2 files changed, 47 insertions, 13 deletions

diff --git a/chain/src/item/default/mod.rs b/chain/src/item/default/mod.rs
index 7ecc70d..1a00368 100644
--- a/chain/src/item/default/mod.rs
+++ b/chain/src/item/default/mod.rs
@@ -267,6 +267,11 @@ impl<T: GraphLabel> Forest<T> for DefaultForest<ForestLabel<T>> {
 
         let mut self_stack = Vec::with_capacity(fragment.nodes_len());
 
+        use std::collections::HashSet;
+
+        let mut frag_seen: HashSet<usize> = HashSet::with_capacity(fragment.nodes_len());
+        let mut self_seen: HashSet<usize> = HashSet::with_capacity(fragment.nodes_len());
+
         let frag_root = if let Some(root) = fragment.root() {
             root
         } else {
@@ -281,24 +286,46 @@ impl<T: GraphLabel> Forest<T> for DefaultForest<ForestLabel<T>> {
         while let (Some(frag_top), Some(self_top)) =
             (frag_stack.last().copied(), self_stack.last().copied())
         {
+            frag_seen.insert(frag_top);
+            self_seen.insert(self_top);
+
             frag_stack.pop();
             self_stack.pop();
 
             if fragment.vertex_label(frag_top)? != self.vertex_label(self_top)? {
                 // not a prefix
+                dbg!(
+                    frag_top,
+                    self_top,
+                    fragment.vertex_label(frag_top)?,
+                    self.vertex_label(self_top)?
+                );
                 return Ok(false);
             }
 
-            let mut self_children = self.children_of(self_top)?;
+            let self_children = self.children_of(self_top)?;
+            let frag_children = fragment.children_of(frag_top)?;
+
+            if frag_children.len() != self_children.len() {
+                dbg!(
+                    frag_top,
+                    self_top,
+                    fragment.vertex_label(frag_top)?,
+                    self.vertex_label(self_top)?
+                );
+                return Ok(false);
+            }
 
-            for child in fragment.children_of(frag_top)? {
-                if let Some(self_child) = self_children.next() {
-                    frag_stack.push(child);
-                    self_stack.push(self_child);
-                } else {
-                    // too few children
+            for (frag_child, self_child) in frag_children.zip(self_children) {
+                if frag_seen.contains(&frag_child) && self_seen.contains(&self_child) {
+                    continue;
+                } else if frag_seen.contains(&frag_child) || self_seen.contains(&self_child) {
+                    dbg!();
                     return Ok(false);
                 }
+
+                frag_stack.push(frag_child);
+                self_stack.push(self_child);
             }
         }
 
@@ -425,6 +452,8 @@ impl<T: GraphLabel> Forest<T> for DefaultForest<ForestLabel<T>> {
             return Err(ForestLabelError::ClonePack.into());
         }
 
+        let is_root_p = self.root() == Some(node_id);
+
         // We are sure old_label is not packed here, so it is safe to
         // unwrap.
         let new_label = old_label
@@ -473,6 +502,10 @@ impl<T: GraphLabel> Forest<T> for DefaultForest<ForestLabel<T>> {
         // Make a new node
         let new_index = builder.add_vertex(rep_label);
 
+        if is_root_p {
+            self.root = Some(new_index);
+        }
+
         // Re-direct parents to the new node.
         //
         // This must be done before pointing the new node to the old
diff --git a/chain/src/item/default/splone.rs b/chain/src/item/default/splone.rs
index 1168539..4f4835b 100644
--- a/chain/src/item/default/splone.rs
+++ b/chain/src/item/default/splone.rs
@@ -1,3 +1,4 @@
+#![allow(dead_code)]
 //! This module implements a function for "closing" and "splitting" a
 //! node in a forest, and hence the name.
 
@@ -595,6 +596,12 @@ mod test_splone {
 
         forest.plant(
             cloned,
+            leaf!(GrammarLabel::new_closed(6, 0, 1), GrammarLabel),
+            true,
+        )?;
+
+        forest.plant(
+            cloned,
             leaf!(GrammarLabel::new_closed(7, 1, 3), GrammarLabel),
             false,
         )?;
@@ -605,12 +612,6 @@ mod test_splone {
             false,
         )?;
 
-        forest.plant(
-            cloned,
-            leaf!(GrammarLabel::new_closed(6, 0, 1), GrammarLabel),
-            true,
-        )?;
-
         let mut builder = PLGBuilderMut::from_graph_mut(&mut forest.graph);
 
         let dummy_label = ForestLabel::from(GrammarLabel::new(0, 0));