(defstruct AssetMissing [id i32])

(defvar cleanups i64)

(defn load [n i32] i32
  (signal (AssetMissing {.id n}))
  100)

(defn middle [n i32] i32
  (defer (set cleanups (+ cleanups 1)))   ; runs on the transfer too
  (+ (load n) 1))

(defn fetch [n i32] i32
  (restart-case (middle n)                ; its value if nothing transfers
    (use-placeholder [] -1)
    (retry           [] 7)))

(defn main []
  (print (fetch 1)) (println "")          ; 101 — nothing handled it

  (handler-bind [(AssetMissing [c] (invoke-restart 'use-placeholder))]
    (print (fetch 2)) (println ""))        ; -1

  (print cleanups) (println ""))          ; 2 — the defer ran both times