[GHC] #3822: guards in arrow notation (Arrows extension) case statement cause compiler panic

[GHC]

#3822: guards in arrow notation (Arrows extension) case statement cause compiler
panic
-----------------------------------------+----------------------------------
    Reporter:  StephenBlackheath         |        Owner:  ross              
        Type:  bug                       |       Status:  new               
    Priority:  high                      |    Milestone:  6.12.3            
   Component:  Compiler                  |      Version:  6.12.1            
    Keywords:  arrows guards case panic  |   Difficulty:                    
          Os:  Unknown/Multiple          |     Testcase:  patternGuard.hs   
Architecture:  Unknown/Multiple          |      Failure:  Compile-time crash
-----------------------------------------+----------------------------------

Comment(by simonmar):

 Ross: sorry for the delay in getting back to you.  Which bit of code is
 responsible for recognising variables as being used?  Is it arrows-
 specific, or somewhere else?  Can you help us fix it?  (Cheers, Simon &
 Simon)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3822#comment:10>
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