[GHC] #10607: Auto derive from top to bottom

[GHC]

#10607: Auto derive from top to bottom
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        Reporter:  songzh            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:  deriving,
                                     |  typeclass, auto
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by songzh):

 2. I am a newbie of TH, but thanks, I will look into `th-expand-syns`

 3. I noticed and understood the reason why we do not need type variable
 `Generic a` in the context finally!! thanks.

 I may request an API for querying whether `Eq a => List a` is an instance
 of Eq typeclass. Thanks.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10607#comment:11>
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