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. :-(
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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