Nil Assert

The .(!nil) assertion converts a nilable pointer to a non-nil pointer, panicking if the value is nil. Use this when you're certain a value isn't nil but the compiler can't prove it.

This is similar to force-unwrapping in Swift or unwrap() in Rust. Use sparingly and prefer nil checks when possible.

Try it: Change findUser(1) to findUser(0) and see the panic.