[GHC] #12944: ghc master (8.1.20161206) panics with assertion failure with devel2 flavor and -O

[GHC]

#12944: ghc master (8.1.20161206) panics with assertion failure with devel2 flavor
and -O
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        Reporter:  pacak             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
  (CodeGen)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 It looks like the failing assertion is this,
 {{{#!hs
 lookupBinding :: IdEnv HowBound -> Id -> HowBound
 lookupBinding env v = case lookupVarEnv env v of
                         Just xx -> xx
                         Nothing -> ASSERT2( isGlobalId v, ppr v )
 ImportBound
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12944#comment:2>
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