basic_ifstream();
explicit basic_ifstream(const char* s,
ios_base::openmode mode = ios_base::in);
explicit basic_ifstream(const filesystem::path::value_type* s,
ios_base::openmode mode = ios_base::in); // wide systems only; see [fstream.syn]
explicit basic_ifstream(const string& s,
ios_base::openmode mode = ios_base::in);
template<class T>
explicit basic_ifstream(const T& s, ios_base::openmode mode = ios_base::in);
basic_ifstream(basic_ifstream&& rhs);
void swap(basic_ifstream& rhs);
template<class charT, class traits>
void swap(basic_ifstream<charT, traits>& x, basic_ifstream<charT, traits>& y);
basic_filebuf<charT, traits>* rdbuf() const;
bool is_open() const;
void open(const char* s, ios_base::openmode mode = ios_base::in);
void open(const filesystem::path::value_type* s,
ios_base::openmode mode = ios_base::in); // wide systems only; see [fstream.syn]
void open(const string& s, ios_base::openmode mode = ios_base::in);
void open(const filesystem::path& s, ios_base::openmode mode = ios_base::in);
void close();