[doctor_phil]

The point is that every function is explicitly telling you if it can or can not return null. Your editor and typechecker will tell you if you need to handle null after calling that function.

If you have a non-null returning function that you need to change so it can return null, then your typechecker will tell you all the places where you now need to handle the new null return.

It doesn't need to be a very large codebase before this becomes a very useful tool to help when refactoring.