Language/12_Expressions/27_Unary_Expressions_A04_t02.dart

/*
 * Copyright (c) 2011, 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 Evaluation of an expression of the form --e is equivalent to e -= 1.
 * @description Checks that evaluation of an expression of the form --e
 * results in invoking operator- on the result of e with the proper argument.
 * @author rodionov
 * @reviewer iefremov
 */
import "../../Utils/expect.dart";

bool minusInvoked = false;

class A {
  final String value;
  
  A(this.value);
  
  operator -(var other) {
    minusInvoked = true;
    return new A("${value}-${other}");
  }
}

main() {
  var foo = new A("foo");
  Expect.isFalse(minusInvoked);
  
  Expect.equals("foo-1", (--foo).value);
  Expect.isTrue(minusInvoked);
  Expect.equals("foo-1", foo.value);
}