IO exception rework

ghc 7.4 comaplains about use of System.IO.Error to catch exceptions.
Ok, use Control.Exception, with variants specialized to only catch IO
exceptions.

Utility/Directory.hs

@@ -16,11 +16,12 @@ import Control.Monad.IfElse
 
 import Utility.SafeCommand
 import Utility.TempFile
+import Utility.Exception
 
 {- Moves one filename to another.
  - First tries a rename, but falls back to moving across devices if needed. -}
 moveFile :: FilePath -> FilePath -> IO ()
-moveFile src dest = try (rename src dest) >>= onrename
+moveFile src dest = tryIO (rename src dest) >>= onrename
 	where
 		onrename (Right _) = return ()
 		onrename (Left e)
@@ -40,11 +41,10 @@ moveFile src dest = try (rename src dest) >>= onrename
 						Param src, Param tmp]
 					unless ok $ do
 						-- delete any partial
-						_ <- try $
-							removeFile tmp
+						_ <- tryIO $ removeFile tmp
 						rethrow
 		isdir f = do
-			r <- try (getFileStatus f)
+			r <- tryIO $ getFileStatus f
 			case r of
 				(Left _) -> return False
 				(Right s) -> return $ isDirectory s

Utility/Exception.hs

@@ -0,0 +1,39 @@
+{- Simple IO exception handling
+ -
+ - Copyright 2011-2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Utility.Exception where
+
+import Prelude hiding (catch)
+import Control.Exception
+import Control.Applicative
+
+{- Catches IO errors and returns a Bool -}
+catchBoolIO :: IO Bool -> IO Bool
+catchBoolIO a = catchDefaultIO a False
+
+{- Catches IO errors and returns a Maybe -}
+catchMaybeIO :: IO a -> IO (Maybe a)
+catchMaybeIO a = catchDefaultIO (Just <$> a) Nothing
+
+{- Catches IO errors and returns a default value. -}
+catchDefaultIO :: IO a -> a -> IO a
+catchDefaultIO a def = catchIO a (const $ return def)
+
+{- Catches IO errors and returns the error message. -}
+catchMsgIO :: IO a -> IO (Either String a)
+catchMsgIO a = dispatch <$> tryIO a
+	where
+		dispatch (Left e) = Left $ show e
+		dispatch (Right v) = Right v
+
+{- catch specialized for IO errors only -}
+catchIO :: IO a -> (IOException -> IO a) -> IO a
+catchIO = catch
+
+{- try specialized for IO errors only -}
+tryIO :: IO a -> IO (Either IOException a)
+tryIO = try

Utility/Misc.hs

@@ -8,9 +8,7 @@
 module Utility.Misc where
 
 import System.IO
-import System.IO.Error (try)
 import Control.Monad
-import Control.Applicative
 
 {- A version of hgetContents that is not lazy. Ensures file is 
  - all read before it gets closed. -}
@@ -37,22 +35,3 @@ separate c l = unbreak $ break c l
 {- Breaks out the first line. -}
 firstLine :: String-> String
 firstLine = takeWhile (/= '\n')
-
-{- Catches IO errors and returns a Bool -}
-catchBoolIO :: IO Bool -> IO Bool
-catchBoolIO a = catchDefaultIO a False
-
-{- Catches IO errors and returns a Maybe -}
-catchMaybeIO :: IO a -> IO (Maybe a)
-catchMaybeIO a = catchDefaultIO (Just <$> a) Nothing
-
-{- Catches IO errors and returns a default value. -}
-catchDefaultIO :: IO a -> a -> IO a
-catchDefaultIO a def = catch a (const $ return def)
-
-{- Catches IO errors and returns the error message. -}
-catchMsgIO :: IO a -> IO (Either String a)
-catchMsgIO a = dispatch <$> try a
-	where
-		dispatch (Left e) = Left $ show e
-		dispatch (Right v) = Right v

Utility/TempFile.hs

@@ -12,7 +12,7 @@ import System.IO
 import System.Posix.Process hiding (executeFile)
 import System.Directory
 
-import Utility.Misc
+import Utility.Exception
 import Utility.Path
 
 {- Runs an action like writeFile, writing to a temp file first and