Yes, those sorts of loopholes would need to be closed. I was imagining a subset of the language, but there might need to be some breaking changes to cover cases

Yes, those sorts of loopholes would need to be closed. I was imagining a subset of the language, but there might need to be some breaking changes to cover cases like that. Maybe it would end up being so different that it would be an entirely different language? I don't know! But it's hard for me to accept that non-soundness in TS is necessary for TS itself rather than just an unfortunate consequence of the JS language and library that it has to build on top of.