[GHC] #4220: EmptyDataDecls + DeriveFunctor == Panic!

[GHC]

#4220: EmptyDataDecls + DeriveFunctor == Panic!
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        Reporter:  conal             |                Owner:  simonpj
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  7.0.1
       Component:  Compiler          |              Version:  6.12.3
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  crash                              |  deriving/should_compile/T4220
      Blocked By:                    |             Blocking:
 Related Tickets:  #4302             |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by thomie):

 * related:   => #4302


Comment:

 commit 6efa3901fd6f1583fb654bd3659e88702dfd579a
 {{{
 Author: simonpj at microsoft.com <unknown>
 Date:   Thu Aug 12 13:13:19 2010 +0000

     Fix Trac #4220

     For deriving Functor, Foldable, Traversable with empty
     data cons I just generate a null equation
        f _ = error "urk"

     There are probably more lurking (eg Enum) but this will do for now.
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4220#comment:9>
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