basic_ifstream& operator=(basic_ifstream&& rhs);
void swap(basic_ifstream& rhs);
Effects: Меняет состояние *this и rhs по вызову basic_istream<charT, traits>::swap(rhs) и sb.swap(rhs.sb).
template <class charT, class traits>
void swap(basic_ifstream<charT, traits>& x,
basic_ifstream<charT, traits>& y);