[Bug libstdc++/70472] is_copy_constructible<vector<unique_ptr<int>>>::value is true

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70472

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
That would only work for vector<T> not vector <T, A>, for the reasons given
above.