Author no doubt understands programming, and the ins and outs of Rust, but has a harder time conveying his ideas in written English.

For one italics are used so much to the point of being annoying after the first 3(!) paragraphs. When something is written in italics, the reader puts more emphasis on the pronunciation of the word, lengthening the amount of time they read it for. Do this enough times and the writer starts coming across as sarcastic, and even seems to be mocking the very language constructs he is writing an advanced tutorial about!

No doubt this was not intended, and I would urge the author to take a few days off before coming back and re-reading their work, so they can try and see it from the perspective of an outsider.