constexpr explicit vector(const Allocator&) noexcept;
constexpr explicit vector(size_type n, const Allocator& = Allocator());
constexpr vector(size_type n, const T& value,
                 const Allocator& = Allocator());
template<class InputIterator>
  constexpr vector(InputIterator first, InputIterator last,
                   const Allocator& = Allocator());
template<container-compatible-range<T> R>
  constexpr vector(from_range_t, R&& rg, const Allocator& = Allocator());