connection.ml

module Connection =
  struct
    type connecting = {
      when_initialized: int;}
    type connected = {
      session_id: string;}
    type disconnected = {
      when_disconnected: int;}
    type state =
      | Connecting of connecting
      | Connected of connected
      | Disconnected of disconnected
    type t = {
      state: state;
      host: string;}
  end

module App =
  struct
    open Connection
    let connection =
      {
        state = ((Connected ({ session_id = "ABC" }))[@explicit_arity ]);
        host = "localhost"
      }
    let _ = print_endline connection.host
    let _ =
      print_endline
        (match connection.state with
         | ((Connected (p))[@explicit_arity ]) -> p.session_id)
  end