anchor.diff:           (cond ((and (not (null applicable-methods))
                        (every 'primary-method-p applicable-methods)
                        (typep (first applicable-methods) 'standard-writer-method)
  -                     (std-class-p (class-of class)))
  +                     (std-class-p (class-of class))
  +                     (slot-exists-in-class-p class (slot-value (first applicable-methods) 'slot-definition)))
                   (let ((location (slot-location class (slot-value (first applicable-methods) 'slot-definition))))
  +                  (assert location)
                     (setf (single-dispatch-emf-entry emf-table class) location)
                     (pushnew gf (class-dependents class))
                     (fast-slot-write (first args) (second args) location)))
  
positive.code:          (cond ((and (not (null applicable-methods))
                       (every 'primary-method-p applicable-methods)
                       (typep (first applicable-methods) 'standard-reader-method)
                       (std-class-p (class-of class)))
                  (let ((location (slot-location class (slot-value (first applicable-methods) 'slot-definition))))
                    (setf (single-dispatch-emf-entry emf-table class) location)
                    (pushnew gf (class-dependents class))
                    (fast-slot-read (first args) location)))
  
negative.code: (defun (setf std-slot-value) (value instance slot-name)
    (multiple-value-bind (slots location)
        (slot-location-in-instance instance slot-name)
      (when (not location)
        (slot-missing (class-of instance) instance slot-name 'setf value)
        (return-from std-slot-value
          value))
      (setf (slot-contents slots location) value)))
  (defun (setf slot-value) (new-value object slot-name)
    (cond ((std-class-p (class-of (class-of object)))
  