[GHC] #11784: panic "hscCmmFile: no_mod" with `-v2 and above

[GHC]

#11784: panic "hscCmmFile: no_mod" with `-v2 and above
-------------------------------------+-------------------------------------
        Reporter:  erikd             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by thomie):

 * priority:  normal => high


Comment:

 This is a regression from 7.10.3.

 To reproduce, create an empty file called `Test.cmm`. Then run:

 {{{
 $ ghc-8.0.1 -c -dcmm-lint Test.cmm -v2
 ...
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.0.20160511 for x86_64-unknown-linux):
         hscCmmFile: no_mod
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11784#comment:1>
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