[GHC] #14080: GHC panic while forcing the thunk for TyThing IsFile (regression)

[GHC]

#14080: GHC panic while forcing the thunk for TyThing IsFile (regression)
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        Reporter:  inaki             |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  high              |            Milestone:  8.2.2
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  hs-boot
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13803, #13981    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ezyang):

 The most relevant commit from me that might be how HEAD fixed it is
 9e9fb57c37c62bb6c90f15b173c5d3632121c66a. If this commit isn't the needed
 one, more sleuthing will be needed.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14080#comment:4>
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