[GHC] #12056: Too aggressive `-w` option

[GHC]

#12056: Too aggressive `-w` option
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        Reporter:  asr               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11429, #11789    |  Differential Rev(s):  Phab:D3581
       Wiki Page:                    |
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Changes (by sgillespie):

 * differential:   => Phab:D3581


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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12056#comment:8>
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