template <class P> iterator insert(P&& x);
template <class P> iterator insert(const_iterator position, P&& x);
Effects: The first form is equivalent to return emplace(std::forward<P>(x)). The second form is equivalent to return emplace_hint(position, std::forward<P>(x)).
Remarks: These signatures shall not participate in overload resolution unless std::is_constructible<value_type, P&&>::value is true.