template <typename T, typename U> struct is_convertible_test {
    static std::true_type test(U);
    static std::false_type test(...);
    static T make_T();

    enum {
        value = std::is_same<decltype(test(make_T())), std::true_type>::value
    };
};

template <typename T, typename U> struct is_base_of_test {
    enum {
        value = is_convertible_test<U, T>::value && !(is_convertible_test<T, U>::value)
    };
};