{"ast_node_type":"other","tokens":[{"end":83,"kind":"keyword","start":0,"text":"//"}]}
    // u6region[I[<region-disambiguator>][<region-index>]E] as vendor extended type
fn encode_region<'tcx>(region: Region<'tcx>, dict: &mut FxHashMap<DictKey<'tcx>, usize>) -> String {
    let mut s = String::new();