[GHC] #9949: zipWith too strict in second argument in GHC-7.10.0

[GHC]

#9949: zipWith too strict in second argument in GHC-7.10.0
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        Reporter:  Lemming           |                   Owner:  ekmett
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:
       Component:  libraries/base    |                 Version:  7.10.1-rc1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:  #9495             |                Blocking:
                                     |  Differential Revisions:
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Comment (by tibbe):

 I think we should

  * revert the change,
  * remove the rule, and
  * document the intended strictness.

 The lack of the latter has proved to be problematic elsewhere (e.g.
 `findWithDefault` in containers.) Without documenting the strictness
 properties users can't really assume anything about the strictness of
 functions. Not even a "lazy unless otherwise specified" assumption is
 warranted, as functions are rarely maximally lazy unless particular care
 is taken (see e.g.
 https://www.haskell.org/haskellwiki/Maintaining_laziness).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9949#comment:8>
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