anchor.diff:                         (slot-name (slot-definition-name slot-def))
                          (effective-slot (find-effective-slot instance slot-name))
                          (new-value (first args)))
  +                  (register-redefinition-flusher gf class)
                     (cond (effective-slot
                            (let* ((location (safe-slot-definition-location effective-slot))
                                   (typecheck (safe-slot-definition-typecheck effective-slot))
  
positive.code:                      (every 'primary-method-p applicable-methods)
                       (typep (first applicable-methods) 'standard-reader-method)
                       (std-class-p (class-of class)))
                  (let* ((instance (first args))
                         (slot-def (accessor-method-slot-definition (first applicable-methods)))
                         (slot-name (slot-definition-name slot-def))
  
negative.code:                                  (slot-def (accessor-method-slot-definition (first applicable-methods)))
                                   (slot-name (slot-definition-name slot-def))
                                   (effective-slot (find-effective-slot instance slot-name)))
                              (register-redefinition-flusher gf class)
                              (cond (effective-slot
                                     (let* ((location (safe-slot-definition-location effective-slot))
                                            (typecheck (safe-slot-definition-typecheck effective-slot))
  