Let's say we have the following type I:
type I = () => () => () => "a" | "b" | "c";
Is there a way to create a generic type Unwrap such that Unwrap<I> evaluates to "a" | "b" | "c"?
type I = () => () => () => "a" | "b" | "c";
type Result = Unwrap<I>; // "a" | "b" | "c"
The following (ofc) produces a circularity error:
type Unwrap<
T extends (...args: any[]) => any,
R = ReturnType<T>
> = R extends (...args: any[]) => any
? Unwrap<R>
: R;
Any help would be greatly appreciated. Thank you!
Well here's the hack which works in TypeScript 3. It's actually not that awful.
type I = () => (() => (() => "a" | "b" | "c")) | "e" | (() => "f" | "g");
type Unwrap<T> =
T extends (...args: any[]) => infer R
? { 0: Unwrap<R> }[T extends any ? 0 : never] // Hack to recurse.
: T;
type Result = Unwrap<I>;
// type Result = "e" | "a" | "b" | "c" | "f" | "g";