Is it possible to pass generic type as generic parameter?

Question

Just pass generic type like a callback :

type FUNC<ARG,RET, F> = (arg: ARG) => F<RET>;
type PROMISE<T> = Promise<T>;
type IDENT<T> = T;
type A = FUNC<number, void, IDENT>;
type A_PROMISE = FUNC<number, void, PROMISE>;

Is this possible?

Answer 1

It is not possible at the moment. There was a discussion back in 2014. See this issue .

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If your intention is to constraint the return type, you may:

type FUNC<ARG,RET extends Promise<any>> = (arg: ARG) => RET;

To get back the wrapped type, you may:

type PromiseType<T> = T extends Promise<infer T> ? T : never

type A = Promise<string>
type B = PromiseType<A> // string