{"ast_node_type":"variable","tokens":[{"end":46,"kind":"keyword","start":0,"text":"let"}]}
        let sm = self.r.tcx.sess.source_map();
        // ahead for the next text to see if `span` is followed by a `{`.
        if let Some(followed_brace_span) = sm.span_look_ahead(span, "{", Some(50)) {