Iceman

@swift-main -enable-upcoming-feature RetroactiveAttribute import Foundation extension Date: Identifiable {}

exit status: 1 with

<stdin>:2:1: warning: extension declares a conformance of imported type 'Date' to imported protocol 'Identifiable'; this will not behave correctly if the owners of 'Foundation' introduce this conformance in the future extension Date: Identifiable {} ^ <stdin>:2:1: note: add '@retroactive' to silence this warning extension Date: Identifiable {} ^ ~~~~~~~~~~~~ @retroactive Identifiable <stdin>:2:1: error: type 'Date' does not conform to protocol 'Identifiable' extension Date: Identifiable {} ^ Swift.Identifiable:3:16: note: candidate would match if 'Date' conformed to 'AnyObject' public var id: ObjectIdentifier { get } ^ Swift.Identifiable:4:9: note: protocol requires property 'id' with type 'ObjectIdentifier' var id: Self.ID { get } ^