flatten token hierarchy

pkg/front_end/lib/src/fasta/scanner/token.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.
 
 library fasta.scanner.token;
 
 import '../../scanner/token.dart' as analyzer;
 import '../../scanner/token.dart' show Token, TokenType;
 
 import 'token_constants.dart' show IDENTIFIER_TOKEN;
 
 import 'string_canonicalizer.dart';
 
 /**
  * A String-valued token. Represents identifiers, string literals,
  * number literals, comments, and error tokens, using the corresponding
  * precedence info.
  */
-class StringToken extends analyzer.TokenWithComment
-    implements analyzer.StringTokenWithComment {
+class StringToken extends analyzer.SimpleToken implements analyzer.StringToken {
   /**
    * The length threshold above which substring tokens are computed lazily.
    *
    * For string tokens that are substrings of the program source, the actual
    * substring extraction is performed lazily. This is beneficial because
    * not all scanned code are actually used. For unused parts, the substrings
    * are never computed and allocated.
    */
   static const int LAZY_THRESHOLD = 4;
 
@@ skipping 105 matching lines @@
   @override
   int get length => 0;
 
   @override
   Token copy() => new SyntheticStringToken(
       type, valueOrLazySubstring, offset, copyComments(precedingComments));
 }
 
 class CommentToken extends StringToken implements analyzer.CommentToken {
   @override
-  analyzer.TokenWithComment parent;
+  analyzer.SimpleToken parent;
 
   /**
    * Creates a lazy comment token. If [canonicalize] is true, the string
    * is canonicalized before the token is created.
    */
   CommentToken.fromSubstring(
       TokenType type, String data, int start, int end, int charOffset,
       {bool canonicalize: false})
       : super.fromSubstring(type, data, start, end, charOffset,
             canonicalize: canonicalize);
@@ skipping 155 matching lines @@
       identical(value, "<=") ||
       identical(value, "<") ||
       identical(value, "&") ||
       identical(value, "^") ||
       identical(value, "|");
 }
 
 bool isTernaryOperator(String value) => identical(value, "[]=");
 
 bool isMinusOperator(String value) => identical(value, "-");