[GHC] #9742: The default definitions of foldl1 and foldr1 are too strict

[GHC]

#9742: The default definitions of foldl1 and foldr1 are too strict
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              Reporter:  dfeuer      |            Owner:  ekmett
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Core        |          Version:  7.9
  Libraries                          |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Easy (less than 1
  Unknown/Multiple                   |  hour)
       Type of failure:  Runtime     |       Blocked By:
  crash                              |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by dfeuer):

 I should say "may have to", actually. The current `foldr1` should be okay
 on snoc lists, say.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9742#comment:2>
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