Just to follow up, the addition of `.syntax` packages was released this week: https://github.com/ocaml/opam-repository/pull/5523

On Tue, Jan 26, 2016 at 5:17 PM, Jeremie Dimino <jdimino@janestreet.com> wrote:
On Tue, Jan 26, 2016 at 4:56 PM, Ivan Gotovchits <ivg@ieee.org> wrote:
> 3. release project.0.3.1, keeping project.0.3 unchanged

The problem is that `project.0.3` will be broken for ever, as well as all dependencies that depend on this particular version. 

Maybe there is actually some misunderstanding, and we're talking about different things. Just to clarify, are you going to go 
through opam-repository and update all archives of old libraries (e.g. sexplib.7.0.5, sexplib.108.00, ...) and remove `<library>.syntax` 
findlib library from it? This is what I'm afraid of. And this is what I name "retroactively".
As according to the PR there is nothing like this. If all old archives will be still available, then it is perfectly fine.

​Indeed, I misunderstood your original ​question. Sorry about that.
We definitely won't touch the archive of any released package. I agree that would be disastrous...

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Jeremie



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Jeremie