let-rec-and generalization happens after resolutions of all mutually recursive funtions

gener.ml

module S1 = struct

  let f p sep =
    let r = p () in
    match r with
    | None -> `A (sep ())
    | Some l -> `B l

end

module S2 = struct

  type t = A
  
  let rec p1 () = A

  and p3 () = None
  
  and f p sep = (* not fully generalized for p1, p2, p4 *)
    let r = p () in
    match r with
    | None -> `A (sep ())
    | Some l -> `B l
 
  and p4 () =
    f p3 p1

end