Proposal: Add Eq instance for Control.Exception.ErrorCall

Michael Snoyman michael at
Tue Nov 27 13:09:14 CET 2012

On Tue, Nov 27, 2012 at 1:59 PM, Henning Thielemann <
lemming at> wrote:

> On Tue, 27 Nov 2012, Michael Snoyman wrote:
>  +1 on the proposal. Even if I'm opposed to partial functions, I'm in
>> favor of making it easier to test them reliably.
> How can you be sure that you get a certain error? Depending on the order
> of evaluation you might get different error messages if there are multiple
> possible ways to fail. I think automated testing against specific error
> messages will not work reliably.

Sure, in some cases that's true. The idea would be to structure the test
case in such a way that we no with certainty which way it will fail.
Simon's initial example will always fail in the same way.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the Libraries mailing list