New haskell exception ambiguous type issue in real word example code BetterPredicate.hs

AnonyousHandle.hs

import Control.Exception (bracket, handle, SomeException)
import System.IO (IOMode(..), hClose, hFileSize, openFile)

{-- snippet getFileSize --}
-- To work around the code that doesn't work in Haskell 6.10
--  Control.Exception is changed to allow ploymophism such that
--      handle (\_ -> return Nothing) doesn't compile
hdl::SomeException -> IO (Maybe a)
hdl _ = return Nothing 

--getFileSize path = handle (\_ -> return Nothing) $
getFileSize path = handle (hdl) $
  bracket (openFile path ReadMode) hClose $ \h -> do
    size <- hFileSize h
    return (Just size)
{-- /snippet getFileSize --}

Aslo check links in this thread in stackoverflow