@swift-5.1.5
protocol A { func isEquatable() -> Bool } extension A { func isEquatable() -> Bool { return false } } extension A where Self: Equatable { func isEquatable() -> Bool { return true } } struct Foo: A { } struct Foo2: A, Equatable { } extension String: A { } print("direct") print(Foo().isEquatable()) print(Foo2().isEquatable()) print(String().isEquatable()) func generics<X: A>(arg: X) { print(arg.isEquatable()) } func existential(arg: A) { print(arg.isEquatable()) } print("from generics") generics(arg: Foo()) generics(arg: Foo2()) generics(arg: String()) print("from existential") existential(arg: Foo()) existential(arg: Foo2()) existential(arg: String()) (edited)
