cleanup fasta token classes

pkg/analyzer/lib/src/dart/ast/utilities.dart

 // Copyright (c) 2014, 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 analyzer.src.dart.ast.utilities;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_ast_factory.dart';
@@ skipping 976 matching lines @@
   void _cloneTokens(Token token, int stopAfter) {
     if (token == null) {
       return;
     }
     Token nonComment(Token token) {
       return token is CommentToken ? token.parent : token;
     }
 
     token = nonComment(token);
     if (_lastCloned == null) {
-      _lastCloned = new Token(TokenType.EOF, -1);
-      _lastCloned.setNext(_lastCloned);
+      _lastCloned = new Token.eof(-1);
     }
     while (token != null) {
       Token clone = token.copy();
       {
         CommentToken c1 = token.precedingComments;
         CommentToken c2 = clone.precedingComments;
         while (c1 != null && c2 != null) {
           _clonedTokens[c1] = c2;
           if (c1 is DocumentationCommentToken &&
               c2 is DocumentationCommentToken) {
@@ skipping 8372 matching lines @@
     if (node.star != null) {
       sink.write("yield* ");
     } else {
       sink.write("yield ");
     }
     safelyVisitNode(node.expression);
     sink.write(";");
     return null;
   }
 }