{"ast_node_type":"function","tokens":[{"end":110,"kind":"keyword","start":0,"text":"fn"}]}
        fn visit_span<$($lt,)? V: $Visitor$(<$lt>)?>(vis: &mut V, span: &$($lt)? $($mut)? Span) -> V::Result {
        )?
            $(${ignore($mut)} vis.visit_span(span))?;