Template parser

utils/template/tokenkind.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// TODO(terry): Need to be consistent with tokens either they're ASCII tokens
+//              e.g., ASTERISK or they're CSS e.g., PSEUDO, COMBINATOR_*.
+class TokenKind {
+  // Common shared tokens used in TokenizerBase.
+  static final int UNUSED = 0;                  // Unused place holder...
+  static final int END_OF_FILE = 1;
+  static final int LPAREN = 2;                  // (
+  static final int RPAREN = 3;                  // )
+  static final int LBRACK = 4;                  // [
+  static final int RBRACK = 5;                  // ]
+  static final int LBRACE = 6;                  // {
+  static final int RBRACE = 7;                  // }
+  static final int DOT = 8;                     // .
+  static final int SEMICOLON = 9;               // ;
+  static final int SPACE = 10;                  // space character
+  static final int TAB = 11;                    // \t
+  static final int NEWLINE = 12;                // \n
+  static final int RETURN = 13;                 // \r
+  static final int COMMA = 14;                  // ,
+
+  // Unique tokens.
+  static final int LESS_THAN = 15;              // <
+  static final int GREATER_THAN = 16;           // >
+  static final int SLASH = 17;                  // /
+  static final int DOLLAR = 18;                 // $
+  static final int HASH = 19;                   // #
+  static final int MINUS = 20;                  // -
+  static final int EQUAL = 21;                  // =
+  static final int DOUBLE_QUOTE = 22;           // "
+  static final int SINGLE_QUOTE = 23;           // '
+
+  // WARNING: END_TOKENS must be 1 greater than the last token above (last
+  //          character in our list).  Also add to kindToString function and the
+  //          constructor for TokenKind.
+
+  static final int END_TOKENS = 24;             // Marker for last token in list
+
+  // Synthesized tokens:
+
+  static final int END_NO_SCOPE_TAG = 50;       // />
+  static final int START_EXPRESSION = 51;       // ${
+  static final int START_COMMAND = 52;          // ${#
+  static final int END_COMMAND = 53;            // ${/
+  static final int EACH_COMMAND = 53;           // ${#each list}
+  static final int WITH_COMMAND = 54;           // ${#with object}
+  static final int IF_COMMAND = 55;             // ${#if (expression)}
+  static final int ELSE_COMMAND = 56;           // ${#else}
+
+  /** [TokenKind] representing integer tokens. */
+  static final int INTEGER = 60;                // TODO(terry): must match base
+
+  /** [TokenKind] representing hex integer tokens. */
+//  static final int HEX_INTEGER = 61;          // TODO(terry): must match base
+
+  /** [TokenKind] representing double tokens. */
+  static final int DOUBLE = 62;                 // TODO(terry): must match base
+
+  /** [TokenKind] representing whitespace tokens. */
+  static final int WHITESPACE = 63;             // TODO(terry): must match base
+
+  /** [TokenKind] representing comment tokens. */
+  static final int COMMENT = 64;                // TODO(terry): must match base
+
+  /** [TokenKind] representing error tokens. */
+  static final int ERROR = 65;                  // TODO(terry): must match base
+
+  /** [TokenKind] representing incomplete string tokens. */
+  static final int INCOMPLETE_STRING = 66;      // TODO(terry): must match base
+
+  /** [TokenKind] representing incomplete comment tokens. */
+  static final int INCOMPLETE_COMMENT = 67;     // TODO(terry): must match base
+
+  // Synthesized Tokens (no character associated with TOKEN).
+  // TODO(terry): Possible common names used by both Dart and CSS tokenizers.
+  static final int ATTR_VALUE = 500;
+  static final int NUMBER = 502;
+  static final int HEX_NUMBER = 503;
+  static final int HTML_COMMENT = 504;          // <!--
+  static final int IDENTIFIER = 511;
+  static final int STRING = 512;
+  static final int STRING_PART = 513;
+
+  static final int TEMPLATE_KEYWORD = 595;      // template keyword
+
+  // Elements
+  /* START_HTML_ELEMENT is first valid element tag name
+   * END_HTML_ELEMENT is the last valid element tag name
+   *
+   */
+  static final int START_HTML_ELEMENT = 600;      // First valid tag name.
+  static final int A_ELEMENT = 600;
+  static final int ABBR_ELEMENT = 601;
+  static final int ACRONYM_ELEMENT = 602;
+  static final int ADDRESS_ELEMENT = 603;
+  static final int APPLET_ELEMENT = 604;
+  static final int AREA_ELEMENT = 605;
+  static final int B_ELEMENT = 606;
+  static final int BASE_ELEMENT = 607;
+  static final int BASEFONT_ELEMENT = 608;
+  static final int BDO_ELEMENT = 609;
+  static final int BIG_ELEMENT = 610;
+  static final int BLOCKQUOTE_ELEMENT = 611;
+  static final int BODY_ELEMENT = 612;
+  static final int BR_ELEMENT = 613;
+  static final int BUTTON_ELEMENT = 614;
+  static final int CAPTION_ELEMENT = 615;
+  static final int CENTER_ELEMENT = 616;
+  static final int CITE_ELEMENT = 617;
+  static final int CODE_ELEMENT = 618;
+  static final int COL_ELEMENT = 619;
+  static final int COLGROUP_ELEMENT = 620;
+  static final int DD_ELEMENT = 621;
+  static final int DEL_ELEMENT = 622;
+  static final int DFN_ELEMENT = 623;
+  static final int DIR_ELEMENT = 624;
+  static final int DIV_ELEMENT = 625;
+  static final int DL_ELEMENT = 626;
+  static final int DT_ELEMENT = 627;
+  static final int EM_ELEMENT = 628;
+  static final int FIELDSET_ELEMENT = 629;
+  static final int FONT_ELEMENT = 630;
+  static final int FORM_ELEMENT = 631;
+  static final int FRAME_ELEMENT = 632;
+  static final int FRAMESET_ELEMENT = 633;
+  static final int H1_ELEMENT = 634;
+  static final int H2_ELEMENT = 635;
+  static final int H3_ELEMENT = 636;
+  static final int H4_ELEMENT = 637;
+  static final int H5_ELEMENT = 638;
+  static final int H6_ELEMENT = 639;
+  static final int HEAD_ELEMENT = 640;
+  static final int HR_ELEMENT = 641;
+  static final int HTML_ELEMENT = 642;
+  static final int I_ELEMENT = 643;
+  static final int IFRAME_ELEMENT = 644;
+  static final int IMG_ELEMENT = 645;
+  static final int INPUT_ELEMENT = 646;
+  static final int INS_ELEMENT = 647;
+  static final int ISINDEX_ELEMENT = 648;
+  static final int KBD_ELEMENT = 649;
+  static final int LABEL_ELEMENT = 650;
+  static final int LEGEND_ELEMENT = 651;
+  static final int LI_ELEMENT = 652;
+  static final int LINK_ELEMENT = 653;
+  static final int MAP_ELEMENT = 654;
+  static final int MENU_ELEMENT = 645;
+  static final int META_ELEMENT = 656;
+  static final int NOFRAMES_ELEMENT = 657;
+  static final int NOSCRIPT_ELEMENT = 658;
+  static final int OBJECT_ELEMENT = 659;
+  static final int OL_ELEMENT = 660;
+  static final int OPTGROUP_ELEMENT = 661;
+  static final int OPTION_ELEMENT = 662;
+  static final int P_ELEMENT = 663;
+  static final int PARAM_ELEMENT = 664;
+  static final int PRE_ELEMENT = 665;
+  static final int Q_ELEMENT = 666;
+  static final int S_ELEMENT = 667;
+  static final int SAMP_ELEMENT = 668;
+  static final int SCRIPT_ELEMENT = 669;
+  static final int SELECT_ELEMENT = 670;
+  static final int SMALL_ELEMENT = 671;
+  static final int SPAN_ELEMENT = 672;
+  static final int STRIKE_ELEMENT = 673;
+  static final int STRONG_ELEMENT = 674;
+  static final int STYLE_ELEMENT = 675;
+  static final int SUB_ELEMENT = 676;
+  static final int SUP_ELEMENT = 677;
+  static final int TABLE_ELEMENT = 678;
+  static final int TBODY_ELEMENT = 679;
+  static final int TD_ELEMENT = 680;
+  static final int TEXTAREA_ELEMENT = 681;
+  static final int TFOOT_ELEMENT = 682;
+  static final int TH_ELEMENT = 683;
+  static final int THEAD_ELEMENT = 684;
+  static final int TITLE_ELEMENT = 685;
+  static final int TR_ELEMENT = 686;
+  static final int TT_ELEMENT = 687;
+  static final int U_ELEMENT = 688;
+  static final int UL_ELEMENT = 689;
+  static final int VAR_ELEMENT = 690;
+  static final int END_HTML_ELEMENT = VAR_ELEMENT;    // Last valid tag name.
+
+  static bool validTagName(int tokId) {
+    return tokId >= TokenKind.START_HTML_ELEMENT &&
+      tokId <= TokenKind.END_HTML_ELEMENT;
+  }
+
+  static final List<Map<int, String>> _KEYWORDS = const [
+    const {'type': TokenKind.TEMPLATE_KEYWORD, 'value' : 'template'},
+  ];
+
+  static final List<Map<int, String>> _ELEMENTS = const [
+    const {'type': TokenKind.A_ELEMENT, 'value' : 'a'},
+    const {'type': TokenKind.ABBR_ELEMENT, 'value' : 'abbr'},
+    const {'type': TokenKind.ACRONYM_ELEMENT, 'value' : 'acronym'},
+    const {'type': TokenKind.ADDRESS_ELEMENT, 'value' : 'address'},
+    const {'type': TokenKind.APPLET_ELEMENT, 'value' : 'applet'},
+    const {'type': TokenKind.AREA_ELEMENT, 'value' : 'area'},
+    const {'type': TokenKind.B_ELEMENT, 'value' : 'b'},
+    const {'type': TokenKind.BASE_ELEMENT, 'value' : 'base'},
+    const {'type': TokenKind.BASEFONT_ELEMENT, 'value' : 'basefont'},
+    const {'type': TokenKind.BDO_ELEMENT, 'value' : 'bdo'},
+    const {'type': TokenKind.BIG_ELEMENT, 'value' : 'big'},
+    const {'type': TokenKind.BLOCKQUOTE_ELEMENT, 'value' : 'blockquote'},
+    const {'type': TokenKind.BODY_ELEMENT, 'value' : 'body'},
+    const {'type': TokenKind.BR_ELEMENT, 'value' : 'br'},
+    const {'type': TokenKind.BUTTON_ELEMENT, 'value' : 'button'},
+    const {'type': TokenKind.CAPTION_ELEMENT, 'value' : 'caption'},
+    const {'type': TokenKind.CENTER_ELEMENT, 'value' : 'center'},
+    const {'type': TokenKind.CITE_ELEMENT, 'value' : 'cite'},
+    const {'type': TokenKind.CODE_ELEMENT, 'value' : 'code'},
+    const {'type': TokenKind.COL_ELEMENT, 'value' : 'col'},
+    const {'type': TokenKind.COLGROUP_ELEMENT, 'value' : 'colgroup'},
+    const {'type': TokenKind.DD_ELEMENT, 'value' : 'dd'},
+    const {'type': TokenKind.DEL_ELEMENT, 'value' : 'del'},
+    const {'type': TokenKind.DFN_ELEMENT, 'value' : 'dfn'},
+    const {'type': TokenKind.DIR_ELEMENT, 'value' : 'dir'},
+    const {'type': TokenKind.DIV_ELEMENT, 'value' : 'div'},
+    const {'type': TokenKind.DL_ELEMENT, 'value' : 'dl'},
+    const {'type': TokenKind.DT_ELEMENT, 'value' : 'dt'},
+    const {'type': TokenKind.EM_ELEMENT, 'value' : 'em'},
+    const {'type': TokenKind.FIELDSET_ELEMENT, 'value' : 'fieldset'},
+    const {'type': TokenKind.FONT_ELEMENT, 'value' : 'font'},
+    const {'type': TokenKind.FORM_ELEMENT, 'value' : 'form'},
+    const {'type': TokenKind.FRAME_ELEMENT, 'value' : 'frame'},
+    const {'type': TokenKind.FRAMESET_ELEMENT, 'value' : 'frameset'},
+    const {'type': TokenKind.H1_ELEMENT, 'value' : 'h1'},
+    const {'type': TokenKind.H2_ELEMENT, 'value' : 'h2'},
+    const {'type': TokenKind.H3_ELEMENT, 'value' : 'h3'},
+    const {'type': TokenKind.H4_ELEMENT, 'value' : 'h4'},
+    const {'type': TokenKind.H5_ELEMENT, 'value' : 'h5'},
+    const {'type': TokenKind.H6_ELEMENT, 'value' : 'h6'},
+    const {'type': TokenKind.HEAD_ELEMENT, 'value' : 'head'},
+    const {'type': TokenKind.HR_ELEMENT, 'value' : 'hr'},
+    const {'type': TokenKind.HTML_ELEMENT, 'value' : 'html'},
+    const {'type': TokenKind.I_ELEMENT, 'value' : 'i'},
+    const {'type': TokenKind.IFRAME_ELEMENT, 'value' : 'iframe'},
+    const {'type': TokenKind.IMG_ELEMENT, 'value' : 'img'},
+    const {'type': TokenKind.INPUT_ELEMENT, 'value' : 'input'},
+    const {'type': TokenKind.INS_ELEMENT, 'value' : 'ins'},
+    const {'type': TokenKind.ISINDEX_ELEMENT, 'value' : 'isindex'},
+    const {'type': TokenKind.KBD_ELEMENT, 'value' : 'kbd'},
+    const {'type': TokenKind.LABEL_ELEMENT, 'value' : 'label'},
+    const {'type': TokenKind.LEGEND_ELEMENT, 'value' : 'legend'},
+    const {'type': TokenKind.LI_ELEMENT, 'value' : 'li'},
+    const {'type': TokenKind.LINK_ELEMENT, 'value' : 'link'},
+    const {'type': TokenKind.MAP_ELEMENT, 'value' : 'map'},
+    const {'type': TokenKind.MENU_ELEMENT, 'value' : 'menu'},
+    const {'type': TokenKind.META_ELEMENT, 'value' : 'meta'},
+    const {'type': TokenKind.NOFRAMES_ELEMENT, 'value' : 'noframes'},
+    const {'type': TokenKind.NOSCRIPT_ELEMENT, 'value' : 'noscript'},
+    const {'type': TokenKind.OBJECT_ELEMENT, 'value' : 'object'},
+    const {'type': TokenKind.OL_ELEMENT, 'value' : 'ol'},
+    const {'type': TokenKind.OPTGROUP_ELEMENT, 'value' : 'optgroup'},
+    const {'type': TokenKind.OPTION_ELEMENT, 'value' : 'option'},
+    const {'type': TokenKind.P_ELEMENT, 'value' : 'p'},
+    const {'type': TokenKind.PARAM_ELEMENT, 'value' : 'param'},
+    const {'type': TokenKind.PRE_ELEMENT, 'value' : 'pre'},
+    const {'type': TokenKind.Q_ELEMENT, 'value' : 'q'},
+    const {'type': TokenKind.S_ELEMENT, 'value' : 's'},
+    const {'type': TokenKind.SAMP_ELEMENT, 'value' : 'samp'},
+    const {'type': TokenKind.SCRIPT_ELEMENT, 'value' : 'script'},
+    const {'type': TokenKind.SELECT_ELEMENT, 'value' : 'select'},
+    const {'type': TokenKind.SMALL_ELEMENT, 'value' : 'small'},
+    const {'type': TokenKind.SPAN_ELEMENT, 'value' : 'span'},
+    const {'type': TokenKind.STRIKE_ELEMENT, 'value' : 'strike'},
+    const {'type': TokenKind.STRONG_ELEMENT, 'value' : 'strong'},
+    const {'type': TokenKind.STYLE_ELEMENT, 'value' : 'style'},
+    const {'type': TokenKind.SUB_ELEMENT, 'value' : 'sub'},
+    const {'type': TokenKind.SUP_ELEMENT, 'value' : 'sup'},
+    const {'type': TokenKind.TABLE_ELEMENT, 'value' : 'table'},
+    const {'type': TokenKind.TBODY_ELEMENT, 'value' : 'tbody'},
+    const {'type': TokenKind.TD_ELEMENT, 'value' : 'td'},
+    const {'type': TokenKind.TEXTAREA_ELEMENT, 'value' : 'textarea'},
+    const {'type': TokenKind.TFOOT_ELEMENT, 'value' : 'tfoot'},
+    const {'type': TokenKind.TH_ELEMENT, 'value' : 'th'},
+    const {'type': TokenKind.THEAD_ELEMENT, 'value' : 'thead'},
+    const {'type': TokenKind.TITLE_ELEMENT, 'value' : 'title'},
+    const {'type': TokenKind.TR_ELEMENT, 'value' : 'tr'},
+    const {'type': TokenKind.TT_ELEMENT, 'value' : 'tt'},
+    const {'type': TokenKind.U_ELEMENT, 'value' : 'u'},
+    const {'type': TokenKind.UL_ELEMENT, 'value' : 'ul'},
+    const {'type': TokenKind.VAR_ELEMENT, 'value' : 'var'},
+  ];
+
+  // Some more constants:
+  static final int ASCII_UPPER_A = 65;    // ASCII value for uppercase A
+  static final int ASCII_UPPER_Z = 90;    // ASCII value for uppercase Z
+
+  List<int> tokens;
+
+  /*
+   * Return the token that matches the unit ident found.
+   */
+  static int matchList(var identList, String tokenField, String text,
+                       int offset, int length) {
+    for (final entry in identList) {
+      String ident = entry['value'];
+      if (length == ident.length) {
+        int idx = offset;
+        bool match = true;
+        for (int identIdx = 0; identIdx < ident.length; identIdx++) {
+          int identChar = ident.charCodeAt(identIdx);
+          int char = text.charCodeAt(idx++);
+          // Compare lowercase to lowercase then check if char is uppercase.
+          match = match && (char == identChar ||
+              ((char >= ASCII_UPPER_A && char <= ASCII_UPPER_Z) &&
+               (char + 32) == identChar));
+          if (!match) {
+            break;
+          }
+        }
+
+        if (match) {
+          // Completely matched; return the token for this unit.
+          return entry[tokenField];
+        }
+      }
+    }
+
+    return -1;  // Not a unit token.
+  }
+
+  /* Map _ELEMENTS type to the real name. */
+  static String elementsToName(int kind) {
+    for (final entry in TokenKind._ELEMENTS) {
+      if (kind == entry['type']) {
+        return entry['value'];
+      }
+    }
+  }
+
+  /*
+   * Return the token that matches the element ident found.
+   */
+  static int matchElements(String text, int offset, int length) {
+    return matchList(_ELEMENTS, 'type', text, offset, length);
+  }
+
+  static String tagNameFromTokenId(int tagTokenId) {
+    if (tagTokenId >= TokenKind.START_HTML_ELEMENT &&
+        tagTokenId <= TokenKind.END_HTML_ELEMENT) {
+      for (final tag in TokenKind._ELEMENTS) {
+        if (tag['type'] == tagTokenId) {
+          return tag['value'];
+        }
+      }
+    }
+  }
+
+  static int matchKeywords(String text, int offset, int length) {
+    return matchList(_KEYWORDS, 'type', text, offset, length);
+  }
+
+  static String kindToString(int kind) {
+    switch(kind) {
+      case TokenKind.UNUSED: return "ERROR";
+      case TokenKind.END_OF_FILE: return "end of file";
+      case TokenKind.LPAREN: return "(";
+      case TokenKind.RPAREN: return ")";
+      case TokenKind.LBRACK: return "[";
+      case TokenKind.RBRACK: return "]";
+      case TokenKind.LBRACE: return "{";
+      case TokenKind.RBRACE: return "}";
+      case TokenKind.DOT: return ".";
+      case TokenKind.SEMICOLON: return ";";
+      case TokenKind.SPACE: return " ";
+      case TokenKind.TAB: return "\t";
+      case TokenKind.NEWLINE: return "\n";
+      case TokenKind.RETURN: return "\r";
+      case TokenKind.COMMA: return ",";
+      case TokenKind.LESS_THAN: return "<";
+      case TokenKind.GREATER_THAN: return ">";
+      case TokenKind.SLASH: return "/";
+      case TokenKind.DOLLAR: return "\$";
+      case TokenKind.HASH: return "#";
+      case TokenKind.MINUS: return '-';
+      case TokenKind.EQUAL: return '=';
+      case TokenKind.DOUBLE_QUOTE: return '"';
+      case TokenKind.SINGLE_QUOTE: return "'";
+      case TokenKind.END_NO_SCOPE_TAG: return '/>';
+      case TokenKind.START_EXPRESSION: return '\${';
+      case TokenKind.START_COMMAND: return '\${#';
+      case TokenKind.END_COMMAND: return '\${/';
+      case TokenKind.EACH_COMMAND: return '\${#each list}';
+      case TokenKind.WITH_COMMAND: return '\${with object}';
+      case TokenKind.IF_COMMAND: return '\${#if (expression)}';
+      case TokenKind.ELSE_COMMAND: return '\${#end}';
+      case TokenKind.INTEGER: return 'integer';
+      case TokenKind.DOUBLE: return 'double';
+      case TokenKind.WHITESPACE: return 'whitespace';
+      case TokenKind.COMMENT: return 'comment';
+      case TokenKind.ERROR: return 'error';
+      case TokenKind.INCOMPLETE_STRING : return 'incomplete string';
+      case TokenKind.INCOMPLETE_COMMENT: return 'incomplete comment';
+      case TokenKind.ATTR_VALUE: return 'attribute value';
+      case TokenKind.NUMBER: return 'number';
+      case TokenKind.HEX_NUMBER: return 'hex number';
+      case TokenKind.HTML_COMMENT: return 'HTML comment <!-- -->';
+      case TokenKind.IDENTIFIER: return 'identifier';
+      case TokenKind.STRING: return 'string';
+      case TokenKind.STRING_PART: return 'string part';
+      case TokenKind.TEMPLATE_KEYWORD: return 'template';
+      default:
+        throw "Unknown TOKEN";
+    }
+  }
+
+  TokenKind() {
+    tokens = [];
+
+    // All tokens must be in TokenKind order.
+    tokens.add(-1);                 // TokenKind.UNUSED
+    tokens.add(0);                  // TokenKind.END_OF_FILE match base
+    tokens.add(TokenKind.kindToString(TokenKind.LPAREN).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.RPAREN).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.LBRACK).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.RBRACK).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.LBRACE).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.RBRACE).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.DOT).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.SEMICOLON).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.SPACE).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.TAB).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.NEWLINE).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.RETURN).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.COMMA).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.LESS_THAN).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.GREATER_THAN).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.SLASH).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.DOLLAR).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.HASH).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.MINUS).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.EQUAL).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.DOUBLE_QUOTE).charCodeAt(0));
+    tokens.add(TokenKind.kindToString(TokenKind.SINGLE_QUOTE).charCodeAt(0));
+
+    assert(tokens.length == TokenKind.END_TOKENS);
+  }
+
+  static bool isIdentifier(int kind) {
+    return kind == IDENTIFIER;
+  }
+}
+
+class NoElementMatchException implements Exception {
+  String _tagName;
+  NoElementMatchException(this._tagName);
+
+  String get name() => _tagName;
+}