[GHC] #11172: Turning on optimisations produces SEGFAULT or Impossible case alternative

[GHC]

#11172: Turning on optimisations produces SEGFAULT or Impossible case alternative
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        Reporter:  nh2               |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 Hmm, I'm afraid I'm having some trouble reproducing this on 7.10.2,
 {{{
 $ ghc --make -O -Wall Main.hs -fforce-recomp && ./Main
 [1 of 2] Compiling Module           ( Module.hs, Module.o )

 Module.hs:34:1: Warning:
     The import of ‘Control.Applicative’ is redundant
       except perhaps to import instances from ‘Control.Applicative’
     To import instances alone, use: import Control.Applicative()
 [2 of 2] Compiling Main             ( Main.hs, Main.o )

 Main.hs:7:1: Warning:
     The import of ‘Control.Applicative’ is redundant
       except perhaps to import instances from ‘Control.Applicative’
     To import instances alone, use: import Control.Applicative()
 Linking Main ...
 Main: Impossible case alternative
 [1826 ben at ben-laptop impossible-case-alternative-repro(master)] $ ghc -V
 The Glorious Glasgow Haskell Compilation System, version 7.10.2
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11172#comment:12>
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