anchor.diff:        into sub-levels
         finally (return (mapcan #'identity (cons top-level sub-levels)))))
   
  -(defun containerp (x)
  -  ;; Alternative: use op:def_kind and a list ot container kinds.
  -  (typep x 'container))
  +(defgeneric containerp (x)
  +  (:method ((x t)) nil)
  +  (:method ((x container)) t))
   
   (define-method lookup ((obj container) search_name)
     ;; FIXME: search_name is a scoped name.
  
positive.code: 
  
  ;;;; Enum
  
  (define-ir-class enum-def (typedef-def)
    :id "IDL:omg.org/CORBA/EnumDef:1.0"
    :attributes ((members))
    :def_kind :dk_Enum
  
negative.code: ;;;; interface AliasDef : TypedefDef
  ;;  attribute IDLType original_type_def;
  
  (define-ir-class alias-def (corba:AliasDef typedef-def)
    :id "IDL:omg.org/CORBA/AliasDef:1.0"
    :attributes ((original_type_def))
    :def_kind :dk_Alias
  