[GHC] #7395: DefaultSignatures conflict with default implementations

[GHC]

#7395: DefaultSignatures conflict with default implementations
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    Reporter:  cgaebel            |       Owner:                           
        Type:  bug                |      Status:  new                      
    Priority:  normal             |   Milestone:                           
   Component:  Compiler           |     Version:  7.6.1                    
    Keywords:  DefaultSignatures  |          Os:  Unknown/Multiple         
Architecture:  Unknown/Multiple   |     Failure:  GHC rejects valid program
  Difficulty:  Unknown            |    Testcase:                           
   Blockedby:                     |    Blocking:                           
     Related:                     |  
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Comment(by cgaebel):

 Doesn't GHC already backtrack for things like UndecidableInstances? Or
 does it do something else? Can we apply that here?

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7395#comment:5>
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