[GHC] #15426: `elemIndex` and `findIndex` still can't fuse

[GHC]

#15426: `elemIndex` and `findIndex` still can't fuse
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        Reporter:  kabuhr            |                Owner:  kabuhr
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  libraries/base    |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  testsuite/tests/perf/should_run/T15426.hs
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |  https://phabricator.haskell.org/D5063
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Comment (by simonpj):

 OK fine. So if I understand aright:

 * Nofib gets no better but no worse
 * More fusion happens in other cases (eg the Description)

 Sounds good to me.  It would be good to include a perf regression test
 that will trip if fusion fails in the future.  And a Note to explain the
 INLINABLE pragma.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15426#comment:9>
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