basic_ifstream& operator=(basic_ifstream&& rhs);
Effects: Move assigns the base and members of *this from the base and corresponding members of rhs.
Returns: *this.
void swap(basic_ifstream& rhs);
Effects: Exchanges the state of *this and rhs by calling basic_istream<charT,traits>::swap(rhs) and sb.swap(rhs.sb).
template <class charT, class traits>
void swap(basic_ifstream<charT, traits>& x,
basic_ifstream<charT, traits>& y);
Effects: x.swap(y).