[GHC] #10182: lookupIfaceGlobal crash with SOURCE import

[GHC]

#10182: lookupIfaceGlobal crash with SOURCE import
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        Reporter:  simonpj           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by ezyang):

 (Note: it has to be a self boot-import; indirecting it through another
 module eliminates the error.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10182#comment:3>
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