[GHC] #8882: internal error (deriving generic / cyclical imports?)

[GHC]

#8882: internal error (deriving generic / cyclical imports?)
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       Reporter:  mf825           |             Owner:
           Type:  bug             |            Status:  new
       Priority:  normal          |         Milestone:
      Component:  Compiler        |           Version:  7.6.3
       Keywords:  panic           |  Operating System:  Linux
   Architecture:  x86_64 (amd64)  |   Type of failure:  GHCi crash
     Difficulty:  Unknown         |         Test Case:
     Blocked By:                  |          Blocking:
Related Tickets:                  |
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 Hi everybody,

 I often get compiler crashes in my larger and less well-maintained
 projects of this sort:

 ghc: panic! (the 'impossible' happened)
   (GHC version 7.6.3 for x86_64-unknown-linux):
         tcIfaceGlobal (local): not found:
 <<details unavailable>>

 This happened on earlier 7.* ghc versions (debian 64bit), and from the
 counter-example I have condensed today my vague guess is that it has
 something to do with cyclical imports and -XDerivingGeneric or some other
 type system related language extension.  I witnessed this in both ghc and
 ghci, but the counter-example is in ghci.

 I want to investigate this further later, but in the hope that somebody
 can immediately see what's wrong, I decided to open this ticket with my
 preliminary findings.

 Just unpack and run ./crash.sh.  (Possibly you don't need to populate the
 sandbox and can crash it manually in your environment right away.)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8882>
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