Doesn't this depend on strict lazy evaluation? I could imagine if the implementation underneath changed (possibly to take advantage of parallel execution), if any segment had side effects, it would be horrible.
I can't think of a case where lazy evaluation would be required, only that the semantics of the && and || operators not change.
It's defined as part of the language that && will not evaluate the right hand side unless the left hand side is truthy. A lot more than using this stuff as branching would break if some implementation arbitrarily decided to not follow that anymore.
