Next step in overload dispatcher refactoring.

tools/dom/scripts/systemhtml.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 system to generate
 Dart:html APIs from the IDL database."""
 
 import emitter
 import os
@@ skipping 837 matching lines @@
 
       self._members_emitter.Emit(
           '  $RENAME$ANNOTATIONS$MODIFIERS$TYPE$TARGET($PARAMS) native;\n',
           RENAME=self._RenamingAnnotation(info.declared_name, target),
           ANNOTATIONS=self._Annotations(info.type_name, info.declared_name),
           MODIFIERS='static ' if info.IsStatic() else '',
           TYPE=TypeOrNothing(native_return_type),
           TARGET=target,
           PARAMS=', '.join(target_parameters))
 
-    def GenerateChecksAndCall(operation, argument_count):
-      GenerateCall(operation, argument_count,
-          self._OverloadChecks(
-            operation,
-            parameter_names,
-            argument_count,
-            can_omit_type_check=lambda type, pos: type == parameter_types[pos]))
-
-    # TODO: Optimize the dispatch to avoid repeated checks.
-    if len(operations) > 1:
-      for operation in operations:
-        for position, argument in enumerate(operation.arguments):
-          if self._IsOptional(operation, argument):
-            GenerateChecksAndCall(operation, position)
-        GenerateChecksAndCall(operation, len(operation.arguments))
-      body.Emit(
-          '    throw new ArgumentError("Incorrect number or type of arguments");'
-          '\n');
-    else:
-      operation = operations[0]
-      argument_count = len(operation.arguments)
-      for position, argument in list(enumerate(operation.arguments))[::-1]:
-        if self._IsOptional(operation, argument):
-          check = '?%s' % parameter_names[position]
-          GenerateCall(operation, position + 1, [check])
-          argument_count = position
-      GenerateCall(operation, argument_count, [])
+    self._GenerateDispatcherBody(
+        body,
+        operations,
+        parameter_names,
+        GenerateCall,
+        self._IsOptional,
+        can_omit_type_check=lambda type, pos: type == parameter_types[pos])
 
   def _AddInterfaceOperation(self, info, html_name):
     self._members_emitter.Emit(
         '\n'
         '  $TYPE $NAME($PARAMS);\n',
         TYPE=self.SecureOutputType(info.type_name),
         NAME=info.name,
         PARAMS=info.ParametersDeclaration(self._NarrowInputType))
 
   def _IsOptional(self, operation, argument):
@@ skipping 146 matching lines @@
     for library_name in libraries:
       self._libraries[library_name] = DartLibrary(
           library_name, template_loader, library_type, output_dir)
 
   def AddFile(self, basename, library_name, path):
     self._libraries[library_name].AddFile(path)
 
   def Emit(self, emitter, auxiliary_dir):
     for lib in self._libraries.values():
       lib.Emit(emitter, auxiliary_dir)