[GHC] #9355: scanr does not participate in stream fusion

[GHC]

#9355: scanr does not participate in stream fusion
-------------------------------------+-------------------------------------
       Reporter:  dfeuer             |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:  7.8.4
      Component:  libraries/base     |                 Version:  7.8.3
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Moderate (less     |         Type of failure:  Runtime
  than a day)                        |  performance bug
     Blocked By:                     |               Test Case:
Related Tickets:                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 This should be a no-brainer—it's trivial two write `scanr` as a foldr,
 making it a good consumer. Wrapping it up in `build` makes it a good
 producer too, but may require back-and-forth RULES.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9355>
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