[GHC] #11555: catch _|_ breaks at -O1

[GHC]

#11555: catch _|_ breaks at -O1
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        Reporter:  slyfox            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1-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 NeilMitchell):

 I talked to Simon offline a few days ago, after that I believe his opinion
 was:

 * {{{catch#}}} should remain strict in it's first argument.
 * {{{catch a b = catch# (lazy a) b}}} is the correct way to express the
 laziness, the {{{evaluate}}} trick certainly avoids the problem for now,
 but it may not be robust in the future.
 * There are places in the IO subsystem which get a significant benefit
 from a strict catch, they should use a more primitive version
 ({{{strictCatch}}} or something).
 * The default exposed {{{catch}}} (and also {{{try}}}, {{{handle}}} etc)
 should use {{{lazy}}}. All these functions seem to share the same
 underlying entry point, so that shouldn't be hard.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11555#comment:11>
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