Test Plan for Runtime Async

[333fred]

Test plan for runtime-generated async state machines

Runtime open issues: https://github.com/dotnet/runtime/issues/109632 Runtime specification: https://github.com/dotnet/runtime/blob/main/docs/design/specs/runtime-async.md Compiler implementation plan: https://github.com/dotnet/roslyn/blob/main/docs/compilers/CSharp/Runtime%20Async%20Design.md

Included in .NET 10 (feature in preview)

• [x] turning feature on (see IsRuntimeAsyncEnabledIn)
  • [x] presence of required AsyncHelpers APIs in corlib
  • [x] honor RuntimeAsyncMethodGenerationAttribute attribute for override
  • [x] check presence of feature flag runtime-async=on
  • [x] check for return type
• [ ] codegen for async methods
  • [x] set method flag MethodImplOptions.Async
  • [x] calls optimized with Await
    • [x] selection of appropriate helper
  • [x] calls using AwaitAwaiter/UnsafeAwaitAwaiter
  • [x] await in catch/finally
  • [x] await using
  • [x] await foreach
  • [x] ref local lifting (https://github.com/dotnet/roslyn/issues/79763)
• methods of validation
  • [x] direct IL verification
  • [x] verifier (caught some issues, although verification rules not yet updated to understand return value expectations: https://github.com/dotnet/runtime/issues/118042)
• [x] block unsupported scenarios for .NET 10 RC1
• [x] disallow application of MethodImplOptions.Async in source
• [x] public APIs
  • [x] IOperation (no impact)
  • [x] GetAwaitExpressionInfo
• [x] consider removing or downgrading the "no await" warning (related issue) https://github.com/dotnet/roslyn/pull/80144
• [ ] analyzer work for RequiresPreviewFeatures (honor attribute on helper APIs)

Post-.NET 10

• [ ] PDBs/symbols for debugging (https://github.com/dotnet/roslyn/issues/79793)
  • sequence points
• [ ] instrumentation
• [ ] dynamic (https://github.com/dotnet/roslyn/issues/79762)
• [ ] disallow directly calling MethodImplOptions.Async methods in some cases?
• [ ] disallow directly calling AsyncHelpers helper methods?
• [ ] manual smoke testing of various scenarios (debugging, EE, EnC)
• [x] execution (pending availability of new runtime, https://github.com/dotnet/roslyn/issues/79791)
• [ ] ensure that every async test also covers runtime-async
• [ ] remove RuntimeAsyncMethodGenerationAttribute and DOTNET_RuntimeAsync once feature is stable
• [ ] replace feature flag with a real switch and make the SDK set it by default
• [ ] use real MethodImplOptions.Async flag (https://github.com/dotnet/roslyn/issues/79792)
• [ ] partner validation (driven by runtime team)
• [ ] follow-up on public announcement
• [ ] codegen for async iterator methods (notes)

Async-iterators

• [ ] codegen https://github.com/dotnet/roslyn/pull/81314
• [ ] debug info/symbols
• [ ] EnC