This is fundamentally impossible to implement in anything anywhere near as powerful as JavaScript, because of side-channel attacks <https://en.wikipedia.org/wik

This is fundamentally impossible to implement in anything anywhere near as powerful as JavaScript, because of side-channel attacks <https://en.wikipedia.org/wiki/Side-channel_attack https://en.wikipedia.org/wiki/Side-channel_attack>. (In practice, you wouldn’t even get that far, because universal taint checking would certainly be deemed unacceptably expensive. You can get away with such stuff for individual types, like in Trusted Types kinda, but imposing it on the entire language is not going to fly.)