It's been a while since I started learning Rust, and have the advantage of learning new constructs as they are being implemented before they even hit stable, so I find it hard to put myself in your shoes. Could you give some examples of alien syntax whose functionality you couldn't extrapolate from other constructs? rust-analyzer does provide on-hover documentation for keywords and (some) sigils, but it isn't as discoverable as it could be and I can believe that there are documentation "bugs" of missing explanations for specific use-cases, even in The Book!
