RE: -fwarn-unused-matches

> Dear  ghc-5.02.2,
> 
>       ghc -c -fwarn-unused-matches
> says
>       Warning: Defined but not used: x
> 
> when compiling the function
> 
>   f :: Eq a => [(a, a)] -> (a, a) -> [(a, a)]
>   f            ps          (x, y) =  [(z, y) | (z, x) <- ps]
> 
> Is it a bug?

No.

Cheers,
        ghc-5.02.2