A couple years ago I had a similar feature request for variant (sum)
constructors, and Jacques Garrigue explained that it is in fact quite
difficult. (The reasons apply to record fields as well.) I suspect that you
are out of luck.

  MPR#7102: Ability to re-export a variant definition with renamed
constructors?
  https://caml.inria.fr/mantis/view.php?id=7102


On Thu, Sep 6, 2018 at 1:36 PM Enrico Tassi <enrico.tassi@inria.fr> wrote:

> Dear caml-list, while refining an API I felt the need to rename a record
> field. I'd like to be nice to my users and have the API evolve without
> breaking compilation but eventually emitting deprecation warnings.
>
> What I'd like to do, concretely is to move from this
>
>   record t = { bad : int; stuff : ty }
>
> to
>
>   record old = { bad : int [@deprecated "use good"]; stuff : ty }
>   record t = old = { good : int; stuff : ty }
>
> The last line does not type check since old and good are different
> names. What I'd like to obtain is to have bad and good act as synonyms,
> and have OCaml generate a warning when bad is used.
>
> This is pretty much what you would do for a function: leave the old one
> in place and stick a deprecate attribute to it.
>
> Is there a way to achieve that for records?
>
> Best,
> --
> Enrico Tassi
>
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