[kbenson]

> Their "bang for the buck" is low, their potential for abuse is high, and adding them to an established language is even less appealing, as it creates a clear old/new code divide.

I'm not a Java programmer, but I agree wholeheartedly WRT addin a feature like this to an existing language with wide use. There's a world of difference between adding a feature that's obviously different than what came before and looks obviously different than adding one that changes functionality but looks identical to prior usage. If people learn a language and during that it's made clear that assignments can have arbitrary side effects, they'll expect that. If they learned the language and that wasn't possible, introducing it at some point is going to mean a lot of programmers have ways of thinking about how control flow works and what happens when you make assignments that is subtly (or greatly) wrong, but only sometimes.

As a programmers, what that can feel like is that the language is actively sabotaging your understanding of it. It's not fun.