[GHC] #9037: Add option to make selected warnings errors

[GHC]

#9037: Add option to make selected warnings errors
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       Reporter:  nh2               |             Owner:
           Type:  feature request   |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  Compiler          |           Version:  7.8.2
       Keywords:                    |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:                    |
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 It would be great if GHC offered a `-ferror-*` flag for every `-fwarn-*`
 flag, that turns the given type of warning into an error.

 For example, I would like to always error on uninitialized record fields,
 but don't want to go full `-Werror`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9037>
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