During the sprint in baires we write some tests to detect the senders of = nil to be replaced with isNil as the issue suggest. We now need to do a rewrite of this methods (this could be done using the refactoring engine as lukas proposed in the issue). However if I do this rewrite on the Dev image I will change code not only in Pharo Core but also in some external packages. Is it the intended scope of the issue?. I think that first we need to do the rewrite on Pharo Core code. And let every package maintainer to decide if he wants to do it or not. Of course for the community maintained packages we can make that decision too. In the future I think would be good to have some kind of "Pharo Coding Practices" (or the name we want) that can be automatically tested. As a community we can discuss this practices and provide some automatic way to ensure that. As soon as posible I will create a Slice with the changes in Pharo Core and post it to the inbox (sorry if it takes me some days but here where are celebrating the argentinean bicentennial so i don't have too much free time this days :) ). Regards, Gabriel