[GHC] #8503: New GeneralizedNewtypeDeriving check still isn't permissive enough

[GHC]

#8503: New GeneralizedNewtypeDeriving check still isn't permissive enough
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        Reporter:  goldfire          |            Owner:  goldfire
            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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Comment (by sweirich):

 Perhaps another option is to generalize TyConAppCo so that it allows the
 heads to differ as long as they are (representationally) equal and we have
 role information for each head. That's slightly more general than changing
 AxiomInstCo as you'd get transititivity...

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8503#comment:3>
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