[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):

 Right enough, I understand a little better now, though the error
 originates from DynFlags.hs:3022.  See '''JB111''' inserted into the code
 and in the output below.

 Just a thought:  would changing '-Wunrecognised-warning-flags' to
 '-unrecognised-warning-flags' do anything to solve the problem?

 {{{
 -- | This is where we handle unrecognised warning flags. We only issue a
 warning
 -- if -Wunrecognised-warning-flags is set. See Trac #11429 for context.
 unrecognisedWarning :: String -> Flag (CmdLineP DynFlags)
 unrecognisedWarning prefix = defFlag prefix (Prefix action)
   where
     action :: String -> EwM (CmdLineP DynFlags) ()
     action flag = do
       f <- wopt Opt_WarnUnrecognisedWarningFlags <$> liftEwM
 getCmdLineState
       when f $ addWarn $ "JB111 unrecognised warning flag: -" ++ prefix ++
 flag
 }}}

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


 on the commandline: warning: JB111 unrecognised warning flag: -Wfoo

 on the commandline: warning: JB111 unrecognised warning flag: -Wbar

 on the commandline: warning: JB111 unrecognised warning flag: -Wa

 on the commandline: warning: JB111 unrecognised warning flag: -Wb

 on the commandline: warning: JB111 unrecognised warning flag: -Wc
 ghc.exe: unrecognised flag: -wfoo
 unrecognised flag: -wbar
 unrecognised flag: -sfoo
 unrecognised flag: -sbar
 unrecognised flag: -Sfoo
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12056#comment:6>
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