[GHC] #11336: GHC craches on this combination of ViewPatterns and PatternSynonyms

[GHC]

#11336: GHC craches on this combination of ViewPatterns and PatternSynonyms
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           Reporter:  baramoglo      |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.2
           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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 The attached file crashes:

 {{{
 $ ghc Bug.hs
 [1 of 1] Compiling Bug              ( Bug.hs, Bug.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.2 for x86_64-unknown-linux):
         Prelude.last: empty list
 }}}

 I wasn't able to shrink the example further despite many attepts.

 Tested on GHC 7.8.3 and 7.10.2.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11336>
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