C++ compile time check if type has mutable fields

问题

All

is it possible to get true/false flag for class having mutable field?

Could I distinguish during compilation between

struct A {
    private: mutable int _x;
};

and

struct B {
    private: int _x;
};

More complex question, is it possible to do so NOT knowing name of the field?

来源：https://stackoverflow.com/questions/35519596/c-compile-time-check-if-type-has-mutable-fields