clang++

cpp.cpp:44:18: error: non-const lvalue reference to type 'X' cannot bind to a temporary of type
      'typename std::remove_reference<X &>::type' (aka 'X')
            swap(std::move(other));         
                 ^~~~~~~~~~~~~~~~
cpp.cpp:8:22: note: passing argument to parameter 'other' here
        void swap(X& other) noexcept
                     ^
cpp.cpp:65:18: error: non-const lvalue reference to type 'X' cannot bind to a temporary of type
      'typename std::remove_reference<X &>::type' (aka 'X')
            swap(std::move(rhs));                   
                 ^~~~~~~~~~~~~~
cpp.cpp:8:22: note: passing argument to parameter 'other' here
        void swap(X& other) noexcept
                     ^
2 errors generated.

g++

cpp.cpp: In constructor ‘X::X(X&&)’:
cpp.cpp:44:27: error: invalid initialization of non-const reference of type ‘X&’ from an rvalue of type ‘std::remove_reference<X&>::type {aka X}’
             swap(std::move(other));         
                           ^
cpp.cpp:8:14: note:   initializing argument 1 of ‘void X::swap(X&)’
         void swap(X& other) noexcept
              ^
cpp.cpp: In member function ‘X& X::operator=(X&&)’:
cpp.cpp:65:27: error: invalid initialization of non-const reference of type ‘X&’ from an rvalue of type ‘std::remove_reference<X&>::type {aka X}’
             swap(std::move(rhs));                   
                           ^
cpp.cpp:8:14: note:   initializing argument 1 of ‘void X::swap(X&)’
         void swap(X& other) noexcept
              ^