What about the fact that the assert causes a panic that crashes the program? Is there not a better alternative of doing your bounds checking as a first class aspect of the function and returning an error? If someone is deep into a session with your application and the cursor somehow drifts into an unknown state (which could be corrected with the “home” key or something else), for example, getting too crazy with assertions seems like a much worse result. (E.g. “assert!(is_on_screen())”)
You never use assert for conditions that are logical (error) conditions that the program is expected to handle.
For example your browser handling 404 HTML error is only an error from the user perspective. From the software correctness perspective there's no error, there's just a logical condition that needs to be reasoned about.
Compare this to a BUG which is a mistake (an error made by the programmer), for example violating some invariant, going out of bounds on an array etc.
This is a scenario where the program is violating its own logic and constraints and as a result is no longer in a valid state. Assert is a tool to catch BUGS made by the programmer and nothing else.
