JSTests/stress/hide-cached-value-of-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 = undefined;
object.__proto__.valueOf = function () {
    return 42;
};
shouldBe(object + 42, 84);