[GHC] #16063: ghc-8.6.3 + Mac OSX + FFI dependency causes 'impossible happened' compiler failure

[GHC]

#16063: ghc-8.6.3 + Mac OSX +  FFI dependency causes 'impossible happened' compiler
failure
-------------------------------------+-------------------------------------
        Reporter:  benselfridge      |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.3
      Resolution:                    |             Keywords:
Operating System:  MacOS X           |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by harpocrates):

 * cc: harpocrates (added)


Comment:

 I can replicate and have a story for what is going wrong here, which
 involves 3d17f1f10fc00540ac052f2fd03182906aa47e35. I'll prepare a patch
 shortly, but testing it might be a bit frustrating (I doubt `grift`'s
 dependencies all easily build on HEAD). I'll try to put together a more
 minimal test case too.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16063#comment:4>
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