[GHC] #12490: With RebindableSyntax, ApplicativeDo should eliminate return/pure

[GHC]

#12490: With RebindableSyntax, ApplicativeDo should eliminate return/pure
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        Reporter:  AaronFriel        |                Owner:  simonmar
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2499
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"043604c7232adb698d5008a46d3f29d532acd12d/ghc" 043604c/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="043604c7232adb698d5008a46d3f29d532acd12d"
 RnExpr: Fix ApplicativeDo desugaring with RebindableSyntax

 We need to compare against the local return and pure, not returnMName
 and pureAName.

 Fixes #12490.

 Test Plan: Validate, add testcase

 Reviewers: austin, simonmar

 Reviewed By: simonmar

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2499

 GHC Trac Issues: #12490
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12490#comment:8>
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