7.6.1 RC1 panic "coVarsOfTcCo:Bind"

[Ganesh Sittampalam]

Hi Simon,

Now I get the below.

I tarred up the project + dependencies and put it at
http://urchin.earth.li/~ganesh/temp/tcproblem.tar.bz (run build.sh), or
I'm happy to keep testing on my machine.

Cheers,

Ganesh


ghc.exe: panic! (the 'impossible' happened)
  (GHC version 7.6.0.20120822 for i386-unknown-mingw32):
        ds_ev_term
    cobox{v a6Aho} [lid] `cast`
(<main:Darcs.Test.Patch.WithState.WithState{tc r1oms}
                                    model{tv t4H} [tv]
                                    (main:Darcs.Witnesses.Ordered.FL{tc
r1iNn} prim{tv t4D} [tv]
                                     main:Darcs.Witnesses.Ordered.:>{tc
r1iNy} main:Darcs.Witnesses.Ordered.FL{tc r1iNn}
                                                                                
prim{tv t4D} [tv])>
                                 ghc-prim:GHC.Types.~{(w) tc 31Q}
main:Darcs.Test.Patch.WithState.WithState{tc r1oms}
                                                                    (Sym
cobox{v a6AgE} [lid])
                                                                   
<main:Darcs.Witnesses.Ordered.FL{tc r1iNn}
                                                                      
prim{tv t4D} [tv]
                                                                    
main:Darcs.Witnesses.Ordered.:>{tc r1iNy}
main:Darcs.Witnesses.Ordered.FL{tc r1iNn}
                                                                                                                
prim{tv t4D} [tv]>)
    (let {EvBinds{cobox{v a6zY5} [lid]
                    = cobox{v a6Aho} [lid] `cast`
(<main:Darcs.Test.Patch.WithState.WithState{tc r1oms}
                                                      model{tv t4H} [tv]
                                                     
(main:Darcs.Witnesses.Ordered.FL{tc r1iNn}
                                                         prim{tv t4D} [tv]
                                                      
main:Darcs.Witnesses.Ordered.:>{tc r1iNy}
main:Darcs.Witnesses.Ordered.FL{tc r1iNn}
                                                                                                  
prim{tv t4D} [tv])>
                                                  
ghc-prim:GHC.Types.~{(w) tc 31Q}
main:Darcs.Test.Patch.WithState.WithState{tc r1oms}
                                                                                     
(Sym
                                                                                        
cobox{v a6AgE} [lid])
                                                                                     
<main:Darcs.Witnesses.Ordered.FL{tc r1iNn}
                                                                                        
prim{tv t4D} [tv]
                                                                                      
main:Darcs.Witnesses.Ordered.:>{tc r1iNy}
main:Darcs.Witnesses.Ordered.FL{tc r1iNn}
                                                                                                                                  
prim{tv t4D} [tv]>)
                  cobox{v a6zY6} [lid] = CO <t{tv a6zY1} [tv]>}}
     cobox{v a6zY5} [lid] <xx{tv a6zY3} [sk]> <yy{tv a6zY4} [sk]>
     -> <t{tv a6zY1} [tv]>)

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

On 22/08/2012 08:40, Simon Peyton-Jones wrote:
> Ah.  Hmm.  I see.
>
> Can you try this in TcEvidence
>
>     -- We expect only coercion bindings
>     go_bind :: EvBind -> VarSet
>     go_bind (EvBind _ (EvCoercion co)) = go co
>     go_bind (EvBind _ (EvId v))        = unitVarSet v
>     go_bind other = pprPanic "coVarsOfTcCo:Bind" (ppr other)
>
> with this instead?
>
>     -- We expect only coercion bindings, so use evTermCoercion 
>     go_bind :: EvBind -> VarSet
>     go_bind (EvBind _ tm) = go (evTermCoercion tm)
>
> I think that'll fix it.
>
> Simon
>
> | -----Original Message-----
> | From: glasgow-haskell-users-bounces at haskell.org [mailto:glasgow-
> | haskell-users-bounces at haskell.org] On Behalf Of Ganesh Sittampalam
> | Sent: 22 August 2012 06:32
> | To: glasgow-haskell-users at haskell.org
> | Subject: 7.6.1 RC1 panic "coVarsOfTcCo:Bind"
> | 
> | Hi,
> | 
> | I'm getting the panic below when building darcs 2.8 with GHC 7.6. It'll
> | take some effort to cut it down or give repro instructions for an
> | uncut-down version (I needed to hack a lot of underlying packages to be
> | able to even get as far as doing this build), so could someone confirm
> | that it's worth it before I do so? I can't spot anything already
> | reporting this in trac.
> | 
> | Cheers,
> | 
> | Ganesh
> | 
> | ghc.exe: panic! (the 'impossible' happened)
> |   (GHC version 7.6.0.20120810 for i386-unknown-mingw32):
> |         coVarsOfTcCo:Bind
> |     cobox{v a6Czs} [lid]
> |       = cobox{v a6CTr} [lid] `cast`
> | (<main:Darcs.Test.Patch.WithState.WithState{tc r1LL8}
> |                                         model{tv tC} [tv]
> | 
> | (main:Darcs.Witnesses.Ordered.FL{tc r1Dy1} prim{tv ty} [tv]
> | 
> | main:Darcs.Witnesses.Ordered.:>{tc r1Dyc}
> | main:Darcs.Witnesses.Ordered.FL{tc r1Dy1}
> | 
> | prim{tv ty} [tv])>
> |                                      ghc-prim:GHC.Types.~{(w) tc 31Q}
> | main:Darcs.Test.Patch.WithState.WithState{tc r1LL8}
> | 
> | (Sym cobox{v a6CSH} [lid])
> | 
> | <main:Darcs.Witnesses.Ordered.FL{tc r1Dy1}
> | 
> | prim{tv ty} [tv]
> | 
> | main:Darcs.Witnesses.Ordered.:>{tc r1Dyc} main:Darcs.Witnesses.Order
> | ed.FL{tc r1Dy1}
> | 
> | prim{tv ty} [tv]>)
> | 
> | Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
> | 
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