RequirementMachine: Skip protocol type aliases that contain unbound dependent member types #80281
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…ependent 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.
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In the below, 'Self.A.A' is not a type parameter; rather, since 'Self.A' is concretely known to be 'S' via a protocol type alias, we resolve it as 'S.A', which performs a name lookup and finds the concrete type alias 'A' of 'S', which is just 'Int':
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.