declare function f<T>(cf: (() => T) | ((x: T) => boolean)): void;

declare function myFn(): Date;
declare function myFn(n: number): void;

f<Date>(myFn); // works
f(myFn); // error

src/a.ts:7:3 - error TS2345: Argument of type '{ (): Date; (n: number): void; }' is not assignable to parameter of type '(() => number) | ((x: number) => boolean)'.
  Type '{ (): Date; (n: number): void; }' is not assignable to type '() => number'.
    Type 'Date' is not assignable to type 'number'.

7 f(myFn); // error