Data and Typeable instances for GenericPackageDescription

[Duncan Coutts]

On Tue, 2010-06-15 at 20:43 +0200, JP Moresmau wrote:
> Hello, I was wondering if there are instances for Typeable and Data
> available somewhere for GenericPackageDescription. Automatic deriving
> fails, probably, if I read the docs right, because some types in there
> have more than 7 parameters. It would help me to use the cabal file
> parsing functions and convert the result automatically to JSON for use
> in Eclipse through Scion. Of course if there isn't I suppose I can
> write my own instances  and maybe share them with who ever is
> interested.

I'm happy to accept patches.

One thing to keep in mind is that the Cabal library must be compilable
with hugs and nhc98 as well as ghc. I think that means we cannot use
deriving Typeable or Data since, as far as I know, neither of those
compilers supports that language extension.

Note that the ModuleName constructor is not exported on purpose. Do Data
instances make sense for abstract types?

Duncan