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

[GHC]

#12056: Too aggressive `-w` option
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        Reporter:  asr               |                Owner:
            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):
       Wiki Page:                    |
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Comment (by wozgonon):

 Seems to occur for any option prefixed with -W.
 Note the warnings for -W<...> are:
 1) displayed first, out of order
 2) displayed with a prefix "\non the commandline:"

 {{{
 ghc -wfoo -wbar -sfoo -sbar -Sfoo -Wfoo -Wbar -Wa -Wb -Wc

 on the commandline: warning: unrecognised warning flag: -Wfoo

 on the commandline: warning: unrecognised warning flag: -Wbar

 on the commandline: warning: unrecognised warning flag: -Wa

 on the commandline: warning: unrecognised warning flag: -Wb

 on the commandline: warning: unrecognised warning flag: -Wc
 ghc.exe: unrecognised flag: -wfoo
 unrecognised flag: -wbar
 unrecognised flag: -sfoo
 unrecognised flag: -sbar
 unrecognised flag: -Sfoo
 }}}

 When -w is added (even as a suffix) warnings for -W<...> options disappear
 {{{
 ghc -wfoo -wbar -sfoo -sbar -Sfoo -Wfoo -Wbar -Wa -Wb -Wc -w
 ghc.exe: unrecognised flag: -wfoo
 unrecognised flag: -wbar
 unrecognised flag: -sfoo
 unrecognised flag: -sbar
 unrecognised flag: -Sfoo
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12056#comment:3>
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