Use ValueTask shared from corelib

src/Common/src/CoreLib/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilder.cs

@@ -40,7 +40,12 @@ public static AsyncValueTaskMethodBuilder<TResult> Create() =>
         /// <param name="stateMachine">The state machine instance, passed by reference.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine =>
+            // will provide the right ExecutionContext semantics
+#if netstandard
+            _methodBuilder.Start(ref stateMachine);
+#else
             AsyncMethodBuilder.Start(ref stateMachine); // will provide the right ExecutionContext semantics
+#endif
 
         /// <summary>Associates the builder with the specified state machine.</summary>
         /// <param name="stateMachine">The state machine instance to associate with the builder.</param>

src/System.Threading.Tasks.Extensions/ref/System.Threading.Tasks.Extensions.cs

@@ -29,18 +29,18 @@ public readonly partial struct ConfiguredValueTaskAwaitable<TResult>
     {
         private readonly object _dummy;
         public System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable<TResult>.ConfiguredValueTaskAwaiter GetAwaiter() { throw null; }
-        public partial struct ConfiguredValueTaskAwaiter : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
+        public readonly partial struct ConfiguredValueTaskAwaiter : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
         {
-            private object _dummy;
+            private readonly object _dummy;
             public bool IsCompleted { get { throw null; } }
             public TResult GetResult() { throw null; }
             public void OnCompleted(System.Action continuation) { }
             public void UnsafeOnCompleted(System.Action continuation) { }
         }
     }
-    public partial struct ValueTaskAwaiter<TResult> : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
+    public readonly partial struct ValueTaskAwaiter<TResult> : System.Runtime.CompilerServices.ICriticalNotifyCompletion, System.Runtime.CompilerServices.INotifyCompletion
     {
-        private object _dummy;
+        private readonly object _dummy;
         public bool IsCompleted { get { throw null; } }
         public TResult GetResult() { throw null; }
         public void OnCompleted(System.Action continuation) { }

src/System.Threading.Tasks.Extensions/src/System.Threading.Tasks.Extensions.csproj

@@ -6,6 +6,7 @@
     <DocumentationFile>$(OutputPath)$(MSBuildProjectName).xml</DocumentationFile>
     <PackageTargetFramework Condition="'$(TargetGroup)' == 'netstandard1.0'">netstandard1.0;portable-net45+win8+wp8+wpa81</PackageTargetFramework>
     <IsPartialFacadeAssembly Condition="'$(TargetGroup)' != 'netstandard' and '$(TargetGroup)' != 'netstandard1.0'">true</IsPartialFacadeAssembly>
+    <DefineConstants Condition="'$(IsPartialFacadeAssembly)' != 'true'">$(DefineConstants);netstandard</DefineConstants>
     <ExcludeResourcesImport Condition="'$(IsPartialFacadeAssembly)'=='true'">true</ExcludeResourcesImport>
     <AssemblyVersion Condition="$(TargetGroup.StartsWith('netstandard'))">4.1.1.0</AssemblyVersion>
   </PropertyGroup>
@@ -23,15 +24,30 @@
     <ReferenceFromRuntime Include="System.Private.CoreLib" />
   </ItemGroup>
   <ItemGroup Condition="'$(IsPartialFacadeAssembly)' != 'true'">
-    <Compile Include="System\Runtime\CompilerServices\AsyncMethodBuilderAttribute.cs" />
-    <Compile Include="System\Runtime\CompilerServices\AsyncValueTaskMethodBuilder.cs" />
-    <Compile Include="System\Runtime\CompilerServices\ConfiguredValueTaskAwaitable.cs" />
-    <Compile Include="System\Runtime\CompilerServices\ValueTaskAwaiter.cs" />
-    <Compile Include="System\Threading\Tasks\ValueTask.cs" />
+    <Compile Include="System\ThrowHelper.cs" />
+    <Compile Include="$(CommonPath)\CoreLib\System\Diagnostics\StackTraceHiddenAttribute.cs">
+      <Link>Common\CoreLib\System\Diagnostics\StackTraceHiddenAttribute.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Runtime\CompilerServices\AsyncMethodBuilderAttribute.cs">
+      <Link>Common\CoreLib\System\Runtime\CompilerServices\AsyncMethodBuilderAttribute.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Runtime\CompilerServices\AsyncValueTaskMethodBuilder.cs">
+      <Link>Common\CoreLib\System\Runtime\CompilerServices\AsyncValueTaskMethodBuilder.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Runtime\CompilerServices\ConfiguredValueTaskAwaitable.cs">
+      <Link>Common\CoreLib\System\Runtime\CompilerServices\ConfiguredValueTaskAwaitable.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Runtime\CompilerServices\ValueTaskAwaiter.cs">
+      <Link>Common\CoreLib\System\Runtime\CompilerServices\ValueTaskAwaiter.cs</Link>
+    </Compile>
+    <Compile Include="$(CommonPath)\CoreLib\System\Threading\Tasks\ValueTask.cs">
+      <Link>Common\CoreLib\System\Threading\Tasks\ValueTask.cs</Link>
+    </Compile>
+
     <Reference Include="System.Collections" />
     <Reference Include="System.Diagnostics.Debug" />
     <Reference Include="System.Runtime" />
     <Reference Include="System.Threading.Tasks" />
   </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
-</Project>
+</Project>