# fun x -> x x;;
- : ('a -> 'b as 'a) -> 'b = <fun>

# (fun x -> x x) (fun x -> x x);;
  C-c C-cInterrupted.

# fun _ -> (fun x -> x x) (fun x -> x x);;
- : 'a -> 'b = <fun>

# (fun x -> x x) (fun x -> x x);;
# let x = (fun x -> x x) in x x;; (* applying the function on the left *)
# (fun x -> x x) (fun x -> x x);; (* inlining the let-binding *)
(* We came back to our original state, infinite loop *)

$ echo 'let x = (fun x -> x x) (fun x -> x x)' > rectypes.ml
$ ocamlc -i -rectypes rectypes.ml
val x : 'a

# let x =
   let rec f () = f () in
   f ();;