[GHC] #3018: Constraints of function in record appears to nullifiy instance constraints.

[GHC]

#3018: Constraints of function in record appears to nullifiy instance constraints.
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Reporter:  ben.kavanagh      |          Owner:                  
    Type:  bug               |         Status:  new             
Priority:  normal            |      Component:  Compiler        
 Version:  6.10.1            |       Severity:  normal          
Keywords:                    |       Testcase:                  
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
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 If an field of a record that has constraints in its type, defining a value
 for this field appears to cause the compiler to ignore outer level
 constraints declared for an instance.

 This problem restricts generic functions written in syb-with-class and
 replib style to functions that do not have constraints.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3018>
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