[msbarnett]

> If you refactor a method to return a different (incompatible) type, you'll have to touch all affected code parts, possibly revealing uninteded consequences of the change.

If you can refactor your code such that you change the return type of a method such that it returns an object of a different type, which nonetheless implements all of the methods used by clients of your type that accept and return types which in turn accept and return types that line up with the expectations of their clients, etc, etc, without having to look at or touch any of those clients, and end up with something that happily compiles but gives an unexpected result, you need to have a long and hard look at how you're using the language's type system, and why it isn't encoding your assumptions in a sane way.

Your code shouldn't be compatible with a different type unless it makes sense for your code to be compatible with that type. That's what the type system is for.

[blauditore]

One single common method is enough if that's the only one used in said context.

Sure, different types shouldn't use the same method name for different functionality, but it happens. And when such a scenario happens, I imagine it will be quite nasty to debug.