When building summaries from ASTs, handle circularities involving .length.

pkg/analyzer/lib/src/summary/link.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.
 
 /**
  * This library is capable of producing linked summaries from unlinked
  * ones (or prelinked ones).  It functions by building a miniature
  * element model to represent the contents of the summaries, and then
  * scanning the element model to gather linked information and adding
  * it to the summary data structures.
@@ skipping 1309 matching lines @@
    */
   bool get isEvaluated;
 
   /**
    * Compute the dependencies of this node.
    */
   List<NodeType> computeDependencies();
 }
 
 /**
+ * Element used for references that result from trying to access a nonstatic
+ * member of an element that is not a container (e.g. accessing the "length"
+ * property of a constant).
+ */
+class NonstaticMemberElementForLink implements ReferenceableElementForLink {
+  /**
+   * If the thing from which a member was accessed is a constant, the
+   * associated [ConstNode].  Otherwise `null`.
+   */
+  final ConstVariableNode _constNode;
+
+  NonstaticMemberElementForLink(this._constNode);
+
+  @override
+  ConstructorElementForLink get asConstructor => null;
+
+  @override
+  ConstVariableNode get asConstVariable => _constNode;
+
+  @override
+  DartTypeForLink buildType(DartTypeForLink getTypeArgument(int i),
+          List<int> implicitFunctionTypeIndices) =>
+      DynamicTypeForLink.instance;
+
+  @override
+  ReferenceableElementForLink getContainedName(String name) => this;
+}
+
+/**
  * Element representing a function or method parameter resynthesized
  * from a summary during linking.
  */
 class ParameterElementForLink implements ParameterElement {
   /**
    * The unlinked representation of the parameter in the summary.
    */
   final UnlinkedParam _unlinkedParam;
 
   /**
@@ skipping 158 matching lines @@
 
   @override
   String get name => unlinkedVariable.name;
 
   @override
   DartTypeForLink buildType(DartTypeForLink getTypeArgument(int i),
           List<int> implicitFunctionTypeIndices) =>
       DynamicTypeForLink.instance;
 
   ReferenceableElementForLink getContainedName(String name) {
-    // TODO(paulberry): implement.
-    // TODO(paulberry): make sure that circularities involving
-    // ".length" are handled correctly.
-    return UndefinedElementForLink.instance;
+    return new NonstaticMemberElementForLink(_constNode);
   }
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
 /**
  * Representation of the void type during linking.
  */
 class VoidTypeForLink extends DartTypeForLink {
@@ skipping 81 matching lines @@
 
   /**
    * Throw away any information produced by a previous call to [link].
    */
   void unlink() {
     for (LibraryElementInBuildUnit library in _librariesInBuildUnit) {
       library.unlink();
     }
   }
 }