impossible happened: splitTyConApp a{tv i6hr}

[Simon Peyton-Jones]

OK, I can reproduce it now. (Previously I was not compiling with -O2.)

It's a bug in 6.4.2 related to GADTs, specifically in the typing of
interface files.  You get a much more informative message if you use the
flag "-dcore-lint".

I think it's fixed in the upcoming 6.4.3 release; at least it works for
me. 

Can you try to download a snapshot distribution of 6.4.3 (the "STABLE"
branch) from
	http://www.haskell.org/ghc/download.html
and try that?

Simon

| -----Original Message-----
| From: Frederik Eaton [mailto:frederik at a5.repetae.net]
| Sent: 16 August 2006 15:48
| To: Simon Peyton-Jones
| Subject: Re: impossible happened: splitTyConApp a{tv i6hr}
| 
| Here:
| 
| http://ofb.net/~frederik/gslhaskell2-ghc-bug1.tar.gz
| 
| The file "General.hs" is the subdirectory "Vector".
| 
| The problem only happens when I edit General.hs and recompile...
| 
| Frederik
| 
| On Wed, Aug 16, 2006 at 03:30:02PM +0100, Simon Peyton-Jones wrote:
| > I'd like to reproduce this, but to do so I'll need either a cut-down
| > version, or all the source code need to get to the point where it
fell
| > over.  Could you manage the former, or if not, the latter?  Thanks
| >
| > S
| >
| > | -----Original Message-----
| > | From: glasgow-haskell-bugs-bounces at haskell.org
| > [mailto:glasgow-haskell-bugs-bounces at haskell.org]
| > | On Behalf Of Frederik Eaton
| > | Sent: 16 August 2006 14:52
| > | To: glasgow-haskell-bugs at haskell.org
| > | Subject: impossible happened: splitTyConApp a{tv i6hr}
| > |
| > | I've attached the code.
| > |
| > | > Skipping  Vector           ( Vector.hs, dist/build/Vector.o )
| > | > Compiling Vector.General   ( ./Vector/General.hs,
| > dist/build/Vector/General.o )
| > | >
| > | > ./Vector/General.hs:29:0:
| > | >     Warning: No explicit method nor default method for
| > `vectorUpdate'
| > | >              In the instance declaration for `Vector (GVector e)
e'
| > | >
| > | > ./Vector/General.hs:29:0:
| > | >     Warning: No explicit method nor default method for `byRow'
| > | >              In the instance declaration for `Vector (GVector e)
e'
| > | > ghc-6.4.2: panic! (the `impossible' happened, GHC version
6.4.2):
| > | >         splitTyConApp a{tv i6hr}
| > | >
| > | > Please report this as a compiler bug.  See:
| > | >   http://www.haskell.org/ghc/reportabug
| > |
| > | --
| > | http://ofb.net/~frederik/
| >
| 
| --
| http://ofb.net/~frederik/