I disagree with the "l33t features" assertion. From your comments regarding Rust in the past, you seem to have distaste for the judicious use of closure-based A

I disagree with the "l33t features" assertion. From your comments regarding Rust in the past, you seem to have distaste for the judicious use of closure-based APIs in Rust, and I would argue that closures make some of the borrow checker's warts easier to handle.