// WeakSet constructor with adder change.

function shouldThrow(func, errorMessage) {
    var errorThrown = false;
    try {
        func();
    } catch (error) {
        errorThrown = true;
        if (String(error) !== errorMessage)
            throw new Error(`Bad error: ${error}`);
    }
    if (!errorThrown)
        throw new Error("Didn't throw!");
}

var originalAdder = WeakSet.prototype.add;
var counter = 0;

WeakSet.prototype.add = function (key) {
    counter++;
    return originalAdder.call(this, key);
};

var obj0 = {};
var obj1 = {};
var obj2 = [];
var obj3 = new Date();
var obj4 = new Error();
var obj5 = JSON;

var values = [
    obj0,
    obj1,
    obj2,
    obj3,
    obj4,
    obj5,
    obj4,
    obj3,
    obj2,
    obj1,
    obj0,
];
var set = new WeakSet(values);
if (counter !== values.length)
    throw new Error("bad counter " + counter);

WeakSet.prototype.add = function () {
    throw new Error("adder called");
};

var set = new WeakSet();
var set = new WeakSet([]);

shouldThrow(() => {
    new WeakSet([ 0 ]);
}, "Error: adder called");

WeakSet.prototype.add = "foo";
shouldThrow(() => {
    new WeakSet([ 0 ]);
}, "TypeError: 'add' property of a WeakSet should be callable.");