Some notes on Rust, mutable aliasing and formal verification

Recently Boats wrote a blog post about Rust, mutable aliasing, and the sad story of local reasoning over many decades of computer science. I recommend that post and agree with its main points! Go read it! But I also thought I'd add a little more detail to an area it's less acutely focused on: formal methods / formal verification.

TL;DR: support for local reasoning is a big factor in the ability to do automated reasoning about programs. Formal verification involves such reasoning. Rust supports it better than many other imperative systems languages -- even some impure functional ones! -- and formal verification people are excited and building tools presently. This is not purely by accident, and is worth understanding as part of what makes Rust valuable beyond "it doesn't need a GC".

The rest of this post is just unpacking and giving details of one or more of the above assertions, which I'll try to address in order of plausible interestingness to the present, but I will also throw in some history because I kinda can't help myself.

The author is Graydon Hoare, the "founder" of Rust and technical lead until around 2013.