{"ast_node_type":"other","tokens":[{"end":86,"kind":"keyword","start":0,"text":"//"}]}
                                // we need to find a more accurate span to end up with
                                // but `lt.span` only points at `'_`, so to suggest `-> Option<()>`
                                // fn g<'a>(mut x: impl Iterator<Item = &'_ ()>) -> Option<()>