The other ambiguity that I questioned right away was whether the language itself guarantees the order or evaluation or if it's compiler dependent? If I switch between Chrome & Firefox would I get different results?

Also, by using non const expressions in case statements you lose the ability to have a large number of cases get mapped into a jump table. Although, I don't even know if more modern languages even support this optimization anymore since I think supporting non const case expressions is becoming the norm in a lot of languages.