[GHC] #11219: Implement fine-grained `-Werror=...` facility

[GHC]

#11219: Implement fine-grained `-Werror=...` facility
-------------------------------------+-------------------------------------
        Reporter:  hvr               |                Owner:  quchen
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11796            |  Differential Rev(s):
       Wiki Page:  Design/Warnings   |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"514acfe4c4e61941c2fa2e06cff02f6e4424e5e6/ghc"
 514acfe4/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="514acfe4c4e61941c2fa2e06cff02f6e4424e5e6"
 Implement fine-grained `-Werror=...` facility

 This patch add new options `-Werror=...`, `-Wwarn=...` and
 `-Wno-error=...` (synonym for `-Wwarn=...`).

 Semantics:

   - `-Werror` marks all warnings as fatal, including those that don't
     have a warning flag, and CPP warnings.
   - `-Werror=...` enables a warning and marks it as fatal
   - `-Wwarn=...` marks a warning as non-fatal, but doesn't disable it

 Test Plan: validate

 Reviewers: austin, bgamari

 Reviewed By: bgamari

 Subscribers: mpickering, svenpanne, RyanGlScott, thomie

 Differential Revision: https://phabricator.haskell.org/D2706

 GHC Trac Issues: #11219
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11219#comment:9>
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