Many type fixes.

lib/compiler/implementation/scanner/scanner_task.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.
 
 class ScannerTask extends CompilerTask {
   ScannerTask(Compiler compiler) : super(compiler);
   String get name() => 'Scanner';
 
   void scan(CompilationUnitElement compilationUnit) {
     measure(() {
@@ skipping 128 matching lines @@
         e = new PrefixElement(prefix, library, tag.getBeginToken());
         library.define(e, compiler);
       }
       if (e.kind !== ElementKind.PREFIX) {
         compiler.withCurrentElement(e, () {
           compiler.reportWarning(new Identifier(e.position()),
                                  'duplicated definition');
         });
         compiler.reportError(tag.prefix, 'duplicate defintion');
       }
+      PrefixElement prefixElement = e;
       imported.forEachExport((Element element) {
-        Element existing = e.imported.putIfAbsent(element.name, () => element);
+        Element existing =
+            prefixElement.imported.putIfAbsent(element.name, () => element);
         if (existing !== element) {
           compiler.withCurrentElement(existing, () {
             compiler.reportWarning(new Identifier(existing.position()),
                                    'duplicated import');
           });
           compiler.withCurrentElement(element, () {
             compiler.reportError(new Identifier(element.position()),
                                  'duplicated import');
           });
         }
@@ skipping 33 matching lines @@
   static final int RESOURCE = 4;
 
   /** Next state. */
   static final List<int> NEXT =
       const <int>[NO_TAG_SEEN,
                   IMPORT, // Only one library tag is allowed.
                   IMPORT,
                   SOURCE,
                   RESOURCE];
 }