Long-lived AsyncMethodVariant in MethodWithGCInfo/MethodWithToken

[jtschuster]

Incorporates feedback from #121218, creating a long-lived async MethodDesc. There will be more warts that need to be worked out once we actually compile these, in particular lots of (EcmaMethod)methodDesc.GetMethodDefinition(), which doesn't work with AsyncMethodVariant.

[Copilot]

Pull Request Overview

This pull request adds support for async method variants in the ReadyToRun compiler. The changes introduce a new AsyncMethodVariant type system abstraction that represents special calling convention variants for async methods.

Key Changes:

• Added new AsyncMethodVariant infrastructure to represent async method implementations and thunks with special calling conventions
• Extended the type system with async-related properties (IsAsync, AsyncMethodKind) across multiple method descriptor types
• Updated ReadyToRun signatures and metadata to track async variant methods
• Modified code generation to create async variants for Task-returning methods

Reviewed Changes

Copilot reviewed 27 out of 28 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
ILCompiler.TypeSystem.csproj	Added new async-related partial class files to the build
ILCompiler.ReadyToRun.csproj	Removed obsolete async method descriptor files
CorInfoImpl.ReadyToRun.cs	Added asyncVariant parameter handling and async method factory
ReadyToRunILProvider.cs	Added early return for async methods that aren't yet implemented
ReadyToRunTableManager.cs	Added IsAsyncThunk condition for generic methods tracking
ReadyToRunCodegenNodeFactory.cs	Fixed whitespace formatting
SignatureBuilder.cs	Added async thunk variant flag to method signatures
MethodWithGCInfo.cs	Added debug assertion and AsyncVariant property
MethodFixupSignature.cs	Added task-returning check to optimization condition
InstanceEntryPointTableNode.cs	Added asyncVariant parameter to signature building
AllMethodsOnTypeNode.cs	Added automatic async variant dependencies for Task-returning methods
ReadyToRunObjectWriter.cs	Removed unused using statement
MethodForRuntimeDeterminedType.cs	Added IsAsync and AsyncMethodKind property forwarding
EcmaMethod.cs	Reorganized flags and added formatting pragma
EcmaMethod.Async.cs	New file implementing async method kind logic
TypeSystemContext.cs	Changed return type to be more specific
TypeSystemContext.Async.cs	New file adding GetAsyncVariant factory method
MethodForInstantiatedType.cs	Refactored signature initialization
MethodForInstantiatedType.Async.cs	New file forwarding AsyncMethodKind from typical method
MethodDesc.cs	Renamed AsyncCallConv flag for consistency
MethodDesc.Async.cs	New file with core async method infrastructure
MethodDelegator.Async.cs	New file making AsyncMethodKind abstract
InstantiatedMethod.Async.cs	New file forwarding AsyncMethodKind from method definition
AsyncMethodVariant.cs	New file implementing the async variant wrapper type
UnboxingMethodDesc.cs	Added AsyncMethodKind property forwarding
CorInfoTypes.cs	Added CORINFO_CALLCONV_ASYNCCALL constant
CorInfoImpl.cs	Added async calling convention handling
ReadyToRunConstants.cs	Changed flags enum to ushort and added async thunk flag

[MichalStrehovsky]

This looks good to me otherwise. We could merge with this feedback addressed.

[MichalStrehovsky]

/ba-g android timeouts