test262/implementation-contributed/javascriptcore/stress/async-arrow-functions-lexical-this-binding.js

function shouldBe(expected, actual, msg) {
    if (msg === void 0)
        msg = "";
    else
        msg = " for " + msg;
    if (actual !== expected)
        throw new Error("bad value" + msg + ": " + actual + ". Expected " + expected);
}

function shouldBeAsync(expected, run, msg) {
    let actual;
    var hadError = false;
    run().then(function(value) { actual = value; },
               function(error) { hadError = true; actual = error; });
    drainMicrotasks();

    if (hadError)
        throw actual;

    shouldBe(expected, actual, msg);
}

var d = ({ x : "bar", y : function() { return async z => this.x + z; }}).y();
var e = { x : "baz", y : d };

shouldBeAsync("barley", () => d("ley"));
shouldBeAsync("barley", () => e.y("ley"));