[GHC] #9761: A module can't usefully use both GeneralizedNewtypeDeriving and DeriveFoldable

[GHC]

#9761: A module can't usefully use both GeneralizedNewtypeDeriving and
DeriveFoldable
-------------------------------------+-------------------------------------
              Reporter:  dfeuer      |            Owner:  dfeuer
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Core        |          Version:  7.9
  Libraries                          |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:  GHC         |  Related Tickets:
  rejects valid program              |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
Changes (by dfeuer):

 * cc: core-libraries-committee@… (added)
 * owner:   => dfeuer
 * component:  Compiler (Type checker) => Core Libraries


Comment:

 Reid Barton thinks this is probably caused by the accidental redundant
 `Foldable` contexts on `Foldable` members.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9761#comment:2>
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