(defvarl thing-count 0)

(defstruct thing ()
  (call-count 0)

  (:init (me)
    (inc thing-count))
  (:function get-thing-count () thing-count)
  (:method get-call-count (me) (inc me.call-count)))

(let ((t1 (new thing))
      (t2 (new thing)))
  (prinl t1.(get-call-count)) ;; prints 1
  (prinl t1.(get-call-count)) ;; prints 2
  (prinl t1.(get-call-count)) ;; prints 3
  (prinl t2.(get-call-count)) ;; prints 1
  (prinl t2.(get-call-count)) ;; prints 2
  (prinl t2.(get-call-count)) ;; prints 3

  (prinl [t1.get-thing-count])  ;; prints 2
  (prinl [t2.get-thing-count])) ;; prints 2