anchor.diff:                       (typep (first applicable-methods) 'standard-reader-method)
                        (std-class-p (class-of class)))
                   (let* ((instance (first args))
  -                       (slot-name (slot-definition-name (accessor-method-slot-definition (first applicable-methods))))
  +                       (slot-def (accessor-method-slot-definition (first applicable-methods)))
  +                       (slot-name (slot-definition-name slot-def))
                          (effective-slot (find-effective-slot instance slot-name)))
                     (cond (effective-slot
                            (let ((location (safe-slot-definition-location effective-slot)))
                              (setf (single-dispatch-emf-entry emf-table class) location)
  -                           (fast-slot-read (first args) location)))
  +                           (fast-slot-read (first args) location slot-def)))
                           (t
                            ;; Slot not present, fall back on SLOT-VALUE.
                            (slot-value instance slot-name)))))
  
positive.code:                                 instance
                                  (if (consp location)
                                      (car location)
                                      (safe-slot-definition-name (elt (safe-class-slots (class-of instance)) location)))))
            val))))
  
  (defun fast-slot-write (new-value instance location)
    (multiple-value-bind (slots layout)
        ;; This is required in case the instance is obsolete.
        (fetch-up-to-date-instance-slots-and-layout instance)
  
negative.code:                 ;; Switch to reader-method.
                  (set-funcallable-instance-function
                   gf
                   (compute-reader-discriminator gf emf-table argument-offset
                                                 (accessor-method-slot-definition (first applicable-methods))))
                  (apply gf args))
                 ((and (not (null applicable-methods))
                       (every 'primary-method-p applicable-methods)
  