JSTests/stress/hide-cached-to-string-property.js

function shouldBe(actual, expected) {
    if (actual !== expected)
        throw new Error('bad value: ' + actual);
}

var object = {};
object.__proto__ = {};
shouldBe(object + 42, `[object Object]42`);
shouldBe(object + 42, `[object Object]42`);
object.__proto__.toString = function () {
    return "Hey";
};
shouldBe(object + 42, `Hey42`);