Better typing and type verification

src/types-inl.h

Index: src/types-inl.h
diff --git a/src/types-inl.h b/src/types-inl.h
index 162e658d673a960bb65dfb19d960d045027cb18a..2e7f8a36fa76325acc2dd57a9b5f84ab8ca28050 100644
--- a/src/types-inl.h
+++ b/src/types-inl.h
@@ -56,6 +56,13 @@ bool TypeImpl<Config>::NowContains(i::Object* value) {
 
 // static
 template<class T>
+T* ZoneTypeConfig::null_handle() {
+  return NULL;
+}
+
+
+// static
+template<class T>
 T* ZoneTypeConfig::handle(T* type) {
   return type;
 }
@@ -199,6 +206,13 @@ void ZoneTypeConfig::struct_set_value(
 
 // static
 template<class T>
+i::Handle<T> HeapTypeConfig::null_handle() {
+  return i::Handle<T>();
+}
+
+
+// static
+template<class T>
 i::Handle<T> HeapTypeConfig::handle(T* type) {
   return i::handle(type, i::HeapObject::cast(type)->GetIsolate());
 }