std::map::insert has an overload for R-values:
std::pair<iterator,bool> insert(value_type&&);
Any expression which binds to this overload will invoke R-value constructors. Since std::map<K,V>::value_type is std::pair<const key_type, mapped_type>, and std::pair has a constructor that takes R-values:
template<class U1, class U2>
pair(U1&& x, U2&& y);
then you are guaranteed that R-value constructors for key_type and mapped_type will be invoked, both in the creation of the pair object, and in the map insertion, as long as you insert the pair using an expression that creates R-values, such as:
map1.insert(std::make_pair(0, Huge());
OR
map1.insert(std::make_pair(0, std::move(huge1));
Of course, all of this is dependent on Huge having a proper R-value constructor:
Huge(Huge&& h)
{
...
}
Finally, you can also use std::map::emplace if you simply want to construct a new Huge object as an element in the map.