[GHC] #13906: ApplicativeDo doesn't handle existentials as well as it could

[GHC]

#13906: ApplicativeDo doesn't handle existentials as well as it could
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  ApplicativeDo
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Doesn't #13875 make all this moot?  All patterns binding existentils are
 srtrict, so (in my imperfect undersatnding) we have to do a monadic bind,
 at the expense of parallelism, but making it straightforward to keep
 existentials in scope.

 I'm beginning to think that an update of the paper, covering strict
 patterns and existentials in the vocabulary and notation of the paper,
 would be a good investment.  I'm getting lost!

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13906#comment:4>
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