605     tail: NodePtr<K, V>,  field
653         if self.tail.is_null() {  in next_back()
657         let prev = self.tail.prev();  in next_back()
658         let obj = unsafe { Box::from_raw(self.tail.0) };  in next_back()
660         self.tail = prev;  in next_back()
684     tail: NodePtr<K, V>,  field
693             tail: self.tail,  in clone()
731         if self.tail == self.head {  in next_back()
735         let (k, v) = unsafe { (&(*self.tail.0).key, &(*self.tail.0).value) };  in next_back()
736         self.tail = self.tail.prev();  in next_back()
760     tail: NodePtr<K, V>,  field
769             tail: self.tail,  in clone()
806         if self.tail == self.head {  in next_back()
810         let (k, v) = unsafe { (&(*self.tail.0).key, &mut (*self.tail.0).value) };  in next_back()
811         self.tail = self.tail.prev();  in next_back()
826                 tail: NodePtr::null(),  in into_iter()
832                 tail: self.last_child(),  in into_iter()
1401             tail: self.last_child(),  in iter()
1412             tail: self.last_child(),  in iter_mut()