[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:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:  deriving
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13117, #7401     |  Differential Rev(s):  Phab:D4047
       Wiki Page:                    |
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Changes (by RyanGlScott):

 * status:  new => patch
 * differential:   => Phab:D4047


Comment:

 Phab:D4047 fixes this ticket in the sense that more classes now use
 `EmptyCase` in derived code for empty data types (namely, `Show`, `Lift`,
 and `Data`). Note that `Eq` and `Ord` are not among these classes—refer to
 the [https://github.com/ghc-proposals/ghc-
 proposals/blob/dbf516088d2839432c9568c3d1f7ae28d46aeb43/proposals/0006
 -deriving-empty.rst proposal] which Phab:D4047 implements.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10577#comment:7>
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