Utility type ReturnType

Constructs a type consisting of the return type
of function Type.

declare function f1(): { a: number; b: string };
 
type T0 = ReturnType<() => string>;
type T0 = string

type T1 = ReturnType<(s: string) => void>;
type T1 = void

type T2 = ReturnType<<T>() => T>;
type T2 = unknown

type T3 = ReturnType<<T extends U, U extends number[]>() => T>;
type T3 = number[]

type T4 = ReturnType<typeof f1>;
type T4 = {
    a: number;
    b: string;
}

type T5 = ReturnType<any>;
type T5 = any

type T6 = ReturnType<never>;
type T6 = never

type T7 = ReturnType<string>;
Type 'string' does not satisfy the constraint '(...args: any) => any'.
type T7 = any

type T8 = ReturnType<Function>;
Type 'Function' does not satisfy the constraint '(...args: any) => any'.
  Type 'Function' provides no match for the signature '(...args: any): any'.
type T8 = any