use of deleted function в c++

#include <iostream>

struct qwer
{
        const int x{1};
};

qwer tt()
{
        qwer xx;
        return xx;
}

int main()
{
        qwer qq;
        qq = tt();

        return 0;
}

Выдает ошибку:

qwer.cpp: In function ‘int main()’:
qwer.cpp:18:10: error: use of deleted function ‘qwer& qwer::operator=(qwer&&)’
   18 |  qq = tt();
      |          ^
qwer.cpp:4:8: note: ‘qwer& qwer::operator=(qwer&&)’ is implicitly deleted because the default definition would be ill-formed:
    4 | struct qwer
      |        ^~~~
qwer.cpp:4:8: error: non-static const member ‘const int qwer::x’, can’t use default assignment operator

Объясните пожалуйста в чем проблема )