[GHC] #13065: Prohibit user-defined Generic and Generic1 instances

[GHC]

#13065: Prohibit user-defined Generic and Generic1 instances
-------------------------------------+-------------------------------------
        Reporter:  dfeuer            |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  Generics
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by dfeuer):

 Yes, sorry. I forgot the real troubles were `Rep` and `Rep1` rather than
 `Generic` and `Generic1`. One possible variation might be to disassociate
 the families from the classes, and only restrict the former.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13065#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler