Many type fixes.

lib/compiler/implementation/compiler.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 WorkItem {
   final Element element;
   TreeElements resolutionTree;
   Function run;
   bool allowSpeculativeOptimization = true;
   List<HTypeGuard> guards = const <HTypeGuard>[];
@@ skipping 248 matching lines @@
         const SourceString('JS_CURRENT_ISOLATE'), library), this);
     library.define(new ForeignElement(
         const SourceString('JS_CALL_IN_ISOLATE'), library), this);
     library.define(new ForeignElement(
         const SourceString('DART_CLOSURE_TO_JS'), library), this);
   }
 
   void runCompiler(Uri uri) {
     scanBuiltinLibraries();
     mainApp = scanner.loadLibrary(uri, null);
-    final Element mainMethod = mainApp.find(MAIN);
-    if (mainMethod === null) {
+    final Element main = mainApp.find(MAIN);
+    if (main === null) {
       withCurrentElement(mainApp, () => cancel('Could not find $MAIN'));
     } else {
-      withCurrentElement(mainMethod, () {
-        if (!mainMethod.isFunction()) {
-          cancel('main is not a function', element: mainMethod);
+      withCurrentElement(main, () {
+        if (!main.isFunction()) {
+          cancel('main is not a function', element: main);
         }
+        FunctionElement mainMethod = main;
         FunctionParameters parameters = mainMethod.computeParameters(this);
         if (parameters.parameterCount > 0) {
           cancel('main cannot have parameters', element: mainMethod);
         }
       });
     }
     native.processNativeClasses(this, universe.libraries.getValues());
-    enqueue(new WorkItem.toCompile(mainMethod));
+    enqueue(new WorkItem.toCompile(main));
     codegenProgress.reset();
     while (!worklist.isEmpty()) {
       WorkItem work = worklist.removeLast();
       withCurrentElement(work.element, () => (work.run)(this));
     }
     workListIsClosed = true;
     assert(enqueuer.checkNoEnqueuedInvokedInstanceMethods());
     enqueuer.registerFieldClosureInvocations();
     emitter.assembleProgram();
     if (!worklist.isEmpty()) {
@@ skipping 246 matching lines @@
   }
 }
 
 class SourceSpan {
   final Uri uri;
   final int begin;
   final int end;
 
   const SourceSpan(this.uri, this.begin, this.end);
 }