Verify that correct number of arguments was passed.

tools/dom/scripts/generator.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 systems to generate
 Dart APIs from the IDL database."""
 
 import copy
 import json
@@ skipping 339 matching lines @@
     argtexts = map(FormatParam, required)
     if optional:
       needs_named = self.requires_named_arguments and not force_optional
       left_bracket, right_bracket = '{}' if needs_named else '[]'
       argtexts.append(
           left_bracket +
           ', '.join(map(FormatParam, optional)) +
           right_bracket)
     return ', '.join(argtexts)
 
+  def NumberOfRequiredInDart(self):
+    """ Returns a number of required arguments in Dart declaration of
+    the operation.
+    """
+    return len(filter(lambda i: not i.is_optional, self.param_infos))
+
   def ParametersAsArgumentList(self, parameter_count=None):
     """Returns a string of the parameter names suitable for passing the
     parameters as arguments.
     """
     def param_name(param_info):
       if self.requires_named_arguments and param_info.is_optional:
         return '%s : %s' % (param_info.name, param_info.name)
       else:
         return param_info.name
 
@@ skipping 733 matching lines @@
           type_name, type_data, dart_interface_name, self)
 
     if type_data.clazz == 'BasicTypedList':
       dart_interface_name = self._renamer.RenameInterface(
           self._database.GetInterface(type_name))
       return BasicTypedListIDLTypeInfo(
           type_name, type_data, dart_interface_name, self)
 
     class_name = '%sIDLTypeInfo' % type_data.clazz
     return globals()[class_name](type_name, type_data)