IMHO it should be a compiler error. This is just so loose... a wheel fell off.

A wheel is generous. This seems more like inviting the computing equivalent of spilling twenty thousand tons of crude into the sea, which then promptly catch fire.

Eh it’s about the same level of footgun you might see in C99. It’s not great but you’re being hyperbolic if you ask me.

I agree that most scenarios are not going to be so perilous. However, GOTO FAIL[1] would fit your C99 foot gun description neatly, with repercussions that would approach the peril of my metaphor within at least an order of magnitude.

https://en.wikipedia.org/wiki/Unreachable_code#goto_fail_bug