31 Input/output library [input.output]

31.7 Formatting and manipulators [iostream.format]

31.7.5 Input streams [input.streams] Rvalue stream extraction [istream.rvalue]

template<class Istream, class T> Istream&& operator>>(Istream&& is, T&& x);
Constraints: The expression is >> std​::​forward<T>(x) is well-formed when treated as an unevaluated operand and Istream is publicly and unambiguously derived from ios_base.
Effects: Equivalent to: is >> std::forward<T>(x); return std::move(is);