[GHC] #12811: GHC tells me to use RankNTypes when it's already enabled

[GHC]

#12811: GHC tells me to use RankNTypes when it's already enabled
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        Reporter:  RyanGlScott       |                Owner:  ruperthorlick
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Poor/confusing    |            Test Case:
  error message                      |  parser/should_fail/T12811
      Blocked By:                    |             Blocking:
 Related Tickets:  #11669            |  Differential Rev(s):  Phab:D3262
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"488a9daa8246e0dd364dc44b8b6b8650fa6f3822/ghc"
 488a9daa/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="488a9daa8246e0dd364dc44b8b6b8650fa6f3822"
 Changed parser message for RankNTypes (#12811)

 Added a check for whether RankNTypes is enabled
 and changed error message accordingly

 Reviewers: austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie, mpickering

 Differential Revision: https://phabricator.haskell.org/D3262
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12811#comment:7>
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