Better arity checks for overloads

Source/bindings/scripts/v8_interface.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 # coding=utf-8
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 337 matching lines @@
     """Returns |overloads| template values for a single name.
 
     Sets |method.overload_index| in place for |method| in |overloads|
     and returns dict of overall overload template values.
     """
     assert len(overloads) > 1  # only apply to overloaded names
     for index, method in enumerate(overloads, 1):
         method['overload_index'] = index
 
     effective_overloads_by_length = effective_overload_set_by_length(overloads)
+    lengths = [length for length, _ in effective_overloads_by_length]
 
     return {
         'deprecate_all_as': common_value(overloads, 'deprecate_as'),  # [DeprecateAs]
         'length_tests_methods': length_tests_methods(effective_overloads_by_length),
+        'minarg': lengths[0],
         # 1. Let maxarg be the length of the longest type list of the
         # entries in S.
-        'maxarg': max(i for i, _ in effective_overloads_by_length),
+        'maxarg': lengths[-1],
         'measure_all_as': common_value(overloads, 'measure_as'),  # [MeasureAs]
-        'minimum_number_of_required_arguments':
-            min(method['number_of_required_arguments'] for method in overloads),
+        'valid_arities': lengths
+            # Only need to report valid arities if there is a gap in the
+            # sequence of possible lengths, otherwise invalid length means
+            # "not enough arguments".
+            if lengths[-1] - lengths[0] != len(lengths) - 1 else None,
     }
 
 
 def effective_overload_set(F):
     """Returns the effective overload set of an overloaded function.
 
     An effective overload set is the set of overloaded functions + signatures
     (type list of arguments, with optional and variadic arguments included or
     not), and is used in the overload resolution algorithm.
 
@@ skipping 620 matching lines @@
         deleter = next(
             method
             for method in interface.operations
             if ('deleter' in method.specials and
                 len(method.arguments) == 1 and
                 str(method.arguments[0].idl_type) == 'DOMString'))
     except StopIteration:
         return None
 
     return property_deleter(deleter)