OCaml variant augmentation boilerplates

Question

Is there a way to efficiently "augment" or attach some more information without much boilerplate?

That is, given types

type orig =
  | A
  | B of orig
  | C of orig * orig
and type dat = int
and type aug =
  | AugA of dat
  | AugB of dat * aug
  | AugC of dat * aug * aug

and functions

let _cnt = ref 0
let gen_dat () =
  let _ = _cnt := !_cnt + 1 in
  !_cnt

let rec augment (o: orig) : ao =
  match o with
  | A -> AugA (gen_dat ())
  | B o -> AugB (gen_dat (), augment o)
  | C (o1, o2) -> AugC (gen_dat (), augment o1, augment o2)

I think this is a trivial structural recursion on its components, and I have to do repeat this type of identical manipulations on several types with 10+ patterns (Multiple augs each with its own augment function associated).

This leads to a long, tedious boilerplate code. Is there a way to abstract away this manipulation in OCaml, e.g., with help of ppx?