[GHC] #8631: Need ImpredicativeTypes for GeneralizedNewtypeDeriving?

[GHC]

#8631: Need ImpredicativeTypes for GeneralizedNewtypeDeriving?
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        Reporter:  goldfire          |            Owner:
            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 nomeata):

 Looking into Q1. There is some code temporarily enabling certain extension
 (`EmptyCase`, `ScopedTypeVariables` and `KindSignatures`) in
 `renameDeriv`, but these just affect the renamer; the error message we see
 occurs later, and I don’t see how we can enable `ImpredicativeTypes` in a
 scoped way, i.e. only applying to the code generated by GND.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8631#comment:7>
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