[GHC] #9757: Warn about derivable instances

[GHC]

#9757: Warn about derivable instances
-------------------------------------+-------------------------------------
              Reporter:  dfeuer      |            Owner:
                  Type:  feature     |           Status:  closed
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.9
             Component:  Compiler    |         Keywords:
            Resolution:  wontfix     |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------

Comment (by NeilMitchell):

 HLint knows nothing about types, has no translation to Core and only has
 approximate information about name binding. Your approach seems feasible
 in GHC, and it might do a reasonable job, but wouldn't be suitable in
 HLint.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9757#comment:9>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler