Promise.all with John Chadwick - TypeScript Type Challenges #20 [MEDIUM]

00:00 description of the challenge
01:12 attempt at a solution
05:11 all tests pass

[fagnersales]

I really like the fact that the challenges keep increasing in the difficulty, but somehow, it still increases in how easy is to understand. Excited to see how advanced challenges will be

[gnorts_mr_alien]

The thing most crucial and hardest to understand here IMO is the need for readonly [...T] and not readonly T (which won't work). I'm trying to figure out why that is strictly needed here.

[QwDragon]

2:25 It was very lucky to write <T extends unknown[]>(values: [...T]) and not <T extends readonly unknown[]>(values: T). I spent 4 minutes fixing test for A2, but I somehow remembered that T and [...T] may have such difference.
4:30 This Awaited is now in standard library since 4.5. Also it was among this challenges as 00189-easy-awaited.

[kasper_]

This is one of the most unintuitive aspects of typescript imo. The fact that a type mapped over a tuple represents a new tuple makes sense when described, but syntatically it always looks like I’m defining a plain object shape and not a tuple.

[yunhaiwang]

type PromiseFlat<T> = T extends Promise<infer R> ? PromiseFlat<R> : T

declare function PromiseAll<T extends unknown[]>(
values: readonly [...T]
): Promise<{
[K in keyof T]: PromiseFlat<T[K]>
}>

[Driver_kw_]

I wrote "[P in keyof T]: T[P] extends Promise<infer R> ? R : T[P]" firstly, but the last case didn't pass until I replace it with Awated<T[P]> after watching your video.Thanks for helping me😁.But I just want to know why the former method didn't work?