[GHC] #10644: Option GADTs specialises a polymorphic value in local bindings (was: Option GADTs invalidates a rank-2 function.)

[GHC]

#10644: Option GADTs specialises a polymorphic value in local bindings
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        Reporter:  bales             |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Linux             |            Architecture:  x86_64
 Type of failure:  GHC rejects       |  (amd64)
  valid program                      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10644#comment:1>
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