Language/Expressions/Unary_Expressions/syntax_t27.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 with a prefix operator which fit into
/// this production don't cause compile-time errors.
/// @author msyabro


class S {
  var x = 1;
  operator -() {return -x;}
  operator [](var ind) {return x;}
  operator []=(var ind, var val) {x = val;}
}

class A extends S {
  test() {
    //prefixOperator postfixExpression
    -x--;
    ~x--;

    //combination of prefix and increment operator
    try {- --x;} catch (e) {}
    try {~--x;} catch (e) {}
    try {-++x;} catch (e) {}
    try {~++x;} catch (e) {}

    //prefixOperator postfixExpression>primary>identifier
    -x;
    ~x;
    ~~x;

    //prefix operators with literals
    try {-1;} catch (e) {}
    try {~2;} catch (e) {}

    try {-this;} catch (e) {}

    !!false;
    !!!true;
    !!!!false;
    !!!!!!true;

    //prefix operators with various expressions
    try {~(1 + 2);} catch (e) {}

    // super with selector
    try {-super[0];} catch (ok) {}
    try {~super.x;} catch (ok) {}
    try {!super[0];} catch (ok) {}
  }
}

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