22 General utilities library [utilities]

22.10 Function objects [function.objects]

22.10.6 Class template reference_wrapper [refwrap]

22.10.6.5 Invocation [refwrap.invoke]

template<class... ArgTypes> constexpr invoke_result_t<T&, ArgTypes...> operator()(ArgTypes&&... args) const noexcept(is_nothrow_invocable_v<T&, ArgTypes...>);
Mandates: T is a complete type.
Returns: INVOKE(get(), std​::​forward<ArgTypes>(args)...).
([func.require])