On Fri, Nov 11, 2005 at 01:20:05PM +0200, Einar Karttunen wrote:

It seems that the type of throwDyn and throwDynTo are dangerously close. ThrowDyn works in with any of the arguments of throwDynTo, which can cause evil situations.

throwDyn :: Typeable exception => exception -> b

Which means e.g. "throwDyn someThreadId SomeException" will work when you wanted to say "throwDynTo someThreadId SomeException" and they both have types which unify with IO ().

How evil! ;-)

I think using a class Typeable => DynamicException a where ... and throwDyn :: DynamicException a => a -> b could make more sense.

You could also do something like: newtype Exn a = Exn a -- not Typeable throwDyn' :: Typeable exception => Exn exception -> b throwDyn' (Exn e) = throwDyn e used as throwDyn' (Exn (some-typeably-thingy)) then neither (throwDyn' someThreadId SomeException) nor (throwDyn' someThreadId (Exn SomeException)) will compile. And you won't have to create instances of DynamicException, but it is probably more ugly. Best regards Tomasz