[GHC] #10971: ExtendedDefaultRules defaults to [] for Foldable/Traversable

[GHC]

#10971: ExtendedDefaultRules defaults to [] for Foldable/Traversable
-------------------------------------+-------------------------------------
           Reporter:  kanetw         |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:  8.0.1
          Component:  Compiler       |           Version:  7.10.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:  10963
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 From goldfire:
 > Extend -XExtendedDefaultRules to allow defaulting when one of the
 classes involved is Foldable or Traversable. (See the current rules
 ​here.) This will mean, essentially, that there will be two lists of
 default types, one list at kind * and one at kind * -> *. Both lists
 should be settable by the user by the default directive. (GHC can figure
 out which list is being set quite easily.) The default default list for *
 -> * will be [].

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10971>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler