Stop copying tokens in incremental scanner

pkg/analyzer/lib/src/generated/scanner.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 engine.scanner;
 
 import 'dart:collection';
 
 import 'error.dart';
 import 'instrumentation.dart';
@@ skipping 387 matching lines @@
    * can be used as identifiers.
    */
   final bool isPseudoKeyword;
 
   /**
    * Initialize a newly created keyword to have the given [name] and [syntax].
    * The keyword is a pseudo-keyword if the [isPseudoKeyword] flag is `true`.
    */
   const Keyword(this.name, this.syntax, [this.isPseudoKeyword = false]);
 
+  @override
+  String toString() => name;
+
   /**
    * Create a table mapping the lexemes of keywords to the corresponding keyword
    * and return the table that was created.
    */
   static Map<String, Keyword> _createKeywordMap() {
     LinkedHashMap<String, Keyword> result =
         new LinkedHashMap<String, Keyword>();
     for (Keyword keyword in values) {
       result[keyword.syntax] = keyword;
     }
@@ skipping 1764 matching lines @@
    */
   final String name;
 
   /**
    * The precedence of tokens of this class, or `0` if the such tokens do not
    * represent an operator.
    */
   final int precedence;
 
   const TokenClass(this.name, [this.precedence = 0]);
+
+  @override
+  String toString() => name;
 }
 
 /**
  * The enumeration `TokenType` defines the types of tokens that can be returned
  * by the scanner.
  */
 class TokenType {
   /**
    * The type of the token that marks the end of the input.
    */
@@ skipping 315 matching lines @@
           identical(lexeme, "<") ||
           identical(lexeme, "&") ||
           identical(lexeme, "^") ||
           identical(lexeme, "|");
 
   /**
    * Return the precedence of the token, or `0` if the token does not represent
    * an operator.
    */
   int get precedence => _tokenClass.precedence;
+
+  @override
+  String toString() => name;
 }
 
 class TokenType_EOF extends TokenType {
   const TokenType_EOF(String name) : super(name, TokenClass.NO_CLASS, "");
 
   @override
   String toString() => "-eof-";
 }
 
 /**
@@ skipping 12 matching lines @@
    */
   TokenWithComment(TokenType type, int offset, this._precedingComment)
       : super(type, offset);
 
   @override
   Token get precedingComments => _precedingComment;
 
   @override
   Token copy() => new TokenWithComment(type, offset, _precedingComment);
 }