LanguageFeatures/Super-mixins/covariance_t07.dart

/*
 * Copyright (c) 2018, 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.
 */
/**
 * @assertion In a mixin declaration like
 * mixin A<X extends S, Y extends T> on B, C implements D, E { body }
 * the on clause declares the interfaces B and C as super-class constraints of
 * the mixin. Having a super-class constaint allows the mixin declaration
 * instance members to perform super-invocations (like super.foo()) if they are
 * allowed by a class implementing both B and C. The mixin introduced by A can
 * then only be applied to classes that implement both B and C.
 *
 * @description Checks that it is a runtime error if mixin is applied to the
 * class which doesn't implement required interface by covariant. See
 * https://github.com/dart-lang/sdk/issues/35111#issuecomment-437291038
 * @issue 35111
 * @author sgrekhov@unipro.ru
 */
import "../../Utils/expect.dart";

class S {}
class X extends S {}
class Y extends X {}

class A<T extends S> {
  bar(T n) {}
}

class B<T extends S> extends A<S> {
  bar(covariant T i) {}
}

mixin M<T extends S> on A<S> {
  test(T t) {
    super.bar(t);
  }
}

class MA extends B<Y> with M<X> {}

main() {
  Expect.throws(() {
    new MA().test(new Y());
  });
}