[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 simonpj):

 OK, well, since there are good reasons to be wary let's not rush to make a
 change.  The status quo is by definition cheaper.

 While the idea was ''precipitated'' by the question of tuples (and the
 overhead of reading interface files etc), it should not be ''driven'' by
 that.  Maybe there's another way to address the perf question.   It was
 only that, if there was a quick consensus, it seemed like an easy way.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13065#comment:10>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler