var v: UIView! = UIView() let v1 = v let v2 = v! type(of: v1) // Optional<__ObjC.UIView>.Type type(of: v2) // __ObjC.UIView.Type let h1 = v.isHidden let h2 = v!.isHidden type(of: h1) // Bool.Type 👈 v1がOptionalなら、これもOptional<Bool>.Type になるべきでは type(of: h2) // Bool.Type