-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?

Answer, please, to  mechvel@xxxxxxxx

-----------------
Serge Mechveliani
mechvel@xxxxxxxx