Fix LineListNode::pjoin_dyn casting a CellByteNode as dense

src/line_list_node.rs

@@ -2637,12 +2637,12 @@ impl<V: Clone + Send + Sync, A: Allocator> TrieNode<V, A> for LineListNode<V, A>
                 unimplemented!()
             },
             CELL_BYTE_NODE_TAG => {
-                let other_dense_node = unsafe{ other.as_dense_unchecked() };
-                let mut new_node = other_dense_node.clone();
+                let other_cell_node = unsafe{ other.as_cell_unchecked() };
+                let mut new_node = other_cell_node.clone();
                 match new_node.merge_from_list_node(self) {
                     //See the DENSE_BYTE_NODE_TAG arm: two empty nodes join to an empty result
                     AlgebraicStatus::None => {
-                        debug_assert!(self.node_is_empty() && other_dense_node.node_is_empty());
+                        debug_assert!(self.node_is_empty() && other_cell_node.node_is_empty());
                         AlgebraicResult::None
                     },
                     AlgebraicStatus::Identity => AlgebraicResult::Identity(COUNTER_IDENT),

src/zipper_head.rs

@@ -1494,4 +1494,25 @@ mod tests {
         assert_eq!(rz.is_val(), false);
         drop(rz);
     }
+
+    /// A ZipperHead turns the parent node into a CellByteNode; joining a list node with it must not
+    /// treat the cell node as a DenseByteNode
+    #[test]
+    fn zipper_head_cell_node_pjoin_test() {
+        let mut b = PathMap::<()>::new();
+        b.set_val_at(b"ax", ());
+        b.set_val_at(b"bx", ());
+        {
+            let zh = b.zipper_head();
+            let mut wz = zh.write_zipper_at_exclusive_path(b"c").unwrap();
+            wz.set_val(());
+        }
+        let mut a = PathMap::<()>::new();
+        a.set_val_at(b"dx", ());
+
+        let joined = a.join(&b);
+        let mut paths: Vec<Vec<u8>> = joined.iter().map(|(p, _)| p).collect();
+        paths.sort();
+        assert_eq!(paths, vec![b"ax".to_vec(), b"bx".to_vec(), b"c".to_vec(), b"dx".to_vec()]);
+    }
 }