Obviously it isn’t totally impossible, but it becomes challenging to know if it’s required or not. It’s hardest when it isn’t just throwing an error but instead

Obviously it isn’t totally impossible, but it becomes challenging to know if it’s required or not. It’s hardest when it isn’t just throwing an error but instead defaulting to something only half-sensible. For example replacing a negative number with 0 or overflowing rather than panicking. When it comes to assumptions about the input, ideally model them in the type system. If you can’t, explicit checks and throws are OK in my book. But don’t check-and-hide any errors. You’ll be hard pressed to debug the issues they’ll cause down the road, since it will usually be far from the implementation that you see the impact.