new language extensions

Duncan Coutts duncan.coutts at
Thu Nov 8 17:42:29 EST 2007

On Thu, 2007-11-08 at 14:27 +0000, Ian Lynagh wrote:
> On Wed, Nov 07, 2007 at 09:40:25PM +0000, Duncan Coutts wrote:
> > Last call for objections or comments.
> > 
> > We'd like to get this into Language.Haskell.Extension asap so we can
> > include it in the Cabal distributed with ghc-6.8.2. Currently there are
> > packages that compiled fine with Cabal and ghc-6.6.x but not with
> > ghc-6.8.x because we're missing these new more fine-grained language
> > extensions.
> > 
> > See
> I'd much rather see
> fixed.

I'd prefer to see this proposal debated properly on this list first.

Also, do you think that is realistic in the time frame for 6.8.2? Adding
new entries is easy.

> Then Cabal would work with future GHCs, with new extensions as
> yet undreamt of, as well.

> This would provide the mechanism we need; the policy, i.e. what the
> extension names mean, should be defined somewhere outside of Cabal.

Ok, but where should they be defined? I'm not sure the right place is in
GHC. Language extensions (names and meanings) are something that needs
to be negotiated within the community and especially between developers
of different Haskell implementations.

So I think keeping the list in Language.Haskell.Extension is not such a
bad idea. Any Haskell implementation that wants a new common extension
can get it included in that module in time for a release.

> (you would still need to add the new extension names defined in 6.8.1 to
> the legacy mapping for 6.6 flags).

Yep, I'll do that.


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