[GHC] #14194: ghci 8.0.2 panics

[GHC]

#14194: ghci 8.0.2 panics
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        Reporter:  jakubdaniel       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Description changed by jakubdaniel:

Old description:

> I know it is rather hard to replicate but (I currently cannot check
> whether it still occurs in 8.0.2+):
>
> git clone https://github.com/jakubdaniel/expressions
> git clone https://github.com/jakubdaniel/expressions-z3
> hg clone https://bitbucket.org/jd823592/z3-haskell
>
> cd expressions-z3
> cabal sandbox init
> cabal sandbox add-source ../expression
> cabal sandbox add-source ../z3-haskell
> cabal install && cabal exec ghci
>
> λ> -- forget to :set -XTypeInType
> λ> :m Z3.Monad Data.Expression
> λ> -- forget to :m Data.Expression.Z3
> λ> evalZ3 $ astToString =<< toZ3 (forall [var "x" :: Var 'IntegralSort]
> (exists [var "y" :: Var 'IntegralSort] (var "x" .+. var "y" .=. cnst 0))
> :: Lia 'BooleanSort)
>
> ghc: panic! (the 'impossible' happened)
>   (GHC version 8.0.2 for x86_64-unknown-linux):
>         initTc: unsolved constraints
>   WC {wc_insol =
>         [W] toZ3_a4CL :: t_a4CK[tau:1] (CHoleCan: toZ3)
>         [W] toZ3_a4Dx :: t_a4Dw[tau:1] (CHoleCan: toZ3)}
>
> Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

New description:

 I know it is rather hard to reproduce but (I currently cannot check
 whether it still occurs in 8.0.2+):

 git clone https://github.com/jakubdaniel/expressions
 git clone https://github.com/jakubdaniel/expressions-z3
 hg clone https://bitbucket.org/jd823592/z3-haskell

 cd expressions-z3
 cabal sandbox init
 cabal sandbox add-source ../expression
 cabal sandbox add-source ../z3-haskell
 cabal install && cabal exec ghci

 λ> -- forget to :set -XTypeInType
 λ> :m Z3.Monad Data.Expression
 λ> -- forget to :m Data.Expression.Z3
 λ> evalZ3 $ astToString =<< toZ3 (forall [var "x" :: Var 'IntegralSort]
 (exists [var "y" :: Var 'IntegralSort] (var "x" .+. var "y" .=. cnst 0))
 :: Lia 'BooleanSort)

 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-unknown-linux):
         initTc: unsolved constraints
   WC {wc_insol =
         [W] toZ3_a4CL :: t_a4CK[tau:1] (CHoleCan: toZ3)
         [W] toZ3_a4Dx :: t_a4Dw[tau:1] (CHoleCan: toZ3)}

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

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14194#comment:1>
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