dart-sdk/tests/language_2/class/additional_interface_adds_optional_args_concrete_subclass_test.dart

// 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.

// @dart = 2.9

class A {
  void foo() {}
}

abstract class I {
  void foo([x]);
}

abstract class B extends A implements I {
  // If this class were concrete, there would be a problem, since `new
  // B().foo(42)` would be statically allowed, but would lead to invalid
  // arguments being passed to A.foo.  But since the class is abstract, there is
  // no problem.
}

class /*@compile-error=unspecified*/ C extends B {
  // However, there is a problem here because this class is concrete and doesn't
  // override foo.
}

void f(B b) {
  b.foo();
}

main() {
  f(new C());
}