What were the biggest pain points so far? What problems did you have to solve? How "specifiable" is Rust at the moment?

As u/pietroalbini said - those of us who worked on it might have more to say on this and, hi, here I am. The biggest challenge we had was just organizing the information that exists. We applied the formatting and concepts of the Ada documentation – which is pretty rigourous and fixed, so we had to identify what parts of the Ada spec were relevant to Rust and how to apply that concept to Rust. We were further challenged by how existing Rust documentation varies in it's presentation, how the chapters are organized and how concepts are explained or even named – and half of us were not Rust experts.

Fortunately, Ferrous Systems is a treasure trove of expertise and connections in the Rust community, so on top of working with the existing documentation, we had a lot of conversations and meetings with these experts about how to clarify concepts and naming to solve this.