[GHC] #11760: runST with lazy blackholing breaks referential transparency

[GHC]

#11760: runST with lazy blackholing breaks referential transparency
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        Reporter:  Yuras             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      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 duncan):

 Right, I was also going to say it'd have to be in `>>=`, not just `runST`.
 The type of `noDuplicate#` should be generalised to not limit it to
 `RealWorld`.

 Is this going to be horribly expensive? Do we need rules to merge
 duplicate `noDuplicate#`s?

 In IO it's clear when we pay this expense since we do it via
 unsafeInterleaveIO, but in lazy ST that just corresponds to "safe" bind.

 For now I'll add some `noDuplicate`s in the zlib binding.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11760#comment:10>
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