Add SyntacticEntity, an interface shared by AstNode and Token.

pkg/analyzer/lib/dart/ast/ast.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.
 
 /**
  * Defines the AST model. The AST (Abstract Syntax Tree) model describes the
  * syntactic (as opposed to semantic) structure of Dart code. The semantic
  * structure of the code is modeled by the
  * [element model](../element/element.dart).
  *
@@ skipping 492 matching lines @@
    * the left-hand-side to the given [element].
    */
   void set staticElement(MethodElement element);
 }
 
 /**
  * A node in the AST structure for a Dart program.
  *
  * Clients may not extend, implement or mix-in this class.
  */
-abstract class AstNode {
+abstract class AstNode implements SyntacticEntity {
   /**
    * An empty list of AST nodes.
    */
   static const List<AstNode> EMPTY_LIST = const <AstNode>[];
 
   /**
    * A comparator that can be used to sort AST nodes in lexical order. In other
    * words, `compare` will return a negative value if the offset of the first
    * node is less than the offset of the second node, zero (0) if the nodes have
    * the same offset, and a positive value if the offset of the first node is
    * greater than the offset of the second node.
    */
   static Comparator<AstNode> LEXICAL_ORDER =
       (AstNode first, AstNode second) => first.offset - second.offset;
 
   /**
    * Return the first token included in this node's source range.
    */
   Token get beginToken;
 
   /**
    * Return an iterator that can be used to iterate through all the entities
    * (either AST nodes or tokens) that make up the contents of this node,
    * including doc comments but excluding other comments.
    */
-  Iterable /* AstNode | Token */ get childEntities;
+  Iterable<SyntacticEntity> get childEntities;
 
   /**
    * Return the offset of the character immediately following the last character
    * of this node's source range. This is equivalent to
    * `node.getOffset() + node.getLength()`. For a compilation unit this will be
    * equal to the length of the unit's source. For synthetic nodes this will be
    * equivalent to the node's offset (because the length is zero (0) by
    * definition).
    */
+  @override
   int get end;
 
   /**
    * Return the last token included in this node's source range.
    */
   Token get endToken;
 
   /**
    * Return `true` if this node is a synthetic node. A synthetic node is a node
    * that was introduced by the parser in order to recover from an error in the
    * code. Synthetic nodes always have a length of zero (`0`).
    */
   bool get isSynthetic;
 
-  /**
-   * Return the number of characters in the node's source range.
-   */
+  @override
   int get length;
 
-  /**
-   * Return the offset from the beginning of the file to the first character in
-   * the node's source range.
-   */
+  @override
   int get offset;
 
   /**
    * Return this node's parent node, or `null` if this node is the root of an
    * AST structure.
    *
    * Note that the relationship between an AST node and its parent node may
    * change over the lifetime of a node.
    */
   AstNode get parent;
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   /**
    * Return the 'yield' keyword.
    */
   Token get yieldKeyword;
 
   /**
    * Return the 'yield' keyword to the given [token].
    */
   void set yieldKeyword(Token token);
 }