[jfkebwjsbx]

> there is no room in the type system to return an error

There is: you panic, like in the array case.

That would have been much robust (at the cost of performance).

[kibwen]

For consistency you would also expect `257u32 as u8` to panic (which it doesn't, and never has); the `as` operator has always been about fast-and-lossy conversions, with the standard library ideally providing methods for more principled conversions.