{"ast_node_type":"other","tokens":[{"end":49,"kind":"keyword","start":0,"text":"builder.open(delimiter.kind,"}]}
    builder.open(delimiter.kind, delimiter.open);
    let delimiter = delimiter.unwrap_or_else(|| tt::Delimiter::invisible_spanned(ctx.call_site));
    let result = expand_subtree(ctx, template, builder, marker);