What's the equivalent of std::is_const for references to const?

Question

Consider the code:

int const  x = 50;
int const& y = x;
cout << std::is_const<decltype(x)>::value << endl; // 1
cout << std::is_const<decltype(y)>::value << endl; // 0

This makes sense, because y is not a const reference, it is a reference to a const.

Is there a foo such that std::foo<decltype(y)>::value is 1? If not, what would it look like to define my own?

Answer 1

Use remove_reference:

#include <string>
#include <iostream>
#include <type_traits>
using namespace std;

int main()
{
    int const  x = 50;
    int const& y = x;
    cout << std::is_const<std::remove_reference<decltype(x)>::type>::value << endl; // 1
    cout << std::is_const<std::remove_reference<decltype(y)>::type>::value << endl; // 1

    return 0;
}

See on coliru