In Emacs/Merlin/Tuareg - The second line shows an error.

let rec i3loop inx outx =
 lwt exlen = Lwt_io.BE.read_int inx in
 lwt buf = Lwt_io.read ~count:exlen inx in
  match buf with
  | "" -> Lwt_io.close inx ; Lwt_io.close outx
  | s -> Lwt_io.write Lwt_io.stdout s ; parse_i3cmdstring s ; i3loop inx outx