some analyzer fixes for compiler

pkg/compiler/lib/src/serialization/element_serialization.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 dart2js.serialization.elements;
 
 import '../common.dart';
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
@@ skipping 363 matching lines @@
     }
     return null;
   }
 
   void serialize(TypeVariableElement element,
                  ObjectEncoder encoder,
                  SerializedElementKind kind) {
     encoder.setElement(Key.TYPE_DECLARATION, element.typeDeclaration);
     encoder.setString(Key.NAME, element.name);
     SerializerUtil.serializePosition(element, encoder);
-    TypeDeclarationElement typeDeclaration = element.typeDeclaration;
     encoder.setType(Key.TYPE, element.type);
     encoder.setInt(Key.INDEX, element.index);
     encoder.setType(Key.BOUND, element.bound);
   }
 }
 
 class ParameterSerializer implements ElementSerializer {
   const ParameterSerializer();
 
   SerializedElementKind getSerializedKind(Element element) {
@@ skipping 153 matching lines @@
       case SerializedElementKind.IMPORT:
         return new ImportElementZ(decoder);
       case SerializedElementKind.EXPORT:
         return new ExportElementZ(decoder);
       case SerializedElementKind.PREFIX:
         return new PrefixElementZ(decoder);
     }
     throw new UnsupportedError("Unexpected element kind '${elementKind}.");
   }
 }