Avoid extra arity and type check on distinguishing argument

Source/bindings/templates/methods.cpp

Index: Source/bindings/templates/methods.cpp
diff --git a/Source/bindings/templates/methods.cpp b/Source/bindings/templates/methods.cpp
index fef73d8f73bad922c0d5f64c9f79ae08713ea9be..8ff7b23615683a5de03f43e33ee78260fc3353aa 100644
--- a/Source/bindings/templates/methods.cpp
+++ b/Source/bindings/templates/methods.cpp
@@ -92,9 +92,11 @@ if (UNLIKELY(info.Length() <= {{argument.index}})) {
     return;
 }
 {% endif %}
-{% if argument.has_type_checking_interface %}
+{% if argument.has_type_checking_interface and argument.index != method.distinguishing_argument_index %}
 {# Type checking for wrapper interface types (if interface not implemented,
-   throw a TypeError), per http://www.w3.org/TR/WebIDL/#es-interface #}
+   throw a TypeError), per http://www.w3.org/TR/WebIDL/#es-interface
+   If the argument is the distinguishing argument for an overloaded method,
+   the type is checked as part of overload resolution instead. #}
 if (info.Length() > {{argument.index}} && {% if argument.is_nullable %}!isUndefinedOrNull(info[{{argument.index}}]) && {% endif %}!V8{{argument.idl_type}}::hasInstance(info[{{argument.index}}], info.GetIsolate())) {
     {{throw_type_error(method, '"parameter %s is not of type \'%s\'."' %
                                (argument.index + 1, argument.idl_type)) | indent}}