Excerpts from Martijn van Steenbergen's message of Wed Jan 28 17:33:18 +0100 2009:

This is a bug in GHC. See:

http://hackage.haskell.org/trac/ghc/ticket/2267

I have the same problem in several of my source files. :-(

Sometimes swaping the import lists does hide this wrong warning. Including in this example.

Michael Snoyman wrote:

...

I was writing code similar to the following and compiling with "-Wall -Werror." Clearly I *am* using Data.ByteString for the function signatures.

{-# OPTIONS_GHC -fwarn-unused-imports -Werror #-} import qualified Data.ByteString as B import qualified Data.ByteString.UTF8 as BU

toString :: B.ByteString -> String toString = BU.toString

fromString :: String -> B.ByteString fromString = BU.fromString

main :: IO () main = putStrLn $ toString $ fromString "Hello World!"

The warning I get is:

Unused.hs:2:0: Warning: Module `Data.ByteString' is imported, but nothing from it is used, except perhaps instances visible in `Data.ByteString' To suppress this warning, use: import Data.ByteString()

Am I doing something wrong or is this a bug in GHC?

Thanks, Michael

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