Also, lifetime annotations are not required on the overwhelming majority of functions. If you have, say, fn substr(text: &str, start: usize, length: usize) -

Also, lifetime annotations are not required on the overwhelming majority of functions. If you have, say, fn substr(text: &str, start: usize, length: usize) -> &str; the compiler will infer automatically that the return value inherits the lifetime of the `text` argument. I don't find that line up there particularly busy.