add Awaited TS challenge

Author: diaz-rodrigo

Languages/Typescript/Generics/00189-easy-awaited.ts

@@ -0,0 +1,66 @@
+/*
+  189 - Awaited
+  -------
+  by Maciej Sikora (@maciejsikora) #easy #promise #built-in
+
+  ### Question
+
+  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?
+
+  ```ts
+  type ExampleType = Promise<string>
+
+  type Result = MyAwaited<ExampleType> // string
+  ```
+
+  > This question is ported from the [original article](https://dev.to/macsikora/advanced-typescript-exercises-question-1-45k4) by [@maciejsikora](https://github.com/maciejsikora)
+
+  > View on GitHub: https://tsch.js.org/189
+*/
+
+/* _____________ Your Code Here _____________ */
+
+type PromiseLike = {
+  then: (onfulfilled: (arg: number) => unknown) => unknown;
+};
+
+type MyAwaited<T extends Promise<unknown> | PromiseLike> = T extends
+  | Promise<infer R>
+  | PromiseLike
+  ? R extends Promise<unknown>
+    ? MyAwaited<R>
+    : R
+  : T;
+
+type ExampleType = Promise<string>;
+
+type Result = MyAwaited<ExampleType>; // string
+
+/* _____________ Test Cases _____________ */
+import type { Equal, Expect } from "@type-challenges/utils";
+
+type X = Promise<string>;
+type Y = Promise<{ field: number }>;
+type Z = Promise<Promise<number | string>>;
+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>;
+
+/* _____________ Further Steps _____________ */
+/*
+  > Share your solutions: https://tsch.js.org/189/answer
+  > View solutions: https://tsch.js.org/189/solutions
+  > More Challenges: https://tsch.js.org
+*/