[GHC] #10752: Print which warning-flag controls/enabled an emitted warning

[GHC]

#10752: Print which warning-flag controls/enabled an emitted warning
-------------------------------------+-------------------------------------
        Reporter:  hvr               |                Owner:  barrucadu
            Type:  feature request   |               Status:  merge
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              Version:
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1943
       Wiki Page:  Design/Warnings   |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"1e6ec1249b4da88fec9024598c2183e6fc0e96cd/ghc" 1e6ec12/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="1e6ec1249b4da88fec9024598c2183e6fc0e96cd"
 Fix misattribution of `-Wunused-local-binds` warnings

 This fixes a bug where warnings actually controlled by

 - `Opt_WarnUnusedMatches`
 - `Opt_WarnUnusedTypePatterns`
 - `Opt_WarnUnusedTopBinds`

 were incorrectly reported as being controlled by
 `Opt_WarnUnusedLocalBinds` as well

 This bug was introduced in bb5afd3c274011c5ea302210b4c290ec1f83209c
 while implementing #10752

 Test Plan: ./validate still running -- testsuite output wiggles expected

 Reviewers: barrucadu, quchen, austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2077
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10752#comment:25>
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