[GHC] #9537: concatMap does not participate in list fusion

[GHC]

#9537: concatMap does not participate in list fusion
-------------------------------------+-------------------------------------
       Reporter:  dfeuer             |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:  7.8.4
      Component:  libraries/base     |                 Version:  7.9
       Keywords:  fusion             |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:  Runtime
     Blocked By:                     |  performance bug
Related Tickets:                     |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 Joachim Breitner raised this issue in an [http://www.haskell.org/pipermail
 /haskell-cafe/2011-December/097228.html email to haskell-cafe] in 2011,
 but he never got a response. For some reason, list comprehensions desugar
 to `concatMap` forms written to fuse, but the actual `concatMap` function
 is not written so. Unless there is a good reason for this, we should make
 it fuse.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9537>
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