29 Input/output library [input.output]

29.7 Formatting and manipulators [iostream.format]

29.7.4 Input streams [input.streams]

29.7.4.5 Rvalue stream extraction [istream.rvalue]

template<class charT, class traits, class T> basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&& is, T&& x);
Constraints: The expression is >> std​::​forward<T>(x) is well-formed when treated as an unevaluated operand.
Effects: Equivalent to:
is >> std::forward<T>(x);
return is;