dotnet/roslyn
EnC: disallow editing async methods with incompatible constraints on their method builders
Aperta
#51.234 aperta il 15 feb 2021
Area-InteractiveConcept-Continuous ImprovementInteractive-EnChelp wanted
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Descrizione
Follow up on discussion: https://github.com/dotnet/roslyn/discussions/51189
In debug builds we emit async state machine types as classes so that we can add fields to them as needed during EnC. Emitting the state machine type as reference type instead of a value type might however conflict with a constraint:
If
- the return type of an async method specifies a custom builder
BviaAsyncMethodBuilder, and B.Start<TStateMachine>(ref TStateMachine),B.AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine), orB.AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)have a constraint onTStateMachinethat disallows it to be a reference type.
Fix: The compiler should identify these cases and keep the state machine type as struct. The IDE should disallow editing such async methods.