They say this in almost every paragraph! For example, five of the first seven paragraphs:
> The first is to express more of the requirements using Rust's type system in order to catch more mistakes at compile time.
> Almeida showed an example of how the Rust type system can eliminate certain kinds of errors.
> … it was exactly that kind of discussion/argument that could be avoided by encapsulating the rules into the Rust types and abstractions; the compiler will know the right thing to do.
> … All of that is enforced through the type system.
> the whole idea is to determine what the constraints are from Viro and other filesystem developers, then to create types and abstractions that can enforce them.
More explicitly:
> The object lifecycles are being encoded into the Rust API, but there is no equivalent of that in C; if someone changes the lifecycle of the object on one side, the other will have bugs.
> As those changes occur, "we will find out whether or not this concept of encoding huge amounts of semantics into the type system is a good thing or a bad thing".
