Store elements in the constant eval dependency graph rather than AST nodes.

pkg/analyzer/lib/src/generated/element.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.element;
 
 import 'dart:collection';
@@ skipping 8661 matching lines @@
 }
 
 /**
  * Interface used by elements that might represent constant variables.
  *
  * This class may be used as a mixin in the case where [constInitializer] is
  * known to return null.
  *
  * This class is not intended to be part of the public API for analyzer.
  */
-abstract class PotentiallyConstVariableElement {
+abstract class PotentiallyConstVariableElement implements VariableElementImpl {
   /**
    * If this element represents a constant variable, and it has an initializer,
    * a copy of the initializer for the constant.  Otherwise `null`.
    *
    * Note that in correct Dart code, all constant variables must have
    * initializers.  However, analyzer also needs to handle incorrect Dart code,
    * in which case there might be some constant variables that lack
    * initializers.
    */
   Expression get constantInitializer => null;
@@ skipping 1665 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }