Add followup async public apis by 333fred · Pull Request #80455 · dotnet/roslyn

333fred · 2025-09-24T17:00:57Z

Adds the followup APIs for await using and await foreach. Closes #80409.

Relates to test plan #75960

…info.

… and await foreach.

333fred · 2025-09-24T17:02:30Z

@dotnet/roslyn-compiler for review. Suggest reviewing commit-by-commit: the first commit consolidates await information into the same location as the rest of the enumeration info, the second actually adds the API.

src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs

src/Compilers/CSharp/Test/Symbol/Microsoft.CodeAnalysis.CSharp.Symbol.UnitTests.csproj

src/Compilers/CSharp/Portable/CSharpExtensions.cs

jcouv

Done with review pass (commit 3)

jcouv

LGTM Thanks (commit 4)

333fred · 2025-09-29T16:21:49Z

@jcouv @dotnet/roslyn-compiler for review

jcouv · 2025-09-29T16:24:34Z

I've already approved the latest commit. It looks like there's a merge conflict to resolve though

333fred · 2025-09-29T16:49:10Z

I've already approved the latest commit. It looks like there's a merge conflict to resolve though

Whoops, sorry. Apparently github didn't load that comment, I'd only seen the commit 3 comments.

AlekseyTs · 2025-10-02T13:59:08Z

src/Compilers/CSharp/Portable/Compilation/SpeculativeSemanticModelWithMemberModel.cs


+        public override AwaitExpressionInfo GetAwaitExpressionInfo(LocalDeclarationStatementSyntax node)
+        {
+            return GetEnclosingMemberModel(node).GetAwaitExpressionInfo(node);


return GetEnclosingMemberModel(node).GetAwaitExpressionInfo(node);

Is this code path covered by a test? #Closed

AlekseyTs · 2025-10-02T13:59:18Z

src/Compilers/CSharp/Portable/Compilation/SpeculativeSemanticModelWithMemberModel.cs

+
+        public override AwaitExpressionInfo GetAwaitExpressionInfo(UsingStatementSyntax node)
+        {
+            return GetEnclosingMemberModel(node).GetAwaitExpressionInfo(node);


return GetEnclosingMemberModel(node).GetAwaitExpressionInfo(node);

Is this code path covered by a test? #Closed

AlekseyTs · 2025-10-02T14:20:01Z

src/Compilers/CSharp/Portable/Compilation/SyntaxTreeSemanticModel.cs

+        public override AwaitExpressionInfo GetAwaitExpressionInfo(LocalDeclarationStatementSyntax node)
+        {
+            MemberSemanticModel memberModel = GetMemberModel(node);
+            return memberModel == null ? default(AwaitExpressionInfo) : memberModel.GetAwaitExpressionInfo(node);


memberModel.GetAwaitExpressionInfo(node)

Is this code path covered by a test? #Closed

Yes, the existing tests go through here.

AlekseyTs · 2025-10-02T14:20:10Z

src/Compilers/CSharp/Portable/Compilation/SyntaxTreeSemanticModel.cs

+        public override AwaitExpressionInfo GetAwaitExpressionInfo(UsingStatementSyntax node)
+        {
+            MemberSemanticModel memberModel = GetMemberModel(node);
+            return memberModel == null ? default(AwaitExpressionInfo) : memberModel.GetAwaitExpressionInfo(node);


memberModel.GetAwaitExpressionInfo(node)

Is this code path covered by a test? #Closed

Yes, the existing tests go through here.

AlekseyTs · 2025-10-02T14:28:05Z

src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_ForEachStatement.cs

                return RewriteInlineArrayForEachStatementAsFor(node);
            }
-            else if (node.AwaitOpt is null && CanRewriteForEachAsFor(node.Syntax, nodeExpressionType, out var indexerGet, out var lengthGetter))
+            else if (node.EnumeratorInfoOpt is { MoveNextAwaitableInfo: null } && CanRewriteForEachAsFor(node.Syntax, nodeExpressionType, out var indexerGet, out var lengthGetter))


node.EnumeratorInfoOpt is { MoveNextAwaitableInfo: null }

It looks like semantically equivalent replacement is node.EnumeratorInfoOpt?.MoveNextAwaitableInfo is null #Closed

AlekseyTs · 2025-10-02T14:32:17Z

src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs

            SyntaxNode syntax = boundForEachStatement.Syntax;
            bool isImplicit = boundForEachStatement.WasCompilerGenerated;
-            bool isAsynchronous = boundForEachStatement.AwaitOpt != null;
+            bool isAsynchronous = boundForEachStatement.EnumeratorInfoOpt is { IsAsync: true };


EnumeratorInfoOpt is { IsAsync: true }

The rewrite doesn't look semantically equivalent. #Closed

AlekseyTs · 2025-10-02T14:48:36Z

src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IForEachLoopStatement.cs


            var expectedOperationTree = @"
 IBlockOperation (1 statements) (OperationKind.Block, Type: null) (Syntax: '{ ... }')
-  IForEachLoopOperation (LoopKind.ForEach, IsAsynchronous, Continue Label Id: 0, Exit Label Id: 1) (OperationKind.Loop, Type: null) (Syntax: 'await forea ... }')


IsAsynchronous

This change looks unexpected #Closed

As discussed offline, this is because of the error scenario that causes EnumeratorInfoOpt to not be populated. I'll investigate a followup change after to base this flag on just whether the loop is await foreach.

AlekseyTs · 2025-10-02T14:52:36Z

src/Compilers/CSharp/Portable/CSharpExtensions.cs

+        {
+            if (semanticModel is CSharpSemanticModel csmodel)
+            {
+                return csmodel.GetAwaitExpressionInfo(awaitUsingDeclaration);


return csmodel.GetAwaitExpressionInfo(awaitUsingDeclaration);

Is this code path covered by a test? #Closed

Yes, TestAwaitUsingDeclarationAwaitInfo

AlekseyTs · 2025-10-02T14:52:46Z

src/Compilers/CSharp/Portable/CSharpExtensions.cs

+        {
+            if (semanticModel is CSharpSemanticModel csmodel)
+            {
+                return csmodel.GetAwaitExpressionInfo(awaitUsingStatement);


return csmodel.GetAwaitExpressionInfo(awaitUsingStatement);

Is this code path covered by a test? #Closed

Yes, TestAwaitUsingStatementAwaitInfo

AlekseyTs · 2025-10-02T15:08:58Z

Done with review pass (commit 4) #Closed

AlekseyTs

LGTM (commit 5)

* upstream/main: (149 commits) Fix Simplify and add additional asserts Update proposal adjuster to acquire feature flags from VS (dotnet#80541) Remove First/Last Docs Docs Deprecate method and use workaround Remove support for ccreating EmbeddedStrings Remove methods Move more into extensions Move more into extensions Proper slice Proper slice Proper slice Move to slices Extract extensions Downstream Simplify the virtual char api Add telemetry indicating when file-based programs are used (dotnet#80538) Fix thread safety issue in BuildServerConnection.TryCreateServer environment variable handling (dotnet#80498) ...

* upstream/main: Extensions: Close some tracked follow-ups (dotnet#80527) Fix outdated 17.15 to 18.0 (dotnet#80570) Update dependencies from https://github.com/dotnet/dotnet build 285582 (dotnet#80551) Fix all-in-one tests [main] Update dependencies from dotnet/arcade (dotnet#80559) Improve error recovery when object initializer uses ':' instead of '=' (dotnet#80553) Support `field` keyword in EE. (dotnet#80515) Log a debug message for ContentModified exceptions. (dotnet#80549) Update dependencies from https://github.com/dotnet/arcade build 20251002.2 (dotnet#80550)

* upstream/main: (252 commits) Move Watch EA to a separate assembly Microsoft.CodeAnalysis.ExternalAccess.HotReload (dotnet#80556) Enable long paths for Windows DartLab CI (dotnet#80581) Ensure that CS8659 is reported on partial properties (dotnet#80573) Fix a wrong relative link in a doc (dotnet#80567) [main] Source code updates from dotnet/dotnet (dotnet#80578) Update dependencies from https://github.com/dotnet/arcade build 20251006.2 (dotnet#80577) Update main configs after VS snap (dotnet#80523) Add followup async public apis (dotnet#80455) Reduce allocations in CSharpSyntaxNode.GetStructure (dotnet#80562) Extensions: Close some tracked follow-ups (dotnet#80527) Fix outdated 17.15 to 18.0 (dotnet#80570) Update dependencies from https://github.com/dotnet/dotnet build 285582 (dotnet#80551) Fix all-in-one tests [main] Update dependencies from dotnet/arcade (dotnet#80559) Improve error recovery when object initializer uses ':' instead of '=' (dotnet#80553) Support `field` keyword in EE. (dotnet#80515) Log a debug message for ContentModified exceptions. (dotnet#80549) Update dependencies from https://github.com/dotnet/arcade build 20251002.2 (dotnet#80550) Fix Simplify and add additional asserts ...

333fred added 2 commits September 22, 2025 11:15

Refactor movenext's awaitable info to be with the rest of enumerator …

a6e75a8

…info.

Add public API implementation for getting await info from await using…

675bbd9

… and await foreach.

333fred requested review from a team as code owners September 24, 2025 17:00

github-actions bot added the Area-Compilers label Sep 24, 2025

dotnet-policy-service bot added the Needs API Review Needs to be reviewed by the API review council label Sep 24, 2025

Update baselines

44cd4ef

jcouv self-assigned this Sep 25, 2025

jcouv added the Feature - Runtime Async label Sep 25, 2025