[GHC] #8165: Use GeneralizedNewtypeDeriving to automatically create associated type families

[GHC]

#8165: Use GeneralizedNewtypeDeriving to automatically create associated type
families
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        Reporter:  MikeIzbicki       |            Owner:
            Type:  feature request   |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by goldfire):

 What should happen in this scenario:

 {{{
 class D a where
   type U a

 instance D Int where
   type U Int = Int

 newtype E = MkE Int
   deriving D
 }}}

 What does `U E` reduce to, `E` or `Int`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8165#comment:1>
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