def test_basic2(self):
        """
        Test that a dispatcher object *without* a pre-compiled overload
        can be used as input to another function with locked-down signature
        """
        a = 1

        @njit
        def foo(x):
            return x + 1

        int_int_fc = types.FunctionType(types.int64(types.int64,))

        @njit(types.int64(int_int_fc))
        def bar(fc):
            return fc(a)

        self.assertEqual(bar(foo), foo(a))

        Test that a dispatcher object *without* a pre-compiled overload
        can be used as input to another function with locked-down signature
        
numba/tests/test_function_type.py