anchor.diff:           (cond ((and (not (null applicable-methods))
                        (every 'primary-method-p applicable-methods)
                        (typep (first applicable-methods) 'standard-reader-method)
  -                     (standardish-class-p (class-of class)))
  +                     (std-class-p (class-of class)))
                   ;; Switch to reader-method.
                   (setf (generic-function-discriminating-function gf)
                         (compute-reader-discriminator gf emf-table argument-offset))
  
positive.code:   (dolist (super (class-direct-superclasses class))
      (ensure-class-finalized super))
    (setf (class-precedence-list class)
          (funcall (if (standardish-class-p (class-of class))
                       #'std-compute-class-precedence-list
                       #'compute-class-precedence-list)
                   class))
    (setf (class-slots class)
          (funcall (if (standardish-class-p (class-of class))
                       #'std-compute-slots
                       #'compute-slots)
                   class))
  
negative.code: (defmethod reinitialize-instance :before ((class structure-class) &rest args)
    (error "Cannot reinitialize structure classes."))
  
  (defmethod slot-value-using-class ((class structure-class) instance (slot standard-effective-slot-definition))
    (let ((def (slot-value class 'structure-definition))
          (slot-name (slot-definition-name slot)))
      (when (not (eql (sys.int::%object-ref-t instance 0) def))
        (error "Class for structure ~S or instance is outdated?" (class-name class)))
      (dolist (slot (sys.int::structure-slots def)
  