Fix dart to native dispatch.

lib/dom/scripts/systemnative.py

 #!/usr/bin/python
 # 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.
 
 """This module provides shared functionality for the systems to generate
 native binding from the IDL database."""
 
 import emitter
 import os
@@ skipping 740 matching lines @@
     html_name = self._html_system.RenameInHtmlLibrary(
         html_interface_name, info.name, implementation_class=True)
 
     if not html_name and info.name == 'item':
       # FIXME: item should be renamed to operator[], not removed.
       html_name = '_item'
 
     if not html_name:
       return
 
+    is_custom = 'Custom' in operation.ext_attrs
+    has_optional_arguments = any(_IsArgumentOptionalInWebCore(argument) for argument in operation.arguments)
+    needs_dispatcher = not is_custom and (len(info.operations) > 1 or has_optional_arguments)
+
+    if not needs_dispatcher:
+      type_renamer = self._DartType
+      default_value = 'null'
+    else:
+      type_renamer = lambda x: 'Dynamic'
+      default_value = '_null'
+
     dart_declaration = '%s%s %s(%s)' % (
         'static ' if info.IsStatic() else '',
         self._DartType(info.type_name),
         html_name,
-        info.ParametersImplementationDeclaration(self._DartType))
+        info.ParametersImplementationDeclaration(type_renamer, default_value))
 
-    is_custom = 'Custom' in operation.ext_attrs
-    has_optional_arguments = any(IsOptional(argument) for argument in operation.arguments)
-    needs_dispatcher = not is_custom and (len(info.operations) > 1 or has_optional_arguments)
     if not needs_dispatcher:
       # Bind directly to native implementation
       argument_count = (0 if info.IsStatic() else 1) + len(info.param_infos)
       cpp_callback_name = self._GenerateNativeBinding(
           info.name, argument_count, dart_declaration, 'Callback', is_custom)
       if not is_custom:
         self._GenerateOperationNativeCallback(operation, operation.arguments, cpp_callback_name)
     else:
       self._GenerateDispatcher(info.operations, dart_declaration, [info.name for info in info.param_infos])
 
@@ skipping 27 matching lines @@
 
       dart_declaration = '%s%s _%s(%s)' % (
           'static ' if operation.is_static else '',
           self._DartType(operation.type.id), overload_name, argument_list)
       cpp_callback_name = self._GenerateNativeBinding(
           overload_name, (0 if operation.is_static else 1) + argument_count,
           dart_declaration, 'Callback', False)
       self._GenerateOperationNativeCallback(operation, operation.arguments[:argument_count], cpp_callback_name)
 
     def GenerateChecksAndCall(operation, argument_count):
-      checks = ['%s === null' % name for name in argument_names]
+      checks = ['%s === _null' % name for name in argument_names]
       for i in range(0, argument_count):
         argument = operation.arguments[i]
-        checks[i] = '%s is %s' % (argument_names[i], self._DartType(argument.type.id))
-        if IsOptional(argument) and 'Callback' in argument.ext_attrs:
-          checks[i] = '(%s or %s === null)' % (checks[position], argument_names[i])
+        argument_name = argument_names[i]
+        checks[i] = '(%s is %s || %s === null)' % (
+            argument_name, self._DartType(argument.type.id), argument_name)
       GenerateCall(operation, argument_count, checks)
 
-    def IsOptionalInWebCore(argument):
-      return IsOptional(argument) and not 'Callback' in argument.ext_attrs
-
     # TODO: Optimize the dispatch to avoid repeated checks.
     if len(operations) > 1:
       for operation in operations:
         for position, argument in enumerate(operation.arguments):
-          if IsOptionalInWebCore(argument):
+          if _IsArgumentOptionalInWebCore(argument):
             GenerateChecksAndCall(operation, position)
         GenerateChecksAndCall(operation, len(operation.arguments))
       body.Emit('    throw "Incorrect number or type of arguments";\n');
     else:
       operation = operations[0]
       for position, argument in list(enumerate(operation.arguments))[::-1]:
-        if IsOptionalInWebCore(argument):
-          check = '%s === null' % argument_names[position]
+        if _IsArgumentOptionalInWebCore(argument):
+          check = '%s === _null' % argument_names[position]
           GenerateCall(operation, position, [check])
       GenerateCall(operation, len(operation.arguments), [])
 
   def AddOperation(self, info):
     self._AddOperation(info)
 
   def AddStaticOperation(self, info):
     self._AddOperation(info)
 
   def AddSecondaryOperation(self, interface, info):
@@ skipping 194 matching lines @@
   for parent in interface.parents:
     parent_name = parent.type.id
     if not database.HasInterface(parent.type.id):
       continue
     parent_interface = database.GetInterface(parent.type.id)
     if callback(parent_interface):
       return parent_interface
     parent_interface = _FindParent(parent_interface, database, callback)
     if parent_interface:
       return parent_interface
+
+def _IsArgumentOptionalInWebCore(argument):
+  return IsOptional(argument) and not 'Callback' in argument.ext_attrs