protocol Proto : AnyObject {} class Box1<X> {} Box1<Proto>() // OK class Box2<X: AnyObject> {} Box2<Proto>() // NG: 'Proto' is not convertible to 'AnyObject'protocol Proto : AnyObject {} class Box1<X> {} Box1<Proto>() // OK class Box2<X: AnyObject> {} Box2<Proto>() // NG: 'Proto' is not convertible to 'AnyObject'