Language/Expressions/Unary_Expressions/syntax_t01.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 Unary expressions invoke unary operators on objects.
 * unaryExpression:
 *   prefixOperator unaryExpression |
 *   awaitExpression |
 *   postfixExpression |
 *   (minusOperator | tildeOperator) super |
 *   incrementOperator assignableExpression
 * ;
 * prefixOperator:
 *   minusOperator |
 *   negationOperator |
 *   tildeOperator
 * ;
 * minusOperator:
 *   ‘-’ |
 * ;
 * negationOperator:
 *   ‘!’ |
 * ;
 * tildeOperator:
 *   ‘˜’
 * ;
 * A unary expression is either a postfix expression, an await expression or
 * an invocation of a prefix operator on an expression or an invocation of a
 * unary operator on either super or an expression e.
 * @description Checks that expressions composed from prefix/unary operators and
 * super that fit into this production don't cause compile-time errors.
 * @author msyabro
 */

class S {
  var x = 1;
  operator -() { return this; }
  operator ~() { return this; }
}

class A extends S {
  test() {
    -super;
    ~super;
    - -super; // should be interpreted as -(-super);
    ~~super;
    try {
      !-super;
    } catch (ok) {}
    ~-super;
    -~super;
    try {
      !~super;
    } catch (ok) {}
  }
}

main() {
  A a = new A();
  a.test();
}