anchor.diff:                                        (car inst-b)
                                       (declare (type (integer 0 #.most-positive-fixnum)
                                                      a-n-1 a-n-2 a-n-3
  -                                                   b-n-1 b-n-2 b-n-3)
  -                                             #-DEBUG
  -                                             ;; only if these depth values are
  -                                             ;; not referenced elsewhere
  -                                             (dynamic-precedence
  -                                              a-n-1 a-n-2 a-n-3
  -                                              b-n-1 b-n-2 b-n-3)
  -                                             )
  +                                                   b-n-1 b-n-2 b-n-3))
  +                                    ;; NB: As sparse as this may seem,
  +                                    ;; it work out in tests.
                                       (cond
                                         ((and (= a-n-1 b-n-1)
                                               (= a-n-2 b-n-2))
  
positive.code: )
  
  ;; see also: spec-mop.lisp
  
negative.code:                         #+NIL (values reachable))
                   ;; FIXME - Cheap convenience hack for iterative computation
                   ;; onto a static form. Uses needless CONS initialization
  
                   (destructuring-bind (param-class param-offset
                                                    &optional (%reachable reachable)) hack
                     #+DEBUG
  