[GHC] #11607: ApplicativeDo easily foiled with `pure`

[GHC]

#11607: ApplicativeDo easily foiled with `pure`
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  patch
        Priority:  high              |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc2
  checker)                           |
      Resolution:                    |             Keywords:  ApplicativeDo
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:  ado/T11607
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1931
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"0c7db61f8a17b2c5c4335b62103eb9ffc5d24154/ghc"
 0c7db61f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="0c7db61f8a17b2c5c4335b62103eb9ffc5d24154"
 ApplicativeDo: Handle terminal `pure` statements

 ApplicativeDo handled terminal `return` statements properly, but not
 `pure`.

 Test Plan: Validate with included testcase

 Reviewers: austin, simonmar

 Reviewed By: austin, simonmar

 Subscribers: simonpj, thomie

 Differential Revision: https://phabricator.haskell.org/D1931

 GHC Trac Issues: #11607
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11607#comment:6>
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