anchor.diff:                         (compute-class implc nil))))
       (cond
         (implc-inst
  -       ;; FIXME: OTHERWISE need to defer evaluation !
  +       ;; FIXME: If no IMPLC-INST -- i.e if the instance's
  +       ;; implementation-class is not yet defined -- need to defer
  +       ;; evaluation ! This may serve to require some extensions in the
  +       ;; compiler environment.
  +
          #+nil
          (warn "Dispatch from CHANGE-CLASS ~S ~S to initialize ~S"
                instance new implc-inst)
   
  -       ;; NB: in PCL this may be the only way that the
  +       ;; NB: in PCL this may be the only way to ensure that the
          ;; direct-supeclasses slot winds up initialized from
          ;; CHANGE-CLASS (??) (FIXME: Evaluate how that's been implemented)
          (shared-initialize implc-inst (list +direct-superclasses-slot+)))
  +      ;; In lieu of deferred evaluation, emit a warning
  +      ;;
  +      ;; NB: In this scenario, the instance's implementation-class may
  +      ;; be manually initialized from outside of CHANGE-CLASS, using a
  +      ;; SHARED-INITIALIZE call similar to the previous.
         (t (warn "~<Unable to initilize unreachable ~
  -implementation class ~S for ~S~>~< during CHANGE-CLASS ~s ~s~>"
  +implementation class ~S for ~S~>~< during (CHANGE-CLASS ~S ~S)~>"
                  implc new
                  instance new)))))
   
  
positive.code:                                                  &allow-other-keys)
    ;; ensure that any call to MAKE-INSTANCE of a SINGLETON will produce
    ;; an object that is a subtype of the original SINGLETON
    ;;
    ;; [FIXME DNW IN SOME POST-HOC APPLICATIONS - NEEDS FURTHER TESTING]
  
    ;; NB: This may be "Early enough" to catch where PCL is initially
    ;; setting the direct-superclasses list for a class definition.
    ;;
    ;; Note that PCL may be (perhaps cheaply) setting the STANDARD-OBJECT
    ;; class into the list of DIRECT-SUPRECLASSES whenever the
    ;; direct-superclasses list is NIL in the initial DEFCLASS form.
    ;;
    ;; Theoretically. that can be removed during ENSURE-TGT-SUPERCLASS below.
    ;; [FIXME / QA]
  
    (let ((tgt-class (find-class 'singleton))
          (unused-class (find-class 'standard-object))
  
negative.code: ;; )
  
  (eval-when ()
  
    (defsingleton x-a ()
      ())
  
    (typep (make-instance 'x-a) 'x-a)
  