[GHC] #8567: Poor error message when GeneralizedNewtypeDeriving fails

[GHC]

#8567: Poor error message when GeneralizedNewtypeDeriving fails
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        Reporter:  goldfire          |            Owner:  nomeata
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Changes (by nomeata):

 * owner:   => nomeata


Comment:

 In discussion with SPJ, we thought about how we can catch missing
 instances already in the code for deriving, at least for non-standalone-
 deriving. I’ll work on that, and on making the error message a bit nicer.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8567#comment:2>
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