let ( let* ) = Lwt.bind
let ( let+ ) x f = Lwt.map f x
let ( let*? ) = Lwt_result.bind
let ( let+? ) x f = Lwt_result.map f x

let list_get_ok l =
  let err = ref None in
  try
    Ok
      (List.map
         (function
           | Error _e as e ->
               err := Some e;
               raise Exit
           | Ok v -> v)
         l)
  with Exit -> ( match !err with None -> assert false | Some v -> v)

let lwt_list_get_ok l =
  let open Lwt.Syntax in
  let+ l = l in
  list_get_ok l