$Call
$Call
@example
// Common use-case
const add = (amount: number) => ({ type: 'ADD' as 'ADD', payload: amount });
type AddAction = $Call<typeof returnOfIncrement>; // { type: 'ADD'; payload: number }
// Examples migrated from Flow docs
type ExtractPropType<T extends { prop: any }> = (arg: T) => T['prop'];
type Obj = { prop: number };
type PropType = $Call<ExtractPropType<Obj>>; // number
type ExtractReturnType<T extends () => any> = (arg: T) => ReturnType<T>;
type Fn = () => number;
type FnReturnType = $Call<ExtractReturnType<Fn>>; // number
type $Call<Fn extends (...args: any[]) => any> = Fn extends (arg: any) => infer RT ? RT : never;