Thanks for this.  Now fixed.

Simon

| -----Original Message-----
| From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Keith
| Wansbrough
| Sent: 26 November 2004 14:36
| To: [EMAIL PROTECTED]
| Subject: GADT bug in 20041124
| 
| Hi all (long time no see!)...
| 
| Keen to try out the new GADT stuff, I downloaded a CVS snapshot of
| ghc-6.3.20041124.  Having built it, I discovered a bug.  The program
| 
| > module GADTest where
| >
| > data Expr :: * -> * where
| >   EInt    :: Int                                 -> Expr Int
| >   EBool   :: Bool                                -> Expr Bool
| >   EIf     :: (Expr Bool) -> (Expr a) -> (Expr a) -> Expr a
| 
| yields
| 
| > [EMAIL PROTECTED]:~/Misc/Haskell$ ghc -fglasgow-exts -c GADTest.hs
| > ghc-6.3.20041124: panic! (the `impossible' happened, GHC version
| > 6.3.20041124):
| >         types/Type.lhs:(996,0)-(997,77): Non-exhaustive patterns in
| >         function zip_ty_env
| >
| >
| > Please report it as a compiler bug to
| > [EMAIL PROTECTED],
| > or http://sourceforge.net/projects/ghc/.
| 
| Note that removing the EIf line, or writing "Expr a" rather than "Expr
| :: * -> *", makes the error go away.  Writing "Expr :: *" instead
| gives a kind error, of course.
| 
| --KW 8-)
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