Ticket #5092 (closed feature request: fixed)
Remove Show instance for GHC.Event.IOCallback
Conal reported that the Show instance for IOCallback conflicts with the more general instance Show (a -> b) defined in Text.Show.Functions.
The attached patch removes the Show instance for IOCallback like Bryan propsed. It also removes the Show instance for FdData since that type contains an IOCallback. I don't think this matters because FdData is an internal type.