open Core
module Deferred = Deferred1

module T = struct
  type 'a t = 'a Option.t Deferred.t
end

include T

include Monad.Make (struct
  include T

  let return a = Deferred.return (Some a)

  let bind t ~f =
    Deferred.bind t ~f:(function
      | Some a -> f a
      | None -> Deferred.return None)
  ;;

  let map t ~f = Deferred.map t ~f:(fun r -> Option.map r ~f)
  let map = `Custom map
end)
