I wish I could tell my compiler like "This argument will always be in this range in practice, so please optimize accordingly, but also blow up if you realize that I forgot to make sure that this is actually the case anywhere in the program"

@rq

Why doesn't checking if it's in the range at the beginning and blowing up if not do what you want?

@robryk@qoto.org String patterns. Let's say function f processes a string and expects certain patterns and length. I wrote it half a year ago. It cannot fail on valid input.

Now, I put f somewhere else, but I forgot to put code that validates it's valid input for f (because at the original calling site, the input was always valid, so I had nothing to check).

The alternative is that every calling site has to error check or I have an unhandled return value or, worse, I have to do multi-return in a language that only has one return

@rq What did you mean by blow up? I thought you meant safely crashing. If so, you can add the verification at the beginning of the function itself and crash there.