[GHC] #10892: ApplicativeDo should use *> and <*

[GHC]

#10892: ApplicativeDo should use *> and <*
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        Reporter:  simonmar          |                Owner:  bollu
            Type:  task              |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:  ApplicativeDo
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:  12143
 Related Tickets:  #13309            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonmar):

 I think they're both equivalent.  Can you write down the desugaring rule?

 It seems to me we can use `*>` for *initial* ApplicativeArgNils in the
 group, and `<*` for *trailing* ApplicativeArgNils in the group.  Anything
 in the middle will just need to behave like a wildcard pattern.  Does that
 seem reasonable?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10892#comment:21>
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