[GHC] #3877: Require XOverlappingInstances for the most specific instance only

[GHC]

#3877: Require XOverlappingInstances for the most specific instance only
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  Reporter:  traz161616                 |          Owner:  igloo                
      Type:  feature request            |         Status:  closed               
  Priority:  normal                     |      Milestone:  7.4.1                
 Component:  Compiler (Type checker)    |        Version:  6.12.1               
Resolution:  fixed                      |       Keywords:  XOverlappingInstances
  Testcase:                             |      Blockedby:                       
Difficulty:                             |             Os:  Unknown/Multiple     
  Blocking:                             |   Architecture:  Unknown/Multiple     
   Failure:  GHC rejects valid program  |  
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Changes (by gidyn):

 * cc: gideon@… (removed)


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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3877#comment:15>
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