Meaning of version tags in cabal files

[Duncan Coutts]

On Mon, 2010-01-18 at 21:41 +0000, C Rodrigues wrote:
> I noticed that cabal will parse, but ignore, version tags.

Yes.

> Arguably this is not the right thing to do, as it changes the
> semantics of versions. 

It's precisely because the semantics of version tags is so useless (and
inconsistent) that we stopped using them.

> I'm not against discarding version tags, but I'd like to know if
> there's a rationale for _silently_ discarding them.

We've not yet removed tag from the parser for backwards compatibility.
Clearly what we should do is add a big warning (or simply error) that
such tags are no longer supported.

I hope in time to get Data.Version changed to eliminate the tags
entirely.

Duncan