substitution_dispatch::operator()

template <class T>
T&& operator()(T&& value) const noexcept; // exposition-only

Returns std::forward<T>(value). When T is not cv- or ref-qualified and is_bitwise_trivially_relocatable_v<T> is true, conversion from the return value to any proxy type shall perform bitwise trivial relocation and does not require that T is move-constructible.