Show instance in System.Event.Manager causes conflicts

[Antoine Latter]

On Mon, Apr 4, 2011 at 12:18 PM, Conal Elliott <conal at conal.net> 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