[GHC] #11982: Typechecking fails for parallel monad comprehensions with polymorphic let (GHC 7.10.3 through 8.6.3)

[GHC]

#11982: Typechecking fails for parallel monad comprehensions with polymorphic let
(GHC 7.10.3 through 8.6.3)
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        Reporter:  simonpj           |                Owner:  josefs
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      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 goldfire):

 OK. I confess I don't understand your syntax (what do the `<-` and `|`
 mean? the former usually requires `do`, but there isn't one; and I'm
 utterly lost on the `|`), but if your solution is just to rejigger the
 desugaring, then I'm sure that's pretty harmless. Thanks!

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11982#comment:12>
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