[GHC] #11600: Panic (ASSERT failed) in compiler/types/TyCoRep.hs:1939

[GHC]

#11600: Panic (ASSERT failed) in compiler/types/TyCoRep.hs:1939
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        Reporter:  hvr               |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Thanks Herbert.  Since you have a working setup, Could you add a
 `HasCallStack` to `Subst.substCo` to extend the trace upwards a bit?  (It
 may take another couple of layers.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11600#comment:8>
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