Why do primitive and user-defined types act differently when returned as 'const' from a function?

Question

#include 

using namespace std;

template
void f(T&&) { cout << \"f(T&&)\" << endl; }

template

        

Answer 1

I don't have a quote from the standard, but cppreference confirms my suspicions:

A non-class non-array prvalue cannot be cv-qualified. (Note: a function call or cast expression may result in a prvalue of non-class cv-qualified type, but the cv-qualifier is immediately stripped out.)

The returned const int is just a normal int prvalue, and makes the non-const overload a better match than the const one.