[GHC] #10457: Revise/remove custom mapM implementation for lists

[GHC]

#10457: Revise/remove custom mapM implementation for lists
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        Reporter:  dolio             |                   Owner:
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:  7.10.2
       Component:  libraries/base    |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:  Phab:D924
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Comment (by simonpj):

 Well someone should preferably just check that whatever fusion used to
 happen still happens, and ideally add a performance test to make sure it
 stays that way.

 That done, go ahead if the Core Libraries Committee is happy.  (And Edward
 is presumably speaking as its chair in comment:4.)

 I'm unconvinced it's worth merging to 7.10.  After all, it changes nothing
 except omitting one line of code from a library, right?

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10457#comment:5>
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