{"ast_node_type":"other","tokens":[{"end":93,"kind":"keyword","start":0,"text":"//"}]}
        // parse out the matcher (i.e., in `$id:ident` this would parse the `:` and `ident`).
        // Given the parsed tree, if there is a metavar and we are expecting matchers, actually
        let tree = parse_tree(tree, &mut iter, part, sess, node_id, features, edition);