[DiscardingTG] Remove reabstraction thunk for () -> Void
to () -> T
#70537
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Concurrency runtime expects discarding task operation entrypoint function not to have result type, but the current SILGen implementation generates reabstraction thunk to convert
() -> Void
to() -> T
for the operation function.Since the
T
is alwaysVoid
for DiscardingTG, the mismatch of result type expectation does not cause any problem on most platforms, but the signature mismatch causes a problem on WebAssembly.This patch introduces new builtin operations for creating discarding task, which always takes
() -> Void
as the operation function type.The issue #63060 was partially fixed by #66219, but #68793 revealed the issue again since it added extra reabstraction for the given operation closure.