[GHC] #4380: Use throwIO instead of throw in an IO context

[GHC]

#4380: Use throwIO instead of throw in an IO context
---------------------------------+------------------------------------------
    Reporter:  basvandijk        |       Owner:                
        Type:  bug               |      Status:  new           
    Priority:  normal            |   Component:  libraries/base
     Version:  6.12.3            |    Keywords:                
    Testcase:                    |   Blockedby:                
          Os:  Unknown/Multiple  |    Blocking:                
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown  
---------------------------------+------------------------------------------
 Some functions in base use `throw` where the type of the expression is
 `IO`. I think they should be using `throwIO` since it guarantees ordering
 with respect to other IO actions.

 See the [http://thread.gmane.org/gmane.comp.lang.haskell.libraries/13851
 thread] on the libraries list.

 Some simple benchmarks in the thread also showed that `throwIO` is faster
 than `throw`.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4380>
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