Link: https://godbolt.org/z/Yd6j6WzrE

The idea is that current 'std::common_reference_with<T, U>' is unlike
'std::same_as<T, U>' such that it's not commutative.

One little change on the definition of the concept
'std::common_reference_with<T, U>' can make it commutative.

The code below proves that:

```

#include <concepts>

// Turn this 1 to 0 and see what happens, then turn it back to 1 to get
the idea.
#if 1
template <class T, class U>
concept common_reference_with =
     std::same_as<std::common_reference_t<T, U>,
std::common_reference_t<U, T>> &&
     std::convertible_to<T, std::common_reference_t<T, U>> &&
     std::convertible_to<U, std::common_reference_t<U, T>>; // Note
here, the current standard is `common_reference_t<T, U>`.
#else
using std::common_reference_with;
#endif

template <class T, class U> requires common_reference_with<T, U>
   void f();

template <class T, class U> requires common_reference_with<U, T> && true
   [[deprecated("Right.")]] void f();


int main()
{
     f<int&, const int&&>();
}

```