How to switch passed value through C++ standard type trait?

I want to switch passed value through C++ standard type trait. Here is the test code show what I mean:

template<typename T>
T _func(T t, std::is_integral<T>||std::is_enum<T>)
{
    return t;
}

template<typename T>
T _func(T t, std::is_floating_point<T>)
{
    return t;
}

template<typename T>
T _func(T t, std::is_same<T, std::string>)
{
    return t;
}

template<typename T>
T func(T t)
{
    return _func(t, T)
}

It doesn't work of course. I try my best to test and find a way to implement this:

int testint(int t){ return t;}
std::string testString(std::string t ){return t;}
float testreal(float t ){return t;}

template <typename T>
T test_string_type(T t, std::true_type) {
    return testString(t);
}

template <typename T>
T test_string_type(T t, std::false_type) {
    return t;
}

template<typename T>
T test_real_type(T t, std::true_type)
{
    return testreal(t) ;
}

template<typename T>
T test_real_type(T t, std::false_type)
{
    return test_string_type(t, std::is_same<T, std::string>());
}

template<typename T>
T test_enum_type(T t, std::true_type)
{
    return testint(t) ;
}

template<typename T>
T test_enum_type(T t, std::false_type)
{
    return test_real_type(t, std::is_floating_point<T>());
}

template<typename T>
T test_integer_type(T t, std::true_type)
{
    return testint(t) ;
}

template<typename T>
T test_integer_type(T t, std::false_type)
{
    return test_enum_type(t, std::is_enum<T>()) ;
}

template<typename T>
T test(T t)
{
    return test_integer_type(t, std::is_integral<T>());
}

It works, but really ugly code. Is there any kind of smart way to solve this?