[Haskell-cafe] GHC's -fwarn-unused-imports ignores function signatures

[Martijn van Steenbergen]

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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