[GHC] #4116: Type supplement for constructor specific uses of sum types

[GHC]

#4116: Type supplement for constructor specific uses of sum types
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    Reporter:  gabrielrf         |       Owner:              
        Type:  proposal          |      Status:  new         
    Priority:  normal            |   Component:  Compiler    
     Version:  6.13              |    Keywords:              
          Os:  Unknown/Multiple  |    Testcase:              
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown
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Comment(by gabrielrf):

 Sorry
 {{{
 headFromJust :: (Maybe (List a)) @ {Just (_:_)} -> a
 }}}

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4116#comment:7>
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