Support enabling type checker.

pkg/compiler/lib/src/typechecker.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.
 
 library dart2js.typechecker;
 
 import 'common.dart';
 import 'common/names.dart' show Identifiers;
 import 'common/resolution.dart' show Resolution;
 import 'common/tasks.dart' show CompilerTask;
@@ skipping 33 matching lines @@
         VariableElement;
 import 'resolution/tree_elements.dart' show TreeElements;
 import 'resolution/class_members.dart' show MembersCreator;
 import 'tree/tree.dart';
 import 'util/util.dart' show Link, LinkBuilder;
 
 class TypeCheckerTask extends CompilerTask {
   TypeCheckerTask(Compiler compiler) : super(compiler);
   String get name => "Type checker";
 
+  bool enabled = false;
+
   void check(AstElement element) {
-    return;
+    if (!enabled) return;
     if (element.isClass) return;
     if (element.isTypedef) return;
     ResolvedAst resolvedAst = element.resolvedAst;
-    if (resolvedAst.node == null) {
-      return;
-      new FiskFisk();
-    }
     reporter.withCurrentElement(element.implementation, () {
       measure(() {
         TypeCheckerVisitor visitor = new TypeCheckerVisitor(
             compiler, resolvedAst.elements, compiler.types);
         if (element.isField) {
           visitor.analyzingInitializer = true;
         }
         resolvedAst.node.accept(visitor);
       });
     });
@@ skipping 1950 matching lines @@
 
   visitTypedef(Typedef node) {
     // Do not typecheck [Typedef] nodes.
   }
 
   visitNode(Node node) {
     reporter.internalError(node,
         'Unexpected node ${node.getObjectDescription()} in the type checker.');
   }
 }