[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,
Operating System:  Unknown/Multiple  |  typeclass, auto
 Type of failure:  None/Unknown      |            Architecture:
      Blocked By:                    |  Unknown/Multiple
 Related Tickets:                    |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
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Comment (by songzh):

 Yes you are right, this is can be one application of TH. However, I am
 only a newbie of TH, I find I cannot query whether type like `Eq a => List
 a` is an instance of `Eq` with TH. And there are also other problems for
 me to implement it, like the situation type synonym with type variables.
 Any Template Haskell expert would like to work this out?

 Replying to [comment:3 goldfire]:
 > To me, this looks like the perfect application of Template Haskell. Yes,
 this ''could'' be built into GHC, but this seems like one step too far. If
 you're keen on this being built-in, perhaps seek out support on mailing
 lists and such to see whether others agree.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10607#comment:4>
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