gadt changes in ghc 6.10

[Don Stewart]

dgorin:
> I've tried adding some signatures (together with - 
> XScopedTypeVariables), but with no luck. Why is it that this no longer  
> compiles? More importantly, how can I make it compile again? :)
> 

If you work out how to make it compile, can you document the soln. here,

    http://haskell.org/haskellwiki/Upgrading_packages#Changes_to_GADT_matching

Cheers,
    Don