[GHC] #13615: Wrong results from what supposed to be pure function with presense of parallel evaluation

[GHC]

#13615: Wrong results from what supposed to be pure function with presense of
parallel evaluation
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        Reporter:  pacak             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.2.1-rc2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 Interesting, forcing `st'` before passing it to `unsafeUpdateM` in the the
 `BitmapIndexed` branch of `Data.HashMap.Strict.unsafeInsertWith` also
 seems to fix the issue. I haven't thought much about why.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13615#comment:4>
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