It's an interesting idea. My only issue is that if you decide to call an existing function from your "neverthrows" function, there's no way to tell whether it's

It's an interesting idea. My only issue is that if you decide to call an existing function from your "neverthrows" function, there's no way to tell whether it's okay to call that function without actually running the compiler. And if you want to take that opportunity to do an audit of null correctness, you're at the mercy of the compiler's error message to hopefully tell you where the offending code is.