[GHC] #7296: ghc-7 assumes incoherent instances without requiring language `IncoherentInstances`

[GHC]

#7296: ghc-7 assumes incoherent instances without requiring language
`IncoherentInstances`
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 Reporter:  maeder                       |          Owner:                  
     Type:  bug                          |         Status:  new             
 Priority:  normal                       |      Component:  Compiler        
  Version:  7.6.1                        |       Keywords:                  
       Os:  Unknown/Multiple             |   Architecture:  Unknown/Multiple
  Failure:  GHC accepts invalid program  |       Testcase:                  
Blockedby:                               |       Blocking:                  
  Related:                               |  
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Comment(by maeder):

 I meant, one may wish that a and b returned equal results, namely that a
 returned "[]" by using the more special instance of Spec2 in the instance
 definition of Spec1.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7296#comment:1>
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