Fix cast exception when a Handle gets a wrong element because of name conflict.

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 1038 matching lines @@
         if (linkedReference.kind == ReferenceKind.function) {
           // Local function
           _references[index] = resolveRef(containingReference)
                   .getLocalFunction(linkedReference.localIndex) ??
               UndefinedElementForLink.instance;
         } else {
           _references[index] =
               resolveRef(containingReference).getContainedName(name);
         }
       } else if (linkedReference.dependency == 0) {
-        if (name == 'void') {
+        if (linkedReference.kind == ReferenceKind.unresolved) {
+          _references[index] = UndefinedElementForLink.instance;
+        } else if (name == 'void') {
           _references[index] = enclosingElement._linker.voidElement;
         } else if (name == '*bottom*') {
           _references[index] = enclosingElement._linker.bottomElement;
         } else if (name == 'dynamic') {
           _references[index] = enclosingElement._linker.dynamicElement;
         } else {
           _references[index] = enclosingElement.getContainedName(name);
         }
       } else {
         LibraryElementForLink dependency =
@@ skipping 4235 matching lines @@
 }
 
 /**
  * This exception is thrown when [ExprTypeComputer] cannot inference the type.
  */
 class _InferenceFailedError {
   final String message;
 
   _InferenceFailedError(this.message);
 }