fasta tokens implement analyzer token API

pkg/front_end/lib/src/scanner/token.dart

 // Copyright (c) 2016, 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.
 
 /**
  * Defines the tokens that are produced by the scanner, used by the parser, and
  * referenced from the [AST structure](ast.dart).
  */
 import 'dart:collection';
 
@@ skipping 582 matching lines @@
       token = token.next;
     }
   }
 
   @override
   Token copy() => new StringTokenWithComment(
       type, lexeme, offset, copyComments(precedingComments));
 }
 
 /**
+ * A synthetic keyword token.
+ */
+class SyntheticKeywordToken extends KeywordToken {
+  /**
+   * Initialize a newly created token to represent the given [keyword] at the
+   * given [offset].
+   */
+  SyntheticKeywordToken(Keyword keyword, int offset) : super(keyword, offset);
+
+  @override
+  int get length => 0;
+
+  @override
+  Token copy() => new SyntheticKeywordToken(keyword, offset);
+}
+
+/**
+ * A token whose value is independent of it's type.
+ */
+class SyntheticStringToken extends StringToken {
+  /**
+   * Initialize a newly created token to represent a token of the given [type]
+   * with the given [value] at the given [offset].
+   */
+  SyntheticStringToken(TokenType type, String value, int offset)
+      : super(type, value, offset);
+
+  @override
+  bool get isSynthetic => true;
+}
+
+/**
  * A token that was scanned from the input. Each token knows which tokens
  * precede and follow it, acting as a link in a doubly linked list of tokens.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 abstract class Token implements SyntacticEntity {
   /**
    * Initialize a newly created token to have the given [type] and [offset].
    */
   factory Token(TokenType type, int offset) = SimpleToken;
@@ skipping 543 matching lines @@
 
   void set precedingComments(CommentToken comment) {
     _precedingComment = comment;
     _setCommentParent(_precedingComment);
   }
 
   @override
   Token copy() =>
       new TokenWithComment(type, offset, copyComments(precedingComments));
 }