Kavon Farvardin 3ae2ce5a7f Witness selection should pick exact matches for effect overloads ...

You can overload a function based on its `async`-ness, and
resolution is carried out based on async-ness of calling
context.

But during protocol conformance checking, for an `async`
requirement we were accidentally choosing the non-`async
overload instead of the `async` one. The `async` one is
the choice people would expect, since the `async` requirement
is in essence the "context" that forwards to the underlying
witness. This intended behavior is also inferred from:

https://github.com/apple/swift/pull/40088

The problem boiled down to a bad check when categorizing the
witness matches prior to ranking them.

Resolves rdar://109135488 / https://github.com/apple/swift/issues/60318

2023-05-12 11:03:48 -07:00

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