The ones near the top changing abilities is perfectly fine, both as a design rule and as them not leading to cascading changes in declarations through all your

The ones near the top changing abilities is perfectly fine, both as a design rule and as them not leading to cascading changes in declarations through all your code. The problem is on the ones deep down. And we don't have very good tools for dealing with them, but they are perfectly workable even with what we have today. (A second large problem is on frameworks running on the top-level of your app. We have some tools for dealing with those, but the situation here is way worse than for libraries.)