Create F.MapAwaitedReturnType fn

[ThomasAribart]

F.MapReturnType works correctly but it does not apply on async functions. I suggest creating a F.MapAwaitedReturnType function:

export type MapAwaitedReturnType<
  FN extends Fn | unset | _ = unset,
  ASYNC_FUNCTION extends ((...args: any[]) => Promise<any>) | _ | unset = unset,
> = PartialApply<MapAwaitedReturnTypeFn, [FN, ASYNC_FUNCTION]>

interface MapAwaitedReturnTypeFn extends Fn {
  return: this['args'] extends [infer FN extends Fn, infer ASYNC_FUNCTION]
    ? ASYNC_FUNCTION extends (...params: infer PARAMS) => Promise<infer RETURN_TYPE>
      ? (...params: PARAMS) => Promise<Call<FN, RETURN_TYPE>>
      : never
    : never
}

@gvergnaud I can create the PR if you want!

[gvergnaud]

I think I'd prefer having a Promises module that has a map function:

type X = H.Functions.MapReturnType<H.Promises.Map<Fn>>

That seems more powerful because Promises.Map could be composed in other ways too. WDYT?

[ThomasAribart]

Yes, I agree 👍