Clean-up of getCompilationUnit.

lib/compiler/implementation/js_backend/emitter.dart

 // Copyright (c) 2012, 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.
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
 class ClosureInvocationElement extends FunctionElement {
   ClosureInvocationElement(SourceString name,
@@ skipping 946 matching lines @@
           }
           return selector.applies(element, compiler);
         }
 
         // If the selector is typed, we check to see if that type may
         // have a user-defined noSuchMethod implementation. If not, we
         // skip the selector altogether.
         Type receiverType = objectType;
         ClassElement receiverClass = objectClass;
         if (selector is TypedSelector) {
-          receiverType = (selector as TypedSelector).receiverType;
+          TypedSelector typedSelector = selector;
+          receiverType = typedSelector.receiverType;
           receiverClass = receiverType.element;
         }
 
         // If the receiver class is guaranteed to have a member that
         // matches what we're looking for, there's no need to
         // introduce a noSuchMethod handler. It will never be called.
         //
         // As an example, consider this class hierarchy:
         //
         //                   A    <-- noSuchMethod
@@ skipping 196 matching lines @@
         sourceName = token.slowToString();
       }
       int totalOffset = bufferOffset + offset;
       sourceMapBuilder.addMapping(
           sourceFile, token.charOffset, sourceName, totalOffset);
     });
   }
 }
 
 typedef void DefineMemberFunction(String invocationName, CodeBuffer definition);