Re: ghci 6.4 panic on HList code.

sorry, i was too fast with my report.  i still consider what i found a
bug in ghci, but it's triggered by a bug in my code.  you can also
trigger it by the much shorter:

module Main where class C a where f :: C a

in contrast, the more correct:

module Main where class C a where f :: a

works.  feel free to fix it anyhow, of course...  (-:

cheers,
matthias



On Fri, Oct 06, 2006 at 03:56:20PM +0200, Matthias Fischmann wrote:
> To: glasgow-haskell-bugs@xxxxxxxxxxx
> From: Matthias Fischmann <fis@xxxxxxxxxxxxxxxxx>
> Date: Fri, 6 Oct 2006 15:56:20 +0200
> Subject: ghci 6.4 panic on HList code.
> 
> 
> 
> Hi,
> 
> I get a reproducible crash with ghci 6.4 (ubuntu package version
> 6.4-4.1ubuntu2).  I am using HList as retrieved yesterday from
> http://darcs.haskell.org/HList.
> 
> If you need further details please let me know.  I am also happy to
> meet on irc/gizmo/skype and talk it through in real-time.
> 
> thanks,
> Matthias
> 
> 
> 
> ======================================================================
> module Main
> where
> 
> import IO
> import Monad
> import List
> import Array
> import HListPrelude
> 
> data T = T Int
> 
> class C a
>     where f :: C a -> Int
> 
> instance C T
>     where f (T i) = i
> 
> class HList l => CList l
> 
> instance CList HNil
> instance (C c, CList cs) => CList (HCons c cs)
> 
> test :: (CList l) => l -> [Int]
> test = hMapOut f
> 
> main :: IO ()
> main = error ""
> 
> ======================================================================
>    ___         ___ _
>   / _ \ /\  /\/ __(_)
>  / /_\// /_/ / /  | |      GHC Interactive, version 6.4, for Haskell 98.
> / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
> \____/\/ /_/\____/|_|      Type :? for help.
> 
> Loading package base-1.0 ... linking ... done.
> Prelude> :load /home/fis/tmp/Main.hs
> Compiling FakePrelude      ( 
> /home/fis/wiwi/reputation/esim/HList/FakePrelude.hs, interpreted )
> Compiling HListPrelude     ( 
> /home/fis/wiwi/reputation/esim/HList/HListPrelude.hs, interpreted )
> Compiling Main             ( /home/fis/tmp/Main.hs, interpreted )
> ghc-6.4: panic! (the `impossible' happened, GHC version 6.4):
>       ds_app_type Main.C{tc r5nj} [a{tv a5oO}]
> 
> Please report it as a compiler bug to ,
> or http://sourceforge.net/projects/ghc/.
> 
> 
> > 
> ======================================================================

-- 
Institute of Information Systems, Humboldt-Universitaet zu Berlin

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