haskell io异常

import Prelude hiding (catch)
import Control.Exception(catch, finally,IOException)
withTempFile :: String -> (FilePath -> Handle -> IO a) -> IO a
withTempFile pattern func =
    do
       tempdir <- catch (getTemporaryDirectory) (_ -> return ".")
       (tempfile, temph) <- openTempFile tempdir pattern
       finally (func tempfile temph)
               (do hClose temph
                   removeFile tempfile)

Prelude>:type catch
catch :: Exception e => IO a -> (e -> IO a) -> IO a
Prelude>:type finally
finally :: IO a -> IO b -> IO a