boundFunctionSubclassing.js

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class func extends Function { }

let inst = new func("x", "return this.bar + x");

// First, ensure that we get sane prototype chains for the bound instance

let bound = inst.bind({bar: 3}, 4);

assertEq(bound instanceof func, true);

assertEq(bound(), 7);

// Check the corner case for Function.prototype.bind where the function has

// a null [[Prototype]]

Object.setPrototypeOf(inst, null);

bound = Function.prototype.bind.call(inst, {bar:1}, 3);

assertEq(Object.getPrototypeOf(bound), null);

assertEq(bound(), 4);

// Check that we actually pass the proper new.target when calling super()

function toBind() { }

var boundArgs = [];

for (let i = 0; i < 5; i++) {

    boundArgs.push(i);

    let bound = toBind.bind(undefined, ...boundArgs);

    // We have to wire it up by hand to allow us to use a bound function

    // as a superclass, but it's doable.

    bound.prototype = {};

    class test extends bound { };

    let passedArgs = [];

    for (let j = 0; j < 15; j++) {

        passedArgs.push(j);

        assertEq(Object.getPrototypeOf(new test(...passedArgs)), test.prototype);

if (typeof reportCompare === 'function')

    reportCompare(0,0,"OK");