[GHC] #12055: Typechecker panic instead of proper error

[GHC]

#12055: Typechecker panic instead of proper error
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        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      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:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"1dcb32ddba605bced2e0e0ce3f52b58e8ff33f5b/ghc"
 1dcb32dd/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="1dcb32ddba605bced2e0e0ce3f52b58e8ff33f5b"
 A second test for Trac #12055

 This one omits the extension, thereby making GHC 8.0 produce
 "GHC internal error".
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12055#comment:4>
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