[GHC] #11812: Template Haskell can induce non-unique Uniques

[GHC]

#11812: Template Haskell can induce non-unique Uniques
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 To make things worse, this program now panics on GHC 8.2.1:

 {{{
 $ /opt/ghc/8.2.1/bin/ghc Bug.hs
 [1 of 1] Compiling Bug              ( Bug.hs, Bug.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.2.1 for x86_64-unknown-linux):
         expectJust zonkTcTyVarToVar
 CallStack (from HasCallStack):
   error, called at compiler/utils/Maybes.hs:53:27 in ghc:Maybes
   expectJust, called at compiler/typecheck/TcType.hs:1583:21 in ghc:TcType
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11812#comment:3>
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