anchor.diff:  (defclass control-error (error))
   
   (defclass restart (condition)
  -  (.associated-condition))
  +  (associated-condition))
   
   ;;; Specific restarts
   (defclass abort (restart))
   (defclass continue (restart))
   (defclass use-value (restart)
  -  (.value))
  +  (value))
   (defclass store-value (restart)
  -  (.value))
  +  (value))
   
   (defgeneric default-handler (condition))
   (defmethod default-handler ((c condition))
  
positive.code:     h))
  
  (defclass handler-frame ()
    (.handlers
     .parent-frame))
  
  (defun make-handler-frame ((handlers list) &optional (parent-frame nil))
    (let ((f (make handler-frame)))
  
negative.code: 
  ;;; Specific errors
  (defclass unbound-variable (error)
    (name
     namespace))
  (defun make-unbound-variable ((name string) (namespace string))
    (let ((e (make unbound-variable)))
      (setf (.name e) name)
  