Parse field modifiers.

dart/frog/leg/tree/nodes.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.
 
 interface Visitor<R> {
   R visitBlock(Block node);
   R visitClassNode(ClassNode node);
   R visitConditional(Conditional node);
   R visitDoWhile(DoWhile node);
   R visitExpressionStatement(ExpressionStatement node);
@@ skipping 773 matching lines @@
     if (expression !== null) expression.accept(visitor);
   }
 
   Token getBeginToken() => beginToken;
 
   Token getEndToken() => beginToken.endGroup;
 }
 
 /** Representation of modifiers such as static, abstract, final, etc. */
 class Modifiers extends Node {
+  /* TODO(ahe): The following should be validated relating to modifiers:
+   * 1. The nodes must come in a certain order.
+   * 2. The keywords "var" and "final" may not be used at the same time.
+   * 3. The type of an element must be null if isVar() is true.
+   */
+
   final NodeList nodes;
   /** Bit pattern to easy check what modifiers are present. */
   final int flags;
 
   static final int FLAG_STATIC = 1;
   static final int FLAG_ABSTRACT = FLAG_STATIC << 1;
   static final int FLAG_FINAL = FLAG_ABSTRACT << 1;
   static final int FLAG_VAR = FLAG_FINAL << 1;
   static final int FLAG_CONST = FLAG_VAR << 1;
 
@@ skipping 86 matching lines @@
 
   UnimplementedStatement(this.description, List<Node> nodes)
     : this.nodes = new NodeList(null, new Link<Node>.fromList(nodes));
 
   toString() => '$description($nodes)';
 
   Token getBeginToken() => nodes.getBeginToken();
 
   Token getEndToken() => nodes.getEndToken();
 }