It depends on what contract you have with the function caller. For example, assertions/panics are fine for reporting programmer's errors (i.e. situations that

It depends on what contract you have with the function caller. For example, assertions/panics are fine for reporting programmer's errors (i.e. situations that happen due to a bug in the software, not due to runtime environment). There's no point to force programmers to write error-handling branches that will never be used in a properly written program. This is the reason why methods like `split_at` just panic if you give them a wrong index. You're not supposed to make invalid indices in the first place.