| // Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| class A {} |
| |
| class B extends A {} |
| |
| class C { |
| void f1(A x) {} |
| void f2([A? x]) {} |
| void f3({A? x}) {} |
| A? f4() {} |
| } |
| |
| class D extends C { |
| void f1(Object x) {} // Ok |
| void f2([Object? x]) {} // Ok |
| void f3({Object? x}) {} // Ok |
| B? f4() {} // Ok |
| } |
| |
| class E extends C { |
| void f1(B x) {} |
| void f2([B? x]) {} |
| void f3({B? x}) {} |
| Object? f4() {} |
| } |
| |
| main() {} |