00189-easy-awaited.ts

// ============= Test Cases =============
import type { Equal, Expect } from './test-utils'

type X = Promise<string>
type Y = Promise<{ field: number }>
type Z = Promise<Promise<string | number>>
type Z1 = Promise<Promise<Promise<string | boolean>>>
type T = { then: (onfulfilled: (arg: number) => any) => any }

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>>,
  Expect<Equal<MyAwaited<T>, number>>,
]

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


// ============= Your Code Here =============
type MyAwaited<T extends Promise<any> | { then: (onfullfilled: ((arg: any) => any)) => any }> = T extends Promise<infer R> ?
  R extends Promise<any> ? MyAwaited<R> : R
  : T extends { then: (onfullfilled: ((arg: infer R) => any)) => any } ? R : never;