> Good, now we just need the ability to declare function parameters and return values non-nullable

But that's already possible, just declare arguments and return values as values instead of references. I mean you'll get the zero value if you don't use those functions properly, but those won't cause nil pointer dereference errors.

I mean, it's a tradeoff between performance and developer competency. To be harsh, I think nil pointer dereferences are developer error, not a flaw in the language.