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]).