(module c4_rewrite
  (data Pair
    (doc "boxed pair of ints")
    (ctor MkPair (con Int) (con Int)))
  (fn both
    (doc "rewrite: destructure rest once via match")
    (type (fn-type (params (own (con Pair))) (ret (own (con Pair)))))
    (params rest)
    (body (match rest (case (pat-ctor MkPair a b) (term-ctor Pair MkPair a b))))))