[GHC] #8851: Standalone deriving and GND behave differently

[GHC]

#8851: Standalone deriving and GND behave differently
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        Reporter:  simonpj                  |            Owner:
            Type:  bug                      |           Status:  new
        Priority:  normal                   |        Milestone:
       Component:  Compiler (Type checker)  |          Version:  7.8.1-rc1
      Resolution:                           |         Keywords:
Operating System:  Unknown/Multiple         |     Architecture:
 Type of failure:  None/Unknown             |  Unknown/Multiple
       Test Case:                           |       Difficulty:  Unknown
        Blocking:                           |       Blocked By:
                                            |  Related Tickets:
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Comment (by simonpj):

 To me rejection (B) looks right. After all, is it safe to coerce between
 `(Monad Parser)` to `(Monad InnerIdrisParser)`?  They might have very
 different instances.

 See Section 3.4 of the [http://research.microsoft.com/en-
 us/um/people/simonpj/papers/ext-f/ Safe Coercions paper].

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8851#comment:2>
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