(module test_mono_recursive_fn_bug
  (class Foo
    (param a)
    (method foo
      (type (fn-type (params a) (ret (con Int))))))
  (instance
    (class Foo)
    (type (con Int))
    (method foo
      (body (lam (params (typed x a)) (ret (con Int)) (body x)))))
  (fn loop
    (type (fn-type (params (con Int) (con Int)) (ret (con Int))))
    (params acc i)
    (body (if (app eq i 0) acc (tail-app loop (app + acc i) (app - i 1)))))
  (fn main
    (type (fn-type (params) (ret (con Unit)) (effects IO)))
    (params)
    (body (app print (app loop 0 5)))))