Fix bug in split_before and split_after for first and last node edge cases

src/lib.rs

@@ -535,13 +535,15 @@ impl<'a, T> CursorMut<'a, T> {
 
  // What the output will become
  let output_len = old_len - new_len;
- let output_front = self.list.front;
+ // We might be at the first node, in which case we don't want to set a new list.front but return an empty list.
+ let mut output_front = None;
  let output_back = prev;
 
  // Break the links between cur and prev
  if let Some(prev) = prev {
  (*cur.as_ptr()).front = None;
  (*prev.as_ptr()).back = None;
+ output_front = self.list.front
  }
 
  // Produce the result:
@@ -598,12 +600,14 @@ impl<'a, T> CursorMut<'a, T> {
  // What the output will become
  let output_len = old_len - new_len;
  let output_front = next;
- let output_back = self.list.back;
+ // We might be at the last node, in which case we don't want to set a new list.back but return an empty list.
+ let mut output_back = None;
 
  // Break the links between cur and next
  if let Some(next) = next {
  (*cur.as_ptr()).back = None;
  (*next.as_ptr()).front = None;
+ output_back = self.list.back;
  }
 
  // Produce the result:
@@ -1197,4 +1201,40 @@ mod test {
 
  assert_eq!(from_front, re_reved);
  }
+
+ #[test]
+ fn marker_split_before_first() {
+ let mut m: LinkedList<u32> = LinkedList::new();
+ m.extend([1, 2, 3, 4, 5, 6]);
+ let mut cursor = m.cursor_mut();
+ cursor.move_next();
+ assert_eq!(cursor.current(), Some(&mut 1));
+
+ let left = cursor.split_before();
+ assert!(left.is_empty());
+ assert!(left.front.is_none() && left.back.is_none());
+
+ assert_eq!(cursor.current(), Some(&mut 1));
+ assert_eq!(m.iter().cloned().collect::<Vec<_>>(), &[1, 2, 3, 4, 5, 6]);
+ assert_eq!(m.len(), 6);
+ }
+
+ #[test]
+ fn split_after_last() {
+ let mut m: LinkedList<u32> = LinkedList::new();
+ m.extend([1, 2, 3, 4, 5, 6]);
+ assert_eq!(m.iter().cloned().collect::<Vec<_>>(), &[1, 2, 3, 4, 5, 6]);
+ let mut cursor = m.cursor_mut();
+
+ cursor.move_prev();
+ assert_eq!(cursor.current(), Some(&mut 6));
+
+ let right = cursor.split_after();
+ assert!(right.is_empty());
+ assert!(right.front.is_none() && right.back.is_none());
+
+ assert_eq!(cursor.current(), Some(&mut 6));
+ assert_eq!(m.iter().cloned().collect::<Vec<_>>(), &[1, 2, 3, 4, 5, 6]);
+ assert_eq!(m.len(), 6);
+ }
 }