Fix ParseGenericTypeArgumentNames for nested generic types#1414
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max-charlamb merged 1 commit intomicrosoft:mainfrom Apr 3, 2026
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ParseGenericTypeArgumentNames used IndexOf('<') to find the start of
generic arguments, which returns the first '<' in the full type name.
For nested generic types like Outer<A>+Inner<B>, this incorrectly
extracts the outer type's arguments (A) instead of the inner type's (B).
This breaks __Canon type resolution for AsyncStateMachineBox<TStateMachine>
because GetConcreteGenericTypeArguments resolves AsyncTaskMethodBuilder's
TResult instead of the state machine type, leaving the StateMachine field
with a null or wrong type after metadata fallback.
Fix: find the last '+' at depth 0 (outside angle brackets) to skip past
outer type names, then search for '<' from there.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
leculver
approved these changes
Apr 3, 2026
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GetConcreteGenericTypeArgumentswas resolvingVoidTaskResult(fromAsyncTaskMethodBuilder) instead of the state machine type, leaving theStateMachinefield with a null or wrong type after metadata fallback. This caused SOSDumpAsyncto crash with an assertion failure.Fix
Find the last
+at depth 0 (outside angle brackets) to skip past outer type names, then search for<from there.Verification
AsyncTaskMethodBuilder<VoidTaskResult>+AsyncStateMachineBox<MyClass+<DoAsync>d__3>VoidTaskResult❌MyClass+<DoAsync>d__3✅Dictionary<String, Int32>String, Int32✅String, Int32✅Dictionary<String, Int32>+EntryString, Int32❌Fixes the regression reported in dotnet/diagnostics#5789.