That's a huge improvement. It means that you've told the type system what it needs to support you. If your function tells the type system you need a reference

That's a huge improvement. It means that you've told the type system what it needs to support you. If your function tells the type system you need a reference to a type, you get a reference to that type. There's no hidden timebomb in there where you might get something that supposedly is that type but can't be treated as that type. This lets you write your functions to accept nulls where appropriate, and require some form of unwrapping at the call site otherwise. It tells you when you've missed something and it lets you refactor without having to constantly repeat all of your checks, once you know something is valid the type system reflects that for you. In short if you have a T in rust, you know that it's not secretly a (not)T that is implicitly allowed anywhere a T can be.