Flow: Getting fulfillment type from Promise?

[bgdavidx]

Let's say I have a function like such:

async function f() { return 1 } // returns Promise<number>

I can get the type it returns via $Call:

type ReturnType = $Call<typeof f> // type is Promise<number>

but how can I get the resolved type of the Promise? In this case it is number.

[manfredxu99]

+1

[brad-alexander]

+1

[vkurchatkin]

You can use a helper type like this:

type UnwrapPromise<T> = $Call<<T>(Promise<T>) => T, T>;