#include <iostream>
#include <type_traits>
#include <utility>

template<typename T>
struct f_caller
{
    void operator () (T&& ) { std::cout << "T&&" << std::endl; }
    void operator () (T const& ) { std::cout << "const T&" << std::endl; }
};


template <typename T>
void f(T&& t)
{
    f_caller<typename std::decay<T>::type>()(std::forward<T>(t));
}

int main()
{
    int i;
    f(42);
    f(i);
}