1 files changed, 1 insertions, 0 deletions
diff --git a/ToDo b/ToDo
index c144100529..476e559371 100644
--- a/ToDo
+++ b/ToDo
@@ -75,6 +75,7 @@ Standard Libraries
 * Hash::new{default} or recommend Hash#fetch?
 * new user-defined marshal scheme. _dump(dumper), _load(restorer)
 * warn, warning for Ruby level
+* hash etc. should handle self referenceing array/hash
 
 Extension Libraries