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