Slava Pestov d77c6f413d RequirementMachine: Skip protocol type aliases that contain unbound dependent member types ...

In the below, 'Self.A.A' is not a type parameter; rather, since
'Self.A' is concretely known to be 'S', we resolve it as 'S.A',
which performs a name lookup and finds the concrete type alias 'A':

    public struct S {
      public typealias A = Int
    }

    public protocol P {
      typealias A = S
    }

    public struct G<T> {}

    public protocol Q: P {
      typealias B = G<Self.A.A>
    }

This is fine, but such a type alias should not participate in
the rewrite system. Let's exclude them like any other invalid
requirement.

The type alias itself is not an error; however, it is an error
to use it from a 'where' clause requirement. This is not
diagnosed yet, though.

Fixes rdar://136686001.

2025-03-26 10:55:23 -04:00

8.8 KiB

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