anchor.diff:  
                (defclass ,%proto-name (,@user-metaclass prototype-class
                                                         ,@superclasses)
  +               ;; NB: See also, the FIXME remark in the definition of
  +               ;; the INITIALIZE-INSTANCE method in this source file.
                  ()
                  (:implementation-class . ,name)
                  (:metaclass prototype-class))
   
                (prog1 (defclass ,name (,@superclasses #+NIL singleton)
  -                      ;; NB: see INITILAIZE-INSTANCE below
                         ,slots
                         (:metaclass ,%proto-name)
                         ,@%params)
  
positive.code:   (subtypep (make-instance 'x-b) 'x-a)
    ;; FIXME while => NIL, T
  
    (subtypep (find-class 'x-b) 'x-a)
    ;; => T, T
    ;; should be same, with or without the added SHARED-INITIALIZE
    ;; as it's consistent onto CLOS
  
  
  ;; -- test the new SHARED-INITIALIZE method with the original DEFSINGLETON macro
  
negative.code: ;; NB: To produce a suclass C2 of a class C1, such that C2 is both an
  ;; instance typep C1 and a subtype of C1 ...
  ;;
  ;; one may define MAKE-INSTANCE => CREATE-IMPLICIT-SUBCLASS
  ;; via ALLOCATE-INSTANCE
  ;;
  ;; This, albeit, may seem to pose some difficulty for typing in the
  