construct-newtarget.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/. */

const GeneratorFunction = function*(){}.constructor;

// Test subclassing %GeneratorFunction% works correctly.

class MyGenerator extends GeneratorFunction {}

var fn = new MyGenerator();

assertEq(fn instanceof MyGenerator, true);

assertEq(fn instanceof GeneratorFunction, true);

assertEq(Object.getPrototypeOf(fn), MyGenerator.prototype);

fn = Reflect.construct(MyGenerator, []);

assertEq(fn instanceof MyGenerator, true);

assertEq(fn instanceof GeneratorFunction, true);

assertEq(Object.getPrototypeOf(fn), MyGenerator.prototype);

fn = Reflect.construct(MyGenerator, [], MyGenerator);

assertEq(fn instanceof MyGenerator, true);

assertEq(fn instanceof GeneratorFunction, true);

assertEq(Object.getPrototypeOf(fn), MyGenerator.prototype);

fn = Reflect.construct(MyGenerator, [], GeneratorFunction);

assertEq(fn instanceof MyGenerator, false);

assertEq(fn instanceof GeneratorFunction, true);

assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);

// Set a different constructor as NewTarget.

fn = Reflect.construct(MyGenerator, [], Array);

assertEq(fn instanceof MyGenerator, false);

assertEq(fn instanceof GeneratorFunction, false);

assertEq(Object.getPrototypeOf(fn), Array.prototype);

fn = Reflect.construct(GeneratorFunction, [], Array);

assertEq(fn instanceof GeneratorFunction, false);

assertEq(Object.getPrototypeOf(fn), Array.prototype);

// The prototype defaults to %GeneratorFunctionPrototype% if null.

function NewTargetNullPrototype() {}

NewTargetNullPrototype.prototype = null;

fn = Reflect.construct(GeneratorFunction, [], NewTargetNullPrototype);

assertEq(fn instanceof GeneratorFunction, true);

assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);

fn = Reflect.construct(MyGenerator, [], NewTargetNullPrototype);

assertEq(fn instanceof MyGenerator, false);

assertEq(fn instanceof GeneratorFunction, true);

assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);

// "prototype" property is retrieved exactly once.

var trapLog = [], getLog = [];

var ProxiedConstructor = new Proxy(GeneratorFunction, new Proxy({

    get(target, propertyKey, receiver) {

        getLog.push(propertyKey);

        return Reflect.get(target, propertyKey, receiver);

}, {

    get(target, propertyKey, receiver) {

        trapLog.push(propertyKey);

        return Reflect.get(target, propertyKey, receiver);

}));

fn = Reflect.construct(GeneratorFunction, [], ProxiedConstructor);

assertEqArray(trapLog, ["get"]);

assertEqArray(getLog, ["prototype"]);

assertEq(fn instanceof GeneratorFunction, true);

assertEq(Object.getPrototypeOf(fn), GeneratorFunction.prototype);

if (typeof reportCompare === "function")

    reportCompare(0, 0);