function assert(b) {
    if (!b)
        throw new Error("Bad assertion")
}
function test(f, n = 1000) {
    for (let i = 0; i < n; i++)
        f();
}

test(function() {
    function foo(x = ()=>this) {
        return x();
    }
    let o = {};
    assert(foo.call(o) === o);
})

test(function() {
    function foo(x = ()=>arguments) {
        assert(x() === arguments);
    }
    foo();
})

test(function() {
    function foo({x = ()=>arguments}) {
        assert(x() === arguments);
    }
    foo({x:undefined});
})

test(function() {
    function foo(x = ()=>arguments) {
        let a = x();
        assert(a.length === 3);
        assert(a[0] === undefined);
        assert(a[1] === 20);
        assert(a[2] === 40);
    }
    foo(undefined, 20, 40);
})

test(function() {
    function foo(x = ()=>new.target) {
        assert(x() === foo);
    }
    new foo(undefined);
})

test(function() {
    function foo({x = ()=>new.target}) {
        assert(x() === foo);
    }
    new foo({});
})

test(function() {
    function foo(x = ()=>arguments) {
        var arguments;
        assert(x() === arguments);
    }
    foo(undefined);
});

test(function() {
    function foo(x = ()=>arguments) {
        var arguments = 25;
        assert(x() === arguments);
    }
    foo(undefined);
});

test(function() {
    function foo(x = (y = ()=>arguments)=>y()) {
        assert(x() === arguments);
    }
    foo(undefined);
});

test(function() {
    function foo({x = (y = ()=>arguments)=>y()}) {
        assert(x() === arguments);
    }
    foo({});
});

test(function() {
    function foo(x = (y = ()=>this)=>y()) {
        return x();
    }
    let o = {};
    foo.call(o);
});

test(function() {
    function foo(x = (y = ()=>new.target)=>y()) {
        assert(x() === foo);
    }
    new foo();
});

test(function() {
    function foo(x = (y = ()=>new.target)=>y()) {
        assert(x() === undefined);
    }
    foo();
});

test(function() {
    class C {
        constructor() { this._x = 45; }
        get foo() { return this._x;}
    }
    class D extends C {
        constructor(x = () => super.foo) {
            super();
            assert(x() === 45);
        }
        x(x = ()=>super.foo) {
            return x();
        }
    }
    assert((new D).x() === 45);
});

test(function() {
    class C {
        constructor() { this._x = 45; }
        get foo() { return this._x;}
    }
    class D extends C {
        x(x = () => {return super.foo}) {
            return x();
        }
    }
    assert((new D).x() === 45);
});

test(function() {
    class C {
        constructor() { this._x = 45; }
        get foo() { return this._x;}
    }
    class D extends C {
        x(x = () => {return () => super.foo}) {
            return x()();
        }
    }
    assert((new D).x() === 45);
});

test(function() {
    class C {
        constructor() { this._x = 45; }
        get foo() { return this._x;}
    }

    class D extends C {
        x(y = (y = () => super.foo) => {return y()}) {
            return y();
        }
    }
    assert((new D).x() === 45);
});

test(function() {
    class C {
        constructor() { this._x = 45; }
        get foo() { return this._x;}
    }

    class D extends C {
        constructor(x = () => super.foo) {
            super();
            this._x_f = x;
        }

        x() {
            return this._x_f(); 
        }
    }
    assert((new D).x() === 45);
});

test(function() {
    class C {
        constructor() { this._x = 45; }
        get foo() { return this._x;}
    }

    class D extends C {

        constructor(x = () => super()) {
            x();
        }

        x() {
            return super.foo;
        }
    }
    assert((new D).x() === 45);
});