Language/12_Expressions/27_Unary_Expressions_A03_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 plusInvoked = false;

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

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