{"ast_node_type":"other","tokens":[{"end":95,"kind":"keyword","start":0,"text":"//"}]}
        // Given the parsed tree, if there is a metavar and we are expecting matchers, actually
    while let Some(tree) = iter.next() {
        // parse out the matcher (i.e., in `$id:ident` this would parse the `:` and `ident`).