[NoTeslaThrow]

> It means that anything strange that happens next isn't a language bug.

This is even more vague. The language is getting blamed regardless. This makes no sense.

[dwattttt]

No: the language defined that e.g. a NonZeroU8 can't contain 0, and the only way it could is via illegal means. You don't need a formal proof to describe that.

To try to characterise what any compiler, hypothetical or not, does if you nonetheless produce one (again, via means that aren't valid) isn't meaningful.