It's in the works for the next release of OCaml, according to Xavier Leroy'sblue storm wrote:
> On Wed, Apr 15, 2009 at 2:44 AM, Yaron Minsky <yminsky@gmail.com> wrote:
> That part is achieved by the pa_records [1] syntax extension.
> To my knowledge, it has not been port to post-3.10 camlp4 yet, but if
> you're interested, I could probably do it.
>
> [1] http://oandrieu.nerim.net/ocaml/#pa_records
talk at the OCaml meeting in Grenoble (Feb 2009).