;; A match arm's binding is a binding, and the escape check has to see it.
;;
;; Reading the payload by hand is a case-field read, which is suspect: a copy
;; of a function value carries whatever environment the original did. Binding
;; it to a name in an arm is the same read, and the store that fills the arm's
;; slot is inside the branch rather than in any form the walk reads as a
;; binding — so without the arm's slots being taken as suspect too, the Vec,
;; slice, struct and pointer spellings of this were all refused while the one
;; that goes through Option and a name was not.

(defn leak [o (Option (Fn [] i32))] (Fn [] i32)
  (match o
    (Some f) f
    None     (fn [] 0)))

(defn main [] i32 0)