[GHC] #3517: GHC has lots of extra hidden IOErrorType values

[GHC]

#3517: GHC has lots of extra hidden IOErrorType values
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Reporter:  duncan            |          Owner:                  
    Type:  bug               |         Status:  new             
Priority:  normal            |      Component:  libraries/base  
 Version:                    |       Severity:  normal          
Keywords:                    |       Testcase:                  
      Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
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 I was fixing bytestring's hGet (see #3514) and I discover that I cannot
 produce the same exception as System.IO.hGet does in the same
 circumstance.

 There are two problems:

 One is that GHC's internal IOError has more information than one can set
 via System.IO.Error.mkIOError. In particular it has a function name.

 The other is that System.IO.hGet throws an `InvalidArgument`
 `IOErrorType`, however this is not exported and there are no smart
 constructors or testers for this error type. This is problematic for two
 reasons, portable code cannot generate these error types to mirror the
 standard System.IO and secondly no code can actually catch these errors
 except in a general "catch all" style because they cannot be distinguished
 from each other.

 Code that wants to mirror System.IO (like bytestring or utf8-string) has
 to import GHC.IO.Exception and use cpp to do it differently for hugs and
 nhc.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3517>
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