error

File "src/x.ml", line 43, characters 36-39:
Error: This expression has type int32 list -> key
       but an expression was expected of type int32

failing.ml

  Lwt_main.run begin
  Imap.connect ~host:host ~port:port ~username:username ~password:password >>= fun imap ->
  Imap.examine imap mbox >>= fun () ->
  Imap.uid_search imap Imap.all >>= fun (uids, _) ->
  Lwt_list.iter_s (fun (uid: Imap.uid) ->
    (* APPARENTLY THE COMPILER DOESN'T LIKE THE FOLLOWING LINE, THE [uid] part *)
     let msg = Imap.(uid_fetch imap [uid] [Request.body_section ~peek:true ()]) in
     Lwt_stream.to_list msg >>= function
     | [_, {Imap.Response.body_section = [([], none), some s]; _}] ->
         Lwt_io.printlf "uid: %ld" uid
         Lwt_io.printlf "body section incorrect for uid: %ld" uid
     | _ ->
         Lwt_io.printlf "error fetching message %ld\n" uid
   ) uids
  >>= fun () -> Imap.disconnect imap
  end

working.ml

  Lwt_main.run begin
  Imap.connect ~host:host ~port:port ~username:username ~password:password >>= fun imap ->
  Imap.examine imap mbox >>= fun () ->
  Imap.uid_search imap Imap.all >>= fun (uids, _) ->
  Lwt_list.iter_s (fun (uid : Imap.uid) -> Lwt_io.printf "uid: %ld\n" uid) uids
  >>= fun () -> Imap.disconnect imap
  end