The way that promises are implemented actively hurts the ecosystem. Trying to e.g. create a sound typing of the Promise API is really, really hard because of it

The way that promises are implemented actively hurts the ecosystem. Trying to e.g. create a sound typing of the Promise API is really, really hard because of it's auto-flattening nature. This severely hampers languages like TypeScript, Flow & ReasonML that build on top of JavaScript.