[GHC] #12609: unused-top-binds wrongly warns about underscore-prefixed field names when DuplicateRecordFields enabled

[GHC]

#12609: unused-top-binds wrongly warns about underscore-prefixed field names when
DuplicateRecordFields enabled
-------------------------------------+-------------------------------------
        Reporter:  jml               |                Owner:  adamgundry
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  newcomer, ORF
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Incorrect         |            Test Case:
  warning at compile-time            |  overloadedrecflds/should_compile/T12609
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2549
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"48ff0843eee29313cc2da14c04dc57f6589ab040/ghc"
 48ff0843/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="48ff0843eee29313cc2da14c04dc57f6589ab040"
 Do not warn about unused underscore-prefixed fields (fixes Trac #12609)

 When DuplicateRecordFields is enabled, the mangling of selector names
 was causing them to be reported as unused even if prefixed by an
 underscore. This corrects the OccName used by the check.

 Test Plan: New test overloadedrecflds/should_compile/T12609

 Reviewers: austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2549

 GHC Trac Issues: #12609
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12609#comment:5>
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