Remove more type casts

pkg/analyzer/lib/src/context/cache.dart

 // Copyright (c) 2015, 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.
 
 library analyzer.src.context.cache;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/dart/element/element.dart'
@@ skipping 341 matching lines @@
     _resultMap.forEach((descriptor, data) {
       TargetedResult result = new TargetedResult(target, descriptor);
       for (TargetedResult dependedOnResult in data.dependedOnResults) {
         ResultData dependedOnData = _partition._getDataFor(dependedOnResult);
         if (dependedOnData != null) {
           dependedOnData.dependentResults.remove(result);
         }
       }
     });
     _resultMap.clear();
-    if (target is ElementImpl) {
-      (target as ElementImpl).setModifier(Modifier.CACHE_KEY, false);
+    AnalysisTarget oldTarget = target;
+    if (oldTarget is ElementImpl) {
+      oldTarget.setModifier(Modifier.CACHE_KEY, false);
     }
   }
 
   /**
    * Fix the state of the [exception] to match the current state of the entry.
    */
   void fixExceptionState() {
     if (!hasErrorState()) {
       _exception = null;
     }
@@ skipping 904 matching lines @@
   void resultAccessed(TargetedResult result) {}
 
   @override
   List<TargetedResult> resultStored(TargetedResult newResult, newValue) {
     return TargetedResult.EMPTY_LIST;
   }
 
   @override
   void targetRemoved(AnalysisTarget target) {}
 }