swift

1c9b6eb7 - Sema: Relax availability of typealiases for inferred type witness.

Sema: Relax availability of typealiases for inferred type witness. Only constrain the availability of the synthesized typealias for an inferred type witness by the availability of the associated type if the associated type is less available than its protocol. Without this, source compatibility is broken for some conformances. For example: ``` struct IdentifiableValue: Identifiable { let id = 42 } extension IdentifiableValue { // error: 'ID' is only available in macOS 10.15 or newer var nextID: ID { return id + 1 } } ``` Fixes a regression introduced by https://github.com/swiftlang/swift/pull/71496. Resolves rdar://134584323