[GHC] #7558: Terrible error message when given and wanted are both insoluble

[GHC]

#7558: Terrible error message when given and wanted are both insoluble
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    Reporter:  simonpj           |       Owner:  simonpj         
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:  7.8.1           
   Component:  Compiler          |     Version:  7.6.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by monoidal):

 This seems to be fixed in HEAD; can someone verify and possibly add a
 test?

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7558#comment:2>
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