(module new_counter_user_adt
  (data Counter (ctor MkCounter (con Int)))
  (fn new (type (fn-type (params (con Int)) (ret (con Counter)))) (params n)
    (body (term-ctor Counter MkCounter n)))
  (fn main (type (fn-type (params) (ret (con Unit)) (effects IO))) (params)
    (body (let c (new Counter 42) (do io/print_str "ok\n")))))