ppx_deriving.make breaks on mutually recurive types

[shonfeder]

In ex.ml

module Ex = struct
  type t = {a : int; b: s}
  [@@deriving make]
  and s = t list
end

With the dune file:

(library
 (name ex)
 (modules ex)
 (preprocess (pps ppx_deriving.make)))

dune build gives

$ dune build                    
File "ex.ml", line 5, characters 2-16:
5 |   and s = t list
      ^^^^^^^^^^^^^^
Error: make can be derived only for record types

If we put another deriving annotation on s and swap the order the types are declared, the compilation goes thru but the make annotation is ignored:

module Ex = struct
  type s = t list
  [@@deriving show]

  and t = {a : int; b: s}
  [@@deriving make]
end

Which produces

[@@@ocaml.ppx.context
  {
    tool_name = "ppx_driver";
    include_dirs = [];
    load_path = [];
    open_modules = [];
    for_package = None;
    debug = false;
    use_threads = false;
    use_vmthreads = false;
    recursive_types = false;
    principal = false;
    transparent_modules = false;
    unboxed_types = false;
    unsafe_string = false;
    cookies = [("library-name", "ex")]
  }]
module Ex =
  struct
    type s = t list[@@deriving show]
    and t = {
      a: int ;
      b: s }[@@deriving make]
    let rec pp_s :
      Ppx_deriving_runtime.Format.formatter -> s -> Ppx_deriving_runtime.unit
      =
      let __0 () = pp in
      ((let open! ((Ppx_deriving_runtime)[@ocaml.warning "-A"]) in
          fun fmt ->
            fun x ->
              Ppx_deriving_runtime.Format.fprintf fmt "@[<2>[";
              ignore
                (List.fold_left
                   (fun sep ->
                      fun x ->
                        if sep
                        then Ppx_deriving_runtime.Format.fprintf fmt ";@ ";
                        ((__0 ()) fmt) x;
                        true) false x);
              Ppx_deriving_runtime.Format.fprintf fmt "@,]@]")
        [@ocaml.warning "-A"])
    and show_s : s -> Ppx_deriving_runtime.string =
      fun x -> Ppx_deriving_runtime.Format.asprintf "%a" pp_s x[@@ocaml.warning
                                                                 "-32"]
    and pp :
      Ppx_deriving_runtime.Format.formatter -> t -> Ppx_deriving_runtime.unit
      =
      let __0 () = pp_s in
      ((let open! ((Ppx_deriving_runtime)[@ocaml.warning "-A"]) in
          fun fmt ->
            fun x ->
              Ppx_deriving_runtime.Format.fprintf fmt "@[<2>{ ";
              ((Ppx_deriving_runtime.Format.fprintf fmt "@[%s =@ " "Ex.Ex.a";
                (Ppx_deriving_runtime.Format.fprintf fmt "%d") x.a;
                Ppx_deriving_runtime.Format.fprintf fmt "@]");
               Ppx_deriving_runtime.Format.fprintf fmt ";@ ";
               Ppx_deriving_runtime.Format.fprintf fmt "@[%s =@ " "b";
               ((__0 ()) fmt) x.b;
               Ppx_deriving_runtime.Format.fprintf fmt "@]");
              Ppx_deriving_runtime.Format.fprintf fmt "@ }@]")
        [@ocaml.warning "-A"])
    and show : t -> Ppx_deriving_runtime.string =
      fun x -> Ppx_deriving_runtime.Format.asprintf "%a" pp x[@@ocaml.warning
                                                               "-32"]
  end

As per dune describe pp ex.ml.

If the additional deriving annotation is not added, we get the same error.