What would be a compile time error? The compiler rejecting unwrap? And then you fix that by bubbling the error case up, which fixes the compiler error and leaves you with a runtime error again. But one that's less ergonomic.

You can't force a config file loaded at run time to be correct at compile time. You can only decide what you're going to do about the failure.

The point they are - trying, apparently - making is that if you had a flag or an annotation that you could make to a function that you do not want that function to be built on top of anything that can 'unwrap' that you can rule out some of these cases of unexpected side effects.