ghc.exe: panic! (the `impossible' happened, GHC version 6.4)

[Simon Peyton-Jones]

Thanks for the report.  You're using a class as a type (in the data type
decl for ScreenStack) and this triggers a bug in 6.4.  It been fixed,
and the fix will be in 6.4.1.

Simon

| -----Original Message-----
| From: glasgow-haskell-bugs-bounces at haskell.org
[mailto:glasgow-haskell-bugs-
| bounces at haskell.org] On Behalf Of Damyan Pepper
| Sent: 24 April 2005 10:29
| To: glasgow-haskell-bugs at haskell.org
| Subject: ghc.exe: panic! (the `impossible' happened, GHC version 6.4)
| 
| The compiler has asked me to send a bug report...so here it is.  This
| is with the Windows distribution of GHC 6.4.
| 
| Compiling the following code:
| 
| import Graphics.UI.ObjectIO hiding (Menu)
| 
| class CScreen a where
|       updateScreen :: a -> a
|       drawScreen :: a -> Draw ()
| 
| data ScreenStack e l = EmptyScreenStack | ScreenStack (CScreen e) l
| 
| 
| Produces the following message:
| 
| ghc -package objectio t.hs
| ghc.exe: panic! (the `impossible' happened, GHC version 6.4):
| 	ds_app_type Main.CScreen{tc r1TC} [e{tv a1V4}]
| 
| Please report it as a compiler bug to
glasgow-haskell-bugs at haskell.org,
| or http://sourceforge.net/projects/ghc/.
| 
| 
| I expect the code isn't correct, but I guess the compiler should give
| a sensible error messge.
| 
| Thanks,
| Damyan.
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