[GHC] #1171: GHC doesn't respect the imprecise exceptions semantics

[GHC]

#1171: GHC doesn't respect the imprecise exceptions semantics
-------------------------------+--------------------------------------------
  Reporter:  neil              |          Owner:                  
      Type:  bug               |         Status:  new             
  Priority:  low               |      Milestone:  _|_             
 Component:  Compiler          |        Version:  6.6             
Resolution:                    |       Keywords:                  
        Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
   Failure:  None/Unknown      |     Difficulty:  Unknown         
  Testcase:  cg059             |      Blockedby:                  
  Blocking:                    |        Related:                  
-------------------------------+--------------------------------------------

Comment(by simonpj):

 Simon PJ and Simon M also discussed `throwIO`, which is a bit more
 preditable than `throw`. Specifically:
 {{{
   throw e   `seq` x  ===> throw e
   throwIO e `seq` x  ===> x
 }}}
 However, `throwIO` currently is still just as strict as `throw`.  For
 example:
 {{{
 f :: (Int,Int) -> IO a
 f x = throwIO (ErrorCall "urk")

 main = throwIO (error "yes")
 }}}
 This will throw `(error "yes")` because `throwIO` evaluates (but doesn't
 unbox) its argument because `throwIO` is strict.

 We could artificially make `throwIO` appear not to diverge, even when
 given two arguments (ie including the state token).  That would have a
 much less bad effect than making `error` or `throw` appear not to diverge;
 and would make `throwIO` still more predictable, but I don't know how
 large the effect would be.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1171#comment:19>
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