==== tests/cases/compiler/specializedSignatureAsCallbackParameter1.ts (3 errors) ====
    function x3(a: number, cb: (x: number) => number);
    function x3(a: string, cb: (x: number) => number);
    function x3(a: any, cb: (x: number) => number) {
       cb(a);
    }
    // both are errors
    x3(1, (x: string) => 1); 
       ~
!!! Argument of type 'number' is not assignable to parameter of type 'string'.
    x3(1, (x: 'hm') => 1); 
       ~
!!! Argument of type 'number' is not assignable to parameter of type 'string'.
          ~~~~~~~~~~~~~~
!!! A signature with an implementation cannot use a string literal type.