[GHC] #828: ghc -e 'Control.Monad.Fix.mfix error' panics

[GHC]

#828: ghc -e 'Control.Monad.Fix.mfix error' panics
-------------------------------+--------------------------------------------
    Reporter:  duncan          |        Owner:         
        Type:  bug             |       Status:  new    
    Priority:  low             |    Milestone:         
   Component:  Driver          |      Version:  6.5    
    Severity:  minor           |     Keywords:         
          Os:  Linux           |   Difficulty:  Unknown
Architecture:  x86_64 (amd64)  |  
-------------------------------+--------------------------------------------
Just for the record, a low priority bug...

 Folk on IRC found this obscure torture test:

 {{{ Control.Monad.Fix.mfix error }}}

 Depending on how you run it it gives different errors.

 Compiling a module {{{ main = mfix error }}} works fine:
 {{{
 ghc foo.hs -o foo
 ./foo
 foo: <<loop>>
 }}}

 It exits with a non-zero exit code as expected.

 {{{ ghci }}} fares a little worse but ok:
 {{{
 Prelude> Control.Monad.Fix.mfix error
 *** Exception: *** Exception: <<loop>>
 }}}

 So actually the only way that goes wrong is {{{ ghc -e }}}:
 {{{
 ghc -e 'Control.Monad.Fix.mfix error'
 *** Exception: ghc-6.4.2: panic! (the `impossible' happened, GHC version
 6.4.2):
         <<loop>>

 Please report this as a compiler bug.  See:
   http://www.haskell.org/ghc/reportabug
 }}}

 Same behaviour with recent ghc-6.5.

 So I'd guess it's just the catching of errors in ghc -e that's not quite
 right, probably because of the way that tring to generate the error
 message generates an error.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/828>
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