[GHC] #10149: The argument of mask does not always restore the masking state

[GHC]

#10149: The argument of mask does not always restore the masking state
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        Reporter:                    |                   Owner:
  facundo.dominguez                  |                  Status:  new
            Type:  bug               |               Milestone:
        Priority:  normal            |                 Version:  7.8.4
       Component:  libraries/base    |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by facundo.dominguez):

 Other failing examples not involving `forkIOWithUnmask`:

 {{{#!hs
 mask $ \unmask -> mask $ \restore ->
   unmask $ restore $ getMaskingState >>= print
 }}}

 {{{#!hs
 uninterruptibleMask $ \unmask -> uninterruptibleMask $ \restore ->
   unmask $ restore $ getMaskingState >>= print
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10149#comment:2>
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