[GHC] #13328: Foldable, Functor, and Traversable deriving handle phantom types badly

[GHC]

#13328: Foldable, Functor, and Traversable deriving handle phantom types badly
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:  deriving-perf
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I do agree that your proposed definition is probably the better one. I
 only ask that we point out this change in strictness in the users' guide
 (and probably the migration guide for whatever GHC release this makes it
 into) so that users aren't too surprised.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13328#comment:3>
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