[GHC] #14249: ApplicativeDo: Pattern matching on a bind forces a Monad constraint

[GHC]

#14249: ApplicativeDo: Pattern matching on a bind forces a Monad constraint
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        Reporter:  mutantmell  |                Owner:  (none)
            Type:  bug         |               Status:  closed
        Priority:  normal      |            Milestone:
       Component:  Compiler    |              Version:  8.2.1
      Resolution:  invalid     |             Keywords:  ApplicativeDo
Operating System:  Linux       |         Architecture:  x86_64 (amd64)
 Type of failure:  Other       |            Test Case:
      Blocked By:              |             Blocking:
 Related Tickets:              |  Differential Rev(s):
       Wiki Page:              |
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Comment (by bgamari):

 So you would like something like,
 {{{
 ApplicativeDo is enabled yet Monad is required due to irrefutable pattern
 match;
 perhaps you want to make the match refutable by adding a ~?
 }}}
 Is this right?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14249#comment:6>
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