(defmacro define-food-box (name food-type : supers . clauses)
  (unless (subtypep food-type 'edible)
    (error "~s requires edible type, not ~s" %fun% food-type))
  ^(defstruct ,name ,supers
     food
     (:method set-food (me food)
       (unless (typep food ',food-type)
         (error "~s: requires ~s object, not ~s" %fun% ',food-type food))
       (set me.food food))
     ,*clauses))