@swift-5.3.3 @swift-5.4.3
protocol P {} struct S: P {} func check(_ maybeS: S?) { print("maybeS = \(maybeS)") print("maybeS is P = \(maybeS is P)") print("maybeS as Any is P = \(maybeS as Any is P)") print("------------------------------------------") } check(S()) check(nil)