Use entities in the TypeSystem interface.

pkg/compiler/lib/src/inferrer/closure_tracer.dart

 // Copyright (c) 2013, 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 compiler.src.inferrer.closure_tracer;
 
 import '../common/names.dart' show Names;
 import '../elements/elements.dart';
 import '../elements/entities.dart';
 import '../js_backend/backend.dart' show JavaScriptBackend;
@@ skipping 14 matching lines @@
       : super(tracedType, inferrer);
 
   ApplyableTypeInformation get tracedType => super.tracedType;
 
   void run() {
     analyze();
     if (!continueAnalyzing) return;
     _callsToAnalyze.forEach(_analyzeCall);
     for (MethodElement element in tracedElements) {
       MethodElement implementation = element.implementation;
-      implementation.functionSignature.forEachParameter((Element parameter) {
+      implementation.functionSignature
+          .forEachParameter((FormalElement _parameter) {
+        ParameterElement parameter = _parameter;
         ElementTypeInformation info =
             inferrer.types.getInferredTypeOfParameter(parameter);
         info.disableInferenceForClosures = false;
       });
     }
   }
 
   void _tagAsFunctionApplyTarget([String reason]) {
     tracedType.mightBePassedToFunctionApply = true;
     if (debug.VERBOSE) {
@@ skipping 91 matching lines @@
   @override
   visitStaticCallSiteTypeInformation(StaticCallSiteTypeInformation info) {
     super.visitStaticCallSiteTypeInformation(info);
     if (info.calledElement == tracedElements.first &&
         info.selector != null &&
         info.selector.isGetter) {
       addNewEscapeInformation(info);
     }
   }
 }