[GHC] #11316: Too many guards warning causes issues

[GHC]

#11316: Too many guards warning causes issues
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        Reporter:  NeilMitchell      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by NeilMitchell):

 Note that at the moment I am not using {{{-Wall}}}, only {{{-Werror}}}, so
 I haven't asked for exhaustiveness checking of the guards (at least I
 haven't turned it on specially), so having a warning that it couldn't
 produce a warning I didn't even ask for seems even more dubious. Is the
 exhaustiveness of guards on by default?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11316#comment:2>
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