,
+        ServiceJsonRpcDescriptor.Formatters.UTF8,
+        ServiceJsonRpcDescriptor.MessageDelimiters.HttpLikeHeaders);
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/HelloWorldService.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/HelloWorldService.cs
new file mode 100644
index 0000000000000..fd85111627ff8
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/HelloWorldService.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.HelloWorld;
+
+#pragma warning disable RS0030 // This is intentionally using System.ComponentModel.Composition for compatibility with MEF service broker.
+[ExportBrokeredService(MonikerName, MonikerVersion, Audience = ServiceAudience.AllClientsIncludingGuests | ServiceAudience.Local)]
+internal class HelloWorldService : IHelloWorld, IExportedBrokeredService
+{
+    internal const string MonikerName = "Microsoft.CodeAnalysis.LanguageServer.IHelloWorld";
+    internal const string MonikerVersion = "0.1";
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public HelloWorldService()
+    {
+    }
+
+    public ServiceRpcDescriptor Descriptor => Descriptors.LocalHelloWorldService;
+
+    public Task InitializeAsync(CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+
+    public Task<string> SayHelloAsync(string name, CancellationToken cancellationToken)
+    {
+        return Task.FromResult($"Greetings {name}, welcome to the C# party :)");
+    }
+
+    public Task<string> CallMeAsync(ServiceMoniker serviceMoniker, CancellationToken cancellationToken)
+    {
+        throw new NotImplementedException();
+    }
+}
+#pragma warning restore RS0030 // Do not used banned APIs
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/IHelloWorld.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/IHelloWorld.cs
new file mode 100644
index 0000000000000..1dc738ce759f5
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/IHelloWorld.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.ServiceHub.Framework;
+using StreamJsonRpc;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.HelloWorld;
+
+/// <summary>
+/// A simple interface used for sanity checking that the brokered service bridge works.
+/// There is an implementation of the same service on the green side that we can talk to.
+/// </summary>
+internal interface IHelloWorld
+{
+    [JsonRpcMethod("sayHello")]
+    Task<string> SayHelloAsync(string name, CancellationToken cancellationToken);
+
+    [JsonRpcMethod("callMe")]
+    Task<string> CallMeAsync(ServiceMoniker serviceMoniker, CancellationToken cancellationToken);
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/RemoteHelloWorldProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/RemoteHelloWorldProvider.cs
new file mode 100644
index 0000000000000..af6a15e5a79a2
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/BrokeredServices/Services/HelloWorld/RemoteHelloWorldProvider.cs
@@ -0,0 +1,73 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel.Composition;
+using System.Diagnostics;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.Extensions.Logging;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.HelloWorld;
+
+#pragma warning disable RS0030 // This is intentionally using System.ComponentModel.Composition for compatibility with MEF service broker.
+[Export]
+internal class RemoteHelloWorldProvider
+{
+    private readonly IServiceBroker _serviceBroker;
+    private readonly TaskCompletionSource _serviceAvailable = new();
+    private readonly ILogger _logger;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public RemoteHelloWorldProvider([Import(typeof(SVsFullAccessServiceBroker))] IServiceBroker serviceBroker, ILoggerFactory loggerFactory)
+    {
+        _serviceBroker = serviceBroker;
+        _logger = loggerFactory.CreateLogger<RemoteHelloWorldProvider>();
+
+        _serviceBroker.AvailabilityChanged += ServiceBroker_AvailabilityChanged;
+    }
+
+    public async Task SayHelloToRemoteServerAsync(CancellationToken cancellationToken)
+    {
+        var response = await TryGetHelloWorldAsync(cancellationToken);
+        if (!response)
+        {
+            await _serviceAvailable.Task;
+            Contract.ThrowIfFalse(await TryGetHelloWorldAsync(cancellationToken), "Was not able to get hello world response from remote");
+        }
+    }
+
+    private void ServiceBroker_AvailabilityChanged(object? sender, BrokeredServicesChangedEventArgs e)
+    {
+        if (e.ImpactedServices.Contains(Descriptors.RemoteHelloWorldService.Moniker))
+            _serviceAvailable.SetResult();
+    }
+
+    private async Task<bool> TryGetHelloWorldAsync(CancellationToken cancellationToken)
+    {
+        var helloWorldService = await _serviceBroker.GetProxyAsync<IHelloWorld>(Descriptors.RemoteHelloWorldService, cancellationToken);
+        using (helloWorldService as IDisposable)
+        {
+            if (helloWorldService is not null)
+            {
+                try
+                {
+                    var response = await helloWorldService.SayHelloAsync("C#", cancellationToken);
+                    _logger.LogDebug("Response from remote: " + response);
+                    return true;
+                }
+                catch (Exception ex)
+                {
+                    _logger.LogError($"Got exception when invoking callback function:{ex}");
+                }
+            }
+        }
+
+        return false;
+    }
+}
+
+#pragma warning restore RS0030 // Do not used banned APIs
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Contracts/ITelemetryReporter.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Contracts/ITelemetryReporter.cs
new file mode 100644
index 0000000000000..1ff7c10d1420c
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Contracts/ITelemetryReporter.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+
+namespace Microsoft.CodeAnalysis.Contracts.Telemetry;
+
+internal interface ITelemetryReporter : IDisposable
+{
+    void InitializeSession(string telemetryLevel, string? sessionId, bool isDefaultSession);
+    void Log(string name, ImmutableDictionary<string, object?> properties);
+    void LogBlockStart(string eventName, int kind, int blockId);
+    void LogBlockEnd(int blockId, ImmutableDictionary<string, object?> properties, CancellationToken cancellationToken);
+    void ReportFault(string eventName, string description, int logLevel, bool forceDump, int processId, Exception exception);
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/CustomExportAssemblyLoader.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/CustomExportAssemblyLoader.cs
new file mode 100644
index 0000000000000..9fb2d2657b0ea
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/CustomExportAssemblyLoader.cs
@@ -0,0 +1,99 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+using Microsoft.VisualStudio.Composition;
+
+namespace Microsoft.CodeAnalysis.LanguageServer;
+
+internal class CustomExportAssemblyLoader : IAssemblyLoader
+{
+    /// <summary>
+    /// Cache assemblies that are already loaded by AssemblyName comparison
+    /// </summary>
+    private readonly Dictionary<AssemblyName, Assembly> _loadedAssemblies = new Dictionary<AssemblyName, Assembly>(AssemblyNameComparer.Instance);
+
+    /// <summary>
+    /// Base directory to search for <see cref="Assembly.LoadFrom(string)"/> if initial load fails
+    /// </summary>
+    private readonly string _baseDirectory;
+
+    public CustomExportAssemblyLoader(string baseDirectory)
+    {
+        _baseDirectory = baseDirectory;
+    }
+
+    public Assembly LoadAssembly(AssemblyName assemblyName)
+    {
+        Assembly? value;
+        lock (_loadedAssemblies)
+        {
+            _loadedAssemblies.TryGetValue(assemblyName, out value);
+        }
+
+        if (value == null)
+        {
+            // Attempt to load the assembly normally, but fall back to Assembly.LoadFrom in the base
+            // directory if the assembly load fails
+            try
+            {
+                value = Assembly.Load(assemblyName);
+            }
+            catch (FileNotFoundException) when (assemblyName.Name is not null)
+            {
+                var filePath = Path.Combine(_baseDirectory, assemblyName.Name)
+                    + (assemblyName.Name.EndsWith(".dll", StringComparison.OrdinalIgnoreCase)
+                        ? ""
+                        : ".dll");
+
+                value = Assembly.LoadFrom(filePath);
+
+                if (value is null)
+                {
+                    throw;
+                }
+            }
+
+            lock (_loadedAssemblies)
+            {
+                _loadedAssemblies[assemblyName] = value;
+                return value;
+            }
+        }
+
+        return value;
+    }
+
+    public Assembly LoadAssembly(string assemblyFullName, string? codeBasePath)
+    {
+        var assemblyName = new AssemblyName(assemblyFullName);
+        return LoadAssembly(assemblyName);
+    }
+
+    private class AssemblyNameComparer : IEqualityComparer<AssemblyName>
+    {
+        public static AssemblyNameComparer Instance = new AssemblyNameComparer();
+
+        public bool Equals(AssemblyName? x, AssemblyName? y)
+        {
+            if (x == null && y == null)
+            {
+                return true;
+            }
+
+            if (x == null || y == null)
+            {
+                return false;
+            }
+
+            return x.Name == y.Name;
+        }
+
+        public int GetHashCode([DisallowNull] AssemblyName obj)
+        {
+            return obj.Name?.GetHashCode(StringComparison.Ordinal) ?? 0;
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/ExportProviderBuilder.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/ExportProviderBuilder.cs
new file mode 100644
index 0000000000000..3afa2dcc69c47
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/ExportProviderBuilder.cs
@@ -0,0 +1,108 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using System.Reflection;
+using System.Runtime.Loader;
+using Microsoft.CodeAnalysis.LanguageServer.Logging;
+using Microsoft.CodeAnalysis.LanguageServer.Services;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.Composition;
+
+namespace Microsoft.CodeAnalysis.LanguageServer;
+
+internal sealed class ExportProviderBuilder
+{
+    public static async Task<ExportProvider> CreateExportProviderAsync(IEnumerable<string> extensionAssemblyPaths, string? sharedDependenciesPath, ILoggerFactory loggerFactory)
+    {
+        var logger = loggerFactory.CreateLogger<ExportProviderBuilder>();
+
+        var baseDirectory = AppContext.BaseDirectory;
+
+        var resolver = new Resolver(new CustomExportAssemblyLoader(baseDirectory));
+
+        // Load any Roslyn assemblies from the extension directory
+        var assemblyPaths = Directory.EnumerateFiles(baseDirectory, "Microsoft.CodeAnalysis*.dll");
+        assemblyPaths = assemblyPaths.Concat(Directory.EnumerateFiles(baseDirectory, "Microsoft.ServiceHub*.dll"));
+
+        // Temporarily explicitly load the dlls we want to add to the MEF composition.  This is due to a runtime bug
+        // in the 7.0.4 runtime where the APIs MEF uses to load assemblies break with R2R assemblies.
+        // See https://github.com/dotnet/runtime/issues/83526
+        //
+        // Once a newer version of the runtime is widely available, we can remove this.
+        foreach (var path in assemblyPaths)
+        {
+            Assembly.LoadFrom(path);
+        }
+
+        var discovery = PartDiscovery.Combine(
+            resolver,
+            new AttributedPartDiscovery(resolver, isNonPublicSupported: true), // "NuGet MEF" attributes (Microsoft.Composition)
+            new AttributedPartDiscoveryV1(resolver));
+
+        var assemblies = new List<Assembly>()
+        {
+            typeof(ExportProviderBuilder).Assembly
+        };
+
+        foreach (var extensionAssemblyPath in extensionAssemblyPaths)
+        {
+            if (AssemblyLoadContextWrapper.TryLoadExtension(extensionAssemblyPath, sharedDependenciesPath, logger, out var extensionAssembly))
+            {
+                assemblies.Add(extensionAssembly);
+            }
+        }
+
+        // TODO - we should likely cache the catalog so we don't have to rebuild it every time.
+        var catalog = ComposableCatalog.Create(resolver)
+            .AddParts(await discovery.CreatePartsAsync(assemblies))
+            .AddParts(await discovery.CreatePartsAsync(assemblyPaths))
+            .WithCompositionService(); // Makes an ICompositionService export available to MEF parts to import
+
+        // Assemble the parts into a valid graph.
+        var config = CompositionConfiguration.Create(catalog);
+
+        // Verify we only have expected errors.
+        ThrowOnUnexpectedErrors(config, logger);
+
+        // Prepare an ExportProvider factory based on this graph.
+        var exportProviderFactory = config.CreateExportProviderFactory();
+
+        // Create an export provider, which represents a unique container of values.
+        // You can create as many of these as you want, but typically an app needs just one.
+        var exportProvider = exportProviderFactory.CreateExportProvider();
+
+        // Immediately set the logger factory, so that way it'll be available for the rest of the composition
+        exportProvider.GetExportedValue<ServerLoggerFactory>().SetFactory(loggerFactory);
+
+        return exportProvider;
+    }
+
+    private static void ThrowOnUnexpectedErrors(CompositionConfiguration configuration, ILogger logger)
+    {
+        // Verify that we have exactly the MEF errors that we expect.  If we have less or more this needs to be updated to assert the expected behavior.
+        // Currently we are expecting the following:
+        //     "----- CompositionError level 1 ------
+        //     Microsoft.CodeAnalysis.ExternalAccess.Pythia.PythiaSignatureHelpProvider.ctor(implementation): expected exactly 1 export matching constraints:
+        //         Contract name: Microsoft.CodeAnalysis.ExternalAccess.Pythia.Api.IPythiaSignatureHelpProviderImplementation
+        //         TypeIdentityName: Microsoft.CodeAnalysis.ExternalAccess.Pythia.Api.IPythiaSignatureHelpProviderImplementation
+        //     but found 0.
+        //         part definition Microsoft.CodeAnalysis.ExternalAccess.Pythia.PythiaSignatureHelpProvider
+        var erroredParts = configuration.CompositionErrors.FirstOrDefault()?.SelectMany(error => error.Parts).Select(part => part.Definition.Type.Name) ?? Enumerable.Empty<string>();
+        var expectedErroredParts = new string[] { "PythiaSignatureHelpProvider" };
+        if (erroredParts.Count() != expectedErroredParts.Length || !erroredParts.All(part => expectedErroredParts.Contains(part)))
+        {
+            try
+            {
+                configuration.ThrowOnErrors();
+            }
+            catch (CompositionFailedException ex)
+            {
+                // The ToString for the composition failed exception doesn't output a nice set of errors by default, so log it separately here.
+                logger.LogError($"Encountered errors in the MEF composition:{Environment.NewLine}{ex.ErrorsAsString}");
+                throw;
+            }
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostServicesProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostServicesProvider.cs
new file mode 100644
index 0000000000000..78ede56831cde
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostServicesProvider.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.VisualStudio.Composition;
+
+namespace Microsoft.CodeAnalysis.LanguageServer;
+
+/// <summary>
+/// A simple type to provide a single copy of <see cref="Microsoft.CodeAnalysis.Host.HostServices"/> for the MEF composition.
+/// </summary>
+[Export(typeof(HostServicesProvider)), Shared]
+internal class HostServicesProvider
+{
+    public HostServices HostServices { get; }
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public HostServicesProvider(ExportProvider exportProvider)
+    {
+        HostServices = VisualStudioMefHostServices.Create(exportProvider);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ExtensionManager.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ExtensionManager.cs
new file mode 100644
index 0000000000000..86d6787244453
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ExtensionManager.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Composition;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Extensions;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[ExportWorkspaceService(typeof(IExtensionManager), ServiceLayer.Host), Shared]
+internal class ExtensionManager : IExtensionManager
+{
+    private readonly ILogger _logger;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ExtensionManager(ILoggerFactory loggerFactory)
+    {
+        _logger = loggerFactory.CreateLogger(nameof(ExtensionManager));
+    }
+
+    public bool CanHandleException(object provider, Exception exception) => true;
+
+    public void HandleException(object provider, Exception exception)
+    {
+        _logger.Log(LogLevel.Error, exception, $"{provider.GetType().ToString()} threw an exception.");
+    }
+
+    public bool IsDisabled(object provider)
+    {
+        // We don't have an UI to allow disabling yet
+        return false;
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/DelegatingFileChangeWatcher.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/DelegatingFileChangeWatcher.cs
new file mode 100644
index 0000000000000..ca98eb5944665
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/DelegatingFileChangeWatcher.cs
@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.CodeAnalysis.ProjectSystem;
+using Microsoft.Extensions.Logging;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Roslyn.Utilities;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.FileWatching;
+
+/// <summary>
+/// A MEF export for <see cref="IFileChangeWatcher" />. This checks if we're able to create an <see cref="LspFileChangeWatcher" /> if the client supports
+/// file watching. If we do, we create that and delegate to it. Otherwise we use a <see cref="SimpleFileChangeWatcher" />.
+/// </summary>
+/// <remarks>
+/// LSP clients don't always support file watching; this allows us to be flexible and use it when we can, but fall back to something else if we can't.
+/// </remarks>
+[Export(typeof(IFileChangeWatcher)), Shared]
+internal sealed class DelegatingFileChangeWatcher : IFileChangeWatcher
+{
+    private readonly ILoggerFactory _loggerFactory;
+    private readonly IAsynchronousOperationListenerProvider _asynchronousOperationListenerProvider;
+    private readonly Lazy<IFileChangeWatcher> _underlyingFileWatcher;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public DelegatingFileChangeWatcher(ILoggerFactory loggerFactory, IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider)
+    {
+        _loggerFactory = loggerFactory;
+        _asynchronousOperationListenerProvider = asynchronousOperationListenerProvider;
+        _underlyingFileWatcher = new Lazy<IFileChangeWatcher>(CreateFileWatcher);
+    }
+
+    private IFileChangeWatcher CreateFileWatcher()
+    {
+        // Do we already have an LSP client that we can confirm works for us?
+        var instance = LanguageServerHost.Instance;
+
+        if (instance != null && LspFileChangeWatcher.SupportsLanguageServerHost(instance))
+        {
+            return new LspFileChangeWatcher(instance, _asynchronousOperationListenerProvider);
+        }
+        else
+        {
+            _loggerFactory.CreateLogger<DelegatingFileChangeWatcher>().LogWarning("We are unable to use LSP file watching; falling back to our in-process watcher.");
+            return new SimpleFileChangeWatcher();
+        }
+    }
+
+    public IFileChangeContext CreateContext(params WatchedDirectory[] watchedDirectories)
+    {
+        return _underlyingFileWatcher.Value.CreateContext(watchedDirectories);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspContractTypes.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspContractTypes.cs
new file mode 100644
index 0000000000000..7635ee9c55452
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspContractTypes.cs
@@ -0,0 +1,53 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+using Newtonsoft.Json;
+
+namespace Microsoft.VisualStudio.LanguageServer.Protocol;
+
+[DataContract]
+internal class DidChangeWatchedFilesRegistrationOptions
+{
+    [DataMember(Name = "watchers")]
+    public required FileSystemWatcher[] Watchers { get; set; }
+}
+
+[DataContract]
+internal class FileSystemWatcher
+{
+    [DataMember(Name = "globPattern")]
+    public required RelativePattern GlobPattern { get; set; }
+
+    [DataMember(Name = "kind")]
+    public WatchKind? Kind { get; set; }
+}
+
+[DataContract]
+internal class RelativePattern
+{
+    [DataMember(Name = "baseUri")]
+    [JsonConverter(typeof(DocumentUriConverter))]
+    public required Uri BaseUri { get; set; }
+
+    [DataMember(Name = "pattern")]
+    public required string Pattern { get; set; }
+}
+
+// The LSP specification has a spelling error in the protocol, but Microsoft.VisualStudio.LanguageServer.Protocol
+// didn't carry that error along. This corrects that.
+[DataContract]
+internal class UnregistrationParamsWithMisspelling
+{
+    [DataMember(Name = "unregisterations")]
+    public required Unregistration[] Unregistrations { get; set; }
+}
+
+[Flags]
+internal enum WatchKind
+{
+    Create = 1,
+    Change = 2,
+    Delete = 4
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspDidChangeWatchedFilesHandler.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspDidChangeWatchedFilesHandler.cs
new file mode 100644
index 0000000000000..04faf2d4433a3
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspDidChangeWatchedFilesHandler.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler;
+using Microsoft.CommonLanguageServerProtocol.Framework;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.FileWatching;
+
+[ExportCSharpVisualBasicStatelessLspService(typeof(LspDidChangeWatchedFilesHandler)), Shared]
+[Method("workspace/didChangeWatchedFiles")]
+internal class LspDidChangeWatchedFilesHandler : ILspServiceNotificationHandler<DidChangeWatchedFilesParams>
+{
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public LspDidChangeWatchedFilesHandler()
+    {
+    }
+
+    public bool MutatesSolutionState => false;
+    public bool RequiresLSPSolution => false;
+
+    Task INotificationHandler<DidChangeWatchedFilesParams, RequestContext>.HandleNotificationAsync(DidChangeWatchedFilesParams request, RequestContext requestContext, CancellationToken cancellationToken)
+    {
+        NotificationRaised?.Invoke(this, request);
+        return Task.CompletedTask;
+    }
+
+    public event EventHandler<DidChangeWatchedFilesParams>? NotificationRaised;
+}
\ No newline at end of file
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspFileChangeWatcher.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspFileChangeWatcher.cs
new file mode 100644
index 0000000000000..85d9e7049c7e1
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/LspFileChangeWatcher.cs
@@ -0,0 +1,248 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.CodeAnalysis.ProjectSystem;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using System.Collections.Immutable;
+using Roslyn.Utilities;
+using FileSystemWatcher = Microsoft.VisualStudio.LanguageServer.Protocol.FileSystemWatcher;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.FileWatching;
+
+/// <summary>
+/// An implementation of <see cref="IFileChangeWatcher" /> that delegates file watching through the LSP protocol to the client.
+/// </summary>
+internal sealed class LspFileChangeWatcher : IFileChangeWatcher
+{
+    private readonly LspDidChangeWatchedFilesHandler _didChangeWatchedFilesHandler;
+    private readonly IClientLanguageServerManager _clientLanguageServerManager;
+    private readonly IAsynchronousOperationListener _asynchronousOperationListener;
+
+    public LspFileChangeWatcher(LanguageServerHost languageServerHost, IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider)
+    {
+        _didChangeWatchedFilesHandler = languageServerHost.GetRequiredLspService<LspDidChangeWatchedFilesHandler>();
+        _clientLanguageServerManager = languageServerHost.GetRequiredLspService<IClientLanguageServerManager>();
+        _asynchronousOperationListener = asynchronousOperationListenerProvider.GetListener(FeatureAttribute.Workspace);
+
+        Contract.ThrowIfFalse(SupportsLanguageServerHost(languageServerHost));
+    }
+
+    public static bool SupportsLanguageServerHost(LanguageServerHost languageServerHost)
+    {
+        // We can only use the LSP client for doing file watching if we support dynamic registration for it
+        var clientCapabilitiesProvider = languageServerHost.GetRequiredLspService<IClientCapabilitiesProvider>();
+        return clientCapabilitiesProvider.GetClientCapabilities().Workspace?.DidChangeWatchedFiles?.DynamicRegistration ?? false;
+    }
+
+    public IFileChangeContext CreateContext(params WatchedDirectory[] watchedDirectories)
+    {
+        return new FileChangeContext(watchedDirectories.ToImmutableArray(), this);
+    }
+
+    private class FileChangeContext : IFileChangeContext
+    {
+        private readonly ImmutableArray<WatchedDirectory> _watchedDirectories;
+        private readonly LspFileChangeWatcher _lspFileChangeWatcher;
+
+        /// <summary>
+        /// The registration for the directory being watched in this context, if some were given.
+        /// </summary>
+        private readonly LspFileWatchRegistration? _directoryWatchRegistration;
+
+        /// <summary>
+        /// A lock to guard updates to <see cref="_watchedFiles" />. Using a reader/writer lock since file change notifications can be pretty chatty
+        /// and so we want to be able to process changes as fast as possible.
+        /// </summary>
+        private readonly ReaderWriterLockSlim _watchedFilesLock = new ReaderWriterLockSlim();
+
+        /// <summary>
+        /// The list of file paths we're watching manually that were outside the directories being watched. The count in this case counts
+        /// the number of 
+        /// </summary>
+        private readonly Dictionary<string, int> _watchedFiles = new Dictionary<string, int>(StringComparer.Ordinal);
+
+        public FileChangeContext(ImmutableArray<WatchedDirectory> watchedDirectories, LspFileChangeWatcher lspFileChangeWatcher)
+        {
+            _watchedDirectories = watchedDirectories;
+            _lspFileChangeWatcher = lspFileChangeWatcher;
+
+            // If we have any watched directories, then watch those directories directly
+            if (watchedDirectories.Any())
+            {
+                var directoryWatches = watchedDirectories.Select(d => new FileSystemWatcher
+                {
+                    GlobPattern = new RelativePattern
+                    {
+                        BaseUri = ProtocolConversions.GetUriFromFilePath(d.Path),
+                        Pattern = d.ExtensionFilter is not null ? "**/*" + d.ExtensionFilter : "**/*"
+                    }
+                }).ToArray();
+
+                _directoryWatchRegistration = new LspFileWatchRegistration(lspFileChangeWatcher, directoryWatches);
+            }
+
+            _lspFileChangeWatcher._didChangeWatchedFilesHandler.NotificationRaised += WatchedFilesHandler_OnNotificationRaised;
+        }
+
+        private void WatchedFilesHandler_OnNotificationRaised(object? sender, DidChangeWatchedFilesParams e)
+        {
+            foreach (var changedFile in e.Changes)
+            {
+                var filePath = changedFile.Uri.LocalPath;
+
+                // Unfortunately the LSP protocol doesn't give us any hint of which of the file watches we might have sent to the client
+                // was the one that registered for this change, so we have to check paths to see if this one we should respond to.
+                if (WatchedDirectory.FilePathCoveredByWatchedDirectories(_watchedDirectories, filePath, StringComparison.Ordinal))
+                {
+                    FileChanged?.Invoke(this, filePath);
+                }
+                else
+                {
+                    bool isFileWatched;
+                    using (_watchedFilesLock.DisposableRead())
+                    {
+                        isFileWatched = _watchedFiles.ContainsKey(filePath);
+                    }
+
+                    if (isFileWatched)
+                        FileChanged?.Invoke(this, filePath);
+                }
+            }
+        }
+
+        public event EventHandler<string>? FileChanged;
+
+        public void Dispose()
+        {
+            _lspFileChangeWatcher._didChangeWatchedFilesHandler.NotificationRaised -= WatchedFilesHandler_OnNotificationRaised;
+            _directoryWatchRegistration?.Dispose();
+        }
+
+        public IWatchedFile EnqueueWatchingFile(string filePath)
+        {
+            // If we already have this file under our path, we may not have to do additional watching
+            if (WatchedDirectory.FilePathCoveredByWatchedDirectories(_watchedDirectories, filePath, StringComparison.OrdinalIgnoreCase))
+                return NoOpWatchedFile.Instance;
+
+            // Record that we're now watching this file
+            using (_watchedFilesLock.DisposableWrite())
+            {
+                _watchedFiles.TryGetValue(filePath, out var existingWatches);
+                _watchedFiles[filePath] = existingWatches + 1;
+            }
+
+            var fileSystemWatcher = new FileSystemWatcher()
+            {
+                // TODO: figure out how I just can do an absolute path watch
+                GlobPattern = new RelativePattern
+                {
+                    BaseUri = ProtocolConversions.GetUriFromFilePath(Path.GetDirectoryName(filePath)!),
+                    Pattern = Path.GetFileName(filePath)
+                }
+            };
+
+            return new WatchedFile(filePath, new LspFileWatchRegistration(_lspFileChangeWatcher, fileSystemWatcher), this);
+        }
+
+        private void RemoveFileFromWatchList(string filePath)
+        {
+            // Record that we're no longer watching this file
+            using (_watchedFilesLock.DisposableWrite())
+            {
+                var existingWatches = _watchedFiles[filePath];
+                if (existingWatches == 1)
+                    _watchedFiles.Remove(filePath);
+                else
+                    _watchedFiles[filePath] = existingWatches - 1;
+            }
+        }
+
+        private class WatchedFile : IWatchedFile
+        {
+            private readonly string _filePath;
+            private readonly LspFileWatchRegistration _fileWatchRegistration;
+            private readonly FileChangeContext _fileChangeContext;
+
+            public WatchedFile(string filePath, LspFileWatchRegistration fileWatchRegistration, FileChangeContext fileChangeContext)
+            {
+                _filePath = filePath;
+                _fileWatchRegistration = fileWatchRegistration;
+                _fileChangeContext = fileChangeContext;
+            }
+
+            public void Dispose()
+            {
+                _fileWatchRegistration.Dispose();
+                _fileChangeContext.RemoveFileFromWatchList(_filePath);
+            }
+        }
+    }
+
+    /// <summary>
+    /// A small class to represent a registration that is sent to the client that we can cancel later. Since we send
+    /// registrations asynchronously, this tracks that so we don't send the unregister too early.
+    /// </summary>
+    private sealed class LspFileWatchRegistration : IDisposable
+    {
+        private readonly LspFileChangeWatcher _changeWatcher;
+        private readonly string _id;
+        private readonly CancellationTokenSource _cancellationTokenSource;
+        private readonly Task _registrationTask;
+
+        public LspFileWatchRegistration(LspFileChangeWatcher changeWatcher, params FileSystemWatcher[] fileSystemWatchers)
+        {
+            _changeWatcher = changeWatcher;
+            _id = Guid.NewGuid().ToString();
+            _cancellationTokenSource = new CancellationTokenSource();
+
+            var registrationParams = new RegistrationParams()
+            {
+                Registrations = new Registration[]
+                {
+                    new Registration
+                    {
+                        Id = _id,
+                        Method = "workspace/didChangeWatchedFiles",
+                        RegisterOptions = new DidChangeWatchedFilesRegistrationOptions
+                        {
+                            Watchers = fileSystemWatchers
+                        }
+                    }
+                }
+            };
+
+            var asyncToken = _changeWatcher._asynchronousOperationListener.BeginAsyncOperation(nameof(LspFileWatchRegistration));
+            _registrationTask = changeWatcher._clientLanguageServerManager.SendRequestAsync("client/registerCapability", registrationParams, _cancellationTokenSource.Token).AsTask();
+            _registrationTask.ReportNonFatalErrorUnlessCancelledAsync(_cancellationTokenSource.Token).CompletesAsyncOperation(asyncToken);
+        }
+
+        public void Dispose()
+        {
+            // We need to remove our file watch. We'll run that once the previous work has completed. We'll run only if the registration completed successfully, since cancellation
+            // means it never actually made it to the client, and fault would mean it never was actually created.
+            _cancellationTokenSource.Cancel();
+
+            var asyncToken = _changeWatcher._asynchronousOperationListener.BeginAsyncOperation(nameof(LspFileWatchRegistration) + "." + nameof(Dispose));
+
+            _registrationTask.ContinueWith(async _ =>
+            {
+                var unregistrationParams = new UnregistrationParamsWithMisspelling()
+                {
+                    Unregistrations = new Unregistration[]
+                    {
+                        new Unregistration()
+                        {
+                            Id = _id,
+                            Method = "workspace/didChangeWatchedFiles"
+                        }
+                    }
+                };
+
+                await _changeWatcher._clientLanguageServerManager.SendRequestAsync("client/unregisterCapability", unregistrationParams, CancellationToken.None);
+            }, CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, TaskScheduler.Default).Unwrap().ReportNonFatalErrorAsync().CompletesAsyncOperation(asyncToken);
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/SimpleFileChangeWatcher.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/SimpleFileChangeWatcher.cs
new file mode 100644
index 0000000000000..67efbd5933831
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/FileWatching/SimpleFileChangeWatcher.cs
@@ -0,0 +1,138 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.ProjectSystem;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace.FileWatching;
+
+/// <summary>
+/// A trivial implementation of <see cref="IFileChangeWatcher" /> that is built atop the framework <see cref="FileSystemWatcher" />. This is used if we can't
+/// use the LSP one.
+/// </summary>
+/// <remarks>
+/// This implementation is not remotely efficient, but is available as a fallback implementation. If this needs to regularly be used, then this should get some improvements.
+/// </remarks>
+internal sealed class SimpleFileChangeWatcher : IFileChangeWatcher
+{
+    public IFileChangeContext CreateContext(params WatchedDirectory[] watchedDirectories)
+    {
+        return new FileChangeContext(watchedDirectories.ToImmutableArray());
+    }
+
+    private class FileChangeContext : IFileChangeContext
+    {
+        private readonly ImmutableArray<WatchedDirectory> _watchedDirectories;
+
+        /// <summary>
+        /// The directory watchers for the <see cref="_watchedDirectories"/>.
+        /// </summary>
+        private readonly ImmutableArray<FileSystemWatcher> _directoryFileSystemWatchers;
+        private readonly ConcurrentSet<IndividualWatchedFile> _individualWatchedFiles = new ConcurrentSet<IndividualWatchedFile>();
+
+        public FileChangeContext(ImmutableArray<WatchedDirectory> watchedDirectories)
+        {
+            var watchedDirectoriesBuilder = ImmutableArray.CreateBuilder<WatchedDirectory>(watchedDirectories.Length);
+            var watcherBuilder = ImmutableArray.CreateBuilder<FileSystemWatcher>(watchedDirectories.Length);
+
+            foreach (var watchedDirectory in watchedDirectories)
+            {
+                // If the directory doesn't exist, we can't create a watcher for changes inside of it. In this case, we'll just skip this as a directory
+                // to watch; any requests for a watch within that directory will still create a one-off watcher for that specific file. That's not likely
+                // to be an issue in practice: directories that are missing would be things like global reference directories -- if it's not there, we
+                // probably won't ever see a watch for a file under there later anyways.
+                if (Directory.Exists(watchedDirectory.Path))
+                {
+                    var watcher = new FileSystemWatcher(watchedDirectory.Path);
+                    watcher.IncludeSubdirectories = true;
+
+                    if (watchedDirectory.ExtensionFilter != null)
+                        watcher.Filter = '*' + watchedDirectory.ExtensionFilter;
+
+                    watcher.Changed += RaiseEvent;
+                    watcher.Created += RaiseEvent;
+                    watcher.Deleted += RaiseEvent;
+                    watcher.Renamed += RaiseEvent;
+
+                    watcher.EnableRaisingEvents = true;
+
+                    watchedDirectoriesBuilder.Add(watchedDirectory);
+                    watcherBuilder.Add(watcher);
+                }
+            }
+
+            _watchedDirectories = watchedDirectoriesBuilder.ToImmutable();
+            _directoryFileSystemWatchers = watcherBuilder.ToImmutable();
+        }
+
+        public event EventHandler<string>? FileChanged;
+
+        public IWatchedFile EnqueueWatchingFile(string filePath)
+        {
+            // If this path is already covered by one of our directory watchers, nothing further to do
+            if (WatchedDirectory.FilePathCoveredByWatchedDirectories(_watchedDirectories, filePath, StringComparison.Ordinal))
+                return NoOpWatchedFile.Instance;
+
+            var individualWatchedFile = new IndividualWatchedFile(filePath, this);
+            _individualWatchedFiles.Add(individualWatchedFile);
+            return individualWatchedFile;
+        }
+
+        private void RaiseEvent(object sender, FileSystemEventArgs e)
+        {
+            FileChanged?.Invoke(this, e.FullPath);
+        }
+
+        public void Dispose()
+        {
+            foreach (var directoryWatcher in _directoryFileSystemWatchers)
+                directoryWatcher.Dispose();
+        }
+
+        private class IndividualWatchedFile : IWatchedFile
+        {
+            private readonly FileChangeContext _context;
+            private readonly FileSystemWatcher? _watcher;
+
+            public IndividualWatchedFile(string filePath, FileChangeContext context)
+            {
+                _context = context;
+
+                // We always must create a watch on an entire directory, so create that, filtered to the single file name
+                var directoryPath = Path.GetDirectoryName(filePath)!;
+
+                // TODO: support missing directories properly
+                if (Directory.Exists(directoryPath))
+                {
+                    _watcher = new FileSystemWatcher(directoryPath, Path.GetFileName(filePath));
+                    _watcher.IncludeSubdirectories = false;
+
+                    _watcher.Changed += _context.RaiseEvent;
+                    _watcher.Created += _context.RaiseEvent;
+                    _watcher.Deleted += _context.RaiseEvent;
+                    _watcher.Renamed += _context.RaiseEvent;
+
+                    _watcher.EnableRaisingEvents = true;
+                }
+                else
+                {
+                    _watcher = null;
+                }
+            }
+
+            public void Dispose()
+            {
+                if (_context._individualWatchedFiles.Remove(this) && _watcher != null)
+                {
+                    _watcher.Changed -= _context.RaiseEvent;
+                    _watcher.Created -= _context.RaiseEvent;
+                    _watcher.Deleted -= _context.RaiseEvent;
+                    _watcher.Renamed -= _context.RaiseEvent;
+                    _watcher.Dispose();
+                }
+            }
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/HostDiagnosticAnalyzerProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/HostDiagnosticAnalyzerProvider.cs
new file mode 100644
index 0000000000000..8bbe02aa13604
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/HostDiagnosticAnalyzerProvider.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+internal class HostDiagnosticAnalyzerProvider : IHostDiagnosticAnalyzerProvider
+{
+    public ImmutableArray<(AnalyzerFileReference reference, string extensionId)> GetAnalyzerReferencesInExtensions()
+    {
+        // Right now we don't expose any way for the extensions in VS Code to provide analyzer references.
+        return ImmutableArray<(AnalyzerFileReference reference, string extensionId)>.Empty;
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectSystem.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectSystem.cs
new file mode 100644
index 0000000000000..2847972cdccc5
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectSystem.cs
@@ -0,0 +1,224 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Concurrent;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using Microsoft.Build.Locator;
+using Microsoft.CodeAnalysis.Collections;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.CodeAnalysis.MSBuild;
+using Microsoft.CodeAnalysis.MSBuild.Build;
+using Microsoft.CodeAnalysis.MSBuild.Logging;
+using Microsoft.CodeAnalysis.ProjectSystem;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.Composition;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[Export(typeof(LanguageServerProjectSystem)), Shared]
+internal sealed class LanguageServerProjectSystem
+{
+    private readonly ProjectFileLoaderRegistry _projectFileLoaderRegistry;
+
+    /// <summary>
+    /// A single gate for code that is adding work to <see cref="_projectsToLoadAndReload" /> and modifying <see cref="_msbuildLoaded" />.
+    /// This is just we don't have code simultaneously trying to load and unload solutions at once.
+    /// </summary>
+    private readonly SemaphoreSlim _gate = new SemaphoreSlim(initialCount: 1);
+
+    private bool _msbuildLoaded = false;
+
+    private readonly AsyncBatchingWorkQueue<string> _projectsToLoadAndReload;
+
+    private readonly LanguageServerWorkspaceFactory _workspaceFactory;
+    private readonly IFileChangeWatcher _fileChangeWatcher;
+    private readonly ILogger _logger;
+
+    /// <summary>
+    /// The list of loaded projects in the workspace, keyed by project file path. The outer dictionary is a concurrent dictionary since we may be loading
+    /// multiple projects at once; the key is a single List we just have a single thread processing any given project file. This is only to be used
+    /// in <see cref="LoadOrReloadProjectsAsync" /> and downstream calls; any other updating of this (like unloading projects) should be achieved by adding
+    /// things to the <see cref="_projectsToLoadAndReload" />.
+    /// </summary>
+    private readonly ConcurrentDictionary<string, List<LoadedProject>> _loadedProjects = new();
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public LanguageServerProjectSystem(
+        LanguageServerWorkspaceFactory workspaceFactory,
+        IFileChangeWatcher fileChangeWatcher,
+        ILoggerFactory loggerFactory,
+        IAsynchronousOperationListenerProvider listenerProvider)
+    {
+        _workspaceFactory = workspaceFactory;
+        _fileChangeWatcher = fileChangeWatcher;
+        _logger = loggerFactory.CreateLogger(nameof(LanguageServerProjectSystem));
+
+        // TODO: remove the DiagnosticReporter that's coupled to the Workspace here
+        _projectFileLoaderRegistry = new ProjectFileLoaderRegistry(workspaceFactory.Workspace.Services.SolutionServices, new DiagnosticReporter(workspaceFactory.Workspace));
+
+        _projectsToLoadAndReload = new AsyncBatchingWorkQueue<string>(
+            TimeSpan.FromMilliseconds(100),
+            LoadOrReloadProjectsAsync,
+            StringComparer.Ordinal,
+            listenerProvider.GetListener(FeatureAttribute.Workspace),
+            CancellationToken.None); // TODO: do we need to introduce a shutdown cancellation token for this?
+    }
+
+    public async Task OpenSolutionAsync(string solutionFilePath)
+    {
+        await TryEnsureMSBuildLoadedAsync(Path.GetDirectoryName(solutionFilePath)!);
+        await OpenSolutionCoreAsync(solutionFilePath);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)] // Don't inline; the caller needs to ensure MSBuild is loaded before we can use MSBuild types here
+    private async Task OpenSolutionCoreAsync(string solutionFilePath)
+    {
+        using (await _gate.DisposableWaitAsync())
+        {
+            _logger.LogInformation($"Loading {solutionFilePath}...");
+            var solutionFile = Microsoft.Build.Construction.SolutionFile.Parse(solutionFilePath);
+            _workspaceFactory.ProjectSystemProjectFactory.SolutionPath = solutionFilePath;
+
+            foreach (var project in solutionFile.ProjectsInOrder)
+            {
+                if (project.ProjectType == Microsoft.Build.Construction.SolutionProjectType.SolutionFolder)
+                {
+                    continue;
+                }
+
+                _projectsToLoadAndReload.AddWork(project.AbsolutePath);
+            }
+
+            // Wait for the in progress batch to complete and send a project initialized notification to the client.
+            await _projectsToLoadAndReload.WaitUntilCurrentBatchCompletesAsync();
+            await ProjectInitializationHandler.SendProjectInitializationCompleteNotificationAsync();
+        }
+    }
+
+    private async Task<bool> TryEnsureMSBuildLoadedAsync(string workingDirectory)
+    {
+        using (await _gate.DisposableWaitAsync())
+        {
+            if (_msbuildLoaded)
+            {
+                return true;
+            }
+            else
+            {
+                var msbuildDiscoveryOptions = new VisualStudioInstanceQueryOptions { DiscoveryTypes = DiscoveryType.DotNetSdk, WorkingDirectory = workingDirectory };
+                var msbuildInstances = MSBuildLocator.QueryVisualStudioInstances(msbuildDiscoveryOptions);
+                var msbuildInstance = msbuildInstances.FirstOrDefault();
+
+                if (msbuildInstance != null)
+                {
+                    MSBuildLocator.RegisterInstance(msbuildInstance);
+                    _logger.LogInformation($"Loaded MSBuild at {msbuildInstance.MSBuildPath}");
+                    _msbuildLoaded = true;
+
+                    return true;
+                }
+                else
+                {
+                    _logger.LogError($"Unable to find a MSBuild to use to load {workingDirectory}.");
+                    return false;
+                }
+            }
+        }
+    }
+
+    private async ValueTask LoadOrReloadProjectsAsync(ImmutableSegmentedList<string> projectPathsToLoadOrReload, CancellationToken cancellationToken)
+    {
+        var stopwatch = Stopwatch.StartNew();
+
+        // TODO: support configuration switching
+        var projectBuildManager = new ProjectBuildManager(additionalGlobalProperties: ImmutableDictionary<string, string>.Empty);
+
+        projectBuildManager.StartBatchBuild();
+
+        try
+        {
+            var tasks = new List<Task>();
+
+            foreach (var projectPathToLoadOrReload in projectPathsToLoadOrReload)
+            {
+                tasks.Add(Task.Run(() => LoadOrReloadProjectAsync(projectPathToLoadOrReload, projectBuildManager, cancellationToken), cancellationToken));
+            }
+
+            await Task.WhenAll(tasks);
+        }
+        finally
+        {
+            projectBuildManager.EndBatchBuild();
+
+            _logger.LogInformation($"Completed (re)load of all projects in {stopwatch.Elapsed}");
+        }
+    }
+
+    private async Task LoadOrReloadProjectAsync(string projectPath, ProjectBuildManager projectBuildManager, CancellationToken cancellationToken)
+    {
+        try
+        {
+            if (_projectFileLoaderRegistry.TryGetLoaderFromProjectPath(projectPath, out var loader))
+            {
+                var loadedFile = await loader.LoadProjectFileAsync(projectPath, projectBuildManager, cancellationToken);
+                var loadedProjectInfos = await loadedFile.GetProjectFileInfosAsync(cancellationToken);
+
+                var existingProjects = _loadedProjects.GetOrAdd(projectPath, static _ => new List<LoadedProject>());
+
+                foreach (var loadedProjectInfo in loadedProjectInfos)
+                {
+                    // If we already have the project, just update it
+                    var existingProject = existingProjects.Find(p => p.GetTargetFramework() == loadedProjectInfo.TargetFramework);
+
+                    if (existingProject != null)
+                    {
+                        await existingProject.UpdateWithNewProjectInfoAsync(loadedProjectInfo);
+                    }
+                    else
+                    {
+                        var projectSystemName = $"{projectPath} (${loadedProjectInfo.TargetFramework})";
+                        var projectCreationInfo = new ProjectSystemProjectCreationInfo { AssemblyName = projectSystemName, FilePath = projectPath };
+
+                        var projectSystemProject = await _workspaceFactory.ProjectSystemProjectFactory.CreateAndAddToWorkspaceAsync(
+                            projectSystemName,
+                            loadedProjectInfo.Language,
+                            projectCreationInfo,
+                            _workspaceFactory.ProjectSystemHostInfo);
+
+                        var loadedProject = new LoadedProject(projectSystemProject, _workspaceFactory.Workspace.Services.SolutionServices, _fileChangeWatcher, _workspaceFactory.TargetFrameworkManager);
+                        loadedProject.NeedsReload += (_, _) => _projectsToLoadAndReload.AddWork(projectPath);
+                        existingProjects.Add(loadedProject);
+
+                        await loadedProject.UpdateWithNewProjectInfoAsync(loadedProjectInfo);
+                    }
+                }
+
+                if (loadedFile.Log.Any())
+                {
+                    foreach (var logItem in loadedFile.Log)
+                    {
+                        _logger.LogWarning($"{logItem.Kind} while loading {logItem.ProjectFilePath}: {logItem.Message}");
+                    }
+                }
+                else
+                {
+                    _logger.LogInformation($"Successfully completed load of {projectPath}");
+                }
+            }
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, $"Exception thrown while loading {projectPath}");
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerWorkspace.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerWorkspace.cs
new file mode 100644
index 0000000000000..9a1526d3d49fe
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerWorkspace.cs
@@ -0,0 +1,117 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
+using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+/// <summary>
+/// Mark this type as an <see cref="ILspWorkspace"/> so that LSP document changes are pushed into this instance, causing
+/// our <see cref="Workspace.CurrentSolution"/> to stay in sync with all the document changes.
+/// <para/>
+/// There is a fundamental race with how solution snapshot data is stored in this type.  Specifically, two entities push
+/// changes into this workspace.  First, the <see cref="LspWorkspaceManager"/> pushes changes into this relating to the
+/// open/closed state of documents, and the current text contents that it knows about from <see
+/// cref="LSP.Methods.TextDocumentDidChange"/> events.  Second, the project system may push changes about what files
+/// actually exist in the workspace or not. As neither of these entities synchronizes on anything, we may hear about
+/// things like changes to files that the project system has or has not told us about, or which it has added/removed
+/// documents for already.
+/// <para/>
+/// Because of this, this type takes the stance that the actual presence/absence of files is dictated by the project
+/// system.  However, if the files are present, the open/closed state and the contents are dictated by the <see
+/// cref="LspWorkspaceManager"/>.  This incongruity is not a problem due to how the <see cref="LspWorkspaceManager"/>
+/// ends up working.  For example, say the manager believes a file exists with some content, but the project system has
+/// removed that file from this workspace.  In that case, the manager will simply not see this type as containing the
+/// document, and it will then add the changed doc to the misc workspace.  Similarly, if the project system and
+/// workspace manager ever disagree on document contents, that is never itself an issue as the workspace manager always
+/// prefers the in-memory source text it is holding onto if the checksums of files change.
+/// <para/>
+/// Put another way, the lsp workspace manager will use the data in the workspace if it sees it is in alignment with
+/// what it believes is the state of the world with respect to <see cref="LSP.Methods.TextDocumentDidOpen"/>/<see
+/// cref="LSP.Methods.TextDocumentDidChange"/>/<see cref="LSP.Methods.TextDocumentDidClose"/>.  However, if it is not,
+/// it will use the local information it has outside of the workspace to ensure it is always matched with the lsp
+/// client.
+/// </summary>
+internal class LanguageServerWorkspace : Workspace, ILspWorkspace
+{
+    /// <summary>
+    /// Will be set by LanguageServerProjectSystem immediately after creating this instance.  Can't be passed into the
+    /// constructor as the factory needs a reference to this type.
+    /// </summary>
+    public ProjectSystemProjectFactory ProjectSystemProjectFactory { private get; set; } = null!;
+
+    public LanguageServerWorkspace(HostServices host)
+        : base(host, WorkspaceKind.Host)
+    {
+    }
+
+    protected internal override bool PartialSemanticsEnabled => true;
+
+    bool ILspWorkspace.SupportsMutation => true;
+
+    ValueTask ILspWorkspace.UpdateTextIfPresentAsync(DocumentId documentId, SourceText sourceText, CancellationToken cancellationToken)
+    {
+        // We need to ensure that our changes, and the changes made by the ProjectSystemProjectFactory don't interleave.
+        // Specifically, ProjectSystemProjectFactory often makes several changes in a row that it thinks cannot be
+        // interrupted.  To ensure this, we call into ProjectSystemProjectFactory to synchronize on the same lock that
+        // it has when making workspace changes.
+        //
+        // https://github.com/dotnet/roslyn/issues/67510 tracks cleaning up ProjectSystemProjectFactory so that it
+        // shares the same sync/lock/application code with the core workspace code.  Once that happens, we won't need
+        // to do special coordination here.
+        return this.ProjectSystemProjectFactory.ApplyChangeToWorkspaceAsync(
+            _ =>
+            {
+                this.OnDocumentTextChanged(documentId, sourceText, PreservationMode.PreserveIdentity, requireDocumentPresent: false);
+                return ValueTask.CompletedTask;
+            },
+            cancellationToken);
+    }
+
+    internal override ValueTask TryOnDocumentOpenedAsync(DocumentId documentId, SourceTextContainer textContainer, bool isCurrentContext, CancellationToken cancellationToken)
+    {
+        return this.ProjectSystemProjectFactory.ApplyChangeToWorkspaceAsync(
+            _ =>
+            {
+                this.OnDocumentOpened(documentId, textContainer, isCurrentContext, requireDocumentPresentAndClosed: false);
+                return ValueTask.CompletedTask;
+            },
+            cancellationToken);
+    }
+
+    internal override ValueTask TryOnDocumentClosedAsync(DocumentId documentId, CancellationToken cancellationToken)
+    {
+        return this.ProjectSystemProjectFactory.ApplyChangeToWorkspaceAsync(
+            async w =>
+            {
+                // TODO(cyrusn): This only works for normal documents currently.  We'll have to rethink how things work
+                // in the world if we ever support additionalfiles/editorconfig in our language server.
+                var document = w.CurrentSolution.GetDocument(documentId);
+
+                if (document is { FilePath: { } filePath })
+                {
+                    TextLoader loader;
+                    if (document.DocumentState.Attributes.DesignTimeOnly)
+                    {
+                        // Dynamic files don't exist on disk so if we were to use the FileTextLoader we'd effectively be emptying out the document.
+                        // We also assume they're not user editable, and hence can't have "unsaved" changes that are expected to go away on close.
+                        // Instead we just maintain their current state as per the LSP view of the world.
+                        var documentText = await document.GetTextAsync(cancellationToken);
+                        loader = new SourceTextLoader(documentText, filePath);
+                    }
+                    else
+                    {
+                        loader = this.ProjectSystemProjectFactory.CreateFileTextLoader(filePath);
+                    }
+
+                    this.OnDocumentClosedEx(documentId, loader, requireDocumentPresentAndOpen: false);
+                }
+            },
+            cancellationToken);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerWorkspaceFactory.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerWorkspaceFactory.cs
new file mode 100644
index 0000000000000..29805c51d2a28
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerWorkspaceFactory.cs
@@ -0,0 +1,81 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using System.Composition;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.ExternalAccess.VSCode.API;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+using Microsoft.CodeAnalysis.ProjectSystem;
+using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.Composition;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[Export(typeof(LanguageServerWorkspaceFactory)), Shared]
+internal sealed class LanguageServerWorkspaceFactory
+{
+    private readonly ILogger _logger;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public LanguageServerWorkspaceFactory(
+        HostServicesProvider hostServicesProvider,
+        VSCodeAnalyzerLoader analyzerLoader,
+        IFileChangeWatcher fileChangeWatcher,
+        [ImportMany] IEnumerable<Lazy<IDynamicFileInfoProvider, Host.Mef.FileExtensionsMetadata>> dynamicFileInfoProviders,
+        ProjectTargetFrameworkManager projectTargetFrameworkManager,
+        ILoggerFactory loggerFactory)
+    {
+        _logger = loggerFactory.CreateLogger(nameof(LanguageServerWorkspaceFactory));
+
+        var workspace = new LanguageServerWorkspace(hostServicesProvider.HostServices);
+        Workspace = workspace;
+        ProjectSystemProjectFactory = new ProjectSystemProjectFactory(Workspace, fileChangeWatcher, static (_, _) => Task.CompletedTask, _ => { });
+        workspace.ProjectSystemProjectFactory = ProjectSystemProjectFactory;
+
+        analyzerLoader.InitializeDiagnosticsServices(Workspace);
+
+        ProjectSystemHostInfo = new ProjectSystemHostInfo(
+            DynamicFileInfoProviders: dynamicFileInfoProviders.ToImmutableArray(),
+            new ProjectSystemDiagnosticSource(),
+            new HostDiagnosticAnalyzerProvider());
+
+        TargetFrameworkManager = projectTargetFrameworkManager;
+    }
+
+    public Workspace Workspace { get; }
+
+    public ProjectSystemProjectFactory ProjectSystemProjectFactory { get; }
+    public ProjectSystemHostInfo ProjectSystemHostInfo { get; }
+    public ProjectTargetFrameworkManager TargetFrameworkManager { get; }
+
+    public async Task InitializeSolutionLevelAnalyzersAsync(ImmutableArray<string> analyzerPaths)
+    {
+        var references = new List<AnalyzerFileReference>();
+        var analyzerLoader = VSCodeAnalyzerLoader.CreateAnalyzerAssemblyLoader();
+
+        foreach (var analyzerPath in analyzerPaths)
+        {
+            if (File.Exists(analyzerPath))
+            {
+                references.Add(new AnalyzerFileReference(analyzerPath, analyzerLoader));
+                _logger.LogDebug($"Solution-level analyzer at {analyzerPath} added to workspace.");
+            }
+            else
+            {
+                _logger.LogWarning($"Solution-level analyzer at {analyzerPath} could not be found.");
+            }
+        }
+
+        await ProjectSystemProjectFactory.ApplyChangeToWorkspaceAsync(w =>
+        {
+            w.SetCurrentSolution(s => s.WithAnalyzerReferences(references), WorkspaceChangeKind.SolutionChanged);
+            return ValueTask.CompletedTask;
+        });
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LoadedProject.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LoadedProject.cs
new file mode 100644
index 0000000000000..dcc1ef6697f14
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LoadedProject.cs
@@ -0,0 +1,195 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+using Microsoft.CodeAnalysis.MSBuild;
+using Microsoft.CodeAnalysis.ProjectSystem;
+using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+/// <summary>
+/// Represents a single project loaded for a single target.
+/// </summary>
+internal sealed class LoadedProject : IDisposable
+{
+    private readonly ProjectSystemProject _projectSystemProject;
+    private readonly ProjectSystemProjectOptionsProcessor _optionsProcessor;
+    private readonly IFileChangeContext _fileChangeContext;
+    private readonly ProjectTargetFrameworkManager _targetFrameworkManager;
+
+    /// <summary>
+    /// The most recent version of the project design time build information; held onto so the next reload we can diff against this.
+    /// </summary>
+    private ProjectFileInfo? _mostRecentFileInfo;
+    private ImmutableArray<CommandLineReference> _mostRecentMetadataReferences = ImmutableArray<CommandLineReference>.Empty;
+
+    public LoadedProject(ProjectSystemProject projectSystemProject, SolutionServices solutionServices, IFileChangeWatcher fileWatcher, ProjectTargetFrameworkManager targetFrameworkManager)
+    {
+        Contract.ThrowIfNull(projectSystemProject.FilePath);
+
+        _projectSystemProject = projectSystemProject;
+        _optionsProcessor = new ProjectSystemProjectOptionsProcessor(projectSystemProject, solutionServices);
+        _targetFrameworkManager = targetFrameworkManager;
+
+        // We'll watch the directory for all source file changes
+        // TODO: we only should listen for add/removals here, but we can't specify such a filter now
+        var projectDirectory = Path.GetDirectoryName(projectSystemProject.FilePath)!;
+        var watchedDirectories = new WatchedDirectory[]
+        {
+            new(projectDirectory, ".cs"),
+            new(projectDirectory, ".cshtml"),
+            new(projectDirectory, ".razor")
+        };
+
+        _fileChangeContext = fileWatcher.CreateContext(watchedDirectories);
+        _fileChangeContext.FileChanged += FileChangedContext_FileChanged;
+
+        // Start watching for file changes for the project file as well
+        _fileChangeContext.EnqueueWatchingFile(projectSystemProject.FilePath);
+    }
+
+    private void FileChangedContext_FileChanged(object? sender, string filePath)
+    {
+        NeedsReload?.Invoke(this, EventArgs.Empty);
+    }
+
+    public event EventHandler? NeedsReload;
+
+    public string? GetTargetFramework()
+    {
+        Contract.ThrowIfNull(_mostRecentFileInfo, "We haven't been given a loaded project yet, so we can't provide the existing TFM.");
+        return _mostRecentFileInfo.TargetFramework;
+    }
+
+    public void Dispose()
+    {
+        _optionsProcessor.Dispose();
+        _projectSystemProject.RemoveFromWorkspace();
+    }
+
+    public async ValueTask UpdateWithNewProjectInfoAsync(ProjectFileInfo newProjectInfo)
+    {
+        if (_mostRecentFileInfo != null)
+        {
+            // We should never be changing the fundamental identity of this project; if this happens we really should have done a full unload/reload.
+            Contract.ThrowIfFalse(newProjectInfo.FilePath == _mostRecentFileInfo.FilePath);
+            Contract.ThrowIfFalse(newProjectInfo.TargetFramework == _mostRecentFileInfo.TargetFramework);
+        }
+
+        await using var batch = _projectSystemProject.CreateBatchScope();
+
+        var projectDisplayName = Path.GetFileNameWithoutExtension(newProjectInfo.FilePath);
+
+        if (newProjectInfo.TargetFramework != null)
+        {
+            projectDisplayName += " (" + newProjectInfo.TargetFramework + ")";
+        }
+
+        _projectSystemProject.OutputFilePath = newProjectInfo.OutputFilePath;
+        _projectSystemProject.OutputRefFilePath = newProjectInfo.OutputRefFilePath;
+
+        if (newProjectInfo.TargetFrameworkIdentifier != null)
+        {
+            _targetFrameworkManager.UpdateIdentifierForProject(_projectSystemProject.Id, newProjectInfo.TargetFrameworkIdentifier);
+        }
+
+        _optionsProcessor.SetCommandLine(newProjectInfo.CommandLineArgs);
+
+        UpdateProjectSystemProjectCollection(
+            newProjectInfo.Documents,
+            _mostRecentFileInfo?.Documents,
+            DocumentFileInfoComparer.Instance,
+            document => _projectSystemProject.AddSourceFile(document.FilePath),
+            document => _projectSystemProject.RemoveSourceFile(document.FilePath));
+
+        var metadataReferences = _optionsProcessor.GetParsedCommandLineArguments().MetadataReferences.Distinct();
+
+        UpdateProjectSystemProjectCollection(
+            metadataReferences,
+            _mostRecentMetadataReferences,
+            EqualityComparer<CommandLineReference>.Default, // CommandLineReference already implements equality
+            reference => _projectSystemProject.AddMetadataReference(reference.Reference, reference.Properties),
+            reference => _projectSystemProject.RemoveMetadataReference(reference.Reference, reference.Properties));
+
+        // Now that we've updated it hold onto the old list of references so we can remove them if there's a later update
+        _mostRecentMetadataReferences = metadataReferences;
+
+        UpdateProjectSystemProjectCollection(
+            newProjectInfo.AdditionalDocuments.Distinct(DocumentFileInfoComparer.Instance), // TODO: figure out why we have duplicates
+            _mostRecentFileInfo?.AdditionalDocuments.Distinct(DocumentFileInfoComparer.Instance),
+            DocumentFileInfoComparer.Instance,
+            document => _projectSystemProject.AddAdditionalFile(document.FilePath),
+            document => _projectSystemProject.RemoveAdditionalFile(document.FilePath));
+
+        UpdateProjectSystemProjectCollection(
+            newProjectInfo.AnalyzerConfigDocuments,
+            _mostRecentFileInfo?.AnalyzerConfigDocuments,
+            DocumentFileInfoComparer.Instance,
+            document => _projectSystemProject.AddAnalyzerConfigFile(document.FilePath),
+            document => _projectSystemProject.RemoveAnalyzerConfigFile(document.FilePath));
+
+        UpdateProjectSystemProjectCollection(
+            newProjectInfo.AdditionalDocuments.Where(TreatAsIsDynamicFile).Distinct(DocumentFileInfoComparer.Instance), // TODO: figure out why we have duplicates
+            _mostRecentFileInfo?.AdditionalDocuments.Where(TreatAsIsDynamicFile).Distinct(DocumentFileInfoComparer.Instance),
+            DocumentFileInfoComparer.Instance,
+            document => _projectSystemProject.AddDynamicSourceFile(document.FilePath, folders: ImmutableArray<string>.Empty),
+            document => _projectSystemProject.RemoveDynamicSourceFile(document.FilePath));
+
+        _mostRecentFileInfo = newProjectInfo;
+
+        return;
+
+        static void UpdateProjectSystemProjectCollection<T>(IEnumerable<T> loadedCollection, IEnumerable<T>? oldLoadedCollection, IEqualityComparer<T> comparer, Action<T> addItem, Action<T> removeItem)
+        {
+            var oldItems = new HashSet<T>(comparer);
+
+            if (oldLoadedCollection != null)
+            {
+                foreach (var item in oldLoadedCollection)
+                    oldItems.Add(item);
+            }
+
+            foreach (var newItem in loadedCollection)
+            {
+                // If oldItems already has this, we don't need to add it again. We'll remove it, and what is left in oldItems is stuff to remove
+                if (!oldItems.Remove(newItem))
+                    addItem(newItem);
+            }
+
+            foreach (var oldItem in oldItems)
+            {
+                removeItem(oldItem);
+            }
+        }
+    }
+
+    private static bool TreatAsIsDynamicFile(DocumentFileInfo info)
+    {
+        var extension = Path.GetExtension(info.FilePath);
+        return extension is ".cshtml" or ".razor";
+    }
+
+    private sealed class DocumentFileInfoComparer : IEqualityComparer<DocumentFileInfo>
+    {
+        public static IEqualityComparer<DocumentFileInfo> Instance = new DocumentFileInfoComparer();
+
+        private DocumentFileInfoComparer()
+        {
+        }
+
+        public bool Equals(DocumentFileInfo? x, DocumentFileInfo? y)
+        {
+            return StringComparer.Ordinal.Equals(x?.FilePath, y?.FilePath);
+        }
+
+        public int GetHashCode(DocumentFileInfo obj)
+        {
+            return StringComparer.Ordinal.GetHashCode(obj.FilePath);
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/MetadataService.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/MetadataService.cs
new file mode 100644
index 0000000000000..7d8bcdd7ad732
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/MetadataService.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[ExportWorkspaceServiceFactory(typeof(IMetadataService), ServiceLayer.Host), Shared]
+internal sealed class MetadataServiceFactory : IWorkspaceServiceFactory
+{
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public MetadataServiceFactory()
+    {
+    }
+
+    public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
+    {
+        return new MetadataService(workspaceServices.GetRequiredService<IDocumentationProviderService>());
+    }
+
+    internal sealed class MetadataService : IMetadataService
+    {
+        private readonly IDocumentationProviderService _documentationProviderService;
+
+        public MetadataService(IDocumentationProviderService documentationProviderService)
+        {
+            _documentationProviderService = documentationProviderService;
+        }
+
+        public PortableExecutableReference GetReference(string resolvedPath, MetadataReferenceProperties properties)
+        {
+            // HACK: right now the FileWatchedPortableExecutableReferenceFactory in Roslyn presumes that each time it calls IMetadataService
+            // it gets a unique instance back; the default MetadataService at the workspace layer has a cache to encourage sharing, but that
+            // breaks the assumption.
+            try
+            {
+                return MetadataReference.CreateFromFile(resolvedPath, properties, _documentationProviderService.GetDocumentationProvider(resolvedPath));
+            }
+            catch (IOException ex)
+            {
+                return new ThrowingExecutableReference(resolvedPath, properties, ex);
+            }
+        }
+
+        private class ThrowingExecutableReference : PortableExecutableReference
+        {
+            private readonly IOException _ex;
+
+            public ThrowingExecutableReference(string resolvedPath, MetadataReferenceProperties properties, IOException ex) : base(properties, resolvedPath)
+            {
+                _ex = ex;
+            }
+
+            protected override DocumentationProvider CreateDocumentationProvider()
+            {
+                throw new NotImplementedException();
+            }
+
+            protected override Metadata GetMetadataImpl()
+            {
+                throw _ex;
+            }
+
+            protected override PortableExecutableReference WithPropertiesImpl(MetadataReferenceProperties properties)
+            {
+                return new ThrowingExecutableReference(FilePath!, properties, _ex);
+            }
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/OpenSolutionHandler.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/OpenSolutionHandler.cs
new file mode 100644
index 0000000000000..da7bf9f0c814b
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/OpenSolutionHandler.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using System.Runtime.Serialization;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler;
+using Microsoft.CommonLanguageServerProtocol.Framework;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[ExportCSharpVisualBasicStatelessLspService(typeof(OpenSolutionHandler)), Shared]
+[Method("solution/open")]
+internal class OpenSolutionHandler : ILspServiceNotificationHandler<OpenSolutionHandler.NotificationParams>
+{
+    private readonly LanguageServerProjectSystem _projectSystem;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public OpenSolutionHandler(LanguageServerProjectSystem projectSystem)
+    {
+        _projectSystem = projectSystem;
+    }
+
+    public bool MutatesSolutionState => false;
+    public bool RequiresLSPSolution => false;
+
+    Task INotificationHandler<NotificationParams, RequestContext>.HandleNotificationAsync(NotificationParams request, RequestContext requestContext, CancellationToken cancellationToken)
+    {
+        return _projectSystem.OpenSolutionAsync(request.Solution.LocalPath);
+    }
+
+    [DataContract]
+    private class NotificationParams
+    {
+        [DataMember(Name = "solution")]
+        public required Uri Solution { get; set; }
+    }
+}
\ No newline at end of file
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ProjectInitializationHandler.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ProjectInitializationHandler.cs
new file mode 100644
index 0000000000000..7607906a2df8c
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ProjectInitializationHandler.cs
@@ -0,0 +1,119 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.Definitions;
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.Extensions.Logging;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using Roslyn.Utilities;
+using StreamJsonRpc;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+#pragma warning disable RS0030 // This is intentionally using System.ComponentModel.Composition for compatibility with MEF service broker.
+[Export]
+internal class ProjectInitializationHandler : IDisposable
+{
+    private const string ProjectInitializationCompleteName = "workspace/projectInitializationComplete";
+
+    private readonly IServiceBroker _serviceBroker;
+    private readonly ServiceBrokerClient _serviceBrokerClient;
+    private readonly ILogger _logger;
+
+    private readonly TaskCompletionSource _serviceAvailable = new();
+    private readonly ProjectInitializationCompleteObserver _projectInitializationCompleteObserver;
+
+    private IDisposable? _subscription;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ProjectInitializationHandler([Import(typeof(SVsFullAccessServiceBroker))] IServiceBroker serviceBroker, ILoggerFactory loggerFactory)
+    {
+        _serviceBroker = serviceBroker;
+        _serviceBroker.AvailabilityChanged += AvailabilityChanged;
+        _serviceBrokerClient = new ServiceBrokerClient(serviceBroker, joinableTaskFactory: null);
+
+        _logger = loggerFactory.CreateLogger<ProjectInitializationHandler>();
+        _projectInitializationCompleteObserver = new ProjectInitializationCompleteObserver(_logger);
+    }
+
+    public static async Task SendProjectInitializationCompleteNotificationAsync()
+    {
+        Contract.ThrowIfNull(LanguageServerHost.Instance, "We don't have an LSP channel yet to send this request through.");
+        var languageServerManager = LanguageServerHost.Instance.GetRequiredLspService<IClientLanguageServerManager>();
+        await languageServerManager.SendNotificationAsync(ProjectInitializationCompleteName, CancellationToken.None);
+    }
+
+    public async Task SubscribeToInitializationCompleteAsync(CancellationToken cancellationToken)
+    {
+        // Use the ServiceBrokerClient so that we actually hold onto the instance of the service to prevent it from being disposed of until we're shutting down.
+        var didSubscribe = await TrySubscribeAsync(cancellationToken);
+        if (!didSubscribe)
+        {
+            // Service might be null the first time we try to access it - wait for it to become available on the remote side.
+            await _serviceAvailable.Task;
+            didSubscribe = await TrySubscribeAsync(cancellationToken);
+            Contract.ThrowIfFalse(didSubscribe, $"Unable to subscribe to {Descriptors.RemoteProjectInitializationStatusService.Moniker}");
+        }
+    }
+
+    private async Task<bool> TrySubscribeAsync(CancellationToken cancellationToken)
+    {
+        using var rental = await _serviceBrokerClient.GetProxyAsync<IProjectInitializationStatusService>(Descriptors.RemoteProjectInitializationStatusService, cancellationToken);
+        if (rental.Proxy is not null)
+        {
+            _subscription = await rental.Proxy.SubscribeInitializationCompletionAsync(_projectInitializationCompleteObserver, cancellationToken);
+            return true;
+        }
+
+        return false;
+    }
+
+    private void AvailabilityChanged(object? sender, BrokeredServicesChangedEventArgs e)
+    {
+        if (e.ImpactedServices.Contains(Descriptors.RemoteProjectInitializationStatusService.Moniker))
+            _serviceAvailable.SetResult();
+    }
+
+    public void Dispose()
+    {
+        _serviceBroker.AvailabilityChanged -= AvailabilityChanged;
+        _subscription?.Dispose();
+        _serviceBrokerClient.Dispose();
+    }
+
+    internal class ProjectInitializationCompleteObserver : IObserver<ProjectInitializationCompletionState>
+    {
+        private readonly ILogger _logger;
+
+        public ProjectInitializationCompleteObserver(ILogger logger)
+        {
+            _logger = logger;
+        }
+
+        [JsonRpcMethod("onCompleted")]
+        public void OnCompleted()
+        {
+            // NoOp - OnNext is the only method that will be called upon completion of initial project load.
+        }
+
+        [JsonRpcMethod("onError", UseSingleObjectParameterDeserialization = true)]
+        public void OnError(Exception error)
+        {
+            _logger.LogError(error, "Devkit project initialization observer failed");
+        }
+
+        [JsonRpcMethod("onNext", UseSingleObjectParameterDeserialization = true)]
+        public void OnNext(ProjectInitializationCompletionState value)
+        {
+            _logger.LogDebug("Devkit project initialization completed");
+            _ = SendProjectInitializationCompleteNotificationAsync().ReportNonFatalErrorAsync();
+        }
+    }
+}
+#pragma warning restore RS0030 // Do not used banned APIs
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ProjectSystemDiagnosticSource.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ProjectSystemDiagnosticSource.cs
new file mode 100644
index 0000000000000..57a11e0431565
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/ProjectSystemDiagnosticSource.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+internal class ProjectSystemDiagnosticSource : IProjectSystemDiagnosticSource
+{
+    public void ClearAllDiagnosticsForProject(ProjectId projectId)
+    {
+    }
+
+    public void ClearAnalyzerReferenceDiagnostics(AnalyzerFileReference fileReference, string language, ProjectId projectId)
+    {
+    }
+
+    public void ClearDiagnosticsForProject(ProjectId projectId, object key)
+    {
+    }
+
+    public DiagnosticData CreateAnalyzerLoadFailureDiagnostic(AnalyzerLoadFailureEventArgs e, string fullPath, ProjectId projectId, string language)
+    {
+        return DocumentAnalysisExecutor.CreateAnalyzerLoadFailureDiagnostic(e, fullPath, projectId, language);
+    }
+
+    public void UpdateDiagnosticsForProject(ProjectId projectId, object key, IEnumerable<DiagnosticData> items)
+    {
+        // TODO: actually store the diagnostics
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorDynamicFileInfoProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorDynamicFileInfoProvider.cs
new file mode 100644
index 0000000000000..627a50e7be348
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorDynamicFileInfoProvider.cs
@@ -0,0 +1,105 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using System.Runtime.Serialization;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[Export(typeof(IDynamicFileInfoProvider)), Shared]
+[ExportMetadata("Extensions", new string[] { "cshtml", "razor", })]
+internal class RazorDynamicFileInfoProvider : IDynamicFileInfoProvider
+{
+    private const string ProvideRazorDynamicFileInfoMethodName = "razor/provideDynamicFileInfo";
+
+    [DataContract]
+    private class ProvideDynamicFileParams
+    {
+        [DataMember(Name = "razorFiles")]
+        public required Uri[] RazorFiles { get; set; }
+    }
+
+    [DataContract]
+    private class ProvideDynamicFileResponse
+    {
+        [DataMember(Name = "generatedFiles")]
+        public required Uri[] GeneratedFiles { get; set; }
+    }
+
+    private const string RemoveRazorDynamicFileInfoMethodName = "razor/removeDynamicFileInfo";
+
+    [DataContract]
+    private class RemoveDynamicFileParams
+    {
+        [DataMember(Name = "razorFiles")]
+        public required Uri[] RazorFiles { get; set; }
+    }
+
+#pragma warning disable CS0067 // We won't fire the Updated event -- we expect Razor to send us textual changes via didChange instead
+    public event EventHandler<string>? Updated;
+#pragma warning restore CS0067
+
+    private readonly Lazy<RazorWorkspaceListenerInitializer> _razorWorkspaceListenerInitializer;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public RazorDynamicFileInfoProvider(Lazy<RazorWorkspaceListenerInitializer> razorWorkspaceListenerInitializer)
+    {
+        _razorWorkspaceListenerInitializer = razorWorkspaceListenerInitializer;
+    }
+
+    public async Task<DynamicFileInfo?> GetDynamicFileInfoAsync(ProjectId projectId, string? projectFilePath, string filePath, CancellationToken cancellationToken)
+    {
+        _razorWorkspaceListenerInitializer.Value.NotifyDynamicFile(projectId);
+
+        var requestParams = new ProvideDynamicFileParams { RazorFiles = new[] { ProtocolConversions.GetUriFromFilePath(filePath) } };
+
+        Contract.ThrowIfNull(LanguageServerHost.Instance, "We don't have an LSP channel yet to send this request through.");
+        var clientLanguageServerManager = LanguageServerHost.Instance.GetRequiredLspService<IClientLanguageServerManager>();
+
+        var response = await clientLanguageServerManager.SendRequestAsync<ProvideDynamicFileParams, ProvideDynamicFileResponse>(
+            ProvideRazorDynamicFileInfoMethodName, requestParams, cancellationToken);
+
+        // Since we only sent one file over, we should get either zero or one URI back
+        var responseUri = response.GeneratedFiles.SingleOrDefault();
+
+        if (responseUri == null)
+        {
+            return null;
+        }
+        else
+        {
+            var dynamicFileInfoFilePath = ProtocolConversions.GetDocumentFilePathFromUri(responseUri);
+            return new DynamicFileInfo(dynamicFileInfoFilePath, SourceCodeKind.Regular, EmptyStringTextLoader.Instance, designTimeOnly: true, documentServiceProvider: null);
+        }
+    }
+
+    public Task RemoveDynamicFileInfoAsync(ProjectId projectId, string? projectFilePath, string filePath, CancellationToken cancellationToken)
+    {
+        var notificationParams = new RemoveDynamicFileParams { RazorFiles = new[] { ProtocolConversions.GetUriFromFilePath(filePath) } };
+
+        Contract.ThrowIfNull(LanguageServerHost.Instance, "We don't have an LSP channel yet to send this request through.");
+        var clientLanguageServerManager = LanguageServerHost.Instance.GetRequiredLspService<IClientLanguageServerManager>();
+
+        return clientLanguageServerManager.SendNotificationAsync(
+            RemoveRazorDynamicFileInfoMethodName, notificationParams, cancellationToken).AsTask();
+    }
+
+    private sealed class EmptyStringTextLoader : TextLoader
+    {
+        public static readonly TextLoader Instance = new EmptyStringTextLoader();
+
+        private EmptyStringTextLoader() { }
+
+        public override Task<TextAndVersion> LoadTextAndVersionAsync(LoadTextOptions options, CancellationToken cancellationToken)
+        {
+            return Task.FromResult(TextAndVersion.Create(SourceText.From(""), VersionStamp.Default));
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorInitializeHandler.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorInitializeHandler.cs
new file mode 100644
index 0000000000000..dd1dd878f1102
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorInitializeHandler.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler;
+using Microsoft.CommonLanguageServerProtocol.Framework;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[ExportCSharpVisualBasicStatelessLspService(typeof(RazorInitializeHandler)), Shared]
+[Method("razor/initialize")]
+internal class RazorInitializeHandler : ILspServiceNotificationHandler<object>
+{
+    private readonly Lazy<RazorWorkspaceListenerInitializer> _razorWorkspaceListenerInitializer;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public RazorInitializeHandler(Lazy<RazorWorkspaceListenerInitializer> razorWorkspaceListenerInitializer)
+    {
+        _razorWorkspaceListenerInitializer = razorWorkspaceListenerInitializer;
+    }
+
+    public bool MutatesSolutionState => false;
+    public bool RequiresLSPSolution => false;
+
+    Task INotificationHandler<object, RequestContext>.HandleNotificationAsync(object request, RequestContext requestContext, CancellationToken cancellationToken)
+    {
+        _razorWorkspaceListenerInitializer.Value.Initialize();
+
+        return Task.CompletedTask;
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorWorkspaceListenerInitializer.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorWorkspaceListenerInitializer.cs
new file mode 100644
index 0000000000000..9b7cdf022a986
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/RazorWorkspaceListenerInitializer.cs
@@ -0,0 +1,84 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.AspNetCore.Razor.ExternalAccess.RoslynWorkspace;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+[Export(typeof(RazorWorkspaceListenerInitializer)), Shared]
+internal sealed class RazorWorkspaceListenerInitializer
+{
+    // This should be moved to the Razor side once things are announced, so defaults are all in one
+    // place, in case things ever need to change
+    private const string _projectRazorJsonFileName = "project.razor.vscode.json";
+
+    private readonly ILogger _logger;
+    private readonly Workspace _workspace;
+    private readonly ILoggerFactory _loggerFactory;
+
+    // Locks all access to _razorWorkspaceListener and _projectIdWithDynamicFiles
+    private readonly object _initializeGate = new();
+    private HashSet<ProjectId> _projectIdWithDynamicFiles = new();
+
+    private RazorWorkspaceListener? _razorWorkspaceListener;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public RazorWorkspaceListenerInitializer(LanguageServerWorkspaceFactory workspaceFactory, ILoggerFactory loggerFactory)
+    {
+        _logger = loggerFactory.CreateLogger(nameof(RazorWorkspaceListenerInitializer));
+
+        _workspace = workspaceFactory.Workspace;
+        _loggerFactory = loggerFactory;
+    }
+
+    internal void Initialize()
+    {
+        HashSet<ProjectId> projectsToInitialize;
+        lock (_initializeGate)
+        {
+            // Only initialize once
+            if (_razorWorkspaceListener is not null)
+            {
+                return;
+            }
+
+            _logger.LogTrace("Initializing the Razor workspace listener");
+            _razorWorkspaceListener = new RazorWorkspaceListener(_loggerFactory);
+            _razorWorkspaceListener.EnsureInitialized(_workspace, _projectRazorJsonFileName);
+
+            projectsToInitialize = _projectIdWithDynamicFiles;
+            // May as well clear out the collection, it will never get used again anyway.
+            _projectIdWithDynamicFiles = new();
+        }
+
+        foreach (var projectId in projectsToInitialize)
+        {
+            _logger.LogTrace("{projectId} notifying a dynamic file for the first time", projectId);
+            _razorWorkspaceListener.NotifyDynamicFile(projectId);
+        }
+    }
+
+    internal void NotifyDynamicFile(ProjectId projectId)
+    {
+        lock (_initializeGate)
+        {
+            if (_razorWorkspaceListener is null)
+            {
+                // We haven't been initialized by the extension yet, so just store the project id, to tell Razor later
+                _logger.LogTrace("{projectId} queuing up a dynamic file notify for later", projectId);
+                _projectIdWithDynamicFiles.Add(projectId);
+
+                return;
+            }
+        }
+
+        // We've been initialized, so just pass the information along
+        _logger.LogTrace("{projectId} forwarding on a dynamic file notification because we're initialized", projectId);
+        _razorWorkspaceListener.NotifyDynamicFile(projectId);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/WorkspaceProject.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/WorkspaceProject.cs
new file mode 100644
index 0000000000000..5367e67e18719
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/WorkspaceProject.cs
@@ -0,0 +1,212 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+using Microsoft.CodeAnalysis.Remote.ProjectSystem;
+using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+
+internal class WorkspaceProject : IWorkspaceProject
+{
+    private readonly ProjectSystemProject _project;
+    private readonly ProjectSystemProjectOptionsProcessor _optionsProcessor;
+    private readonly ProjectTargetFrameworkManager _targetFrameworkManager;
+
+    public WorkspaceProject(ProjectSystemProject project, SolutionServices solutionServices, ProjectTargetFrameworkManager targetFrameworkManager)
+    {
+        _project = project;
+        _optionsProcessor = new ProjectSystemProjectOptionsProcessor(_project, solutionServices);
+        _targetFrameworkManager = targetFrameworkManager;
+    }
+
+    public async Task AddAdditionalFilesAsync(IReadOnlyList<string> additionalFilePaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var additionalFilePath in additionalFilePaths)
+            _project.AddAdditionalFile(additionalFilePath);
+    }
+
+    public async Task AddAnalyzerConfigFilesAsync(IReadOnlyList<string> analyzerConfigPaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var analyzerConfigPath in analyzerConfigPaths)
+            _project.AddAnalyzerConfigFile(analyzerConfigPath);
+    }
+
+    public async Task AddAnalyzerReferencesAsync(IReadOnlyList<string> analyzerPaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var analyzerPath in analyzerPaths)
+            _project.AddAnalyzerReference(analyzerPath);
+    }
+
+    public async Task AddDynamicFilesAsync(IReadOnlyList<string> dynamicFilePaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var dynamicFilePath in dynamicFilePaths)
+            _project.AddDynamicSourceFile(dynamicFilePath, folders: ImmutableArray<string>.Empty);
+    }
+
+    public async Task AddMetadataReferencesAsync(IReadOnlyList<MetadataReferenceInfo> metadataReferences, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var metadataReference in metadataReferences)
+            _project.AddMetadataReference(metadataReference.FilePath, metadataReference.CreateProperties());
+    }
+
+    public async Task AddSourceFilesAsync(IReadOnlyList<SourceFileInfo> sourceFiles, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var sourceFile in sourceFiles)
+            _project.AddSourceFile(sourceFile.FilePath, folders: sourceFile.FolderNames.ToImmutableArray());
+    }
+
+    public void Dispose()
+    {
+        _project.RemoveFromWorkspace();
+    }
+
+    public async Task RemoveAdditionalFilesAsync(IReadOnlyList<string> additionalFilePaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var additionalFilePath in additionalFilePaths)
+            _project.RemoveAdditionalFile(additionalFilePath);
+    }
+
+    public async Task RemoveAnalyzerConfigFilesAsync(IReadOnlyList<string> analyzerConfigPaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var analyzerConfigPath in analyzerConfigPaths)
+            _project.RemoveAnalyzerConfigFile(analyzerConfigPath);
+    }
+
+    public async Task RemoveAnalyzerReferencesAsync(IReadOnlyList<string> analyzerPaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var analyzerPath in analyzerPaths)
+            _project.RemoveAnalyzerReference(analyzerPath);
+    }
+
+    public async Task RemoveDynamicFilesAsync(IReadOnlyList<string> dynamicFilePaths, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var dynamicFilePath in dynamicFilePaths)
+            _project.RemoveDynamicSourceFile(dynamicFilePath);
+    }
+
+    public async Task RemoveMetadataReferencesAsync(IReadOnlyList<MetadataReferenceInfo> metadataReferences, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var metadataReference in metadataReferences)
+            _project.RemoveMetadataReference(metadataReference.FilePath, metadataReference.CreateProperties());
+    }
+
+    public async Task RemoveSourceFilesAsync(IReadOnlyList<string> sourceFiles, CancellationToken _)
+    {
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var sourceFile in sourceFiles)
+            _project.RemoveSourceFile(sourceFile);
+    }
+
+    public async Task SetBuildSystemPropertiesAsync(IReadOnlyDictionary<string, string> properties, CancellationToken _)
+    {
+        // Create a batch scope, just so we have asynchronous closing and application of the batch.
+        await using var batchScope = _project.CreateBatchScope();
+
+        foreach (var (name, value) in properties)
+        {
+            var valueOrNull = string.IsNullOrEmpty(value) ? null : value;
+
+            switch (name)
+            {
+                case "AssemblyName": _project.AssemblyName = value; break;
+                case "MaxSupportedLangVersion": _project.MaxLangVersion = value; break;
+                case "RootNamespace": _project.DefaultNamespace = valueOrNull; break;
+                case "RunAnalyzers": _project.RunAnalyzers = bool.Parse(valueOrNull ?? bool.TrueString); break;
+                case "RunAnalyzersDuringLiveAnalysis": _project.RunAnalyzersDuringLiveAnalysis = bool.Parse(valueOrNull ?? bool.TrueString); break;
+                case "TargetPath": _project.OutputFilePath = GetFullyQualifiedPath(valueOrNull); break;
+                case "TargetRefPath": _project.OutputRefFilePath = GetFullyQualifiedPath(valueOrNull); break;
+                case "TargetFrameworkIdentifier": _targetFrameworkManager.UpdateIdentifierForProject(_project.Id, valueOrNull); break;
+            }
+        }
+
+        // Workaround for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1830960
+        _project.CompilationOutputAssemblyFilePath = _project.OutputFilePath;
+
+        string? GetFullyQualifiedPath(string? propertyValue)
+        {
+            Contract.ThrowIfNull(_project.FilePath, "We don't have a project path at this point.");
+
+            if (propertyValue is not null)
+                return Path.Combine(_project.FilePath, propertyValue);
+            else
+                return null;
+        }
+    }
+
+    public async Task SetCommandLineArgumentsAsync(IReadOnlyList<string> arguments, CancellationToken _)
+    {
+        // Create a batch scope, just so we have asynchronous closing and application of the batch.
+        await using var batchScope = _project.CreateBatchScope();
+        _optionsProcessor.SetCommandLine(arguments.ToImmutableArray());
+    }
+
+    public async Task SetDisplayNameAsync(string displayName, CancellationToken _)
+    {
+        // Create a batch scope, just so we have asynchronous closing and application of the batch.
+        await using var batchScope = _project.CreateBatchScope();
+        _project.DisplayName = displayName;
+    }
+
+    public async Task SetProjectHasAllInformationAsync(bool hasAllInformation, CancellationToken _)
+    {
+        // Create a batch scope, just so we have asynchronous closing and application of the batch.
+        await using var batchScope = _project.CreateBatchScope();
+        _project.HasAllInformation = hasAllInformation;
+    }
+
+    public Task<IWorkspaceProjectBatch> StartBatchAsync(CancellationToken cancellationToken)
+    {
+        return Task.FromResult<IWorkspaceProjectBatch>(new WorkspaceProjectBatch(_project.CreateBatchScope()));
+    }
+
+    private class WorkspaceProjectBatch : IWorkspaceProjectBatch
+    {
+        private IAsyncDisposable? _batch;
+
+        public WorkspaceProjectBatch(IAsyncDisposable batch)
+        {
+            _batch = batch;
+        }
+
+        public async Task ApplyAsync(CancellationToken cancellationToken)
+        {
+            if (_batch == null)
+                throw new InvalidOperationException("The batch has already been applied.");
+
+            await _batch.DisposeAsync().ConfigureAwait(false);
+            _batch = null;
+        }
+
+        public void Dispose()
+        {
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/WorkspaceProjectFactoryService.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/WorkspaceProjectFactoryService.cs
new file mode 100644
index 0000000000000..906994584d08a
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/WorkspaceProjectFactoryService.cs
@@ -0,0 +1,65 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using System.ComponentModel.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Remote.ProjectSystem;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+#pragma warning disable RS0030 // This is intentionally using System.ComponentModel.Composition for compatibility with MEF service broker.
+/// <summary>
+/// An implementation of the brokered service <see cref="IWorkspaceProjectFactoryService"/> that just maps calls to the underlying project system.
+/// </summary>
+[ExportBrokeredService("Microsoft.VisualStudio.LanguageServices.WorkspaceProjectFactoryService", null, Audience = ServiceAudience.Local)]
+internal class WorkspaceProjectFactoryService : IWorkspaceProjectFactoryService, IExportedBrokeredService
+{
+    private readonly LanguageServerWorkspaceFactory _workspaceFactory;
+    private readonly ProjectInitializationHandler _projectInitializationHandler;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public WorkspaceProjectFactoryService(LanguageServerWorkspaceFactory workspaceFactory, ProjectInitializationHandler projectInitializationHandler)
+    {
+        _workspaceFactory = workspaceFactory;
+        _projectInitializationHandler = projectInitializationHandler;
+    }
+
+    ServiceRpcDescriptor IExportedBrokeredService.Descriptor => WorkspaceProjectFactoryServiceDescriptor.ServiceDescriptor;
+
+    async Task IExportedBrokeredService.InitializeAsync(CancellationToken cancellationToken)
+    {
+        await _projectInitializationHandler.SubscribeToInitializationCompleteAsync(cancellationToken);
+    }
+
+    public async Task<IWorkspaceProject> CreateAndAddProjectAsync(WorkspaceProjectCreationInfo creationInfo, CancellationToken _)
+    {
+        if (creationInfo.BuildSystemProperties.TryGetValue("SolutionPath", out var solutionPath))
+        {
+            _workspaceFactory.ProjectSystemProjectFactory.SolutionPath = solutionPath;
+        }
+
+        var project = await _workspaceFactory.ProjectSystemProjectFactory.CreateAndAddToWorkspaceAsync(
+            creationInfo.DisplayName,
+            creationInfo.Language,
+            new Workspaces.ProjectSystem.ProjectSystemProjectCreationInfo { FilePath = creationInfo.FilePath },
+            _workspaceFactory.ProjectSystemHostInfo);
+
+        var workspaceProject = new WorkspaceProject(project, _workspaceFactory.Workspace.Services.SolutionServices, _workspaceFactory.TargetFrameworkManager);
+
+        // We've created a new project, so initialize properties we have
+        await workspaceProject.SetBuildSystemPropertiesAsync(creationInfo.BuildSystemProperties, CancellationToken.None);
+
+        return workspaceProject;
+    }
+
+    public Task<IReadOnlyCollection<string>> GetSupportedBuildSystemPropertiesAsync(CancellationToken _)
+    {
+        // TODO: implement
+        return Task.FromResult((IReadOnlyCollection<string>)ImmutableArray<string>.Empty);
+    }
+}
+#pragma warning restore RS0030 // Do not used banned APIs
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/ProjectDebugConfiguration.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/ProjectDebugConfiguration.cs
new file mode 100644
index 0000000000000..82e2ab5fa530c
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/ProjectDebugConfiguration.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+using Newtonsoft.Json;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+
+[DataContract]
+internal class ProjectDebugConfiguration
+{
+    public ProjectDebugConfiguration(string projectPath, string outputPath, string projectName, bool targetsDotnetCore, bool isExe, string? solutionPath)
+    {
+        ProjectPath = projectPath;
+        OutputPath = outputPath;
+        ProjectName = projectName;
+        TargetsDotnetCore = targetsDotnetCore;
+        IsExe = isExe;
+        SolutionPath = solutionPath;
+    }
+
+    [JsonProperty(PropertyName = "projectPath")]
+    public string ProjectPath { get; }
+
+    [JsonProperty(PropertyName = "outputPath")]
+    public string OutputPath { get; }
+
+    [JsonProperty(PropertyName = "projectName")]
+    public string ProjectName { get; }
+
+    [JsonProperty(PropertyName = "targetsDotnetCore")]
+    public bool TargetsDotnetCore { get; }
+
+    [JsonProperty(PropertyName = "isExe")]
+    public bool IsExe { get; }
+
+    [JsonProperty(PropertyName = "solutionPath")]
+    public string? SolutionPath { get; }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/ProjectTargetFrameworkManager.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/ProjectTargetFrameworkManager.cs
new file mode 100644
index 0000000000000..be3a3b21ae97b
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/ProjectTargetFrameworkManager.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Concurrent;
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+
+/// <summary>
+/// Keeps track of which project uses what TFM.
+/// </summary>
+[Export, Shared]
+internal class ProjectTargetFrameworkManager
+{
+    private readonly ConcurrentDictionary<ProjectId, string?> _projectToTargetFrameworkIdentifer = new();
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ProjectTargetFrameworkManager()
+    {
+    }
+
+    public void UpdateIdentifierForProject(ProjectId projectId, string? identifier)
+    {
+        _ = _projectToTargetFrameworkIdentifer.AddOrUpdate(projectId, identifier, (project, oldIdentifier) => identifier);
+    }
+
+    public bool IsDotnetCoreProject(ProjectId projectId)
+    {
+        if (_projectToTargetFrameworkIdentifer.TryGetValue(projectId, out var identifier) && identifier != null)
+        {
+            return IsDotnetCoreIdentifier(identifier);
+        }
+
+        return false;
+    }
+
+    private static bool IsDotnetCoreIdentifier(string identifier)
+    {
+        // This is the condition suggested by the SDK/MSBuild for determining if a project targets .net core.
+        return identifier.StartsWith(".NETCoreApp") || identifier.StartsWith(".NETStandard");
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/WorkspaceDebugConfigurationHandler.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/WorkspaceDebugConfigurationHandler.cs
new file mode 100644
index 0000000000000..5042fb751b12d
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/WorkspaceDebugConfigurationHandler.cs
@@ -0,0 +1,72 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+
+[ExportCSharpVisualBasicStatelessLspService(typeof(WorkspaceDebugConfigurationHandler)), Shared]
+[Method(MethodName)]
+internal class WorkspaceDebugConfigurationHandler : ILspServiceRequestHandler<WorkspaceDebugConfigurationParams, ProjectDebugConfiguration[]>
+{
+    private const string MethodName = "workspace/debugConfiguration";
+
+    private readonly ProjectTargetFrameworkManager _targetFrameworkManager;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public WorkspaceDebugConfigurationHandler(ProjectTargetFrameworkManager targetFrameworkManager)
+    {
+        _targetFrameworkManager = targetFrameworkManager;
+    }
+
+    public bool MutatesSolutionState => false;
+
+    public bool RequiresLSPSolution => true;
+
+    public Task<ProjectDebugConfiguration[]> HandleRequestAsync(WorkspaceDebugConfigurationParams request, RequestContext context, CancellationToken cancellationToken)
+    {
+        Contract.ThrowIfNull(context.Solution, nameof(context.Solution));
+
+        var projects = context.Solution.Projects
+            .Where(p => p.FilePath != null && p.OutputFilePath != null)
+            .Where(p => IsProjectInWorkspace(request.WorkspacePath, p))
+            .Select(GetProjectDebugConfiguration).ToArray();
+        return Task.FromResult(projects);
+    }
+
+    private static bool IsProjectInWorkspace(Uri workspacePath, Project project)
+    {
+        return PathUtilities.IsSameDirectoryOrChildOf(project.FilePath!, workspacePath.LocalPath);
+    }
+
+    private ProjectDebugConfiguration GetProjectDebugConfiguration(Project project)
+    {
+        var isExe = project.CompilationOptions?.OutputKind is OutputKind.ConsoleApplication or OutputKind.WindowsApplication;
+        var targetsDotnetCore = _targetFrameworkManager.IsDotnetCoreProject(project.Id);
+        return new ProjectDebugConfiguration(project.FilePath!, project.OutputFilePath!, GetProjectName(project), targetsDotnetCore, isExe, project.Solution.FilePath);
+    }
+
+    private static string GetProjectName(Project project)
+    {
+        var (_, flavor) = project.State.NameAndFlavor;
+        if (string.IsNullOrEmpty(flavor))
+        {
+            return project.Name;
+        }
+        else
+        {
+            var projectPath = project.FilePath!;
+            var projectFileName = Path.GetFileName(projectPath);
+            return $"{projectFileName} ({flavor}) - {projectPath}";
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/WorkspaceDebugConfigurationParams.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/WorkspaceDebugConfigurationParams.cs
new file mode 100644
index 0000000000000..a286f9bdf9f4a
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/Handler/DebugConfiguration/WorkspaceDebugConfigurationParams.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Newtonsoft.Json;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.DebugConfiguration;
+
+[DataContract]
+internal record WorkspaceDebugConfigurationParams(
+    [JsonProperty(PropertyName = "workspacePath"), JsonConverter(typeof(DocumentUriConverter))] Uri WorkspacePath);
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/LanguageServerHost.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/LanguageServerHost.cs
new file mode 100644
index 0000000000000..03803c10aad83
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/LanguageServerHost.cs
@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.LanguageServer.Handler;
+using Microsoft.CodeAnalysis.LanguageServer.Logging;
+using Microsoft.CommonLanguageServerProtocol.Framework;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.Composition;
+using StreamJsonRpc;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+
+#pragma warning disable CA1001 // The JsonRpc instance is disposed of by the AbstractLanguageServer during shutdown
+internal sealed class LanguageServerHost
+#pragma warning restore CA1001 // The JsonRpc instance is disposed of by the AbstractLanguageServer during shutdown
+{
+    // TODO: replace this with a MEF part instead
+    /// <summary>
+    /// A static reference to the server instance.
+    /// Used by components to send notifications and requests back to the client.
+    /// </summary>
+    internal static LanguageServerHost? Instance { get; private set; }
+
+    private readonly ILogger _logger;
+    private readonly AbstractLanguageServer<RequestContext> _roslynLanguageServer;
+    private readonly JsonRpc _jsonRpc;
+
+    public LanguageServerHost(Stream inputStream, Stream outputStream, ExportProvider exportProvider, ILogger logger)
+    {
+        var handler = new HeaderDelimitedMessageHandler(outputStream, inputStream, new JsonMessageFormatter());
+
+        // If there is a jsonrpc disconnect or server shutdown, that is handled by the AbstractLanguageServer.  No need to do anything here.
+        _jsonRpc = new JsonRpc(handler)
+        {
+            ExceptionStrategy = ExceptionProcessing.CommonErrorData,
+        };
+
+        var roslynLspFactory = exportProvider.GetExportedValue<ILanguageServerFactory>();
+        var capabilitiesProvider = new ServerCapabilitiesProvider(exportProvider.GetExportedValue<ExperimentalCapabilitiesProvider>());
+
+        _logger = logger;
+        var lspLogger = new LspServiceLogger(_logger);
+
+        var hostServices = exportProvider.GetExportedValue<HostServicesProvider>().HostServices;
+        _roslynLanguageServer = roslynLspFactory.Create(_jsonRpc, capabilitiesProvider, WellKnownLspServerKinds.CSharpVisualBasicLspServer, lspLogger, hostServices);
+    }
+
+    public void Start()
+    {
+        _logger.LogInformation("Starting server...");
+        _jsonRpc.StartListening();
+
+        // Now that the server is started, update the our instance reference
+        Instance = this;
+    }
+
+    public async Task WaitForExitAsync()
+    {
+        await _jsonRpc.Completion;
+        await _roslynLanguageServer.WaitForExitAsync();
+    }
+
+    public T GetRequiredLspService<T>() where T : ILspService
+    {
+        return _roslynLanguageServer.GetLspServices().GetRequiredService<T>();
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/ServerCapabilitiesProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/ServerCapabilitiesProvider.cs
new file mode 100644
index 0000000000000..1b8b495b941ef
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/ServerCapabilitiesProvider.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+
+internal sealed class ServerCapabilitiesProvider : ICapabilitiesProvider
+{
+    private readonly ExperimentalCapabilitiesProvider _roslynCapabilities;
+
+    public ServerCapabilitiesProvider(ExperimentalCapabilitiesProvider roslynCapabilities)
+    {
+        _roslynCapabilities = roslynCapabilities;
+    }
+
+    public ServerCapabilities GetCapabilities(ClientCapabilities clientCapabilities)
+    {
+        var roslynCapabilities = _roslynCapabilities.GetCapabilities(clientCapabilities);
+        return roslynCapabilities;
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/WorkspaceRegistrationService.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/WorkspaceRegistrationService.cs
new file mode 100644
index 0000000000000..fed1eeb89123f
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/LanguageServer/WorkspaceRegistrationService.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+
+/// <summary>
+/// Implements the workspace registration service so that any new workspaces we
+/// create are automatically registered by <see cref="LspWorkspaceRegistrationEventListener"/>
+/// </summary>
+[Export(typeof(LspWorkspaceRegistrationService)), Shared]
+internal class WorkspaceRegistrationService : LspWorkspaceRegistrationService
+{
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public WorkspaceRegistrationService()
+    {
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspLogMessageLogger.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspLogMessageLogger.cs
new file mode 100644
index 0000000000000..a461af8c5ecf1
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspLogMessageLogger.cs
@@ -0,0 +1,80 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using StreamJsonRpc;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Logging;
+
+/// <summary>
+/// Implements an ILogger that seamlessly switches from a fallback logger
+/// to LSP log messages as soon as the server initializes.
+/// </summary>
+internal sealed class LspLogMessageLogger : ILogger
+{
+    private readonly string _categoryName;
+    private readonly ILogger _fallbackLogger;
+
+    public LspLogMessageLogger(string categoryName, ILoggerFactory fallbackLoggerFactory)
+    {
+        _categoryName = categoryName;
+        _fallbackLogger = fallbackLoggerFactory.CreateLogger(categoryName);
+    }
+
+    public IDisposable BeginScope<TState>(TState state)
+    {
+        throw new NotImplementedException();
+    }
+
+    public bool IsEnabled(LogLevel logLevel)
+    {
+        return true;
+    }
+
+    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
+    {
+        var server = LanguageServerHost.Instance;
+        if (server == null)
+        {
+            // If the language server has not been initialized yet, log using the fallback logger.
+            _fallbackLogger.Log(logLevel, eventId, state, exception, formatter);
+            return;
+        }
+
+        var message = formatter(state, exception);
+
+        // HACK: work around https://github.com/dotnet/runtime/issues/67597: the formatter function we passed the exception to completely ignores the exception,
+        // we'll add an exception message back in. If we didn't have a message, we'll just replace it with the exception text.
+        if (exception != null)
+        {
+            var exceptionString = exception.ToString();
+            if (message == "[null]") // https://github.com/dotnet/runtime/blob/013ca673f6316dbbe71c7b327d7b8fa41cf8c992/src/libraries/Microsoft.Extensions.Logging.Abstractions/src/FormattedLogValues.cs#L19
+                message = exceptionString;
+            else
+                message += " " + exceptionString;
+        }
+
+        if (message != null && logLevel != LogLevel.None)
+        {
+            message = $"[{_categoryName}]{message}";
+            var _ = server.GetRequiredLspService<IClientLanguageServerManager>().SendNotificationAsync(Methods.WindowLogMessageName, new LogMessageParams()
+            {
+                Message = message,
+                MessageType = logLevel switch
+                {
+                    LogLevel.Trace => MessageType.Log,
+                    LogLevel.Debug => MessageType.Log,
+                    LogLevel.Information => MessageType.Info,
+                    LogLevel.Warning => MessageType.Warning,
+                    LogLevel.Error => MessageType.Error,
+                    LogLevel.Critical => MessageType.Error,
+                    _ => throw new InvalidOperationException($"Unexpected logLevel argument {logLevel}"),
+                }
+            }, CancellationToken.None);
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspLogMessageLoggerProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspLogMessageLoggerProvider.cs
new file mode 100644
index 0000000000000..1f216c21c4550
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspLogMessageLoggerProvider.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Concurrent;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Logging;
+internal class LspLogMessageLoggerProvider : ILoggerProvider
+{
+    private readonly ILoggerFactory _fallbackLoggerFactory;
+    private readonly ConcurrentDictionary<string, LspLogMessageLogger> _loggers = new(StringComparer.OrdinalIgnoreCase);
+
+    public LspLogMessageLoggerProvider(ILoggerFactory fallbackLoggerFactory)
+    {
+        _fallbackLoggerFactory = fallbackLoggerFactory;
+    }
+
+    public ILogger CreateLogger(string categoryName)
+    {
+        return _loggers.GetOrAdd(categoryName, new LspLogMessageLogger(categoryName, _fallbackLoggerFactory));
+    }
+
+    public void Dispose()
+    {
+        _loggers.Clear();
+        _fallbackLoggerFactory.Dispose();
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspServiceLogger.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspServiceLogger.cs
new file mode 100644
index 0000000000000..5da7012ea5e5d
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/LspServiceLogger.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Logging;
+
+/// <summary>
+/// Implements <see cref="ILspServiceLogger"/> by sending LSP log messages back to the client.
+/// </summary>
+internal sealed class LspServiceLogger : ILspServiceLogger
+{
+    private readonly ILogger _hostLogger;
+
+    public LspServiceLogger(ILogger hostLogger)
+    {
+        _hostLogger = hostLogger;
+    }
+
+    public void LogEndContext(string message, params object[] @params) => _hostLogger.LogDebug($"[{DateTime.UtcNow:hh:mm:ss.fff}][End]{message}", @params);
+
+    public void LogError(string message, params object[] @params) => _hostLogger.LogError(message, @params);
+
+    public void LogException(Exception exception, string? message = null, params object[] @params) => _hostLogger.LogError(exception, message, @params);
+
+    /// <summary>
+    /// TODO - This should call LogInformation, however we need to introduce a LogDebug call in clasp first.
+    /// </summary>
+    public void LogInformation(string message, params object[] @params) => _hostLogger.LogDebug(message, @params);
+
+    public void LogStartContext(string message, params object[] @params) => _hostLogger.LogDebug($"[{DateTime.UtcNow:hh:mm:ss.fff}][Start]{message}", @params);
+
+    public void LogWarning(string message, params object[] @params) => _hostLogger.LogWarning(message, @params);
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/RoslynLogger.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/RoslynLogger.cs
new file mode 100644
index 0000000000000..957cd1f146d0c
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/RoslynLogger.cs
@@ -0,0 +1,235 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Concurrent;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using Microsoft.CodeAnalysis.Common;
+using Microsoft.CodeAnalysis.Contracts.Telemetry;
+using Microsoft.CodeAnalysis.ErrorReporting;
+using Microsoft.CodeAnalysis.Internal.Log;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Logging
+{
+    internal class RoslynLogger : ILogger
+    {
+        private static RoslynLogger? _instance;
+        private static readonly ConcurrentDictionary<FunctionId, string> s_eventMap = new();
+        private static readonly ConcurrentDictionary<(FunctionId id, string name), string> s_propertyMap = new();
+
+        private readonly ConcurrentDictionary<int, object> _pendingScopes = new(concurrencyLevel: 2, capacity: 10);
+        private static ITelemetryReporter? _telemetryReporter;
+
+        private RoslynLogger()
+        {
+        }
+
+        public static void Initialize(ITelemetryReporter? reporter, string? telemetryLevel, string? sessionId)
+        {
+            Contract.ThrowIfTrue(_instance is not null);
+
+            FatalError.Handler = ReportFault;
+            FatalError.CopyHandlerTo(typeof(Compilation).Assembly);
+
+            if (reporter is not null && telemetryLevel is not null)
+            {
+                reporter.InitializeSession(telemetryLevel, sessionId, isDefaultSession: true);
+                _telemetryReporter = reporter;
+            }
+
+            _instance = new();
+
+            var currentLogger = Logger.GetLogger();
+            if (currentLogger is null)
+            {
+                Logger.SetLogger(_instance);
+            }
+            else
+            {
+                Logger.SetLogger(AggregateLogger.Create(currentLogger, _instance));
+            }
+        }
+
+        private static void ReportFault(Exception exception, ErrorSeverity severity, bool forceDump)
+        {
+            try
+            {
+                if (exception is OperationCanceledException { InnerException: { } oceInnerException })
+                {
+                    ReportFault(oceInnerException, severity, forceDump);
+                    return;
+                }
+
+                if (exception is AggregateException aggregateException)
+                {
+                    // We (potentially) have multiple exceptions; let's just report each of them
+                    foreach (var innerException in aggregateException.Flatten().InnerExceptions)
+                        ReportFault(innerException, severity, forceDump);
+
+                    return;
+                }
+
+                if (_telemetryReporter is not null)
+                {
+                    var eventName = GetEventName(FunctionId.NonFatalWatson);
+                    var description = GetDescription(exception);
+                    var currentProcess = Process.GetCurrentProcess();
+                    _telemetryReporter.ReportFault(eventName, description, (int)severity, forceDump, currentProcess.Id, exception);
+                }
+            }
+            catch (OutOfMemoryException)
+            {
+                FailFast.OnFatalException(exception);
+            }
+            catch (Exception e)
+            {
+                FailFast.OnFatalException(e);
+            }
+        }
+
+        public bool IsEnabled(FunctionId functionId)
+            => _telemetryReporter is not null;
+
+        public void Log(FunctionId functionId, LogMessage logMessage)
+        {
+            var name = GetEventName(functionId);
+            var properties = GetProperties(functionId, logMessage, delta: null);
+
+            try
+            {
+                _telemetryReporter?.Log(name, properties);
+            }
+            catch
+            {
+            }
+        }
+
+        public void LogBlockStart(FunctionId functionId, LogMessage logMessage, int blockId, CancellationToken cancellationToken)
+        {
+            var eventName = GetEventName(functionId);
+            var kind = GetKind(logMessage);
+
+            try
+            {
+                _telemetryReporter?.LogBlockStart(eventName, (int)kind, blockId);
+            }
+            catch
+            {
+            }
+        }
+
+        public void LogBlockEnd(FunctionId functionId, LogMessage logMessage, int blockId, int delta, CancellationToken cancellationToken)
+        {
+            var properties = GetProperties(functionId, logMessage, delta);
+            try
+            {
+                _telemetryReporter?.LogBlockEnd(blockId, properties, cancellationToken);
+            }
+            catch
+            {
+            }
+        }
+
+        public static void ShutdownAndReportSessionTelemetry()
+        {
+            if (_instance is null)
+            {
+                return;
+            }
+
+            FeaturesSessionTelemetry.Report();
+
+            (var currentReporter, _telemetryReporter) = (_telemetryReporter, null);
+            currentReporter?.Dispose();
+            _instance = null;
+        }
+
+        private static string GetDescription(Exception exception)
+        {
+            const string CodeAnalysisNamespace = nameof(Microsoft) + "." + nameof(CodeAnalysis);
+
+            // Be resilient to failing here.  If we can't get a suitable name, just fall back to the standard name we
+            // used to report.
+            try
+            {
+                // walk up the stack looking for the first call from a type that isn't in the ErrorReporting namespace.
+                var frames = new StackTrace(exception).GetFrames();
+
+                // On the .NET Framework, GetFrames() can return null even though it's not documented as such.
+                // At least one case here is if the exception's stack trace itself is null.
+                if (frames != null)
+                {
+                    foreach (var frame in frames)
+                    {
+                        var method = frame?.GetMethod();
+                        var methodName = method?.Name;
+                        if (methodName == null)
+                            continue;
+
+                        var declaringTypeName = method?.DeclaringType?.FullName;
+                        if (declaringTypeName == null)
+                            continue;
+
+                        if (!declaringTypeName.StartsWith(CodeAnalysisNamespace))
+                            continue;
+
+                        return declaringTypeName + "." + methodName;
+                    }
+                }
+            }
+            catch
+            {
+            }
+
+            // If we couldn't get a stack, do this
+            return exception.Message;
+        }
+
+        private const string EventPrefix = "vs/ide/vbcs/";
+        private const string PropertyPrefix = "vs.ide.vbcs.";
+
+        private static string GetEventName(FunctionId id)
+            => s_eventMap.GetOrAdd(id, id => EventPrefix + GetTelemetryName(id, separator: '/'));
+
+        private static string GetPropertyName(FunctionId id, string name)
+            => s_propertyMap.GetOrAdd((id, name), key => PropertyPrefix + GetTelemetryName(id, separator: '.') + "." + key.name.ToLowerInvariant());
+
+        private static string GetTelemetryName(FunctionId id, char separator)
+                => Enum.GetName(typeof(FunctionId), id)!.Replace('_', separator).ToLowerInvariant();
+
+        private static LogType GetKind(LogMessage logMessage)
+                => logMessage is KeyValueLogMessage kvLogMessage
+                                    ? kvLogMessage.Kind
+                                    : logMessage.LogLevel switch
+                                    {
+                                        >= LogLevel.Information => LogType.UserAction,
+                                        _ => LogType.Trace
+                                    };
+
+        private static ImmutableDictionary<string, object?> GetProperties(FunctionId id, LogMessage logMessage, int? delta)
+        {
+            var builder = ImmutableDictionary.CreateBuilder<string, object?>();
+
+            if (logMessage is KeyValueLogMessage kvLogMessage)
+            {
+                foreach (var (name, val) in kvLogMessage.Properties)
+                {
+                    builder.Add(GetPropertyName(id, name), val);
+                }
+            }
+            else
+            {
+                builder.Add(GetPropertyName(id, "Message"), logMessage.GetMessage());
+            }
+
+            if (delta.HasValue)
+            {
+                builder.Add(GetPropertyName(id, "Delta"), delta.Value);
+            }
+
+            return builder.ToImmutableDictionary();
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/ServerLoggerFactory.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/ServerLoggerFactory.cs
new file mode 100644
index 0000000000000..84ea12bffbd89
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Logging/ServerLoggerFactory.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.Extensions.Logging;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Logging;
+
+[Export(typeof(ILoggerFactory))]
+[Export(typeof(ServerLoggerFactory))]
+[Shared]
+internal class ServerLoggerFactory : ILoggerFactory
+{
+    private ILoggerFactory? _loggerFactory;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ServerLoggerFactory()
+    {
+    }
+
+    public void SetFactory(ILoggerFactory loggerFactory)
+    {
+        Contract.ThrowIfTrue(_loggerFactory is not null);
+        _loggerFactory = loggerFactory;
+    }
+
+    void ILoggerFactory.AddProvider(ILoggerProvider provider)
+    {
+        Contract.ThrowIfNull(_loggerFactory);
+        _loggerFactory.AddProvider(provider);
+    }
+
+    ILogger ILoggerFactory.CreateLogger(string categoryName)
+    {
+        Contract.ThrowIfNull(_loggerFactory);
+        return _loggerFactory.CreateLogger(categoryName);
+    }
+
+    void IDisposable.Dispose()
+    {
+        _loggerFactory?.Dispose();
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj
new file mode 100644
index 0000000000000..2b1f80340c838
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Microsoft.CodeAnalysis.LanguageServer.csproj
@@ -0,0 +1,131 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net7.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+      
+        <ServerGarbageCollection>true</ServerGarbageCollection>
+        <!--
+            Build a nuget package for this project.  This is not consumed as a standard NuGet package; it just contains
+            the server executables that we need to ship inside the extension vsix.  The extension will download this and extract the
+            executables when it builds.  NuGet just happens to be a convenient way to share build artifacts.
+        -->
+        <IsPackable>true</IsPackable> 
+        <!--
+            Publish all the platform specific executables before any of the pack related targets run.
+            This is important to ensure that the content files exist on the project before nuget looks for them.
+            
+            Note that BeforeTargets="Pack" is not enough, as the determination of what to include in the package runs
+            before the actual "Pack" target runs.
+        -->
+        <BeforePack>PublishAllRids;$(BeforePack)</BeforePack>
+        <!-- Since this is not a standard nuget package and is only consumed by the extension build, we don't care if the folder structure doesn't match what nuget expects. -->
+        <NoWarn>NU5100</NoWarn>
+
+        <!-- Publishing settings -->
+        <SelfContained>false</SelfContained> 
+        <PublishDir Condition="'$(RuntimeIdentifier)' != ''">$(ArtifactsDir)/LanguageServer/$(Configuration)/$(TargetFramework)/$(RuntimeIdentifier)</PublishDir>
+        <PublishDir Condition="'$(RuntimeIdentifier)' == ''">$(ArtifactsDir)/LanguageServer/$(Configuration)/$(TargetFramework)/neutral</PublishDir>
+        <!--
+            Set the minimum runtime to a .NET 7 prerelease so that prerelease SDKs will be considered during rollForward.
+            RollForward values for roslyn are set in eng/config/runtimeconfig.template.json
+        -->
+        <RuntimeFrameworkVersion>7.0.0-preview.7.22362.8</RuntimeFrameworkVersion>
+
+        <!-- List of runtime identifiers that we want to publish an executable for -->
+        <RuntimeIdentifiers>win-x64;win-x86;win-arm64;linux-x64;linux-arm64;alpine-x64;alpine-arm64;osx-x64;osx-arm64</RuntimeIdentifiers> 
+        <!-- Publish ready to run executables when we're publishing platform specific executables. -->
+        <PublishReadyToRun Condition="'$(RuntimeIdentifier)' != '' Or '$(RestoreWithR2R)' == 'true'">true</PublishReadyToRun>
+    </PropertyGroup>
+
+    <ItemGroup Label="Project References">
+        <ProjectReference Include="..\..\..\Workspaces\Core\MSBuild\Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj" />
+        <ProjectReference Include="..\..\..\Workspaces\Remote\Core\Microsoft.CodeAnalysis.Remote.Workspaces.csproj" />
+        <ProjectReference Include="..\Protocol\Microsoft.CodeAnalysis.LanguageServer.Protocol.csproj" />
+
+        <!-- Dlls we don't directly reference but need to include to build the MEF composition -->
+        <ProjectReference Include="..\..\CSharp\Portable\Microsoft.CodeAnalysis.CSharp.Features.csproj" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.Build" Version="$(RefOnlyMicrosoftBuildVersion)" ExcludeAssets="Runtime" PrivateAssets="All" />
+        <PackageReference Include="Microsoft.Build.Locator" Version="$(MicrosoftBuildLocatorVersion)" />
+        <PackageReference Include="Microsoft.Extensions.Logging" Version="$(MicrosoftExtensionsLoggingVersion)" />
+        <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="$(MicrosoftExtensionsLoggingAbstractionsVersion)" />
+        <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="$(MicrosoftExtensionsLoggingConsoleVersion)" />
+        <PackageReference Include="Microsoft.ServiceHub.Framework" Version="$(MicrosoftServiceHubFrameworkVersion)" />
+        <PackageReference Include="Microsoft.VisualStudio.Composition" Version="$(MicrosoftVisualStudioCompositionVersion)" />
+        <PackageReference Include="Microsoft.VisualStudio.LanguageServer.Protocol" Version="$(MicrosoftVisualStudioLanguageServerProtocolVersion)" />
+        <PackageReference Include="Microsoft.AspNetCore.Razor.ExternalAccess.RoslynWorkspace" Version="$(MicrosoftAspNetCoreRazorExternalAccessRoslynWorkspaceVersion)" />
+        <PackageReference Include="StreamJsonRpc" Version="$(StreamJsonRpcVersion)" />
+        <PackageReference Include="System.CommandLine" Version="$(SystemCommandLineVersion)" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.UnitTests" />
+
+        <!--
+          Only allow C# DevKit to use types from Microsoft.CodeAnalysis.Contracts namespace. The contracts should not introduce breaking changes between versions,
+          because the versions of C# DevKit and C# Extension might not be aligned.
+        -->
+        <RestrictedInternalsVisibleTo Include="Microsoft.VisualStudio.LanguageServices.DevKit" Namespace="Microsoft.CodeAnalysis.Contracts" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <RoslynVersionFile Include="$(OutDir)\RoslynVersion.txt" />
+        <FileWrites Include="@(RoslynVersionFile)" />
+    </ItemGroup>
+
+    <Target Name="WriteRoslynVersion" AfterTargets="Build">
+        <WriteLinesToFile File="@(RoslynVersionFile)" Lines="$(MicrosoftCodeAnalysisVersion)" Overwrite="true" />
+    </Target>
+
+    <Target Name="PublishRoslynVersion" AfterTargets="Publish">
+        <Copy SourceFiles="@(RoslynVersionFile)" DestinationFolder="$(PublishDir)" />
+    </Target>
+
+    <!--
+        This target runs publishing for all of the RIDs that we've specified in the project to create platform specific
+        executables.  It then updates the Content in the project to include the executables we built in the NuGet package.
+
+        This is also partially a workaround for lack of support for publishing multiple RIDs directly in a csproj.  See https://github.com/dotnet/sdk/issues/9363
+
+        Notes:
+          1.  We depend on the "Publish" target to ensure that we include the platform neutral versions of the project.
+          2.  It is important that the Content is added dynamically in this target.  If we had it in a normal ItemGroup in the
+              project, when msbuild evaluation runs the published server artifacts won't exist and so the content will be empty.
+    -->
+    <Target Name="PublishAllRids" DependsOnTargets="Publish">
+        <Message Text="Publishing builds for each runtime identifier..." Importance="High" />
+
+        <ItemGroup>
+            <!-- Transform RuntimeIdentifiers property to item -->
+            <RuntimeIdentifierForPublish Include="$(RuntimeIdentifiers)" />
+
+            <!-- Transform RuntimeIdentifierForPublish items to project items to pass to MSBuild task -->
+            <ProjectToPublish Include="@(RuntimeIdentifierForPublish->'$(MSBuildProjectFullPath)')">
+                <AdditionalProperties>RuntimeIdentifier=%(RuntimeIdentifierForPublish.Identity)</AdditionalProperties>
+            </ProjectToPublish>
+        </ItemGroup>
+
+        <!--
+            We have to run restore first with the PublishReadyToRun flag set to true to ensure that the correct crossgen packages get restored.
+            See https://github.com/dotnet/sdk/issues/20701
+        -->
+        <MSBuild Projects="$(MSBuildProjectFullPath)" Targets="Restore" Properties="RestoreWithR2R=true" />
+
+        <MSBuild Projects="@(ProjectToPublish)" Targets="Publish" BuildInParallel="true" />
+
+        <!-- We have to add the content files in a target (and not just defined in a normal item group) since they are produced by the prior step and won't exist at evaluation time. -->
+        <Message Text="Adding content files for language server artifacts..." Importance="High" />
+        <ItemGroup>
+            <Content Include="$(ArtifactsDir)/LanguageServer/$(Configuration)/$(TargetFramework)/**/*.*">
+                <Pack>true</Pack>
+                <PackagePath>content\LanguageServer</PackagePath>
+                <CopyToOutput>false</CopyToOutput>
+                <BuildAction>None</BuildAction>
+            </Content>
+        </ItemGroup>
+    </Target>
+</Project>
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Program.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Program.cs
new file mode 100644
index 0000000000000..cb542d92f6c5c
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Program.cs
@@ -0,0 +1,204 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using System.CommandLine;
+using System.CommandLine.Builder;
+using System.CommandLine.Parsing;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using Microsoft.CodeAnalysis.Contracts.Telemetry;
+using Microsoft.CodeAnalysis.LanguageServer;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services.HelloWorld;
+using Microsoft.CodeAnalysis.LanguageServer.HostWorkspace;
+using Microsoft.CodeAnalysis.LanguageServer.LanguageServer;
+using Microsoft.CodeAnalysis.LanguageServer.Logging;
+using Microsoft.CodeAnalysis.LanguageServer.StarredSuggestions;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Console;
+
+// Setting the title can fail if the process is run without a window, such
+// as when launched detached from nodejs
+try
+{
+    Console.Title = "Microsoft.CodeAnalysis.LanguageServer";
+}
+catch (IOException)
+{
+}
+
+WindowsErrorReporting.SetErrorModeOnWindows();
+
+var parser = CreateCommandLineParser();
+return await parser.InvokeAsync(args);
+
+static async Task RunAsync(
+    bool launchDebugger,
+    LogLevel minimumLogLevel,
+    string? starredCompletionPath,
+    string? telemetryLevel,
+    string? sessionId,
+    string? sharedDependenciesPath,
+    IEnumerable<string> extensionAssemblyPaths,
+    CancellationToken cancellationToken)
+{
+    // Before we initialize the LSP server we can't send LSP log messages.
+    // Create a console logger as a fallback to use before the LSP server starts.
+    using var loggerFactory = LoggerFactory.Create(builder =>
+    {
+        builder.SetMinimumLevel(minimumLogLevel);
+        builder.AddProvider(new LspLogMessageLoggerProvider(fallbackLoggerFactory:
+            // Add a console logger as a fallback for when the LSP server has not finished initializing.
+            LoggerFactory.Create(builder =>
+            {
+                builder.SetMinimumLevel(minimumLogLevel);
+                builder.AddConsole(options => options.LogToStandardErrorThreshold = LogLevel.Trace);
+                // The console logger outputs control characters on unix for colors which don't render correctly in VSCode.
+                builder.AddSimpleConsole(formatterOptions => formatterOptions.ColorBehavior = LoggerColorBehavior.Disabled);
+            })
+        ));
+    });
+
+    if (launchDebugger)
+    {
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+        {
+            // Debugger.Launch() only works on Windows.
+            _ = Debugger.Launch();
+        }
+        else
+        {
+            var logger = loggerFactory.CreateLogger<Program>();
+            var timeout = TimeSpan.FromMinutes(1);
+            logger.LogCritical($"Server started with process ID {Environment.ProcessId}");
+            logger.LogCritical($"Waiting {timeout:g} for a debugger to attach");
+            using var timeoutSource = new CancellationTokenSource(timeout);
+            while (!Debugger.IsAttached && !timeoutSource.Token.IsCancellationRequested)
+            {
+                await Task.Delay(100, CancellationToken.None);
+            }
+        }
+    }
+
+    using var exportProvider = await ExportProviderBuilder.CreateExportProviderAsync(extensionAssemblyPaths, sharedDependenciesPath, loggerFactory);
+
+    // Initialize the fault handler if it's available
+    var telemetryReporter = exportProvider.GetExports<ITelemetryReporter>().SingleOrDefault()?.Value;
+    RoslynLogger.Initialize(telemetryReporter, telemetryLevel, sessionId);
+
+    // Create the workspace first, since right now the language server will assume there's at least one Workspace
+    var workspaceFactory = exportProvider.GetExportedValue<LanguageServerWorkspaceFactory>();
+
+    var analyzerPaths = new DirectoryInfo(AppContext.BaseDirectory).GetFiles("*.dll")
+        .Where(f => f.Name.StartsWith("Microsoft.CodeAnalysis.", StringComparison.Ordinal) && !f.Name.Contains("LanguageServer", StringComparison.Ordinal))
+        .Select(f => f.FullName)
+        .ToImmutableArray();
+
+    await workspaceFactory.InitializeSolutionLevelAnalyzersAsync(analyzerPaths);
+
+    var serviceBrokerFactory = exportProvider.GetExportedValue<ServiceBrokerFactory>();
+    StarredCompletionAssemblyHelper.InitializeInstance(starredCompletionPath, loggerFactory, serviceBrokerFactory);
+
+    // TODO: Remove, the path should match exactly. Workaround for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1830914.
+    Microsoft.CodeAnalysis.EditAndContinue.EditAndContinueMethodDebugInfoReader.IgnoreCaseWhenComparingDocumentNames = Path.DirectorySeparatorChar == '\\';
+
+    var server = new LanguageServerHost(Console.OpenStandardInput(), Console.OpenStandardOutput(), exportProvider, loggerFactory.CreateLogger(nameof(LanguageServerHost)));
+    server.Start();
+
+    try
+    {
+        await server.WaitForExitAsync();
+    }
+    finally
+    {
+        // After the LSP server shutdown, report session wide telemetry
+        RoslynLogger.ShutdownAndReportSessionTelemetry();
+
+        // Server has exited, cancel our service broker service
+        await serviceBrokerFactory.ShutdownAndWaitForCompletionAsync();
+    }
+}
+
+static Parser CreateCommandLineParser()
+{
+    var debugOption = new Option<bool>("--debug", getDefaultValue: () => false)
+    {
+        Description = "Flag indicating if the debugger should be launched on startup.",
+        IsRequired = false,
+    };
+    var brokeredServicePipeNameOption = new Option<string?>("--brokeredServicePipeName")
+    {
+        Description = "The name of the pipe used to connect to a remote process (if one exists).",
+        IsRequired = false,
+    };
+
+    var logLevelOption = new Option<LogLevel>("--logLevel", description: "The minimum log verbosity.", parseArgument: result =>
+    {
+        var value = result.Tokens.Single().Value;
+        return !Enum.TryParse<LogLevel>(value, out var logLevel)
+            ? throw new InvalidOperationException($"Unexpected logLevel argument {result}")
+            : logLevel;
+    })
+    {
+        IsRequired = true,
+    };
+    var starredCompletionsPathOption = new Option<string?>("--starredCompletionComponentPath")
+    {
+        Description = "The location of the starred completion component (if one exists).",
+        IsRequired = false,
+    };
+
+    var telemetryLevelOption = new Option<string?>("--telemetryLevel")
+    {
+        Description = "Telemetry level, Defaults to 'off'. Example values: 'all', 'crash', 'error', or 'off'.",
+        IsRequired = false,
+    };
+
+    var sessionIdOption = new Option<string?>("--sessionId")
+    {
+        Description = "Session Id to use for telemetry",
+        IsRequired = false
+    };
+
+    var sharedDependenciesOption = new Option<string?>("--sharedDependencies")
+    {
+        Description = "Full path of the directory containing shared assemblies (optional).",
+        IsRequired = false
+    };
+
+    var extensionAssemblyPathsOption = new Option<string[]?>(new string[] { "--extension", "--extensions" }) // TODO: remove plural form
+    {
+        Description = "Full paths of extension assemblies to load (optional).",
+        IsRequired = false
+    };
+
+    var rootCommand = new RootCommand()
+    {
+        debugOption,
+        brokeredServicePipeNameOption,
+        logLevelOption,
+        starredCompletionsPathOption,
+        telemetryLevelOption,
+        sessionIdOption,
+        sharedDependenciesOption,
+        extensionAssemblyPathsOption,
+    };
+    rootCommand.SetHandler(context =>
+    {
+        var cancellationToken = context.GetCancellationToken();
+        var launchDebugger = context.ParseResult.GetValueForOption(debugOption);
+        var logLevel = context.ParseResult.GetValueForOption(logLevelOption);
+        var starredCompletionsPath = context.ParseResult.GetValueForOption(starredCompletionsPathOption);
+        var telemetryLevel = context.ParseResult.GetValueForOption(telemetryLevelOption);
+        var sessionId = context.ParseResult.GetValueForOption(sessionIdOption);
+        var sharedDependenciesPath = context.ParseResult.GetValueForOption(sharedDependenciesOption);
+        var extensionAssemblyPaths = context.ParseResult.GetValueForOption(extensionAssemblyPathsOption) ?? Array.Empty<string>();
+
+        return RunAsync(launchDebugger, logLevel, starredCompletionsPath, telemetryLevel, sessionId, sharedDependenciesPath, extensionAssemblyPaths, cancellationToken);
+    });
+
+    return new CommandLineBuilder(rootCommand).UseDefaults().Build();
+}
+
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/AssemblyLoadContextWrapper.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/AssemblyLoadContextWrapper.cs
new file mode 100644
index 0000000000000..d61012c2aafb7
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/AssemblyLoadContextWrapper.cs
@@ -0,0 +1,173 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.Loader;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Services
+{
+    internal sealed class AssemblyLoadContextWrapper : IDisposable
+    {
+        private static readonly ConcurrentDictionary<AssemblyName, Assembly?> s_loadedSharedAssemblies = new(AssemblyNameComparer.Default);
+
+        private AssemblyLoadContext? _assemblyLoadContext;
+        private readonly ImmutableDictionary<string, Assembly> _loadedAssemblies;
+        private readonly ILogger? _logger;
+
+        private AssemblyLoadContextWrapper(AssemblyLoadContext assemblyLoadContext, ImmutableDictionary<string, Assembly> loadedFiles, ILogger? logger)
+        {
+            _assemblyLoadContext = assemblyLoadContext;
+            _loadedAssemblies = loadedFiles;
+            _logger = logger;
+        }
+
+        public static bool TryLoadExtension(string assemblyFilePath, string? sharedDependenciesPath, ILogger? logger, [NotNullWhen(true)] out Assembly? assembly)
+        {
+            var dir = Path.GetDirectoryName(assemblyFilePath);
+            var fileName = Path.GetFileName(assemblyFilePath);
+            var fileNameNoExt = Path.GetFileNameWithoutExtension(assemblyFilePath);
+
+            Contract.ThrowIfNull(dir);
+            Contract.ThrowIfNull(fileName);
+            Contract.ThrowIfNull(fileNameNoExt);
+
+            var loadContext = TryCreate(fileNameNoExt, dir, sharedDependenciesPath, logger);
+            if (loadContext != null)
+            {
+                assembly = loadContext.GetAssembly(fileName);
+                return true;
+            }
+
+            assembly = null;
+            return false;
+        }
+
+        public static AssemblyLoadContextWrapper? TryCreate(string name, string assembliesDirectoryPath, string? sharedDependenciesPath, ILogger? logger)
+        {
+            try
+            {
+                var loadContext = CreateLoadContext(name, sharedDependenciesPath);
+                var directory = new DirectoryInfo(assembliesDirectoryPath);
+                var builder = new Dictionary<string, Assembly>();
+                foreach (var file in directory.GetFiles("*.dll"))
+                {
+                    builder.Add(file.Name, loadContext.LoadFromAssemblyPath(file.FullName));
+                }
+
+                return new AssemblyLoadContextWrapper(loadContext, builder.ToImmutableDictionary(), logger);
+            }
+            catch (Exception ex)
+            {
+                logger?.LogError(ex, "Failed to initialize AssemblyLoadContext {name}", name);
+                return null;
+            }
+        }
+
+        private static AssemblyLoadContext CreateLoadContext(string name, string? sharedDependenciesPath)
+        {
+            var loadContext = new AssemblyLoadContext(name);
+
+            if (sharedDependenciesPath != null)
+            {
+                loadContext.Resolving += (_, assemblyName) =>
+                {
+                    if (assemblyName.Name is null)
+                    {
+                        return null;
+                    }
+
+                    if (s_loadedSharedAssemblies.TryGetValue(assemblyName, out var loadedAssembly))
+                    {
+                        return loadedAssembly;
+                    }
+
+                    var candidatePath = assemblyName.CultureName is not null
+                        ? Path.Combine(sharedDependenciesPath, assemblyName.CultureName, $"{assemblyName.Name}.dll")
+                        : Path.Combine(sharedDependenciesPath, $"{assemblyName.Name}.dll");
+
+                    if (File.Exists(candidatePath))
+                    {
+                        loadedAssembly = loadContext.LoadFromAssemblyPath(candidatePath);
+                    }
+
+                    s_loadedSharedAssemblies.TryAdd(assemblyName, loadedAssembly);
+
+                    return s_loadedSharedAssemblies[assemblyName];
+                };
+            }
+
+            return loadContext;
+        }
+
+        public Assembly GetAssembly(string name) => _loadedAssemblies[name];
+
+        public MethodInfo? TryGetMethodInfo(string assemblyName, string className, string methodName)
+        {
+            try
+            {
+                return GetMethodInfo(assemblyName, className, methodName);
+            }
+            catch (Exception ex)
+            {
+                _logger?.LogError(ex, "Failed to get method information from {assembly} for {class}.{method}", assemblyName, className, methodName);
+                return null;
+            }
+        }
+
+        public MethodInfo GetMethodInfo(string assemblyName, string className, string methodName)
+        {
+            var assembly = GetAssembly(assemblyName);
+            var completionHelperType = assembly.GetType(className);
+            if (completionHelperType == null)
+            {
+                throw new ArgumentException($"{assembly.FullName} assembly did not contain {className} class");
+            }
+            var createCompletionProviderMethodInto = completionHelperType?.GetMethod(methodName);
+            if (createCompletionProviderMethodInto == null)
+            {
+                throw new ArgumentException($"{className} from {assembly.FullName} assembly did not contain {methodName} method");
+            }
+            return createCompletionProviderMethodInto;
+        }
+
+        public void Dispose()
+        {
+            _assemblyLoadContext?.Unload();
+            _assemblyLoadContext = null;
+        }
+
+        private sealed class AssemblyNameComparer : IEqualityComparer<AssemblyName>
+        {
+            public static readonly AssemblyNameComparer Default = new();
+
+            public bool Equals(AssemblyName? x, AssemblyName? y)
+            {
+                if (ReferenceEquals(x, y))
+                    return true;
+
+                if (x == null || y == null)
+                    return false;
+
+                return string.Equals(x.Name, y.Name, StringComparison.OrdinalIgnoreCase)
+                    && string.Equals(x.CultureName, y.CultureName, StringComparison.OrdinalIgnoreCase);
+            }
+
+            public int GetHashCode(AssemblyName obj)
+                => HashCode.Combine(
+                    StringComparer.OrdinalIgnoreCase.GetHashCode(obj.Name ?? string.Empty),
+                    StringComparer.OrdinalIgnoreCase.GetHashCode(obj.CultureName ?? string.Empty));
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/StarredCompletions/StarredCompletionProvider.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/StarredCompletions/StarredCompletionProvider.cs
new file mode 100644
index 0000000000000..2fceb3ddfa578
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/StarredCompletions/StarredCompletionProvider.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Composition;
+using System.Threading;
+using Microsoft.CodeAnalysis.Completion;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
+using Microsoft.CodeAnalysis.LanguageService;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.StarredSuggestions;
+
+[ExportCompletionProvider("CSharpStarredCompletionProvider", LanguageNames.CSharp), Shared]
+internal class StarredCompletionProvider : CompletionProvider
+{
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public StarredCompletionProvider() { }
+
+    public override async Task ProvideCompletionsAsync(CompletionContext context)
+    {
+        var provider = await StarredCompletionAssemblyHelper.GetCompletionProviderAsync(context.CancellationToken);
+        if (provider == null)
+        {
+            return; //no-op if provider cannot be retrieved from assembly
+        }
+        await provider.ProvideCompletionsAsync(context);
+    }
+
+    public override async Task<CompletionChange> GetChangeAsync(Document document, CompletionItem item, char? commitKey = null, CancellationToken cancellationToken = default)
+    {
+        var provider = await StarredCompletionAssemblyHelper.GetCompletionProviderAsync(cancellationToken);
+        Contract.ThrowIfNull(provider, "ProvideCompletionsAsync must have completed successfully for GetChangeAsync to be called");
+        return await provider.GetChangeAsync(document, item, commitKey, cancellationToken).ConfigureAwait(false);
+    }
+
+    internal override async Task<CompletionDescription?> GetDescriptionAsync(Document document, CompletionItem item, CompletionOptions options, SymbolDescriptionOptions displayOptions, CancellationToken cancellationToken)
+    {
+        var provider = await StarredCompletionAssemblyHelper.GetCompletionProviderAsync(cancellationToken);
+        Contract.ThrowIfNull(provider, "ProvideCompletionsAsync must have completed successfully for GetDescriptionAsync to be called");
+        return await provider.GetDescriptionAsync(document, item, options, displayOptions, cancellationToken);
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/StarredCompletions/StarredCompletionsAssemblyHelper.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/StarredCompletions/StarredCompletionsAssemblyHelper.cs
new file mode 100644
index 0000000000000..03a581634f047
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/Services/StarredCompletions/StarredCompletionsAssemblyHelper.cs
@@ -0,0 +1,122 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+using System.Runtime.Loader;
+using Microsoft.CodeAnalysis.Completion;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices;
+using Microsoft.CodeAnalysis.LanguageServer.BrokeredServices.Services;
+using Microsoft.CodeAnalysis.LanguageServer.Services;
+using Microsoft.Extensions.Logging;
+using Microsoft.ServiceHub.Framework;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.StarredSuggestions;
+internal static class StarredCompletionAssemblyHelper
+{
+    private const string CompletionsDllName = "Microsoft.VisualStudio.IntelliCode.CSharp.dll";
+    private const string ALCName = "IntelliCode-ALC";
+    private const string CompletionHelperClassFullName = "PythiaCSDevKit.CSDevKitCompletionHelper";
+    private const string CreateCompletionProviderMethodName = "CreateCompletionProviderAsync";
+
+    // The following fields are only set as a part of the call to InitializeInstance, which is only called once for the lifetime of the process. Thus, it is safe to assume that once
+    // set, they will never change again.
+    private static string? s_completionsAssemblyLocation;
+    private static ILogger? s_logger;
+    private static ServiceBrokerFactory? s_serviceBrokerFactory;
+
+    /// <summary>
+    /// A gate to guard the actual creation of <see cref="s_completionProvider"/>. This just prevents us from trying to create the provider more than once; once the field is set it
+    /// won't change again.
+    /// </summary>
+    private static readonly SemaphoreSlim s_gate = new SemaphoreSlim(initialCount: 1);
+    private static bool s_previousCreationFailed = false;
+    private static CompletionProvider? s_completionProvider;
+
+    /// <summary>
+    /// Initializes CompletionsAssemblyHelper singleton
+    /// </summary>
+    /// <param name="completionsAssemblyLocation">Location of dll for starred completion</param>
+    /// <param name="loggerFactory">Factory for creating new logger</param>
+    /// <param name="serviceBrokerFactory">Service broker with access to necessary remote services</param>
+    internal static void InitializeInstance(string? completionsAssemblyLocation, ILoggerFactory loggerFactory, ServiceBrokerFactory serviceBrokerFactory)
+    {
+        // No location provided means it wasn't passed through from C# Dev Kit, so we don't need to initialize anything further
+        if (string.IsNullOrEmpty(completionsAssemblyLocation))
+        {
+            return;
+        }
+
+        // C# Dev Kit must be installed, so we should be able to provide this; however we may not yet have a connection to the Dev Kit service broker, so we need to defer the actual creation
+        // until that point.
+        s_completionsAssemblyLocation = completionsAssemblyLocation;
+        s_logger = loggerFactory.CreateLogger(typeof(StarredCompletionAssemblyHelper));
+        s_serviceBrokerFactory = serviceBrokerFactory;
+    }
+
+    internal static async Task<CompletionProvider?> GetCompletionProviderAsync(CancellationToken cancellationToken)
+    {
+        // Short cut: if we already have a provider, return it
+        if (s_completionProvider is CompletionProvider completionProvider)
+            return completionProvider;
+
+        // If we don't have one because we previously failed to create one, then just return failure
+        if (s_previousCreationFailed)
+            return null;
+
+        // If we were never initialized with any information from Dev Kit, we can't create one
+        if (s_completionsAssemblyLocation is null || s_logger is null || s_serviceBrokerFactory is null)
+            return null;
+
+        // If we don't have a connection to a service broker yet, we also can't create one
+        var serviceBroker = s_serviceBrokerFactory.TryGetFullAccessServiceBroker();
+        if (serviceBroker is null)
+            return null;
+
+        // At this point, we have everything we need to go and create the provider, so let's do it
+        using (await s_gate.DisposableWaitAsync(cancellationToken))
+        {
+            // Re-check this inside the lock, since we could have had a success between the earlier check and now
+            if (s_completionProvider is CompletionProvider completionProviderInsideLock)
+                return completionProviderInsideLock;
+
+            // Re-check this inside the lock, since we could have had a failure between the earlier check and now
+            if (s_previousCreationFailed)
+                return null;
+
+            try
+            {
+                var alc = AssemblyLoadContextWrapper.TryCreate(ALCName, s_completionsAssemblyLocation, sharedDependenciesPath: null, s_logger);
+                if (alc is null)
+                {
+                    s_previousCreationFailed = true;
+                    return null;
+                }
+
+                var createCompletionProviderMethodInfo = alc.GetMethodInfo(CompletionsDllName, CompletionHelperClassFullName, CreateCompletionProviderMethodName);
+
+                s_completionProvider = await CreateCompletionProviderAsync(createCompletionProviderMethodInfo, serviceBroker, s_completionsAssemblyLocation, s_logger);
+                return s_completionProvider;
+            }
+            catch (Exception ex)
+            {
+                s_previousCreationFailed = true;
+                s_logger.LogError(ex, "Unable to create the StarredCompletionProvider.");
+                throw;
+            }
+        }
+    }
+
+    private static async Task<CompletionProvider> CreateCompletionProviderAsync(MethodInfo createCompletionProviderMethodInfo, IServiceBroker serviceBroker, string modelBasePath, ILogger logger)
+    {
+        var completionProviderObj = createCompletionProviderMethodInfo.Invoke(null, new object[4] { serviceBroker, BrokeredServices.Services.Descriptors.RemoteModelService, modelBasePath, logger });
+        if (completionProviderObj == null)
+        {
+            throw new NotSupportedException($"{createCompletionProviderMethodInfo.Name} method could not be invoked");
+        }
+        var completionProvider = (Task<CompletionProvider>)completionProviderObj;
+        return await completionProvider;
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/WindowsErrorReporting.cs b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/WindowsErrorReporting.cs
new file mode 100644
index 0000000000000..f11f0b62d8cb4
--- /dev/null
+++ b/src/Features/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/WindowsErrorReporting.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+internal class WindowsErrorReporting
+{
+    internal static void SetErrorModeOnWindows()
+    {
+        if (!OperatingSystem.IsWindows())
+        {
+            return;
+        }
+
+        SetErrorMode(ErrorModes.SYSTEM_DEFAULT);
+
+        // There have been reports that SetErrorMode wasn't working correctly, so double
+        // check in Debug builds that it actually set
+        Debug.Assert(GetErrorMode() == (uint)ErrorModes.SYSTEM_DEFAULT);
+    }
+
+    [DllImport("kernel32.dll")]
+    private static extern ErrorModes SetErrorMode(ErrorModes uMode);
+
+    [DllImport("kernel32.dll")]
+    private static extern uint GetErrorMode();
+
+    [Flags]
+    private enum ErrorModes : uint
+    {
+        SYSTEM_DEFAULT = 0x0,
+        SEM_FAILCRITICALERRORS = 0x0001,
+        SEM_NOGPFAULTERRORBOX = 0x0002,
+        SEM_NOALIGNMENTFAULTEXCEPT = 0x0004,
+        SEM_NOOPENFILEERRORBOX = 0x8000
+    }
+}
diff --git a/src/Features/LanguageServer/Microsoft.CommonLanguageServerProtocol.Framework/QueueItem.cs b/src/Features/LanguageServer/Microsoft.CommonLanguageServerProtocol.Framework/QueueItem.cs
index 8dcb9e1f04a41..6874d32e77673 100644
--- a/src/Features/LanguageServer/Microsoft.CommonLanguageServerProtocol.Framework/QueueItem.cs
+++ b/src/Features/LanguageServer/Microsoft.CommonLanguageServerProtocol.Framework/QueueItem.cs
@@ -147,10 +147,7 @@ public async Task StartRequestAsync(TRequestContext? context, CancellationToken
             }
             else
             {
-                throw new NotImplementedException(
-                    $"Unrecognized {nameof(IMethodHandler)} implementation {_handler.GetType()}. " +
-                    $"TRequest is {typeof(TRequest)}. " +
-                    $"TResponse is {typeof(TResponse)}.");
+                throw new NotImplementedException($"Unrecognized {nameof(IMethodHandler)} implementation {_handler.GetType()}. ");
             }
         }
         catch (OperationCanceledException ex)
diff --git a/src/Features/LanguageServer/Protocol/DefaultCapabilitiesProvider.cs b/src/Features/LanguageServer/Protocol/DefaultCapabilitiesProvider.cs
index 803821542f104..66bc7aeb5d53e 100644
--- a/src/Features/LanguageServer/Protocol/DefaultCapabilitiesProvider.cs
+++ b/src/Features/LanguageServer/Protocol/DefaultCapabilitiesProvider.cs
@@ -11,6 +11,7 @@
 using Microsoft.CodeAnalysis.Completion;
 using Microsoft.CodeAnalysis.Completion.Providers;
 using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.Completion;
 using Microsoft.CodeAnalysis.LanguageServer.Handler.SemanticTokens;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 
@@ -45,13 +46,14 @@ public void Initialize()
         public ServerCapabilities GetCapabilities(ClientCapabilities clientCapabilities)
         {
             var supportsVsExtensions = clientCapabilities.HasVisualStudioLspCapability();
-            var capabilities = supportsVsExtensions ? GetVSServerCapabilities() : new ServerCapabilities();
+            var capabilities = supportsVsExtensions ? GetVSServerCapabilities() : new VSInternalServerCapabilities();
 
-            var commitCharacters = CompletionRules.Default.DefaultCommitCharacters.Select(c => c.ToString()).ToArray();
+            var commitCharacters = AbstractLspCompletionResultCreationService.DefaultCommitCharactersArray;
             var triggerCharacters = _completionProviders.SelectMany(
                 lz => CommonCompletionUtilities.GetTriggerCharacters(lz.Value)).Distinct().Select(c => c.ToString()).ToArray();
 
             capabilities.DefinitionProvider = true;
+            capabilities.DocumentHighlightProvider = true;
             capabilities.RenameProvider = true;
             capabilities.ImplementationProvider = true;
             capabilities.CodeActionProvider = new CodeActionOptions { CodeActionKinds = new[] { CodeActionKind.QuickFix, CodeActionKind.Refactor }, ResolveProvider = true };
@@ -93,8 +95,8 @@ public ServerCapabilities GetCapabilities(ClientCapabilities clientCapabilities)
                 Range = true,
                 Legend = new SemanticTokensLegend
                 {
-                    TokenTypes = SemanticTokensSchema.GetSchema(clientCapabilities).AllTokenTypes.ToArray(),
-                    TokenModifiers = new string[] { SemanticTokenModifiers.Static }
+                    TokenTypes = SemanticTokensSchema.GetSchema(clientCapabilities.HasVisualStudioLspCapability()).AllTokenTypes.ToArray(),
+                    TokenModifiers = SemanticTokensSchema.TokenModifiers
                 }
             };
 
@@ -112,6 +114,9 @@ public ServerCapabilities GetCapabilities(ClientCapabilities clientCapabilities)
                 WorkDoneProgress = false,
             };
 
+            // Using VS server capabilities because we have our own custom client.
+            capabilities.OnAutoInsertProvider = new VSInternalDocumentOnAutoInsertOptions { TriggerCharacters = new[] { "'", "/", "\n" } };
+
             if (!supportsVsExtensions)
             {
                 capabilities.DiagnosticOptions = new DiagnosticOptions
@@ -125,11 +130,9 @@ public ServerCapabilities GetCapabilities(ClientCapabilities clientCapabilities)
             return capabilities;
         }
 
-        private static VSServerCapabilities GetVSServerCapabilities()
-            => new VSInternalServerCapabilities
+        private static VSInternalServerCapabilities GetVSServerCapabilities()
+            => new()
             {
-                OnAutoInsertProvider = new VSInternalDocumentOnAutoInsertOptions { TriggerCharacters = new[] { "'", "/", "\n" } },
-                DocumentHighlightProvider = true,
                 ProjectContextProvider = true,
                 BreakableRangeProvider = true,
 
diff --git a/src/Features/LanguageServer/Protocol/Extensions/Extensions.cs b/src/Features/LanguageServer/Protocol/Extensions/Extensions.cs
index 170bb5a2285ae..53da6d3deb3e2 100644
--- a/src/Features/LanguageServer/Protocol/Extensions/Extensions.cs
+++ b/src/Features/LanguageServer/Protocol/Extensions/Extensions.cs
@@ -77,16 +77,23 @@ public static ImmutableArray<DocumentId> GetDocumentIds(this Solution solution,
             // For now we do our best to handle as many cases as we can.
             // Tracking issue - https://github.com/dotnet/roslyn/issues/68083
 
-            var documentIds = solution.GetDocumentIdsWithFilePath(documentUri.AbsolutePath);
-            if (documentIds.Any())
-                return documentIds;
+            // If the uri is a file then use the simplified absolute or local path.
+            // In other cases (e.g. git files) use the full uri string. This ensures documents
+            // with the same local path (e.g. git://someFilePath and file://someFilePath) are differentiated.
+            if (documentUri.IsFile)
+            {
+                var fileDocumentIds = solution.GetDocumentIdsWithFilePath(documentUri.AbsolutePath);
+                if (fileDocumentIds.Any())
+                    return fileDocumentIds;
 
-            documentIds = solution.GetDocumentIdsWithFilePath(documentUri.LocalPath);
-            if (documentIds.Any())
+                fileDocumentIds = solution.GetDocumentIdsWithFilePath(documentUri.LocalPath);
+                return fileDocumentIds;
+            }
+            else
+            {
+                var documentIds = solution.GetDocumentIdsWithFilePath(documentUri.OriginalString);
                 return documentIds;
-
-            documentIds = solution.GetDocumentIdsWithFilePath(documentUri.OriginalString);
-            return documentIds;
+            }
         }
 
         public static Document? GetDocument(this Solution solution, TextDocumentIdentifier documentIdentifier)
diff --git a/src/Features/LanguageServer/Protocol/Extensions/ProtocolConversions.cs b/src/Features/LanguageServer/Protocol/Extensions/ProtocolConversions.cs
index b214ff92d3204..54eb27da30665 100644
--- a/src/Features/LanguageServer/Protocol/Extensions/ProtocolConversions.cs
+++ b/src/Features/LanguageServer/Protocol/Extensions/ProtocolConversions.cs
@@ -151,6 +151,12 @@ static async Task<char> GetInsertionCharacterAsync(Document document, int positi
             }
         }
 
+        // If we have a file:///xyz URI, we'll store the actual file path string in the document file path.
+        // Otherwise we have a URI that doesn't point to an actual file. In such a scenario, we'll store the full URI string (including schema).
+        // This will allow correct round-tripping of the URI for features that need it until we support URI as a first class document concept.
+        // Tracking issue - https://github.com/dotnet/roslyn/issues/68083
+        public static string GetDocumentFilePathFromUri(Uri uri) => uri.IsFile ? uri.LocalPath : uri.OriginalString;
+
         public static Uri GetUriFromFilePath(string filePath)
         {
             if (filePath is null)
@@ -193,7 +199,6 @@ public static LSP.VersionedTextDocumentIdentifier DocumentToVersionedTextDocumen
 
         public static LinePosition PositionToLinePosition(LSP.Position position)
             => new LinePosition(position.Line, position.Character);
-
         public static LinePositionSpan RangeToLinePositionSpan(LSP.Range range)
             => new(PositionToLinePosition(range.Start), PositionToLinePosition(range.End));
 
diff --git a/src/Features/LanguageServer/Protocol/ExternalAccess/VSCode/API/VSCodeTelemetryLogger.cs b/src/Features/LanguageServer/Protocol/ExternalAccess/VSCode/API/VSCodeTelemetryLogger.cs
deleted file mode 100644
index 4d7a0cb5ff504..0000000000000
--- a/src/Features/LanguageServer/Protocol/ExternalAccess/VSCode/API/VSCodeTelemetryLogger.cs
+++ /dev/null
@@ -1,53 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System.Collections.Generic;
-using System.Threading;
-using Microsoft.CodeAnalysis.Internal.Log;
-
-namespace Microsoft.CodeAnalysis.LanguageServer.ExternalAccess.VSCode.API;
-
-/// <summary>
-/// Allows VSCode to implement a telemetry logger for <see cref="ILogger"/> events.
-/// </summary>
-internal abstract class VSCodeTelemetryLogger : ILogger
-{
-    bool ILogger.IsEnabled(FunctionId functionId)
-    {
-        return IsEnabled(functionId.Convert());
-    }
-
-    void ILogger.Log(FunctionId functionId, LogMessage logMessage)
-    {
-        Log(functionId.Convert(), GetProperties(logMessage), CancellationToken.None);
-    }
-
-    void ILogger.LogBlockStart(FunctionId functionId, LogMessage logMessage, int uniquePairId, CancellationToken cancellationToken)
-    {
-        LogBlockStart(functionId.Convert(), GetProperties(logMessage), cancellationToken);
-    }
-
-    void ILogger.LogBlockEnd(FunctionId functionId, LogMessage logMessage, int uniquePairId, int delta, CancellationToken cancellationToken)
-    {
-        LogBlockEnd(functionId.Convert(), GetProperties(logMessage), cancellationToken);
-    }
-
-    public void Register()
-    {
-        Logger.SetLogger(this);
-    }
-
-    public abstract bool IsEnabled(string functionId);
-
-    public abstract void Log(string functionId, IEnumerable<KeyValuePair<string, object?>>? properties, CancellationToken cancellationToken);
-
-    public abstract void LogBlockStart(string functionId, IEnumerable<KeyValuePair<string, object?>>? properties, CancellationToken cancellationToken);
-
-    public abstract void LogBlockEnd(string functionId, IEnumerable<KeyValuePair<string, object?>>? properties, CancellationToken cancellationToken);
-
-    private static IEnumerable<KeyValuePair<string, object?>>? GetProperties(LogMessage logMessage)
-    {
-        return logMessage is KeyValueLogMessage kvMessage ? kvMessage.Properties : null;
-    }
-}
diff --git a/src/Features/LanguageServer/Protocol/Features/CodeFixes/CodeFixService.cs b/src/Features/LanguageServer/Protocol/Features/CodeFixes/CodeFixService.cs
index 5b607594d103b..a85c939575d78 100644
--- a/src/Features/LanguageServer/Protocol/Features/CodeFixes/CodeFixService.cs
+++ b/src/Features/LanguageServer/Protocol/Features/CodeFixes/CodeFixService.cs
@@ -27,6 +27,7 @@
 using Microsoft.CodeAnalysis.Shared.Utilities;
 using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.CodeAnalysis.Text;
+using Microsoft.VisualStudio.Threading;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CodeFixes
@@ -99,9 +100,17 @@ public CodeFixService(
         public async Task<FirstFixResult> GetMostSevereFixAsync(
             TextDocument document, TextSpan range, ICodeActionRequestPriorityProvider priorityProvider, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken)
         {
-            var (allDiagnostics, upToDate) = await _diagnosticService.TryGetDiagnosticsForSpanAsync(
-                document, range, GetShouldIncludeDiagnosticPredicate(document, priorityProvider),
-                includeSuppressedDiagnostics: false, priorityProvider, DiagnosticKind.All, isExplicit: false, cancellationToken).ConfigureAwait(false);
+            using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.CodeFix_Summary, $"Pri{(int)priorityProvider.Priority}.{nameof(GetMostSevereFixAsync)}");
+
+            ImmutableArray<DiagnosticData> allDiagnostics;
+            bool upToDate;
+
+            using (TelemetryLogging.LogBlockTimeAggregated(FunctionId.CodeFix_Summary, $"Pri{(int)priorityProvider.Priority}.{nameof(GetMostSevereFixAsync)}.{nameof(_diagnosticService.GetDiagnosticsForSpanAsync)}"))
+            {
+                (allDiagnostics, upToDate) = await _diagnosticService.TryGetDiagnosticsForSpanAsync(
+                    document, range, GetShouldIncludeDiagnosticPredicate(document, priorityProvider),
+                    includeSuppressedDiagnostics: false, priorityProvider, DiagnosticKind.All, isExplicit: false, cancellationToken).ConfigureAwait(false);
+            }
 
             var buildOnlyDiagnosticsService = document.Project.Solution.Services.GetRequiredService<IBuildOnlyDiagnosticsService>();
             allDiagnostics.AddRange(buildOnlyDiagnosticsService.GetBuildOnlyDiagnostics(document.Id));
@@ -162,6 +171,8 @@ public async IAsyncEnumerable<CodeFixCollection> StreamFixesAsync(
             Func<string, IDisposable?> addOperationScope,
             [EnumeratorCancellation] CancellationToken cancellationToken)
         {
+            using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.CodeFix_Summary, $"Pri{(int)priorityProvider.Priority}");
+
             // We only need to compute suppression/configuration fixes when request priority is
             // 'CodeActionPriorityRequest.Lowest' or 'CodeActionPriorityRequest.None'.
             var includeSuppressionFixes = priorityProvider.Priority is CodeActionRequestPriority.Lowest or CodeActionRequestPriority.None;
@@ -176,10 +187,15 @@ public async IAsyncEnumerable<CodeFixCollection> StreamFixesAsync(
 
             // We mark requests to GetDiagnosticsForSpanAsync as 'isExplicit = true' to indicate
             // user-invoked diagnostic requests, for example, user invoked Ctrl + Dot operation for lightbulb.
-            var diagnostics = await _diagnosticService.GetDiagnosticsForSpanAsync(
-                document, range, GetShouldIncludeDiagnosticPredicate(document, priorityProvider),
-                includeCompilerDiagnostics: true, includeSuppressedDiagnostics: includeSuppressionFixes, priorityProvider,
-                addOperationScope, DiagnosticKind.All, isExplicit: true, cancellationToken).ConfigureAwait(false);
+            ImmutableArray<DiagnosticData> diagnostics;
+
+            using (TelemetryLogging.LogBlockTimeAggregated(FunctionId.CodeFix_Summary, $"Pri{(int)priorityProvider.Priority}.{nameof(_diagnosticService.GetDiagnosticsForSpanAsync)}"))
+            {
+                diagnostics = await _diagnosticService.GetDiagnosticsForSpanAsync(
+                    document, range, GetShouldIncludeDiagnosticPredicate(document, priorityProvider),
+                    includeCompilerDiagnostics: true, includeSuppressedDiagnostics: includeSuppressionFixes, priorityProvider,
+                    addOperationScope, DiagnosticKind.All, isExplicit: true, cancellationToken).ConfigureAwait(false);
+            }
 
             var buildOnlyDiagnosticsService = document.Project.Solution.Services.GetRequiredService<IBuildOnlyDiagnosticsService>();
             var buildOnlyDiagnostics = buildOnlyDiagnosticsService.GetBuildOnlyDiagnostics(document.Id);
@@ -258,9 +274,16 @@ private static SortedDictionary<TextSpan, List<DiagnosticData>> ConvertToMap(
         {
             cancellationToken.ThrowIfCancellationRequested();
 
-            var diagnostics = await _diagnosticService.GetDiagnosticsForSpanAsync(
-                document, range, diagnosticId, includeSuppressedDiagnostics: false, priorityProvider: new DefaultCodeActionRequestPriorityProvider(),
-                addOperationScope: null, DiagnosticKind.All, isExplicit: false, cancellationToken).ConfigureAwait(false);
+            using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.CodeFix_Summary, $"{nameof(GetDocumentFixAllForIdInSpanAsync)}");
+            ImmutableArray<DiagnosticData> diagnostics;
+
+            using (TelemetryLogging.LogBlockTimeAggregated(FunctionId.CodeFix_Summary, $"{nameof(GetDocumentFixAllForIdInSpanAsync)}.{nameof(_diagnosticService.GetDiagnosticsForSpanAsync)}"))
+            {
+                diagnostics = await _diagnosticService.GetDiagnosticsForSpanAsync(
+                    document, range, diagnosticId, includeSuppressedDiagnostics: false, priorityProvider: new DefaultCodeActionRequestPriorityProvider(),
+                    addOperationScope: null, DiagnosticKind.All, isExplicit: false, cancellationToken).ConfigureAwait(false);
+            }
+
             diagnostics = diagnostics.WhereAsArray(d => d.Severity.IsMoreSevereThanOrEqualTo(minimumSeverity));
             if (!diagnostics.Any())
                 return null;
@@ -482,12 +505,20 @@ private async IAsyncEnumerable<CodeFixCollection> StreamFixesAsync(
 
                     foreach (var (span, diagnostics) in fixerToRangesAndDiagnostics[fixer])
                     {
+                        // Log an individual telemetry event for slow codefix computations to
+                        // allow targeted trace notifications for further investigation. 500 ms seemed like
+                        // a good value so as to not be too noisy, but if fired, indicates a potential
+                        // area requiring investigation.
+                        const int CodeFixTelemetryDelay = 500;
+
+                        var fixerName = fixer.GetType().Name;
+                        using var _ = TelemetryLogging.LogBlockTime(FunctionId.CodeFix_Delay, $"{fixerName}", CodeFixTelemetryDelay);
+
                         var codeFixCollection = await TryGetFixesOrConfigurationsAsync(
                             document, span, diagnostics, fixAllForInSpan, fixer,
                             hasFix: d => this.GetFixableDiagnosticIds(fixer, extensionManager).Contains(d.Id),
                             getFixes: dxs =>
                             {
-                                var fixerName = fixer.GetType().Name;
                                 var fixerMetadata = TryGetMetadata(fixer);
 
                                 using (addOperationScope(fixerName))
diff --git a/src/Features/LanguageServer/Protocol/Features/Diagnostics/DiagnosticAnalyzerService.cs b/src/Features/LanguageServer/Protocol/Features/Diagnostics/DiagnosticAnalyzerService.cs
index 3d76bdd469550..7185f7b4aca8a 100644
--- a/src/Features/LanguageServer/Protocol/Features/Diagnostics/DiagnosticAnalyzerService.cs
+++ b/src/Features/LanguageServer/Protocol/Features/Diagnostics/DiagnosticAnalyzerService.cs
@@ -10,6 +10,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.Diagnostics.EngineV2;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Options;
@@ -45,7 +46,8 @@ public DiagnosticAnalyzerService(
             IDiagnosticUpdateSourceRegistrationService registrationService,
             IAsynchronousOperationListenerProvider listenerProvider,
             DiagnosticAnalyzerInfoCache.SharedGlobalCache globalCache,
-            IGlobalOptionService globalOptions)
+            IGlobalOptionService globalOptions,
+            IDiagnosticsRefresher diagnosticsRefresher)
         {
             AnalyzerInfoCache = globalCache.AnalyzerInfoCache;
             Listener = listenerProvider.GetListener(FeatureAttribute.DiagnosticService);
@@ -56,9 +58,23 @@ public DiagnosticAnalyzerService(
             _eventQueue = new TaskQueue(Listener, TaskScheduler.Default);
 
             registrationService.Register(this);
-            GlobalOptions = globalOptions;
+
+            globalOptions.AddOptionChangedHandler(this, (_, e) =>
+            {
+                if (IsGlobalOptionAffectingDiagnostics(e.Option))
+                {
+                    diagnosticsRefresher.RequestWorkspaceRefresh();
+                }
+            });
         }
 
+        public static bool IsGlobalOptionAffectingDiagnostics(IOption2 option)
+            => option == NamingStyleOptions.NamingPreferences ||
+               option.Definition.Group.Parent == CodeStyleOptionGroups.CodeStyle ||
+               option == SolutionCrawlerOptionsStorage.BackgroundAnalysisScopeOption ||
+               option == SolutionCrawlerOptionsStorage.SolutionBackgroundAnalysisScopeOption ||
+               option == SolutionCrawlerOptionsStorage.CompilerDiagnosticsScopeOption;
+
         public void Reanalyze(Workspace workspace, IEnumerable<ProjectId>? projectIds, IEnumerable<DocumentId>? documentIds, bool highPriority)
         {
             var service = workspace.Services.GetService<ISolutionCrawlerService>();
@@ -83,6 +99,8 @@ public void Reanalyze(Workspace workspace, IEnumerable<ProjectId>? projectIds, I
                 // always make sure that analyzer is called on background thread.
                 return Task.Run(async () =>
                 {
+                    priorityProvider ??= new DefaultCodeActionRequestPriorityProvider();
+
                     using var _ = ArrayBuilder<DiagnosticData>.GetInstance(out var diagnostics);
                     var upToDate = await analyzer.TryAppendDiagnosticsForSpanAsync(
                         document, range, diagnostics, shouldIncludeDiagnostic,
@@ -109,6 +127,8 @@ public Task<ImmutableArray<DiagnosticData>> GetDiagnosticsForSpanAsync(
         {
             if (_map.TryGetValue(document.Project.Solution.Workspace, out var analyzer))
             {
+                priorityProvider ??= new DefaultCodeActionRequestPriorityProvider();
+
                 // always make sure that analyzer is called on background thread.
                 return Task.Run(() => analyzer.GetDiagnosticsForSpanAsync(
                     document, range, shouldIncludeDiagnostic, includeSuppressedDiagnostics, includeCompilerDiagnostics,
diff --git a/src/Features/LanguageServer/Protocol/Features/Diagnostics/DocumentAnalysisExecutor.cs b/src/Features/LanguageServer/Protocol/Features/Diagnostics/DocumentAnalysisExecutor.cs
index 0e079e85a2f17..4d2597c9fb150 100644
--- a/src/Features/LanguageServer/Protocol/Features/Diagnostics/DocumentAnalysisExecutor.cs
+++ b/src/Features/LanguageServer/Protocol/Features/Diagnostics/DocumentAnalysisExecutor.cs
@@ -14,6 +14,7 @@
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.CodeAnalysis.Workspaces.Diagnostics;
 using Roslyn.Utilities;
@@ -235,6 +236,8 @@ private async Task<ImmutableArray<DiagnosticData>> GetSyntaxDiagnosticsAsync(Dia
 
             if (_lazySyntaxDiagnostics == null)
             {
+                using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.RequestDiagnostics_Summary, $"{nameof(GetSyntaxDiagnosticsAsync)}.{nameof(GetAnalysisResultAsync)}");
+
                 var analysisScope = AnalysisScope.WithAnalyzers(_compilationBasedAnalyzersInAnalysisScope);
                 var syntaxDiagnostics = await GetAnalysisResultAsync(analysisScope, cancellationToken).ConfigureAwait(false);
                 Interlocked.CompareExchange(ref _lazySyntaxDiagnostics, syntaxDiagnostics, null);
@@ -269,6 +272,8 @@ private async Task<ImmutableArray<DiagnosticData>> GetSemanticDiagnosticsAsync(D
 
             if (_lazySemanticDiagnostics == null)
             {
+                using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.RequestDiagnostics_Summary, $"{nameof(GetSemanticDiagnosticsAsync)}.{nameof(GetAnalysisResultAsync)}");
+
                 var analysisScope = AnalysisScope.WithAnalyzers(_compilationBasedAnalyzersInAnalysisScope);
                 var semanticDiagnostics = await GetAnalysisResultAsync(analysisScope, cancellationToken).ConfigureAwait(false);
                 Interlocked.CompareExchange(ref _lazySemanticDiagnostics, semanticDiagnostics, null);
diff --git a/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.cs b/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.cs
index a161c98f4e887..218e1e8ebbe3a 100644
--- a/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.cs
+++ b/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.cs
@@ -70,17 +70,11 @@ public DiagnosticIncrementalAnalyzer(
 
         private void OnGlobalOptionChanged(object? sender, OptionChangedEventArgs e)
         {
-            if (e.Option == NamingStyleOptions.NamingPreferences ||
-                e.Option.Definition.Group.Parent == CodeStyleOptionGroups.CodeStyle ||
-                e.Option == SolutionCrawlerOptionsStorage.BackgroundAnalysisScopeOption ||
-                e.Option == SolutionCrawlerOptionsStorage.SolutionBackgroundAnalysisScopeOption ||
-                e.Option == SolutionCrawlerOptionsStorage.CompilerDiagnosticsScopeOption)
+            if (DiagnosticAnalyzerService.IsGlobalOptionAffectingDiagnostics(e.Option) &&
+                GlobalOptions.GetOption(SolutionCrawlerRegistrationService.EnableSolutionCrawler))
             {
-                if (GlobalOptions.GetOption(SolutionCrawlerRegistrationService.EnableSolutionCrawler))
-                {
-                    var service = Workspace.Services.GetService<ISolutionCrawlerService>();
-                    service?.Reanalyze(Workspace, this, projectIds: null, documentIds: null, highPriority: false);
-                }
+                var service = Workspace.Services.GetService<ISolutionCrawlerService>();
+                service?.Reanalyze(Workspace, this, projectIds: null, documentIds: null, highPriority: false);
             }
         }
 
diff --git a/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs b/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs
index d8d3ee061917c..8e2cfaf1b5bea 100644
--- a/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs
+++ b/src/Features/LanguageServer/Protocol/Features/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_GetDiagnosticsForSpan.cs
@@ -15,6 +15,7 @@
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
@@ -216,6 +217,8 @@ public async Task<bool> TryGetAsync(ArrayBuilder<DiagnosticData> list, Cancellat
                     using var _2 = ArrayBuilder<AnalyzerWithState>.GetInstance(out var semanticSpanBasedAnalyzers);
                     using var _3 = ArrayBuilder<AnalyzerWithState>.GetInstance(out var semanticDocumentBasedAnalyzers);
 
+                    using var _4 = TelemetryLogging.LogBlockTimeAggregated(FunctionId.RequestDiagnostics_Summary, $"Pri{(int)_priorityProvider.Priority}");
+
                     foreach (var stateSet in _stateSets)
                     {
                         var analyzer = stateSet.Analyzer;
@@ -420,6 +423,8 @@ private async Task ComputeDocumentDiagnosticsAsync(
                 ImmutableDictionary<DiagnosticAnalyzer, ImmutableArray<DiagnosticData>> diagnosticsMap;
                 if (incrementalAnalysis)
                 {
+                    using var _2 = TelemetryLogging.LogBlockTimeAggregated(FunctionId.RequestDiagnostics_Summary, $"Pri{(int)_priorityProvider.Priority}.Incremental");
+
                     diagnosticsMap = await _owner._incrementalMemberEditAnalyzer.ComputeDiagnosticsAsync(
                         executor,
                         analyzersWithState,
@@ -430,6 +435,8 @@ private async Task ComputeDocumentDiagnosticsAsync(
                 }
                 else
                 {
+                    using var _2 = TelemetryLogging.LogBlockTimeAggregated(FunctionId.RequestDiagnostics_Summary, $"Pri{(int)_priorityProvider.Priority}.Document");
+
                     diagnosticsMap = await ComputeDocumentDiagnosticsCoreAsync(executor, cancellationToken).ConfigureAwait(false);
                 }
 
diff --git a/src/Features/LanguageServer/Protocol/Features/Options/SolutionCrawlerOptionsStorage.cs b/src/Features/LanguageServer/Protocol/Features/Options/SolutionCrawlerOptionsStorage.cs
index 1f9772394ef7c..7952e5e081d4f 100644
--- a/src/Features/LanguageServer/Protocol/Features/Options/SolutionCrawlerOptionsStorage.cs
+++ b/src/Features/LanguageServer/Protocol/Features/Options/SolutionCrawlerOptionsStorage.cs
@@ -10,32 +10,34 @@ namespace Microsoft.CodeAnalysis.SolutionCrawler;
 
 internal static class SolutionCrawlerOptionsStorage
 {
+    private static readonly OptionGroup s_backgroundAnalysisOptionGroup = new(name: "background_analysis", description: "");
+
     /// <summary>
     /// Option to turn configure background analysis scope for the current user.
     /// </summary>
     public static readonly PerLanguageOption2<BackgroundAnalysisScope> BackgroundAnalysisScopeOption = new(
-        "dotnet_solution_crawler_background_analysis_scope", defaultValue: BackgroundAnalysisScope.Default, serializer: EditorConfigValueSerializer.CreateSerializerForEnum<BackgroundAnalysisScope>());
+        "dotnet_solution_crawler_background_analysis_scope", defaultValue: BackgroundAnalysisScope.Default, group: s_backgroundAnalysisOptionGroup, serializer: EditorConfigValueSerializer.CreateSerializerForEnum<BackgroundAnalysisScope>());
 
     /// <summary>
     /// Option to turn configure background analysis scope for the current solution.
     /// </summary>
     public static readonly Option2<BackgroundAnalysisScope?> SolutionBackgroundAnalysisScopeOption = new(
-        "SolutionCrawlerOptionsStorage_SolutionBackgroundAnalysisScopeOption", defaultValue: null, serializer: EditorConfigValueSerializer.CreateSerializerForNullableEnum<BackgroundAnalysisScope>());
+        "SolutionCrawlerOptionsStorage_SolutionBackgroundAnalysisScopeOption", defaultValue: null, group: s_backgroundAnalysisOptionGroup, serializer: EditorConfigValueSerializer.CreateSerializerForNullableEnum<BackgroundAnalysisScope>());
 
     /// <summary>
     /// Option to configure compiler diagnostics scope for the current user.
     /// </summary>
     public static readonly PerLanguageOption2<CompilerDiagnosticsScope> CompilerDiagnosticsScopeOption = new(
-        "dotnet_compiler_diagnostics_scope", defaultValue: CompilerDiagnosticsScope.OpenFiles, serializer: EditorConfigValueSerializer.CreateSerializerForEnum<CompilerDiagnosticsScope>());
+        "dotnet_compiler_diagnostics_scope", defaultValue: CompilerDiagnosticsScope.OpenFiles, group: s_backgroundAnalysisOptionGroup, serializer: EditorConfigValueSerializer.CreateSerializerForEnum<CompilerDiagnosticsScope>());
 
     public static readonly PerLanguageOption2<bool> RemoveDocumentDiagnosticsOnDocumentClose = new(
-        "remove_document_diagnostics_on_document_close", defaultValue: false);
+        "remove_document_diagnostics_on_document_close", defaultValue: false, group: s_backgroundAnalysisOptionGroup);
 
     public static readonly Option2<bool?> EnableDiagnosticsInSourceGeneratedFiles = new(
-        "dotnet_enable_diagnostics_in_source_generated_files", defaultValue: null);
+        "dotnet_enable_diagnostics_in_source_generated_files", defaultValue: null, group: s_backgroundAnalysisOptionGroup);
 
     public static readonly Option2<bool> EnableDiagnosticsInSourceGeneratedFilesFeatureFlag = new(
-        "dotnet_enable_diagnostics_in_source_generated_files_feature_flag", defaultValue: false);
+        "dotnet_enable_diagnostics_in_source_generated_files_feature_flag", defaultValue: false, group: s_backgroundAnalysisOptionGroup);
 
     /// <summary>
     /// Enables forced <see cref="BackgroundAnalysisScope.Minimal"/> scope when low VM is detected to improve performance.
diff --git a/src/Features/LanguageServer/Protocol/Features/UnifiedSuggestions/UnifiedSuggestedActionsSource.cs b/src/Features/LanguageServer/Protocol/Features/UnifiedSuggestions/UnifiedSuggestedActionsSource.cs
index 2c79d2dc38334..9d61bf4a90017 100644
--- a/src/Features/LanguageServer/Protocol/Features/UnifiedSuggestions/UnifiedSuggestedActionsSource.cs
+++ b/src/Features/LanguageServer/Protocol/Features/UnifiedSuggestions/UnifiedSuggestedActionsSource.cs
@@ -181,13 +181,14 @@ private static void AddFix(
             ArrayBuilder<CodeFixGroupKey> order)
         {
             var groupKey = GetGroupKey(fix);
-            if (!map.ContainsKey(groupKey))
+            if (!map.TryGetValue(groupKey, out var suggestedActions))
             {
                 order.Add(groupKey);
-                map[groupKey] = ImmutableArray.CreateBuilder<IUnifiedSuggestedAction>();
+                suggestedActions = ImmutableArray.CreateBuilder<IUnifiedSuggestedAction>();
+                map[groupKey] = suggestedActions;
             }
 
-            map[groupKey].Add(suggestedAction);
+            suggestedActions.Add(suggestedAction);
             return;
 
             static CodeFixGroupKey GetGroupKey(CodeFix fix)
diff --git a/src/Features/LanguageServer/Protocol/Handler/AbstractRefreshQueue.cs b/src/Features/LanguageServer/Protocol/Handler/AbstractRefreshQueue.cs
new file mode 100644
index 0000000000000..0935cf7cbbfea
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/AbstractRefreshQueue.cs
@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Collections;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler
+{
+    internal abstract class AbstractRefreshQueue :
+        IOnInitialized,
+        ILspService,
+        IDisposable
+    {
+        private AsyncBatchingWorkQueue<Uri?>? _refreshQueue;
+
+        private readonly LspWorkspaceManager _lspWorkspaceManager;
+        private readonly IClientLanguageServerManager _notificationManager;
+
+        private readonly IAsynchronousOperationListener _asyncListener;
+        private readonly CancellationTokenSource _disposalTokenSource;
+        private readonly LspWorkspaceRegistrationService _lspWorkspaceRegistrationService;
+
+        protected bool _isQueueCreated;
+
+        protected abstract string GetFeatureAttribute();
+        protected abstract bool? GetRefreshSupport(ClientCapabilities clientCapabilities);
+        protected abstract string GetWorkspaceRefreshName();
+
+        public AbstractRefreshQueue(
+            IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider,
+            LspWorkspaceRegistrationService lspWorkspaceRegistrationService,
+            LspWorkspaceManager lspWorkspaceManager,
+            IClientLanguageServerManager notificationManager)
+        {
+            _isQueueCreated = false;
+            _asyncListener = asynchronousOperationListenerProvider.GetListener(GetFeatureAttribute());
+            _lspWorkspaceRegistrationService = lspWorkspaceRegistrationService;
+            _disposalTokenSource = new();
+            _lspWorkspaceManager = lspWorkspaceManager;
+            _notificationManager = notificationManager;
+        }
+
+        public Task OnInitializedAsync(ClientCapabilities clientCapabilities, CancellationToken cancellationToken)
+        {
+            if (_refreshQueue is null && GetRefreshSupport(clientCapabilities) is true)
+            {
+                // Only send a refresh notification to the client every 2s (if needed) in order to avoid
+                // sending too many notifications at once.  This ensures we batch up workspace notifications,
+                // but also means we send soon enough after a compilation-computation to not make the user wait
+                // an enormous amount of time.
+                _refreshQueue = new AsyncBatchingWorkQueue<Uri?>(
+                    delay: TimeSpan.FromMilliseconds(2000),
+                    processBatchAsync: (documentUris, cancellationToken)
+                        => FilterLspTrackedDocumentsAsync(_lspWorkspaceManager, _notificationManager, documentUris, cancellationToken),
+                    equalityComparer: EqualityComparer<Uri?>.Default,
+                    asyncListener: _asyncListener,
+                    _disposalTokenSource.Token);
+                _isQueueCreated = true;
+                _lspWorkspaceRegistrationService.LspSolutionChanged += OnLspSolutionChanged;
+            }
+
+            return Task.CompletedTask;
+        }
+
+        private void OnLspSolutionChanged(object? sender, WorkspaceChangeEventArgs e)
+        {
+            if (e.DocumentId is not null && e.Kind is WorkspaceChangeKind.DocumentChanged)
+            {
+                var document = e.NewSolution.GetRequiredDocument(e.DocumentId);
+                var documentUri = document.GetURI();
+
+                // We enqueue the URI since there's a chance the client is already tracking the
+                // document, in which case we don't need to send a refresh notification.
+                // We perform the actual check when processing the batch to ensure we have the
+                // most up-to-date list of tracked documents.
+                EnqueueRefreshNotification(documentUri);
+            }
+            else
+            {
+                EnqueueRefreshNotification(documentUri: null);
+            }
+        }
+
+        protected void EnqueueRefreshNotification(Uri? documentUri)
+        {
+            if (_isQueueCreated)
+            {
+                Contract.ThrowIfNull(_refreshQueue);
+                _refreshQueue.AddWork(documentUri);
+            }
+        }
+
+        private ValueTask FilterLspTrackedDocumentsAsync(
+            LspWorkspaceManager lspWorkspaceManager,
+            IClientLanguageServerManager notificationManager,
+            ImmutableSegmentedList<Uri?> documentUris,
+            CancellationToken cancellationToken)
+        {
+            var trackedDocuments = lspWorkspaceManager.GetTrackedLspText();
+            foreach (var documentUri in documentUris)
+            {
+                if (documentUri is null || !trackedDocuments.ContainsKey(documentUri))
+                {
+                    return notificationManager.SendRequestAsync(GetWorkspaceRefreshName(), cancellationToken);
+                }
+            }
+
+            // LSP is already tracking all changed documents so we don't need to send a refresh request.
+            return ValueTaskFactory.CompletedTask;
+        }
+
+        public virtual void Dispose()
+        {
+            _lspWorkspaceRegistrationService.LspSolutionChanged -= OnLspSolutionChanged;
+            _disposalTokenSource.Cancel();
+            _disposalTokenSource.Dispose();
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/CodeLens/CodeLensRefreshQueue.cs b/src/Features/LanguageServer/Protocol/Handler/CodeLens/CodeLensRefreshQueue.cs
new file mode 100644
index 0000000000000..890c9f94ef16d
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/CodeLens/CodeLensRefreshQueue.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.CodeLens
+{
+    internal class CodeLensRefreshQueue : AbstractRefreshQueue
+    {
+        public CodeLensRefreshQueue(
+            IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider,
+            LspWorkspaceRegistrationService lspWorkspaceRegistrationService,
+            LspWorkspaceManager lspWorkspaceManager,
+            IClientLanguageServerManager notificationManager)
+            : base(asynchronousOperationListenerProvider, lspWorkspaceRegistrationService, lspWorkspaceManager, notificationManager)
+        {
+        }
+
+        protected override string GetFeatureAttribute()
+            => FeatureAttribute.CodeLens;
+
+        protected override bool? GetRefreshSupport(ClientCapabilities clientCapabilities)
+        {
+            return clientCapabilities.Workspace?.CodeLens?.RefreshSupport;
+        }
+
+        protected override string GetWorkspaceRefreshName()
+        {
+            return Methods.WorkspaceCodeLensRefreshName;
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/CodeLens/CodeLensRefreshQueueFactory.cs b/src/Features/LanguageServer/Protocol/Handler/CodeLens/CodeLensRefreshQueueFactory.cs
new file mode 100644
index 0000000000000..1102b80c71eb6
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/CodeLens/CodeLensRefreshQueueFactory.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.CodeLens
+{
+    [ExportCSharpVisualBasicLspServiceFactory(typeof(CodeLensRefreshQueue)), Shared]
+    internal sealed class CodeLensRefreshQueueFactory : ILspServiceFactory
+    {
+        private readonly IAsynchronousOperationListenerProvider _asyncListenerProvider;
+        private readonly LspWorkspaceRegistrationService _lspWorkspaceRegistrationService;
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public CodeLensRefreshQueueFactory(
+            IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider,
+            LspWorkspaceRegistrationService lspWorkspaceRegistrationService,
+            IGlobalOptionService globalOptionService)
+        {
+            _asyncListenerProvider = asynchronousOperationListenerProvider;
+            _lspWorkspaceRegistrationService = lspWorkspaceRegistrationService;
+        }
+
+        public ILspService CreateILspService(LspServices lspServices, WellKnownLspServerKinds serverKind)
+        {
+            var notificationManager = lspServices.GetRequiredService<IClientLanguageServerManager>();
+            var lspWorkspaceManager = lspServices.GetRequiredService<LspWorkspaceManager>();
+
+            return new CodeLensRefreshQueue(_asyncListenerProvider, _lspWorkspaceRegistrationService, lspWorkspaceManager, notificationManager);
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/AbstractLspCompletionResultCreationService.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/AbstractLspCompletionResultCreationService.cs
new file mode 100644
index 0000000000000..b6c2785ef5eb7
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/Completion/AbstractLspCompletionResultCreationService.cs
@@ -0,0 +1,468 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Completion;
+using Microsoft.CodeAnalysis.Completion.Providers;
+using Microsoft.CodeAnalysis.Completion.Providers.Snippets;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.PooledObjects;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
+using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Completion
+{
+    internal abstract class AbstractLspCompletionResultCreationService : ILspCompletionResultCreationService
+    {
+        protected abstract Task<LSP.CompletionItem> CreateItemAndPopulateTextEditAsync(Document document, SourceText documentText, bool snippetsSupported, bool itemDefaultsSupported, TextSpan defaultSpan, string typedText, CompletionItem item, CompletionService completionService, CancellationToken cancellationToken);
+        public abstract Task<LSP.CompletionItem> ResolveAsync(LSP.CompletionItem lspItem, CompletionItem roslynItem, LSP.TextDocumentIdentifier textDocumentIdentifier, Document document, CompletionCapabilityHelper capabilityHelper, CompletionService completionService, CompletionOptions completionOptions, SymbolDescriptionOptions symbolDescriptionOptions, CancellationToken cancellationToken);
+
+        public static string[] DefaultCommitCharactersArray { get; } = CreateCommitCharacterArrayFromRules(CompletionItemRules.Default);
+
+        public async Task<LSP.CompletionList> ConvertToLspCompletionListAsync(
+            Document document,
+            int position,
+            CompletionCapabilityHelper capabilityHelper,
+            CompletionList list, bool isIncomplete, long resultId,
+            CancellationToken cancellationToken)
+        {
+            if (list.ItemsList.Count == 0)
+            {
+                return new LSP.VSInternalCompletionList
+                {
+                    Items = Array.Empty<LSP.CompletionItem>(),
+                    // If we have a suggestion mode item, we just need to keep the list in suggestion mode.
+                    // We don't need to return the fake suggestion mode item.
+                    SuggestionMode = list.SuggestionModeItem is not null,
+                    IsIncomplete = isIncomplete,
+                };
+            }
+
+            var lspVSClientCapability = capabilityHelper.SupportVSInternalClientCapabilities;
+            var defaultEditRangeSupported = capabilityHelper.SupportDefaultEditRange;
+
+            var documentText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
+
+            // Set resolve data on list if the client supports it, otherwise set it on each item.
+            var resolveData = new CompletionResolveData() { ResultId = resultId };
+            var completionItemResolveData = capabilityHelper.SupportCompletionListData || capabilityHelper.SupportVSInternalCompletionListData
+                ? null : resolveData;
+
+            using var _ = ArrayBuilder<LSP.CompletionItem>.GetInstance(out var lspCompletionItems);
+            var commitCharactersRuleCache = new Dictionary<ImmutableArray<CharacterSetModificationRule>, string[]>(CommitCharacterArrayComparer.Instance);
+
+            var creationService = document.Project.Solution.Services.GetRequiredService<ILspCompletionResultCreationService>();
+            var completionService = document.GetRequiredLanguageService<CompletionService>();
+
+            // By default, Roslyn would treat continuous alphabetical text as a single word for completion purpose.
+            // e.g. when user triggers completion at the location of {$} in "pub{$}class", the span would cover "pubclass",
+            // which is used for subsequent matching and commit.
+            // This works fine for VS async-completion, where we have full control of entire completion process.
+            // However, the insert mode in VSCode (i.e. the mode our LSP server supports) expects us to return TextEdit that only
+            // covers the span ends at the cursor location, e.g. "pub" in the example above. Here we detect when that occurs and
+            // adjust the span accordingly.
+            var defaultSpan = !capabilityHelper.SupportVSInternalClientCapabilities && position < list.Span.End
+                ? new(list.Span.Start, length: position - list.Span.Start)
+                : list.Span;
+
+            var typedText = documentText.GetSubText(defaultSpan).ToString();
+            foreach (var item in list.ItemsList)
+            {
+                item.Span = defaultSpan;    // item.Span will be used to generate change, adjust it if needed
+                lspCompletionItems.Add(await CreateLSPCompletionItemAsync(item, typedText).ConfigureAwait(false));
+            }
+
+            var completionList = new LSP.VSInternalCompletionList
+            {
+                // public LSP
+                Items = lspCompletionItems.ToArray(),
+                IsIncomplete = isIncomplete,
+                ItemDefaults = new LSP.CompletionListItemDefaults
+                {
+                    EditRange = capabilityHelper.SupportDefaultEditRange ? ProtocolConversions.TextSpanToRange(defaultSpan, documentText) : null,
+                    Data = capabilityHelper.SupportCompletionListData ? resolveData : null
+                },
+
+                // VS internal
+                //
+                // If we have a suggestion mode item, we just need to keep the list in suggestion mode.
+                // We don't need to return the fake suggestion mode item.
+                SuggestionMode = list.SuggestionModeItem != null,
+                Data = capabilityHelper.SupportVSInternalCompletionListData ? resolveData : null,
+            };
+
+            PromoteCommonCommitCharactersOntoList();
+
+            if (completionList.ItemDefaults.EditRange is null && completionList.ItemDefaults.CommitCharacters is null && completionList.ItemDefaults.Data is null)
+                completionList.ItemDefaults = null;
+
+            return capabilityHelper.SupportVSInternalClientCapabilities
+                ? new LSP.OptimizedVSCompletionList(completionList)
+                : completionList;
+
+            async Task<LSP.CompletionItem> CreateLSPCompletionItemAsync(CompletionItem item, string typedText)
+            {
+                // Defer to host to create the actual completion item (including potential subclasses), and add any
+                // custom information.
+                var lspItem = await CreateItemAndPopulateTextEditAsync(
+                    document, documentText, capabilityHelper.SupportSnippets, defaultEditRangeSupported, defaultSpan, typedText, item, completionService, cancellationToken).ConfigureAwait(false);
+
+                if (!item.InlineDescription.IsEmpty())
+                    lspItem.LabelDetails = new() { Description = item.InlineDescription };
+
+                // Now add data common to all hosts.
+                lspItem.Data = completionItemResolveData;
+
+                if (!lspItem.Label.Equals(item.SortText, StringComparison.Ordinal))
+                    lspItem.SortText = item.SortText;
+
+                if (!lspItem.Label.Equals(item.FilterText, StringComparison.Ordinal))
+                    lspItem.FilterText = item.FilterText;
+
+                lspItem.Kind = GetCompletionKind(item.Tags, capabilityHelper.SupportedItemKinds);
+                lspItem.Preselect = item.Rules.MatchPriority == MatchPriority.Preselect;
+
+                if (!lspItem.Preselect &&
+                    !lspVSClientCapability &&
+                    typedText.Length == 0 &&
+                    item.Rules.SelectionBehavior != CompletionItemSelectionBehavior.HardSelection)
+                {
+                    // VSCode does not have the concept of soft selection, the list is always hard selected.
+                    // In order to emulate soft selection behavior for things like argument completion, regex completion,
+                    // datetime completion, etc. we create a completion item without any specific commit characters.
+                    // This means only tab / enter will commit. VS supports soft selection, so we only do this for non-VS clients.
+                    //
+                    // Note this only applies when user hasn't actually typed anything and completion provider does not request the item
+                    // to be hard-selected. Otherwise, we set its commit characters as normal. This also means we'd need to set IsIncomplete to true
+                    // to make sure the client will ask us again when user starts typing so we can provide items with proper commit characters.
+                    lspItem.CommitCharacters = Array.Empty<string>();
+                    isIncomplete = true;
+                }
+                else
+                {
+                    lspItem.CommitCharacters = GetCommitCharacters(item, commitCharactersRuleCache);
+                }
+
+                return lspItem;
+            }
+
+            static LSP.CompletionItemKind GetCompletionKind(
+                ImmutableArray<string> tags,
+                ISet<LSP.CompletionItemKind> supportedClientKinds)
+            {
+                foreach (var tag in tags)
+                {
+                    if (ProtocolConversions.RoslynTagToCompletionItemKinds.TryGetValue(tag, out var completionItemKinds))
+                    {
+                        // Always at least pick the core kind provided.
+                        var kind = completionItemKinds[0];
+
+                        // If better kinds are preferred, return them if the client supports them.
+                        for (var i = 1; i < completionItemKinds.Length; i++)
+                        {
+                            var preferredKind = completionItemKinds[i];
+                            if (supportedClientKinds.Contains(preferredKind))
+                                kind = preferredKind;
+                        }
+
+                        return kind;
+                    }
+                }
+
+                return LSP.CompletionItemKind.Text;
+            }
+
+            static string[] GetCommitCharacters(
+                CompletionItem item,
+                Dictionary<ImmutableArray<CharacterSetModificationRule>, string[]> currentRuleCache)
+            {
+                if (item.Rules.CommitCharacterRules.IsEmpty)
+                    return DefaultCommitCharactersArray;
+
+                if (!currentRuleCache.TryGetValue(item.Rules.CommitCharacterRules, out var cachedCommitCharacters))
+                {
+                    cachedCommitCharacters = CreateCommitCharacterArrayFromRules(item.Rules);
+                    currentRuleCache.Add(item.Rules.CommitCharacterRules, cachedCommitCharacters);
+                }
+
+                return cachedCommitCharacters;
+            }
+
+            void PromoteCommonCommitCharactersOntoList()
+            {
+                // If client doesn't support default commit characters on list, we want to set commit characters for each item with default to null.
+                // This way client will default to the commit chars server provided in ServerCapabilities.CompletionProvider.AllCommitCharacters.
+                if (!(capabilityHelper.SupportDefaultCommitCharacters || capabilityHelper.SupportVSInternalDefaultCommitCharacters))
+                {
+                    foreach (var completionItem in completionList.Items)
+                    {
+                        if (completionItem.CommitCharacters == DefaultCommitCharactersArray)
+                            completionItem.CommitCharacters = null;
+                    }
+
+                    return;
+                }
+
+                if (completionList.Items.IsEmpty())
+                    return;
+
+                var commitCharacterReferences = new Dictionary<object, int>();
+                var mostUsedCount = 0;
+                string[]? mostUsedCommitCharacters = null;
+
+                for (var i = 0; i < completionList.Items.Length; i++)
+                {
+                    var completionItem = completionList.Items[i];
+                    var commitCharacters = completionItem.CommitCharacters;
+
+                    Contract.ThrowIfNull(commitCharacters);
+
+                    commitCharacterReferences.TryGetValue(commitCharacters, out var existingCount);
+                    existingCount++;
+
+                    if (existingCount > mostUsedCount)
+                    {
+                        // Capture the most used commit character counts so we don't need to re-iterate the array later
+                        mostUsedCommitCharacters = commitCharacters;
+                        mostUsedCount = existingCount;
+                    }
+
+                    commitCharacterReferences[commitCharacters] = existingCount;
+                }
+
+                // Promoted the most used commit characters onto the list and then remove these from child items.
+                // public LSP
+                if (capabilityHelper.SupportDefaultCommitCharacters)
+                {
+                    completionList.ItemDefaults.CommitCharacters = mostUsedCommitCharacters;
+                }
+
+                // VS internal
+                if (capabilityHelper.SupportVSInternalDefaultCommitCharacters)
+                {
+                    completionList.CommitCharacters = mostUsedCommitCharacters;
+                }
+
+                foreach (var completionItem in completionList.Items)
+                {
+                    if (completionItem.CommitCharacters == mostUsedCommitCharacters)
+                    {
+                        completionItem.CommitCharacters = null;
+                    }
+                }
+            }
+        }
+
+        public static string[] CreateCommitCharacterArrayFromRules(CompletionItemRules rules)
+        {
+            using var _ = PooledHashSet<char>.GetInstance(out var commitCharacters);
+            commitCharacters.AddAll(CompletionRules.Default.DefaultCommitCharacters);
+            foreach (var rule in rules.CommitCharacterRules)
+            {
+                switch (rule.Kind)
+                {
+                    case CharacterSetModificationKind.Add:
+                        commitCharacters.UnionWith(rule.Characters);
+                        continue;
+                    case CharacterSetModificationKind.Remove:
+                        commitCharacters.ExceptWith(rule.Characters);
+                        continue;
+                    case CharacterSetModificationKind.Replace:
+                        commitCharacters.Clear();
+                        commitCharacters.AddRange(rule.Characters);
+                        break;
+                }
+            }
+
+            return commitCharacters.Select(c => c.ToString()).ToArray();
+        }
+
+        private sealed class CommitCharacterArrayComparer : IEqualityComparer<ImmutableArray<CharacterSetModificationRule>>
+        {
+            public static readonly CommitCharacterArrayComparer Instance = new();
+
+            private CommitCharacterArrayComparer()
+            {
+            }
+
+            public bool Equals([AllowNull] ImmutableArray<CharacterSetModificationRule> x, [AllowNull] ImmutableArray<CharacterSetModificationRule> y)
+            {
+                if (x == y)
+                    return true;
+
+                for (var i = 0; i < x.Length; i++)
+                {
+                    var xKind = x[i].Kind;
+                    var yKind = y[i].Kind;
+                    if (xKind != yKind)
+                    {
+                        return false;
+                    }
+
+                    var xCharacters = x[i].Characters;
+                    var yCharacters = y[i].Characters;
+                    if (xCharacters.Length != yCharacters.Length)
+                    {
+                        return false;
+                    }
+
+                    for (var j = 0; j < xCharacters.Length; j++)
+                    {
+                        if (xCharacters[j] != yCharacters[j])
+                        {
+                            return false;
+                        }
+                    }
+                }
+
+                return true;
+            }
+
+            public int GetHashCode([DisallowNull] ImmutableArray<CharacterSetModificationRule> obj)
+            {
+                var combinedHash = Hash.CombineValues(obj);
+                return combinedHash;
+            }
+        }
+
+        protected static void PopulateTextEdit(
+            LSP.CompletionItem lspItem,
+            TextSpan completionChangeSpan,
+            string completionChangeNewText,
+            SourceText documentText,
+            bool itemDefaultsSupported,
+            TextSpan defaultSpan)
+        {
+            if (itemDefaultsSupported && completionChangeSpan == defaultSpan)
+            {
+                // We only need to store the new text as the text edit text when it differs from Label.
+                if (!lspItem.Label.Equals(completionChangeNewText, StringComparison.Ordinal))
+                    lspItem.TextEditText = completionChangeNewText;
+            }
+            else
+            {
+                lspItem.TextEdit = new LSP.TextEdit()
+                {
+                    NewText = completionChangeNewText,
+                    Range = ProtocolConversions.TextSpanToRange(completionChangeSpan, documentText),
+                };
+            }
+        }
+
+        protected static async Task GetChangeAndPopulateSimpleTextEditAsync(
+            Document document,
+            SourceText documentText,
+            bool itemDefaultsSupported,
+            TextSpan defaultSpan,
+            CompletionItem item,
+            LSP.CompletionItem lspItem,
+            CompletionService completionService,
+            CancellationToken cancellationToken)
+        {
+            Contract.ThrowIfTrue(item.IsComplexTextEdit);
+            Contract.ThrowIfNull(lspItem.Label);
+
+            var completionChange = await completionService.GetChangeAsync(document, item, cancellationToken: cancellationToken).ConfigureAwait(false);
+            var change = completionChange.TextChange;
+
+            // If the change's span is different from default, then the item should be mark as IsComplexTextEdit.
+            // But since we don't have a way to enforce this, we'll just check for it here.
+            Debug.Assert(change.Span == defaultSpan);
+            PopulateTextEdit(lspItem, change.Span, change.NewText ?? string.Empty, documentText, itemDefaultsSupported, defaultSpan);
+        }
+
+        public static async Task<LSP.TextEdit[]?> GenerateAdditionalTextEditForImportCompletionAsync(
+            CompletionItem selectedItem,
+            Document document,
+            CompletionService completionService,
+            CancellationToken cancellationToken)
+        {
+            Debug.Assert(selectedItem.Flags.IsExpanded());
+            selectedItem = ImportCompletionItem.MarkItemToAlwaysAddMissingImport(selectedItem);
+            var completionChange = await completionService.GetChangeAsync(document, selectedItem, cancellationToken: cancellationToken).ConfigureAwait(false);
+
+            var sourceText = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
+            using var _ = ArrayBuilder<LSP.TextEdit>.GetInstance(out var builder);
+            foreach (var change in completionChange.TextChanges)
+            {
+                if (change.NewText == selectedItem.DisplayText)
+                    continue;
+
+                builder.Add(new LSP.TextEdit()
+                {
+                    NewText = change.NewText!,
+                    Range = ProtocolConversions.TextSpanToRange(change.Span, sourceText),
+                });
+            }
+
+            return builder.ToArray();
+        }
+
+        public static async Task<(LSP.TextEdit edit, bool isSnippetString, int? newPosition)> GenerateComplexTextEditAsync(
+            Document document,
+            CompletionService completionService,
+            CompletionItem selectedItem,
+            bool snippetsSupported,
+            bool insertNewPositionPlaceholder,
+            CancellationToken cancellationToken)
+        {
+            Debug.Assert(selectedItem.IsComplexTextEdit);
+
+            var completionChange = await completionService.GetChangeAsync(document, selectedItem, cancellationToken: cancellationToken).ConfigureAwait(false);
+            var completionChangeSpan = completionChange.TextChange.Span;
+            var newText = completionChange.TextChange.NewText;
+            Contract.ThrowIfNull(newText);
+
+            var documentText = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
+            var textEdit = new LSP.TextEdit()
+            {
+                NewText = newText,
+                Range = ProtocolConversions.TextSpanToRange(completionChangeSpan, documentText),
+            };
+
+            var isSnippetString = false;
+            var newPosition = completionChange.NewPosition;
+
+            if (snippetsSupported)
+            {
+                if (SnippetCompletionItem.IsSnippet(selectedItem)
+                    && completionChange.Properties.TryGetValue(SnippetCompletionItem.LSPSnippetKey, out var lspSnippetChangeText))
+                {
+                    textEdit.NewText = lspSnippetChangeText;
+                    isSnippetString = true;
+                    newPosition = null;
+                }
+                else if (insertNewPositionPlaceholder)
+                {
+                    var caretPosition = completionChange.NewPosition;
+                    if (caretPosition.HasValue)
+                    {
+                        // caretPosition is the absolute position of the caret in the document.
+                        // We want the position relative to the start of the snippet.
+                        var relativeCaretPosition = caretPosition.Value - completionChangeSpan.Start;
+
+                        // The caret could technically be placed outside the bounds of the text
+                        // being inserted. This situation is currently unsupported in LSP, so in
+                        // these cases we won't move the caret.
+                        if (relativeCaretPosition >= 0 && relativeCaretPosition <= newText.Length)
+                        {
+                            textEdit.NewText = textEdit.NewText.Insert(relativeCaretPosition, "$0");
+                        }
+                    }
+                }
+            }
+
+            return (textEdit, isSnippetString, newPosition);
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionCapabilityHelper.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionCapabilityHelper.cs
new file mode 100644
index 0000000000000..9892f33d66cd1
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionCapabilityHelper.cs
@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Completion
+{
+    internal sealed class CompletionCapabilityHelper
+    {
+        public const string CommitCharactersPropertyName = "commitCharacters";
+        public const string DataPropertyName = "data";
+        public const string EditRangePropertyName = "editRange";
+
+        private readonly CompletionSetting? _completionSetting;
+        private readonly VSInternalCompletionSetting? _vsCompletionSetting;
+
+        public bool SupportVSInternalClientCapabilities { get; }
+        public bool SupportDefaultEditRange { get; }
+        public bool SupportCompletionListData { get; }
+        public bool SupportVSInternalCompletionListData { get; }
+        public bool SupportDefaultCommitCharacters { get; }
+        public bool SupportVSInternalDefaultCommitCharacters { get; }
+        public bool SupportSnippets { get; }
+        public bool SupportsMarkdownDocumentation { get; }
+        public ISet<CompletionItemKind> SupportedItemKinds { get; }
+
+        public CompletionCapabilityHelper(ClientCapabilities clientCapabilities)
+        {
+            // public LSP
+            _completionSetting = clientCapabilities.TextDocument?.Completion;
+
+            SupportSnippets = _completionSetting?.CompletionItem?.SnippetSupport ?? false;
+            SupportDefaultEditRange = _completionSetting?.CompletionListSetting?.ItemDefaults?.Contains(EditRangePropertyName) == true;
+            SupportsMarkdownDocumentation = _completionSetting?.CompletionItem?.DocumentationFormat?.Contains(MarkupKind.Markdown) == true;
+            SupportCompletionListData = _completionSetting?.CompletionListSetting?.ItemDefaults?.Contains(DataPropertyName) == true;
+            SupportDefaultCommitCharacters = _completionSetting?.CompletionListSetting?.ItemDefaults?.Contains(CommitCharactersPropertyName) == true;
+            SupportedItemKinds = _completionSetting?.CompletionItemKind?.ValueSet?.ToSet() ?? SpecializedCollections.EmptySet<CompletionItemKind>();
+
+            // internal VS LSP
+            if (clientCapabilities.HasVisualStudioLspCapability())
+            {
+                SupportVSInternalClientCapabilities = true;
+                _vsCompletionSetting = ((VSInternalClientCapabilities)clientCapabilities).TextDocument?.Completion as VSInternalCompletionSetting;
+            }
+            else
+            {
+                SupportVSInternalClientCapabilities = false;
+                _vsCompletionSetting = null;
+            }
+
+            SupportVSInternalCompletionListData = SupportVSInternalClientCapabilities && _vsCompletionSetting?.CompletionList?.Data == true;
+            SupportVSInternalDefaultCommitCharacters = SupportVSInternalClientCapabilities && _vsCompletionSetting?.CompletionList?.CommitCharacters == true;
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionHandler.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionHandler.cs
index 84dbb97bd1a92..2741c24cd9d4f 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionHandler.cs
@@ -3,14 +3,12 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Composition;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Completion;
-using Microsoft.CodeAnalysis.Completion.Providers;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.LanguageServer.Handler.Completion;
 using Microsoft.CodeAnalysis.Options;
@@ -29,10 +27,7 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler
     [Method(LSP.Methods.TextDocumentCompletionName)]
     internal sealed partial class CompletionHandler : ILspServiceDocumentRequestHandler<LSP.CompletionParams, LSP.CompletionList?>
     {
-
         private readonly IGlobalOptionService _globalOptions;
-        private readonly ImmutableHashSet<char> _csharpTriggerCharacters;
-        private readonly ImmutableHashSet<char> _vbTriggerCharacters;
 
         public bool MutatesSolutionState => false;
         public bool RequiresLSPSolution => true;
@@ -40,15 +35,9 @@ internal sealed partial class CompletionHandler : ILspServiceDocumentRequestHand
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public CompletionHandler(
-            IGlobalOptionService globalOptions,
-            [ImportMany] IEnumerable<Lazy<CompletionProvider, CompletionProviderMetadata>> completionProviders)
+            IGlobalOptionService globalOptions)
         {
             _globalOptions = globalOptions;
-
-            _csharpTriggerCharacters = completionProviders.Where(lz => lz.Metadata.Language == LanguageNames.CSharp).SelectMany(
-                lz => CommonCompletionUtilities.GetTriggerCharacters(lz.Value)).ToImmutableHashSet();
-            _vbTriggerCharacters = completionProviders.Where(lz => lz.Metadata.Language == LanguageNames.VisualBasic).SelectMany(
-                lz => CommonCompletionUtilities.GetTriggerCharacters(lz.Value)).ToImmutableHashSet();
         }
 
         public LSP.TextDocumentIdentifier GetTextDocumentIdentifier(LSP.CompletionParams request) => request.TextDocument;
@@ -56,51 +45,34 @@ public CompletionHandler(
         public async Task<LSP.CompletionList?> HandleRequestAsync(
             LSP.CompletionParams request, RequestContext context, CancellationToken cancellationToken)
         {
-            var document = context.Document;
-            Contract.ThrowIfNull(document);
+            Contract.ThrowIfNull(context.Document);
             Contract.ThrowIfNull(context.Solution);
-            var clientCapabilities = context.GetRequiredClientCapabilities();
-
-            // C# and VB share the same LSP language server, and thus share the same default trigger characters.
-            // We need to ensure the trigger character is valid in the document's language. For example, the '{'
-            // character, while a trigger character in VB, is not a trigger character in C#.
-            if (request.Context != null &&
-                request.Context.TriggerKind == LSP.CompletionTriggerKind.TriggerCharacter &&
-                !char.TryParse(request.Context.TriggerCharacter, out var triggerCharacter) &&
-                !char.IsLetterOrDigit(triggerCharacter) &&
-                !IsValidTriggerCharacterForDocument(document, triggerCharacter))
+
+            var document = context.Document;
+            var documentText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
+            var capabilityHelper = new CompletionCapabilityHelper(context.GetRequiredClientCapabilities());
+
+            var position = await document.GetPositionFromLinePositionAsync(ProtocolConversions.PositionToLinePosition(request.Position), cancellationToken).ConfigureAwait(false);
+            var completionTrigger = await ProtocolConversions.LSPToRoslynCompletionTriggerAsync(request.Context, document, position, cancellationToken).ConfigureAwait(false);
+            var completionOptions = GetCompletionOptions(document, capabilityHelper);
+            var completionService = document.GetRequiredLanguageService<CompletionService>();
+
+            // Let CompletionService decide if we should trigger completion, unless the request is for incomplete results, in which case we always trigger. 
+            if (request.Context?.TriggerKind is not LSP.CompletionTriggerKind.TriggerForIncompleteCompletions
+                && !completionService.ShouldTriggerCompletion(document.Project, document.Project.Services, documentText, position, completionTrigger, completionOptions, document.Project.Solution.Options, roles: null))
             {
                 return null;
             }
 
-            var completionOptions = GetCompletionOptions(document);
-            var completionService = document.GetRequiredLanguageService<CompletionService>();
-            var documentText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
-
             var completionListResult = await GetFilteredCompletionListAsync(request, context, documentText, document, completionOptions, completionService, cancellationToken).ConfigureAwait(false);
             if (completionListResult == null)
                 return null;
 
             var (list, isIncomplete, resultId) = completionListResult.Value;
-            return await ConvertToLspCompletionListAsync(document, clientCapabilities, list, isIncomplete, resultId, cancellationToken)
-                .ConfigureAwait(false);
-
-            // Local function
-            bool IsValidTriggerCharacterForDocument(Document document, char triggerCharacter)
-            {
-                if (document.Project.Language == LanguageNames.CSharp)
-                {
-                    return _csharpTriggerCharacters.Contains(triggerCharacter);
-                }
-                else if (document.Project.Language == LanguageNames.VisualBasic)
-                {
-                    return _vbTriggerCharacters.Contains(triggerCharacter);
-                }
 
-                // Typescript still calls into this for completion.
-                // Since we don't know what their trigger characters are, just return true.
-                return true;
-            }
+            var creationService = document.Project.Solution.Services.GetRequiredService<ILspCompletionResultCreationService>();
+            return await creationService.ConvertToLspCompletionListAsync(document, position, capabilityHelper, list, isIncomplete, resultId, cancellationToken)
+                .ConfigureAwait(false);
         }
 
         private async Task<(CompletionList CompletionList, bool IsIncomplete, long ResultId)?> GetFilteredCompletionListAsync(
@@ -173,7 +145,11 @@ private static (CompletionList CompletionList, bool IsIncomplete) FilterCompleti
             CompletionTrigger completionTrigger,
             SourceText sourceText)
         {
+            if (completionListMaxSize < 0 || completionListMaxSize >= completionList.ItemsList.Count)
+                return (completionList, false);
+
             var filterText = sourceText.GetSubText(completionList.Span).ToString();
+            var filterReason = GetFilterReason(completionTrigger);
 
             // Use pattern matching to determine which items are most relevant out of the calculated items.
             using var _ = ArrayBuilder<MatchResult>.GetInstance(out var matchResultsBuilder);
@@ -184,7 +160,7 @@ private static (CompletionList CompletionList, bool IsIncomplete) FilterCompleti
                 if (helper.TryCreateMatchResult(
                     item,
                     completionTrigger.Kind,
-                    GetFilterReason(completionTrigger),
+                    filterReason,
                     recentItemIndex: -1,
                     includeMatchSpans: false,
                     index,
@@ -201,10 +177,10 @@ private static (CompletionList CompletionList, bool IsIncomplete) FilterCompleti
             // Finally, truncate the list to 1000 items plus any preselected items that occur after the first 1000.
             var filteredList = matchResultsBuilder
                 .Take(completionListMaxSize)
-                .Concat(matchResultsBuilder.Skip(completionListMaxSize).Where(match => ShouldItemBePreselected(match.CompletionItem)))
+                .Concat(matchResultsBuilder.Skip(completionListMaxSize).Where(match => match.CompletionItem.Rules.MatchPriority == MatchPriority.Preselect))
                 .Select(matchResult => matchResult.CompletionItem)
                 .ToImmutableArray();
-            var newCompletionList = completionList.WithItems(filteredList);
+            var newCompletionList = completionList.WithItemsList(filteredList);
 
             // Per the LSP spec, the completion list should be marked with isIncomplete = false when further insertions will
             // not generate any more completion items.  This means that we should be checking if the matchedResults is larger
@@ -233,32 +209,36 @@ static CompletionFilterReason GetFilterReason(CompletionTrigger trigger)
             }
         }
 
-        public static bool ShouldItemBePreselected(CompletionItem completionItem)
+        private CompletionOptions GetCompletionOptions(Document document, CompletionCapabilityHelper capabilityHelper)
         {
-            // An item should be preselected for LSP when the match priority is preselect and the item is hard selected.
-            // LSP does not support soft preselection, so we do not preselect in that scenario to avoid interfering with
-            // typing.
-            return completionItem.Rules.MatchPriority == MatchPriority.Preselect && completionItem.Rules.SelectionBehavior == CompletionItemSelectionBehavior.HardSelection;
-        }
+            var options = _globalOptions.GetCompletionOptions(document.Project.Language);
 
-        internal CompletionOptions GetCompletionOptions(Document document)
-        {
-            // Filter out unimported types for now as there are two issues with providing them:
-            // 1.  LSP client does not currently provide a way to provide detail text on the completion item to show the namespace.
-            //     https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1076759
-            // 2.  We need to figure out how to provide the text edits along with the completion item or provide them in the resolve request.
-            //     https://devdiv.visualstudio.com/DevDiv/_workitems/edit/985860/
-            // 3.  LSP client should support completion filters / expanders
-            //
-            // Also don't trigger completion in argument list automatically, since LSP currently has no concept of soft selection.
-            // We want to avoid committing selected item with commit chars like `"` and `)`.
-            return _globalOptions.GetCompletionOptions(document.Project.Language) with
+            if (capabilityHelper.SupportVSInternalClientCapabilities)
             {
-                ShowItemsFromUnimportedNamespaces = false,
-                ExpandedCompletionBehavior = ExpandedCompletionMode.NonExpandedItemsOnly,
-                UpdateImportCompletionCacheInBackground = false,
-                TriggerInArgumentLists = false
-            };
+                // Filter out unimported types for now as there are two issues with providing them:
+                // 1.  LSP client does not currently provide a way to provide detail text on the completion item to show the namespace.
+                //     https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1076759
+                // 2.  We need to figure out how to provide the text edits along with the completion item or provide them in the resolve request.
+                //     https://devdiv.visualstudio.com/DevDiv/_workitems/edit/985860/
+                // 3.  LSP client should support completion filters / expanders
+                options = options with
+                {
+                    ShowItemsFromUnimportedNamespaces = false,
+                    ExpandedCompletionBehavior = ExpandedCompletionMode.NonExpandedItemsOnly,
+                    UpdateImportCompletionCacheInBackground = false,
+                };
+            }
+            else
+            {
+                var updateImportCompletionCacheInBackground = options.ShowItemsFromUnimportedNamespaces is true;
+                options = options with
+                {
+                    ShowNewSnippetExperienceUserOption = false,
+                    UpdateImportCompletionCacheInBackground = updateImportCompletionCacheInBackground
+                };
+            }
+
+            return options;
         }
     }
 }
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionHandler_CreateLspList.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionHandler_CreateLspList.cs
deleted file mode 100644
index 128c78b40acb7..0000000000000
--- a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionHandler_CreateLspList.cs
+++ /dev/null
@@ -1,281 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System;
-using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Diagnostics.CodeAnalysis;
-using System.Linq;
-using System.Threading;
-using System.Threading.Tasks;
-using Microsoft.CodeAnalysis.Completion;
-using Microsoft.CodeAnalysis.LanguageServer.Handler.Completion;
-using Microsoft.CodeAnalysis.PooledObjects;
-using Microsoft.CodeAnalysis.Shared.Extensions;
-using Roslyn.Utilities;
-using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
-
-namespace Microsoft.CodeAnalysis.LanguageServer.Handler
-{
-    internal sealed partial class CompletionHandler
-    {
-        internal const string EditRangeSetting = "editRange";
-
-        private static async Task<LSP.CompletionList> ConvertToLspCompletionListAsync(
-            Document document,
-            LSP.ClientCapabilities clientCapabilities,
-            CompletionList list, bool isIncomplete, long resultId,
-            CancellationToken cancellationToken)
-        {
-            if (list.ItemsList.Count == 0)
-            {
-                return new LSP.VSInternalCompletionList
-                {
-                    Items = Array.Empty<LSP.CompletionItem>(),
-                    // If we have a suggestion mode item, we just need to keep the list in suggestion mode.
-                    // We don't need to return the fake suggestion mode item.
-                    SuggestionMode = list.SuggestionModeItem is not null,
-                    IsIncomplete = isIncomplete,
-                };
-            }
-
-            var lspVSClientCapability = clientCapabilities.HasVisualStudioLspCapability() == true;
-
-            var completionCapabilities = clientCapabilities.TextDocument?.Completion;
-            var supportedKinds = completionCapabilities?.CompletionItemKind?.ValueSet?.ToSet() ?? new HashSet<LSP.CompletionItemKind>();
-            var itemDefaultsSupported = completionCapabilities?.CompletionListSetting?.ItemDefaults?.Contains(EditRangeSetting) == true;
-
-            // We use the default completion list span as our comparison point for optimization when generating the TextEdits later on.
-            var defaultSpan = list.Span;
-            var documentText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
-            var defaultRange = ProtocolConversions.TextSpanToRange(defaultSpan, documentText);
-
-            // Set resolve data on list if the client supports it, otherwise set it on each item.
-            var resolveData = new CompletionResolveData() { ResultId = resultId };
-            var (completionItemResolveData, completionListResolvedData) = clientCapabilities.HasCompletionListDataCapability()
-                ? (null as CompletionResolveData, resolveData)
-                : (resolveData, null);
-
-            using var _ = ArrayBuilder<LSP.CompletionItem>.GetInstance(out var lspCompletionItems);
-            var commitCharactersRuleCache = new Dictionary<ImmutableArray<CharacterSetModificationRule>, string[]>(CommitCharacterArrayComparer.Instance);
-
-            foreach (var item in list.ItemsList)
-                lspCompletionItems.Add(await CreateLSPCompletionItemAsync(item).ConfigureAwait(false));
-
-            var completionList = new LSP.VSInternalCompletionList
-            {
-                Items = lspCompletionItems.ToArray(),
-                SuggestionMode = list.SuggestionModeItem != null,
-                IsIncomplete = isIncomplete,
-                Data = completionListResolvedData,
-            };
-
-            if (clientCapabilities.HasCompletionListCommitCharactersCapability())
-                PromoteCommonCommitCharactersOntoList(completionList);
-
-            if (itemDefaultsSupported)
-            {
-                completionList.ItemDefaults = new LSP.CompletionListItemDefaults
-                {
-                    EditRange = defaultRange,
-                };
-            }
-
-            return new LSP.OptimizedVSCompletionList(completionList);
-
-            async Task<LSP.CompletionItem> CreateLSPCompletionItemAsync(CompletionItem item)
-            {
-                var snippetsSupported = completionCapabilities?.CompletionItem?.SnippetSupport ?? false;
-                var creationService = document.Project.Solution.Services.GetRequiredService<ILspCompletionResultCreationService>();
-
-                // Defer to host to create the actual completion item (including potential subclasses), and add any
-                // custom information.
-                var lspItem = await creationService.CreateAsync(
-                    document, documentText, snippetsSupported, itemDefaultsSupported, defaultSpan, item, cancellationToken).ConfigureAwait(false);
-
-                // Now add data common to all hosts.
-                lspItem.Data = completionItemResolveData;
-                lspItem.Label = $"{item.DisplayTextPrefix}{item.DisplayText}{item.DisplayTextSuffix}";
-
-                lspItem.SortText = item.SortText;
-                lspItem.FilterText = item.FilterText;
-
-                lspItem.Kind = GetCompletionKind(item.Tags, supportedKinds);
-                lspItem.Preselect = ShouldItemBePreselected(item);
-
-                lspItem.CommitCharacters = GetCommitCharacters(item, commitCharactersRuleCache, lspVSClientCapability);
-
-                return lspItem;
-            }
-
-            static LSP.CompletionItemKind GetCompletionKind(
-                ImmutableArray<string> tags,
-                ISet<LSP.CompletionItemKind> supportedClientKinds)
-            {
-                foreach (var tag in tags)
-                {
-                    if (ProtocolConversions.RoslynTagToCompletionItemKinds.TryGetValue(tag, out var completionItemKinds))
-                    {
-                        // Always at least pick the core kind provided.
-                        var kind = completionItemKinds[0];
-
-                        // If better kinds are preferred, return them if the client supports them.
-                        for (var i = 1; i < completionItemKinds.Length; i++)
-                        {
-                            var preferredKind = completionItemKinds[i];
-                            if (supportedClientKinds.Contains(preferredKind))
-                                kind = preferredKind;
-                        }
-
-                        return kind;
-                    }
-                }
-
-                return LSP.CompletionItemKind.Text;
-            }
-
-            static string[]? GetCommitCharacters(
-                CompletionItem item,
-                Dictionary<ImmutableArray<CharacterSetModificationRule>, string[]> currentRuleCache,
-                bool supportsVSExtensions)
-            {
-                // VSCode does not have the concept of soft selection, the list is always hard selected.
-                // In order to emulate soft selection behavior for things like argument completion, regex completion, datetime completion, etc
-                // we create a completion item without any specific commit characters.  This means only tab / enter will commit.
-                // VS supports soft selection, so we only do this for non-VS clients.
-                if (!supportsVSExtensions && item.Rules.SelectionBehavior == CompletionItemSelectionBehavior.SoftSelection)
-                    return Array.Empty<string>();
-
-                var commitCharacterRules = item.Rules.CommitCharacterRules;
-
-                // VS will use the default commit characters if no items are specified on the completion item.
-                // However, other clients like VSCode do not support this behavior so we must specify
-                // commit characters on every completion item - https://github.com/microsoft/vscode/issues/90987
-                if (supportsVSExtensions && commitCharacterRules.IsEmpty)
-                    return null;
-
-                if (!currentRuleCache.TryGetValue(commitCharacterRules, out var cachedCommitCharacters))
-                {
-                    using var _ = PooledHashSet<char>.GetInstance(out var commitCharacters);
-                    commitCharacters.AddAll(CompletionRules.Default.DefaultCommitCharacters);
-                    foreach (var rule in commitCharacterRules)
-                    {
-                        switch (rule.Kind)
-                        {
-                            case CharacterSetModificationKind.Add:
-                                commitCharacters.UnionWith(rule.Characters);
-                                continue;
-                            case CharacterSetModificationKind.Remove:
-                                commitCharacters.ExceptWith(rule.Characters);
-                                continue;
-                            case CharacterSetModificationKind.Replace:
-                                commitCharacters.Clear();
-                                commitCharacters.AddRange(rule.Characters);
-                                break;
-                        }
-                    }
-
-                    cachedCommitCharacters = commitCharacters.Select(c => c.ToString()).ToArray();
-                    currentRuleCache.Add(item.Rules.CommitCharacterRules, cachedCommitCharacters);
-                }
-
-                return cachedCommitCharacters;
-            }
-
-            static void PromoteCommonCommitCharactersOntoList(LSP.VSInternalCompletionList completionList)
-            {
-                if (completionList.Items.IsEmpty())
-                {
-                    return;
-                }
-
-                var defaultCommitCharacters = CompletionRules.Default.DefaultCommitCharacters.Select(c => c.ToString()).ToArray();
-                var commitCharacterReferences = new Dictionary<object, int>();
-                var mostUsedCount = 0;
-                string[]? mostUsedCommitCharacters = null;
-                for (var i = 0; i < completionList.Items.Length; i++)
-                {
-                    var completionItem = completionList.Items[i];
-                    var commitCharacters = completionItem.CommitCharacters;
-                    // The commit characters on the item are null, this means the commit characters are actually
-                    // the default commit characters we passed in the initialize request.
-                    commitCharacters ??= defaultCommitCharacters;
-
-                    commitCharacterReferences.TryGetValue(commitCharacters, out var existingCount);
-                    existingCount++;
-
-                    if (existingCount > mostUsedCount)
-                    {
-                        // Capture the most used commit character counts so we don't need to re-iterate the array later
-                        mostUsedCommitCharacters = commitCharacters;
-                        mostUsedCount = existingCount;
-                    }
-
-                    commitCharacterReferences[commitCharacters] = existingCount;
-                }
-
-                Contract.ThrowIfNull(mostUsedCommitCharacters);
-
-                // Promoted the most used commit characters onto the list and then remove these from child items.
-                completionList.CommitCharacters = mostUsedCommitCharacters;
-                for (var i = 0; i < completionList.Items.Length; i++)
-                {
-                    var completionItem = completionList.Items[i];
-                    if (completionItem.CommitCharacters == mostUsedCommitCharacters)
-                    {
-                        completionItem.CommitCharacters = null;
-                    }
-                }
-            }
-        }
-
-        private sealed class CommitCharacterArrayComparer : IEqualityComparer<ImmutableArray<CharacterSetModificationRule>>
-        {
-            public static readonly CommitCharacterArrayComparer Instance = new();
-
-            private CommitCharacterArrayComparer()
-            {
-            }
-
-            public bool Equals([AllowNull] ImmutableArray<CharacterSetModificationRule> x, [AllowNull] ImmutableArray<CharacterSetModificationRule> y)
-            {
-                if (x == y)
-                    return true;
-
-                for (var i = 0; i < x.Length; i++)
-                {
-                    var xKind = x[i].Kind;
-                    var yKind = y[i].Kind;
-                    if (xKind != yKind)
-                    {
-                        return false;
-                    }
-
-                    var xCharacters = x[i].Characters;
-                    var yCharacters = y[i].Characters;
-                    if (xCharacters.Length != yCharacters.Length)
-                    {
-                        return false;
-                    }
-
-                    for (var j = 0; j < xCharacters.Length; j++)
-                    {
-                        if (xCharacters[j] != yCharacters[j])
-                        {
-                            return false;
-                        }
-                    }
-                }
-
-                return true;
-            }
-
-            public int GetHashCode([DisallowNull] ImmutableArray<CharacterSetModificationRule> obj)
-            {
-                var combinedHash = Hash.CombineValues(obj);
-                return combinedHash;
-            }
-        }
-    }
-}
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveData.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveData.cs
index 65e3842672af9..ae7d7f77a6e55 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveData.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveData.cs
@@ -2,16 +2,15 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Microsoft.CodeAnalysis.LanguageServer.Handler.Completion;
 using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
 
-namespace Microsoft.CodeAnalysis.LanguageServer.Handler
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Completion
 {
     /// <summary>
     /// Provides the intermediate data passed from CompletionHandler to CompletionResolveHandler.
     /// Passed along via <see cref="LSP.CompletionItem.Data"/>.
     /// </summary>
-    internal class CompletionResolveData
+    internal sealed class CompletionResolveData
     {
         /// <summary>
         /// ID associated with the item's completion list.
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveHandler.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveHandler.cs
index 000bc5ea483b9..5160438651564 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Completion/CompletionResolveHandler.cs
@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -44,11 +43,6 @@ public CompletionResolveHandler(IGlobalOptionService globalOptions, CompletionLi
 
         public async Task<LSP.CompletionItem> HandleRequestAsync(LSP.CompletionItem completionItem, RequestContext context, CancellationToken cancellationToken)
         {
-            var document = context.GetRequiredDocument();
-            var clientCapabilities = context.GetRequiredClientCapabilities();
-
-            var completionService = document.Project.Services.GetRequiredService<CompletionService>();
-
             var cacheEntry = GetCompletionListCacheEntry(completionItem);
             if (cacheEntry == null)
             {
@@ -57,6 +51,9 @@ public CompletionResolveHandler(IGlobalOptionService globalOptions, CompletionLi
                 return completionItem;
             }
 
+            var document = context.GetRequiredDocument();
+            var completionService = document.Project.Services.GetRequiredService<CompletionService>();
+
             // Find the matching completion item in the completion list
             var selectedItem = cacheEntry.CompletionList.ItemsList.FirstOrDefault(cachedCompletionItem => MatchesLSPCompletionItem(completionItem, cachedCompletionItem));
 
@@ -69,8 +66,9 @@ public CompletionResolveHandler(IGlobalOptionService globalOptions, CompletionLi
                 await creationService.ResolveAsync(
                     completionItem,
                     selectedItem,
+                    cacheEntry.TextDocument,
                     document,
-                    clientCapabilities,
+                    new CompletionCapabilityHelper(context.GetRequiredClientCapabilities()),
                     completionService,
                     completionOptions,
                     symbolDescriptionOptions,
@@ -82,24 +80,7 @@ await creationService.ResolveAsync(
 
         private static bool MatchesLSPCompletionItem(LSP.CompletionItem lspCompletionItem, CompletionItem completionItem)
         {
-            if (!lspCompletionItem.Label.StartsWith(completionItem.DisplayTextPrefix, StringComparison.Ordinal))
-            {
-                return false;
-            }
-
-            // The prefix matches, consume the matching prefix from the lsp completion item label.
-            var displayTextWithSuffix = lspCompletionItem.Label[completionItem.DisplayTextPrefix.Length..];
-            if (!displayTextWithSuffix.EndsWith(completionItem.DisplayTextSuffix, StringComparison.Ordinal))
-            {
-                return false;
-            }
-
-            // The suffix matches, consume the matching suffix from the lsp completion item label.
-            var originalDisplayText = displayTextWithSuffix[..^completionItem.DisplayTextSuffix.Length];
-
-            // Now we're left with what should be the original display text for the lsp completion item.
-            // Check to make sure it matches the cached completion item label.
-            return string.Equals(originalDisplayText, completionItem.DisplayText);
+            return lspCompletionItem.Label == completionItem.GetEntireDisplayText();
         }
 
         private CompletionListCache.CacheEntry? GetCompletionListCacheEntry(LSP.CompletionItem request)
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/DefaultLspCompletionResultCreationService.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/DefaultLspCompletionResultCreationService.cs
new file mode 100644
index 0000000000000..cf0262481470a
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/Completion/DefaultLspCompletionResultCreationService.cs
@@ -0,0 +1,114 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Completion;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageService;
+using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
+using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Completion
+{
+    [ExportWorkspaceService(typeof(ILspCompletionResultCreationService), ServiceLayer.Default), Shared]
+    internal sealed class DefaultLspCompletionResultCreationService : AbstractLspCompletionResultCreationService
+    {
+        /// <summary>
+        /// Command name implemented by the client and invoked when an item with complex edit is committed.
+        /// </summary>
+        public const string CompleteComplexEditCommand = "roslyn.client.completionComplexEdit";
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public DefaultLspCompletionResultCreationService()
+        {
+        }
+
+        protected override async Task<LSP.CompletionItem> CreateItemAndPopulateTextEditAsync(Document document,
+            SourceText documentText,
+            bool snippetsSupported,
+            bool itemDefaultsSupported,
+            TextSpan defaultSpan,
+            string typedText,
+            CompletionItem item,
+            CompletionService completionService,
+            CancellationToken cancellationToken)
+        {
+            var lspItem = new LSP.CompletionItem() { Label = item.GetEntireDisplayText() };
+
+            if (item.IsComplexTextEdit)
+            {
+                //await completionService.GetChangeAsync(document, item, cancellationToken: cancellationToken).ConfigureAwait(false);
+                // For unimported item, we use display text (type or method name) as the text edit text, and rely on resolve handler to add missing import as additional edit.
+                // For other complex edit item, we return a no-op edit and rely on resolve handler to compute the actual change and provide the command to apply it.
+                var completionChangeNewText = item.Flags.IsExpanded() ? item.DisplayText : typedText;
+                PopulateTextEdit(lspItem, completionChangeSpan: defaultSpan, completionChangeNewText, documentText, itemDefaultsSupported, defaultSpan: defaultSpan);
+            }
+            else
+            {
+                await GetChangeAndPopulateSimpleTextEditAsync(
+                    document,
+                    documentText,
+                    itemDefaultsSupported,
+                    defaultSpan,
+                    item,
+                    lspItem,
+                    completionService,
+                    cancellationToken).ConfigureAwait(false);
+            }
+
+            return lspItem;
+        }
+
+        public override async Task<LSP.CompletionItem> ResolveAsync(
+            LSP.CompletionItem lspItem,
+            CompletionItem roslynItem,
+            LSP.TextDocumentIdentifier textDocumentIdentifier,
+            Document document,
+            CompletionCapabilityHelper capabilityHelper,
+            CompletionService completionService,
+            CompletionOptions completionOptions,
+            SymbolDescriptionOptions symbolDescriptionOptions,
+            CancellationToken cancellationToken)
+        {
+            var description = await completionService.GetDescriptionAsync(document, roslynItem, completionOptions, symbolDescriptionOptions, cancellationToken).ConfigureAwait(false)!;
+            if (description != null)
+            {
+                lspItem.Documentation = ProtocolConversions.GetDocumentationMarkupContent(description.TaggedParts, document, capabilityHelper.SupportsMarkdownDocumentation);
+            }
+
+            if (roslynItem.IsComplexTextEdit)
+            {
+                if (roslynItem.Flags.IsExpanded())
+                {
+                    var additionalEdits = await GenerateAdditionalTextEditForImportCompletionAsync(roslynItem, document, completionService, cancellationToken).ConfigureAwait(false);
+                    lspItem.AdditionalTextEdits = additionalEdits;
+                }
+                else
+                {
+                    var (textEdit, isSnippetString, newPosition) = await GenerateComplexTextEditAsync(
+                        document, completionService, roslynItem, capabilityHelper.SupportSnippets, insertNewPositionPlaceholder: false, cancellationToken).ConfigureAwait(false);
+
+                    var lspOffset = newPosition is null ? -1 : newPosition.Value;
+
+                    lspItem.Command = lspItem.Command = new LSP.Command()
+                    {
+                        CommandIdentifier = CompleteComplexEditCommand,
+                        Title = nameof(CompleteComplexEditCommand),
+                        Arguments = new object[] { textDocumentIdentifier.Uri, textEdit, isSnippetString, lspOffset }
+                    };
+                }
+            }
+
+            if (!roslynItem.InlineDescription.IsEmpty())
+                lspItem.LabelDetails = new() { Description = roslynItem.InlineDescription };
+
+            return lspItem;
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/Completion/ILspCompletionResultCreationService.cs b/src/Features/LanguageServer/Protocol/Handler/Completion/ILspCompletionResultCreationService.cs
index b955a56962ec4..b197f18bcea41 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Completion/ILspCompletionResultCreationService.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Completion/ILspCompletionResultCreationService.cs
@@ -2,119 +2,34 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Composition;
-using System.Diagnostics;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Completion;
 using Microsoft.CodeAnalysis.Host;
-using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.LanguageService;
-using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Text;
-using Roslyn.Utilities;
 using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Completion
 {
     internal interface ILspCompletionResultCreationService : IWorkspaceService
     {
-        Task<LSP.CompletionItem> CreateAsync(
+        Task<LSP.CompletionList> ConvertToLspCompletionListAsync(
             Document document,
-            SourceText documentText,
-            bool snippetsSupported,
-            bool itemDefaultsSupported,
-            TextSpan defaultSpan,
-            CompletionItem item,
+            int position,
+            CompletionCapabilityHelper capabilityHelper,
+            CompletionList list, bool isIncomplete, long resultId,
             CancellationToken cancellationToken);
 
         Task<LSP.CompletionItem> ResolveAsync(
-            LSP.CompletionItem completionItem,
-            CompletionItem selectedItem,
+            LSP.CompletionItem lspItem,
+            CompletionItem roslynItem,
+            LSP.TextDocumentIdentifier textDocumentIdentifier,
             Document document,
-            LSP.ClientCapabilities clientCapabilities,
+            CompletionCapabilityHelper capabilityHelper,
             CompletionService completionService,
             CompletionOptions completionOptions,
             SymbolDescriptionOptions symbolDescriptionOptions,
             CancellationToken cancellationToken);
     }
-
-    [ExportWorkspaceService(typeof(ILspCompletionResultCreationService)), Shared]
-    internal sealed class DefaultLspCompletionResultCreationService : ILspCompletionResultCreationService
-    {
-        [ImportingConstructor]
-        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public DefaultLspCompletionResultCreationService()
-        {
-        }
-
-        public async Task<LSP.CompletionItem> CreateAsync(
-            Document document,
-            SourceText documentText,
-            bool snippetsSupported,
-            bool itemDefaultsSupported,
-            TextSpan defaultSpan,
-            CompletionItem item,
-            CancellationToken cancellationToken)
-        {
-            var completionItem = new LSP.CompletionItem();
-            await PopulateTextEditAsync(document, documentText, itemDefaultsSupported, defaultSpan, item, completionItem, cancellationToken).ConfigureAwait(false);
-            return completionItem;
-        }
-
-        public async Task<LSP.CompletionItem> ResolveAsync(
-            LSP.CompletionItem completionItem,
-            CompletionItem selectedItem,
-            Document document,
-            LSP.ClientCapabilities clientCapabilities,
-            CompletionService completionService,
-            CompletionOptions completionOptions,
-            SymbolDescriptionOptions symbolDescriptionOptions,
-            CancellationToken cancellationToken)
-        {
-            var description = await completionService.GetDescriptionAsync(document, selectedItem, completionOptions, symbolDescriptionOptions, cancellationToken).ConfigureAwait(false)!;
-            if (description != null)
-            {
-                var clientSupportsMarkdown = clientCapabilities.TextDocument?.Completion?.CompletionItem?.DocumentationFormat?.Contains(LSP.MarkupKind.Markdown) == true;
-                completionItem.Documentation = ProtocolConversions.GetDocumentationMarkupContent(description.TaggedParts, document, clientSupportsMarkdown);
-            }
-
-            return completionItem;
-        }
-
-        public static async Task PopulateTextEditAsync(
-            Document document,
-            SourceText documentText,
-            bool itemDefaultsSupported,
-            TextSpan defaultSpan,
-            CompletionItem item,
-            LSP.CompletionItem lspItem,
-            CancellationToken cancellationToken)
-        {
-            var completionService = document.GetRequiredLanguageService<CompletionService>();
-
-            var completionChange = await completionService.GetChangeAsync(
-                document, item, cancellationToken: cancellationToken).ConfigureAwait(false);
-            var completionChangeSpan = completionChange.TextChange.Span;
-            var newText = completionChange.TextChange.NewText ?? "";
-
-            if (itemDefaultsSupported && completionChangeSpan == defaultSpan)
-            {
-                // The span is the same as the default, we just need to store the new text as
-                // the insert text so the client can create the text edit from it and the default range.
-                lspItem.InsertText = newText;
-            }
-            else
-            {
-                Debug.Assert(completionChangeSpan == defaultSpan || item.IsComplexTextEdit);
-                lspItem.TextEdit = new LSP.TextEdit()
-                {
-                    NewText = newText,
-                    Range = ProtocolConversions.TextSpanToRange(completionChangeSpan, documentText),
-                };
-            }
-        }
-    }
 }
diff --git a/src/Features/LanguageServer/Protocol/Handler/Configuration/DidChangeConfigurationNotificationHandler_OptionList.cs b/src/Features/LanguageServer/Protocol/Handler/Configuration/DidChangeConfigurationNotificationHandler_OptionList.cs
index ba6470f52af46..e2e25c2880876 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Configuration/DidChangeConfigurationNotificationHandler_OptionList.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Configuration/DidChangeConfigurationNotificationHandler_OptionList.cs
@@ -5,11 +5,13 @@
 using System.Collections.Immutable;
 using Microsoft.CodeAnalysis.Completion;
 using Microsoft.CodeAnalysis.DocumentHighlighting;
+using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.ImplementType;
 using Microsoft.CodeAnalysis.InlineHints;
 using Microsoft.CodeAnalysis.MetadataAsSource;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.QuickInfo;
+using Microsoft.CodeAnalysis.SolutionCrawler;
 using Microsoft.CodeAnalysis.SymbolSearch;
 
 namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Configuration
@@ -26,6 +28,7 @@ internal partial class DidChangeConfigurationNotificationHandler
             CompletionOptionsStorage.ShowNameSuggestions,
             CompletionOptionsStorage.ShowItemsFromUnimportedNamespaces,
             CompletionOptionsStorage.ProvideRegexCompletions,
+            CompletionOptionsStorage.ShowItemsFromUnimportedNamespaces,
             QuickInfoOptionsStorage.ShowRemarksInQuickInfo,
             // Go to definition
             MetadataAsSourceOptionsStorage.NavigateToDecompiledSources,
@@ -44,6 +47,15 @@ internal partial class DidChangeConfigurationNotificationHandler
             InlineHintsOptionsStorage.EnabledForTypes,
             InlineHintsOptionsStorage.ForImplicitVariableTypes,
             InlineHintsOptionsStorage.ForLambdaParameterTypes,
-            InlineHintsOptionsStorage.ForImplicitObjectCreation);
+            InlineHintsOptionsStorage.ForImplicitObjectCreation,
+            // EditorConfig
+            FormattingOptions2.TabSize,
+            FormattingOptions2.IndentationSize,
+            FormattingOptions2.UseTabs,
+            FormattingOptions2.NewLine,
+            FormattingOptions2.InsertFinalNewLine,
+            // Background analysis
+            SolutionCrawlerOptionsStorage.BackgroundAnalysisScopeOption,
+            SolutionCrawlerOptionsStorage.CompilerDiagnosticsScopeOption);
     }
 }
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/AbstractPullDiagnosticHandler.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/AbstractPullDiagnosticHandler.cs
index 8a25b1a252647..6f0a770f4fadb 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/AbstractPullDiagnosticHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/AbstractPullDiagnosticHandler.cs
@@ -6,10 +6,10 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.EditAndContinue;
 using Microsoft.CodeAnalysis.LanguageServer.Features.Diagnostics;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.PooledObjects;
@@ -25,8 +25,8 @@ internal abstract class AbstractDocumentPullDiagnosticHandler<TDiagnosticsParams
     {
         public AbstractDocumentPullDiagnosticHandler(
             IDiagnosticAnalyzerService diagnosticAnalyzerService,
-            EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
-            IGlobalOptionService globalOptions) : base(diagnosticAnalyzerService, editAndContinueDiagnosticUpdateSource, globalOptions)
+            IDiagnosticsRefresher diagnosticRefresher,
+            IGlobalOptionService globalOptions) : base(diagnosticAnalyzerService, diagnosticRefresher, globalOptions)
         {
         }
 
@@ -50,30 +50,30 @@ internal abstract partial class AbstractPullDiagnosticHandler<TDiagnosticsParams
         protected const int WorkspaceDiagnosticIdentifier = 1;
         protected const int DocumentDiagnosticIdentifier = 2;
 
-        private readonly EditAndContinueDiagnosticUpdateSource _editAndContinueDiagnosticUpdateSource;
+        private readonly IDiagnosticsRefresher _diagnosticRefresher;
         protected readonly IGlobalOptionService GlobalOptions;
 
         protected readonly IDiagnosticAnalyzerService DiagnosticAnalyzerService;
 
         /// <summary>
         /// Cache where we store the data produced by prior requests so that they can be returned if nothing of significance 
-        /// changed. The VersionStamp is produced by <see cref="Project.GetDependentVersionAsync(CancellationToken)"/> while the 
-        /// Checksum is produced by <see cref="Project.GetDependentChecksumAsync(CancellationToken)"/>.  The former is faster
+        /// changed. The <see cref="VersionStamp"/> is produced by <see cref="Project.GetDependentVersionAsync(CancellationToken)"/> while the 
+        /// <see cref="Checksum"/> is produced by <see cref="Project.GetDependentChecksumAsync(CancellationToken)"/>.  The former is faster
         /// and works well for us in the normal case.  The latter still allows us to reuse diagnostics when changes happen that
         /// update the version stamp but not the content (for example, forking LSP text).
         /// </summary>
-        private readonly ConcurrentDictionary<string, VersionedPullCache<(int, VersionStamp?), (int, Checksum)>> _categoryToVersionedCache = new();
+        private readonly ConcurrentDictionary<string, VersionedPullCache<(int globalStateVersion, VersionStamp? dependentVersion), (int globalStateVersion, Checksum dependentChecksum)>> _categoryToVersionedCache = new();
 
         public bool MutatesSolutionState => false;
         public bool RequiresLSPSolution => true;
 
         protected AbstractPullDiagnosticHandler(
             IDiagnosticAnalyzerService diagnosticAnalyzerService,
-            EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+            IDiagnosticsRefresher diagnosticRefresher,
             IGlobalOptionService globalOptions)
         {
             DiagnosticAnalyzerService = diagnosticAnalyzerService;
-            _editAndContinueDiagnosticUpdateSource = editAndContinueDiagnosticUpdateSource;
+            _diagnosticRefresher = diagnosticRefresher;
             GlobalOptions = globalOptions;
         }
 
@@ -163,7 +163,7 @@ protected virtual Task WaitForChangesAsync(RequestContext context, CancellationT
 
             foreach (var diagnosticSource in orderedSources)
             {
-                var encVersion = _editAndContinueDiagnosticUpdateSource.Version;
+                var globalStateVersion = _diagnosticRefresher.GlobalStateVersion;
 
                 var project = diagnosticSource.GetProject();
 
@@ -171,8 +171,8 @@ protected virtual Task WaitForChangesAsync(RequestContext context, CancellationT
                     documentToPreviousDiagnosticParams,
                     diagnosticSource.GetId(),
                     project,
-                    computeCheapVersionAsync: async () => (encVersion, await project.GetDependentVersionAsync(cancellationToken).ConfigureAwait(false)),
-                    computeExpensiveVersionAsync: async () => (encVersion, await project.GetDependentChecksumAsync(cancellationToken).ConfigureAwait(false)),
+                    computeCheapVersionAsync: async () => (globalStateVersion, await project.GetDependentVersionAsync(cancellationToken).ConfigureAwait(false)),
+                    computeExpensiveVersionAsync: async () => (globalStateVersion, await project.GetDependentChecksumAsync(cancellationToken).ConfigureAwait(false)),
                     cancellationToken).ConfigureAwait(false);
                 if (newResultId != null)
                 {
@@ -317,10 +317,7 @@ private void HandleRemovedDocuments(RequestContext context, ImmutableArray<Previ
 
         private ImmutableArray<LSP.Diagnostic> ConvertDiagnostic(IDiagnosticSource diagnosticSource, DiagnosticData diagnosticData, ClientCapabilities capabilities)
         {
-            // VSCode throws on hidden diagnostics without a message (all hint diagnostic messages are rendered on hover).
-            // Roslyn creates these for example in remove unnecessary imports, see RemoveUnnecessaryImportsConstants.DiagnosticFixableId.
-            // TODO - We should probably not be creating these as separate diagnostics or have a 'really really' hidden tag.
-            if (!capabilities.HasVisualStudioLspCapability() && string.IsNullOrEmpty(diagnosticData.Message) && diagnosticData.Severity == DiagnosticSeverity.Hidden)
+            if (!ShouldIncludeHiddenDiagnostic(diagnosticData, capabilities))
             {
                 return ImmutableArray<LSP.Diagnostic>.Empty;
             }
@@ -350,20 +347,38 @@ private void HandleRemovedDocuments(RequestContext context, ImmutableArray<Previ
                 return ImmutableArray.Create<LSP.Diagnostic>(diagnostic);
             }
 
-            // Roslyn produces unnecessary diagnostics by using additional locations, however LSP doesn't support tagging
-            // additional locations separately.  Instead we just create multiple hidden diagnostics for unnecessary squiggling.
-            using var _ = ArrayBuilder<LSP.Diagnostic>.GetInstance(out var diagnosticsBuilder);
-            diagnosticsBuilder.Add(diagnostic);
-            foreach (var location in unnecessaryLocations)
+            if (capabilities.HasVisualStudioLspCapability())
             {
-                var additionalDiagnostic = CreateLspDiagnostic(diagnosticData, project, capabilities);
-                additionalDiagnostic.Severity = LSP.DiagnosticSeverity.Hint;
-                additionalDiagnostic.Range = GetRange(location);
-                additionalDiagnostic.Tags = new DiagnosticTag[] { DiagnosticTag.Unnecessary, VSDiagnosticTags.HiddenInEditor, VSDiagnosticTags.HiddenInErrorList, VSDiagnosticTags.SuppressEditorToolTip };
-                diagnosticsBuilder.Add(additionalDiagnostic);
-            }
+                // Roslyn produces unnecessary diagnostics by using additional locations, however LSP doesn't support tagging
+                // additional locations separately.  Instead we just create multiple hidden diagnostics for unnecessary squiggling.
+                using var _ = ArrayBuilder<LSP.Diagnostic>.GetInstance(out var diagnosticsBuilder);
+                diagnosticsBuilder.Add(diagnostic);
+                foreach (var location in unnecessaryLocations)
+                {
+                    var additionalDiagnostic = CreateLspDiagnostic(diagnosticData, project, capabilities);
+                    additionalDiagnostic.Severity = LSP.DiagnosticSeverity.Hint;
+                    additionalDiagnostic.Range = GetRange(location);
+                    additionalDiagnostic.Tags = new DiagnosticTag[] { DiagnosticTag.Unnecessary, VSDiagnosticTags.HiddenInEditor, VSDiagnosticTags.HiddenInErrorList, VSDiagnosticTags.SuppressEditorToolTip };
+                    diagnosticsBuilder.Add(additionalDiagnostic);
+                }
 
-            return diagnosticsBuilder.ToImmutableArray();
+                return diagnosticsBuilder.ToImmutableArray();
+            }
+            else
+            {
+                diagnostic.Tags = diagnostic.Tags != null ? diagnostic.Tags.Append(DiagnosticTag.Unnecessary) : new DiagnosticTag[] { DiagnosticTag.Unnecessary };
+                var diagnosticRelatedInformation = unnecessaryLocations.Value.Select(l => new DiagnosticRelatedInformation
+                {
+                    Location = new LSP.Location
+                    {
+                        Range = GetRange(l),
+                        Uri = ProtocolConversions.GetUriFromFilePath(l.UnmappedFileSpan.Path)
+                    },
+                    Message = diagnostic.Message
+                }).ToArray();
+                diagnostic.RelatedInformation = diagnosticRelatedInformation;
+                return ImmutableArray.Create<LSP.Diagnostic>(diagnostic);
+            }
 
             LSP.VSDiagnostic CreateLspDiagnostic(
                 DiagnosticData diagnosticData,
@@ -435,6 +450,39 @@ static LSP.Range GetRange(DiagnosticDataLocation dataLocation)
                     }
                 };
             }
+
+            static bool ShouldIncludeHiddenDiagnostic(DiagnosticData diagnosticData, ClientCapabilities capabilities)
+            {
+                // VS can handle us reporting any kind of diagnostic using VS custom tags.
+                if (capabilities.HasVisualStudioLspCapability() == true)
+                {
+                    return true;
+                }
+
+                // Diagnostic isn't hidden - we should report this diagnostic in all scenarios.
+                if (diagnosticData.Severity != DiagnosticSeverity.Hidden)
+                {
+                    return true;
+                }
+
+                // Roslyn creates these for example in remove unnecessary imports, see RemoveUnnecessaryImportsConstants.DiagnosticFixableId.
+                // These aren't meant to be visible in anyway, so we can safely exclude them.
+                // TODO - We should probably not be creating these as separate diagnostics or have a 'really really' hidden tag.
+                if (string.IsNullOrEmpty(diagnosticData.Message))
+                {
+                    return false;
+                }
+
+                // Hidden diagnostics that are unnecessary are visible to the user in the form of fading.
+                // We can report these diagnostics.
+                if (diagnosticData.CustomTags.Contains(WellKnownDiagnosticTags.Unnecessary))
+                {
+                    return true;
+                }
+
+                // We have a hidden diagnostic that has no fading.  This diagnostic can't be visible so don't send it to the client.
+                return false;
+            }
         }
 
         private static VSDiagnosticRank? ConvertRank(DiagnosticData diagnosticData)
@@ -459,7 +507,7 @@ private static LSP.DiagnosticSeverity ConvertDiagnosticSeverity(DiagnosticSeveri
                 // Hidden is translated in ConvertTags to pass along appropriate _ms tags
                 // that will hide the item in a client that knows about those tags.
                 DiagnosticSeverity.Hidden => LSP.DiagnosticSeverity.Hint,
-                DiagnosticSeverity.Info => LSP.DiagnosticSeverity.Hint,
+                DiagnosticSeverity.Info => LSP.DiagnosticSeverity.Information,
                 DiagnosticSeverity.Warning => LSP.DiagnosticSeverity.Warning,
                 DiagnosticSeverity.Error => LSP.DiagnosticSeverity.Error,
                 _ => throw ExceptionUtilities.UnexpectedValue(severity),
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DiagnosticsRefreshQueue.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DiagnosticsRefreshQueue.cs
new file mode 100644
index 0000000000000..c06bc461d1415
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DiagnosticsRefreshQueue.cs
@@ -0,0 +1,107 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using System.Threading;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics;
+
+internal sealed class DiagnosticsRefreshQueue : AbstractRefreshQueue
+{
+    [ExportCSharpVisualBasicLspServiceFactory(typeof(DiagnosticsRefreshQueue)), Shared]
+    internal sealed class Factory : ILspServiceFactory
+    {
+        private readonly IAsynchronousOperationListenerProvider _asyncListenerProvider;
+        private readonly LspWorkspaceRegistrationService _lspWorkspaceRegistrationService;
+        private readonly Refresher _refresher;
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public Factory(
+            IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider,
+            LspWorkspaceRegistrationService lspWorkspaceRegistrationService,
+            Refresher refresher)
+        {
+            _asyncListenerProvider = asynchronousOperationListenerProvider;
+            _lspWorkspaceRegistrationService = lspWorkspaceRegistrationService;
+            _refresher = refresher;
+        }
+
+        public ILspService CreateILspService(LspServices lspServices, WellKnownLspServerKinds serverKind)
+        {
+            var notificationManager = lspServices.GetRequiredService<IClientLanguageServerManager>();
+            var lspWorkspaceManager = lspServices.GetRequiredService<LspWorkspaceManager>();
+
+            return new DiagnosticsRefreshQueue(_asyncListenerProvider, _lspWorkspaceRegistrationService, lspWorkspaceManager, notificationManager, _refresher);
+        }
+    }
+
+    [Shared]
+    [Export(typeof(Refresher))]
+    [Export(typeof(IDiagnosticsRefresher))]
+    internal sealed class Refresher : IDiagnosticsRefresher
+    {
+        /// <summary>
+        /// Incremented every time a refresh is requested.
+        /// </summary>
+        private int _globalStateVersion;
+
+        public event Action? WorkspaceRefreshRequested;
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public Refresher()
+        {
+        }
+
+        public void RequestWorkspaceRefresh()
+        {
+            // bump version before sending the request to the client:
+            Interlocked.Increment(ref _globalStateVersion);
+
+            WorkspaceRefreshRequested?.Invoke();
+        }
+
+        public int GlobalStateVersion
+            => _globalStateVersion;
+    }
+
+    private readonly Refresher _refresher;
+
+    private DiagnosticsRefreshQueue(
+        IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider,
+        LspWorkspaceRegistrationService lspWorkspaceRegistrationService,
+        LspWorkspaceManager lspWorkspaceManager,
+        IClientLanguageServerManager notificationManager,
+        Refresher refresher)
+        : base(asynchronousOperationListenerProvider, lspWorkspaceRegistrationService, lspWorkspaceManager, notificationManager)
+    {
+        _refresher = refresher;
+
+        refresher.WorkspaceRefreshRequested += WorkspaceRefreshRequested;
+    }
+
+    public override void Dispose()
+    {
+        base.Dispose();
+        _refresher.WorkspaceRefreshRequested -= WorkspaceRefreshRequested;
+    }
+
+    private void WorkspaceRefreshRequested()
+        => EnqueueRefreshNotification(documentUri: null);
+
+    protected override string GetFeatureAttribute()
+        => FeatureAttribute.DiagnosticService;
+
+    protected override bool? GetRefreshSupport(ClientCapabilities clientCapabilities)
+        => clientCapabilities.Workspace?.Diagnostics?.RefreshSupport;
+
+    protected override string GetWorkspaceRefreshName()
+        => Methods.WorkspaceDiagnosticRefreshName;
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandler.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandler.cs
index 17a924111bbb7..97cfd5ead2fb0 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandler.cs
@@ -20,9 +20,9 @@ internal partial class DocumentPullDiagnosticHandler : AbstractDocumentPullDiagn
     {
         public DocumentPullDiagnosticHandler(
             IDiagnosticAnalyzerService analyzerService,
-            EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+            IDiagnosticsRefresher diagnosticRefresher,
             IGlobalOptionService globalOptions)
-            : base(analyzerService, editAndContinueDiagnosticUpdateSource, globalOptions)
+            : base(analyzerService, diagnosticRefresher, globalOptions)
         {
         }
 
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandlerFactory.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandlerFactory.cs
index 78e885a953ef5..73300e9cc99dd 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandlerFactory.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/DocumentPullDiagnosticHandlerFactory.cs
@@ -5,7 +5,6 @@
 using System;
 using System.Composition;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.EditAndContinue;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Options;
 
@@ -15,22 +14,22 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics
     internal class DocumentPullDiagnosticHandlerFactory : ILspServiceFactory
     {
         private readonly IDiagnosticAnalyzerService _analyzerService;
-        private readonly EditAndContinueDiagnosticUpdateSource _editAndContinueDiagnosticUpdateSource;
+        private readonly IDiagnosticsRefresher _diagnosticsRefresher;
         private readonly IGlobalOptionService _globalOptions;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public DocumentPullDiagnosticHandlerFactory(
             IDiagnosticAnalyzerService analyzerService,
-            EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+            IDiagnosticsRefresher diagnosticsRefresher,
             IGlobalOptionService globalOptions)
         {
             _analyzerService = analyzerService;
-            _editAndContinueDiagnosticUpdateSource = editAndContinueDiagnosticUpdateSource;
+            _diagnosticsRefresher = diagnosticsRefresher;
             _globalOptions = globalOptions;
         }
 
         public ILspService CreateILspService(LspServices lspServices, WellKnownLspServerKinds serverKind)
-            => new DocumentPullDiagnosticHandler(_analyzerService, _editAndContinueDiagnosticUpdateSource, _globalOptions);
+            => new DocumentPullDiagnosticHandler(_analyzerService, _diagnosticsRefresher, _globalOptions);
     }
 }
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticHandlerFactory.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticHandlerFactory.cs
index fe9355b3b15e7..baade1214bde0 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticHandlerFactory.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticHandlerFactory.cs
@@ -16,24 +16,24 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics.Public;
 // by n DocumentDiagnosticPartialResult literals.
 // See https://github.com/microsoft/vscode-languageserver-node/blob/main/protocol/src/common/proposed.diagnostics.md#textDocument_diagnostic
 [ExportCSharpVisualBasicLspServiceFactory(typeof(PublicDocumentPullDiagnosticsHandler)), Shared]
-internal class PublicDocumentPullDiagnosticHandlerFactory : ILspServiceFactory
+internal sealed class PublicDocumentPullDiagnosticHandlerFactory : ILspServiceFactory
 {
     private readonly IDiagnosticAnalyzerService _analyzerService;
-    private readonly EditAndContinueDiagnosticUpdateSource _editAndContinueDiagnosticUpdateSource;
+    private readonly IDiagnosticsRefresher _diagnosticRefresher;
     private readonly IGlobalOptionService _globalOptions;
 
     [ImportingConstructor]
     [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
     public PublicDocumentPullDiagnosticHandlerFactory(
         IDiagnosticAnalyzerService analyzerService,
-        EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+        IDiagnosticsRefresher diagnosticRefresher,
         IGlobalOptionService globalOptions)
     {
         _analyzerService = analyzerService;
-        _editAndContinueDiagnosticUpdateSource = editAndContinueDiagnosticUpdateSource;
+        _diagnosticRefresher = diagnosticRefresher;
         _globalOptions = globalOptions;
     }
 
     public ILspService CreateILspService(LspServices lspServices, WellKnownLspServerKinds serverKind)
-        => new PublicDocumentPullDiagnosticsHandler(_analyzerService, _editAndContinueDiagnosticUpdateSource, _globalOptions);
+        => new PublicDocumentPullDiagnosticsHandler(_analyzerService, _diagnosticRefresher, _globalOptions);
 }
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticsHandler.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticsHandler.cs
index 882ca44e152c7..af74b572008ac 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticsHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicDocumentPullDiagnosticsHandler.cs
@@ -23,13 +23,13 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics.Public;
 using DocumentDiagnosticPartialReport = SumType<RelatedFullDocumentDiagnosticReport, RelatedUnchangedDocumentDiagnosticReport, DocumentDiagnosticReportPartialResult>;
 
 [Method(Methods.TextDocumentDiagnosticName)]
-internal class PublicDocumentPullDiagnosticsHandler : AbstractDocumentPullDiagnosticHandler<DocumentDiagnosticParams, DocumentDiagnosticPartialReport, DocumentDiagnosticReport?>
+internal sealed class PublicDocumentPullDiagnosticsHandler : AbstractDocumentPullDiagnosticHandler<DocumentDiagnosticParams, DocumentDiagnosticPartialReport, DocumentDiagnosticReport?>
 {
     public PublicDocumentPullDiagnosticsHandler(
         IDiagnosticAnalyzerService analyzerService,
-        EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+        IDiagnosticsRefresher diagnosticsRefresher,
         IGlobalOptionService globalOptions)
-        : base(analyzerService, editAndContinueDiagnosticUpdateSource, globalOptions)
+        : base(analyzerService, diagnosticsRefresher, globalOptions)
     {
     }
 
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticHandlerFactory.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticHandlerFactory.cs
index dfca2c14ca1ac..de2a1e0e78290 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticHandlerFactory.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticHandlerFactory.cs
@@ -12,11 +12,11 @@
 namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics.Public;
 
 [ExportCSharpVisualBasicLspServiceFactory(typeof(PublicWorkspacePullDiagnosticsHandler)), Shared]
-internal class PublicWorkspacePullDiagnosticHandlerFactory : ILspServiceFactory
+internal sealed class PublicWorkspacePullDiagnosticHandlerFactory : ILspServiceFactory
 {
     private readonly LspWorkspaceRegistrationService _registrationService;
     private readonly IDiagnosticAnalyzerService _analyzerService;
-    private readonly EditAndContinueDiagnosticUpdateSource _editAndContinueDiagnosticUpdateSource;
+    private readonly IDiagnosticsRefresher _diagnosticsRefresher;
     private readonly IGlobalOptionService _globalOptions;
 
     [ImportingConstructor]
@@ -24,18 +24,18 @@ internal class PublicWorkspacePullDiagnosticHandlerFactory : ILspServiceFactory
     public PublicWorkspacePullDiagnosticHandlerFactory(
         LspWorkspaceRegistrationService registrationService,
         IDiagnosticAnalyzerService analyzerService,
-        EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+        IDiagnosticsRefresher diagnosticsRefresher,
         IGlobalOptionService globalOptions)
     {
         _registrationService = registrationService;
         _analyzerService = analyzerService;
-        _editAndContinueDiagnosticUpdateSource = editAndContinueDiagnosticUpdateSource;
+        _diagnosticsRefresher = diagnosticsRefresher;
         _globalOptions = globalOptions;
     }
 
     public ILspService CreateILspService(LspServices lspServices, WellKnownLspServerKinds serverKind)
     {
         var workspaceManager = lspServices.GetRequiredService<LspWorkspaceManager>();
-        return new PublicWorkspacePullDiagnosticsHandler(workspaceManager, _registrationService, _analyzerService, _editAndContinueDiagnosticUpdateSource, _globalOptions);
+        return new PublicWorkspacePullDiagnosticsHandler(workspaceManager, _registrationService, _analyzerService, _diagnosticsRefresher, _globalOptions);
     }
 }
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticsHandler.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticsHandler.cs
index 4815fd9c3bc54..96149017fbc0c 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticsHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/Public/PublicWorkspacePullDiagnosticsHandler.cs
@@ -22,7 +22,7 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics.Public;
 using WorkspaceDiagnosticPartialReport = SumType<WorkspaceDiagnosticReport, WorkspaceDiagnosticReportPartialResult>;
 
 [Method(Methods.WorkspaceDiagnosticName)]
-internal class PublicWorkspacePullDiagnosticsHandler : AbstractPullDiagnosticHandler<WorkspaceDiagnosticParams, WorkspaceDiagnosticPartialReport, WorkspaceDiagnosticReport?>, IDisposable
+internal sealed class PublicWorkspacePullDiagnosticsHandler : AbstractPullDiagnosticHandler<WorkspaceDiagnosticParams, WorkspaceDiagnosticPartialReport, WorkspaceDiagnosticReport?>, IDisposable
 {
     private readonly LspWorkspaceRegistrationService _workspaceRegistrationService;
     private readonly LspWorkspaceManager _workspaceManager;
@@ -39,9 +39,9 @@ public PublicWorkspacePullDiagnosticsHandler(
         LspWorkspaceManager workspaceManager,
         LspWorkspaceRegistrationService registrationService,
         IDiagnosticAnalyzerService analyzerService,
-        EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+        IDiagnosticsRefresher diagnosticRefresher,
         IGlobalOptionService globalOptions)
-        : base(analyzerService, editAndContinueDiagnosticUpdateSource, globalOptions)
+        : base(analyzerService, diagnosticRefresher, globalOptions)
     {
         _workspaceManager = workspaceManager;
         _workspaceRegistrationService = registrationService;
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandler.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandler.cs
index 62b117d747003..b108c3cab4464 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandler.cs
@@ -8,7 +8,6 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.EditAndContinue;
 using Microsoft.CodeAnalysis.ExternalAccess.Razor.Api;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Options;
@@ -23,8 +22,8 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics
     [Method(VSInternalMethods.WorkspacePullDiagnosticName)]
     internal sealed partial class WorkspacePullDiagnosticHandler : AbstractPullDiagnosticHandler<VSInternalWorkspaceDiagnosticsParams, VSInternalWorkspaceDiagnosticReport[], VSInternalWorkspaceDiagnosticReport[]>
     {
-        public WorkspacePullDiagnosticHandler(IDiagnosticAnalyzerService analyzerService, EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource, IGlobalOptionService globalOptions)
-            : base(analyzerService, editAndContinueDiagnosticUpdateSource, globalOptions)
+        public WorkspacePullDiagnosticHandler(IDiagnosticAnalyzerService analyzerService, IDiagnosticsRefresher diagnosticsRefresher, IGlobalOptionService globalOptions)
+            : base(analyzerService, diagnosticsRefresher, globalOptions)
         {
         }
 
diff --git a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandlerFactory.cs b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandlerFactory.cs
index 04f24be5da13f..70430c10ec498 100644
--- a/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandlerFactory.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/Diagnostics/WorkspacePullDiagnosticHandlerFactory.cs
@@ -5,7 +5,6 @@
 using System;
 using System.Composition;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.EditAndContinue;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Options;
 
@@ -15,22 +14,22 @@ namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics
     internal class WorkspacePullDiagnosticHandlerFactory : ILspServiceFactory
     {
         private readonly IDiagnosticAnalyzerService _analyzerService;
-        private readonly EditAndContinueDiagnosticUpdateSource _editAndContinueDiagnosticUpdateSource;
+        private readonly IDiagnosticsRefresher _diagnosticsRefresher;
         private readonly IGlobalOptionService _globalOptions;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public WorkspacePullDiagnosticHandlerFactory(
             IDiagnosticAnalyzerService analyzerService,
-            EditAndContinueDiagnosticUpdateSource editAndContinueDiagnosticUpdateSource,
+            IDiagnosticsRefresher diagnosticsRefresher,
             IGlobalOptionService globalOptions)
         {
             _analyzerService = analyzerService;
-            _editAndContinueDiagnosticUpdateSource = editAndContinueDiagnosticUpdateSource;
+            _diagnosticsRefresher = diagnosticsRefresher;
             _globalOptions = globalOptions;
         }
 
         public ILspService CreateILspService(LspServices lspServices, WellKnownLspServerKinds serverKind)
-            => new WorkspacePullDiagnosticHandler(_analyzerService, _editAndContinueDiagnosticUpdateSource, _globalOptions);
+            => new WorkspacePullDiagnosticHandler(_analyzerService, _diagnosticsRefresher, _globalOptions);
     }
 }
diff --git a/src/Features/LanguageServer/Protocol/Handler/EditAndContinue/RegisterSolutionSnapshotHandler.cs b/src/Features/LanguageServer/Protocol/Handler/EditAndContinue/RegisterSolutionSnapshotHandler.cs
new file mode 100644
index 0000000000000..bc2a111664bc3
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/EditAndContinue/RegisterSolutionSnapshotHandler.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using System.Runtime.Serialization;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.EditAndContinue;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.EditAndContinue;
+
+[DataContract]
+internal readonly record struct LspSolutionSnapshotId([property: DataMember(Name = "id")] int Id);
+
+[ExportCSharpVisualBasicStatelessLspService(typeof(RegisterSolutionSnapshotHandler)), Shared]
+[Method("workspace/_vs_registerSolutionSnapshot")]
+internal sealed class RegisterSolutionSnapshotHandler : ILspServiceRequestHandler<LspSolutionSnapshotId>
+{
+    private readonly ISolutionSnapshotRegistry _registry;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public RegisterSolutionSnapshotHandler(ISolutionSnapshotRegistry registry)
+    {
+        _registry = registry;
+    }
+
+    public bool MutatesSolutionState => false;
+    public bool RequiresLSPSolution => true;
+
+    public Task<LspSolutionSnapshotId> HandleRequestAsync(RequestContext context, CancellationToken cancellationToken)
+    {
+        Contract.ThrowIfNull(context.Solution);
+        var id = _registry.RegisterSolutionSnapshot(context.Solution);
+        return Task.FromResult(new LspSolutionSnapshotId(id.Id));
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/InlayHint/InlayHintRefreshQueue.cs b/src/Features/LanguageServer/Protocol/Handler/InlayHint/InlayHintRefreshQueue.cs
new file mode 100644
index 0000000000000..8e1c0703cf7d4
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/InlayHint/InlayHintRefreshQueue.cs
@@ -0,0 +1,66 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.InlineHints;
+using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.InlayHint
+{
+    internal class InlayHintRefreshQueue : AbstractRefreshQueue
+    {
+        private readonly IGlobalOptionService _globalOptionService;
+
+        public InlayHintRefreshQueue(
+            IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider,
+            LspWorkspaceRegistrationService lspWorkspaceRegistrationService,
+            IGlobalOptionService globalOptionService,
+            LspWorkspaceManager lspWorkspaceManager,
+            IClientLanguageServerManager notificationManager)
+            : base(asynchronousOperationListenerProvider, lspWorkspaceRegistrationService, lspWorkspaceManager, notificationManager)
+        {
+            _globalOptionService = globalOptionService;
+            _globalOptionService.AddOptionChangedHandler(this, OnOptionChanged);
+        }
+
+        public override void Dispose()
+        {
+            base.Dispose();
+            _globalOptionService.RemoveOptionChangedHandler(this, OnOptionChanged);
+        }
+
+        private void OnOptionChanged(object? sender, OptionChangedEventArgs e)
+        {
+            if (e.Option.Equals(InlineHintsOptionsStorage.EnabledForParameters) ||
+                e.Option.Equals(InlineHintsOptionsStorage.ForIndexerParameters) ||
+                e.Option.Equals(InlineHintsOptionsStorage.ForLiteralParameters) ||
+                e.Option.Equals(InlineHintsOptionsStorage.ForOtherParameters) ||
+                e.Option.Equals(InlineHintsOptionsStorage.ForObjectCreationParameters) ||
+                e.Option.Equals(InlineHintsOptionsStorage.SuppressForParametersThatDifferOnlyBySuffix) ||
+                e.Option.Equals(InlineHintsOptionsStorage.SuppressForParametersThatMatchArgumentName) ||
+                e.Option.Equals(InlineHintsOptionsStorage.SuppressForParametersThatMatchMethodIntent) ||
+                e.Option.Equals(InlineHintsOptionsStorage.EnabledForTypes) ||
+                e.Option.Equals(InlineHintsOptionsStorage.ForImplicitVariableTypes) ||
+                e.Option.Equals(InlineHintsOptionsStorage.ForLambdaParameterTypes) ||
+                e.Option.Equals(InlineHintsOptionsStorage.ForImplicitObjectCreation))
+            {
+                EnqueueRefreshNotification(documentUri: null);
+            }
+        }
+
+        protected override string GetFeatureAttribute()
+            => FeatureAttribute.InlineHints;
+
+        protected override bool? GetRefreshSupport(ClientCapabilities clientCapabilities)
+        {
+            return clientCapabilities.Workspace?.InlayHint?.RefreshSupport;
+        }
+
+        protected override string GetWorkspaceRefreshName()
+        {
+            return Methods.WorkspaceInlayHintRefreshName;
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/InlayHint/InlayHintRefreshQueueFactory.cs b/src/Features/LanguageServer/Protocol/Handler/InlayHint/InlayHintRefreshQueueFactory.cs
new file mode 100644
index 0000000000000..232a9858c26ac
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Handler/InlayHint/InlayHintRefreshQueueFactory.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Composition;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.InlayHint;
+using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Handler.InlayHint
+{
+    [ExportCSharpVisualBasicLspServiceFactory(typeof(InlayHintRefreshQueue)), Shared]
+    internal sealed class InlayHintRefreshQueueFactory : ILspServiceFactory
+    {
+        private readonly IAsynchronousOperationListenerProvider _asyncListenerProvider;
+        private readonly LspWorkspaceRegistrationService _lspWorkspaceRegistrationService;
+        private readonly IGlobalOptionService _globalOptionService;
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public InlayHintRefreshQueueFactory(
+            IAsynchronousOperationListenerProvider asynchronousOperationListenerProvider,
+            LspWorkspaceRegistrationService lspWorkspaceRegistrationService,
+            IGlobalOptionService globalOptionService)
+        {
+            _asyncListenerProvider = asynchronousOperationListenerProvider;
+            _lspWorkspaceRegistrationService = lspWorkspaceRegistrationService;
+            _globalOptionService = globalOptionService;
+        }
+
+        public ILspService CreateILspService(LspServices lspServices, WellKnownLspServerKinds serverKind)
+        {
+            var notificationManager = lspServices.GetRequiredService<IClientLanguageServerManager>();
+            var lspWorkspaceManager = lspServices.GetRequiredService<LspWorkspaceManager>();
+
+            return new InlayHintRefreshQueue(_asyncListenerProvider, _lspWorkspaceRegistrationService, _globalOptionService, lspWorkspaceManager, notificationManager);
+        }
+    }
+}
diff --git a/src/Features/LanguageServer/Protocol/Handler/OnAutoInsert/OnAutoInsertHandler.cs b/src/Features/LanguageServer/Protocol/Handler/OnAutoInsert/OnAutoInsertHandler.cs
index 09c5631ba41c9..4abc6158ac136 100644
--- a/src/Features/LanguageServer/Protocol/Handler/OnAutoInsert/OnAutoInsertHandler.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/OnAutoInsert/OnAutoInsertHandler.cs
@@ -70,6 +70,7 @@ public OnAutoInsertHandler(
 
                 var documentationCommentResponse = await GetDocumentationCommentResponseAsync(
                     request, document, service, docCommentOptions, cancellationToken).ConfigureAwait(false);
+
                 if (documentationCommentResponse != null)
                 {
                     return documentationCommentResponse;
@@ -112,7 +113,7 @@ public OnAutoInsertHandler(
 
             var result = autoInsertParams.Character == "\n"
                 ? service.GetDocumentationCommentSnippetOnEnterTyped(syntaxTree, sourceText, position, options, cancellationToken)
-                : service.GetDocumentationCommentSnippetOnCharacterTyped(syntaxTree, sourceText, position, options, cancellationToken);
+                : service.GetDocumentationCommentSnippetOnCharacterTyped(syntaxTree, sourceText, position, options, cancellationToken, addIndentation: false);
 
             if (result == null)
             {
diff --git a/src/Features/LanguageServer/Protocol/Handler/References/FindUsagesLSPContext.cs b/src/Features/LanguageServer/Protocol/Handler/References/FindUsagesLSPContext.cs
index bbeb38f60ccb1..37b793532c502 100644
--- a/src/Features/LanguageServer/Protocol/Handler/References/FindUsagesLSPContext.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/References/FindUsagesLSPContext.cs
@@ -91,7 +91,7 @@ public FindUsagesLSPContext(
             _metadataAsSourceFileService = metadataAsSourceFileService;
             _globalOptions = globalOptions;
             _workQueue = new AsyncBatchingWorkQueue<SumType<VSInternalReferenceItem, LSP.Location>>(
-                TimeSpan.FromMilliseconds(500), ReportReferencesAsync, asyncListener, cancellationToken);
+                DelayTimeSpan.Medium, ReportReferencesAsync, asyncListener, cancellationToken);
         }
 
         public override ValueTask<FindUsagesOptions> GetOptionsAsync(string language, CancellationToken cancellationToken)
diff --git a/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensHelpers.cs b/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensHelpers.cs
index ea4dfd8756b84..21a2fc5b28bda 100644
--- a/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensHelpers.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensHelpers.cs
@@ -31,7 +31,7 @@ public static async Task<int[]> ComputeSemanticTokensDataAsync(
             ClassificationOptions options,
             CancellationToken cancellationToken)
         {
-            var tokenTypesToIndex = SemanticTokensSchema.GetSchema(capabilities).TokenTypeToIndex;
+            var tokenTypesToIndex = SemanticTokensSchema.GetSchema(capabilities.HasVisualStudioLspCapability()).TokenTypeToIndex;
 
             var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
             var text = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
@@ -182,7 +182,7 @@ private static int[] ComputeTokens(
             var lastLineNumber = 0;
             var lastStartCharacter = 0;
 
-            var tokenTypeMap = SemanticTokensSchema.GetSchema(capabilities).TokenTypeMap;
+            var tokenTypeMap = SemanticTokensSchema.GetSchema(capabilities.HasVisualStudioLspCapability()).TokenTypeMap;
 
             for (var currentClassifiedSpanIndex = 0; currentClassifiedSpanIndex < classifiedSpans.Length; currentClassifiedSpanIndex++)
             {
diff --git a/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensSchema.cs b/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensSchema.cs
index 88634c5597f05..4265be9758086 100644
--- a/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensSchema.cs
+++ b/src/Features/LanguageServer/Protocol/Handler/SemanticTokens/SemanticTokensSchema.cs
@@ -115,8 +115,8 @@ public SemanticTokensSchema(IReadOnlyDictionary<string, string> tokenTypeMap)
             TokenTypeToIndex = tokenTypeToIndex;
         }
 
-        public static SemanticTokensSchema GetSchema(ClientCapabilities capabilities)
-            => capabilities.HasVisualStudioLspCapability()
+        public static SemanticTokensSchema GetSchema(bool clientSupportsVisualStudioExtensions)
+            => clientSupportsVisualStudioExtensions
                 ? s_vsTokenSchema
                 : s_pureLspTokenSchema;
 
@@ -125,5 +125,12 @@ public static SemanticTokensSchema LegacyTokenSchemaForRazor
 
         public static SemanticTokensSchema LegacyTokensSchemaForLSIF
             => s_vsTokenSchema;
+
+        public static string[] TokenModifiers = new string[]
+        {
+            // This must be in the same order as SemanticTokens.TokenModifiers, but skip the "None" item
+            SemanticTokenModifiers.Static,
+            nameof(SemanticTokens.TokenModifiers.ReassignedVariable)
+        };
     }
 }
diff --git a/src/Features/LanguageServer/Protocol/LspOptionsStorage.cs b/src/Features/LanguageServer/Protocol/LspOptionsStorage.cs
index 995a0880fc0bb..cedb7e097c9bb 100644
--- a/src/Features/LanguageServer/Protocol/LspOptionsStorage.cs
+++ b/src/Features/LanguageServer/Protocol/LspOptionsStorage.cs
@@ -11,6 +11,7 @@ internal sealed class LspOptionsStorage
         /// <summary>
         /// This sets the max list size we will return in response to a completion request.
         /// If there are more than this many items, we will set the isIncomplete flag on the returned completion list.
+        /// If set to negative value, we will always return the full list.
         /// </summary>
         public static readonly Option2<int> MaxCompletionListSize = new("dotnet_lsp_max_completion_list_size", defaultValue: 1000);
 
diff --git a/src/Features/LanguageServer/Protocol/Microsoft.CodeAnalysis.LanguageServer.Protocol.csproj b/src/Features/LanguageServer/Protocol/Microsoft.CodeAnalysis.LanguageServer.Protocol.csproj
index 0c624c6d95306..cbdbe98365b8e 100644
--- a/src/Features/LanguageServer/Protocol/Microsoft.CodeAnalysis.LanguageServer.Protocol.csproj
+++ b/src/Features/LanguageServer/Protocol/Microsoft.CodeAnalysis.LanguageServer.Protocol.csproj
@@ -4,7 +4,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.LanguageServer</RootNamespace>
-    <TargetFrameworks>net6.0;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>net7.0;netstandard2.0</TargetFrameworks>
     <IsPackable>true</IsPackable>
     <PackageDescription>
       .NET Compiler Platform ("Roslyn") support for Language Server Protocol.
@@ -42,7 +42,7 @@
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.CSharp.EditorFeatures" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.CSharp.Features.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.CSharp.EditorFeatures.UnitTests" />
-    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.CSharp.LanguageServer.Protocol" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.VisualBasic.EditorFeatures" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.VisualBasic.Features.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.VisualBasic.EditorFeatures.UnitTests" />
@@ -68,10 +68,10 @@
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.Remote.ServiceHub" />
     <InternalsVisibleTo Include="Roslyn.VisualStudio.Next.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServerIndexFormat.Generator" />
+    <InternalsVisibleTo Include="Microsoft.VisualStudio.LanguageServices.DevKit" />
     <InternalsVisibleTo Include="IdeCoreBenchmarks" />
     <InternalsVisibleTo Include="IdeBenchmarks" />
     <InternalsVisibleTo Include="AnalyzerRunner" />
-    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" Key="$(MicrosoftCodeAnalysisLanguageServerKey)" />
     <!-- BEGIN MONODEVELOP
     These MonoDevelop dependencies don't ship with Visual Studio, so can't break our
     binary insertions and are exempted from the ExternalAccess adapter assembly policies.
diff --git a/src/Features/LanguageServer/Protocol/Workspaces/LspMiscellaneousFilesWorkspace.cs b/src/Features/LanguageServer/Protocol/Workspaces/LspMiscellaneousFilesWorkspace.cs
index 9227f60046bdb..015a6c6d469bb 100644
--- a/src/Features/LanguageServer/Protocol/Workspaces/LspMiscellaneousFilesWorkspace.cs
+++ b/src/Features/LanguageServer/Protocol/Workspaces/LspMiscellaneousFilesWorkspace.cs
@@ -55,12 +55,7 @@ public LspMiscellaneousFilesWorkspace(HostServices hostServices) : base(hostServ
         /// </summary>
         public Document? AddMiscellaneousDocument(Uri uri, SourceText documentText, string languageId, ILspLogger logger)
         {
-            // If we have a file:///xyz URI, we'll store the actual file path string in the document file path.
-            // Otherwise we have a URI that doesn't point to an actual file.  In such a scenario, we'll store the full URI string (including schema).
-            // This will allow correct round-tripping of the URI for features that need it until we support URI as a first class document concept.
-            // Tracking issue - https://github.com/dotnet/roslyn/issues/68083
-            var documentFilePath = uri.IsFile ? uri.LocalPath : uri.OriginalString;
-
+            var documentFilePath = ProtocolConversions.GetDocumentFilePathFromUri(uri);
             var languageInformation = GetLanguageInformation(documentFilePath, languageId);
             if (languageInformation == null)
             {
@@ -122,24 +117,5 @@ public ValueTask UpdateTextIfPresentAsync(DocumentId documentId, SourceText sour
                 _ => null,
             };
         }
-
-        private sealed class SourceTextLoader : TextLoader
-        {
-            private readonly SourceText _sourceText;
-            private readonly string _fileUri;
-
-            public SourceTextLoader(SourceText sourceText, string fileUri)
-            {
-                _sourceText = sourceText;
-                _fileUri = fileUri;
-            }
-
-            internal override string? FilePath
-                => _fileUri;
-
-            // TODO (https://github.com/dotnet/roslyn/issues/63583): Use options.ChecksumAlgorithm 
-            public override Task<TextAndVersion> LoadTextAndVersionAsync(LoadTextOptions options, CancellationToken cancellationToken)
-                => Task.FromResult(TextAndVersion.Create(_sourceText, VersionStamp.Create(), _fileUri));
-        }
     }
 }
diff --git a/src/Features/LanguageServer/Protocol/Workspaces/SourceTextLoader.cs b/src/Features/LanguageServer/Protocol/Workspaces/SourceTextLoader.cs
new file mode 100644
index 0000000000000..945991d6657a5
--- /dev/null
+++ b/src/Features/LanguageServer/Protocol/Workspaces/SourceTextLoader.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.CodeAnalysis.LanguageServer
+{
+    internal sealed class SourceTextLoader : TextLoader
+    {
+        private readonly SourceText _sourceText;
+        private readonly string _fileUri;
+
+        public SourceTextLoader(SourceText sourceText, string fileUri)
+        {
+            _sourceText = sourceText;
+            _fileUri = fileUri;
+        }
+
+        internal override string? FilePath
+            => _fileUri;
+
+        // TODO (https://github.com/dotnet/roslyn/issues/63583): Use options.ChecksumAlgorithm 
+        public override Task<TextAndVersion> LoadTextAndVersionAsync(LoadTextOptions options, CancellationToken cancellationToken)
+            => Task.FromResult(TextAndVersion.Create(_sourceText, VersionStamp.Create(), _fileUri));
+    }
+}
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionFeaturesTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionFeaturesTests.cs
new file mode 100644
index 0000000000000..2d0617479b584
--- /dev/null
+++ b/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionFeaturesTests.cs
@@ -0,0 +1,493 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#nullable disable
+
+using System;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Completion;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.LanguageServer.Handler.Completion;
+using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Roslyn.Test.Utilities;
+using Xunit;
+using Xunit.Abstractions;
+using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests.Completion;
+
+public class CompletionFeaturesTests : AbstractLanguageServerProtocolTests
+{
+    protected override TestComposition Composition => FeaturesLspComposition;
+
+    private ClientCapabilities DefaultClientCapabilities { get; }
+    = new LSP.ClientCapabilities
+    {
+        TextDocument = new LSP.TextDocumentClientCapabilities
+        {
+            Completion = new LSP.CompletionSetting
+            {
+                CompletionItem = new LSP.CompletionItemSetting
+                {
+                    CommitCharactersSupport = true,
+                    LabelDetailsSupport = true,
+                    ResolveSupport = new LSP.ResolveSupportSetting
+                    {
+                        Properties = new string[] { "documentation", "additionalTextEdits", "command", "labelDetail" }
+                    }
+                },
+
+                CompletionListSetting = new LSP.CompletionListSetting
+                {
+                    ItemDefaults = new string[] { CompletionCapabilityHelper.EditRangePropertyName, CompletionCapabilityHelper.DataPropertyName, CompletionCapabilityHelper.CommitCharactersPropertyName }
+                },
+            },
+        }
+    };
+
+    public CompletionFeaturesTests(ITestOutputHelper testOutputHelper) : base(testOutputHelper)
+    {
+    }
+
+    [Theory, CombinatorialData, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1801810")]
+    public async Task TestDoesNotThrowInComplexEditWhenDisplayTextShorterThanDefaultSpanAsync(bool mutatingLspWorkspace)
+    {
+        var markup =
+@"
+using System;
+using System.Text;
+
+public class A
+{
+    public int M()
+    {
+        return{|caret:|}
+    }
+}";
+        await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, DefaultClientCapabilities);
+        var caret = testLspServer.GetLocations("caret").Single();
+        var completionParams = new LSP.CompletionParams()
+        {
+            TextDocument = CreateTextDocumentIdentifier(caret.Uri),
+            Position = caret.Range.Start,
+            Context = new LSP.CompletionContext()
+            {
+                TriggerKind = LSP.CompletionTriggerKind.Invoked,
+            }
+        };
+
+        var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
+
+        var results = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None);
+        AssertEx.NotNull(results);
+        Assert.NotEmpty(results.Items);
+    }
+
+    [Theory, CombinatorialData]
+    public async Task TestImportCompletion(bool mutatingLspWorkspace)
+    {
+        var markup =
+@"
+class A
+{
+    void M()
+    {
+        Task{|caret:|}
+    }
+}";
+        await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, DefaultClientCapabilities);
+        var completionParams = CreateCompletionParams(
+            testLspServer.GetLocations("caret").Single(),
+            invokeKind: LSP.VSInternalCompletionInvokeKind.Explicit,
+            triggerCharacter: "\0",
+            triggerKind: LSP.CompletionTriggerKind.Invoked);
+
+        // Make sure the unimported types option is on by default.
+        testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(CompletionOptionsStorage.ShowItemsFromUnimportedNamespaces, LanguageNames.CSharp, true);
+        testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(CompletionOptionsStorage.ForceExpandedCompletionIndexCreation, true);
+
+        var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
+
+        var completionResult = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None).ConfigureAwait(false);
+        Assert.NotNull(completionResult.ItemDefaults.EditRange);
+        Assert.NotNull(completionResult.ItemDefaults.Data);
+        Assert.NotNull(completionResult.ItemDefaults.CommitCharacters);
+
+        var actualItem = completionResult.Items.First(i => i.Label == "Task");
+        Assert.Equal("System.Threading.Tasks", actualItem.LabelDetails.Description);
+        Assert.Equal("~Task  System.Threading.Tasks", actualItem.SortText);
+        Assert.Equal(CompletionItemKind.Class, actualItem.Kind);
+        Assert.Null(actualItem.LabelDetails.Detail);
+        Assert.Null(actualItem.FilterText);
+        Assert.Null(actualItem.TextEdit);
+        Assert.Null(actualItem.TextEditText);
+        Assert.Null(actualItem.AdditionalTextEdits);
+        Assert.Null(actualItem.Command);
+        Assert.Null(actualItem.CommitCharacters);
+        Assert.Null(actualItem.Data);
+        Assert.Null(actualItem.Detail);
+        Assert.Null(actualItem.Documentation);
+
+        actualItem.Data = completionResult.ItemDefaults.Data;
+
+        var resolvedItem = await testLspServer.ExecuteRequestAsync<LSP.CompletionItem, LSP.CompletionItem>(LSP.Methods.TextDocumentCompletionResolveName, actualItem, CancellationToken.None).ConfigureAwait(false);
+        Assert.Equal("System.Threading.Tasks", resolvedItem.LabelDetails.Description);
+        Assert.Equal("~Task  System.Threading.Tasks", resolvedItem.SortText);
+        Assert.Equal(CompletionItemKind.Class, resolvedItem.Kind);
+
+        var expectedAdditionalEdit = new TextEdit() { NewText = "using System.Threading.Tasks;\r\n\r\n", Range = new() { Start = new(1, 0), End = new(1, 0) } };
+        AssertJsonEquals(new[] { expectedAdditionalEdit }, resolvedItem.AdditionalTextEdits);
+
+        Assert.Null(resolvedItem.LabelDetails.Detail);
+        Assert.Null(resolvedItem.FilterText);
+        Assert.Null(resolvedItem.TextEdit);
+        Assert.Null(resolvedItem.TextEditText);
+        Assert.Null(resolvedItem.Command);
+        Assert.Null(resolvedItem.Detail);
+
+        var expectedDocumentation = new MarkupContent()
+        {
+            Kind = LSP.MarkupKind.PlainText,
+            Value = "(awaitable) class System.Threading.Tasks.Task"
+        };
+        AssertJsonEquals(resolvedItem.Documentation, expectedDocumentation);
+    }
+
+    [Theory, CombinatorialData]
+    public async Task TestResolveComplexEdit(bool mutatingLspWorkspace)
+    {
+        var markup =
+@"
+/// <summ{|caret:|}
+class A { }";
+
+        await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, DefaultClientCapabilities);
+        var completionParams = CreateCompletionParams(
+            testLspServer.GetLocations("caret").Single(),
+            invokeKind: LSP.VSInternalCompletionInvokeKind.Explicit,
+            triggerCharacter: "\0",
+            triggerKind: LSP.CompletionTriggerKind.Invoked);
+
+        var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
+
+        var completionResult = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None).ConfigureAwait(false);
+        Assert.NotNull(completionResult.ItemDefaults.EditRange);
+        Assert.NotNull(completionResult.ItemDefaults.Data);
+        Assert.NotNull(completionResult.ItemDefaults.CommitCharacters);
+
+        var actualItem = completionResult.Items.First(i => i.Label == "summary");
+        Assert.Equal(CompletionItemKind.Keyword, actualItem.Kind);
+        Assert.Equal("summ", actualItem.TextEditText);
+        Assert.Null(actualItem.LabelDetails);
+        Assert.Null(actualItem.SortText);
+        Assert.Null(actualItem.FilterText);
+        Assert.Null(actualItem.TextEdit);
+        Assert.Null(actualItem.AdditionalTextEdits);
+        Assert.Null(actualItem.Command);
+        Assert.Null(actualItem.CommitCharacters);
+        Assert.Null(actualItem.Data);
+        Assert.Null(actualItem.Detail);
+        Assert.Null(actualItem.Documentation);
+
+        actualItem.Data = completionResult.ItemDefaults.Data;
+
+        var resolvedItem = await testLspServer.ExecuteRequestAsync<LSP.CompletionItem, LSP.CompletionItem>(LSP.Methods.TextDocumentCompletionResolveName, actualItem, CancellationToken.None).ConfigureAwait(false);
+        var expectedEdit = new TextEdit { Range = new LSP.Range { Start = new(1, 5), End = new(1, 9) }, NewText = "summary" };
+
+        Assert.Equal(DefaultLspCompletionResultCreationService.CompleteComplexEditCommand, resolvedItem.Command.CommandIdentifier);
+        Assert.Equal(nameof(DefaultLspCompletionResultCreationService.CompleteComplexEditCommand), resolvedItem.Command.Title);
+        Assert.Equal(completionParams.TextDocument.Uri, new System.Uri((string)resolvedItem.Command.Arguments[0]));
+        AssertJsonEquals(expectedEdit, resolvedItem.Command.Arguments[1]);
+        Assert.Equal(false, resolvedItem.Command.Arguments[2]);
+        Assert.Equal((long)14, resolvedItem.Command.Arguments[3]);
+    }
+
+    [Theory, CombinatorialData, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1755955")]
+    public async Task TestSoftSelectionWhenFilterTextIsEmptyAsync(bool mutatingLspWorkspace)
+    {
+        var markup =
+@"
+using System;
+using System.Text;
+
+public class A
+{
+    public void M(string someText)
+    {
+        var x = new StringBuilder();
+        x.Append({|caret:|}
+    }
+}";
+
+        await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, DefaultClientCapabilities);
+        var caretLocation = testLspServer.GetLocations("caret").Single();
+        await testLspServer.OpenDocumentAsync(caretLocation.Uri);
+
+        testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(CompletionOptionsStorage.TriggerInArgumentLists, LanguageNames.CSharp, true);
+
+        var completionParams = CreateCompletionParams(
+            caretLocation,
+            invokeKind: LSP.VSInternalCompletionInvokeKind.Typing,
+            triggerCharacter: "(",
+            triggerKind: LSP.CompletionTriggerKind.Invoked);
+
+        var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
+        var results = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None).ConfigureAwait(false);
+
+        Assert.True(results.IsIncomplete);
+        var someTextItem = results.Items.First(item => item.Label == "someText");
+
+        if (results.ItemDefaults.CommitCharacters == null)
+        {
+            Assert.True(!someTextItem.Preselect && someTextItem.CommitCharacters != null && someTextItem.CommitCharacters.Length == 0);
+        }
+        else
+        {
+            Assert.True(results.ItemDefaults.CommitCharacters.Length == 0);
+            Assert.True(!someTextItem.Preselect && someTextItem.CommitCharacters == null);
+        }
+
+        await testLspServer.InsertTextAsync(caretLocation.Uri, (caretLocation.Range.End.Line, caretLocation.Range.End.Character, "s"));
+
+        completionParams = CreateCompletionParams(
+            GetLocationPlusOne(caretLocation),
+            invokeKind: LSP.VSInternalCompletionInvokeKind.Typing,
+            triggerCharacter: "s",
+            triggerKind: LSP.CompletionTriggerKind.TriggerForIncompleteCompletions);
+
+        results = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None).ConfigureAwait(false);
+        someTextItem = results.Items.First(item => item.Label == "someText");
+
+        if (results.ItemDefaults.CommitCharacters == null)
+        {
+            Assert.False(someTextItem.Preselect);
+            Assert.NotEmpty(someTextItem.CommitCharacters);
+        }
+        else
+        {
+            Assert.NotEmpty(results.ItemDefaults.CommitCharacters);
+            Assert.False(someTextItem.Preselect);
+            Assert.Null(someTextItem.CommitCharacters);
+        }
+    }
+
+    [Theory, CombinatorialData]
+    public async Task TestPromotingDefaultCommitCharactersAsync(bool mutatingLspWorkspace, bool hasDefaultCommitCharCapability)
+    {
+        var markup =
+@"using System;
+class A
+{
+    void M()
+    {
+        item{|caret:|}
+    }
+}";
+        var clientCapability = DefaultClientCapabilities;
+        if (!hasDefaultCommitCharCapability)
+        {
+            clientCapability.TextDocument.Completion.CompletionListSetting.ItemDefaults
+                = new string[] { CompletionCapabilityHelper.EditRangePropertyName, CompletionCapabilityHelper.DataPropertyName };
+        }
+
+        await using var testLspServer = await CreateTestLspServerAsync(new[] { markup }, LanguageNames.CSharp, mutatingLspWorkspace,
+            new InitializationOptions { ClientCapabilities = clientCapability, CallInitialized = true },
+            extraExportedTypes: new[] { typeof(CSharpLspMockCompletionService.Factory) }.ToList());
+
+        var mockService = testLspServer.TestWorkspace.Services.GetLanguageServices(LanguageNames.CSharp).GetRequiredService<CompletionService>() as CSharpLspMockCompletionService;
+        // return 10 items, all use default commit characters
+        mockService.ItemCounts = (10, 0);
+
+        var completionParams = CreateCompletionParams(
+            testLspServer.GetLocations("caret").Single(),
+            invokeKind: LSP.VSInternalCompletionInvokeKind.Explicit,
+            triggerCharacter: "\0",
+            triggerKind: LSP.CompletionTriggerKind.Invoked);
+
+        var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
+
+        var results = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None);
+
+        Assert.NotNull(results);
+        Assert.NotEmpty(results.Items);
+
+        var defaultCharArray = CompletionRules.Default.DefaultCommitCharacters.Select(c => c.ToString()).ToArray();
+
+        if (hasDefaultCommitCharCapability)
+        {
+            // if default commit char on list is supported, then it should be set to default array
+            // and all item commit chars should be null
+            Assert.NotNull(results.ItemDefaults.CommitCharacters);
+            AssertEx.SetEqual(defaultCharArray, results.ItemDefaults.CommitCharacters);
+
+            Assert.All(results.Items, (item) => Assert.Null(item.CommitCharacters));
+        }
+        else
+        {
+            // otherwise, the list default should be null, and all item commit chars should be set to null too
+            // so client will use the default array we returned as part of server capability.
+            Assert.Null(results.ItemDefaults.CommitCharacters);
+            Assert.All(results.Items, (item) => Assert.Null(item.CommitCharacters));
+        }
+    }
+
+    [Theory, CombinatorialData]
+    public async Task TestUsingServerDefaultCommitCharacters(bool mutatingLspWorkspace, bool shouldPromoteDefaultCommitCharsToList)
+    {
+        var markup = "Item{|caret:|}";
+        await using var testLspServer = await CreateTestLspServerAsync(new[] { markup }, LanguageNames.CSharp, mutatingLspWorkspace,
+            new InitializationOptions { ClientCapabilities = DefaultClientCapabilities, CallInitialized = true },
+            extraExportedTypes: new[] { typeof(CSharpLspMockCompletionService.Factory) }.ToList());
+
+        var mockService = testLspServer.TestWorkspace.Services.GetLanguageServices(LanguageNames.CSharp).GetRequiredService<CompletionService>() as CSharpLspMockCompletionService;
+        mockService.ItemCounts = shouldPromoteDefaultCommitCharsToList ? (20, 10) : (10, 20);
+
+        var caret = testLspServer.GetLocations("caret").Single();
+        var completionParams = new LSP.CompletionParams()
+        {
+            TextDocument = CreateTextDocumentIdentifier(caret.Uri),
+            Position = caret.Range.Start,
+            Context = new LSP.CompletionContext()
+            {
+                TriggerKind = LSP.CompletionTriggerKind.Invoked,
+            }
+        };
+
+        var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
+
+        var results = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None);
+        Assert.NotNull(results.ItemDefaults.CommitCharacters);
+
+        var defaultCharArray = CompletionRules.Default.DefaultCommitCharacters.Select(c => c.ToString()).ToArray();
+        var nonDefaultCharArray = AbstractLspCompletionResultCreationService.CreateCommitCharacterArrayFromRules(mockService.NonDefaultRule);
+
+        if (shouldPromoteDefaultCommitCharsToList)
+        {
+            AssertEx.SetEqual(defaultCharArray, results.ItemDefaults.CommitCharacters);
+            foreach (var item in results.Items)
+            {
+                if (item.Label.StartsWith("ItemWithDefaultChar"))
+                {
+                    Assert.Null(item.CommitCharacters);
+                }
+                else if (item.Label.StartsWith("ItemWithNonDefaultChar"))
+                {
+                    Assert.NotNull(item.CommitCharacters);
+                    AssertEx.SetEqual(nonDefaultCharArray, item.CommitCharacters);
+                }
+            }
+        }
+        else
+        {
+            AssertEx.SetEqual(nonDefaultCharArray, results.ItemDefaults.CommitCharacters);
+            foreach (var item in results.Items)
+            {
+                if (item.Label.StartsWith("ItemWithDefaultChar"))
+                {
+                    Assert.NotNull(item.CommitCharacters);
+                    AssertEx.SetEqual(defaultCharArray, item.CommitCharacters);
+                }
+                else if (item.Label.StartsWith("ItemWithNonDefaultChar"))
+                {
+                    Assert.Null(item.CommitCharacters);
+                }
+            }
+        }
+    }
+
+    private sealed class CSharpLspMockCompletionService : CompletionService
+    {
+        private CSharpLspMockCompletionService(SolutionServices services, IAsynchronousOperationListenerProvider listenerProvider) : base(services, listenerProvider)
+        {
+        }
+
+        public override string Language => LanguageNames.CSharp;
+
+        internal override CompletionRules GetRules(CodeAnalysis.Completion.CompletionOptions options)
+            => CompletionRules.Default;
+
+        internal override bool ShouldTriggerCompletion(
+            Project project, LanguageServices languageServices, SourceText text, int caretPosition, CompletionTrigger trigger,
+            CodeAnalysis.Completion.CompletionOptions options, OptionSet passThroughOptions, ImmutableHashSet<string> roles = null)
+        {
+            return true;
+        }
+
+        public CompletionItemRules NonDefaultRule { get; } = CompletionItemRules.Default.WithCommitCharacterRule(CharacterSetModificationRule.Create(CharacterSetModificationKind.Remove, ' ', '('));
+
+        public (int defaultItemCount, int nonDefaultItemCount) ItemCounts { get; set; }
+
+        internal override async Task<CodeAnalysis.Completion.CompletionList> GetCompletionsAsync(
+            Document document, int caretPosition, CodeAnalysis.Completion.CompletionOptions options, OptionSet passThroughOptions,
+            CompletionTrigger trigger = default, ImmutableHashSet<string> roles = null, CancellationToken cancellationToken = default)
+        {
+            var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
+            var defaultItemSpan = GetDefaultCompletionListSpan(text, caretPosition);
+
+            var builder = ImmutableArray.CreateBuilder<CodeAnalysis.Completion.CompletionItem>();
+
+            for (var i = 0; i < ItemCounts.defaultItemCount; ++i)
+                builder.Add(CodeAnalysis.Completion.CompletionItem.Create($"ItemWithDefaultChar{i}", rules: CompletionItemRules.Default));
+
+            for (var i = 0; i < ItemCounts.nonDefaultItemCount; ++i)
+                builder.Add(CodeAnalysis.Completion.CompletionItem.Create($"ItemNonDefaultChar{i}", rules: NonDefaultRule));
+
+            return CodeAnalysis.Completion.CompletionList.Create(defaultItemSpan, builder.ToImmutable());
+        }
+
+        [ExportLanguageServiceFactory(typeof(CompletionService), LanguageNames.CSharp, ServiceLayer.Test), Shared]
+        internal sealed class Factory : ILanguageServiceFactory
+        {
+            private readonly IAsynchronousOperationListenerProvider _listenerProvider;
+
+            [ImportingConstructor]
+            [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+            public Factory(IAsynchronousOperationListenerProvider listenerProvider)
+            {
+                _listenerProvider = listenerProvider;
+            }
+
+            public ILanguageService CreateLanguageService(HostLanguageServices languageServices)
+            {
+                return new CSharpLspMockCompletionService(languageServices.LanguageServices.SolutionServices, _listenerProvider);
+            }
+        }
+    }
+
+    [Theory, CombinatorialData, WorkItem("https://github.com/dotnet/vscode-csharp/issues/5777")]
+    public async Task EditRangeShouldEndAtCursorPosition(bool mutatingLspWorkspace)
+    {
+        var markup =
+@"public class C1 {}
+
+pub{|caret:|}class";
+        await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, DefaultClientCapabilities);
+        var caret = testLspServer.GetLocations("caret").Single();
+        var completionParams = new LSP.CompletionParams()
+        {
+            TextDocument = CreateTextDocumentIdentifier(caret.Uri),
+            Position = caret.Range.Start,
+            Context = new LSP.CompletionContext()
+            {
+                TriggerKind = LSP.CompletionTriggerKind.Invoked,
+            }
+        };
+
+        var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
+
+        var results = await testLspServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None);
+        AssertEx.NotNull(results);
+        Assert.NotEmpty(results.Items);
+        Assert.Equal(new() { Start = new(2, 0), End = caret.Range.Start }, results.ItemDefaults.EditRange.Value.First);
+    }
+}
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionResolveTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionResolveTests.cs
index c97dea3c05655..a2a7fa539ddf7 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionResolveTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionResolveTests.cs
@@ -182,8 +182,8 @@ class B : A
             var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
 
             var selectedItem = CodeAnalysis.Completion.CompletionItem.Create(displayText: "M", isComplexTextEdit: true);
-            var textEdit = await EditorLspCompletionResultCreationService.GenerateTextEditAsync(
-                document, new TestCaretOutOfScopeCompletionService(testLspServer.TestWorkspace.Services.SolutionServices), selectedItem, snippetsSupported: true, CancellationToken.None).ConfigureAwait(false);
+            var (textEdit, _, _) = await AbstractLspCompletionResultCreationService.GenerateComplexTextEditAsync(
+                document, new TestCaretOutOfScopeCompletionService(testLspServer.TestWorkspace.Services.SolutionServices), selectedItem, snippetsSupported: true, insertNewPositionPlaceholder: true, CancellationToken.None).ConfigureAwait(false);
 
             Assert.Equal(@"public override void M()
     {
@@ -357,6 +357,7 @@ private static VSInternalCompletionItem Clone(VSInternalCompletionItem completio
             return new VSInternalCompletionItem()
             {
                 Label = completionItem.Label,
+                LabelDetails = completionItem.LabelDetails,
                 Kind = completionItem.Kind,
                 Detail = completionItem.Detail,
                 Documentation = completionItem.Documentation,
@@ -366,6 +367,7 @@ private static VSInternalCompletionItem Clone(VSInternalCompletionItem completio
                 InsertText = completionItem.InsertText,
                 InsertTextFormat = completionItem.InsertTextFormat,
                 TextEdit = completionItem.TextEdit,
+                TextEditText = completionItem.TextEditText,
                 AdditionalTextEdits = completionItem.AdditionalTextEdits,
                 CommitCharacters = completionItem.CommitCharacters,
                 Command = completionItem.Command,
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionTests.cs
index 4a21b8f3c86d3..80b3fa380dde6 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/Completion/CompletionTests.cs
@@ -10,10 +10,9 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Completion;
-using Microsoft.CodeAnalysis.LanguageServer.Handler;
-using Microsoft.CodeAnalysis.LanguageServer.Handler.CodeActions;
 using Microsoft.CodeAnalysis.LanguageServer.Handler.Completion;
 using Microsoft.CodeAnalysis.Options;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Roslyn.Test.Utilities;
 using Xunit;
 using Xunit.Abstractions;
@@ -31,13 +30,18 @@ private static LSP.VSInternalClientCapabilities CreateCoreCompletionCapabilities
                 SupportsVisualStudioExtensions = true,
                 TextDocument = new()
                 {
-                    Completion = new()
+                    Completion = new VSInternalCompletionSetting()
                     {
-                        CompletionListSetting = new()
+                        CompletionListSetting = new CompletionListSetting()
                         {
-                            ItemDefaults = new[] { CompletionHandler.EditRangeSetting },
+                            ItemDefaults = new[] { CompletionCapabilityHelper.EditRangePropertyName },
                         },
                         CompletionItemKind = new(),
+
+                        CompletionList = new VSInternalCompletionListSetting()
+                        {
+                            CommitCharacters = true,
+                        }
                     },
                 },
             };
@@ -47,8 +51,12 @@ public CompletionTests(ITestOutputHelper testOutputHelper) : base(testOutputHelp
         }
 
         [Theory, CombinatorialData]
-        public async Task TestGetCompletionsAsync_PromotesCommitCharactersToListAsync(bool mutatingLspWorkspace)
+        public async Task TestGetCompletionsAsync_PromotesCommitCharactersToListAsync(bool mutatingLspWorkspace, bool isPublicDefaultCommitChars)
         {
+            var itemDefaultArray = isPublicDefaultCommitChars
+                ? new string[] { CompletionCapabilityHelper.EditRangePropertyName, CompletionCapabilityHelper.CommitCharactersPropertyName }
+                : new string[] { CompletionCapabilityHelper.EditRangePropertyName };
+
             var clientCapabilities = new LSP.VSInternalClientCapabilities
             {
                 SupportsVisualStudioExtensions = true,
@@ -58,12 +66,10 @@ public async Task TestGetCompletionsAsync_PromotesCommitCharactersToListAsync(bo
                     {
                         CompletionListSetting = new LSP.CompletionListSetting
                         {
-                            ItemDefaults = new string[] { CompletionHandler.EditRangeSetting }
+                            ItemDefaults = itemDefaultArray
+
                         },
-                        CompletionList = new LSP.VSInternalCompletionListSetting
-                        {
-                            CommitCharacters = true,
-                        }
+                        CompletionList = isPublicDefaultCommitChars ? null : new LSP.VSInternalCompletionListSetting { CommitCharacters = true }
                     },
                 }
             };
@@ -94,7 +100,11 @@ void M()
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             AssertJsonEquals(expected, results.Items.First());
             var vsCompletionList = Assert.IsAssignableFrom<LSP.VSInternalCompletionList>(results);
-            Assert.Equal(expectedCommitCharacters, vsCompletionList.CommitCharacters.Value.First);
+
+            if (isPublicDefaultCommitChars)
+                Assert.Equal(expectedCommitCharacters, vsCompletionList.ItemDefaults.CommitCharacters);
+            else
+                Assert.Equal(expectedCommitCharacters, vsCompletionList.CommitCharacters.Value.First);
         }
 
         [Theory, CombinatorialData]
@@ -109,7 +119,7 @@ public async Task TestGetCompletions_PromotesNothingWhenNoCommitCharactersAsync(
                     {
                         CompletionListSetting = new LSP.CompletionListSetting
                         {
-                            ItemDefaults = new string[] { CompletionHandler.EditRangeSetting }
+                            ItemDefaults = new string[] { CompletionCapabilityHelper.EditRangePropertyName }
                         },
                         CompletionList = new LSP.VSInternalCompletionListSetting
                         {
@@ -132,7 +142,7 @@ public async Task TestGetCompletions_PromotesNothingWhenNoCommitCharactersAsync(
             var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
 
             var expected = await CreateCompletionItemAsync(label: "A", kind: LSP.CompletionItemKind.Class, tags: new string[] { "Class", "Internal" },
-                request: completionParams, document: document, commitCharacters: CompletionRules.Default.DefaultCommitCharacters, insertText: "A").ConfigureAwait(false);
+                request: completionParams, document: document, commitCharacters: CompletionRules.Default.DefaultCommitCharacters).ConfigureAwait(false);
             var expectedCommitCharacters = expected.CommitCharacters;
 
             // Null out the commit characters since we're expecting the commit characters will be lifted onto the completion list.
@@ -286,8 +296,9 @@ void M()
             await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, s_vsCompletionCapabilities);
             var solution = testLspServer.TestWorkspace.CurrentSolution;
 
-            // Make sure the unimported types option is on by default.
+            // Make sure the unimported types option is on
             testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(CompletionOptionsStorage.ShowItemsFromUnimportedNamespaces, LanguageNames.CSharp, true);
+            testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(CompletionOptionsStorage.ForceExpandedCompletionIndexCreation, true);
 
             var completionParams = CreateCompletionParams(
                 testLspServer.GetLocations("caret").Single(),
@@ -401,7 +412,8 @@ void M()
             var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
 
             var expected = await CreateCompletionItemAsync(
-                label: "d", kind: LSP.CompletionItemKind.Text, tags: new string[] { "Text" }, request: completionParams, document: document, sortText: "0000").ConfigureAwait(false);
+                label: "d", kind: LSP.CompletionItemKind.Text, tags: new string[] { "Text" }, request: completionParams, document: document, sortText: "0000",
+                labelDetails: new() { Description = "shortdate" }).ConfigureAwait(false);
 
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             AssertJsonEquals(expected, results.Items.First());
@@ -461,8 +473,8 @@ void M()
             };
 
             var expected = await CreateCompletionItemAsync(
-                label: @"\A", kind: LSP.CompletionItemKind.Text, tags: new string[] { "Text" }, request: completionParams, document: document, insertText: @"\\A",
-                sortText: "0000").ConfigureAwait(false);
+                label: @"\A", kind: LSP.CompletionItemKind.Text, tags: new string[] { "Text" }, request: completionParams, document: document, textEditText: @"\\A",
+                sortText: "0000", labelDetails: new() { Description = "startofstringonly" }).ConfigureAwait(false);
 
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             AssertJsonEquals(expected, results.Items.First());
@@ -499,7 +511,7 @@ void M()
 
             var expected = await CreateCompletionItemAsync(
                 label: @"\A", kind: LSP.CompletionItemKind.Text, tags: new string[] { "Text" }, request: completionParams, document: document,
-                sortText: "0000", vsResolveTextEditOnCommit: true).ConfigureAwait(false);
+                sortText: "0000", vsResolveTextEditOnCommit: true, labelDetails: new() { Description = "startofstringonly" }).ConfigureAwait(false);
 
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             AssertJsonEquals(expected, results.Items.First());
@@ -536,7 +548,7 @@ void M()
 
             var expected = await CreateCompletionItemAsync(
                 label: @"\A", kind: LSP.CompletionItemKind.Text, tags: new string[] { "Text" }, request: completionParams, document: document,
-                sortText: "0000", vsResolveTextEditOnCommit: true).ConfigureAwait(false);
+                sortText: "0000", vsResolveTextEditOnCommit: true, labelDetails: new() { Description = "startofstringonly" }).ConfigureAwait(false);
 
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             AssertJsonEquals(expected, results.Items.First());
@@ -557,7 +569,13 @@ public async Task TestGetRegexCompletionsWithoutItemDefaultSupportAsync(bool mut
                         {
                             ItemDefaults = null,
                         },
+
+                        CompletionList = new VSInternalCompletionListSetting
+                        {
+                            CommitCharacters = true,
+                        }
                     },
+
                 }
             };
 
@@ -584,7 +602,7 @@ void M()
 
             var expected = await CreateCompletionItemAsync(
                 label: @"\A", kind: LSP.CompletionItemKind.Text, tags: new string[] { "Text" }, request: completionParams, document: document, textEdit: textEdit,
-                sortText: "0000").ConfigureAwait(false);
+                sortText: "0000", labelDetails: new() { Description = "startofstringonly" }).ConfigureAwait(false);
 
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             AssertJsonEquals(expected, results.Items.First());
@@ -738,33 +756,6 @@ partial class C
             Assert.Null(results.Items.First().InsertText);
         }
 
-        [Theory, CombinatorialData]
-        public async Task TestAlwaysHasCommitCharactersWithoutVSCapabilityAsync(bool mutatingLspWorkspace)
-        {
-            var markup =
-@"using System;
-class A
-{
-    void M()
-    {
-        {|caret:|}
-    }
-}";
-            await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace);
-            var completionParams = CreateCompletionParams(
-                testLspServer.GetLocations("caret").Single(),
-                invokeKind: LSP.VSInternalCompletionInvokeKind.Explicit,
-                triggerCharacter: "\0",
-                triggerKind: LSP.CompletionTriggerKind.Invoked);
-
-            var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
-
-            var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
-            Assert.NotNull(results);
-            Assert.NotEmpty(results.Items);
-            Assert.All(results.Items, (item) => Assert.NotNull(item.CommitCharacters));
-        }
-
         [Theory, CombinatorialData]
         public async Task TestSoftSelectedItemsHaveNoCommitCharactersWithoutVSCapabilityAsync(bool mutatingLspWorkspace)
         {
@@ -789,7 +780,7 @@ void M()
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             Assert.NotNull(results);
             Assert.NotEmpty(results.Items);
-            Assert.All(results.Items, (item) => Assert.Null(item.CommitCharacters));
+            Assert.All(results.Items, (item) => Assert.Empty(item.CommitCharacters));
         }
 
         [Theory, CombinatorialData]
@@ -1158,7 +1149,7 @@ void M()
 
     void M2()
     {
-        Console.W{|secondCaret:|}
+        Console.WH{|secondCaret:|}
     }
 }";
             await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, s_vsCompletionCapabilities);
@@ -1170,22 +1161,22 @@ void M2()
                 firstCaret,
                 invokeKind: LSP.VSInternalCompletionInvokeKind.Typing,
                 triggerCharacter: "T",
-                triggerKind: LSP.CompletionTriggerKind.Invoked);
+                triggerKind: LSP.CompletionTriggerKind.TriggerCharacter);
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             Assert.Equal(1000, results.Items.Length);
             Assert.True(results.IsIncomplete);
-            Assert.Equal("T", results.Items.First().Label);
+            Assert.Contains(results.Items, i => i.Label == "T"); // It's client's responsibility to sort, so we can't assume the best match is the first item.
 
             // Make a second completion request, but not for the original incomplete list.
             completionParams = CreateCompletionParams(
                 testLspServer.GetLocations("secondCaret").Single(),
                 invokeKind: LSP.VSInternalCompletionInvokeKind.Typing,
-                triggerCharacter: "W",
-                triggerKind: LSP.CompletionTriggerKind.Invoked);
+                triggerCharacter: "H",
+                triggerKind: LSP.CompletionTriggerKind.TriggerForIncompleteCompletions);
             results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             Assert.False(results.IsIncomplete);
             Assert.True(results.Items.Length < 1000);
-            Assert.Equal("WindowHeight", results.Items.First().Label);
+            Assert.Contains(results.Items, i => i.Label == "WindowHeight"); // It's client's responsibility to sort, so we can't assume the best match is the first item.
         }
 
         [Theory, CombinatorialData]
@@ -1333,16 +1324,6 @@ void M2()
             Assert.True(results.Items.Length < 1000);
             Assert.DoesNotContain(results.Items, item => item.Label == "Saaa");
             Assert.Contains(results.Items, item => item.Label == "Taaa");
-
-            static LSP.Location GetLocationPlusOne(LSP.Location originalLocation)
-            {
-                var newPosition = new LSP.Position { Character = originalLocation.Range.Start.Character + 1, Line = originalLocation.Range.Start.Line };
-                return new LSP.Location
-                {
-                    Uri = originalLocation.Uri,
-                    Range = new LSP.Range { Start = newPosition, End = newPosition }
-                };
-            }
         }
 
         [Theory, CombinatorialData]
@@ -1439,7 +1420,7 @@ void M()
         }
 
         [Theory, CombinatorialData, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1755138")]
-        public async Task TestOnlyHasSuggestionModeItemAsync(bool mutatingLspWorkspace)
+        public async Task TestHasSuggestionModeItemAsync(bool mutatingLspWorkspace)
         {
             var markup =
 @"using System.Threading.Tasks;
@@ -1461,37 +1442,33 @@ void M()
 
             var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
             var list = (LSP.VSInternalCompletionList)results;
-            Assert.Empty(list.Items);
+            Assert.False(list.IsIncomplete);
+            Assert.NotEmpty(list.Items); // it client's responsibility to filter, server should return all items available regardless of the filter text (unless item counts exceeds the limit)
             Assert.True(list.SuggestionMode);
         }
 
-        [Theory, CombinatorialData, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1755955")]
-        public async Task TestNotTriggerCompletionInArgumentListAsync(bool mutatingLspWorkspace)
+        [Theory, CombinatorialData]
+        public async Task EditRangeShouldNotEndAtCursorPosition(bool mutatingLspWorkspace)
         {
             var markup =
-@"
-using System;
-using System.Text;
+@"public class C1 {}
+
+pub{|caret:|}class";
 
-public class A
-{
-    public void M()
-    {
-        var x = new StringBuilder();
-        x.Append({|caret:|}
-    }
-}";
             await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, s_vsCompletionCapabilities);
+            var caret = testLspServer.GetLocations("caret").Single();
+            testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(CompletionOptionsStorage.SnippetsBehavior, LanguageNames.CSharp, SnippetsRule.NeverInclude);
+
             var completionParams = CreateCompletionParams(
-                testLspServer.GetLocations("caret").Single(),
-                invokeKind: LSP.VSInternalCompletionInvokeKind.Typing,
-                triggerCharacter: "(",
+                caret,
+                invokeKind: LSP.VSInternalCompletionInvokeKind.Explicit,
+                triggerCharacter: "\0",
                 triggerKind: LSP.CompletionTriggerKind.Invoked);
 
-            var document = testLspServer.GetCurrentSolution().Projects.First().Documents.First();
-
-            var results = await RunGetCompletionsAsync(testLspServer, completionParams).ConfigureAwait(false);
-            Assert.Null(results);
+            var results = await RunGetCompletionsAsync(testLspServer, completionParams);
+            AssertEx.NotNull(results);
+            Assert.NotEmpty(results.Items);
+            Assert.Equal(new() { Start = new(2, 0), End = new(2, 8) }, results.ItemDefaults.EditRange.Value.First);
         }
 
         internal static Task<LSP.CompletionList> RunGetCompletionsAsync(TestLspServer testLspServer, LSP.CompletionParams completionParams)
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/Configuration/DidChangeConfigurationNotificationHandlerTest.cs b/src/Features/LanguageServer/ProtocolUnitTests/Configuration/DidChangeConfigurationNotificationHandlerTest.cs
index 7bd4012f3d5bb..5288270ce0394 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/Configuration/DidChangeConfigurationNotificationHandlerTest.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/Configuration/DidChangeConfigurationNotificationHandlerTest.cs
@@ -25,7 +25,7 @@ public class DidChangeConfigurationNotificationHandlerTest : AbstractLanguageSer
     {
         // A regex help to check the message we send to client.
         // It should look like "feature_group.feature_name"
-        private static readonly string s_clientSideSectionPattern = @"^((csharp|visual_basic)\|)?([\w_]+)\.([\w_]+)$";
+        private static readonly string s_clientSideSectionPattern = @"^((csharp|visual_basic)\|)?([\w_|\.]+)([\w_]+)$";
 
         public DidChangeConfigurationNotificationHandlerTest(ITestOutputHelper? testOutputHelper) : base(testOutputHelper)
         {
@@ -206,6 +206,11 @@ private static string GenerateDefaultValue(IOption2 option)
 
             private static object? GetNonDefaultValue(IOption2 option)
             {
+                if (TryGetValueNonDefaultValueBasedOnName(option, out var nonDefaultValue))
+                {
+                    return nonDefaultValue;
+                }
+
                 var type = option.Type;
                 if (type == typeof(bool))
                 {
@@ -242,7 +247,7 @@ private static string GenerateDefaultValue(IOption2 option)
                 }
                 else
                 {
-                    throw new Exception("Please return a non-default value based on the config name.");
+                    throw new Exception($"Please return a non-default value based on the config name, config name: {option.Name}.");
                 }
 
                 object GetDifferentEnumValue(Type enumType, object enumValue)
@@ -257,6 +262,18 @@ object GetDifferentEnumValue(Type enumType, object enumValue)
 
                     throw new ArgumentException($"{enumType.Name} has only one value.");
                 }
+
+                static bool TryGetValueNonDefaultValueBasedOnName(IOption option, out object? nonDefaultValue)
+                {
+                    if (option.Name is "end_of_line")
+                    {
+                        nonDefaultValue = "\n";
+                        return true;
+                    }
+
+                    nonDefaultValue = null;
+                    return false;
+                }
             }
 
             private static void AssertSectionPattern(string? section)
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/Definitions/GoToDefinitionTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/Definitions/GoToDefinitionTests.cs
index 2ebc90b31346c..72f26342b4d8b 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/Definitions/GoToDefinitionTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/Definitions/GoToDefinitionTests.cs
@@ -152,6 +152,33 @@ End Class
             AssertLocationsEqual(testLspServer.GetLocations("definition"), results);
         }
 
+        [Theory, CombinatorialData]
+        [WorkItem("https://github.com/dotnet/vscode-csharp/issues/5740")]
+        public async Task TestGotoDefinitionPartialMethods(bool mutatingLspWorkspace)
+        {
+            var markup =
+                """
+                using System;
+
+                public partial class C
+                {
+                    partial void {|caret:|}P();
+                }
+
+                public partial class C
+                {
+                    partial void {|definition:P|}()
+                    {
+                        Console.WriteLine(");
+                    }
+                }
+                """;
+            await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace);
+
+            var results = await RunGotoDefinitionAsync(testLspServer, testLspServer.GetLocations("caret").Single());
+            AssertLocationsEqual(testLspServer.GetLocations("definition"), results);
+        }
+
         private static async Task<LSP.Location[]> RunGotoDefinitionAsync(TestLspServer testLspServer, LSP.Location caret)
         {
             return await testLspServer.ExecuteRequestAsync<LSP.TextDocumentPositionParams, LSP.Location[]>(LSP.Methods.TextDocumentDefinitionName,
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/Diagnostics/PullDiagnosticTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/Diagnostics/PullDiagnosticTests.cs
index 019f280170539..d87841e466794 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/Diagnostics/PullDiagnosticTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/Diagnostics/PullDiagnosticTests.cs
@@ -8,7 +8,6 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.EditAndContinue;
 using Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -298,7 +297,7 @@ public async Task TestNoChangeIfDocumentDiagnosticsCalledTwice(bool useVSDiagnos
 
         [Theory, CombinatorialData]
         [WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1481208")]
-        public async Task TestDocumentDiagnosticsWhenEnCVersionChanges(bool useVSDiagnostics, bool mutatingLspWorkspace)
+        public async Task TestDocumentDiagnosticsWhenGlobalStateChanges(bool useVSDiagnostics, bool mutatingLspWorkspace)
         {
             var markup =
 @"class A {";
@@ -317,10 +316,9 @@ public async Task TestDocumentDiagnosticsWhenEnCVersionChanges(bool useVSDiagnos
 
             var resultId = results.Single().ResultId;
 
-            // Create a fake diagnostic to trigger a change in edit and continue, without a document change
-            var encDiagnosticsSource = testLspServer.TestWorkspace.ExportProvider.GetExportedValue<EditAndContinueDiagnosticUpdateSource>();
-            var rudeEdits = ImmutableArray.Create((document.Id, ImmutableArray.Create(new RudeEditDiagnostic(RudeEditKind.Update, default))));
-            encDiagnosticsSource.ReportDiagnostics(testLspServer.TestWorkspace, testLspServer.TestWorkspace.CurrentSolution, ImmutableArray<DiagnosticData>.Empty, rudeEdits);
+            // Trigger refresh due to a change to global state that affects diagnostics.
+            var refresher = testLspServer.TestWorkspace.ExportProvider.GetExportedValue<IDiagnosticsRefresher>();
+            refresher.RequestWorkspaceRefresh();
 
             results = await RunGetDocumentPullDiagnosticsAsync(
                 testLspServer, document.GetURI(), useVSDiagnostics, previousResultId: resultId);
@@ -775,17 +773,32 @@ void M()
             var results = await RunGetDocumentPullDiagnosticsAsync(
                 testLspServer, document.GetURI(), useVSDiagnostics);
 
-            // The first line should have a diagnostic on it that is not marked as unnecessary.
-            Assert.False(results.Single().Diagnostics![0].Tags!.Contains(DiagnosticTag.Unnecessary));
-            Assert.Equal(lineLocation, results.Single().Diagnostics![0].Range);
+            if (useVSDiagnostics)
+            {
+                // The first line should have a diagnostic on it that is not marked as unnecessary.
+                Assert.False(results.Single().Diagnostics![0].Tags!.Contains(DiagnosticTag.Unnecessary));
+                Assert.Equal(lineLocation, results.Single().Diagnostics![0].Range);
+
+                // The open paren should have an unnecessary diagnostic.
+                Assert.True(results.Single().Diagnostics![1].Tags!.Contains(DiagnosticTag.Unnecessary));
+                Assert.Equal(openLocation, results.Single().Diagnostics![1].Range);
+
+                // The close paren should have an unnecessary diagnostic.
+                Assert.True(results.Single().Diagnostics![2].Tags!.Contains(DiagnosticTag.Unnecessary));
+                Assert.Equal(closeLocation, results.Single().Diagnostics![2].Range);
+            }
+            else
+            {
+                // There should be one unnecessary diagnostic.
+                Assert.True(results.Single().Diagnostics.Single().Tags!.Contains(DiagnosticTag.Unnecessary));
+                Assert.Equal(lineLocation, results.Single().Diagnostics.Single().Range);
 
-            // The open paren should have an unnecessary diagnostic.
-            Assert.True(results.Single().Diagnostics![1].Tags!.Contains(DiagnosticTag.Unnecessary));
-            Assert.Equal(openLocation, results.Single().Diagnostics![1].Range);
+                // There should be an additional location for the open paren.
+                Assert.Equal(openLocation, results.Single().Diagnostics.Single().RelatedInformation![0].Location.Range);
 
-            // The close paren should have an unnecessary diagnostic.
-            Assert.True(results.Single().Diagnostics![2].Tags!.Contains(DiagnosticTag.Unnecessary));
-            Assert.Equal(closeLocation, results.Single().Diagnostics![2].Range);
+                // There should be an additional location for the close paren.
+                Assert.Equal(closeLocation, results.Single().Diagnostics.Single().RelatedInformation![1].Location.Range);
+            }
         }
 
         [Theory, CombinatorialData, WorkItem("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1806590")]
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/CSharpInlayHintTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/CSharpInlayHintTests.cs
index 345c243e74a9b..a338d1d753c80 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/CSharpInlayHintTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/CSharpInlayHintTests.cs
@@ -9,6 +9,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.InlineHints;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Microsoft.CodeAnalysis.LanguageServer.Handler.InlayHint;
 using Microsoft.CodeAnalysis.Text;
 using Newtonsoft.Json;
@@ -160,7 +161,18 @@ void M()
 
         private async Task RunVerifyInlayHintAsync(string markup, bool mutatingLspWorkspace, bool hasTextEdits = true)
         {
-            await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace, CapabilitiesWithVSExtensions);
+            await using var testLspServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace,
+                new LSP.VSInternalClientCapabilities
+                {
+                    SupportsVisualStudioExtensions = true,
+                    Workspace = new WorkspaceClientCapabilities
+                    {
+                        InlayHint = new InlayHintWorkspaceSetting
+                        {
+                            RefreshSupport = true
+                        }
+                    }
+                });
             testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(InlineHintsOptionsStorage.EnabledForParameters, LanguageNames.CSharp, true);
             testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(InlineHintsOptionsStorage.EnabledForTypes, LanguageNames.CSharp, true);
             await VerifyInlayHintAsync(testLspServer, hasTextEdits);
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/VisualBasicInlayHintTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/VisualBasicInlayHintTests.cs
index 98ec33170d732..8c813143bf2e0 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/VisualBasicInlayHintTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/InlayHint/VisualBasicInlayHintTests.cs
@@ -8,8 +8,10 @@
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.InlineHints;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
 using Xunit;
 using Xunit.Abstractions;
+using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.LanguageServer.UnitTests.InlayHint
 {
@@ -51,7 +53,20 @@ End Sub
 
         private async Task RunVerifyInlayHintAsync(string markup, bool mutatingLspWorkspace)
         {
-            await using var testLspServer = await CreateVisualBasicTestLspServerAsync(markup, mutatingLspWorkspace);
+            await using var testLspServer = await CreateVisualBasicTestLspServerAsync(markup, mutatingLspWorkspace, new InitializationOptions
+            {
+                ClientCapabilities = new LSP.VSInternalClientCapabilities
+                {
+                    SupportsVisualStudioExtensions = true,
+                    Workspace = new WorkspaceClientCapabilities
+                    {
+                        InlayHint = new InlayHintWorkspaceSetting
+                        {
+                            RefreshSupport = true
+                        }
+                    }
+                }
+            });
             testLspServer.TestWorkspace.GlobalOptions.SetGlobalOption(InlineHintsOptionsStorage.EnabledForParameters, LanguageNames.VisualBasic, true);
             await VerifyInlayHintAsync(testLspServer);
         }
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/OnAutoInsert/OnAutoInsertTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/OnAutoInsert/OnAutoInsertTests.cs
index 12e4c1aae7fca..028f9bfacd476 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/OnAutoInsert/OnAutoInsertTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/OnAutoInsert/OnAutoInsertTests.cs
@@ -37,8 +37,8 @@ void M()
 @"class A
 {
     /// <summary>
-    /// $0
-    /// </summary>
+/// $0
+/// </summary>
     void M()
     {
     }
@@ -61,8 +61,8 @@ void M()
 @"class A
 {
     /// <summary>
-    /// $0This is an existing comment
-    /// </summary>
+/// $0This is an existing comment
+/// </summary>
     void M()
     {
     }
@@ -85,8 +85,8 @@ void M()
 @"class A
 {
     /// <summary>
-    /// $0This is an existing comment
-    /// </summary>
+/// $0This is an existing comment
+/// </summary>
     void M()
     {
     }
@@ -106,8 +106,8 @@ End Sub
             var expected =
 @"Class A
     ''' <summary>
-    ''' $0
-    ''' </summary>
+''' $0
+''' </summary>
     Sub M()
     End Sub
 End Class";
@@ -129,11 +129,11 @@ string M(int foo, bool bar)
 @"class A
 {
     /// <summary>
-    /// $0
-    /// </summary>
-    /// <param name=""foo""></param>
-    /// <param name=""bar""></param>
-    /// <returns></returns>
+/// $0
+/// </summary>
+/// <param name=""foo""></param>
+/// <param name=""bar""></param>
+/// <returns></returns>
     string M(int foo, bool bar)
     {
     }
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/AbstractSemanticTokensTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/AbstractSemanticTokensTests.cs
index 2143858418bc8..007afa5b15ee1 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/AbstractSemanticTokensTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/AbstractSemanticTokensTests.cs
@@ -28,7 +28,7 @@ protected AbstractSemanticTokensTests(ITestOutputHelper testOutputHelper) : base
         }
 
         private protected static IReadOnlyDictionary<string, int> GetTokenTypeToIndex(TestLspServer server)
-            => SemanticTokensSchema.GetSchema(server.ClientCapabilities).TokenTypeToIndex;
+            => SemanticTokensSchema.GetSchema(server.ClientCapabilities.HasVisualStudioLspCapability()).TokenTypeToIndex;
 
         private protected static async Task<LSP.SemanticTokens> RunGetSemanticTokensRangeAsync(TestLspServer testLspServer, LSP.Location caret, LSP.Range range)
         {
@@ -111,7 +111,7 @@ protected static ImmutableArray<string> ConvertToReadableFormat(
             ClientCapabilities capabilities, int[] data)
         {
             var convertedStringsBuilder = ImmutableArray.CreateBuilder<string>(data.Length / 5);
-            var tokenTypeToIndex = SemanticTokensSchema.GetSchema(capabilities).TokenTypeToIndex;
+            var tokenTypeToIndex = SemanticTokensSchema.GetSchema(capabilities.HasVisualStudioLspCapability()).TokenTypeToIndex;
 
             for (var i = 0; i < data.Length; i += 5)
             {
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/SemanticTokensRangeTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/SemanticTokensRangeTests.cs
index 30af4b0f8d4cd..ad3bd913945b7 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/SemanticTokensRangeTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/SemanticTokens/SemanticTokensRangeTests.cs
@@ -487,7 +487,7 @@ void M()
         public void TestGetSemanticTokensRange_AssertCustomTokenTypes(bool isVS)
         {
             var capabilities = GetCapabilities(isVS);
-            var schema = SemanticTokensSchema.GetSchema(capabilities);
+            var schema = SemanticTokensSchema.GetSchema(capabilities.HasVisualStudioLspCapability());
 
             var expectedNames = ClassificationTypeNames.AllTypeNames.Where(s => !ClassificationTypeNames.AdditiveTypeNames.Contains(s));
             foreach (var expectedClassificationName in expectedNames)
diff --git a/src/Features/LanguageServer/ProtocolUnitTests/UriTests.cs b/src/Features/LanguageServer/ProtocolUnitTests/UriTests.cs
index a27a39b0a910e..e800811f074fb 100644
--- a/src/Features/LanguageServer/ProtocolUnitTests/UriTests.cs
+++ b/src/Features/LanguageServer/ProtocolUnitTests/UriTests.cs
@@ -101,4 +101,35 @@ public class A
         Assert.Equal(expectedDocumentUri, document.GetURI());
         Assert.Equal(documentFilePath, document.FilePath);
     }
+
+    [Theory, CombinatorialData]
+    public async Task TestWorkspaceDocument_WithFileAndGitScheme(bool mutatingLspWorkspace)
+    {
+        // Start with an empty workspace.
+        await using var testLspServer = await CreateTestLspServerAsync(
+            "Initial Disk Contents", mutatingLspWorkspace, new InitializationOptions { ServerKind = WellKnownLspServerKinds.CSharpVisualBasicLspServer });
+
+        var fileDocumentUri = testLspServer.TestWorkspace.CurrentSolution.Projects.Single().Documents.Single().GetURI();
+        var fileDocumentText = "FileText";
+        await testLspServer.OpenDocumentAsync(fileDocumentUri, fileDocumentText);
+
+        // Add a git version of this document. Instead of "file://FILEPATH" the uri is "git://FILEPATH"
+        var gitDocumentUri = new Uri(fileDocumentUri.ToString().Replace("file", "git"));
+        var gitDocumentText = "GitText";
+        await testLspServer.OpenDocumentAsync(gitDocumentUri, gitDocumentText);
+
+        // Verify file is added to the workspace and the text matches the file document
+        var (workspace, _, fileDocument) = await testLspServer.GetManager().GetLspDocumentInfoAsync(new LSP.TextDocumentIdentifier { Uri = fileDocumentUri }, CancellationToken.None);
+        AssertEx.NotNull(fileDocument);
+        var fileTextResult = await fileDocument.GetTextAsync();
+        Assert.Equal(fileDocumentUri, fileDocument.GetURI());
+        Assert.Equal(fileDocumentText, fileTextResult.ToString());
+
+        // Verify file is added to the workspace and the text matches the git document
+        var (gitWorkspace, _, gitDocument) = await testLspServer.GetManager().GetLspDocumentInfoAsync(new LSP.TextDocumentIdentifier { Uri = gitDocumentUri }, CancellationToken.None);
+        AssertEx.NotNull(gitDocument);
+        var gitText = await gitDocument.GetTextAsync();
+        Assert.Equal(gitDocumentUri, gitDocument.GetURI());
+        Assert.Equal(gitDocumentText, gitText.ToString());
+    }
 }
diff --git a/src/Features/TestUtilities/Microsoft.CodeAnalysis.Features.Test.Utilities.csproj b/src/Features/TestUtilities/Microsoft.CodeAnalysis.Features.Test.Utilities.csproj
index 002cd493e6d3a..1f27a22f88f83 100644
--- a/src/Features/TestUtilities/Microsoft.CodeAnalysis.Features.Test.Utilities.csproj
+++ b/src/Features/TestUtilities/Microsoft.CodeAnalysis.Features.Test.Utilities.csproj
@@ -33,6 +33,7 @@
     <PackageReference Include="SQLitePCLRaw.bundle_green" Version="$(SQLitePCLRawbundle_greenVersion)" />
     <PackageReference Include="StreamJsonRpc" Version="$(StreamJsonRpcVersion)" />
     <PackageReference Include="Microsoft.ServiceHub.Client" Version="$(MicrosoftServiceHubClientVersion)" />
+    <PackageReference Include="Microsoft.ServiceHub.Framework" Version="$(MicrosoftServiceHubFrameworkVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Editor" Version="$(MicrosoftVisualStudioEditorVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Platform.VSEditor" Version="$(MicrosoftVisualStudioPlatformVSEditorVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.ComponentModelHost" Version="$(MicrosoftVisualStudioComponentModelHostVersion)" />
diff --git a/src/Features/VisualBasic/Portable/AddImport/VisualBasicAddImportFeatureService.vb b/src/Features/VisualBasic/Portable/AddImport/VisualBasicAddImportFeatureService.vb
index 35aa5d41d3a07..c001287736e24 100644
--- a/src/Features/VisualBasic/Portable/AddImport/VisualBasicAddImportFeatureService.vb
+++ b/src/Features/VisualBasic/Portable/AddImport/VisualBasicAddImportFeatureService.vb
@@ -318,7 +318,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
             Return AddImportAsync(contextNode, document, importsStatement, options, cancellationToken)
         End Function
 
-        Private Function CreateNameSyntax(nameSpaceParts As IReadOnlyList(Of String), index As Integer) As NameSyntax
+        Private Shared Function CreateNameSyntax(nameSpaceParts As IReadOnlyList(Of String), index As Integer) As NameSyntax
             Dim namePiece = SyntaxFactory.IdentifierName(nameSpaceParts(index))
             Return If(index = 0,
                 DirectCast(namePiece, NameSyntax),
diff --git a/src/Features/VisualBasic/Portable/Completion/CompletionProviders/ImplementsClauseCompletionProvider.vb b/src/Features/VisualBasic/Portable/Completion/CompletionProviders/ImplementsClauseCompletionProvider.vb
index 860d5189bedd9..d69a14b56c35a 100644
--- a/src/Features/VisualBasic/Portable/Completion/CompletionProviders/ImplementsClauseCompletionProvider.vb
+++ b/src/Features/VisualBasic/Portable/Completion/CompletionProviders/ImplementsClauseCompletionProvider.vb
@@ -135,7 +135,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
             Return memberKindKeyword = SyntaxKind.EventKeyword
         End Function
 
-        Private Function GetDottedMembers(position As Integer, qualifiedName As QualifiedNameSyntax, semanticModel As SemanticModel, memberKindKeyword As SyntaxKind, cancellationToken As CancellationToken) As ImmutableArray(Of ISymbol)
+        Private Shared Function GetDottedMembers(position As Integer, qualifiedName As QualifiedNameSyntax, semanticModel As SemanticModel, memberKindKeyword As SyntaxKind, cancellationToken As CancellationToken) As ImmutableArray(Of ISymbol)
             Dim containingType = semanticModel.GetEnclosingNamedType(position, cancellationToken)
             If containingType Is Nothing Then
                 Return ImmutableArray(Of ISymbol).Empty
@@ -225,7 +225,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
             Return result
         End Function
 
-        Private Sub AddAliasesAndContainers(symbol As ISymbol, interfacesAndContainers As ICollection(Of ISymbol), node As SyntaxNode, semanticModel As SemanticModel)
+        Private Shared Sub AddAliasesAndContainers(symbol As ISymbol, interfacesAndContainers As ICollection(Of ISymbol), node As SyntaxNode, semanticModel As SemanticModel)
             ' Add aliases, if any for 'symbol'
             AddAlias(symbol, interfacesAndContainers, node, semanticModel)
 
diff --git a/src/Features/VisualBasic/Portable/Diagnostics/Analyzers/VisualBasicSimplifyTypeNamesDiagnosticAnalyzer.vb b/src/Features/VisualBasic/Portable/Diagnostics/Analyzers/VisualBasicSimplifyTypeNamesDiagnosticAnalyzer.vb
index 726ca5bc0c81e..46efe4ebd0df2 100644
--- a/src/Features/VisualBasic/Portable/Diagnostics/Analyzers/VisualBasicSimplifyTypeNamesDiagnosticAnalyzer.vb
+++ b/src/Features/VisualBasic/Portable/Diagnostics/Analyzers/VisualBasicSimplifyTypeNamesDiagnosticAnalyzer.vb
@@ -35,14 +35,16 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeFixes.SimplifyTypeNames
                 codeBlock.IsKind(SyntaxKind.DelegateFunctionStatement)
         End Function
 
-        Protected Overrides Function AnalyzeCodeBlock(context As CodeBlockAnalysisContext) As ImmutableArray(Of Diagnostic)
+        Protected Overrides Function AnalyzeCodeBlock(context As CodeBlockAnalysisContext, root As SyntaxNode) As ImmutableArray(Of Diagnostic)
+            Debug.Assert(context.CodeBlock.DescendantNodesAndSelf().Contains(root))
+
             Dim semanticModel = context.SemanticModel
             Dim cancellationToken = context.CancellationToken
 
             Dim simplifierOptions = context.GetVisualBasicAnalyzerOptions().GetSimplifierOptions()
 
             Dim simplifier As New TypeSyntaxSimplifierWalker(Me, semanticModel, simplifierOptions, ignoredSpans:=Nothing, cancellationToken)
-            simplifier.Visit(context.CodeBlock)
+            simplifier.Visit(root)
             Return simplifier.Diagnostics
         End Function
 
diff --git a/src/Features/VisualBasic/Portable/EditAndContinue/SyntaxComparer.vb b/src/Features/VisualBasic/Portable/EditAndContinue/SyntaxComparer.vb
index dec16319bd967..f14f76193e3e3 100644
--- a/src/Features/VisualBasic/Portable/EditAndContinue/SyntaxComparer.vb
+++ b/src/Features/VisualBasic/Portable/EditAndContinue/SyntaxComparer.vb
@@ -72,8 +72,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
             TypeParameterList                ' tied to parent
             TypeParameter                    ' tied to parent
 
-            ParameterList                    ' tied to parent
-            Parameter                        ' tied to parent
             FieldOrParameterName             ' tied to grand-grandparent (type or method declaration)
 
             AttributeList                    ' tied to parent
@@ -197,6 +195,9 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
             OrderingLambda                      ' tied to parent (OrderByClause)
             JoinConditionLambda                 ' tied to parent (JoinClause)
 
+            ParameterList                       ' tied to parent
+            Parameter                           ' tied to parent
+
             LocalVariableName                   ' tied to parent 
 
             BodyEnd                             ' tied to parent
@@ -313,7 +314,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
                 Return ClassifyStatementSyntax(kind, nodeOpt, isLeaf)
             End If
 
-            Return ClassifyTopSytnax(kind, nodeOpt, isLeaf, ignoreVariableDeclarations)
+            Return ClassifyTopSyntax(kind, nodeOpt, isLeaf, ignoreVariableDeclarations)
         End Function
 
         Friend Shared Function ClassifyStatementSyntax(kind As SyntaxKind, nodeOpt As SyntaxNode, ByRef isLeaf As Boolean) As Label
@@ -345,8 +346,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
 
                 Case SyntaxKind.SubLambdaHeader,
                      SyntaxKind.FunctionLambdaHeader
-                    ' Header is a leaf so that we don't descent into lambda parameters.
-                    isLeaf = True
                     Return Label.LambdaBodyBegin
 
                 Case SyntaxKind.EndSubStatement,
@@ -625,9 +624,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
 
                 Case SyntaxKind.FunctionLambdaHeader,
                      SyntaxKind.SubLambdaHeader
-                    ' TODO: Parameters are not mapped?
-                    isLeaf = True
-                    Return Label.Ignored
+                    Return Label.LambdaBodyBegin
+
+                Case SyntaxKind.ParameterList
+                    Return Label.ParameterList
+
+                Case SyntaxKind.Parameter
+                    Return Label.Parameter
 
                 Case SyntaxKind.QueryExpression
                     Return Label.QueryExpression
@@ -720,7 +723,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
             End Select
         End Function
 
-        Private Shared Function ClassifyTopSytnax(kind As SyntaxKind, nodeOpt As SyntaxNode, ByRef isLeaf As Boolean, ignoreVariableDeclarations As Boolean) As Label
+        Private Shared Function ClassifyTopSyntax(kind As SyntaxKind, nodeOpt As SyntaxNode, ByRef isLeaf As Boolean, ignoreVariableDeclarations As Boolean) As Label
             Select Case kind
                 Case SyntaxKind.CompilationUnit
                     isLeaf = False
diff --git a/src/Features/VisualBasic/Portable/EditAndContinue/VisualBasicEditAndContinueAnalyzer.vb b/src/Features/VisualBasic/Portable/EditAndContinue/VisualBasicEditAndContinueAnalyzer.vb
index b5adb50c35fb1..545648be093b7 100644
--- a/src/Features/VisualBasic/Portable/EditAndContinue/VisualBasicEditAndContinueAnalyzer.vb
+++ b/src/Features/VisualBasic/Portable/EditAndContinue/VisualBasicEditAndContinueAnalyzer.vb
@@ -4,7 +4,6 @@
 
 Imports System.Collections.Immutable
 Imports System.Composition
-Imports System.Runtime.CompilerServices
 Imports System.Runtime.InteropServices
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Differencing
@@ -657,6 +656,47 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
             Return SyntaxComparer.TopLevel.ComputeMatch(oldCompilationUnit, newCompilationUnit)
         End Function
 
+        Protected Overrides Function ComputeParameterMap(oldDeclaration As SyntaxNode, newDeclaration As SyntaxNode) As BidirectionalMap(Of SyntaxNode)?
+            Dim oldParameterLists = GetDeclarationParameterLists(oldDeclaration)
+            Dim newParameterLists = GetDeclarationParameterLists(newDeclaration)
+
+            Dim primaryMatch = GetTopLevelMatch(oldParameterLists.Primary, newParameterLists.Primary)
+            Dim secondaryMatch = GetTopLevelMatch(oldParameterLists.Secondary, newParameterLists.Secondary)
+
+            If primaryMatch Is Nothing AndAlso secondaryMatch Is Nothing Then
+                Return Nothing
+            End If
+
+            Dim map = BidirectionalMap(Of SyntaxNode).FromMatch(If(primaryMatch, secondaryMatch))
+
+            If primaryMatch IsNot Nothing AndAlso secondaryMatch IsNot Nothing Then
+                map = map.WithMatch(secondaryMatch)
+            End If
+
+            Return map
+        End Function
+
+        Private Shared Function GetTopLevelMatch(oldNode As SyntaxNode, newNode As SyntaxNode) As Match(Of SyntaxNode)
+            Return If(oldNode IsNot Nothing AndAlso newNode IsNot Nothing, SyntaxComparer.TopLevel.ComputeMatch(oldNode, newNode), Nothing)
+        End Function
+
+        Private Shared Function GetDeclarationParameterLists(declaration As SyntaxNode) As (Primary As SyntaxNode, Secondary As SyntaxNode)
+            Select Case declaration.Kind
+                ' Indexer accessor may have two parameter lists: one on the property and ther other on the accessor
+                Case SyntaxKind.GetAccessorBlock,
+                     SyntaxKind.SetAccessorBlock
+                    Return (DirectCast(declaration.Parent, PropertyBlockSyntax).PropertyStatement.ParameterList,
+                            DirectCast(declaration, AccessorBlockSyntax).AccessorStatement.ParameterList)
+
+                Case SyntaxKind.AddHandlerAccessorBlock,
+                     SyntaxKind.RemoveHandlerAccessorBlock,
+                     SyntaxKind.RaiseEventAccessorBlock
+                    Return (DirectCast(declaration, AccessorBlockSyntax).AccessorStatement.ParameterList, Nothing)
+            End Select
+
+            Return (declaration.GetParameterList(), Nothing)
+        End Function
+
         Protected Overrides Function ComputeTopLevelDeclarationMatch(oldDeclaration As SyntaxNode, newDeclaration As SyntaxNode) As Match(Of SyntaxNode)
             Contract.ThrowIfNull(oldDeclaration.Parent)
             Contract.ThrowIfNull(newDeclaration.Parent)
@@ -815,7 +855,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
             Return False
         End Function
 
-        Protected Overrides Function GetGlobalStatementDiagnosticSpan(node As SyntaxNode) As TextSpan
+        Protected Overrides Function GetGlobalStatementDiagnosticSpan(node As SyntaxNode, editKind As EditKind) As TextSpan
             Return Nothing
         End Function
 
@@ -1097,11 +1137,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
             End Select
         End Function
 
-        Friend Overrides Function IsRecordPrimaryConstructorParameter(declaration As SyntaxNode) As Boolean
-            Return False
-        End Function
-
-        Friend Overrides Function IsPropertyAccessorDeclarationMatchingPrimaryConstructorParameter(declaration As SyntaxNode, newContainingType As INamedTypeSymbol, ByRef isFirstAccessor As Boolean) As Boolean
+        Friend Overrides Function IsPrimaryConstructorDeclaration(declaration As SyntaxNode) As Boolean
             Return False
         End Function
 
@@ -1123,8 +1159,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
         ''' For example, a method with a body is represented by a SubBlock/FunctionBlock while a method without a body
         ''' is represented by its declaration statement.
         ''' </summary>
-        Protected Overrides Function GetSymbolDeclarationSyntax(reference As SyntaxReference, cancellationToken As CancellationToken) As SyntaxNode
-            Dim syntax = reference.GetSyntax(cancellationToken)
+        Protected Overrides Function GetSymbolDeclarationSyntax(symbol As ISymbol, selector As Func(Of ImmutableArray(Of SyntaxReference), SyntaxReference), cancellationToken As CancellationToken) As SyntaxNode
+            Dim syntax = selector(symbol.DeclaringSyntaxReferences).GetSyntax(cancellationToken)
             Dim parent = syntax.Parent
 
             Select Case syntax.Kind
@@ -1199,7 +1235,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
                 ' declarations that never have a block
 
                 Case SyntaxKind.ModifiedIdentifier
-                    Contract.ThrowIfFalse(parent.Parent.IsKind(SyntaxKind.FieldDeclaration))
+                    Contract.ThrowIfFalse(
+                        parent.Parent.IsKind(SyntaxKind.FieldDeclaration) OrElse parent.Parent.IsKind(SyntaxKind.LocalDeclarationStatement))
                     Dim variableDeclaration = CType(parent, VariableDeclaratorSyntax)
                     Return If(variableDeclaration.Names.Count = 1, parent, syntax)
 
@@ -1212,8 +1249,28 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
             End Select
         End Function
 
-        Friend Overrides Function IsConstructorWithMemberInitializers(declaration As SyntaxNode) As Boolean
-            Dim ctor = TryCast(declaration, ConstructorBlockSyntax)
+        Protected Overrides Function GetDeclaredSymbol(model As SemanticModel, declaration As SyntaxNode, cancellationToken As CancellationToken) As ISymbol
+            Return model.GetDeclaredSymbol(declaration, cancellationToken)
+        End Function
+
+        Friend Overrides Function IsConstructorWithMemberInitializers(symbol As ISymbol, cancellationToken As CancellationToken) As Boolean
+            Dim method = TryCast(symbol, IMethodSymbol)
+            If method Is Nothing OrElse (method.MethodKind <> MethodKind.Constructor AndAlso method.MethodKind <> MethodKind.SharedConstructor) Then
+                Return False
+            End If
+
+            ' static constructor has initializers:
+            If method.IsStatic Then
+                Return True
+            End If
+
+            ' Default constructor has initializers unless the type is a struct.
+            ' Instance member initializers in a struct are not supported in VB.
+            If method.IsImplicitlyDeclared Then
+                Return method.ContainingType.TypeKind <> TypeKind.Struct
+            End If
+
+            Dim ctor = TryCast(symbol.DeclaringSyntaxReferences(0).GetSyntax(cancellationToken).Parent, ConstructorBlockSyntax)
             If ctor Is Nothing Then
                 Return False
             End If
@@ -1339,15 +1396,15 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
                         Return OneOrMany(Of (ISymbol, ISymbol, EditKind)).Empty
                     End If
 
-                    Dim oldSymbol = oldModel.GetDeclaredSymbol(oldNode, cancellationToken)
-                    Dim newSymbol = newModel.GetDeclaredSymbol(newNode, cancellationToken)
+                    Dim oldSymbol = GetDeclaredSymbol(oldModel, oldNode, cancellationToken)
+                    Dim newSymbol = GetDeclaredSymbol(newModel, newNode, cancellationToken)
                     Return OneOrMany.Create((oldSymbol, newSymbol, editKind))
             End Select
 
             Throw ExceptionUtilities.UnexpectedValue(editKind)
         End Function
 
-        Private Shared Function TryGetSyntaxNodesForEdit(
+        Private Function TryGetSyntaxNodesForEdit(
             editKind As EditKind,
             node As SyntaxNode,
             model As SemanticModel,
@@ -1363,7 +1420,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
                 Case SyntaxKind.VariableDeclarator
                     Dim variableDeclarator = CType(node, VariableDeclaratorSyntax)
                     If variableDeclarator.Names.Count > 1 Then
-                        symbols = OneOrMany.Create(variableDeclarator.Names.SelectAsArray(Function(n) model.GetDeclaredSymbol(n, cancellationToken)))
+                        symbols = OneOrMany.Create(variableDeclarator.Names.SelectAsArray(Function(n) GetDeclaredSymbol(model, n, cancellationToken)))
                         Return True
                     End If
 
@@ -1378,7 +1435,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
                             symbols = OneOrMany.Create(
                                 (From declarator In field.Declarators
                                  From name In declarator.Names
-                                 Select model.GetDeclaredSymbol(name, cancellationToken)).ToImmutableArray())
+                                 Select GetDeclaredSymbol(model, name, cancellationToken)).ToImmutableArray())
 
                             Return True
                         End If
@@ -1386,7 +1443,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.EditAndContinue
 
             End Select
 
-            Dim symbol = model.GetDeclaredSymbol(node, cancellationToken)
+            Dim symbol = GetDeclaredSymbol(model, node, cancellationToken)
             If symbol Is Nothing Then
                 Return False
             End If
diff --git a/src/Features/VisualBasic/Portable/ExtractInterface/VisualBasicExtractInterfaceService.vb b/src/Features/VisualBasic/Portable/ExtractInterface/VisualBasicExtractInterfaceService.vb
index 840f96f5f5f48..c2e0ddcb8a28d 100644
--- a/src/Features/VisualBasic/Portable/ExtractInterface/VisualBasicExtractInterfaceService.vb
+++ b/src/Features/VisualBasic/Portable/ExtractInterface/VisualBasicExtractInterfaceService.vb
@@ -83,8 +83,9 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExtractInterface
 
             For Each docId In documentIds
                 ' We include this check just so that we're resilient to cases that we haven't considered.
-                If docToRootMap.ContainsKey(docId) Then
-                    finalSolution = finalSolution.WithDocumentSyntaxRoot(docId, docToRootMap(docId), PreservationMode.PreserveIdentity)
+                Dim root As CompilationUnitSyntax = Nothing
+                If docToRootMap.TryGetValue(docId, root) Then
+                    finalSolution = finalSolution.WithDocumentSyntaxRoot(docId, root, PreservationMode.PreserveIdentity)
                 End If
             Next
 
@@ -117,9 +118,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExtractInterface
                 Dim currentRoot As CompilationUnitSyntax = Nothing
 
                 For Each candidateDocId In documentIds
-                    If docToRootMap.ContainsKey(candidateDocId) Then
-                        currentRoot = docToRootMap(candidateDocId)
-                    Else
+                    If Not docToRootMap.TryGetValue(candidateDocId, currentRoot) Then
                         Dim document = Await unformattedSolution.GetDocument(candidateDocId).GetSyntaxRootAsync(cancellationToken).ConfigureAwait(False)
                         currentRoot = CType(document, CompilationUnitSyntax)
                     End If
diff --git a/src/Features/VisualBasic/Portable/ExtractMethod/VisualBasicMethodExtractor.TriviaResult.vb b/src/Features/VisualBasic/Portable/ExtractMethod/VisualBasicMethodExtractor.TriviaResult.vb
index 83e7359a7a83a..594e6c6da55c1 100644
--- a/src/Features/VisualBasic/Portable/ExtractMethod/VisualBasicMethodExtractor.TriviaResult.vb
+++ b/src/Features/VisualBasic/Portable/ExtractMethod/VisualBasicMethodExtractor.TriviaResult.vb
@@ -88,11 +88,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExtractMethod
                               SpecializedCollections.EmptyEnumerable(Of SyntaxTrivia)())
                 End If
 
-                Dim previousTriviaPair = If(triviaMap.ContainsKey(tokenPair.PreviousToken), triviaMap(tokenPair.PreviousToken), Nothing)
-                Dim nextTriviaPair = If(triviaMap.ContainsKey(tokenPair.NextToken), triviaMap(tokenPair.NextToken), Nothing)
+                Dim previousTriviaPair As LeadingTrailingTriviaPair = Nothing
+                Dim trailingTrivia = If(triviaMap.TryGetValue(tokenPair.PreviousToken, previousTriviaPair),
+                                        previousTriviaPair.TrailingTrivia, SpecializedCollections.EmptyEnumerable(Of SyntaxTrivia)())
 
-                Dim trailingTrivia = If(previousTriviaPair.TrailingTrivia, SpecializedCollections.EmptyEnumerable(Of SyntaxTrivia)())
-                Dim leadingTrivia = If(nextTriviaPair.LeadingTrivia, SpecializedCollections.EmptyEnumerable(Of SyntaxTrivia)())
+                Dim nextTriviaPair As LeadingTrailingTriviaPair = Nothing
+                Dim leadingTrivia = If(triviaMap.TryGetValue(tokenPair.NextToken, nextTriviaPair),
+                                       nextTriviaPair.LeadingTrivia, SpecializedCollections.EmptyEnumerable(Of SyntaxTrivia)())
 
                 Dim list = trailingTrivia.Concat(leadingTrivia)
 
diff --git a/src/Features/VisualBasic/Portable/GenerateType/VisualBasicGenerateTypeService.vb b/src/Features/VisualBasic/Portable/GenerateType/VisualBasicGenerateTypeService.vb
index 3a28e4d6e3bc7..c5ea754cfb486 100644
--- a/src/Features/VisualBasic/Portable/GenerateType/VisualBasicGenerateTypeService.vb
+++ b/src/Features/VisualBasic/Portable/GenerateType/VisualBasicGenerateTypeService.vb
@@ -454,7 +454,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.GenerateType
             Return (globalNamespace, rootNamespaceOrType, afterThisLocation)
         End Function
 
-        Private Function GetDeclaringNamespace(containers As List(Of String), indexDone As Integer, compilationUnit As CompilationUnitSyntax) As NamespaceStatementSyntax
+        Private Shared Function GetDeclaringNamespace(containers As List(Of String), indexDone As Integer, compilationUnit As CompilationUnitSyntax) As NamespaceStatementSyntax
             For Each member In compilationUnit.Members
                 Dim namespaceDeclaration = GetDeclaringNamespace(containers, indexDone, member)
                 If namespaceDeclaration IsNot Nothing Then
@@ -465,7 +465,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.GenerateType
             Return Nothing
         End Function
 
-        Private Function GetDeclaringNamespace(containers As List(Of String), indexDone As Integer, localRoot As SyntaxNode) As NamespaceStatementSyntax
+        Private Shared Function GetDeclaringNamespace(containers As List(Of String), indexDone As Integer, localRoot As SyntaxNode) As NamespaceStatementSyntax
             Dim namespaceBlock = TryCast(localRoot, NamespaceBlockSyntax)
             If namespaceBlock IsNot Nothing Then
                 Dim matchingNamesCount = MatchingNamesFromNamespaceName(containers, indexDone, namespaceBlock.NamespaceStatement)
@@ -494,7 +494,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.GenerateType
 
         End Function
 
-        Private Function MatchingNamesFromNamespaceName(containers As List(Of String), indexDone As Integer, namespaceStatementSyntax As NamespaceStatementSyntax) As Integer
+        Private Shared Function MatchingNamesFromNamespaceName(containers As List(Of String), indexDone As Integer, namespaceStatementSyntax As NamespaceStatementSyntax) As Integer
 
             If namespaceStatementSyntax Is Nothing Then
                 Return -1
@@ -521,7 +521,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.GenerateType
             Return True
         End Function
 
-        Private Sub GetNamespaceContainers(name As NameSyntax, namespaceContainers As List(Of String))
+        Private Shared Sub GetNamespaceContainers(name As NameSyntax, namespaceContainers As List(Of String))
             If TypeOf name Is QualifiedNameSyntax Then
                 GetNamespaceContainers(DirectCast(name, QualifiedNameSyntax).Left, namespaceContainers)
                 namespaceContainers.Add(DirectCast(name, QualifiedNameSyntax).Right.Identifier.ValueText)
diff --git a/src/Features/VisualBasic/Portable/Highlighting/KeywordHighlighters/TryBlockHighlighter.vb b/src/Features/VisualBasic/Portable/Highlighting/KeywordHighlighters/TryBlockHighlighter.vb
index faf02ab7d0985..9f4e6ccf532b6 100644
--- a/src/Features/VisualBasic/Portable/Highlighting/KeywordHighlighters/TryBlockHighlighter.vb
+++ b/src/Features/VisualBasic/Portable/Highlighting/KeywordHighlighters/TryBlockHighlighter.vb
@@ -54,7 +54,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.KeywordHighlighting
             End With
         End Sub
 
-        Private Sub HighlightRelatedStatements(node As SyntaxNode, highlights As List(Of TextSpan))
+        Private Shared Sub HighlightRelatedStatements(node As SyntaxNode, highlights As List(Of TextSpan))
             If node.Kind = SyntaxKind.ExitTryStatement Then
                 highlights.Add(node.Span)
             Else
diff --git a/src/Features/VisualBasic/Portable/InlineHints/VisualBasicInlineParameterNameHintsService.vb b/src/Features/VisualBasic/Portable/InlineHints/VisualBasicInlineParameterNameHintsService.vb
index dc22808b0ea30..76f12f22011ca 100644
--- a/src/Features/VisualBasic/Portable/InlineHints/VisualBasicInlineParameterNameHintsService.vb
+++ b/src/Features/VisualBasic/Portable/InlineHints/VisualBasicInlineParameterNameHintsService.vb
@@ -57,7 +57,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.InlineHints
             Next
         End Sub
 
-        Private Function GetKind(arg As ExpressionSyntax) As HintKind
+        Private Shared Function GetKind(arg As ExpressionSyntax) As HintKind
             If TypeOf arg Is LiteralExpressionSyntax OrElse
                TypeOf arg Is InterpolatedStringExpressionSyntax Then
                 Return HintKind.Literal
diff --git a/src/Features/VisualBasic/Portable/NavigationBar/VisualBasicNavigationBarItemService.vb b/src/Features/VisualBasic/Portable/NavigationBar/VisualBasicNavigationBarItemService.vb
index c6ccb4d99cce3..d01bfc6af3c46 100644
--- a/src/Features/VisualBasic/Portable/NavigationBar/VisualBasicNavigationBarItemService.vb
+++ b/src/Features/VisualBasic/Portable/NavigationBar/VisualBasicNavigationBarItemService.vb
@@ -341,8 +341,9 @@ Namespace Microsoft.CodeAnalysis.NavigationBar
 
             ' Generate an item for each event
             For Each e In accessibleEvents
-                If eventToImplementingMethods.ContainsKey(e) Then
-                    Dim methodLocation = GetSymbolLocation(solution, eventToImplementingMethods(e).First(), semanticModel.SyntaxTree, symbolDeclarationService)
+                Dim methods As List(Of IMethodSymbol) = Nothing
+                If eventToImplementingMethods.TryGetValue(e, methods) Then
+                    Dim methodLocation = GetSymbolLocation(solution, methods.First(), semanticModel.SyntaxTree, symbolDeclarationService)
                     If methodLocation IsNot Nothing Then
                         rightHandMemberItems.Add(New SymbolItem(
                             e.Name,
diff --git a/src/Tools/BuildActionTelemetryTable/BuildActionTelemetryTable.csproj b/src/Tools/BuildActionTelemetryTable/BuildActionTelemetryTable.csproj
index 0f1b3e758751d..8cfb39921b9d8 100644
--- a/src/Tools/BuildActionTelemetryTable/BuildActionTelemetryTable.csproj
+++ b/src/Tools/BuildActionTelemetryTable/BuildActionTelemetryTable.csproj
@@ -21,13 +21,13 @@
 
   <!-- These are dependencies that are never deployed but that we need to reflect over the Microsoft.CodeAnalysis.EditorFeatures assemblies -->
   <ItemGroup>
+    <PackageReference Include="Microsoft.IO.Redist" Version="$(MicrosoftIORedistVersion)" NoWarn="NU1701" />
     <PackageReference Include="Microsoft.VisualStudio.ImageCatalog" Version="$(MicrosoftVisualStudioImageCatalogVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.LanguageServer.Client" Version="$(MicrosoftVisualStudioLanguageServerClientVersion)" NoWarn="NU1701" />
     <PackageReference Include="Microsoft.VisualStudio.Shell.15.0" Version="$(MicrosoftVisualStudioShell150Version)" NoWarn="NU1701" />
     <PackageReference Include="Microsoft.VisualStudio.Shell.Framework" Version="$(MicrosoftVisualStudioShellFrameworkVersion)" NoWarn="NU1701" />
     <PackageReference Include="Microsoft.VisualStudio.GraphModel" Version="$(MicrosoftVisualStudioGraphModelVersion)" NoWarn="NU1701" />
     <PackageReference Include="Microsoft.VisualStudio.Imaging" Version="$(MicrosoftVisualStudioImagingVersion)" NoWarn="NU1701" />
-    <PackageReference Include="Microsoft.IO.Redist" Version="$(MicrosoftIORedistVersion)" NoWarn="NU1701"/>
   </ItemGroup>
 
   <ItemGroup>
diff --git a/src/Tools/BuildValidator/BuildValidator.csproj b/src/Tools/BuildValidator/BuildValidator.csproj
index f07af0728e425..c9518866ce352 100644
--- a/src/Tools/BuildValidator/BuildValidator.csproj
+++ b/src/Tools/BuildValidator/BuildValidator.csproj
@@ -30,6 +30,7 @@
     <PackageReference Include="Microsoft.DiaSymReader.Converter.Xml" Version="$(MicrosoftDiaSymReaderConverterXmlVersion)" />
     <PackageReference Include="Newtonsoft.Json" Version="$(NewtonsoftJsonVersion)" />
     <PackageReference Include="System.CommandLine" Version="$(SystemCommandLineVersion)" />
+    <PackageReference Include="System.CommandLine.NamingConventionBinder" Version="$(SystemCommandLineNamingConventionBinderVersion)" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/src/Tools/BuildValidator/Program.cs b/src/Tools/BuildValidator/Program.cs
index 179d2de624eaf..4d91d066b0db3 100644
--- a/src/Tools/BuildValidator/Program.cs
+++ b/src/Tools/BuildValidator/Program.cs
@@ -6,7 +6,7 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.CommandLine;
-using System.CommandLine.Invocation;
+using System.CommandLine.NamingConventionBinder;
 using System.IO;
 using System.Linq;
 using System.Reflection.PortableExecutable;
@@ -33,18 +33,18 @@ static int Main(string[] args)
             System.Diagnostics.Trace.Listeners.Clear();
             var rootCommand = new RootCommand
             {
-                new Option<string>(
+                new Option<string[]>(
                     "--assembliesPath", BuildValidatorResources.Path_to_assemblies_to_rebuild_can_be_specified_one_or_more_times
-                ) { IsRequired = true, Argument = { Arity = ArgumentArity.OneOrMore } },
-                new Option<string>(
+                ) { IsRequired = true, Arity = ArgumentArity.OneOrMore },
+                new Option<string[]>(
                     "--exclude", BuildValidatorResources.Assemblies_to_be_excluded_substring_match
-                ) { Argument = { Arity = ArgumentArity.ZeroOrMore } },
+                ) { Arity = ArgumentArity.ZeroOrMore },
                 new Option<string>(
                     "--sourcePath", BuildValidatorResources.Path_to_sources_to_use_in_rebuild
                 ) { IsRequired = true },
-                new Option<string>(
+                new Option<string[]>(
                     "--referencesPath", BuildValidatorResources.Path_to_referenced_assemblies_can_be_specified_zero_or_more_times
-                ) { Argument = { Arity = ArgumentArity.ZeroOrMore } },
+                ) { Arity = ArgumentArity.ZeroOrMore },
                 new Option<bool>(
                     "--verbose", BuildValidatorResources.Output_verbose_log_information
                 ),
diff --git a/src/Tools/ExternalAccess/FSharp/Internal/Structure/FSharpBlockStructureService.cs b/src/Tools/ExternalAccess/FSharp/Internal/Structure/FSharpBlockStructureService.cs
index 5826b8fdda73d..c537e2bd13867 100644
--- a/src/Tools/ExternalAccess/FSharp/Internal/Structure/FSharpBlockStructureService.cs
+++ b/src/Tools/ExternalAccess/FSharp/Internal/Structure/FSharpBlockStructureService.cs
@@ -34,7 +34,8 @@ public override async Task<BlockStructure> GetBlockStructureAsync(Document docum
             var blockStructure = await _service.GetBlockStructureAsync(document, cancellationToken).ConfigureAwait(false);
             if (blockStructure != null)
             {
-                return new BlockStructure(blockStructure.Spans.SelectAsArray(x => new BlockSpan(x.Type, x.IsCollapsible, x.TextSpan, x.HintSpan, x.BannerText, x.AutoCollapse, x.IsDefaultCollapsed)));
+                return new BlockStructure(blockStructure.Spans.SelectAsArray(
+                    x => new BlockSpan(x.Type, x.IsCollapsible, x.TextSpan, x.HintSpan, primarySpans: null, x.BannerText, x.AutoCollapse, x.IsDefaultCollapsed)));
             }
             else
             {
diff --git a/src/Tools/ExternalAccess/Razor/IRazorCapabilitiesProvider.cs b/src/Tools/ExternalAccess/Razor/IRazorCapabilitiesProvider.cs
index c9b790c4bb598..81463e63d70aa 100644
--- a/src/Tools/ExternalAccess/Razor/IRazorCapabilitiesProvider.cs
+++ b/src/Tools/ExternalAccess/Razor/IRazorCapabilitiesProvider.cs
@@ -2,12 +2,22 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.Razor
 {
+    [Obsolete("Use IRazorTestCapabilitiesProvider")]
     internal interface IRazorCapabilitiesProvider
     {
         ServerCapabilities GetCapabilities(ClientCapabilities clientCapabilities);
     }
+
+    /// <summary>
+    /// A capabilities provider that should only be used from Razor tests
+    /// </summary>
+    internal interface IRazorTestCapabilitiesProvider
+    {
+        string GetServerCapabilitiesJson(string clientCapabilitiesJson);
+    }
 }
diff --git a/src/Tools/ExternalAccess/Razor/IRazorLanguageServerFactory.cs b/src/Tools/ExternalAccess/Razor/IRazorLanguageServerFactory.cs
index 0d0026b998cb5..85be19516aab8 100644
--- a/src/Tools/ExternalAccess/Razor/IRazorLanguageServerFactory.cs
+++ b/src/Tools/ExternalAccess/Razor/IRazorLanguageServerFactory.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Host;
@@ -11,8 +12,11 @@ namespace Microsoft.CodeAnalysis.ExternalAccess.Razor
 {
     internal interface IRazorLanguageServerFactoryWrapper
     {
+        [Obsolete("Use the overload that takes a IRazorTestCapabilitiesProvider")]
         IRazorLanguageServerTarget CreateLanguageServer(JsonRpc jsonRpc, IRazorCapabilitiesProvider capabilitiesProvider, HostServices hostServices);
 
+        IRazorLanguageServerTarget CreateLanguageServer(JsonRpc jsonRpc, IRazorTestCapabilitiesProvider capabilitiesProvider, HostServices hostServices);
+
         DocumentInfo CreateDocumentInfo(
             DocumentId id,
             string name,
diff --git a/src/Tools/ExternalAccess/Razor/InternalAPI.Unshipped.txt b/src/Tools/ExternalAccess/Razor/InternalAPI.Unshipped.txt
index a8157c4c62a07..c0bf885d558c4 100644
--- a/src/Tools/ExternalAccess/Razor/InternalAPI.Unshipped.txt
+++ b/src/Tools/ExternalAccess/Razor/InternalAPI.Unshipped.txt
@@ -24,9 +24,12 @@ Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorDynamicFileInfoProvider.Update
 Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerFactoryWrapper
 Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerFactoryWrapper.CreateDocumentInfo(Microsoft.CodeAnalysis.DocumentId! id, string! name, System.Collections.Generic.IReadOnlyList<string!>? folders = null, Microsoft.CodeAnalysis.SourceCodeKind sourceCodeKind = Microsoft.CodeAnalysis.SourceCodeKind.Regular, Microsoft.CodeAnalysis.TextLoader? loader = null, string? filePath = null, bool isGenerated = false, bool designTimeOnly = false, Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorDocumentServiceProvider? razorDocumentServiceProvider = null) -> Microsoft.CodeAnalysis.DocumentInfo!
 Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerFactoryWrapper.CreateLanguageServer(StreamJsonRpc.JsonRpc! jsonRpc, Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorCapabilitiesProvider! capabilitiesProvider, Microsoft.CodeAnalysis.Host.HostServices! hostServices) -> Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerTarget!
+Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerFactoryWrapper.CreateLanguageServer(StreamJsonRpc.JsonRpc! jsonRpc, Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorTestCapabilitiesProvider! capabilitiesProvider, Microsoft.CodeAnalysis.Host.HostServices! hostServices) -> Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerTarget!
 Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerTarget
 Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorSpanMappingService
 Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorSpanMappingService.MapSpansAsync(Microsoft.CodeAnalysis.Document! document, System.Collections.Generic.IEnumerable<Microsoft.CodeAnalysis.Text.TextSpan>! spans, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorMappedSpanResult>>!
+Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorTestCapabilitiesProvider
+Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorTestCapabilitiesProvider.GetServerCapabilitiesJson(string! clientCapabilitiesJson) -> string!
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorAsynchronousOperationListenerProviderAccessor
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorAsynchronousOperationListenerProviderAccessor.GetListener(string! featureName) -> Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorAsynchronousOperationListenerWrapper
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorAsynchronousOperationListenerProviderAccessor.RazorAsynchronousOperationListenerProviderAccessor(Microsoft.CodeAnalysis.Shared.TestHooks.IAsynchronousOperationListenerProvider! implementation) -> void
@@ -94,6 +97,7 @@ Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorIndentationOptions.UseTabs.init
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorLanguageServerFactoryWrapper
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorLanguageServerFactoryWrapper.CreateDocumentInfo(Microsoft.CodeAnalysis.DocumentId! id, string! name, System.Collections.Generic.IReadOnlyList<string!>? folders = null, Microsoft.CodeAnalysis.SourceCodeKind sourceCodeKind = Microsoft.CodeAnalysis.SourceCodeKind.Regular, Microsoft.CodeAnalysis.TextLoader? loader = null, string? filePath = null, bool isGenerated = false, bool designTimeOnly = false, Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorDocumentServiceProvider? razorDocumentServiceProvider = null) -> Microsoft.CodeAnalysis.DocumentInfo!
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorLanguageServerFactoryWrapper.CreateLanguageServer(StreamJsonRpc.JsonRpc! jsonRpc, Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorCapabilitiesProvider! razorCapabilitiesProvider, Microsoft.CodeAnalysis.Host.HostServices! hostServices) -> Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerTarget!
+Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorLanguageServerFactoryWrapper.CreateLanguageServer(StreamJsonRpc.JsonRpc! jsonRpc, Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorTestCapabilitiesProvider! razorCapabilitiesProvider, Microsoft.CodeAnalysis.Host.HostServices! hostServices) -> Microsoft.CodeAnalysis.ExternalAccess.Razor.IRazorLanguageServerTarget!
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorLanguageServerFactoryWrapper.RazorLanguageServerFactoryWrapper(Microsoft.CodeAnalysis.LanguageServer.ILanguageServerFactory! languageServerFactory) -> void
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorLanguageServerTargetWrapper
 Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorLanguageServerTargetWrapper.DisposeAsync() -> System.Threading.Tasks.ValueTask
@@ -397,6 +401,8 @@ static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorPredefinedCodeRefactorin
 static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorPredefinedCodeRefactoringProviderNames.Wrapping.get -> string!
 static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorRemoteHostClient.TryGetClientAsync(Microsoft.CodeAnalysis.Host.HostWorkspaceServices! services, Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorServiceDescriptorsWrapper serviceDescriptors, Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorRemoteServiceCallbackDispatcherRegistry! callbackDispatchers, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorRemoteHostClient?>!
 static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorRemoteServiceCallbackIdWrapper.implicit operator Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorRemoteServiceCallbackIdWrapper(Microsoft.CodeAnalysis.Remote.RemoteServiceCallbackId id) -> Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorRemoteServiceCallbackIdWrapper
+static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorSemanticTokensAccessor.GetTokenModifiers() -> string![]!
+static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorSemanticTokensAccessor.GetTokenTypes(bool clientSupportsVisualStudioExtensions) -> System.Collections.Immutable.ImmutableArray<string!>
 static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorSemanticTokensAccessor.GetTokenTypes(Microsoft.VisualStudio.LanguageServer.Protocol.ClientCapabilities! capabilities) -> System.Collections.Immutable.ImmutableArray<string!>
 static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorSemanticTokensAccessor.RoslynTokenTypes.get -> System.Collections.Immutable.ImmutableArray<string!>
 static Microsoft.CodeAnalysis.ExternalAccess.Razor.RazorTestAnalyzerLoader.CreateAnalyzerAssemblyLoader() -> Microsoft.CodeAnalysis.IAnalyzerAssemblyLoader!
diff --git a/src/Tools/ExternalAccess/Razor/RazorLanguageServerFactoryWrapper.cs b/src/Tools/ExternalAccess/Razor/RazorLanguageServerFactoryWrapper.cs
index b8f103be209ec..0b8878091b24e 100644
--- a/src/Tools/ExternalAccess/Razor/RazorLanguageServerFactoryWrapper.cs
+++ b/src/Tools/ExternalAccess/Razor/RazorLanguageServerFactoryWrapper.cs
@@ -15,6 +15,7 @@
 using Newtonsoft.Json.Linq;
 using StreamJsonRpc;
 using Microsoft.VisualStudio.Composition;
+using Newtonsoft.Json;
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.Razor
 {
@@ -36,6 +37,15 @@ public RazorLanguageServerFactoryWrapper(ILanguageServerFactory languageServerFa
             _languageServerFactory = languageServerFactory;
         }
 
+        public IRazorLanguageServerTarget CreateLanguageServer(JsonRpc jsonRpc, IRazorTestCapabilitiesProvider razorCapabilitiesProvider, HostServices hostServices)
+        {
+            var capabilitiesProvider = new RazorCapabilitiesProvider(razorCapabilitiesProvider);
+            var languageServer = _languageServerFactory.Create(jsonRpc, capabilitiesProvider, WellKnownLspServerKinds.RazorLspServer, NoOpLspLogger.Instance, hostServices);
+
+            return new RazorLanguageServerTargetWrapper(languageServer);
+        }
+
+        [Obsolete("Use the overload that takes IRazorTestCapabilitiesProvider")]
         public IRazorLanguageServerTarget CreateLanguageServer(JsonRpc jsonRpc, IRazorCapabilitiesProvider razorCapabilitiesProvider, HostServices hostServices)
         {
             var capabilitiesProvider = new RazorCapabilitiesProvider(razorCapabilitiesProvider);
@@ -70,15 +80,43 @@ public DocumentInfo CreateDocumentInfo(
 
         private class RazorCapabilitiesProvider : ICapabilitiesProvider
         {
-            private readonly IRazorCapabilitiesProvider _razorCapabilitiesProvider;
+#pragma warning disable CS0618 // Type or member is obsolete
+            private readonly IRazorCapabilitiesProvider? _razorCapabilitiesProvider;
+#pragma warning restore CS0618 // Type or member is obsolete
+            private readonly IRazorTestCapabilitiesProvider? _razorTestCapabilitiesProvider;
 
+            public RazorCapabilitiesProvider(IRazorTestCapabilitiesProvider razorTestCapabilitiesProvider)
+            {
+                _razorTestCapabilitiesProvider = razorTestCapabilitiesProvider;
+            }
+
+#pragma warning disable CS0618 // Type or member is obsolete
             public RazorCapabilitiesProvider(IRazorCapabilitiesProvider razorCapabilitiesProvider)
+#pragma warning restore CS0618 // Type or member is obsolete
             {
                 _razorCapabilitiesProvider = razorCapabilitiesProvider;
             }
 
             public ServerCapabilities GetCapabilities(ClientCapabilities clientCapabilities)
-                => _razorCapabilitiesProvider.GetCapabilities(clientCapabilities);
+            {
+                if (_razorTestCapabilitiesProvider is not null)
+                {
+                    // To avoid exposing types from MS.VS.LanguageServer.Protocol types we serialize and deserialize the capabilities
+                    // so we can just pass string around. This is obviously not great for perf, but it is only used in Razor tests.
+                    var clientCapabilitiesJson = JsonConvert.SerializeObject(clientCapabilities);
+                    var serverCapabilitiesJson = _razorTestCapabilitiesProvider.GetServerCapabilitiesJson(clientCapabilitiesJson);
+                    var serverCapabilities = JsonConvert.DeserializeObject<VSInternalServerCapabilities>(serverCapabilitiesJson);
+
+                    if (serverCapabilities is null)
+                    {
+                        throw new InvalidOperationException("Could not deserialize server capabilities as VSInternalServerCapabilities");
+                    }
+
+                    return serverCapabilities;
+                }
+
+                return _razorCapabilitiesProvider!.GetCapabilities(clientCapabilities);
+            }
         }
     }
 }
diff --git a/src/Tools/ExternalAccess/Razor/RazorSemanticTokensAccessor.cs b/src/Tools/ExternalAccess/Razor/RazorSemanticTokensAccessor.cs
index 63c36ea0d900a..500251f41e92e 100644
--- a/src/Tools/ExternalAccess/Razor/RazorSemanticTokensAccessor.cs
+++ b/src/Tools/ExternalAccess/Razor/RazorSemanticTokensAccessor.cs
@@ -14,6 +14,11 @@ internal class RazorSemanticTokensAccessor
         [Obsolete("Use GetTokenTypes")]
         public static ImmutableArray<string> RoslynTokenTypes => SemanticTokensSchema.LegacyTokenSchemaForRazor.AllTokenTypes;
 
-        public static ImmutableArray<string> GetTokenTypes(ClientCapabilities capabilities) => SemanticTokensSchema.GetSchema(capabilities).AllTokenTypes;
+        [Obsolete("Use GetTokenTypes(bool)")]
+        public static ImmutableArray<string> GetTokenTypes(ClientCapabilities capabilities) => SemanticTokensSchema.GetSchema(capabilities is VSInternalClientCapabilities { SupportsVisualStudioExtensions: true }).AllTokenTypes;
+
+        public static ImmutableArray<string> GetTokenTypes(bool clientSupportsVisualStudioExtensions) => SemanticTokensSchema.GetSchema(clientSupportsVisualStudioExtensions).AllTokenTypes;
+
+        public static string[] GetTokenModifiers() => SemanticTokensSchema.TokenModifiers;
     }
 }
diff --git a/src/Tools/IdeBenchmarks/Lsp/LspCompletionSerializationBenchmarks.cs b/src/Tools/IdeBenchmarks/Lsp/LspCompletionSerializationBenchmarks.cs
new file mode 100644
index 0000000000000..d171ac617d04b
--- /dev/null
+++ b/src/Tools/IdeBenchmarks/Lsp/LspCompletionSerializationBenchmarks.cs
@@ -0,0 +1,178 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using BenchmarkDotNet.Attributes;
+using Microsoft.CodeAnalysis.LanguageServer.UnitTests.Completion;
+using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Newtonsoft.Json.Converters;
+using Newtonsoft.Json;
+using Roslyn.Test.Utilities;
+using Xunit;
+using LSP = Microsoft.VisualStudio.LanguageServer.Protocol;
+using static System.Windows.Forms.VisualStyles.VisualStyleElement.TextBox;
+using static Roslyn.Test.Utilities.AbstractLanguageServerProtocolTests;
+using System.Threading;
+using Microsoft.CodeAnalysis.LanguageServer;
+using Microsoft.CodeAnalysis.PooledObjects;
+
+namespace IdeBenchmarks.Lsp
+{
+    [MemoryDiagnoser]
+    public class LspCompletionSerializationBenchmarks : AbstractLanguageServerProtocolTests
+    {
+        protected override TestComposition Composition => FeaturesLspComposition;
+        private readonly UseExportProviderAttribute _useExportProviderAttribute = new();
+
+        private LSP.CompletionList? _list;
+
+        public LspCompletionSerializationBenchmarks() : base(null)
+        {
+        }
+
+        [GlobalSetup]
+        public void GlobalSetup()
+        {
+        }
+
+        [IterationSetup]
+        public void IterationSetup()
+        {
+            _useExportProviderAttribute.Before(null);
+            LoadSolutionAsync().Wait();
+        }
+
+        [IterationCleanup]
+        public void CleanupAsync()
+        {
+            _useExportProviderAttribute.Before(null);
+        }
+
+        private async Task LoadSolutionAsync()
+        {
+            var markup =
+@"using System;
+using System.Buffers;
+using System.Buffers.Binary;
+using System.Buffers.Text;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.ComponentModel.Design;
+using System.Configuration;
+using System.Data;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Drawing;
+using System.Dynamic;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Media;
+using System.Net;
+using System.Net.Http;
+using System.Net.Http.Json;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+class A
+{
+    void M()
+    {
+        {|caret:|}
+    }
+}";
+            await using var testServer = await CreateTestLspServerAsync(markup, mutatingLspWorkspace: false, new LSP.VSInternalClientCapabilities
+            {
+                TextDocument = new LSP.TextDocumentClientCapabilities
+                {
+                    Completion = new LSP.CompletionSetting
+                    {
+                        CompletionListSetting = new LSP.CompletionListSetting
+                        {
+                            ItemDefaults = new string[] { "editRange", "commitCharacters", "data" },
+                        }
+                    }
+                }
+            }).ConfigureAwait(false);
+
+            var globalOptions = testServer.TestWorkspace.GetService<IGlobalOptionService>();
+            globalOptions.SetGlobalOption(LspOptionsStorage.MaxCompletionListSize, -1);
+
+            var caret = testServer.GetLocations("caret").Single();
+            var completionParams = new LSP.CompletionParams()
+            {
+                TextDocument = CreateTextDocumentIdentifier(caret.Uri),
+                Position = caret.Range.Start,
+                Context = new LSP.CompletionContext()
+                {
+                    TriggerKind = LSP.CompletionTriggerKind.Invoked,
+                }
+            };
+
+            var document = testServer.GetCurrentSolution().Projects.First().Documents.First();
+            var results = await testServer.ExecuteRequestAsync<LSP.CompletionParams, LSP.CompletionList>(LSP.Methods.TextDocumentCompletionName, completionParams, CancellationToken.None);
+
+            var list = (await CompletionTests.RunGetCompletionsAsync(testServer, completionParams));
+            if (list.Items.Length == 0)
+                throw new System.Exception();
+
+            using var _ = ArrayBuilder<LSP.CompletionItem>.GetInstance(out var builder);
+            while (builder.Count < 10000)
+            {
+                foreach (var item in list.Items)
+                {
+                    builder.Add(item);
+                    if (item.CommitCharacters is not null || item.Data is not null)
+                        throw new InvalidDataException();
+
+                    if (builder.Count == 10000)
+                        break;
+                }
+            }
+
+            list.Items = builder.ToArray();
+            _list = list;
+        }
+
+        [Benchmark]
+        public async Task Serialization()
+        {
+            var serializer = new JsonSerializer();
+            serializer.Formatting = Formatting.None;
+            serializer.NullValueHandling = NullValueHandling.Ignore;
+            serializer.DefaultValueHandling = DefaultValueHandling.Ignore;
+
+            using var stream = new MemoryStream();
+            var sw = new StreamWriter(stream);
+            var jsonWriter = new JsonTextWriter(sw);
+            {
+                serializer.Serialize(jsonWriter, _list);
+                await jsonWriter.FlushAsync();
+            }
+
+            stream.Seek(0, SeekOrigin.Begin);
+
+            using (var sr = new StreamReader(stream))
+            using (var jsonReader = new JsonTextReader(sr))
+            {
+                var list = serializer.Deserialize<LSP.CompletionList>(jsonReader);
+                if (list!.Items.Length != _list!.Items.Length)
+                    throw new System.Exception();
+            }
+        }
+
+        [Fact]
+        public async Task Test()
+        {
+            await LoadSolutionAsync();
+            await Serialization();
+        }
+    }
+}
diff --git a/src/Tools/Source/CompilerGeneratorTools/Source/VisualBasicSyntaxGenerator/XML/ParseTreeDescription.vb b/src/Tools/Source/CompilerGeneratorTools/Source/VisualBasicSyntaxGenerator/XML/ParseTreeDescription.vb
index ad840b49dc955..a653d78803abb 100644
--- a/src/Tools/Source/CompilerGeneratorTools/Source/VisualBasicSyntaxGenerator/XML/ParseTreeDescription.vb
+++ b/src/Tools/Source/CompilerGeneratorTools/Source/VisualBasicSyntaxGenerator/XML/ParseTreeDescription.vb
@@ -196,16 +196,18 @@ Public Class ParseTree
 
         If typeString.StartsWith("@", StringComparison.Ordinal) Then
             Dim nodeTypeString = typeString.Substring(1)
-            If Not NodeStructures.ContainsKey(nodeTypeString) Then
+            Dim nodeStructure As ParseNodeStructure = Nothing
+            If Not NodeStructures.TryGetValue(nodeTypeString, nodeStructure) Then
                 ReportError(referencingNode, "Unknown structure '@{0}'", nodeTypeString)
                 Return Nothing
             End If
 
-            Return NodeStructures(nodeTypeString).GetAllKinds()
+            Return nodeStructure.GetAllKinds()
         End If
 
-        If Aliases.ContainsKey(typeString) Then
-            Return ParseNodeKind(Aliases(typeString).AliasKinds, referencingNode)
+        Dim nodeKindAlias As ParseNodeKindAlias = Nothing
+        If Aliases.TryGetValue(typeString, nodeKindAlias) Then
+            Return ParseNodeKind(nodeKindAlias.AliasKinds, referencingNode)
         End If
 
         Return ParseOneNodeKind(typeString, referencingNode)
@@ -259,11 +261,12 @@ Public Class ParseNodeStructure
             If String.IsNullOrEmpty(ParentStructureId) Then
                 Return Nothing
             Else
-                If Not ParseTree.NodeStructures.ContainsKey(ParentStructureId) Then
+                Dim nodeStructure As ParseNodeStructure = Nothing
+                If Not ParseTree.NodeStructures.TryGetValue(ParentStructureId, nodeStructure) Then
                     ParseTree.ReportError(Element, "Unknown parent structure '{0}' for node-structure '{1}'", ParentStructureId, Name)
                     Return Nothing
                 End If
-                Return ParseTree.NodeStructures(ParentStructureId)
+                Return nodeStructure
             End If
         End Get
     End Property
@@ -377,11 +380,12 @@ Public Class ParseNodeKind
             If String.IsNullOrEmpty(StructureId) Then
                 Return Nothing
             Else
-                If Not ParseTree.NodeStructures.ContainsKey(StructureId) Then
+                Dim parseNodeStructure As ParseNodeStructure = Nothing
+                If Not ParseTree.NodeStructures.TryGetValue(StructureId, parseNodeStructure) Then
                     ParseTree.ReportError(Element, "Unknown structure '{0}' for node-kind '{1}'", StructureId, Name)
                     Return Nothing
                 End If
-                Return ParseTree.NodeStructures(StructureId)
+                Return parseNodeStructure
             End If
         End Get
     End Property
diff --git a/src/Tools/Source/RunTests/Options.cs b/src/Tools/Source/RunTests/Options.cs
index c2d4a47731523..d3ce7af3ed56d 100644
--- a/src/Tools/Source/RunTests/Options.cs
+++ b/src/Tools/Source/RunTests/Options.cs
@@ -87,6 +87,12 @@ internal class Options
         /// </summary>
         public string? HelixQueueName { get; set; }
 
+        /// <summary>
+        /// Access token to send jobs to helix (only valid when <see cref="UseHelix" /> is <see langword="true" />).
+        /// This should only be set when using internal helix queues.
+        /// </summary>
+        public string? HelixApiAccessToken { get; set; }
+
         /// <summary>
         /// Path to the dotnet executable we should use for running dotnet test
         /// </summary>
@@ -142,6 +148,7 @@ public Options(
             var sequential = false;
             var helix = false;
             var helixQueueName = "Windows.10.Amd64.Open";
+            string? helixApiAccessToken = null;
             var retry = false;
             string? testFilter = null;
             int? timeout = null;
@@ -168,6 +175,7 @@ public Options(
                 { "sequential", "Run tests sequentially", o => sequential = o is object },
                 { "helix", "Run tests on Helix", o => helix = o is object },
                 { "helixQueueName=", "Name of the Helix queue to run tests on", (string s) => helixQueueName = s },
+                { "helixApiAccessToken=", "Access token for internal helix queues", (string s) => helixApiAccessToken = s },
                 { "testfilter=", "xUnit string to pass to --filter, e.g. FullyQualifiedName~TestClass1|Category=CategoryA", (string s) => testFilter = s },
                 { "timeout=", "Minute timeout to limit the tests to", (int i) => timeout = i },
                 { "out=", "Test result file directory (when running on Helix, this is relative to the Helix work item directory)", (string s) => resultFileDirectory = s },
@@ -254,6 +262,7 @@ public Options(
                 Sequential = sequential,
                 UseHelix = helix,
                 HelixQueueName = helixQueueName,
+                HelixApiAccessToken = helixApiAccessToken,
                 IncludeHtml = includeHtml,
                 TestFilter = testFilter,
                 Timeout = timeout is { } t ? TimeSpan.FromMinutes(t) : null,
diff --git a/src/Tools/Source/RunTests/TestRunner.cs b/src/Tools/Source/RunTests/TestRunner.cs
index 573174594f74a..4907b8db5a1b6 100644
--- a/src/Tools/Source/RunTests/TestRunner.cs
+++ b/src/Tools/Source/RunTests/TestRunner.cs
@@ -108,7 +108,6 @@ internal async Task<RunAllResult> RunAllOnHelixAsync(ImmutableArray<WorkItemInfo
         <HelixType>test</HelixType>
         <HelixBuild>" + buildNumber + @"</HelixBuild>
         <HelixTargetQueues>" + _options.HelixQueueName + @"</HelixTargetQueues>
-        <Creator>" + queuedBy + @"</Creator>
         <IncludeDotNetCli>true</IncludeDotNetCli>
         <DotNetCliVersion>" + globalJson.sdk.version + @"</DotNetCliVersion>
         <DotNetCliPackageType>sdk</DotNetCliPackageType>
@@ -123,9 +122,22 @@ internal async Task<RunAllResult> RunAllOnHelixAsync(ImmutableArray<WorkItemInfo
 
             File.WriteAllText("helix-tmp.csproj", project);
 
+            var arguments = $"build helix-tmp.csproj";
+            if (!string.IsNullOrEmpty(_options.HelixApiAccessToken))
+            {
+                // Internal queues require an access token.
+                // We don't put it in the project string itself since it can cause escaping issues.
+                arguments += $" /p:HelixAccessToken={_options.HelixApiAccessToken}";
+            }
+            else
+            {
+                // If we're not using authenticated access we need to specify a creator.
+                arguments += $" /p:Creator={queuedBy}";
+            }
+
             var process = ProcessRunner.CreateProcess(
                 executable: _options.DotnetFilePath,
-                arguments: "build helix-tmp.csproj",
+                arguments: arguments,
                 captureOutput: true,
                 onOutputDataReceived: (e) => { Debug.Assert(e.Data is not null); ConsoleUtil.WriteLine(e.Data); },
                 cancellationToken: cancellationToken);
diff --git a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.cs.xlf b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.cs.xlf
index 7ee98c14ddaaf..e14de190dc86a 100644
--- a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.cs.xlf
+++ b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.cs.xlf
@@ -114,9 +114,9 @@ Zvýrazňovat odkazy na symbol pod kurzorem;
 Zvýrazňovat související klíčová slova pod kurzorem;
 Sbalení;
 Po otevření souborů přejít do režimu osnovy;
-Zobrazit oddělovače řádků procedur;
-Zobrazit sbalení pro konstrukty na úrovni deklarace;
-Zobrazit sbalení pro konstrukty na úrovni kódu;
+Sbalit #regions při otevření souboru;
+Sbalit použití při otevření souboru;
+Sbalit implementace metadat při otevření souboru;
 Zobrazovat oddělovače řádků procedur;
 Zobrazit sbalení pro konstrukty na úrovni deklarace;
 Zobrazit sbalení pro konstrukty na úrovni kódu;
diff --git a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.de.xlf b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.de.xlf
index be72d2b43b739..cbf0b8f641337 100644
--- a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.de.xlf
+++ b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.de.xlf
@@ -114,7 +114,7 @@ Verweise auf Symbol unter Cursor hervorheben;
 Verwandte Schlüsselbegriffe unter Cursor hervorheben;
 Gliederung;
 Gliederungsmodus beim Öffnen von Dateien starten;
-#Regionen beim Öffnen der Datei reduzieren;
+#regions beim Öffnen der Datei reduzieren;
 Verarbeitungen beim Öffnen von Dateien reduzieren;
 Metadatenimplementierungen beim Öffnen von Dateien reduzieren;
 Vorgangsreihentrenner anzeigen;
diff --git a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.fr.xlf b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.fr.xlf
index ae1e4c953856e..ccbcc30835826 100644
--- a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.fr.xlf
+++ b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.fr.xlf
@@ -114,7 +114,7 @@ Mettre en évidence les références au symbole sous le curseur ;
 Mettre en évidence les mots-clés associés sous le curseur ; 
 Contournement ;
 Entrer dans le mode contour lorsque les fichiers sont ouverts ;
-Réduire les #régions à l'ouverture du fichier ;
+Réduire les #regions à l'ouverture du fichier ;
  Réduire les utilisations à l'ouverture du fichier ;
  Réduire les implémentations de métadonnées à l'ouverture du fichier ;
 Afficher les séparateurs de lignes de procédure ;
diff --git a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.it.xlf b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.it.xlf
index d6f0fc7436af7..403ea8b6092ce 100644
--- a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.it.xlf
+++ b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.it.xlf
@@ -114,7 +114,7 @@ Evidenzia riferimenti al simbolo sotto il cursore;
 Evidenzia parole chiave correlate sotto il cursore;
 Struttura;
 Attiva la modalità struttura all'apertura del file;
-Comprimi #regioni all’apertura del file 
+Comprimi #regions all’apertura del file 
 Comprimi gli utilizzi all’apertura del file;
 Comprimi le implementazioni dei metadati all’apertura del file;
 Mostra separatori di riga routine;
diff --git a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.pl.xlf b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.pl.xlf
index 03bd80115f0c8..c2dccb5b52ca1 100644
--- a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.pl.xlf
+++ b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.pl.xlf
@@ -114,7 +114,7 @@ Wyróżnij odwołania do symbolu pod kursorem;
 Wyróżnij pokrewne słowa kluczowe pod kursorem;
 Konspekt;
 Przejdź do trybu konspektu przy otwieraniu pliku;
-Zwijaj #regiony przy otwieraniu pliku;
+Zwijaj #regions przy otwieraniu pliku;
 Zwijaj używania przy otwieraniu pliku;
 Zwijaj implementacje metadanych przy otwieraniu pliku;
 Pokaż separatory wierszy procedur;
diff --git a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.tr.xlf b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.tr.xlf
index e1be61df96e4d..7a7cec52a10e5 100644
--- a/src/VisualStudio/CSharp/Impl/xlf/VSPackage.tr.xlf
+++ b/src/VisualStudio/CSharp/Impl/xlf/VSPackage.tr.xlf
@@ -114,7 +114,7 @@ Vurgulama;
 İmlecin altındaki ilgili anahtar sözcükleri vurgula;
 Ana Hat Oluşturma;
 Dosyalar açılırken ana hat oluşturma moduna gir;
-Dosya açılırken #bölgeleri daralt;
+Dosya açılırken #regions daralt;
 Dosya açılırken using yönergelerini daralt;
 Dosya açılırken meta veri uygulamalarını daralt;
 Yordam satır ayırıcılarını göster;
diff --git a/src/VisualStudio/CSharp/Test/Interactive/Commands/ResetInteractiveTests.cs b/src/VisualStudio/CSharp/Test/Interactive/Commands/ResetInteractiveTests.cs
index eabf3d0f69453..c5285e4b94bbc 100644
--- a/src/VisualStudio/CSharp/Test/Interactive/Commands/ResetInteractiveTests.cs
+++ b/src/VisualStudio/CSharp/Test/Interactive/Commands/ResetInteractiveTests.cs
@@ -140,7 +140,7 @@ private async Task AssertResetInteractiveAsync(
         /// <param name="workspace">Workspace with the solution.</param>
         /// <param name="project">A project that should be built.</param>
         /// <returns>A list of paths that should be referenced.</returns>
-        private IEnumerable<string> GetProjectReferences(TestWorkspace workspace, Project project)
+        private static IEnumerable<string> GetProjectReferences(TestWorkspace workspace, Project project)
         {
             var metadataReferences = project.MetadataReferences.Select(r => r.Display);
             var projectReferences = project.ProjectReferences.SelectMany(p => GetProjectReferences(
diff --git a/src/VisualStudio/Core/Def/ChangeSignature/AddParameterDialogViewModel.cs b/src/VisualStudio/Core/Def/ChangeSignature/AddParameterDialogViewModel.cs
index ed05ed72a491c..d622ff51f0648 100644
--- a/src/VisualStudio/Core/Def/ChangeSignature/AddParameterDialogViewModel.cs
+++ b/src/VisualStudio/Core/Def/ChangeSignature/AddParameterDialogViewModel.cs
@@ -227,7 +227,7 @@ private bool IsParameterTypeSyntacticallyValid(string typeName)
             return languageService.IsTypeNameValid(typeName);
         }
 
-        private bool DoesTypeFullyBind(ITypeSymbol? type)
+        private static bool DoesTypeFullyBind(ITypeSymbol? type)
         {
             if (type == null || type.IsErrorType())
             {
diff --git a/src/VisualStudio/Core/Def/CodeDefinitionWindow/VisualStudioCodeDefinitionWindowService.cs b/src/VisualStudio/Core/Def/CodeDefinitionWindow/VisualStudioCodeDefinitionWindowService.cs
index 4c18efe7458ba..a7be240eb21ca 100644
--- a/src/VisualStudio/Core/Def/CodeDefinitionWindow/VisualStudioCodeDefinitionWindowService.cs
+++ b/src/VisualStudio/Core/Def/CodeDefinitionWindow/VisualStudioCodeDefinitionWindowService.cs
@@ -5,7 +5,6 @@
 using System;
 using System.Collections.Immutable;
 using System.Composition;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.InteropServices;
 using System.Threading;
@@ -13,7 +12,6 @@
 using Microsoft.CodeAnalysis.CodeDefinitionWindow;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
 
 namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeDefinitionWindow
@@ -21,35 +19,20 @@ namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeDefinitionW
     [Export(typeof(ICodeDefinitionWindowService)), Shared]
     internal sealed class VisualStudioCodeDefinitionWindowService : ICodeDefinitionWindowService
     {
-        private readonly IAsyncServiceProvider _asyncServiceProvider;
+        private readonly IVsService<IVsCodeDefView> _codeDefView;
         private readonly IThreadingContext _threadingContext;
 
-        [DisallowNull]
-        private IVsCodeDefView? _lazyCodeDefView;
-
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public VisualStudioCodeDefinitionWindowService(SVsServiceProvider asyncServiceProvider, IThreadingContext threadingContext)
+        public VisualStudioCodeDefinitionWindowService(IVsService<SVsCodeDefView, IVsCodeDefView> codeDefView, IThreadingContext threadingContext)
         {
-            _asyncServiceProvider = (IAsyncServiceProvider)asyncServiceProvider;
+            _codeDefView = codeDefView;
             _threadingContext = threadingContext;
         }
 
-        private async Task<IVsCodeDefView> GetVsCodeDefViewAsync()
-        {
-            if (_lazyCodeDefView is not null)
-            {
-                return _lazyCodeDefView;
-            }
-
-            _lazyCodeDefView = await _asyncServiceProvider.GetServiceAsync<SVsCodeDefView, IVsCodeDefView>(_threadingContext.JoinableTaskFactory).ConfigureAwait(true);
-
-            return _lazyCodeDefView;
-        }
-
         public async Task<bool> IsWindowOpenAsync(CancellationToken cancellationToken)
         {
-            var vsCodeDefView = await GetVsCodeDefViewAsync().ConfigureAwait(true);
+            var vsCodeDefView = await _codeDefView.GetValueAsync(cancellationToken).ConfigureAwait(true);
 
             // Switch to the UI thread before using the IVsCodeDefView service
             await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
@@ -67,7 +50,7 @@ public async Task SetContextAsync(ImmutableArray<CodeDefinitionWindowLocation> l
                 return;
             }
 
-            var vsCodeDefView = await GetVsCodeDefViewAsync().ConfigureAwait(true);
+            var vsCodeDefView = await _codeDefView.GetValueAsync(cancellationToken).ConfigureAwait(true);
 
             // Switch to the UI thread before using the IVsCodeDefView service
             await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
diff --git a/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.ClassificationVerifier.cs b/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.ClassificationVerifier.cs
index 158595d0ccb26..e2e4d1032e8e9 100644
--- a/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.ClassificationVerifier.cs
+++ b/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.ClassificationVerifier.cs
@@ -61,23 +61,19 @@ private static ImmutableDictionary<string, uint> BlueLightThemeForeground
                 }.ToImmutableDictionary();
 
             private readonly IThreadingContext _threadingContext;
-            private readonly IAsyncServiceProvider _asyncServiceProvider;
+            private readonly IVsService<IVsFontAndColorStorage> _fontAndColorStorage;
             private readonly ImmutableArray<string> _classifications;
             private readonly ImmutableDictionary<ColorSchemeName, ImmutableDictionary<Guid, ImmutableDictionary<string, uint>>> _colorSchemes;
 
             // The High Contrast theme is not included because we do not want to make changes when the user is in High Contrast mode.
 
-            private IVsFontAndColorStorage? _fontAndColorStorage;
-            private IVsFontAndColorUtilities? _fontAndColorUtilities;
-
             public ClassificationVerifier(
                 IThreadingContext threadingContext,
-                IAsyncServiceProvider serviceProvider,
+                IVsService<IVsFontAndColorStorage> fontAndColorStorage,
                 ImmutableDictionary<ColorSchemeName, ColorScheme> colorSchemes)
             {
                 _threadingContext = threadingContext;
-                _asyncServiceProvider = serviceProvider;
-
+                _fontAndColorStorage = fontAndColorStorage;
                 _colorSchemes = colorSchemes.ToImmutableDictionary(
                     nameAndScheme => nameAndScheme.Key,
                     nameAndScheme => nameAndScheme.Value.Themes.ToImmutableDictionary(
@@ -107,28 +103,24 @@ public async Task<bool> AreForegroundColorsCustomizedAsync(
                 }
 
                 // Ensure we are initialized
-                if (_fontAndColorStorage is null)
-                {
-                    await TaskScheduler.Default;
-                    _fontAndColorStorage = await _asyncServiceProvider.GetServiceAsync<SVsFontAndColorStorage, IVsFontAndColorStorage>(_threadingContext.JoinableTaskFactory).ConfigureAwait(false);
-                }
+                var fontAndColorStorage = await _fontAndColorStorage.GetValueAsync(cancellationToken).ConfigureAwait(true);
 
                 await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
-                _fontAndColorUtilities ??= (IVsFontAndColorUtilities)_fontAndColorStorage;
+                var fontAndColorUtilities = (IVsFontAndColorUtilities)fontAndColorStorage;
 
                 var coreThemeColors = themeId == KnownColorThemes.Dark
                     ? DarkThemeForeground
                     : BlueLightThemeForeground;
 
                 // Open Text Editor category for readonly access and do not load items if they are defaulted.
-                if (_fontAndColorStorage.OpenCategory(TextEditorMEFItemsColorCategory, (uint)__FCSTORAGEFLAGS.FCSF_READONLY) == VSConstants.S_OK)
+                if (fontAndColorStorage.OpenCategory(TextEditorMEFItemsColorCategory, (uint)__FCSTORAGEFLAGS.FCSF_READONLY) == VSConstants.S_OK)
                 {
                     try
                     {
                         foreach (var classification in _classifications)
                         {
                             var colorItems = new ColorableItemInfo[1];
-                            if (_fontAndColorStorage.GetItem(classification, colorItems) != VSConstants.S_OK)
+                            if (fontAndColorStorage.GetItem(classification, colorItems) != VSConstants.S_OK)
                             {
                                 // Classifications that are still defaulted will not have entries.
                                 continue;
@@ -136,7 +128,7 @@ public async Task<bool> AreForegroundColorsCustomizedAsync(
 
                             var colorItem = colorItems[0];
 
-                            if (IsClassificationCustomized(coreThemeColors, colorSchemeTheme, colorItem, classification))
+                            if (IsClassificationCustomized(coreThemeColors, colorSchemeTheme, fontAndColorUtilities, colorItem, classification))
                             {
                                 return true;
                             }
@@ -144,7 +136,7 @@ public async Task<bool> AreForegroundColorsCustomizedAsync(
                     }
                     finally
                     {
-                        _fontAndColorStorage.CloseCategory();
+                        fontAndColorStorage.CloseCategory();
                     }
                 }
 
@@ -158,15 +150,15 @@ public async Task<bool> AreForegroundColorsCustomizedAsync(
             private bool IsClassificationCustomized(
                 ImmutableDictionary<string, uint> coreThemeColors,
                 ImmutableDictionary<string, uint> schemeThemeColors,
+                IVsFontAndColorUtilities fontAndColorUtilities,
                 ColorableItemInfo colorItem,
                 string classification)
             {
                 _threadingContext.ThrowIfNotOnUIThread();
-                Contract.ThrowIfNull(_fontAndColorUtilities);
 
                 var foregroundColorRef = colorItem.crForeground;
 
-                if (_fontAndColorUtilities.GetColorType(foregroundColorRef, out var foregroundColorType) != VSConstants.S_OK)
+                if (fontAndColorUtilities.GetColorType(foregroundColorRef, out var foregroundColorType) != VSConstants.S_OK)
                 {
                     // Without being able to check color type, we cannot make a determination.
                     return false;
diff --git a/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.cs b/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.cs
index dbaea0b282afb..030718375f0fb 100644
--- a/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.cs
+++ b/src/VisualStudio/Core/Def/ColorSchemes/ColorSchemeApplier.cs
@@ -13,9 +13,11 @@
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Options;
+using Microsoft.VisualStudio;
 using Microsoft.VisualStudio.PlatformUI;
 using Microsoft.VisualStudio.Settings;
 using Microsoft.VisualStudio.Shell;
+using Microsoft.VisualStudio.Shell.Interop;
 using Microsoft.VisualStudio.Threading;
 using Task = System.Threading.Tasks.Task;
 
@@ -43,6 +45,7 @@ internal sealed partial class ColorSchemeApplier
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public ColorSchemeApplier(
             IThreadingContext threadingContext,
+            IVsService<SVsFontAndColorStorage, IVsFontAndColorStorage> fontAndColorStorage,
             IGlobalOptionService globalOptions,
             SVsServiceProvider serviceProvider)
         {
@@ -52,7 +55,7 @@ public ColorSchemeApplier(
 
             _settings = new ColorSchemeSettings(threadingContext, _serviceProvider, globalOptions);
             _colorSchemes = ColorSchemeSettings.GetColorSchemes();
-            _classificationVerifier = new ClassificationVerifier(threadingContext, _asyncServiceProvider, _colorSchemes);
+            _classificationVerifier = new ClassificationVerifier(threadingContext, fontAndColorStorage, _colorSchemes);
         }
 
         public async Task InitializeAsync(CancellationToken cancellationToken)
diff --git a/src/VisualStudio/Core/Def/Diagnostics/DiagnosticProgressReporter.cs b/src/VisualStudio/Core/Def/Diagnostics/DiagnosticProgressReporter.cs
index 668e1c63e7e01..da37475dc76ba 100644
--- a/src/VisualStudio/Core/Def/Diagnostics/DiagnosticProgressReporter.cs
+++ b/src/VisualStudio/Core/Def/Diagnostics/DiagnosticProgressReporter.cs
@@ -6,10 +6,8 @@
 using System.ComponentModel.Composition;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.SolutionCrawler;
-using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.TaskStatusCenter;
 using Roslyn.Utilities;
 
@@ -34,8 +32,8 @@ internal sealed class TaskCenterSolutionAnalysisProgressReporter
         /// report UI changes concurrently.
         /// </summary>
         private readonly object _lock = new();
-        private readonly IThreadingContext _threadingContext;
         private readonly VisualStudioWorkspace _workspace;
+        private readonly IVsService<IVsTaskStatusCenterService> _taskStatusCenterService;
 
         /// <summary>
         /// Task used to trigger throttled UI updates in an interval
@@ -87,16 +85,16 @@ internal sealed class TaskCenterSolutionAnalysisProgressReporter
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public TaskCenterSolutionAnalysisProgressReporter(
-            IThreadingContext threadingContext,
-            VisualStudioWorkspace workspace)
+            VisualStudioWorkspace workspace,
+            IVsService<SVsTaskStatusCenterService, IVsTaskStatusCenterService> taskStatusCenterService)
         {
-            _threadingContext = threadingContext;
             _workspace = workspace;
+            _taskStatusCenterService = taskStatusCenterService;
         }
 
-        public async Task InitializeAsync(IAsyncServiceProvider serviceProvider)
+        public async Task InitializeAsync()
         {
-            _taskCenterService = await serviceProvider.GetServiceAsync<SVsTaskStatusCenterService, IVsTaskStatusCenterService>(_threadingContext.JoinableTaskFactory).ConfigureAwait(false);
+            _taskCenterService = await _taskStatusCenterService.GetValueAsync().ConfigureAwait(false);
 
             var crawlerService = _workspace.Services.GetRequiredService<ISolutionCrawlerService>();
             var reporter = crawlerService.GetProgressReporter(_workspace);
diff --git a/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerProvider.WorkspaceEventListener.cs b/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerProvider.WorkspaceEventListener.cs
index f846f4c9e42c1..9d9338d6c5c22 100644
--- a/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerProvider.WorkspaceEventListener.cs
+++ b/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerProvider.WorkspaceEventListener.cs
@@ -4,12 +4,10 @@
 
 using System;
 using System.Composition;
-using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.ErrorReporting;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Host.Mef;
@@ -70,7 +68,7 @@ private async Task InitializeWorkspaceAsync(ISolutionAnalyzerSetterWorkspaceServ
 
             private static void LogWorkspaceAnalyzerCount(int analyzerCount)
             {
-                Logger.Log(FunctionId.DiagnosticAnalyzerService_Analyzers, KeyValueLogMessage.Create(m => m["AnalyzerCount"] = analyzerCount));
+                Logger.Log(FunctionId.DiagnosticAnalyzerService_Analyzers, KeyValueLogMessage.Create(m => m["AnalyzerCount"] = analyzerCount, LogLevel.Debug));
             }
         }
     }
diff --git a/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerService.cs b/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerService.cs
index 59ad0a82e6dd3..5c0915f53981f 100644
--- a/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerService.cs
+++ b/src/VisualStudio/Core/Def/Diagnostics/VisualStudioDiagnosticAnalyzerService.cs
@@ -9,6 +9,7 @@
 using System.ComponentModel.Design;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
@@ -24,6 +25,7 @@
 using Microsoft.VisualStudio.LanguageServices.Setup;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
+using Microsoft.VisualStudio.Threading;
 using Roslyn.Utilities;
 using Task = System.Threading.Tasks.Task;
 
@@ -37,6 +39,7 @@ internal partial class VisualStudioDiagnosticAnalyzerService : IVisualStudioDiag
         private const int RunCodeAnalysisForSelectedProjectCommandId = 1647;
 
         private readonly VisualStudioWorkspace _workspace;
+        private readonly IVsService<IVsStatusbar> _statusbar;
         private readonly IDiagnosticAnalyzerService _diagnosticService;
         private readonly IThreadingContext _threadingContext;
         private readonly IVsHierarchyItemManager _vsHierarchyItemManager;
@@ -50,6 +53,7 @@ internal partial class VisualStudioDiagnosticAnalyzerService : IVisualStudioDiag
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public VisualStudioDiagnosticAnalyzerService(
             VisualStudioWorkspace workspace,
+            IVsService<SVsStatusbar, IVsStatusbar> statusbar,
             IDiagnosticAnalyzerService diagnosticService,
             IThreadingContext threadingContext,
             IVsHierarchyItemManager vsHierarchyItemManager,
@@ -58,6 +62,7 @@ public VisualStudioDiagnosticAnalyzerService(
             IGlobalOptionService globalOptions)
         {
             _workspace = workspace;
+            _statusbar = statusbar;
             _diagnosticService = diagnosticService;
             _threadingContext = threadingContext;
             _vsHierarchyItemManager = vsHierarchyItemManager;
@@ -335,35 +340,31 @@ public void RunAnalyzers(IVsHierarchy? hierarchy)
                 }
             }
 
-            // Add a message to VS status bar that we are running code analysis.
-            var statusBar = _serviceProvider?.GetService(typeof(SVsStatusbar)) as IVsStatusbar;
-            var totalProjectCount = project != null ? (1 + otherProjectsForMultiTfmProject.Length) : solution.ProjectIds.Count;
-            var statusBarUpdater = statusBar != null
-                ? new StatusBarUpdater(statusBar, _threadingContext, projectOrSolutionName, (uint)totalProjectCount)
-                : null;
-
             // Force complete analyzer execution in background.
-            var asyncToken = _listener.BeginAsyncOperation($"{nameof(VisualStudioDiagnosticAnalyzerService)}_{nameof(RunAnalyzers)}");
-            Task.Run(async () =>
+            _threadingContext.JoinableTaskFactory.RunAsync(async () =>
             {
-                try
-                {
-                    var onProjectAnalyzed = statusBarUpdater != null ? statusBarUpdater.OnProjectAnalyzed : (Action<Project>)((Project _) => { });
-                    await _diagnosticService.ForceAnalyzeAsync(solution, onProjectAnalyzed, project?.Id, CancellationToken.None).ConfigureAwait(false);
+                using var asyncToken = _listener.BeginAsyncOperation($"{nameof(VisualStudioDiagnosticAnalyzerService)}_{nameof(RunAnalyzers)}");
 
-                    foreach (var otherProject in otherProjectsForMultiTfmProject)
-                        await _diagnosticService.ForceAnalyzeAsync(solution, onProjectAnalyzed, otherProject.Id, CancellationToken.None).ConfigureAwait(false);
+                // Add a message to VS status bar that we are running code analysis.
+                var statusBar = await _statusbar.GetValueOrNullAsync().ConfigureAwait(true);
+                var totalProjectCount = project != null ? (1 + otherProjectsForMultiTfmProject.Length) : solution.ProjectIds.Count;
+                using var statusBarUpdater = statusBar != null
+                    ? new StatusBarUpdater(statusBar, _threadingContext, projectOrSolutionName, (uint)totalProjectCount)
+                    : null;
 
-                    // If user has disabled live analyzer execution for any project(s), i.e. set RunAnalyzersDuringLiveAnalysis = false,
-                    // then ForceAnalyzeAsync will not cause analyzers to execute.
-                    // We explicitly fetch diagnostics for such projects and report these as "Host" diagnostics.
-                    HandleProjectsWithDisabledAnalysis();
-                }
-                finally
-                {
-                    statusBarUpdater?.Dispose();
-                }
-            }).CompletesAsyncOperation(asyncToken);
+                await TaskScheduler.Default;
+
+                var onProjectAnalyzed = statusBarUpdater != null ? statusBarUpdater.OnProjectAnalyzed : (Action<Project>)((Project _) => { });
+                await _diagnosticService.ForceAnalyzeAsync(solution, onProjectAnalyzed, project?.Id, CancellationToken.None).ConfigureAwait(false);
+
+                foreach (var otherProject in otherProjectsForMultiTfmProject)
+                    await _diagnosticService.ForceAnalyzeAsync(solution, onProjectAnalyzed, otherProject.Id, CancellationToken.None).ConfigureAwait(false);
+
+                // If user has disabled live analyzer execution for any project(s), i.e. set RunAnalyzersDuringLiveAnalysis = false,
+                // then ForceAnalyzeAsync will not cause analyzers to execute.
+                // We explicitly fetch diagnostics for such projects and report these as "Host" diagnostics.
+                HandleProjectsWithDisabledAnalysis();
+            });
 
             return;
 
diff --git a/src/VisualStudio/Core/Def/EditAndContinue/EditAndContinueFeedbackDiagnosticFileProvider.cs b/src/VisualStudio/Core/Def/EditAndContinue/EditAndContinueFeedbackDiagnosticFileProvider.cs
index 6240fe711aab7..670396231af7a 100644
--- a/src/VisualStudio/Core/Def/EditAndContinue/EditAndContinueFeedbackDiagnosticFileProvider.cs
+++ b/src/VisualStudio/Core/Def/EditAndContinue/EditAndContinueFeedbackDiagnosticFileProvider.cs
@@ -39,7 +39,7 @@ internal sealed class EditAndContinueFeedbackDiagnosticFileProvider : IFeedbackD
     /// Watching the file is currently the only way to detect the feedback session.
     /// </summary>
     private readonly string _vsFeedbackSemaphoreFullPath;
-    private readonly FileSystemWatcher _vsFeedbackSemaphoreFileWatcher;
+    private readonly FileSystemWatcher? _vsFeedbackSemaphoreFileWatcher;
 
     private readonly int _vsProcessId;
     private readonly DateTime _vsProcessStartTime;
@@ -65,6 +65,12 @@ public EditAndContinueFeedbackDiagnosticFileProvider(
         var vsFeedbackTempDir = Path.Combine(_tempDir, VSFeedbackSemaphoreDir);
         _vsFeedbackSemaphoreFullPath = Path.Combine(vsFeedbackTempDir, VSFeedbackSemaphoreFileName);
 
+        // Directory may not exist in scenarios such as Razor integration tests
+        if (!Directory.Exists(vsFeedbackTempDir))
+        {
+            return;
+        }
+
         _vsFeedbackSemaphoreFileWatcher = new FileSystemWatcher(vsFeedbackTempDir, VSFeedbackSemaphoreFileName);
         _vsFeedbackSemaphoreFileWatcher.Created += (_, _) => OnFeedbackSemaphoreCreatedOrChanged();
         _vsFeedbackSemaphoreFileWatcher.Changed += (_, _) => OnFeedbackSemaphoreCreatedOrChanged();
@@ -93,7 +99,9 @@ private string GetZipFilePath()
         => Path.Combine(Path.Combine(_tempDir, $"EnC_{_vsProcessId}", ZipFileName));
 
     public IReadOnlyCollection<string> GetFiles()
-        => new[] { GetZipFilePath() };
+        => _vsFeedbackSemaphoreFileWatcher is null
+           ? Array.Empty<string>()
+           : (IReadOnlyCollection<string>)(new[] { GetZipFilePath() });
 
     private void OnFeedbackSemaphoreCreatedOrChanged()
     {
diff --git a/src/VisualStudio/Core/Def/ErrorReporting/VisualStudioErrorReportingService.cs b/src/VisualStudio/Core/Def/ErrorReporting/VisualStudioErrorReportingService.cs
index 24ea82692ae19..d6a2f959a1ce7 100644
--- a/src/VisualStudio/Core/Def/ErrorReporting/VisualStudioErrorReportingService.cs
+++ b/src/VisualStudio/Core/Def/ErrorReporting/VisualStudioErrorReportingService.cs
@@ -10,6 +10,7 @@
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.CodeAnalysis.Telemetry;
+using Microsoft.VisualStudio;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
 
@@ -19,21 +20,22 @@ namespace Microsoft.CodeAnalysis.ErrorReporting
     internal partial class VisualStudioErrorReportingService : IErrorReportingService
     {
         private readonly IThreadingContext _threadingContext;
+        private readonly IVsService<IVsActivityLog> _activityLog;
         private readonly IAsynchronousOperationListener _listener;
         private readonly VisualStudioInfoBar _infoBar;
-        private readonly SVsServiceProvider _serviceProvider;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public VisualStudioErrorReportingService(
             IThreadingContext threadingContext,
+            IVsService<SVsActivityLog, IVsActivityLog> activityLog,
             IAsynchronousOperationListenerProvider listenerProvider,
             SVsServiceProvider serviceProvider)
         {
             _threadingContext = threadingContext;
+            _activityLog = activityLog;
             _listener = listenerProvider.GetListener(FeatureAttribute.Workspace);
             _infoBar = new VisualStudioInfoBar(threadingContext, serviceProvider, listenerProvider);
-            _serviceProvider = serviceProvider;
         }
 
         public string HostDisplayName => "Visual Studio";
@@ -81,7 +83,7 @@ private void LogGlobalErrorToActivityLog(string message, string? detailedError)
 
                 await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(_threadingContext.DisposalToken);
 
-                var activityLog = await ((IAsyncServiceProvider)_serviceProvider).GetServiceAsync<SVsActivityLog, IVsActivityLog>(_threadingContext.JoinableTaskFactory).ConfigureAwait(true);
+                var activityLog = await _activityLog.GetValueAsync(_threadingContext.DisposalToken).ConfigureAwait(true);
 
                 activityLog.LogEntry(
                     (uint)__ACTIVITYLOG_ENTRYTYPE.ALE_ERROR,
diff --git a/src/VisualStudio/Core/Def/FindReferences/Contexts/AbstractTableDataSourceFindUsagesContext.cs b/src/VisualStudio/Core/Def/FindReferences/Contexts/AbstractTableDataSourceFindUsagesContext.cs
index 255016b4531b9..1f9283d391f3d 100644
--- a/src/VisualStudio/Core/Def/FindReferences/Contexts/AbstractTableDataSourceFindUsagesContext.cs
+++ b/src/VisualStudio/Core/Def/FindReferences/Contexts/AbstractTableDataSourceFindUsagesContext.cs
@@ -158,7 +158,7 @@ protected AbstractTableDataSourceFindUsagesContext(
                 // To ensure a reasonable experience, we instead add the progress into a queue and
                 // only update the UI a few times a second so as to not overload it.
                 _progressQueue = new AsyncBatchingWorkQueue<(int current, int maximum)>(
-                    TimeSpan.FromMilliseconds(250),
+                    DelayTimeSpan.Short,
                     this.UpdateTableProgressAsync,
                     presenter._asyncListener,
                     CancellationTokenSource.Token);
diff --git a/src/VisualStudio/Core/Def/Interop/CleanableWeakComHandleTable.cs b/src/VisualStudio/Core/Def/Interop/CleanableWeakComHandleTable.cs
index 7bc1ff3f56f79..e3deb808f774d 100644
--- a/src/VisualStudio/Core/Def/Interop/CleanableWeakComHandleTable.cs
+++ b/src/VisualStudio/Core/Def/Interop/CleanableWeakComHandleTable.cs
@@ -9,6 +9,7 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.VisualStudio.LanguageServices.Implementation.Utilities;
@@ -136,7 +137,7 @@ async Task RemoveDeadKeysAsync()
 
             async Task ResetTimeSliceAsync()
             {
-                await listener.Delay(TimeSpan.FromMilliseconds(50), ThreadingContext.DisposalToken).ConfigureAwait(true);
+                await listener.Delay(DelayTimeSpan.NearImmediate, ThreadingContext.DisposalToken).ConfigureAwait(true);
                 timeSlice = new TimeSlice(CleanUpTimeSlice);
             }
         }
diff --git a/src/VisualStudio/Core/Def/LanguageClient/VisualStudioLogHubLoggerFactory.cs b/src/VisualStudio/Core/Def/LanguageClient/VisualStudioLogHubLoggerFactory.cs
index 8bef6ee54258b..436f195c0487f 100644
--- a/src/VisualStudio/Core/Def/LanguageClient/VisualStudioLogHubLoggerFactory.cs
+++ b/src/VisualStudio/Core/Def/LanguageClient/VisualStudioLogHubLoggerFactory.cs
@@ -7,15 +7,12 @@
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.LanguageServer;
 using Microsoft.CommonLanguageServerProtocol.Framework;
 using Microsoft.ServiceHub.Framework;
 using Microsoft.VisualStudio.LogHub;
 using Microsoft.VisualStudio.RpcContracts.Logging;
-using Microsoft.VisualStudio.Shell;
-using Microsoft.VisualStudio.Shell.Interop;
 using Microsoft.VisualStudio.Shell.ServiceBroker;
 using StreamJsonRpc;
 
@@ -30,17 +27,14 @@ internal class VisualStudioLogHubLoggerFactory : ILspServiceLoggerFactory
         /// </summary>
         private static int s_logHubSessionId;
 
-        private readonly IAsyncServiceProvider _asyncServiceProvider;
-        private readonly IThreadingContext _threadingContext;
+        private readonly IVsService<IBrokeredServiceContainer> _brokeredServiceContainer;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public VisualStudioLogHubLoggerFactory(
-            [Import(typeof(SAsyncServiceProvider))] IAsyncServiceProvider asyncServiceProvider,
-            IThreadingContext threadingContext)
+            IVsService<SVsBrokeredServiceContainer, IBrokeredServiceContainer> brokeredServiceContainer)
         {
-            _asyncServiceProvider = asyncServiceProvider;
-            _threadingContext = threadingContext;
+            _brokeredServiceContainer = brokeredServiceContainer;
         }
 
         public async Task<ILspServiceLogger> CreateLoggerAsync(string serverTypeName, JsonRpc jsonRpc, CancellationToken cancellationToken)
@@ -48,7 +42,7 @@ public async Task<ILspServiceLogger> CreateLoggerAsync(string serverTypeName, Js
             var logName = $"Roslyn.{serverTypeName}.{Interlocked.Increment(ref s_logHubSessionId)}";
             var logId = new LogId(logName, new ServiceMoniker(typeof(AbstractLanguageServer<>).FullName));
 
-            var serviceContainer = await _asyncServiceProvider.GetServiceAsync<SVsBrokeredServiceContainer, IBrokeredServiceContainer>(_threadingContext.JoinableTaskFactory).ConfigureAwait(false);
+            var serviceContainer = await _brokeredServiceContainer.GetValueAsync(cancellationToken).ConfigureAwait(false);
             var service = serviceContainer.GetFullAccessServiceBroker();
 
             var configuration = await TraceConfiguration.CreateTraceConfigurationInstanceAsync(service, ownsServiceBroker: true, cancellationToken).ConfigureAwait(false);
diff --git a/src/VisualStudio/Core/Def/LanguageService/AbstractLanguageService`2.IVsImmediateStatementCompletion2.cs b/src/VisualStudio/Core/Def/LanguageService/AbstractLanguageService`2.IVsImmediateStatementCompletion2.cs
index 8d7df4d8ac993..91d777f937332 100644
--- a/src/VisualStudio/Core/Def/LanguageService/AbstractLanguageService`2.IVsImmediateStatementCompletion2.cs
+++ b/src/VisualStudio/Core/Def/LanguageService/AbstractLanguageService`2.IVsImmediateStatementCompletion2.cs
@@ -49,8 +49,7 @@ int IVsImmediateStatementCompletion2.InstallStatementCompletion(int install, IVs
             // of textview->filters.
             if (install != 0)
             {
-                DebuggerIntelliSenseFilter filter;
-                if (!this.filters.ContainsKey(textView))
+                if (!this.filters.TryGetValue(textView, out var filter))
                 {
                     filter = new DebuggerIntelliSenseFilter(
                         this.EditorAdaptersFactoryService.GetWpfTextView(textView),
@@ -61,7 +60,7 @@ int IVsImmediateStatementCompletion2.InstallStatementCompletion(int install, IVs
                     filter.SetNextFilter(nextFilter);
                 }
 
-                this.filters[textView].SetContentType(install: true);
+                filter.SetContentType(install: true);
             }
             else
             {
diff --git a/src/VisualStudio/Core/Def/Microsoft.VisualStudio.LanguageServices.csproj b/src/VisualStudio/Core/Def/Microsoft.VisualStudio.LanguageServices.csproj
index a317c736ed3a0..8c8a0022f196d 100644
--- a/src/VisualStudio/Core/Def/Microsoft.VisualStudio.LanguageServices.csproj
+++ b/src/VisualStudio/Core/Def/Microsoft.VisualStudio.LanguageServices.csproj
@@ -124,6 +124,7 @@
     <PackageReference Include="Microsoft.Internal.VisualStudio.Interop" Version="$(MicrosoftInternalVisualStudioInteropVersion)" />
     <PackageReference Include="Microsoft.Internal.VisualStudio.Shell.Framework" Version="$(MicrosoftInternalVisualStudioShellFrameworkVersion)" />
     <PackageReference Include="Microsoft.ServiceHub.Client" Version="$(MicrosoftServiceHubClientVersion)" />
+    <PackageReference Include="Microsoft.ServiceHub.Framework" Version="$(MicrosoftServiceHubFrameworkVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Debugger.Engine-implementation" Version="$(MicrosoftVisualStudioDebuggerEngineimplementationVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Designer.Interfaces" Version="$(MicrosoftVisualStudioDesignerInterfacesVersion)" />
     <PackageReference Include="Microsoft.VisualStudio.Telemetry" Version="$(MicrosoftVisualStudioTelemetryVersion)" />
diff --git a/src/VisualStudio/Core/Def/Options/LocalUserRegistryOptionPersister.cs b/src/VisualStudio/Core/Def/Options/LocalUserRegistryOptionPersister.cs
index da16cf6c45a06..ebf373d6db3a0 100644
--- a/src/VisualStudio/Core/Def/Options/LocalUserRegistryOptionPersister.cs
+++ b/src/VisualStudio/Core/Def/Options/LocalUserRegistryOptionPersister.cs
@@ -3,13 +3,9 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Diagnostics.CodeAnalysis;
-using System.IO;
-using System.Linq;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Options;
-using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
 using Microsoft.Win32;
 using Roslyn.Utilities;
@@ -29,13 +25,9 @@ private LocalUserRegistryOptionPersister(RegistryKey registryKey)
             _registryKey = registryKey;
         }
 
-        public static async Task<LocalUserRegistryOptionPersister> CreateAsync(IAsyncServiceProvider provider)
+        public static LocalUserRegistryOptionPersister Create(ILocalRegistry4 localRegistry)
         {
             // SLocalRegistry service is free-threaded -- see https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1408594.
-            // Note: not using IAsyncServiceProvider.GetServiceAsync<TService, TInterface> since the extension method might switch to UI thread.
-            // See https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1408619/.
-            var localRegistry = (ILocalRegistry4?)await provider.GetServiceAsync(typeof(SLocalRegistry)).ConfigureAwait(false);
-            Contract.ThrowIfNull(localRegistry);
             Contract.ThrowIfFalse(ErrorHandler.Succeeded(localRegistry.GetLocalRegistryRootEx((uint)__VsLocalRegistryType.RegType_UserSettings, out var rootHandle, out var rootPath)));
 
             var handle = (__VsLocalRegistryRootHandle)rootHandle;
diff --git a/src/VisualStudio/Core/Def/Options/VisualStudioOptionPersisterProvider.cs b/src/VisualStudio/Core/Def/Options/VisualStudioOptionPersisterProvider.cs
index d7df9f3b8f33f..2015613c4fb50 100644
--- a/src/VisualStudio/Core/Def/Options/VisualStudioOptionPersisterProvider.cs
+++ b/src/VisualStudio/Core/Def/Options/VisualStudioOptionPersisterProvider.cs
@@ -9,13 +9,11 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
-using Microsoft.CodeAnalysis.ErrorReporting;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.Internal.VisualStudio.Shell.Interop;
 using Microsoft.VisualStudio.Settings;
-using IAsyncServiceProvider = Microsoft.VisualStudio.Shell.IAsyncServiceProvider;
-using SAsyncServiceProvider = Microsoft.VisualStudio.Shell.Interop.SAsyncServiceProvider;
+using Microsoft.VisualStudio.Shell.Interop;
 
 namespace Microsoft.VisualStudio.LanguageServices.Options
 {
@@ -23,33 +21,56 @@ namespace Microsoft.VisualStudio.LanguageServices.Options
     [Export(typeof(VisualStudioOptionPersisterProvider))]
     internal sealed class VisualStudioOptionPersisterProvider : IOptionPersisterProvider
     {
-        private readonly IAsyncServiceProvider _serviceProvider;
+        private readonly IVsService<ILocalRegistry4> _localRegistryService;
+        private readonly IVsService<ISettingsManager> _settingsManagerService;
+        private readonly IVsService<IVsFeatureFlags> _featureFlagsService;
         private readonly ILegacyGlobalOptionService _legacyGlobalOptions;
 
         // maps config name to a read fallback:
         private readonly ImmutableDictionary<string, Lazy<IVisualStudioStorageReadFallback, OptionNameMetadata>> _readFallbacks;
 
-        private VisualStudioOptionPersister? _lazyPersister;
+        // Use vs-threading's JTF-aware AsyncLazy<T>. Ensure only one persister instance is created (even in the face of
+        // parallel requests for the value) because the constructor registers global event handler callbacks.
+        private readonly Threading.AsyncLazy<IOptionPersister> _lazyPersister;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public VisualStudioOptionPersisterProvider(
-            [Import(typeof(SAsyncServiceProvider))] IAsyncServiceProvider serviceProvider,
+            IVsService<SLocalRegistry, ILocalRegistry4> localRegistryService,
+            IVsService<SVsSettingsPersistenceManager, ISettingsManager> settingsManagerService,
+            IVsService<SVsFeatureFlags, IVsFeatureFlags> featureFlagsService,
             [ImportMany] IEnumerable<Lazy<IVisualStudioStorageReadFallback, OptionNameMetadata>> readFallbacks,
             IThreadingContext threadingContext,
             ILegacyGlobalOptionService legacyGlobalOptions)
         {
-            _serviceProvider = serviceProvider;
+            _localRegistryService = localRegistryService;
+            _settingsManagerService = settingsManagerService;
+            _featureFlagsService = featureFlagsService;
             _legacyGlobalOptions = legacyGlobalOptions;
             _readFallbacks = readFallbacks.ToImmutableDictionary(item => item.Metadata.ConfigName, item => item);
+            _lazyPersister = new Threading.AsyncLazy<IOptionPersister>(() => CreatePersisterAsync(threadingContext.DisposalToken), threadingContext.JoinableTaskFactory);
         }
 
-        public async ValueTask<IOptionPersister> GetOrCreatePersisterAsync(CancellationToken cancellationToken)
-            => _lazyPersister ??=
-                new VisualStudioOptionPersister(
-                    new VisualStudioSettingsOptionPersister(RefreshOption, _readFallbacks, await TryGetServiceAsync<SVsSettingsPersistenceManager, ISettingsManager>().ConfigureAwait(true)),
-                    await LocalUserRegistryOptionPersister.CreateAsync(_serviceProvider).ConfigureAwait(false),
-                    new FeatureFlagPersister(await TryGetServiceAsync<SVsFeatureFlags, IVsFeatureFlags>().ConfigureAwait(false)));
+        public ValueTask<IOptionPersister> GetOrCreatePersisterAsync(CancellationToken cancellationToken)
+            => new(_lazyPersister.GetValueAsync(cancellationToken));
+
+        private async Task<IOptionPersister> CreatePersisterAsync(CancellationToken cancellationToken)
+        {
+            // Obtain services before creating instances. This avoids state corruption in the event cancellation is
+            // requested (some of the constructors register event handlers that could leak if cancellation occurred
+            // in the middle of construction).
+            var settingsManager = await _settingsManagerService.GetValueAsync(cancellationToken).ConfigureAwait(true);
+            var localRegistry = await _localRegistryService.GetValueAsync(cancellationToken).ConfigureAwait(true);
+            var featureFlags = await _featureFlagsService.GetValueOrNullAsync(cancellationToken).ConfigureAwait(true);
+
+            // Cancellation is not allowed after this point
+            cancellationToken = CancellationToken.None;
+
+            return new VisualStudioOptionPersister(
+                new VisualStudioSettingsOptionPersister(RefreshOption, _readFallbacks, settingsManager),
+                LocalUserRegistryOptionPersister.Create(localRegistry),
+                new FeatureFlagPersister(featureFlags));
+        }
 
         private void RefreshOption(OptionKey2 optionKey, object? newValue)
         {
@@ -60,17 +81,5 @@ private void RefreshOption(OptionKey2 optionKey, object? newValue)
                 _legacyGlobalOptions.UpdateRegisteredWorkspaces();
             }
         }
-
-        private async ValueTask<I?> TryGetServiceAsync<T, I>() where I : class
-        {
-            try
-            {
-                return (I?)await _serviceProvider.GetServiceAsync(typeof(T)).ConfigureAwait(false);
-            }
-            catch (Exception e) when (FatalError.ReportAndCatch(e))
-            {
-                return null;
-            }
-        }
     }
 }
diff --git a/src/VisualStudio/Core/Def/Options/VisualStudioSettingsOptionPersister.cs b/src/VisualStudio/Core/Def/Options/VisualStudioSettingsOptionPersister.cs
index 8af0447abb77e..1ee7256edae2b 100644
--- a/src/VisualStudio/Core/Def/Options/VisualStudioSettingsOptionPersister.cs
+++ b/src/VisualStudio/Core/Def/Options/VisualStudioSettingsOptionPersister.cs
@@ -3,13 +3,9 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel;
-using System.Diagnostics;
 using System.Linq;
-using System.Reflection;
-using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using System.Xml.Linq;
 using Microsoft.CodeAnalysis;
@@ -27,11 +23,7 @@ namespace Microsoft.VisualStudio.LanguageServices.Options
     /// </summary>
     internal sealed class VisualStudioSettingsOptionPersister
     {
-        // NOTE: This service is not public or intended for use by teams/individuals outside of Microsoft. Any data stored is subject to deletion without warning.
-        [Guid("9B164E40-C3A2-4363-9BC5-EB4039DEF653")]
-        private class SVsSettingsPersistenceManager { };
-
-        private readonly ISettingsManager? _settingManager;
+        private readonly ISettingsManager _settingManager;
         private readonly Action<OptionKey2, object?> _refreshOption;
         private readonly ImmutableDictionary<string, Lazy<IVisualStudioStorageReadFallback, OptionNameMetadata>> _readFallbacks;
 
@@ -45,20 +37,14 @@ private class SVsSettingsPersistenceManager { };
         /// <remarks>
         /// We make sure this code is from the UI by asking for all <see cref="IOptionPersister"/> in <see cref="RoslynPackage.InitializeAsync"/>
         /// </remarks>
-        public VisualStudioSettingsOptionPersister(Action<OptionKey2, object?> refreshOption, ImmutableDictionary<string, Lazy<IVisualStudioStorageReadFallback, OptionNameMetadata>> readFallbacks, ISettingsManager? settingsManager)
+        public VisualStudioSettingsOptionPersister(Action<OptionKey2, object?> refreshOption, ImmutableDictionary<string, Lazy<IVisualStudioStorageReadFallback, OptionNameMetadata>> readFallbacks, ISettingsManager settingsManager)
         {
             _settingManager = settingsManager;
             _refreshOption = refreshOption;
             _readFallbacks = readFallbacks;
 
-            // While the settings persistence service should be available in all SKUs it is possible an ISO shell author has undefined the
-            // contributing package. In that case persistence of settings won't work (we don't bother with a backup solution for persistence
-            // as the scenario seems exceedingly unlikely), but we shouldn't crash the IDE.
-            if (_settingManager != null)
-            {
-                var settingsSubset = _settingManager.GetSubset("*");
-                settingsSubset.SettingChangedAsync += OnSettingChangedAsync;
-            }
+            var settingsSubset = _settingManager.GetSubset("*");
+            settingsSubset.SettingChangedAsync += OnSettingChangedAsync;
         }
 
         private Task OnSettingChangedAsync(object sender, PropertyChangedEventArgs args)
diff --git a/src/VisualStudio/Core/Def/Packaging/PackageInstallerServiceFactory.cs b/src/VisualStudio/Core/Def/Packaging/PackageInstallerServiceFactory.cs
index 35849273a1202..8f1f4b7fac4a7 100644
--- a/src/VisualStudio/Core/Def/Packaging/PackageInstallerServiceFactory.cs
+++ b/src/VisualStudio/Core/Def/Packaging/PackageInstallerServiceFactory.cs
@@ -56,8 +56,8 @@ internal partial class PackageInstallerService : AbstractDelayStartedService, IP
         private const string NugetTitle = "NuGet";
 
         private readonly VSUtilities.IUIThreadOperationExecutor _operationExecutor;
+        private readonly IVsService<IBrokeredServiceContainer> _brokeredServiceContainer;
         private readonly SVsServiceProvider _serviceProvider;
-        private readonly Shell.IAsyncServiceProvider _asyncServiceProvider;
         private readonly IVsEditorAdaptersFactoryService _editorAdaptersFactoryService;
         private readonly IAsynchronousOperationListener _listener;
 
@@ -98,8 +98,8 @@ public PackageInstallerService(
             IAsynchronousOperationListenerProvider listenerProvider,
             VisualStudioWorkspaceImpl workspace,
             IGlobalOptionService globalOptions,
+            IVsService<SVsBrokeredServiceContainer, IBrokeredServiceContainer> brokeredServiceContainer,
             SVsServiceProvider serviceProvider,
-            [Import("Microsoft.VisualStudio.Shell.Interop.SAsyncServiceProvider")] object asyncServiceProvider,
             IVsEditorAdaptersFactoryService editorAdaptersFactoryService,
             [Import(AllowDefault = true)] Lazy<IVsPackageInstaller2>? packageInstaller,
             [Import(AllowDefault = true)] Lazy<IVsPackageUninstaller>? packageUninstaller,
@@ -113,11 +113,8 @@ public PackageInstallerService(
         {
             _operationExecutor = operationExecutor;
 
+            _brokeredServiceContainer = brokeredServiceContainer;
             _serviceProvider = serviceProvider;
-            // MEFv2 doesn't support type based contract for Import above and for this particular contract
-            // (SAsyncServiceProvider) actual type cast doesn't work. (https://github.com/microsoft/vs-mef/issues/138)
-            // workaround by getting the service as object and cast to actual interface
-            _asyncServiceProvider = (Shell.IAsyncServiceProvider)asyncServiceProvider;
 
             _editorAdaptersFactoryService = editorAdaptersFactoryService;
             _packageInstaller = packageInstaller;
@@ -500,7 +497,7 @@ await PerformNuGetProjectServiceWorkAsync<object>(async (nugetService, cancellat
             // GetServiceAsync/GetProxyAsync and the cast below are all explicitly documented as being BG thread safe.
             await TaskScheduler.Default;
 
-            var serviceContainer = (IBrokeredServiceContainer?)await _asyncServiceProvider.GetServiceAsync(typeof(SVsBrokeredServiceContainer)).ConfigureAwait(false);
+            var serviceContainer = await _brokeredServiceContainer.GetValueOrNullAsync(cancellationToken).ConfigureAwait(false);
             var serviceBroker = serviceContainer?.GetFullAccessServiceBroker();
             if (serviceBroker == null)
                 return default;
diff --git a/src/VisualStudio/Core/Def/ProjectSystem/FileChangeWatcher.cs b/src/VisualStudio/Core/Def/ProjectSystem/FileChangeWatcher.cs
index 645fcac519b40..0aa18f88ed9c4 100644
--- a/src/VisualStudio/Core/Def/ProjectSystem/FileChangeWatcher.cs
+++ b/src/VisualStudio/Core/Def/ProjectSystem/FileChangeWatcher.cs
@@ -7,7 +7,6 @@
 using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Linq;
-using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Collections;
@@ -417,19 +416,8 @@ public void Dispose()
             public IWatchedFile EnqueueWatchingFile(string filePath)
             {
                 // If we already have this file under our path, we may not have to do additional watching
-                foreach (var watchedDirectory in _watchedDirectories)
-                {
-                    if (filePath.StartsWith(watchedDirectory.Path, StringComparison.OrdinalIgnoreCase))
-                    {
-                        // If ExtensionFilter is null, then we're watching for all files in the directory so the prior check
-                        // of the directory containment was sufficient. If it isn't null, then we have to check the extension
-                        // matches.
-                        if (watchedDirectory.ExtensionFilter == null || filePath.EndsWith(watchedDirectory.ExtensionFilter, StringComparison.OrdinalIgnoreCase))
-                        {
-                            return NoOpWatchedFile.Instance;
-                        }
-                    }
-                }
+                if (WatchedDirectory.FilePathCoveredByWatchedDirectories(_watchedDirectories, filePath, StringComparison.OrdinalIgnoreCase))
+                    return NoOpWatchedFile.Instance;
 
                 var token = new RegularWatchedFile(this);
 
@@ -510,23 +498,6 @@ int IVsFileChangeEvents.FilesChanged(uint cChanges, string[] rgpszFile, uint[] r
             int IVsFileChangeEvents.DirectoryChanged(string pszDirectory)
                 => VSConstants.E_NOTIMPL;
 
-            /// <summary>
-            /// When a FileChangeWatcher already has a watch on a directory, a request to watch a specific file is a no-op. In that case, we return this token,
-            /// which when disposed also does nothing.
-            /// </summary>
-            internal sealed class NoOpWatchedFile : IWatchedFile
-            {
-                public static readonly IWatchedFile Instance = new NoOpWatchedFile();
-
-                private NoOpWatchedFile()
-                {
-                }
-
-                public void Dispose()
-                {
-                }
-            }
-
             public sealed class RegularWatchedFile : IWatchedFile
             {
                 public RegularWatchedFile(Context context)
diff --git a/src/VisualStudio/Core/Def/ProjectSystem/MiscellaneousFilesWorkspace.cs b/src/VisualStudio/Core/Def/ProjectSystem/MiscellaneousFilesWorkspace.cs
index d8636c6153b84..0279d545117b7 100644
--- a/src/VisualStudio/Core/Def/ProjectSystem/MiscellaneousFilesWorkspace.cs
+++ b/src/VisualStudio/Core/Def/ProjectSystem/MiscellaneousFilesWorkspace.cs
@@ -10,20 +10,13 @@
 using System.ComponentModel.Composition;
 using System.IO;
 using System.Linq;
-using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Features.Workspaces;
-using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.MetadataAsSource;
-using Microsoft.CodeAnalysis.Scripting;
-using Microsoft.CodeAnalysis.Scripting.Hosting;
 using Microsoft.CodeAnalysis.Text;
-using Microsoft.VisualStudio.Editor;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.Interop;
 using Microsoft.VisualStudio.Text;
@@ -36,7 +29,7 @@ namespace Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem
     [Export(typeof(MiscellaneousFilesWorkspace))]
     internal sealed partial class MiscellaneousFilesWorkspace : Workspace, IOpenTextBufferEventListener
     {
-        private readonly IThreadingContext _threadingContext;
+        private readonly IVsService<IVsTextManager> _textManagerService;
         private readonly OpenTextBufferProvider _openTextBufferProvider;
         private readonly IMetadataAsSourceFileService _fileTrackingMetadataAsSourceService;
 
@@ -64,6 +57,7 @@ internal sealed partial class MiscellaneousFilesWorkspace : Workspace, IOpenText
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public MiscellaneousFilesWorkspace(
             IThreadingContext threadingContext,
+            IVsService<SVsTextManager, IVsTextManager> textManagerService,
             OpenTextBufferProvider openTextBufferProvider,
             IMetadataAsSourceFileService fileTrackingMetadataAsSourceService,
             VisualStudioWorkspace visualStudioWorkspace)
@@ -71,7 +65,7 @@ public MiscellaneousFilesWorkspace(
         {
             _foregroundThreadAffinitization = new ForegroundThreadAffinitizedObject(threadingContext, assertIsForeground: false);
 
-            _threadingContext = threadingContext;
+            _textManagerService = textManagerService;
             _openTextBufferProvider = openTextBufferProvider;
             _fileTrackingMetadataAsSourceService = fileTrackingMetadataAsSourceService;
 
@@ -80,10 +74,10 @@ public MiscellaneousFilesWorkspace(
             _openTextBufferProvider.AddListener(this);
         }
 
-        public async Task InitializeAsync(IAsyncServiceProvider serviceProvider)
+        public async Task InitializeAsync()
         {
             await TaskScheduler.Default;
-            _textManager = await serviceProvider.GetServiceAsync<SVsTextManager, IVsTextManager>(_threadingContext.JoinableTaskFactory).ConfigureAwait(false);
+            _textManager = await _textManagerService.GetValueAsync().ConfigureAwait(false);
         }
 
         void IOpenTextBufferEventListener.OnOpenDocument(string moniker, ITextBuffer textBuffer, IVsHierarchy _) => TrackOpenedDocument(moniker, textBuffer);
diff --git a/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioProjectFactory.cs b/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioProjectFactory.cs
index 1034e8969eadb..2dd25f6dbba80 100644
--- a/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioProjectFactory.cs
+++ b/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioProjectFactory.cs
@@ -6,15 +6,12 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel.Composition;
-using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
-using EnvDTE;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.CodeAnalysis.Text;
 using Microsoft.CodeAnalysis.Workspaces.ProjectSystem;
 using Microsoft.VisualStudio.LanguageServices.ExternalAccess.VSTypeScript.Api;
 using Microsoft.VisualStudio.LanguageServices.Implementation.Diagnostics;
@@ -38,7 +35,7 @@ internal sealed class VisualStudioProjectFactory : IVsTypeScriptVisualStudioProj
         private readonly ImmutableArray<Lazy<IDynamicFileInfoProvider, FileExtensionsMetadata>> _dynamicFileInfoProviders;
         private readonly HostDiagnosticUpdateSource _hostDiagnosticUpdateSource;
         private readonly IVisualStudioDiagnosticAnalyzerProviderFactory _vsixAnalyzerProviderFactory;
-        private readonly Shell.IAsyncServiceProvider _serviceProvider;
+        private readonly IVsService<SVsSolution, IVsSolution2> _solution2;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
@@ -48,14 +45,14 @@ public VisualStudioProjectFactory(
             [ImportMany] IEnumerable<Lazy<IDynamicFileInfoProvider, FileExtensionsMetadata>> fileInfoProviders,
             HostDiagnosticUpdateSource hostDiagnosticUpdateSource,
             IVisualStudioDiagnosticAnalyzerProviderFactory vsixAnalyzerProviderFactory,
-            SVsServiceProvider serviceProvider)
+            IVsService<SVsSolution, IVsSolution2> solution2)
         {
             _threadingContext = threadingContext;
             _visualStudioWorkspaceImpl = visualStudioWorkspaceImpl;
             _dynamicFileInfoProviders = fileInfoProviders.AsImmutableOrEmpty();
             _hostDiagnosticUpdateSource = hostDiagnosticUpdateSource;
             _vsixAnalyzerProviderFactory = vsixAnalyzerProviderFactory;
-            _serviceProvider = (Shell.IAsyncServiceProvider)serviceProvider;
+            _solution2 = solution2;
         }
 
         public Task<ProjectSystemProject> CreateAndAddToWorkspaceAsync(string projectSystemName, string language, CancellationToken cancellationToken)
@@ -72,11 +69,10 @@ public async Task<ProjectSystemProject> CreateAndAddToWorkspaceAsync(
 
             _visualStudioWorkspaceImpl.SubscribeExternalErrorDiagnosticUpdateSourceToSolutionBuildEvents();
 
+#pragma warning disable CA2007 // Consider calling ConfigureAwait on the awaited task
             // Since we're on the UI thread here anyways, use that as an opportunity to grab the
             // IVsSolution object and solution file path.
-            //
-            // ConfigureAwait(true) as we have to come back to the UI thread to do the cast to IVsSolution2.
-            var solution = (IVsSolution2?)await _serviceProvider.GetServiceAsync(typeof(SVsSolution)).ConfigureAwait(true);
+            var solution = await _solution2.GetValueOrNullAsync(cancellationToken);
             var solutionFilePath = solution != null && ErrorHandler.Succeeded(solution.GetSolutionInfo(out _, out var filePath, out _))
                 ? filePath
                 : null;
@@ -87,7 +83,6 @@ public async Task<ProjectSystemProject> CreateAndAddToWorkspaceAsync(
             // system creates project synchronously, and during solution load we've seen traces where the thread pool is sufficiently saturated that this
             // switch can't be completed quickly. For the rest of this method, we won't use ConfigureAwait(false) since we're expecting VS threading
             // rules to apply.
-#pragma warning disable CA2007 // Consider calling ConfigureAwait on the awaited task
             if (!_threadingContext.JoinableTaskContext.IsMainThreadBlocked())
             {
                 await TaskScheduler.Default;
diff --git a/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioWorkspaceImpl.cs b/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioWorkspaceImpl.cs
index 7703de23edde3..49b2a40bd4561 100644
--- a/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioWorkspaceImpl.cs
+++ b/src/VisualStudio/Core/Def/ProjectSystem/VisualStudioWorkspaceImpl.cs
@@ -823,7 +823,7 @@ private void AddDocumentCore(DocumentInfo info, SourceText initialText, TextDocu
         private static bool IsWebsite(EnvDTE.Project project)
             => project.Kind == VsWebSite.PrjKind.prjKindVenusProject;
 
-        private IEnumerable<string> FilterFolderForProjectType(EnvDTE.Project project, IEnumerable<string> folders)
+        private static IEnumerable<string> FilterFolderForProjectType(EnvDTE.Project project, IEnumerable<string> folders)
         {
             foreach (var folder in folders)
             {
@@ -836,7 +836,7 @@ private IEnumerable<string> FilterFolderForProjectType(EnvDTE.Project project, I
             }
         }
 
-        private IEnumerable<ProjectItem> GetAllItems(ProjectItems projectItems)
+        private static IEnumerable<ProjectItem> GetAllItems(ProjectItems projectItems)
         {
             if (projectItems == null)
             {
diff --git a/src/VisualStudio/Core/Def/Remote/VisualStudioRemoteHostClientProvider.cs b/src/VisualStudio/Core/Def/Remote/VisualStudioRemoteHostClientProvider.cs
index 1642ad607b6df..fd21cfe3e2ecf 100644
--- a/src/VisualStudio/Core/Def/Remote/VisualStudioRemoteHostClientProvider.cs
+++ b/src/VisualStudio/Core/Def/Remote/VisualStudioRemoteHostClientProvider.cs
@@ -17,7 +17,6 @@
 using Microsoft.CodeAnalysis.Remote;
 using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.CodeAnalysis.SolutionCrawler;
-using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.ServiceBroker;
 using Roslyn.Utilities;
 using VSThreading = Microsoft.VisualStudio.Threading;
@@ -29,8 +28,8 @@ internal sealed class VisualStudioRemoteHostClientProvider : IRemoteHostClientPr
         [ExportWorkspaceServiceFactory(typeof(IRemoteHostClientProvider), WorkspaceKind.Host), Shared]
         internal sealed class Factory : IWorkspaceServiceFactory
         {
-            private readonly IAsyncServiceProvider _vsServiceProvider;
             private readonly VisualStudioWorkspace _vsWorkspace;
+            private readonly IVsService<IBrokeredServiceContainer> _brokeredServiceContainer;
             private readonly AsynchronousOperationListenerProvider _listenerProvider;
             private readonly RemoteServiceCallbackDispatcherRegistry _callbackDispatchers;
             private readonly IGlobalOptionService _globalOptions;
@@ -43,15 +42,15 @@ internal sealed class Factory : IWorkspaceServiceFactory
             [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
             public Factory(
                 VisualStudioWorkspace vsWorkspace,
-                SVsServiceProvider vsServiceProvider,
+                IVsService<SVsBrokeredServiceContainer, IBrokeredServiceContainer> brokeredServiceContainer,
                 AsynchronousOperationListenerProvider listenerProvider,
                 IGlobalOptionService globalOptions,
                 IThreadingContext threadingContext,
                 [ImportMany] IEnumerable<Lazy<IRemoteServiceCallbackDispatcher, RemoteServiceCallbackDispatcherRegistry.ExportMetadata>> callbackDispatchers)
             {
-                _vsServiceProvider = (IAsyncServiceProvider)vsServiceProvider;
                 _globalOptions = globalOptions;
                 _vsWorkspace = vsWorkspace;
+                _brokeredServiceContainer = brokeredServiceContainer;
                 _listenerProvider = listenerProvider;
                 _threadingContext = threadingContext;
                 _callbackDispatchers = new RemoteServiceCallbackDispatcherRegistry(callbackDispatchers);
@@ -78,7 +77,7 @@ workspaceServices.Workspace is not (VisualStudioWorkspace or PreviewWorkspace) |
                     // If we have a cached vs instance, then we can return that instance since we know they have the same host services.
                     // Otherwise, create and cache an instance based on vs workspace for future callers with same services.
                     if (_cachedVSInstance is null)
-                        _cachedVSInstance = new VisualStudioRemoteHostClientProvider(_vsWorkspace.Services.SolutionServices, _globalOptions, _vsServiceProvider, _threadingContext, _listenerProvider, _callbackDispatchers);
+                        _cachedVSInstance = new VisualStudioRemoteHostClientProvider(_vsWorkspace.Services.SolutionServices, _globalOptions, _brokeredServiceContainer, _threadingContext, _listenerProvider, _callbackDispatchers);
 
                     return _cachedVSInstance;
                 }
@@ -88,23 +87,21 @@ workspaceServices.Workspace is not (VisualStudioWorkspace or PreviewWorkspace) |
         public readonly SolutionServices Services;
         private readonly IGlobalOptionService _globalOptions;
         private readonly VSThreading.AsyncLazy<RemoteHostClient?> _lazyClient;
-        private readonly IAsyncServiceProvider _vsServiceProvider;
-        private readonly IThreadingContext _threadingContext;
+        private readonly IVsService<IBrokeredServiceContainer> _brokeredServiceContainer;
         private readonly AsynchronousOperationListenerProvider _listenerProvider;
         private readonly RemoteServiceCallbackDispatcherRegistry _callbackDispatchers;
 
         private VisualStudioRemoteHostClientProvider(
             SolutionServices services,
             IGlobalOptionService globalOptions,
-            IAsyncServiceProvider vsServiceProvider,
+            IVsService<IBrokeredServiceContainer> brokeredServiceContainer,
             IThreadingContext threadingContext,
             AsynchronousOperationListenerProvider listenerProvider,
             RemoteServiceCallbackDispatcherRegistry callbackDispatchers)
         {
             Services = services;
             _globalOptions = globalOptions;
-            _vsServiceProvider = vsServiceProvider;
-            _threadingContext = threadingContext;
+            _brokeredServiceContainer = brokeredServiceContainer;
             _listenerProvider = listenerProvider;
             _callbackDispatchers = callbackDispatchers;
 
@@ -117,7 +114,7 @@ private VisualStudioRemoteHostClientProvider(
         {
             try
             {
-                var brokeredServiceContainer = await _vsServiceProvider.GetServiceAsync<SVsBrokeredServiceContainer, IBrokeredServiceContainer>(_threadingContext.JoinableTaskFactory).ConfigureAwait(false);
+                var brokeredServiceContainer = await _brokeredServiceContainer.GetValueAsync().ConfigureAwait(false);
                 var serviceBroker = brokeredServiceContainer.GetFullAccessServiceBroker();
 
                 var configuration =
diff --git a/src/VisualStudio/Core/Def/RoslynPackage.cs b/src/VisualStudio/Core/Def/RoslynPackage.cs
index 805f5f17d2c45..19cb47a354609 100644
--- a/src/VisualStudio/Core/Def/RoslynPackage.cs
+++ b/src/VisualStudio/Core/Def/RoslynPackage.cs
@@ -9,13 +9,11 @@
 using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.CodeAnalysis.ChangeSignature;
 using Microsoft.CodeAnalysis.ColorSchemes;
-using Microsoft.CodeAnalysis.Completion.Log;
+using Microsoft.CodeAnalysis.Common;
 using Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.AsyncCompletion;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.ErrorReporting;
-using Microsoft.CodeAnalysis.Logging;
 using Microsoft.CodeAnalysis.Notification;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Remote.ProjectSystem;
@@ -173,7 +171,7 @@ protected override async Task InitializeAsync(CancellationToken cancellationToke
             // Misc workspace has to be up and running by the time our package is usable so that it can track running
             // doc events and appropriately map files to/from it and other relevant workspaces (like the
             // metadata-as-source workspace).
-            await this.ComponentModel.GetService<MiscellaneousFilesWorkspace>().InitializeAsync(this).ConfigureAwait(false);
+            await this.ComponentModel.GetService<MiscellaneousFilesWorkspace>().InitializeAsync().ConfigureAwait(false);
 
             // Proffer in-process service broker services
             var serviceBrokerContainer = await this.GetServiceAsync<SVsBrokeredServiceContainer, IBrokeredServiceContainer>(this.JoinableTaskFactory).ConfigureAwait(false);
@@ -220,7 +218,7 @@ protected override async Task LoadComponentsAsync(CancellationToken cancellation
 
             // we need to load it as early as possible since we can have errors from
             // package from each language very early
-            await this.ComponentModel.GetService<TaskCenterSolutionAnalysisProgressReporter>().InitializeAsync(this).ConfigureAwait(false);
+            await this.ComponentModel.GetService<TaskCenterSolutionAnalysisProgressReporter>().InitializeAsync().ConfigureAwait(false);
             await this.ComponentModel.GetService<VisualStudioSuppressionFixService>().InitializeAsync(this).ConfigureAwait(false);
             await this.ComponentModel.GetService<VisualStudioDiagnosticListTableCommandHandler>().InitializeAsync(this, cancellationToken).ConfigureAwait(false);
             await this.ComponentModel.GetService<VisualStudioDiagnosticListSuppressionStateService>().InitializeAsync(this, cancellationToken).ConfigureAwait(false);
@@ -322,11 +320,9 @@ protected override void Dispose(bool disposing)
 
         private void ReportSessionWideTelemetry()
         {
-            SolutionLogger.ReportTelemetry();
             AsyncCompletionLogger.ReportTelemetry();
-            CompletionProvidersLogger.ReportTelemetry();
-            ChangeSignatureLogger.ReportTelemetry();
             InheritanceMarginLogger.ReportTelemetry();
+            FeaturesSessionTelemetry.Report();
             ComponentModel.GetService<VisualStudioSourceGeneratorTelemetryCollectorWorkspaceServiceFactory>().ReportOtherWorkspaceTelemetry();
         }
 
diff --git a/src/VisualStudio/Core/Def/Storage/VisualStudioCloudCacheStorageService.cs b/src/VisualStudio/Core/Def/Storage/VisualStudioCloudCacheStorageService.cs
index 43515fda63e93..ead75b0670bfb 100644
--- a/src/VisualStudio/Core/Def/Storage/VisualStudioCloudCacheStorageService.cs
+++ b/src/VisualStudio/Core/Def/Storage/VisualStudioCloudCacheStorageService.cs
@@ -7,13 +7,11 @@
 using System.Composition;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Storage.CloudCache;
 using Microsoft.ServiceHub.Framework;
 using Microsoft.VisualStudio.RpcContracts.Caching;
-using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Shell.ServiceBroker;
 using Roslyn.Utilities;
 
@@ -24,34 +22,30 @@ internal class VisualStudioCloudCacheStorageService : AbstractCloudCachePersiste
         [ExportWorkspaceServiceFactory(typeof(ICloudCacheStorageService), ServiceLayer.Host), Shared]
         internal class ServiceFactory : IWorkspaceServiceFactory
         {
-            private readonly IAsyncServiceProvider _serviceProvider;
-            private readonly IThreadingContext _threadingContext;
+            private readonly IVsService<IBrokeredServiceContainer> _brokeredServiceContainer;
 
             [ImportingConstructor]
             [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-            public ServiceFactory(SVsServiceProvider serviceProvider, IThreadingContext threadingContext)
+            public ServiceFactory(IVsService<SVsBrokeredServiceContainer, IBrokeredServiceContainer> brokeredServiceContainer)
             {
-                _serviceProvider = (IAsyncServiceProvider)serviceProvider;
-                _threadingContext = threadingContext;
+                _brokeredServiceContainer = brokeredServiceContainer;
             }
 
             public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
-                => new VisualStudioCloudCacheStorageService(_serviceProvider, _threadingContext, workspaceServices.GetRequiredService<IPersistentStorageConfiguration>());
+                => new VisualStudioCloudCacheStorageService(_brokeredServiceContainer, workspaceServices.GetRequiredService<IPersistentStorageConfiguration>());
         }
 
-        private readonly IAsyncServiceProvider _serviceProvider;
-        private readonly IThreadingContext _threadingContext;
+        private readonly IVsService<IBrokeredServiceContainer> _brokeredServiceContainer;
 
-        public VisualStudioCloudCacheStorageService(IAsyncServiceProvider serviceProvider, IThreadingContext threadingContext, IPersistentStorageConfiguration configuration)
+        public VisualStudioCloudCacheStorageService(IVsService<IBrokeredServiceContainer> brokeredServiceContainer, IPersistentStorageConfiguration configuration)
             : base(configuration)
         {
-            _serviceProvider = serviceProvider;
-            _threadingContext = threadingContext;
+            _brokeredServiceContainer = brokeredServiceContainer;
         }
 
         protected sealed override async ValueTask<ICacheService> CreateCacheServiceAsync(string solutionFolder, CancellationToken cancellationToken)
         {
-            var serviceContainer = await _serviceProvider.GetServiceAsync<SVsBrokeredServiceContainer, IBrokeredServiceContainer>(_threadingContext.JoinableTaskFactory).ConfigureAwait(false);
+            var serviceContainer = await _brokeredServiceContainer.GetValueAsync(cancellationToken).ConfigureAwait(false);
             var serviceBroker = serviceContainer.GetFullAccessServiceBroker();
 
 #pragma warning disable ISB001 // Dispose of proxies
diff --git a/src/VisualStudio/Core/Def/SymbolSearch/AbstractDelayStartedService.cs b/src/VisualStudio/Core/Def/SymbolSearch/AbstractDelayStartedService.cs
index d7efe102f8247..153254b73d7bd 100644
--- a/src/VisualStudio/Core/Def/SymbolSearch/AbstractDelayStartedService.cs
+++ b/src/VisualStudio/Core/Def/SymbolSearch/AbstractDelayStartedService.cs
@@ -64,7 +64,7 @@ protected AbstractDelayStartedService(
             _perLanguageOptions = perLanguageOptions;
 
             _optionChangedWorkQueue = new AsyncBatchingWorkQueue(
-                TimeSpan.FromMilliseconds(500),
+                DelayTimeSpan.Medium,
                 ProcessOptionChangesAsync,
                 listenerProvider.GetListener(FeatureAttribute.Workspace),
                 this.DisposalToken);
diff --git a/src/VisualStudio/Core/Def/Telemetry/AggregatingTelemetryLog.cs b/src/VisualStudio/Core/Def/Telemetry/AggregatingTelemetryLog.cs
new file mode 100644
index 0000000000000..af888e4351857
--- /dev/null
+++ b/src/VisualStudio/Core/Def/Telemetry/AggregatingTelemetryLog.cs
@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.Internal.Log;
+using Microsoft.VisualStudio.Telemetry;
+using Microsoft.VisualStudio.Telemetry.Metrics;
+using Microsoft.VisualStudio.Telemetry.Metrics.Events;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.Telemetry
+{
+    /// <summary>
+    /// Provides a wrapper around the VSTelemetry histogram APIs to support aggregated telemetry. Each instance
+    /// of this class corresponds to a specific FunctionId operation and can support aggregated values for each
+    /// metric name logged.
+    /// </summary>
+    internal sealed class AggregatingTelemetryLog : ITelemetryLog
+    {
+        // Indicates version information which vs telemetry will use for our aggregated telemetry. This can be used
+        // by Kusto queries to filter against telemetry versions which have the specified version and thus desired shape.
+        private const string MeterVersion = "0.40";
+
+        private readonly IMeter _meter;
+        private readonly TelemetrySession _session;
+        private readonly HistogramConfiguration? _histogramConfiguration;
+        private readonly string _eventName;
+        private readonly AggregatingTelemetryLogManager _aggregatingTelemetryLogManager;
+
+        private ImmutableDictionary<string, IHistogram<int>> _histograms = ImmutableDictionary<string, IHistogram<int>>.Empty;
+
+        /// <summary>
+        /// Creates a new aggregating telemetry log
+        /// </summary>
+        /// <param name="session">Telemetry session used to post events</param>
+        /// <param name="functionId">Used to derive meter name</param>
+        /// <param name="bucketBoundaries">Optional values indicating bucket boundaries in milliseconds. If not specified, 
+        /// all histograms created will use the default histogram configuration</param>
+        public AggregatingTelemetryLog(TelemetrySession session, FunctionId functionId, double[]? bucketBoundaries, AggregatingTelemetryLogManager aggregatingTelemetryLogManager)
+        {
+            var meterName = TelemetryLogger.GetPropertyName(functionId, "meter");
+            var meterProvider = new VSTelemetryMeterProvider();
+
+            _session = session;
+            _meter = meterProvider.CreateMeter(meterName, version: MeterVersion);
+            _eventName = TelemetryLogger.GetEventName(functionId);
+            _aggregatingTelemetryLogManager = aggregatingTelemetryLogManager;
+
+            if (bucketBoundaries != null)
+            {
+                _histogramConfiguration = new HistogramConfiguration(bucketBoundaries);
+            }
+        }
+
+        /// <summary>
+        /// Adds aggregated information for the metric and value passed in via logMessage. The Name/Value properties
+        /// are used as the metric name and value to record.
+        /// </summary>
+        /// <param name="logMessage"></param>
+        public void Log(LogMessage logMessage)
+        {
+            if (!IsEnabled)
+                return;
+
+            if (logMessage is not KeyValueLogMessage kvLogMessage)
+                throw ExceptionUtilities.Unreachable();
+
+            if (!kvLogMessage.TryGetValue(TelemetryLogging.AggregatedKeyName, out var nameValue) || nameValue is not string metricName)
+                throw ExceptionUtilities.Unreachable();
+
+            if (!kvLogMessage.TryGetValue(TelemetryLogging.AggregatedKeyValue, out var valueValue) || valueValue is not int value)
+                throw ExceptionUtilities.Unreachable();
+
+            var histogram = ImmutableInterlocked.GetOrAdd(ref _histograms, metricName, metricName => _meter.CreateHistogram<int>(metricName, _histogramConfiguration));
+
+            histogram.Record(value);
+
+            _aggregatingTelemetryLogManager.EnsureTelemetryWorkQueued();
+        }
+
+        public IDisposable? LogBlockTime(string name, int minThresholdMs)
+        {
+            if (!IsEnabled)
+                return null;
+
+            return new TimedTelemetryLogBlock(name, minThresholdMs, telemetryLog: this);
+        }
+
+        private bool IsEnabled => _session.IsOptedIn;
+
+        public void PostTelemetry(TelemetrySession session)
+        {
+            foreach (var histogram in _histograms.Values)
+            {
+                var telemetryEvent = new TelemetryEvent(_eventName);
+                var histogramEvent = new TelemetryHistogramEvent<int>(telemetryEvent, histogram);
+
+                session.PostMetricEvent(histogramEvent);
+            }
+
+            _histograms = ImmutableDictionary<string, IHistogram<int>>.Empty;
+        }
+    }
+}
diff --git a/src/VisualStudio/Core/Def/Telemetry/AggregatingTelemetryLogManager.cs b/src/VisualStudio/Core/Def/Telemetry/AggregatingTelemetryLogManager.cs
new file mode 100644
index 0000000000000..9a2c8d2d858a9
--- /dev/null
+++ b/src/VisualStudio/Core/Def/Telemetry/AggregatingTelemetryLogManager.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Immutable;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Internal.Log;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.VisualStudio.Telemetry;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.Telemetry
+{
+    /// <summary>
+    /// Manages creation and obtaining aggregated telemetry logs. Also, notifies logs to
+    /// send aggregated events every 30 minutes.
+    /// </summary>
+    internal sealed class AggregatingTelemetryLogManager
+    {
+        private static readonly TimeSpan s_batchedTelemetryCollectionPeriod = TimeSpan.FromMinutes(30);
+
+        private readonly TelemetrySession _session;
+        private readonly AsyncBatchingWorkQueue _postTelemetryQueue;
+
+        private ImmutableDictionary<FunctionId, AggregatingTelemetryLog> _aggregatingLogs = ImmutableDictionary<FunctionId, AggregatingTelemetryLog>.Empty;
+
+        public AggregatingTelemetryLogManager(TelemetrySession session, IAsynchronousOperationListener asyncListener)
+        {
+            _session = session;
+
+            _postTelemetryQueue = new AsyncBatchingWorkQueue(
+                s_batchedTelemetryCollectionPeriod,
+                PostCollectedTelemetryAsync,
+                asyncListener,
+                CancellationToken.None);
+        }
+
+        public ITelemetryLog? GetLog(FunctionId functionId, double[]? bucketBoundaries)
+        {
+            if (!_session.IsOptedIn)
+                return null;
+
+            return ImmutableInterlocked.GetOrAdd(ref _aggregatingLogs, functionId, functionId => new AggregatingTelemetryLog(_session, functionId, bucketBoundaries, this));
+        }
+
+        public void EnsureTelemetryWorkQueued()
+        {
+            // Ensure PostCollectedTelemetryAsync will get fired after the collection period.
+            _postTelemetryQueue.AddWork();
+        }
+
+        private ValueTask PostCollectedTelemetryAsync(CancellationToken token)
+        {
+            token.ThrowIfCancellationRequested();
+
+            PostCollectedTelemetry();
+
+            return ValueTaskFactory.CompletedTask;
+        }
+
+        private void PostCollectedTelemetry()
+        {
+            if (!_session.IsOptedIn)
+                return;
+
+            foreach (var log in _aggregatingLogs.Values)
+            {
+                log.PostTelemetry(_session);
+            }
+        }
+    }
+}
diff --git a/src/VisualStudio/Core/Def/Telemetry/TelemetryLogProvider.cs b/src/VisualStudio/Core/Def/Telemetry/TelemetryLogProvider.cs
new file mode 100644
index 0000000000000..aa82b492ae938
--- /dev/null
+++ b/src/VisualStudio/Core/Def/Telemetry/TelemetryLogProvider.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.Internal.Log;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.CodeAnalysis.Telemetry;
+using Microsoft.VisualStudio.Telemetry;
+
+namespace Microsoft.VisualStudio.LanguageServices.Telemetry
+{
+    /// <summary>
+    /// Provides access to an appropriate <see cref="ITelemetryLogProvider"/> for logging telemetry.
+    /// </summary>
+    internal sealed class TelemetryLogProvider : ITelemetryLogProvider
+    {
+        private readonly AggregatingTelemetryLogManager _aggregatingTelemetryLogManager;
+        private readonly VisualStudioTelemetryLogManager _visualStudioTelemetryLogManager;
+
+        private TelemetryLogProvider(TelemetrySession session, ILogger telemetryLogger, IAsynchronousOperationListener asyncListener)
+        {
+            _aggregatingTelemetryLogManager = new AggregatingTelemetryLogManager(session, asyncListener);
+            _visualStudioTelemetryLogManager = new VisualStudioTelemetryLogManager(session, telemetryLogger);
+        }
+
+        public static TelemetryLogProvider Create(TelemetrySession session, ILogger telemetryLogger, IAsynchronousOperationListener asyncListener)
+        {
+            var logProvider = new TelemetryLogProvider(session, telemetryLogger, asyncListener);
+
+            TelemetryLogging.SetLogProvider(logProvider);
+
+            return logProvider;
+        }
+
+        /// <summary>
+        /// Returns an <see cref="ITelemetryLog"/> for logging telemetry.
+        /// </summary>
+        public ITelemetryLog? GetLog(FunctionId functionId)
+        {
+            return _visualStudioTelemetryLogManager.GetLog(functionId);
+        }
+
+        /// <summary>
+        /// Returns an aggregating <see cref="ITelemetryLog"/> for logging telemetry.
+        /// </summary>
+        public ITelemetryLog? GetAggregatingLog(FunctionId functionId, double[]? bucketBoundaries)
+        {
+            return _aggregatingTelemetryLogManager.GetLog(functionId, bucketBoundaries);
+        }
+    }
+}
diff --git a/src/VisualStudio/Core/Def/Telemetry/TelemetryLogger.cs b/src/VisualStudio/Core/Def/Telemetry/TelemetryLogger.cs
index ebeef7d25da1f..3c0e8f3260780 100644
--- a/src/VisualStudio/Core/Def/Telemetry/TelemetryLogger.cs
+++ b/src/VisualStudio/Core/Def/Telemetry/TelemetryLogger.cs
@@ -5,12 +5,11 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Linq;
 using System.Threading;
-using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Internal.Log;
-using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+using Microsoft.VisualStudio.LanguageServices.Telemetry;
 using Microsoft.VisualStudio.Telemetry;
 using Roslyn.Utilities;
 
@@ -22,12 +21,24 @@ private sealed class Implementation : TelemetryLogger
         {
             private readonly TelemetrySession _session;
 
-            public Implementation(TelemetrySession session, bool logDelta)
+            private Implementation(TelemetrySession session, bool logDelta)
             {
                 _session = session;
                 LogDelta = logDelta;
             }
 
+            public static new Implementation Create(TelemetrySession session, bool logDelta, IAsynchronousOperationListenerProvider asyncListenerProvider)
+            {
+                var logger = new Implementation(session, logDelta);
+                var asyncListener = asyncListenerProvider.GetListener(FeatureAttribute.Telemetry);
+
+                // Two stage initialization as TelemetryLogProvider.Create needs access to
+                //  the ILogger that this class implements.
+                TelemetryLogProvider.Create(session, logger, asyncListener);
+
+                return logger;
+            }
+
             protected override bool LogDelta { get; }
 
             public override bool IsEnabled(FunctionId functionId)
@@ -84,8 +95,8 @@ internal static string GetPropertyName(FunctionId id, string name)
         private static string GetTelemetryName(FunctionId id, char separator)
             => Enum.GetName(typeof(FunctionId), id)!.Replace('_', separator).ToLowerInvariant();
 
-        public static TelemetryLogger Create(TelemetrySession session, bool logDelta)
-            => new Implementation(session, logDelta);
+        public static TelemetryLogger Create(TelemetrySession session, bool logDelta, IAsynchronousOperationListenerProvider asyncListenerProvider)
+            => Implementation.Create(session, logDelta, asyncListenerProvider);
 
         public abstract bool IsEnabled(FunctionId functionId);
         protected abstract void PostEvent(TelemetryEvent telemetryEvent);
diff --git a/src/VisualStudio/Core/Def/Telemetry/TimedTelemetryLogBlock.cs b/src/VisualStudio/Core/Def/Telemetry/TimedTelemetryLogBlock.cs
new file mode 100644
index 0000000000000..449ac620d04e0
--- /dev/null
+++ b/src/VisualStudio/Core/Def/Telemetry/TimedTelemetryLogBlock.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using Microsoft.CodeAnalysis.Internal.Log;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.Telemetry
+{
+    /// <summary>
+    /// Provides a mechanism to log telemetry information containing the execution time between
+    /// creation and disposal of this object.
+    /// </summary>
+    internal sealed class TimedTelemetryLogBlock : IDisposable
+    {
+#pragma warning disable IDE0052 // Remove unread private members - Not used in debug builds
+        private readonly string _name;
+        private readonly int _minThresholdMs;
+        private readonly ITelemetryLog _telemetryLog;
+        private readonly SharedStopwatch _stopwatch;
+#pragma warning restore IDE0052 // Remove unread private members
+
+        public TimedTelemetryLogBlock(string name, int minThresholdMs, ITelemetryLog telemetryLog)
+        {
+            _name = name;
+            _minThresholdMs = minThresholdMs;
+            _telemetryLog = telemetryLog;
+            _stopwatch = SharedStopwatch.StartNew();
+        }
+
+        public void Dispose()
+        {
+            // Don't add elapsed information in debug bits or while under debugger.
+#if !DEBUG
+            if (Debugger.IsAttached)
+                return;
+
+            var elapsed = (int)_stopwatch.Elapsed.TotalMilliseconds;
+            if (elapsed >= _minThresholdMs)
+            {
+                var logMessage = KeyValueLogMessage.Create(m =>
+                {
+                    m[TelemetryLogging.AggregatedKeyName] = _name;
+                    m[TelemetryLogging.AggregatedKeyValue] = elapsed;
+                });
+
+                _telemetryLog.Log(logMessage);
+            }
+#endif
+        }
+    }
+}
diff --git a/src/VisualStudio/Core/Def/Telemetry/VisualStudioTelemetryLog.cs b/src/VisualStudio/Core/Def/Telemetry/VisualStudioTelemetryLog.cs
new file mode 100644
index 0000000000000..406f2704e2572
--- /dev/null
+++ b/src/VisualStudio/Core/Def/Telemetry/VisualStudioTelemetryLog.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Microsoft.CodeAnalysis.Internal.Log;
+using Microsoft.CodeAnalysis.Telemetry;
+
+namespace Microsoft.VisualStudio.LanguageServices.Telemetry
+{
+    internal sealed class VisualStudioTelemetryLog : ITelemetryLog
+    {
+        private readonly ILogger _telemetryLogger;
+        private readonly FunctionId _functionId;
+
+        public VisualStudioTelemetryLog(ILogger telemetryLogger, FunctionId functionId)
+        {
+            _telemetryLogger = telemetryLogger;
+            _functionId = functionId;
+        }
+
+        public void Log(LogMessage logMessage)
+        {
+            _telemetryLogger.Log(_functionId, logMessage);
+        }
+
+        public IDisposable? LogBlockTime(string name, int minThresholdMs)
+        {
+            return new TimedTelemetryLogBlock(name, minThresholdMs, telemetryLog: this);
+        }
+    }
+}
diff --git a/src/VisualStudio/Core/Def/Telemetry/VisualStudioTelemetryLogManager.cs b/src/VisualStudio/Core/Def/Telemetry/VisualStudioTelemetryLogManager.cs
new file mode 100644
index 0000000000000..a52716fe50c11
--- /dev/null
+++ b/src/VisualStudio/Core/Def/Telemetry/VisualStudioTelemetryLogManager.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.Internal.Log;
+using Microsoft.CodeAnalysis.Telemetry;
+using Microsoft.VisualStudio.Telemetry;
+
+namespace Microsoft.VisualStudio.LanguageServices.Telemetry
+{
+    internal sealed class VisualStudioTelemetryLogManager
+    {
+        private readonly TelemetrySession _session;
+        private readonly ILogger _telemetryLogger;
+
+        private ImmutableDictionary<FunctionId, VisualStudioTelemetryLog> _logs = ImmutableDictionary<FunctionId, VisualStudioTelemetryLog>.Empty;
+
+        public VisualStudioTelemetryLogManager(TelemetrySession session, ILogger telemetryLogger)
+        {
+            _session = session;
+            _telemetryLogger = telemetryLogger;
+        }
+
+        public ITelemetryLog? GetLog(FunctionId functionId)
+        {
+            if (!_session.IsOptedIn)
+                return null;
+
+            return ImmutableInterlocked.GetOrAdd(ref _logs, functionId, functionId => new VisualStudioTelemetryLog(_telemetryLogger, functionId));
+        }
+    }
+}
diff --git a/src/VisualStudio/Core/Def/Telemetry/VisualStudioWorkspaceTelemetryService.cs b/src/VisualStudio/Core/Def/Telemetry/VisualStudioWorkspaceTelemetryService.cs
index c4a4c4a7b9410..bb3a0df7bae4e 100644
--- a/src/VisualStudio/Core/Def/Telemetry/VisualStudioWorkspaceTelemetryService.cs
+++ b/src/VisualStudio/Core/Def/Telemetry/VisualStudioWorkspaceTelemetryService.cs
@@ -5,7 +5,6 @@
 using System;
 using System.Composition;
 using System.Diagnostics;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -13,6 +12,7 @@
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Remote;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.VisualStudio.Telemetry;
 using Roslyn.Utilities;
@@ -24,22 +24,25 @@ internal sealed class VisualStudioWorkspaceTelemetryService : AbstractWorkspaceT
     {
         private readonly VisualStudioWorkspace _workspace;
         private readonly IGlobalOptionService _globalOptions;
+        private readonly IAsynchronousOperationListenerProvider _asyncListenerProvider;
 
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
         public VisualStudioWorkspaceTelemetryService(
             VisualStudioWorkspace workspace,
-            IGlobalOptionService globalOptions)
+            IGlobalOptionService globalOptions,
+            IAsynchronousOperationListenerProvider asyncListenerProvider)
         {
             _workspace = workspace;
             _globalOptions = globalOptions;
+            _asyncListenerProvider = asyncListenerProvider;
         }
 
         protected override ILogger CreateLogger(TelemetrySession telemetrySession, bool logDelta)
             => AggregateLogger.Create(
                 CodeMarkerLogger.Instance,
                 new EtwLogger(FunctionIdOptions.CreateFunctionIsEnabledPredicate(_globalOptions)),
-                TelemetryLogger.Create(telemetrySession, logDelta),
+                TelemetryLogger.Create(telemetrySession, logDelta, _asyncListenerProvider),
                 new FileLogger(_globalOptions),
                 Logger.GetLogger());
 
diff --git a/src/VisualStudio/Core/Def/Workspace/SourceGeneratedFileManager.cs b/src/VisualStudio/Core/Def/Workspace/SourceGeneratedFileManager.cs
index 008b4a3d202f4..8da8b8f1173f5 100644
--- a/src/VisualStudio/Core/Def/Workspace/SourceGeneratedFileManager.cs
+++ b/src/VisualStudio/Core/Def/Workspace/SourceGeneratedFileManager.cs
@@ -80,7 +80,7 @@ public SourceGeneratedFileManager(
             _threadingContext = threadingContext;
             _foregroundThreadAffinitizedObject = new ForegroundThreadAffinitizedObject(threadingContext, assertIsForeground: false);
             _textDocumentFactoryService = textDocumentFactoryService;
-            _temporaryDirectory = Path.Combine(Path.GetTempPath(), "VSGeneratedDocuments");
+            _temporaryDirectory = PathUtilities.EnsureTrailingSeparator(Path.Combine(Path.GetTempPath(), "VSGeneratedDocuments"));
             _visualStudioWorkspace = visualStudioWorkspace;
             _visualStudioDocumentNavigationService = visualStudioDocumentNavigationService;
 
@@ -108,7 +108,8 @@ public Func<CancellationToken, Task<bool>> GetNavigationCallback(SourceGenerated
             var temporaryFilePath = Path.Combine(
                 _temporaryDirectory,
                 document.Id.Id.ToString(),
-                document.HintName);
+                // Normalize hint name (it always contains forward slashes).
+                document.HintName.Replace('/', Path.DirectorySeparatorChar));
 
             Directory.CreateDirectory(Path.GetDirectoryName(temporaryFilePath));
 
@@ -149,13 +150,27 @@ public bool TryGetGeneratedFileInformation(
 
             identity = default;
 
+            // Find GUID in "temporary directory/GUID/path/to/file.cs".
             if (!filePath.StartsWith(_temporaryDirectory))
             {
                 return false;
             }
 
-            var fileInfo = new FileInfo(filePath);
-            return Guid.TryParse(fileInfo.Directory.Name, out var guid) &&
+            // Remove temporary directory prefix (note that it always has trailing separator).
+            var slice = filePath.AsSpan()[_temporaryDirectory.Length..];
+            if (slice.IsEmpty)
+            {
+                return false;
+            }
+
+            var separatorIndex = slice.IndexOf(Path.DirectorySeparatorChar);
+            if (separatorIndex < 0)
+            {
+                return false;
+            }
+
+            var guidDirName = slice[..separatorIndex];
+            return Guid.TryParse(guidDirName.ToString(), out var guid) &&
                 _directoryInfoOnDiskByContainingDirectoryId.TryGetValue(guid, out identity);
         }
 
diff --git a/src/VisualStudio/Core/Def/Workspace/VisualStudioWorkspaceStatusServiceFactory.cs b/src/VisualStudio/Core/Def/Workspace/VisualStudioWorkspaceStatusServiceFactory.cs
index fd17d3a85d7bf..dd3dc25f10076 100644
--- a/src/VisualStudio/Core/Def/Workspace/VisualStudioWorkspaceStatusServiceFactory.cs
+++ b/src/VisualStudio/Core/Def/Workspace/VisualStudioWorkspaceStatusServiceFactory.cs
@@ -145,7 +145,7 @@ public async Task WaitUntilFullyLoadedAsync(CancellationToken cancellationToken)
                     }
 
                     var completionTask = status.WaitForCompletionAsync();
-                    Logger.Log(FunctionId.PartialLoad_FullyLoaded, KeyValueLogMessage.Create(LogType.Trace, m => m["AlreadyFullyLoaded"] = completionTask.IsCompleted));
+                    Logger.Log(FunctionId.PartialLoad_FullyLoaded, KeyValueLogMessage.Create(LogType.Trace, m => m["AlreadyFullyLoaded"] = completionTask.IsCompleted, LogLevel.Debug));
 
                     // TODO: WaitForCompletionAsync should accept cancellation directly.
                     //       for now, use WithCancellation to indirectly add cancellation
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.cs.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.cs.xlf
index 73de65a705232..fb10a4f58e2d5 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.cs.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.cs.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Všechno sbalit</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Všechno sbalit</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Všechno sbalit</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Rozbalit vše</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Rozbalit vše</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Rozbalit vše</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Seřadit podle názvu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Seřadit podle názvu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Seřadit podle názvu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Seřadit podle pořadí</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Seřadit podle pořadí</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Seřadit podle pořadí</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Seřadit podle typu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Seřadit podle typu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Seřadit podle typu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Osnova dokumentu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.de.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.de.xlf
index 1b691d303d30a..8202da4b8d209 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.de.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.de.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Alle reduzieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Alle reduzieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Alle reduzieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Alle erweitern</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Alle erweitern</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Alle erweitern</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Nach Namen sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Nach Namen sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Nach Namen sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Nach Reihenfolge sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Nach Reihenfolge sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Nach Reihenfolge sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Nach Typ sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Nach Typ sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Nach Typ sortieren</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Dokumentgliederung</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.es.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.es.xlf
index 5e06357e6edde..545811cc8e1f4 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.es.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.es.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Contraer todo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Contraer todo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Contraer todo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Expandir todo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Expandir todo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Expandir todo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ordenar por nombre</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ordenar por nombre</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ordenar por nombre</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Ordenar por orden</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Ordenar por orden</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Ordenar por orden</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Ordenar por tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Ordenar por tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Ordenar por tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Esquema del documento</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.fr.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.fr.xlf
index 6f4ad425b3680..c89376f1e5b3f 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.fr.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.fr.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Tout réduire</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Tout réduire</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Tout réduire</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Développer tout</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Développer tout</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Développer tout</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Trier par nom</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Trier par nom</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Trier par nom</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Trier par ordre</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Trier par ordre</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Trier par ordre</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Trier par type</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Trier par type</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Trier par type</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Structure du document</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.it.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.it.xlf
index f375449879649..c41d686a9bafd 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.it.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.it.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Comprimi tutto</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Comprimi tutto</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Comprimi tutto</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Espandi tutto</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Espandi tutto</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Espandi tutto</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ordina per nome</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ordina per nome</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ordina per nome</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Ordina per ordine</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Ordina per ordine</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Ordina per ordine</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Ordina per tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Ordina per tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Ordina per tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Struttura documento</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.ja.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.ja.xlf
index 55efb45c0de4f..281517420df69 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.ja.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.ja.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">すべて折りたたむ</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">すべて折りたたむ</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">すべて折りたたむ</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">すべて展開</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">すべて展開</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">すべて展開</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">名前で並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">名前で並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">名前で並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">順番に並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">順番に並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">順番に並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">種類で並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">型で並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">型で並べ替え</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">ドキュメント アウトライン</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.ko.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.ko.xlf
index 3e79866cf4ce6..c3b6e6b1d3c8f 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.ko.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.ko.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">모두 접기</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">모두 축소</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">모두 접기</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">모두 펼치기</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">모두 펼치기</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">모두 확장</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">이름순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">이름순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">이름순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">순서순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">정렬 기준 순서</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">순서순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">형식순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">형식순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">형식순 정렬</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">문서 개요</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.pl.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.pl.xlf
index 60d7906e2dc31..5885186b46af0 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.pl.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.pl.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Zwiń wszystko</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Zwiń wszystko</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Zwiń wszystko</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Rozwiń wszystkie</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Rozwiń wszystkie</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Rozwiń wszystkie</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Sortuj według nazwy</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Sortuj według nazwy</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Sortuj według nazwy</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Sortuj według kolejności</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Sortuj według kolejności</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Sortuj według kolejności</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Sortuj według typu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Sortuj według typu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Sortuj według typu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Konspekt dokumentu</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.pt-BR.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.pt-BR.xlf
index e1e6a8f71d6f6..2f478a6918bbe 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.pt-BR.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.pt-BR.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Recolher Tudo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Recolher Tudo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Recolher Tudo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Expandir Tudo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Expandir Tudo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Expandir Tudo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Classificar Por Nome</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Classificar Por Nome</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Classificar Por Nome</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Classificar Por Ordem</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Classificar Por Ordem</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Classificar Por Ordem</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Classificar Por Tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Classificar Por Tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Classificar Por Tipo</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Estrutura de Tópicos do Documento</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.ru.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.ru.xlf
index a48596deae61f..b5cdee03ec545 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.ru.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.ru.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Свернуть все</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Свернуть все</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Свернуть все</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Развернуть все</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Развернуть все</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Развернуть все</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Сортировать по имени</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Сортировать по имени</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Сортировать по имени</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Сортировать по порядку</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Сортировать по порядку</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Сортировать по порядку</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Сортировать по типу</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Сортировать по типу</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Сортировать по типу</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Структура документа</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.tr.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.tr.xlf
index 27a1f3e5d7e0d..a9df5482c7eb6 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.tr.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.tr.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Tümünü Daralt</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Tümünü Daralt</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">Tümünü Daralt</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Tümünü Genişlet</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Tümünü Genişlet</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">Tümünü Genişlet</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ada Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ada Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">Ada Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Sıralamaya Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Sıralamaya Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">Sıralamaya Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Türe Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Türe Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">Türe Göre Sırala</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">Belge Ana Hattı</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hans.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hans.xlf
index 19c37c76b6fac..ba5b26cbbebbc 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hans.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hans.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">全部折叠</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">全部折叠</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">全部折叠</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">全部展开</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">全部展开</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">全部展开</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">按名称排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">按名称排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">按名称排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">按顺序排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">按顺序排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">按顺序排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">按类型排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">按类型排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">按类型排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">文档大纲</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hant.xlf b/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hant.xlf
index 46f628d787209..f00d585a07053 100644
--- a/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hant.xlf
+++ b/src/VisualStudio/Core/Def/xlf/Commands.vsct.zh-Hant.xlf
@@ -184,112 +184,112 @@
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ButtonText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">全部摺疊</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|LocCanonicalName">
         <source>DocumentOutlineCollapseAll</source>
-        <target state="new">DocumentOutlineCollapseAll</target>
+        <target state="translated">DocumentOutlineCollapseAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|MenuText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">全部摺疊</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineCollapseAll|ToolTipText">
         <source>Collapse All</source>
-        <target state="new">Collapse All</target>
+        <target state="translated">全部摺疊</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ButtonText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">全部展開</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|LocCanonicalName">
         <source>DocumentOutlineExpandAll</source>
-        <target state="new">DocumentOutlineExpandAll</target>
+        <target state="translated">DocumentOutlineExpandAll</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|MenuText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">全部展開</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineExpandAll|ToolTipText">
         <source>Expand All</source>
-        <target state="new">Expand All</target>
+        <target state="translated">全部展開</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ButtonText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">依名稱排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|LocCanonicalName">
         <source>DocumentOutlineSortByName</source>
-        <target state="new">DocumentOutlineSortByName</target>
+        <target state="translated">DocumentOutlineSortByName</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|MenuText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">依名稱排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByName|ToolTipText">
         <source>Sort By Name</source>
-        <target state="new">Sort By Name</target>
+        <target state="translated">依名稱排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ButtonText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">依順序排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|LocCanonicalName">
         <source>DocumentOutlineSortByOrder</source>
-        <target state="new">DocumentOutlineSortByOrder</target>
+        <target state="translated">DocumentOutlineSortByOrder</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|MenuText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">依順序排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByOrder|ToolTipText">
         <source>Sort By Order</source>
-        <target state="new">Sort By Order</target>
+        <target state="translated">依順序排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ButtonText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">依類型排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|LocCanonicalName">
         <source>DocumentOutlineSortByType</source>
-        <target state="new">DocumentOutlineSortByType</target>
+        <target state="translated">DocumentOutlineSortByType</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|MenuText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">依類型排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineSortByType|ToolTipText">
         <source>Sort By Type</source>
-        <target state="new">Sort By Type</target>
+        <target state="translated">依類型排序</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|ButtonText">
         <source>Document Outline</source>
-        <target state="new">Document Outline</target>
+        <target state="translated">文件大綱</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidDocumentOutlineToolbar|LocCanonicalName">
         <source>RoslynDocumentOutlineToolbar</source>
-        <target state="new">RoslynDocumentOutlineToolbar</target>
+        <target state="translated">RoslynDocumentOutlineToolbar</target>
         <note />
       </trans-unit>
       <trans-unit id="cmdidErrorListSetSeverityDefault|ButtonText">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf
index 01db9869f7f69..05bfb5b9a2b00 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.cs.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Upřednostňovat primární konstruktory</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Spustit analýzu kódu na nejnovějším rozhraní .NET (vyžaduje restartování)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf
index bf3471c48b31d..b56590a46ac44 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.de.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Primäre Konstruktoren bevorzugen</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Codeanalyse für die neueste .NET-Version ausführen (Neustart erforderlich)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf
index 4ac46b76d9017..48e367efc566a 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.es.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Preferir constructores principales</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Ejecutar análisis de código en la versión más reciente de .NET (requiere reiniciar)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf
index 1930037e325b9..2782c878086e4 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.fr.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Préférez les constructeurs primaires</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Exécutez l'analyse de code sur le dernier .NET (nécessite un redémarrage)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf
index 0552b6437f858..10f949f72ef59 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.it.xlf
@@ -254,7 +254,7 @@
       </trans-unit>
       <trans-unit id="Collapse_regions_on_file_open">
         <source>Collapse #regions on file open</source>
-        <target state="translated">Comprimi #regioni all'apertura del file</target>
+        <target state="translated">Comprimi #regions all'apertura del file</target>
         <note />
       </trans-unit>
       <trans-unit id="Collapse_sourcelink_embedded_decompiled_files_on_open">
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Preferisci costruttori primari</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Esegui Code Analysis nella versione più recente di .NET (richiede il riavvio)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf
index 660120c2cdcb1..6ec37159b0347 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ja.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">プライマリ コンストラクターを優先する</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">最新の .NET でコード分析を実行する (再起動が必要)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf
index 301e6330ff39e..e486e0d7b377d 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ko.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">기본 생성자 선호</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">최신 .NET에서 코드 분석 실행(다시 시작 필요)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf
index 88f902d576b47..28057a2fed885 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pl.xlf
@@ -254,7 +254,7 @@
       </trans-unit>
       <trans-unit id="Collapse_regions_on_file_open">
         <source>Collapse #regions on file open</source>
-        <target state="translated">Zwiń #regiony przy otwieraniu pliku</target>
+        <target state="translated">Zwiń #regions przy otwieraniu pliku</target>
         <note />
       </trans-unit>
       <trans-unit id="Collapse_sourcelink_embedded_decompiled_files_on_open">
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Preferuj konstruktory podstawowe</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Uruchamianie analizy kodu na najnowszej platformie .NET (wymaga ponownego uruchomienia)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf
index 1945880d36896..70b989cb85599 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.pt-BR.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Preferir construtores primários</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Executar análise de código no .NET mais recente (requer reinicialização)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf
index aee9640f833a2..04bcb979d221b 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.ru.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Предпочитать основные конструкторы</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">Выполнить анализ кода на последней версии .NET (требуется перезапуск)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf
index b81ebe3b9e628..e33c2afa6844c 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.tr.xlf
@@ -254,7 +254,7 @@
       </trans-unit>
       <trans-unit id="Collapse_regions_on_file_open">
         <source>Collapse #regions on file open</source>
-        <target state="translated">Dosya açılırken #bölgeleri daralt</target>
+        <target state="translated">Dosya #regions dosyayı daralt</target>
         <note />
       </trans-unit>
       <trans-unit id="Collapse_sourcelink_embedded_decompiled_files_on_open">
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">Birincil oluşturucuları tercih et</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">En son .NET'te kod analizi çalıştırın (yeniden başlatma gerektirir)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
@@ -2795,7 +2795,7 @@ Ek bilgiler: {1}</target>
       </trans-unit>
       <trans-unit id="Collapse_regions_when_collapsing_to_definitions">
         <source>Collapse #regions when collapsing to definitions</source>
-        <target state="translated">Tanımlara daraltırken #region öğelerini daralt</target>
+        <target state="translated">Tanımlara daraltırken #regions öğelerini daralt</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_null_propagation">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf
index e9a406e11056d..4cb4f247025b8 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hans.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">首选主构造函数</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">在最新 .NET 上运行代码分析(需要重启)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf
index 5bf8db450155f..38a738cba5bfc 100644
--- a/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf
+++ b/src/VisualStudio/Core/Def/xlf/ServicesVSResources.zh-Hant.xlf
@@ -1114,7 +1114,7 @@
       </trans-unit>
       <trans-unit id="Prefer_primary_constructors">
         <source>Prefer primary constructors</source>
-        <target state="new">Prefer primary constructors</target>
+        <target state="translated">偏好使用主要建構函式</target>
         <note />
       </trans-unit>
       <trans-unit id="Prefer_range_operator">
@@ -1289,7 +1289,7 @@
       </trans-unit>
       <trans-unit id="Run_code_analysis_on_latest_dotnet_requires_restart">
         <source>Run code analysis on latest .NET (requires restart)</source>
-        <target state="new">Run code analysis on latest .NET (requires restart)</target>
+        <target state="translated">針對最新的 .NET 執行程式碼分析 (需要重新啟動)</target>
         <note />
       </trans-unit>
       <trans-unit id="Running_code_analysis_for_0">
diff --git a/src/VisualStudio/Core/Impl/CodeModel/ProjectCodeModelFactory.cs b/src/VisualStudio/Core/Impl/CodeModel/ProjectCodeModelFactory.cs
index 994c9368495fd..52a934f5ee878 100644
--- a/src/VisualStudio/Core/Impl/CodeModel/ProjectCodeModelFactory.cs
+++ b/src/VisualStudio/Core/Impl/CodeModel/ProjectCodeModelFactory.cs
@@ -83,7 +83,7 @@ private async ValueTask ProcessNextDocumentBatchAsync(
             // have, we wait 50ms before continuing.  These constants are just what we defined from
             // legacy, and otherwise have no special meaning.
             const int MaxTimeSlice = 15;
-            var delayBetweenProcessing = TimeSpan.FromMilliseconds(50);
+            var delayBetweenProcessing = DelayTimeSpan.NearImmediate;
 
             Debug.Assert(!_threadingContext.JoinableTaskContext.IsOnMainThread, "The following context switch is not expected to cause runtime overhead.");
             await TaskScheduler.Default;
diff --git a/src/VisualStudio/Core/Test.Next/Remote/SnapshotSerializationTests.cs b/src/VisualStudio/Core/Test.Next/Remote/SnapshotSerializationTests.cs
index bb60c5addb4e1..89c12c55bf395 100644
--- a/src/VisualStudio/Core/Test.Next/Remote/SnapshotSerializationTests.cs
+++ b/src/VisualStudio/Core/Test.Next/Remote/SnapshotSerializationTests.cs
@@ -705,8 +705,8 @@ private static AnalyzerFileReference CreateShadowCopiedAnalyzerReference(TempRoo
 
         private class MissingAnalyzerLoader : AnalyzerAssemblyLoader
         {
-            protected override string PreparePathToLoad(string fullPath) =>
-                throw new FileNotFoundException(fullPath);
+            protected override string PreparePathToLoad(string fullPath)
+                => throw new FileNotFoundException(fullPath);
         }
 
         private class MissingMetadataReference : PortableExecutableReference
diff --git a/src/VisualStudio/Core/Test/Preview/PreviewChangesTests.vb b/src/VisualStudio/Core/Test/Preview/PreviewChangesTests.vb
index ea0f70bb7fda8..2063a2949d819 100644
--- a/src/VisualStudio/Core/Test/Preview/PreviewChangesTests.vb
+++ b/src/VisualStudio/Core/Test/Preview/PreviewChangesTests.vb
@@ -311,7 +311,7 @@ End Class
             End Using
         End Sub
 
-        Private Sub AssertTreeStructure(expectedItems As List(Of Tuple(Of String, Integer)), topLevelList As ChangeList)
+        Private Shared Sub AssertTreeStructure(expectedItems As List(Of Tuple(Of String, Integer)), topLevelList As ChangeList)
             Dim flatteningResult = New List(Of Tuple(Of String, Integer))()
             FlattenTree(topLevelList, flatteningResult, 0)
 
@@ -322,7 +322,7 @@ End Class
             Next
         End Sub
 
-        Private Sub FlattenTree(list As ChangeList, result As List(Of Tuple(Of String, Integer)), depth As Integer)
+        Private Shared Sub FlattenTree(list As ChangeList, result As List(Of Tuple(Of String, Integer)), depth As Integer)
             For Each change In list.Changes
                 Dim text As String = Nothing
                 change.GetText(Nothing, text)
@@ -336,7 +336,7 @@ End Class
 
         ' Check each of the most-nested children whose names appear in checkItems.
         ' Uncheck the rest
-        Private Sub SetCheckedChildren(checkedItems As List(Of String), topLevelList As ChangeList)
+        Private Shared Sub SetCheckedChildren(checkedItems As List(Of String), topLevelList As ChangeList)
             For Each change In topLevelList.Changes
                 Dim text As String = Nothing
                 change.GetText(Nothing, text)
diff --git a/src/VisualStudio/DevKit/Impl/.npmrc b/src/VisualStudio/DevKit/Impl/.npmrc
new file mode 100644
index 0000000000000..816fed5f83098
--- /dev/null
+++ b/src/VisualStudio/DevKit/Impl/.npmrc
@@ -0,0 +1,3 @@
+# This must be located directly next to the package.json for compliance.
+registry=https://pkgs.dev.azure.com/dnceng/internal/_packaging/dotnet-tools-internal/npm/registry/ 
+always-auth=true
\ No newline at end of file
diff --git a/src/VisualStudio/DevKit/Impl/EditAndContinue/ManagedHotReloadLanguageServiceBridge.cs b/src/VisualStudio/DevKit/Impl/EditAndContinue/ManagedHotReloadLanguageServiceBridge.cs
new file mode 100644
index 0000000000000..fe716761b9f7a
--- /dev/null
+++ b/src/VisualStudio/DevKit/Impl/EditAndContinue/ManagedHotReloadLanguageServiceBridge.cs
@@ -0,0 +1,69 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.ComponentModel.Composition;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.BrokeredServices;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Debugger.Contracts.HotReload;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using InternalContracts = Microsoft.CodeAnalysis.Contracts.EditAndContinue;
+
+namespace Microsoft.CodeAnalysis.EditAndContinue;
+
+[ExportBrokeredService(MonikerName, ServiceVersion, Audience = ServiceAudience.Local)]
+internal sealed partial class ManagedHotReloadLanguageServiceBridge : IManagedHotReloadLanguageService, IExportedBrokeredService
+{
+    private const string ServiceName = "ManagedHotReloadLanguageService";
+    private const string ServiceVersion = "0.1";
+    private const string MonikerName = BrokeredServiceDescriptors.LanguageServerComponentNamespace + "." + BrokeredServiceDescriptors.LanguageServerComponentName + "." + ServiceName;
+
+    public static readonly ServiceJsonRpcDescriptor ServiceDescriptor = BrokeredServiceDescriptors.CreateServerServiceDescriptor(ServiceName, new(ServiceVersion));
+    private readonly InternalContracts.IManagedHotReloadLanguageService _service;
+
+    static ManagedHotReloadLanguageServiceBridge()
+        => Debug.Assert(ServiceDescriptor.Moniker.Name == MonikerName);
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ManagedHotReloadLanguageServiceBridge(InternalContracts.IManagedHotReloadLanguageService service)
+        => _service = service;
+
+    ServiceRpcDescriptor IExportedBrokeredService.Descriptor
+        => ServiceDescriptor;
+
+    public Task InitializeAsync(CancellationToken cancellationToken)
+        => Task.CompletedTask;
+
+    public ValueTask StartSessionAsync(CancellationToken cancellationToken)
+        => _service.StartSessionAsync(cancellationToken);
+
+    public ValueTask EndSessionAsync(CancellationToken cancellationToken)
+        => _service.EndSessionAsync(cancellationToken);
+
+    public ValueTask EnterBreakStateAsync(CancellationToken cancellationToken)
+        => _service.EnterBreakStateAsync(cancellationToken);
+
+    public ValueTask ExitBreakStateAsync(CancellationToken cancellationToken)
+        => _service.ExitBreakStateAsync(cancellationToken);
+
+    public ValueTask OnCapabilitiesChangedAsync(CancellationToken cancellationToken)
+        => _service.OnCapabilitiesChangedAsync(cancellationToken);
+
+    public async ValueTask<ManagedHotReloadUpdates> GetUpdatesAsync(CancellationToken cancellationToken)
+        => (await _service.GetUpdatesAsync(cancellationToken).ConfigureAwait(false)).FromContract();
+
+    public ValueTask CommitUpdatesAsync(CancellationToken cancellationToken)
+        => _service.CommitUpdatesAsync(cancellationToken);
+
+    public ValueTask DiscardUpdatesAsync(CancellationToken cancellationToken)
+        => _service.DiscardUpdatesAsync(cancellationToken);
+
+    public ValueTask<bool> HasChangesAsync(string? sourceFilePath, CancellationToken cancellationToken)
+        => _service.HasChangesAsync(sourceFilePath, cancellationToken);
+}
diff --git a/src/VisualStudio/DevKit/Impl/Logging/VSCodeTelemetryLogger.cs b/src/VisualStudio/DevKit/Impl/Logging/VSCodeTelemetryLogger.cs
new file mode 100644
index 0000000000000..99a3ba5c79839
--- /dev/null
+++ b/src/VisualStudio/DevKit/Impl/Logging/VSCodeTelemetryLogger.cs
@@ -0,0 +1,194 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Diagnostics;
+using System.Text;
+using System.Threading;
+using Microsoft.CodeAnalysis.Contracts.Telemetry;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.VisualStudio.Telemetry;
+
+namespace Microsoft.CodeAnalysis.LanguageServer.Logging;
+
+[Export(typeof(ITelemetryReporter)), Shared]
+internal sealed class VSCodeTelemetryLogger : ITelemetryReporter
+{
+    private TelemetrySession? _telemetrySession;
+    private const string CollectorApiKey = "0c6ae279ed8443289764825290e4f9e2-1a736e7c-1324-4338-be46-fc2a58ae4d14-7255";
+    private static int _dumpsSubmitted = 0;
+
+    private static readonly ConcurrentDictionary<int, object> _pendingScopes = new(concurrencyLevel: 2, capacity: 10);
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public VSCodeTelemetryLogger()
+    {
+    }
+
+    public void InitializeSession(string telemetryLevel, string? sessionId, bool isDefaultSession)
+    {
+        Debug.Assert(_telemetrySession == null);
+
+        var sessionSettingsJson = CreateSessionSettingsJson(telemetryLevel, sessionId);
+        var session = new TelemetrySession($"{{{sessionSettingsJson}}}");
+
+        if (isDefaultSession)
+        {
+            TelemetryService.SetDefaultSession(session);
+        }
+
+        session.Start();
+        session.RegisterForReliabilityEvent();
+
+        _telemetrySession = session;
+    }
+
+    public void Log(string name, ImmutableDictionary<string, object?> properties)
+    {
+        Debug.Assert(_telemetrySession != null);
+
+        var telemetryEvent = new TelemetryEvent(name);
+        SetProperties(telemetryEvent, properties);
+        _telemetrySession.PostEvent(telemetryEvent);
+    }
+
+    public void LogBlockStart(string eventName, int kind, int blockId)
+    {
+        Debug.Assert(_telemetrySession != null);
+
+        _pendingScopes[blockId] = kind switch
+        {
+            0 => _telemetrySession.StartOperation(eventName), // LogType.Trace
+            1 => _telemetrySession.StartUserTask(eventName),  // LogType.UserAction
+            _ => new InvalidOperationException($"Unknown BlockStart kind: {kind}")
+        };
+    }
+
+    public void LogBlockEnd(int blockId, ImmutableDictionary<string, object?> properties, CancellationToken cancellationToken)
+    {
+        var found = _pendingScopes.TryRemove(blockId, out var scope);
+        Debug.Assert(found);
+
+        var endEvent = GetEndEvent(scope);
+        SetProperties(endEvent, properties);
+
+        var result = cancellationToken.IsCancellationRequested ? TelemetryResult.UserCancel : TelemetryResult.Success;
+
+        if (scope is TelemetryScope<OperationEvent> operation)
+            operation.End(result);
+        else if (scope is TelemetryScope<UserTaskEvent> userTask)
+            userTask.End(result);
+        else
+            throw new InvalidCastException($"Unexpected value for scope: {scope}");
+    }
+
+    public void ReportFault(string eventName, string description, int logLevel, bool forceDump, int processId, Exception exception)
+    {
+        Debug.Assert(_telemetrySession != null);
+
+        var faultEvent = new FaultEvent(
+            eventName: eventName,
+            description: description,
+            (FaultSeverity)logLevel,
+            exceptionObject: exception,
+            gatherEventDetails: faultUtility =>
+            {
+                if (forceDump)
+                {
+                    // Let's just send a maximum of three; number chosen arbitrarily
+                    if (Interlocked.Increment(ref _dumpsSubmitted) <= 3)
+                        faultUtility.AddProcessDump(processId);
+                }
+
+                if (faultUtility is FaultEvent { IsIncludedInWatsonSample: true })
+                {
+                    // if needed, add any extra logs here
+                }
+
+                // Returning "0" signals that, if sampled, we should send data to Watson. 
+                // Any other value will cancel the Watson report. We never want to trigger a process dump manually, 
+                // we'll let TargetedNotifications determine if a dump should be collected.
+                // See https://aka.ms/roslynnfwdocs for more details
+                return 0;
+            });
+
+        _telemetrySession.PostEvent(faultEvent);
+    }
+
+    public void Dispose()
+    {
+        _telemetrySession?.Dispose();
+        _telemetrySession = null;
+    }
+
+    private static string CreateSessionSettingsJson(string telemetryLevel, string? sessionId)
+    {
+        sessionId ??= Guid.NewGuid().ToString();
+
+        // Generate a new startTime for process to be consumed by Telemetry Settings
+        using var curProcess = Process.GetCurrentProcess();
+        var processStartTime = curProcess.StartTime.ToFileTimeUtc().ToString();
+
+        var sb = new StringBuilder();
+
+        var kvp = new Dictionary<string, string>
+        {
+            { "Id", StringToJsonValue(sessionId) },
+            { "HostName", StringToJsonValue("Default") },
+
+            // Insert Telemetry Level instead of Opt-Out status. The telemetry service handles
+            // validation of this value so there is no need to do so on this end. If it's invalid,
+            // it defaults to off.
+            { "TelemetryLevel", StringToJsonValue(telemetryLevel) },
+
+            // this sets the Telemetry Session Created by LSP Server to be the Root Initial session
+            // This means that the SessionID set here by "Id" will be the SessionID used by cloned session
+            // further down stream
+            { "IsInitialSession", "true" },
+            { "CollectorApiKey", StringToJsonValue(CollectorApiKey) },
+
+            // using 1010 to indicate VS Code and not to match it to devenv 1000
+            { "AppId", "1010" },
+            { "ProcessStartTime", processStartTime },
+        };
+
+        foreach (var keyValue in kvp)
+        {
+            sb.AppendFormat("\"{0}\":{1},", keyValue.Key, keyValue.Value);
+        }
+
+        return sb.ToString().TrimEnd(',');
+
+        static string StringToJsonValue(string? value)
+        {
+            if (value == null)
+            {
+                return "null";
+            }
+
+            return '"' + value + '"';
+        }
+    }
+
+    private static TelemetryEvent GetEndEvent(object? scope)
+        => scope switch
+        {
+            TelemetryScope<OperationEvent> operation => operation.EndEvent,
+            TelemetryScope<UserTaskEvent> userTask => userTask.EndEvent,
+            _ => throw new InvalidCastException($"Unexpected value for scope: {scope}")
+        };
+
+    private static void SetProperties(TelemetryEvent telemetryEvent, ImmutableDictionary<string, object?> properties)
+    {
+        foreach (var (name, value) in properties)
+        {
+            telemetryEvent.Properties.Add(name, value);
+        }
+    }
+}
diff --git a/src/VisualStudio/DevKit/Impl/Microsoft.VisualStudio.LanguageServices.DevKit.csproj b/src/VisualStudio/DevKit/Impl/Microsoft.VisualStudio.LanguageServices.DevKit.csproj
new file mode 100644
index 0000000000000..2788a1c7d4357
--- /dev/null
+++ b/src/VisualStudio/DevKit/Impl/Microsoft.VisualStudio.LanguageServices.DevKit.csproj
@@ -0,0 +1,105 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE file in the project root for more information. -->
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <IsPackable>true</IsPackable>
+    <PackageDescription>
+      .NET Compiler Platform ("Roslyn") Language Server Protocol internal.
+    </PackageDescription>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="..\..\..\Compilers\Core\Portable\Collections\ImmutableArrayExtensions.cs" Link="Utilities\ImmutableArrayExtensions.cs" />
+    <Compile Include="..\..\..\Compilers\Core\Portable\Collections\TemporaryArray`1.cs" Link="Utilities\TemporaryArray`1.cs" />
+    <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\NonCopyableAttribute.cs" Link="Utilities\NonCopyableAttribute.cs" />
+    <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\ExceptionUtilities.cs" Link="Utilities\ExceptionUtilities.cs" />
+    <Compile Include="..\..\..\Workspaces\SharedUtilitiesAndExtensions\Workspace\Core\Workspace\Mef\MefConstruction.cs" Link="Utilities\MefConstruction.cs" />
+    <Compile Include="..\..\..\EditorFeatures\Core\EditAndContinue\Contracts\ContractWrappers.cs" Link="EditAndContinue\ContractWrappers.cs" />
+    <Compile Include="..\..\..\EditorFeatures\Core\EditAndContinue\Contracts\ManagedHotReloadServiceImpl.cs" Link="EditAndContinue\ManagedHotReloadServiceImpl.cs" />
+    <Compile Include="..\..\..\Workspaces\Remote\Core\BrokeredServiceDescriptors.cs" Link="BrokeredServiceDescriptors.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- Can only reference internal Microsoft.CodeAnalysis.Contracts namespace (via Restricted IVT) or public APIs. -->
+    <ProjectReference Include="..\..\..\Features\LanguageServer\Microsoft.CodeAnalysis.LanguageServer\Microsoft.CodeAnalysis.LanguageServer.csproj" />
+
+    <!-- Can only reference internal Microsoft.CodeAnalysis.Contracts namespace (via Restricted IVT) or public APIs. -->
+    <ProjectReference Include="..\..\..\Features\Core\Portable\Microsoft.CodeAnalysis.Features.csproj" />
+
+    <!-- Hide workspaces behind extern alias to avoid ambiguities in linked files -->
+    <ProjectReference Include="..\..\..\Workspaces\Core\Portable\Microsoft.CodeAnalysis.Workspaces.csproj">
+      <Aliases>DoNotUse</Aliases>
+    </ProjectReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.VisualStudio.Internal.MicroBuild.NpmPack" PrivateAssets="all" Version="$(MicrosoftVisualStudioInternalMicroBuildNpmPackVersion)" Condition="'$(IsNpmPackable)' == 'true'" />
+    <PackageReference Include="System.Composition" Version="$(SystemCompositionVersion)" />
+    <PackageReference Include="Microsoft.ServiceHub.Framework" Version="$(MicrosoftServiceHubFrameworkVersion)" />
+
+    <!-- 
+    Runtime dependency is required to pack in npm. Do not remove GeneratePathProperty="True" as it defines PkgMicrosoft_VisualStudio_Telemetry 
+    -->
+    <PackageReference Include="Microsoft.VisualStudio.Telemetry" Version="$(MicrosoftVisualStudioTelemetryVersion)" GeneratePathProperty="True" />
+
+    <!--
+    Runtime dependency is required to pack in npm. Do not remove GeneratePathProperty="True" as it defines PkgMicrosoft_VisualStudio_RemoteControl
+    -->
+    <PackageReference Include="Microsoft.VisualStudio.RemoteControl" Version="$(MicrosoftVisualStudioRemoteControlVersion)" GeneratePathProperty="True" />
+
+    <!--
+    Runtime dependency is required to pack in npm. Do not remove GeneratePathProperty="True" as it defines PkgMicrosoft_VisualStudio_Utilities_Internal
+    -->
+    <PackageReference Include="Microsoft.VisualStudio.Utilities.Internal" Version="$(MicrosoftVisualStudioUtilitiesInternalVersion)" GeneratePathProperty="True" />
+
+    <!--
+    Runtime dependency is required to pack in npm. Do not remove GeneratePathProperty="True" as it defines PkgSystem_Configuration_ConfigurationManager
+    -->
+    <PackageReference Include="System.Configuration.ConfigurationManager" Version="$(SystemConfigurationConfigurationManagerVersion)" GeneratePathProperty="True" />
+
+    <!--
+    Runtime dependency is required to pack in npm. Do not remove GeneratePathProperty="True" as it defines PkgSystem_Configuration_ConfigurationManager
+    -->
+    <PackageReference Include="Microsoft.VisualStudio.Debugger.Contracts" Version="$(MicrosoftVisualStudioDebuggerContractsVersion)" GeneratePathProperty="True" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="Microsoft.VisualStudio.LanguageServices.DevKit.UnitTests" />
+  </ItemGroup>
+
+  <Import Project="..\..\..\Dependencies\Collections\Microsoft.CodeAnalysis.Collections.projitems" Label="Shared" />
+  <Import Project="..\..\..\Dependencies\PooledObjects\Microsoft.CodeAnalysis.PooledObjects.projitems" Label="Shared" />
+
+  <PropertyGroup>
+    <StageForNpmPackDependsOn>$(StageForNpmPackDependsOn);CollectNpmInputs</StageForNpmPackDependsOn>
+  </PropertyGroup>
+
+  <Target Name="GetBuildVersion">
+    <PropertyGroup>
+      <NpmPackageVersion>$(PackageVersion)</NpmPackageVersion>
+    </PropertyGroup>
+  </Target>
+
+  <Target Name="CollectNpmInputs" DependsOnTargets="Build" Returns="@(NpmContent)">
+    <Message Text="Package version is $(PackageVersion)" />
+    <Message Text="Version is $(Version)" />
+    <ItemGroup>
+      <NpmContent Include="$(PkgMicrosoft_VisualStudio_Telemetry)\lib\netstandard2.0\Microsoft.VisualStudio.Telemetry.dll" />
+      <NpmContent Include="$(PkgMicrosoft_VisualStudio_RemoteControl)\lib\netstandard2.0\Microsoft.VisualStudio.RemoteControl.dll" />
+      <NpmContent Include="$(PkgMicrosoft_VisualStudio_Utilities_Internal)\lib\netstandard2.0\Microsoft.VisualStudio.Utilities.Internal.dll" />
+      <NpmContent Include="$(PkgSystem_Configuration_ConfigurationManager)\lib\netstandard2.0\System.Configuration.ConfigurationManager.dll" />
+      <NpmContent Include="$(PkgMicrosoft_VisualStudio_Debugger_Contracts)\lib\netstandard2.0\Microsoft.VisualStudio.Debugger.Contracts.dll" />
+      <NpmContent Include="$(TargetPath)" />
+      <NpmContent Include="@(AppConfigWithTargetPath->'$(OutDir)%(TargetPath)')" />
+      <NpmContent Include="$(ProjectDepsFilePath)" />
+      <NpmContent Include="@(ReferenceCopyLocalPaths->'$(OutDir)%(DestinationSubDirectory)%(Filename)%(Extension)')" PackagePath="%(ReferenceCopyLocalPaths.DestinationSubDirectory)" Condition="'%(Extension)'!='.xml'" />
+      <NpmContent Include="@(None)" PackagePath="%(None.TargetPath)" Condition="'%(None.CopyToOutputDirectory)'=='PreserveNewest'" />
+    </ItemGroup>
+  </Target>
+  <ItemGroup>
+    <Content Include="package.json" />
+  </ItemGroup>
+</Project>
diff --git a/src/VisualStudio/DevKit/Impl/package.json b/src/VisualStudio/DevKit/Impl/package.json
new file mode 100644
index 0000000000000..cf3f56c469c13
--- /dev/null
+++ b/src/VisualStudio/DevKit/Impl/package.json
@@ -0,0 +1,4 @@
+{
+  "name": "@microsoft/visualstudio-languageservices-devkit",
+  "version": "0.0.1"
+}
\ No newline at end of file
diff --git a/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpReferenceHighlighting.cs b/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpReferenceHighlighting.cs
index f71a5113767b0..8e8d612b36e1b 100644
--- a/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpReferenceHighlighting.cs
+++ b/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpReferenceHighlighting.cs
@@ -126,14 +126,14 @@ private void Verify(string marker, IDictionary<string, ImmutableArray<TextSpan>>
 
             AssertEx.SetEqual(spans["definition"], VisualStudio.Editor.GetTagSpans(DefinitionHighlightTag.TagId), message: "Testing 'definition'\r\n");
 
-            if (spans.ContainsKey("reference"))
+            if (spans.TryGetValue("reference", out var referenceSpans))
             {
-                AssertEx.SetEqual(spans["reference"], VisualStudio.Editor.GetTagSpans(ReferenceHighlightTag.TagId), message: "Testing 'reference'\r\n");
+                AssertEx.SetEqual(referenceSpans, VisualStudio.Editor.GetTagSpans(ReferenceHighlightTag.TagId), message: "Testing 'reference'\r\n");
             }
 
-            if (spans.ContainsKey("writtenreference"))
+            if (spans.TryGetValue("writtenreference", out var writtenReferenceSpans))
             {
-                AssertEx.SetEqual(spans["writtenreference"], VisualStudio.Editor.GetTagSpans(WrittenReferenceHighlightTag.TagId), message: "Testing 'writtenreference'\r\n");
+                AssertEx.SetEqual(writtenReferenceSpans, VisualStudio.Editor.GetTagSpans(WrittenReferenceHighlightTag.TagId), message: "Testing 'writtenreference'\r\n");
             }
         }
 
diff --git a/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpCodeActions.cs b/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpCodeActions.cs
index 62a53b274babc..b1843152da8af 100644
--- a/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpCodeActions.cs
+++ b/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpCodeActions.cs
@@ -1458,5 +1458,39 @@ await TestServices.EditorVerifier.CodeActionAsync(
 
             AssertEx.EqualOrDiff(expectedText, await TestServices.Editor.GetTextAsync(HangMitigatingCancellationToken));
         }
+
+        [IdeFact, Trait(Traits.Feature, Traits.Features.CodeGeneration)]
+        public async Task TestRefactoringsAreSortedByPriority()
+        {
+            var codeFormat = @"
+#pragma warning disable IDE0060 // Remove unused parameter
+class C
+{ 
+    public C(int x1, int x2, int x3)
+    {
+    }
+};";
+            for (var i = 1; i <= 3; i++)
+            {
+                var code = codeFormat.Replace($"x{i}", $"$$x{i}");
+                await SetUpEditorAsync(code, HangMitigatingCancellationToken);
+
+                var expectedItems = new[]
+                {
+                    $"Create and assign property 'X{i}'",
+                    $"Create and assign field 'x{i}'",
+                    "Create and assign remaining as properties",
+                    "Create and assign remaining as fields",
+                    "Change signature...",
+                    "Wrap every parameter",
+                    "Align wrapped parameters",
+                    "Indent all parameters",
+                    "Indent wrapped parameters",
+                    "Unwrap and indent all parameters",
+                };
+
+                await TestServices.EditorVerifier.CodeActionsAsync(expectedItems, ensureExpectedItemsAreOrdered: true, cancellationToken: HangMitigatingCancellationToken);
+            }
+        }
     }
 }
diff --git a/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpSourceGenerators.cs b/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpSourceGenerators.cs
index d8d5430912df5..ba1e0ce3b48e4 100644
--- a/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpSourceGenerators.cs
+++ b/src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpSourceGenerators.cs
@@ -62,6 +62,22 @@ public static void Main()
             Assert.Equal(HelloWorldGenerator.GeneratedEnglishClassName, await TestServices.Editor.GetSelectedTextAsync(HangMitigatingCancellationToken));
         }
 
+        [IdeFact]
+        public async Task GoToDefinitionOpensGeneratedFile_InFolder()
+        {
+            await TestServices.Editor.SetTextAsync($$"""
+                class C
+                {
+                    void M({{HelloWorldGenerator.GeneratedFolderClassName}} x) { }
+                }
+                """, HangMitigatingCancellationToken);
+
+            await TestServices.Editor.PlaceCaretAsync(HelloWorldGenerator.GeneratedFolderClassName, charsOffset: 0, HangMitigatingCancellationToken);
+            await TestServices.Editor.GoToDefinitionAsync(HangMitigatingCancellationToken);
+            Assert.Equal($"{HelloWorldGenerator.GeneratedFolderName}/{HelloWorldGenerator.GeneratedFolderClassName}.cs {ServicesVSResources.generated_suffix}", await TestServices.Shell.GetActiveWindowCaptionAsync(HangMitigatingCancellationToken));
+            Assert.Equal(HelloWorldGenerator.GeneratedFolderClassName, await TestServices.Editor.GetSelectedTextAsync(HangMitigatingCancellationToken));
+        }
+
         [IdeTheory(Skip = "https://github.com/dotnet/roslyn/issues/64721")]
         [CombinatorialData]
         public async Task FindReferencesForFileWithDefinitionInSourceGeneratedFile(bool invokeFromSourceGeneratedFile)
@@ -154,7 +170,19 @@ public async Task InvokeNavigateToForGeneratedFile()
             await TestServices.Workarounds.WaitForNavigationAsync(HangMitigatingCancellationToken);
 
             Assert.Equal($"{HelloWorldGenerator.GeneratedEnglishClassName}.cs [generated]", await TestServices.Shell.GetActiveWindowCaptionAsync(HangMitigatingCancellationToken));
-            Assert.Equal("HelloWorld", await TestServices.Editor.GetSelectedTextAsync(HangMitigatingCancellationToken));
+            Assert.Equal(HelloWorldGenerator.GeneratedEnglishClassName, await TestServices.Editor.GetSelectedTextAsync(HangMitigatingCancellationToken));
+        }
+
+        [IdeFact]
+        public async Task InvokeNavigateToForGeneratedFile_InFolder()
+        {
+            await TestServices.Shell.ShowNavigateToDialogAsync(HangMitigatingCancellationToken);
+
+            await TestServices.Input.SendToNavigateToAsync(new InputKey[] { HelloWorldGenerator.GeneratedFolderClassName, VirtualKeyCode.RETURN }, HangMitigatingCancellationToken);
+            await TestServices.Workarounds.WaitForNavigationAsync(HangMitigatingCancellationToken);
+
+            Assert.Equal($"{HelloWorldGenerator.GeneratedFolderName}/{HelloWorldGenerator.GeneratedFolderClassName}.cs [generated]", await TestServices.Shell.GetActiveWindowCaptionAsync(HangMitigatingCancellationToken));
+            Assert.Equal(HelloWorldGenerator.GeneratedFolderClassName, await TestServices.Editor.GetSelectedTextAsync(HangMitigatingCancellationToken));
         }
     }
 }
diff --git a/src/VisualStudio/IntegrationTest/New.IntegrationTests/InProcess/EditorVerifierInProcess.cs b/src/VisualStudio/IntegrationTest/New.IntegrationTests/InProcess/EditorVerifierInProcess.cs
index a71c8f225550f..593c9dfcc5cb7 100644
--- a/src/VisualStudio/IntegrationTest/New.IntegrationTests/InProcess/EditorVerifierInProcess.cs
+++ b/src/VisualStudio/IntegrationTest/New.IntegrationTests/InProcess/EditorVerifierInProcess.cs
@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
@@ -272,16 +272,20 @@ await TestServices.Workspace.WaitForAllAsyncOperationsAsync(
                 Assert.Equal(expectedTag.tooltipText, actualTooltipText);
             }
 
-            static string CollectTextInRun(ContainerElement containerElement)
+            static string CollectTextInRun(ContainerElement? containerElement)
             {
                 var builder = new StringBuilder();
-                foreach (var element in containerElement.Elements)
+
+                if (containerElement is not null)
                 {
-                    if (element is ClassifiedTextElement classifiedTextElement)
+                    foreach (var element in containerElement.Elements)
                     {
-                        foreach (var run in classifiedTextElement.Runs)
+                        if (element is ClassifiedTextElement classifiedTextElement)
                         {
-                            builder.Append(run.Text);
+                            foreach (var run in classifiedTextElement.Runs)
+                            {
+                                builder.Append(run.Text);
+                            }
                         }
                     }
                 }
diff --git a/src/VisualStudio/IntegrationTest/New.IntegrationTests/Microsoft.VisualStudio.LanguageServices.New.IntegrationTests.csproj b/src/VisualStudio/IntegrationTest/New.IntegrationTests/Microsoft.VisualStudio.LanguageServices.New.IntegrationTests.csproj
index 43eb3d7562387..64fa338b5a8e2 100644
--- a/src/VisualStudio/IntegrationTest/New.IntegrationTests/Microsoft.VisualStudio.LanguageServices.New.IntegrationTests.csproj
+++ b/src/VisualStudio/IntegrationTest/New.IntegrationTests/Microsoft.VisualStudio.LanguageServices.New.IntegrationTests.csproj
@@ -61,7 +61,6 @@
     <PackageReference Include="Microsoft.VisualStudio.Imaging.Interop.14.0.DesignTime" Version="$(MicrosoftVisualStudioImagingInterop140DesignTimeVersion)" />
     <PackageReference Include="NuGet.SolutionRestoreManager.Interop" Version="$(NuGetSolutionRestoreManagerInteropVersion)" />
     <PackageReference Include="UIAComWrapper" Version="$(UIAComWrapperVersion)" />
-    <PackageReference Include="xunit.assert" Version="$(xunitassertVersion)" />
     <PackageReference Include="xunit.extensibility.core" Version="$(xunitextensibilitycoreVersion)" />
     <PackageReference Include="xunit.extensibility.execution" Version="$(xunitextensibilityexecutionVersion)" />
   </ItemGroup>
diff --git a/src/VisualStudio/IntegrationTest/TestUtilities/InProcess/TextViewWindow_InProc.cs b/src/VisualStudio/IntegrationTest/TestUtilities/InProcess/TextViewWindow_InProc.cs
index 8d65b69a06a63..fa0ff04d0cd5a 100644
--- a/src/VisualStudio/IntegrationTest/TestUtilities/InProcess/TextViewWindow_InProc.cs
+++ b/src/VisualStudio/IntegrationTest/TestUtilities/InProcess/TextViewWindow_InProc.cs
@@ -347,7 +347,7 @@ public string[] GetLightBulbActions()
             });
         }
 
-        private async Task<IEnumerable<ISuggestedAction>> GetLightBulbActionsAsync(ILightBulbBroker broker, IWpfTextView view)
+        private static async Task<IEnumerable<ISuggestedAction>> GetLightBulbActionsAsync(ILightBulbBroker broker, IWpfTextView view)
         {
             await JoinableTaskFactory.SwitchToMainThreadAsync();
 
@@ -389,7 +389,7 @@ public bool ApplyLightBulbAction(string actionName, FixAllScope? fixAllScope, bo
             return true;
         }
 
-        private Func<IWpfTextView, Task<bool>> GetLightBulbApplicationAction(string actionName, FixAllScope? fixAllScope, bool willBlockUntilComplete)
+        private static Func<IWpfTextView, Task<bool>> GetLightBulbApplicationAction(string actionName, FixAllScope? fixAllScope, bool willBlockUntilComplete)
         {
             return async view =>
             {
@@ -471,7 +471,7 @@ private Func<IWpfTextView, Task<bool>> GetLightBulbApplicationAction(string acti
             };
         }
 
-        private async Task<IEnumerable<ISuggestedAction>> SelectActionsAsync(IEnumerable<SuggestedActionSet> actionSets)
+        private static async Task<IEnumerable<ISuggestedAction>> SelectActionsAsync(IEnumerable<SuggestedActionSet> actionSets)
         {
             await JoinableTaskFactory.SwitchToMainThreadAsync();
 
diff --git a/src/VisualStudio/TestUtilities2/CodeModel/CodeModelTestHelpers.vb b/src/VisualStudio/TestUtilities2/CodeModel/CodeModelTestHelpers.vb
index 24e2dc092c1d3..36852491d393e 100644
--- a/src/VisualStudio/TestUtilities2/CodeModel/CodeModelTestHelpers.vb
+++ b/src/VisualStudio/TestUtilities2/CodeModel/CodeModelTestHelpers.vb
@@ -8,6 +8,7 @@ Imports System.Runtime.InteropServices
 Imports EnvDTE
 Imports Microsoft.CodeAnalysis
 Imports Microsoft.CodeAnalysis.Editor.Shared.Utilities
+Imports Microsoft.CodeAnalysis.Editor.UnitTests
 Imports Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
 Imports Microsoft.CodeAnalysis.Shared.TestHooks
 Imports Microsoft.CodeAnalysis.Test.Utilities
@@ -25,6 +26,8 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.CodeModel
 
         Public ReadOnly Composition As TestComposition = VisualStudioTestCompositions.LanguageServices.AddParts(
             GetType(MockServiceProvider),
+            GetType(StubVsServiceExporter(Of )),
+            GetType(StubVsServiceExporter(Of ,)),
             GetType(MockVisualStudioWorkspace),
             GetType(ProjectCodeModelFactory))
 
diff --git a/src/VisualStudio/TestUtilities2/MockServiceProvider.vb b/src/VisualStudio/TestUtilities2/MockServiceProvider.vb
index 45444d9342d49..ba0c4ce7e703c 100644
--- a/src/VisualStudio/TestUtilities2/MockServiceProvider.vb
+++ b/src/VisualStudio/TestUtilities2/MockServiceProvider.vb
@@ -3,24 +3,33 @@
 ' See the LICENSE file in the project root for more information.
 
 Imports System.ComponentModel.Composition
+Imports Microsoft.CodeAnalysis.Editor.UnitTests
 Imports Microsoft.CodeAnalysis.Host.Mef
+Imports Microsoft.Internal.VisualStudio.Shell.Interop
 Imports Microsoft.VisualStudio.ComponentModelHost
+Imports Microsoft.VisualStudio.Settings
+Imports Microsoft.VisualStudio.Settings.Internal
 Imports Microsoft.VisualStudio.Shell
 Imports Microsoft.VisualStudio.Shell.Interop
 Imports Moq
+Imports Roslyn.Utilities
 
 Namespace Microsoft.VisualStudio.LanguageServices.UnitTests
 
     <PartNotDiscoverable>
     <Export>
     <Export(GetType(SVsServiceProvider))>
+    <Export(GetType(SAsyncServiceProvider))>
     Friend Class MockServiceProvider
         Implements IServiceProvider
         Implements SVsServiceProvider ' The shell service provider actually implements this too for people using that type directly
         Implements IAsyncServiceProvider
+        Implements IAsyncServiceProvider2
 
         Private ReadOnly _exportProvider As Composition.ExportProvider
-        Private ReadOnly _fileChangeEx As MockVsFileChangeEx = New MockVsFileChangeEx
+        Private ReadOnly _fileChangeEx As New MockVsFileChangeEx
+        Private ReadOnly _localRegistry As New StubLocalRegistry
+        Private _settingsManager As ISettingsManager
 
         Public MockMonitorSelection As IVsMonitorSelection
 
@@ -52,13 +61,32 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests
                 Case GetType(SVsFileChangeEx)
                     Return _fileChangeEx
 
+                Case GetType(SLocalRegistry)
+                    Return _localRegistry
+
+                Case GetType(SVsSettingsPersistenceManager)
+                    If _settingsManager Is Nothing Then
+                        LoggerFactory.Reset()
+                        _settingsManager = SettingsManagerFactory.CreateInstance(New StubSettingsManagerHost())
+                    End If
+
+                    Return _settingsManager
+
                 Case Else
                     Throw New Exception($"{NameOf(MockServiceProvider)} does not implement {serviceType.FullName}.")
             End Select
         End Function
 
         Public Function GetServiceAsync(serviceType As Type) As Task(Of Object) Implements IAsyncServiceProvider.GetServiceAsync
-            Return System.Threading.Tasks.Task.FromResult(GetService(serviceType))
+            Return GetServiceAsync(serviceType, False)
+        End Function
+
+        Public Function GetServiceAsync(serviceType As Type, swallowExceptions As Boolean) As Task(Of Object) Implements IAsyncServiceProvider2.GetServiceAsync
+            Try
+                Return Task.FromResult(GetService(serviceType))
+            Catch ex As Exception When swallowExceptions
+                Return SpecializedTasks.Null(Of Object)()
+            End Try
         End Function
 
         Friend Function GetComponentModelMock() As IComponentModel
diff --git a/src/VisualStudio/TestUtilities2/ProjectSystemShim/Framework/TestEnvironment.vb b/src/VisualStudio/TestUtilities2/ProjectSystemShim/Framework/TestEnvironment.vb
index 2ea5a752e911c..fd973ec00660e 100644
--- a/src/VisualStudio/TestUtilities2/ProjectSystemShim/Framework/TestEnvironment.vb
+++ b/src/VisualStudio/TestUtilities2/ProjectSystemShim/Framework/TestEnvironment.vb
@@ -11,7 +11,6 @@ Imports Microsoft.CodeAnalysis
 Imports Microsoft.CodeAnalysis.Diagnostics
 Imports Microsoft.CodeAnalysis.Editor.Shared.Utilities
 Imports Microsoft.CodeAnalysis.Editor.UnitTests
-Imports Microsoft.CodeAnalysis.Editor.UnitTests.Diagnostics
 Imports Microsoft.CodeAnalysis.FindSymbols
 Imports Microsoft.CodeAnalysis.Host.Mef
 Imports Microsoft.CodeAnalysis.Shared.TestHooks
@@ -19,7 +18,6 @@ Imports Microsoft.CodeAnalysis.Test.Utilities
 Imports Microsoft.VisualStudio.Composition
 Imports Microsoft.VisualStudio.LanguageServices.Implementation
 Imports Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel
-Imports Microsoft.VisualStudio.LanguageServices.Implementation.Diagnostics
 Imports Microsoft.VisualStudio.LanguageServices.Implementation.Library.ObjectBrowser.Lists
 Imports Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem
 Imports Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem.CPS
@@ -27,7 +25,6 @@ Imports Microsoft.VisualStudio.LanguageServices.Implementation.ProjectSystem.Leg
 Imports Microsoft.VisualStudio.LanguageServices.Implementation.TaskList
 Imports Microsoft.VisualStudio.LanguageServices.UnitTests.CodeModel
 Imports Microsoft.VisualStudio.LanguageServices.UnitTests.Diagnostics
-Imports Microsoft.VisualStudio.Shell
 Imports Microsoft.VisualStudio.Shell.Interop
 
 Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Framework
@@ -60,6 +57,8 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim.Fr
                 GetType(VisualStudioProjectFactory),
                 GetType(MockVisualStudioDiagnosticAnalyzerProviderFactory),
                 GetType(MockServiceProvider),
+                GetType(StubVsServiceExporter(Of )),
+                GetType(StubVsServiceExporter(Of ,)),
                 GetType(SolutionEventsBatchScopeCreator),
                 GetType(ProjectCodeModelFactory),
                 GetType(CPSProjectFactory),
diff --git a/src/VisualStudio/VisualBasic/Impl/Help/VisualBasicHelpContextService.vb b/src/VisualStudio/VisualBasic/Impl/Help/VisualBasicHelpContextService.vb
index cd96771090e84..2e7baf5f435c4 100644
--- a/src/VisualStudio/VisualBasic/Impl/Help/VisualBasicHelpContextService.vb
+++ b/src/VisualStudio/VisualBasic/Impl/Help/VisualBasicHelpContextService.vb
@@ -87,7 +87,7 @@ Namespace Microsoft.VisualStudio.LanguageServices.VisualBasic.Help
             Return FormatSymbol(symbol, isContainingType:=False)
         End Function
 
-        Private Overloads Function FormatSymbol(symbol As ISymbol, isContainingType As Boolean) As String
+        Private Overloads Shared Function FormatSymbol(symbol As ISymbol, isContainingType As Boolean) As String
             Dim symbolType = symbol.GetSymbolType()
 
             If TypeOf symbolType Is IArrayTypeSymbol Then
diff --git a/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.ko.xlf b/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.ko.xlf
index 23993ee93cb1e..dd3ec505f7e48 100644
--- a/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.ko.xlf
+++ b/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.ko.xlf
@@ -44,7 +44,7 @@ JSON,
 JSON 문자열 색상 지정,
 잘못된 JSON 문자열 보고,
 감지 및 제공 JSON 문자열용 편집기 기능,
-파일 열기 시 #region 축소,
+파일 열기 시 #regions 축소,
 파일 열기 시 가져오기 축소,
 파일 열기 시 메타데이터 구현 축소,
 향상된 색상 사용, 편집기 색상 구성표, 상속 여백, 지시문 가져오기,</target>
diff --git a/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.pl.xlf b/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.pl.xlf
index db2e1b685ffd7..1018c8a1f8bf9 100644
--- a/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.pl.xlf
+++ b/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.pl.xlf
@@ -44,7 +44,7 @@ JSON,
 Kolorowanie ciągów JSON; 
 Zgłaszanie nieprawidłowych ciągów JSON;
 Wykrywanie i oferowanie funkcji edytowania dla ciągów JSON;
-Zwijanie #regionów przy otwieraniu pliku;
+Zwijanie #regions przy otwieraniu pliku;
 Zwijanie importów przy otwieraniu pliku;
 Zwijanie implementacji metadanych przy otwieraniu pliku;
 Używanie rozszerzonych kolorów; Schemat kolorów edytora;Margines dziedziczenia;Dyrektywy importu;</target>
diff --git a/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.tr.xlf b/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.tr.xlf
index 8bb1beee41b72..81e4a19a73a15 100644
--- a/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.tr.xlf
+++ b/src/VisualStudio/VisualBasic/Impl/xlf/VSPackage.tr.xlf
@@ -44,7 +44,7 @@ JSON;
 JSON dizelerini renklendir;
 Geçersiz JSON dizelerini bildir;
 JSON dizeleri için düzenleyici özelliklerini algıla ve öner;
-Dosya açılırken #bölgeleri daralt;
+Dosya açılırken #regions daralt;
 Dosya açılırken İçeri Aktarmaları daralt;
 Dosya açılırken meta veri uygulamalarını daralt;
 Gelişmiş renkleri kullan;Düzenleyici Renk Düzeni;Devralma Kenar Boşluğu;İçeri Aktarma Yönergeleri;</target>
diff --git a/src/Workspaces/CSharp/Portable/Rename/CSharpRenameRewriterLanguageService.cs b/src/Workspaces/CSharp/Portable/Rename/CSharpRenameRewriterLanguageService.cs
index e97548fddcafb..bb7a2c6927913 100644
--- a/src/Workspaces/CSharp/Portable/Rename/CSharpRenameRewriterLanguageService.cs
+++ b/src/Workspaces/CSharp/Portable/Rename/CSharpRenameRewriterLanguageService.cs
@@ -975,9 +975,9 @@ private static void AddSymbolSourceSpans(
                     // does not contain the text of it's name (e.g. the getter of "int X { get; }"
                     // does not contain the text "get_X" so conflicting renames to "get_X" will not
                     // have added the getter to reverseMappedLocations).
-                    if (location.IsInSource && reverseMappedLocations.ContainsKey(location))
+                    if (location.IsInSource && reverseMappedLocations.TryGetValue(location, out var conflictingLocation))
                     {
-                        conflicts.Add(reverseMappedLocations[location]);
+                        conflicts.Add(conflictingLocation);
                     }
                 }
             }
diff --git a/src/Workspaces/CSharp/Portable/Simplification/CSharpSimplificationService.Expander.cs b/src/Workspaces/CSharp/Portable/Simplification/CSharpSimplificationService.Expander.cs
index 7ff18d4e955fb..c4caf75b40b65 100644
--- a/src/Workspaces/CSharp/Portable/Simplification/CSharpSimplificationService.Expander.cs
+++ b/src/Workspaces/CSharp/Portable/Simplification/CSharpSimplificationService.Expander.cs
@@ -809,7 +809,7 @@ private static bool IsInvocationWithDynamicArguments(SimpleNameSyntax originalSi
                 return false;
             }
 
-            private bool IsTypeArgumentDefinedRecursive(ISymbol symbol, IList<ISymbol> typeArgumentSymbols, bool enterContainingSymbol)
+            private static bool IsTypeArgumentDefinedRecursive(ISymbol symbol, IList<ISymbol> typeArgumentSymbols, bool enterContainingSymbol)
             {
                 if (Equals(symbol, symbol.OriginalDefinition))
                 {
@@ -830,7 +830,7 @@ private bool IsTypeArgumentDefinedRecursive(ISymbol symbol, IList<ISymbol> typeA
                 return false;
             }
 
-            private void TypeArgumentsInAllContainingSymbol(ISymbol symbol, IList<ISymbol> typeArgumentSymbols, bool enterContainingSymbol, bool isRecursive)
+            private static void TypeArgumentsInAllContainingSymbol(ISymbol symbol, IList<ISymbol> typeArgumentSymbols, bool enterContainingSymbol, bool isRecursive)
             {
                 if (symbol == null || symbol.IsNamespace())
                 {
diff --git a/src/Workspaces/Core/MSBuild/MSBuild/Constants/PropertyNames.cs b/src/Workspaces/Core/MSBuild/MSBuild/Constants/PropertyNames.cs
index 2691c30f7e5e5..84fadee0836c9 100644
--- a/src/Workspaces/Core/MSBuild/MSBuild/Constants/PropertyNames.cs
+++ b/src/Workspaces/Core/MSBuild/MSBuild/Constants/PropertyNames.cs
@@ -60,6 +60,7 @@ internal static class PropertyNames
         public const string TargetCompactFramework = nameof(TargetCompactFramework);
         public const string TargetFramework = nameof(TargetFramework);
         public const string TargetFrameworks = nameof(TargetFrameworks);
+        public const string TargetFrameworkIdentifier = nameof(TargetFrameworkIdentifier);
         public const string TargetPath = nameof(TargetPath);
         public const string TargetRefPath = nameof(TargetRefPath);
         public const string TreatWarningsAsErrors = nameof(TreatWarningsAsErrors);
diff --git a/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFile.cs b/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFile.cs
index 62c2ac0ad3ad4..708e01d35a78e 100644
--- a/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFile.cs
+++ b/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFile.cs
@@ -146,6 +146,8 @@ private ProjectFileInfo CreateProjectFileInfo(MSB.Execution.ProjectInstance proj
                 targetFramework = null;
             }
 
+            var targetFrameworkIdentifier = project.ReadPropertyString(PropertyNames.TargetFrameworkIdentifier);
+
             var docs = project.GetDocuments()
                 .Where(IsNotTemporaryGeneratedFile)
                 .Select(MakeDocumentFileInfo)
@@ -167,6 +169,7 @@ private ProjectFileInfo CreateProjectFileInfo(MSB.Execution.ProjectInstance proj
                 intermediateOutputFilePath,
                 defaultNamespace,
                 targetFramework,
+                targetFrameworkIdentifier,
                 commandLineArgs,
                 docs,
                 additionalDocs,
diff --git a/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFileInfo.cs b/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFileInfo.cs
index 561322651a523..71128b114258b 100644
--- a/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFileInfo.cs
+++ b/src/Workspaces/Core/MSBuild/MSBuild/ProjectFile/ProjectFileInfo.cs
@@ -62,6 +62,12 @@ internal sealed class ProjectFileInfo
         /// </summary>
         public string? TargetFramework { get; }
 
+        /// <summary>
+        /// The target framework identifier of this project.
+        /// Used to determine if a project is targeting .net core.
+        /// </summary>
+        public string? TargetFrameworkIdentifier { get; }
+
         /// <summary>
         /// The command line args used to compile the project.
         /// </summary>
@@ -107,6 +113,7 @@ private ProjectFileInfo(
             string? intermediateOutputFilePath,
             string? defaultNamespace,
             string? targetFramework,
+            string? targetFrameworkIdentifier,
             ImmutableArray<string> commandLineArgs,
             ImmutableArray<DocumentFileInfo> documents,
             ImmutableArray<DocumentFileInfo> additionalDocuments,
@@ -124,6 +131,7 @@ private ProjectFileInfo(
             this.IntermediateOutputFilePath = intermediateOutputFilePath;
             this.DefaultNamespace = defaultNamespace;
             this.TargetFramework = targetFramework;
+            this.TargetFrameworkIdentifier = targetFrameworkIdentifier;
             this.CommandLineArgs = commandLineArgs;
             this.Documents = documents;
             this.AdditionalDocuments = additionalDocuments;
@@ -140,6 +148,7 @@ public static ProjectFileInfo Create(
             string? intermediateOutputFilePath,
             string? defaultNamespace,
             string? targetFramework,
+            string? targetFrameworkIdentifier,
             ImmutableArray<string> commandLineArgs,
             ImmutableArray<DocumentFileInfo> documents,
             ImmutableArray<DocumentFileInfo> additionalDocuments,
@@ -155,6 +164,7 @@ public static ProjectFileInfo Create(
                 intermediateOutputFilePath,
                 defaultNamespace,
                 targetFramework,
+                targetFrameworkIdentifier,
                 commandLineArgs,
                 documents,
                 additionalDocuments,
@@ -172,6 +182,7 @@ public static ProjectFileInfo CreateEmpty(string language, string? filePath, Dia
                 intermediateOutputFilePath: null,
                 defaultNamespace: null,
                 targetFramework: null,
+                targetFrameworkIdentifier: null,
                 commandLineArgs: ImmutableArray<string>.Empty,
                 documents: ImmutableArray<DocumentFileInfo>.Empty,
                 additionalDocuments: ImmutableArray<DocumentFileInfo>.Empty,
diff --git a/src/Workspaces/Core/MSBuild/Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj b/src/Workspaces/Core/MSBuild/Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj
index 075262492f489..7d0bdc9c66649 100644
--- a/src/Workspaces/Core/MSBuild/Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj
+++ b/src/Workspaces/Core/MSBuild/Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj
@@ -39,7 +39,7 @@
     <EmbeddedResource Update="WorkspaceMSBuildResources.resx" GenerateSource="true" />
   </ItemGroup>
   <ItemGroup>
-    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" Key="$(MicrosoftCodeAnalysisLanguageServerKey)" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.Workspaces.Test.Utilities" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.Workspaces.MSBuild.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.EditorFeatures2.UnitTests" />
diff --git a/src/Workspaces/Core/Portable/Classification/ClassifiedSpan.cs b/src/Workspaces/Core/Portable/Classification/ClassifiedSpan.cs
index c8a8334d73f1e..1414624c6c6a2 100644
--- a/src/Workspaces/Core/Portable/Classification/ClassifiedSpan.cs
+++ b/src/Workspaces/Core/Portable/Classification/ClassifiedSpan.cs
@@ -8,22 +8,16 @@
 
 namespace Microsoft.CodeAnalysis.Classification
 {
-    public readonly struct ClassifiedSpan : IEquatable<ClassifiedSpan>
+    public readonly struct ClassifiedSpan(TextSpan textSpan, string classificationType) : IEquatable<ClassifiedSpan>
     {
-        public string ClassificationType { get; }
-        public TextSpan TextSpan { get; }
+        public string ClassificationType { get; } = classificationType;
+        public TextSpan TextSpan { get; } = textSpan;
 
         public ClassifiedSpan(string classificationType, TextSpan textSpan)
             : this(textSpan, classificationType)
         {
         }
 
-        public ClassifiedSpan(TextSpan textSpan, string classificationType)
-        {
-            this.ClassificationType = classificationType;
-            this.TextSpan = textSpan;
-        }
-
         public override int GetHashCode()
             => Hash.Combine(this.ClassificationType, this.TextSpan.GetHashCode());
 
diff --git a/src/Workspaces/Core/Portable/Classification/ClassifiedText.cs b/src/Workspaces/Core/Portable/Classification/ClassifiedText.cs
index e8d7fae36d45f..223bae97bb010 100644
--- a/src/Workspaces/Core/Portable/Classification/ClassifiedText.cs
+++ b/src/Workspaces/Core/Portable/Classification/ClassifiedText.cs
@@ -4,15 +4,9 @@
 
 namespace Microsoft.CodeAnalysis.Classification
 {
-    internal readonly struct ClassifiedText
+    internal readonly struct ClassifiedText(string classificationType, string text)
     {
-        public string ClassificationType { get; }
-        public string Text { get; }
-
-        public ClassifiedText(string classificationType, string text)
-        {
-            ClassificationType = classificationType;
-            Text = text;
-        }
+        public string ClassificationType { get; } = classificationType;
+        public string Text { get; } = text;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Classification/IRemoteSemanticClassificationService.cs b/src/Workspaces/Core/Portable/Classification/IRemoteSemanticClassificationService.cs
index dfe68ee04cb18..68036b60b4036 100644
--- a/src/Workspaces/Core/Portable/Classification/IRemoteSemanticClassificationService.cs
+++ b/src/Workspaces/Core/Portable/Classification/IRemoteSemanticClassificationService.cs
@@ -46,19 +46,13 @@ ValueTask<SerializableClassifiedSpans> GetClassificationsAsync(
     /// second and third ints encode the span.
     /// </summary>
     [DataContract]
-    internal sealed class SerializableClassifiedSpans
+    internal sealed class SerializableClassifiedSpans(ImmutableArray<string> classificationTypes, ImmutableArray<int> classificationTriples)
     {
         [DataMember(Order = 0)]
-        public readonly ImmutableArray<string> ClassificationTypes;
+        public readonly ImmutableArray<string> ClassificationTypes = classificationTypes;
 
         [DataMember(Order = 1)]
-        public readonly ImmutableArray<int> ClassificationTriples;
-
-        public SerializableClassifiedSpans(ImmutableArray<string> classificationTypes, ImmutableArray<int> classificationTriples)
-        {
-            ClassificationTypes = classificationTypes;
-            ClassificationTriples = classificationTriples;
-        }
+        public readonly ImmutableArray<int> ClassificationTriples = classificationTriples;
 
         internal static SerializableClassifiedSpans Dehydrate(ImmutableArray<ClassifiedSpan> classifiedSpans)
         {
diff --git a/src/Workspaces/Core/Portable/CodeActions/CodeAction.cs b/src/Workspaces/Core/Portable/CodeActions/CodeAction.cs
index 1fc12b8c1ddac..d0adc66addb38 100644
--- a/src/Workspaces/Core/Portable/CodeActions/CodeAction.cs
+++ b/src/Workspaces/Core/Portable/CodeActions/CodeAction.cs
@@ -17,13 +17,14 @@
 using Microsoft.CodeAnalysis.Editing;
 using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.Options;
-using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Collections;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Utilities;
 using Microsoft.CodeAnalysis.Simplification;
 using Microsoft.CodeAnalysis.Tags;
+using Microsoft.CodeAnalysis.Telemetry;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CodeActions
@@ -169,6 +170,8 @@ public Task<ImmutableArray<CodeActionOperation>> GetPreviewOperationsAsync(Cance
         internal async Task<ImmutableArray<CodeActionOperation>> GetPreviewOperationsAsync(
             Solution originalSolution, CancellationToken cancellationToken)
         {
+            using var _ = TelemetryLogging.LogBlockTimeAggregated(FunctionId.SuggestedAction_Preview_Summary, $"Total");
+
             var operations = await this.ComputePreviewOperationsAsync(cancellationToken).ConfigureAwait(false);
 
             if (operations != null)
diff --git a/src/Workspaces/Core/Portable/CodeActions/Operations/ApplyChangesOperation.cs b/src/Workspaces/Core/Portable/CodeActions/Operations/ApplyChangesOperation.cs
index aa874245f361e..1c3b4a01bc908 100644
--- a/src/Workspaces/Core/Portable/CodeActions/Operations/ApplyChangesOperation.cs
+++ b/src/Workspaces/Core/Portable/CodeActions/Operations/ApplyChangesOperation.cs
@@ -34,12 +34,9 @@ namespace Microsoft.CodeAnalysis.CodeActions
     /// </list>
     /// </summary>
 #pragma warning restore RS0030 // Do not used banned APIs
-    public sealed class ApplyChangesOperation : CodeActionOperation
+    public sealed class ApplyChangesOperation(Solution changedSolution) : CodeActionOperation
     {
-        public Solution ChangedSolution { get; }
-
-        public ApplyChangesOperation(Solution changedSolution)
-            => ChangedSolution = changedSolution ?? throw new ArgumentNullException(nameof(changedSolution));
+        public Solution ChangedSolution { get; } = changedSolution ?? throw new ArgumentNullException(nameof(changedSolution));
 
         internal override bool ApplyDuringTests => true;
 
diff --git a/src/Workspaces/Core/Portable/CodeActions/Operations/OpenDocumentOperation.cs b/src/Workspaces/Core/Portable/CodeActions/Operations/OpenDocumentOperation.cs
index 0cfdebefe00d1..2f1813154ee5a 100644
--- a/src/Workspaces/Core/Portable/CodeActions/Operations/OpenDocumentOperation.cs
+++ b/src/Workspaces/Core/Portable/CodeActions/Operations/OpenDocumentOperation.cs
@@ -10,16 +10,9 @@ namespace Microsoft.CodeAnalysis.CodeActions
     /// <summary>
     /// A code action operation for requesting a document be opened in the host environment.
     /// </summary>
-    public sealed class OpenDocumentOperation : CodeActionOperation
+    public sealed class OpenDocumentOperation(DocumentId documentId, bool activateIfAlreadyOpen = false) : CodeActionOperation
     {
-        private readonly DocumentId _documentId;
-        private readonly bool _activate;
-
-        public OpenDocumentOperation(DocumentId documentId, bool activateIfAlreadyOpen = false)
-        {
-            _documentId = documentId ?? throw new ArgumentNullException(nameof(documentId));
-            _activate = activateIfAlreadyOpen;
-        }
+        private readonly DocumentId _documentId = documentId ?? throw new ArgumentNullException(nameof(documentId));
 
         public DocumentId DocumentId => _documentId;
 
@@ -27,7 +20,7 @@ public override void Apply(Workspace workspace, CancellationToken cancellationTo
         {
             if (workspace.CanOpenDocuments)
             {
-                workspace.OpenDocument(_documentId, _activate);
+                workspace.OpenDocument(_documentId, activateIfAlreadyOpen);
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/CodeCleanup/Providers/FormatCodeCleanupProvider.cs b/src/Workspaces/Core/Portable/CodeCleanup/Providers/FormatCodeCleanupProvider.cs
index 5648e03677d65..0460a0aac0826 100644
--- a/src/Workspaces/Core/Portable/CodeCleanup/Providers/FormatCodeCleanupProvider.cs
+++ b/src/Workspaces/Core/Portable/CodeCleanup/Providers/FormatCodeCleanupProvider.cs
@@ -14,22 +14,15 @@
 
 namespace Microsoft.CodeAnalysis.CodeCleanup.Providers
 {
-    internal sealed class FormatCodeCleanupProvider : ICodeCleanupProvider
+    internal sealed class FormatCodeCleanupProvider(IEnumerable<AbstractFormattingRule>? rules = null) : ICodeCleanupProvider
     {
-        private readonly IEnumerable<AbstractFormattingRule>? _rules;
-
-        public FormatCodeCleanupProvider(IEnumerable<AbstractFormattingRule>? rules = null)
-        {
-            _rules = rules;
-        }
-
         public string Name => PredefinedCodeCleanupProviderNames.Format;
 
         public async Task<Document> CleanupAsync(Document document, ImmutableArray<TextSpan> spans, CodeCleanupOptions options, CancellationToken cancellationToken)
         {
             var formatter = document.GetRequiredLanguageService<ISyntaxFormattingService>();
             var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
-            var result = formatter.GetFormattingResult(root, spans, options.FormattingOptions, _rules, cancellationToken);
+            var result = formatter.GetFormattingResult(root, spans, options.FormattingOptions, rules, cancellationToken);
 
             // apply changes to an old text if it already exists
             return document.TryGetText(out var oldText)
@@ -40,7 +33,7 @@ public async Task<Document> CleanupAsync(Document document, ImmutableArray<TextS
         public Task<SyntaxNode> CleanupAsync(SyntaxNode root, ImmutableArray<TextSpan> spans, SyntaxFormattingOptions options, SolutionServices services, CancellationToken cancellationToken)
         {
             var formatter = services.GetRequiredLanguageService<ISyntaxFormattingService>(root.Language);
-            var result = formatter.GetFormattingResult(root, spans, options, _rules, cancellationToken);
+            var result = formatter.GetFormattingResult(root, spans, options, rules, cancellationToken);
 
             // apply changes to an old text if it already exists
             return (root.SyntaxTree != null && root.SyntaxTree.TryGetText(out var oldText))
diff --git a/src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllProvider.cs b/src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllProvider.cs
index f947bd88320f1..7ed08d1337598 100644
--- a/src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllProvider.cs
+++ b/src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllProvider.cs
@@ -95,20 +95,12 @@ public static FixAllProvider Create(
             => this.GetFixAsync((FixAllContext)fixAllContext);
         #endregion
 
-        private class CallbackDocumentBasedFixAllProvider : DocumentBasedFixAllProvider
+        private class CallbackDocumentBasedFixAllProvider(
+            Func<FixAllContext, Document, ImmutableArray<Diagnostic>, Task<Document?>> fixAllAsync,
+            ImmutableArray<FixAllScope> supportedFixAllScopes) : DocumentBasedFixAllProvider(supportedFixAllScopes)
         {
-            private readonly Func<FixAllContext, Document, ImmutableArray<Diagnostic>, Task<Document?>> _fixAllAsync;
-
-            public CallbackDocumentBasedFixAllProvider(
-                Func<FixAllContext, Document, ImmutableArray<Diagnostic>, Task<Document?>> fixAllAsync,
-                ImmutableArray<FixAllScope> supportedFixAllScopes)
-                : base(supportedFixAllScopes)
-            {
-                _fixAllAsync = fixAllAsync;
-            }
-
             protected override Task<Document?> FixAllAsync(FixAllContext context, Document document, ImmutableArray<Diagnostic> diagnostics)
-                => _fixAllAsync(context, document, diagnostics);
+                => fixAllAsync(context, document, diagnostics);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/CodeFixesAndRefactorings/FixAllProviderInfo.cs b/src/Workspaces/Core/Portable/CodeFixesAndRefactorings/FixAllProviderInfo.cs
index 7c30b95ceb3df..7b8f147c8a0be 100644
--- a/src/Workspaces/Core/Portable/CodeFixesAndRefactorings/FixAllProviderInfo.cs
+++ b/src/Workspaces/Core/Portable/CodeFixesAndRefactorings/FixAllProviderInfo.cs
@@ -112,49 +112,30 @@ private FixAllProviderInfo(
 
         public abstract bool CanBeFixed(Diagnostic diagnostic);
 
-        private class CodeFixerFixAllProviderInfo : FixAllProviderInfo
+        private class CodeFixerFixAllProviderInfo(
+            IFixAllProvider fixAllProvider,
+            IEnumerable<string> supportedDiagnosticIds,
+            ImmutableArray<FixAllScope> supportedScopes) : FixAllProviderInfo(fixAllProvider, supportedScopes)
         {
-            private readonly IEnumerable<string> _supportedDiagnosticIds;
-
-            public CodeFixerFixAllProviderInfo(
-                IFixAllProvider fixAllProvider,
-                IEnumerable<string> supportedDiagnosticIds,
-                ImmutableArray<FixAllScope> supportedScopes)
-                : base(fixAllProvider, supportedScopes)
-            {
-                _supportedDiagnosticIds = supportedDiagnosticIds;
-            }
-
             public override bool CanBeFixed(Diagnostic diagnostic)
-                => _supportedDiagnosticIds.Contains(diagnostic.Id);
+                => supportedDiagnosticIds.Contains(diagnostic.Id);
         }
 
-        private class SuppressionFixerFixAllProviderInfo : FixAllProviderInfo
+        private class SuppressionFixerFixAllProviderInfo(
+            IFixAllProvider fixAllProvider,
+            IConfigurationFixProvider suppressionFixer,
+            ImmutableArray<FixAllScope> supportedScopes) : FixAllProviderInfo(fixAllProvider, supportedScopes)
         {
-            private readonly Func<Diagnostic, bool> _canBeSuppressedOrUnsuppressed;
-
-            public SuppressionFixerFixAllProviderInfo(
-                IFixAllProvider fixAllProvider,
-                IConfigurationFixProvider suppressionFixer,
-                ImmutableArray<FixAllScope> supportedScopes)
-                : base(fixAllProvider, supportedScopes)
-            {
-                _canBeSuppressedOrUnsuppressed = suppressionFixer.IsFixableDiagnostic;
-            }
+            private readonly Func<Diagnostic, bool> _canBeSuppressedOrUnsuppressed = suppressionFixer.IsFixableDiagnostic;
 
             public override bool CanBeFixed(Diagnostic diagnostic)
                 => _canBeSuppressedOrUnsuppressed(diagnostic);
         }
 
-        private class CodeRefactoringFixAllProviderInfo : FixAllProviderInfo
+        private class CodeRefactoringFixAllProviderInfo(
+            IFixAllProvider fixAllProvider,
+            ImmutableArray<FixAllScope> supportedScopes) : FixAllProviderInfo(fixAllProvider, supportedScopes)
         {
-            public CodeRefactoringFixAllProviderInfo(
-                IFixAllProvider fixAllProvider,
-                ImmutableArray<FixAllScope> supportedScopes)
-                : base(fixAllProvider, supportedScopes)
-            {
-            }
-
             public override bool CanBeFixed(Diagnostic diagnostic)
                 => throw ExceptionUtilities.Unreachable();
         }
diff --git a/src/Workspaces/Core/Portable/CodeRefactorings/FixAllOccurences/FixAllProvider.cs b/src/Workspaces/Core/Portable/CodeRefactorings/FixAllOccurences/FixAllProvider.cs
index 2bb4ff04afe87..e5630334ec0de 100644
--- a/src/Workspaces/Core/Portable/CodeRefactorings/FixAllOccurences/FixAllProvider.cs
+++ b/src/Workspaces/Core/Portable/CodeRefactorings/FixAllOccurences/FixAllProvider.cs
@@ -91,20 +91,12 @@ public static FixAllProvider Create(
             return new CallbackDocumentBasedFixAllProvider(fixAllAsync, supportedFixAllScopes);
         }
 
-        private sealed class CallbackDocumentBasedFixAllProvider : DocumentBasedFixAllProvider
+        private sealed class CallbackDocumentBasedFixAllProvider(
+            Func<FixAllContext, Document, Optional<ImmutableArray<TextSpan>>, Task<Document?>> fixAllAsync,
+            ImmutableArray<FixAllScope> supportedFixAllScopes) : DocumentBasedFixAllProvider(supportedFixAllScopes)
         {
-            private readonly Func<FixAllContext, Document, Optional<ImmutableArray<TextSpan>>, Task<Document?>> _fixAllAsync;
-
-            public CallbackDocumentBasedFixAllProvider(
-                Func<FixAllContext, Document, Optional<ImmutableArray<TextSpan>>, Task<Document?>> fixAllAsync,
-                ImmutableArray<FixAllScope> supportedFixAllScopes)
-                : base(supportedFixAllScopes)
-            {
-                _fixAllAsync = fixAllAsync;
-            }
-
             protected override Task<Document?> FixAllAsync(FixAllContext context, Document document, Optional<ImmutableArray<TextSpan>> fixAllSpans)
-                => _fixAllAsync(context, document, fixAllSpans);
+                => fixAllAsync(context, document, fixAllSpans);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalysisResultBuilder.cs b/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalysisResultBuilder.cs
index 542eda6177f74..b979722942bc7 100644
--- a/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalysisResultBuilder.cs
+++ b/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalysisResultBuilder.cs
@@ -17,30 +17,18 @@ namespace Microsoft.CodeAnalysis.Workspaces.Diagnostics
     /// We have this builder to avoid creating collections unnecessarily.
     /// Expectation is that, most of time, most of analyzers doesn't have any diagnostics. so no need to actually create any objects.
     /// </summary>
-    internal struct DiagnosticAnalysisResultBuilder
+    internal struct DiagnosticAnalysisResultBuilder(Project project, VersionStamp version)
     {
-        public readonly Project Project;
-        public readonly VersionStamp Version;
+        public readonly Project Project = project;
+        public readonly VersionStamp Version = version;
 
-        private HashSet<DocumentId>? _lazyDocumentsWithDiagnostics;
+        private HashSet<DocumentId>? _lazyDocumentsWithDiagnostics = null;
 
-        private Dictionary<DocumentId, List<DiagnosticData>>? _lazySyntaxLocals;
-        private Dictionary<DocumentId, List<DiagnosticData>>? _lazySemanticLocals;
-        private Dictionary<DocumentId, List<DiagnosticData>>? _lazyNonLocals;
+        private Dictionary<DocumentId, List<DiagnosticData>>? _lazySyntaxLocals = null;
+        private Dictionary<DocumentId, List<DiagnosticData>>? _lazySemanticLocals = null;
+        private Dictionary<DocumentId, List<DiagnosticData>>? _lazyNonLocals = null;
 
-        private List<DiagnosticData>? _lazyOthers;
-
-        public DiagnosticAnalysisResultBuilder(Project project, VersionStamp version)
-        {
-            Project = project;
-            Version = version;
-
-            _lazyDocumentsWithDiagnostics = null;
-            _lazySyntaxLocals = null;
-            _lazySemanticLocals = null;
-            _lazyNonLocals = null;
-            _lazyOthers = null;
-        }
+        private List<DiagnosticData>? _lazyOthers = null;
 
         public readonly ImmutableHashSet<DocumentId> DocumentIds => _lazyDocumentsWithDiagnostics == null ? ImmutableHashSet<DocumentId>.Empty : _lazyDocumentsWithDiagnostics.ToImmutableHashSet();
         public readonly ImmutableDictionary<DocumentId, ImmutableArray<DiagnosticData>> SyntaxLocals => Convert(_lazySyntaxLocals);
diff --git a/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalyzerInfoCache.cs b/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalyzerInfoCache.cs
index 8d425ae0f4aa5..750435e5c00bf 100644
--- a/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalyzerInfoCache.cs
+++ b/src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalyzerInfoCache.cs
@@ -44,18 +44,11 @@ internal sealed partial class DiagnosticAnalyzerInfoCache
         /// </summary>
         private readonly ConcurrentDictionary<string, DiagnosticDescriptor?> _idToDescriptorsMap;
 
-        private sealed class DiagnosticDescriptorsInfo
+        private sealed class DiagnosticDescriptorsInfo(ImmutableArray<DiagnosticDescriptor> supportedDescriptors, bool telemetryAllowed)
         {
-            public readonly ImmutableArray<DiagnosticDescriptor> SupportedDescriptors;
-            public readonly bool TelemetryAllowed;
-            public readonly bool HasCompilationEndDescriptor;
-
-            public DiagnosticDescriptorsInfo(ImmutableArray<DiagnosticDescriptor> supportedDescriptors, bool telemetryAllowed)
-            {
-                SupportedDescriptors = supportedDescriptors;
-                TelemetryAllowed = telemetryAllowed;
-                HasCompilationEndDescriptor = supportedDescriptors.Any(DiagnosticDescriptorExtensions.IsCompilationEnd);
-            }
+            public readonly ImmutableArray<DiagnosticDescriptor> SupportedDescriptors = supportedDescriptors;
+            public readonly bool TelemetryAllowed = telemetryAllowed;
+            public readonly bool HasCompilationEndDescriptor = supportedDescriptors.Any(DiagnosticDescriptorExtensions.IsCompilationEnd);
         }
 
         [Export, Shared]
diff --git a/src/Workspaces/Core/Portable/Diagnostics/DiagnosticData.cs b/src/Workspaces/Core/Portable/Diagnostics/DiagnosticData.cs
index 400f5a578188e..576cc8750fcf5 100644
--- a/src/Workspaces/Core/Portable/Diagnostics/DiagnosticData.cs
+++ b/src/Workspaces/Core/Portable/Diagnostics/DiagnosticData.cs
@@ -18,61 +18,78 @@
 namespace Microsoft.CodeAnalysis.Diagnostics
 {
     [DataContract]
-    internal sealed class DiagnosticData : IEquatable<DiagnosticData?>
+    internal sealed class DiagnosticData(
+        string id,
+        string category,
+        string? message,
+        DiagnosticSeverity severity,
+        DiagnosticSeverity defaultSeverity,
+        bool isEnabledByDefault,
+        int warningLevel,
+        ImmutableArray<string> customTags,
+        ImmutableDictionary<string, string?> properties,
+        ProjectId? projectId,
+        DiagnosticDataLocation location,
+        ImmutableArray<DiagnosticDataLocation> additionalLocations = default,
+        string? language = null,
+        string? title = null,
+        string? description = null,
+        string? helpLink = null,
+        bool isSuppressed = false) : IEquatable<DiagnosticData?>
     {
         [DataMember(Order = 0)]
-        public readonly string Id;
+        public readonly string Id = id;
 
         [DataMember(Order = 1)]
-        public readonly string Category;
+        public readonly string Category = category;
 
         [DataMember(Order = 2)]
-        public readonly string? Message;
+        public readonly string? Message = message;
 
         [DataMember(Order = 3)]
-        public readonly DiagnosticSeverity Severity;
+        public readonly DiagnosticSeverity Severity = severity;
 
         [DataMember(Order = 4)]
-        public readonly DiagnosticSeverity DefaultSeverity;
+        public readonly DiagnosticSeverity DefaultSeverity = defaultSeverity;
 
         [DataMember(Order = 5)]
-        public readonly bool IsEnabledByDefault;
+        public readonly bool IsEnabledByDefault = isEnabledByDefault;
 
         [DataMember(Order = 6)]
-        public readonly int WarningLevel;
+        public readonly int WarningLevel = warningLevel;
 
         [DataMember(Order = 7)]
-        public readonly ImmutableArray<string> CustomTags;
+        public readonly ImmutableArray<string> CustomTags = customTags;
 
         [DataMember(Order = 8)]
-        public readonly ImmutableDictionary<string, string?> Properties;
+        public readonly ImmutableDictionary<string, string?> Properties = properties;
 
         [DataMember(Order = 9)]
-        public readonly ProjectId? ProjectId;
+        public readonly ProjectId? ProjectId = projectId;
 
         [DataMember(Order = 10)]
-        public readonly DiagnosticDataLocation DataLocation;
+        public readonly DiagnosticDataLocation DataLocation = location;
 
         [DataMember(Order = 11)]
-        public readonly ImmutableArray<DiagnosticDataLocation> AdditionalLocations;
+        public readonly ImmutableArray<DiagnosticDataLocation> AdditionalLocations = additionalLocations.NullToEmpty();
 
         /// <summary>
         /// Language name (<see cref="LanguageNames"/>) or null if the diagnostic is not associated with source code.
         /// </summary>
         [DataMember(Order = 12)]
-        public readonly string? Language;
+        public readonly string? Language = language;
 
         [DataMember(Order = 13)]
-        public readonly string? Title;
+        public readonly string? Title = title;
 
         [DataMember(Order = 14)]
-        public readonly string? Description;
+        public readonly string? Description = description;
 
         [DataMember(Order = 15)]
-        public readonly string? HelpLink;
+        public readonly string? HelpLink = helpLink;
 
         [DataMember(Order = 16)]
-        public readonly bool IsSuppressed;
+        public readonly bool IsSuppressed = isSuppressed;
 
         /// <summary>
         /// Properties for a diagnostic generated by an explicit build.
@@ -80,47 +97,6 @@ internal sealed class DiagnosticData : IEquatable<DiagnosticData?>
         internal static ImmutableDictionary<string, string> PropertiesForBuildDiagnostic { get; }
             = ImmutableDictionary<string, string>.Empty.Add(WellKnownDiagnosticPropertyNames.Origin, WellKnownDiagnosticTags.Build);
 
-        public DiagnosticData(
-            string id,
-            string category,
-            string? message,
-            DiagnosticSeverity severity,
-            DiagnosticSeverity defaultSeverity,
-            bool isEnabledByDefault,
-            int warningLevel,
-            ImmutableArray<string> customTags,
-            ImmutableDictionary<string, string?> properties,
-            ProjectId? projectId,
-            DiagnosticDataLocation location,
-            ImmutableArray<DiagnosticDataLocation> additionalLocations = default,
-            string? language = null,
-            string? title = null,
-            string? description = null,
-            string? helpLink = null,
-            bool isSuppressed = false)
-        {
-            Id = id;
-            Category = category;
-            Message = message;
-
-            Severity = severity;
-            DefaultSeverity = defaultSeverity;
-            IsEnabledByDefault = isEnabledByDefault;
-            WarningLevel = warningLevel;
-            CustomTags = customTags;
-            Properties = properties;
-
-            ProjectId = projectId;
-            DataLocation = location;
-            AdditionalLocations = additionalLocations.NullToEmpty();
-
-            Language = language;
-            Title = title;
-            Description = description;
-            HelpLink = helpLink;
-            IsSuppressed = isSuppressed;
-        }
-
         public DiagnosticData WithLocations(DiagnosticDataLocation location, ImmutableArray<DiagnosticDataLocation> additionalLocations)
             => new(Id, Category, Message, Severity, DefaultSeverity, IsEnabledByDefault,
                 WarningLevel, CustomTags, Properties, ProjectId, location, additionalLocations,
diff --git a/src/Workspaces/Core/Portable/Diagnostics/Extensions.cs b/src/Workspaces/Core/Portable/Diagnostics/Extensions.cs
index f93de2a68ffe0..ca103c3c7418f 100644
--- a/src/Workspaces/Core/Portable/Diagnostics/Extensions.cs
+++ b/src/Workspaces/Core/Portable/Diagnostics/Extensions.cs
@@ -350,7 +350,7 @@ private static async Task<AnalysisResult> GetAnalysisResultAsync(
                     }
                     else
                     {
-                        return await compilationWithAnalyzers.GetAnalysisResultAsync(documentAnalysisScope.AdditionalFile, documentAnalysisScope.Analyzers, cancellationToken).ConfigureAwait(false);
+                        return await compilationWithAnalyzers.GetAnalysisResultAsync(documentAnalysisScope.AdditionalFile, documentAnalysisScope.Span, documentAnalysisScope.Analyzers, cancellationToken).ConfigureAwait(false);
                     }
 
                 case AnalysisKind.Semantic:
diff --git a/src/Workspaces/Core/Portable/Diagnostics/SerializableDiagnosticAnalysisResultMap.cs b/src/Workspaces/Core/Portable/Diagnostics/SerializableDiagnosticAnalysisResultMap.cs
index 905849d221f69..8ba5248e5cdb5 100644
--- a/src/Workspaces/Core/Portable/Diagnostics/SerializableDiagnosticAnalysisResultMap.cs
+++ b/src/Workspaces/Core/Portable/Diagnostics/SerializableDiagnosticAnalysisResultMap.cs
@@ -9,52 +9,38 @@
 namespace Microsoft.CodeAnalysis.Diagnostics
 {
     [DataContract]
-    internal readonly struct SerializableDiagnosticAnalysisResults
+    internal readonly struct SerializableDiagnosticAnalysisResults(
+        ImmutableArray<(string analyzerId, SerializableDiagnosticMap diagnosticMap)> diagnostics,
+        ImmutableArray<(string analyzerId, AnalyzerTelemetryInfo)> telemetry)
     {
         public static readonly SerializableDiagnosticAnalysisResults Empty = new(
             ImmutableArray<(string, SerializableDiagnosticMap)>.Empty,
             ImmutableArray<(string, AnalyzerTelemetryInfo)>.Empty);
 
         [DataMember(Order = 0)]
-        internal readonly ImmutableArray<(string analyzerId, SerializableDiagnosticMap diagnosticMap)> Diagnostics;
+        internal readonly ImmutableArray<(string analyzerId, SerializableDiagnosticMap diagnosticMap)> Diagnostics = diagnostics;
 
         [DataMember(Order = 1)]
-        internal readonly ImmutableArray<(string analyzerId, AnalyzerTelemetryInfo telemetry)> Telemetry;
-
-        public SerializableDiagnosticAnalysisResults(
-            ImmutableArray<(string analyzerId, SerializableDiagnosticMap diagnosticMap)> diagnostics,
-            ImmutableArray<(string analyzerId, AnalyzerTelemetryInfo)> telemetry)
-        {
-            Diagnostics = diagnostics;
-            Telemetry = telemetry;
-        }
+        internal readonly ImmutableArray<(string analyzerId, AnalyzerTelemetryInfo telemetry)> Telemetry = telemetry;
     }
 
     [DataContract]
-    internal readonly struct SerializableDiagnosticMap
+    internal readonly struct SerializableDiagnosticMap(
+        ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> syntax,
+        ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> semantic,
+        ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> nonLocal,
+        ImmutableArray<DiagnosticData> other)
     {
         [DataMember(Order = 0)]
-        public readonly ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> Syntax;
+        public readonly ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> Syntax = syntax;
 
         [DataMember(Order = 1)]
-        public readonly ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> Semantic;
+        public readonly ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> Semantic = semantic;
 
         [DataMember(Order = 2)]
-        public readonly ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> NonLocal;
+        public readonly ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> NonLocal = nonLocal;
 
         [DataMember(Order = 3)]
-        public readonly ImmutableArray<DiagnosticData> Other;
-
-        public SerializableDiagnosticMap(
-            ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> syntax,
-            ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> semantic,
-            ImmutableArray<(DocumentId, ImmutableArray<DiagnosticData>)> nonLocal,
-            ImmutableArray<DiagnosticData> other)
-        {
-            Syntax = syntax;
-            Semantic = semantic;
-            NonLocal = nonLocal;
-            Other = other;
-        }
+        public readonly ImmutableArray<DiagnosticData> Other = other;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Diagnostics/WorkspaceAnalyzerOptions.cs b/src/Workspaces/Core/Portable/Diagnostics/WorkspaceAnalyzerOptions.cs
index 24a115b519d03..0a0a8d96fbdfb 100644
--- a/src/Workspaces/Core/Portable/Diagnostics/WorkspaceAnalyzerOptions.cs
+++ b/src/Workspaces/Core/Portable/Diagnostics/WorkspaceAnalyzerOptions.cs
@@ -17,15 +17,9 @@ namespace Microsoft.CodeAnalysis.Diagnostics
     /// Analyzer options with workspace.
     /// These are used to fetch the workspace options by our internal analyzers (e.g. simplification analyzer).
     /// </summary>
-    internal sealed class WorkspaceAnalyzerOptions : AnalyzerOptions
+    internal sealed class WorkspaceAnalyzerOptions(AnalyzerOptions options, IdeAnalyzerOptions ideOptions) : AnalyzerOptions(options.AdditionalFiles, options.AnalyzerConfigOptionsProvider)
     {
-        public IdeAnalyzerOptions IdeOptions { get; }
-
-        public WorkspaceAnalyzerOptions(AnalyzerOptions options, IdeAnalyzerOptions ideOptions)
-            : base(options.AdditionalFiles, options.AnalyzerConfigOptionsProvider)
-        {
-            IdeOptions = ideOptions;
-        }
+        public IdeAnalyzerOptions IdeOptions { get; } = ideOptions;
 
         public override bool Equals(object obj)
         {
diff --git a/src/Workspaces/Core/Portable/Differencing/LongestCommonSubsequence.cs b/src/Workspaces/Core/Portable/Differencing/LongestCommonSubsequence.cs
index 98e2356df8b6d..5e68d431a99b5 100644
--- a/src/Workspaces/Core/Portable/Differencing/LongestCommonSubsequence.cs
+++ b/src/Workspaces/Core/Portable/Differencing/LongestCommonSubsequence.cs
@@ -190,18 +190,11 @@ public VArray Push()
         }
 
         // VArray struct enables array indexing in range [-d...d].
-        protected readonly struct VArray
+        protected readonly struct VArray(int[] buffer, int start, int length)
         {
-            private readonly int[] _buffer;
-            private readonly int _start;
-            private readonly int _length;
-
-            public VArray(int[] buffer, int start, int length)
-            {
-                _buffer = buffer;
-                _start = start;
-                _length = length;
-            }
+            private readonly int[] _buffer = buffer;
+            private readonly int _start = start;
+            private readonly int _length = length;
 
             public void InitializeFrom(VArray other)
             {
diff --git a/src/Workspaces/Core/Portable/Differencing/SequenceEdit.cs b/src/Workspaces/Core/Portable/Differencing/SequenceEdit.cs
index 86b365d04e06b..b1b473969c917 100644
--- a/src/Workspaces/Core/Portable/Differencing/SequenceEdit.cs
+++ b/src/Workspaces/Core/Portable/Differencing/SequenceEdit.cs
@@ -93,15 +93,10 @@ private string GetDebuggerDisplay()
         internal TestAccessor GetTestAccessor()
             => new(this);
 
-        internal readonly struct TestAccessor
+        internal readonly struct TestAccessor(SequenceEdit sequenceEdit)
         {
-            private readonly SequenceEdit _sequenceEdit;
-
-            public TestAccessor(SequenceEdit sequenceEdit)
-                => _sequenceEdit = sequenceEdit;
-
             internal string GetDebuggerDisplay()
-                => _sequenceEdit.GetDebuggerDisplay();
+                => sequenceEdit.GetDebuggerDisplay();
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Editing/SolutionEditor.cs b/src/Workspaces/Core/Portable/Editing/SolutionEditor.cs
index 7dc0732695bf0..e8f95c0cad5fa 100644
--- a/src/Workspaces/Core/Portable/Editing/SolutionEditor.cs
+++ b/src/Workspaces/Core/Portable/Editing/SolutionEditor.cs
@@ -13,20 +13,14 @@ namespace Microsoft.CodeAnalysis.Editing
     /// <summary>
     /// An editor for making changes to multiple documents in a solution.
     /// </summary>
-    public class SolutionEditor
+    public class SolutionEditor(Solution solution)
     {
-        private readonly Solution _solution;
         private readonly Dictionary<DocumentId, DocumentEditor> _documentEditors = new();
 
-        public SolutionEditor(Solution solution)
-        {
-            _solution = solution;
-        }
-
         /// <summary>
         /// The <see cref="Solution"/> that was specified when the <see cref="SolutionEditor"/> was constructed.
         /// </summary>
-        public Solution OriginalSolution => _solution;
+        public Solution OriginalSolution => solution;
 
         /// <summary>
         /// Gets the <see cref="DocumentEditor"/> for the corresponding <see cref="DocumentId"/>.
@@ -35,7 +29,7 @@ public async Task<DocumentEditor> GetDocumentEditorAsync(DocumentId id, Cancella
         {
             if (!_documentEditors.TryGetValue(id, out var editor))
             {
-                editor = await DocumentEditor.CreateAsync(_solution.GetDocument(id), cancellationToken).ConfigureAwait(false);
+                editor = await DocumentEditor.CreateAsync(solution.GetDocument(id), cancellationToken).ConfigureAwait(false);
                 _documentEditors.Add(id, editor);
             }
 
@@ -47,7 +41,7 @@ public async Task<DocumentEditor> GetDocumentEditorAsync(DocumentId id, Cancella
         /// </summary>
         public Solution GetChangedSolution()
         {
-            var changedSolution = _solution;
+            var changedSolution = solution;
 
             foreach (var docEd in _documentEditors.Values)
             {
diff --git a/src/Workspaces/Core/Portable/Editing/SyntaxEditor.cs b/src/Workspaces/Core/Portable/Editing/SyntaxEditor.cs
index 1fd3be19768c8..f4f3d92dda54e 100644
--- a/src/Workspaces/Core/Portable/Editing/SyntaxEditor.cs
+++ b/src/Workspaces/Core/Portable/Editing/SyntaxEditor.cs
@@ -244,12 +244,9 @@ private void CheckNodeInOriginalTree(SyntaxNode node)
             throw new ArgumentException(WorkspacesResources.The_node_is_not_part_of_the_tree, nameof(node));
         }
 
-        private abstract class Change
+        private abstract class Change(SyntaxNode node)
         {
-            internal readonly SyntaxNode OriginalNode;
-
-            public Change(SyntaxNode node)
-                => OriginalNode = node;
+            internal readonly SyntaxNode OriginalNode = node;
 
             public SyntaxNode Apply(SyntaxNode root, SyntaxGenerator generator)
             {
@@ -266,29 +263,16 @@ protected static SyntaxNode ValidateNewRoot(SyntaxNode? root)
             protected abstract SyntaxNode Apply(SyntaxNode root, SyntaxNode currentNode, SyntaxGenerator generator);
         }
 
-        private sealed class NoChange : Change
+        private sealed class NoChange(SyntaxNode node) : Change(node)
         {
-            public NoChange(SyntaxNode node)
-                : base(node)
-            {
-            }
-
             protected override SyntaxNode Apply(SyntaxNode root, SyntaxNode currentNode, SyntaxGenerator generator)
                 => root;
         }
 
-        private sealed class RemoveChange : Change
+        private sealed class RemoveChange(SyntaxNode node, SyntaxRemoveOptions options) : Change(node)
         {
-            private readonly SyntaxRemoveOptions _options;
-
-            public RemoveChange(SyntaxNode node, SyntaxRemoveOptions options)
-                : base(node)
-            {
-                _options = options;
-            }
-
             protected override SyntaxNode Apply(SyntaxNode root, SyntaxNode currentNode, SyntaxGenerator generator)
-                => ValidateNewRoot(generator.RemoveNode(root, currentNode, _options));
+                => ValidateNewRoot(generator.RemoveNode(root, currentNode, options));
         }
 
         private sealed class ReplaceChange : Change
@@ -308,55 +292,29 @@ protected override SyntaxNode Apply(SyntaxNode root, SyntaxNode currentNode, Syn
                 => ValidateNewRoot(generator.ReplaceNode(root, currentNode, _modifier(currentNode, generator)));
         }
 
-        private sealed class ReplaceWithCollectionChange : Change
+        private sealed class ReplaceWithCollectionChange(
+            SyntaxNode node,
+            Func<SyntaxNode, SyntaxGenerator, IEnumerable<SyntaxNode>> modifier) : Change(node)
         {
-            private readonly Func<SyntaxNode, SyntaxGenerator, IEnumerable<SyntaxNode>> _modifier;
-
-            public ReplaceWithCollectionChange(
-                SyntaxNode node,
-                Func<SyntaxNode, SyntaxGenerator, IEnumerable<SyntaxNode>> modifier)
-                : base(node)
-            {
-                _modifier = modifier;
-            }
-
             protected override SyntaxNode Apply(SyntaxNode root, SyntaxNode currentNode, SyntaxGenerator generator)
-                => SyntaxGenerator.ReplaceNode(root, currentNode, _modifier(currentNode, generator));
+                => SyntaxGenerator.ReplaceNode(root, currentNode, modifier(currentNode, generator));
         }
 
-        private sealed class ReplaceChange<TArgument> : Change
+        private sealed class ReplaceChange<TArgument>(
+            SyntaxNode node,
+            Func<SyntaxNode, SyntaxGenerator, TArgument, SyntaxNode> modifier,
+            TArgument argument) : Change(node)
         {
-            private readonly Func<SyntaxNode, SyntaxGenerator, TArgument, SyntaxNode> _modifier;
-            private readonly TArgument _argument;
-
-            public ReplaceChange(
-                SyntaxNode node,
-                Func<SyntaxNode, SyntaxGenerator, TArgument, SyntaxNode> modifier,
-                TArgument argument)
-                : base(node)
-            {
-                _modifier = modifier;
-                _argument = argument;
-            }
-
             protected override SyntaxNode Apply(SyntaxNode root, SyntaxNode currentNode, SyntaxGenerator generator)
-                => ValidateNewRoot(generator.ReplaceNode(root, currentNode, _modifier(currentNode, generator, _argument)));
+                => ValidateNewRoot(generator.ReplaceNode(root, currentNode, modifier(currentNode, generator, argument)));
         }
 
-        private sealed class InsertChange : Change
+        private sealed class InsertChange(SyntaxNode node, IEnumerable<SyntaxNode> newNodes, bool isBefore) : Change(node)
         {
-            private readonly List<SyntaxNode> _newNodes;
-            private readonly bool _isBefore;
-
-            public InsertChange(SyntaxNode node, IEnumerable<SyntaxNode> newNodes, bool isBefore)
-                : base(node)
-            {
-                _newNodes = newNodes.ToList();
-                _isBefore = isBefore;
-            }
+            private readonly List<SyntaxNode> _newNodes = newNodes.ToList();
 
             protected override SyntaxNode Apply(SyntaxNode root, SyntaxNode currentNode, SyntaxGenerator generator)
-                => _isBefore
+                => isBefore
                     ? generator.InsertNodesBefore(root, currentNode, _newNodes)
                     : generator.InsertNodesAfter(root, currentNode, _newNodes);
         }
diff --git a/src/Workspaces/Core/Portable/ExternalAccess/Pythia/Api/PythiaEditDistanceWrapper.cs b/src/Workspaces/Core/Portable/ExternalAccess/Pythia/Api/PythiaEditDistanceWrapper.cs
index 115ae824a636d..04bb4d3f65b30 100644
--- a/src/Workspaces/Core/Portable/ExternalAccess/Pythia/Api/PythiaEditDistanceWrapper.cs
+++ b/src/Workspaces/Core/Portable/ExternalAccess/Pythia/Api/PythiaEditDistanceWrapper.cs
@@ -7,12 +7,9 @@
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.Pythia.Api
 {
-    internal readonly struct PythiaEditDistanceWrapper : IDisposable
+    internal readonly struct PythiaEditDistanceWrapper(string str) : IDisposable
     {
-        private readonly EditDistance _underlyingObject;
-
-        public PythiaEditDistanceWrapper(string str)
-            => _underlyingObject = new EditDistance(str);
+        private readonly EditDistance _underlyingObject = new EditDistance(str);
 
         public double GetEditDistance(string target)
             => _underlyingObject.GetEditDistance(target);
diff --git a/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingChecksumWrapper.cs b/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingChecksumWrapper.cs
index ffe61c0583912..8f34e08a577e7 100644
--- a/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingChecksumWrapper.cs
+++ b/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingChecksumWrapper.cs
@@ -6,12 +6,9 @@
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.UnitTesting.Api
 {
-    internal readonly struct UnitTestingChecksumWrapper
+    internal readonly struct UnitTestingChecksumWrapper(Checksum underlyingObject)
     {
-        private Checksum UnderlyingObject { get; }
-
-        public UnitTestingChecksumWrapper(Checksum underlyingObject)
-            => UnderlyingObject = underlyingObject ?? throw new ArgumentNullException(nameof(underlyingObject));
+        private Checksum UnderlyingObject { get; } = underlyingObject ?? throw new ArgumentNullException(nameof(underlyingObject));
 
         public bool IsEqualTo(UnitTestingChecksumWrapper other)
             => other.UnderlyingObject == UnderlyingObject;
diff --git a/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingTextDocumentEventArgsWrapper.cs b/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingTextDocumentEventArgsWrapper.cs
index deb86da6ad60c..563ffbf85544e 100644
--- a/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingTextDocumentEventArgsWrapper.cs
+++ b/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingTextDocumentEventArgsWrapper.cs
@@ -7,13 +7,10 @@
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.UnitTesting.Api
 {
-    internal readonly struct UnitTestingTextDocumentEventArgsWrapper
+    internal readonly struct UnitTestingTextDocumentEventArgsWrapper(TextDocumentEventArgs underlyingObject)
     {
-        internal TextDocumentEventArgs UnderlyingObject { get; }
+        internal TextDocumentEventArgs UnderlyingObject { get; } = underlyingObject ?? throw new ArgumentNullException(nameof(underlyingObject));
 
         public TextDocument Document => UnderlyingObject.Document;
-
-        public UnitTestingTextDocumentEventArgsWrapper(TextDocumentEventArgs underlyingObject)
-            => UnderlyingObject = underlyingObject ?? throw new ArgumentNullException(nameof(underlyingObject));
     }
 }
diff --git a/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/UnitTestingIncrementalAnalyzer.cs b/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/UnitTestingIncrementalAnalyzer.cs
index 073d2adfb1554..554e4e40bfaf7 100644
--- a/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/UnitTestingIncrementalAnalyzer.cs
+++ b/src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/UnitTestingIncrementalAnalyzer.cs
@@ -12,46 +12,41 @@
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.UnitTesting
 {
-    internal class UnitTestingIncrementalAnalyzer : IIncrementalAnalyzer
+    internal class UnitTestingIncrementalAnalyzer(IUnitTestingIncrementalAnalyzerImplementation implementation) : IIncrementalAnalyzer
     {
-        private readonly IUnitTestingIncrementalAnalyzerImplementation _implementation;
-
-        public UnitTestingIncrementalAnalyzer(IUnitTestingIncrementalAnalyzerImplementation implementation)
-            => _implementation = implementation;
-
         public Task AnalyzeDocumentAsync(Document document, SyntaxNode bodyOpt, InvocationReasons reasons, CancellationToken cancellationToken)
-            => _implementation.AnalyzeDocumentAsync(document, bodyOpt, new UnitTestingInvocationReasonsWrapper(reasons), cancellationToken);
+            => implementation.AnalyzeDocumentAsync(document, bodyOpt, new UnitTestingInvocationReasonsWrapper(reasons), cancellationToken);
 
         public Task AnalyzeProjectAsync(Project project, bool semanticsChanged, InvocationReasons reasons, CancellationToken cancellationToken)
-            => _implementation.AnalyzeProjectAsync(project, semanticsChanged, new UnitTestingInvocationReasonsWrapper(reasons), cancellationToken);
+            => implementation.AnalyzeProjectAsync(project, semanticsChanged, new UnitTestingInvocationReasonsWrapper(reasons), cancellationToken);
 
         public Task AnalyzeSyntaxAsync(Document document, InvocationReasons reasons, CancellationToken cancellationToken)
-            => _implementation.AnalyzeSyntaxAsync(document, new UnitTestingInvocationReasonsWrapper(reasons), cancellationToken);
+            => implementation.AnalyzeSyntaxAsync(document, new UnitTestingInvocationReasonsWrapper(reasons), cancellationToken);
 
         public Task DocumentCloseAsync(Document document, CancellationToken cancellationToken)
-            => _implementation.DocumentCloseAsync(document, cancellationToken);
+            => implementation.DocumentCloseAsync(document, cancellationToken);
 
         public Task DocumentOpenAsync(Document document, CancellationToken cancellationToken)
-            => _implementation.DocumentOpenAsync(document, cancellationToken);
+            => implementation.DocumentOpenAsync(document, cancellationToken);
 
         public Task DocumentResetAsync(Document document, CancellationToken cancellationToken)
-            => _implementation.DocumentResetAsync(document, cancellationToken);
+            => implementation.DocumentResetAsync(document, cancellationToken);
 
         public Task ActiveDocumentSwitchedAsync(TextDocument document, CancellationToken cancellationToken)
             => Task.CompletedTask;
 
         public Task NewSolutionSnapshotAsync(Solution solution, CancellationToken cancellationToken)
-            => _implementation.NewSolutionSnapshotAsync(solution, cancellationToken);
+            => implementation.NewSolutionSnapshotAsync(solution, cancellationToken);
 
         public Task RemoveDocumentAsync(DocumentId documentId, CancellationToken cancellationToken)
         {
-            _implementation.RemoveDocument(documentId);
+            implementation.RemoveDocument(documentId);
             return Task.CompletedTask;
         }
 
         public Task RemoveProjectAsync(ProjectId projectId, CancellationToken cancellationToken)
         {
-            _implementation.RemoveProject(projectId);
+            implementation.RemoveProject(projectId);
             return Task.CompletedTask;
         }
 
diff --git a/src/Workspaces/Core/Portable/ExternalAccess/VSTypeScript/Api/VSTypeScriptDocumentationCommentWrapper.cs b/src/Workspaces/Core/Portable/ExternalAccess/VSTypeScript/Api/VSTypeScriptDocumentationCommentWrapper.cs
index 3fafdaa40f90f..3cb5f12022e0c 100644
--- a/src/Workspaces/Core/Portable/ExternalAccess/VSTypeScript/Api/VSTypeScriptDocumentationCommentWrapper.cs
+++ b/src/Workspaces/Core/Portable/ExternalAccess/VSTypeScript/Api/VSTypeScriptDocumentationCommentWrapper.cs
@@ -6,24 +6,19 @@
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.VSTypeScript.Api
 {
-    internal readonly struct VSTypeScriptDocumentationCommentWrapper
+    internal readonly struct VSTypeScriptDocumentationCommentWrapper(DocumentationComment underlyingObject)
     {
-        private readonly DocumentationComment _underlyingObject;
-
-        public VSTypeScriptDocumentationCommentWrapper(DocumentationComment underlyingObject)
-            => _underlyingObject = underlyingObject;
-
         public static VSTypeScriptDocumentationCommentWrapper FromXmlFragment(string xml)
             => new(DocumentationComment.FromXmlFragment(xml));
 
         public bool IsDefault
-            => _underlyingObject == null;
+            => underlyingObject == null;
 
         public string? SummaryTextOpt
-            => _underlyingObject?.SummaryText;
+            => underlyingObject?.SummaryText;
 
         public string? GetParameterTextOpt(string parameterName)
-            => _underlyingObject?.GetParameterText(parameterName);
+            => underlyingObject?.GetParameterText(parameterName);
 
     }
 }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/DependentTypeFinder_ProjectIndex.cs b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/DependentTypeFinder_ProjectIndex.cs
index abb7813a4db36..22df0954414ae 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/DependentTypeFinder_ProjectIndex.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/DependentTypeFinder_ProjectIndex.cs
@@ -14,29 +14,20 @@ namespace Microsoft.CodeAnalysis.FindSymbols
 {
     internal static partial class DependentTypeFinder
     {
-        private sealed class ProjectIndex
+        private sealed class ProjectIndex(
+            MultiDictionary<DocumentId, DeclaredSymbolInfo> classesAndRecordsThatMayDeriveFromSystemObject,
+            MultiDictionary<DocumentId, DeclaredSymbolInfo> valueTypes,
+            MultiDictionary<DocumentId, DeclaredSymbolInfo> enums,
+            MultiDictionary<DocumentId, DeclaredSymbolInfo> delegates,
+            MultiDictionary<string, (DocumentId, DeclaredSymbolInfo)> namedTypes)
         {
             private static readonly ConditionalWeakTable<ProjectState, AsyncLazy<ProjectIndex>> s_projectToIndex = new();
 
-            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> ClassesAndRecordsThatMayDeriveFromSystemObject;
-            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> ValueTypes;
-            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> Enums;
-            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> Delegates;
-            public readonly MultiDictionary<string, (DocumentId, DeclaredSymbolInfo)> NamedTypes;
-
-            public ProjectIndex(
-                MultiDictionary<DocumentId, DeclaredSymbolInfo> classesAndRecordsThatMayDeriveFromSystemObject,
-                MultiDictionary<DocumentId, DeclaredSymbolInfo> valueTypes,
-                MultiDictionary<DocumentId, DeclaredSymbolInfo> enums,
-                MultiDictionary<DocumentId, DeclaredSymbolInfo> delegates,
-                MultiDictionary<string, (DocumentId, DeclaredSymbolInfo)> namedTypes)
-            {
-                ClassesAndRecordsThatMayDeriveFromSystemObject = classesAndRecordsThatMayDeriveFromSystemObject;
-                ValueTypes = valueTypes;
-                Enums = enums;
-                Delegates = delegates;
-                NamedTypes = namedTypes;
-            }
+            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> ClassesAndRecordsThatMayDeriveFromSystemObject = classesAndRecordsThatMayDeriveFromSystemObject;
+            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> ValueTypes = valueTypes;
+            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> Enums = enums;
+            public readonly MultiDictionary<DocumentId, DeclaredSymbolInfo> Delegates = delegates;
+            public readonly MultiDictionary<string, (DocumentId, DeclaredSymbolInfo)> NamedTypes = namedTypes;
 
             public static Task<ProjectIndex> GetIndexAsync(
                 Project project, CancellationToken cancellationToken)
diff --git a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesDocumentState.cs b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesDocumentState.cs
index b63974b370d18..c0f6f3e18ff32 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesDocumentState.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesDocumentState.cs
@@ -8,38 +8,24 @@
 
 namespace Microsoft.CodeAnalysis.FindSymbols
 {
-    internal class FindReferencesDocumentState
+    internal class FindReferencesDocumentState(
+        Document document,
+        SemanticModel semanticModel,
+        SyntaxNode root,
+        FindReferenceCache cache,
+        HashSet<string>? globalAliases)
     {
         private static readonly HashSet<string> s_empty = new();
 
-        public readonly Document Document;
-        public readonly SemanticModel SemanticModel;
-        public readonly SyntaxNode Root;
-        public readonly FindReferenceCache Cache;
-        public readonly HashSet<string> GlobalAliases;
+        public readonly Document Document = document;
+        public readonly SemanticModel SemanticModel = semanticModel;
+        public readonly SyntaxNode Root = root;
+        public readonly FindReferenceCache Cache = cache;
+        public readonly HashSet<string> GlobalAliases = globalAliases ?? s_empty;
 
-        public readonly Solution Solution;
-        public readonly SyntaxTree SyntaxTree;
-        public readonly ISyntaxFactsService SyntaxFacts;
-        public readonly ISemanticFactsService SemanticFacts;
-
-        public FindReferencesDocumentState(
-            Document document,
-            SemanticModel semanticModel,
-            SyntaxNode root,
-            FindReferenceCache cache,
-            HashSet<string>? globalAliases)
-        {
-            Document = document;
-            SemanticModel = semanticModel;
-            Root = root;
-            Cache = cache;
-            GlobalAliases = globalAliases ?? s_empty;
-
-            Solution = document.Project.Solution;
-            SyntaxTree = semanticModel.SyntaxTree;
-            SyntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
-            SemanticFacts = document.GetRequiredLanguageService<ISemanticFactsService>();
-        }
+        public readonly Solution Solution = document.Project.Solution;
+        public readonly SyntaxTree SyntaxTree = semanticModel.SyntaxTree;
+        public readonly ISyntaxFactsService SyntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
+        public readonly ISemanticFactsService SemanticFacts = document.GetRequiredLanguageService<ISemanticFactsService>();
     }
 }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.NonCascadingSymbolSet.cs b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.NonCascadingSymbolSet.cs
index 1b2de9b3250bd..9eb7677806792 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.NonCascadingSymbolSet.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.NonCascadingSymbolSet.cs
@@ -14,12 +14,9 @@ internal partial class FindReferencesSearchEngine
         /// A symbol set used when the find refs caller does not want cascading.  This is a trivial impl that basically
         /// just wraps the initial symbol provided and doesn't need to do anything beyond that.
         /// </summary>
-        private sealed class NonCascadingSymbolSet : SymbolSet
+        private sealed class NonCascadingSymbolSet(FindReferencesSearchEngine engine, MetadataUnifyingSymbolHashSet searchSymbols) : SymbolSet(engine)
         {
-            private readonly ImmutableArray<ISymbol> _symbols;
-
-            public NonCascadingSymbolSet(FindReferencesSearchEngine engine, MetadataUnifyingSymbolHashSet searchSymbols) : base(engine)
-                => _symbols = searchSymbols.ToImmutableArray();
+            private readonly ImmutableArray<ISymbol> _symbols = searchSymbols.ToImmutableArray();
 
             public override ImmutableArray<ISymbol> GetAllSymbols()
                 => _symbols;
diff --git a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.UnidirectionalSymbolSet.cs b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.UnidirectionalSymbolSet.cs
index 0ca82137e9063..f89728a31b054 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.UnidirectionalSymbolSet.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/FindReferencesSearchEngine.UnidirectionalSymbolSet.cs
@@ -22,32 +22,24 @@ internal partial class FindReferencesSearchEngine
         /// runtime.  See the docs of <see cref="FindReferencesSearchOptions.UnidirectionalHierarchyCascade"/> for more
         /// information on this.
         /// </summary>
-        private sealed class UnidirectionalSymbolSet : SymbolSet
+        private sealed class UnidirectionalSymbolSet(
+            FindReferencesSearchEngine engine,
+            MetadataUnifyingSymbolHashSet initialSymbols,
+            MetadataUnifyingSymbolHashSet upSymbols) : SymbolSet(engine)
         {
-            private readonly MetadataUnifyingSymbolHashSet _initialAndDownSymbols;
 
             /// <summary>
             /// When we're doing a unidirectional find-references, the initial set of up-symbols can never change.
             /// That's because we have computed the up set entirely up front, and no down symbols can produce new
             /// up-symbols (as going down then up would not be unidirectional).
             /// </summary>
-            private readonly ImmutableHashSet<ISymbol> _upSymbols;
-
-            public UnidirectionalSymbolSet(
-                FindReferencesSearchEngine engine,
-                MetadataUnifyingSymbolHashSet initialSymbols,
-                MetadataUnifyingSymbolHashSet upSymbols)
-                : base(engine)
-            {
-                _initialAndDownSymbols = initialSymbols;
-                _upSymbols = upSymbols.ToImmutableHashSet(MetadataUnifyingEquivalenceComparer.Instance);
-            }
+            private readonly ImmutableHashSet<ISymbol> _upSymbols = upSymbols.ToImmutableHashSet(MetadataUnifyingEquivalenceComparer.Instance);
 
             public override ImmutableArray<ISymbol> GetAllSymbols()
             {
                 var result = new MetadataUnifyingSymbolHashSet();
                 result.AddRange(_upSymbols);
-                result.AddRange(_initialAndDownSymbols);
+                result.AddRange(initialSymbols);
                 return result.ToImmutableArray();
             }
 
@@ -55,7 +47,7 @@ public override async Task InheritanceCascadeAsync(Project project, Cancellation
             {
                 // Start searching using the existing set of symbols found at the start (or anything found below that).
                 var workQueue = new Stack<ISymbol>();
-                workQueue.Push(_initialAndDownSymbols);
+                workQueue.Push(initialSymbols);
 
                 var projects = ImmutableHashSet.Create(project);
 
@@ -64,7 +56,7 @@ public override async Task InheritanceCascadeAsync(Project project, Cancellation
                     var current = workQueue.Pop();
 
                     // Keep adding symbols downwards in this project as long as we keep finding new symbols.
-                    await AddDownSymbolsAsync(this.Engine, current, _initialAndDownSymbols, workQueue, projects, cancellationToken).ConfigureAwait(false);
+                    await AddDownSymbolsAsync(this.Engine, current, initialSymbols, workQueue, projects, cancellationToken).ConfigureAwait(false);
                 }
             }
         }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/FinderLocation.cs b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/FinderLocation.cs
index 7533d1f6590e3..7efa9393cd87d 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/FinderLocation.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/FinderLocation.cs
@@ -4,14 +4,14 @@
 
 namespace Microsoft.CodeAnalysis.FindSymbols.Finders
 {
-    internal readonly struct FinderLocation
+    internal readonly struct FinderLocation(SyntaxNode node, ReferenceLocation location)
     {
         /// <summary>
         /// The actual node that we found the reference on.  Normally the 'Name' portion
         /// of any piece of syntax.  Might also be something like a 'foreach' statement node
         /// when finding results for something like GetEnumerator.
         /// </summary>
-        public readonly SyntaxNode Node;
+        public readonly SyntaxNode Node = node;
 
         /// <summary>
         /// The location we want want to return through the FindRefs API.  The location contains
@@ -24,13 +24,7 @@ internal readonly struct FinderLocation
         /// location we will take the user to will be the zero-length position immediately preceding
         /// the `[` character.
         /// </summary>
-        public readonly ReferenceLocation Location;
-
-        public FinderLocation(SyntaxNode node, ReferenceLocation location)
-        {
-            Node = node;
-            Location = location;
-        }
+        public readonly ReferenceLocation Location = location;
 
         public void Deconstruct(out SyntaxNode node, out ReferenceLocation location)
         {
diff --git a/src/Workspaces/Core/Portable/FindSymbols/ReferencedSymbol.cs b/src/Workspaces/Core/Portable/FindSymbols/ReferencedSymbol.cs
index 6d00873881c7c..f2a9b2753fc9a 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/ReferencedSymbol.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/ReferencedSymbol.cs
@@ -55,15 +55,10 @@ private string GetDebuggerDisplay()
         internal TestAccessor GetTestAccessor()
             => new(this);
 
-        internal readonly struct TestAccessor
+        internal readonly struct TestAccessor(ReferencedSymbol referencedSymbol)
         {
-            private readonly ReferencedSymbol _referencedSymbol;
-
-            public TestAccessor(ReferencedSymbol referencedSymbol)
-                => _referencedSymbol = referencedSymbol;
-
             internal string GetDebuggerDisplay()
-                => _referencedSymbol.GetDebuggerDisplay();
+                => referencedSymbol.GetDebuggerDisplay();
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/StreamingProgressCollector.cs b/src/Workspaces/Core/Portable/FindSymbols/StreamingProgressCollector.cs
index 005c24ffff2f5..02a6c61b38482 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/StreamingProgressCollector.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/StreamingProgressCollector.cs
@@ -23,26 +23,19 @@ namespace Microsoft.CodeAnalysis.FindSymbols
     /// APIs to return all the results at the end of the operation, as opposed to broadcasting
     /// the results as they are found.
     /// </summary>
-    internal class StreamingProgressCollector : IStreamingFindReferencesProgress
+    internal class StreamingProgressCollector(
+        IStreamingFindReferencesProgress underlyingProgress) : IStreamingFindReferencesProgress
     {
         private readonly object _gate = new();
-        private readonly IStreamingFindReferencesProgress _underlyingProgress;
-
         private readonly Dictionary<ISymbol, List<ReferenceLocation>> _symbolToLocations = new();
 
-        public IStreamingProgressTracker ProgressTracker => _underlyingProgress.ProgressTracker;
+        public IStreamingProgressTracker ProgressTracker => underlyingProgress.ProgressTracker;
 
         public StreamingProgressCollector()
             : this(NoOpStreamingFindReferencesProgress.Instance)
         {
         }
 
-        public StreamingProgressCollector(
-            IStreamingFindReferencesProgress underlyingProgress)
-        {
-            _underlyingProgress = underlyingProgress;
-        }
-
         public ImmutableArray<ReferencedSymbol> GetReferencedSymbols()
         {
             lock (_gate)
@@ -55,11 +48,11 @@ public ImmutableArray<ReferencedSymbol> GetReferencedSymbols()
             }
         }
 
-        public ValueTask OnStartedAsync(CancellationToken cancellationToken) => _underlyingProgress.OnStartedAsync(cancellationToken);
-        public ValueTask OnCompletedAsync(CancellationToken cancellationToken) => _underlyingProgress.OnCompletedAsync(cancellationToken);
+        public ValueTask OnStartedAsync(CancellationToken cancellationToken) => underlyingProgress.OnStartedAsync(cancellationToken);
+        public ValueTask OnCompletedAsync(CancellationToken cancellationToken) => underlyingProgress.OnCompletedAsync(cancellationToken);
 
-        public ValueTask OnFindInDocumentCompletedAsync(Document document, CancellationToken cancellationToken) => _underlyingProgress.OnFindInDocumentCompletedAsync(document, cancellationToken);
-        public ValueTask OnFindInDocumentStartedAsync(Document document, CancellationToken cancellationToken) => _underlyingProgress.OnFindInDocumentStartedAsync(document, cancellationToken);
+        public ValueTask OnFindInDocumentCompletedAsync(Document document, CancellationToken cancellationToken) => underlyingProgress.OnFindInDocumentCompletedAsync(document, cancellationToken);
+        public ValueTask OnFindInDocumentStartedAsync(Document document, CancellationToken cancellationToken) => underlyingProgress.OnFindInDocumentStartedAsync(document, cancellationToken);
 
         public ValueTask OnDefinitionFoundAsync(SymbolGroup group, CancellationToken cancellationToken)
         {
@@ -71,7 +64,7 @@ public ValueTask OnDefinitionFoundAsync(SymbolGroup group, CancellationToken can
                         _symbolToLocations[definition] = new List<ReferenceLocation>();
                 }
 
-                return _underlyingProgress.OnDefinitionFoundAsync(group, cancellationToken);
+                return underlyingProgress.OnDefinitionFoundAsync(group, cancellationToken);
             }
             catch (Exception ex) when (FatalError.ReportAndPropagateUnlessCanceled(ex, cancellationToken))
             {
@@ -86,7 +79,7 @@ public ValueTask OnReferenceFoundAsync(SymbolGroup group, ISymbol definition, Re
                 _symbolToLocations[definition].Add(location);
             }
 
-            return _underlyingProgress.OnReferenceFoundAsync(group, definition, location, cancellationToken);
+            return underlyingProgress.OnReferenceFoundAsync(group, definition, location, cancellationToken);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindLiteralsServerCallback.cs b/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindLiteralsServerCallback.cs
index 1b0d8e6b7afe4..99b15be523fb7 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindLiteralsServerCallback.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindLiteralsServerCallback.cs
@@ -12,29 +12,20 @@ namespace Microsoft.CodeAnalysis.FindSymbols
 {
     public static partial class SymbolFinder
     {
-        internal sealed class FindLiteralsServerCallback
+        internal sealed class FindLiteralsServerCallback(
+            Solution solution,
+            IStreamingFindLiteralReferencesProgress progress)
         {
-            private readonly Solution _solution;
-            private readonly IStreamingFindLiteralReferencesProgress _progress;
-
-            public FindLiteralsServerCallback(
-                Solution solution,
-                IStreamingFindLiteralReferencesProgress progress)
-            {
-                _solution = solution;
-                _progress = progress;
-            }
-
             public ValueTask AddItemsAsync(int count, CancellationToken cancellationToken)
-                => _progress.ProgressTracker.AddItemsAsync(count, cancellationToken);
+                => progress.ProgressTracker.AddItemsAsync(count, cancellationToken);
 
             public ValueTask ItemsCompletedAsync(int count, CancellationToken cancellationToken)
-                => _progress.ProgressTracker.ItemsCompletedAsync(count, cancellationToken);
+                => progress.ProgressTracker.ItemsCompletedAsync(count, cancellationToken);
 
             public async ValueTask OnLiteralReferenceFoundAsync(DocumentId documentId, TextSpan span, CancellationToken cancellationToken)
             {
-                var document = _solution.GetRequiredDocument(documentId);
-                await _progress.OnReferenceFoundAsync(document, span, cancellationToken).ConfigureAwait(false);
+                var document = solution.GetRequiredDocument(documentId);
+                await progress.OnReferenceFoundAsync(document, span, cancellationToken).ConfigureAwait(false);
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindReferencesServerCallback.cs b/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindReferencesServerCallback.cs
index 1c26f07869644..5bb143b0512ac 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindReferencesServerCallback.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SymbolFinder.FindReferencesServerCallback.cs
@@ -20,45 +20,36 @@ public static partial class SymbolFinder
         /// Callback object we pass to the OOP server to hear about the result 
         /// of the FindReferencesEngine as it executes there.
         /// </summary>
-        internal sealed class FindReferencesServerCallback
+        internal sealed class FindReferencesServerCallback(
+            Solution solution,
+            IStreamingFindReferencesProgress progress)
         {
-            private readonly Solution _solution;
-            private readonly IStreamingFindReferencesProgress _progress;
-
             private readonly object _gate = new();
             private readonly Dictionary<SerializableSymbolGroup, SymbolGroup> _groupMap = new();
             private readonly Dictionary<SerializableSymbolAndProjectId, ISymbol> _definitionMap = new();
 
-            public FindReferencesServerCallback(
-                Solution solution,
-                IStreamingFindReferencesProgress progress)
-            {
-                _solution = solution;
-                _progress = progress;
-            }
-
             public ValueTask AddItemsAsync(int count, CancellationToken cancellationToken)
-                => _progress.ProgressTracker.AddItemsAsync(count, cancellationToken);
+                => progress.ProgressTracker.AddItemsAsync(count, cancellationToken);
 
             public ValueTask ItemsCompletedAsync(int count, CancellationToken cancellationToken)
-                => _progress.ProgressTracker.ItemsCompletedAsync(count, cancellationToken);
+                => progress.ProgressTracker.ItemsCompletedAsync(count, cancellationToken);
 
             public ValueTask OnStartedAsync(CancellationToken cancellationToken)
-                => _progress.OnStartedAsync(cancellationToken);
+                => progress.OnStartedAsync(cancellationToken);
 
             public ValueTask OnCompletedAsync(CancellationToken cancellationToken)
-                => _progress.OnCompletedAsync(cancellationToken);
+                => progress.OnCompletedAsync(cancellationToken);
 
             public async ValueTask OnFindInDocumentStartedAsync(DocumentId documentId, CancellationToken cancellationToken)
             {
-                var document = await _solution.GetRequiredDocumentAsync(documentId, includeSourceGenerated: true, cancellationToken).ConfigureAwait(false);
-                await _progress.OnFindInDocumentStartedAsync(document, cancellationToken).ConfigureAwait(false);
+                var document = await solution.GetRequiredDocumentAsync(documentId, includeSourceGenerated: true, cancellationToken).ConfigureAwait(false);
+                await progress.OnFindInDocumentStartedAsync(document, cancellationToken).ConfigureAwait(false);
             }
 
             public async ValueTask OnFindInDocumentCompletedAsync(DocumentId documentId, CancellationToken cancellationToken)
             {
-                var document = await _solution.GetRequiredDocumentAsync(documentId, includeSourceGenerated: true, cancellationToken).ConfigureAwait(false);
-                await _progress.OnFindInDocumentCompletedAsync(document, cancellationToken).ConfigureAwait(false);
+                var document = await solution.GetRequiredDocumentAsync(documentId, includeSourceGenerated: true, cancellationToken).ConfigureAwait(false);
+                await progress.OnFindInDocumentCompletedAsync(document, cancellationToken).ConfigureAwait(false);
             }
 
             public async ValueTask OnDefinitionFoundAsync(SerializableSymbolGroup dehydrated, CancellationToken cancellationToken)
@@ -69,7 +60,7 @@ public async ValueTask OnDefinitionFoundAsync(SerializableSymbolGroup dehydrated
 
                 foreach (var symbolAndProjectId in dehydrated.Symbols)
                 {
-                    var symbol = await symbolAndProjectId.TryRehydrateAsync(_solution, cancellationToken).ConfigureAwait(false);
+                    var symbol = await symbolAndProjectId.TryRehydrateAsync(solution, cancellationToken).ConfigureAwait(false);
                     if (symbol == null)
                         return;
 
@@ -84,7 +75,7 @@ public async ValueTask OnDefinitionFoundAsync(SerializableSymbolGroup dehydrated
                         _definitionMap[pair.Key] = pair.Value;
                 }
 
-                await _progress.OnDefinitionFoundAsync(symbolGroup, cancellationToken).ConfigureAwait(false);
+                await progress.OnDefinitionFoundAsync(symbolGroup, cancellationToken).ConfigureAwait(false);
             }
 
             public async ValueTask OnReferenceFoundAsync(
@@ -112,9 +103,9 @@ public async ValueTask OnReferenceFoundAsync(
                 }
 
                 var referenceLocation = await reference.RehydrateAsync(
-                    _solution, cancellationToken).ConfigureAwait(false);
+                    solution, cancellationToken).ConfigureAwait(false);
 
-                await _progress.OnReferenceFoundAsync(symbolGroup, symbol, referenceLocation, cancellationToken).ConfigureAwait(false);
+                await progress.OnReferenceFoundAsync(symbolGroup, symbol, referenceLocation, cancellationToken).ConfigureAwait(false);
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo.Node.cs b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo.Node.cs
index 4cddecc696ca7..43ba11acad848 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo.Node.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo.Node.cs
@@ -22,20 +22,13 @@ internal partial class SymbolTreeInfo
         /// these to <see cref="Node"/>s.
         /// </summary>
         [DebuggerDisplay("{GetDebuggerDisplay(),nq}")]
-        private readonly struct BuilderNode
+        private readonly struct BuilderNode(string name, int parentIndex, MultiDictionary<MetadataNode, ParameterTypeInfo>.ValueSet parameterTypeInfos = default)
         {
             public static readonly BuilderNode RootNode = new("", RootNodeParentIndex, default);
 
-            public readonly string Name;
-            public readonly int ParentIndex;
-            public readonly MultiDictionary<MetadataNode, ParameterTypeInfo>.ValueSet ParameterTypeInfos;
-
-            public BuilderNode(string name, int parentIndex, MultiDictionary<MetadataNode, ParameterTypeInfo>.ValueSet parameterTypeInfos = default)
-            {
-                Name = name;
-                ParentIndex = parentIndex;
-                ParameterTypeInfos = parameterTypeInfos;
-            }
+            public readonly string Name = name;
+            public readonly int ParentIndex = parentIndex;
+            public readonly MultiDictionary<MetadataNode, ParameterTypeInfo>.ValueSet ParameterTypeInfos = parameterTypeInfos;
 
             public bool IsRoot => ParentIndex == RootNodeParentIndex;
 
@@ -44,25 +37,19 @@ private string GetDebuggerDisplay()
         }
 
         [DebuggerDisplay("{GetDebuggerDisplay(),nq}")]
-        private readonly struct Node
+        private readonly struct Node(string name, int parentIndex)
         {
             /// <summary>
             /// The Name of this Node.
             /// </summary>
-            public readonly string Name;
+            public readonly string Name = name;
 
             /// <summary>
             /// Index in <see cref="_nodes"/> of the parent Node of this Node.
             /// Value will be <see cref="RootNodeParentIndex"/> if this is the 
             /// Node corresponding to the root symbol.
             /// </summary>
-            public readonly int ParentIndex;
-
-            public Node(string name, int parentIndex)
-            {
-                Name = name;
-                ParentIndex = parentIndex;
-            }
+            public readonly int ParentIndex = parentIndex;
 
             public bool IsRoot => ParentIndex == RootNodeParentIndex;
 
@@ -76,14 +63,14 @@ private string GetDebuggerDisplay()
                 => Name + ", " + ParentIndex;
         }
 
-        private readonly struct ParameterTypeInfo
+        private readonly struct ParameterTypeInfo(string name, bool isComplex, bool isArray)
         {
             /// <summary>
             /// This is the type name of the parameter when <see cref="IsComplexType"/> is false. 
             /// For array types, this is just the elemtent type name.
             /// e.g. `int` for `int[][,]` 
             /// </summary>
-            public readonly string Name;
+            public readonly string Name = name;
 
             /// <summary>
             /// Indicate if the type of parameter is any kind of array.
@@ -92,7 +79,7 @@ private readonly struct ParameterTypeInfo
             /// - array of complex type like T[], T[][], etc are all represented as "[]" in index, 
             ///   in contrast to just "" for non-array types.
             /// </summary>
-            public readonly bool IsArray;
+            public readonly bool IsArray = isArray;
 
             /// <summary>
             /// Similar to <see cref="TopLevelSyntaxTreeIndex.ExtensionMethodInfo"/>, we divide extension methods into
@@ -106,34 +93,21 @@ private readonly struct ParameterTypeInfo
             /// - By reference type of any types above
             /// - Array types with element of any types above
             /// </summary>
-            public readonly bool IsComplexType;
-
-            public ParameterTypeInfo(string name, bool isComplex, bool isArray)
-            {
-                Name = name;
-                IsComplexType = isComplex;
-                IsArray = isArray;
-            }
+            public readonly bool IsComplexType = isComplex;
         }
 
-        public readonly struct ExtensionMethodInfo
+        public readonly struct ExtensionMethodInfo(string fullyQualifiedContainerName, string name)
         {
             /// <summary>
             /// Name of the extension method. 
             /// This can be used to retrive corresponding symbols via <see cref="INamespaceOrTypeSymbol.GetMembers(string)"/>
             /// </summary>
-            public readonly string Name;
+            public readonly string Name = name;
 
             /// <summary>
             /// Fully qualified name for the type that contains this extension method.
             /// </summary>
-            public readonly string FullyQualifiedContainerName;
-
-            public ExtensionMethodInfo(string fullyQualifiedContainerName, string name)
-            {
-                FullyQualifiedContainerName = fullyQualifiedContainerName;
-                Name = name;
-            }
+            public readonly string FullyQualifiedContainerName = fullyQualifiedContainerName;
         }
 
         private sealed class ParameterTypeInfoProvider : ISignatureTypeProvider<ParameterTypeInfo, object?>
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheService.cs b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheService.cs
index 859c8af0e2157..af48bb4af2848 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheService.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheService.cs
@@ -236,21 +236,14 @@ private void RemoveMetadataReferences(ProjectId projectId)
         public TestAccessor GetTestAccessor()
             => new(this);
 
-        public struct TestAccessor
+        public struct TestAccessor(SymbolTreeInfoCacheService service)
         {
-            private readonly SymbolTreeInfoCacheService _services;
-
-            public TestAccessor(SymbolTreeInfoCacheService service)
-            {
-                _services = service;
-            }
-
             public readonly Task AnalyzeSolutionAsync()
             {
-                foreach (var projectId in _services._workspace.CurrentSolution.ProjectIds)
-                    _services._workQueue.AddWork(projectId);
+                foreach (var projectId in service._workspace.CurrentSolution.ProjectIds)
+                    service._workQueue.AddWork(projectId);
 
-                return _services._workQueue.WaitUntilCurrentBatchCompletesAsync();
+                return service._workQueue.WaitUntilCurrentBatchCompletesAsync();
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheServiceFactory.cs b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheServiceFactory.cs
index 85772f815bdf9..818cf4d2884f4 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheServiceFactory.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfoCacheServiceFactory.cs
@@ -11,17 +11,12 @@
 namespace Microsoft.CodeAnalysis.FindSymbols.SymbolTree;
 
 [ExportWorkspaceServiceFactory(typeof(ISymbolTreeInfoCacheService)), Shared]
-internal sealed partial class SymbolTreeInfoCacheServiceFactory : IWorkspaceServiceFactory
+[method: ImportingConstructor]
+[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+internal sealed partial class SymbolTreeInfoCacheServiceFactory(
+    IAsynchronousOperationListenerProvider listenerProvider) : IWorkspaceServiceFactory
 {
-    private readonly IAsynchronousOperationListener _listener;
-
-    [ImportingConstructor]
-    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-    public SymbolTreeInfoCacheServiceFactory(
-        IAsynchronousOperationListenerProvider listenerProvider)
-    {
-        _listener = listenerProvider.GetListener(FeatureAttribute.SolutionCrawlerLegacy);
-    }
+    private readonly IAsynchronousOperationListener _listener = listenerProvider.GetListener(FeatureAttribute.SolutionCrawlerLegacy);
 
     public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
         => new SymbolTreeInfoCacheService(workspaceServices.Workspace, _listener);
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo_Metadata.cs b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo_Metadata.cs
index 17940e9387814..7376b38a2bd2e 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo_Metadata.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo_Metadata.cs
@@ -256,17 +256,14 @@ private static string GetMetadataKeySuffix(PortableExecutableReference reference
                 cancellationToken);
         }
 
-        private struct MetadataInfoCreator : IDisposable
+        private struct MetadataInfoCreator(
+            Checksum checksum, Metadata? metadata) : IDisposable
         {
             private static readonly Predicate<string> s_isNotNullOrEmpty = s => !string.IsNullOrEmpty(s);
             private static readonly ObjectPool<List<string>> s_stringListPool = SharedPools.Default<List<string>>();
-
-            private readonly Checksum _checksum;
-            private readonly Metadata? _metadata;
-
-            private readonly OrderPreservingMultiDictionary<string, string> _inheritanceMap;
-            private readonly OrderPreservingMultiDictionary<MetadataNode, MetadataNode> _parentToChildren;
-            private readonly MetadataNode _rootNode;
+            private readonly OrderPreservingMultiDictionary<string, string> _inheritanceMap = OrderPreservingMultiDictionary<string, string>.GetInstance();
+            private readonly OrderPreservingMultiDictionary<MetadataNode, MetadataNode> _parentToChildren = OrderPreservingMultiDictionary<MetadataNode, MetadataNode>.GetInstance();
+            private readonly MetadataNode _rootNode = MetadataNode.Allocate(name: "");
 
             // The set of type definitions we've read out of the current metadata reader.
             private readonly List<MetadataDefinition> _allTypeDefinitions = new();
@@ -279,19 +276,7 @@ private struct MetadataInfoCreator : IDisposable
             //      public static bool AnotherExtensionMethod1(this bool x);
             //
             private readonly MultiDictionary<MetadataNode, ParameterTypeInfo> _extensionMethodToParameterTypeInfo = new();
-            private bool _containsExtensionsMethod;
-
-            public MetadataInfoCreator(
-                Checksum checksum, Metadata? metadata)
-            {
-                _checksum = checksum;
-                _metadata = metadata;
-                _containsExtensionsMethod = false;
-
-                _inheritanceMap = OrderPreservingMultiDictionary<string, string>.GetInstance();
-                _parentToChildren = OrderPreservingMultiDictionary<MetadataNode, MetadataNode>.GetInstance();
-                _rootNode = MetadataNode.Allocate(name: "");
-            }
+            private bool _containsExtensionsMethod = false;
 
             private static ImmutableArray<ModuleMetadata> GetModuleMetadata(Metadata? metadata)
             {
@@ -318,7 +303,7 @@ private static ImmutableArray<ModuleMetadata> GetModuleMetadata(Metadata? metada
 
             internal SymbolTreeInfo Create()
             {
-                foreach (var moduleMetadata in GetModuleMetadata(_metadata))
+                foreach (var moduleMetadata in GetModuleMetadata(metadata))
                 {
                     try
                     {
@@ -348,7 +333,7 @@ internal SymbolTreeInfo Create()
                 var unsortedNodes = GenerateUnsortedNodes(receiverTypeNameToExtensionMethodMap);
 
                 return CreateSymbolTreeInfo(
-                    _checksum, unsortedNodes, _inheritanceMap, receiverTypeNameToExtensionMethodMap);
+                    checksum, unsortedNodes, _inheritanceMap, receiverTypeNameToExtensionMethodMap);
             }
 
             public readonly void Dispose()
@@ -605,7 +590,7 @@ private readonly void PopulateInheritance(
                 }
             }
 
-            private readonly void AddBaseTypeNameParts(
+            private static void AddBaseTypeNameParts(
                 MetadataReader metadataReader,
                 EntityHandle baseTypeOrInterfaceHandle,
                 List<string> simpleNames)
@@ -621,7 +606,7 @@ private readonly void AddBaseTypeNameParts(
                 }
             }
 
-            private readonly void AddTypeDefinitionNameParts(
+            private static void AddTypeDefinitionNameParts(
                 MetadataReader metadataReader,
                 TypeDefinitionHandle handle,
                 List<string> simpleNames)
@@ -678,7 +663,7 @@ private static void AddNamespaceParts(
                 }
             }
 
-            private readonly void AddNamespaceParts(
+            private static void AddNamespaceParts(
                 MetadataReader metadataReader,
                 NamespaceDefinitionHandle namespaceHandle,
                 List<string> simpleNames)
@@ -842,32 +827,23 @@ private enum MetadataDefinitionKind
             Member,
         }
 
-        private readonly struct MetadataDefinition
+        private readonly struct MetadataDefinition(
+            MetadataDefinitionKind kind,
+            string name,
+            ParameterTypeInfo receiverTypeInfo = default,
+            NamespaceDefinition @namespace = default,
+            TypeDefinition type = default)
         {
-            public string Name { get; }
-            public MetadataDefinitionKind Kind { get; }
+            public string Name { get; } = name;
+            public MetadataDefinitionKind Kind { get; } = kind;
 
             /// <summary>
             /// Only applies to member kind. Represents the type info of the first parameter.
             /// </summary>
-            public ParameterTypeInfo ReceiverTypeInfo { get; }
-
-            public NamespaceDefinition Namespace { get; }
-            public TypeDefinition Type { get; }
+            public ParameterTypeInfo ReceiverTypeInfo { get; } = receiverTypeInfo;
 
-            public MetadataDefinition(
-                MetadataDefinitionKind kind,
-                string name,
-                ParameterTypeInfo receiverTypeInfo = default,
-                NamespaceDefinition @namespace = default,
-                TypeDefinition type = default)
-            {
-                Kind = kind;
-                Name = name;
-                ReceiverTypeInfo = receiverTypeInfo;
-                Namespace = @namespace;
-                Type = type;
-            }
+            public NamespaceDefinition Namespace { get; } = @namespace;
+            public TypeDefinition Type { get; } = type;
 
             public static MetadataDefinition Create(
                 MetadataReader reader, NamespaceDefinitionHandle namespaceHandle)
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.IdentifierInfo.cs b/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.IdentifierInfo.cs
index 4d69a45bc65f0..a664678825c56 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.IdentifierInfo.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.IdentifierInfo.cs
@@ -10,18 +10,12 @@ namespace Microsoft.CodeAnalysis.FindSymbols
 {
     internal partial class SyntaxTreeIndex
     {
-        private readonly struct IdentifierInfo
+        private readonly struct IdentifierInfo(
+            BloomFilter identifierFilter,
+            BloomFilter escapedIdentifierFilter)
         {
-            private readonly BloomFilter _identifierFilter;
-            private readonly BloomFilter _escapedIdentifierFilter;
-
-            public IdentifierInfo(
-                BloomFilter identifierFilter,
-                BloomFilter escapedIdentifierFilter)
-            {
-                _identifierFilter = identifierFilter ?? throw new ArgumentNullException(nameof(identifierFilter));
-                _escapedIdentifierFilter = escapedIdentifierFilter ?? throw new ArgumentNullException(nameof(escapedIdentifierFilter));
-            }
+            private readonly BloomFilter _identifierFilter = identifierFilter ?? throw new ArgumentNullException(nameof(identifierFilter));
+            private readonly BloomFilter _escapedIdentifierFilter = escapedIdentifierFilter ?? throw new ArgumentNullException(nameof(escapedIdentifierFilter));
 
             /// <summary>
             /// Returns true when the identifier is probably (but not guaranteed) to be within the
diff --git a/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.LiteralInfo.cs b/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.LiteralInfo.cs
index ce2f3f57e3f9c..fb2efa9f95e91 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.LiteralInfo.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/SyntaxTree/SyntaxTreeIndex.LiteralInfo.cs
@@ -10,12 +10,9 @@ namespace Microsoft.CodeAnalysis.FindSymbols
 {
     internal partial class SyntaxTreeIndex
     {
-        private readonly struct LiteralInfo
+        private readonly struct LiteralInfo(BloomFilter literalsFilter)
         {
-            private readonly BloomFilter _literalsFilter;
-
-            public LiteralInfo(BloomFilter literalsFilter)
-                => _literalsFilter = literalsFilter ?? throw new ArgumentNullException(nameof(literalsFilter));
+            private readonly BloomFilter _literalsFilter = literalsFilter ?? throw new ArgumentNullException(nameof(literalsFilter));
 
             /// <summary>
             /// Returns true when the identifier is probably (but not guaranteed) to be within the
diff --git a/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/DeclaredSymbolInfo.cs b/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/DeclaredSymbolInfo.cs
index d20e62242d597..e2b3ab9c31a01 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/DeclaredSymbolInfo.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/DeclaredSymbolInfo.cs
@@ -37,19 +37,27 @@ internal enum DeclaredSymbolInfoKind : byte
     }
 
     [DataContract]
-    internal readonly struct DeclaredSymbolInfo : IEquatable<DeclaredSymbolInfo>
+    [method: Obsolete("Do not call directly.  Only around for serialization.  Use Create instead")]
+    internal readonly struct DeclaredSymbolInfo(
+        string name,
+        string? nameSuffix,
+        string? containerDisplayName,
+        string fullyQualifiedContainerName,
+        TextSpan span,
+        ImmutableArray<string> inheritanceNames,
+        uint flags) : IEquatable<DeclaredSymbolInfo>
     {
         /// <summary>
         /// The name to pattern match against, and to show in a final presentation layer.
         /// </summary>
         [DataMember(Order = 0)]
-        public readonly string Name;
+        public readonly string Name = name;
 
         /// <summary>
         /// An optional suffix to be shown in a presentation layer appended to <see cref="Name"/>.
         /// </summary>
         [DataMember(Order = 1)]
-        public readonly string? NameSuffix;
+        public readonly string? NameSuffix = nameSuffix;
 
         /// <summary>
         /// Container of the symbol that can be shown in a final presentation layer. 
@@ -59,7 +67,7 @@ internal enum DeclaredSymbolInfoKind : byte
         /// to indicate where the symbol is located.
         /// </summary>
         [DataMember(Order = 2)]
-        public readonly string? ContainerDisplayName;
+        public readonly string? ContainerDisplayName = containerDisplayName;
 
         /// <summary>
         /// Dotted container name of the symbol, used for pattern matching.  For example
@@ -69,21 +77,21 @@ internal enum DeclaredSymbolInfoKind : byte
         /// match against this.  This should not be shown in a presentation layer.
         /// </summary>
         [DataMember(Order = 3)]
-        public readonly string FullyQualifiedContainerName;
+        public readonly string FullyQualifiedContainerName = fullyQualifiedContainerName;
 
         [DataMember(Order = 4)]
-        public readonly TextSpan Span;
+        public readonly TextSpan Span = span;
 
         /// <summary>
         /// The names directly referenced in source that this type inherits from.
         /// </summary>
         [DataMember(Order = 5)]
-        public ImmutableArray<string> InheritanceNames { get; }
+        public ImmutableArray<string> InheritanceNames { get; } = inheritanceNames;
 
         // Store the kind (5 bits), accessibility (4 bits), parameter-count (4 bits), and type-parameter-count (4 bits)
         // in a single int.
         [DataMember(Order = 6)]
-        private readonly uint _flags;
+        private readonly uint _flags = flags;
 
         private const uint Lower4BitMask = 0b1111;
         private const uint Lower5BitMask = 0b11111;
@@ -96,25 +104,6 @@ internal enum DeclaredSymbolInfoKind : byte
         public bool IsPartial => GetIsPartial(_flags);
         public bool HasAttributes => GetHasAttributes(_flags);
 
-        [Obsolete("Do not call directly.  Only around for serialization.  Use Create instead")]
-        public DeclaredSymbolInfo(
-            string name,
-            string? nameSuffix,
-            string? containerDisplayName,
-            string fullyQualifiedContainerName,
-            TextSpan span,
-            ImmutableArray<string> inheritanceNames,
-            uint flags)
-        {
-            Name = name;
-            NameSuffix = nameSuffix;
-            ContainerDisplayName = containerDisplayName;
-            FullyQualifiedContainerName = fullyQualifiedContainerName;
-            Span = span;
-            InheritanceNames = inheritanceNames;
-            _flags = flags;
-        }
-
         public static DeclaredSymbolInfo Create(
             StringTable stringTable,
             string name,
diff --git a/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.DeclarationInfo.cs b/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.DeclarationInfo.cs
index f1d7d70cccfde..d44f5ca36cee8 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.DeclarationInfo.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.DeclarationInfo.cs
@@ -11,12 +11,9 @@ namespace Microsoft.CodeAnalysis.FindSymbols
 {
     internal sealed partial class TopLevelSyntaxTreeIndex
     {
-        private readonly struct DeclarationInfo
+        private readonly struct DeclarationInfo(ImmutableArray<DeclaredSymbolInfo> declaredSymbolInfos)
         {
-            public ImmutableArray<DeclaredSymbolInfo> DeclaredSymbolInfos { get; }
-
-            public DeclarationInfo(ImmutableArray<DeclaredSymbolInfo> declaredSymbolInfos)
-                => DeclaredSymbolInfos = declaredSymbolInfos;
+            public ImmutableArray<DeclaredSymbolInfo> DeclaredSymbolInfos { get; } = declaredSymbolInfos;
 
             public void WriteTo(ObjectWriter writer)
             {
diff --git a/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.ExtensionMethodInfo.cs b/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.ExtensionMethodInfo.cs
index 02c956d880ca0..3e10b8d41fdbb 100644
--- a/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.ExtensionMethodInfo.cs
+++ b/src/Workspaces/Core/Portable/FindSymbols/TopLevelSyntaxTree/TopLevelSyntaxTreeIndex.ExtensionMethodInfo.cs
@@ -11,7 +11,7 @@ namespace Microsoft.CodeAnalysis.FindSymbols
 {
     internal sealed partial class TopLevelSyntaxTreeIndex
     {
-        private readonly struct ExtensionMethodInfo
+        private readonly struct ExtensionMethodInfo(ImmutableDictionary<string, ImmutableArray<int>> receiverTypeNameToExtensionMethodMap)
         {
             // We divide extension methods into two categories, simple and complex, for filtering purpose.
             // Whether a method is simple is determined based on if we can determine it's receiver type easily
@@ -39,15 +39,10 @@ private readonly struct ExtensionMethodInfo
             /// T (where T is a type parameter) => ""
             /// T[,] (where T is a type parameter) => "T[]"
             /// </summary>
-            public readonly ImmutableDictionary<string, ImmutableArray<int>> ReceiverTypeNameToExtensionMethodMap { get; }
+            public readonly ImmutableDictionary<string, ImmutableArray<int>> ReceiverTypeNameToExtensionMethodMap { get; } = receiverTypeNameToExtensionMethodMap;
 
             public bool ContainsExtensionMethod => !ReceiverTypeNameToExtensionMethodMap.IsEmpty;
 
-            public ExtensionMethodInfo(ImmutableDictionary<string, ImmutableArray<int>> receiverTypeNameToExtensionMethodMap)
-            {
-                ReceiverTypeNameToExtensionMethodMap = receiverTypeNameToExtensionMethodMap;
-            }
-
             public void WriteTo(ObjectWriter writer)
             {
                 writer.WriteInt32(ReceiverTypeNameToExtensionMethodMap.Count);
diff --git a/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileDiffMergingSession.cs b/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileDiffMergingSession.cs
index ae35044134a46..c41e872a776ea 100644
--- a/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileDiffMergingSession.cs
+++ b/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileDiffMergingSession.cs
@@ -17,34 +17,23 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    internal sealed class LinkedFileDiffMergingSession
+    internal sealed class LinkedFileDiffMergingSession(Solution oldSolution, Solution newSolution, SolutionChanges solutionChanges)
     {
-        private readonly Solution _oldSolution;
-        private readonly Solution _newSolution;
-        private readonly SolutionChanges _solutionChanges;
-
-        public LinkedFileDiffMergingSession(Solution oldSolution, Solution newSolution, SolutionChanges solutionChanges)
-        {
-            _oldSolution = oldSolution;
-            _newSolution = newSolution;
-            _solutionChanges = solutionChanges;
-        }
-
         internal async Task<LinkedFileMergeSessionResult> MergeDiffsAsync(IMergeConflictHandler mergeConflictHandler, CancellationToken cancellationToken)
         {
             var sessionInfo = new LinkedFileDiffMergingSessionInfo();
 
-            var linkedDocumentGroupsWithChanges = _solutionChanges
+            var linkedDocumentGroupsWithChanges = solutionChanges
                 .GetProjectChanges()
                 .SelectMany(p => p.GetChangedDocuments())
-                .GroupBy(d => _oldSolution.GetDocument(d).FilePath, StringComparer.OrdinalIgnoreCase);
+                .GroupBy(d => oldSolution.GetDocument(d).FilePath, StringComparer.OrdinalIgnoreCase);
 
             var linkedFileMergeResults = new List<LinkedFileMergeResult>();
 
-            var updatedSolution = _newSolution;
+            var updatedSolution = newSolution;
             foreach (var linkedDocumentsWithChanges in linkedDocumentGroupsWithChanges)
             {
-                var documentInNewSolution = _newSolution.GetDocument(linkedDocumentsWithChanges.First());
+                var documentInNewSolution = newSolution.GetDocument(linkedDocumentsWithChanges.First());
 
                 // Ensure the first document in the group is the first in the list of 
                 var allLinkedDocuments = documentInNewSolution.GetLinkedDocumentIds().Add(documentInNewSolution.Id);
@@ -62,7 +51,7 @@ internal async Task<LinkedFileMergeSessionResult> MergeDiffsAsync(IMergeConflict
                 }
                 else
                 {
-                    mergedText = await _newSolution.GetDocument(linkedDocumentsWithChanges.Single()).GetValueTextAsync(cancellationToken).ConfigureAwait(false);
+                    mergedText = await newSolution.GetDocument(linkedDocumentsWithChanges.Single()).GetValueTextAsync(cancellationToken).ConfigureAwait(false);
                 }
 
                 foreach (var documentId in allLinkedDocuments)
@@ -85,15 +74,15 @@ private async Task<LinkedFileMergeResult> MergeLinkedDocumentGroupAsync(
 
             // Automatically merge non-conflicting diffs while collecting the conflicting diffs
 
-            var textDifferencingService = _oldSolution.Services.GetRequiredService<IDocumentTextDifferencingService>();
-            var appliedChanges = await textDifferencingService.GetTextChangesAsync(_oldSolution.GetDocument(linkedDocumentGroup.First()), _newSolution.GetDocument(linkedDocumentGroup.First()), cancellationToken).ConfigureAwait(false);
+            var textDifferencingService = oldSolution.Services.GetRequiredService<IDocumentTextDifferencingService>();
+            var appliedChanges = await textDifferencingService.GetTextChangesAsync(oldSolution.GetDocument(linkedDocumentGroup.First()), newSolution.GetDocument(linkedDocumentGroup.First()), cancellationToken).ConfigureAwait(false);
             var unmergedChanges = new List<UnmergedDocumentChanges>();
 
             foreach (var documentId in linkedDocumentGroup.Skip(1))
             {
                 appliedChanges = await AddDocumentMergeChangesAsync(
-                    _oldSolution.GetDocument(documentId),
-                    _newSolution.GetDocument(documentId),
+                    oldSolution.GetDocument(documentId),
+                    newSolution.GetDocument(documentId),
                     appliedChanges.ToList(),
                     unmergedChanges,
                     groupSessionInfo,
@@ -101,7 +90,7 @@ private async Task<LinkedFileMergeResult> MergeLinkedDocumentGroupAsync(
                     cancellationToken).ConfigureAwait(false);
             }
 
-            var originalDocument = _oldSolution.GetDocument(linkedDocumentGroup.First());
+            var originalDocument = oldSolution.GetDocument(linkedDocumentGroup.First());
             var originalSourceText = await originalDocument.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
 
             // Add comments in source explaining diffs that could not be merged
@@ -111,7 +100,7 @@ private async Task<LinkedFileMergeResult> MergeLinkedDocumentGroupAsync(
 
             if (unmergedChanges.Any())
             {
-                mergeConflictHandler ??= _oldSolution.GetDocument(linkedDocumentGroup.First()).GetLanguageService<ILinkedFileMergeConflictCommentAdditionService>();
+                mergeConflictHandler ??= oldSolution.GetDocument(linkedDocumentGroup.First()).GetLanguageService<ILinkedFileMergeConflictCommentAdditionService>();
                 var mergeConflictTextEdits = mergeConflictHandler.CreateEdits(originalSourceText, unmergedChanges);
 
                 allChanges = MergeChangesWithMergeFailComments(appliedChanges, mergeConflictTextEdits, mergeConflictResolutionSpan, groupSessionInfo);
@@ -121,7 +110,7 @@ private async Task<LinkedFileMergeResult> MergeLinkedDocumentGroupAsync(
                 allChanges = appliedChanges;
             }
 
-            groupSessionInfo.LinkedDocuments = _newSolution.GetDocumentIdsWithFilePath(originalDocument.FilePath).Length;
+            groupSessionInfo.LinkedDocuments = newSolution.GetDocumentIdsWithFilePath(originalDocument.FilePath).Length;
             groupSessionInfo.DocumentsWithChanges = linkedDocumentGroup.Count();
             sessionInfo.LogLinkedFileResult(groupSessionInfo);
 
diff --git a/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileMergeResult.cs b/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileMergeResult.cs
index 4b068a489a9b3..772d2b1377a28 100644
--- a/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileMergeResult.cs
+++ b/src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileMergeResult.cs
@@ -10,18 +10,11 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    internal sealed class LinkedFileMergeResult
+    internal sealed class LinkedFileMergeResult(IEnumerable<DocumentId> documentIds, SourceText mergedSourceText, IEnumerable<TextSpan> mergeConflictResolutionSpans)
     {
-        public IEnumerable<DocumentId> DocumentIds { get; internal set; }
-        public SourceText MergedSourceText { get; internal set; }
-        public IEnumerable<TextSpan> MergeConflictResolutionSpans { get; }
+        public IEnumerable<DocumentId> DocumentIds { get; internal set; } = documentIds;
+        public SourceText MergedSourceText { get; internal set; } = mergedSourceText;
+        public IEnumerable<TextSpan> MergeConflictResolutionSpans { get; } = mergeConflictResolutionSpans;
         public bool HasMergeConflicts { get { return MergeConflictResolutionSpans.Any(); } }
-
-        public LinkedFileMergeResult(IEnumerable<DocumentId> documentIds, SourceText mergedSourceText, IEnumerable<TextSpan> mergeConflictResolutionSpans)
-        {
-            DocumentIds = documentIds;
-            MergedSourceText = mergedSourceText;
-            MergeConflictResolutionSpans = mergeConflictResolutionSpans;
-        }
     }
 }
diff --git a/src/Workspaces/Core/Portable/LinkedFileDiffMerging/UnmergedDocumentChanges.cs b/src/Workspaces/Core/Portable/LinkedFileDiffMerging/UnmergedDocumentChanges.cs
index 24641c125c941..dc556c927988c 100644
--- a/src/Workspaces/Core/Portable/LinkedFileDiffMerging/UnmergedDocumentChanges.cs
+++ b/src/Workspaces/Core/Portable/LinkedFileDiffMerging/UnmergedDocumentChanges.cs
@@ -9,17 +9,10 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    internal sealed class UnmergedDocumentChanges
+    internal sealed class UnmergedDocumentChanges(IEnumerable<TextChange> unmergedChanges, string projectName, DocumentId documentId)
     {
-        public IEnumerable<TextChange> UnmergedChanges { get; }
-        public string ProjectName { get; }
-        public DocumentId DocumentId { get; }
-
-        public UnmergedDocumentChanges(IEnumerable<TextChange> unmergedChanges, string projectName, DocumentId documentId)
-        {
-            UnmergedChanges = unmergedChanges;
-            ProjectName = projectName;
-            DocumentId = documentId;
-        }
+        public IEnumerable<TextChange> UnmergedChanges { get; } = unmergedChanges;
+        public string ProjectName { get; } = projectName;
+        public DocumentId DocumentId { get; } = documentId;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Log/EtwLogger.cs b/src/Workspaces/Core/Portable/Log/EtwLogger.cs
index 0221e670d55f6..b14f5ad32e9d8 100644
--- a/src/Workspaces/Core/Portable/Log/EtwLogger.cs
+++ b/src/Workspaces/Core/Portable/Log/EtwLogger.cs
@@ -14,19 +14,15 @@ namespace Microsoft.CodeAnalysis.Internal.Log
     /// <summary>
     /// A logger that publishes events to ETW using an EventSource.
     /// </summary>
-    internal sealed class EtwLogger : ILogger
+    internal sealed class EtwLogger(Func<FunctionId, bool> isEnabledPredicate) : ILogger
     {
-        private readonly Func<FunctionId, bool> _isEnabledPredicate;
 
         // Due to ETW specifics, RoslynEventSource.Instance needs to be initialized during EtwLogger construction 
         // so that we can enable the listeners synchronously before any events are logged.
         private readonly RoslynEventSource _source = RoslynEventSource.Instance;
 
-        public EtwLogger(Func<FunctionId, bool> isEnabledPredicate)
-            => _isEnabledPredicate = isEnabledPredicate;
-
         public bool IsEnabled(FunctionId functionId)
-            => _source.IsEnabled() && _isEnabledPredicate(functionId);
+            => _source.IsEnabled() && isEnabledPredicate(functionId);
 
         public void Log(FunctionId functionId, LogMessage logMessage)
             => _source.Log(GetMessage(logMessage), functionId);
diff --git a/src/Workspaces/Core/Portable/Log/InteractionClass.cs b/src/Workspaces/Core/Portable/Log/InteractionClass.cs
index 67ec23d3b1e6b..820d8bc60f0c0 100644
--- a/src/Workspaces/Core/Portable/Log/InteractionClass.cs
+++ b/src/Workspaces/Core/Portable/Log/InteractionClass.cs
@@ -29,13 +29,8 @@ internal enum InteractionClass
     }
 
     [AttributeUsage(AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
-    internal class PerfGoalAttribute : Attribute
+    internal class PerfGoalAttribute(InteractionClass interactionClass) : Attribute
     {
-        private readonly InteractionClass _interactionClass;
-
-        public PerfGoalAttribute(InteractionClass interactionClass)
-            => _interactionClass = interactionClass;
-
-        public InteractionClass InteractionClass => _interactionClass;
+        public InteractionClass InteractionClass => interactionClass;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Log/KeyValueLogMessage.cs b/src/Workspaces/Core/Portable/Log/KeyValueLogMessage.cs
index dbbcc1029dbdc..971b99a06671d 100644
--- a/src/Workspaces/Core/Portable/Log/KeyValueLogMessage.cs
+++ b/src/Workspaces/Core/Portable/Log/KeyValueLogMessage.cs
@@ -81,6 +81,12 @@ public bool ContainsProperty
             }
         }
 
+        public bool TryGetValue(string key, out object? value)
+        {
+            EnsureMap();
+            return _lazyMap.TryGetValue(key, out value);
+        }
+
         protected override string CreateMessage()
         {
             EnsureMap();
@@ -176,11 +182,11 @@ internal enum LogType
         /// <summary>
         /// Log some traces of an activity (default)
         /// </summary>
-        Trace,
+        Trace = 0,
 
         /// <summary>
         /// Log an user explicit action
         /// </summary>
-        UserAction,
+        UserAction = 1,
     }
 }
diff --git a/src/Workspaces/Core/Portable/Log/PiiValue.cs b/src/Workspaces/Core/Portable/Log/PiiValue.cs
index 775cf2227ab26..0bbac7b214613 100644
--- a/src/Workspaces/Core/Portable/Log/PiiValue.cs
+++ b/src/Workspaces/Core/Portable/Log/PiiValue.cs
@@ -10,12 +10,9 @@ namespace Microsoft.CodeAnalysis.Internal.Log
     /// <summary>
     /// Represents telemetry data that's classified as personally identifiable information.
     /// </summary>
-    internal sealed class PiiValue
+    internal sealed class PiiValue(object value)
     {
-        public readonly object Value;
-
-        public PiiValue(object value)
-            => Value = value;
+        public readonly object Value = value;
 
         public override string? ToString()
             => Value.ToString();
diff --git a/src/Workspaces/Core/Portable/Log/StatisticResult.cs b/src/Workspaces/Core/Portable/Log/StatisticResult.cs
index 2c8b19e495bfd..469a17e20b410 100644
--- a/src/Workspaces/Core/Portable/Log/StatisticResult.cs
+++ b/src/Workspaces/Core/Portable/Log/StatisticResult.cs
@@ -9,7 +9,7 @@
 
 namespace Microsoft.CodeAnalysis.Internal.Log
 {
-    internal readonly struct StatisticResult
+    internal readonly struct StatisticResult(int max, int min, double mean, int range, int? mode, int count)
     {
         public static StatisticResult FromList(List<int> values)
         {
@@ -42,42 +42,32 @@ public static StatisticResult FromList(List<int> values)
         /// <summary>
         /// maximum value
         /// </summary>
-        public readonly int Maximum;
+        public readonly int Maximum = max;
 
         /// <summary>
         /// minimum value
         /// </summary>
-        public readonly int Minimum;
+        public readonly int Minimum = min;
 
         /// <summary>
         /// average value of the total data set
         /// </summary>
-        public readonly double Mean;
+        public readonly double Mean = mean;
 
         /// <summary>
         /// most frequent value in the total data set
         /// </summary>
-        public readonly int? Mode;
+        public readonly int? Mode = mode;
 
         /// <summary>
         /// difference between max and min value
         /// </summary>
-        public readonly int Range;
+        public readonly int Range = range;
 
         /// <summary>
         /// number of data points in the total data set
         /// </summary>
-        public readonly int Count;
-
-        public StatisticResult(int max, int min, double mean, int range, int? mode, int count)
-        {
-            this.Maximum = max;
-            this.Minimum = min;
-            this.Mean = mean;
-            this.Range = range;
-            this.Mode = mode;
-            this.Count = count;
-        }
+        public readonly int Count = count;
 
         /// <summary>
         /// Writes out these statistics to a property bag for sending to telemetry.
diff --git a/src/Workspaces/Core/Portable/Log/TraceLogger.cs b/src/Workspaces/Core/Portable/Log/TraceLogger.cs
index 1fa359d24c610..abcf3bc3391c8 100644
--- a/src/Workspaces/Core/Portable/Log/TraceLogger.cs
+++ b/src/Workspaces/Core/Portable/Log/TraceLogger.cs
@@ -11,17 +11,12 @@ namespace Microsoft.CodeAnalysis.Internal.Log
     /// <summary>
     /// Implementation of <see cref="ILogger"/> that produce timing debug output. 
     /// </summary>
-    internal sealed class TraceLogger : ILogger
+    internal sealed class TraceLogger(Func<FunctionId, bool>? isEnabledPredicate) : ILogger
     {
         public static readonly TraceLogger Instance = new(isEnabledPredicate: null);
 
-        private readonly Func<FunctionId, bool>? _isEnabledPredicate;
-
-        public TraceLogger(Func<FunctionId, bool>? isEnabledPredicate)
-            => _isEnabledPredicate = isEnabledPredicate;
-
         public bool IsEnabled(FunctionId functionId)
-            => _isEnabledPredicate == null || _isEnabledPredicate(functionId);
+            => isEnabledPredicate == null || isEnabledPredicate(functionId);
 
         public void Log(FunctionId functionId, LogMessage logMessage)
             => Trace.WriteLine(string.Format("[{0}] {1} - {2}", Environment.CurrentManagedThreadId, functionId.ToString(), logMessage.GetMessage()));
diff --git a/src/Workspaces/Core/Portable/Microsoft.CodeAnalysis.Workspaces.csproj b/src/Workspaces/Core/Portable/Microsoft.CodeAnalysis.Workspaces.csproj
index 27fa7e51c329c..a1f280799b925 100644
--- a/src/Workspaces/Core/Portable/Microsoft.CodeAnalysis.Workspaces.csproj
+++ b/src/Workspaces/Core/Portable/Microsoft.CodeAnalysis.Workspaces.csproj
@@ -55,13 +55,15 @@
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.Debugger" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.UnitTesting" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.Features" />
+    <InternalsVisibleTo Include="Microsoft.VisualStudio.LanguageServices.DevKit" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.BuildManager" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.BuildManager.Core" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.BuildManager.UnitTests" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.Orchestrator" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.Orchestrator.UnitTests" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.Test.Utilities" Partner="UnitTesting" Key="$(UnitTestingKey)" />
-    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" Key="$(MicrosoftCodeAnalysisLanguageServerKey)" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.Protocol" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.Protocol.UnitTests" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServerIndexFormat.Generator" />
diff --git a/src/Workspaces/Core/Portable/Notification/AbstractGlobalOperationNotificationService.GlobalOperationRegistration.cs b/src/Workspaces/Core/Portable/Notification/AbstractGlobalOperationNotificationService.GlobalOperationRegistration.cs
index d6cdf2421ccc0..1f38256b88c40 100644
--- a/src/Workspaces/Core/Portable/Notification/AbstractGlobalOperationNotificationService.GlobalOperationRegistration.cs
+++ b/src/Workspaces/Core/Portable/Notification/AbstractGlobalOperationNotificationService.GlobalOperationRegistration.cs
@@ -10,17 +10,12 @@ namespace Microsoft.CodeAnalysis.Notification;
 
 internal partial class AbstractGlobalOperationNotificationService
 {
-    private class GlobalOperationRegistration : IDisposable
+    private class GlobalOperationRegistration(AbstractGlobalOperationNotificationService service) : IDisposable
     {
-        private readonly AbstractGlobalOperationNotificationService _service;
-
-        public GlobalOperationRegistration(AbstractGlobalOperationNotificationService service)
-            => _service = service;
-
         public void Dispose()
         {
             // Inform any listeners that we're finished.
-            _service.Done(this);
+            service.Done(this);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Options/GlobalOptionService.cs b/src/Workspaces/Core/Portable/Options/GlobalOptionService.cs
index 6d8d8a0e1c353..86eb14e8de8ba 100644
--- a/src/Workspaces/Core/Portable/Options/GlobalOptionService.cs
+++ b/src/Workspaces/Core/Portable/Options/GlobalOptionService.cs
@@ -17,34 +17,25 @@
 namespace Microsoft.CodeAnalysis.Options
 {
     [Export(typeof(IGlobalOptionService)), Shared]
-    internal sealed class GlobalOptionService : IGlobalOptionService
+    [method: ImportingConstructor]
+    [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    internal sealed class GlobalOptionService(
+        [Import(AllowDefault = true)] IWorkspaceThreadingService? workspaceThreadingService,
+        [ImportMany] IEnumerable<Lazy<IOptionPersisterProvider>> optionPersisters) : IGlobalOptionService
     {
-        private readonly IWorkspaceThreadingService? _workspaceThreadingService;
-        private readonly ImmutableArray<Lazy<IOptionPersisterProvider>> _optionPersisterProviders;
+        private readonly ImmutableArray<Lazy<IOptionPersisterProvider>> _optionPersisterProviders = optionPersisters.ToImmutableArray();
 
         private readonly object _gate = new();
 
         #region Guarded by _gate
 
         private ImmutableArray<IOptionPersister> _lazyOptionPersisters;
-        private ImmutableDictionary<OptionKey2, object?> _currentValues;
+        private ImmutableDictionary<OptionKey2, object?> _currentValues = ImmutableDictionary.Create<OptionKey2, object?>();
 
         #endregion
 
         private readonly WeakEvent<OptionChangedEventArgs> _optionChanged = new();
 
-        [ImportingConstructor]
-        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public GlobalOptionService(
-            [Import(AllowDefault = true)] IWorkspaceThreadingService? workspaceThreadingService,
-            [ImportMany] IEnumerable<Lazy<IOptionPersisterProvider>> optionPersisters)
-        {
-            _workspaceThreadingService = workspaceThreadingService;
-            _optionPersisterProviders = optionPersisters.ToImmutableArray();
-
-            _currentValues = ImmutableDictionary.Create<OptionKey2, object?>();
-        }
-
         private ImmutableArray<IOptionPersister> GetOptionPersisters()
         {
             if (_lazyOptionPersisters.IsDefault)
@@ -55,7 +46,7 @@ private ImmutableArray<IOptionPersister> GetOptionPersisters()
 
                 ImmutableInterlocked.InterlockedInitialize(
                     ref _lazyOptionPersisters,
-                    GetOptionPersistersSlow(_workspaceThreadingService, _optionPersisterProviders, CancellationToken.None));
+                    GetOptionPersistersSlow(workspaceThreadingService, _optionPersisterProviders, CancellationToken.None));
             }
 
             return _lazyOptionPersisters;
diff --git a/src/Workspaces/Core/Portable/Options/LegacyGlobalCodeActionOptionsWorkspaceService.cs b/src/Workspaces/Core/Portable/Options/LegacyGlobalCodeActionOptionsWorkspaceService.cs
index 20a7881d40970..3c3fdb47c529c 100644
--- a/src/Workspaces/Core/Portable/Options/LegacyGlobalCodeActionOptionsWorkspaceService.cs
+++ b/src/Workspaces/Core/Portable/Options/LegacyGlobalCodeActionOptionsWorkspaceService.cs
@@ -23,52 +23,42 @@ namespace Microsoft.CodeAnalysis.Options;
 /// Enables legacy APIs to access global options from workspace.
 /// </summary>
 [ExportWorkspaceService(typeof(ILegacyGlobalCleanCodeGenerationOptionsWorkspaceService)), Shared]
-internal sealed class LegacyGlobalCleanCodeGenerationOptionsWorkspaceService : ILegacyGlobalCleanCodeGenerationOptionsWorkspaceService
+[method: ImportingConstructor]
+[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+internal sealed class LegacyGlobalCleanCodeGenerationOptionsWorkspaceService(IGlobalOptionService globalOptions) : ILegacyGlobalCleanCodeGenerationOptionsWorkspaceService
 {
-    public CleanCodeGenerationOptionsProvider Provider { get; }
+    public CleanCodeGenerationOptionsProvider Provider { get; } = new ProviderImpl(globalOptions);
 
-    [ImportingConstructor]
-    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-    public LegacyGlobalCleanCodeGenerationOptionsWorkspaceService(IGlobalOptionService globalOptions)
+    private sealed class ProviderImpl(IOptionsReader options) : CleanCodeGenerationOptionsProvider
     {
-        Provider = new ProviderImpl(globalOptions);
-    }
-
-    private sealed class ProviderImpl : CleanCodeGenerationOptionsProvider
-    {
-        private readonly IOptionsReader _options;
-
-        public ProviderImpl(IOptionsReader options)
-            => _options = options;
-
         ValueTask<LineFormattingOptions> OptionsProvider<LineFormattingOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetLineFormattingOptions(languageServices.Language, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetLineFormattingOptions(languageServices.Language, fallbackOptions: null));
 
         ValueTask<DocumentFormattingOptions> OptionsProvider<DocumentFormattingOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetDocumentFormattingOptions(fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetDocumentFormattingOptions(fallbackOptions: null));
 
         ValueTask<SyntaxFormattingOptions> OptionsProvider<SyntaxFormattingOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetSyntaxFormattingOptions(languageServices, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetSyntaxFormattingOptions(languageServices, fallbackOptions: null));
 
         ValueTask<SimplifierOptions> OptionsProvider<SimplifierOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetSimplifierOptions(languageServices, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetSimplifierOptions(languageServices, fallbackOptions: null));
 
         ValueTask<AddImportPlacementOptions> OptionsProvider<AddImportPlacementOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetAddImportPlacementOptions(languageServices, allowInHiddenRegions: null, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetAddImportPlacementOptions(languageServices, allowInHiddenRegions: null, fallbackOptions: null));
 
         ValueTask<CodeCleanupOptions> OptionsProvider<CodeCleanupOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetCodeCleanupOptions(languageServices, allowImportsInHiddenRegions: null, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetCodeCleanupOptions(languageServices, allowImportsInHiddenRegions: null, fallbackOptions: null));
 
         ValueTask<CleanCodeGenerationOptions> OptionsProvider<CleanCodeGenerationOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetCleanCodeGenerationOptions(languageServices, allowImportsInHiddenRegions: null, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetCleanCodeGenerationOptions(languageServices, allowImportsInHiddenRegions: null, fallbackOptions: null));
 
         ValueTask<CodeAndImportGenerationOptions> OptionsProvider<CodeAndImportGenerationOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetCodeAndImportGenerationOptions(languageServices, allowImportsInHiddenRegions: null, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetCodeAndImportGenerationOptions(languageServices, allowImportsInHiddenRegions: null, fallbackOptions: null));
 
         ValueTask<CodeGenerationOptions> OptionsProvider<CodeGenerationOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetCodeGenerationOptions(languageServices, fallbackOptions: null));
+            => ValueTaskFactory.FromResult(options.GetCodeGenerationOptions(languageServices, fallbackOptions: null));
 
         ValueTask<NamingStylePreferences> OptionsProvider<NamingStylePreferences>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GetOption(NamingStyleOptions.NamingPreferences, languageServices.Language));
+            => ValueTaskFactory.FromResult(options.GetOption(NamingStyleOptions.NamingPreferences, languageServices.Language));
     }
 }
diff --git a/src/Workspaces/Core/Portable/Options/LegacyWorkspaceOptionService.cs b/src/Workspaces/Core/Portable/Options/LegacyWorkspaceOptionService.cs
index c09829e856e3a..16d75f3afa5e5 100644
--- a/src/Workspaces/Core/Portable/Options/LegacyWorkspaceOptionService.cs
+++ b/src/Workspaces/Core/Portable/Options/LegacyWorkspaceOptionService.cs
@@ -14,37 +14,27 @@
 namespace Microsoft.CodeAnalysis.Options;
 
 [Export(typeof(ILegacyGlobalOptionService)), Shared]
-internal sealed class LegacyGlobalOptionService : ILegacyGlobalOptionService
+[method: ImportingConstructor]
+[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+internal sealed class LegacyGlobalOptionService(IGlobalOptionService globalOptionService) : ILegacyGlobalOptionService
 {
     [ExportWorkspaceService(typeof(ILegacyWorkspaceOptionService)), Shared]
-    internal sealed class WorkspaceService : ILegacyWorkspaceOptionService
+    [method: ImportingConstructor]
+    [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    internal sealed class WorkspaceService(ILegacyGlobalOptionService legacyGlobalOptions) : ILegacyWorkspaceOptionService
     {
-        public ILegacyGlobalOptionService LegacyGlobalOptions { get; }
-
-        [ImportingConstructor]
-        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public WorkspaceService(ILegacyGlobalOptionService legacyGlobalOptions)
-            => LegacyGlobalOptions = legacyGlobalOptions;
+        public ILegacyGlobalOptionService LegacyGlobalOptions { get; } = legacyGlobalOptions;
     }
 
-    public IGlobalOptionService GlobalOptions { get; }
+    public IGlobalOptionService GlobalOptions { get; } = globalOptionService;
 
     // access is interlocked
-    private ImmutableArray<WeakReference<Workspace>> _registeredWorkspaces;
+    private ImmutableArray<WeakReference<Workspace>> _registeredWorkspaces = ImmutableArray<WeakReference<Workspace>>.Empty;
 
     /// <summary>
     /// Stores options that are not defined by Roslyn and do not implement <see cref="IOption2"/>.
     /// </summary>
-    private ImmutableDictionary<OptionKey, object?> _currentExternallyDefinedOptionValues;
-
-    [ImportingConstructor]
-    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-    public LegacyGlobalOptionService(IGlobalOptionService globalOptionService)
-    {
-        GlobalOptions = globalOptionService;
-        _registeredWorkspaces = ImmutableArray<WeakReference<Workspace>>.Empty;
-        _currentExternallyDefinedOptionValues = ImmutableDictionary.Create<OptionKey, object?>();
-    }
+    private ImmutableDictionary<OptionKey, object?> _currentExternallyDefinedOptionValues = ImmutableDictionary.Create<OptionKey, object?>();
 
     public object? GetExternallyDefinedOption(OptionKey key)
     {
diff --git a/src/Workspaces/Core/Portable/Packaging/IPackageInstallerService.cs b/src/Workspaces/Core/Portable/Packaging/IPackageInstallerService.cs
index 883ed7f7d15d5..3a2baaceebd65 100644
--- a/src/Workspaces/Core/Portable/Packaging/IPackageInstallerService.cs
+++ b/src/Workspaces/Core/Portable/Packaging/IPackageInstallerService.cs
@@ -45,19 +45,13 @@ Task<bool> TryInstallPackageAsync(
     }
 
     [DataContract]
-    internal readonly struct PackageSource : IEquatable<PackageSource>
+    internal readonly struct PackageSource(string name, string source) : IEquatable<PackageSource>
     {
         [DataMember(Order = 0)]
-        public readonly string Name;
+        public readonly string Name = name;
 
         [DataMember(Order = 1)]
-        public readonly string Source;
-
-        public PackageSource(string name, string source)
-        {
-            Name = name;
-            Source = source;
-        }
+        public readonly string Source = source;
 
         public override bool Equals(object? obj)
             => obj is PackageSource source && Equals(source);
diff --git a/src/Workspaces/Core/Portable/PatternMatching/AllLowerCamelCaseMatcher.cs b/src/Workspaces/Core/Portable/PatternMatching/AllLowerCamelCaseMatcher.cs
index 9571c2b790d07..787a79e2fdcfb 100644
--- a/src/Workspaces/Core/Portable/PatternMatching/AllLowerCamelCaseMatcher.cs
+++ b/src/Workspaces/Core/Portable/PatternMatching/AllLowerCamelCaseMatcher.cs
@@ -21,24 +21,13 @@ internal partial class PatternMatcher
         /// a candidate using CamelCase matching. i.e. this code is responsible for finding the
         /// match between "cofipro" and "CodeFixProvider". 
         /// </summary>
-        private readonly struct AllLowerCamelCaseMatcher
+        private readonly struct AllLowerCamelCaseMatcher(
+            bool includeMatchedSpans,
+            string candidate,
+            string patternChunkText,
+            TextInfo textInfo)
         {
-            private readonly bool _includeMatchedSpans;
-            private readonly string _candidate;
-            private readonly string _patternText;
-            private readonly TextInfo _textInfo;
-
-            public AllLowerCamelCaseMatcher(
-                bool includeMatchedSpans,
-                string candidate,
-                string patternChunkText,
-                TextInfo textInfo)
-            {
-                _includeMatchedSpans = includeMatchedSpans;
-                _candidate = candidate;
-                _patternText = patternChunkText;
-                _textInfo = textInfo;
-            }
+            private readonly TextInfo _textInfo = textInfo;
 
             /// <summary>
             /// Returns null if no match was found, 1 if a contiguous match was found, 2 if a 
@@ -65,7 +54,7 @@ public AllLowerCamelCaseMatcher(
                     return null;
                 }
 
-                matchedSpans = _includeMatchedSpans && result.Value.MatchedSpansInReverse != null
+                matchedSpans = includeMatchedSpans && result.Value.MatchedSpansInReverse != null
                     ? new NormalizedTextSpanCollection(result.Value.MatchedSpansInReverse).ToImmutableArray()
                     : ImmutableArray<TextSpan>.Empty;
 
@@ -79,11 +68,11 @@ private static PatternMatchKind GetKind(CamelCaseResult result, in TemporaryArra
             private CamelCaseResult? TryMatch(
                 int patternIndex, int candidateHumpIndex, bool? contiguous, in TemporaryArray<TextSpan> candidateHumps)
             {
-                if (patternIndex == _patternText.Length)
+                if (patternIndex == patternChunkText.Length)
                 {
                     // We hit the end.  So we were able to match against this candidate.
                     // We are contiguous if our contiguous tracker was not set to false.
-                    var matchedSpansInReverse = _includeMatchedSpans ? ArrayBuilder<TextSpan>.GetInstance() : null;
+                    var matchedSpansInReverse = includeMatchedSpans ? ArrayBuilder<TextSpan>.GetInstance() : null;
                     return new CamelCaseResult(
                         fromStart: false,
                         contiguous: contiguous != false,
@@ -94,7 +83,7 @@ private static PatternMatchKind GetKind(CamelCaseResult result, in TemporaryArra
                 var bestResult = (CamelCaseResult?)null;
 
                 // Look for a hump in the candidate that matches the current letter we're on.
-                var patternCharacter = _patternText[patternIndex];
+                var patternCharacter = patternChunkText[patternIndex];
                 for (int humpIndex = candidateHumpIndex, n = candidateHumps.Count; humpIndex < n; humpIndex++)
                 {
                     // If we've been contiguous, but we jumped past a hump, then we're no longer contiguous.
@@ -104,7 +93,7 @@ private static PatternMatchKind GetKind(CamelCaseResult result, in TemporaryArra
                     }
 
                     var candidateHump = candidateHumps[humpIndex];
-                    if (ToLower(_candidate[candidateHump.Start], _textInfo) == patternCharacter)
+                    if (ToLower(candidate[candidateHump.Start], _textInfo) == patternCharacter)
                     {
                         // Found a hump in the candidate string that matches the current pattern
                         // character we're on.  i.e. we matched the c in cofipro against the C in 
@@ -163,15 +152,15 @@ private static char ToLowerAsciiInvariant(char c)
 
                 var candidateHump = candidateHumps[humpIndex];
 
-                var maxPatternHumpLength = _patternText.Length - patternIndex;
+                var maxPatternHumpLength = patternChunkText.Length - patternIndex;
                 var maxCandidateHumpLength = candidateHump.Length;
 
                 var maxHumpMatchLength = Math.Min(maxPatternHumpLength, maxCandidateHumpLength);
                 for (var possibleHumpMatchLength = 1; possibleHumpMatchLength <= maxHumpMatchLength; possibleHumpMatchLength++)
                 {
                     if (!LowercaseSubstringsMatch(
-                            _candidate, candidateHump.Start,
-                            _patternText, patternIndex, possibleHumpMatchLength))
+                            candidate, candidateHump.Start,
+                            patternChunkText, patternIndex, possibleHumpMatchLength))
                     {
                         // Stop trying to consume once the pattern contents no longer matches
                         // against the current candidate hump.
diff --git a/src/Workspaces/Core/Portable/PatternMatching/PatternMatcher.PatternSegment.cs b/src/Workspaces/Core/Portable/PatternMatching/PatternMatcher.PatternSegment.cs
index 5f0df83552c97..5f912cea3b674 100644
--- a/src/Workspaces/Core/Portable/PatternMatching/PatternMatcher.PatternSegment.cs
+++ b/src/Workspaces/Core/Portable/PatternMatching/PatternMatcher.PatternSegment.cs
@@ -18,24 +18,18 @@ internal partial class PatternMatcher
         /// can break the segment into.
         /// </summary>
         [NonCopyable]
-        private struct PatternSegment : IDisposable
+        private struct PatternSegment(string text, bool allowFuzzyMatching) : IDisposable
         {
             // Information about the entire piece of text between the dots.  For example, if the 
             // text between the dots is 'Get-Keyword', then TotalTextChunk.Text will be 'Get-Keyword' and 
             // TotalTextChunk.CharacterSpans will correspond to 'G', 'et', 'K' and 'eyword'.
-            public TextChunk TotalTextChunk;
+            public TextChunk TotalTextChunk = new TextChunk(text, allowFuzzyMatching);
 
             // Information about the subwords compromising the total word.  For example, if the 
             // text between the dots is 'Get-Keyword', then the subwords will be 'Get' and 'Keyword'
             // Those individual words will have CharacterSpans of ('G' and 'et') and ('K' and 'eyword')
             // respectively.
-            public readonly TextChunk[] SubWordTextChunks;
-
-            public PatternSegment(string text, bool allowFuzzyMatching)
-            {
-                this.TotalTextChunk = new TextChunk(text, allowFuzzyMatching);
-                this.SubWordTextChunks = BreakPatternIntoSubWords(text, allowFuzzyMatching);
-            }
+            public readonly TextChunk[] SubWordTextChunks = BreakPatternIntoSubWords(text, allowFuzzyMatching);
 
             public void Dispose()
             {
diff --git a/src/Workspaces/Core/Portable/Recommendations/IRecommendationService.cs b/src/Workspaces/Core/Portable/Recommendations/IRecommendationService.cs
index 9227fe209690c..ce16806bbaf03 100644
--- a/src/Workspaces/Core/Portable/Recommendations/IRecommendationService.cs
+++ b/src/Workspaces/Core/Portable/Recommendations/IRecommendationService.cs
@@ -17,32 +17,24 @@ RecommendedSymbols GetRecommendedSymbolsInContext(
             CancellationToken cancellationToken);
     }
 
-    internal readonly struct RecommendedSymbols
+    internal readonly struct RecommendedSymbols(
+        ImmutableArray<ISymbol> namedSymbols,
+        ImmutableArray<ISymbol> unnamedSymbols = default)
     {
-        private readonly ImmutableArray<ISymbol> _namedSymbols;
-        private readonly ImmutableArray<ISymbol> _unnamedSymbols;
 
         /// <summary>
         /// The named symbols to recommend.
         /// </summary>
-        public ImmutableArray<ISymbol> NamedSymbols => _namedSymbols.NullToEmpty();
+        public ImmutableArray<ISymbol> NamedSymbols => namedSymbols.NullToEmpty();
 
         /// <summary>
         /// The unnamed symbols to recommend.  For example, operators, conversions and indexers.
         /// </summary>
-        public ImmutableArray<ISymbol> UnnamedSymbols => _unnamedSymbols.NullToEmpty();
+        public ImmutableArray<ISymbol> UnnamedSymbols => unnamedSymbols.NullToEmpty();
 
         public RecommendedSymbols(ImmutableArray<ISymbol> namedSymbols)
             : this(namedSymbols, default)
         {
         }
-
-        public RecommendedSymbols(
-            ImmutableArray<ISymbol> namedSymbols,
-            ImmutableArray<ISymbol> unnamedSymbols = default)
-        {
-            _namedSymbols = namedSymbols;
-            _unnamedSymbols = unnamedSymbols;
-        }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Remote/RemoteArguments.cs b/src/Workspaces/Core/Portable/Remote/RemoteArguments.cs
index b049cf47751ff..de37b47ad66e8 100644
--- a/src/Workspaces/Core/Portable/Remote/RemoteArguments.cs
+++ b/src/Workspaces/Core/Portable/Remote/RemoteArguments.cs
@@ -21,19 +21,13 @@ namespace Microsoft.CodeAnalysis.Remote
     #region FindReferences
 
     [DataContract]
-    internal sealed class SerializableSymbolAndProjectId : IEquatable<SerializableSymbolAndProjectId>
+    internal sealed class SerializableSymbolAndProjectId(string symbolKeyData, ProjectId projectId) : IEquatable<SerializableSymbolAndProjectId>
     {
         [DataMember(Order = 0)]
-        public readonly string SymbolKeyData;
+        public readonly string SymbolKeyData = symbolKeyData;
 
         [DataMember(Order = 1)]
-        public readonly ProjectId ProjectId;
-
-        public SerializableSymbolAndProjectId(string symbolKeyData, ProjectId projectId)
-        {
-            SymbolKeyData = symbolKeyData;
-            ProjectId = projectId;
-        }
+        public readonly ProjectId ProjectId = projectId;
 
         public override bool Equals(object? obj)
             => Equals(obj as SerializableSymbolAndProjectId);
@@ -132,46 +126,35 @@ public static bool TryCreate(
     }
 
     [DataContract]
-    internal readonly struct SerializableReferenceLocation
+    internal readonly struct SerializableReferenceLocation(
+        DocumentId document,
+        SerializableSymbolAndProjectId? alias,
+        TextSpan location,
+        bool isImplicit,
+        SymbolUsageInfo symbolUsageInfo,
+        ImmutableDictionary<string, string> additionalProperties,
+        CandidateReason candidateReason)
     {
         [DataMember(Order = 0)]
-        public readonly DocumentId Document;
+        public readonly DocumentId Document = document;
 
         [DataMember(Order = 1)]
-        public readonly SerializableSymbolAndProjectId? Alias;
+        public readonly SerializableSymbolAndProjectId? Alias = alias;
 
         [DataMember(Order = 2)]
-        public readonly TextSpan Location;
+        public readonly TextSpan Location = location;
 
         [DataMember(Order = 3)]
-        public readonly bool IsImplicit;
+        public readonly bool IsImplicit = isImplicit;
 
         [DataMember(Order = 4)]
-        public readonly SymbolUsageInfo SymbolUsageInfo;
+        public readonly SymbolUsageInfo SymbolUsageInfo = symbolUsageInfo;
 
         [DataMember(Order = 5)]
-        public readonly ImmutableDictionary<string, string> AdditionalProperties;
+        public readonly ImmutableDictionary<string, string> AdditionalProperties = additionalProperties;
 
         [DataMember(Order = 6)]
-        public readonly CandidateReason CandidateReason;
-
-        public SerializableReferenceLocation(
-            DocumentId document,
-            SerializableSymbolAndProjectId? alias,
-            TextSpan location,
-            bool isImplicit,
-            SymbolUsageInfo symbolUsageInfo,
-            ImmutableDictionary<string, string> additionalProperties,
-            CandidateReason candidateReason)
-        {
-            Document = document;
-            Alias = alias;
-            Location = location;
-            IsImplicit = isImplicit;
-            SymbolUsageInfo = symbolUsageInfo;
-            AdditionalProperties = additionalProperties;
-            CandidateReason = candidateReason;
-        }
+        public readonly CandidateReason CandidateReason = candidateReason;
 
         public static SerializableReferenceLocation Dehydrate(
             ReferenceLocation referenceLocation, CancellationToken cancellationToken)
@@ -215,18 +198,13 @@ public async ValueTask<ReferenceLocation> RehydrateAsync(
     }
 
     [DataContract]
-    internal class SerializableSymbolGroup : IEquatable<SerializableSymbolGroup>
+    internal class SerializableSymbolGroup(HashSet<SerializableSymbolAndProjectId> symbols) : IEquatable<SerializableSymbolGroup>
     {
         [DataMember(Order = 0)]
-        public readonly HashSet<SerializableSymbolAndProjectId> Symbols;
+        public readonly HashSet<SerializableSymbolAndProjectId> Symbols = new HashSet<SerializableSymbolAndProjectId>(symbols);
 
         private int _hashCode;
 
-        public SerializableSymbolGroup(HashSet<SerializableSymbolAndProjectId> symbols)
-        {
-            Symbols = new HashSet<SerializableSymbolAndProjectId>(symbols);
-        }
-
         public override bool Equals(object? obj)
             => obj is SerializableSymbolGroup group && Equals(group);
 
diff --git a/src/Workspaces/Core/Portable/Remote/RemoteOptionsProvider.cs b/src/Workspaces/Core/Portable/Remote/RemoteOptionsProvider.cs
index 0a04ed87b04c8..4c76bad83736c 100644
--- a/src/Workspaces/Core/Portable/Remote/RemoteOptionsProvider.cs
+++ b/src/Workspaces/Core/Portable/Remote/RemoteOptionsProvider.cs
@@ -14,17 +14,8 @@ namespace Microsoft.CodeAnalysis.Remote;
 /// Can be used when the remote API does not have an existing callback. If it does it can implement 
 /// <see cref="GetOptionsAsync(string, CancellationToken)"/> itself.
 /// </summary>
-internal sealed class RemoteOptionsProvider<TOptions>
+internal sealed class RemoteOptionsProvider<TOptions>(SolutionServices services, OptionsProvider<TOptions> optionsProvider)
 {
-    private readonly SolutionServices _services;
-    private readonly OptionsProvider<TOptions> _optionsProvider;
-
-    public RemoteOptionsProvider(SolutionServices services, OptionsProvider<TOptions> optionsProvider)
-    {
-        _services = services;
-        _optionsProvider = optionsProvider;
-    }
-
     internal ValueTask<TOptions> GetOptionsAsync(string language, CancellationToken cancellationToken)
-        => _optionsProvider.GetOptionsAsync(_services.GetLanguageServices(language), cancellationToken);
+        => optionsProvider.GetOptionsAsync(services.GetLanguageServices(language), cancellationToken);
 }
diff --git a/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatcher.cs b/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatcher.cs
index 4ed51833c319c..a9dfef4c69798 100644
--- a/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatcher.cs
+++ b/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatcher.cs
@@ -16,20 +16,13 @@ internal interface IRemoteServiceCallbackDispatcher
 
     internal class RemoteServiceCallbackDispatcher : IRemoteServiceCallbackDispatcher
     {
-        internal readonly struct Handle : IDisposable
+        internal readonly struct Handle(ConcurrentDictionary<RemoteServiceCallbackId, object> callbackInstances, RemoteServiceCallbackId callbackId) : IDisposable
         {
-            private readonly ConcurrentDictionary<RemoteServiceCallbackId, object> _callbackInstances;
-            public readonly RemoteServiceCallbackId Id;
-
-            public Handle(ConcurrentDictionary<RemoteServiceCallbackId, object> callbackInstances, RemoteServiceCallbackId callbackId)
-            {
-                _callbackInstances = callbackInstances;
-                Id = callbackId;
-            }
+            public readonly RemoteServiceCallbackId Id = callbackId;
 
             public void Dispose()
             {
-                Contract.ThrowIfTrue(_callbackInstances?.TryRemove(Id, out _) == false);
+                Contract.ThrowIfTrue(callbackInstances?.TryRemove(Id, out _) == false);
             }
         }
 
diff --git a/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatchers.cs b/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatchers.cs
index 47e8fb1ccaeff..6a51ebded63e5 100644
--- a/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatchers.cs
+++ b/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackDispatchers.cs
@@ -9,7 +9,7 @@
 
 namespace Microsoft.CodeAnalysis.Remote
 {
-    internal sealed class RemoteServiceCallbackDispatcherRegistry : IRemoteServiceCallbackDispatcherProvider
+    internal sealed class RemoteServiceCallbackDispatcherRegistry(IEnumerable<Lazy<IRemoteServiceCallbackDispatcher, RemoteServiceCallbackDispatcherRegistry.ExportMetadata>> dispatchers) : IRemoteServiceCallbackDispatcherProvider
     {
         public sealed class ExportMetadata
         {
@@ -26,10 +26,7 @@ public ExportMetadata(IDictionary<string, object> data)
             }
         }
 
-        private readonly ImmutableDictionary<Type, Lazy<IRemoteServiceCallbackDispatcher, ExportMetadata>> _callbackDispatchers;
-
-        public RemoteServiceCallbackDispatcherRegistry(IEnumerable<Lazy<IRemoteServiceCallbackDispatcher, ExportMetadata>> dispatchers)
-            => _callbackDispatchers = dispatchers.ToImmutableDictionary(d => d.Metadata.ServiceInterface);
+        private readonly ImmutableDictionary<Type, Lazy<IRemoteServiceCallbackDispatcher, ExportMetadata>> _callbackDispatchers = dispatchers.ToImmutableDictionary(d => d.Metadata.ServiceInterface);
 
         public IRemoteServiceCallbackDispatcher GetDispatcher(Type serviceType)
             => _callbackDispatchers[serviceType].Value;
diff --git a/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackId.cs b/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackId.cs
index 04108ca36efbc..d1277acb9f0da 100644
--- a/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackId.cs
+++ b/src/Workspaces/Core/Portable/Remote/RemoteServiceCallbackId.cs
@@ -8,13 +8,10 @@
 namespace Microsoft.CodeAnalysis.Remote
 {
     [DataContract]
-    internal readonly struct RemoteServiceCallbackId : IEquatable<RemoteServiceCallbackId>
+    internal readonly struct RemoteServiceCallbackId(int id) : IEquatable<RemoteServiceCallbackId>
     {
         [DataMember(Order = 0)]
-        public readonly int Id;
-
-        public RemoteServiceCallbackId(int id)
-            => Id = id;
+        public readonly int Id = id;
 
         public override bool Equals(object? obj)
             => obj is RemoteServiceCallbackId id && Equals(id);
diff --git a/src/Workspaces/Core/Portable/Rename/ConflictEngine/ComplexifiedSpan.cs b/src/Workspaces/Core/Portable/Rename/ConflictEngine/ComplexifiedSpan.cs
index a807d161e7a35..56970e4161422 100644
--- a/src/Workspaces/Core/Portable/Rename/ConflictEngine/ComplexifiedSpan.cs
+++ b/src/Workspaces/Core/Portable/Rename/ConflictEngine/ComplexifiedSpan.cs
@@ -9,22 +9,15 @@
 namespace Microsoft.CodeAnalysis.Rename.ConflictEngine
 {
     [DataContract]
-    internal readonly struct ComplexifiedSpan
+    internal readonly struct ComplexifiedSpan(TextSpan originalSpan, TextSpan newSpan, ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)> modifiedSubSpans)
     {
         [DataMember(Order = 0)]
-        public readonly TextSpan OriginalSpan;
+        public readonly TextSpan OriginalSpan = originalSpan;
 
         [DataMember(Order = 1)]
-        public readonly TextSpan NewSpan;
+        public readonly TextSpan NewSpan = newSpan;
 
         [DataMember(Order = 2)]
-        public readonly ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)> ModifiedSubSpans;
-
-        public ComplexifiedSpan(TextSpan originalSpan, TextSpan newSpan, ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)> modifiedSubSpans)
-        {
-            OriginalSpan = originalSpan;
-            NewSpan = newSpan;
-            ModifiedSubSpans = modifiedSubSpans;
-        }
+        public readonly ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)> ModifiedSubSpans = modifiedSubSpans;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Rename/ConflictEngine/ConflictingIdentifierTracker.cs b/src/Workspaces/Core/Portable/Rename/ConflictEngine/ConflictingIdentifierTracker.cs
index 432875ac8efe4..b950cbf186d25 100644
--- a/src/Workspaces/Core/Portable/Rename/ConflictEngine/ConflictingIdentifierTracker.cs
+++ b/src/Workspaces/Core/Portable/Rename/ConflictEngine/ConflictingIdentifierTracker.cs
@@ -6,22 +6,15 @@
 
 namespace Microsoft.CodeAnalysis.Rename.ConflictEngine
 {
-    internal sealed class ConflictingIdentifierTracker
+    internal sealed class ConflictingIdentifierTracker(SyntaxToken tokenBeingRenamed, IEqualityComparer<string> identifierComparer)
     {
         /// <summary>
         /// The core data structure of the tracker. This is a dictionary of variable name to the
         /// current identifier tokens that are declaring variables. This should only ever be updated
         /// via the AddIdentifier and RemoveIdentifier helpers.
         /// </summary>
-        private readonly Dictionary<string, List<SyntaxToken>> _currentIdentifiersInScope;
+        private readonly Dictionary<string, List<SyntaxToken>> _currentIdentifiersInScope = new Dictionary<string, List<SyntaxToken>>(identifierComparer);
         private readonly HashSet<SyntaxToken> _conflictingTokensToReport = new();
-        private readonly SyntaxToken _tokenBeingRenamed;
-
-        public ConflictingIdentifierTracker(SyntaxToken tokenBeingRenamed, IEqualityComparer<string> identifierComparer)
-        {
-            _currentIdentifiersInScope = new Dictionary<string, List<SyntaxToken>>(identifierComparer);
-            _tokenBeingRenamed = tokenBeingRenamed;
-        }
 
         public IEnumerable<SyntaxToken> ConflictingTokens => _conflictingTokensToReport;
 
@@ -41,11 +34,11 @@ public void AddIdentifier(SyntaxToken token)
                 // If at least one of the identifiers is the one we're renaming,
                 // track it. This means that conflicts unrelated to our rename (that
                 // were there when we started) we won't flag.
-                if (conflictingTokens.Contains(_tokenBeingRenamed))
+                if (conflictingTokens.Contains(tokenBeingRenamed))
                 {
                     foreach (var conflictingToken in conflictingTokens)
                     {
-                        if (conflictingToken != _tokenBeingRenamed)
+                        if (conflictingToken != tokenBeingRenamed)
                         {
                             // conflictingTokensToReport is a set, so we won't get duplicates
                             _conflictingTokensToReport.Add(conflictingToken);
diff --git a/src/Workspaces/Core/Portable/Rename/ConflictEngine/MutableConflictResolution.cs b/src/Workspaces/Core/Portable/Rename/ConflictEngine/MutableConflictResolution.cs
index f65e659e3654a..61a17c0b2c2a5 100644
--- a/src/Workspaces/Core/Portable/Rename/ConflictEngine/MutableConflictResolution.cs
+++ b/src/Workspaces/Core/Portable/Rename/ConflictEngine/MutableConflictResolution.cs
@@ -18,55 +18,43 @@ namespace Microsoft.CodeAnalysis.Rename.ConflictEngine
     /// <summary>
     /// The result of the conflict engine. Can be made immutable by calling <see cref="ToConflictResolution()"/>.
     /// </summary>
-    internal sealed class MutableConflictResolution
+    internal sealed class MutableConflictResolution(
+        Solution oldSolution,
+        RenamedSpansTracker renamedSpansTracker,
+        string replacementText,
+        bool replacementTextValid)
     {
-        // Used to map spans from oldSolution to the newSolution
-        private readonly RenamedSpansTracker _renamedSpansTracker;
 
         // List of All the Locations that were renamed and conflict-complexified
-        public readonly List<RelatedLocation> RelatedLocations;
+        public readonly List<RelatedLocation> RelatedLocations = new List<RelatedLocation>();
 
         /// <summary>
         /// The base workspace snapshot
         /// </summary>
-        public readonly Solution OldSolution;
+        public readonly Solution OldSolution = oldSolution;
 
         /// <summary>
         /// Whether the text that was resolved with was even valid. This may be false if the
         /// identifier was not valid in some language that was involved in the rename.
         /// </summary>
-        public readonly bool ReplacementTextValid;
+        public readonly bool ReplacementTextValid = replacementTextValid;
 
         /// <summary>
         /// The original text that is the rename replacement.
         /// </summary>
-        public readonly string ReplacementText;
+        public readonly string ReplacementText = replacementText;
 
         /// <summary>
         /// The solution snapshot as it is being updated with specific rename steps.
         /// </summary>
-        public Solution CurrentSolution { get; private set; }
+        public Solution CurrentSolution { get; private set; } = oldSolution;
 
         private (DocumentId documentId, string newName) _renamedDocument;
 
-        public MutableConflictResolution(
-            Solution oldSolution,
-            RenamedSpansTracker renamedSpansTracker,
-            string replacementText,
-            bool replacementTextValid)
-        {
-            OldSolution = oldSolution;
-            CurrentSolution = oldSolution;
-            _renamedSpansTracker = renamedSpansTracker;
-            ReplacementText = replacementText;
-            ReplacementTextValid = replacementTextValid;
-            RelatedLocations = new List<RelatedLocation>();
-        }
-
         internal void ClearDocuments(IEnumerable<DocumentId> conflictLocationDocumentIds)
         {
             RelatedLocations.RemoveAll(r => conflictLocationDocumentIds.Contains(r.DocumentId));
-            _renamedSpansTracker.ClearDocuments(conflictLocationDocumentIds);
+            renamedSpansTracker.ClearDocuments(conflictLocationDocumentIds);
         }
 
         internal void UpdateCurrentSolution(Solution solution)
@@ -80,7 +68,7 @@ internal async Task<Solution> RemoveAllRenameAnnotationsAsync(
         {
             foreach (var documentId in documentWithRenameAnnotations)
             {
-                if (_renamedSpansTracker.IsDocumentChanged(documentId))
+                if (renamedSpansTracker.IsDocumentChanged(documentId))
                 {
                     var document = CurrentSolution.GetRequiredDocument(documentId);
                     var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
@@ -139,7 +127,7 @@ internal void RenameDocumentToMatchNewSymbol(Document document)
         }
 
         public int GetAdjustedTokenStartingPosition(int startingPosition, DocumentId documentId)
-            => _renamedSpansTracker.GetAdjustedPosition(startingPosition, documentId);
+            => renamedSpansTracker.GetAdjustedPosition(startingPosition, documentId);
 
         internal void AddRelatedLocation(RelatedLocation location)
             => RelatedLocations.Add(location);
@@ -155,13 +143,13 @@ internal void AddOrReplaceRelatedLocation(RelatedLocation location)
 
         public ConflictResolution ToConflictResolution()
         {
-            var documentIds = _renamedSpansTracker.DocumentIds.Concat(
+            var documentIds = renamedSpansTracker.DocumentIds.Concat(
                 this.RelatedLocations.Select(l => l.DocumentId)).Distinct().ToImmutableArray();
 
             var relatedLocations = this.RelatedLocations.ToImmutableArray();
 
-            var documentToModifiedSpansMap = _renamedSpansTracker.GetDocumentToModifiedSpansMap();
-            var documentToComplexifiedSpansMap = _renamedSpansTracker.GetDocumentToComplexifiedSpansMap();
+            var documentToModifiedSpansMap = renamedSpansTracker.GetDocumentToModifiedSpansMap();
+            var documentToComplexifiedSpansMap = renamedSpansTracker.GetDocumentToComplexifiedSpansMap();
             var documentToRelatedLocationsMap = this.RelatedLocations.GroupBy(loc => loc.DocumentId).ToImmutableDictionary(
                 g => g.Key, g => g.ToImmutableArray());
 
diff --git a/src/Workspaces/Core/Portable/Rename/ConflictEngine/RelatedLocation.cs b/src/Workspaces/Core/Portable/Rename/ConflictEngine/RelatedLocation.cs
index 4ea108faea20a..de591f335e514 100644
--- a/src/Workspaces/Core/Portable/Rename/ConflictEngine/RelatedLocation.cs
+++ b/src/Workspaces/Core/Portable/Rename/ConflictEngine/RelatedLocation.cs
@@ -13,39 +13,30 @@ namespace Microsoft.CodeAnalysis.Rename.ConflictEngine
     /// Gives information about an identifier span that was affected by Rename (Reference or Non reference)
     /// </summary>
     [DataContract]
-    internal readonly struct RelatedLocation : IEquatable<RelatedLocation>
+    internal readonly struct RelatedLocation(TextSpan conflictCheckSpan, DocumentId documentId, RelatedLocationType type, bool isReference = false, TextSpan complexifiedTargetSpan = default) : IEquatable<RelatedLocation>
     {
         /// <summary>
         /// The Span of the original identifier if it was in source, otherwise the span to check for implicit
         /// references.
         /// </summary>
         [DataMember(Order = 0)]
-        public readonly TextSpan ConflictCheckSpan;
+        public readonly TextSpan ConflictCheckSpan = conflictCheckSpan;
 
         [DataMember(Order = 1)]
-        public readonly DocumentId DocumentId;
+        public readonly DocumentId DocumentId = documentId;
 
         [DataMember(Order = 2)]
-        public readonly RelatedLocationType Type;
+        public readonly RelatedLocationType Type = type;
 
         [DataMember(Order = 3)]
-        public readonly bool IsReference;
+        public readonly bool IsReference = isReference;
 
         /// <summary>
         /// If there was a conflict at ConflictCheckSpan during rename, then the next phase in rename uses
         /// ComplexifiedTargetSpan span to be expanded to resolve the conflict.
         /// </summary>
         [DataMember(Order = 4)]
-        public readonly TextSpan ComplexifiedTargetSpan;
-
-        public RelatedLocation(TextSpan conflictCheckSpan, DocumentId documentId, RelatedLocationType type, bool isReference = false, TextSpan complexifiedTargetSpan = default)
-        {
-            ConflictCheckSpan = conflictCheckSpan;
-            Type = type;
-            IsReference = isReference;
-            DocumentId = documentId;
-            ComplexifiedTargetSpan = complexifiedTargetSpan;
-        }
+        public readonly TextSpan ComplexifiedTargetSpan = complexifiedTargetSpan;
 
         public RelatedLocation WithType(RelatedLocationType type)
             => new(ConflictCheckSpan, DocumentId, type, IsReference, ComplexifiedTargetSpan);
diff --git a/src/Workspaces/Core/Portable/Rename/ConflictEngine/RenamedSpansTracker.cs b/src/Workspaces/Core/Portable/Rename/ConflictEngine/RenamedSpansTracker.cs
index bf0f680d53c00..192d8c2093aca 100644
--- a/src/Workspaces/Core/Portable/Rename/ConflictEngine/RenamedSpansTracker.cs
+++ b/src/Workspaces/Core/Portable/Rename/ConflictEngine/RenamedSpansTracker.cs
@@ -53,9 +53,9 @@ internal void AddComplexifiedSpan(DocumentId documentId, TextSpan oldSpan, TextS
         // Given a position in the old solution, we get back the new adjusted position 
         internal int GetAdjustedPosition(int startingPosition, DocumentId documentId)
         {
-            var documentReplacementSpans = _documentToModifiedSpansMap.ContainsKey(documentId)
-                ? _documentToModifiedSpansMap[documentId].Where(pair => pair.oldSpan.Start < startingPosition) :
-                SpecializedCollections.EmptyEnumerable<(TextSpan oldSpan, TextSpan newSpan)>();
+            var documentReplacementSpans = _documentToModifiedSpansMap.TryGetValue(documentId, out var modifiedSpans)
+                ? modifiedSpans.Where(pair => pair.oldSpan.Start < startingPosition)
+                : SpecializedCollections.EmptyEnumerable<(TextSpan oldSpan, TextSpan newSpan)>();
 
             var adjustedStartingPosition = startingPosition;
             foreach (var (oldSpan, newSpan) in documentReplacementSpans)
@@ -63,9 +63,9 @@ internal int GetAdjustedPosition(int startingPosition, DocumentId documentId)
                 adjustedStartingPosition += newSpan.Length - oldSpan.Length;
             }
 
-            var documentComplexifiedSpans = _documentToComplexifiedSpansMap.ContainsKey(documentId)
-            ? _documentToComplexifiedSpansMap[documentId].Where(c => c.OriginalSpan.Start <= startingPosition) :
-            SpecializedCollections.EmptyEnumerable<MutableComplexifiedSpan>();
+            var documentComplexifiedSpans = _documentToComplexifiedSpansMap.TryGetValue(documentId, out var complexifiedSpans)
+                ? complexifiedSpans.Where(c => c.OriginalSpan.Start <= startingPosition)
+                : SpecializedCollections.EmptyEnumerable<MutableComplexifiedSpan>();
 
             var appliedTextSpans = new HashSet<TextSpan>();
             foreach (var c in documentComplexifiedSpans.Reverse())
@@ -118,19 +118,12 @@ internal int GetAdjustedPosition(int startingPosition, DocumentId documentId)
         ///     "a", "NS3.a"
         /// 
         /// </summary>
-        private class MutableComplexifiedSpan
+        private class MutableComplexifiedSpan(
+            TextSpan originalSpan, TextSpan newSpan, List<(TextSpan oldSpan, TextSpan newSpan)> modifiedSubSpans)
         {
-            public TextSpan OriginalSpan;
-            public TextSpan NewSpan;
-            public List<(TextSpan oldSpan, TextSpan newSpan)> ModifiedSubSpans;
-
-            public MutableComplexifiedSpan(
-                TextSpan originalSpan, TextSpan newSpan, List<(TextSpan oldSpan, TextSpan newSpan)> modifiedSubSpans)
-            {
-                OriginalSpan = originalSpan;
-                NewSpan = newSpan;
-                ModifiedSubSpans = modifiedSubSpans;
-            }
+            public TextSpan OriginalSpan = originalSpan;
+            public TextSpan NewSpan = newSpan;
+            public List<(TextSpan oldSpan, TextSpan newSpan)> ModifiedSubSpans = modifiedSubSpans;
         }
 
         internal void ClearDocuments(IEnumerable<DocumentId> conflictLocationDocumentIds)
diff --git a/src/Workspaces/Core/Portable/Rename/IRemoteRenamerService.cs b/src/Workspaces/Core/Portable/Rename/IRemoteRenamerService.cs
index a99489336a6fb..2efb2693e5883 100644
--- a/src/Workspaces/Core/Portable/Rename/IRemoteRenamerService.cs
+++ b/src/Workspaces/Core/Portable/Rename/IRemoteRenamerService.cs
@@ -73,46 +73,35 @@ public ValueTask<CodeCleanupOptions> GetOptionsAsync(RemoteServiceCallbackId cal
     }
 
     [DataContract]
-    internal readonly struct SerializableRenameLocation
+    internal readonly struct SerializableRenameLocation(
+        TextSpan location,
+        DocumentId documentId,
+        CandidateReason candidateReason,
+        bool isRenamableAliasUsage,
+        bool isRenamableAccessor,
+        TextSpan containingLocationForStringOrComment,
+        bool isWrittenTo)
     {
         [DataMember(Order = 0)]
-        public readonly TextSpan Location;
+        public readonly TextSpan Location = location;
 
         [DataMember(Order = 1)]
-        public readonly DocumentId DocumentId;
+        public readonly DocumentId DocumentId = documentId;
 
         [DataMember(Order = 2)]
-        public readonly CandidateReason CandidateReason;
+        public readonly CandidateReason CandidateReason = candidateReason;
 
         [DataMember(Order = 3)]
-        public readonly bool IsRenamableAliasUsage;
+        public readonly bool IsRenamableAliasUsage = isRenamableAliasUsage;
 
         [DataMember(Order = 4)]
-        public readonly bool IsRenamableAccessor;
+        public readonly bool IsRenamableAccessor = isRenamableAccessor;
 
         [DataMember(Order = 5)]
-        public readonly TextSpan ContainingLocationForStringOrComment;
+        public readonly TextSpan ContainingLocationForStringOrComment = containingLocationForStringOrComment;
 
         [DataMember(Order = 6)]
-        public readonly bool IsWrittenTo;
-
-        public SerializableRenameLocation(
-            TextSpan location,
-            DocumentId documentId,
-            CandidateReason candidateReason,
-            bool isRenamableAliasUsage,
-            bool isRenamableAccessor,
-            TextSpan containingLocationForStringOrComment,
-            bool isWrittenTo)
-        {
-            Location = location;
-            DocumentId = documentId;
-            CandidateReason = candidateReason;
-            IsRenamableAliasUsage = isRenamableAliasUsage;
-            IsRenamableAccessor = isRenamableAccessor;
-            ContainingLocationForStringOrComment = containingLocationForStringOrComment;
-            IsWrittenTo = isWrittenTo;
-        }
+        public readonly bool IsWrittenTo = isWrittenTo;
 
         public static SerializableRenameLocation Dehydrate(RenameLocation location)
             => new(location.Location.SourceSpan,
@@ -179,31 +168,23 @@ internal partial class SymbolicRenameLocations
     }
 
     [DataContract]
-    internal sealed class SerializableRenameLocations
+    internal sealed class SerializableRenameLocations(
+        SymbolRenameOptions options,
+        ImmutableArray<SerializableRenameLocation> locations,
+        ImmutableArray<SerializableReferenceLocation> implicitLocations,
+        ImmutableArray<SerializableSymbolAndProjectId> referencedSymbols)
     {
         [DataMember(Order = 0)]
-        public readonly SymbolRenameOptions Options;
+        public readonly SymbolRenameOptions Options = options;
 
         [DataMember(Order = 1)]
-        public readonly ImmutableArray<SerializableRenameLocation> Locations;
+        public readonly ImmutableArray<SerializableRenameLocation> Locations = locations;
 
         [DataMember(Order = 2)]
-        public readonly ImmutableArray<SerializableReferenceLocation> ImplicitLocations;
+        public readonly ImmutableArray<SerializableReferenceLocation> ImplicitLocations = implicitLocations;
 
         [DataMember(Order = 3)]
-        public readonly ImmutableArray<SerializableSymbolAndProjectId> ReferencedSymbols;
-
-        public SerializableRenameLocations(
-            SymbolRenameOptions options,
-            ImmutableArray<SerializableRenameLocation> locations,
-            ImmutableArray<SerializableReferenceLocation> implicitLocations,
-            ImmutableArray<SerializableSymbolAndProjectId> referencedSymbols)
-        {
-            Options = options;
-            Locations = locations;
-            ImplicitLocations = implicitLocations;
-            ReferencedSymbols = referencedSymbols;
-        }
+        public readonly ImmutableArray<SerializableSymbolAndProjectId> ReferencedSymbols = referencedSymbols;
 
         public async ValueTask<ImmutableArray<RenameLocation>> RehydrateLocationsAsync(
             Solution solution, CancellationToken cancellationToken)
@@ -217,19 +198,13 @@ public async ValueTask<ImmutableArray<RenameLocation>> RehydrateLocationsAsync(
     }
 
     [DataContract]
-    internal sealed class SerializableConflictResolution
+    internal sealed class SerializableConflictResolution(string? errorMessage, SuccessfulConflictResolution? resolution)
     {
         [DataMember(Order = 0)]
-        public readonly string? ErrorMessage;
+        public readonly string? ErrorMessage = errorMessage;
 
         [DataMember(Order = 1)]
-        public readonly SuccessfulConflictResolution? Resolution;
-
-        public SerializableConflictResolution(string? errorMessage, SuccessfulConflictResolution? resolution)
-        {
-            ErrorMessage = errorMessage;
-            Resolution = resolution;
-        }
+        public readonly SuccessfulConflictResolution? Resolution = resolution;
 
         public async Task<ConflictResolution> RehydrateAsync(Solution oldSolution, CancellationToken cancellationToken)
         {
@@ -255,51 +230,39 @@ public async Task<ConflictResolution> RehydrateAsync(Solution oldSolution, Cance
     }
 
     [DataContract]
-    internal sealed class SuccessfulConflictResolution
+    internal sealed class SuccessfulConflictResolution(
+        bool replacementTextValid,
+        (DocumentId documentId, string newName) renamedDocument,
+        ImmutableArray<DocumentId> documentIds,
+        ImmutableArray<RelatedLocation> relatedLocations,
+        ImmutableArray<(DocumentId, ImmutableArray<TextChange>)> documentTextChanges,
+        ImmutableDictionary<DocumentId, ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)>> documentToModifiedSpansMap,
+        ImmutableDictionary<DocumentId, ImmutableArray<ComplexifiedSpan>> documentToComplexifiedSpansMap,
+        ImmutableDictionary<DocumentId, ImmutableArray<RelatedLocation>> documentToRelatedLocationsMap)
     {
         [DataMember(Order = 0)]
-        public readonly bool ReplacementTextValid;
+        public readonly bool ReplacementTextValid = replacementTextValid;
 
         [DataMember(Order = 1)]
-        public readonly (DocumentId documentId, string newName) RenamedDocument;
+        public readonly (DocumentId documentId, string newName) RenamedDocument = renamedDocument;
 
         [DataMember(Order = 2)]
-        public readonly ImmutableArray<DocumentId> DocumentIds;
+        public readonly ImmutableArray<DocumentId> DocumentIds = documentIds;
 
         [DataMember(Order = 3)]
-        public readonly ImmutableArray<RelatedLocation> RelatedLocations;
+        public readonly ImmutableArray<RelatedLocation> RelatedLocations = relatedLocations;
 
         [DataMember(Order = 4)]
-        public readonly ImmutableArray<(DocumentId, ImmutableArray<TextChange>)> DocumentTextChanges;
+        public readonly ImmutableArray<(DocumentId, ImmutableArray<TextChange>)> DocumentTextChanges = documentTextChanges;
 
         [DataMember(Order = 5)]
-        public readonly ImmutableDictionary<DocumentId, ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)>> DocumentToModifiedSpansMap;
+        public readonly ImmutableDictionary<DocumentId, ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)>> DocumentToModifiedSpansMap = documentToModifiedSpansMap;
 
         [DataMember(Order = 6)]
-        public readonly ImmutableDictionary<DocumentId, ImmutableArray<ComplexifiedSpan>> DocumentToComplexifiedSpansMap;
+        public readonly ImmutableDictionary<DocumentId, ImmutableArray<ComplexifiedSpan>> DocumentToComplexifiedSpansMap = documentToComplexifiedSpansMap;
 
         [DataMember(Order = 7)]
-        public readonly ImmutableDictionary<DocumentId, ImmutableArray<RelatedLocation>> DocumentToRelatedLocationsMap;
-
-        public SuccessfulConflictResolution(
-            bool replacementTextValid,
-            (DocumentId documentId, string newName) renamedDocument,
-            ImmutableArray<DocumentId> documentIds,
-            ImmutableArray<RelatedLocation> relatedLocations,
-            ImmutableArray<(DocumentId, ImmutableArray<TextChange>)> documentTextChanges,
-            ImmutableDictionary<DocumentId, ImmutableArray<(TextSpan oldSpan, TextSpan newSpan)>> documentToModifiedSpansMap,
-            ImmutableDictionary<DocumentId, ImmutableArray<ComplexifiedSpan>> documentToComplexifiedSpansMap,
-            ImmutableDictionary<DocumentId, ImmutableArray<RelatedLocation>> documentToRelatedLocationsMap)
-        {
-            ReplacementTextValid = replacementTextValid;
-            RenamedDocument = renamedDocument;
-            DocumentIds = documentIds;
-            RelatedLocations = relatedLocations;
-            DocumentTextChanges = documentTextChanges;
-            DocumentToModifiedSpansMap = documentToModifiedSpansMap;
-            DocumentToComplexifiedSpansMap = documentToComplexifiedSpansMap;
-            DocumentToRelatedLocationsMap = documentToRelatedLocationsMap;
-        }
+        public readonly ImmutableDictionary<DocumentId, ImmutableArray<RelatedLocation>> DocumentToRelatedLocationsMap = documentToRelatedLocationsMap;
     }
 
     internal partial struct ConflictResolution
diff --git a/src/Workspaces/Core/Portable/Rename/RenameLocation.cs b/src/Workspaces/Core/Portable/Rename/RenameLocation.cs
index 52b7fca387f53..61163be1d4994 100644
--- a/src/Workspaces/Core/Portable/Rename/RenameLocation.cs
+++ b/src/Workspaces/Core/Portable/Rename/RenameLocation.cs
@@ -8,36 +8,25 @@
 
 namespace Microsoft.CodeAnalysis.Rename
 {
-    internal readonly struct RenameLocation : IEquatable<RenameLocation>
+    internal readonly struct RenameLocation(
+        Location location,
+        DocumentId documentId,
+        CandidateReason candidateReason = CandidateReason.None,
+        bool isRenamableAliasUsage = false,
+        bool isRenamableAccessor = false,
+        bool isWrittenTo = false,
+        TextSpan containingLocationForStringOrComment = default) : IEquatable<RenameLocation>
     {
-        public readonly Location Location;
-        public readonly DocumentId DocumentId;
-        public readonly CandidateReason CandidateReason;
-        public readonly bool IsRenamableAliasUsage;
-        public readonly bool IsRenamableAccessor;
-        public readonly TextSpan ContainingLocationForStringOrComment;
-        public readonly bool IsWrittenTo;
+        public readonly Location Location = location;
+        public readonly DocumentId DocumentId = documentId;
+        public readonly CandidateReason CandidateReason = candidateReason;
+        public readonly bool IsRenamableAliasUsage = isRenamableAliasUsage;
+        public readonly bool IsRenamableAccessor = isRenamableAccessor;
+        public readonly TextSpan ContainingLocationForStringOrComment = containingLocationForStringOrComment;
+        public readonly bool IsWrittenTo = isWrittenTo;
 
         public bool IsRenameInStringOrComment => ContainingLocationForStringOrComment != default;
 
-        public RenameLocation(
-            Location location,
-            DocumentId documentId,
-            CandidateReason candidateReason = CandidateReason.None,
-            bool isRenamableAliasUsage = false,
-            bool isRenamableAccessor = false,
-            bool isWrittenTo = false,
-            TextSpan containingLocationForStringOrComment = default)
-        {
-            Location = location;
-            DocumentId = documentId;
-            CandidateReason = candidateReason;
-            IsRenamableAliasUsage = isRenamableAliasUsage;
-            IsRenamableAccessor = isRenamableAccessor;
-            IsWrittenTo = isWrittenTo;
-            ContainingLocationForStringOrComment = containingLocationForStringOrComment;
-        }
-
         public RenameLocation(ReferenceLocation referenceLocation, DocumentId documentId)
             : this(referenceLocation.Location, documentId,
                    candidateReason: referenceLocation.CandidateReason,
diff --git a/src/Workspaces/Core/Portable/Rename/RenameRewriterParameters.cs b/src/Workspaces/Core/Portable/Rename/RenameRewriterParameters.cs
index 1d077cb4f7008..d527438758c54 100644
--- a/src/Workspaces/Core/Portable/Rename/RenameRewriterParameters.cs
+++ b/src/Workspaces/Core/Portable/Rename/RenameRewriterParameters.cs
@@ -11,67 +11,44 @@
 
 namespace Microsoft.CodeAnalysis.Rename
 {
-    internal class RenameRewriterParameters
+    internal class RenameRewriterParameters(
+        RenameAnnotation renamedSymbolDeclarationAnnotation,
+        Document document,
+        SemanticModel semanticModel,
+        SyntaxNode syntaxRoot,
+        string replacementText,
+        string originalText,
+        ImmutableArray<string> possibleNameConflicts,
+        ImmutableDictionary<TextSpan, RenameLocation> renameLocations,
+        ImmutableDictionary<TextSpan, ImmutableSortedSet<TextSpan>?> stringAndCommentTextSpans,
+        ImmutableHashSet<TextSpan> conflictLocationSpans,
+        Solution originalSolution,
+        ISymbol renameSymbol,
+        bool replacementTextValid,
+        RenamedSpansTracker renameSpansTracker,
+        bool isRenamingInStrings,
+        bool isRenamingInComments,
+        AnnotationTable<RenameAnnotation> renameAnnotations,
+        CancellationToken cancellationToken)
     {
-        internal readonly CancellationToken CancellationToken;
-        internal readonly ImmutableHashSet<TextSpan> ConflictLocationSpans;
-        internal readonly bool IsRenamingInStrings;
-        internal readonly bool IsRenamingInComments;
-        internal readonly Solution OriginalSolution;
-        internal readonly SyntaxTree OriginalSyntaxTree;
-        internal readonly string OriginalText;
-        internal readonly ImmutableArray<string> PossibleNameConflicts;
-        internal readonly RenameAnnotation RenamedSymbolDeclarationAnnotation;
-        internal readonly ImmutableDictionary<TextSpan, RenameLocation> RenameLocations;
-        internal readonly RenamedSpansTracker RenameSpansTracker;
-        internal readonly ISymbol RenameSymbol;
-        internal readonly string ReplacementText;
-        internal readonly bool ReplacementTextValid;
-        internal readonly ImmutableDictionary<TextSpan, ImmutableSortedSet<TextSpan>?> StringAndCommentTextSpans;
-        internal readonly SyntaxNode SyntaxRoot;
-        internal readonly Document Document;
-        internal readonly SemanticModel SemanticModel;
-        internal readonly AnnotationTable<RenameAnnotation> RenameAnnotations;
-
-        public RenameRewriterParameters(
-            RenameAnnotation renamedSymbolDeclarationAnnotation,
-            Document document,
-            SemanticModel semanticModel,
-            SyntaxNode syntaxRoot,
-            string replacementText,
-            string originalText,
-            ImmutableArray<string> possibleNameConflicts,
-            ImmutableDictionary<TextSpan, RenameLocation> renameLocations,
-            ImmutableDictionary<TextSpan, ImmutableSortedSet<TextSpan>?> stringAndCommentTextSpans,
-            ImmutableHashSet<TextSpan> conflictLocationSpans,
-            Solution originalSolution,
-            ISymbol renameSymbol,
-            bool replacementTextValid,
-            RenamedSpansTracker renameSpansTracker,
-            bool isRenamingInStrings,
-            bool isRenamingInComments,
-            AnnotationTable<RenameAnnotation> renameAnnotations,
-            CancellationToken cancellationToken)
-        {
-            RenamedSymbolDeclarationAnnotation = renamedSymbolDeclarationAnnotation;
-            Document = document;
-            SemanticModel = semanticModel;
-            SyntaxRoot = syntaxRoot;
-            OriginalSyntaxTree = semanticModel.SyntaxTree;
-            ReplacementText = replacementText;
-            OriginalText = originalText;
-            PossibleNameConflicts = possibleNameConflicts;
-            RenameLocations = renameLocations;
-            StringAndCommentTextSpans = stringAndCommentTextSpans;
-            ConflictLocationSpans = conflictLocationSpans;
-            OriginalSolution = originalSolution;
-            RenameSymbol = renameSymbol;
-            ReplacementTextValid = replacementTextValid;
-            CancellationToken = cancellationToken;
-            RenameSpansTracker = renameSpansTracker;
-            IsRenamingInStrings = isRenamingInStrings;
-            IsRenamingInComments = isRenamingInComments;
-            RenameAnnotations = renameAnnotations;
-        }
+        internal readonly CancellationToken CancellationToken = cancellationToken;
+        internal readonly ImmutableHashSet<TextSpan> ConflictLocationSpans = conflictLocationSpans;
+        internal readonly bool IsRenamingInStrings = isRenamingInStrings;
+        internal readonly bool IsRenamingInComments = isRenamingInComments;
+        internal readonly Solution OriginalSolution = originalSolution;
+        internal readonly SyntaxTree OriginalSyntaxTree = semanticModel.SyntaxTree;
+        internal readonly string OriginalText = originalText;
+        internal readonly ImmutableArray<string> PossibleNameConflicts = possibleNameConflicts;
+        internal readonly RenameAnnotation RenamedSymbolDeclarationAnnotation = renamedSymbolDeclarationAnnotation;
+        internal readonly ImmutableDictionary<TextSpan, RenameLocation> RenameLocations = renameLocations;
+        internal readonly RenamedSpansTracker RenameSpansTracker = renameSpansTracker;
+        internal readonly ISymbol RenameSymbol = renameSymbol;
+        internal readonly string ReplacementText = replacementText;
+        internal readonly bool ReplacementTextValid = replacementTextValid;
+        internal readonly ImmutableDictionary<TextSpan, ImmutableSortedSet<TextSpan>?> StringAndCommentTextSpans = stringAndCommentTextSpans;
+        internal readonly SyntaxNode SyntaxRoot = syntaxRoot;
+        internal readonly Document Document = document;
+        internal readonly SemanticModel SemanticModel = semanticModel;
+        internal readonly AnnotationTable<RenameAnnotation> RenameAnnotations = renameAnnotations;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Rename/Renamer.RenameDocumentAction.cs b/src/Workspaces/Core/Portable/Rename/Renamer.RenameDocumentAction.cs
index c3b122458e520..e32368c8e5028 100644
--- a/src/Workspaces/Core/Portable/Rename/Renamer.RenameDocumentAction.cs
+++ b/src/Workspaces/Core/Portable/Rename/Renamer.RenameDocumentAction.cs
@@ -43,16 +43,10 @@ public ImmutableArray<string> GetErrors(CultureInfo? culture = null)
 
             internal abstract Task<Solution> GetModifiedSolutionAsync(Document document, DocumentRenameOptions options, CancellationToken cancellationToken);
 
-            internal readonly struct ErrorResource
+            internal readonly struct ErrorResource(string formatString, object[] arguments)
             {
-                public string FormatString { get; }
-                public object[] Arguments { get; }
-
-                public ErrorResource(string formatString, object[] arguments)
-                {
-                    FormatString = formatString;
-                    Arguments = arguments;
-                }
+                public string FormatString { get; } = formatString;
+                public object[] Arguments { get; } = arguments;
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/Rename/Renamer.RenameSymbolDocumentAction.cs b/src/Workspaces/Core/Portable/Rename/Renamer.RenameSymbolDocumentAction.cs
index 66faad591827e..be197e6ad7fec 100644
--- a/src/Workspaces/Core/Portable/Rename/Renamer.RenameSymbolDocumentAction.cs
+++ b/src/Workspaces/Core/Portable/Rename/Renamer.RenameSymbolDocumentAction.cs
@@ -120,39 +120,31 @@ internal override async Task<Solution> GetModifiedSolutionAsync(Document documen
                     symbol.Name);
             }
 
-            private readonly struct AnalysisResult
+            private readonly struct AnalysisResult(
+                Document document,
+                string newDocumentName,
+                string newSymbolName,
+                string originalSymbolName)
             {
                 /// <summary>
                 /// Name of the document that the action was produced for.
                 /// </summary>
-                public string OriginalDocumentName { get; }
+                public string OriginalDocumentName { get; } = document.Name;
 
                 /// <summary>
                 /// The new document name that will be used.
                 /// </summary>
-                public string NewDocumentName { get; }
+                public string NewDocumentName { get; } = newDocumentName;
 
                 /// <summary>
                 /// The original name of the symbol that will be changed.
                 /// </summary>
-                public string OriginalSymbolName { get; }
+                public string OriginalSymbolName { get; } = originalSymbolName;
 
                 /// <summary>
                 /// The new name for the symbol.
                 /// </summary>
-                public string NewSymbolName { get; }
-
-                public AnalysisResult(
-                    Document document,
-                    string newDocumentName,
-                    string newSymbolName,
-                    string originalSymbolName)
-                {
-                    OriginalDocumentName = document.Name;
-                    NewDocumentName = newDocumentName;
-                    NewSymbolName = newSymbolName;
-                    OriginalSymbolName = originalSymbolName;
-                }
+                public string NewSymbolName { get; } = newSymbolName;
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/Rename/Renamer.SyncNamespaceDocumentAction.cs b/src/Workspaces/Core/Portable/Rename/Renamer.SyncNamespaceDocumentAction.cs
index 1cf0290d24749..4071b58f02393 100644
--- a/src/Workspaces/Core/Portable/Rename/Renamer.SyncNamespaceDocumentAction.cs
+++ b/src/Workspaces/Core/Portable/Rename/Renamer.SyncNamespaceDocumentAction.cs
@@ -87,14 +87,9 @@ internal override async Task<Solution> GetModifiedSolutionAsync(Document documen
                 }
             }
 
-            private readonly struct AnalysisResult
+            private readonly struct AnalysisResult(string targetNamespace)
             {
-                public string TargetNamespace { get; }
-
-                public AnalysisResult(string targetNamespace)
-                {
-                    TargetNamespace = targetNamespace;
-                }
+                public string TargetNamespace { get; } = targetNamespace;
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/Rename/TokenRenameInfo.cs b/src/Workspaces/Core/Portable/Rename/TokenRenameInfo.cs
index f8ca1c5c9f08e..5e243864d2b86 100644
--- a/src/Workspaces/Core/Portable/Rename/TokenRenameInfo.cs
+++ b/src/Workspaces/Core/Portable/Rename/TokenRenameInfo.cs
@@ -7,18 +7,11 @@
 
 namespace Microsoft.CodeAnalysis.Rename
 {
-    internal sealed class TokenRenameInfo
+    internal sealed class TokenRenameInfo(bool hasSymbols, IEnumerable<ISymbol> symbols, bool isMemberGroup)
     {
-        public bool HasSymbols { get; private set; }
-        public IEnumerable<ISymbol> Symbols { get; private set; }
-        public bool IsMemberGroup { get; private set; }
-
-        public TokenRenameInfo(bool hasSymbols, IEnumerable<ISymbol> symbols, bool isMemberGroup)
-        {
-            HasSymbols = hasSymbols;
-            Symbols = symbols;
-            IsMemberGroup = isMemberGroup;
-        }
+        public bool HasSymbols { get; private set; } = hasSymbols;
+        public IEnumerable<ISymbol> Symbols { get; private set; } = symbols;
+        public bool IsMemberGroup { get; private set; } = isMemberGroup;
 
         public static TokenRenameInfo CreateMemberGroupTokenInfo(IEnumerable<ISymbol> symbols)
         {
diff --git a/src/Workspaces/Core/Portable/SemanticModelReuse/SemanticModelWorkspaceServiceFactory.SemanticModelWorkspaceService.cs b/src/Workspaces/Core/Portable/SemanticModelReuse/SemanticModelWorkspaceServiceFactory.SemanticModelWorkspaceService.cs
index 77c43c63b86ae..e36b1e874423b 100644
--- a/src/Workspaces/Core/Portable/SemanticModelReuse/SemanticModelWorkspaceServiceFactory.SemanticModelWorkspaceService.cs
+++ b/src/Workspaces/Core/Portable/SemanticModelReuse/SemanticModelWorkspaceServiceFactory.SemanticModelWorkspaceService.cs
@@ -13,37 +13,29 @@
 
 namespace Microsoft.CodeAnalysis.SemanticModelReuse
 {
-    internal readonly struct SemanticModelReuseInfo
+    internal readonly struct SemanticModelReuseInfo(SemanticModel previousNonSpeculativeSemanticModel, SemanticModel currentSemanticModel, SyntaxNode bodyNode, VersionStamp topLevelSementicVersion)
     {
         /// <summary>
         /// The original <em>non-speculative</em> semantic model we retrieved for this document at some point.
         /// </summary>
-        public readonly SemanticModel PreviousNonSpeculativeSemanticModel;
+        public readonly SemanticModel PreviousNonSpeculativeSemanticModel = previousNonSpeculativeSemanticModel;
 
         /// <summary>
         /// The current semantic model we retrieved <see cref="SemanticModel"/> for the <see cref="BodyNode"/>.  Could
         /// be speculative or non-speculative.
         /// </summary>
-        public readonly SemanticModel CurrentSemanticModel;
+        public readonly SemanticModel CurrentSemanticModel = currentSemanticModel;
 
         /// <summary>
         /// The current method body we retrieved the <see cref="CurrentSemanticModel"/> for.
         /// </summary>
-        public readonly SyntaxNode BodyNode;
+        public readonly SyntaxNode BodyNode = bodyNode;
 
         /// <summary>
         /// The top level version of the project when we retrieved <see cref="SemanticModel"/>.  As long as this is the
         /// same we can continue getting speculative models to use.
         /// </summary>
-        public readonly VersionStamp TopLevelSemanticVersion;
-
-        public SemanticModelReuseInfo(SemanticModel previousNonSpeculativeSemanticModel, SemanticModel currentSemanticModel, SyntaxNode bodyNode, VersionStamp topLevelSementicVersion)
-        {
-            PreviousNonSpeculativeSemanticModel = previousNonSpeculativeSemanticModel;
-            CurrentSemanticModel = currentSemanticModel;
-            BodyNode = bodyNode;
-            TopLevelSemanticVersion = topLevelSementicVersion;
-        }
+        public readonly VersionStamp TopLevelSemanticVersion = topLevelSementicVersion;
     }
 
     internal partial class SemanticModelReuseWorkspaceServiceFactory : IWorkspaceServiceFactory
diff --git a/src/Workspaces/Core/Portable/Serialization/SerializerService_ChecksumWithChildren.cs b/src/Workspaces/Core/Portable/Serialization/SerializerService_ChecksumWithChildren.cs
index ff759f3340de4..1c7b2f667cedc 100644
--- a/src/Workspaces/Core/Portable/Serialization/SerializerService_ChecksumWithChildren.cs
+++ b/src/Workspaces/Core/Portable/Serialization/SerializerService_ChecksumWithChildren.cs
@@ -48,7 +48,7 @@ public void SerializeChecksumWithChildren(ChecksumWithChildren checksums, Object
             }
         }
 
-        private ChecksumWithChildren DeserializeChecksumWithChildren(ObjectReader reader, CancellationToken cancellationToken)
+        private static ChecksumWithChildren DeserializeChecksumWithChildren(ObjectReader reader, CancellationToken cancellationToken)
         {
             cancellationToken.ThrowIfCancellationRequested();
 
diff --git a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.AnonymousTypeRemover.cs b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.AnonymousTypeRemover.cs
index ced1df3aff99d..c83b1180019c1 100644
--- a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.AnonymousTypeRemover.cs
+++ b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.AnonymousTypeRemover.cs
@@ -11,13 +11,8 @@ namespace Microsoft.CodeAnalysis.Shared.Extensions
 {
     internal partial class ITypeSymbolExtensions
     {
-        private class AnonymousTypeRemover : SymbolVisitor<ITypeSymbol>
+        private class AnonymousTypeRemover(Compilation compilation) : SymbolVisitor<ITypeSymbol>
         {
-            private readonly Compilation _compilation;
-
-            public AnonymousTypeRemover(Compilation compilation)
-                => _compilation = compilation;
-
             public override ITypeSymbol DefaultVisit(ISymbol node)
                 => throw new NotImplementedException();
 
@@ -32,7 +27,7 @@ public override ITypeSymbol VisitArrayType(IArrayTypeSymbol symbol)
                     return symbol;
                 }
 
-                return _compilation.CreateArrayTypeSymbol(elementType, symbol.Rank);
+                return compilation.CreateArrayTypeSymbol(elementType, symbol.Rank);
             }
 
             public override ITypeSymbol VisitFunctionPointerType(IFunctionPointerTypeSymbol symbol)
@@ -46,7 +41,7 @@ public override ITypeSymbol VisitFunctionPointerType(IFunctionPointerTypeSymbol
             public override ITypeSymbol VisitNamedType(INamedTypeSymbol symbol)
             {
                 if (symbol.IsAnonymousType())
-                    return _compilation.ObjectType;
+                    return compilation.ObjectType;
 
                 var arguments = symbol.TypeArguments.Select(t => t.Accept(this)).ToArray();
                 if (arguments.SequenceEqual(symbol.TypeArguments))
@@ -63,7 +58,7 @@ public override ITypeSymbol VisitPointerType(IPointerTypeSymbol symbol)
                     return symbol;
                 }
 
-                return _compilation.CreatePointerTypeSymbol(elementType);
+                return compilation.CreatePointerTypeSymbol(elementType);
             }
 
             public override ITypeSymbol VisitTypeParameter(ITypeParameterSymbol symbol)
diff --git a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.CompilationTypeGenerator.cs b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.CompilationTypeGenerator.cs
index dec289b3a5c72..66268e730ea36 100644
--- a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.CompilationTypeGenerator.cs
+++ b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.CompilationTypeGenerator.cs
@@ -8,18 +8,13 @@ namespace Microsoft.CodeAnalysis.Shared.Extensions
 {
     internal partial class ITypeSymbolExtensions
     {
-        private class CompilationTypeGenerator : ITypeGenerator
+        private class CompilationTypeGenerator(Compilation compilation) : ITypeGenerator
         {
-            private readonly Compilation _compilation;
-
-            public CompilationTypeGenerator(Compilation compilation)
-                => _compilation = compilation;
-
             public ITypeSymbol CreateArrayTypeSymbol(ITypeSymbol elementType, int rank)
-                => _compilation.CreateArrayTypeSymbol(elementType, rank);
+                => compilation.CreateArrayTypeSymbol(elementType, rank);
 
             public ITypeSymbol CreatePointerTypeSymbol(ITypeSymbol pointedAtType)
-                => _compilation.CreatePointerTypeSymbol(pointedAtType);
+                => compilation.CreatePointerTypeSymbol(pointedAtType);
 
             public ITypeSymbol Construct(INamedTypeSymbol namedType, ITypeSymbol[] typeArguments)
                 => namedType.Construct(typeArguments);
diff --git a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnavailableTypeParameterRemover.cs b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnavailableTypeParameterRemover.cs
index e2a93fc44e4df..25aea3e8c24aa 100644
--- a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnavailableTypeParameterRemover.cs
+++ b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnavailableTypeParameterRemover.cs
@@ -12,17 +12,8 @@ namespace Microsoft.CodeAnalysis.Shared.Extensions
 {
     internal static partial class ITypeSymbolExtensions
     {
-        private class UnavailableTypeParameterRemover : SymbolVisitor<ITypeSymbol>
+        private class UnavailableTypeParameterRemover(Compilation compilation, ISet<string> availableTypeParameterNames) : SymbolVisitor<ITypeSymbol>
         {
-            private readonly Compilation _compilation;
-            private readonly ISet<string> _availableTypeParameterNames;
-
-            public UnavailableTypeParameterRemover(Compilation compilation, ISet<string> availableTypeParameterNames)
-            {
-                _compilation = compilation;
-                _availableTypeParameterNames = availableTypeParameterNames;
-            }
-
             public override ITypeSymbol DefaultVisit(ISymbol node)
                 => throw new NotImplementedException();
 
@@ -37,7 +28,7 @@ public override ITypeSymbol VisitArrayType(IArrayTypeSymbol symbol)
                     return symbol;
                 }
 
-                return _compilation.CreateArrayTypeSymbol(elementType, symbol.Rank);
+                return compilation.CreateArrayTypeSymbol(elementType, symbol.Rank);
             }
 
             public override ITypeSymbol VisitFunctionPointerType(IFunctionPointerTypeSymbol symbol)
@@ -65,17 +56,17 @@ public override ITypeSymbol VisitPointerType(IPointerTypeSymbol symbol)
                     return symbol;
                 }
 
-                return _compilation.CreatePointerTypeSymbol(elementType);
+                return compilation.CreatePointerTypeSymbol(elementType);
             }
 
             public override ITypeSymbol VisitTypeParameter(ITypeParameterSymbol symbol)
             {
-                if (_availableTypeParameterNames.Contains(symbol.Name))
+                if (availableTypeParameterNames.Contains(symbol.Name))
                 {
                     return symbol;
                 }
 
-                return _compilation.ObjectType;
+                return compilation.ObjectType;
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnnamedErrorTypeRemover.cs b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnnamedErrorTypeRemover.cs
index 851680b25423e..43f24f015381d 100644
--- a/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnnamedErrorTypeRemover.cs
+++ b/src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.UnnamedErrorTypeRemover.cs
@@ -11,13 +11,8 @@ namespace Microsoft.CodeAnalysis.Shared.Extensions
 {
     internal partial class ITypeSymbolExtensions
     {
-        private class UnnamedErrorTypeRemover : SymbolVisitor<ITypeSymbol>
+        private class UnnamedErrorTypeRemover(Compilation compilation) : SymbolVisitor<ITypeSymbol>
         {
-            private readonly Compilation _compilation;
-
-            public UnnamedErrorTypeRemover(Compilation compilation)
-                => _compilation = compilation;
-
             public override ITypeSymbol DefaultVisit(ISymbol node)
                 => throw new NotImplementedException();
 
@@ -32,7 +27,7 @@ public override ITypeSymbol VisitArrayType(IArrayTypeSymbol symbol)
                     return symbol;
                 }
 
-                return _compilation.CreateArrayTypeSymbol(elementType, symbol.Rank);
+                return compilation.CreateArrayTypeSymbol(elementType, symbol.Rank);
             }
 
             public override ITypeSymbol VisitFunctionPointerType(IFunctionPointerTypeSymbol symbol)
@@ -45,7 +40,7 @@ public override ITypeSymbol VisitNamedType(INamedTypeSymbol symbol)
             {
                 if (symbol.IsErrorType() && symbol.Name == string.Empty)
                 {
-                    return _compilation.ObjectType;
+                    return compilation.ObjectType;
                 }
 
                 var arguments = symbol.TypeArguments.Select(t => t.Accept(this)).ToArray();
@@ -65,7 +60,7 @@ public override ITypeSymbol VisitPointerType(IPointerTypeSymbol symbol)
                     return symbol;
                 }
 
-                return _compilation.CreatePointerTypeSymbol(elementType);
+                return compilation.CreatePointerTypeSymbol(elementType);
             }
 
             public override ITypeSymbol VisitTypeParameter(ITypeParameterSymbol symbol)
diff --git a/src/Workspaces/Core/Portable/Shared/Extensions/TokenSemanticInfo.cs b/src/Workspaces/Core/Portable/Shared/Extensions/TokenSemanticInfo.cs
index a21d810cf958b..a02fcdba4fcf4 100644
--- a/src/Workspaces/Core/Portable/Shared/Extensions/TokenSemanticInfo.cs
+++ b/src/Workspaces/Core/Portable/Shared/Extensions/TokenSemanticInfo.cs
@@ -11,33 +11,23 @@
 
 namespace Microsoft.CodeAnalysis.Shared.Extensions
 {
-    internal readonly struct TokenSemanticInfo
+    internal readonly struct TokenSemanticInfo(
+        ISymbol declaredSymbol,
+        IAliasSymbol aliasSymbol,
+        ImmutableArray<ISymbol> referencedSymbols,
+        ITypeSymbol type,
+        ITypeSymbol convertedType,
+        TextSpan span)
     {
         public static readonly TokenSemanticInfo Empty = new(
             null, null, ImmutableArray<ISymbol>.Empty, null, null, default);
 
-        public readonly ISymbol DeclaredSymbol;
-        public readonly IAliasSymbol AliasSymbol;
-        public readonly ImmutableArray<ISymbol> ReferencedSymbols;
-        public readonly ITypeSymbol Type;
-        public readonly ITypeSymbol ConvertedType;
-        public readonly TextSpan Span;
-
-        public TokenSemanticInfo(
-            ISymbol declaredSymbol,
-            IAliasSymbol aliasSymbol,
-            ImmutableArray<ISymbol> referencedSymbols,
-            ITypeSymbol type,
-            ITypeSymbol convertedType,
-            TextSpan span)
-        {
-            DeclaredSymbol = declaredSymbol;
-            AliasSymbol = aliasSymbol;
-            ReferencedSymbols = referencedSymbols;
-            Type = type;
-            ConvertedType = convertedType;
-            Span = span;
-        }
+        public readonly ISymbol DeclaredSymbol = declaredSymbol;
+        public readonly IAliasSymbol AliasSymbol = aliasSymbol;
+        public readonly ImmutableArray<ISymbol> ReferencedSymbols = referencedSymbols;
+        public readonly ITypeSymbol Type = type;
+        public readonly ITypeSymbol ConvertedType = convertedType;
+        public readonly TextSpan Span = span;
 
         public ImmutableArray<ISymbol> GetSymbols(bool includeType)
         {
diff --git a/src/Workspaces/Core/Portable/Shared/TestHooks/AsynchronousOperationListener+DiagnosticAsyncToken.cs b/src/Workspaces/Core/Portable/Shared/TestHooks/AsynchronousOperationListener+DiagnosticAsyncToken.cs
index f84e807da3fd6..c87396b2c4e3e 100644
--- a/src/Workspaces/Core/Portable/Shared/TestHooks/AsynchronousOperationListener+DiagnosticAsyncToken.cs
+++ b/src/Workspaces/Core/Portable/Shared/TestHooks/AsynchronousOperationListener+DiagnosticAsyncToken.cs
@@ -13,28 +13,19 @@ internal sealed partial class AsynchronousOperationListener
         /// Stores the source information for an <see cref="IAsyncToken"/> value.  Helpful when 
         /// tracking down tokens which aren't properly disposed.
         /// </summary>
-        internal sealed class DiagnosticAsyncToken : AsyncToken
+        internal sealed class DiagnosticAsyncToken(
+            AsynchronousOperationListener listener,
+            string name,
+            object? tag,
+            string filePath,
+            int lineNumber) : AsyncToken(listener)
         {
-            public string Name { get; }
-            public string FilePath { get; }
-            public int LineNumber { get; }
-            public object? Tag { get; }
+            public string Name { get; } = name;
+            public string FilePath { get; } = filePath;
+            public int LineNumber { get; } = lineNumber;
+            public object? Tag { get; } = tag;
             public Task? Task { get; set; }
 
-            public DiagnosticAsyncToken(
-                AsynchronousOperationListener listener,
-                string name,
-                object? tag,
-                string filePath,
-                int lineNumber)
-                : base(listener)
-            {
-                Name = name;
-                Tag = tag;
-                FilePath = filePath;
-                LineNumber = lineNumber;
-            }
-
             internal void AssociateWithTask(Task task)
                 => Task = task;
 
diff --git a/src/Workspaces/Core/Portable/Shared/TestHooks/FeatureAttribute.cs b/src/Workspaces/Core/Portable/Shared/TestHooks/FeatureAttribute.cs
index 08f2b9ac04510..fc2cba96afb4a 100644
--- a/src/Workspaces/Core/Portable/Shared/TestHooks/FeatureAttribute.cs
+++ b/src/Workspaces/Core/Portable/Shared/TestHooks/FeatureAttribute.cs
@@ -14,6 +14,7 @@ internal static class FeatureAttribute
         public const string CallHierarchy = nameof(CallHierarchy);
         public const string Classification = nameof(Classification);
         public const string CodeDefinitionWindow = nameof(CodeDefinitionWindow);
+        public const string CodeLens = nameof(CodeLens);
         public const string CodeModel = nameof(CodeModel);
         public const string CompletionSet = nameof(CompletionSet);
         public const string DesignerAttributes = nameof(DesignerAttributes);
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`0.cs b/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`0.cs
index ad7914453c8c5..24b266705dabc 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`0.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`0.cs
@@ -12,17 +12,12 @@
 namespace Roslyn.Utilities
 {
     /// <inheritdoc cref="AsyncBatchingWorkQueue{TItem, TResult}"/>
-    internal class AsyncBatchingWorkQueue : AsyncBatchingWorkQueue<VoidResult>
+    internal class AsyncBatchingWorkQueue(
+        TimeSpan delay,
+        Func<CancellationToken, ValueTask> processBatchAsync,
+        IAsynchronousOperationListener asyncListener,
+        CancellationToken cancellationToken) : AsyncBatchingWorkQueue<VoidResult>(delay, Convert(processBatchAsync), EqualityComparer<VoidResult>.Default, asyncListener, cancellationToken)
     {
-        public AsyncBatchingWorkQueue(
-            TimeSpan delay,
-            Func<CancellationToken, ValueTask> processBatchAsync,
-            IAsynchronousOperationListener asyncListener,
-            CancellationToken cancellationToken)
-            : base(delay, Convert(processBatchAsync), EqualityComparer<VoidResult>.Default, asyncListener, cancellationToken)
-        {
-        }
-
         private static Func<ImmutableSegmentedList<VoidResult>, CancellationToken, ValueTask> Convert(Func<CancellationToken, ValueTask> processBatchAsync)
             => (items, ct) => processBatchAsync(ct);
 
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`1.cs b/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`1.cs
index e0e31db4c4770..49aa45138199e 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`1.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue`1.cs
@@ -12,7 +12,12 @@
 namespace Roslyn.Utilities
 {
     /// <inheritdoc cref="AsyncBatchingWorkQueue{TItem, TResult}"/>
-    internal class AsyncBatchingWorkQueue<TItem> : AsyncBatchingWorkQueue<TItem, VoidResult>
+    internal class AsyncBatchingWorkQueue<TItem>(
+        TimeSpan delay,
+        Func<ImmutableSegmentedList<TItem>, CancellationToken, ValueTask> processBatchAsync,
+        IEqualityComparer<TItem>? equalityComparer,
+        IAsynchronousOperationListener asyncListener,
+        CancellationToken cancellationToken) : AsyncBatchingWorkQueue<TItem, VoidResult>(delay, Convert(processBatchAsync), equalityComparer, asyncListener, cancellationToken)
     {
         public AsyncBatchingWorkQueue(
             TimeSpan delay,
@@ -27,16 +32,6 @@ public AsyncBatchingWorkQueue(
         {
         }
 
-        public AsyncBatchingWorkQueue(
-            TimeSpan delay,
-            Func<ImmutableSegmentedList<TItem>, CancellationToken, ValueTask> processBatchAsync,
-            IEqualityComparer<TItem>? equalityComparer,
-            IAsynchronousOperationListener asyncListener,
-            CancellationToken cancellationToken)
-            : base(delay, Convert(processBatchAsync), equalityComparer, asyncListener, cancellationToken)
-        {
-        }
-
         private static Func<ImmutableSegmentedList<TItem>, CancellationToken, ValueTask<VoidResult>> Convert(Func<ImmutableSegmentedList<TItem>, CancellationToken, ValueTask> processBatchAsync)
             => async (items, ct) =>
             {
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/EditorBrowsableHelpers.cs b/src/Workspaces/Core/Portable/Shared/Utilities/EditorBrowsableHelpers.cs
index e2a7aa1eefd3f..bd3ee13658e80 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/EditorBrowsableHelpers.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/EditorBrowsableHelpers.cs
@@ -11,25 +11,15 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal static class EditorBrowsableHelpers
     {
-        public readonly struct EditorBrowsableInfo
+        public readonly struct EditorBrowsableInfo(Compilation compilation)
         {
-            public Compilation Compilation { get; }
-            public INamedTypeSymbol? HideModuleNameAttribute { get; }
-            public IMethodSymbol? EditorBrowsableAttributeConstructor { get; }
-            public ImmutableArray<IMethodSymbol> TypeLibTypeAttributeConstructors { get; }
-            public ImmutableArray<IMethodSymbol> TypeLibFuncAttributeConstructors { get; }
-            public ImmutableArray<IMethodSymbol> TypeLibVarAttributeConstructors { get; }
+            public Compilation Compilation { get; } = compilation;
+            public INamedTypeSymbol? HideModuleNameAttribute { get; } = compilation.HideModuleNameAttribute();
+            public IMethodSymbol? EditorBrowsableAttributeConstructor { get; } = GetSpecialEditorBrowsableAttributeConstructor(compilation);
+            public ImmutableArray<IMethodSymbol> TypeLibTypeAttributeConstructors { get; } = GetSpecialTypeLibTypeAttributeConstructors(compilation);
+            public ImmutableArray<IMethodSymbol> TypeLibFuncAttributeConstructors { get; } = GetSpecialTypeLibFuncAttributeConstructors(compilation);
+            public ImmutableArray<IMethodSymbol> TypeLibVarAttributeConstructors { get; } = GetSpecialTypeLibVarAttributeConstructors(compilation);
             public bool IsDefault => Compilation == null;
-
-            public EditorBrowsableInfo(Compilation compilation)
-            {
-                Compilation = compilation;
-                HideModuleNameAttribute = compilation.HideModuleNameAttribute();
-                EditorBrowsableAttributeConstructor = GetSpecialEditorBrowsableAttributeConstructor(compilation);
-                TypeLibTypeAttributeConstructors = GetSpecialTypeLibTypeAttributeConstructors(compilation);
-                TypeLibFuncAttributeConstructors = GetSpecialTypeLibFuncAttributeConstructors(compilation);
-                TypeLibVarAttributeConstructors = GetSpecialTypeLibVarAttributeConstructors(compilation);
-            }
         }
 
         /// <summary>
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/ExtensionOrderer.Node.cs b/src/Workspaces/Core/Portable/Shared/Utilities/ExtensionOrderer.Node.cs
index 4bcbb3a4bb768..9ab267f4ff034 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/ExtensionOrderer.Node.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/ExtensionOrderer.Node.cs
@@ -11,14 +11,11 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class ExtensionOrderer
     {
-        private class Node<TExtension, TMetadata>
+        private class Node<TExtension, TMetadata>(Lazy<TExtension, TMetadata> extension)
         {
-            public readonly Lazy<TExtension, TMetadata> Extension;
+            public readonly Lazy<TExtension, TMetadata> Extension = extension;
             public readonly HashSet<Node<TExtension, TMetadata>> ExtensionsBeforeMeSet = new();
 
-            public Node(Lazy<TExtension, TMetadata> extension)
-                => this.Extension = extension;
-
             public void CheckForCycles()
                 => this.CheckForCycles(new HashSet<Node<TExtension, TMetadata>>());
 
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/IStreamingProgressTrackerExtensions.cs b/src/Workspaces/Core/Portable/Shared/Utilities/IStreamingProgressTrackerExtensions.cs
index 87544727ed625..961da5739654a 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/IStreamingProgressTrackerExtensions.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/IStreamingProgressTrackerExtensions.cs
@@ -23,19 +23,10 @@ public static async Task<IAsyncDisposable> AddSingleItemAsync(this IStreamingPro
         public static ValueTask ItemCompletedAsync(this IStreamingProgressTracker tracker, CancellationToken cancellationToken)
             => tracker.ItemsCompletedAsync(1, cancellationToken);
 
-        private class StreamingProgressDisposer : IAsyncDisposable
+        private class StreamingProgressDisposer(IStreamingProgressTracker progressTracker, CancellationToken cancellationToken) : IAsyncDisposable
         {
-            private readonly IStreamingProgressTracker _progressTracker;
-            private readonly CancellationToken _cancellationToken;
-
-            public StreamingProgressDisposer(IStreamingProgressTracker progressTracker, CancellationToken cancellationToken)
-            {
-                _progressTracker = progressTracker;
-                _cancellationToken = cancellationToken;
-            }
-
             public async ValueTask DisposeAsync()
-                => await _progressTracker.ItemCompletedAsync(_cancellationToken).ConfigureAwait(false);
+                => await progressTracker.ItemCompletedAsync(cancellationToken).ConfigureAwait(false);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/ProgressTracker.cs b/src/Workspaces/Core/Portable/Shared/Utilities/ProgressTracker.cs
index 55f00ab8bd1bf..acac99ae440bb 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/ProgressTracker.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/ProgressTracker.cs
@@ -12,22 +12,17 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
     /// <summary>
     /// Utility class that can be used to track the progress of an operation in a threadsafe manner.
     /// </summary>
-    internal class ProgressTracker : IProgressTracker
+    internal class ProgressTracker(Action<string, int, int> updateActionOpt) : IProgressTracker
     {
         private string _description;
         private int _completedItems;
         private int _totalItems;
 
-        private readonly Action<string, int, int> _updateActionOpt;
-
         public ProgressTracker()
             : this(null)
         {
         }
 
-        public ProgressTracker(Action<string, int, int> updateActionOpt)
-            => _updateActionOpt = updateActionOpt;
-
         public string Description
         {
             get => _description;
@@ -63,6 +58,6 @@ public void Clear()
         }
 
         private void Update()
-            => _updateActionOpt?.Invoke(_description, _completedItems, _totalItems);
+            => updateActionOpt?.Invoke(_description, _completedItems, _totalItems);
     }
 }
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/SemanticMap.Walker.cs b/src/Workspaces/Core/Portable/Shared/Utilities/SemanticMap.Walker.cs
index 25317e9d4ae17..5daea7dddbb28 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/SemanticMap.Walker.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/SemanticMap.Walker.cs
@@ -11,26 +11,14 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class SemanticMap
     {
-        private class Walker : SyntaxWalker
+        private class Walker(SemanticModel semanticModel, SemanticMap map, CancellationToken cancellationToken) : SyntaxWalker(SyntaxWalkerDepth.Token)
         {
-            private readonly SemanticModel _semanticModel;
-            private readonly SemanticMap _map;
-            private readonly CancellationToken _cancellationToken;
-
-            public Walker(SemanticModel semanticModel, SemanticMap map, CancellationToken cancellationToken)
-                : base(SyntaxWalkerDepth.Token)
-            {
-                _semanticModel = semanticModel;
-                _map = map;
-                _cancellationToken = cancellationToken;
-            }
-
             public override void Visit(SyntaxNode node)
             {
-                var info = _semanticModel.GetSymbolInfo(node);
+                var info = semanticModel.GetSymbolInfo(node);
                 if (!IsNone(info))
                 {
-                    _map._expressionToInfoMap.Add(node, info);
+                    map._expressionToInfoMap.Add(node, info);
                 }
 
                 base.Visit(node);
@@ -38,10 +26,10 @@ public override void Visit(SyntaxNode node)
 
             protected override void VisitToken(SyntaxToken token)
             {
-                var info = _semanticModel.GetSymbolInfo(token, _cancellationToken);
+                var info = semanticModel.GetSymbolInfo(token, cancellationToken);
                 if (!IsNone(info))
                 {
-                    _map._tokenToInfoMap.Add(token, info);
+                    map._tokenToInfoMap.Add(token, info);
                 }
 
                 base.VisitToken(token);
diff --git a/src/Workspaces/Core/Portable/Shared/Utilities/StreamingProgressTracker.cs b/src/Workspaces/Core/Portable/Shared/Utilities/StreamingProgressTracker.cs
index 69f59ccf8382f..6a06dbd703d51 100644
--- a/src/Workspaces/Core/Portable/Shared/Utilities/StreamingProgressTracker.cs
+++ b/src/Workspaces/Core/Portable/Shared/Utilities/StreamingProgressTracker.cs
@@ -11,16 +11,11 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
     /// <summary>
     /// Utility class that can be used to track the progress of an operation in a threadsafe manner.
     /// </summary>
-    internal sealed class StreamingProgressTracker : IStreamingProgressTracker
+    internal sealed class StreamingProgressTracker(Func<int, int, CancellationToken, ValueTask>? updateAction = null) : IStreamingProgressTracker
     {
         private int _completedItems;
         private int _totalItems;
 
-        private readonly Func<int, int, CancellationToken, ValueTask>? _updateAction;
-
-        public StreamingProgressTracker(Func<int, int, CancellationToken, ValueTask>? updateAction = null)
-            => _updateAction = updateAction;
-
         public ValueTask AddItemsAsync(int count, CancellationToken cancellationToken)
         {
             Interlocked.Add(ref _totalItems, count);
@@ -34,6 +29,6 @@ public ValueTask ItemsCompletedAsync(int count, CancellationToken cancellationTo
         }
 
         private ValueTask UpdateAsync(CancellationToken cancellationToken)
-            => _updateAction?.Invoke(Volatile.Read(ref _completedItems), Volatile.Read(ref _totalItems), cancellationToken) ?? default;
+            => updateAction?.Invoke(Volatile.Read(ref _completedItems), Volatile.Read(ref _totalItems), cancellationToken) ?? default;
     }
 }
diff --git a/src/Workspaces/Core/Portable/SolutionCrawler/ExportIncrementalAnalyzerProviderAttribute.cs b/src/Workspaces/Core/Portable/SolutionCrawler/ExportIncrementalAnalyzerProviderAttribute.cs
index bd535cbcaad1b..8ee2c1f742cb7 100644
--- a/src/Workspaces/Core/Portable/SolutionCrawler/ExportIncrementalAnalyzerProviderAttribute.cs
+++ b/src/Workspaces/Core/Portable/SolutionCrawler/ExportIncrementalAnalyzerProviderAttribute.cs
@@ -11,19 +11,11 @@ namespace Microsoft.CodeAnalysis.SolutionCrawler
 {
     [MetadataAttribute]
     [AttributeUsage(AttributeTargets.Class)]
-    internal class ExportIncrementalAnalyzerProviderAttribute : ExportAttribute
+    internal class ExportIncrementalAnalyzerProviderAttribute(string name, string[] workspaceKinds) : ExportAttribute(typeof(IIncrementalAnalyzerProvider))
     {
-        public bool HighPriorityForActiveFile { get; }
-        public string Name { get; }
-        public string[] WorkspaceKinds { get; }
-
-        public ExportIncrementalAnalyzerProviderAttribute(string name, string[] workspaceKinds)
-            : base(typeof(IIncrementalAnalyzerProvider))
-        {
-            this.WorkspaceKinds = workspaceKinds;
-            this.Name = name ?? throw new ArgumentNullException(nameof(name));
-            this.HighPriorityForActiveFile = false;
-        }
+        public bool HighPriorityForActiveFile { get; } = false;
+        public string Name { get; } = name ?? throw new ArgumentNullException(nameof(name));
+        public string[] WorkspaceKinds { get; } = workspaceKinds;
 
         public ExportIncrementalAnalyzerProviderAttribute(bool highPriorityForActiveFile, string name, string[] workspaceKinds)
             : this(name, workspaceKinds)
diff --git a/src/Workspaces/Core/Portable/SolutionCrawler/InvocationReasons.cs b/src/Workspaces/Core/Portable/SolutionCrawler/InvocationReasons.cs
index 9bfd6168b6b75..a1a33340e065a 100644
--- a/src/Workspaces/Core/Portable/SolutionCrawler/InvocationReasons.cs
+++ b/src/Workspaces/Core/Portable/SolutionCrawler/InvocationReasons.cs
@@ -10,21 +10,18 @@
 namespace Microsoft.CodeAnalysis.SolutionCrawler
 {
     [DataContract]
-    internal partial struct InvocationReasons : IEnumerable<string>
+    internal partial struct InvocationReasons(ImmutableHashSet<string> reasons) : IEnumerable<string>
     {
         public static readonly InvocationReasons Empty = new(ImmutableHashSet<string>.Empty);
 
         [DataMember(Order = 0)]
-        private readonly ImmutableHashSet<string> _reasons;
+        private readonly ImmutableHashSet<string> _reasons = reasons ?? ImmutableHashSet<string>.Empty;
 
         public InvocationReasons(string reason)
             : this(ImmutableHashSet.Create(reason))
         {
         }
 
-        public InvocationReasons(ImmutableHashSet<string> reasons)
-            => _reasons = reasons ?? ImmutableHashSet<string>.Empty;
-
         public bool IsEmpty => _reasons.IsEmpty;
 
         public bool Contains(string reason)
diff --git a/src/Workspaces/Core/Portable/Storage/AbstractPersistentStorageService.cs b/src/Workspaces/Core/Portable/Storage/AbstractPersistentStorageService.cs
index 69ee4e874a597..fd3ea452678a8 100644
--- a/src/Workspaces/Core/Portable/Storage/AbstractPersistentStorageService.cs
+++ b/src/Workspaces/Core/Portable/Storage/AbstractPersistentStorageService.cs
@@ -167,15 +167,10 @@ private void Shutdown()
         internal TestAccessor GetTestAccessor()
             => new(this);
 
-        internal readonly struct TestAccessor
+        internal readonly struct TestAccessor(AbstractPersistentStorageService service)
         {
-            private readonly AbstractPersistentStorageService _service;
-
-            public TestAccessor(AbstractPersistentStorageService service)
-                => _service = service;
-
             public void Shutdown()
-                => _service.Shutdown();
+                => service.Shutdown();
         }
 
         /// <summary>
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/Interop/SqlException.cs b/src/Workspaces/Core/Portable/Storage/SQLite/Interop/SqlException.cs
index 27dc41ad6970a..fbab320358318 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/Interop/SqlException.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/Interop/SqlException.cs
@@ -6,14 +6,8 @@
 
 namespace Microsoft.CodeAnalysis.SQLite.Interop
 {
-    internal class SqlException : Exception
+    internal class SqlException(Result result, string message) : Exception(message)
     {
-        public readonly Result Result;
-
-        public SqlException(Result result, string message)
-            : base(message)
-        {
-            this.Result = result;
-        }
+        public readonly Result Result = result;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/ResettableSqlStatement.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/ResettableSqlStatement.cs
index 6815b7559f2eb..5bac6cea63203 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/ResettableSqlStatement.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/ResettableSqlStatement.cs
@@ -24,12 +24,9 @@ namespace Microsoft.CodeAnalysis.SQLite.v2.Interop
     /// as it will happen to all prepared statemnets when the <see cref="SqlStatement"/> is
     /// <see cref="SqlStatement.Close_OnlyForUseBySqlConnection"/>d.
     /// </summary>
-    internal readonly struct ResettableSqlStatement : IDisposable
+    internal readonly struct ResettableSqlStatement(SqlStatement statement) : IDisposable
     {
-        public readonly SqlStatement Statement;
-
-        public ResettableSqlStatement(SqlStatement statement)
-            => Statement = statement;
+        public readonly SqlStatement Statement = statement;
 
         public void Dispose()
         {
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/SqlStatement.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/SqlStatement.cs
index c012eca753301..431c3c23f17cb 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/SqlStatement.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/Interop/SqlStatement.cs
@@ -27,29 +27,20 @@ namespace Microsoft.CodeAnalysis.SQLite.v2.Interop
     /// Finalization/destruction of the underlying raw sqlite statement is handled
     /// by <see cref="SqlConnection.Close_OnlyForUseBySQLiteConnectionPool"/>.</para>
     /// </summary>
-    internal readonly struct SqlStatement
+    internal readonly struct SqlStatement(SqlConnection connection, SafeSqliteStatementHandle statement)
     {
-        private readonly SqlConnection _connection;
-        private readonly SafeSqliteStatementHandle _rawStatement;
-
-        public SqlStatement(SqlConnection connection, SafeSqliteStatementHandle statement)
-        {
-            _connection = connection;
-            _rawStatement = statement;
-        }
-
         internal void Close_OnlyForUseBySqlConnection()
-            => _rawStatement.Dispose();
+            => statement.Dispose();
 
         public void ClearBindings()
-            => _connection.ThrowIfNotOk(NativeMethods.sqlite3_clear_bindings(_rawStatement));
+            => connection.ThrowIfNotOk(NativeMethods.sqlite3_clear_bindings(statement));
 
         public void Reset()
-            => _connection.ThrowIfNotOk(NativeMethods.sqlite3_reset(_rawStatement));
+            => connection.ThrowIfNotOk(NativeMethods.sqlite3_reset(statement));
 
         public Result Step(bool throwOnError = true)
         {
-            var stepResult = NativeMethods.sqlite3_step(_rawStatement);
+            var stepResult = NativeMethods.sqlite3_step(statement);
 
             // Anything other than DONE or ROW is an error when stepping.
             // throw if the caller wants that, or just return the value
@@ -58,7 +49,7 @@ public Result Step(bool throwOnError = true)
             {
                 if (throwOnError)
                 {
-                    _connection.Throw(stepResult);
+                    connection.Throw(stepResult);
                     throw ExceptionUtilities.Unreachable();
                 }
             }
@@ -101,27 +92,27 @@ internal void BindStringParameter(int parameterIndex, string value)
                         }
                     }
 #endif
-                    _connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_text(_rawStatement, parameterIndex, bytes));
+                    connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_text(statement, parameterIndex, bytes));
                     return;
                 }
             }
 
-            _connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_text(_rawStatement, parameterIndex, value));
+            connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_text(statement, parameterIndex, value));
         }
 
         internal void BindInt64Parameter(int parameterIndex, long value)
-            => _connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_int64(_rawStatement, parameterIndex, value));
+            => connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_int64(statement, parameterIndex, value));
 
         internal void BindBlobParameter(int parameterIndex, ReadOnlySpan<byte> bytes)
-            => _connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_blob(_rawStatement, parameterIndex, bytes));
+            => connection.ThrowIfNotOk(NativeMethods.sqlite3_bind_blob(statement, parameterIndex, bytes));
 
         internal int GetInt32At(int columnIndex)
-            => NativeMethods.sqlite3_column_int(_rawStatement, columnIndex);
+            => NativeMethods.sqlite3_column_int(statement, columnIndex);
 
         internal long GetInt64At(int columnIndex)
-            => NativeMethods.sqlite3_column_int64(_rawStatement, columnIndex);
+            => NativeMethods.sqlite3_column_int64(statement, columnIndex);
 
         internal string GetStringAt(int columnIndex)
-            => NativeMethods.sqlite3_column_text(_rawStatement, columnIndex);
+            => NativeMethods.sqlite3_column_text(statement, columnIndex);
     }
 }
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool+PooledConnection.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool+PooledConnection.cs
index 0c37cdf95d740..282225e30c551 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool+PooledConnection.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool+PooledConnection.cs
@@ -9,19 +9,12 @@ namespace Microsoft.CodeAnalysis.SQLite.v2
 {
     internal partial class SQLiteConnectionPool
     {
-        internal readonly struct PooledConnection : IDisposable
+        internal readonly struct PooledConnection(SQLiteConnectionPool connectionPool, SqlConnection sqlConnection) : IDisposable
         {
-            private readonly SQLiteConnectionPool _connectionPool;
-            public readonly SqlConnection Connection;
-
-            public PooledConnection(SQLiteConnectionPool connectionPool, SqlConnection sqlConnection)
-            {
-                _connectionPool = connectionPool;
-                Connection = sqlConnection;
-            }
+            public readonly SqlConnection Connection = sqlConnection;
 
             public void Dispose()
-                => _connectionPool.ReleaseConnection(Connection);
+                => connectionPool.ReleaseConnection(Connection);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool.cs
index 19f6d981ebaf9..aa3ef1fe45322 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLiteConnectionPool.cs
@@ -11,7 +11,7 @@
 
 namespace Microsoft.CodeAnalysis.SQLite.v2
 {
-    internal sealed partial class SQLiteConnectionPool : IDisposable
+    internal sealed partial class SQLiteConnectionPool(SQLiteConnectionPoolService connectionPoolService, IPersistentStorageFaultInjector? faultInjector, string databasePath, IDisposable ownershipLock) : IDisposable
     {
         // We pool connections to the DB so that we don't have to take the hit of 
         // reconnecting.  The connections also cache the prepared statements used
@@ -22,19 +22,6 @@ internal sealed partial class SQLiteConnectionPool : IDisposable
 
         private readonly CancellationTokenSource _shutdownTokenSource = new();
 
-        private readonly SQLiteConnectionPoolService _connectionPoolService;
-        private readonly IPersistentStorageFaultInjector? _faultInjector;
-        private readonly string _databasePath;
-        private readonly IDisposable _ownershipLock;
-
-        public SQLiteConnectionPool(SQLiteConnectionPoolService connectionPoolService, IPersistentStorageFaultInjector? faultInjector, string databasePath, IDisposable ownershipLock)
-        {
-            _connectionPoolService = connectionPoolService;
-            _faultInjector = faultInjector;
-            _databasePath = databasePath;
-            _ownershipLock = ownershipLock;
-        }
-
         internal void Initialize(
             Action<SqlConnection, CancellationToken> initializer,
             CancellationToken cancellationToken)
@@ -58,7 +45,7 @@ public void Dispose()
             finally
             {
                 // let the lock go
-                _ownershipLock.Dispose();
+                ownershipLock.Dispose();
             }
         }
 
@@ -96,7 +83,7 @@ private PooledConnection GetPooledConnection(bool checkScheduler, out SqlConnect
             if (checkScheduler)
             {
                 var scheduler = TaskScheduler.Current;
-                if (scheduler != _connectionPoolService.Scheduler.ConcurrentScheduler && scheduler != _connectionPoolService.Scheduler.ExclusiveScheduler)
+                if (scheduler != connectionPoolService.Scheduler.ConcurrentScheduler && scheduler != connectionPoolService.Scheduler.ExclusiveScheduler)
                     throw new InvalidOperationException($"Cannot get a connection to the DB unless running on one of {nameof(SQLiteConnectionPoolService)}'s schedulers");
             }
 
@@ -117,7 +104,7 @@ private SqlConnection GetConnection()
             }
 
             // Otherwise create a new connection.
-            return SqlConnection.Create(_faultInjector, _databasePath);
+            return SqlConnection.Create(faultInjector, databasePath);
         }
 
         private void ReleaseConnection(SqlConnection connection)
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorageService.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorageService.cs
index a08a98b5d9273..113726cce4838 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorageService.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorageService.cs
@@ -16,26 +16,22 @@
 
 namespace Microsoft.CodeAnalysis.SQLite.v2
 {
-    internal sealed class SQLitePersistentStorageService : AbstractPersistentStorageService, IWorkspaceService
+    internal sealed class SQLitePersistentStorageService(
+        SQLiteConnectionPoolService connectionPoolService,
+        IPersistentStorageConfiguration configuration,
+        IAsynchronousOperationListener asyncListener) : AbstractPersistentStorageService(configuration), IWorkspaceService
     {
         [ExportWorkspaceServiceFactory(typeof(SQLitePersistentStorageService)), Shared]
-        internal sealed class ServiceFactory : IWorkspaceServiceFactory
+        [method: ImportingConstructor]
+        [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        internal sealed class ServiceFactory(
+            SQLiteConnectionPoolService connectionPoolService,
+            IAsynchronousOperationListenerProvider asyncOperationListenerProvider) : IWorkspaceServiceFactory
         {
-            private readonly SQLiteConnectionPoolService _connectionPoolService;
-            private readonly IAsynchronousOperationListener _asyncListener;
-
-            [ImportingConstructor]
-            [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-            public ServiceFactory(
-                SQLiteConnectionPoolService connectionPoolService,
-                IAsynchronousOperationListenerProvider asyncOperationListenerProvider)
-            {
-                _connectionPoolService = connectionPoolService;
-                _asyncListener = asyncOperationListenerProvider.GetListener(FeatureAttribute.PersistentStorage);
-            }
+            private readonly IAsynchronousOperationListener _asyncListener = asyncOperationListenerProvider.GetListener(FeatureAttribute.PersistentStorage);
 
             public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
-                => new SQLitePersistentStorageService(_connectionPoolService, workspaceServices.GetRequiredService<IPersistentStorageConfiguration>(), _asyncListener);
+                => new SQLitePersistentStorageService(connectionPoolService, workspaceServices.GetRequiredService<IPersistentStorageConfiguration>(), _asyncListener);
         }
 
         private const string StorageExtension = "sqlite3";
@@ -65,20 +61,8 @@ private static bool TryInitializeLibrariesLazy()
             return true;
         }
 
-        private readonly SQLiteConnectionPoolService _connectionPoolService;
-        private readonly IAsynchronousOperationListener _asyncListener;
         private readonly IPersistentStorageFaultInjector? _faultInjector;
 
-        public SQLitePersistentStorageService(
-            SQLiteConnectionPoolService connectionPoolService,
-            IPersistentStorageConfiguration configuration,
-            IAsynchronousOperationListener asyncListener)
-            : base(configuration)
-        {
-            _connectionPoolService = connectionPoolService;
-            _asyncListener = asyncListener;
-        }
-
         public SQLitePersistentStorageService(
             SQLiteConnectionPoolService connectionPoolService,
             IPersistentStorageConfiguration configuration,
@@ -108,11 +92,11 @@ protected override string GetDatabaseFilePath(string workingFolderPath)
                 return new(NoOpPersistentStorage.GetOrThrow(Configuration.ThrowOnFailure));
 
             return new(SQLitePersistentStorage.TryCreate(
-                _connectionPoolService,
+                connectionPoolService,
                 solutionKey,
                 workingFolderPath,
                 databaseFilePath,
-                _asyncListener,
+                asyncListener,
                 _faultInjector));
         }
 
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_DocumentSerialization.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_DocumentSerialization.cs
index 5e3c1a5cf5074..13d50c5c11c2c 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_DocumentSerialization.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_DocumentSerialization.cs
@@ -30,18 +30,13 @@ protected override Task<bool> WriteStreamAsync(DocumentKey documentKey, Document
         /// <see cref="Accessor{TKey, TDatabaseId}"/> responsible for storing and 
         /// retrieving data from <see cref="DocumentDataTableName"/>.
         /// </summary>
-        private sealed class DocumentAccessor : Accessor<DocumentKey, DocumentPrimaryKey>
+        private sealed class DocumentAccessor(SQLitePersistentStorage storage) : Accessor<DocumentKey, DocumentPrimaryKey>(Table.Document,
+                  storage,
+                  (ProjectPathIdColumnName, SQLiteIntegerType),
+                  (ProjectNameIdColumnName, SQLiteIntegerType),
+                  (DocumentFolderIdColumnName, SQLiteIntegerType),
+                  (DocumentNameIdColumnName, SQLiteIntegerType))
         {
-            public DocumentAccessor(SQLitePersistentStorage storage)
-                : base(Table.Document,
-                      storage,
-                      (ProjectPathIdColumnName, SQLiteIntegerType),
-                      (ProjectNameIdColumnName, SQLiteIntegerType),
-                      (DocumentFolderIdColumnName, SQLiteIntegerType),
-                      (DocumentNameIdColumnName, SQLiteIntegerType))
-            {
-            }
-
             protected override DocumentPrimaryKey? TryGetDatabaseKey(SqlConnection connection, DocumentKey key, bool allowWrite)
                 => Storage.TryGetDocumentPrimaryKey(connection, key, allowWrite);
 
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_ProjectSerialization.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_ProjectSerialization.cs
index 4da91b2910ed8..44177bdec1766 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_ProjectSerialization.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_ProjectSerialization.cs
@@ -30,16 +30,11 @@ protected override Task<bool> WriteStreamAsync(ProjectKey projectKey, Project? p
         /// <see cref="Accessor{TKey, TDatabaseId}"/> responsible for storing and
         /// retrieving data from <see cref="ProjectDataTableName"/>.
         /// </summary>
-        private sealed class ProjectAccessor : Accessor<ProjectKey, ProjectPrimaryKey>
+        private sealed class ProjectAccessor(SQLitePersistentStorage storage) : Accessor<ProjectKey, ProjectPrimaryKey>(Table.Project,
+                  storage,
+                  (ProjectPathIdColumnName, SQLiteIntegerType),
+                  (ProjectNameIdColumnName, SQLiteIntegerType))
         {
-            public ProjectAccessor(SQLitePersistentStorage storage)
-                : base(Table.Project,
-                      storage,
-                      (ProjectPathIdColumnName, SQLiteIntegerType),
-                      (ProjectNameIdColumnName, SQLiteIntegerType))
-            {
-            }
-
             protected override ProjectPrimaryKey? TryGetDatabaseKey(SqlConnection connection, ProjectKey projectKey, bool allowWrite)
                 => Storage.TryGetProjectPrimaryKey(connection, projectKey, allowWrite);
 
diff --git a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_SolutionSerialization.cs b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_SolutionSerialization.cs
index cf52ab79a3437..da2eded2ff706 100644
--- a/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_SolutionSerialization.cs
+++ b/src/Workspaces/Core/Portable/Storage/SQLite/v2/SQLitePersistentStorage_SolutionSerialization.cs
@@ -31,13 +31,9 @@ public override Task<bool> WriteStreamAsync(string name, Stream stream, Checksum
         /// retrieving data from <see cref="SolutionDataTableName"/>.  Note that with the Solution 
         /// table there is no need for key->id translation.  i.e. the key acts as the ID itself.
         /// </summary>
-        private sealed class SolutionAccessor : Accessor<SolutionKey, SolutionPrimaryKey>
+        private sealed class SolutionAccessor(SQLitePersistentStorage storage) : Accessor<SolutionKey, SolutionPrimaryKey>(Table.Solution,
+                  storage)
         {
-            public SolutionAccessor(SQLitePersistentStorage storage)
-                : base(Table.Solution,
-                      storage)
-            {
-            }
 
             // For the SolutionDataTable the key itself acts as the data-id.
             protected override SolutionPrimaryKey? TryGetDatabaseKey(SqlConnection connection, SolutionKey key, bool allowWrite)
diff --git a/src/Workspaces/Core/Portable/SymbolSearch/ISymbolSearchService.cs b/src/Workspaces/Core/Portable/SymbolSearch/ISymbolSearchService.cs
index 5f1cf8d3bb7c0..83d019f780d9e 100644
--- a/src/Workspaces/Core/Portable/SymbolSearch/ISymbolSearchService.cs
+++ b/src/Workspaces/Core/Portable/SymbolSearch/ISymbolSearchService.cs
@@ -70,45 +70,31 @@ protected PackageResult(string packageName, int rank)
     }
 
     [DataContract]
-    internal sealed class PackageWithTypeResult : PackageResult
+    internal sealed class PackageWithTypeResult(
+        string packageName,
+        int rank,
+        string typeName,
+        string? version,
+        ImmutableArray<string> containingNamespaceNames) : PackageResult(packageName, rank)
     {
         [DataMember(Order = 2)]
-        public readonly string TypeName;
+        public readonly string TypeName = typeName;
 
         [DataMember(Order = 3)]
-        public readonly string? Version;
+        public readonly string? Version = version;
 
         [DataMember(Order = 4)]
-        public readonly ImmutableArray<string> ContainingNamespaceNames;
-
-        public PackageWithTypeResult(
-            string packageName,
-            int rank,
-            string typeName,
-            string? version,
-            ImmutableArray<string> containingNamespaceNames)
-            : base(packageName, rank)
-        {
-            TypeName = typeName;
-            Version = version;
-            ContainingNamespaceNames = containingNamespaceNames;
-        }
+        public readonly ImmutableArray<string> ContainingNamespaceNames = containingNamespaceNames;
     }
 
     [DataContract]
-    internal sealed class PackageWithAssemblyResult : PackageResult, IEquatable<PackageWithAssemblyResult?>, IComparable<PackageWithAssemblyResult?>
+    internal sealed class PackageWithAssemblyResult(
+        string packageName,
+        int rank,
+        string version) : PackageResult(packageName, rank), IEquatable<PackageWithAssemblyResult?>, IComparable<PackageWithAssemblyResult?>
     {
         [DataMember(Order = 2)]
-        public readonly string? Version;
-
-        public PackageWithAssemblyResult(
-            string packageName,
-            int rank,
-            string version)
-            : base(packageName, rank)
-        {
-            Version = version;
-        }
+        public readonly string? Version = version;
 
         public override int GetHashCode()
             => PackageName.GetHashCode();
@@ -132,26 +118,19 @@ public int CompareTo(PackageWithAssemblyResult? other)
     }
 
     [DataContract]
-    internal sealed class ReferenceAssemblyWithTypeResult
+    internal sealed class ReferenceAssemblyWithTypeResult(
+        string assemblyName,
+        string typeName,
+        ImmutableArray<string> containingNamespaceNames)
     {
         [DataMember(Order = 0)]
-        public readonly string AssemblyName;
+        public readonly string AssemblyName = assemblyName;
 
         [DataMember(Order = 1)]
-        public readonly string TypeName;
+        public readonly string TypeName = typeName;
 
         [DataMember(Order = 2)]
-        public readonly ImmutableArray<string> ContainingNamespaceNames;
-
-        public ReferenceAssemblyWithTypeResult(
-            string assemblyName,
-            string typeName,
-            ImmutableArray<string> containingNamespaceNames)
-        {
-            AssemblyName = assemblyName;
-            TypeName = typeName;
-            ContainingNamespaceNames = containingNamespaceNames;
-        }
+        public readonly ImmutableArray<string> ContainingNamespaceNames = containingNamespaceNames;
     }
 
     [ExportWorkspaceService(typeof(ISymbolSearchService)), Shared]
diff --git a/src/Workspaces/Core/Portable/TaskList/TaskListItemDescriptor.cs b/src/Workspaces/Core/Portable/TaskList/TaskListItemDescriptor.cs
index 4e15badad56ec..644aa4ea0463f 100644
--- a/src/Workspaces/Core/Portable/TaskList/TaskListItemDescriptor.cs
+++ b/src/Workspaces/Core/Portable/TaskList/TaskListItemDescriptor.cs
@@ -20,18 +20,12 @@ internal enum TaskListItemPriority
     /// Description of a TODO comment type to find in a user's comments.
     /// </summary>
     [DataContract]
-    internal readonly struct TaskListItemDescriptor
+    internal readonly struct TaskListItemDescriptor(string text, TaskListItemPriority priority)
     {
         [DataMember(Order = 0)]
-        public string Text { get; }
+        public string Text { get; } = text;
         [DataMember(Order = 1)]
-        public TaskListItemPriority Priority { get; }
-
-        public TaskListItemDescriptor(string text, TaskListItemPriority priority)
-        {
-            Text = text;
-            Priority = priority;
-        }
+        public TaskListItemPriority Priority { get; } = priority;
 
         public static ImmutableArray<TaskListItemDescriptor> Parse(ImmutableArray<string> items)
         {
diff --git a/src/Workspaces/Core/Portable/Telemetry/ITelemetryLog.cs b/src/Workspaces/Core/Portable/Telemetry/ITelemetryLog.cs
new file mode 100644
index 0000000000000..3c4d0f7772992
--- /dev/null
+++ b/src/Workspaces/Core/Portable/Telemetry/ITelemetryLog.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Microsoft.CodeAnalysis.Internal.Log;
+
+namespace Microsoft.CodeAnalysis.Telemetry
+{
+    internal interface ITelemetryLog
+    {
+        /// <summary>
+        /// Adds a telemetry event with values obtained from context message <paramref name="logMessage"/>
+        /// </summary>
+        public void Log(LogMessage logMessage);
+
+        /// <summary>
+        /// Adds an execution time telemetry event representing the <paramref name="name"/> operation
+        /// only if  block duration meets or exceeds <paramref name="minThresholdMs"/> milliseconds.
+        /// </summary>
+        /// <param name="minThresholdMs">Optional parameter used to determine whether to send the telemetry event (in milliseconds)</param>
+        public IDisposable? LogBlockTime(string name, int minThresholdMs = -1);
+    }
+}
diff --git a/src/Workspaces/Core/Portable/Telemetry/ITelemetryLogProvider.cs b/src/Workspaces/Core/Portable/Telemetry/ITelemetryLogProvider.cs
new file mode 100644
index 0000000000000..eb84d9917571b
--- /dev/null
+++ b/src/Workspaces/Core/Portable/Telemetry/ITelemetryLogProvider.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.Internal.Log;
+
+namespace Microsoft.CodeAnalysis.Telemetry
+{
+    internal interface ITelemetryLogProvider
+    {
+        /// <summary>
+        /// Returns an <see cref="ITelemetryLog"/> for logging telemetry.
+        /// </summary>
+        /// <param name="functionId">FunctionId representing the telemetry operation</param>
+        public ITelemetryLog? GetLog(FunctionId functionId);
+
+        /// <summary>
+        /// Returns an aggregating <see cref="ITelemetryLog"/> for logging telemetry.
+        /// </summary>
+        /// <param name="functionId">FunctionId representing the telemetry operation</param>
+        /// <param name="bucketBoundaries">Optional values indicating bucket boundaries in milliseconds. If not specified, 
+        /// all aggregating events created will use a default configuration</param>
+        public ITelemetryLog? GetAggregatingLog(FunctionId functionId, double[]? bucketBoundaries = null);
+    }
+}
diff --git a/src/Workspaces/Core/Portable/Telemetry/TelemetryLogging.cs b/src/Workspaces/Core/Portable/Telemetry/TelemetryLogging.cs
new file mode 100644
index 0000000000000..086ea859a5716
--- /dev/null
+++ b/src/Workspaces/Core/Portable/Telemetry/TelemetryLogging.cs
@@ -0,0 +1,90 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Microsoft.CodeAnalysis.Internal.Log;
+
+namespace Microsoft.CodeAnalysis.Telemetry
+{
+    /// <summary>
+    /// Provides access to posting telemetry events or adding information
+    /// to aggregated telemetry events.
+    /// </summary>
+    internal static class TelemetryLogging
+    {
+        private static ITelemetryLogProvider? s_logProvider;
+
+        public const string AggregatedKeyName = "Name";
+        public const string AggregatedKeyValue = "Value";
+
+        public static void SetLogProvider(ITelemetryLogProvider logProvider)
+        {
+            s_logProvider = logProvider;
+        }
+
+        /// <summary>
+        /// Posts a telemetry event representing the <paramref name="functionId"/> operation with context message <paramref name="logMessage"/>
+        /// </summary>
+        public static void Log(FunctionId functionId, LogMessage logMessage)
+        {
+            GetLog(functionId)?.Log(logMessage);
+        }
+
+        /// <summary>
+        /// Posts a telemetry event representing the <paramref name="functionId"/> operation 
+        /// only if the block duration meets or exceeds <paramref name="minThresholdMs"/> milliseconds.
+        /// This event will contain properties from which both <paramref name="name"/> and <paramref name="minThresholdMs"/>.
+        /// and block execution time can be determined.
+        /// </summary>
+        /// <param name="minThresholdMs">Optional parameter used to determine whether to send the telemetry event</param>
+        public static IDisposable? LogBlockTime(FunctionId functionId, TelemetryLoggingInterpolatedStringHandler name, int minThresholdMs = -1)
+        {
+            return GetLog(functionId)?.LogBlockTime(name.GetFormattedText(), minThresholdMs);
+        }
+
+        /// <summary>
+        /// Adds information to an aggregated telemetry event representing the <paramref name="functionId"/> operation 
+        /// with the specified name and value.
+        /// </summary>
+        public static void LogAggregated(FunctionId functionId, TelemetryLoggingInterpolatedStringHandler name, int value)
+        {
+            if (GetAggregatingLog(functionId) is not { } aggregatingLog)
+                return;
+
+            var logMessage = KeyValueLogMessage.Create(m =>
+            {
+                m[AggregatedKeyName] = name.GetFormattedText();
+                m[AggregatedKeyValue] = value;
+            });
+
+            aggregatingLog.Log(logMessage);
+        }
+
+        /// <summary>
+        /// Adds block execution time to an aggregated telemetry event representing the <paramref name="functionId"/> operation 
+        /// with metric <paramref name="metricName"/> only if the block duration meets or exceeds <paramref name="minThresholdMs"/> milliseconds.
+        /// </summary>
+        /// <param name="minThresholdMs">Optional parameter used to determine whether to send the telemetry event</param>
+        public static IDisposable? LogBlockTimeAggregated(FunctionId functionId, TelemetryLoggingInterpolatedStringHandler metricName, int minThresholdMs = -1)
+        {
+            return GetAggregatingLog(functionId)?.LogBlockTime(metricName.GetFormattedText(), minThresholdMs);
+        }
+
+        /// <summary>
+        /// Returns non-aggregating telemetry log.
+        /// </summary>
+        public static ITelemetryLog? GetLog(FunctionId functionId)
+        {
+            return s_logProvider?.GetLog(functionId);
+        }
+
+        /// <summary>
+        /// Returns aggregating telemetry log.
+        /// </summary>
+        public static ITelemetryLog? GetAggregatingLog(FunctionId functionId, double[]? bucketBoundaries = null)
+        {
+            return s_logProvider?.GetAggregatingLog(functionId, bucketBoundaries);
+        }
+    }
+}
diff --git a/src/Workspaces/Core/Portable/Telemetry/TelemetryLoggingInterpolatedStringHandler.cs b/src/Workspaces/Core/Portable/Telemetry/TelemetryLoggingInterpolatedStringHandler.cs
new file mode 100644
index 0000000000000..3670ff8a34520
--- /dev/null
+++ b/src/Workspaces/Core/Portable/Telemetry/TelemetryLoggingInterpolatedStringHandler.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using System.Text;
+
+namespace Microsoft.CodeAnalysis.Telemetry
+{
+    [InterpolatedStringHandler]
+    internal readonly struct TelemetryLoggingInterpolatedStringHandler
+    {
+        private readonly StringBuilder _stringBuilder;
+
+        public TelemetryLoggingInterpolatedStringHandler(int literalLength, int _)
+        {
+            _stringBuilder = new StringBuilder(capacity: literalLength);
+        }
+
+        public void AppendLiteral(string value) => _stringBuilder.Append(value);
+
+        public void AppendFormatted<T>(T value) => _stringBuilder.Append(value?.ToString());
+
+        public string GetFormattedText() => _stringBuilder.ToString();
+    }
+}
diff --git a/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.Factory.cs b/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.Factory.cs
index 90d90f98035a8..1fd7e36878ea7 100644
--- a/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.Factory.cs
+++ b/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.Factory.cs
@@ -13,18 +13,11 @@ namespace Microsoft.CodeAnalysis.Host
     internal partial class TemporaryStorageService
     {
         [ExportWorkspaceServiceFactory(typeof(ITemporaryStorageServiceInternal), ServiceLayer.Default), Shared]
-        internal partial class Factory : IWorkspaceServiceFactory
+        [method: ImportingConstructor]
+        [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        internal partial class Factory(
+            [Import(AllowDefault = true)] IWorkspaceThreadingService? workspaceThreadingService) : IWorkspaceServiceFactory
         {
-            private readonly IWorkspaceThreadingService? _workspaceThreadingService;
-
-            [ImportingConstructor]
-            [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-            public Factory(
-                [Import(AllowDefault = true)] IWorkspaceThreadingService? workspaceThreadingService)
-            {
-                _workspaceThreadingService = workspaceThreadingService;
-            }
-
             [Obsolete(MefConstruction.FactoryMethodMessage, error: true)]
             public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
             {
@@ -34,7 +27,7 @@ public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
                 // and .NET Core Windows. For non-Windows .NET Core scenarios, we can return the TrivialTemporaryStorageService
                 // until https://github.com/dotnet/runtime/issues/30878 is fixed.
                 return PlatformInformation.IsWindows || PlatformInformation.IsRunningOnMono
-                    ? new TemporaryStorageService(_workspaceThreadingService, textFactory)
+                    ? new TemporaryStorageService(workspaceThreadingService, textFactory)
                     : TrivialTemporaryStorageService.Instance;
             }
         }
diff --git a/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.MemoryMappedInfo.cs b/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.MemoryMappedInfo.cs
index aaf83a633bd54..f496a63624d0b 100644
--- a/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.MemoryMappedInfo.cs
+++ b/src/Workspaces/Core/Portable/TemporaryStorage/TemporaryStorageService.MemoryMappedInfo.cs
@@ -34,7 +34,7 @@ internal partial class TemporaryStorageService
         /// Update: Dispose, Finalization, and Resource Management</see>. Additional notes regarding operating system
         /// behavior leveraged for efficiency are given in comments.</para>
         /// </remarks>
-        internal sealed class MemoryMappedInfo : IDisposable
+        internal sealed class MemoryMappedInfo(ReferenceCountedDisposable<MemoryMappedFile> memoryMappedFile, string name, long offset, long size) : IDisposable
         {
             /// <summary>
             /// The memory mapped file.
@@ -44,7 +44,7 @@ internal sealed class MemoryMappedInfo : IDisposable
             /// However, the operating system does not actually close the views which are in use until the file handles
             /// are closed as well, even if the file is disposed first.</para>
             /// </remarks>
-            private readonly ReferenceCountedDisposable<MemoryMappedFile> _memoryMappedFile;
+            private readonly ReferenceCountedDisposable<MemoryMappedFile> _memoryMappedFile = memoryMappedFile;
 
             /// <summary>
             /// A weak reference to a read-only view for the memory mapped file.
@@ -61,14 +61,6 @@ internal sealed class MemoryMappedInfo : IDisposable
             /// </remarks>
             private ReferenceCountedDisposable<MemoryMappedViewAccessor>.WeakReference _weakReadAccessor;
 
-            public MemoryMappedInfo(ReferenceCountedDisposable<MemoryMappedFile> memoryMappedFile, string name, long offset, long size)
-            {
-                _memoryMappedFile = memoryMappedFile;
-                Name = name;
-                Offset = offset;
-                Size = size;
-            }
-
             public MemoryMappedInfo(string name, long offset, long size)
                 : this(new ReferenceCountedDisposable<MemoryMappedFile>(MemoryMappedFile.OpenExisting(name)), name, offset, size)
             {
@@ -77,19 +69,19 @@ public MemoryMappedInfo(string name, long offset, long size)
             /// <summary>
             /// The name of the memory mapped file.
             /// </summary>
-            public string Name { get; }
+            public string Name { get; } = name;
 
             /// <summary>
             /// The offset into the memory mapped file of the region described by the current
             /// <see cref="MemoryMappedInfo"/>.
             /// </summary>
-            public long Offset { get; }
+            public long Offset { get; } = offset;
 
             /// <summary>
             /// The size of the region of the memory mapped file described by the current
             /// <see cref="MemoryMappedInfo"/>.
             /// </summary>
-            public long Size { get; }
+            public long Size { get; } = size;
 
             /// <summary>
             /// Caller is responsible for disposing the returned stream.
diff --git a/src/Workspaces/Core/Portable/Utilities/Documentation/DeferredDocumentationProvider.cs b/src/Workspaces/Core/Portable/Utilities/Documentation/DeferredDocumentationProvider.cs
index 0ab3f5eb7f582..c9e4f0bcaaf69 100644
--- a/src/Workspaces/Core/Portable/Utilities/Documentation/DeferredDocumentationProvider.cs
+++ b/src/Workspaces/Core/Portable/Utilities/Documentation/DeferredDocumentationProvider.cs
@@ -21,16 +21,9 @@ namespace Microsoft.CodeAnalysis
     /// symbols in practice, this should not be expensive to hold onto.  Importantly, semantic models and 
     /// complex method binding/caching should never really happen with this compilation.
     /// </summary>
-    internal class DeferredDocumentationProvider : DocumentationProvider
+    internal class DeferredDocumentationProvider(Compilation compilation) : DocumentationProvider
     {
-        private readonly Compilation _compilation;
-
-        public DeferredDocumentationProvider(Compilation compilation)
-        {
-            // Ensure we are getting a clone of this compilation so that we are only holding onto the decl table and
-            // not rooting a full compilation that might be quite expensive.
-            _compilation = compilation.Clone();
-        }
+        private readonly Compilation _compilation = compilation.Clone();
 
         protected override string? GetDocumentationForSymbol(string documentationMemberID, CultureInfo preferredCulture, CancellationToken cancellationToken = default)
         {
diff --git a/src/Workspaces/Core/Portable/Utilities/FlowControlHelper.cs b/src/Workspaces/Core/Portable/Utilities/FlowControlHelper.cs
index d0d283ee26f52..7cd654ac8a783 100644
--- a/src/Workspaces/Core/Portable/Utilities/FlowControlHelper.cs
+++ b/src/Workspaces/Core/Portable/Utilities/FlowControlHelper.cs
@@ -12,20 +12,13 @@ internal static class FlowControlHelper
         public static AsyncFlowControlHelper TrySuppressFlow()
             => new(ExecutionContext.IsFlowSuppressed() ? default : ExecutionContext.SuppressFlow());
 
-        public readonly struct AsyncFlowControlHelper : IDisposable
+        public readonly struct AsyncFlowControlHelper(AsyncFlowControl asyncFlowControl) : IDisposable
         {
-            private readonly AsyncFlowControl _asyncFlowControl;
-
-            public AsyncFlowControlHelper(AsyncFlowControl asyncFlowControl)
-            {
-                _asyncFlowControl = asyncFlowControl;
-            }
-
             public void Dispose()
             {
-                if (_asyncFlowControl != default)
+                if (asyncFlowControl != default)
                 {
-                    _asyncFlowControl.Dispose();
+                    asyncFlowControl.Dispose();
                 }
             }
         }
diff --git a/src/Workspaces/Core/Portable/Utilities/SpellChecker.cs b/src/Workspaces/Core/Portable/Utilities/SpellChecker.cs
index 2c8385707d516..1790c2d349e7b 100644
--- a/src/Workspaces/Core/Portable/Utilities/SpellChecker.cs
+++ b/src/Workspaces/Core/Portable/Utilities/SpellChecker.cs
@@ -10,19 +10,11 @@
 
 namespace Roslyn.Utilities
 {
-    internal readonly struct SpellChecker : IObjectWritable, IChecksummedObject
+    internal readonly struct SpellChecker(Checksum checksum, BKTree bKTree) : IObjectWritable, IChecksummedObject
     {
         private const string SerializationFormat = "3";
 
-        public Checksum Checksum { get; }
-
-        private readonly BKTree _bkTree;
-
-        public SpellChecker(Checksum checksum, BKTree bKTree)
-        {
-            Checksum = checksum;
-            _bkTree = bKTree;
-        }
+        public Checksum Checksum { get; } = checksum;
 
         public SpellChecker(Checksum checksum, IEnumerable<string> corpus)
             : this(checksum, BKTree.Create(corpus))
@@ -34,7 +26,7 @@ public void FindSimilarWords(ref TemporaryArray<string> similarWords, string val
             using var result = TemporaryArray<string>.Empty;
             using var checker = new WordSimilarityChecker(value, substringsAreSimilar);
 
-            _bkTree.Find(ref result.AsRef(), value, threshold: null);
+            bKTree.Find(ref result.AsRef(), value, threshold: null);
 
             foreach (var current in result)
             {
@@ -49,7 +41,7 @@ public void WriteTo(ObjectWriter writer)
         {
             writer.WriteString(SerializationFormat);
             Checksum.WriteTo(writer);
-            _bkTree.WriteTo(writer);
+            bKTree.WriteTo(writer);
         }
 
         internal static SpellChecker? TryReadFrom(ObjectReader reader)
diff --git a/src/Workspaces/Core/Portable/Workspace/AdhocWorkspace.cs b/src/Workspaces/Core/Portable/Workspace/AdhocWorkspace.cs
index 4f846b8cd017b..806dc1e0eed47 100644
--- a/src/Workspaces/Core/Portable/Workspace/AdhocWorkspace.cs
+++ b/src/Workspaces/Core/Portable/Workspace/AdhocWorkspace.cs
@@ -16,13 +16,8 @@ namespace Microsoft.CodeAnalysis
     /// A workspace that allows full manipulation of projects and documents,
     /// but does not persist changes.
     /// </summary>
-    public sealed class AdhocWorkspace : Workspace
+    public sealed class AdhocWorkspace(HostServices host, string workspaceKind = WorkspaceKind.Custom) : Workspace(host, workspaceKind)
     {
-        public AdhocWorkspace(HostServices host, string workspaceKind = WorkspaceKind.Custom)
-            : base(host, workspaceKind)
-        {
-        }
-
         public AdhocWorkspace()
             : this(Host.Mef.MefHostServices.DefaultHost)
         {
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/DocumentService/IDocumentExcerptService.cs b/src/Workspaces/Core/Portable/Workspace/Host/DocumentService/IDocumentExcerptService.cs
index 52c539408ef1a..df88e069b4558 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/DocumentService/IDocumentExcerptService.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/DocumentService/IDocumentExcerptService.cs
@@ -37,45 +37,35 @@ internal enum ExcerptMode
     /// <summary>
     /// Result of excerpt
     /// </summary>
-    internal readonly struct ExcerptResult
+    internal readonly struct ExcerptResult(SourceText content, TextSpan mappedSpan, ImmutableArray<ClassifiedSpan> classifiedSpans, Document document, TextSpan span)
     {
         /// <summary>
         /// excerpt content
         /// </summary>
-        public readonly SourceText Content;
+        public readonly SourceText Content = content;
 
         /// <summary>
         /// span on <see cref="Content"/> that given <see cref="Span"/> got mapped to
         /// </summary>
-        public readonly TextSpan MappedSpan;
+        public readonly TextSpan MappedSpan = mappedSpan;
 
         /// <summary>
         /// classification information on the <see cref="Content"/>
         /// </summary>
-        public readonly ImmutableArray<ClassifiedSpan> ClassifiedSpans;
+        public readonly ImmutableArray<ClassifiedSpan> ClassifiedSpans = classifiedSpans;
 
         /// <summary>
         /// <see cref="Document"/> this excerpt is from
         /// 
         /// should be same document in <see cref="IDocumentExcerptService.TryExcerptAsync(Document, TextSpan, ExcerptMode, ClassificationOptions, CancellationToken)" />
         /// </summary>
-        public readonly Document Document;
+        public readonly Document Document = document;
 
         /// <summary>
         /// span on <see cref="Document"/> this excerpt is from
         /// 
         /// should be same text span in <see cref="IDocumentExcerptService.TryExcerptAsync(Document, TextSpan, ExcerptMode, ClassificationOptions, CancellationToken)" />
         /// </summary>
-        public readonly TextSpan Span;
-
-        public ExcerptResult(SourceText content, TextSpan mappedSpan, ImmutableArray<ClassifiedSpan> classifiedSpans, Document document, TextSpan span)
-        {
-            Content = content;
-            MappedSpan = mappedSpan;
-            ClassifiedSpans = classifiedSpans;
-
-            Document = document;
-            Span = span;
-        }
+        public readonly TextSpan Span = span;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/EventListener/EventListenerTracker.cs b/src/Workspaces/Core/Portable/Workspace/Host/EventListener/EventListenerTracker.cs
index 1040b76535ff5..c32d599d17db6 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/EventListener/EventListenerTracker.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/EventListener/EventListenerTracker.cs
@@ -17,19 +17,14 @@ namespace Microsoft.CodeAnalysis.Host
     /// currently, this helper only supports services whose lifetime is same as Host (ex, VS)
     /// </summary>
     /// <typeparam name="TService">TService for <see cref="IEventListener{TService}"/></typeparam>
-    internal class EventListenerTracker<TService>
+    internal class EventListenerTracker<TService>(
+        IEnumerable<Lazy<IEventListener, EventListenerMetadata>> eventListeners, string kind)
     {
         /// <summary>
         /// Workspace kind this event listener is initialized for
         /// </summary>
         private readonly HashSet<string> _eventListenerInitialized = new();
-        private readonly ImmutableArray<Lazy<IEventListener, EventListenerMetadata>> _eventListeners;
-
-        public EventListenerTracker(
-            IEnumerable<Lazy<IEventListener, EventListenerMetadata>> eventListeners, string kind)
-        {
-            _eventListeners = eventListeners.Where(el => el.Metadata.Service == kind).ToImmutableArray();
-        }
+        private readonly ImmutableArray<Lazy<IEventListener, EventListenerMetadata>> _eventListeners = eventListeners.Where(el => el.Metadata.Service == kind).ToImmutableArray();
 
         public void EnsureEventListener(Workspace workspace, TService serviceOpt)
         {
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/EventListener/IWorkspaceEventListenerProvider.cs b/src/Workspaces/Core/Portable/Workspace/Host/EventListener/IWorkspaceEventListenerProvider.cs
index 11300a9a106db..d657e0592da95 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/EventListener/IWorkspaceEventListenerProvider.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/EventListener/IWorkspaceEventListenerProvider.cs
@@ -22,41 +22,22 @@ internal interface IWorkspaceEventListenerService : IWorkspaceService
     }
 
     [ExportWorkspaceServiceFactory(typeof(IWorkspaceEventListenerService), layer: ServiceLayer.Default), Shared]
-    internal class DefaultWorkspaceEventListenerServiceFactory : IWorkspaceServiceFactory
+    [method: ImportingConstructor]
+    [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    internal class DefaultWorkspaceEventListenerServiceFactory(
+        [ImportMany] IEnumerable<Lazy<IEventListener, EventListenerMetadata>> eventListeners) : IWorkspaceServiceFactory
     {
-        private readonly IEnumerable<Lazy<IEventListener, EventListenerMetadata>> _eventListeners;
-
-        [ImportingConstructor]
-        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public DefaultWorkspaceEventListenerServiceFactory(
-            [ImportMany] IEnumerable<Lazy<IEventListener, EventListenerMetadata>> eventListeners)
-        {
-            // we use this indirect abstraction to deliver IEventLister to workspace. 
-            // otherwise, each Workspace implementation need to explicitly tell base event listeners either through
-            // constructor or through virtual property. 
-            // taking indirect approach since i dont believe all workspaces need to know about this. 
-            _eventListeners = eventListeners;
-        }
-
         public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
         {
             var workspace = workspaceServices.Workspace;
-            return new Service(workspace, EventListenerTracker<object>.GetListeners(workspace, _eventListeners));
+            return new Service(workspace, EventListenerTracker<object>.GetListeners(workspace, eventListeners));
         }
 
-        private class Service : IWorkspaceEventListenerService
+        private class Service(Workspace workspace, IEnumerable<IEventListener<object>> eventListeners) : IWorkspaceEventListenerService
         {
             private readonly object _gate = new();
             private bool _initialized = false;
-
-            private readonly Workspace _workspace;
-            private readonly ImmutableArray<IEventListener<object>> _eventListeners;
-
-            public Service(Workspace workspace, IEnumerable<IEventListener<object>> eventListeners)
-            {
-                _workspace = workspace;
-                _eventListeners = eventListeners.ToImmutableArray();
-            }
+            private readonly ImmutableArray<IEventListener<object>> _eventListeners = eventListeners.ToImmutableArray();
 
             public void EnsureListeners()
             {
@@ -73,7 +54,7 @@ public void EnsureListeners()
 
                 foreach (var listener in _eventListeners)
                 {
-                    listener.StartListening(_workspace, serviceOpt: null);
+                    listener.StartListening(workspace, serviceOpt: null);
                 }
             }
 
@@ -89,7 +70,7 @@ public void Stop()
 
                     foreach (var listener in _eventListeners.OfType<IEventListenerStoppable>())
                     {
-                        listener.StopListening(_workspace);
+                        listener.StopListening(workspace);
                     }
                 }
             }
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/ISupportedChangesService.cs b/src/Workspaces/Core/Portable/Workspace/Host/ISupportedChangesService.cs
index a9614ea147523..d2a7a95ecf38c 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/ISupportedChangesService.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/ISupportedChangesService.cs
@@ -36,23 +36,16 @@ public DefaultSupportedChangesServiceFactory()
         public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
             => new DefaultSupportedChangesService(workspaceServices.Workspace);
 
-        private sealed class DefaultSupportedChangesService : ISupportedChangesService
+        private sealed class DefaultSupportedChangesService(Workspace workspace) : ISupportedChangesService
         {
-            private readonly Workspace _workspace;
-
-            public DefaultSupportedChangesService(Workspace workspace)
-            {
-                _workspace = workspace;
-            }
-
             public bool CanApplyChange(ApplyChangesKind kind)
-                => _workspace.CanApplyChange(kind);
+                => workspace.CanApplyChange(kind);
 
             public bool CanApplyCompilationOptionChange(CompilationOptions oldOptions, CompilationOptions newOptions, Project project)
-                => _workspace.CanApplyCompilationOptionChange(oldOptions, newOptions, project);
+                => workspace.CanApplyCompilationOptionChange(oldOptions, newOptions, project);
 
             public bool CanApplyParseOptionChange(ParseOptions oldOptions, ParseOptions newOptions, Project project)
-                => _workspace.CanApplyParseOptionChange(oldOptions, newOptions, project);
+                => workspace.CanApplyParseOptionChange(oldOptions, newOptions, project);
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/Mef/MefHostServices.cs b/src/Workspaces/Core/Portable/Workspace/Host/Mef/MefHostServices.cs
index f6143fcb5fd5a..fac07e578c2af 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/Mef/MefHostServices.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/Mef/MefHostServices.cs
@@ -15,7 +15,7 @@
 
 namespace Microsoft.CodeAnalysis.Host.Mef
 {
-    public class MefHostServices : HostServices, IMefHostExportProvider
+    public class MefHostServices(CompositionContext compositionContext) : HostServices, IMefHostExportProvider
     {
         internal delegate MefHostServices CreationHook(IEnumerable<Assembly> assemblies);
 
@@ -25,11 +25,6 @@ public class MefHostServices : HostServices, IMefHostExportProvider
         /// <seealso cref="TestAccessor.HookServiceCreation"/>
         private static CreationHook s_creationHook;
 
-        private readonly CompositionContext _compositionContext;
-
-        public MefHostServices(CompositionContext compositionContext)
-            => _compositionContext = compositionContext;
-
         public static MefHostServices Create(CompositionContext compositionContext)
         {
             if (compositionContext == null)
@@ -61,12 +56,12 @@ protected internal override HostWorkspaceServices CreateWorkspaceServices(Worksp
             => new MefWorkspaceServices(this, workspace);
 
         IEnumerable<Lazy<TExtension>> IMefHostExportProvider.GetExports<TExtension>()
-            => _compositionContext.GetExports<TExtension>().Select(e => new Lazy<TExtension>(() => e));
+            => compositionContext.GetExports<TExtension>().Select(e => new Lazy<TExtension>(() => e));
 
         IEnumerable<Lazy<TExtension, TMetadata>> IMefHostExportProvider.GetExports<TExtension, TMetadata>()
         {
             var importer = new WithMetadataImporter<TExtension, TMetadata>();
-            _compositionContext.SatisfyImports(importer);
+            compositionContext.SatisfyImports(importer);
             return importer.Exports;
         }
 
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/Metadata/AnalyzerAssemblyLoaderOptions.cs b/src/Workspaces/Core/Portable/Workspace/Host/Metadata/AnalyzerAssemblyLoaderOptions.cs
index 4e4f0c5beee46..64f8ff2e9b5f4 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/Metadata/AnalyzerAssemblyLoaderOptions.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/Metadata/AnalyzerAssemblyLoaderOptions.cs
@@ -4,13 +4,8 @@
 
 namespace Microsoft.CodeAnalysis.Host
 {
-    internal readonly struct AnalyzerAssemblyLoaderOptions
+    internal readonly struct AnalyzerAssemblyLoaderOptions(bool shadowCopy)
     {
-        public bool ShadowCopy { get; }
-
-        public AnalyzerAssemblyLoaderOptions(bool shadowCopy)
-        {
-            ShadowCopy = shadowCopy;
-        }
+        public bool ShadowCopy { get; } = shadowCopy;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataReferenceCache.cs b/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataReferenceCache.cs
index 0c1e5b7b889fc..a30b508146aca 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataReferenceCache.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataReferenceCache.cs
@@ -14,15 +14,12 @@ namespace Microsoft.CodeAnalysis.Host
     /// <summary>
     /// A cache for metadata references.
     /// </summary>
-    internal class MetadataReferenceCache
+    internal class MetadataReferenceCache(Func<string, MetadataReferenceProperties, MetadataReference> createReference)
     {
         private ImmutableDictionary<string, ReferenceSet> _referenceSets
             = ImmutableDictionary<string, ReferenceSet>.Empty;
 
-        private readonly Func<string, MetadataReferenceProperties, MetadataReference> _createReference;
-
-        public MetadataReferenceCache(Func<string, MetadataReferenceProperties, MetadataReference> createReference)
-            => _createReference = createReference ?? throw new ArgumentNullException(nameof(createReference));
+        private readonly Func<string, MetadataReferenceProperties, MetadataReference> _createReference = createReference ?? throw new ArgumentNullException(nameof(createReference));
 
         public MetadataReference GetReference(string path, MetadataReferenceProperties properties)
         {
@@ -37,19 +34,14 @@ public MetadataReference GetReference(string path, MetadataReferenceProperties p
         /// <summary>
         /// A collection of references to the same underlying metadata, each with different properties.
         /// </summary>
-        private class ReferenceSet
+        private class ReferenceSet(MetadataReferenceCache cache)
         {
-            private readonly MetadataReferenceCache _cache;
-
             private readonly NonReentrantLock _gate = new();
 
             // metadata references are held weakly, so even though this is a cache that enables reuse, it does not control lifetime.
             private readonly Dictionary<MetadataReferenceProperties, WeakReference<MetadataReference>> _references
                 = new();
 
-            public ReferenceSet(MetadataReferenceCache cache)
-                => _cache = cache;
-
             public MetadataReference GetAddOrUpdate(string path, MetadataReferenceProperties properties)
             {
                 using (_gate.DisposableWait())
@@ -67,7 +59,7 @@ public MetadataReference GetAddOrUpdate(string path, MetadataReferenceProperties
                             }
                         }
 
-                        mref ??= _cache._createReference(path, properties);
+                        mref ??= cache._createReference(path, properties);
 
                         _references[properties] = new WeakReference<MetadataReference>(mref);
                     }
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataServiceFactory.cs b/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataServiceFactory.cs
index 21d7384dab987..dbc4e87e8b737 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataServiceFactory.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/Metadata/MetadataServiceFactory.cs
@@ -22,15 +22,10 @@ public MetadataServiceFactory()
         public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
             => new Service(workspaceServices.GetService<IDocumentationProviderService>());
 
-        private sealed class Service : IMetadataService
+        private sealed class Service(IDocumentationProviderService documentationService) : IMetadataService
         {
-            private readonly MetadataReferenceCache _metadataCache;
-
-            public Service(IDocumentationProviderService documentationService)
-            {
-                _metadataCache = new MetadataReferenceCache((path, properties) =>
+            private readonly MetadataReferenceCache _metadataCache = new MetadataReferenceCache((path, properties) =>
                     MetadataReference.CreateFromFile(path, properties, documentationService.GetDocumentationProvider(path)));
-            }
 
             public PortableExecutableReference GetReference(string resolvedPath, MetadataReferenceProperties properties)
                 => (PortableExecutableReference)_metadataCache.GetReference(resolvedPath, properties);
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/DocumentKey.cs b/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/DocumentKey.cs
index 677ee89e21db2..87f947bc5c3ba 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/DocumentKey.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/DocumentKey.cs
@@ -16,27 +16,19 @@ namespace Microsoft.CodeAnalysis.Storage
     /// solution load), but querying the data is still desired.
     /// </summary>
     [DataContract]
-    internal readonly struct DocumentKey : IEqualityComparer<DocumentKey>, IEquatable<DocumentKey>
+    internal readonly struct DocumentKey(ProjectKey project, DocumentId id, string? filePath, string name) : IEqualityComparer<DocumentKey>, IEquatable<DocumentKey>
     {
         [DataMember(Order = 0)]
-        public readonly ProjectKey Project;
+        public readonly ProjectKey Project = project;
 
         [DataMember(Order = 1)]
-        public readonly DocumentId Id;
+        public readonly DocumentId Id = id;
 
         [DataMember(Order = 2)]
-        public readonly string? FilePath;
+        public readonly string? FilePath = filePath;
 
         [DataMember(Order = 3)]
-        public readonly string Name;
-
-        public DocumentKey(ProjectKey project, DocumentId id, string? filePath, string name)
-        {
-            Project = project;
-            Id = id;
-            FilePath = filePath;
-            Name = name;
-        }
+        public readonly string Name = name;
 
         public static DocumentKey ToDocumentKey(Document document)
             => ToDocumentKey(ProjectKey.ToProjectKey(document.Project), document.State);
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/ProjectKey.cs b/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/ProjectKey.cs
index 74ee810b5a2f9..fa5a3f4585c94 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/ProjectKey.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/ProjectKey.cs
@@ -14,31 +14,22 @@ namespace Microsoft.CodeAnalysis.Storage
     /// solution load), but querying the data is still desired.
     /// </summary>
     [DataContract]
-    internal readonly struct ProjectKey
+    internal readonly struct ProjectKey(SolutionKey solution, ProjectId id, string? filePath, string name, Checksum parseOptionsChecksum)
     {
         [DataMember(Order = 0)]
-        public readonly SolutionKey Solution;
+        public readonly SolutionKey Solution = solution;
 
         [DataMember(Order = 1)]
-        public readonly ProjectId Id;
+        public readonly ProjectId Id = id;
 
         [DataMember(Order = 2)]
-        public readonly string? FilePath;
+        public readonly string? FilePath = filePath;
 
         [DataMember(Order = 3)]
-        public readonly string Name;
+        public readonly string Name = name;
 
         [DataMember(Order = 4)]
-        public readonly Checksum ParseOptionsChecksum;
-
-        public ProjectKey(SolutionKey solution, ProjectId id, string? filePath, string name, Checksum parseOptionsChecksum)
-        {
-            Solution = solution;
-            Id = id;
-            FilePath = filePath;
-            Name = name;
-            ParseOptionsChecksum = parseOptionsChecksum;
-        }
+        public readonly Checksum ParseOptionsChecksum = parseOptionsChecksum;
 
         public static ProjectKey ToProjectKey(Project project)
             => ToProjectKey(project.Solution.State, project.State);
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/SolutionKey.cs b/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/SolutionKey.cs
index 5a9cc440d96b6..70fcd8ecc31cc 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/SolutionKey.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/SolutionKey.cs
@@ -14,19 +14,13 @@ namespace Microsoft.CodeAnalysis.Storage
     /// solution load), but querying the data is still desired.
     /// </summary>
     [DataContract]
-    internal readonly struct SolutionKey
+    internal readonly struct SolutionKey(SolutionId id, string? filePath)
     {
         [DataMember(Order = 0)]
-        public readonly SolutionId Id;
+        public readonly SolutionId Id = id;
 
         [DataMember(Order = 1)]
-        public readonly string? FilePath;
-
-        public SolutionKey(SolutionId id, string? filePath)
-        {
-            Id = id;
-            FilePath = filePath;
-        }
+        public readonly string? FilePath = filePath;
 
         public static SolutionKey ToSolutionKey(Solution solution)
             => ToSolutionKey(solution.State);
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/SourceFiles/DynamicFileInfo.cs b/src/Workspaces/Core/Portable/Workspace/Host/SourceFiles/DynamicFileInfo.cs
index 51d128bb56531..723cadd92a958 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/SourceFiles/DynamicFileInfo.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/SourceFiles/DynamicFileInfo.cs
@@ -10,41 +10,33 @@ namespace Microsoft.CodeAnalysis.Host
     /// this will be used to provide dynamic content such as generated content from cshtml to workspace
     /// we acquire this from <see cref="IDynamicFileInfoProvider"/> exposed from external components such as razor for cshtml
     /// </summary>
-    internal sealed class DynamicFileInfo
+    internal sealed class DynamicFileInfo(string filePath, SourceCodeKind sourceCodeKind, TextLoader textLoader, bool designTimeOnly, IDocumentServiceProvider? documentServiceProvider)
     {
-        public DynamicFileInfo(string filePath, SourceCodeKind sourceCodeKind, TextLoader textLoader, bool designTimeOnly, IDocumentServiceProvider? documentServiceProvider)
-        {
-            FilePath = filePath;
-            SourceCodeKind = sourceCodeKind;
-            TextLoader = textLoader;
-            DocumentServiceProvider = documentServiceProvider;
-            DesignTimeOnly = designTimeOnly;
-        }
 
         /// <summary>
         /// The path to the generated file. in future, we will use this to get right options from editorconfig
         /// </summary>
-        public string FilePath { get; }
+        public string FilePath { get; } = filePath;
 
         /// <summary>
         /// return <see cref="SourceCodeKind"/> for this file
         /// </summary>
-        public SourceCodeKind SourceCodeKind { get; }
+        public SourceCodeKind SourceCodeKind { get; } = sourceCodeKind;
 
         /// <summary>
         /// return <see cref="TextLoader"/> to load content for the dynamic file
         /// </summary>
-        public TextLoader TextLoader { get; }
+        public TextLoader TextLoader { get; } = textLoader;
 
         /// <summary>
         /// True if the source code contained in the document is only used in design-time (e.g. for completion),
         /// but is not passed to the compiler when the containing project is built, e.g. a Razor view.
         /// </summary>
-        public bool DesignTimeOnly { get; }
+        public bool DesignTimeOnly { get; } = designTimeOnly;
 
         /// <summary>
         /// return <see cref="IDocumentServiceProvider"/> for the content it provided
         /// </summary>
-        public IDocumentServiceProvider? DocumentServiceProvider { get; }
+        public IDocumentServiceProvider? DocumentServiceProvider { get; } = documentServiceProvider;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Host/TaskScheduler/WorkspaceAsynchronousOperationListenerProvider.cs b/src/Workspaces/Core/Portable/Workspace/Host/TaskScheduler/WorkspaceAsynchronousOperationListenerProvider.cs
index 431161c07ebb8..83bd04517ff9c 100644
--- a/src/Workspaces/Core/Portable/Workspace/Host/TaskScheduler/WorkspaceAsynchronousOperationListenerProvider.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Host/TaskScheduler/WorkspaceAsynchronousOperationListenerProvider.cs
@@ -11,14 +11,11 @@ namespace Microsoft.CodeAnalysis.Host
 {
     [ExportWorkspaceService(typeof(IWorkspaceAsynchronousOperationListenerProvider), ServiceLayer.Default)]
     [Shared]
-    internal sealed class WorkspaceAsynchronousOperationListenerProvider : IWorkspaceAsynchronousOperationListenerProvider
+    [method: ImportingConstructor]
+    [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    internal sealed class WorkspaceAsynchronousOperationListenerProvider(IAsynchronousOperationListenerProvider listenerProvider) : IWorkspaceAsynchronousOperationListenerProvider
     {
-        private readonly IAsynchronousOperationListener _listener;
-
-        [ImportingConstructor]
-        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public WorkspaceAsynchronousOperationListenerProvider(IAsynchronousOperationListenerProvider listenerProvider)
-            => _listener = listenerProvider.GetListener(FeatureAttribute.Workspace);
+        private readonly IAsynchronousOperationListener _listener = listenerProvider.GetListener(FeatureAttribute.Workspace);
 
         public IAsynchronousOperationListener GetListener()
             => _listener;
diff --git a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/FileWatchedPortableExecutableReferenceFactory.cs b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/FileWatchedPortableExecutableReferenceFactory.cs
index a49d837f98f6a..3aaef92c7a5f4 100644
--- a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/FileWatchedPortableExecutableReferenceFactory.cs
+++ b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/FileWatchedPortableExecutableReferenceFactory.cs
@@ -5,6 +5,8 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Host;
@@ -19,9 +21,10 @@ internal sealed class FileWatchedPortableExecutableReferenceFactory
         private readonly SolutionServices _solutionServices;
 
         /// <summary>
-        /// A file change context used to watch metadata references.
+        /// A file change context used to watch metadata references. This is lazy to avoid creating this immediately during our LSP process startup, when we
+        /// don't yet know the LSP client's capabilities.
         /// </summary>
-        private readonly IFileChangeContext _fileReferenceChangeContext;
+        private readonly Lazy<IFileChangeContext> _fileReferenceChangeContext;
 
         /// <summary>
         /// File watching tokens from <see cref="_fileReferenceChangeContext"/> that are watching metadata references. These are only created once we are actually applying a batch because
@@ -42,21 +45,49 @@ public FileWatchedPortableExecutableReferenceFactory(
         {
             _solutionServices = solutionServices;
 
-            var watchedDirectories = new List<WatchedDirectory>();
-
-            if (PlatformInformation.IsWindows)
+            _fileReferenceChangeContext = new Lazy<IFileChangeContext>(() =>
             {
-                // We will do a single directory watch on the Reference Assemblies folder to avoid having to create separate file
-                // watches on individual .dlls that effectively never change.
-                var referenceAssembliesPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), "Reference Assemblies", "Microsoft", "Framework");
-                watchedDirectories.Add(new WatchedDirectory(referenceAssembliesPath, ".dll"));
-            }
+                var referenceDirectories = new HashSet<string>();
+
+                // On each platform, there is a place that reference assemblies for the framework are installed. These are rarely going to be changed
+                // but are the most common places that we're going to create file watches. Rather than either creating a huge number of file watchers
+                // for every single file, or eventually realizing we should just watch these directories, we just create the single directory watchers now.
+                // We'll collect this from two places: constructing it from known environment variables, and also for the defaults where those environment
+                // variables would usually point, as a fallback.
+
+                if (Environment.GetEnvironmentVariable("DOTNET_ROOT") is string dotnetRoot && !string.IsNullOrEmpty(dotnetRoot))
+                {
+                    referenceDirectories.Add(Path.Combine(dotnetRoot, "packs"));
+                }
 
-            // TODO: set this to watch the NuGet directory as well; there's some concern that watching the entire directory
-            // might make restores take longer because we'll be watching changes that may not impact your project.
+                if (PlatformInformation.IsWindows)
+                {
+                    referenceDirectories.Add(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), "Reference Assemblies", "Microsoft", "Framework"));
+                    referenceDirectories.Add(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), "dotnet", "packs"));
+                }
+                else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+                {
+                    referenceDirectories.Add("/usr/lib/dotnet/packs");
+                    referenceDirectories.Add("/usr/share/dotnet/packs");
+                }
+                else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+                {
+                    referenceDirectories.Add("/usr/local/share/dotnet/packs");
+                }
+
+                // Also watch the NuGet restore path; we don't do this (yet) on Windows due to potential concerns about whether
+                // this creates additional overhead responding to changes during a restore.
+                // TODO: remove this condition
+                if (!PlatformInformation.IsWindows)
+                {
+                    referenceDirectories.Add(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".nuget", "packages"));
+                }
 
-            _fileReferenceChangeContext = fileChangeWatcher.CreateContext(watchedDirectories.ToArray());
-            _fileReferenceChangeContext.FileChanged += FileReferenceChangeContext_FileChanged;
+                var directoriesToWatch = referenceDirectories.Select(static d => new WatchedDirectory(d, ".dll")).ToArray();
+                var fileReferenceChangeContext = fileChangeWatcher.CreateContext(directoriesToWatch);
+                fileReferenceChangeContext.FileChanged += FileReferenceChangeContext_FileChanged;
+                return fileReferenceChangeContext;
+            });
         }
 
         public event EventHandler<string>? ReferenceChanged;
@@ -66,7 +97,7 @@ public PortableExecutableReference CreateReferenceAndStartWatchingFile(string fu
             lock (_gate)
             {
                 var reference = _solutionServices.GetRequiredService<IMetadataService>().GetReference(fullFilePath, properties);
-                var fileWatchingToken = _fileReferenceChangeContext.EnqueueWatchingFile(fullFilePath);
+                var fileWatchingToken = _fileReferenceChangeContext.Value.EnqueueWatchingFile(fullFilePath);
 
                 _metadataReferenceFileWatchingTokens.Add(reference, fileWatchingToken);
 
diff --git a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/IFileChangeWatcher.cs b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/IFileChangeWatcher.cs
index 358b4ed163703..fb9727e2d6936 100644
--- a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/IFileChangeWatcher.cs
+++ b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/IFileChangeWatcher.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Collections.Immutable;
 
 namespace Microsoft.CodeAnalysis.ProjectSystem
 {
@@ -27,8 +28,8 @@ internal sealed class WatchedDirectory
     {
         public WatchedDirectory(string path, string? extensionFilter)
         {
-            // We are doing string comparisons with this path, so ensure it has a trailing \ so we don't get confused with sibling
-            // paths that won't actually be covered.
+            // We are doing string comparisons with this path, so ensure it has a trailing directory separator so we don't get confused with sibling
+            // paths that won't actually be covered. For example, if we're watching C:\Directory we wouldn't see changes to C:\DirectorySibling\Foo.txt.
             if (!path.EndsWith(System.IO.Path.DirectorySeparatorChar.ToString()))
             {
                 path += System.IO.Path.DirectorySeparatorChar;
@@ -49,6 +50,25 @@ public WatchedDirectory(string path, string? extensionFilter)
         /// If non-null, only watch the directory for changes to a specific extension. String always starts with a period.
         /// </summary>
         public string? ExtensionFilter { get; }
+
+        public static bool FilePathCoveredByWatchedDirectories(ImmutableArray<WatchedDirectory> watchedDirectories, string filePath, StringComparison stringComparison)
+        {
+            foreach (var watchedDirectory in watchedDirectories)
+            {
+                if (filePath.StartsWith(watchedDirectory.Path, stringComparison))
+                {
+                    // If ExtensionFilter is null, then we're watching for all files in the directory so the prior check
+                    // of the directory containment was sufficient. If it isn't null, then we have to check the extension
+                    // matches.
+                    if (watchedDirectory.ExtensionFilter == null || filePath.EndsWith(watchedDirectory.ExtensionFilter, stringComparison))
+                    {
+                        return true;
+                    }
+                }
+            }
+
+            return false;
+        }
     }
 
     /// <summary>
@@ -72,4 +92,21 @@ internal interface IFileChangeContext : IDisposable
     internal interface IWatchedFile : IDisposable
     {
     }
+
+    /// <summary>
+    /// When a FileChangeWatcher already has a watch on a directory, a request to watch a specific file is a no-op. In that case, we return this token,
+    /// which when disposed also does nothing.
+    /// </summary>
+    internal sealed class NoOpWatchedFile : IWatchedFile
+    {
+        public static readonly IWatchedFile Instance = new NoOpWatchedFile();
+
+        private NoOpWatchedFile()
+        {
+        }
+
+        public void Dispose()
+        {
+        }
+    }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProject.BatchingDocumentCollection.cs b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProject.BatchingDocumentCollection.cs
index 916231184d82f..1da7f3141f254 100644
--- a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProject.BatchingDocumentCollection.cs
+++ b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProject.BatchingDocumentCollection.cs
@@ -92,7 +92,7 @@ public DocumentId AddFile(string fullPath, SourceCodeKind sourceCodeKind, Immuta
                 }
 
                 var documentId = DocumentId.CreateNewId(_project.Id, fullPath);
-                var textLoader = new WorkspaceFileTextLoader(_project._projectSystemProjectFactory.Workspace.Services.SolutionServices, fullPath, defaultEncoding: null);
+                var textLoader = _project._projectSystemProjectFactory.CreateFileTextLoader(fullPath);
                 var documentInfo = DocumentInfo.Create(
                     documentId,
                     name: FileNameUtilities.GetFileName(fullPath),
diff --git a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectFactory.cs b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectFactory.cs
index 3e21a91d3b76a..09529fc7eaf3c 100644
--- a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectFactory.cs
+++ b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectFactory.cs
@@ -75,6 +75,9 @@ public ProjectSystemProjectFactory(Workspace workspace, IFileChangeWatcher fileC
             _onProjectRemoved = onProjectRemoved;
         }
 
+        public FileTextLoader CreateFileTextLoader(string fullPath)
+            => new WorkspaceFileTextLoader(this.Workspace.Services.SolutionServices, fullPath, defaultEncoding: null);
+
         public async Task<ProjectSystemProject> CreateAndAddToWorkspaceAsync(string projectSystemName, string language, ProjectSystemProjectCreationInfo creationInfo, ProjectSystemHostInfo hostInfo)
         {
             var projectId = ProjectId.CreateNewId(projectSystemName);
@@ -192,9 +195,9 @@ public void ApplyChangeToWorkspace(Action<Workspace> action)
         /// <summary>
         /// Applies a single operation to the workspace. <paramref name="action"/> should be a call to one of the protected Workspace.On* methods.
         /// </summary>
-        public async ValueTask ApplyChangeToWorkspaceAsync(Func<Workspace, ValueTask> action)
+        public async ValueTask ApplyChangeToWorkspaceAsync(Func<Workspace, ValueTask> action, CancellationToken cancellationToken = default)
         {
-            using (await _gate.DisposableWaitAsync().ConfigureAwait(false))
+            using (await _gate.DisposableWaitAsync(cancellationToken).ConfigureAwait(false))
             {
                 await action(Workspace).ConfigureAwait(false);
             }
diff --git a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectOptionsProcessor.cs b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectOptionsProcessor.cs
index 04fb5aabf157e..eff75f9389d16 100644
--- a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectOptionsProcessor.cs
+++ b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/ProjectSystemProjectOptionsProcessor.cs
@@ -178,8 +178,13 @@ private void UpdateProjectOptions_NoLock()
 
                 if (effectiveRuleSetPath != null)
                 {
-                    _ruleSetFile = _workspaceServices.GetRequiredService<IRuleSetManager>().GetOrCreateRuleSet(effectiveRuleSetPath);
-                    _ruleSetFile.Target.Value.UpdatedOnDisk += RuleSetFile_UpdatedOnDisk;
+                    // Ruleset service is not required across all our platforms
+                    _ruleSetFile = _workspaceServices.GetService<IRuleSetManager>()?.GetOrCreateRuleSet(effectiveRuleSetPath);
+
+                    if (_ruleSetFile != null)
+                    {
+                        _ruleSetFile.Target.Value.UpdatedOnDisk += RuleSetFile_UpdatedOnDisk;
+                    }
                 }
             }
 
diff --git a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/SolutionChangeAccumulator.cs b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/SolutionChangeAccumulator.cs
index eedd91579f77f..b83b44a793eb7 100644
--- a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/SolutionChangeAccumulator.cs
+++ b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/SolutionChangeAccumulator.cs
@@ -10,7 +10,7 @@ namespace Microsoft.CodeAnalysis.Workspaces.ProjectSystem
     /// A little helper type to hold onto the <see cref="Solution"/> being updated in a batch, which also
     /// keeps track of the right <see cref="CodeAnalysis.WorkspaceChangeKind"/> to raise when we are done.
     /// </summary>
-    internal sealed class SolutionChangeAccumulator
+    internal sealed class SolutionChangeAccumulator(Solution startingSolution)
     {
         /// <summary>
         /// The kind that encompasses all the changes we've made. It's null if no changes have been made,
@@ -20,10 +20,7 @@ internal sealed class SolutionChangeAccumulator
         private WorkspaceChangeKind? _workspaceChangeKind;
         private readonly List<DocumentId> _documentIdsRemoved = new();
 
-        public SolutionChangeAccumulator(Solution startingSolution)
-            => Solution = startingSolution;
-
-        public Solution Solution { get; private set; }
+        public Solution Solution { get; private set; } = startingSolution;
         public IEnumerable<DocumentId> DocumentIdsRemoved => _documentIdsRemoved;
 
         public bool HasChange => _workspaceChangeKind.HasValue;
diff --git a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/VisualStudioAnalyzer.cs b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/VisualStudioAnalyzer.cs
index 2b41f36c0219e..a4cd344d9b472 100644
--- a/src/Workspaces/Core/Portable/Workspace/ProjectSystem/VisualStudioAnalyzer.cs
+++ b/src/Workspaces/Core/Portable/Workspace/ProjectSystem/VisualStudioAnalyzer.cs
@@ -11,7 +11,7 @@ namespace Microsoft.CodeAnalysis.Workspaces.ProjectSystem
 {
     // TODO: Remove. This is only needed to support Solution Explorer Analyzer node population. 
     // Analyzers should not be loaded in devenv process (see https://github.com/dotnet/roslyn/issues/43008).
-    internal sealed class ProjectAnalyzerReference : IDisposable
+    internal sealed class ProjectAnalyzerReference(string fullPath, IProjectSystemDiagnosticSource projectSystemDiagnosticSource, ProjectId projectId, string language) : IDisposable
     {
         // Shadow copy analyzer files coming from packages to avoid locking the files in NuGet cache.
         // NOTE: It is important that we share the same shadow copy assembly loader for all VisualStudioAnalyzer instances.
@@ -19,24 +19,12 @@ internal sealed class ProjectAnalyzerReference : IDisposable
         private static readonly IAnalyzerAssemblyLoader s_analyzerAssemblyLoader =
             new ShadowCopyAnalyzerAssemblyLoader(Path.Combine(Path.GetTempPath(), "VS", "AnalyzerAssemblyLoader"));
 
-        private readonly ProjectId _projectId;
-        private readonly IProjectSystemDiagnosticSource _projectSystemDiagnosticSource;
-        private readonly string _language;
-
         // these 2 are mutable states that must be guarded under the _gate.
         private readonly object _gate = new();
         private AnalyzerReference? _analyzerReference;
         private ImmutableArray<DiagnosticData> _analyzerLoadErrors = ImmutableArray<DiagnosticData>.Empty;
 
-        public ProjectAnalyzerReference(string fullPath, IProjectSystemDiagnosticSource projectSystemDiagnosticSource, ProjectId projectId, string language)
-        {
-            FullPath = fullPath;
-            _projectSystemDiagnosticSource = projectSystemDiagnosticSource;
-            _projectId = projectId;
-            _language = language;
-        }
-
-        public string FullPath { get; }
+        public string FullPath { get; } = fullPath;
 
         public AnalyzerReference GetReference()
         {
@@ -58,12 +46,12 @@ public AnalyzerReference GetReference()
 
         private void OnAnalyzerLoadError(object? sender, AnalyzerLoadFailureEventArgs e)
         {
-            var data = _projectSystemDiagnosticSource.CreateAnalyzerLoadFailureDiagnostic(e, FullPath, _projectId, _language);
+            var data = projectSystemDiagnosticSource.CreateAnalyzerLoadFailureDiagnostic(e, FullPath, projectId, language);
 
             lock (_gate)
             {
                 _analyzerLoadErrors = _analyzerLoadErrors.Add(data);
-                _projectSystemDiagnosticSource.UpdateDiagnosticsForProject(_projectId, this, _analyzerLoadErrors);
+                projectSystemDiagnosticSource.UpdateDiagnosticsForProject(projectId, this, _analyzerLoadErrors);
             }
         }
 
@@ -77,10 +65,10 @@ public void Dispose()
 
                 if (!loadErrors.IsEmpty)
                 {
-                    _projectSystemDiagnosticSource.ClearDiagnosticsForProject(_projectId, this);
+                    projectSystemDiagnosticSource.ClearDiagnosticsForProject(projectId, this);
                 }
 
-                _projectSystemDiagnosticSource.ClearAnalyzerReferenceDiagnostics(fileReference, _language, _projectId);
+                projectSystemDiagnosticSource.ClearAnalyzerReferenceDiagnostics(fileReference, language, projectId);
             }
         }
 
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/AdditionalTextWithState.cs b/src/Workspaces/Core/Portable/Workspace/Solution/AdditionalTextWithState.cs
index bd2c335acc41f..dc204f1d87207 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/AdditionalTextWithState.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/AdditionalTextWithState.cs
@@ -11,15 +11,12 @@ namespace Microsoft.CodeAnalysis.Diagnostics
     /// <summary>
     /// An implementation of <see cref="AdditionalText"/> for the compiler that wraps a <see cref="AdditionalDocumentState"/>.
     /// </summary>
-    internal sealed class AdditionalTextWithState : AdditionalText
+    /// <remarks>
+    /// Create a <see cref="SourceText"/> from a <see cref="AdditionalDocumentState"/>.
+    /// </remarks>
+    internal sealed class AdditionalTextWithState(AdditionalDocumentState documentState) : AdditionalText
     {
-        private readonly AdditionalDocumentState _documentState;
-
-        /// <summary>
-        /// Create a <see cref="SourceText"/> from a <see cref="AdditionalDocumentState"/>.
-        /// </summary>
-        public AdditionalTextWithState(AdditionalDocumentState documentState)
-            => _documentState = documentState ?? throw new ArgumentNullException(nameof(documentState));
+        private readonly AdditionalDocumentState _documentState = documentState ?? throw new ArgumentNullException(nameof(documentState));
 
         /// <summary>
         /// Resolved path of the document.
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/AnalyzerConfigData.cs b/src/Workspaces/Core/Portable/Workspace/Solution/AnalyzerConfigData.cs
index 99371f49965bb..1555df3765c3c 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/AnalyzerConfigData.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/AnalyzerConfigData.cs
@@ -10,16 +10,9 @@ namespace Microsoft.CodeAnalysis;
 /// <summary>
 /// Aggregate analyzer config options for a specific path.
 /// </summary>
-internal readonly struct AnalyzerConfigData
+internal readonly struct AnalyzerConfigData(AnalyzerConfigOptionsResult result)
 {
-    public readonly StructuredAnalyzerConfigOptions ConfigOptions;
-    public readonly ImmutableDictionary<string, string> AnalyzerOptions;
-    public readonly ImmutableDictionary<string, ReportDiagnostic> TreeOptions;
-
-    public AnalyzerConfigData(AnalyzerConfigOptionsResult result)
-    {
-        ConfigOptions = StructuredAnalyzerConfigOptions.Create(result.AnalyzerOptions);
-        AnalyzerOptions = result.AnalyzerOptions;
-        TreeOptions = result.TreeOptions;
-    }
+    public readonly StructuredAnalyzerConfigOptions ConfigOptions = StructuredAnalyzerConfigOptions.Create(result.AnalyzerOptions);
+    public readonly ImmutableDictionary<string, string> AnalyzerOptions = result.AnalyzerOptions;
+    public readonly ImmutableDictionary<string, ReportDiagnostic> TreeOptions = result.TreeOptions;
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/Checksum.cs b/src/Workspaces/Core/Portable/Workspace/Solution/Checksum.cs
index c3ae1f521642b..ebb552d5a9622 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/Checksum.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/Checksum.cs
@@ -21,7 +21,7 @@ namespace Microsoft.CodeAnalysis
     /// without actually comparing data itself
     /// </summary>
     [DataContract]
-    internal sealed partial class Checksum : IObjectWritable, IEquatable<Checksum>
+    internal sealed partial class Checksum(Checksum.HashData hash) : IObjectWritable, IEquatable<Checksum>
     {
         /// <summary>
         /// The intended size of the <see cref="HashData"/> structure. 
@@ -31,10 +31,7 @@ internal sealed partial class Checksum : IObjectWritable, IEquatable<Checksum>
         public static readonly Checksum Null = new(default);
 
         [DataMember(Order = 0)]
-        private readonly HashData _checksum;
-
-        public Checksum(HashData hash)
-            => _checksum = hash;
+        private readonly HashData _checksum = hash;
 
         /// <summary>
         /// Create Checksum from given byte array. if byte array is bigger than <see cref="HashSize"/>, it will be
@@ -137,23 +134,16 @@ public static Checksum ReadFrom(ObjectReader reader)
         /// </summary>
         [DataContract]
         [StructLayout(LayoutKind.Explicit, Size = HashSize)]
-        public readonly struct HashData : IEquatable<HashData>
+        public readonly struct HashData(long data1, long data2, int data3) : IEquatable<HashData>
         {
             [FieldOffset(0), DataMember(Order = 0)]
-            private readonly long Data1;
+            private readonly long Data1 = data1;
 
             [FieldOffset(8), DataMember(Order = 1)]
-            private readonly long Data2;
+            private readonly long Data2 = data2;
 
             [FieldOffset(16), DataMember(Order = 2)]
-            private readonly int Data3;
-
-            public HashData(long data1, long data2, int data3)
-            {
-                Data1 = data1;
-                Data2 = data2;
-                Data3 = data3;
-            }
+            private readonly int Data3 = data3;
 
             public static bool operator ==(HashData x, HashData y)
                 => x.Equals(y);
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumCollection.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumCollection.cs
index e68ae66ea7978..b4495a9b4c5c5 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumCollection.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumCollection.cs
@@ -17,16 +17,12 @@ namespace Microsoft.CodeAnalysis.Serialization
     /// <summary>
     /// collection which children is checksum.
     /// </summary>
-    internal class ChecksumCollection : ChecksumWithChildren, IReadOnlyCollection<Checksum>
+    internal class ChecksumCollection(ImmutableArray<object> checksums) : ChecksumWithChildren(checksums), IReadOnlyCollection<Checksum>
     {
         public ChecksumCollection(ImmutableArray<Checksum> checksums) : this(checksums.CastArray<object>())
         {
         }
 
-        public ChecksumCollection(ImmutableArray<object> checksums) : base(checksums)
-        {
-        }
-
         public int Count => Children.Length;
         public Checksum this[int index] => (Checksum)Children[index];
 
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumWithChildren.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumWithChildren.cs
index e459e21006ba6..bf2d02a802d19 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumWithChildren.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ChecksumWithChildren.cs
@@ -11,17 +11,11 @@ namespace Microsoft.CodeAnalysis.Serialization
     /// <summary>
     /// this is a collection that has its own checksum and contains only checksum or checksum collection as its children.
     /// </summary>
-    internal abstract class ChecksumWithChildren : IChecksummedObject
+    internal abstract class ChecksumWithChildren(ImmutableArray<object> children) : IChecksummedObject
     {
-        public ChecksumWithChildren(ImmutableArray<object> children)
-        {
-            Checksum = CreateChecksum(children);
-            Children = children;
-        }
-
-        public Checksum Checksum { get; }
+        public Checksum Checksum { get; } = CreateChecksum(children);
 
-        public ImmutableArray<object> Children { get; }
+        public ImmutableArray<object> Children { get; } = children;
 
         private static Checksum CreateChecksum(ImmutableArray<object> children)
         {
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ConstantTextAndVersionSource.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ConstantTextAndVersionSource.cs
index 290ffbd0d2071..32714a34a1c44 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ConstantTextAndVersionSource.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ConstantTextAndVersionSource.cs
@@ -12,14 +12,9 @@ namespace Microsoft.CodeAnalysis;
 /// <summary>
 /// This value source keeps a strong reference to a value.
 /// </summary>
-internal sealed class ConstantTextAndVersionSource : ITextAndVersionSource
+internal sealed class ConstantTextAndVersionSource(TextAndVersion value) : ITextAndVersionSource
 {
-    private readonly TextAndVersion _value;
-
-    public ConstantTextAndVersionSource(TextAndVersion value)
-    {
-        _value = value;
-    }
+    private readonly TextAndVersion _value = value;
 
     public bool CanReloadText
         => false;
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentDiagnostic.cs b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentDiagnostic.cs
index ec11511cf57f7..19eb5a9c2e937 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentDiagnostic.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentDiagnostic.cs
@@ -6,14 +6,8 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    public class DocumentDiagnostic : WorkspaceDiagnostic
+    public class DocumentDiagnostic(WorkspaceDiagnosticKind kind, string message, DocumentId documentId) : WorkspaceDiagnostic(kind, message)
     {
-        public DocumentId DocumentId { get; }
-
-        public DocumentDiagnostic(WorkspaceDiagnosticKind kind, string message, DocumentId documentId)
-            : base(kind, message)
-        {
-            this.DocumentId = documentId;
-        }
+        public DocumentId DocumentId { get; } = documentId;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentInfo.cs b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentInfo.cs
index de436542b7c4a..99f39147215aa 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentInfo.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentInfo.cs
@@ -147,63 +147,52 @@ private string GetDebuggerDisplay()
         /// type that contains information regarding this document itself but
         /// no tree information such as document info
         /// </summary>
-        internal sealed class DocumentAttributes : IChecksummedObject, IObjectWritable
+        internal sealed class DocumentAttributes(
+            DocumentId id,
+            string name,
+            IReadOnlyList<string> folders,
+            SourceCodeKind sourceCodeKind,
+            string? filePath,
+            bool isGenerated,
+            bool designTimeOnly) : IChecksummedObject, IObjectWritable
         {
             private Checksum? _lazyChecksum;
 
             /// <summary>
             /// The Id of the document.
             /// </summary>
-            public DocumentId Id { get; }
+            public DocumentId Id { get; } = id;
 
             /// <summary>
             /// The name of the document.
             /// </summary>
-            public string Name { get; }
+            public string Name { get; } = name;
 
             /// <summary>
             /// The names of the logical nested folders the document is contained in.
             /// </summary>
-            public IReadOnlyList<string> Folders { get; }
+            public IReadOnlyList<string> Folders { get; } = folders;
 
             /// <summary>
             /// The kind of the source code.
             /// </summary>
-            public SourceCodeKind SourceCodeKind { get; }
+            public SourceCodeKind SourceCodeKind { get; } = sourceCodeKind;
 
             /// <summary>
             /// The file path of the document.
             /// </summary>
-            public string? FilePath { get; }
+            public string? FilePath { get; } = filePath;
 
             /// <summary>
             /// True if the document is a side effect of the build.
             /// </summary>
-            public bool IsGenerated { get; }
+            public bool IsGenerated { get; } = isGenerated;
 
             /// <summary>
             /// True if the source code contained in the document is only used in design-time (e.g. for completion),
             /// but is not passed to the compiler when the containing project is built, e.g. a Razor view
             /// </summary>
-            public bool DesignTimeOnly { get; }
-
-            public DocumentAttributes(
-                DocumentId id,
-                string name,
-                IReadOnlyList<string> folders,
-                SourceCodeKind sourceCodeKind,
-                string? filePath,
-                bool isGenerated,
-                bool designTimeOnly)
-            {
-                Id = id;
-                Name = name;
-                Folders = folders;
-                SourceCodeKind = sourceCodeKind;
-                FilePath = filePath;
-                IsGenerated = isGenerated;
-                DesignTimeOnly = designTimeOnly;
-            }
+            public bool DesignTimeOnly { get; } = designTimeOnly;
 
             public DocumentAttributes With(
                 DocumentId? id = null,
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState.EquivalenceResult.cs b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState.EquivalenceResult.cs
index 01ff61f58d22f..60543ea086cb9 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState.EquivalenceResult.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState.EquivalenceResult.cs
@@ -8,16 +8,10 @@ namespace Microsoft.CodeAnalysis
 {
     internal partial class DocumentState
     {
-        internal class EquivalenceResult
+        internal class EquivalenceResult(bool topLevelEquivalent, bool interiorEquivalent)
         {
-            public readonly bool TopLevelEquivalent;
-            public readonly bool InteriorEquivalent;
-
-            public EquivalenceResult(bool topLevelEquivalent, bool interiorEquivalent)
-            {
-                this.TopLevelEquivalent = topLevelEquivalent;
-                this.InteriorEquivalent = interiorEquivalent;
-            }
+            public readonly bool TopLevelEquivalent = topLevelEquivalent;
+            public readonly bool InteriorEquivalent = interiorEquivalent;
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState_TreeTextSource.cs b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState_TreeTextSource.cs
index 774ab49902669..ea6c25ab3a1c7 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState_TreeTextSource.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/DocumentState_TreeTextSource.cs
@@ -15,35 +15,28 @@ internal partial class DocumentState
         /// <summary>
         /// A source for <see cref="TextAndVersion"/> constructed from an syntax tree.
         /// </summary>
-        private sealed class TreeTextSource : ITextAndVersionSource
+        private sealed class TreeTextSource(AsyncLazy<SourceText> textSource, VersionStamp version) : ITextAndVersionSource
         {
-            private readonly AsyncLazy<SourceText> _textSource;
-            private readonly VersionStamp _version;
+            private readonly VersionStamp _version = version;
 
             public bool CanReloadText
                 => false;
 
-            public TreeTextSource(AsyncLazy<SourceText> textSource, VersionStamp version)
-            {
-                _textSource = textSource;
-                _version = version;
-            }
-
             public async Task<TextAndVersion> GetValueAsync(LoadTextOptions options, CancellationToken cancellationToken)
             {
-                var text = await _textSource.GetValueAsync(cancellationToken).ConfigureAwait(false);
+                var text = await textSource.GetValueAsync(cancellationToken).ConfigureAwait(false);
                 return TextAndVersion.Create(text, _version);
             }
 
             public TextAndVersion GetValue(LoadTextOptions options, CancellationToken cancellationToken)
             {
-                var text = _textSource.GetValue(cancellationToken);
+                var text = textSource.GetValue(cancellationToken);
                 return TextAndVersion.Create(text, _version);
             }
 
             public bool TryGetValue(LoadTextOptions options, [NotNullWhen(true)] out TextAndVersion? value)
             {
-                if (_textSource.TryGetValue(out var text))
+                if (textSource.TryGetValue(out var text))
                 {
                     value = TextAndVersion.Create(text, _version);
                     return true;
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/LoadTextOptions.cs b/src/Workspaces/Core/Portable/Workspace/Solution/LoadTextOptions.cs
index 5f01a2368766a..a64ded278c05c 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/LoadTextOptions.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/LoadTextOptions.cs
@@ -11,12 +11,9 @@ namespace Microsoft.CodeAnalysis;
 /// <summary>
 /// Options used to load <see cref="SourceText"/>.
 /// </summary>
-public readonly struct LoadTextOptions : IEquatable<LoadTextOptions>
+public readonly struct LoadTextOptions(SourceHashAlgorithm checksumAlgorithm) : IEquatable<LoadTextOptions>
 {
-    public SourceHashAlgorithm ChecksumAlgorithm { get; }
-
-    public LoadTextOptions(SourceHashAlgorithm checksumAlgorithm)
-        => ChecksumAlgorithm = checksumAlgorithm;
+    public SourceHashAlgorithm ChecksumAlgorithm { get; } = checksumAlgorithm;
 
     public bool Equals(LoadTextOptions other)
         => ChecksumAlgorithm == other.ChecksumAlgorithm;
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/LoadableTextAndVersionSource.cs b/src/Workspaces/Core/Portable/Workspace/Solution/LoadableTextAndVersionSource.cs
index 94b3467cdf651..70417d9b9dbad 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/LoadableTextAndVersionSource.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/LoadableTextAndVersionSource.cs
@@ -10,12 +10,12 @@
 
 namespace Microsoft.CodeAnalysis;
 
-internal sealed class LoadableTextAndVersionSource : ITextAndVersionSource
+internal sealed class LoadableTextAndVersionSource(TextLoader loader, bool cacheResult) : ITextAndVersionSource
 {
-    private sealed class LazyValueWithOptions
+    private sealed class LazyValueWithOptions(LoadableTextAndVersionSource source, LoadTextOptions options)
     {
-        public readonly LoadableTextAndVersionSource Source;
-        public readonly LoadTextOptions Options;
+        public readonly LoadableTextAndVersionSource Source = source;
+        public readonly LoadTextOptions Options = options;
 
         private readonly SemaphoreSlim _gate = new(initialCount: 1);
 
@@ -34,12 +34,6 @@ private sealed class LazyValueWithOptions
         /// </summary>
         private WeakReference<TextAndVersion>? _weakInstance;
 
-        public LazyValueWithOptions(LoadableTextAndVersionSource source, LoadTextOptions options)
-        {
-            Source = source;
-            Options = options;
-        }
-
         private Task<TextAndVersion> LoadAsync(CancellationToken cancellationToken)
             => Source.Loader.LoadTextAsync(Options, cancellationToken);
 
@@ -108,17 +102,11 @@ private void UpdateWeakAndStrongReferences_NoLock(TextAndVersion textAndVersion)
         }
     }
 
-    public readonly TextLoader Loader;
-    public readonly bool CacheResult;
+    public readonly TextLoader Loader = loader;
+    public readonly bool CacheResult = cacheResult;
 
     private LazyValueWithOptions? _lazyValue;
 
-    public LoadableTextAndVersionSource(TextLoader loader, bool cacheResult)
-    {
-        Loader = loader;
-        CacheResult = cacheResult;
-    }
-
     public bool CanReloadText
         => Loader.CanReloadText;
 
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/Project.EquivalenceResult.cs b/src/Workspaces/Core/Portable/Workspace/Solution/Project.EquivalenceResult.cs
index 281fa15ae1f9f..73361de7fe833 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/Project.EquivalenceResult.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/Project.EquivalenceResult.cs
@@ -8,16 +8,10 @@ namespace Microsoft.CodeAnalysis
 {
     public partial class Project
     {
-        private class EquivalenceResult
+        private class EquivalenceResult(bool publiclyEquivalent, bool privatelyEquivalent)
         {
-            public readonly bool PubliclyEquivalent;
-            public readonly bool PrivatelyEquivalent;
-
-            public EquivalenceResult(bool publiclyEquivalent, bool privatelyEquivalent)
-            {
-                this.PubliclyEquivalent = publiclyEquivalent;
-                this.PrivatelyEquivalent = privatelyEquivalent;
-            }
+            public readonly bool PubliclyEquivalent = publiclyEquivalent;
+            public readonly bool PrivatelyEquivalent = privatelyEquivalent;
         }
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDependencyGraph.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDependencyGraph.cs
index 4593d8b9c5c70..2e007ad813eca 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDependencyGraph.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDependencyGraph.cs
@@ -512,12 +512,8 @@ private static void ValidateReverseReferences(
         internal TestAccessor GetTestAccessor()
             => new(this);
 
-        internal readonly struct TestAccessor
+        internal readonly struct TestAccessor(ProjectDependencyGraph instance)
         {
-            private readonly ProjectDependencyGraph _instance;
-
-            public TestAccessor(ProjectDependencyGraph instance)
-                => _instance = instance;
 
             /// <summary>
             /// Gets the list of projects that directly or transitively depend on this project, if it has already been
@@ -530,7 +526,7 @@ public TestAccessor(ProjectDependencyGraph instance)
                     throw new ArgumentNullException(nameof(projectId));
                 }
 
-                _instance._reverseTransitiveReferencesMap.TryGetValue(projectId, out var projects);
+                instance._reverseTransitiveReferencesMap.TryGetValue(projectId, out var projects);
                 return projects;
             }
         }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDiagnostic.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDiagnostic.cs
index 00a253b11a6ef..5853ea69fd651 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDiagnostic.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectDiagnostic.cs
@@ -6,14 +6,8 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    public class ProjectDiagnostic : WorkspaceDiagnostic
+    public class ProjectDiagnostic(WorkspaceDiagnosticKind kind, string message, ProjectId projectId) : WorkspaceDiagnostic(kind, message)
     {
-        public ProjectId ProjectId { get; }
-
-        public ProjectDiagnostic(WorkspaceDiagnosticKind kind, string message, ProjectId projectId)
-            : base(kind, message)
-        {
-            this.ProjectId = projectId;
-        }
+        public ProjectId ProjectId { get; } = projectId;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectInfo.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectInfo.cs
index e5e764550992c..7cb79c6d61aaa 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectInfo.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectInfo.cs
@@ -399,7 +399,22 @@ internal string GetDebuggerDisplay()
         /// type that contains information regarding this project itself but
         /// no tree information such as document info
         /// </summary>
-        internal sealed class ProjectAttributes : IChecksummedObject, IObjectWritable
+        internal sealed class ProjectAttributes(
+            ProjectId id,
+            VersionStamp version,
+            string name,
+            string assemblyName,
+            string language,
+            CompilationOutputInfo compilationOutputFilePaths,
+            SourceHashAlgorithm checksumAlgorithm,
+            string? defaultNamespace = null,
+            string? filePath = null,
+            string? outputFilePath = null,
+            string? outputRefFilePath = null,
+            Guid telemetryId = default,
+            bool isSubmission = false,
+            bool hasAllInformation = true,
+            bool runAnalyzers = true) : IChecksummedObject, IObjectWritable
         {
             /// <summary>
             /// Matches names like: Microsoft.CodeAnalysis.Features (netcoreapp3.1)
@@ -409,79 +424,79 @@ internal sealed class ProjectAttributes : IChecksummedObject, IObjectWritable
             /// <summary>
             /// The unique Id of the project.
             /// </summary>
-            public ProjectId Id { get; }
+            public ProjectId Id { get; } = id;
 
             /// <summary>
             /// The version of the project.
             /// </summary>
-            public VersionStamp Version { get; }
+            public VersionStamp Version { get; } = version;
 
             /// <summary>
             /// The name of the project. This may differ from the project's filename.
             /// </summary>
-            public string Name { get; }
+            public string Name { get; } = name;
 
             /// <summary>
             /// The name of the assembly that this project will create, without file extension.
             /// </summary>,
-            public string AssemblyName { get; }
+            public string AssemblyName { get; } = assemblyName;
 
             /// <summary>
             /// The language of the project.
             /// </summary>
-            public string Language { get; }
+            public string Language { get; } = language;
 
             /// <summary>
             /// The path to the project file or null if there is no project file.
             /// </summary>
-            public string? FilePath { get; }
+            public string? FilePath { get; } = filePath;
 
             /// <summary>
             /// The path to the output file (module or assembly).
             /// </summary>
-            public string? OutputFilePath { get; }
+            public string? OutputFilePath { get; } = outputFilePath;
 
             /// <summary>
             /// The path to the reference assembly output file.
             /// </summary>
-            public string? OutputRefFilePath { get; }
+            public string? OutputRefFilePath { get; } = outputRefFilePath;
 
             /// <summary>
             /// Paths to the compiler output files.
             /// </summary>
-            public CompilationOutputInfo CompilationOutputInfo { get; }
+            public CompilationOutputInfo CompilationOutputInfo { get; } = compilationOutputFilePaths;
 
             /// <summary>
             /// The default namespace of the project.
             /// </summary>
-            public string? DefaultNamespace { get; }
+            public string? DefaultNamespace { get; } = defaultNamespace;
 
             /// <summary>
             /// Algorithm to calculate content checksum for debugging purposes.
             /// </summary>
-            public SourceHashAlgorithm ChecksumAlgorithm { get; }
+            public SourceHashAlgorithm ChecksumAlgorithm { get; } = checksumAlgorithm;
 
             /// <summary>
             /// True if this is a submission project for interactive sessions.
             /// </summary>
-            public bool IsSubmission { get; }
+            public bool IsSubmission { get; } = isSubmission;
 
             /// <summary>
             /// True if project information is complete. In some workspace hosts, it is possible
             /// a project only has partial information. In such cases, a project might not have all
             /// information on its files or references.
             /// </summary>
-            public bool HasAllInformation { get; }
+            public bool HasAllInformation { get; } = hasAllInformation;
 
             /// <summary>
             /// True if we should run analyzers for this project.
             /// </summary>
-            public bool RunAnalyzers { get; }
+            public bool RunAnalyzers { get; } = runAnalyzers;
 
             /// <summary>
             /// The id report during telemetry events.
             /// </summary>
-            public Guid TelemetryId { get; }
+            public Guid TelemetryId { get; } = telemetryId;
 
             private StrongBox<(string?, string?)>? _lazyNameAndFlavor;
             private Checksum? _lazyChecksum;
@@ -506,41 +521,6 @@ internal sealed class ProjectAttributes : IChecksummedObject, IObjectWritable
                 }
             }
 
-            public ProjectAttributes(
-                ProjectId id,
-                VersionStamp version,
-                string name,
-                string assemblyName,
-                string language,
-                CompilationOutputInfo compilationOutputFilePaths,
-                SourceHashAlgorithm checksumAlgorithm,
-                string? defaultNamespace = null,
-                string? filePath = null,
-                string? outputFilePath = null,
-                string? outputRefFilePath = null,
-                Guid telemetryId = default,
-                bool isSubmission = false,
-                bool hasAllInformation = true,
-                bool runAnalyzers = true)
-            {
-                Id = id;
-                Name = name;
-                Language = language;
-                AssemblyName = assemblyName;
-
-                Version = version;
-                FilePath = filePath;
-                OutputFilePath = outputFilePath;
-                OutputRefFilePath = outputRefFilePath;
-                CompilationOutputInfo = compilationOutputFilePaths;
-                DefaultNamespace = defaultNamespace;
-                ChecksumAlgorithm = checksumAlgorithm;
-                IsSubmission = isSubmission;
-                HasAllInformation = hasAllInformation;
-                RunAnalyzers = runAnalyzers;
-                TelemetryId = telemetryId;
-            }
-
             public ProjectAttributes With(
                 VersionStamp? version = null,
                 string? name = null,
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs
index bb2385fc184f8..f003f4264167a 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/ProjectState.cs
@@ -291,16 +291,12 @@ public AnalyzerConfigData GetAnalyzerOptionsForPath(string path, CancellationTok
             return GetAnalyzerOptionsForPath(sourceFilePath, CancellationToken.None);
         }
 
-        internal sealed class ProjectAnalyzerConfigOptionsProvider : AnalyzerConfigOptionsProvider
+        internal sealed class ProjectAnalyzerConfigOptionsProvider(ProjectState projectState) : AnalyzerConfigOptionsProvider
         {
-            private readonly ProjectState _projectState;
             private RazorDesignTimeAnalyzerConfigOptions? _lazyRazorDesignTimeOptions = null;
 
-            public ProjectAnalyzerConfigOptionsProvider(ProjectState projectState)
-                => _projectState = projectState;
-
             private AnalyzerConfigOptionsCache GetCache()
-                => _projectState._lazyAnalyzerConfigOptions.GetValue(CancellationToken.None);
+                => projectState._lazyAnalyzerConfigOptions.GetValue(CancellationToken.None);
 
             public override AnalyzerConfigOptions GlobalOptions
                 => GetCache().GlobalConfigOptions.ConfigOptions;
@@ -309,7 +305,7 @@ public override AnalyzerConfigOptions GetOptions(SyntaxTree tree)
             {
                 var documentId = DocumentState.GetDocumentIdForTree(tree);
                 var cache = GetCache();
-                if (documentId != null && _projectState.DocumentStates.TryGetState(documentId, out var documentState))
+                if (documentId != null && projectState.DocumentStates.TryGetState(documentId, out var documentState))
                 {
                     return GetOptions(cache, documentState);
                 }
@@ -319,13 +315,13 @@ public override AnalyzerConfigOptions GetOptions(SyntaxTree tree)
 
             internal async ValueTask<StructuredAnalyzerConfigOptions> GetOptionsAsync(DocumentState documentState, CancellationToken cancellationToken)
             {
-                var cache = await _projectState._lazyAnalyzerConfigOptions.GetValueAsync(cancellationToken).ConfigureAwait(false);
+                var cache = await projectState._lazyAnalyzerConfigOptions.GetValueAsync(cancellationToken).ConfigureAwait(false);
                 return GetOptions(cache, documentState);
             }
 
             private StructuredAnalyzerConfigOptions GetOptions(in AnalyzerConfigOptionsCache cache, DocumentState documentState)
             {
-                var services = _projectState.LanguageServices.SolutionServices;
+                var services = projectState.LanguageServices.SolutionServices;
 
                 if (documentState.IsRazorDocument())
                 {
@@ -341,7 +337,7 @@ private StructuredAnalyzerConfigOptions GetOptions(in AnalyzerConfigOptionsCache
                 var legacyDocumentOptionsProvider = services.GetService<ILegacyDocumentOptionsProvider>();
                 if (legacyDocumentOptionsProvider != null)
                 {
-                    return StructuredAnalyzerConfigOptions.Create(legacyDocumentOptionsProvider.GetOptions(_projectState.Id, filePath));
+                    return StructuredAnalyzerConfigOptions.Create(legacyDocumentOptionsProvider.GetOptions(projectState.Id, filePath));
                 }
 
                 return GetOptionsForSourcePath(cache, filePath);
@@ -366,7 +362,7 @@ private static StructuredAnalyzerConfigOptions GetOptionsForSourcePath(in Analyz
                 // We need to work out path to this document. Documents may not have a "real" file path if they're something created
                 // as a part of a code action, but haven't been written to disk yet.
 
-                var projectFilePath = _projectState.FilePath;
+                var projectFilePath = projectState.FilePath;
 
                 if (documentState.Name != null && projectFilePath != null)
                 {
@@ -389,15 +385,9 @@ private static StructuredAnalyzerConfigOptions GetOptionsForSourcePath(in Analyz
         /// are only available in-proc and the same for all Razor design-time documents.
         /// This type emulates these options as analyzer config options.
         /// </summary>
-        private sealed class RazorDesignTimeAnalyzerConfigOptions : StructuredAnalyzerConfigOptions
+        private sealed class RazorDesignTimeAnalyzerConfigOptions(SolutionServices services) : StructuredAnalyzerConfigOptions
         {
-            private readonly ILegacyGlobalOptionsWorkspaceService? _globalOptions;
-
-            public RazorDesignTimeAnalyzerConfigOptions(SolutionServices services)
-            {
-                // not available OOP:
-                _globalOptions = services.GetService<ILegacyGlobalOptionsWorkspaceService>();
-            }
+            private readonly ILegacyGlobalOptionsWorkspaceService? _globalOptions = services.GetService<ILegacyGlobalOptionsWorkspaceService>();
 
             public override bool TryGetValue(string key, [NotNullWhen(true)] out string? value)
             {
@@ -437,12 +427,9 @@ public override NamingStylePreferences GetNamingStylePreferences()
                 => NamingStylePreferences.Empty;
         }
 
-        private sealed class ProjectSyntaxTreeOptionsProvider : SyntaxTreeOptionsProvider
+        private sealed class ProjectSyntaxTreeOptionsProvider(AsyncLazy<AnalyzerConfigOptionsCache> lazyAnalyzerConfigSet) : SyntaxTreeOptionsProvider
         {
-            private readonly AsyncLazy<AnalyzerConfigOptionsCache> _lazyAnalyzerConfigSet;
-
-            public ProjectSyntaxTreeOptionsProvider(AsyncLazy<AnalyzerConfigOptionsCache> lazyAnalyzerConfigSet)
-                => _lazyAnalyzerConfigSet = lazyAnalyzerConfigSet;
+            private readonly AsyncLazy<AnalyzerConfigOptionsCache> _lazyAnalyzerConfigSet = lazyAnalyzerConfigSet;
 
             public override GeneratedKind IsGenerated(SyntaxTree tree, CancellationToken cancellationToken)
             {
@@ -493,17 +480,11 @@ private static AsyncLazy<AnalyzerConfigOptionsCache> ComputeAnalyzerConfigOption
                 });
         }
 
-        private readonly struct AnalyzerConfigOptionsCache
+        private readonly struct AnalyzerConfigOptionsCache(AnalyzerConfigSet configSet)
         {
             private readonly ConcurrentDictionary<string, AnalyzerConfigData> _sourcePathToResult = new();
-            private readonly Func<string, AnalyzerConfigData> _computeFunction;
-            private readonly Lazy<AnalyzerConfigData> _global;
-
-            public AnalyzerConfigOptionsCache(AnalyzerConfigSet configSet)
-            {
-                _global = new Lazy<AnalyzerConfigData>(() => new AnalyzerConfigData(configSet.GlobalConfigOptions));
-                _computeFunction = path => new AnalyzerConfigData(configSet.GetOptionsForSourcePath(path));
-            }
+            private readonly Func<string, AnalyzerConfigData> _computeFunction = path => new AnalyzerConfigData(configSet.GetOptionsForSourcePath(path));
+            private readonly Lazy<AnalyzerConfigData> _global = new Lazy<AnalyzerConfigData>(() => new AnalyzerConfigData(configSet.GlobalConfigOptions));
 
             public AnalyzerConfigData GlobalConfigOptions
                 => _global.Value;
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/RecoverableTextAndVersion.cs b/src/Workspaces/Core/Portable/Workspace/Solution/RecoverableTextAndVersion.cs
index 8cdcafcb896bd..1a6e08f39440e 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/RecoverableTextAndVersion.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/RecoverableTextAndVersion.cs
@@ -15,22 +15,14 @@ namespace Microsoft.CodeAnalysis
     /// <summary>
     /// A recoverable TextAndVersion source that saves its text to temporary storage.
     /// </summary>
-    internal sealed partial class RecoverableTextAndVersion : ITextAndVersionSource
+    internal sealed partial class RecoverableTextAndVersion(ITextAndVersionSource initialSource, SolutionServices services) : ITextAndVersionSource
     {
-        private readonly SolutionServices _services;
 
         // Starts as ITextAndVersionSource and is replaced with RecoverableText when the TextAndVersion value is requested.
         // At that point the initial source is no longer referenced and can be garbage collected.
-        private object _initialSourceOrRecoverableText;
+        private object _initialSourceOrRecoverableText = initialSource;
 
-        public bool CanReloadText { get; }
-
-        public RecoverableTextAndVersion(ITextAndVersionSource initialSource, SolutionServices services)
-        {
-            _initialSourceOrRecoverableText = initialSource;
-            _services = services;
-            CanReloadText = initialSource.CanReloadText;
-        }
+        public bool CanReloadText { get; } = initialSource.CanReloadText;
 
         /// <returns>
         /// True if the <paramref name="source"/> is available, false if <paramref name="text"/> is returned.
@@ -96,7 +88,7 @@ private async ValueTask<RecoverableText> GetRecoverableTextAsync(
 
                 Interlocked.CompareExchange(
                     ref _initialSourceOrRecoverableText,
-                    value: new RecoverableText(source, textAndVersion, options, _services),
+                    value: new RecoverableText(source, textAndVersion, options, services),
                     comparand: source);
             }
 
@@ -110,7 +102,7 @@ private async ValueTask<RecoverableText> GetRecoverableTextAsync(
                     : recoverableText.InitialSource.GetValue(options, cancellationToken);
                 Interlocked.Exchange(
                     ref _initialSourceOrRecoverableText,
-                    new RecoverableText(recoverableText.InitialSource, textAndVersion, options, _services));
+                    new RecoverableText(recoverableText.InitialSource, textAndVersion, options, services));
             }
 
             return (RecoverableText)_initialSourceOrRecoverableText;
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionInfo.cs b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionInfo.cs
index 4119d66a3f197..a70e6a0abd6eb 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionInfo.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionInfo.cs
@@ -94,37 +94,29 @@ internal SolutionInfo WithTelemetryId(Guid telemetryId)
         /// type that contains information regarding this solution itself but
         /// no tree information such as project info
         /// </summary>
-        internal sealed class SolutionAttributes : IChecksummedObject, IObjectWritable
+        internal sealed class SolutionAttributes(SolutionId id, VersionStamp version, string? filePath, Guid telemetryId) : IChecksummedObject, IObjectWritable
         {
             private Checksum? _lazyChecksum;
 
             /// <summary>
             /// The unique Id of the solution.
             /// </summary>
-            public SolutionId Id { get; }
+            public SolutionId Id { get; } = id;
 
             /// <summary>
             /// The version of the solution.
             /// </summary>
-            public VersionStamp Version { get; }
+            public VersionStamp Version { get; } = version;
 
             /// <summary>
             /// The path to the solution file, or null if there is no solution file.
             /// </summary>
-            public string? FilePath { get; }
+            public string? FilePath { get; } = filePath;
 
             /// <summary>
             /// The id report during telemetry events.
             /// </summary>
-            public Guid TelemetryId { get; }
-
-            public SolutionAttributes(SolutionId id, VersionStamp version, string? filePath, Guid telemetryId)
-            {
-                Id = id;
-                Version = version;
-                FilePath = filePath;
-                TelemetryId = telemetryId;
-            }
+            public Guid TelemetryId { get; } = telemetryId;
 
             public SolutionAttributes With(
                 VersionStamp? version = null,
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationAndGeneratorDriverTranslationAction_Actions.cs b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationAndGeneratorDriverTranslationAction_Actions.cs
index 636d8676cdaa1..6e6e2d359417b 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationAndGeneratorDriverTranslationAction_Actions.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationAndGeneratorDriverTranslationAction_Actions.cs
@@ -18,16 +18,10 @@ internal partial class SolutionState
     {
         private abstract partial class CompilationAndGeneratorDriverTranslationAction
         {
-            internal sealed class TouchDocumentAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class TouchDocumentAction(DocumentState oldState, DocumentState newState) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly DocumentState _oldState;
-                private readonly DocumentState _newState;
-
-                public TouchDocumentAction(DocumentState oldState, DocumentState newState)
-                {
-                    _oldState = oldState;
-                    _newState = newState;
-                }
+                private readonly DocumentState _oldState = oldState;
+                private readonly DocumentState _newState = newState;
 
                 public override Task<Compilation> TransformCompilationAsync(Compilation oldCompilation, CancellationToken cancellationToken)
                 {
@@ -52,16 +46,10 @@ public override Task<Compilation> TransformCompilationAsync(Compilation oldCompi
                 }
             }
 
-            internal sealed class TouchAdditionalDocumentAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class TouchAdditionalDocumentAction(AdditionalDocumentState oldState, AdditionalDocumentState newState) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly AdditionalDocumentState _oldState;
-                private readonly AdditionalDocumentState _newState;
-
-                public TouchAdditionalDocumentAction(AdditionalDocumentState oldState, AdditionalDocumentState newState)
-                {
-                    _oldState = oldState;
-                    _newState = newState;
-                }
+                private readonly AdditionalDocumentState _oldState = oldState;
+                private readonly AdditionalDocumentState _newState = newState;
 
                 // Changing an additional document doesn't change the compilation directly, so we can "apply" the
                 // translation (which is a no-op). Since we use a 'false' here to mean that it's not worth keeping
@@ -88,19 +76,12 @@ public TouchAdditionalDocumentAction(AdditionalDocumentState oldState, Additiona
                 }
             }
 
-            internal sealed class RemoveDocumentsAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class RemoveDocumentsAction(ImmutableArray<DocumentState> documents) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly ImmutableArray<DocumentState> _documents;
-
-                public RemoveDocumentsAction(ImmutableArray<DocumentState> documents)
-                {
-                    _documents = documents;
-                }
-
                 public override async Task<Compilation> TransformCompilationAsync(Compilation oldCompilation, CancellationToken cancellationToken)
                 {
-                    var syntaxTrees = new List<SyntaxTree>(_documents.Length);
-                    foreach (var document in _documents)
+                    var syntaxTrees = new List<SyntaxTree>(documents.Length);
+                    foreach (var document in documents)
                     {
                         cancellationToken.ThrowIfCancellationRequested();
                         syntaxTrees.Add(await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false));
@@ -113,19 +94,12 @@ public override async Task<Compilation> TransformCompilationAsync(Compilation ol
                 public override bool CanUpdateCompilationWithStaleGeneratedTreesIfGeneratorsGiveSameOutput => true;
             }
 
-            internal sealed class AddDocumentsAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class AddDocumentsAction(ImmutableArray<DocumentState> documents) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly ImmutableArray<DocumentState> _documents;
-
-                public AddDocumentsAction(ImmutableArray<DocumentState> documents)
-                {
-                    _documents = documents;
-                }
-
                 public override async Task<Compilation> TransformCompilationAsync(Compilation oldCompilation, CancellationToken cancellationToken)
                 {
-                    var syntaxTrees = new List<SyntaxTree>(capacity: _documents.Length);
-                    foreach (var document in _documents)
+                    var syntaxTrees = new List<SyntaxTree>(capacity: documents.Length);
+                    foreach (var document in documents)
                     {
                         cancellationToken.ThrowIfCancellationRequested();
                         syntaxTrees.Add(await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false));
@@ -138,22 +112,13 @@ public override async Task<Compilation> TransformCompilationAsync(Compilation ol
                 public override bool CanUpdateCompilationWithStaleGeneratedTreesIfGeneratorsGiveSameOutput => true;
             }
 
-            internal sealed class ReplaceAllSyntaxTreesAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class ReplaceAllSyntaxTreesAction(ProjectState state, bool isParseOptionChange) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly ProjectState _state;
-                private readonly bool _isParseOptionChange;
-
-                public ReplaceAllSyntaxTreesAction(ProjectState state, bool isParseOptionChange)
-                {
-                    _state = state;
-                    _isParseOptionChange = isParseOptionChange;
-                }
-
                 public override async Task<Compilation> TransformCompilationAsync(Compilation oldCompilation, CancellationToken cancellationToken)
                 {
-                    var syntaxTrees = new List<SyntaxTree>(capacity: _state.DocumentStates.Count);
+                    var syntaxTrees = new List<SyntaxTree>(capacity: state.DocumentStates.Count);
 
-                    foreach (var documentState in _state.DocumentStates.GetStatesInCompilationOrder())
+                    foreach (var documentState in state.DocumentStates.GetStatesInCompilationOrder())
                     {
                         cancellationToken.ThrowIfCancellationRequested();
                         syntaxTrees.Add(await documentState.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false));
@@ -167,10 +132,10 @@ public override async Task<Compilation> TransformCompilationAsync(Compilation ol
 
                 public override GeneratorDriver? TransformGeneratorDriver(GeneratorDriver generatorDriver)
                 {
-                    if (_isParseOptionChange)
+                    if (isParseOptionChange)
                     {
-                        RoslynDebug.AssertNotNull(_state.ParseOptions);
-                        return generatorDriver.WithUpdatedParseOptions(_state.ParseOptions);
+                        RoslynDebug.AssertNotNull(state.ParseOptions);
+                        return generatorDriver.WithUpdatedParseOptions(state.ParseOptions);
                     }
                     else
                     {
@@ -181,21 +146,12 @@ public override async Task<Compilation> TransformCompilationAsync(Compilation ol
                 }
             }
 
-            internal sealed class ProjectCompilationOptionsAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class ProjectCompilationOptionsAction(ProjectState state, bool isAnalyzerConfigChange) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly ProjectState _state;
-                private readonly bool _isAnalyzerConfigChange;
-
-                public ProjectCompilationOptionsAction(ProjectState state, bool isAnalyzerConfigChange)
-                {
-                    _state = state;
-                    _isAnalyzerConfigChange = isAnalyzerConfigChange;
-                }
-
                 public override Task<Compilation> TransformCompilationAsync(Compilation oldCompilation, CancellationToken cancellationToken)
                 {
-                    RoslynDebug.AssertNotNull(_state.CompilationOptions);
-                    return Task.FromResult(oldCompilation.WithOptions(_state.CompilationOptions));
+                    RoslynDebug.AssertNotNull(state.CompilationOptions);
+                    return Task.FromResult(oldCompilation.WithOptions(state.CompilationOptions));
                 }
 
                 // Updating the options of a compilation doesn't require us to reparse trees, so we can use this to update
@@ -204,9 +160,9 @@ public override Task<Compilation> TransformCompilationAsync(Compilation oldCompi
 
                 public override GeneratorDriver? TransformGeneratorDriver(GeneratorDriver generatorDriver)
                 {
-                    if (_isAnalyzerConfigChange)
+                    if (isAnalyzerConfigChange)
                     {
-                        return generatorDriver.WithUpdatedAnalyzerConfigOptions(_state.AnalyzerOptions.AnalyzerConfigOptionsProvider);
+                        return generatorDriver.WithUpdatedAnalyzerConfigOptions(state.AnalyzerOptions.AnalyzerConfigOptionsProvider);
                     }
                     else
                     {
@@ -217,18 +173,11 @@ public override Task<Compilation> TransformCompilationAsync(Compilation oldCompi
                 }
             }
 
-            internal sealed class ProjectAssemblyNameAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class ProjectAssemblyNameAction(string assemblyName) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly string _assemblyName;
-
-                public ProjectAssemblyNameAction(string assemblyName)
-                {
-                    _assemblyName = assemblyName;
-                }
-
                 public override Task<Compilation> TransformCompilationAsync(Compilation oldCompilation, CancellationToken cancellationToken)
                 {
-                    return Task.FromResult(oldCompilation.WithAssemblyName(_assemblyName));
+                    return Task.FromResult(oldCompilation.WithAssemblyName(assemblyName));
                 }
 
                 // Updating the options of a compilation doesn't require us to reparse trees, so we can use this to update
@@ -236,18 +185,8 @@ public override Task<Compilation> TransformCompilationAsync(Compilation oldCompi
                 public override bool CanUpdateCompilationWithStaleGeneratedTreesIfGeneratorsGiveSameOutput => true;
             }
 
-            internal sealed class AddOrRemoveAnalyzerReferencesAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class AddOrRemoveAnalyzerReferencesAction(string language, ImmutableArray<AnalyzerReference> referencesToAdd = default, ImmutableArray<AnalyzerReference> referencesToRemove = default) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly string _language;
-                private readonly ImmutableArray<AnalyzerReference> _referencesToAdd;
-                private readonly ImmutableArray<AnalyzerReference> _referencesToRemove;
-
-                public AddOrRemoveAnalyzerReferencesAction(string language, ImmutableArray<AnalyzerReference> referencesToAdd = default, ImmutableArray<AnalyzerReference> referencesToRemove = default)
-                {
-                    _language = language;
-                    _referencesToAdd = referencesToAdd;
-                    _referencesToRemove = referencesToRemove;
-                }
 
                 // Changing analyzer references doesn't change the compilation directly, so we can "apply" the
                 // translation (which is a no-op). Since we use a 'false' here to mean that it's not worth keeping
@@ -256,28 +195,22 @@ public AddOrRemoveAnalyzerReferencesAction(string language, ImmutableArray<Analy
 
                 public override GeneratorDriver? TransformGeneratorDriver(GeneratorDriver generatorDriver)
                 {
-                    if (!_referencesToRemove.IsDefaultOrEmpty)
+                    if (!referencesToRemove.IsDefaultOrEmpty)
                     {
-                        generatorDriver = generatorDriver.RemoveGenerators(_referencesToRemove.SelectMany(r => r.GetGenerators(_language)).ToImmutableArray());
+                        generatorDriver = generatorDriver.RemoveGenerators(referencesToRemove.SelectMany(r => r.GetGenerators(language)).ToImmutableArray());
                     }
 
-                    if (!_referencesToAdd.IsDefaultOrEmpty)
+                    if (!referencesToAdd.IsDefaultOrEmpty)
                     {
-                        generatorDriver = generatorDriver.AddGenerators(_referencesToAdd.SelectMany(r => r.GetGenerators(_language)).ToImmutableArray());
+                        generatorDriver = generatorDriver.AddGenerators(referencesToAdd.SelectMany(r => r.GetGenerators(language)).ToImmutableArray());
                     }
 
                     return generatorDriver;
                 }
             }
 
-            internal sealed class AddAdditionalDocumentsAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class AddAdditionalDocumentsAction(ImmutableArray<AdditionalDocumentState> additionalDocuments) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly ImmutableArray<AdditionalDocumentState> _additionalDocuments;
-
-                public AddAdditionalDocumentsAction(ImmutableArray<AdditionalDocumentState> additionalDocuments)
-                {
-                    _additionalDocuments = additionalDocuments;
-                }
 
                 // Changing an additional document doesn't change the compilation directly, so we can "apply" the
                 // translation (which is a no-op). Since we use a 'false' here to mean that it's not worth keeping
@@ -286,18 +219,12 @@ public AddAdditionalDocumentsAction(ImmutableArray<AdditionalDocumentState> addi
 
                 public override GeneratorDriver? TransformGeneratorDriver(GeneratorDriver generatorDriver)
                 {
-                    return generatorDriver.AddAdditionalTexts(_additionalDocuments.SelectAsArray(static documentState => documentState.AdditionalText));
+                    return generatorDriver.AddAdditionalTexts(additionalDocuments.SelectAsArray(static documentState => documentState.AdditionalText));
                 }
             }
 
-            internal sealed class RemoveAdditionalDocumentsAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class RemoveAdditionalDocumentsAction(ImmutableArray<AdditionalDocumentState> additionalDocuments) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly ImmutableArray<AdditionalDocumentState> _additionalDocuments;
-
-                public RemoveAdditionalDocumentsAction(ImmutableArray<AdditionalDocumentState> additionalDocuments)
-                {
-                    _additionalDocuments = additionalDocuments;
-                }
 
                 // Changing an additional document doesn't change the compilation directly, so we can "apply" the
                 // translation (which is a no-op). Since we use a 'false' here to mean that it's not worth keeping
@@ -306,31 +233,22 @@ public RemoveAdditionalDocumentsAction(ImmutableArray<AdditionalDocumentState> a
 
                 public override GeneratorDriver? TransformGeneratorDriver(GeneratorDriver generatorDriver)
                 {
-                    return generatorDriver.RemoveAdditionalTexts(_additionalDocuments.SelectAsArray(static documentState => documentState.AdditionalText));
+                    return generatorDriver.RemoveAdditionalTexts(additionalDocuments.SelectAsArray(static documentState => documentState.AdditionalText));
                 }
             }
 
-            internal sealed class ReplaceGeneratorDriverAction : CompilationAndGeneratorDriverTranslationAction
+            internal sealed class ReplaceGeneratorDriverAction(GeneratorDriver oldGeneratorDriver, ProjectState newProjectState) : CompilationAndGeneratorDriverTranslationAction
             {
-                private readonly GeneratorDriver _oldGeneratorDriver;
-                private readonly ProjectState _newProjectState;
-
-                public ReplaceGeneratorDriverAction(GeneratorDriver oldGeneratorDriver, ProjectState newProjectState)
-                {
-                    _oldGeneratorDriver = oldGeneratorDriver;
-                    _newProjectState = newProjectState;
-                }
-
                 public override bool CanUpdateCompilationWithStaleGeneratedTreesIfGeneratorsGiveSameOutput => true;
 
                 public override GeneratorDriver? TransformGeneratorDriver(GeneratorDriver _)
                 {
                     // The GeneratorDriver that we have here is from a prior version of the Project, it may be missing state changes due
                     // to changes to the project. We'll update everything here.
-                    var generatorDriver = _oldGeneratorDriver.ReplaceAdditionalTexts(_newProjectState.AdditionalDocumentStates.SelectAsArray(static documentState => documentState.AdditionalText))
-                                                     .WithUpdatedParseOptions(_newProjectState.ParseOptions!)
-                                                     .WithUpdatedAnalyzerConfigOptions(_newProjectState.AnalyzerOptions.AnalyzerConfigOptionsProvider)
-                                                     .ReplaceGenerators(_newProjectState.SourceGenerators.ToImmutableArray());
+                    var generatorDriver = oldGeneratorDriver.ReplaceAdditionalTexts(newProjectState.AdditionalDocumentStates.SelectAsArray(static documentState => documentState.AdditionalText))
+                                                     .WithUpdatedParseOptions(newProjectState.ParseOptions!)
+                                                     .WithUpdatedAnalyzerConfigOptions(newProjectState.AnalyzerOptions.AnalyzerConfigOptionsProvider)
+                                                     .ReplaceGenerators(newProjectState.SourceGenerators.ToImmutableArray());
 
                     return generatorDriver;
                 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.CompilationTrackerState.cs b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.CompilationTrackerState.cs
index 933e96fa4a16c..a868673465012 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.CompilationTrackerState.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.CompilationTrackerState.cs
@@ -171,12 +171,8 @@ public static CompilationTrackerState Create(
             /// State used when we potentially have some information (like prior generated documents)
             /// but no compilation.
             /// </summary>
-            private sealed class NoCompilationState : CompilationTrackerState
+            private sealed class NoCompilationState(CompilationTrackerGeneratorInfo generatorInfo) : CompilationTrackerState(compilationWithoutGeneratedDocuments: null, generatorInfo)
             {
-                public NoCompilationState(CompilationTrackerGeneratorInfo generatorInfo)
-                    : base(compilationWithoutGeneratedDocuments: null, generatorInfo)
-                {
-                }
             }
 
             /// <summary>
@@ -219,12 +215,8 @@ public InProgressState(
             /// A built compilation for the tracker that contains the fully built DeclarationTable,
             /// but may not have references initialized
             /// </summary>
-            private sealed class AllSyntaxTreesParsedState : CompilationTrackerState
+            private sealed class AllSyntaxTreesParsedState(Compilation declarationCompilation, CompilationTrackerGeneratorInfo generatorInfo) : CompilationTrackerState(declarationCompilation, generatorInfo)
             {
-                public AllSyntaxTreesParsedState(Compilation declarationCompilation, CompilationTrackerGeneratorInfo generatorInfo)
-                    : base(declarationCompilation, generatorInfo)
-                {
-                }
             }
 
             /// <summary>
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.cs b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.cs
index 271fc07a31363..66ba400688187 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.CompilationTracker.cs
@@ -670,18 +670,11 @@ private async Task<CompilationInfo> BuildFinalStateFromInProgressStateAsync(
                 }
             }
 
-            private readonly struct CompilationInfo
+            private readonly struct CompilationInfo(Compilation compilation, bool hasSuccessfullyLoaded, CompilationTrackerGeneratorInfo generatorInfo)
             {
-                public Compilation Compilation { get; }
-                public bool HasSuccessfullyLoaded { get; }
-                public CompilationTrackerGeneratorInfo GeneratorInfo { get; }
-
-                public CompilationInfo(Compilation compilation, bool hasSuccessfullyLoaded, CompilationTrackerGeneratorInfo generatorInfo)
-                {
-                    Compilation = compilation;
-                    HasSuccessfullyLoaded = hasSuccessfullyLoaded;
-                    GeneratorInfo = generatorInfo;
-                }
+                public Compilation Compilation { get; } = compilation;
+                public bool HasSuccessfullyLoaded { get; } = hasSuccessfullyLoaded;
+                public CompilationTrackerGeneratorInfo GeneratorInfo { get; } = generatorInfo;
             }
 
             /// <summary>
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.GeneratedFileReplacingCompilationTracker.cs b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.GeneratedFileReplacingCompilationTracker.cs
index 7bd4c264c810f..f61dddd18e496 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.GeneratedFileReplacingCompilationTracker.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.GeneratedFileReplacingCompilationTracker.cs
@@ -19,10 +19,8 @@ internal partial class SolutionState
         /// to return a generated document with a specific content, regardless of what the generator actually produces. In other words, it says
         /// "take the compilation this other thing produced, and pretend the generator gave this content, even if it wouldn't."
         /// </summary>
-        private class GeneratedFileReplacingCompilationTracker : ICompilationTracker
+        private class GeneratedFileReplacingCompilationTracker(ICompilationTracker underlyingTracker, SourceGeneratedDocumentState replacementDocumentState) : ICompilationTracker
         {
-            private readonly SourceGeneratedDocumentState _replacedGeneratedDocumentState;
-
             private AsyncLazy<Checksum>? _lazyDependentChecksum;
 
             /// <summary>
@@ -32,17 +30,10 @@ private class GeneratedFileReplacingCompilationTracker : ICompilationTracker
             [DisallowNull]
             private Compilation? _compilationWithReplacement;
 
-            public ICompilationTracker UnderlyingTracker { get; }
-            public SkeletonReferenceCache SkeletonReferenceCache { get; }
+            public ICompilationTracker UnderlyingTracker { get; } = underlyingTracker;
+            public SkeletonReferenceCache SkeletonReferenceCache { get; } = underlyingTracker.SkeletonReferenceCache.Clone();
             public ProjectState ProjectState => UnderlyingTracker.ProjectState;
 
-            public GeneratedFileReplacingCompilationTracker(ICompilationTracker underlyingTracker, SourceGeneratedDocumentState replacementDocumentState)
-            {
-                UnderlyingTracker = underlyingTracker;
-                _replacedGeneratedDocumentState = replacementDocumentState;
-                SkeletonReferenceCache = underlyingTracker.SkeletonReferenceCache.Clone();
-            }
-
             public GeneratorDriver? GeneratorDriver => UnderlyingTracker.GeneratorDriver;
 
             public bool ContainsAssemblyOrModuleOrDynamic(ISymbol symbol, bool primary)
@@ -83,11 +74,11 @@ public async Task<Compilation> GetCompilationAsync(SolutionState solution, Cance
                 var underlyingCompilation = await UnderlyingTracker.GetCompilationAsync(solution, cancellationToken).ConfigureAwait(false);
                 var underlyingSourceGeneratedDocuments = await UnderlyingTracker.GetSourceGeneratedDocumentStatesAsync(solution, cancellationToken).ConfigureAwait(false);
 
-                underlyingSourceGeneratedDocuments.TryGetState(_replacedGeneratedDocumentState.Id, out var existingState);
+                underlyingSourceGeneratedDocuments.TryGetState(replacementDocumentState.Id, out var existingState);
 
                 Compilation newCompilation;
 
-                var newSyntaxTree = await _replacedGeneratedDocumentState.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
+                var newSyntaxTree = await replacementDocumentState.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
 
                 if (existingState != null)
                 {
@@ -131,7 +122,7 @@ public Task<Checksum> GetDependentChecksumAsync(SolutionState solution, Cancella
             private async Task<Checksum> ComputeDependentChecksumAsync(SolutionState solution, CancellationToken cancellationToken)
                 => Checksum.Create(
                     await UnderlyingTracker.GetDependentChecksumAsync(solution, cancellationToken).ConfigureAwait(false),
-                    await _replacedGeneratedDocumentState.GetChecksumAsync(cancellationToken).ConfigureAwait(false));
+                    await replacementDocumentState.GetChecksumAsync(cancellationToken).ConfigureAwait(false));
 
             public MetadataReference? GetPartialMetadataReference(ProjectState fromProject, ProjectReference projectReference)
             {
@@ -149,11 +140,11 @@ public async ValueTask<TextDocumentStates<SourceGeneratedDocumentState>> GetSour
             {
                 var underlyingGeneratedDocumentStates = await UnderlyingTracker.GetSourceGeneratedDocumentStatesAsync(solution, cancellationToken).ConfigureAwait(false);
 
-                if (underlyingGeneratedDocumentStates.Contains(_replacedGeneratedDocumentState.Id))
+                if (underlyingGeneratedDocumentStates.Contains(replacementDocumentState.Id))
                 {
                     // The generated file still exists in the underlying compilation, but the contents may not match the open file if the open file
                     // is stale. Replace the syntax tree so we have a tree that matches the text.
-                    return underlyingGeneratedDocumentStates.SetState(_replacedGeneratedDocumentState.Id, _replacedGeneratedDocumentState);
+                    return underlyingGeneratedDocumentStates.SetState(replacementDocumentState.Id, replacementDocumentState);
                 }
                 else
                 {
@@ -161,7 +152,7 @@ public async ValueTask<TextDocumentStates<SourceGeneratedDocumentState>> GetSour
                     // an edit which would cause this file to no longer exist, but they're still operating on an open representation
                     // of that file. To ensure that this snapshot is still usable, we'll just add this document back in. This is not a
                     // semantically correct operation, but working on stale snapshots never has that guarantee.
-                    return underlyingGeneratedDocumentStates.AddRange(ImmutableArray.Create(_replacedGeneratedDocumentState));
+                    return underlyingGeneratedDocumentStates.AddRange(ImmutableArray.Create(replacementDocumentState));
                 }
             }
 
@@ -178,9 +169,9 @@ public bool TryGetCompilation([NotNullWhen(true)] out Compilation? compilation)
 
             public SourceGeneratedDocumentState? TryGetSourceGeneratedDocumentStateForAlreadyGeneratedId(DocumentId documentId)
             {
-                if (documentId == _replacedGeneratedDocumentState.Id)
+                if (documentId == replacementDocumentState.Id)
                 {
-                    return _replacedGeneratedDocumentState;
+                    return replacementDocumentState;
                 }
                 else
                 {
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.SkeletonReferenceSet.cs b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.SkeletonReferenceSet.cs
index f54584e3a3341..87b1baf85b295 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.SkeletonReferenceSet.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.SkeletonReferenceSet.cs
@@ -12,21 +12,19 @@ namespace Microsoft.CodeAnalysis;
 
 internal partial class SolutionState
 {
-    private sealed class SkeletonReferenceSet
+    /// <param name="metadata">
+    /// The actual assembly metadata produced from another compilation.
+    /// </param>
+    /// <param name="documentationProvider">
+    /// The documentation provider used to lookup xml docs for any metadata reference we pass out.  See
+    /// docs on <see cref="DeferredDocumentationProvider"/> for why this is safe to hold onto despite it
+    /// rooting a compilation internally.
+    /// </param>
+    private sealed class SkeletonReferenceSet(
+        AssemblyMetadata metadata,
+        string? assemblyName,
+        DeferredDocumentationProvider documentationProvider)
     {
-        /// <summary>
-        /// The actual assembly metadata produced from another compilation.
-        /// </summary>
-        private readonly AssemblyMetadata _metadata;
-
-        private readonly string? _assemblyName;
-
-        /// <summary>
-        /// The documentation provider used to lookup xml docs for any metadata reference we pass out.  See
-        /// docs on <see cref="DeferredDocumentationProvider"/> for why this is safe to hold onto despite it
-        /// rooting a compilation internally.
-        /// </summary>
-        private readonly DeferredDocumentationProvider _documentationProvider;
 
         /// <summary>
         /// Lock this object while reading/writing from it.  Used so we can return the same reference for the same
@@ -36,27 +34,17 @@ private sealed class SkeletonReferenceSet
         /// </summary>
         private readonly Dictionary<MetadataReferenceProperties, PortableExecutableReference> _referenceMap = new();
 
-        public SkeletonReferenceSet(
-            AssemblyMetadata metadata,
-            string? assemblyName,
-            DeferredDocumentationProvider documentationProvider)
-        {
-            _metadata = metadata;
-            _assemblyName = assemblyName;
-            _documentationProvider = documentationProvider;
-        }
-
         public PortableExecutableReference GetOrCreateMetadataReference(MetadataReferenceProperties properties)
         {
             lock (_referenceMap)
             {
                 if (!_referenceMap.TryGetValue(properties, out var value))
                 {
-                    value = _metadata.GetReference(
-                        _documentationProvider,
+                    value = metadata.GetReference(
+                        documentationProvider,
                         aliases: properties.Aliases,
                         embedInteropTypes: properties.EmbedInteropTypes,
-                        display: _assemblyName);
+                        display: assemblyName);
 
                     _referenceMap.Add(properties, value);
                 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.cs b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.cs
index fa3f8727ce9f9..17493bf2da5b0 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.cs
@@ -2059,18 +2059,11 @@ internal bool ContainsTransitiveReference(ProjectId fromProjectId, ProjectId toP
 
         internal TestAccessor GetTestAccessor() => new TestAccessor(this);
 
-        internal readonly struct TestAccessor
+        internal readonly struct TestAccessor(SolutionState solutionState)
         {
-            private readonly SolutionState _solutionState;
-
-            public TestAccessor(SolutionState solutionState)
-            {
-                _solutionState = solutionState;
-            }
-
             public GeneratorDriver? GetGeneratorDriver(Project project)
             {
-                return project.SupportsCompilation ? _solutionState.GetCompilationTracker(project.Id).GeneratorDriver : null;
+                return project.SupportsCompilation ? solutionState.GetCompilationTracker(project.Id).GeneratorDriver : null;
             }
         }
     }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/StateChecksums.cs b/src/Workspaces/Core/Portable/Workspace/Solution/StateChecksums.cs
index 3105296413193..ca676f26d73c8 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/StateChecksums.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/StateChecksums.cs
@@ -13,7 +13,7 @@
 
 namespace Microsoft.CodeAnalysis.Serialization
 {
-    internal sealed class SolutionStateChecksums : ChecksumWithChildren
+    internal sealed class SolutionStateChecksums(ImmutableArray<object> children) : ChecksumWithChildren(children)
     {
         public SolutionStateChecksums(
             Checksum attributesChecksum,
@@ -25,10 +25,6 @@ public SolutionStateChecksums(
         {
         }
 
-        public SolutionStateChecksums(ImmutableArray<object> children) : base(children)
-        {
-        }
-
         public Checksum Attributes => (Checksum)Children[0];
         public ChecksumCollection Projects => (ChecksumCollection)Children[1];
         public ChecksumCollection AnalyzerReferences => (ChecksumCollection)Children[2];
@@ -89,7 +85,7 @@ public async Task FindAsync(
         }
     }
 
-    internal class ProjectStateChecksums : ChecksumWithChildren
+    internal class ProjectStateChecksums(ImmutableArray<object> children) : ChecksumWithChildren(children)
     {
         public ProjectStateChecksums(
             Checksum infoChecksum,
@@ -114,10 +110,6 @@ public ProjectStateChecksums(
         {
         }
 
-        public ProjectStateChecksums(ImmutableArray<object> children) : base(children)
-        {
-        }
-
         public Checksum Info => (Checksum)Children[0];
         public Checksum CompilationOptions => (Checksum)Children[1];
         public Checksum ParseOptions => (Checksum)Children[2];
@@ -207,17 +199,13 @@ public async Task FindAsync(
         }
     }
 
-    internal class DocumentStateChecksums : ChecksumWithChildren
+    internal class DocumentStateChecksums(ImmutableArray<object> children) : ChecksumWithChildren(children)
     {
         public DocumentStateChecksums(Checksum infoChecksum, Checksum textChecksum)
             : this(ImmutableArray.Create<object>(infoChecksum, textChecksum))
         {
         }
 
-        public DocumentStateChecksums(ImmutableArray<object> children) : base(children)
-        {
-        }
-
         public Checksum Info => (Checksum)Children[0];
         public Checksum Text => (Checksum)Children[1];
 
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/TreeAndVersion.cs b/src/Workspaces/Core/Portable/Workspace/Solution/TreeAndVersion.cs
index fc6b7e6928be0..9b50046ccd383 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/TreeAndVersion.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/TreeAndVersion.cs
@@ -10,22 +10,16 @@ namespace Microsoft.CodeAnalysis
     /// <summary>
     /// A class that represents both a tree and its top level signature version
     /// </summary>
-    internal sealed class TreeAndVersion
+    internal sealed class TreeAndVersion(SyntaxTree tree, VersionStamp version)
     {
         /// <summary>
         /// The syntax tree
         /// </summary>
-        public SyntaxTree Tree { get; }
+        public SyntaxTree Tree { get; } = tree;
 
         /// <summary>
         /// The version of the top level signature of the tree
         /// </summary>
-        public VersionStamp Version { get; }
-
-        public TreeAndVersion(SyntaxTree tree, VersionStamp version)
-        {
-            Tree = tree;
-            Version = version;
-        }
+        public VersionStamp Version { get; } = version;
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Solution/VersionStamp.cs b/src/Workspaces/Core/Portable/Workspace/Solution/VersionStamp.cs
index b69c7a9afaa2a..803540865ab20 100644
--- a/src/Workspaces/Core/Portable/Workspace/Solution/VersionStamp.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Solution/VersionStamp.cs
@@ -232,26 +232,22 @@ private static int GetNextGlobalVersion()
         internal TestAccessor GetTestAccessor()
             => new(this);
 
-        internal readonly struct TestAccessor
+        internal readonly struct TestAccessor(VersionStamp versionStamp)
         {
-            private readonly VersionStamp _versionStamp;
-
-            public TestAccessor(in VersionStamp versionStamp)
-                => _versionStamp = versionStamp;
 
             /// <summary>
             /// True if this VersionStamp is newer than the specified one.
             /// </summary>
             internal bool IsNewerThan(in VersionStamp version)
             {
-                if (_versionStamp._utcLastModified > version._utcLastModified)
+                if (versionStamp._utcLastModified > version._utcLastModified)
                 {
                     return true;
                 }
 
-                if (_versionStamp._utcLastModified == version._utcLastModified)
+                if (versionStamp._utcLastModified == version._utcLastModified)
                 {
-                    return GetGlobalVersion(_versionStamp) > GetGlobalVersion(version);
+                    return GetGlobalVersion(versionStamp) > GetGlobalVersion(version);
                 }
 
                 return false;
diff --git a/src/Workspaces/Core/Portable/Workspace/TextDocumentEventArgs.cs b/src/Workspaces/Core/Portable/Workspace/TextDocumentEventArgs.cs
index 9ed3305bcbf14..9c382c57019f3 100644
--- a/src/Workspaces/Core/Portable/Workspace/TextDocumentEventArgs.cs
+++ b/src/Workspaces/Core/Portable/Workspace/TextDocumentEventArgs.cs
@@ -7,13 +7,8 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    public sealed class TextDocumentEventArgs : EventArgs
+    public sealed class TextDocumentEventArgs(TextDocument document) : EventArgs
     {
-        public TextDocument Document { get; }
-
-        public TextDocumentEventArgs(TextDocument document)
-        {
-            this.Document = document ?? throw new ArgumentNullException(nameof(document));
-        }
+        public TextDocument Document { get; } = document ?? throw new ArgumentNullException(nameof(document));
     }
 }
diff --git a/src/Workspaces/Core/Portable/Workspace/Workspace.cs b/src/Workspaces/Core/Portable/Workspace/Workspace.cs
index df886377f94f3..bb25d445a059b 100644
--- a/src/Workspaces/Core/Portable/Workspace/Workspace.cs
+++ b/src/Workspaces/Core/Portable/Workspace/Workspace.cs
@@ -13,6 +13,7 @@
 using System.Xml;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.ErrorReporting;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.Options;
@@ -254,6 +255,7 @@ private protected (bool updated, Solution newSolution) SetCurrentSolution(
 
                     return UnifyLinkedDocumentContents(oldSolution, newSolution);
                 },
+                mayRaiseEvents: true,
                 onBeforeUpdate: static (oldSolution, newSolution, data) =>
                 {
                     data.onBeforeUpdate?.Invoke(oldSolution, newSolution);
@@ -342,6 +344,10 @@ static Solution UpdateExistingDocumentsToChangedDocumentContents(Solution soluti
         /// <param name="transformation">Solution transformation. This may be run multiple times.  As such it should be
         /// a purely functional transformation on the solution instance passed to it.  It should not make stateful
         /// changes elsewhere.</param>
+        /// <param name="mayRaiseEvents"><see langword="true"/> if this operation may raise observable events;
+        /// otherwise, <see langword="false"/>. If <see langword="true"/>, the operation will call
+        /// <see cref="EnsureEventListeners"/> to ensure listeners are registered prior to callbacks that may raise
+        /// events.</param>
         /// <param name="onBeforeUpdate">Action to perform immediately prior to updating <see cref="CurrentSolution"/>.
         /// The action will be passed the old <see cref="CurrentSolution"/> that will be replaced and the exact solution
         /// it will be replaced with. The latter may be different than the solution returned by <paramref
@@ -355,6 +361,7 @@ static Solution UpdateExistingDocumentsToChangedDocumentContents(Solution soluti
         private protected (Solution oldSolution, Solution newSolution) SetCurrentSolution<TData>(
             TData data,
             Func<Solution, TData, Solution> transformation,
+            bool mayRaiseEvents = true,
             Action<Solution, Solution, TData>? onBeforeUpdate = null,
             Action<Solution, Solution, TData>? onAfterUpdate = null)
         {
@@ -363,6 +370,7 @@ private protected (Solution oldSolution, Solution newSolution) SetCurrentSolutio
                 useAsync: false,
                 data,
                 transformation,
+                mayRaiseEvents,
                 onBeforeUpdate,
                 onAfterUpdate,
                 CancellationToken.None);
@@ -371,54 +379,67 @@ private protected (Solution oldSolution, Solution newSolution) SetCurrentSolutio
 #pragma warning restore CA2012 // Use ValueTasks correctly
         }
 
-        /// <inheritdoc cref="SetCurrentSolution{TData}(TData, Func{Solution, TData, Solution}, Action{Solution, Solution, TData}?, Action{Solution, Solution, TData}?)"/>
+        /// <inheritdoc cref="SetCurrentSolution{TData}(TData, Func{Solution, TData, Solution}, bool, Action{Solution, Solution, TData}?, Action{Solution, Solution, TData}?)"/>
         private protected async ValueTask<(Solution oldSolution, Solution newSolution)> SetCurrentSolutionAsync<TData>(
             bool useAsync,
             TData data,
             Func<Solution, TData, Solution> transformation,
+            bool mayRaiseEvents,
             Action<Solution, Solution, TData>? onBeforeUpdate,
             Action<Solution, Solution, TData>? onAfterUpdate,
             CancellationToken cancellationToken)
         {
             Contract.ThrowIfNull(transformation);
 
-            var oldSolution = Volatile.Read(ref _latestSolution);
-
-            // Ensure our event handlers are realized prior to taking this lock.  We don't want to deadlock trying
-            // to obtain them when calling one of our callbacks. See https://github.com/dotnet/roslyn/issues/64681
-            EnsureEventListeners();
-
-            while (true)
+            try
             {
-                // Run the transformation outside of the lock as it should not be making any state changes to us.
-                var newSolution = transformation(oldSolution, data);
+                var oldSolution = Volatile.Read(ref _latestSolution);
 
-                // if it did nothing, then no need to proceed.
-                if (oldSolution == newSolution)
-                    return (oldSolution, newSolution);
+                if (mayRaiseEvents)
+                {
+                    // Ensure our event handlers are realized prior to taking this lock.  We don't want to deadlock trying
+                    // to obtain them when calling one of our callbacks. See https://github.com/dotnet/roslyn/issues/64681
+                    EnsureEventListeners();
+                }
 
-                // Now, take the lock and try to update our internal state.
-                using (useAsync ? await _serializationLock.DisposableWaitAsync(cancellationToken).ConfigureAwait(false) : _serializationLock.DisposableWait(cancellationToken))
+                while (true)
                 {
-                    if (_latestSolution != oldSolution)
+                    // Run the transformation outside of the lock as it should not be making any state changes to us.
+                    var newSolution = transformation(oldSolution, data);
+
+                    // if it did nothing, then no need to proceed.
+                    if (oldSolution == newSolution)
+                        return (oldSolution, newSolution);
+
+                    // Now, take the lock and try to update our internal state.
+                    using (useAsync ? await _serializationLock.DisposableWaitAsync(cancellationToken).ConfigureAwait(false) : _serializationLock.DisposableWait(cancellationToken))
                     {
-                        // something else snuck in and wrote to _latestSolution. Restart and try again.
-                        oldSolution = _latestSolution;
-                        continue;
-                    }
+                        if (_latestSolution != oldSolution)
+                        {
+                            // something else snuck in and wrote to _latestSolution. Restart and try again.
+                            oldSolution = _latestSolution;
+                            continue;
+                        }
 
-                    newSolution = newSolution.WithNewWorkspace(oldSolution.WorkspaceKind, oldSolution.WorkspaceVersion + 1, oldSolution.Services);
+                        newSolution = newSolution.WithNewWorkspace(oldSolution.WorkspaceKind, oldSolution.WorkspaceVersion + 1, oldSolution.Services);
 
-                    // Prior to updating the latest solution, let the caller do any other state updates they want.
-                    onBeforeUpdate?.Invoke(oldSolution, newSolution, data);
+                        // Prior to updating the latest solution, let the caller do any other state updates they want.
+                        onBeforeUpdate?.Invoke(oldSolution, newSolution, data);
 
-                    _latestSolution = newSolution;
+                        _latestSolution = newSolution;
 
-                    // Once we've updated _latestSolution, perform any requested callbacks.
-                    onAfterUpdate?.Invoke(oldSolution, newSolution, data);
-                    return (oldSolution, newSolution);
+                        // Once we've updated _latestSolution, perform any requested callbacks.
+                        onAfterUpdate?.Invoke(oldSolution, newSolution, data);
+                        return (oldSolution, newSolution);
+                    }
                 }
             }
+            catch (Exception e) when (FatalError.ReportAndPropagate(e, ErrorSeverity.Critical))
+            {
+                // We'll rethrow the exception to the caller, since this exception could represent a bug in a third-party workspace, and if at this point our workspace
+                // is corrupted we want the caller to know.
+                throw ExceptionUtilities.Unreachable();
+            }
         }
 
         /// <summary>
@@ -499,6 +520,7 @@ private void ClearSolution(bool reportChangeEvent)
             this.SetCurrentSolution(
                 data: /*unused*/ 0,
                 (oldSolution, _) => this.CreateSolution(oldSolution.Id),
+                mayRaiseEvents: reportChangeEvent,
                 onBeforeUpdate: (_, _, _) => this.ClearSolutionData(),
                 onAfterUpdate: (oldSolution, newSolution, _) =>
                 {
diff --git a/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnostic.cs b/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnostic.cs
index 8e5acbcbf8cb6..abd3b4e0289b2 100644
--- a/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnostic.cs
+++ b/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnostic.cs
@@ -8,16 +8,10 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    public class WorkspaceDiagnostic
+    public class WorkspaceDiagnostic(WorkspaceDiagnosticKind kind, string message)
     {
-        public WorkspaceDiagnosticKind Kind { get; }
-        public string Message { get; }
-
-        public WorkspaceDiagnostic(WorkspaceDiagnosticKind kind, string message)
-        {
-            this.Kind = kind;
-            this.Message = message;
-        }
+        public WorkspaceDiagnosticKind Kind { get; } = kind;
+        public string Message { get; } = message;
 
         public override string ToString()
         {
diff --git a/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnosticEventArgs.cs b/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnosticEventArgs.cs
index 8ba3626eddfbe..2303b7cde9223 100644
--- a/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnosticEventArgs.cs
+++ b/src/Workspaces/Core/Portable/Workspace/WorkspaceDiagnosticEventArgs.cs
@@ -8,11 +8,8 @@
 
 namespace Microsoft.CodeAnalysis
 {
-    public class WorkspaceDiagnosticEventArgs : EventArgs
+    public class WorkspaceDiagnosticEventArgs(WorkspaceDiagnostic diagnostic) : EventArgs
     {
-        public WorkspaceDiagnostic Diagnostic { get; }
-
-        public WorkspaceDiagnosticEventArgs(WorkspaceDiagnostic diagnostic)
-            => this.Diagnostic = diagnostic;
+        public WorkspaceDiagnostic Diagnostic { get; } = diagnostic;
     }
 }
diff --git a/src/Workspaces/CoreTest/CodeCleanup/CodeCleanupTests.cs b/src/Workspaces/CoreTest/CodeCleanup/CodeCleanupTests.cs
index 97ebb13851341..9409718ae3bfc 100644
--- a/src/Workspaces/CoreTest/CodeCleanup/CodeCleanupTests.cs
+++ b/src/Workspaces/CoreTest/CodeCleanup/CodeCleanupTests.cs
@@ -378,7 +378,7 @@ private static void VerifyRange(string codeWithMarker, string language = Languag
             MarkupTestFile.GetSpans(codeWithMarker,
                 out var codeWithoutMarker, out IDictionary<string, ImmutableArray<TextSpan>> namedSpans);
 
-            var expectedResult = namedSpans.ContainsKey("r") ? namedSpans["r"] as IEnumerable<TextSpan> : SpecializedCollections.EmptyEnumerable<TextSpan>();
+            var expectedResult = namedSpans.TryGetValue("r", out var spans) ? spans : SpecializedCollections.EmptyEnumerable<TextSpan>();
 
             VerifyRange(codeWithoutMarker, ImmutableArray<ICodeCleanupProvider>.Empty, namedSpans["b"], ref expectedResult, language);
         }
diff --git a/src/Workspaces/CoreTest/SymbolKeyTests.cs b/src/Workspaces/CoreTest/SymbolKeyTests.cs
index b978b5ad21a99..4562466fa5ce5 100644
--- a/src/Workspaces/CoreTest/SymbolKeyTests.cs
+++ b/src/Workspaces/CoreTest/SymbolKeyTests.cs
@@ -1412,7 +1412,7 @@ private static Compilation GetCompilation(string source, string language, string
             throw new NotSupportedException();
         }
 
-        private List<ISymbol> GetAllSymbols(
+        private static List<ISymbol> GetAllSymbols(
             SemanticModel model, Func<SyntaxNode, bool> predicate = null)
         {
             var list = new List<ISymbol>();
@@ -1420,7 +1420,7 @@ private List<ISymbol> GetAllSymbols(
             return list;
         }
 
-        private void GetAllSymbols(
+        private static void GetAllSymbols(
             SemanticModel model, SyntaxNode node,
             List<ISymbol> list, Func<SyntaxNode, bool> predicate)
         {
@@ -1448,14 +1448,14 @@ private void GetAllSymbols(
             }
         }
 
-        private List<ISymbol> GetDeclaredSymbols(Compilation compilation)
+        private static List<ISymbol> GetDeclaredSymbols(Compilation compilation)
         {
             var list = new List<ISymbol>();
             GetDeclaredSymbols(compilation.Assembly.GlobalNamespace, list);
             return list;
         }
 
-        private void GetDeclaredSymbols(INamespaceOrTypeSymbol container, List<ISymbol> symbols)
+        private static void GetDeclaredSymbols(INamespaceOrTypeSymbol container, List<ISymbol> symbols)
         {
             foreach (var member in container.GetMembers())
             {
diff --git a/src/Workspaces/CoreTestUtilities/Microsoft.CodeAnalysis.Workspaces.Test.Utilities.csproj b/src/Workspaces/CoreTestUtilities/Microsoft.CodeAnalysis.Workspaces.Test.Utilities.csproj
index bff1a9ca6a24a..e8dffa1e2da8b 100644
--- a/src/Workspaces/CoreTestUtilities/Microsoft.CodeAnalysis.Workspaces.Test.Utilities.csproj
+++ b/src/Workspaces/CoreTestUtilities/Microsoft.CodeAnalysis.Workspaces.Test.Utilities.csproj
@@ -32,7 +32,6 @@
     <PackageReference Include="Nerdbank.Streams" Version="$(NerdbankStreamsVersion)" />
     <PackageReference Include="System.Threading.Tasks.Dataflow" Version="$(SystemThreadingTasksDataflowVersion)" />
     <PackageReference Include="System.Buffers" Version="$(SystemBuffersVersion)" />
-    <PackageReference Include="xunit.assert" Version="$(xunitassertVersion)" />
     <PackageReference Include="xunit.extensibility.core" Version="$(xunitextensibilitycoreVersion)" />
     <PackageReference Include="xunit.extensibility.execution" Version="$(xunitextensibilityexecutionVersion)" />
   </ItemGroup>
diff --git a/src/Workspaces/Remote/Core/BrokeredServiceDescriptors.cs b/src/Workspaces/Remote/Core/BrokeredServiceDescriptors.cs
new file mode 100644
index 0000000000000..97b7a4341fb3b
--- /dev/null
+++ b/src/Workspaces/Remote/Core/BrokeredServiceDescriptors.cs
@@ -0,0 +1,99 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Microsoft.ServiceHub.Framework;
+using StreamJsonRpc;
+using static Microsoft.ServiceHub.Framework.ServiceJsonRpcDescriptor;
+
+namespace Microsoft.CodeAnalysis.BrokeredServices;
+
+/// <summary>
+/// Descriptors of brokered services not used by Roslyn remoting infrastructure.
+/// </summary>
+internal static class BrokeredServiceDescriptors
+{
+    /// <summary>
+    /// Descriptors for client services written in TypeScript.
+    /// </summary>
+    private sealed class ClientServiceDescriptor : ServiceJsonRpcDescriptor
+    {
+        private const string AsyncSuffix = "Async";
+
+        private static readonly Func<string, string> NameNormalize =
+            name => CommonMethodNameTransforms.CamelCase(name.EndsWith(AsyncSuffix, StringComparison.OrdinalIgnoreCase) ? name.Substring(0, name.Length - AsyncSuffix.Length) : name);
+
+        public ClientServiceDescriptor(ServiceMoniker serviceMoniker, Type? clientInterface = null)
+            : base(serviceMoniker, clientInterface, Formatters.MessagePack, MessageDelimiters.BigEndianInt32LengthHeader)
+        {
+        }
+
+        public ClientServiceDescriptor(ClientServiceDescriptor copyFrom)
+            : base(copyFrom)
+        {
+        }
+
+        protected override ServiceRpcDescriptor Clone()
+            => new ClientServiceDescriptor(this);
+
+        protected override JsonRpcConnection CreateConnection(JsonRpc jsonRpc)
+        {
+            // allow TypeScript to name async methods without "Async" suffix
+
+            var connection = base.CreateConnection(jsonRpc);
+            connection.LocalRpcTargetOptions.MethodNameTransform = NameNormalize;
+            connection.LocalRpcTargetOptions.EventNameTransform = NameNormalize;
+            connection.LocalRpcProxyOptions.MethodNameTransform = NameNormalize;
+            connection.LocalRpcProxyOptions.EventNameTransform = NameNormalize;
+            return connection;
+        }
+    }
+
+    internal const string LanguageServerComponentNamespace = "Microsoft.CodeAnalysis";
+    internal const string VisualStudioComponentNamespace = "Microsoft.VisualStudio";
+
+    /// <summary>
+    /// Services proffered by Language Server process.
+    /// </summary>
+    internal const string LanguageServerComponentName = "LanguageServer";
+
+    /// <summary>
+    /// Services proffered by language client in the Extension Host process.
+    /// </summary>
+    internal const string LanguageClientComponentName = "LanguageClient";
+
+    /// <summary>
+    /// Services proffered by one of the Debugger processes.
+    /// </summary>
+    internal const string DebuggerComponentName = "Debugger";
+
+    public static readonly ServiceRpcDescriptor SolutionSnapshotProvider = CreateClientServiceDescriptor("SolutionSnapshotProvider", new Version(0, 1));
+    public static readonly ServiceRpcDescriptor DebuggerManagedHotReloadService = CreateDebuggerServiceDescriptor("ManagedHotReloadService", new Version(0, 1));
+
+    public static ServiceMoniker CreateMoniker(string namespaceName, string componentName, string serviceName, Version? version)
+        => new(namespaceName + "." + componentName + "." + serviceName, version);
+
+    /// <summary>
+    /// Descriptor for services proferred by the client extension (implemented in TypeScript).
+    /// </summary>
+    public static ServiceJsonRpcDescriptor CreateClientServiceDescriptor(string serviceName, Version? version)
+        => new ClientServiceDescriptor(CreateMoniker(LanguageServerComponentNamespace, LanguageClientComponentName, serviceName, version), clientInterface: null)
+           .WithExceptionStrategy(ExceptionProcessing.ISerializable);
+
+    /// <summary>
+    /// Descriptor for services proferred by Roslyn server (implemented in C#). 
+    /// </summary>
+    public static ServiceJsonRpcDescriptor CreateServerServiceDescriptor(string serviceName, Version? version)
+        => CreateDescriptor(CreateMoniker(LanguageServerComponentNamespace, LanguageServerComponentName, serviceName, version));
+
+    /// <summary>
+    /// Descriptor for services proferred by the debugger server (implemented in C#). 
+    /// </summary>
+    public static ServiceJsonRpcDescriptor CreateDebuggerServiceDescriptor(string serviceName, Version? version)
+        => CreateDescriptor(CreateMoniker(VisualStudioComponentNamespace, DebuggerComponentName, serviceName, version));
+
+    private static ServiceJsonRpcDescriptor CreateDescriptor(ServiceMoniker moniker)
+        => new ServiceJsonRpcDescriptor(moniker, Formatters.MessagePack, MessageDelimiters.BigEndianInt32LengthHeader)
+           .WithExceptionStrategy(ExceptionProcessing.ISerializable);
+}
diff --git a/src/Workspaces/Remote/Core/EditAndContinue/ISolutionSnapshotProvider.cs b/src/Workspaces/Remote/Core/EditAndContinue/ISolutionSnapshotProvider.cs
new file mode 100644
index 0000000000000..7653654c181b2
--- /dev/null
+++ b/src/Workspaces/Remote/Core/EditAndContinue/ISolutionSnapshotProvider.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.BrokeredServices;
+using Microsoft.CodeAnalysis.Contracts.Client;
+using Microsoft.ServiceHub.Framework;
+
+namespace Microsoft.CodeAnalysis.EditAndContinue;
+
+internal sealed class SolutionSnapshotProviderProxy : BrokeredServiceProxy<ISolutionSnapshotProvider>, ISolutionSnapshotProvider
+{
+    public SolutionSnapshotProviderProxy(IServiceBroker serviceBroker)
+        : base(serviceBroker, BrokeredServiceDescriptors.SolutionSnapshotProvider)
+    {
+    }
+
+    public ValueTask<SolutionSnapshotId> RegisterSolutionSnapshotAsync(CancellationToken cancellationToken)
+        => InvokeAsync((service, cancellationToken) => service.RegisterSolutionSnapshotAsync(cancellationToken), cancellationToken);
+}
diff --git a/src/Workspaces/Remote/Core/EditAndContinue/ManagedHotReloadLanguageService.cs b/src/Workspaces/Remote/Core/EditAndContinue/ManagedHotReloadLanguageService.cs
new file mode 100644
index 0000000000000..01ec5b471d988
--- /dev/null
+++ b/src/Workspaces/Remote/Core/EditAndContinue/ManagedHotReloadLanguageService.cs
@@ -0,0 +1,309 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Immutable;
+using System.ComponentModel.Composition;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Contracts.Client;
+using Microsoft.CodeAnalysis.Contracts.EditAndContinue;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.ErrorReporting;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.ServiceHub.Framework;
+using Microsoft.VisualStudio.Shell.ServiceBroker;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.EditAndContinue;
+
+[Export(typeof(IManagedHotReloadLanguageService))]
+internal sealed partial class ManagedHotReloadLanguageService : IManagedHotReloadLanguageService
+{
+    private sealed class PdbMatchingSourceTextProvider : IPdbMatchingSourceTextProvider
+    {
+        public static readonly PdbMatchingSourceTextProvider Instance = new();
+
+        // Returning null will check the file on disk:
+        public ValueTask<string?> TryGetMatchingSourceTextAsync(string filePath, ImmutableArray<byte> requiredChecksum, SourceHashAlgorithm checksumAlgorithm, CancellationToken cancellationToken)
+            => ValueTaskFactory.FromResult<string?>(null);
+    }
+
+    private static readonly ActiveStatementSpanProvider s_emptyActiveStatementProvider =
+        (_, _, _) => ValueTaskFactory.FromResult(ImmutableArray<ActiveStatementSpan>.Empty);
+
+    private readonly IManagedHotReloadService _debuggerService;
+    private readonly ISolutionSnapshotProvider _solutionSnapshotProvider;
+    private readonly IEditAndContinueService _encService;
+    private readonly SolutionSnapshotRegistry _solutionSnapshotRegistry;
+
+    private bool _disabled;
+    private DebuggingSessionId? _debuggingSession;
+    private Solution? _committedDesignTimeSolution;
+    private Solution? _pendingUpdatedDesignTimeSolution;
+
+    [ImportingConstructor]
+    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+    public ManagedHotReloadLanguageService(
+        [Import(typeof(SVsFullAccessServiceBroker))] IServiceBroker serviceBroker,
+        IEditAndContinueService encService,
+        SolutionSnapshotRegistry registry)
+    {
+        _debuggerService = new ManagedHotReloadServiceProxy(serviceBroker);
+        _solutionSnapshotProvider = new SolutionSnapshotProviderProxy(serviceBroker);
+        _encService = encService;
+        _solutionSnapshotRegistry = registry;
+    }
+
+    private void Disable()
+    {
+        _disabled = true;
+        _debuggingSession = null;
+        _committedDesignTimeSolution = null;
+        _pendingUpdatedDesignTimeSolution = null;
+        _solutionSnapshotRegistry.Clear();
+    }
+
+    private async ValueTask<Solution> GetCurrentDesignTimeSolutionAsync(CancellationToken cancellationToken)
+    {
+        // First, calls to the client to get the current snapshot id.
+        // The client service calls the LSP client, which sends message to the LSP server, which in turn calls back to RegisterSolutionSnapshot.
+        // Once complete the snapshot should be registered.
+        var id = await _solutionSnapshotProvider.RegisterSolutionSnapshotAsync(cancellationToken).ConfigureAwait(false);
+
+        return _solutionSnapshotRegistry.GetRegisteredSolutionSnapshot(id);
+    }
+
+    private static Solution GetCurrentCompileTimeSolution(Solution currentDesignTimeSolution)
+        => currentDesignTimeSolution.Services.GetRequiredService<ICompileTimeSolutionProvider>().GetCompileTimeSolution(currentDesignTimeSolution);
+
+    public async ValueTask StartSessionAsync(CancellationToken cancellationToken)
+    {
+        if (_disabled)
+        {
+            return;
+        }
+
+        try
+        {
+            var currentDesignTimeSolution = await GetCurrentDesignTimeSolutionAsync(cancellationToken).ConfigureAwait(false);
+            _committedDesignTimeSolution = currentDesignTimeSolution;
+            var compileTimeSolution = GetCurrentCompileTimeSolution(currentDesignTimeSolution);
+
+            // TODO: use remote proxy once we transition to pull diagnostics
+            _debuggingSession = await _encService.StartDebuggingSessionAsync(
+                compileTimeSolution,
+                _debuggerService,
+                PdbMatchingSourceTextProvider.Instance,
+                captureMatchingDocuments: ImmutableArray<DocumentId>.Empty,
+                captureAllMatchingDocuments: false,
+                reportDiagnostics: true,
+                cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+        {
+            // the service failed, error has been reported - disable further operations
+            Disable();
+        }
+    }
+
+    private ValueTask BreakStateOrCapabilitiesChangedAsync(bool? inBreakState, CancellationToken cancellationToken)
+    {
+        if (_disabled)
+        {
+            return ValueTaskFactory.CompletedTask;
+        }
+
+        try
+        {
+            Contract.ThrowIfNull(_debuggingSession);
+            _encService.BreakStateOrCapabilitiesChanged(_debuggingSession.Value, inBreakState, out _);
+        }
+        catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+        {
+            Disable();
+        }
+
+        return ValueTaskFactory.CompletedTask;
+    }
+
+    public ValueTask EnterBreakStateAsync(CancellationToken cancellationToken)
+        => BreakStateOrCapabilitiesChangedAsync(inBreakState: true, cancellationToken);
+
+    public ValueTask ExitBreakStateAsync(CancellationToken cancellationToken)
+        => BreakStateOrCapabilitiesChangedAsync(inBreakState: false, cancellationToken);
+
+    public ValueTask OnCapabilitiesChangedAsync(CancellationToken cancellationToken)
+        => BreakStateOrCapabilitiesChangedAsync(inBreakState: null, cancellationToken);
+
+    public ValueTask CommitUpdatesAsync(CancellationToken cancellationToken)
+    {
+        if (_disabled)
+        {
+            return ValueTaskFactory.CompletedTask;
+        }
+
+        try
+        {
+            Contract.ThrowIfNull(_debuggingSession);
+            var committedDesignTimeSolution = Interlocked.Exchange(ref _pendingUpdatedDesignTimeSolution, null);
+            Contract.ThrowIfNull(committedDesignTimeSolution);
+
+            _committedDesignTimeSolution = committedDesignTimeSolution;
+
+            _encService.CommitSolutionUpdate(_debuggingSession.Value, out _);
+        }
+        catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+        {
+            Disable();
+        }
+
+        return ValueTaskFactory.CompletedTask;
+    }
+
+    public ValueTask DiscardUpdatesAsync(CancellationToken cancellationToken)
+    {
+        if (_disabled)
+        {
+            return ValueTaskFactory.CompletedTask;
+        }
+
+        try
+        {
+            Contract.ThrowIfNull(_debuggingSession);
+            Contract.ThrowIfNull(Interlocked.Exchange(ref _pendingUpdatedDesignTimeSolution, null));
+
+            _encService.DiscardSolutionUpdate(_debuggingSession.Value);
+        }
+        catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+        {
+            Disable();
+        }
+
+        return ValueTaskFactory.CompletedTask;
+    }
+
+    public ValueTask EndSessionAsync(CancellationToken cancellationToken)
+    {
+        if (_disabled)
+        {
+            return ValueTaskFactory.CompletedTask;
+        }
+
+        try
+        {
+            Contract.ThrowIfNull(_debuggingSession);
+
+            _encService.EndDebuggingSession(_debuggingSession.Value, out _);
+
+            _debuggingSession = null;
+            _committedDesignTimeSolution = null;
+            _pendingUpdatedDesignTimeSolution = null;
+        }
+        catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+        {
+            Disable();
+        }
+
+        return ValueTaskFactory.CompletedTask;
+    }
+
+    /// <summary>
+    /// Returns true if any changes have been made to the source since the last changes had been applied.
+    /// For performance reasons it only implements a heuristic and may return both false positives and false negatives.
+    /// If the result is a false negative the debugger will not apply the changes unless the user explicitly triggers apply change command.
+    /// The background diagnostic analysis will still report rude edits for these ignored changes. It may also happen that these rude edits 
+    /// will disappear once the debuggee is resumed - if they are caused by presence of active statements around the change.
+    /// If the result is a false positive the debugger attempts to apply the changes, which will result in a delay but will correctly end up
+    /// with no actual deltas to be applied.
+    /// 
+    /// If <paramref name="sourceFilePath"/> is specified checks for changes only in a document of the given path.
+    /// This is not supported (returns false) for source-generated documents.
+    /// </summary>
+    public async ValueTask<bool> HasChangesAsync(string? sourceFilePath, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var debuggingSession = _debuggingSession;
+            if (debuggingSession == null)
+            {
+                return false;
+            }
+
+            Contract.ThrowIfNull(_committedDesignTimeSolution);
+            var oldSolution = _committedDesignTimeSolution;
+
+            var newSolution = await GetCurrentDesignTimeSolutionAsync(cancellationToken).ConfigureAwait(false);
+
+            return (sourceFilePath != null)
+                ? await EditSession.HasChangesAsync(oldSolution, newSolution, sourceFilePath, cancellationToken).ConfigureAwait(false)
+                : await EditSession.HasChangesAsync(oldSolution, newSolution, cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+        {
+            return true;
+        }
+    }
+
+    public async ValueTask<ManagedHotReloadUpdates> GetUpdatesAsync(CancellationToken cancellationToken)
+    {
+        if (_disabled)
+        {
+            return new ManagedHotReloadUpdates(ImmutableArray<ManagedHotReloadUpdate>.Empty, ImmutableArray<ManagedHotReloadDiagnostic>.Empty);
+        }
+
+        try
+        {
+            Contract.ThrowIfNull(_debuggingSession);
+
+            var designTimeSolution = await GetCurrentDesignTimeSolutionAsync(cancellationToken).ConfigureAwait(false);
+            var solution = GetCurrentCompileTimeSolution(designTimeSolution);
+
+            ModuleUpdates moduleUpdates;
+            ImmutableArray<DiagnosticData> diagnosticData;
+            ImmutableArray<(DocumentId DocumentId, ImmutableArray<RudeEditDiagnostic> Diagnostics)> rudeEdits;
+            DiagnosticData? syntaxError;
+
+            try
+            {
+                var results = await _encService.EmitSolutionUpdateAsync(_debuggingSession.Value, solution, s_emptyActiveStatementProvider, cancellationToken).ConfigureAwait(false);
+
+                moduleUpdates = results.ModuleUpdates;
+                diagnosticData = results.Diagnostics.ToDiagnosticData(solution);
+                rudeEdits = results.RudeEdits;
+                syntaxError = results.GetSyntaxErrorData(solution);
+            }
+            catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+            {
+                var descriptor = EditAndContinueDiagnosticDescriptors.GetDescriptor(RudeEditKind.InternalError);
+
+                var diagnostic = Diagnostic.Create(
+                    descriptor,
+                    Location.None,
+                    string.Format(descriptor.MessageFormat.ToString(), "", e.Message));
+
+                diagnosticData = ImmutableArray.Create(DiagnosticData.Create(designTimeSolution, diagnostic, project: null));
+                rudeEdits = ImmutableArray<(DocumentId DocumentId, ImmutableArray<RudeEditDiagnostic> Diagnostics)>.Empty;
+                moduleUpdates = new ModuleUpdates(ModuleUpdateStatus.RestartRequired, ImmutableArray<ManagedHotReloadUpdate>.Empty);
+                syntaxError = null;
+            }
+
+            // Only store the solution if we have any changes to apply, otherwise CommitUpdatesAsync/DiscardUpdatesAsync won't be called.
+            if (moduleUpdates.Status == ModuleUpdateStatus.Ready)
+            {
+                _pendingUpdatedDesignTimeSolution = designTimeSolution;
+            }
+
+            var diagnostics = await EmitSolutionUpdateResults.GetHotReloadDiagnosticsAsync(solution, diagnosticData, rudeEdits, syntaxError, moduleUpdates.Status, cancellationToken).ConfigureAwait(false);
+            return new ManagedHotReloadUpdates(moduleUpdates.Updates, diagnostics);
+        }
+        catch (Exception e) when (FatalError.ReportAndCatchUnlessCanceled(e, cancellationToken))
+        {
+            Disable();
+            return new ManagedHotReloadUpdates(ImmutableArray<ManagedHotReloadUpdate>.Empty, ImmutableArray<ManagedHotReloadDiagnostic>.Empty);
+        }
+    }
+}
diff --git a/src/Workspaces/Remote/Core/EditAndContinue/ManagedHotReloadServiceProxy.cs b/src/Workspaces/Remote/Core/EditAndContinue/ManagedHotReloadServiceProxy.cs
new file mode 100644
index 0000000000000..5dbdede70efe9
--- /dev/null
+++ b/src/Workspaces/Remote/Core/EditAndContinue/ManagedHotReloadServiceProxy.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Immutable;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.BrokeredServices;
+using Microsoft.CodeAnalysis.Contracts.EditAndContinue;
+using Microsoft.ServiceHub.Framework;
+
+namespace Microsoft.CodeAnalysis.EditAndContinue;
+
+internal sealed class ManagedHotReloadServiceProxy : BrokeredServiceProxy<IManagedHotReloadService>, IManagedHotReloadService
+{
+    public ManagedHotReloadServiceProxy(IServiceBroker serviceBroker)
+        : base(serviceBroker, BrokeredServiceDescriptors.DebuggerManagedHotReloadService)
+    {
+    }
+
+    public ValueTask<ImmutableArray<ManagedActiveStatementDebugInfo>> GetActiveStatementsAsync(CancellationToken cancellationToken)
+        => InvokeAsync((service, cancellationToken) => service.GetActiveStatementsAsync(cancellationToken), cancellationToken);
+
+    public ValueTask<ManagedHotReloadAvailability> GetAvailabilityAsync(Guid module, CancellationToken cancellationToken)
+        => InvokeAsync((service, module, cancellationToken) => service.GetAvailabilityAsync(module, cancellationToken), module, cancellationToken);
+
+    public ValueTask<ImmutableArray<string>> GetCapabilitiesAsync(CancellationToken cancellationToken)
+        => InvokeAsync((service, cancellationToken) => service.GetCapabilitiesAsync(cancellationToken), cancellationToken);
+
+    public ValueTask PrepareModuleForUpdateAsync(Guid module, CancellationToken cancellationToken)
+        => InvokeAsync((service, module, cancellationToken) => service.PrepareModuleForUpdateAsync(module, cancellationToken), module, cancellationToken);
+}
diff --git a/src/Workspaces/Remote/Core/Microsoft.CodeAnalysis.Remote.Workspaces.csproj b/src/Workspaces/Remote/Core/Microsoft.CodeAnalysis.Remote.Workspaces.csproj
index a792c6aee9825..61d644de63643 100644
--- a/src/Workspaces/Remote/Core/Microsoft.CodeAnalysis.Remote.Workspaces.csproj
+++ b/src/Workspaces/Remote/Core/Microsoft.CodeAnalysis.Remote.Workspaces.csproj
@@ -30,6 +30,7 @@
     <PackageReference Include="Microsoft.VisualStudio.Telemetry" Version="$(MicrosoftVisualStudioTelemetryVersion)" PrivateAssets="all" />
     <PackageReference Include="Newtonsoft.Json" Version="$(NewtonsoftJsonVersion)" />
     <PackageReference Include="Microsoft.ServiceHub.Client" Version="$(MicrosoftServiceHubClientVersion)" />
+    <PackageReference Include="Microsoft.ServiceHub.Framework" Version="$(MicrosoftServiceHubFrameworkVersion)" />
   </ItemGroup>
   <ItemGroup>
     <PublicAPI Include="PublicAPI.Shipped.txt" />
@@ -45,8 +46,8 @@
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.BuildManager.Core" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.UnitTesting.SourceBasedTestDiscovery" Partner="UnitTesting" Key="$(UnitTestingKey)" />
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.UnitTesting.SourceBasedTestDiscovery.Core" Partner="UnitTesting" Key="$(UnitTestingKey)" />
-    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" Key="$(MicrosoftCodeAnalysisLanguageServerKey)" />
-    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.UnitTests" Key="$(MicrosoftCodeAnalysisLanguageServerKey)" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.LanguageServer.UnitTests" />
     <InternalsVisibleTo Include="Roslyn.VisualStudio.DiagnosticsWindow" />
     <InternalsVisibleTo Include="Microsoft.VisualStudio.LanguageServices" />
     <InternalsVisibleTo Include="Microsoft.VisualStudio.LanguageServices.CodeLens" />
diff --git a/src/Workspaces/Remote/Core/Serialization/MessagePackFormatters.cs b/src/Workspaces/Remote/Core/Serialization/MessagePackFormatters.cs
index 2c8b9f80fe6bc..58076b05fcaf5 100644
--- a/src/Workspaces/Remote/Core/Serialization/MessagePackFormatters.cs
+++ b/src/Workspaces/Remote/Core/Serialization/MessagePackFormatters.cs
@@ -146,12 +146,12 @@ internal sealed class EncodingFormatter : IMessagePackFormatter<Encoding?>
                     }
 
                     var name = reader.ReadString();
-                    if (name != null)
+                    if (name is null)
                     {
-                        return Encoding.GetEncoding(name);
+                        return null;
                     }
 
-                    return null;
+                    return Encoding.GetEncoding(name);
                 }
                 catch (Exception e) when (e is not MessagePackSerializationException)
                 {
diff --git a/src/Workspaces/Remote/Core/ServiceBrokerExtensions.cs b/src/Workspaces/Remote/Core/ServiceBrokerExtensions.cs
new file mode 100644
index 0000000000000..c15e8c154203b
--- /dev/null
+++ b/src/Workspaces/Remote/Core/ServiceBrokerExtensions.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.ServiceHub.Framework;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.BrokeredServices;
+
+internal abstract class BrokeredServiceProxy<TService> where TService : class
+{
+    private readonly IServiceBroker _serviceBroker;
+    private readonly ServiceRpcDescriptor _descriptor;
+
+    public BrokeredServiceProxy(IServiceBroker serviceBroker, ServiceRpcDescriptor descriptor)
+    {
+        _serviceBroker = serviceBroker;
+        _descriptor = descriptor;
+    }
+
+    protected async ValueTask InvokeAsync(Func<TService, CancellationToken, ValueTask> operation, CancellationToken cancellationToken)
+    {
+        var service = await _serviceBroker.GetProxyAsync<TService>(_descriptor, cancellationToken).ConfigureAwait(false);
+        using ((IDisposable?)service)
+        {
+            Contract.ThrowIfNull(service);
+            await operation(service, cancellationToken).ConfigureAwait(false);
+        }
+    }
+
+    protected async ValueTask<TResult> InvokeAsync<TResult>(Func<TService, CancellationToken, ValueTask<TResult>> operation, CancellationToken cancellationToken)
+    {
+        var service = await _serviceBroker.GetProxyAsync<TService>(_descriptor, cancellationToken).ConfigureAwait(false);
+        using ((IDisposable?)service)
+        {
+            Contract.ThrowIfNull(service);
+            return await operation(service, cancellationToken).ConfigureAwait(false);
+        }
+    }
+
+    protected async ValueTask<TResult> InvokeAsync<TArgs, TResult>(Func<TService, TArgs, CancellationToken, ValueTask<TResult>> operation, TArgs args, CancellationToken cancellationToken)
+    {
+        var service = await _serviceBroker.GetProxyAsync<TService>(_descriptor, cancellationToken).ConfigureAwait(false);
+        using ((IDisposable?)service)
+        {
+            Contract.ThrowIfNull(service);
+            return await operation(service, args, cancellationToken).ConfigureAwait(false);
+        }
+    }
+
+    protected async ValueTask InvokeAsync<TArgs>(Func<TService, TArgs, CancellationToken, ValueTask> operation, TArgs args, CancellationToken cancellationToken)
+    {
+        var service = await _serviceBroker.GetProxyAsync<TService>(_descriptor, cancellationToken).ConfigureAwait(false);
+        using ((IDisposable?)service)
+        {
+            Contract.ThrowIfNull(service);
+            await operation(service, args, cancellationToken).ConfigureAwait(false);
+        }
+    }
+}
diff --git a/src/Workspaces/Remote/Core/SolutionAssetStorage.cs b/src/Workspaces/Remote/Core/SolutionAssetStorage.cs
index 49f24e59fd067..a6cb958cc05f3 100644
--- a/src/Workspaces/Remote/Core/SolutionAssetStorage.cs
+++ b/src/Workspaces/Remote/Core/SolutionAssetStorage.cs
@@ -35,13 +35,13 @@ public Scope GetScope(Checksum solutionChecksum)
     {
         lock (_gate)
         {
-            if (!_checksumToScope.ContainsKey(solutionChecksum))
+            if (!_checksumToScope.TryGetValue(solutionChecksum, out var scope))
             {
                 Debug.Fail($"Request for solution-checksum '{solutionChecksum}' that was not pinned on the host side.");
                 throw new InvalidOperationException($"Request for solution-checksum '{solutionChecksum}' that was not pinned on the host side.");
             }
 
-            return _checksumToScope[solutionChecksum];
+            return scope;
         }
     }
 
diff --git a/src/Workspaces/Remote/ServiceHub/Microsoft.CodeAnalysis.Remote.ServiceHub.csproj b/src/Workspaces/Remote/ServiceHub/Microsoft.CodeAnalysis.Remote.ServiceHub.csproj
index d24eebbe46ad2..8015698f35fa7 100644
--- a/src/Workspaces/Remote/ServiceHub/Microsoft.CodeAnalysis.Remote.ServiceHub.csproj
+++ b/src/Workspaces/Remote/ServiceHub/Microsoft.CodeAnalysis.Remote.ServiceHub.csproj
@@ -16,6 +16,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\..\Features\Core\Portable\Microsoft.CodeAnalysis.Features.csproj" />
     <ProjectReference Include="..\..\..\Tools\ExternalAccess\Razor\Microsoft.CodeAnalysis.ExternalAccess.Razor.csproj" />
+    <ProjectReference Include="..\..\..\Tools\ExternalAccess\RazorCompiler\Microsoft.CodeAnalysis.ExternalAccess.RazorCompiler.csproj" />
     <ProjectReference Include="..\..\..\Tools\ExternalAccess\AspNetCore\Microsoft.CodeAnalysis.ExternalAccess.AspNetCore.csproj" />
     <ProjectReference Include="..\Core\Microsoft.CodeAnalysis.Remote.Workspaces.csproj" />
   </ItemGroup>
@@ -39,8 +40,14 @@
     <Compile Include="..\..\..\VisualStudio\Core\Def\Storage\CloudCachePersistentStorage.cs" Link="Host\Storage\CloudCachePersistentStorage.cs" />
     <Compile Include="..\..\..\VisualStudio\Core\Def\Storage\ProjectContainerKeyCache.cs" Link="Host\Storage\ProjectContainerKeyCache.cs" />
     <Compile Include="..\..\..\VisualStudio\Core\Def\Storage\FileDownloader.cs" Link="Host\Storage\FileDownloader.cs" />
-    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\TelemetryLogger.cs" Link="Services\ProcessTelemetry\TelemetryLogger.cs" />
     <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\AbstractWorkspaceTelemetryService.cs" Link="Services\ProcessTelemetry\AbstractWorkspaceTelemetryService.cs" />
+    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\AggregatingTelemetryLog.cs" Link="Services\ProcessTelemetry\AggregatingTelemetryLog.cs" />
+    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\AggregatingTelemetryLogManager.cs" Link="Services\ProcessTelemetry\AggregatingTelemetryLogManager.cs" />
+    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\TelemetryLogger.cs" Link="Services\ProcessTelemetry\TelemetryLogger.cs" />
+    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\TelemetryLogProvider.cs" Link="Services\ProcessTelemetry\TelemetryLogProvider.cs" />
+    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\TimedTelemetryLogBlock.cs" Link="Services\ProcessTelemetry\TimedTelemetryLogBlock.cs" />
+    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\VisualStudioTelemetryLog.cs" Link="Services\ProcessTelemetry\VisualStudioTelemetryLog.cs" />
+    <Compile Include="..\..\..\VisualStudio\Core\Def\Telemetry\VisualStudioTelemetryLogManager.cs" Link="Services\ProcessTelemetry\VisualStudioTelemetryLogManager.cs" />
   </ItemGroup>
   <ItemGroup>
     <RestrictedInternalsVisibleTo Include="Microsoft.CodeAnalysis.LiveUnitTesting.BuildManager" Partner="UnitTesting" Key="$(UnitTestingKey)" />
diff --git a/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/DiagnosticComputer.cs b/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/DiagnosticComputer.cs
index 2355bc5317845..8368934227e02 100644
--- a/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/DiagnosticComputer.cs
+++ b/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/DiagnosticComputer.cs
@@ -326,6 +326,10 @@ private async Task<SerializableDiagnosticAnalysisResults> GetDiagnosticsAsync(
             CancellationToken cancellationToken)
         {
             var (compilationWithAnalyzers, analyzerToIdMap) = await GetOrCreateCompilationWithAnalyzersAsync(cancellationToken).ConfigureAwait(false);
+            if (compilationWithAnalyzers == null)
+            {
+                return SerializableDiagnosticAnalysisResults.Empty;
+            }
 
             var analyzers = GetAnalyzers(analyzerToIdMap, analyzerIds);
             if (analyzers.IsEmpty)
@@ -467,7 +471,7 @@ private static ImmutableArray<DiagnosticAnalyzer> GetAnalyzers(BidirectionalMap<
             return builder.ToImmutable();
         }
 
-        private async Task<(CompilationWithAnalyzers compilationWithAnalyzers, BidirectionalMap<string, DiagnosticAnalyzer> analyzerToIdMap)> GetOrCreateCompilationWithAnalyzersAsync(CancellationToken cancellationToken)
+        private async Task<(CompilationWithAnalyzers? compilationWithAnalyzers, BidirectionalMap<string, DiagnosticAnalyzer> analyzerToIdMap)> GetOrCreateCompilationWithAnalyzersAsync(CancellationToken cancellationToken)
         {
             var cacheEntry = await GetOrCreateCacheEntryAsync().ConfigureAwait(false);
             return (cacheEntry.CompilationWithAnalyzers, cacheEntry.AnalyzerToIdMap);
@@ -522,7 +526,9 @@ private async Task<CompilationWithAnalyzersCacheEntry> CreateCompilationWithAnal
                 analyzerMapBuilder.AppendAnalyzerMap(analyzers);
             }
 
-            var compilationWithAnalyzers = await CreateCompilationWithAnalyzerAsync(analyzerBuilder.ToImmutable(), cancellationToken).ConfigureAwait(false);
+            var compilationWithAnalyzers = analyzerBuilder.Count > 0
+                ? await CreateCompilationWithAnalyzerAsync(analyzerBuilder.ToImmutable(), cancellationToken).ConfigureAwait(false)
+                : null;
             var analyzerToIdMap = new BidirectionalMap<string, DiagnosticAnalyzer>(analyzerMapBuilder);
 
             return new CompilationWithAnalyzersCacheEntry(_solutionChecksum, _project, compilationWithAnalyzers, analyzerToIdMap);
@@ -530,6 +536,8 @@ private async Task<CompilationWithAnalyzersCacheEntry> CreateCompilationWithAnal
 
         private async Task<CompilationWithAnalyzers> CreateCompilationWithAnalyzerAsync(ImmutableArray<DiagnosticAnalyzer> analyzers, CancellationToken cancellationToken)
         {
+            Contract.ThrowIfFalse(!analyzers.IsEmpty);
+
             // Always run analyzers concurrently in OOP
             const bool concurrentAnalysis = true;
 
@@ -560,10 +568,10 @@ private sealed class CompilationWithAnalyzersCacheEntry
         {
             public Checksum SolutionChecksum { get; }
             public Project Project { get; }
-            public CompilationWithAnalyzers CompilationWithAnalyzers { get; }
+            public CompilationWithAnalyzers? CompilationWithAnalyzers { get; }
             public BidirectionalMap<string, DiagnosticAnalyzer> AnalyzerToIdMap { get; }
 
-            public CompilationWithAnalyzersCacheEntry(Checksum solutionChecksum, Project project, CompilationWithAnalyzers compilationWithAnalyzers, BidirectionalMap<string, DiagnosticAnalyzer> analyzerToIdMap)
+            public CompilationWithAnalyzersCacheEntry(Checksum solutionChecksum, Project project, CompilationWithAnalyzers? compilationWithAnalyzers, BidirectionalMap<string, DiagnosticAnalyzer> analyzerToIdMap)
             {
                 SolutionChecksum = solutionChecksum;
                 Project = project;
diff --git a/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/PerformanceTrackerService.cs b/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/PerformanceTrackerService.cs
index fac32a789f619..b3b7473d5da76 100644
--- a/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/PerformanceTrackerService.cs
+++ b/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/PerformanceTrackerService.cs
@@ -14,6 +14,7 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Internal.Log;
+using Microsoft.CodeAnalysis.Telemetry;
 
 namespace Microsoft.CodeAnalysis.Remote.Diagnostics
 {
@@ -61,6 +62,33 @@ private PerformanceQueue GetQueue(bool forSpanAnalysis)
 
         public void AddSnapshot(IEnumerable<AnalyzerPerformanceInfo> snapshot, int unitCount, bool forSpanAnalysis)
         {
+            foreach (var perfInfo in snapshot)
+            {
+                const int PerformAnalysisTelemetryDelay = 250;
+
+                var delay = (int)perfInfo.TimeSpan.TotalMilliseconds;
+
+                TelemetryLogging.LogAggregated(FunctionId.PerformAnalysis_Summary, $"IndividualTimes", delay);
+
+                if (delay > PerformAnalysisTelemetryDelay)
+                {
+                    const string AnalyzerId = nameof(AnalyzerId);
+                    const string Delay = nameof(Delay);
+                    const string ForSpanAnalysis = nameof(ForSpanAnalysis);
+
+                    var analyzerId = perfInfo.BuiltIn ? perfInfo.AnalyzerId : perfInfo.BuiltIn.GetHashCode().ToString();
+
+                    var logMessage = KeyValueLogMessage.Create(m =>
+                    {
+                        m[AnalyzerId] = analyzerId;
+                        m[Delay] = delay;
+                        m[ForSpanAnalysis] = forSpanAnalysis;
+                    });
+
+                    TelemetryLogging.Log(FunctionId.PerformAnalysis_Delay, logMessage);
+                }
+            }
+
             Logger.Log(FunctionId.PerformanceTrackerService_AddSnapshot, s_snapshotLogger, snapshot, unitCount, forSpanAnalysis);
 
             RecordBuiltInAnalyzers(snapshot);
diff --git a/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/RemoteDiagnosticAnalyzerService.cs b/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/RemoteDiagnosticAnalyzerService.cs
index 9a458e4f1ab51..4ad5733315f63 100644
--- a/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/RemoteDiagnosticAnalyzerService.cs
+++ b/src/Workspaces/Remote/ServiceHub/Services/DiagnosticAnalyzer/RemoteDiagnosticAnalyzerService.cs
@@ -4,8 +4,6 @@
 
 using System.Collections.Immutable;
 using System.Diagnostics;
-using System.IO;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -13,6 +11,7 @@
 using Microsoft.CodeAnalysis.Remote.Diagnostics;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.SolutionCrawler;
+using Microsoft.CodeAnalysis.Telemetry;
 using Roslyn.Utilities;
 using RoslynLogger = Microsoft.CodeAnalysis.Internal.Log.Logger;
 
@@ -58,6 +57,7 @@ public async ValueTask<SerializableDiagnosticAnalysisResults> CalculateDiagnosti
             // Complete RPC right away so the client can start reading from the stream.
             // The fire-and forget task starts writing to the output stream and the client will read it until it reads all expected data.
 
+            using (TelemetryLogging.LogBlockTimeAggregated(FunctionId.PerformAnalysis_Summary, $"Total"))
             using (RoslynLogger.LogBlock(FunctionId.CodeAnalysisService_CalculateDiagnosticsAsync, arguments.ProjectId.DebugName, cancellationToken))
             {
                 return await RunWithSolutionAsync(
diff --git a/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.PerformanceReporter.cs b/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.PerformanceReporter.cs
index acd7a9b86881d..80677fb3051ad 100644
--- a/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.PerformanceReporter.cs
+++ b/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.PerformanceReporter.cs
@@ -6,7 +6,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Internal.Log;
@@ -79,7 +78,7 @@ protected override Task ExecuteAsync()
                                 m[nameof(analyzerInfo.Average)] = analyzerInfo.Average;
                                 m[nameof(analyzerInfo.AdjustedStandardDeviation)] = analyzerInfo.AdjustedStandardDeviation;
                                 m[nameof(forSpanAnalysis)] = forSpanAnalysis;
-                            }));
+                            }, LogLevel.Debug));
                         }
                     }
 
diff --git a/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.cs b/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.cs
index 9aae8b543af2d..3a027de44d3a0 100644
--- a/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.cs
+++ b/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteProcessTelemetryService.cs
@@ -3,9 +3,9 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Diagnostics;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.Linq;
 using System.Runtime.InteropServices;
 using System.Threading;
@@ -15,7 +15,6 @@
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.Notification;
 using Microsoft.CodeAnalysis.Remote.Diagnostics;
-using Microsoft.CodeAnalysis.Storage;
 using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.VisualStudio.LanguageServices.Telemetry;
 using Microsoft.VisualStudio.Telemetry;
diff --git a/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteWorkspaceTelemetryService.cs b/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteWorkspaceTelemetryService.cs
index 142e5cf35cfa9..a10b972079b9a 100644
--- a/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteWorkspaceTelemetryService.cs
+++ b/src/Workspaces/Remote/ServiceHub/Services/ProcessTelemetry/RemoteWorkspaceTelemetryService.cs
@@ -6,7 +6,7 @@
 using System.Composition;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.Internal.Log;
-using Microsoft.CodeAnalysis.Options;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
 using Microsoft.CodeAnalysis.Telemetry;
 using Microsoft.VisualStudio.Telemetry;
 
@@ -15,15 +15,18 @@ namespace Microsoft.VisualStudio.LanguageServices.Telemetry
     [ExportWorkspaceService(typeof(IWorkspaceTelemetryService)), Shared]
     internal sealed class RemoteWorkspaceTelemetryService : AbstractWorkspaceTelemetryService
     {
+        private readonly IAsynchronousOperationListenerProvider _asyncListenerProvider;
+
         [ImportingConstructor]
         [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-        public RemoteWorkspaceTelemetryService()
+        public RemoteWorkspaceTelemetryService(IAsynchronousOperationListenerProvider asyncListenerProvider)
         {
+            _asyncListenerProvider = asyncListenerProvider;
         }
 
         protected override ILogger CreateLogger(TelemetrySession telemetrySession, bool logDelta)
             => AggregateLogger.Create(
-                TelemetryLogger.Create(telemetrySession, logDelta),
+                TelemetryLogger.Create(telemetrySession, logDelta, _asyncListenerProvider),
                 Logger.GetLogger());
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SemanticFacts/CSharpSemanticFacts.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SemanticFacts/CSharpSemanticFacts.cs
index 6dd5a8204c602..bd7f3d78bd169 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SemanticFacts/CSharpSemanticFacts.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SemanticFacts/CSharpSemanticFacts.cs
@@ -153,7 +153,7 @@ private static void AppendAliasNames(SyntaxList<UsingDirectiveSyntax> usings, Im
             }
         }
 
-        private void AppendAliasNames(IEnumerable<BaseNamespaceDeclarationSyntax> namespaces, ImmutableHashSet<string>.Builder builder, CancellationToken cancellationToken)
+        private static void AppendAliasNames(IEnumerable<BaseNamespaceDeclarationSyntax> namespaces, ImmutableHashSet<string>.Builder builder, CancellationToken cancellationToken)
         {
             foreach (var @namespace in namespaces)
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxFacts.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxFacts.cs
index caafc045b5bfa..af9b5eade763d 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxFacts.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxFacts.cs
@@ -1063,7 +1063,7 @@ public IEnumerable<SyntaxNode> GetConstructors(SyntaxNode? root, CancellationTok
             return constructors;
         }
 
-        private void AppendConstructors(SyntaxList<MemberDeclarationSyntax> members, List<SyntaxNode> constructors, CancellationToken cancellationToken)
+        private static void AppendConstructors(SyntaxList<MemberDeclarationSyntax> members, List<SyntaxNode> constructors, CancellationToken cancellationToken)
         {
             foreach (var member in members)
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxKinds.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxKinds.cs
index c8551694fa50e..7df129dc6270d 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxKinds.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxKinds.cs
@@ -135,6 +135,7 @@ public int Convert<TSyntaxKind>(TSyntaxKind kind) where TSyntaxKind : struct
 
         public int ExpressionStatement => (int)SyntaxKind.ExpressionStatement;
         public int ForEachStatement => (int)SyntaxKind.ForEachStatement;
+        public int ForStatement => (int)SyntaxKind.ForStatement;
         public int IfStatement => (int)SyntaxKind.IfStatement;
         public int LocalDeclarationStatement => (int)SyntaxKind.LocalDeclarationStatement;
         public int? LocalFunctionStatement => (int)SyntaxKind.LocalFunctionStatement;
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeGeneration/CodeGenerationOptions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeGeneration/CodeGenerationOptions.cs
index 4e5151fad0a49..39332a9f6ceee 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeGeneration/CodeGenerationOptions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeGeneration/CodeGenerationOptions.cs
@@ -65,24 +65,19 @@ internal static CodeAndImportGenerationOptions GetDefault(LanguageServices langu
     internal CodeAndImportGenerationOptionsProvider CreateProvider()
         => new Provider(this);
 
-    private sealed class Provider : CodeAndImportGenerationOptionsProvider
+    private sealed class Provider(CodeAndImportGenerationOptions options) : CodeAndImportGenerationOptionsProvider
     {
-        private readonly CodeAndImportGenerationOptions _options;
-
-        public Provider(CodeAndImportGenerationOptions options)
-            => _options = options;
-
         ValueTask<CodeAndImportGenerationOptions> OptionsProvider<CodeAndImportGenerationOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options);
+            => ValueTaskFactory.FromResult(options);
 
         ValueTask<CodeGenerationOptions> OptionsProvider<CodeGenerationOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GenerationOptions);
+            => ValueTaskFactory.FromResult(options.GenerationOptions);
 
         ValueTask<NamingStylePreferences> OptionsProvider<NamingStylePreferences>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.GenerationOptions.NamingStyle);
+            => ValueTaskFactory.FromResult(options.GenerationOptions.NamingStyle);
 
         ValueTask<AddImportPlacementOptions> OptionsProvider<AddImportPlacementOptions>.GetOptionsAsync(LanguageServices languageServices, CancellationToken cancellationToken)
-            => ValueTaskFactory.FromResult(_options.AddImportOptions);
+            => ValueTaskFactory.FromResult(options.AddImportOptions);
     }
 #endif
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeStyle/CodeStyleOption2`1.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeStyle/CodeStyleOption2`1.cs
index 7b2ec42c9ce3d..91818de8f2687 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeStyle/CodeStyleOption2`1.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CodeStyle/CodeStyleOption2`1.cs
@@ -75,7 +75,7 @@ public static CodeStyleOption2<bool> GetCodeStyle(bool value, NotificationOption
     /// then those values will write back as false/true.
     /// </summary>
     [DataContract]
-    internal sealed partial class CodeStyleOption2<T> : ICodeStyleOption2, IEquatable<CodeStyleOption2<T>?>
+    internal sealed partial class CodeStyleOption2<T>(T value, NotificationOption2 notification) : ICodeStyleOption2, IEquatable<CodeStyleOption2<T>?>
     {
         public static readonly CodeStyleOption2<T> Default = new(default!, NotificationOption2.Silent);
 
@@ -88,16 +88,10 @@ internal sealed partial class CodeStyleOption2<T> : ICodeStyleOption2, IEquatabl
         private const string XmlAttribute_DiagnosticSeverity = "DiagnosticSeverity";
 
         [DataMember(Order = 0)]
-        public T Value { get; }
+        public T Value { get; } = value;
 
         [DataMember(Order = 1)]
-        public NotificationOption2 Notification { get; }
-
-        public CodeStyleOption2(T value, NotificationOption2 notification)
-        {
-            Value = value;
-            Notification = notification;
-        }
+        public NotificationOption2 Notification { get; } = notification;
 
         object? ICodeStyleOption.Value => this.Value;
         ICodeStyleOption ICodeStyleOption.WithValue(object value) => WithValue((T)value);
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CompilerExtensions.projitems b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CompilerExtensions.projitems
index 0bafea49791c3..b6a831d0cfaa0 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CompilerExtensions.projitems
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/CompilerExtensions.projitems
@@ -25,6 +25,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)..\..\..\..\Compilers\Core\Portable\InternalUtilities\CompilerFeatureRequiredAttribute.cs" Link="InternalUtilities\CompilerFeatureRequiredAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)..\..\..\..\Compilers\Core\Portable\InternalUtilities\RequiredMemberAttribute.cs" Link="InternalUtilities\RequiredMemberAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)..\..\..\..\Compilers\Core\Portable\InternalUtilities\SetsRequiredMembersAttribute.cs" Link="InternalUtilities\SetsRequiredMembersAttribute.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)..\..\..\..\Compilers\Core\Portable\InternalUtilities\ReadOnlyMemoryOfCharComparer.cs" Link="InternalUtilities\ReadOnlyMemoryOfCharComparer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)..\..\..\..\Compilers\Core\Portable\InternalUtilities\ReferenceEqualityComparer.cs" Link="InternalUtilities\ReferenceEqualityComparer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)..\..\..\..\Compilers\Core\Portable\InternalUtilities\RoslynString.cs" Link="InternalUtilities\RoslynString.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)..\..\..\..\Compilers\Core\Portable\InternalUtilities\SpecializedCollections.cs" Link="InternalUtilities\SpecializedCollections.cs" />
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EditorConfig/Parsing/Sections/SectionMatcher.Lexer.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EditorConfig/Parsing/Sections/SectionMatcher.Lexer.cs
index 32f53af3097bb..c6d2cbfa302e0 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EditorConfig/Parsing/Sections/SectionMatcher.Lexer.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EditorConfig/Parsing/Sections/SectionMatcher.Lexer.cs
@@ -8,29 +8,22 @@ namespace Microsoft.CodeAnalysis.EditorConfig.Parsing
 {
     internal readonly partial struct SectionMatcher
     {
-        private struct Lexer
+        private struct Lexer(string headerText)
         {
-            private readonly string _headerText;
-            public int Position { get; set; }
+            public int Position { get; set; } = 0;
 
-            public Lexer(string headerText)
-            {
-                _headerText = headerText;
-                Position = 0;
-            }
-
-            public readonly bool IsDone => Position >= _headerText.Length;
+            public readonly bool IsDone => Position >= headerText.Length;
 
             public TokenKind Lex()
             {
-                var tokenKind = GetTokenKindAtPosition(_headerText, Position);
+                var tokenKind = GetTokenKindAtPosition(headerText, Position);
                 switch (tokenKind)
                 {
                     case TokenKind.StarStar:
                         Position += 2;
                         break;
                     case TokenKind.SimpleCharacter:
-                        if (_headerText[Position] == '\\')
+                        if (headerText[Position] == '\\')
                         {
                             // Backslash escapes the next character
                             Position++;
@@ -58,9 +51,9 @@ public readonly bool TryPeekNext(out TokenKind kind)
             {
                 var position = Position;
                 position++;
-                if (position < _headerText.Length)
+                if (position < headerText.Length)
                 {
-                    kind = GetTokenKindAtPosition(_headerText, position);
+                    kind = GetTokenKindAtPosition(headerText, position);
                     return true;
                 }
 
@@ -74,7 +67,7 @@ public readonly bool TryPeekPrevious(out TokenKind kind)
                 position--;
                 if (position >= 0)
                 {
-                    kind = GetTokenKindAtPosition(_headerText, position);
+                    kind = GetTokenKindAtPosition(headerText, position);
                     return true;
                 }
 
@@ -128,9 +121,9 @@ private static TokenKind GetTokenKindAtPosition(string headerText, int position)
                 }
             }
 
-            public readonly char CurrentCharacter => _headerText[Position];
+            public readonly char CurrentCharacter => headerText[Position];
 
-            public char EatCurrentCharacter() => _headerText[Position++];
+            public char EatCurrentCharacter() => headerText[Position++];
 
             public bool TryEatCurrentCharacter(out char nextChar)
             {
@@ -146,7 +139,7 @@ public bool TryEatCurrentCharacter(out char nextChar)
                 }
             }
 
-            public readonly char this[int position] => _headerText[position];
+            public readonly char this[int position] => headerText[position];
 
             public string? TryLexNumber()
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/Common/EmbeddedSeparatedSyntaxNodeList.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/Common/EmbeddedSeparatedSyntaxNodeList.cs
index 4cd837cabae59..9981de119896b 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/Common/EmbeddedSeparatedSyntaxNodeList.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/Common/EmbeddedSeparatedSyntaxNodeList.cs
@@ -76,30 +76,22 @@ public TDerivedNode this[int index]
 
         public Enumerator GetEnumerator() => new(this);
 
-        public struct Enumerator
+        public struct Enumerator(EmbeddedSeparatedSyntaxNodeList<TSyntaxKind, TSyntaxNode, TDerivedNode> list)
         {
-            private readonly EmbeddedSeparatedSyntaxNodeList<TSyntaxKind, TSyntaxNode, TDerivedNode> _list;
-            private int _currentIndex;
+            private int _currentIndex = -1;
 
-            public Enumerator(EmbeddedSeparatedSyntaxNodeList<TSyntaxKind, TSyntaxNode, TDerivedNode> list)
-            {
-                _list = list;
-                _currentIndex = -1;
-                Current = null!;
-            }
-
-            public TDerivedNode Current { get; private set; }
+            public TDerivedNode Current { get; private set; } = null!;
 
             public bool MoveNext()
             {
                 _currentIndex++;
-                if (_currentIndex >= _list.Length)
+                if (_currentIndex >= list.Length)
                 {
                     Current = null!;
                     return false;
                 }
 
-                Current = _list[_currentIndex];
+                Current = list[_currentIndex];
                 return true;
             }
         }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs
index 0db80681639a7..5382f40499196 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs
@@ -34,25 +34,20 @@ protected Chunk()
         /// This will be the common construct we generate when getting the
         /// <see cref="Chunk"/> for a string token that has escapes in it.
         /// </summary>
-        private class ImmutableSegmentedListChunk : Chunk
+        private class ImmutableSegmentedListChunk(ImmutableSegmentedList<VirtualChar> array) : Chunk
         {
-            private readonly ImmutableSegmentedList<VirtualChar> _array;
-
-            public ImmutableSegmentedListChunk(ImmutableSegmentedList<VirtualChar> array)
-                => _array = array;
-
-            public override int Length => _array.Count;
-            public override VirtualChar this[int index] => _array[index];
+            public override int Length => array.Count;
+            public override VirtualChar this[int index] => array[index];
 
             public override VirtualChar? Find(int position)
             {
-                if (_array.IsEmpty)
+                if (array.IsEmpty)
                     return null;
 
-                if (position < _array[0].Span.Start || position >= _array[^1].Span.End)
+                if (position < array[0].Span.Start || position >= array[^1].Span.End)
                     return null;
 
-                var index = _array.BinarySearch(position, static (ch, position) =>
+                var index = array.BinarySearch(position, static (ch, position) =>
                 {
                     if (position < ch.Span.Start)
                         return 1;
@@ -68,7 +63,7 @@ public ImmutableSegmentedListChunk(ImmutableSegmentedList<VirtualChar> array)
                 if (index < 0)
                     return null;
 
-                return _array[index];
+                return array[index];
             }
         }
 
@@ -77,30 +72,20 @@ public ImmutableSegmentedListChunk(ImmutableSegmentedList<VirtualChar> array)
         /// string.  This is the common case of the type of the sequence we would
         /// create for a normal string token without any escapes in it.
         /// </summary>
-        private class StringChunk : Chunk
+        /// <param name="data">
+        /// The underlying string that we're returning virtual chars from.  Note:
+        /// this will commonly include things like quote characters.  Clients who
+        /// do not want that should then ask for an appropriate <see cref="VirtualCharSequence.GetSubSequence"/>
+        /// back that does not include those characters.
+        /// </param>
+        private class StringChunk(int firstVirtualCharPosition, string data) : Chunk
         {
-            private readonly int _firstVirtualCharPosition;
-
-            /// <summary>
-            /// The underlying string that we're returning virtual chars from.  Note:
-            /// this will commonly include things like quote characters.  Clients who
-            /// do not want that should then ask for an appropriate <see cref="VirtualCharSequence.GetSubSequence"/>
-            /// back that does not include those characters.
-            /// </summary>
-            private readonly string _underlyingData;
-
-            public StringChunk(int firstVirtualCharPosition, string data)
-            {
-                _firstVirtualCharPosition = firstVirtualCharPosition;
-                _underlyingData = data;
-            }
-
-            public override int Length => _underlyingData.Length;
+            public override int Length => data.Length;
 
             public override VirtualChar? Find(int position)
             {
-                var stringIndex = position - _firstVirtualCharPosition;
-                if (stringIndex < 0 || stringIndex >= _underlyingData.Length)
+                var stringIndex = position - firstVirtualCharPosition;
+                if (stringIndex < 0 || stringIndex >= data.Length)
                     return null;
 
                 return this[stringIndex];
@@ -113,15 +98,15 @@ public override VirtualChar this[int index]
 #if DEBUG
                     // We should never have a properly paired high/low surrogate in a StringChunk. We are only created
                     // when the string has the same number of chars as there are VirtualChars.
-                    if (char.IsHighSurrogate(_underlyingData[index]))
+                    if (char.IsHighSurrogate(data[index]))
                     {
-                        Debug.Assert(index + 1 >= _underlyingData.Length ||
-                                     !char.IsLowSurrogate(_underlyingData[index + 1]));
+                        Debug.Assert(index + 1 >= data.Length ||
+                                     !char.IsLowSurrogate(data[index + 1]));
                     }
 #endif
 
-                    var span = new TextSpan(_firstVirtualCharPosition + index, length: 1);
-                    var ch = _underlyingData[index];
+                    var span = new TextSpan(firstVirtualCharPosition + index, length: 1);
+                    var ch = data[index];
                     return char.IsSurrogate(ch)
                         ? VirtualChar.Create(ch, span)
                         : VirtualChar.Create(new Rune(ch), span);
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Enumerator.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Enumerator.cs
index 512cb7012c4c1..22b01647fe044 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Enumerator.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Enumerator.cs
@@ -10,19 +10,12 @@ namespace Microsoft.CodeAnalysis.EmbeddedLanguages.VirtualChars
 {
     internal partial struct VirtualCharSequence
     {
-        public struct Enumerator : IEnumerator<VirtualChar>
+        public struct Enumerator(VirtualCharSequence virtualCharSequence) : IEnumerator<VirtualChar>
         {
-            private readonly VirtualCharSequence _virtualCharSequence;
-            private int _position;
+            private int _position = -1;
 
-            public Enumerator(VirtualCharSequence virtualCharSequence)
-            {
-                _virtualCharSequence = virtualCharSequence;
-                _position = -1;
-            }
-
-            public bool MoveNext() => ++_position < _virtualCharSequence.Length;
-            public readonly VirtualChar Current => _virtualCharSequence[_position];
+            public bool MoveNext() => ++_position < virtualCharSequence.Length;
+            public readonly VirtualChar Current => virtualCharSequence[_position];
 
             public void Reset()
                 => _position = -1;
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/AnalysisContextExtensions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/AnalysisContextExtensions.cs
index 9b2a3af2adbc6..6c6bc2b050686 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/AnalysisContextExtensions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/AnalysisContextExtensions.cs
@@ -5,41 +5,215 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis
 {
     internal static class AnalysisContextExtensions
     {
+        private static bool ShouldAnalyze(TextSpan? contextFilterSpan, TextSpan span)
+            => !contextFilterSpan.HasValue || span.IntersectsWith(contextFilterSpan.Value);
+
         /// <summary>
         /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
         /// i.e. either of the following is true:
-        ///  - <see cref="SyntaxTreeAnalysisContext.FilterSpan"/> is <code>null</code> (we are analyzing the entire tree)
+        ///  - <see cref="SyntaxTreeAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
         ///  OR
         ///  - <paramref name="span"/> intersects with <see cref="SyntaxTreeAnalysisContext.FilterSpan"/>.
         /// </summary>
         public static bool ShouldAnalyzeSpan(this SyntaxTreeAnalysisContext context, TextSpan span)
-            => !context.FilterSpan.HasValue || span.IntersectsWith(context.FilterSpan.Value);
+            => ShouldAnalyze(context.FilterSpan, span);
 
         /// <summary>
         /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
         /// i.e. either of the following is true:
-        ///  - <see cref="SemanticModelAnalysisContext.FilterSpan"/> is <code>null</code> (we are analyzing the entire tree)
+        ///  - <see cref="SemanticModelAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
         ///  OR
         ///  - <paramref name="span"/> intersects with <see cref="SemanticModelAnalysisContext.FilterSpan"/>.
         /// </summary>
         public static bool ShouldAnalyzeSpan(this SemanticModelAnalysisContext context, TextSpan span)
-            => !context.FilterSpan.HasValue || span.IntersectsWith(context.FilterSpan.Value);
+            => ShouldAnalyze(context.FilterSpan, span);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="SymbolStartAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="SymbolStartAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this SymbolStartAnalysisContext context, TextSpan span, SyntaxTree tree)
+            => context.FilterTree == null || (context.FilterTree == tree && ShouldAnalyze(context.FilterSpan, span));
+
+        /// <summary>
+        /// Returns true if the given <paramref name="location"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="SymbolStartAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="location"/> intersects with <see cref="SymbolStartAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeLocation(this SymbolStartAnalysisContext context, Location location)
+            => location.SourceTree != null && context.ShouldAnalyzeSpan(location.SourceSpan, location.SourceTree);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="SymbolAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="SymbolAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this SymbolAnalysisContext context, TextSpan span, SyntaxTree tree)
+            => context.FilterTree == null || (context.FilterTree == tree && ShouldAnalyze(context.FilterSpan, span));
+
+        /// <summary>
+        /// Returns true if the given <paramref name="location"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="SymbolAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="location"/> intersects with <see cref="SymbolAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeLocation(this SymbolAnalysisContext context, Location location)
+            => location.SourceTree != null && context.ShouldAnalyzeSpan(location.SourceSpan, location.SourceTree);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="AdditionalFileAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire file)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="AdditionalFileAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this AdditionalFileAnalysisContext context, TextSpan span)
+            => ShouldAnalyze(context.FilterSpan, span);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="OperationBlockStartAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="OperationBlockStartAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this OperationBlockStartAnalysisContext context, TextSpan span)
+            => ShouldAnalyze(context.FilterSpan, span);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="OperationBlockAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="OperationBlockAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this OperationBlockAnalysisContext context, TextSpan span)
+            => ShouldAnalyze(context.FilterSpan, span);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="OperationAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="OperationAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this OperationAnalysisContext context, TextSpan span)
+            => ShouldAnalyze(context.FilterSpan, span);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="SyntaxNodeAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="SyntaxNodeAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this SyntaxNodeAnalysisContext context, TextSpan span)
+            => ShouldAnalyze(context.FilterSpan, span);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="CodeBlockStartAnalysisContext{TSytnaxKind}.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="CodeBlockStartAnalysisContext{TSytnaxKind}.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan<TSytnaxKind>(this CodeBlockStartAnalysisContext<TSytnaxKind> context, TextSpan span) where TSytnaxKind : struct
+            => ShouldAnalyze(context.FilterSpan, span);
+
+        /// <summary>
+        /// Returns true if the given <paramref name="span"/> should be analyzed for the given <paramref name="context"/>,
+        /// i.e. either of the following is true:
+        ///  - <see cref="CodeBlockAnalysisContext.FilterSpan"/> is <see langword="null"/> (we are analyzing the entire tree)
+        ///  OR
+        ///  - <paramref name="span"/> intersects with <see cref="CodeBlockAnalysisContext.FilterSpan"/>.
+        /// </summary>
+        public static bool ShouldAnalyzeSpan(this CodeBlockAnalysisContext context, TextSpan span)
+            => ShouldAnalyze(context.FilterSpan, span);
 
         /// <summary>
         /// Gets the root node in the analysis span for the given <paramref name="context"/>.
         /// </summary>
         public static SyntaxNode GetAnalysisRoot(this SyntaxTreeAnalysisContext context, bool findInTrivia, bool getInnermostNodeForTie = false)
-            => context.Tree.GetNodeForSpan(context.FilterSpan, findInTrivia, getInnermostNodeForTie, context.CancellationToken);
+            => context.Tree.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie, context.CancellationToken);
 
         /// <summary>
         /// Gets the root node in the analysis span for the given <paramref name="context"/>.
         /// </summary>
         public static SyntaxNode GetAnalysisRoot(this SemanticModelAnalysisContext context, bool findInTrivia, bool getInnermostNodeForTie = false)
-            => context.SemanticModel.SyntaxTree.GetNodeForSpan(context.FilterSpan, findInTrivia, getInnermostNodeForTie, context.CancellationToken);
+            => context.SemanticModel.SyntaxTree.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie, context.CancellationToken);
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// NOTE: This method expects <see cref="SymbolStartAnalysisContext.FilterTree"/>
+        /// and <see cref="SymbolStartAnalysisContext.FilterSpan"/> to be non-null. 
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot(this SymbolStartAnalysisContext context, bool findInTrivia, bool getInnermostNodeForTie = false)
+        {
+            Contract.ThrowIfNull(context.FilterTree);
+            Contract.ThrowIfFalse(context.FilterSpan.HasValue);
+            return context.FilterTree.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie, context.CancellationToken);
+        }
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// NOTE: This method expects <see cref="SymbolAnalysisContext.FilterTree"/>
+        /// and <see cref="SymbolAnalysisContext.FilterSpan"/> to be non-null. 
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot(this SymbolAnalysisContext context, bool findInTrivia, bool getInnermostNodeForTie = false)
+        {
+            Contract.ThrowIfNull(context.FilterTree);
+            Contract.ThrowIfFalse(context.FilterSpan.HasValue);
+            return context.FilterTree.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie, context.CancellationToken);
+        }
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot(this OperationBlockStartAnalysisContext context, IOperation operationBlock, bool findInTrivia, bool getInnermostNodeForTie = false)
+            => operationBlock.Syntax.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie);
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot(this OperationBlockAnalysisContext context, IOperation operationBlock, bool findInTrivia, bool getInnermostNodeForTie = false)
+            => operationBlock.Syntax.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie);
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot(this OperationAnalysisContext context, bool findInTrivia, bool getInnermostNodeForTie = false)
+            => context.Operation.Syntax.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie);
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot(this SyntaxNodeAnalysisContext context, bool findInTrivia, bool getInnermostNodeForTie = false)
+            => context.Node.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie);
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot<TSyntaxKind>(this CodeBlockStartAnalysisContext<TSyntaxKind> context, bool findInTrivia, bool getInnermostNodeForTie = false) where TSyntaxKind : struct
+            => context.CodeBlock.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie);
+
+        /// <summary>
+        /// Gets the root node in the analysis span for the given <paramref name="context"/>.
+        /// </summary>
+        public static SyntaxNode GetAnalysisRoot(this CodeBlockAnalysisContext context, bool findInTrivia, bool getInnermostNodeForTie = false)
+            => context.CodeBlock.FindNode(context.FilterSpan, findInTrivia, getInnermostNodeForTie);
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/DirectiveInfo.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/DirectiveInfo.cs
index cbc40d6a9060c..703819142f982 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/DirectiveInfo.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/DirectiveInfo.cs
@@ -8,21 +8,15 @@
 
 namespace Microsoft.CodeAnalysis.Shared.Extensions
 {
-    internal sealed class DirectiveInfo<TDirectiveTriviaSyntax>
+    internal sealed class DirectiveInfo<TDirectiveTriviaSyntax>(
+        Dictionary<TDirectiveTriviaSyntax, TDirectiveTriviaSyntax?> directiveMap,
+        Dictionary<TDirectiveTriviaSyntax, ImmutableArray<TDirectiveTriviaSyntax>> conditionalMap)
         where TDirectiveTriviaSyntax : SyntaxNode
     {
         // Maps a directive to its pair
-        public Dictionary<TDirectiveTriviaSyntax, TDirectiveTriviaSyntax?> DirectiveMap { get; }
+        public Dictionary<TDirectiveTriviaSyntax, TDirectiveTriviaSyntax?> DirectiveMap { get; } = directiveMap;
 
         // Maps a #If/#elif/#else/#endIf directive to its list of matching #If/#elif/#else/#endIf directives
-        public Dictionary<TDirectiveTriviaSyntax, ImmutableArray<TDirectiveTriviaSyntax>> ConditionalMap { get; }
-
-        public DirectiveInfo(
-            Dictionary<TDirectiveTriviaSyntax, TDirectiveTriviaSyntax?> directiveMap,
-            Dictionary<TDirectiveTriviaSyntax, ImmutableArray<TDirectiveTriviaSyntax>> conditionalMap)
-        {
-            this.DirectiveMap = directiveMap;
-            this.ConditionalMap = conditionalMap;
-        }
+        public Dictionary<TDirectiveTriviaSyntax, ImmutableArray<TDirectiveTriviaSyntax>> ConditionalMap { get; } = conditionalMap;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxNodeExtensions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxNodeExtensions.cs
index e23b2bc195126..4f8d8a278d853 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxNodeExtensions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxNodeExtensions.cs
@@ -796,6 +796,17 @@ public static SyntaxToken WithoutTrailingTrivia(this SyntaxToken token)
             return token.WithTrailingTrivia(default(SyntaxTriviaList));
         }
 
+        /// <summary>
+        /// Finds the node within the given <paramref name="root"/> corresponding to the given <paramref name="span"/>.
+        /// If the <paramref name="span"/> is <see langword="null"/>, then returns the given <paramref name="root"/> node.
+        /// </summary>
+        public static SyntaxNode FindNode(this SyntaxNode root, TextSpan? span, bool findInTrivia, bool getInnermostNodeForTie)
+        {
+            return span.HasValue
+                ? root.FindNode(span.Value, findInTrivia, getInnermostNodeForTie)
+                : root;
+        }
+
         // Copy of the same function in SyntaxNode.cs
         public static SyntaxNode? GetParent(this SyntaxNode node, bool ascendOutOfTrivia)
         {
@@ -958,37 +969,18 @@ void FinishIf(TDirectiveTriviaSyntax? directive)
         public static ValueAncestorsAndSelfEnumerable ValueAncestorsAndSelf(this SyntaxNode syntaxNode, bool ascendOutOfTrivia = true)
             => new(syntaxNode, ascendOutOfTrivia);
 
-        public readonly struct ValueAncestorsAndSelfEnumerable
+        public readonly struct ValueAncestorsAndSelfEnumerable(SyntaxNode syntaxNode, bool ascendOutOfTrivia)
         {
-            private readonly SyntaxNode _syntaxNode;
-            private readonly bool _ascendOutOfTrivia;
-
-            public ValueAncestorsAndSelfEnumerable(SyntaxNode syntaxNode, bool ascendOutOfTrivia)
-            {
-                _syntaxNode = syntaxNode;
-                _ascendOutOfTrivia = ascendOutOfTrivia;
-            }
-
             public Enumerator GetEnumerator()
-                => new(_syntaxNode, _ascendOutOfTrivia);
+                => new(syntaxNode, ascendOutOfTrivia);
 
-            public struct Enumerator
+            public struct Enumerator(SyntaxNode syntaxNode, bool ascendOutOfTrivia)
             {
-                private readonly SyntaxNode _start;
-                private readonly bool _ascendOutOfTrivia;
-
-                public Enumerator(SyntaxNode syntaxNode, bool ascendOutOfTrivia)
-                {
-                    _start = syntaxNode;
-                    _ascendOutOfTrivia = ascendOutOfTrivia;
-                    Current = null!;
-                }
-
-                public SyntaxNode Current { get; private set; }
+                public SyntaxNode Current { get; private set; } = null!;
 
                 public bool MoveNext()
                 {
-                    Current = Current == null ? _start : GetParent(Current, _ascendOutOfTrivia)!;
+                    Current = Current == null ? syntaxNode : GetParent(Current, ascendOutOfTrivia)!;
                     return Current != null;
                 }
             }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxTreeExtensions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxTreeExtensions.cs
index 49004c289b220..f4c36b4225e2b 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxTreeExtensions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxTreeExtensions.cs
@@ -243,15 +243,13 @@ public static bool IsGeneratedCode(this SyntaxTree syntaxTree, AnalyzerOptions?
         }
 
         /// <summary>
-        /// Gets the node in the given <paramref name="syntaxTree"/> corresponding to the given <paramref name="span"/>.
-        /// If the <paramref name="span"/> is <code>null</code>, then returns the root node of the tree.
+        /// Finds the node in the given <paramref name="syntaxTree"/> corresponding to the given <paramref name="span"/>.
+        /// If the <paramref name="span"/> is <see langword="null"/>, then returns the root node of the tree.
         /// </summary>
-        public static SyntaxNode GetNodeForSpan(this SyntaxTree syntaxTree, TextSpan? span, bool findInTrivia, bool getInnermostNodeForTie, CancellationToken cancellationToken)
+        public static SyntaxNode FindNode(this SyntaxTree syntaxTree, TextSpan? span, bool findInTrivia, bool getInnermostNodeForTie, CancellationToken cancellationToken)
         {
             var root = syntaxTree.GetRoot(cancellationToken);
-            return span.HasValue
-                ? root.FindNode(span.Value, findInTrivia, getInnermostNodeForTie)
-                : root;
+            return root.FindNode(span, findInTrivia, getInnermostNodeForTie);
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/FlowAnalysis/SymbolUsageAnalysis/SymbolUsageResult.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/FlowAnalysis/SymbolUsageAnalysis/SymbolUsageResult.cs
index b7c930e30ddab..ce542a5c0dfe2 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/FlowAnalysis/SymbolUsageAnalysis/SymbolUsageResult.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/FlowAnalysis/SymbolUsageAnalysis/SymbolUsageResult.cs
@@ -11,15 +11,10 @@
 
 namespace Microsoft.CodeAnalysis.FlowAnalysis.SymbolUsageAnalysis
 {
-    internal readonly struct SymbolUsageResult
+    internal readonly struct SymbolUsageResult(
+        ImmutableDictionary<(ISymbol symbol, IOperation write), bool> symbolWritesMap,
+        ImmutableHashSet<ISymbol> symbolsRead)
     {
-        public SymbolUsageResult(
-            ImmutableDictionary<(ISymbol symbol, IOperation write), bool> symbolWritesMap,
-            ImmutableHashSet<ISymbol> symbolsRead)
-        {
-            SymbolWritesMap = symbolWritesMap;
-            SymbolsRead = symbolsRead;
-        }
 
         /// <summary>
         /// Map from each symbol write to a boolean indicating if the value assinged
@@ -37,12 +32,12 @@ public SymbolUsageResult(
         ///        Value = 'true', because value assigned to 'x' here **may be** read on
         ///        some control flow path.
         /// </summary>
-        public ImmutableDictionary<(ISymbol symbol, IOperation write), bool> SymbolWritesMap { get; }
+        public ImmutableDictionary<(ISymbol symbol, IOperation write), bool> SymbolWritesMap { get; } = symbolWritesMap;
 
         /// <summary>
         /// Set of locals/parameters that are read at least once.
         /// </summary>
-        public ImmutableHashSet<ISymbol> SymbolsRead { get; }
+        public ImmutableHashSet<ISymbol> SymbolsRead { get; } = symbolsRead;
 
         public bool HasUnreadSymbolWrites()
             => SymbolWritesMap.Values.Any(value => !value);
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.AnchorData.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.AnchorData.cs
index 01de97733daff..62af62c742900 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.AnchorData.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.AnchorData.cs
@@ -13,26 +13,17 @@ internal partial class FormattingContext
         /// <summary>
         /// data that will be used in an interval tree related to Anchor.
         /// </summary>
-        private class AnchorData
+        private class AnchorData(AnchorIndentationOperation operation, SyntaxToken anchorToken, int originalColumn)
         {
-            private readonly AnchorIndentationOperation _operation;
+            public TextSpan TextSpan => operation.TextSpan;
 
-            public AnchorData(AnchorIndentationOperation operation, SyntaxToken anchorToken, int originalColumn)
-            {
-                _operation = operation;
-                this.AnchorToken = anchorToken;
-                this.OriginalColumn = originalColumn;
-            }
+            public SyntaxToken StartToken => operation.StartToken;
 
-            public TextSpan TextSpan => _operation.TextSpan;
+            public SyntaxToken EndToken => operation.EndToken;
 
-            public SyntaxToken StartToken => _operation.StartToken;
+            public SyntaxToken AnchorToken { get; } = anchorToken;
 
-            public SyntaxToken EndToken => _operation.EndToken;
-
-            public SyntaxToken AnchorToken { get; }
-
-            public int OriginalColumn { get; }
+            public int OriginalColumn { get; } = originalColumn;
         }
 
         private readonly struct FormattingContextIntervalIntrospector
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.IndentationData.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.IndentationData.cs
index 6b15b8f849ebf..da8240ae2202d 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.IndentationData.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.IndentationData.cs
@@ -15,12 +15,9 @@ internal partial class FormattingContext
         /// <summary>
         /// data that will be used in an interval tree related to indentation.
         /// </summary>
-        private abstract class IndentationData
+        private abstract class IndentationData(TextSpan textSpan)
         {
-            public IndentationData(TextSpan textSpan)
-                => this.TextSpan = textSpan;
-
-            public TextSpan TextSpan { get; }
+            public TextSpan TextSpan { get; } = textSpan;
             public abstract int Indentation { get; }
 
             public IndentationData WithTextSpan(TextSpan span)
@@ -29,21 +26,13 @@ public IndentationData WithTextSpan(TextSpan span)
             protected abstract IndentationData WithTextSpanCore(TextSpan span);
         }
 
-        private sealed class SimpleIndentationData : IndentationData
+        private sealed class SimpleIndentationData(TextSpan textSpan, int indentation) : IndentationData(textSpan)
         {
-            private readonly int _indentation;
-
-            public SimpleIndentationData(TextSpan textSpan, int indentation)
-                : base(textSpan)
-            {
-                _indentation = indentation;
-            }
-
-            public override int Indentation => _indentation;
+            public override int Indentation => indentation;
 
             protected override IndentationData WithTextSpanCore(TextSpan span)
             {
-                return new SimpleIndentationData(span, _indentation);
+                return new SimpleIndentationData(span, indentation);
             }
         }
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.cs
index df46f5c1b8a75..7f2ec734cfd3b 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/FormattingContext.cs
@@ -529,13 +529,13 @@ public SyntaxToken GetAnchorToken(SyntaxToken token)
         public int GetDeltaFromPreviousChangesMap(SyntaxToken token, Dictionary<SyntaxToken, int> previousChangesMap)
         {
             // no changes
-            if (!previousChangesMap.ContainsKey(token))
+            if (!previousChangesMap.TryGetValue(token, out var value))
             {
                 return 0;
             }
 
             var currentColumn = _tokenStream.GetCurrentColumn(token);
-            return currentColumn - previousChangesMap[token];
+            return currentColumn - value;
         }
 
         public SyntaxToken GetEndTokenForAnchorSpan(TokenData tokenData)
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressSpacingData.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressSpacingData.cs
index ba581c7170ff7..9885f30e55c7d 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressSpacingData.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressSpacingData.cs
@@ -9,11 +9,8 @@ namespace Microsoft.CodeAnalysis.Formatting
     /// <summary>
     /// data that will be used in an interval tree related to suppressing spacing operations.
     /// </summary>
-    internal class SuppressSpacingData
+    internal class SuppressSpacingData(TextSpan textSpan)
     {
-        public SuppressSpacingData(TextSpan textSpan)
-            => this.TextSpan = textSpan;
-
-        public TextSpan TextSpan { get; }
+        public TextSpan TextSpan { get; } = textSpan;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressWrappingData.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressWrappingData.cs
index 7962b620a5fd2..89d537eb155c5 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressWrappingData.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Context/SuppressWrappingData.cs
@@ -9,16 +9,10 @@ namespace Microsoft.CodeAnalysis.Formatting
     /// <summary>
     /// data that will be used in an interval tree related to suppressing wrapping operations.
     /// </summary>
-    internal class SuppressWrappingData
+    internal class SuppressWrappingData(TextSpan textSpan, bool ignoreElastic)
     {
-        public SuppressWrappingData(TextSpan textSpan, bool ignoreElastic)
-        {
-            this.TextSpan = textSpan;
-            this.IgnoreElastic = ignoreElastic;
-        }
-
-        public TextSpan TextSpan { get; }
-        public bool IgnoreElastic { get; }
+        public TextSpan TextSpan { get; } = textSpan;
+        public bool IgnoreElastic { get; } = ignoreElastic;
 
 #if DEBUG
         public override string ToString()
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/AbstractFormatEngine.OperationApplier.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/AbstractFormatEngine.OperationApplier.cs
index f97724d36fe85..c6ea71d1661ec 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/AbstractFormatEngine.OperationApplier.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/AbstractFormatEngine.OperationApplier.cs
@@ -18,17 +18,8 @@ internal abstract partial class AbstractFormatEngine
         /// <summary>
         /// this actually applies formatting operations to trivia between two tokens
         /// </summary>
-        private class OperationApplier
+        private class OperationApplier(FormattingContext context, ChainedFormattingRules formattingRules)
         {
-            private readonly FormattingContext _context;
-            private readonly ChainedFormattingRules _formattingRules;
-
-            public OperationApplier(FormattingContext context, ChainedFormattingRules formattingRules)
-            {
-                _context = context;
-                _formattingRules = formattingRules;
-            }
-
             public bool Apply(AdjustSpacesOperation operation, int pairIndex)
             {
                 if (operation.Option == AdjustSpacesOption.PreserveSpaces)
@@ -51,7 +42,7 @@ public bool Apply(AdjustSpacesOperation operation, int pairIndex)
 
             private bool ApplyDynamicSpacesOperation(AdjustSpacesOperation operation, int pairIndex)
             {
-                var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
 
                 if (triviaInfo.SecondTokenIsFirstTokenOnLine)
                 {
@@ -60,20 +51,20 @@ private bool ApplyDynamicSpacesOperation(AdjustSpacesOperation operation, int pa
 
                 Contract.ThrowIfFalse(triviaInfo.LineBreaks == 0);
 
-                var indentation = _context.GetBaseIndentation(_context.TokenStream.GetToken(pairIndex + 1));
+                var indentation = context.GetBaseIndentation(context.TokenStream.GetToken(pairIndex + 1));
 
-                var previousToken = _context.TokenStream.GetToken(pairIndex);
-                _context.TokenStream.GetTokenLength(previousToken, out var tokenLength, out var multipleLines);
+                var previousToken = context.TokenStream.GetToken(pairIndex);
+                context.TokenStream.GetTokenLength(previousToken, out var tokenLength, out var multipleLines);
 
                 // get end column of previous token
-                var endColumnOfPreviousToken = multipleLines ? tokenLength : _context.TokenStream.GetCurrentColumn(previousToken) + tokenLength;
+                var endColumnOfPreviousToken = multipleLines ? tokenLength : context.TokenStream.GetCurrentColumn(previousToken) + tokenLength;
 
                 // check whether current position is less than indentation
                 if (endColumnOfPreviousToken < indentation)
                 {
-                    Debug.Assert(!_context.IsFormattingDisabled(pairIndex));
+                    Debug.Assert(!context.IsFormattingDisabled(pairIndex));
 
-                    _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(indentation - endColumnOfPreviousToken, _context, _formattingRules));
+                    context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(indentation - endColumnOfPreviousToken, context, formattingRules));
                     return true;
                 }
 
@@ -83,7 +74,7 @@ private bool ApplyDynamicSpacesOperation(AdjustSpacesOperation operation, int pa
 
             private bool ApplyPreserveSpacesOperation(AdjustSpacesOperation operation, int pairIndex)
             {
-                var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
                 var space = operation.Space;
 
                 if (triviaInfo.SecondTokenIsFirstTokenOnLine)
@@ -98,30 +89,30 @@ private bool ApplyPreserveSpacesOperation(AdjustSpacesOperation operation, int p
                     return false;
                 }
 
-                Debug.Assert(!_context.IsFormattingDisabled(pairIndex));
+                Debug.Assert(!context.IsFormattingDisabled(pairIndex));
 
-                _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(space, _context, _formattingRules));
+                context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(space, context, formattingRules));
                 return true;
             }
 
             public bool ApplyForceSpacesOperation(AdjustSpacesOperation operation, int pairIndex)
             {
-                var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
 
                 if (triviaInfo.LineBreaks == 0 && triviaInfo.Spaces == operation.Space)
                 {
                     return false;
                 }
 
-                Debug.Assert(!_context.IsFormattingDisabled(pairIndex));
+                Debug.Assert(!context.IsFormattingDisabled(pairIndex));
 
-                _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(operation.Space, _context, _formattingRules));
+                context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(operation.Space, context, formattingRules));
                 return true;
             }
 
             private bool ApplySpaceIfSingleLine(AdjustSpacesOperation operation, int pairIndex)
             {
-                var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
                 var space = operation.Space;
 
                 if (triviaInfo.SecondTokenIsFirstTokenOnLine)
@@ -136,9 +127,9 @@ private bool ApplySpaceIfSingleLine(AdjustSpacesOperation operation, int pairInd
                     return false;
                 }
 
-                Debug.Assert(!_context.IsFormattingDisabled(pairIndex));
+                Debug.Assert(!context.IsFormattingDisabled(pairIndex));
 
-                _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(space, _context, _formattingRules));
+                context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithSpace(space, context, formattingRules));
                 return true;
             }
 
@@ -160,8 +151,8 @@ public bool Apply(AdjustNewLinesOperation operation, int pairIndex, Cancellation
                     // else we leave the tokens as it is (Note: We should not preserve too. If we
                     // we do, then that will be counted as a line operation and the indentation of
                     // the second token will be modified)
-                    if (_context.TokenStream.TwoTokensOnSameLine(_context.TokenStream.GetToken(pairIndex),
-                                                        _context.TokenStream.GetToken(pairIndex + 1)))
+                    if (context.TokenStream.TwoTokensOnSameLine(context.TokenStream.GetToken(pairIndex),
+                                                        context.TokenStream.GetToken(pairIndex + 1)))
                     {
                         return ApplyForceLinesOperation(operation, pairIndex, cancellationToken);
                     }
@@ -174,9 +165,9 @@ public bool Apply(AdjustNewLinesOperation operation, int pairIndex, Cancellation
 
             private bool ApplyForceLinesOperation(AdjustNewLinesOperation operation, int pairIndex, CancellationToken cancellationToken)
             {
-                var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
 
-                var indentation = _context.GetBaseIndentation(_context.TokenStream.GetToken(pairIndex + 1));
+                var indentation = context.GetBaseIndentation(context.TokenStream.GetToken(pairIndex + 1));
                 if (triviaInfo.LineBreaks == operation.Line && triviaInfo.Spaces == indentation && !triviaInfo.TreatAsElastic)
                 {
                     // things are already in the shape we want, so we don't actually need to do
@@ -184,27 +175,27 @@ private bool ApplyForceLinesOperation(AdjustNewLinesOperation operation, int pai
                     return true;
                 }
 
-                Debug.Assert(!_context.IsFormattingDisabled(pairIndex));
+                Debug.Assert(!context.IsFormattingDisabled(pairIndex));
 
                 // well, force it regardless original content
-                _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithLine(operation.Line, indentation, _context, _formattingRules, cancellationToken));
+                context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithLine(operation.Line, indentation, context, formattingRules, cancellationToken));
                 return true;
             }
 
             public bool ApplyPreserveLinesOperation(
                 AdjustNewLinesOperation operation, int pairIndex, CancellationToken cancellationToken)
             {
-                var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
 
                 // okay, check whether there is line between token more than we want
                 // check whether we should force it if it is less than given number
-                var indentation = _context.GetBaseIndentation(_context.TokenStream.GetToken(pairIndex + 1));
+                var indentation = context.GetBaseIndentation(context.TokenStream.GetToken(pairIndex + 1));
                 if (operation.Line > triviaInfo.LineBreaks)
                 {
-                    Debug.Assert(!_context.IsFormattingDisabled(pairIndex));
+                    Debug.Assert(!context.IsFormattingDisabled(pairIndex));
 
                     // alright force them
-                    _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithLine(operation.Line, indentation, _context, _formattingRules, cancellationToken));
+                    context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithLine(operation.Line, indentation, context, formattingRules, cancellationToken));
                     return true;
                 }
 
@@ -215,9 +206,9 @@ public bool ApplyPreserveLinesOperation(
                     // Formatting can only be disabled for entire lines. This block only modifies the line containing
                     // the second token of the current pair, so we only need to check for disabled formatting at the
                     // starting position of the second token of the pair.
-                    Debug.Assert(!_context.IsFormattingDisabled(new TextSpan(_context.TokenStream.GetToken(pairIndex + 1).SpanStart, 0)));
+                    Debug.Assert(!context.IsFormattingDisabled(new TextSpan(context.TokenStream.GetToken(pairIndex + 1).SpanStart, 0)));
 
-                    _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithIndentation(indentation, _context, _formattingRules, cancellationToken));
+                    context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithIndentation(indentation, context, formattingRules, cancellationToken));
                     return true;
                 }
 
@@ -283,7 +274,7 @@ public bool ApplyAlignment(
                         break;
 
                     case AlignTokensOption.AlignIndentationOfTokensToFirstTokenOfBaseTokenLine:
-                        if (!ApplyAlignment(_context.TokenStream.FirstTokenOfBaseTokenLine(operation.BaseToken), operation.Tokens, previousChangesMap, out tokenData, cancellationToken))
+                        if (!ApplyAlignment(context.TokenStream.FirstTokenOfBaseTokenLine(operation.BaseToken), operation.Tokens, previousChangesMap, out tokenData, cancellationToken))
                         {
                             return false;
                         }
@@ -307,14 +298,14 @@ private void ApplyIndentationToAlignWithGivenToken(
             {
                 // rather than having external new changes map, having snapshot concept
                 // in token stream might be easier to understand.
-                var baseSpaceOrIndentation = _context.TokenStream.GetCurrentColumn(token);
+                var baseSpaceOrIndentation = context.TokenStream.GetCurrentColumn(token);
 
                 for (var i = 0; i < list.Count; i++)
                 {
                     var currentToken = list[i];
-                    var previousToken = _context.TokenStream.GetPreviousTokenData(currentToken);
+                    var previousToken = context.TokenStream.GetPreviousTokenData(currentToken);
 
-                    var triviaInfo = _context.TokenStream.GetTriviaData(previousToken, currentToken);
+                    var triviaInfo = context.TokenStream.GetTriviaData(previousToken, currentToken);
                     if (!triviaInfo.SecondTokenIsFirstTokenOnLine)
                     {
                         continue;
@@ -344,20 +335,20 @@ private void ApplyIndentationToGivenPosition(
 
                 // before make any change, check whether spacing is allowed
                 var spanBetweenTokens = TextSpan.FromBounds(previousToken.Token.Span.End, currentToken.Token.SpanStart);
-                if (_context.IsSpacingSuppressed(spanBetweenTokens, triviaInfo.TreatAsElastic))
+                if (context.IsSpacingSuppressed(spanBetweenTokens, triviaInfo.TreatAsElastic))
                 {
                     return;
                 }
 
-                if (_context.IsFormattingDisabled(spanBetweenTokens))
+                if (context.IsFormattingDisabled(spanBetweenTokens))
                 {
                     return;
                 }
 
                 // okay, update indentation
-                _context.TokenStream.ApplyChange(
+                context.TokenStream.ApplyChange(
                     previousToken.IndexInStream,
-                    triviaInfo.WithIndentation(baseSpaceOrIndentation, _context, _formattingRules, cancellationToken));
+                    triviaInfo.WithIndentation(baseSpaceOrIndentation, context, formattingRules, cancellationToken));
             }
 
             private IList<TokenData> GetTokenWithIndices(IEnumerable<SyntaxToken> tokens)
@@ -371,7 +362,7 @@ private IList<TokenData> GetTokenWithIndices(IEnumerable<SyntaxToken> tokens)
                         continue;
                     }
 
-                    var tokenWithIndex = _context.TokenStream.GetTokenData(token);
+                    var tokenWithIndex = context.TokenStream.GetTokenData(token);
                     if (tokenWithIndex.IndexInStream < 0)
                     {
                         // this token is not inside of the formatting span, ignore
@@ -394,7 +385,7 @@ private bool ApplyIndentationChangesToDependentTokens(
 
                     // first check whether the token moved by alignment operation have affected an anchor token. if it has,
                     // then find the last token of that anchor span.
-                    var endAnchorToken = _context.GetEndTokenForAnchorSpan(firstToken);
+                    var endAnchorToken = context.GetEndTokenForAnchorSpan(firstToken);
                     if (endAnchorToken.RawKind == 0)
                     {
                         // this means given token is not anchor token, no need to do anything
@@ -402,10 +393,10 @@ private bool ApplyIndentationChangesToDependentTokens(
                     }
 
                     // first token was anchor token, now find last token with index
-                    var lastToken = _context.TokenStream.GetTokenData(endAnchorToken);
+                    var lastToken = context.TokenStream.GetTokenData(endAnchorToken);
                     if (lastToken.IndexInStream < 0)
                     {
-                        lastToken = _context.TokenStream.LastTokenInStream;
+                        lastToken = context.TokenStream.LastTokenInStream;
                     }
 
                     ApplyBaseTokenIndentationChangesFromTo(firstToken, firstToken, lastToken, newChangesMap, cancellationToken);
@@ -424,14 +415,14 @@ private void ApplyIndentationDeltaFromTo(
                 // can this run parallel? at least finding out all first token on line.
                 for (var pairIndex = firstToken.IndexInStream; pairIndex < lastToken.IndexInStream; pairIndex++)
                 {
-                    var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                    var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
                     if (!triviaInfo.SecondTokenIsFirstTokenOnLine)
                     {
                         continue;
                     }
 
                     // spacing is suppressed. don't change any spacing
-                    if (_context.IsSpacingSuppressed(pairIndex))
+                    if (context.IsSpacingSuppressed(pairIndex))
                     {
                         continue;
                     }
@@ -439,7 +430,7 @@ private void ApplyIndentationDeltaFromTo(
                     // bail fast here.
                     // if an entity is in the map, then it means indentation has been applied to the token pair already.
                     // no reason to do same work again.
-                    var currentToken = _context.TokenStream.GetToken(pairIndex + 1);
+                    var currentToken = context.TokenStream.GetToken(pairIndex + 1);
                     if (previousChangesMap.ContainsKey(currentToken))
                     {
                         continue;
@@ -467,14 +458,14 @@ private void ApplyIndentationDelta(
                     return;
                 }
 
-                Debug.Assert(!_context.IsFormattingDisabled(pairIndex));
+                Debug.Assert(!context.IsFormattingDisabled(pairIndex));
 
                 // record the fact that this pair has been moved
                 Debug.Assert(!previousChangesMap.ContainsKey(currentToken));
                 previousChangesMap.Add(currentToken, triviaInfo.Spaces);
 
                 // okay, update indentation
-                _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithIndentation(indentation, _context, _formattingRules, cancellationToken));
+                context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithIndentation(indentation, context, formattingRules, cancellationToken));
             }
 
             public bool ApplyBaseTokenIndentationChangesFromTo(
@@ -486,9 +477,9 @@ public bool ApplyBaseTokenIndentationChangesFromTo(
             {
                 Contract.ThrowIfFalse(baseToken.RawKind != 0 && startToken.RawKind != 0 && endToken.RawKind != 0);
 
-                var baseTokenWithIndex = _context.TokenStream.GetTokenData(baseToken);
-                var firstTokenWithIndex = _context.TokenStream.GetTokenData(startToken).GetPreviousTokenData();
-                var lastTokenWithIndex = _context.TokenStream.GetTokenData(endToken);
+                var baseTokenWithIndex = context.TokenStream.GetTokenData(baseToken);
+                var firstTokenWithIndex = context.TokenStream.GetTokenData(startToken).GetPreviousTokenData();
+                var lastTokenWithIndex = context.TokenStream.GetTokenData(endToken);
 
                 return ApplyBaseTokenIndentationChangesFromTo(
                     baseTokenWithIndex, firstTokenWithIndex, lastTokenWithIndex, previousChangesMap, cancellationToken);
@@ -521,7 +512,7 @@ private bool ApplyBaseTokenIndentationChangesFromTo(
                     // okay, this token is not moved, check one before me as long as it is on the same line
                     var tokenPairIndex = tokenWithIndex.IndexInStream - 1;
                     if (tokenPairIndex < 0 ||
-                        _context.TokenStream.GetTriviaData(tokenPairIndex).SecondTokenIsFirstTokenOnLine)
+                        context.TokenStream.GetTriviaData(tokenPairIndex).SecondTokenIsFirstTokenOnLine)
                     {
                         return false;
                     }
@@ -536,14 +527,14 @@ private bool ApplyBaseTokenIndentationChangesFromTo(
                 }
 
                 // we are not moved
-                var indentationDelta = _context.GetDeltaFromPreviousChangesMap(tokenWithIndex.Token, previousChangesMap);
+                var indentationDelta = context.GetDeltaFromPreviousChangesMap(tokenWithIndex.Token, previousChangesMap);
                 if (indentationDelta == 0)
                 {
                     return false;
                 }
 
-                startToken = startToken.IndexInStream < 0 ? _context.TokenStream.FirstTokenInStream : startToken;
-                endToken = endToken.IndexInStream < 0 ? _context.TokenStream.LastTokenInStream : endToken;
+                startToken = startToken.IndexInStream < 0 ? context.TokenStream.FirstTokenInStream : startToken;
+                endToken = endToken.IndexInStream < 0 ? context.TokenStream.LastTokenInStream : endToken;
 
                 ApplyIndentationDeltaFromTo(startToken, endToken, indentationDelta, previousChangesMap, cancellationToken);
                 return true;
@@ -552,7 +543,7 @@ private bool ApplyBaseTokenIndentationChangesFromTo(
             public bool ApplyAnchorIndentation(
                 int pairIndex, Dictionary<SyntaxToken, int> previousChangesMap, CancellationToken cancellationToken)
             {
-                var triviaInfo = _context.TokenStream.GetTriviaData(pairIndex);
+                var triviaInfo = context.TokenStream.GetTriviaData(pairIndex);
 
                 if (!triviaInfo.SecondTokenIsFirstTokenOnLine)
                 {
@@ -560,13 +551,13 @@ public bool ApplyAnchorIndentation(
                 }
 
                 // don't apply anchor is spacing is suppressed
-                if (_context.IsSpacingSuppressed(pairIndex))
+                if (context.IsSpacingSuppressed(pairIndex))
                 {
                     return false;
                 }
 
-                var firstTokenOnLine = _context.TokenStream.GetToken(pairIndex + 1);
-                var indentation = triviaInfo.Spaces + _context.GetAnchorDeltaFromOriginalColumn(firstTokenOnLine);
+                var firstTokenOnLine = context.TokenStream.GetToken(pairIndex + 1);
+                var indentation = triviaInfo.Spaces + context.GetAnchorDeltaFromOriginalColumn(firstTokenOnLine);
 
                 if (triviaInfo.Spaces != indentation)
                 {
@@ -574,7 +565,7 @@ public bool ApplyAnchorIndentation(
                     previousChangesMap.Add(firstTokenOnLine, triviaInfo.Spaces);
 
                     // okay, update indentation
-                    _context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithIndentation(indentation, _context, _formattingRules, cancellationToken));
+                    context.TokenStream.ApplyChange(pairIndex, triviaInfo.WithIndentation(indentation, context, formattingRules, cancellationToken));
                     return true;
                 }
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TokenStream.Iterator.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TokenStream.Iterator.cs
index fd8fc491ce50a..8fb0772a22df5 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TokenStream.Iterator.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TokenStream.Iterator.cs
@@ -10,15 +10,10 @@ internal partial class TokenStream
     {
         // gain of having hand written iterator seems about 50-100ms over auto generated one.
         // not sure whether it is worth it. but I already wrote it to test, so going to just keep it.
-        public readonly struct Iterator
+        public readonly struct Iterator(SegmentedList<SyntaxToken> tokensIncludingZeroWidth)
         {
-            private readonly SegmentedList<SyntaxToken> _tokensIncludingZeroWidth;
-
-            public Iterator(SegmentedList<SyntaxToken> tokensIncludingZeroWidth)
-                => _tokensIncludingZeroWidth = tokensIncludingZeroWidth;
-
             public Enumerator GetEnumerator()
-                => new(_tokensIncludingZeroWidth);
+                => new(tokensIncludingZeroWidth);
 
             public struct Enumerator
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TreeData.Debug.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TreeData.Debug.cs
index ccceb9b050a82..be6a6589db203 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TreeData.Debug.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TreeData.Debug.cs
@@ -9,15 +9,9 @@ namespace Microsoft.CodeAnalysis.Formatting
 {
     internal abstract partial class TreeData
     {
-        private class Debug : NodeAndText
+        private class Debug(SyntaxNode root, SourceText text) : NodeAndText(root, text)
         {
-            private readonly TreeData _debugNodeData;
-
-            public Debug(SyntaxNode root, SourceText text)
-                : base(root, text)
-            {
-                _debugNodeData = new Node(root);
-            }
+            private readonly TreeData _debugNodeData = new Node(root);
 
             public override string GetTextBetween(SyntaxToken token1, SyntaxToken token2)
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TriviaDataWithList.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TriviaDataWithList.cs
index 6355f59d66642..e16791e971edc 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TriviaDataWithList.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Engine/TriviaDataWithList.cs
@@ -7,13 +7,8 @@
 
 namespace Microsoft.CodeAnalysis.Formatting
 {
-    internal abstract class TriviaDataWithList : TriviaData
+    internal abstract class TriviaDataWithList(SyntaxFormattingOptions options, string language) : TriviaData(options, language)
     {
-        public TriviaDataWithList(SyntaxFormattingOptions options, string language)
-            : base(options, language)
-        {
-        }
-
         public abstract SyntaxTriviaList GetTriviaList(CancellationToken cancellationToken);
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAlignTokensOperationAction.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAlignTokensOperationAction.cs
index 809441ee6f8b6..5ea039b6f9105 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAlignTokensOperationAction.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAlignTokensOperationAction.cs
@@ -9,39 +9,26 @@
 namespace Microsoft.CodeAnalysis.Formatting.Rules
 {
     [NonDefaultable]
-    internal readonly struct NextAlignTokensOperationAction
+    internal readonly struct NextAlignTokensOperationAction(
+        ImmutableArray<AbstractFormattingRule> formattingRules,
+        int index,
+        SyntaxNode node,
+        List<AlignTokensOperation> list)
     {
-        private readonly ImmutableArray<AbstractFormattingRule> _formattingRules;
-        private readonly int _index;
-        private readonly SyntaxNode _node;
-        private readonly List<AlignTokensOperation> _list;
-
-        public NextAlignTokensOperationAction(
-            ImmutableArray<AbstractFormattingRule> formattingRules,
-            int index,
-            SyntaxNode node,
-            List<AlignTokensOperation> list)
-        {
-            _formattingRules = formattingRules;
-            _index = index;
-            _node = node;
-            _list = list;
-        }
-
         private NextAlignTokensOperationAction NextAction
-            => new(_formattingRules, _index + 1, _node, _list);
+            => new(formattingRules, index + 1, node, list);
 
         public void Invoke()
         {
             // If we have no remaining handlers to execute, then we'll execute our last handler
-            if (_index >= _formattingRules.Length)
+            if (index >= formattingRules.Length)
             {
                 return;
             }
             else
             {
                 // Call the handler at the index, passing a continuation that will come back to here with index + 1
-                _formattingRules[_index].AddAlignTokensOperations(_list, _node, NextAction);
+                formattingRules[index].AddAlignTokensOperations(list, node, NextAction);
                 return;
             }
         }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAnchorIndentationOperationAction.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAnchorIndentationOperationAction.cs
index 977d195e43940..570c300709fba 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAnchorIndentationOperationAction.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextAnchorIndentationOperationAction.cs
@@ -9,39 +9,26 @@
 namespace Microsoft.CodeAnalysis.Formatting.Rules
 {
     [NonDefaultable]
-    internal readonly struct NextAnchorIndentationOperationAction
+    internal readonly struct NextAnchorIndentationOperationAction(
+        ImmutableArray<AbstractFormattingRule> formattingRules,
+        int index,
+        SyntaxNode node,
+        List<AnchorIndentationOperation> list)
     {
-        private readonly ImmutableArray<AbstractFormattingRule> _formattingRules;
-        private readonly int _index;
-        private readonly SyntaxNode _node;
-        private readonly List<AnchorIndentationOperation> _list;
-
-        public NextAnchorIndentationOperationAction(
-            ImmutableArray<AbstractFormattingRule> formattingRules,
-            int index,
-            SyntaxNode node,
-            List<AnchorIndentationOperation> list)
-        {
-            _formattingRules = formattingRules;
-            _index = index;
-            _node = node;
-            _list = list;
-        }
-
         private NextAnchorIndentationOperationAction NextAction
-            => new(_formattingRules, _index + 1, _node, _list);
+            => new(formattingRules, index + 1, node, list);
 
         public void Invoke()
         {
             // If we have no remaining handlers to execute, then we'll execute our last handler
-            if (_index >= _formattingRules.Length)
+            if (index >= formattingRules.Length)
             {
                 return;
             }
             else
             {
                 // Call the handler at the index, passing a continuation that will come back to here with index + 1
-                _formattingRules[_index].AddAnchorIndentationOperations(_list, _node, NextAction);
+                formattingRules[index].AddAnchorIndentationOperations(list, node, NextAction);
                 return;
             }
         }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustNewLinesOperation.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustNewLinesOperation.cs
index 8867ee98cf217..c410167abbde6 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustNewLinesOperation.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustNewLinesOperation.cs
@@ -8,33 +8,24 @@
 namespace Microsoft.CodeAnalysis.Formatting.Rules
 {
     [NonDefaultable]
-    internal readonly struct NextGetAdjustNewLinesOperation
+    internal readonly struct NextGetAdjustNewLinesOperation(
+        ImmutableArray<AbstractFormattingRule> formattingRules,
+        int index)
     {
-        private readonly ImmutableArray<AbstractFormattingRule> _formattingRules;
-        private readonly int _index;
-
-        public NextGetAdjustNewLinesOperation(
-            ImmutableArray<AbstractFormattingRule> formattingRules,
-            int index)
-        {
-            _formattingRules = formattingRules;
-            _index = index;
-        }
-
         private NextGetAdjustNewLinesOperation NextOperation
-            => new(_formattingRules, _index + 1);
+            => new(formattingRules, index + 1);
 
         public AdjustNewLinesOperation? Invoke(in SyntaxToken previousToken, in SyntaxToken currentToken)
         {
             // If we have no remaining handlers to execute, then we'll execute our last handler
-            if (_index >= _formattingRules.Length)
+            if (index >= formattingRules.Length)
             {
                 return null;
             }
             else
             {
                 // Call the handler at the index, passing a continuation that will come back to here with index + 1
-                return _formattingRules[_index].GetAdjustNewLinesOperation(in previousToken, in currentToken, NextOperation);
+                return formattingRules[index].GetAdjustNewLinesOperation(in previousToken, in currentToken, NextOperation);
             }
         }
     }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustSpacesOperation.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustSpacesOperation.cs
index 7642c2d665312..8fc77ca50da25 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustSpacesOperation.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextGetAdjustSpacesOperation.cs
@@ -8,33 +8,24 @@
 namespace Microsoft.CodeAnalysis.Formatting.Rules
 {
     [NonDefaultable]
-    internal readonly struct NextGetAdjustSpacesOperation
+    internal readonly struct NextGetAdjustSpacesOperation(
+        ImmutableArray<AbstractFormattingRule> formattingRules,
+        int index)
     {
-        private readonly ImmutableArray<AbstractFormattingRule> _formattingRules;
-        private readonly int _index;
-
-        public NextGetAdjustSpacesOperation(
-            ImmutableArray<AbstractFormattingRule> formattingRules,
-            int index)
-        {
-            _formattingRules = formattingRules;
-            _index = index;
-        }
-
         private NextGetAdjustSpacesOperation NextOperation
-            => new(_formattingRules, _index + 1);
+            => new(formattingRules, index + 1);
 
         public AdjustSpacesOperation? Invoke(in SyntaxToken previousToken, in SyntaxToken currentToken)
         {
             // If we have no remaining handlers to execute, then we'll execute our last handler
-            if (_index >= _formattingRules.Length)
+            if (index >= formattingRules.Length)
             {
                 return null;
             }
             else
             {
                 // Call the handler at the index, passing a continuation that will come back to here with index + 1
-                return _formattingRules[_index].GetAdjustSpacesOperation(in previousToken, in currentToken, NextOperation);
+                return formattingRules[index].GetAdjustSpacesOperation(in previousToken, in currentToken, NextOperation);
             }
         }
     }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextIndentBlockOperationAction.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextIndentBlockOperationAction.cs
index 43c5495f1319d..1daa18b2606d8 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextIndentBlockOperationAction.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextIndentBlockOperationAction.cs
@@ -9,39 +9,26 @@
 namespace Microsoft.CodeAnalysis.Formatting.Rules
 {
     [NonDefaultable]
-    internal readonly struct NextIndentBlockOperationAction
+    internal readonly struct NextIndentBlockOperationAction(
+        ImmutableArray<AbstractFormattingRule> formattingRules,
+        int index,
+        SyntaxNode node,
+        List<IndentBlockOperation> list)
     {
-        private readonly ImmutableArray<AbstractFormattingRule> _formattingRules;
-        private readonly int _index;
-        private readonly SyntaxNode _node;
-        private readonly List<IndentBlockOperation> _list;
-
-        public NextIndentBlockOperationAction(
-            ImmutableArray<AbstractFormattingRule> formattingRules,
-            int index,
-            SyntaxNode node,
-            List<IndentBlockOperation> list)
-        {
-            _formattingRules = formattingRules;
-            _index = index;
-            _node = node;
-            _list = list;
-        }
-
         private NextIndentBlockOperationAction NextAction
-            => new(_formattingRules, _index + 1, _node, _list);
+            => new(formattingRules, index + 1, node, list);
 
         public void Invoke()
         {
             // If we have no remaining handlers to execute, then we'll execute our last handler
-            if (_index >= _formattingRules.Length)
+            if (index >= formattingRules.Length)
             {
                 return;
             }
             else
             {
                 // Call the handler at the index, passing a continuation that will come back to here with index + 1
-                _formattingRules[_index].AddIndentBlockOperations(_list, _node, NextAction);
+                formattingRules[index].AddIndentBlockOperations(list, node, NextAction);
                 return;
             }
         }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextSuppressOperationAction.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextSuppressOperationAction.cs
index 349dbda54f592..5c1e18873bc8a 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextSuppressOperationAction.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/Rules/NextSuppressOperationAction.cs
@@ -9,39 +9,26 @@
 namespace Microsoft.CodeAnalysis.Formatting.Rules
 {
     [NonDefaultable]
-    internal readonly struct NextSuppressOperationAction
+    internal readonly struct NextSuppressOperationAction(
+        ImmutableArray<AbstractFormattingRule> formattingRules,
+        int index,
+        SyntaxNode node,
+        List<SuppressOperation> list)
     {
-        private readonly ImmutableArray<AbstractFormattingRule> _formattingRules;
-        private readonly int _index;
-        private readonly SyntaxNode _node;
-        private readonly List<SuppressOperation> _list;
-
-        public NextSuppressOperationAction(
-            ImmutableArray<AbstractFormattingRule> formattingRules,
-            int index,
-            SyntaxNode node,
-            List<SuppressOperation> list)
-        {
-            _formattingRules = formattingRules;
-            _index = index;
-            _node = node;
-            _list = list;
-        }
-
         private NextSuppressOperationAction NextAction
-            => new(_formattingRules, _index + 1, _node, _list);
+            => new(formattingRules, index + 1, node, list);
 
         public void Invoke()
         {
             // If we have no remaining handlers to execute, then we'll execute our last handler
-            if (_index >= _formattingRules.Length)
+            if (index >= formattingRules.Length)
             {
                 return;
             }
             else
             {
                 // Call the handler at the index, passing a continuation that will come back to here with index + 1
-                _formattingRules[_index].AddSuppressOperations(_list, _node, NextAction);
+                formattingRules[index].AddSuppressOperations(list, node, NextAction);
                 return;
             }
         }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumn.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumn.cs
index 1d2eba6d515da..134aba94b6fac 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumn.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumn.cs
@@ -4,31 +4,24 @@
 
 namespace Microsoft.CodeAnalysis.Formatting
 {
-    internal readonly struct LineColumn
+    internal readonly struct LineColumn(int line, int column, bool whitespaceOnly)
     {
         public static LineColumn Default = new(line: 0, column: 0, whitespaceOnly: true);
 
         /// <summary>
         /// absolute line number from first token
         /// </summary>
-        public readonly int Line;
+        public readonly int Line = line;
 
         /// <summary>
         /// absolute column from beginning of a line
         /// </summary>
-        public readonly int Column;
+        public readonly int Column = column;
 
         /// <summary>
         /// there is only whitespace on this line
         /// </summary>
-        public readonly bool WhitespaceOnly;
-
-        public LineColumn(int line, int column, bool whitespaceOnly)
-        {
-            Line = line;
-            Column = column;
-            WhitespaceOnly = whitespaceOnly;
-        }
+        public readonly bool WhitespaceOnly = whitespaceOnly;
 
         public LineColumn With(LineColumnDelta delta)
         {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnDelta.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnDelta.cs
index 727539bbae0ef..df4107cab8ce7 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnDelta.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnDelta.cs
@@ -4,38 +4,29 @@
 
 namespace Microsoft.CodeAnalysis.Formatting
 {
-    internal readonly struct LineColumnDelta
+    internal readonly struct LineColumnDelta(int lines, int spaces)
     {
         public static LineColumnDelta Default = new(lines: 0, spaces: 0, whitespaceOnly: true, forceUpdate: false);
 
         /// <summary>
         /// relative line number between calls
         /// </summary>
-        public readonly int Lines;
+        public readonly int Lines = lines;
 
         /// <summary>
         /// relative spaces between calls
         /// </summary>
-        public readonly int Spaces;
+        public readonly int Spaces = spaces;
 
         /// <summary>
         /// there is only whitespace in this space
         /// </summary>
-        public readonly bool WhitespaceOnly;
+        public readonly bool WhitespaceOnly = true;
 
         /// <summary>
         /// force text change regardless line and space changes
         /// </summary>
-        public readonly bool ForceUpdate;
-
-        public LineColumnDelta(int lines, int spaces)
-        {
-            this.Lines = lines;
-            this.Spaces = spaces;
-
-            this.WhitespaceOnly = true;
-            this.ForceUpdate = false;
-        }
+        public readonly bool ForceUpdate = false;
 
         public LineColumnDelta(int lines, int spaces, bool whitespaceOnly)
             : this(lines, spaces)
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnRule.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnRule.cs
index 998497b4e439a..70e55d1ea453f 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnRule.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/LineColumnRule.cs
@@ -4,31 +4,21 @@
 
 namespace Microsoft.CodeAnalysis.Formatting
 {
-    internal readonly struct LineColumnRule
+    internal readonly struct LineColumnRule(
+LineColumnRule.SpaceOperations spaceOperation,
+LineColumnRule.LineOperations lineOperation,
+LineColumnRule.IndentationOperations indentationOperation,
+        int lines,
+        int spaces,
+        int indentation)
     {
-        public readonly SpaceOperations SpaceOperation;
-        public readonly LineOperations LineOperation;
-        public readonly IndentationOperations IndentationOperation;
-
-        public readonly int Lines;
-        public readonly int Spaces;
-        public readonly int Indentation;
-
-        public LineColumnRule(
-            SpaceOperations spaceOperation,
-            LineOperations lineOperation,
-            IndentationOperations indentationOperation,
-            int lines,
-            int spaces,
-            int indentation)
-        {
-            SpaceOperation = spaceOperation;
-            LineOperation = lineOperation;
-            IndentationOperation = indentationOperation;
-            Lines = lines;
-            Spaces = spaces;
-            Indentation = indentation;
-        }
+        public readonly SpaceOperations SpaceOperation = spaceOperation;
+        public readonly LineOperations LineOperation = lineOperation;
+        public readonly IndentationOperations IndentationOperation = indentationOperation;
+
+        public readonly int Lines = lines;
+        public readonly int Spaces = spaces;
+        public readonly int Indentation = indentation;
 
         public LineColumnRule With(int? lines = null, int? spaces = null, int? indentation = null, LineOperations? lineOperation = null, SpaceOperations? spaceOperation = null, IndentationOperations? indentationOperation = null)
             => new(
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/TriviaList.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/TriviaList.cs
index a567feed689f9..fa0dcfbc22333 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/TriviaList.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Formatting/TriviaEngine/TriviaList.cs
@@ -4,16 +4,10 @@
 
 namespace Microsoft.CodeAnalysis.Formatting
 {
-    internal readonly struct TriviaList
+    internal readonly struct TriviaList(SyntaxTriviaList list1, SyntaxTriviaList list2)
     {
-        private readonly SyntaxTriviaList _list1;
-        private readonly SyntaxTriviaList _list2;
-
-        public TriviaList(SyntaxTriviaList list1, SyntaxTriviaList list2)
-        {
-            _list1 = list1;
-            _list2 = list2;
-        }
+        private readonly SyntaxTriviaList _list1 = list1;
+        private readonly SyntaxTriviaList _list2 = list2;
 
         public int Count => _list1.Count + _list2.Count;
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Helpers/RemoveUnnecessaryImports/AbstractUnnecessaryImportsProvider.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Helpers/RemoveUnnecessaryImports/AbstractUnnecessaryImportsProvider.cs
index bff5179c55721..7510e3d731290 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Helpers/RemoveUnnecessaryImports/AbstractUnnecessaryImportsProvider.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Helpers/RemoveUnnecessaryImports/AbstractUnnecessaryImportsProvider.cs
@@ -29,7 +29,7 @@ public ImmutableArray<TSyntaxNode> GetUnnecessaryImports(
             if (span.HasValue)
             {
                 // Bail out if there are no usings/imports in the filter span.
-                var node = model.SyntaxTree.GetNodeForSpan(span, findInTrivia: false, getInnermostNodeForTie: false, cancellationToken);
+                var node = model.SyntaxTree.FindNode(span, findInTrivia: false, getInnermostNodeForTie: false, cancellationToken);
                 if (node.FirstAncestorOrSelf<TSyntaxNode>() is null)
                     return ImmutableArray<TSyntaxNode>.Empty;
             }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/FunctionId.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/FunctionId.cs
index fb265dad84e82..3797e50636776 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/FunctionId.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/FunctionId.cs
@@ -594,5 +594,27 @@ internal enum FunctionId
 
         // 680-690 LSP Initialization info ids.
         LSP_Initialize = 680,
+
+        // 700-799 Performance logging. Typically pairs with Delay/Summary values.
+        //  Summary is a aggregation of all times collected.
+        //  Delay is used as a non-aggregated value for an unexpectedly poor performing scenario.
+        CodeFix_Delay = 700,
+        CodeFix_Summary = 701,
+
+        CodeRefactoring_Delay = 710,
+        CodeRefactoring_Summary = 711,
+
+        PerformAnalysis_Delay = 720,
+        PerformAnalysis_Summary = 721,
+
+        RequestDiagnostics_Delay = 730,
+        RequestDiagnostics_Summary = 731,
+
+        SuggestedAction_Delay = 740,
+        SuggestedAction_Summary = 741,
+        SuggestedAction_Application_Delay = 742,
+        SuggestedAction_Application_Summary = 743,
+        SuggestedAction_Preview_Delay = 744,
+        SuggestedAction_Preview_Summary = 745,
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/Logger.LogBlock.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/Logger.LogBlock.cs
index 84f2be87c7de4..4a81d3c1207b1 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/Logger.LogBlock.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Log/Logger.LogBlock.cs
@@ -29,9 +29,8 @@ private static IDisposable CreateLogBlock(FunctionId functionId, LogMessage mess
         /// This tracks the logged message. On instantiation, it logs 'Started block' with other event data.
         /// On dispose, it logs 'Ended block' with the same event data so we can track which block started and ended when looking at logs.
         /// </summary>
-        private class RoslynLogBlock : IDisposable
+        private class RoslynLogBlock(ObjectPool<RoslynLogBlock> pool) : IDisposable
         {
-            private readonly ObjectPool<RoslynLogBlock> _pool;
 
             // these need to be cleared before putting back to pool
             private ILogger? _logger;
@@ -42,9 +41,6 @@ private class RoslynLogBlock : IDisposable
             private int _tick;
             private int _blockId;
 
-            public RoslynLogBlock(ObjectPool<RoslynLogBlock> pool)
-                => _pool = pool;
-
             public void Construct(ILogger logger, FunctionId functionId, LogMessage logMessage, int blockId, CancellationToken cancellationToken)
             {
                 _logger = logger;
@@ -77,7 +73,7 @@ public void Dispose()
                 _logger = null;
                 _cancellationToken = default;
 
-                _pool.Free(this);
+                pool.Free(this);
             }
         }
     }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingRule.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingRule.cs
index bd378ffe4efd1..2094e21802731 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingRule.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingRule.cs
@@ -8,17 +8,10 @@
 
 namespace Microsoft.CodeAnalysis.Diagnostics.Analyzers.NamingStyles
 {
-    internal readonly struct NamingRule
+    internal readonly struct NamingRule(SymbolSpecification symbolSpecification, NamingStyle namingStyle, ReportDiagnostic enforcementLevel)
     {
-        public readonly SymbolSpecification SymbolSpecification;
-        public readonly NamingStyle NamingStyle;
-        public readonly ReportDiagnostic EnforcementLevel;
-
-        public NamingRule(SymbolSpecification symbolSpecification, NamingStyle namingStyle, ReportDiagnostic enforcementLevel)
-        {
-            SymbolSpecification = symbolSpecification;
-            NamingStyle = namingStyle;
-            EnforcementLevel = enforcementLevel;
-        }
+        public readonly SymbolSpecification SymbolSpecification = symbolSpecification;
+        public readonly NamingStyle NamingStyle = namingStyle;
+        public readonly ReportDiagnostic EnforcementLevel = enforcementLevel;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyle.WordSpanEnumerable.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyle.WordSpanEnumerable.cs
index 002f122a32965..35185d8055050 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyle.WordSpanEnumerable.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyle.WordSpanEnumerable.cs
@@ -10,21 +10,10 @@ namespace Microsoft.CodeAnalysis.NamingStyles
 {
     internal partial record struct NamingStyle
     {
-        private readonly struct WordSpanEnumerable
+        private readonly struct WordSpanEnumerable(string name, TextSpan nameSpan, string wordSeparator)
         {
-            private readonly string _name;
-            private readonly TextSpan _nameSpan;
-            private readonly string _wordSeparator;
-
-            public WordSpanEnumerable(string name, TextSpan nameSpan, string wordSeparator)
-            {
-                _name = name;
-                _nameSpan = nameSpan;
-                _wordSeparator = wordSeparator;
-            }
-
             public WordSpanEnumerator GetEnumerator()
-                => new(_name, _nameSpan, _wordSeparator);
+                => new(name, nameSpan, wordSeparator);
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyleRules.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyleRules.cs
index b03ed854586c5..6903f5d38b352 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyleRules.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/NamingStyleRules.cs
@@ -10,9 +10,9 @@
 
 namespace Microsoft.CodeAnalysis.Diagnostics.Analyzers.NamingStyles
 {
-    internal class NamingStyleRules
+    internal class NamingStyleRules(ImmutableArray<NamingRule> namingRules)
     {
-        public ImmutableArray<NamingRule> NamingRules { get; }
+        public ImmutableArray<NamingRule> NamingRules { get; } = namingRules;
 
         private readonly ImmutableArray<SymbolKind> _symbolKindsThatCanBeOverridden =
             ImmutableArray.Create(
@@ -20,9 +20,6 @@ internal class NamingStyleRules
                 SymbolKind.Property,
                 SymbolKind.Event);
 
-        public NamingStyleRules(ImmutableArray<NamingRule> namingRules)
-            => NamingRules = namingRules;
-
         internal bool TryGetApplicableRule(ISymbol symbol, out NamingRule applicableRule)
         {
             if (NamingRules != null &&
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/MutableNamingStyle.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/MutableNamingStyle.cs
index b1a28c50f8db9..403ec5d491c62 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/MutableNamingStyle.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/MutableNamingStyle.cs
@@ -9,9 +9,9 @@
 
 namespace Microsoft.CodeAnalysis.Diagnostics.Analyzers.NamingStyles
 {
-    internal class MutableNamingStyle
+    internal class MutableNamingStyle(NamingStyle namingStyle)
     {
-        public NamingStyle NamingStyle { get; private set; }
+        public NamingStyle NamingStyle { get; private set; } = namingStyle;
 
         public Guid ID => NamingStyle.ID;
 
@@ -50,9 +50,6 @@ public MutableNamingStyle()
         {
         }
 
-        public MutableNamingStyle(NamingStyle namingStyle)
-            => NamingStyle = namingStyle;
-
         internal MutableNamingStyle Clone()
             => new(NamingStyle);
     }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/SymbolSpecification.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/SymbolSpecification.cs
index c25c355f299ac..846293b07d41a 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/SymbolSpecification.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/NamingStyles/Serialization/SymbolSpecification.cs
@@ -25,38 +25,29 @@ namespace Microsoft.CodeAnalysis.Diagnostics.Analyzers.NamingStyles
 {
     [DataContract]
     [DebuggerDisplay("{GetDebuggerDisplay(),nq}")]
-    internal sealed class SymbolSpecification : IEquatable<SymbolSpecification>, IObjectWritable
+    internal sealed class SymbolSpecification(
+        Guid id,
+        string name,
+        ImmutableArray<SymbolSpecification.SymbolKindOrTypeKind> symbolKindList,
+        ImmutableArray<Accessibility> accessibilityList = default,
+        ImmutableArray<SymbolSpecification.ModifierKind> modifiers = default) : IEquatable<SymbolSpecification>, IObjectWritable
     {
         private static readonly SymbolSpecification DefaultSymbolSpecificationTemplate = CreateDefaultSymbolSpecification();
 
         [DataMember(Order = 0)]
-        public Guid ID { get; }
+        public Guid ID { get; } = id;
 
         [DataMember(Order = 1)]
-        public string Name { get; }
+        public string Name { get; } = name;
 
         [DataMember(Order = 2)]
-        public ImmutableArray<SymbolKindOrTypeKind> ApplicableSymbolKindList { get; }
+        public ImmutableArray<SymbolKindOrTypeKind> ApplicableSymbolKindList { get; } = symbolKindList.IsDefault ? DefaultSymbolSpecificationTemplate.ApplicableSymbolKindList : symbolKindList;
 
         [DataMember(Order = 3)]
-        public ImmutableArray<Accessibility> ApplicableAccessibilityList { get; }
+        public ImmutableArray<Accessibility> ApplicableAccessibilityList { get; } = accessibilityList.IsDefault ? DefaultSymbolSpecificationTemplate.ApplicableAccessibilityList : accessibilityList;
 
         [DataMember(Order = 4)]
-        public ImmutableArray<ModifierKind> RequiredModifierList { get; }
-
-        public SymbolSpecification(
-            Guid id,
-            string name,
-            ImmutableArray<SymbolKindOrTypeKind> symbolKindList,
-            ImmutableArray<Accessibility> accessibilityList = default,
-            ImmutableArray<ModifierKind> modifiers = default)
-        {
-            ID = id;
-            Name = name;
-            ApplicableSymbolKindList = symbolKindList.IsDefault ? DefaultSymbolSpecificationTemplate.ApplicableSymbolKindList : symbolKindList;
-            ApplicableAccessibilityList = accessibilityList.IsDefault ? DefaultSymbolSpecificationTemplate.ApplicableAccessibilityList : accessibilityList;
-            RequiredModifierList = modifiers.IsDefault ? DefaultSymbolSpecificationTemplate.RequiredModifierList : modifiers;
-        }
+        public ImmutableArray<ModifierKind> RequiredModifierList { get; } = modifiers.IsDefault ? DefaultSymbolSpecificationTemplate.RequiredModifierList : modifiers;
 
         private string GetDebuggerDisplay()
             => Name;
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/ObjectPools/PooledDisposer.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/ObjectPools/PooledDisposer.cs
index 337358e4cda92..0f7c919e026e1 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/ObjectPools/PooledDisposer.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/ObjectPools/PooledDisposer.cs
@@ -8,15 +8,10 @@
 namespace Microsoft.CodeAnalysis.PooledObjects
 {
     [NonCopyable]
-    internal readonly struct PooledDisposer<TPoolable> : IDisposable
+    internal readonly struct PooledDisposer<TPoolable>(TPoolable instance) : IDisposable
         where TPoolable : class, IPooled
     {
-        private readonly TPoolable _pooledObject;
-
-        public PooledDisposer(TPoolable instance)
-            => _pooledObject = instance;
-
         void IDisposable.Dispose()
-            => _pooledObject?.Free();
+            => instance?.Free();
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/EditorConfigValueSerializer`1.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/EditorConfigValueSerializer`1.cs
index cfb2d1fc095ad..e1083e0e40f95 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/EditorConfigValueSerializer`1.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/EditorConfigValueSerializer`1.cs
@@ -12,25 +12,15 @@ namespace Microsoft.CodeAnalysis.Options
     /// <summary>
     /// Specifies that an option should be read from an .editorconfig file.
     /// </summary>
-    internal sealed class EditorConfigValueSerializer<T> : IEditorConfigValueSerializer
+    internal sealed class EditorConfigValueSerializer<T>(
+        Func<string, Optional<T>> parseValue,
+        Func<T, string> serializeValue) : IEditorConfigValueSerializer
     {
         public static readonly EditorConfigValueSerializer<T> Unsupported = new(
             parseValue: _ => throw new NotSupportedException("Option does not support serialization to editorconfig format"),
             serializeValue: _ => throw new NotSupportedException("Option does not support serialization to editorconfig format"));
-
-        private readonly Func<string, Optional<T>> _parseValue;
-        private readonly Func<T, string> _serializeValue;
-
         private readonly ConcurrentDictionary<string, Optional<T>> _cachedValues = new();
 
-        public EditorConfigValueSerializer(
-            Func<string, Optional<T>> parseValue,
-            Func<T, string> serializeValue)
-        {
-            _parseValue = parseValue;
-            _serializeValue = serializeValue;
-        }
-
         bool IEditorConfigValueSerializer.TryParse(string value, out object? result)
         {
             if (TryParseValue(value, out var typedResult))
@@ -45,7 +35,7 @@ bool IEditorConfigValueSerializer.TryParse(string value, out object? result)
 
         internal bool TryParseValue(string value, [MaybeNullWhen(false)] out T result)
         {
-            var optionalValue = _cachedValues.GetOrAdd(value, _parseValue);
+            var optionalValue = _cachedValues.GetOrAdd(value, parseValue);
             if (optionalValue.HasValue)
             {
                 result = optionalValue.Value;
@@ -60,7 +50,7 @@ internal bool TryParseValue(string value, [MaybeNullWhen(false)] out T result)
 
         public string GetEditorConfigStringValue(T value)
         {
-            var editorConfigStringForValue = _serializeValue(value);
+            var editorConfigStringForValue = serializeValue(value);
             Contract.ThrowIfTrue(RoslynString.IsNullOrEmpty(editorConfigStringForValue));
             return editorConfigStringForValue;
         }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/IOptionReader.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/IOptionReader.cs
index 1d3a60418f6c8..249b399bd8c17 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/IOptionReader.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/IOptionReader.cs
@@ -16,14 +16,9 @@ internal interface IOptionsReader
     bool TryGetOption<T>(OptionKey2 optionKey, out T value);
 }
 
-internal sealed class AnalyzerConfigOptionsReader : IOptionsReader
+internal sealed class AnalyzerConfigOptionsReader(AnalyzerConfigOptions options) : IOptionsReader
 {
-    public readonly AnalyzerConfigOptions Options;
-
-    public AnalyzerConfigOptionsReader(AnalyzerConfigOptions options)
-    {
-        Options = options;
-    }
+    public readonly AnalyzerConfigOptions Options = options;
 
     public bool TryGetOption<T>(OptionKey2 optionKey, out T value)
         => Options.TryGetEditorConfigOption(optionKey.Option, out value);
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/InternalOptionStorageMapping.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/InternalOptionStorageMapping.cs
index 7435c45e6929c..801e96425ac41 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/InternalOptionStorageMapping.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/InternalOptionStorageMapping.cs
@@ -8,15 +8,12 @@ namespace Microsoft.CodeAnalysis.Options;
 /// Some options store their values in a type that's not accessible publicly.
 /// The mapping provides translation between the two representations.
 /// </summary>
-internal abstract class OptionStorageMapping
+internal abstract class OptionStorageMapping(IOption2 internalOption)
 {
     /// <summary>
     /// The option that stores the value internally.
     /// </summary>
-    public IOption2 InternalOption { get; }
-
-    public OptionStorageMapping(IOption2 internalOption)
-        => InternalOption = internalOption;
+    public IOption2 InternalOption { get; } = internalOption;
 
     /// <summary>
     /// Converts inernal option value representation to public.
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionDefinition.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionDefinition.cs
index ffd43e4502011..24c76a80ea24d 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionDefinition.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionDefinition.cs
@@ -97,23 +97,16 @@ public static bool IsSupportedOptionType(Type type)
                type == typeof(ImmutableArray<long>);
     }
 
-    internal sealed class OptionDefinition<T> : OptionDefinition
+    internal sealed class OptionDefinition<T>(
+        T defaultValue,
+        EditorConfigValueSerializer<T>? serializer,
+        OptionGroup? group,
+        string configName,
+        OptionStorageMapping? storageMapping,
+        bool isEditorConfigOption) : OptionDefinition(group, configName, defaultValue, storageMapping, isEditorConfigOption)
     {
-        public new T DefaultValue { get; }
-        public new EditorConfigValueSerializer<T> Serializer { get; }
-
-        public OptionDefinition(
-            T defaultValue,
-            EditorConfigValueSerializer<T>? serializer,
-            OptionGroup? group,
-            string configName,
-            OptionStorageMapping? storageMapping,
-            bool isEditorConfigOption)
-            : base(group, configName, defaultValue, storageMapping, isEditorConfigOption)
-        {
-            DefaultValue = defaultValue;
-            Serializer = serializer ?? EditorConfigValueSerializer.Default<T>();
-        }
+        public new T DefaultValue { get; } = defaultValue;
+        public new EditorConfigValueSerializer<T> Serializer { get; } = serializer ?? EditorConfigValueSerializer.Default<T>();
 
         public override Type Type
             => typeof(T);
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionGroup.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionGroup.cs
index b32932097274c..ddb4628f7fd84 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionGroup.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/OptionGroup.cs
@@ -9,36 +9,28 @@ namespace Microsoft.CodeAnalysis.Options
     /// <summary>
     /// Group/sub-feature associated with an option.
     /// </summary>
-    internal sealed class OptionGroup
+    internal sealed class OptionGroup(string name, string description, int priority = int.MaxValue, OptionGroup? parent = null)
     {
         public static readonly OptionGroup Default = new(string.Empty, string.Empty, int.MaxValue);
 
-        public OptionGroup(string name, string description, int priority = int.MaxValue, OptionGroup? parent = null)
-        {
-            Description = description;
-            Priority = priority;
-            Parent = parent;
-            Name = name;
-        }
-
         /// <summary>
         /// Optional parent group.
         /// </summary>
-        public OptionGroup? Parent { get; }
+        public OptionGroup? Parent { get; } = parent;
 
         /// <summary>
         /// A localizable resource description string for the option group.
         /// </summary>
-        public string Description { get; }
+        public string Description { get; } = description;
 
         /// <summary>
         /// Name of the option group
         /// </summary>
-        public string Name { get; }
+        public string Name { get; } = name;
 
         /// <summary>
         /// Relative priority of the option group with respect to other option groups within the same feature.
         /// </summary>
-        public int Priority { get; }
+        public int Priority { get; } = priority;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/PublicOptionFactory.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/PublicOptionFactory.cs
index 170fdd0d2d5df..920bc71a34801 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/PublicOptionFactory.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Options/PublicOptionFactory.cs
@@ -37,23 +37,13 @@ public static PerLanguageOption2<CodeStyleOption2<T>> WithPublicOption<T>(this P
 #pragma warning restore
 #else
 #pragma warning disable RS0030 // Do not used banned APIs: Option<T>, PerLanguageOption<T>
-    private sealed class StorageMapping : OptionStorageMapping
+    private sealed class StorageMapping(IOption2 internalOption, Func<object?, object?> toPublicValue, Func<object?, object?> toInternalValue) : OptionStorageMapping(internalOption)
     {
-        private readonly Func<object?, object?> _toPublicValue;
-        private readonly Func<object?, object?> _toInternalValue;
-
-        public StorageMapping(IOption2 internalOption, Func<object?, object?> toPublicValue, Func<object?, object?> toInternalValue)
-            : base(internalOption)
-        {
-            _toPublicValue = toPublicValue;
-            _toInternalValue = toInternalValue;
-        }
-
         public override object? ToPublicOptionValue(object? internalValue)
-            => _toPublicValue(internalValue);
+            => toPublicValue(internalValue);
 
         public override object? UpdateInternalOptionValue(object? currentInternalValue, object? newPublicValue)
-            => _toInternalValue(newPublicValue);
+            => toInternalValue(newPublicValue);
     }
 
     private static OptionDefinition<TPublicValue> ToPublicOptionDefinition<T, TPublicValue>(this OptionDefinition<T> definition, IOption2 internalOption, Func<T, TPublicValue> toPublicValue, Func<TPublicValue, T> toInternalValue)
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ExternalSourceInfo.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ExternalSourceInfo.cs
index ed9952eed6a42..2901b52459e8a 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ExternalSourceInfo.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ExternalSourceInfo.cs
@@ -6,15 +6,9 @@
 
 namespace Microsoft.CodeAnalysis.LanguageService
 {
-    internal readonly struct ExternalSourceInfo
+    internal readonly struct ExternalSourceInfo(int? startLine, bool ends)
     {
-        public readonly int? StartLine;
-        public readonly bool Ends;
-
-        public ExternalSourceInfo(int? startLine, bool ends)
-        {
-            this.StartLine = startLine;
-            this.Ends = ends;
-        }
+        public readonly int? StartLine = startLine;
+        public readonly bool Ends = ends;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxFactsExtensions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxFactsExtensions.cs
index 71017634ed37c..322e028bc75c9 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxFactsExtensions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxFactsExtensions.cs
@@ -895,6 +895,9 @@ public static bool IsExpressionStatement(this ISyntaxFacts syntaxFacts, [NotNull
         public static bool IsForEachStatement(this ISyntaxFacts syntaxFacts, [NotNullWhen(true)] SyntaxNode? node)
             => node?.RawKind == syntaxFacts.SyntaxKinds.ForEachStatement;
 
+        public static bool IsForStatement(this ISyntaxFacts syntaxFacts, [NotNullWhen(true)] SyntaxNode? node)
+            => node?.RawKind == syntaxFacts.SyntaxKinds.ForStatement;
+
         public static bool IsIfStatement(this ISyntaxFacts syntaxFacts, [NotNullWhen(true)] SyntaxNode? node)
             => node?.RawKind == syntaxFacts.SyntaxKinds.IfStatement;
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxKinds.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxKinds.cs
index 65afa53adc726..845bb8f2ddbb1 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxKinds.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxKinds.cs
@@ -178,6 +178,7 @@ internal interface ISyntaxKinds
 
         int ExpressionStatement { get; }
         int ForEachStatement { get; }
+        int ForStatement { get; }
         int IfStatement { get; }
         int LocalDeclarationStatement { get; }
         int? LocalFunctionStatement { get; }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.ComparisonOptions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.ComparisonOptions.cs
index df85fe3fd88dd..30a02677953cf 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.ComparisonOptions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.ComparisonOptions.cs
@@ -8,7 +8,7 @@ namespace Microsoft.CodeAnalysis
 {
     internal partial struct SymbolKey
     {
-        private readonly struct ComparisonOptions
+        private readonly struct ComparisonOptions(bool ignoreCase, bool ignoreAssemblyKeys)
         {
             [Flags]
             private enum Option : byte
@@ -18,14 +18,9 @@ private enum Option : byte
                 IgnoreAssemblyKeys = 0x2,
             }
 
-            private readonly Option _flags;
-
-            public ComparisonOptions(bool ignoreCase, bool ignoreAssemblyKeys)
-            {
-                _flags =
+            private readonly Option _flags =
                     BoolToOption(ignoreCase, Option.IgnoreCase) |
                     BoolToOption(ignoreAssemblyKeys, Option.IgnoreAssemblyKeys);
-            }
 
             public bool IgnoreCase => (_flags & Option.IgnoreCase) == Option.IgnoreCase;
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.SymbolKeyReader.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.SymbolKeyReader.cs
index 1826bd1cfed1f..e8de3a3151e00 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.SymbolKeyReader.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.SymbolKeyReader.cs
@@ -438,34 +438,16 @@ private void PopContextualSymbol(ISymbol? contextualSymbol)
             public ISymbol? CurrentContextualSymbol
                 => _contextualSymbolStack.Count == 0 ? null : _contextualSymbolStack.Peek();
 
-            public readonly ref struct MethodPopper
+            public readonly ref struct MethodPopper(SymbolKeyReader reader, IMethodSymbol? method)
             {
-                private readonly SymbolKeyReader _reader;
-                private readonly IMethodSymbol? _method;
-
-                public MethodPopper(SymbolKeyReader reader, IMethodSymbol? method)
-                {
-                    _reader = reader;
-                    _method = method;
-                }
-
                 public void Dispose()
-                    => _reader.PopMethod(_method);
+                    => reader.PopMethod(method);
             }
 
-            public readonly ref struct ContextualSymbolPopper
+            public readonly ref struct ContextualSymbolPopper(SymbolKeyReader reader, ISymbol? contextualSymbol)
             {
-                private readonly SymbolKeyReader _reader;
-                private readonly ISymbol? _contextualSymbol;
-
-                public ContextualSymbolPopper(SymbolKeyReader reader, ISymbol? contextualSymbol)
-                {
-                    _reader = reader;
-                    _contextualSymbol = contextualSymbol;
-                }
-
                 public void Dispose()
-                    => _reader.PopContextualSymbol(_contextualSymbol);
+                    => reader.PopContextualSymbol(contextualSymbol);
             }
 
             internal SyntaxTree? GetSyntaxTree(string filePath)
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.cs
index 2590702ff28c1..8c9156344405c 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/SymbolKey/SymbolKey.cs
@@ -107,7 +107,7 @@ namespace Microsoft.CodeAnalysis
     /// </para>
     /// </summary>
     [DataContract]
-    internal partial struct SymbolKey : IEquatable<SymbolKey>
+    internal partial struct SymbolKey(string data) : IEquatable<SymbolKey>
     {
         /// <summary>
         /// Current format version.  Any time we change anything about our format, we should
@@ -118,15 +118,7 @@ internal partial struct SymbolKey : IEquatable<SymbolKey>
         internal const int FormatVersion = 5;
 
         [DataMember(Order = 0)]
-        private readonly string _symbolKeyData;
-
-        /// <summary>
-        /// Constructs a new <see cref="SymbolKey"/> using the result of a previous call to
-        /// <see cref="ToString()"/> from this same session.  Instantiating with a string 
-        /// from any other source is not supported.
-        /// </summary>
-        public SymbolKey(string data)
-            => _symbolKeyData = data ?? throw new ArgumentNullException(nameof(data));
+        private readonly string _symbolKeyData = data ?? throw new ArgumentNullException(nameof(data));
 
         /// <summary>
         /// Constructs a new <see cref="SymbolKey"/> representing the provided <paramref name="symbol"/>.
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AnnotationTable.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AnnotationTable.cs
index c1fe7b3f74a61..b162a803b5414 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AnnotationTable.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AnnotationTable.cs
@@ -24,18 +24,13 @@ namespace Roslyn.Utilities
     /// 
     /// also, note that this table is not thread safe.
     /// </summary>
-    internal class AnnotationTable<TAnnotation> where TAnnotation : class
+    internal class AnnotationTable<TAnnotation>(string annotationKind) where TAnnotation : class
     {
         private int _globalId;
 
         private readonly Dictionary<TAnnotation, SyntaxAnnotation> _realAnnotationMap = new();
         private readonly Dictionary<string, TAnnotation> _annotationMap = new();
 
-        private readonly string _annotationKind;
-
-        public AnnotationTable(string annotationKind)
-            => _annotationKind = annotationKind;
-
         private IEnumerable<SyntaxAnnotation> GetOrCreateRealAnnotations(TAnnotation[] annotations)
         {
             foreach (var annotation in annotations)
@@ -51,7 +46,7 @@ private SyntaxAnnotation GetOrCreateRealAnnotation(TAnnotation annotation)
                 var id = Interlocked.Increment(ref _globalId);
                 var idString = id.ToString();
 
-                realAnnotation = new SyntaxAnnotation(_annotationKind, idString);
+                realAnnotation = new SyntaxAnnotation(annotationKind, idString);
                 _annotationMap.Add(idString, annotation);
                 _realAnnotationMap.Add(annotation, realAnnotation);
             }
@@ -114,16 +109,16 @@ private IEnumerable<TAnnotation> GetAnnotations(IEnumerable<SyntaxAnnotation> re
         }
 
         public IEnumerable<TAnnotation> GetAnnotations(SyntaxNode node)
-            => GetAnnotations(node.GetAnnotations(_annotationKind));
+            => GetAnnotations(node.GetAnnotations(annotationKind));
 
         public IEnumerable<TAnnotation> GetAnnotations(SyntaxToken token)
-            => GetAnnotations(token.GetAnnotations(_annotationKind));
+            => GetAnnotations(token.GetAnnotations(annotationKind));
 
         public IEnumerable<TAnnotation> GetAnnotations(SyntaxTrivia trivia)
-            => GetAnnotations(trivia.GetAnnotations(_annotationKind));
+            => GetAnnotations(trivia.GetAnnotations(annotationKind));
 
         public IEnumerable<TAnnotation> GetAnnotations(SyntaxNodeOrToken nodeOrToken)
-            => GetAnnotations(nodeOrToken.GetAnnotations(_annotationKind));
+            => GetAnnotations(nodeOrToken.GetAnnotations(annotationKind));
 
         public IEnumerable<TSpecificAnnotation> GetAnnotations<TSpecificAnnotation>(SyntaxNode node) where TSpecificAnnotation : TAnnotation
             => this.GetAnnotations(node).OfType<TSpecificAnnotation>();
@@ -138,16 +133,16 @@ public IEnumerable<TSpecificAnnotation> GetAnnotations<TSpecificAnnotation>(Synt
             => this.GetAnnotations(nodeOrToken).OfType<TSpecificAnnotation>();
 
         public bool HasAnnotations(SyntaxNode node)
-            => node.HasAnnotations(_annotationKind);
+            => node.HasAnnotations(annotationKind);
 
         public bool HasAnnotations(SyntaxToken token)
-            => token.HasAnnotations(_annotationKind);
+            => token.HasAnnotations(annotationKind);
 
         public bool HasAnnotations(SyntaxTrivia trivia)
-            => trivia.HasAnnotations(_annotationKind);
+            => trivia.HasAnnotations(annotationKind);
 
         public bool HasAnnotations(SyntaxNodeOrToken nodeOrToken)
-            => nodeOrToken.HasAnnotations(_annotationKind);
+            => nodeOrToken.HasAnnotations(annotationKind);
 
         public bool HasAnnotations<TSpecificAnnotation>(SyntaxNode node) where TSpecificAnnotation : TAnnotation
             => this.GetAnnotations(node).OfType<TSpecificAnnotation>().Any();
@@ -174,27 +169,27 @@ public bool HasAnnotation(SyntaxNodeOrToken nodeOrToken, TAnnotation annotation)
             => nodeOrToken.HasAnnotation(this.GetRealAnnotation(annotation));
 
         public IEnumerable<SyntaxNodeOrToken> GetAnnotatedNodesAndTokens(SyntaxNode node)
-            => node.GetAnnotatedNodesAndTokens(_annotationKind);
+            => node.GetAnnotatedNodesAndTokens(annotationKind);
 
         public IEnumerable<SyntaxNode> GetAnnotatedNodes(SyntaxNode node)
-            => node.GetAnnotatedNodesAndTokens(_annotationKind).Where(nt => nt.IsNode).Select(nt => nt.AsNode()!);
+            => node.GetAnnotatedNodesAndTokens(annotationKind).Where(nt => nt.IsNode).Select(nt => nt.AsNode()!);
 
         public IEnumerable<SyntaxToken> GetAnnotatedTokens(SyntaxNode node)
-            => node.GetAnnotatedNodesAndTokens(_annotationKind).Where(nt => nt.IsToken).Select(nt => nt.AsToken());
+            => node.GetAnnotatedNodesAndTokens(annotationKind).Where(nt => nt.IsToken).Select(nt => nt.AsToken());
 
         public IEnumerable<SyntaxTrivia> GetAnnotatedTrivia(SyntaxNode node)
-            => node.GetAnnotatedTrivia(_annotationKind);
+            => node.GetAnnotatedTrivia(annotationKind);
 
         public IEnumerable<SyntaxNodeOrToken> GetAnnotatedNodesAndTokens<TSpecificAnnotation>(SyntaxNode node) where TSpecificAnnotation : TAnnotation
-            => node.GetAnnotatedNodesAndTokens(_annotationKind).Where(this.HasAnnotations<TSpecificAnnotation>);
+            => node.GetAnnotatedNodesAndTokens(annotationKind).Where(this.HasAnnotations<TSpecificAnnotation>);
 
         public IEnumerable<SyntaxNode> GetAnnotatedNodes<TSpecificAnnotation>(SyntaxNode node) where TSpecificAnnotation : TAnnotation
-            => node.GetAnnotatedNodesAndTokens(_annotationKind).Where(nt => nt.IsNode && this.HasAnnotations<TSpecificAnnotation>(nt)).Select(nt => nt.AsNode()!);
+            => node.GetAnnotatedNodesAndTokens(annotationKind).Where(nt => nt.IsNode && this.HasAnnotations<TSpecificAnnotation>(nt)).Select(nt => nt.AsNode()!);
 
         public IEnumerable<SyntaxToken> GetAnnotatedTokens<TSpecificAnnotation>(SyntaxNode node) where TSpecificAnnotation : TAnnotation
-            => node.GetAnnotatedNodesAndTokens(_annotationKind).Where(nt => nt.IsToken && this.HasAnnotations<TSpecificAnnotation>(nt)).Select(nt => nt.AsToken());
+            => node.GetAnnotatedNodesAndTokens(annotationKind).Where(nt => nt.IsToken && this.HasAnnotations<TSpecificAnnotation>(nt)).Select(nt => nt.AsToken());
 
         public IEnumerable<SyntaxTrivia> GetAnnotatedTrivia<TSpecificAnnotation>(SyntaxNode node) where TSpecificAnnotation : TAnnotation
-            => node.GetAnnotatedTrivia(_annotationKind).Where(this.HasAnnotations<TSpecificAnnotation>);
+            => node.GetAnnotatedTrivia(annotationKind).Where(this.HasAnnotations<TSpecificAnnotation>);
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AsyncLazy`1.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AsyncLazy`1.cs
index fc47a6158836c..779bba564f612 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AsyncLazy`1.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/AsyncLazy`1.cs
@@ -130,16 +130,11 @@ private WaitThatValidatesInvariants TakeLock(CancellationToken cancellationToken
             return new WaitThatValidatesInvariants(this);
         }
 
-        private readonly struct WaitThatValidatesInvariants : IDisposable
+        private readonly struct WaitThatValidatesInvariants(AsyncLazy<T> asyncLazy) : IDisposable
         {
-            private readonly AsyncLazy<T> _asyncLazy;
-
-            public WaitThatValidatesInvariants(AsyncLazy<T> asyncLazy)
-                => _asyncLazy = asyncLazy;
-
             public void Dispose()
             {
-                _asyncLazy.AssertInvariants_NoLock();
+                asyncLazy.AssertInvariants_NoLock();
                 s_gate.Release();
             }
         }
@@ -367,16 +362,10 @@ private AsynchronousComputationToStart RegisterAsynchronousComputation_NoLock()
             return new AsynchronousComputationToStart(_asynchronousComputeFunction, _asynchronousComputationCancellationSource);
         }
 
-        private readonly struct AsynchronousComputationToStart
+        private readonly struct AsynchronousComputationToStart(Func<CancellationToken, Task<T>> asynchronousComputeFunction, CancellationTokenSource cancellationTokenSource)
         {
-            public readonly Func<CancellationToken, Task<T>> AsynchronousComputeFunction;
-            public readonly CancellationTokenSource CancellationTokenSource;
-
-            public AsynchronousComputationToStart(Func<CancellationToken, Task<T>> asynchronousComputeFunction, CancellationTokenSource cancellationTokenSource)
-            {
-                AsynchronousComputeFunction = asynchronousComputeFunction;
-                CancellationTokenSource = cancellationTokenSource;
-            }
+            public readonly Func<CancellationToken, Task<T>> AsynchronousComputeFunction = asynchronousComputeFunction;
+            public readonly CancellationTokenSource CancellationTokenSource = cancellationTokenSource;
         }
 
         private void StartAsynchronousComputation(AsynchronousComputationToStart computationToStart, Request? requestToCompleteSynchronously, CancellationToken callerCancellationToken)
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Builder.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Builder.cs
index 63c7053500e93..5fdbfb7aa2b35 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Builder.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Builder.cs
@@ -283,14 +283,11 @@ private bool TryGetChildIndex(BuilderNode currentNode, int currentNodeIndex, int
                 return false;
             }
 
-            private struct BuilderNode
+            private struct BuilderNode(TextSpan characterSpan)
             {
-                public readonly TextSpan CharacterSpan;
+                public readonly TextSpan CharacterSpan = characterSpan;
                 public int EdgeCount;
                 public Dictionary<int, int>? SpilloverEdges;
-
-                public BuilderNode(TextSpan characterSpan)
-                    => this.CharacterSpan = characterSpan;
             }
         }
     }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Edge.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Edge.cs
index c385a3d85fccc..07692d5432316 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Edge.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Edge.cs
@@ -6,20 +6,14 @@ namespace Roslyn.Utilities
 {
     internal readonly partial struct BKTree
     {
-        private readonly struct Edge
+        private readonly struct Edge(int editDistance, int childNodeIndex)
         {
             // The edit distance between the child and parent connected by this edge.
             // The child can be found in _nodes at ChildNodeIndex. 
-            public readonly int EditDistance;
+            public readonly int EditDistance = editDistance;
 
             /// <summary>Where the child node can be found in <see cref="_nodes"/>.</summary>
-            public readonly int ChildNodeIndex;
-
-            public Edge(int editDistance, int childNodeIndex)
-            {
-                EditDistance = editDistance;
-                ChildNodeIndex = childNodeIndex;
-            }
+            public readonly int ChildNodeIndex = childNodeIndex;
 
             internal void WriteTo(ObjectWriter writer)
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Node.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Node.cs
index 26cbd119eb5fc..d74f9ee0326db 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Node.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/BKTree.Node.cs
@@ -8,28 +8,21 @@ namespace Roslyn.Utilities
 {
     internal readonly partial struct BKTree
     {
-        private readonly struct Node
+        private readonly struct Node(TextSpan wordSpan, int edgeCount, int firstEdgeIndex)
         {
             /// <summary>
             /// The string this node corresponds to.  Specifically, this span is the range of
             /// <see cref="_concatenatedLowerCaseWords"/> for that string.
             /// </summary>
-            public readonly TextSpan WordSpan;
+            public readonly TextSpan WordSpan = wordSpan;
 
             ///<summary>How many child edges this node has.</summary>
-            public readonly int EdgeCount;
+            public readonly int EdgeCount = edgeCount;
 
             ///<summary>Where the first edge can be found in <see cref="_edges"/>.  The edges 
             ///are in the range _edges[FirstEdgeIndex, FirstEdgeIndex + EdgeCount)
             ///</summary>
-            public readonly int FirstEdgeIndex;
-
-            public Node(TextSpan wordSpan, int edgeCount, int firstEdgeIndex)
-            {
-                WordSpan = wordSpan;
-                EdgeCount = edgeCount;
-                FirstEdgeIndex = firstEdgeIndex;
-            }
+            public readonly int FirstEdgeIndex = firstEdgeIndex;
 
             internal void WriteTo(ObjectWriter writer)
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ConcatImmutableArray`1.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ConcatImmutableArray`1.cs
index 75f845cda7d7f..57b0f338f1291 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ConcatImmutableArray`1.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ConcatImmutableArray`1.cs
@@ -11,27 +11,18 @@
 
 namespace Roslyn.Utilities
 {
-    internal readonly struct ConcatImmutableArray<T> : IEnumerable<T>
+    internal readonly struct ConcatImmutableArray<T>(ImmutableArray<T> first, ImmutableArray<T> second) : IEnumerable<T>
     {
-        private readonly ImmutableArray<T> _first;
-        private readonly ImmutableArray<T> _second;
-
-        public ConcatImmutableArray(ImmutableArray<T> first, ImmutableArray<T> second)
-        {
-            _first = first;
-            _second = second;
-        }
-
-        public int Length => _first.Length + _second.Length;
+        public int Length => first.Length + second.Length;
 
         public bool Any(Func<T, bool> predicate)
-            => _first.Any(predicate) || _second.Any(predicate);
+            => first.Any(predicate) || second.Any(predicate);
 
         public Enumerator GetEnumerator()
-            => new(_first, _second);
+            => new(first, second);
 
         public ImmutableArray<T> ToImmutableArray()
-            => _first.NullToEmpty().AddRange(_second.NullToEmpty());
+            => first.NullToEmpty().AddRange(second.NullToEmpty());
 
         IEnumerator<T> IEnumerable<T>.GetEnumerator()
             => GetEnumerator();
@@ -39,16 +30,10 @@ IEnumerator<T> IEnumerable<T>.GetEnumerator()
         IEnumerator IEnumerable.GetEnumerator()
             => GetEnumerator();
 
-        public struct Enumerator : IEnumerator<T>
+        public struct Enumerator(ImmutableArray<T> first, ImmutableArray<T> second) : IEnumerator<T>
         {
-            private ImmutableArray<T>.Enumerator _current;
-            private ImmutableArray<T> _next;
-
-            public Enumerator(ImmutableArray<T> first, ImmutableArray<T> second)
-            {
-                _current = first.NullToEmpty().GetEnumerator();
-                _next = second.NullToEmpty();
-            }
+            private ImmutableArray<T>.Enumerator _current = first.NullToEmpty().GetEnumerator();
+            private ImmutableArray<T> _next = second.NullToEmpty();
 
             public T Current => _current.Current;
             object? IEnumerator.Current => Current;
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EditDistance.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EditDistance.cs
index bf76ac5bd6d95..f62f215e9f7ce 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EditDistance.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EditDistance.cs
@@ -28,7 +28,7 @@ namespace Roslyn.Utilities
     /// Specifically, this implementation satisfies the following inequality: D(x, y) + D(y, z) >= D(x, z)
     /// (where D is the edit distance).
     ///</summary> 
-    internal readonly struct EditDistance : IDisposable
+    internal readonly struct EditDistance(string text) : IDisposable
     {
         // Our edit distance algorithm makes use of an 'infinite' value.  A value so high that it 
         // could never participate in an edit distance (and effectively means the path through it
@@ -45,14 +45,8 @@ namespace Roslyn.Utilities
 
         public const int BeyondThreshold = int.MaxValue;
 
-        private readonly string _source;
-        private readonly char[] _sourceLowerCaseCharacters;
-
-        public EditDistance(string text)
-        {
-            _source = text ?? throw new ArgumentNullException(nameof(text));
-            _sourceLowerCaseCharacters = ConvertToLowercaseArray(text);
-        }
+        private readonly string _source = text ?? throw new ArgumentNullException(nameof(text));
+        private readonly char[] _sourceLowerCaseCharacters = ConvertToLowercaseArray(text);
 
         private static char[] ConvertToLowercaseArray(string text)
         {
@@ -607,14 +601,10 @@ private static void SetValue(int[,] matrix, int i, int j, int val)
         }
     }
 
-    internal class SimplePool<T> where T : class
+    internal class SimplePool<T>(Func<T> allocate) where T : class
     {
         private readonly object _gate = new();
         private readonly Stack<T> _values = new();
-        private readonly Func<T> _allocate;
-
-        public SimplePool(Func<T> allocate)
-            => _allocate = allocate;
 
         public T Allocate()
         {
@@ -625,7 +615,7 @@ public T Allocate()
                     return _values.Pop();
                 }
 
-                return _allocate();
+                return allocate();
             }
         }
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EventMap.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EventMap.cs
index 78f87cd91db26..6d13ecabff2c9 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EventMap.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/EventMap.cs
@@ -94,13 +94,10 @@ private void SetRegistries_NoLock<TEventHandler>(string eventName, ImmutableArra
             _eventNameToRegistries[eventName] = registries;
         }
 
-        internal class Registry<TEventHandler> : IEquatable<Registry<TEventHandler>?>
+        internal class Registry<TEventHandler>(TEventHandler handler) : IEquatable<Registry<TEventHandler>?>
             where TEventHandler : class
         {
-            private TEventHandler? _handler;
-
-            public Registry(TEventHandler handler)
-                => _handler = handler;
+            private TEventHandler? _handler = handler;
 
             public void Unregister()
                 => _handler = null;
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/IReadOnlyListExtensions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/IReadOnlyListExtensions.cs
index e4cdba9b8f338..44e81cbfc1094 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/IReadOnlyListExtensions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/IReadOnlyListExtensions.cs
@@ -35,17 +35,12 @@ public static int IndexOf<T>(this IReadOnlyList<T> list, T value, int startIndex
             return -1;
         }
 
-        private class ReadOnlyList<T> : IReadOnlyList<T>
+        private class ReadOnlyList<T>(IList<T> list) : IReadOnlyList<T>
         {
-            private readonly IList<T> _list;
-
-            public ReadOnlyList(IList<T> list)
-                => _list = list;
-
-            public T this[int index] => _list[index];
-            public int Count => _list.Count;
-            public IEnumerator<T> GetEnumerator() => _list.GetEnumerator();
-            IEnumerator IEnumerable.GetEnumerator() => _list.GetEnumerator();
+            public T this[int index] => list[index];
+            public int Count => list.Count;
+            public IEnumerator<T> GetEnumerator() => list.GetEnumerator();
+            IEnumerator IEnumerable.GetEnumerator() => list.GetEnumerator();
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.ChoiceMatcher.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.ChoiceMatcher.cs
index 94aa3026b1f68..c140659ba0402 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.ChoiceMatcher.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.ChoiceMatcher.cs
@@ -8,12 +8,9 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class Matcher<T>
     {
-        private class ChoiceMatcher : Matcher<T>
+        private class ChoiceMatcher(params Matcher<T>[] matchers) : Matcher<T>
         {
-            private readonly IEnumerable<Matcher<T>> _matchers;
-
-            public ChoiceMatcher(params Matcher<T>[] matchers)
-                => _matchers = matchers;
+            private readonly IEnumerable<Matcher<T>> _matchers = matchers;
 
             public override bool TryMatch(IList<T> sequence, ref int index)
             {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.RepeatMatcher.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.RepeatMatcher.cs
index 40ee33ae80857..d8078f49a60b7 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.RepeatMatcher.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.RepeatMatcher.cs
@@ -8,16 +8,11 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class Matcher<T>
     {
-        private class RepeatMatcher : Matcher<T>
+        private class RepeatMatcher(Matcher<T> matcher) : Matcher<T>
         {
-            private readonly Matcher<T> _matcher;
-
-            public RepeatMatcher(Matcher<T> matcher)
-                => _matcher = matcher;
-
             public override bool TryMatch(IList<T> sequence, ref int index)
             {
-                while (_matcher.TryMatch(sequence, ref index))
+                while (matcher.TryMatch(sequence, ref index))
                 {
                 }
 
@@ -25,7 +20,7 @@ public override bool TryMatch(IList<T> sequence, ref int index)
             }
 
             public override string ToString()
-                => string.Format("({0}*)", _matcher);
+                => string.Format("({0}*)", matcher);
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SequenceMatcher.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SequenceMatcher.cs
index 2019979daf83b..7574ecc562bdd 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SequenceMatcher.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SequenceMatcher.cs
@@ -8,17 +8,12 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class Matcher<T>
     {
-        private class SequenceMatcher : Matcher<T>
+        private class SequenceMatcher(params Matcher<T>[] matchers) : Matcher<T>
         {
-            private readonly Matcher<T>[] _matchers;
-
-            public SequenceMatcher(params Matcher<T>[] matchers)
-                => _matchers = matchers;
-
             public override bool TryMatch(IList<T> sequence, ref int index)
             {
                 var currentIndex = index;
-                foreach (var matcher in _matchers)
+                foreach (var matcher in matchers)
                 {
                     if (!matcher.TryMatch(sequence, ref currentIndex))
                     {
@@ -31,7 +26,7 @@ public override bool TryMatch(IList<T> sequence, ref int index)
             }
 
             public override string ToString()
-                => string.Format("({0})", string.Join(",", (object[])_matchers));
+                => string.Format("({0})", string.Join(",", (object[])matchers));
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SingleMatcher.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SingleMatcher.cs
index 5706b1ab296b4..4d98a1540839a 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SingleMatcher.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/Matcher.SingleMatcher.cs
@@ -9,20 +9,11 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class Matcher<T>
     {
-        private class SingleMatcher : Matcher<T>
+        private class SingleMatcher(Func<T, bool> predicate, string description) : Matcher<T>
         {
-            private readonly Func<T, bool> _predicate;
-            private readonly string _description;
-
-            public SingleMatcher(Func<T, bool> predicate, string description)
-            {
-                _predicate = predicate;
-                _description = description;
-            }
-
             public override bool TryMatch(IList<T> sequence, ref int index)
             {
-                if (index < sequence.Count && _predicate(sequence[index]))
+                if (index < sequence.Count && predicate(sequence[index]))
                 {
                     index++;
                     return true;
@@ -32,7 +23,7 @@ public override bool TryMatch(IList<T> sequence, ref int index)
             }
 
             public override string ToString()
-                => _description;
+                => description;
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/NonReentrantLock.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/NonReentrantLock.cs
index e7a97bdf33724..95d8ecf2f733d 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/NonReentrantLock.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/NonReentrantLock.cs
@@ -240,15 +240,10 @@ public SemaphoreDisposer DisposableWait(CancellationToken cancellationToken = de
         /// <summary>
         /// Since we want to avoid boxing the return from <see cref="NonReentrantLock.DisposableWait"/>, this type must be public.
         /// </summary>
-        public readonly struct SemaphoreDisposer : IDisposable
+        public readonly struct SemaphoreDisposer(NonReentrantLock semaphore) : IDisposable
         {
-            private readonly NonReentrantLock _semaphore;
-
-            public SemaphoreDisposer(NonReentrantLock semaphore)
-                => _semaphore = semaphore;
-
             public void Dispose()
-                => _semaphore.Release();
+                => semaphore.Release();
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposable.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposable.cs
index 7ddb2f5fdb583..72b47d877d620 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposable.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposable.cs
@@ -306,7 +306,7 @@ public WeakReference(ReferenceCountedDisposable<T> reference)
         /// <summary>
         /// Holds the reference count associated with a disposable object.
         /// </summary>
-        private sealed class BoxedReferenceCount
+        private sealed class BoxedReferenceCount(int referenceCount)
         {
             /// <summary>
             /// Holds the weak reference used by instances of <see cref="WeakReference"/> to obtain a reference-counted
@@ -319,12 +319,7 @@ private sealed class BoxedReferenceCount
             [DisallowNull]
             public WeakReference<T>? _weakInstance;
 
-            public int _referenceCount;
-
-            public BoxedReferenceCount(int referenceCount)
-            {
-                _referenceCount = referenceCount;
-            }
+            public int _referenceCount = referenceCount;
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposableCache.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposableCache.cs
index cd86b1d66a3e5..64ebb559837dc 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposableCache.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/ReferenceCountedDisposableCache.cs
@@ -57,25 +57,17 @@ public void Evict(TKey key)
             }
         }
 
-        private sealed class Entry : IDisposable, ICacheEntry<TKey, TValue>
+        private sealed class Entry(ReferenceCountedDisposableCache<TKey, TValue> cache, TKey key, TValue value) : IDisposable, ICacheEntry<TKey, TValue>
         {
-            private readonly ReferenceCountedDisposableCache<TKey, TValue> _cache;
 
-            public TKey Key { get; }
-            public TValue Value { get; }
-
-            public Entry(ReferenceCountedDisposableCache<TKey, TValue> cache, TKey key, TValue value)
-            {
-                _cache = cache;
-                Key = key;
-                Value = value;
-            }
+            public TKey Key { get; } = key;
+            public TValue Value { get; } = value;
 
             public void Dispose()
             {
                 // Evict us out of the cache. We already know that cache entry is going to be expired: any further calls on the WeakReference would give nothing,
                 // but we don't want to be holding onto the key either.
-                _cache.Evict(Key);
+                cache.Evict(Key);
 
                 // Dispose the underlying value
                 Value.Dispose();
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/RestrictedInternalsVisibleToAttribute.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/RestrictedInternalsVisibleToAttribute.cs
index 4ac623c3e3e68..dd04d5c364120 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/RestrictedInternalsVisibleToAttribute.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/RestrictedInternalsVisibleToAttribute.cs
@@ -7,15 +7,9 @@
 namespace System.Runtime.CompilerServices
 {
     [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
-    internal sealed class RestrictedInternalsVisibleToAttribute : Attribute
+    internal sealed class RestrictedInternalsVisibleToAttribute(string assemblyName, params string[] allowedNamespaces) : Attribute
     {
-        public RestrictedInternalsVisibleToAttribute(string assemblyName, params string[] allowedNamespaces)
-        {
-            AssemblyName = assemblyName;
-            AllowedNamespaces = allowedNamespaces.ToImmutableArray();
-        }
-
-        public string AssemblyName { get; }
-        public ImmutableArray<string> AllowedNamespaces { get; }
+        public string AssemblyName { get; } = assemblyName;
+        public ImmutableArray<string> AllowedNamespaces { get; } = allowedNamespaces.ToImmutableArray();
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SerializableBytes.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SerializableBytes.cs
index ea9c2543f13f6..c2b3f4e937a53 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SerializableBytes.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SerializableBytes.cs
@@ -291,13 +291,8 @@ public override void Write(byte[] buffer, int offset, int count)
                 => throw new NotSupportedException();
         }
 
-        private class ReadStream : PooledStream
+        private class ReadStream(long length, byte[][] chunks) : PooledStream(length, new List<byte[]>(chunks))
         {
-            public ReadStream(long length, byte[][] chunks)
-                : base(length, new List<byte[]>(chunks))
-            {
-
-            }
         }
 
         private class ReadWriteStream : PooledStream
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.EquivalenceVisitor.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.EquivalenceVisitor.cs
index a97aabca44428..5fa1f53a92e95 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.EquivalenceVisitor.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.EquivalenceVisitor.cs
@@ -15,21 +15,11 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class SymbolEquivalenceComparer
     {
-        private class EquivalenceVisitor
+        private class EquivalenceVisitor(
+            SymbolEquivalenceComparer symbolEquivalenceComparer,
+            bool compareMethodTypeParametersByIndex,
+            bool objectAndDynamicCompareEqually)
         {
-            private readonly bool _compareMethodTypeParametersByIndex;
-            private readonly bool _objectAndDynamicCompareEqually;
-            private readonly SymbolEquivalenceComparer _symbolEquivalenceComparer;
-
-            public EquivalenceVisitor(
-                SymbolEquivalenceComparer symbolEquivalenceComparer,
-                bool compareMethodTypeParametersByIndex,
-                bool objectAndDynamicCompareEqually)
-            {
-                _symbolEquivalenceComparer = symbolEquivalenceComparer;
-                _compareMethodTypeParametersByIndex = compareMethodTypeParametersByIndex;
-                _objectAndDynamicCompareEqually = objectAndDynamicCompareEqually;
-            }
 
 #if TRACKDEPTH
             private int depth = 0;
@@ -65,7 +55,7 @@ public bool AreEquivalent(ISymbol? x, ISymbol? y, Dictionary<INamedTypeSymbol, I
                     // Special case.  If we're comparing signatures then we want to compare 'object'
                     // and 'dynamic' as the same.  However, since they're different types, we don't
                     // want to bail out using the above check.
-                    if (_objectAndDynamicCompareEqually)
+                    if (objectAndDynamicCompareEqually)
                     {
                         return (xKind == SymbolKind.DynamicType && IsObjectType(y)) ||
                                (yKind == SymbolKind.DynamicType && IsObjectType(x));
@@ -108,7 +98,7 @@ internal bool AreEquivalent(ImmutableArray<CustomModifier> x, ImmutableArray<Cus
             }
 
             private bool NullableAnnotationsEquivalent(ITypeSymbol x, ITypeSymbol y)
-                => _symbolEquivalenceComparer._ignoreNullableAnnotations || x.NullableAnnotation == y.NullableAnnotation;
+                => symbolEquivalenceComparer._ignoreNullableAnnotations || x.NullableAnnotation == y.NullableAnnotation;
 
             private bool AreEquivalentWorker(ISymbol x, ISymbol y, SymbolKind k, Dictionary<INamedTypeSymbol, INamedTypeSymbol>? equivalentTypesWithDifferingAssemblies)
             {
@@ -148,7 +138,7 @@ private bool ArrayTypesAreEquivalent(IArrayTypeSymbol x, IArrayTypeSymbol y, Dic
             }
 
             private bool AssembliesAreEquivalent(IAssemblySymbol x, IAssemblySymbol y)
-                => _symbolEquivalenceComparer._assemblyComparerOpt?.Equals(x, y) ?? true;
+                => symbolEquivalenceComparer._assemblyComparerOpt?.Equals(x, y) ?? true;
 
             private bool FieldsAreEquivalent(IFieldSymbol x, IFieldSymbol y, Dictionary<INamedTypeSymbol, INamedTypeSymbol>? equivalentTypesWithDifferingAssemblies)
             {
@@ -413,7 +403,7 @@ private bool HandleTupleTypes(INamedTypeSymbol x, INamedTypeSymbol y, Dictionary
                     return false;
 
                 // Check names first if necessary.
-                if (_symbolEquivalenceComparer._tupleNamesMustMatch)
+                if (symbolEquivalenceComparer._tupleNamesMustMatch)
                 {
                     for (var i = 0; i < xElements.Length; i++)
                     {
@@ -461,7 +451,7 @@ private bool ParametersAreEquivalent(
 
                 for (var i = 0; i < count; i++)
                 {
-                    if (!_symbolEquivalenceComparer.ParameterEquivalenceComparer.Equals(xParameters[i], yParameters[i], equivalentTypesWithDifferingAssemblies, compareParameterName, isParameterNameCaseSensitive))
+                    if (!symbolEquivalenceComparer.ParameterEquivalenceComparer.Equals(xParameters[i], yParameters[i], equivalentTypesWithDifferingAssemblies, compareParameterName, isParameterNameCaseSensitive))
                     {
                         return false;
                     }
@@ -472,7 +462,7 @@ private bool ParametersAreEquivalent(
 
             internal bool ReturnTypesAreEquivalent(IMethodSymbol x, IMethodSymbol y, Dictionary<INamedTypeSymbol, INamedTypeSymbol>? equivalentTypesWithDifferingAssemblies = null)
             {
-                return _symbolEquivalenceComparer.SignatureTypeEquivalenceComparer.Equals(x.ReturnType, y.ReturnType, equivalentTypesWithDifferingAssemblies) &&
+                return symbolEquivalenceComparer.SignatureTypeEquivalenceComparer.Equals(x.ReturnType, y.ReturnType, equivalentTypesWithDifferingAssemblies) &&
                        AreEquivalent(x.ReturnTypeCustomModifiers, y.ReturnTypeCustomModifiers, equivalentTypesWithDifferingAssemblies);
             }
 
@@ -539,7 +529,7 @@ private bool NamespacesAreEquivalent(INamespaceSymbol x, INamespaceSymbol y, Dic
                     return false;
                 }
 
-                if (x.IsGlobalNamespace && _symbolEquivalenceComparer._assemblyComparerOpt == null)
+                if (x.IsGlobalNamespace && symbolEquivalenceComparer._assemblyComparerOpt == null)
                 {
                     // No need to compare the containers of global namespace when assembly identities are ignored.
                     return true;
@@ -617,7 +607,7 @@ private bool TypeParametersAreEquivalent(ITypeParameterSymbol x, ITypeParameterS
                 // If this is a method type parameter, and we are in 'non-recurse' mode (because
                 // we're comparing method parameters), then we're done at this point.  The types are
                 // equal.
-                if (x.TypeParameterKind == TypeParameterKind.Method && _compareMethodTypeParametersByIndex)
+                if (x.TypeParameterKind == TypeParameterKind.Method && compareMethodTypeParametersByIndex)
                 {
                     return true;
                 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.ParameterSymbolEqualityComparer.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.ParameterSymbolEqualityComparer.cs
index 709cd723dec3c..6028cd1dd9666 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.ParameterSymbolEqualityComparer.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.ParameterSymbolEqualityComparer.cs
@@ -11,19 +11,10 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class SymbolEquivalenceComparer
     {
-        internal class ParameterSymbolEqualityComparer : IEqualityComparer<IParameterSymbol?>
+        internal class ParameterSymbolEqualityComparer(
+            SymbolEquivalenceComparer symbolEqualityComparer,
+            bool distinguishRefFromOut) : IEqualityComparer<IParameterSymbol?>
         {
-            private readonly SymbolEquivalenceComparer _symbolEqualityComparer;
-            private readonly bool _distinguishRefFromOut;
-
-            public ParameterSymbolEqualityComparer(
-                SymbolEquivalenceComparer symbolEqualityComparer,
-                bool distinguishRefFromOut)
-            {
-                _symbolEqualityComparer = symbolEqualityComparer;
-                _distinguishRefFromOut = distinguishRefFromOut;
-            }
-
             public bool Equals(
                 IParameterSymbol? x,
                 IParameterSymbol? y,
@@ -53,10 +44,10 @@ public bool Equals(
                 // equality, then we want to consider method type parameters by index only.
 
                 return
-                    AreRefKindsEquivalent(x.RefKind, y.RefKind, _distinguishRefFromOut) &&
+                    AreRefKindsEquivalent(x.RefKind, y.RefKind, distinguishRefFromOut) &&
                     nameComparisonCheck &&
-                    _symbolEqualityComparer.GetEquivalenceVisitor().AreEquivalent(x.CustomModifiers, y.CustomModifiers, equivalentTypesWithDifferingAssemblies) &&
-                    _symbolEqualityComparer.SignatureTypeEquivalenceComparer.Equals(x.Type, y.Type, equivalentTypesWithDifferingAssemblies);
+                    symbolEqualityComparer.GetEquivalenceVisitor().AreEquivalent(x.CustomModifiers, y.CustomModifiers, equivalentTypesWithDifferingAssemblies) &&
+                    symbolEqualityComparer.SignatureTypeEquivalenceComparer.Equals(x.Type, y.Type, equivalentTypesWithDifferingAssemblies);
             }
 
             public bool Equals(IParameterSymbol? x, IParameterSymbol? y)
@@ -74,7 +65,7 @@ public int GetHashCode(IParameterSymbol? x)
 
                 return
                     Hash.Combine(x.IsRefOrOut(),
-                    _symbolEqualityComparer.SignatureTypeEquivalenceComparer.GetHashCode(x.Type));
+                    symbolEqualityComparer.SignatureTypeEquivalenceComparer.GetHashCode(x.Type));
             }
         }
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.SignatureTypeSymbolEquivalenceComparer.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.SignatureTypeSymbolEquivalenceComparer.cs
index c3fbf019e7f42..cfab690699e04 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.SignatureTypeSymbolEquivalenceComparer.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/SymbolEquivalenceComparer.SignatureTypeSymbolEquivalenceComparer.cs
@@ -8,21 +8,16 @@ namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
     internal partial class SymbolEquivalenceComparer
     {
-        internal class SignatureTypeSymbolEquivalenceComparer : IEqualityComparer<ITypeSymbol?>
+        internal class SignatureTypeSymbolEquivalenceComparer(SymbolEquivalenceComparer symbolEquivalenceComparer) : IEqualityComparer<ITypeSymbol?>
         {
-            private readonly SymbolEquivalenceComparer _symbolEquivalenceComparer;
-
-            public SignatureTypeSymbolEquivalenceComparer(SymbolEquivalenceComparer symbolEquivalenceComparer)
-                => _symbolEquivalenceComparer = symbolEquivalenceComparer;
-
             public bool Equals(ITypeSymbol? x, ITypeSymbol? y)
                 => this.Equals(x, y, null);
 
             public bool Equals(ITypeSymbol? x, ITypeSymbol? y, Dictionary<INamedTypeSymbol, INamedTypeSymbol>? equivalentTypesWithDifferingAssemblies)
-                => _symbolEquivalenceComparer.GetEquivalenceVisitor(compareMethodTypeParametersByIndex: true, objectAndDynamicCompareEqually: true).AreEquivalent(x, y, equivalentTypesWithDifferingAssemblies);
+                => symbolEquivalenceComparer.GetEquivalenceVisitor(compareMethodTypeParametersByIndex: true, objectAndDynamicCompareEqually: true).AreEquivalent(x, y, equivalentTypesWithDifferingAssemblies);
 
             public int GetHashCode(ITypeSymbol? x)
-                => _symbolEquivalenceComparer.GetGetHashCodeVisitor(compareMethodTypeParametersByIndex: true, objectAndDynamicCompareEqually: true).GetHashCode(x, currentHash: 0);
+                => symbolEquivalenceComparer.GetGetHashCodeVisitor(compareMethodTypeParametersByIndex: true, objectAndDynamicCompareEqually: true).GetHashCode(x, currentHash: 0);
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/TaskExtensions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/TaskExtensions.cs
index 6973b3d6de850..2db0269f19be9 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/TaskExtensions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/TaskExtensions.cs
@@ -383,5 +383,21 @@ public static void VerifyCompleted(this Task task)
             // Propagate any exceptions that may have been thrown.
             task.GetAwaiter().GetResult();
         }
+
+        /// <summary>
+        /// Asserts the <see cref="Task"/> passed has already been completed.
+        /// </summary>
+        /// <remarks>
+        /// This is useful for a specific case: sometimes you might be calling an API that is "sometimes" async, and you're
+        /// calling it from a synchronous method where you know it should have completed synchronously. This is an easy
+        /// way to assert that while silencing any compiler complaints.
+        /// </remarks>
+        public static TResult VerifyCompleted<TResult>(this Task<TResult> task)
+        {
+            Contract.ThrowIfFalse(task.IsCompleted);
+
+            // Propagate any exceptions that may have been thrown.
+            return task.GetAwaiter().GetResult();
+        }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/WordSimilarityChecker.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/WordSimilarityChecker.cs
index 3f2edd035f2d9..9a75f7906af0e 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/WordSimilarityChecker.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/WordSimilarityChecker.cs
@@ -9,18 +9,11 @@ namespace Roslyn.Utilities
 {
     internal struct WordSimilarityChecker : IDisposable
     {
-        private readonly struct CacheResult
+        private readonly struct CacheResult(string candidate, bool areSimilar, double similarityWeight)
         {
-            public readonly string CandidateText;
-            public readonly bool AreSimilar;
-            public readonly double SimilarityWeight;
-
-            public CacheResult(string candidate, bool areSimilar, double similarityWeight)
-            {
-                CandidateText = candidate;
-                AreSimilar = areSimilar;
-                SimilarityWeight = similarityWeight;
-            }
+            public readonly string CandidateText = candidate;
+            public readonly bool AreSimilar = areSimilar;
+            public readonly double SimilarityWeight = similarityWeight;
         }
 
         // Cache the result of the last call to AreSimilar.  We'll often be called with the same
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxFacts.vb b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxFacts.vb
index d6f7d38d6dd6b..eaee489a68494 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxFacts.vb
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxFacts.vb
@@ -1110,7 +1110,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.LanguageService
             Return constructors
         End Function
 
-        Private Sub AppendConstructors(members As SyntaxList(Of StatementSyntax), constructors As List(Of SyntaxNode), cancellationToken As CancellationToken)
+        Private Shared Sub AppendConstructors(members As SyntaxList(Of StatementSyntax), constructors As List(Of SyntaxNode), cancellationToken As CancellationToken)
             For Each member As StatementSyntax In members
                 cancellationToken.ThrowIfCancellationRequested()
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxKinds.vb b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxKinds.vb
index 349c90c91504f..0269b9dc2e909 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxKinds.vb
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxKinds.vb
@@ -138,6 +138,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.LanguageService
 
         Public ReadOnly Property ExpressionStatement As Integer = SyntaxKind.ExpressionStatement Implements ISyntaxKinds.ExpressionStatement
         Public ReadOnly Property ForEachStatement As Integer = SyntaxKind.ForEachStatement Implements ISyntaxKinds.ForEachStatement
+        Public ReadOnly Property ForStatement As Integer = SyntaxKind.ForStatement Implements ISyntaxKinds.ForStatement
         Public ReadOnly Property IfStatement As Integer = SyntaxKind.IfStatement Implements ISyntaxKinds.IfStatement
         Public ReadOnly Property LocalDeclarationStatement As Integer = SyntaxKind.LocalDeclarationStatement Implements ISyntaxKinds.LocalDeclarationStatement
         Public ReadOnly Property LocalFunctionStatement As Integer? Implements ISyntaxKinds.LocalFunctionStatement
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpRemoveUnnecessaryImportsService.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpRemoveUnnecessaryImportsService.cs
index 9f9f79000da9b..262a14ee60c4f 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpRemoveUnnecessaryImportsService.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpRemoveUnnecessaryImportsService.cs
@@ -85,7 +85,7 @@ public override async Task<Document> RemoveUnnecessaryImportsAsync(
             }
         }
 
-        private void AddFormattingSpans(
+        private static void AddFormattingSpans(
             CompilationUnitSyntax compilationUnit,
             List<TextSpan> spans,
             CancellationToken cancellationToken)
@@ -97,7 +97,7 @@ private void AddFormattingSpans(
                 AddFormattingSpans(@namespace, spans, cancellationToken);
         }
 
-        private void AddFormattingSpans(
+        private static void AddFormattingSpans(
             BaseNamespaceDeclarationSyntax namespaceMember,
             List<TextSpan> spans,
             CancellationToken cancellationToken)
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpTypeInferenceService.TypeInferrer.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpTypeInferenceService.TypeInferrer.cs
index a9d97b5c31664..8829f7489f294 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpTypeInferenceService.TypeInferrer.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/LanguageServices/CSharpTypeInferenceService.TypeInferrer.cs
@@ -609,7 +609,7 @@ private IEnumerable<TypeInferenceInfo> InferTypeInArgument(int index, IEnumerabl
                 return InferTypeInArgument(index, methods.SelectAsArray(m => m.Parameters), argumentOpt);
             }
 
-            private IMethodSymbol Instantiate(IMethodSymbol method, IList<ITypeSymbol> invocationTypes)
+            private static IMethodSymbol Instantiate(IMethodSymbol method, IList<ITypeSymbol> invocationTypes)
             {
                 // No need to instantiate if this isn't a generic method.
                 if (method.TypeArguments.Length == 0)
@@ -655,14 +655,14 @@ private IMethodSymbol Instantiate(IMethodSymbol method, IList<ITypeSymbol> invoc
                 return method.ConstructedFrom.Construct(typeArguments);
             }
 
-            private Dictionary<ITypeParameterSymbol, ITypeSymbol> DetermineTypeParameterMapping(ITypeSymbol inferredType, ITypeSymbol returnType)
+            private static Dictionary<ITypeParameterSymbol, ITypeSymbol> DetermineTypeParameterMapping(ITypeSymbol inferredType, ITypeSymbol returnType)
             {
                 var result = new Dictionary<ITypeParameterSymbol, ITypeSymbol>();
                 DetermineTypeParameterMapping(inferredType, returnType, result);
                 return result;
             }
 
-            private void DetermineTypeParameterMapping(ITypeSymbol inferredType, ITypeSymbol returnType, Dictionary<ITypeParameterSymbol, ITypeSymbol> result)
+            private static void DetermineTypeParameterMapping(ITypeSymbol inferredType, ITypeSymbol returnType, Dictionary<ITypeParameterSymbol, ITypeSymbol> result)
             {
                 if (inferredType == null || returnType == null)
                 {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CodeActionOptions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CodeActionOptions.cs
index 7e23c66c9eefe..0da3632208114 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CodeActionOptions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CodeActionOptions.cs
@@ -145,15 +145,10 @@ ValueTask<CodeAndImportGenerationOptions> OptionsProvider<CodeAndImportGeneratio
 #endif
     }
 
-    internal sealed class DelegatingCodeActionOptionsProvider : AbstractCodeActionOptionsProvider
+    internal sealed class DelegatingCodeActionOptionsProvider(Func<LanguageServices, CodeActionOptions> @delegate) : AbstractCodeActionOptionsProvider
     {
-        private readonly Func<LanguageServices, CodeActionOptions> _delegate;
-
-        public DelegatingCodeActionOptionsProvider(Func<LanguageServices, CodeActionOptions> @delegate)
-            => _delegate = @delegate;
-
         public override CodeActionOptions GetOptions(LanguageServices languageService)
-            => _delegate(languageService);
+            => @delegate(languageService);
     }
 
     internal static class CodeActionOptionsProviders
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CustomCodeActions.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CustomCodeActions.cs
index 97b0dcbd89f06..a561ebe63e13b 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CustomCodeActions.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CustomCodeActions.cs
@@ -24,60 +24,39 @@ internal enum CodeActionPriority
 
     internal static class CustomCodeActions
     {
-        internal abstract class SimpleCodeAction : CodeAction
+        internal abstract class SimpleCodeAction(
+            string title,
+            string? equivalenceKey) : CodeAction
         {
-            public SimpleCodeAction(
-                string title,
-                string? equivalenceKey)
-            {
-                Title = title;
-                EquivalenceKey = equivalenceKey;
-            }
-
-            public sealed override string Title { get; }
-            public sealed override string? EquivalenceKey { get; }
+            public sealed override string Title { get; } = title;
+            public sealed override string? EquivalenceKey { get; } = equivalenceKey;
         }
 
-        internal class DocumentChangeAction : SimpleCodeAction
+        internal class DocumentChangeAction(
+            string title,
+            Func<CancellationToken, Task<Document>> createChangedDocument,
+            string? equivalenceKey,
+            CodeActionPriority priority) : SimpleCodeAction(title, equivalenceKey)
         {
-            private readonly Func<CancellationToken, Task<Document>> _createChangedDocument;
 
 #if CODE_STYLE
-            internal CodeActionPriority Priority { get; }
+            internal CodeActionPriority Priority { get; } = priority;
 #else
-            internal override CodeActionPriority Priority { get; }
-#endif
+            internal override CodeActionPriority Priority { get; } = priority;
 
-            public DocumentChangeAction(
-                string title,
-                Func<CancellationToken, Task<Document>> createChangedDocument,
-                string? equivalenceKey,
-                CodeActionPriority priority)
-                : base(title, equivalenceKey)
-            {
-                _createChangedDocument = createChangedDocument;
-                Priority = priority;
-            }
+#endif
 
             protected sealed override Task<Document> GetChangedDocumentAsync(CancellationToken cancellationToken)
-                => _createChangedDocument(cancellationToken);
+                => createChangedDocument(cancellationToken);
         }
 
-        internal class SolutionChangeAction : SimpleCodeAction
+        internal class SolutionChangeAction(
+            string title,
+            Func<CancellationToken, Task<Solution>> createChangedSolution,
+            string? equivalenceKey) : SimpleCodeAction(title, equivalenceKey)
         {
-            private readonly Func<CancellationToken, Task<Solution>> _createChangedSolution;
-
-            public SolutionChangeAction(
-                string title,
-                Func<CancellationToken, Task<Solution>> createChangedSolution,
-                string? equivalenceKey)
-                : base(title, equivalenceKey)
-            {
-                _createChangedSolution = createChangedSolution;
-            }
-
             protected sealed override Task<Solution?> GetChangedSolutionAsync(CancellationToken cancellationToken)
-                => _createChangedSolution(cancellationToken).AsNullable();
+                => createChangedSolution(cancellationToken).AsNullable();
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationArrayTypeSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationArrayTypeSymbol.cs
index 5b9c8126e0b60..dca2d8c337b8c 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationArrayTypeSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationArrayTypeSymbol.cs
@@ -7,18 +7,11 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationArrayTypeSymbol : CodeGenerationTypeSymbol, IArrayTypeSymbol
+    internal class CodeGenerationArrayTypeSymbol(ITypeSymbol elementType, int rank, NullableAnnotation nullableAnnotation) : CodeGenerationTypeSymbol(null, null, default, Accessibility.NotApplicable, default, string.Empty, SpecialType.None, nullableAnnotation), IArrayTypeSymbol
     {
-        public CodeGenerationArrayTypeSymbol(ITypeSymbol elementType, int rank, NullableAnnotation nullableAnnotation)
-            : base(null, null, default, Accessibility.NotApplicable, default, string.Empty, SpecialType.None, nullableAnnotation)
-        {
-            this.ElementType = elementType;
-            this.Rank = rank;
-        }
-
-        public ITypeSymbol ElementType { get; }
+        public ITypeSymbol ElementType { get; } = elementType;
 
-        public int Rank { get; }
+        public int Rank { get; } = rank;
 
         public bool IsSZArray
         {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationAttributeData.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationAttributeData.cs
index fb36ae94478ce..52cfb981322c8 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationAttributeData.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationAttributeData.cs
@@ -9,26 +9,18 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationAttributeData : AttributeData
+    internal class CodeGenerationAttributeData(
+        INamedTypeSymbol attributeClass,
+        ImmutableArray<TypedConstant> constructorArguments,
+        ImmutableArray<KeyValuePair<string, TypedConstant>> namedArguments) : AttributeData
     {
-        private readonly INamedTypeSymbol _attributeClass;
-        private readonly ImmutableArray<TypedConstant> _constructorArguments;
-        private readonly ImmutableArray<KeyValuePair<string, TypedConstant>> _namedArguments;
+        private readonly ImmutableArray<TypedConstant> _constructorArguments = constructorArguments.NullToEmpty();
+        private readonly ImmutableArray<KeyValuePair<string, TypedConstant>> _namedArguments = namedArguments.NullToEmpty();
 
-        protected override INamedTypeSymbol CommonAttributeClass => _attributeClass;
+        protected override INamedTypeSymbol CommonAttributeClass => attributeClass;
         protected override IMethodSymbol CommonAttributeConstructor => null;
         protected override ImmutableArray<TypedConstant> CommonConstructorArguments => _constructorArguments;
         protected override ImmutableArray<KeyValuePair<string, TypedConstant>> CommonNamedArguments => _namedArguments;
         protected override SyntaxReference CommonApplicationSyntaxReference => null;
-
-        public CodeGenerationAttributeData(
-            INamedTypeSymbol attributeClass,
-            ImmutableArray<TypedConstant> constructorArguments,
-            ImmutableArray<KeyValuePair<string, TypedConstant>> namedArguments)
-        {
-            _attributeClass = attributeClass;
-            _constructorArguments = constructorArguments.NullToEmpty();
-            _namedArguments = namedArguments.NullToEmpty();
-        }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConstructorSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConstructorSymbol.cs
index be6376ceae81d..c1c9be8a76ef9 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConstructorSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConstructorSymbol.cs
@@ -14,28 +14,23 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationConstructorSymbol : CodeGenerationMethodSymbol
+    internal class CodeGenerationConstructorSymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes,
+        Accessibility accessibility,
+        DeclarationModifiers modifiers,
+        ImmutableArray<IParameterSymbol> parameters) : CodeGenerationMethodSymbol(containingType,
+               attributes,
+               accessibility,
+               modifiers,
+               returnType: null,
+               refKind: RefKind.None,
+               explicitInterfaceImplementations: default,
+               name: string.Empty,
+               typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
+               parameters: parameters,
+               returnTypeAttributes: ImmutableArray<AttributeData>.Empty)
     {
-        public CodeGenerationConstructorSymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes,
-            Accessibility accessibility,
-            DeclarationModifiers modifiers,
-            ImmutableArray<IParameterSymbol> parameters)
-            : base(containingType,
-                   attributes,
-                   accessibility,
-                   modifiers,
-                   returnType: null,
-                   refKind: RefKind.None,
-                   explicitInterfaceImplementations: default,
-                   name: string.Empty,
-                   typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
-                   parameters: parameters,
-                   returnTypeAttributes: ImmutableArray<AttributeData>.Empty)
-        {
-        }
-
         public override MethodKind MethodKind => MethodKind.Constructor;
 
         protected override CodeGenerationSymbol Clone()
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConversionSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConversionSymbol.cs
index 2239363eb1c04..409de23fe5d25 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConversionSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationConversionSymbol.cs
@@ -14,35 +14,30 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationConversionSymbol : CodeGenerationMethodSymbol
-    {
-        public CodeGenerationConversionSymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes,
-            Accessibility declaredAccessibility,
-            DeclarationModifiers modifiers,
-            ITypeSymbol toType,
-            IParameterSymbol fromType,
-            bool isImplicit,
-            ImmutableArray<AttributeData> toTypeAttributes,
-            string documentationCommentXml)
-            : base(containingType,
-                  attributes,
-                  declaredAccessibility,
-                  modifiers,
-                  returnType: toType,
-                  refKind: RefKind.None,
-                  explicitInterfaceImplementations: default,
-                  name: isImplicit
+    internal class CodeGenerationConversionSymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes,
+        Accessibility declaredAccessibility,
+        DeclarationModifiers modifiers,
+        ITypeSymbol toType,
+        IParameterSymbol fromType,
+        bool isImplicit,
+        ImmutableArray<AttributeData> toTypeAttributes,
+        string documentationCommentXml) : CodeGenerationMethodSymbol(containingType,
+              attributes,
+              declaredAccessibility,
+              modifiers,
+              returnType: toType,
+              refKind: RefKind.None,
+              explicitInterfaceImplementations: default,
+              name: isImplicit
                       ? WellKnownMemberNames.ImplicitConversionName
                       : WellKnownMemberNames.ExplicitConversionName,
-                  typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
-                  parameters: ImmutableArray.Create(fromType),
-                  returnTypeAttributes: toTypeAttributes,
-                  documentationCommentXml)
-        {
-        }
-
+              typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
+              parameters: ImmutableArray.Create(fromType),
+              returnTypeAttributes: toTypeAttributes,
+              documentationCommentXml)
+    {
         public override MethodKind MethodKind => MethodKind.Conversion;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationDestructorSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationDestructorSymbol.cs
index 1c4f6403a89b8..1508534c952c6 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationDestructorSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationDestructorSymbol.cs
@@ -8,25 +8,20 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationDestructorSymbol : CodeGenerationMethodSymbol
+    internal class CodeGenerationDestructorSymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes) : CodeGenerationMethodSymbol(containingType,
+             attributes,
+             Accessibility.NotApplicable,
+             default,
+             returnType: null,
+             refKind: RefKind.None,
+             explicitInterfaceImplementations: default,
+             name: string.Empty,
+             typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
+             parameters: ImmutableArray<IParameterSymbol>.Empty,
+             returnTypeAttributes: ImmutableArray<AttributeData>.Empty)
     {
-        public CodeGenerationDestructorSymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes)
-            : base(containingType,
-                 attributes,
-                 Accessibility.NotApplicable,
-                 default,
-                 returnType: null,
-                 refKind: RefKind.None,
-                 explicitInterfaceImplementations: default,
-                 name: string.Empty,
-                 typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
-                 parameters: ImmutableArray<IParameterSymbol>.Empty,
-                 returnTypeAttributes: ImmutableArray<AttributeData>.Empty)
-        {
-        }
-
         public override MethodKind MethodKind => MethodKind.Destructor;
 
         protected override CodeGenerationSymbol Clone()
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationEventSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationEventSymbol.cs
index 7a519574807ca..910219f0342bb 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationEventSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationEventSymbol.cs
@@ -12,36 +12,26 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationEventSymbol : CodeGenerationSymbol, IEventSymbol
+    internal class CodeGenerationEventSymbol(
+        INamedTypeSymbol? containingType,
+        ImmutableArray<AttributeData> attributes,
+        Accessibility declaredAccessibility,
+        DeclarationModifiers modifiers,
+        ITypeSymbol type,
+        ImmutableArray<IEventSymbol> explicitInterfaceImplementations,
+        string name,
+        IMethodSymbol? addMethod,
+        IMethodSymbol? removeMethod,
+        IMethodSymbol? raiseMethod) : CodeGenerationSymbol(containingType?.ContainingAssembly, containingType, attributes, declaredAccessibility, modifiers, name), IEventSymbol
     {
-        public ITypeSymbol Type { get; }
+        public ITypeSymbol Type { get; } = type;
         public NullableAnnotation NullableAnnotation => Type.NullableAnnotation;
 
-        public ImmutableArray<IEventSymbol> ExplicitInterfaceImplementations { get; }
+        public ImmutableArray<IEventSymbol> ExplicitInterfaceImplementations { get; } = explicitInterfaceImplementations.NullToEmpty();
 
-        public IMethodSymbol? AddMethod { get; }
-        public IMethodSymbol? RemoveMethod { get; }
-        public IMethodSymbol? RaiseMethod { get; }
-
-        public CodeGenerationEventSymbol(
-            INamedTypeSymbol? containingType,
-            ImmutableArray<AttributeData> attributes,
-            Accessibility declaredAccessibility,
-            DeclarationModifiers modifiers,
-            ITypeSymbol type,
-            ImmutableArray<IEventSymbol> explicitInterfaceImplementations,
-            string name,
-            IMethodSymbol? addMethod,
-            IMethodSymbol? removeMethod,
-            IMethodSymbol? raiseMethod)
-            : base(containingType?.ContainingAssembly, containingType, attributes, declaredAccessibility, modifiers, name)
-        {
-            this.Type = type;
-            this.ExplicitInterfaceImplementations = explicitInterfaceImplementations.NullToEmpty();
-            this.AddMethod = addMethod;
-            this.RemoveMethod = removeMethod;
-            this.RaiseMethod = raiseMethod;
-        }
+        public IMethodSymbol? AddMethod { get; } = addMethod;
+        public IMethodSymbol? RemoveMethod { get; } = removeMethod;
+        public IMethodSymbol? RaiseMethod { get; } = raiseMethod;
 
         protected override CodeGenerationSymbol Clone()
         {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationFieldSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationFieldSymbol.cs
index 4ccdb599c4406..5a315659e20d8 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationFieldSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationFieldSymbol.cs
@@ -14,28 +14,20 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationFieldSymbol : CodeGenerationSymbol, IFieldSymbol
+    internal class CodeGenerationFieldSymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes,
+        Accessibility accessibility,
+        DeclarationModifiers modifiers,
+        ITypeSymbol type,
+        string name,
+        bool hasConstantValue,
+        object constantValue) : CodeGenerationSymbol(containingType?.ContainingAssembly, containingType, attributes, accessibility, modifiers, name), IFieldSymbol
     {
-        public ITypeSymbol Type { get; }
+        public ITypeSymbol Type { get; } = type;
         public NullableAnnotation NullableAnnotation => Type.NullableAnnotation;
-        public object ConstantValue { get; }
-        public bool HasConstantValue { get; }
-
-        public CodeGenerationFieldSymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes,
-            Accessibility accessibility,
-            DeclarationModifiers modifiers,
-            ITypeSymbol type,
-            string name,
-            bool hasConstantValue,
-            object constantValue)
-            : base(containingType?.ContainingAssembly, containingType, attributes, accessibility, modifiers, name)
-        {
-            this.Type = type;
-            this.HasConstantValue = hasConstantValue;
-            this.ConstantValue = constantValue;
-        }
+        public object ConstantValue { get; } = constantValue;
+        public bool HasConstantValue { get; } = hasConstantValue;
 
         protected override CodeGenerationSymbol Clone()
         {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationNamespaceSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationNamespaceSymbol.cs
index 3abdc3e60df66..6cfb14840c4dc 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationNamespaceSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationNamespaceSymbol.cs
@@ -11,15 +11,9 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationNamespaceSymbol : CodeGenerationNamespaceOrTypeSymbol, INamespaceSymbol
+    internal class CodeGenerationNamespaceSymbol(string name, IList<INamespaceOrTypeSymbol> members) : CodeGenerationNamespaceOrTypeSymbol(null, null, default, Accessibility.NotApplicable, default, name), INamespaceSymbol
     {
-        private readonly IList<INamespaceOrTypeSymbol> _members;
-
-        public CodeGenerationNamespaceSymbol(string name, IList<INamespaceOrTypeSymbol> members)
-            : base(null, null, default, Accessibility.NotApplicable, default, name)
-        {
-            _members = members ?? SpecializedCollections.EmptyList<INamespaceOrTypeSymbol>();
-        }
+        private readonly IList<INamespaceOrTypeSymbol> _members = members ?? SpecializedCollections.EmptyList<INamespaceOrTypeSymbol>();
 
         public override bool IsNamespace => true;
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationOperatorSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationOperatorSymbol.cs
index 20c17ee27a840..dd63d294240f3 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationOperatorSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationOperatorSymbol.cs
@@ -15,33 +15,28 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationOperatorSymbol : CodeGenerationMethodSymbol
+    internal class CodeGenerationOperatorSymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes,
+        Accessibility accessibility,
+        DeclarationModifiers modifiers,
+        ITypeSymbol returnType,
+        CodeGenerationOperatorKind operatorKind,
+        ImmutableArray<IParameterSymbol> parameters,
+        ImmutableArray<AttributeData> returnTypeAttributes,
+        string documentationCommentXml) : CodeGenerationMethodSymbol(containingType,
+             attributes,
+             accessibility,
+             modifiers,
+             returnType,
+             refKind: RefKind.None,
+             explicitInterfaceImplementations: default,
+             GetMetadataName(operatorKind),
+             typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
+             parameters,
+             returnTypeAttributes,
+             documentationCommentXml)
     {
-        public CodeGenerationOperatorSymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes,
-            Accessibility accessibility,
-            DeclarationModifiers modifiers,
-            ITypeSymbol returnType,
-            CodeGenerationOperatorKind operatorKind,
-            ImmutableArray<IParameterSymbol> parameters,
-            ImmutableArray<AttributeData> returnTypeAttributes,
-            string documentationCommentXml)
-            : base(containingType,
-                 attributes,
-                 accessibility,
-                 modifiers,
-                 returnType,
-                 refKind: RefKind.None,
-                 explicitInterfaceImplementations: default,
-                 GetMetadataName(operatorKind),
-                 typeParameters: ImmutableArray<ITypeParameterSymbol>.Empty,
-                 parameters,
-                 returnTypeAttributes,
-                 documentationCommentXml)
-        {
-        }
-
         public override MethodKind MethodKind => MethodKind.UserDefinedOperator;
 
         public static int GetParameterCount(CodeGenerationOperatorKind operatorKind)
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationParameterSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationParameterSymbol.cs
index 4a7d499181501..29e81ca85ca88 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationParameterSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationParameterSymbol.cs
@@ -14,37 +14,26 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationParameterSymbol : CodeGenerationSymbol, IParameterSymbol
+    internal class CodeGenerationParameterSymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes,
+        RefKind refKind,
+        bool isParams,
+        ITypeSymbol type,
+        string name,
+        bool isOptional,
+        bool hasDefaultValue,
+        object defaultValue) : CodeGenerationSymbol(containingType?.ContainingAssembly, containingType, attributes, Accessibility.NotApplicable, new DeclarationModifiers(), name), IParameterSymbol
     {
-        public RefKind RefKind { get; }
-        public bool IsParams { get; }
-        public ITypeSymbol Type { get; }
+        public RefKind RefKind { get; } = refKind;
+        public bool IsParams { get; } = isParams;
+        public ITypeSymbol Type { get; } = type;
         public NullableAnnotation NullableAnnotation => Type.NullableAnnotation;
-        public bool IsOptional { get; }
+        public bool IsOptional { get; } = isOptional;
         public int Ordinal { get; }
 
-        public bool HasExplicitDefaultValue { get; }
-        public object ExplicitDefaultValue { get; }
-
-        public CodeGenerationParameterSymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes,
-            RefKind refKind,
-            bool isParams,
-            ITypeSymbol type,
-            string name,
-            bool isOptional,
-            bool hasDefaultValue,
-            object defaultValue)
-            : base(containingType?.ContainingAssembly, containingType, attributes, Accessibility.NotApplicable, new DeclarationModifiers(), name)
-        {
-            this.RefKind = refKind;
-            this.IsParams = isParams;
-            this.Type = type;
-            this.IsOptional = isOptional;
-            this.HasExplicitDefaultValue = hasDefaultValue;
-            this.ExplicitDefaultValue = defaultValue;
-        }
+        public bool HasExplicitDefaultValue { get; } = hasDefaultValue;
+        public object ExplicitDefaultValue { get; } = defaultValue;
 
         protected override CodeGenerationSymbol Clone()
         {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPointerTypeSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPointerTypeSymbol.cs
index c82e5d662af3f..2eb74d7b11fe7 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPointerTypeSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPointerTypeSymbol.cs
@@ -6,15 +6,9 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationPointerTypeSymbol : CodeGenerationTypeSymbol, IPointerTypeSymbol
+    internal class CodeGenerationPointerTypeSymbol(ITypeSymbol pointedAtType) : CodeGenerationTypeSymbol(null, null, default, Accessibility.NotApplicable, default, string.Empty, SpecialType.None, NullableAnnotation.None), IPointerTypeSymbol
     {
-        public ITypeSymbol PointedAtType { get; }
-
-        public CodeGenerationPointerTypeSymbol(ITypeSymbol pointedAtType)
-            : base(null, null, default, Accessibility.NotApplicable, default, string.Empty, SpecialType.None, NullableAnnotation.None)
-        {
-            this.PointedAtType = pointedAtType;
-        }
+        public ITypeSymbol PointedAtType { get; } = pointedAtType;
 
         protected override CodeGenerationTypeSymbol CloneWithNullableAnnotation(NullableAnnotation nullableAnnotation)
         {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPropertySymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPropertySymbol.cs
index 9478d48d01f27..4ba30d3f00673 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPropertySymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationPropertySymbol.cs
@@ -14,42 +14,29 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationPropertySymbol : CodeGenerationSymbol, IPropertySymbol
+    internal class CodeGenerationPropertySymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes,
+        Accessibility declaredAccessibility,
+        DeclarationModifiers modifiers,
+        ITypeSymbol type,
+        RefKind refKind,
+        ImmutableArray<IPropertySymbol> explicitInterfaceImplementations,
+        string name,
+        bool isIndexer,
+        ImmutableArray<IParameterSymbol> parametersOpt,
+        IMethodSymbol getMethod,
+        IMethodSymbol setMethod) : CodeGenerationSymbol(containingType?.ContainingAssembly, containingType, attributes, declaredAccessibility, modifiers, name), IPropertySymbol
     {
-        private readonly RefKind _refKind;
-        public ITypeSymbol Type { get; }
+        public ITypeSymbol Type { get; } = type;
         public NullableAnnotation NullableAnnotation => Type.NullableAnnotation;
-        public bool IsIndexer { get; }
-
-        public ImmutableArray<IParameterSymbol> Parameters { get; }
-        public ImmutableArray<IPropertySymbol> ExplicitInterfaceImplementations { get; }
-
-        public IMethodSymbol GetMethod { get; }
-        public IMethodSymbol SetMethod { get; }
-
-        public CodeGenerationPropertySymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes,
-            Accessibility declaredAccessibility,
-            DeclarationModifiers modifiers,
-            ITypeSymbol type,
-            RefKind refKind,
-            ImmutableArray<IPropertySymbol> explicitInterfaceImplementations,
-            string name,
-            bool isIndexer,
-            ImmutableArray<IParameterSymbol> parametersOpt,
-            IMethodSymbol getMethod,
-            IMethodSymbol setMethod)
-            : base(containingType?.ContainingAssembly, containingType, attributes, declaredAccessibility, modifiers, name)
-        {
-            this.Type = type;
-            _refKind = refKind;
-            this.IsIndexer = isIndexer;
-            this.Parameters = parametersOpt.NullToEmpty();
-            this.ExplicitInterfaceImplementations = explicitInterfaceImplementations.NullToEmpty();
-            this.GetMethod = getMethod;
-            this.SetMethod = setMethod;
-        }
+        public bool IsIndexer { get; } = isIndexer;
+
+        public ImmutableArray<IParameterSymbol> Parameters { get; } = parametersOpt.NullToEmpty();
+        public ImmutableArray<IPropertySymbol> ExplicitInterfaceImplementations { get; } = explicitInterfaceImplementations.NullToEmpty();
+
+        public IMethodSymbol GetMethod { get; } = getMethod;
+        public IMethodSymbol SetMethod { get; } = setMethod;
 
         protected override CodeGenerationSymbol Clone()
         {
@@ -85,11 +72,11 @@ public override TResult Accept<TArgument, TResult>(SymbolVisitor<TArgument, TRes
 
         public new IPropertySymbol OriginalDefinition => this;
 
-        public RefKind RefKind => _refKind;
+        public RefKind RefKind => refKind;
 
-        public bool ReturnsByRef => _refKind == RefKind.Ref;
+        public bool ReturnsByRef => refKind == RefKind.Ref;
 
-        public bool ReturnsByRefReadonly => _refKind == RefKind.RefReadOnly;
+        public bool ReturnsByRefReadonly => refKind == RefKind.RefReadOnly;
 
         public IPropertySymbol OverriddenProperty => null;
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationTypeParameterSymbol.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationTypeParameterSymbol.cs
index 852e315c0ddd2..8f115657a4d55 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationTypeParameterSymbol.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/Symbols/CodeGenerationTypeParameterSymbol.cs
@@ -8,41 +8,28 @@
 
 namespace Microsoft.CodeAnalysis.CodeGeneration
 {
-    internal class CodeGenerationTypeParameterSymbol : CodeGenerationTypeSymbol, ITypeParameterSymbol
+    internal class CodeGenerationTypeParameterSymbol(
+        INamedTypeSymbol containingType,
+        ImmutableArray<AttributeData> attributes,
+        VarianceKind varianceKind,
+        string name,
+        NullableAnnotation nullableAnnotation,
+        ImmutableArray<ITypeSymbol> constraintTypes,
+        bool hasConstructorConstraint,
+        bool hasReferenceConstraint,
+        bool hasValueConstraint,
+        bool hasUnmanagedConstraint,
+        bool hasNotNullConstraint,
+        int ordinal) : CodeGenerationTypeSymbol(containingType?.ContainingAssembly, containingType, attributes, Accessibility.NotApplicable, default, name, SpecialType.None, nullableAnnotation), ITypeParameterSymbol
     {
-        public VarianceKind Variance { get; }
-        public ImmutableArray<ITypeSymbol> ConstraintTypes { get; internal set; }
-        public bool HasConstructorConstraint { get; }
-        public bool HasReferenceTypeConstraint { get; }
-        public bool HasValueTypeConstraint { get; }
-        public bool HasUnmanagedTypeConstraint { get; }
-        public bool HasNotNullConstraint { get; }
-        public int Ordinal { get; }
-
-        public CodeGenerationTypeParameterSymbol(
-            INamedTypeSymbol containingType,
-            ImmutableArray<AttributeData> attributes,
-            VarianceKind varianceKind,
-            string name,
-            NullableAnnotation nullableAnnotation,
-            ImmutableArray<ITypeSymbol> constraintTypes,
-            bool hasConstructorConstraint,
-            bool hasReferenceConstraint,
-            bool hasValueConstraint,
-            bool hasUnmanagedConstraint,
-            bool hasNotNullConstraint,
-            int ordinal)
-            : base(containingType?.ContainingAssembly, containingType, attributes, Accessibility.NotApplicable, default, name, SpecialType.None, nullableAnnotation)
-        {
-            this.Variance = varianceKind;
-            this.ConstraintTypes = constraintTypes;
-            this.Ordinal = ordinal;
-            this.HasConstructorConstraint = hasConstructorConstraint;
-            this.HasReferenceTypeConstraint = hasReferenceConstraint;
-            this.HasValueTypeConstraint = hasValueConstraint;
-            this.HasUnmanagedTypeConstraint = hasUnmanagedConstraint;
-            this.HasNotNullConstraint = hasNotNullConstraint;
-        }
+        public VarianceKind Variance { get; } = varianceKind;
+        public ImmutableArray<ITypeSymbol> ConstraintTypes { get; internal set; } = constraintTypes;
+        public bool HasConstructorConstraint { get; } = hasConstructorConstraint;
+        public bool HasReferenceTypeConstraint { get; } = hasReferenceConstraint;
+        public bool HasValueTypeConstraint { get; } = hasValueConstraint;
+        public bool HasUnmanagedTypeConstraint { get; } = hasUnmanagedConstraint;
+        public bool HasNotNullConstraint { get; } = hasNotNullConstraint;
+        public int Ordinal { get; } = ordinal;
 
         protected override CodeGenerationTypeSymbol CloneWithNullableAnnotation(NullableAnnotation nullableAnnotation)
         {
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Extensions/ITypeSymbolExtensions.CollectTypeParameterSymbolsVisitor.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Extensions/ITypeSymbolExtensions.CollectTypeParameterSymbolsVisitor.cs
index a24b2991a7b0c..c9cfc9388084d 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Extensions/ITypeSymbolExtensions.CollectTypeParameterSymbolsVisitor.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Extensions/ITypeSymbolExtensions.CollectTypeParameterSymbolsVisitor.cs
@@ -11,19 +11,11 @@ namespace Microsoft.CodeAnalysis.Shared.Extensions
 {
     internal partial class ITypeSymbolExtensions
     {
-        private class CollectTypeParameterSymbolsVisitor : SymbolVisitor
+        private class CollectTypeParameterSymbolsVisitor(
+             IList<ITypeParameterSymbol> typeParameters,
+            bool onlyMethodTypeParameters) : SymbolVisitor
         {
             private readonly HashSet<ISymbol> _visited = new();
-            private readonly bool _onlyMethodTypeParameters;
-            private readonly IList<ITypeParameterSymbol> _typeParameters;
-
-            public CollectTypeParameterSymbolsVisitor(
-                 IList<ITypeParameterSymbol> typeParameters,
-                bool onlyMethodTypeParameters)
-            {
-                _onlyMethodTypeParameters = onlyMethodTypeParameters;
-                _typeParameters = typeParameters;
-            }
 
             public override void DefaultVisit(ISymbol node)
                 => throw new NotImplementedException();
@@ -82,11 +74,11 @@ public override void VisitTypeParameter(ITypeParameterSymbol symbol)
             {
                 if (_visited.Add(symbol))
                 {
-                    if (symbol.TypeParameterKind == TypeParameterKind.Method || !_onlyMethodTypeParameters)
+                    if (symbol.TypeParameterKind == TypeParameterKind.Method || !onlyMethodTypeParameters)
                     {
-                        if (!_typeParameters.Contains(symbol))
+                        if (!typeParameters.Contains(symbol))
                         {
-                            _typeParameters.Add(symbol);
+                            typeParameters.Add(symbol);
                         }
                     }
 
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Rename/Annotations/RenameActionAnnotation.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Rename/Annotations/RenameActionAnnotation.cs
index 823bb9b605b05..271cbbcf524dd 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Rename/Annotations/RenameActionAnnotation.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Rename/Annotations/RenameActionAnnotation.cs
@@ -13,76 +13,63 @@ namespace Microsoft.CodeAnalysis.Rename.ConflictEngine
     /// check if the semantics have been changes (conflict detection).
     /// </summary>
     /// <remarks>This annotation should be put on tokens only.</remarks>
-    internal class RenameActionAnnotation : RenameAnnotation
+    internal class RenameActionAnnotation(
+        TextSpan originalSpan,
+        bool isRenameLocation,
+        string prefix,
+        string suffix,
+        bool isOriginalTextLocation,
+        RenameDeclarationLocationReference[] renameDeclarationLocations,
+        bool isNamespaceDeclarationReference,
+        bool isInvocationExpression,
+        bool isMemberGroupReference) : RenameAnnotation
     {
         /// <summary>
         /// The span this token occupied in the original syntax tree. Can be used to show e.g. conflicts in the UI.
         /// </summary>
-        public readonly TextSpan OriginalSpan;
+        public readonly TextSpan OriginalSpan = originalSpan;
 
         /// <summary>
         /// A flag indicating whether this is a location that needs to be renamed or just tracked for conflicts.
         /// </summary>
-        public readonly bool IsRenameLocation;
+        public readonly bool IsRenameLocation = isRenameLocation;
 
         /// <summary>
         /// A flag indicating whether the token at this location has the same ValueText then the original name 
         /// of the symbol that gets renamed.
         /// </summary>
-        public readonly bool IsOriginalTextLocation;
+        public readonly bool IsOriginalTextLocation = isOriginalTextLocation;
 
         /// <summary>
         /// When replacing the annotated token this string will be prepended to the token's value. This is used when renaming compiler 
         /// generated fields and methods backing properties (e.g. "get_X" or "_X" for property "X").
         /// </summary>
-        public readonly string Prefix;
+        public readonly string Prefix = prefix;
 
         /// <summary>
         /// When replacing the annotated token this string will be appended to the token's value. This is used when renaming compiler 
         /// generated types whose names are derived from user given names (e.g. "XEventHandler" for event "X").
         /// </summary>
-        public readonly string Suffix;
+        public readonly string Suffix = suffix;
 
         /// <summary>
         /// A single dimensional array of annotations to verify after rename.
         /// </summary>
-        public readonly RenameDeclarationLocationReference[] RenameDeclarationLocationReferences;
+        public readonly RenameDeclarationLocationReference[] RenameDeclarationLocationReferences = renameDeclarationLocations;
 
         /// <summary>
         /// States if this token is a Namespace Declaration Reference
         /// </summary>
-        public readonly bool IsNamespaceDeclarationReference;
+        public readonly bool IsNamespaceDeclarationReference = isNamespaceDeclarationReference;
 
         /// <summary>
         /// States if this token is a member group reference, typically found in NameOf expressions
         /// </summary>
-        public readonly bool IsMemberGroupReference;
+        public readonly bool IsMemberGroupReference = isMemberGroupReference;
 
         /// <summary>
         /// States if this token is annotated as a part of the Invocation Expression that needs to be checked for the Conflicts
         /// </summary>
-        public readonly bool IsInvocationExpression;
-
-        public RenameActionAnnotation(
-            TextSpan originalSpan,
-            bool isRenameLocation,
-            string prefix,
-            string suffix,
-            bool isOriginalTextLocation,
-            RenameDeclarationLocationReference[] renameDeclarationLocations,
-            bool isNamespaceDeclarationReference,
-            bool isInvocationExpression,
-            bool isMemberGroupReference)
-        {
-            this.OriginalSpan = originalSpan;
-            this.IsRenameLocation = isRenameLocation;
-            this.Prefix = prefix;
-            this.Suffix = suffix;
-            this.RenameDeclarationLocationReferences = renameDeclarationLocations;
-            this.IsOriginalTextLocation = isOriginalTextLocation;
-            this.IsNamespaceDeclarationReference = isNamespaceDeclarationReference;
-            this.IsInvocationExpression = isInvocationExpression;
-            this.IsMemberGroupReference = isMemberGroupReference;
-        }
+        public readonly bool IsInvocationExpression = isInvocationExpression;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/IProgressTracker.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/IProgressTracker.cs
index 04d5b88d22cd3..1b8e8f210ea26 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/IProgressTracker.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/IProgressTracker.cs
@@ -32,18 +32,11 @@ public static ItemCompletedDisposer ItemCompletedScope(this IProgressTracker tra
             return new ItemCompletedDisposer(tracker);
         }
 
-        public readonly struct ItemCompletedDisposer : IDisposable
+        public readonly struct ItemCompletedDisposer(IProgressTracker tracker) : IDisposable
         {
-            private readonly IProgressTracker _tracker;
-
-            public ItemCompletedDisposer(IProgressTracker tracker)
-            {
-                _tracker = tracker;
-            }
-
             public void Dispose()
             {
-                _tracker.ItemCompleted();
+                tracker.ItemCompleted();
             }
         }
     }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/NameGenerator.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/NameGenerator.cs
index d6013b284708f..85e41eaeef53a 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/NameGenerator.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/NameGenerator.cs
@@ -184,5 +184,23 @@ public static string GenerateUniqueName(string baseName, string extension, Func<
 
             return name;
         }
+
+        public static string GenerateUniqueName(IEnumerable<string> baseNames, Func<string, bool> canUse)
+        {
+            int? index = null;
+
+            while (true)
+            {
+                foreach (var name in baseNames)
+                {
+                    var modifiedName = name + index;
+
+                    if (canUse(modifiedName))
+                        return modifiedName;
+                }
+
+                index = index is null ? 1 : index + 1;
+            }
+        }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/TextReaderWithLength.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/TextReaderWithLength.cs
index 49d932868fb34..3bb34dabaff26 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/TextReaderWithLength.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Utilities/TextReaderWithLength.cs
@@ -8,11 +8,8 @@
 
 namespace Microsoft.CodeAnalysis.Shared.Utilities
 {
-    internal abstract class TextReaderWithLength : TextReader
+    internal abstract class TextReaderWithLength(int length) : TextReader
     {
-        public TextReaderWithLength(int length)
-            => Length = length;
-
-        public int Length { get; }
+        public int Length { get; } = length;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/LanguageServiceMetadata.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/LanguageServiceMetadata.cs
index ce463c5bf0cef..46aa7d78eb7c8 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/LanguageServiceMetadata.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/LanguageServiceMetadata.cs
@@ -12,19 +12,11 @@ namespace Microsoft.CodeAnalysis.Host.Mef
     /// <summary>
     /// MEF metadata class used for finding <see cref="ILanguageService"/> and <see cref="ILanguageServiceFactory"/> exports.
     /// </summary>
-    internal class LanguageServiceMetadata : LanguageMetadata
+    internal class LanguageServiceMetadata(IDictionary<string, object> data) : LanguageMetadata(data)
     {
-        public string ServiceType { get; }
-        public string Layer { get; }
+        public string ServiceType { get; } = (string)data.GetValueOrDefault("ServiceType");
+        public string Layer { get; } = (string)data.GetValueOrDefault("Layer");
 
-        public IReadOnlyDictionary<string, object> Data { get; }
-
-        public LanguageServiceMetadata(IDictionary<string, object> data)
-            : base(data)
-        {
-            this.ServiceType = (string)data.GetValueOrDefault("ServiceType");
-            this.Layer = (string)data.GetValueOrDefault("Layer");
-            this.Data = (IReadOnlyDictionary<string, object>)data;
-        }
+        public IReadOnlyDictionary<string, object> Data { get; } = (IReadOnlyDictionary<string, object>)data;
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefLanguageServices.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefLanguageServices.cs
index 63d9a29e51e4b..23c4d12255fb9 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefLanguageServices.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefLanguageServices.cs
@@ -127,15 +127,10 @@ private static bool TryGetServiceByLayer(string layer, IEnumerable<Lazy<ILanguag
             return service != null;
         }
 
-        internal sealed class LazyServiceMetadataDebuggerProxy
+        internal sealed class LazyServiceMetadataDebuggerProxy(ImmutableArray<Lazy<ILanguageService, LanguageServiceMetadata>> services)
         {
-            private readonly ImmutableArray<Lazy<ILanguageService, LanguageServiceMetadata>> _services;
-
-            public LazyServiceMetadataDebuggerProxy(ImmutableArray<Lazy<ILanguageService, LanguageServiceMetadata>> services)
-                => _services = services;
-
             public (string type, string layer)[] Metadata
-                => _services.Select(s => (s.Metadata.ServiceType, s.Metadata.Layer)).ToArray();
+                => services.Select(s => (s.Metadata.ServiceType, s.Metadata.Layer)).ToArray();
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefWorkspaceServices.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefWorkspaceServices.cs
index 4269c84ff1c19..d6b5e40891cc9 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefWorkspaceServices.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/Workspace/Mef/MefWorkspaceServices.cs
@@ -208,15 +208,10 @@ public override IEnumerable<TLanguageService> FindLanguageServices<TLanguageServ
         internal bool TryGetLanguageServices(string languageName, out MefLanguageServices languageServices)
             => _languageServicesMap.TryGetValue(languageName, out languageServices);
 
-        internal sealed class LazyServiceMetadataDebuggerProxy
+        internal sealed class LazyServiceMetadataDebuggerProxy(ImmutableArray<Lazy<IWorkspaceService, WorkspaceServiceMetadata>> services)
         {
-            private readonly ImmutableArray<Lazy<IWorkspaceService, WorkspaceServiceMetadata>> _services;
-
-            public LazyServiceMetadataDebuggerProxy(ImmutableArray<Lazy<IWorkspaceService, WorkspaceServiceMetadata>> services)
-                => _services = services;
-
             public (string type, string layer)[] Metadata
-                => _services.Select(s => (s.Metadata.ServiceType, s.Metadata.Layer)).ToArray();
+                => services.Select(s => (s.Metadata.ServiceType, s.Metadata.Layer)).ToArray();
         }
     }
 }
diff --git a/src/Workspaces/TestAnalyzerReference/HelloWorldGenerator.cs b/src/Workspaces/TestAnalyzerReference/HelloWorldGenerator.cs
index 65fb21fe3f1a4..cf5e8866d86ad 100644
--- a/src/Workspaces/TestAnalyzerReference/HelloWorldGenerator.cs
+++ b/src/Workspaces/TestAnalyzerReference/HelloWorldGenerator.cs
@@ -13,6 +13,8 @@ public sealed class HelloWorldGenerator : ISourceGenerator
     {
         public const string GeneratedEnglishClassName = "HelloWorld";
         public const string GeneratedSpanishClassName = "HolaMundo";
+        public const string GeneratedFolderName = "Folder";
+        public const string GeneratedFolderClassName = "HelloFolder";
 
         public void Initialize(GeneratorInitializationContext context)
         {
@@ -40,6 +42,10 @@ public static string GetMessage()
     }
 }
 ", encoding: Encoding.UTF8));
+
+            context.AddSource($"{GeneratedFolderName}/{GeneratedFolderClassName}", $$"""
+                class {{GeneratedFolderClassName}} { }
+                """);
         }
     }
 }
diff --git a/src/Workspaces/VisualBasic/Portable/CodeCleanup/Providers/RemoveUnnecessaryLineContinuationCodeCleanupProvider.vb b/src/Workspaces/VisualBasic/Portable/CodeCleanup/Providers/RemoveUnnecessaryLineContinuationCodeCleanupProvider.vb
index 3dbcee28ef4f8..42eeaecefeb26 100644
--- a/src/Workspaces/VisualBasic/Portable/CodeCleanup/Providers/RemoveUnnecessaryLineContinuationCodeCleanupProvider.vb
+++ b/src/Workspaces/VisualBasic/Portable/CodeCleanup/Providers/RemoveUnnecessaryLineContinuationCodeCleanupProvider.vb
@@ -76,21 +76,21 @@ Namespace Microsoft.CodeAnalysis.CodeCleanup.Providers
                                                      Dim token = n
 
                                                      ' replace token if needed
-                                                     If _tokens.ContainsKey(token) Then
-                                                         token = _tokens(token)
+                                                     Dim remappedToken As SyntaxToken = Nothing
+                                                     If _tokens.TryGetValue(token, remappedToken) Then
+                                                         token = remappedToken
                                                      End If
 
                                                      ' replace leading trivia if needed
                                                      Dim current = token
-                                                     If _leading.ContainsKey(token) Then
-                                                         Dim leading = _leading(token)
-                                                         current = current.WithLeadingTrivia(leading)
+                                                     Dim triviaList As SyntaxTriviaList = Nothing
+                                                     If _leading.TryGetValue(token, triviaList) Then
+                                                         current = current.WithLeadingTrivia(triviaList)
                                                      End If
 
                                                      ' replace trailing trivia if needed
-                                                     If _trailing.ContainsKey(token) Then
-                                                         Dim trailing = _trailing(token)
-                                                         current = current.WithTrailingTrivia(trailing)
+                                                     If _trailing.TryGetValue(token, triviaList) Then
+                                                         current = current.WithTrailingTrivia(triviaList)
                                                      End If
 
                                                      Return current
diff --git a/src/Workspaces/VisualBasic/Portable/CodeCleanup/VisualBasicCodeCleanerService.vb b/src/Workspaces/VisualBasic/Portable/CodeCleanup/VisualBasicCodeCleanerService.vb
index 4987fc157cb9f..a2c6b0b6e4a1a 100644
--- a/src/Workspaces/VisualBasic/Portable/CodeCleanup/VisualBasicCodeCleanerService.vb
+++ b/src/Workspaces/VisualBasic/Portable/CodeCleanup/VisualBasicCodeCleanerService.vb
@@ -43,7 +43,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeCleanup
             Return result.ToImmutableAndFree()
         End Function
 
-        Private Sub ProcessNode(node As SyntaxNode, result As ArrayBuilder(Of TextSpan))
+        Private Shared Sub ProcessNode(node As SyntaxNode, result As ArrayBuilder(Of TextSpan))
             If SkipProcessing(node, result) Then
                 Return
             End If
@@ -57,7 +57,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeCleanup
             Next
         End Sub
 
-        Private Sub ProcessToken(token As SyntaxToken, result As ArrayBuilder(Of TextSpan))
+        Private Shared Sub ProcessToken(token As SyntaxToken, result As ArrayBuilder(Of TextSpan))
             If SkipProcessing(token, result) Then
                 Return
             End If
@@ -98,7 +98,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeCleanup
                 End Function)
         End Function
 
-        Private Function GetMultiLineContainer(node As SyntaxNode) As SyntaxNode
+        Private Shared Function GetMultiLineContainer(node As SyntaxNode) As SyntaxNode
             If node Is Nothing Then
                 Return Nothing
             End If
diff --git a/src/Workspaces/VisualBasic/Portable/CodeGeneration/VisualBasicSyntaxGenerator.vb b/src/Workspaces/VisualBasic/Portable/CodeGeneration/VisualBasicSyntaxGenerator.vb
index 1e5dd6c7f899d..b354dbc0046f7 100644
--- a/src/Workspaces/VisualBasic/Portable/CodeGeneration/VisualBasicSyntaxGenerator.vb
+++ b/src/Workspaces/VisualBasic/Portable/CodeGeneration/VisualBasicSyntaxGenerator.vb
@@ -1253,7 +1253,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             End Select
         End Function
 
-        Private Function GetNameAsIdentifier(type As SyntaxNode) As String
+        Private Shared Function GetNameAsIdentifier(type As SyntaxNode) As String
             Dim name = TryCast(type, IdentifierNameSyntax)
             If name IsNot Nothing Then
                 Return name.Identifier.ValueText
@@ -1695,7 +1695,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
                     Return compilationUnit.Attributes(0).AttributeLists
                 End If
             End If
-            Return Me.Flatten(declaration.GetAttributeLists())
+            Return Flatten(declaration.GetAttributeLists())
         End Function
 
         Public Overrides Function InsertAttributes(declaration As SyntaxNode, index As Integer, attributes As IEnumerable(Of SyntaxNode)) As SyntaxNode
@@ -1744,7 +1744,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
         End Function
 
         Public Overrides Function GetReturnAttributes(declaration As SyntaxNode) As IReadOnlyList(Of SyntaxNode)
-            Return Me.Flatten(GetReturnAttributeLists(declaration))
+            Return Flatten(GetReturnAttributeLists(declaration))
         End Function
 
         Public Overrides Function InsertReturnAttributes(declaration As SyntaxNode, index As Integer, attributes As IEnumerable(Of SyntaxNode)) As SyntaxNode
@@ -1769,7 +1769,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             Else
                 Dim lists = GetReturnAttributeLists(declaration)
                 Dim newLists = lists.AddRange(newAttributes)
-                Return Me.WithReturnAttributeLists(declaration, newLists)
+                Return WithReturnAttributeLists(declaration, newLists)
             End If
         End Function
 
@@ -1787,7 +1787,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             Return Nothing
         End Function
 
-        Private Function WithReturnAttributeLists(declaration As SyntaxNode, lists As IEnumerable(Of AttributeListSyntax)) As SyntaxNode
+        Private Shared Function WithReturnAttributeLists(declaration As SyntaxNode, lists As IEnumerable(Of AttributeListSyntax)) As SyntaxNode
             If declaration Is Nothing Then
                 Return Nothing
             End If
@@ -2013,13 +2013,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             Return VisualBasicSyntaxFacts.IsChildOfVariableDeclaration(node)
         End Function
 
-        Private Function Isolate(declaration As SyntaxNode, editor As Func(Of SyntaxNode, SyntaxNode)) As SyntaxNode
+        Private Shared Function Isolate(declaration As SyntaxNode, editor As Func(Of SyntaxNode, SyntaxNode)) As SyntaxNode
             Dim isolated = AsIsolatedDeclaration(declaration)
 
             Return PreserveTrivia(isolated, editor)
         End Function
 
-        Private Function GetFullDeclaration(declaration As SyntaxNode) As SyntaxNode
+        Private Shared Function GetFullDeclaration(declaration As SyntaxNode) As SyntaxNode
             Select Case declaration.Kind
                 Case SyntaxKind.ModifiedIdentifier
                     If IsChildOf(declaration, SyntaxKind.VariableDeclarator) Then
@@ -2043,7 +2043,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             Return declaration
         End Function
 
-        Private Function AsIsolatedDeclaration(declaration As SyntaxNode) As SyntaxNode
+        Private Shared Function AsIsolatedDeclaration(declaration As SyntaxNode) As SyntaxNode
             Select Case declaration.Kind
                 Case SyntaxKind.ModifiedIdentifier
                     Dim full = GetFullDeclaration(declaration)
@@ -2570,7 +2570,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             End If
         End Function
 
-        Private Function WithModifierTokens(declaration As SyntaxNode, tokens As SyntaxTokenList) As SyntaxNode
+        Private Shared Function WithModifierTokens(declaration As SyntaxNode, tokens As SyntaxTokenList) As SyntaxNode
             Select Case declaration.Kind
                 Case SyntaxKind.ClassBlock
                     Return DirectCast(declaration, ClassBlockSyntax).WithClassStatement(DirectCast(declaration, ClassBlockSyntax).ClassStatement.WithModifiers(tokens))
@@ -2625,7 +2625,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
                      SyntaxKind.RemoveHandlerAccessorBlock,
                     SyntaxKind.RaiseEventAccessorBlock
                     Return DirectCast(declaration, AccessorBlockSyntax).WithAccessorStatement(
-                        DirectCast(Me.WithModifierTokens(DirectCast(declaration, AccessorBlockSyntax).AccessorStatement, tokens), AccessorStatementSyntax))
+                        DirectCast(WithModifierTokens(DirectCast(declaration, AccessorBlockSyntax).AccessorStatement, tokens), AccessorStatementSyntax))
                 Case SyntaxKind.GetAccessorStatement,
                      SyntaxKind.SetAccessorStatement,
                      SyntaxKind.AddHandlerAccessorStatement,
@@ -3109,7 +3109,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
         End Function
 
         Public Overrides Function GetNamespaceImports(declaration As SyntaxNode) As IReadOnlyList(Of SyntaxNode)
-            Return Me.Flatten(GetUnflattenedNamespaceImports(declaration))
+            Return Flatten(GetUnflattenedNamespaceImports(declaration))
         End Function
 
         Private Shared Function GetUnflattenedNamespaceImports(declaration As SyntaxNode) As IReadOnlyList(Of SyntaxNode)
@@ -3648,8 +3648,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             End If
 
             If root.Span.Contains(declaration.Span) Then
-                Dim newFullDecl = Me.AsIsolatedDeclaration(newDeclaration)
-                Dim fullDecl = Me.GetFullDeclaration(declaration)
+                Dim newFullDecl = AsIsolatedDeclaration(newDeclaration)
+                Dim fullDecl = GetFullDeclaration(declaration)
 
                 ' special handling for replacing at location of a sub-declaration
                 If fullDecl IsNot declaration AndAlso fullDecl.IsKind(newFullDecl.Kind) Then
@@ -3675,7 +3675,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
         End Function
 
         ' return true if one sub-declaration can be replaced in-line with another sub-declaration
-        Private Function AreInlineReplaceableSubDeclarations(decl1 As SyntaxNode, decl2 As SyntaxNode) As Boolean
+        Private Shared Function AreInlineReplaceableSubDeclarations(decl1 As SyntaxNode, decl2 As SyntaxNode) As Boolean
             Dim kind = decl1.Kind
             If Not decl2.IsKind(kind) Then
                 Return False
@@ -3692,7 +3692,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             Return False
         End Function
 
-        Private Function AreSimilarExceptForSubDeclarations(decl1 As SyntaxNode, decl2 As SyntaxNode) As Boolean
+        Private Shared Function AreSimilarExceptForSubDeclarations(decl1 As SyntaxNode, decl2 As SyntaxNode) As Boolean
             If decl1 Is Nothing OrElse decl2 Is Nothing Then
                 Return False
             End If
@@ -3735,7 +3735,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
         End Function
 
         Private Function InsertDeclarationsBeforeInternal(root As SyntaxNode, declaration As SyntaxNode, newDeclarations As IEnumerable(Of SyntaxNode)) As SyntaxNode
-            Dim fullDecl = Me.GetFullDeclaration(declaration)
+            Dim fullDecl = GetFullDeclaration(declaration)
             If fullDecl Is declaration OrElse GetDeclarationCount(fullDecl) = 1 Then
                 Return MyBase.InsertNodesBefore(root, declaration, newDeclarations)
             End If
@@ -3761,7 +3761,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
         End Function
 
         Private Function InsertNodesAfterInternal(root As SyntaxNode, declaration As SyntaxNode, newDeclarations As IEnumerable(Of SyntaxNode)) As SyntaxNode
-            Dim fullDecl = Me.GetFullDeclaration(declaration)
+            Dim fullDecl = GetFullDeclaration(declaration)
             If fullDecl Is declaration OrElse GetDeclarationCount(fullDecl) = 1 Then
                 Return MyBase.InsertNodesAfter(root, declaration, newDeclarations)
             End If
@@ -3831,13 +3831,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
             End Select
         End Function
 
-        Private Function Flatten(members As IReadOnlyList(Of SyntaxNode)) As IReadOnlyList(Of SyntaxNode)
+        Private Shared Function Flatten(members As IReadOnlyList(Of SyntaxNode)) As IReadOnlyList(Of SyntaxNode)
             Dim builder = ArrayBuilder(Of SyntaxNode).GetInstance()
             Flatten(builder, members)
             Return builder.ToImmutableAndFree()
         End Function
 
-        Private Sub Flatten(builder As ArrayBuilder(Of SyntaxNode), members As IReadOnlyList(Of SyntaxNode))
+        Private Shared Sub Flatten(builder As ArrayBuilder(Of SyntaxNode), members As IReadOnlyList(Of SyntaxNode))
             For Each member In members
                 If GetDeclarationCount(member) > 1 Then
                     Select Case member.Kind
@@ -3868,13 +3868,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeGeneration
 
         Public Overrides Function RemoveNode(root As SyntaxNode, declaration As SyntaxNode, options As SyntaxRemoveOptions) As SyntaxNode
             If root.Span.Contains(declaration.Span) Then
-                Return Isolate(root.TrackNodes(declaration), Function(r) Me.RemoveNodeInternal(r, r.GetCurrentNode(declaration), options))
+                Return Isolate(root.TrackNodes(declaration), Function(r) RemoveNodeInternal(r, r.GetCurrentNode(declaration), options))
             Else
                 Return MyBase.RemoveNode(root, declaration, options)
             End If
         End Function
 
-        Private Function RemoveNodeInternal(root As SyntaxNode, node As SyntaxNode, options As SyntaxRemoveOptions) As SyntaxNode
+        Private Shared Function RemoveNodeInternal(root As SyntaxNode, node As SyntaxNode, options As SyntaxRemoveOptions) As SyntaxNode
 
             ' special case handling for nodes that remove their parents too
             Select Case node.Kind
diff --git a/src/Workspaces/VisualBasic/Portable/Formatting/Engine/Trivia/TriviaDataFactory.TriviaRewriter.vb b/src/Workspaces/VisualBasic/Portable/Formatting/Engine/Trivia/TriviaDataFactory.TriviaRewriter.vb
index 4e46623e5a223..6130e887292bb 100644
--- a/src/Workspaces/VisualBasic/Portable/Formatting/Engine/Trivia/TriviaDataFactory.TriviaRewriter.vb
+++ b/src/Workspaces/VisualBasic/Portable/Formatting/Engine/Trivia/TriviaDataFactory.TriviaRewriter.vb
@@ -139,17 +139,18 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Formatting
                 Dim leadingTrivia = token.LeadingTrivia
                 Dim trailingTrivia = token.TrailingTrivia
 
-                If _trailingTriviaMap.ContainsKey(token) Then
+                Dim triviaList As SyntaxTriviaList = Nothing
+                If _trailingTriviaMap.TryGetValue(token, triviaList) Then
                     ' okay, we have this situation
                     ' token|trivia
-                    trailingTrivia = _trailingTriviaMap(token)
+                    trailingTrivia = triviaList
                     hasChanges = True
                 End If
 
-                If _leadingTriviaMap.ContainsKey(token) Then
+                If _leadingTriviaMap.TryGetValue(token, triviaList) Then
                     ' okay, we have this situation
                     ' trivia|token
-                    leadingTrivia = _leadingTriviaMap(token)
+                    leadingTrivia = triviaList
                     hasChanges = True
                 End If