[GHC] #13058: Use coercions to implement fmapDefault and foldMapDefault

[GHC]

#13058: Use coercions to implement fmapDefault and foldMapDefault
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        Reporter:  dfeuer            |                Owner:  dfeuer
            Type:  task              |               Status:  patch
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Core Libraries    |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2916
       Wiki Page:                    |
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Changes (by dfeuer):

 * differential:  Phab: D2916 => Phab:D2916


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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13058#comment:5>
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