On Mon, Dec 27, 2010 at 12:36:33PM +0000, Ian Lynagh wrote:
Prelude and System.IO.Error both export an old version of catch, which only catches IOError's, and System.IO.Error additionally exports try with the same problem.
These exports are annoying for people who want to use the modern exception handling functions in Control.Exception, as you need to explicitly either import the Prelude with catch hidden, or give the module of the function you want to use.
They may also be confusing for beginners, who may not expect to have to use anything other than the catch function in the default scope to catch all exceptions.
I believe these functions are only there for historical reasons, and are old cruft that we should tidy up, so I propose that in the base package that comes with GHC 7.2 we deprecate these old functions, and in 7.4 we remove them.
The case for removing Prelude.catch is stronger than the one for removing System.IO.Error.{catch,try} -- the new exception interface is not ready for standardization because it relies on existential types and because of concerns over catching asynchronous exceptions.