Availability checking for protocol conformances

[rlovelett (Ryan Lovelett)]

I think I had encountered this error about a month back.

Protocol inheritance does not trigger @available compiler errors

The @available on Identifiable does not get tripped at compile time when it is inherited. This feels like a bug (maybe even is a known bug). I have tried to minimize a reproducible case. This seems pretty close. import XCTest protocol ProtocolIdentifiable: Identifiable {} func use<I: ProtocolIdentifiable>(_ item: I) { print(item.id) } struct Conformance: ProtocolIdentifiable { let id = UUID() } final class ProtocolIdentifiableTests: XCTestCase { func testExample() { use(Confo…