rest-parameter-aray-iterator.js

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/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// Destructuring rest arrays call the array iterator. This behaviour is

// observable when Array.prototype[Symbol.iterator] is overridden.

const oldArrayIterator = Array.prototype[Symbol.iterator];

try {

    let callCount = 0;

    Array.prototype[Symbol.iterator] = function() {

        callCount += 1;

        return oldArrayIterator.call(this);

};

    // Array iterator called exactly once.

    function arrayIterCalledOnce(...[]) { }

    assertEq(callCount, 0);

    arrayIterCalledOnce();

    assertEq(callCount, 1);

    // Array iterator not called before rest parameter.

    callCount = 0;

    function arrayIterNotCalledBeforeRest(t = assertEq(callCount, 0), ...[]) { }

    assertEq(callCount, 0);

    arrayIterNotCalledBeforeRest();

    assertEq(callCount, 1);

    // Array iterator called when rest parameter is processed.

    callCount = 0;

    function arrayIterCalledWhenDestructuring(...[t = assertEq(callCount, 1)]) { }

    assertEq(callCount, 0);

    arrayIterCalledWhenDestructuring();

    assertEq(callCount, 1);

} finally {

    Array.prototype[Symbol.iterator] = oldArrayIterator;

if (typeof reportCompare === "function")

    reportCompare(0, 0);