[kd5bjo]

> Panicing is not in line with how `as` casts are supposed to act. (e.g. `u32value as u8` does not panic but just takes the "lower" one byte.)

So, instead of this being traditional UB, it was a combination of two separate issues:

- Rustc erroneously emitting code that exercised an LLVM UB case, and

- Imprecise Rust documentation around the exact behavior of float -> int ‘as’ casts

[pwdisswordfish2]

That phrasing seemingly implies that there was a generally-agreed intended behaviour for that case that was unfortunately neither documented nor actually exhibited. But that was not the case. The overflow behaviour of float-to-int casts was undefined, full stop. There was some consensus as to what such casts should not do, but no agreement on what the actual behaviour should be. Eventually, the discussion settled on defining casting overflow to saturate, and the implementation was altered to match.