Emplacing vector into map

Question

Given this type:

std::map<int, std::vector<T>> map;

How to directly emplace elements?

map.emplace(10, /* ? */);

I can do it by separately creating the vector first, and then using that identifier in the call to emplace, but that is undesirable in case it's possible to do it directly somehow.

Answer 1

Both

map.emplace(typename decltype(map)::value_type(10, {1, 2, 3}));

and

map.emplace(10, std::initializer_list<int>{1, 2, 3});

should work fine.

I'm sure there is a reason why gcc rejects my first attempt:

map.emplace(10, {1, 2, 3});

but I don't know if it is a good reason or a defect.

Edit: It seems to have to do with the fact that the braced initializer list ({1, 2, 3}) does not have a type, making it impossible to use with perfect forwarding (which is necessary for map.emplace). There are several relevant SO posts about this point, such as this answer.