[GHC] #10831: Document conditions on deriving Functor

[GHC]

#10831: Document conditions on deriving Functor
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        Reporter:  htebalaka         |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  low               |               Milestone:
       Component:  Compiler (Type    |                 Version:  7.10.2
  checker)                           |
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Documentation     |  Unknown/Multiple
  bug                                |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by rwbarton):

 Replying to [comment:4 RyanGlScott]:
 > Replying to [comment:3 simonpj]:
 > > But I think we still lack a user-oriented specification, and such a
 thing would be tremendously welcome.
 >
 > What exactly would we want from a "user-oriented specification"? Do we
 want to see the compile-time error messages improved? Or do we want to see
 particular portions of the Commentary page and/or users' guide fleshed
 out?

 The user's guide should contain an explanation sufficient for a user to
 understand what types will and will not work with deriving Functor.
 Ideally this should contain examples of both sorts.

 The wiki is intended for developer-facing documentation; users shouldn't
 have to consult the wiki to find out how to use a feature.

 I think the errors (at least the error appearing in this ticket; I haven't
 looked at others if there are any) are fine, assuming that there is
 documentation added to the user's guide that explains in more detail what
 is wrong here.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10831#comment:5>
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