// 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

import "package:expect/expect.dart";

class A {}

class B extends A {}

void main() {
  B b;
  A a1 = new B();
  A a2 = new A();
  b ??= a1; // No error - types compatible
  b ??= a2; // No error - assignment has no effect
  b = null;
  Expect.throwsTypeError(() {
    b ??= a2;
  });
}