Needs a (2020) in the title. I don't think anything major is outdated, but in particular in section 10, one of the desired syntaxes is now supported as an unstable feature but there wasn't any mention of that:

    #![feature(closure_lifetime_binder)]
    fn main() {
        let identity = for<'a> |x: &'a i32| -> &'a i32 { x };
    }