[GHC] #10577: Use empty cases where appropriate when deriving instances for empty types

[GHC]

#10577: Use empty cases where appropriate when deriving instances for empty types
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        Reporter:  rwbarton          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13117, #7401     |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by dfeuer):

 * related:   => #13117, #7401


Comment:

 This is fixed for `Functor`, `Foldable`, `Traversable`, `Generic`, and
 `Generic1`. I believe some `Data` methods already do the right thing here,
 but I don't know if they all do.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10577#comment:4>
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