[Typescript Challenges] 7. Easy - Awaited

If we have a type which is wrapped type like Promise. How we can get a type which is inside the wrapped type?

For example: if we have Promise<ExampleType> how to get ExampleType?

type ExampleType = Promise<string>

type Result = MyAwaited<ExampleType> // string

 

/* _____________ Your Code Here _____________ */

type MyAwaited<T extends Promise<any>> = T extends Promise<infer P> 
    ? P extends Promise<any> 
        ? MyAwaited<P> 
        : P
    : T;


/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

type X = Promise<string>
type Y = Promise<{ field: number }>
type Z = Promise<Promise<string | number>>
type Z1 = Promise<Promise<Promise<string | boolean>>>

type cases = [
  Expect<Equal<MyAwaited<X>, string>>,
  Expect<Equal<MyAwaited<Y>, { field: number }>>,
  Expect<Equal<MyAwaited<Z>, string | number>>,
  Expect<Equal<MyAwaited<Z1>, string | boolean>>,
]

// @ts-expect-error
type error = MyAwaited<number>