new undefine argument telling if variable with no more references should be...

new undefine argument telling if variable with no more references should be removed (False by default for consistency with old behaviour)

nodes.py

@@ -103,7 +103,7 @@
         # root is None during parsing
         return root is not None and root.should_register_op
 
-    def remove_node(self, node):
+    def remove_node(self, node, undefine=False):
         """remove the given node from the tree
 
         USE THIS METHOD INSTEAD OF .remove to get correct variable references
@@ -112,8 +112,8 @@
         # unregister variable references in the removed subtree
         for varref in node.iget_nodes(VariableRef):
             varref.unregister_reference()
-            #if not varref.variable.references():
-            #    node.root.undefine_variable(varref.variable)
+            if undefine and not varref.variable.stinfo['references']:
+                node.stmt.undefine_variable(varref.variable)
         if self.should_register_op:
             from rql.undo import RemoveNodeOperation
             self.undo_manager.add_operation(RemoveNodeOperation(node))