[GHC] #16033: Rank-n typechecking regression between GHC 8.4 and 8.6

[GHC]

#16033: Rank-n typechecking regression between GHC 8.4 and 8.6
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler (Type    |              Version:  8.6.3
  checker)                           |
      Resolution:                    |             Keywords:  RankNTypes
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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Changes (by RyanGlScott):

 * cc: goldfire (added)


Comment:

 Commit faec8d358985e5d0bf363bd96f23fe76c9e281f7 (`Track type variable
 scope more carefully.`) is the culprit.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16033#comment:2>
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