{"ast_node_type":"function","tokens":[{"end":94,"kind":"keyword","start":0,"text":"//"}]}
                                // fn g<'a>(mut x: impl Iterator<Item = &'_ ()>) -> Option<()>
                                // we need to find a more accurate span to end up with
                                sugg = vec![(span.with_hi(mut_ty.ty.span.lo()), String::new())];