Subclassing ES6 objects with ES5 syntax.

[Domenic Denicola]

From: es-discuss [mailto:es-discuss-bounces at mozilla.org] On Behalf Of C. Scott Ananian

> But in the code given previously, I've used `Object.setPrototypeOf` to effectively change the type of the object -- but [[PromiseConstructor]] doesn't follow along.

That is exactly the kind of tampering that the unforgable [[PromiseConstructor]] mechanism is meant to prevent.