[GHC] #1220: Newtype deriving should only work if superclasses are newtype-derived

[GHC]

#1220: Newtype deriving should only work if superclasses are newtype-derived
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 Reporter:  simonpj                  |          Owner:            
     Type:  bug                      |         Status:  closed    
 Priority:  normal                   |      Milestone:  6.8 branch
Component:  Compiler (Type checker)  |        Version:  6.6       
 Severity:  normal                   |     Resolution:  invalid   
 Keywords:                           |     Difficulty:  Unknown   
 Testcase:                           |   Architecture:  Unknown   
       Os:  Unknown                  |  
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Changes (by simonpj):

  * status:  new => closed
  * resolution:  => invalid

Comment:

 No rejoinders, so closing this as 'invalid'.  But I'll add a pointer to
 this exchange to the source code, with `Note [Newtype deriving
 superclasses]` in `TcDeriv`.

 Simon

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1220#comment:2>
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