Example code for GetOpt doesn't compile

[Bryn Keller]

On NT4.0 sp3, ghc 5.01 thrill-seeker's release, I get the following 
compile error when trying to build the example snippet at the end of 
 the GetOpt section in the manual. I've also included the code, in case 
it's changed from the version I have...

---
Administrator at BRK /NextGen/src/magellan/src/haskell
$ ghc -package util scratch.hs

scratch.hs:28:
    Couldn't match `String' against `IOError'
        Expected type: String
        Inferred type: IOError
    In the application `userError ((concat errs)
                                   ++ (usageInfo header options))'
    In the first argument of `fail', namely
        `(userError ((concat errs) ++ (usageInfo header options)))'

Administrator at BRK /NextGen/src/magellan/src/haskell
$
---

module Opts where

import GetOpt
import Maybe ( fromMaybe )

data Flag
 = Verbose  | Version
 | Input String | Output String | LibDir String
   deriving Show

options :: [OptDescr Flag]
options =
 [ Option ['v']     ["verbose"] (NoArg Verbose)       "chatty output on 
stderr"
 , Option ['V','?'] ["version"] (NoArg Version)       "show version number"
 , Option ['o']     ["output"]  (OptArg outp "FILE")  "output FILE"
 , Option ['c']     []          (OptArg inp  "FILE")  "input FILE"
 , Option ['L']     ["libdir"]  (ReqArg LibDir "DIR") "library directory"
 ]

inp,outp :: Maybe String -> Flag
outp = Output . fromMaybe "stdout"
inp  = Input  . fromMaybe "stdout"

compilerOpts :: [String] -> IO ([Flag], [String])
compilerOpts argv =
   case (getOpt Permute options argv) of
      (o,n,[]  ) -> return (o,n)
      (_,_,errs) -> fail (userError (concat errs ++ usageInfo header 
options))
  where header = "Usage: ic [OPTION...] files..."