[GHC] #4508: DeriveFoldable should not require DeriveFunctor

[GHC]

#4508: DeriveFoldable should not require DeriveFunctor
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    Reporter:  batterseapower    |       Owner:                                   
        Type:  bug               |      Status:  new                              
    Priority:  normal            |   Component:  Compiler                         
     Version:  6.12.3            |    Keywords:                                   
    Testcase:                    |   Blockedby:                                   
          Os:  Unknown/Multiple  |    Blocking:                                   
Architecture:  Unknown/Multiple  |     Failure:  Incorrect warning at compile-time
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 Functor is not a superclass of Foldable, so there is no reason to require
 DeriveFunctor to be on if you use the DeriveFoldable flag. However, at the
 moment GHC requires you to use both flags even if you only derive
 Foldable.

 (Yes, surprisingly some things are Foldable but not Functor -- such as
 Data.Set).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4508>
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