[GHC] #5498: Generalized newtype deriving allows creating of instances I can't create by hand

[GHC]

#5498: Generalized newtype deriving allows creating of instances I can't create by
hand
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        Reporter:  dterei                      |            Owner:
            Type:  bug                         |           Status:  closed
        Priority:  normal                      |        Milestone:  7.6.2
       Component:  Compiler                    |          Version:  7.3
      Resolution:  fixed                       |         Keywords:
Operating System:  Unknown/Multiple            |     Architecture:
 Type of failure:  None/Unknown                |  Unknown/Multiple
       Test Case:  deriving/should_fail/T5498  |       Difficulty:  Unknown
        Blocking:                              |       Blocked By:  1496
                                               |  Related Tickets:
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Changes (by simonpj):

 * testcase:   => deriving/should_fail/T5498


Comment:

 Indeed.  The program is indeed rejected, although the error message is not
 fantastic. I've added it as a test.

 I think you can enable GND in Safe Haskell.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5498#comment:10>
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