[GHC] #12925: GHC panic: Can't serialise IfaceTcTyVar

[GHC]

#12925: GHC panic: Can't serialise IfaceTcTyVar
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        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
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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Comment (by simonpj):

 So you have this in your tree?
 {{{
 commit f8c8de8ebf73cd77faa0249d92f280e33a8d2624
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Tue Nov 29 14:03:46 2016 +0000

     Zonk the free tvs of a RULE lhs to TyVars
 }}}
 If not, that should fix it.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12925#comment:1>
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