Add Null class to dart:core.

runtime/vm/flow_graph_builder.cc

 // 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.
 
 #include "vm/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/code_descriptors.h"
@@ skipping 1204 matching lines @@
     ReturnDefinition(new ConstantInstr(negate_result ?
                                        Bool::False() : Bool::True()));
     return;
   }
 
   // Eliminate the test if it can be performed successfully at compile time.
   if ((node->left() != NULL) &&
       node->left()->IsLiteralNode() &&
       type.IsInstantiated()) {
     const Instance& literal_value = node->left()->AsLiteralNode()->literal();
-    const Class& cls = Class::Handle(literal_value.clazz());
     ConstantInstr* result = NULL;
-    if (cls.IsNullClass()) {
-      // A null object is only an instance of Object and dynamic, which has
-      // already been checked above (if the type is instantiated). So we can
-      // return false here if the instance is null (and if the type is
-      // instantiated).
-      result = new ConstantInstr(negate_result ? Bool::True() : Bool::False());
+
+    Error& malformed_error = Error::Handle();
+    if (literal_value.IsInstanceOf(type,
+                                   TypeArguments::Handle(),
+                                   &malformed_error)) {
+      result = new ConstantInstr(negate_result ?
+                                 Bool::False() : Bool::True());
     } else {
-      Error& malformed_error = Error::Handle();
-      if (literal_value.IsInstanceOf(type,
-                                     TypeArguments::Handle(),
-                                     &malformed_error)) {
-        result = new ConstantInstr(negate_result ?
-                                   Bool::False() : Bool::True());
-      } else {
-        result = new ConstantInstr(negate_result ?
-                                   Bool::True() : Bool::False());
-      }
-      ASSERT(malformed_error.IsNull());
+      result = new ConstantInstr(negate_result ?
+                                 Bool::True() : Bool::False());
     }
+    ASSERT(malformed_error.IsNull());
+
     ReturnDefinition(result);
     return;
   }
 
   ValueGraphVisitor for_left_value(owner(), temp_index());
   node->left()->Visit(&for_left_value);
   Append(for_left_value);
   PushArgumentInstr* push_left = PushArgument(for_left_value.value());
   PushArgumentInstr* push_instantiator = NULL;
   PushArgumentInstr* push_type_args = NULL;
@@ skipping 2421 matching lines @@
   intptr_t len = OS::SNPrint(NULL, 0, kFormat, function_name, reason) + 1;
   char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
   OS::SNPrint(chars, len, kFormat, function_name, reason);
   const Error& error = Error::Handle(
       LanguageError::New(String::Handle(String::New(chars))));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 
 }  // namespace dart