Ganesh Sittampalam | 22 Aug 07:31 2012
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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}

(Continue reading)

Simon Peyton-Jones | 22 Aug 09:40 2012
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RE: 7.6.1 RC1 panic "coVarsOfTcCo:Bind"

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
(Continue reading)

Ganesh Sittampalam | 24 Aug 08:09 2012
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Re: 7.6.1 RC1 panic "coVarsOfTcCo:Bind"

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}
(Continue reading)


Gmane