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

[GHC]

#8851: Standalone deriving and GND behave differently
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        Reporter:  simonpj                  |            Owner:  goldfire
            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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Changes (by goldfire):

 * owner:   => goldfire


Comment:

 I took a briefish look at this yesterday and am somewhat confused, but
 I'll take a closer look and submit a fix in the next few days.

 I actually think acceptance is correct because of Joachim's (nomeata's)
 reasoning. It is indeed unsafe to convert a ''dictionary'' for `Monad
 Parser` to a ''dictionary'' for `Monad InnerIdrisParser`. But, the
 `notFollowedBy` function takes this dictionary as a parameter, and so
 coherence is somehow not an issue. Even as I'm writing this, I don't fully
 believe it, but my hunch is still that "accept" is the right answer. I'll
 elaborate more when I can put some more consecutive cycles into this.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8851#comment:4>
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