{"ast_node_type":"variable","tokens":[{"end":63,"kind":"keyword","start":0,"text":"let"}]}
            let b_principal_def_id = data_b.principal_def_id();
                old_info.expect("unsized_info: missing old info for trait upcasting coercion");
            if data_a.principal_def_id() == b_principal_def_id || b_principal_def_id.is_none() {