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 1157 matching lines @@
     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()) {

[rmacnak, 2013/08/14 16:25:30]

This doesn't need to be a special case. The else clause below will handle it.

[Lasse Reichstein Nielsen, 2013/08/15 12:24:44]

Done.

-      // 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
+      // A null object is only an instance of Object, dynamic and Null, the
+      // first two of which has already been checked above (if the type is
       // instantiated).
-      result = new ConstantInstr(negate_result ? Bool::True() : Bool::False());
+      const bool is_type = type.IsNullType();
+      result = new ConstantInstr((is_type != negate_result) ? Bool::True()
+                                                            : Bool::False());
     } 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());
@@ skipping 2432 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