{"ast_node_type":"variable","tokens":[{"end":73,"kind":"keyword","start":0,"text":"let"}]}
    let location = tcx.sess.source_map().span_to_embeddable_string(span);
fn comment(tcx: TyCtxt<'_>, SourceInfo { span, scope }: SourceInfo) -> String {
    format!("scope {} at {}", scope.index(), location,)