Why should we overload forwarding constructors for the case of initializer_list?

Question

std::optional provides constructors that forwards arguments to the constructor of the owned object:

 template<class...Args>
 optional(in_place_t,Args&&...args)

But it also provides this overload:

 template<class U,class...Args>
 optional(in_place_t,initializer_list<U> l,Args&&...args)

What are the benefits of this last overload?

Answer 1

It's to allow you to do this:

 optional<vector<int>> o(in_place_t, {1, 2, 3, 4, 5});

That's much shorter than:

 optional<vector<int>> o(in_place_t, std::initializer_list<int>{1, 2, 3, 4, 5});