[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 hvr):

 Replying to [comment:8 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.)

 Here's a couple more CallStack context (do you need more)?

 {{{
 ghc-stage1: panic! (the 'impossible' happened)
   (GHC version 8.1.20160219 for x86_64-unknown-linux):
         ASSERT failed!
   CallStack (from HasCallStack):
   assertPprPanic, called at compiler/types/TyCoRep.hs:1932:56 in
 ghc:TyCoRep
   checkValidSubst, called at compiler/types/TyCoRep.hs:2076:17 in
 ghc:TyCoRep
   substCo, called at compiler/coreSyn/CoreSubst.hs:607:20 in ghc:CoreSubst
   substCo, called at compiler/coreSyn/CoreSubst.hs:382:39 in ghc:CoreSubst
   go, called at compiler/coreSyn/CoreSubst.hs:374:5 in ghc:CoreSubst
   subst_expr, called at compiler/coreSyn/CoreSubst.hs:370:33 in
 ghc:CoreSubst
   substExpr, called at compiler/coreSyn/CoreUnfold.hs:158:27 in
 ghc:CoreUnfold
   specUnfolding, called at compiler/specialise/Specialise.hs:1312:32 in
 ghc:Specialise

 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11600#comment:9>
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