On Mon, Apr 4, 2011 at 12:18 PM, Conal Elliott wrote:

System.Event.Manager [1] contains the following type alias and Show instance:

-- | Callback invoked on I/O events. type IOCallback = FdKey -> Event -> IO ()

instance Show IOCallback where show _ = "IOCallback"

This specialized instance conflicts with the more general instance Show (a -> b) defined in Text.Show.Functions.

Stefan found this conflict when trying to compile the checkers package on ghc 7.0.3. I suspect it will arise with other packages as well.

My suggestion is to remove the specialized Show instance and instead import Text.Show.Functions as needed.

Other thoughts?

Is there a reason that this instance is orphaned? Can we make it non-orphaned, so that we don't run into this problem again? This would require putting the instance into the Prelude. Antoine