;; A handler-bind is an expression and its value is its body's, so it is a way
;; for a function value to be a function's answer — and it would have walked
;; straight past a check that only looked at [return] and at the last form of
;; a block. with-allocator and restart-case are the same shape and are checked
;; the same way.
(defstruct C [id i32])
(defonce seen i32)

(defn keep [f (Fn [] i32)] (Fn [] i32)
  (handler-bind [(C [c] (set seen (.id c)))] f))

(defn main [] i32 0)