Re: GADT pattern match in non-rigid context

Hi Simon,

> You should be giving a type signature to rewrap!  That should fix it.

Thanks, all works fine now 

Neil

>
> | -----Original Message-----
> | From: glasgow-haskell-users-bounces <at> haskell.org
[mailto:glasgow-haskell-users-bounces <at> haskell.org] On Behalf Of
> | Neil Mitchell
> | Sent: 17 December 2007 16:23
> | To: glasgow-haskell-users <at> haskell.org
> | Subject: GADT pattern match in non-rigid context
> |
> | Hi,
> |
> | Upgrading from GHC 6.6 to 6.8 has caused some code to stop working:
> |
> | ----------------------------------------------------------------------
> | {-# OPTIONS_GHC -fglasgow-exts #-}
> |
> | module Data2 where
> |
> | data CCompany
> |
> | data Paradise :: * -> * where
> |     CC :: Paradise CCompany
> |
> | rewrapCC CC = []
> | ----------------------------------------------------------------------
> |
> | [1 of 1] Compiling Data2            ( Data2.hs, interpreted )
> |
> | Data2.hs:12:9:
> |     GADT pattern match in non-rigid context for `CC'
> |       Tell GHC HQ if you'd like this to unify the context
> |     In the pattern: CC
> |     In the definition of `rewrapCC': rewrapCC CC = []
> |
> | This code is from the Uniplate benchmarking code, which runs the
> | Paradise benchmark from SYB on Uniplate, Compos and SYB. The Compos
> | code uses GADT's, so the program first needs to convert from standard
> | data structures to GADT's before it can work, then back at the end.
> | It's the problem of converting from a GADT to a normal data structure
> | that is failing.
> |
> | So is there an easy workaround? Or should I be asking GHC HQ to unify things?
> |
> | Thanks
> |
> | Neil
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>