Merge branch 'master' into nullable-states

eng/Versions.props

@@ -278,10 +278,10 @@
     <UsingToolXliff>true</UsingToolXliff>
     <UsingToolXUnit>true</UsingToolXUnit>
     <!-- 
-       During the transition period from Microsoft.Net.Compilers to Microsoft.Net.Compilers.Toolset
-       we are always doing custom importing here.
+      When using a bootstrap builder we don't want to use the Microsoft.Net.Compilers.Toolset package but
+      rather explicitly override it. 
     -->
-    <UsingToolMicrosoftNetCompilers>false</UsingToolMicrosoftNetCompilers>
+    <UsingToolMicrosoftNetCompilers Condition="'$(BootstrapBuildPath)' == ''">true</UsingToolMicrosoftNetCompilers>
   </PropertyGroup>
   <PropertyGroup>
     <RestoreSources>

eng/targets/Settings.props

@@ -130,14 +130,6 @@
   -->
   <Import Project="Bootstrap.props" Condition="'$(BootstrapBuildPath)' != ''" />
 
-  <!--
-     During the transition period from Microsoft.Net.Compilers to Microsoft.Net.Compilers.Toolset
-     we need our own PackageReference
-  -->
-  <ItemGroup>
-    <PackageReference Include="Microsoft.Net.Compilers.Toolset" Version="$(MicrosoftNetCompilersToolsetVersion)" Condition="'$(BootstrapBuildPath)' == ''" PrivateAssets="all" IsImplicitlyDefined="true" />
-  </ItemGroup>
-
   <!--
     Analyzers
   -->

src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs

@@ -1974,7 +1974,43 @@ private BoundExpression BindRangeExpression(RangeExpressionSyntax node, Diagnost
 
             if (!rangeType.IsErrorType())
             {
-                symbolOpt = (MethodSymbol)GetWellKnownTypeMember(Compilation, WellKnownMember.System_Range__ctor, diagnostics, syntax: node);
+                // Depending on the available arguments to the range expression, there are four
+                // possible well-known members we could bind to. The constructor is always the
+                // fallback member, usable in any situation. However, if any of the other members
+                // are available and applicable, we will prefer that.
+
+                WellKnownMember? memberOpt = null;
+                if (node.LeftOperand is null && node.RightOperand is null)
+                {
+                    memberOpt = WellKnownMember.System_Range__get_All;
+                }
+                else if (node.LeftOperand is null)
+                {
+                    memberOpt = WellKnownMember.System_Range__EndAt;
+                }
+                else if (node.RightOperand is null)
+                {
+                    memberOpt = WellKnownMember.System_Range__StartAt;
+                }
+
+                if (!(memberOpt is null))
+                {
+                    symbolOpt = (MethodSymbol)GetWellKnownTypeMember(
+                        Compilation,
+                        memberOpt.GetValueOrDefault(),
+                        diagnostics,
+                        syntax: node,
+                        isOptional: true);
+                }
+
+                if (symbolOpt is null)
+                {
+                    symbolOpt = (MethodSymbol)GetWellKnownTypeMember(
+                        Compilation,
+                        WellKnownMember.System_Range__ctor,
+                        diagnostics,
+                        syntax: node);
+                }
             }
 
             BoundExpression left = BindRangeExpressionOperand(node.LeftOperand, diagnostics);
@@ -6864,8 +6900,11 @@ private BoundExpression BindArrayAccess(ExpressionSyntax node, BoundExpression e
                 }
             }
 
-            var resultType = rank == 1 &&
-                TypeSymbol.Equals(convertedArguments[0].Type, Compilation.GetWellKnownType(WellKnownType.System_Range), TypeCompareKind.ConsiderEverything2)
+            TypeSymbol resultType = rank == 1 &&
+                TypeSymbol.Equals(
+                    convertedArguments[0].Type,
+                    Compilation.GetWellKnownType(WellKnownType.System_Range),
+                    TypeCompareKind.ConsiderEverything)
                 ? arrayType
                 : arrayType.ElementType.TypeSymbol;
 
@@ -6893,9 +6932,30 @@ private BoundExpression ConvertToArrayIndex(BoundExpression index, SyntaxNode no
 
             if (result is null && allowIndexAndRange)
             {
-                result =
-                    TryImplicitConversionToArrayIndex(index, WellKnownType.System_Index, node, diagnostics) ??
-                    TryImplicitConversionToArrayIndex(index, WellKnownType.System_Range, node, diagnostics);
+                result = TryImplicitConversionToArrayIndex(index, WellKnownType.System_Index, node, diagnostics);
+
+                if (result is null)
+                {
+                    result = TryImplicitConversionToArrayIndex(index, WellKnownType.System_Range, node, diagnostics);
+                    if (!(result is null))
+                    {
+                        // This member is needed for lowering and should produce an error if not present
+                        _ = GetWellKnownTypeMember(
+                            Compilation,
+                            WellKnownMember.System_Runtime_CompilerServices_RuntimeHelpers__GetSubArray_T,
+                            diagnostics,
+                            syntax: node);
+                    }
+                }
+                else
+                {
+                    // This member is needed for lowering and should produce an error if not present
+                    _ = GetWellKnownTypeMember(
+                        Compilation,
+                        WellKnownMember.System_Index__GetOffset,
+                        diagnostics,
+                        syntax: node);
+                }
             }
 
             if (result is null)
@@ -7216,43 +7276,6 @@ private BoundExpression BindIndexerOrIndexedPropertyAccess(
 
                 if (!analyzedArguments.HasErrors)
                 {
-                    // https://github.com/dotnet/roslyn/issues/30620
-                    // Pretend like there are indexers that support range and index
-                    if (receiverOpt?.Type.SpecialType == SpecialType.System_String &&
-                        analyzedArguments.Arguments.Count == 1)
-                    {
-                        var argType = analyzedArguments.Arguments[0].Type;
-                        TypeSymbol resultType = null;
-                        if (TypeSymbol.Equals(argType, Compilation.GetWellKnownType(WellKnownType.System_Index), TypeCompareKind.ConsiderEverything2))
-                        {
-                            resultType = GetSpecialType(SpecialType.System_Char, diagnostics, syntax);
-                        }
-                        else if (TypeSymbol.Equals(argType, Compilation.GetWellKnownType(WellKnownType.System_Range), TypeCompareKind.ConsiderEverything2))
-                        {
-                            resultType = GetSpecialType(SpecialType.System_String, diagnostics, syntax);
-                        }
-
-                        if (!(resultType is null))
-                        {
-                            var args = analyzedArguments.Arguments.ToImmutable();
-
-                            overloadResolutionResult.Free();
-                            return new BoundIndexerAccess(
-                                syntax,
-                                receiverOpt,
-                                candidates[0],
-                                args,
-                                argumentNames,
-                                argumentRefKinds,
-                                expanded: false,
-                                argsToParamsOpt: default,
-                                binderOpt: this,
-                                useSetterForDefaultArgumentGeneration: false,
-                                resultType,
-                                hasErrors: false);
-                        }
-                    }
-
                     // Dev10 uses the "this" keyword as the method name for indexers.
                     var candidate = candidates[0];
                     var name = candidate.IsIndexer ? SyntaxFacts.GetText(SyntaxKind.ThisKeyword) : candidate.Name;

src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml

@@ -344,8 +344,8 @@
     <!-- Non-null type is required for this node kind -->
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
 
-    <Field Name="LeftOperand" Type="BoundExpression" Null="allow"/>
-    <Field Name="RightOperand" Type="BoundExpression" Null="allow"/>
+    <Field Name="LeftOperandOpt" Type="BoundExpression" Null="allow"/>
+    <Field Name="RightOperandOpt" Type="BoundExpression" Null="allow"/>
     <Field Name="MethodOpt" Type="MethodSymbol" Null="allow"/>
   </Node>
 

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -994,7 +994,7 @@
     <value>A params parameter must be the last parameter in a formal parameter list</value>
   </data>
   <data name="ERR_SizeofUnsafe" xml:space="preserve">
-    <value>'{0}' does not have a predefined size, therefore sizeof can only be used in an unsafe context (consider using System.Runtime.InteropServices.Marshal.SizeOf)</value>
+    <value>'{0}' does not have a predefined size, therefore sizeof can only be used in an unsafe context</value>
   </data>
   <data name="ERR_DottedTypeNameNotFoundInNS" xml:space="preserve">
     <value>The type or namespace name '{0}' does not exist in the namespace '{1}' (are you missing an assembly reference?)</value>
@@ -5796,4 +5796,4 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_FeatureInPreview" xml:space="preserve">
     <value>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</value>
   </data>
-</root>
+</root>

src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs

@@ -2099,14 +2099,14 @@ public override BoundNode VisitUnaryOperator(BoundUnaryOperator node)
 
         public override BoundNode VisitRangeExpression(BoundRangeExpression node)
         {
-            if (node.LeftOperand != null)
+            if (node.LeftOperandOpt != null)
             {
-                VisitRvalue(node.LeftOperand);
+                VisitRvalue(node.LeftOperandOpt);
             }
 
-            if (node.RightOperand != null)
+            if (node.RightOperandOpt != null)
             {
-                VisitRvalue(node.RightOperand);
+                VisitRvalue(node.RightOperandOpt);
             }
 
             return null;

src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs

@@ -4651,19 +4651,7 @@ private void VisitIndexerAccess(BoundIndexerAccess node, out PropertySymbol inde
 
             VisitArguments(node, node.Arguments, node.ArgumentRefKindsOpt, node.Indexer, node.ArgsToParamsOpt, node.Expanded);
 
-            // https://github.com/dotnet/roslyn/issues/30620 remove before shipping dev16
-            TypeWithState type;
-            if (node.Arguments.Length == 1 &&
-                TypeSymbol.Equals(node.Arguments[0].Type, compilation.GetWellKnownType(WellKnownType.System_Range), TypeCompareKind.ConsiderEverything2))
-            {
-                type = new TypeWithState(node.Type, NullableFlowState.NotNull);
-            }
-            else
-            {
-                type = indexer.Type.ToTypeWithState();
-            }
-
-            SetResult(type, indexer.Type);
+            LvalueResultType = node.Indexer.Type;
         }
 
         public override BoundNode VisitEventAccess(BoundEventAccess node)