--- a/rust/hg-core/src/dirstate_tree/on_disk.rs	Mon May 06 16:29:00 2024 +0200
+++ b/rust/hg-core/src/dirstate_tree/on_disk.rs	Mon May 06 13:02:52 2024 +0200
@@ -691,9 +691,11 @@
         // First accumulate serialized nodes in a `Vec`
         let mut on_disk_nodes = Vec::with_capacity(nodes_len);
         for node in nodes {
-            let children =
-                self.write_nodes(node.children(self.dirstate_map.on_disk)?)?;
+            let children = node.children(self.dirstate_map.on_disk)?;
             let full_path = node.full_path(self.dirstate_map.on_disk)?;
+            self.check_children(&children, full_path)?;
+
+            let children = self.write_nodes(children)?;
             let full_path = self.write_path(full_path.as_bytes());
             let copy_source = if let Some(source) =
                 node.copy_source(self.dirstate_map.on_disk)?
@@ -771,6 +773,37 @@
         Ok(ChildNodes { start, len })
     }
 
+    /// Catch some dirstate corruptions before writing them to disk
+    fn check_children(
+        &mut self,
+        children: &dirstate_map::ChildNodesRef,
+        full_path: &HgPath,
+    ) -> Result<(), DirstateError> {
+        for child in children.iter() {
+            let child_full_path =
+                child.full_path(self.dirstate_map.on_disk)?;
+
+            let prefix_length = child_full_path.len()
+                // remove the filename
+                - child.base_name(self.dirstate_map.on_disk)?.len()
+                // remove the slash
+                - 1;
+
+            let child_prefix = &child_full_path.as_bytes()[..prefix_length];
+
+            if child_prefix != full_path.as_bytes() {
+                let explanation = format!(
+                    "dirstate child node's path '{}' \
+                        does not start with its parent's path '{}'",
+                    child_full_path, full_path,
+                );
+
+                return Err(HgError::corrupted(explanation).into());
+            }
+        }
+        Ok(())
+    }
+
     /// If the given slice of items is within `on_disk`, returns its offset
     /// from the start of `on_disk`.
     fn on_disk_offset_of<T>(&self, slice: &[T]) -> Option<Offset>