Skip expensive hasInstance() type-checks in overloads

Source/bindings/templates/methods.cpp

 {##############################################################################}
 {% macro generate_method(method, world_suffix) %}
 {% filter conditional(method.conditional_string) %}
-static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const v8::FunctionCallbackInfo<v8::Value>& info)
+static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const v8::FunctionCallbackInfo<v8::Value>& info{% if method.overload_index %}, int typeCheckedArgumentIndex{% endif %})
 {
     {# Local variables #}
     {% if method.has_exception_state %}
     ExceptionState exceptionState(ExceptionState::ExecutionContext, "{{method.name}}", "{{interface_name}}", info.Holder(), info.GetIsolate());
     {% endif %}
     {# Overloaded methods have length checked during overload resolution #}
     {% if method.number_of_required_arguments and not method.overload_index %}
     if (UNLIKELY(info.Length() < {{method.number_of_required_arguments}})) {
         {{throw_minimum_arity_type_error(method, method.number_of_required_arguments) | indent(8)}}
         return;
@@ skipping 150 matching lines @@
 {% elif argument.is_dictionary %}
 {# Dictionaries must have type Undefined, Null or Object:
 http://heycam.github.io/webidl/#es-dictionary #}
 if (!isUndefinedOrNull(info[{{argument.index}}]) && !info[{{argument.index}}]->IsObject()) {
     {{throw_type_error(method, '"parameter %s (\'%s\') is not an object."' %
                                (argument.index + 1, argument.name)) | indent}}
     return;
 }
 {{argument.v8_value_to_local_cpp_value}};
 {% else %}{# argument.is_nullable #}
+{# Optionally do an "unsafe" type conversion if meaningful for this argument's
+   type and if this method is overloaded and the argument's type was checked as
+   part of overload resolution for this particular call. #}
+{% if argument.is_ever_distinguishing_argument and
+      argument.v8_value_to_local_cpp_value_without_type_check %}
+if (typeCheckedArgumentIndex == {{argument.index}})
+    {{argument.v8_value_to_local_cpp_value_without_type_check}};
+else
+    {{argument.v8_value_to_local_cpp_value}};
+{% else %}
 {{argument.v8_value_to_local_cpp_value}};
+{% endif %}
 {% endif %}{# argument.is_nullable #}
 {# Type checking, possibly throw a TypeError, per:
    http://www.w3.org/TR/WebIDL/#es-type-mapping #}
 {% if argument.has_type_checking_unrestricted %}
 {# Non-finite floating point values (NaN, +Infinity or −Infinity), per:
    http://heycam.github.io/webidl/#es-float
    http://heycam.github.io/webidl/#es-double #}
 if (!std::isfinite({{argument.name}})) {
     {{throw_type_error(method, '"%s parameter %s is non-finite."' %
                                (argument.idl_type, argument.index + 1)) | indent}}
@@ skipping 184 matching lines @@
     UseCounter::countDeprecation(callingExecutionContext(info.GetIsolate()), UseCounter::{{overloads.deprecate_all_as}});
     {% endif %}
     {# First resolve by length #}
     {# 2. Initialize argcount to be min(maxarg, n). #}
     switch (std::min({{overloads.maxarg}}, info.Length())) {
     {# 3. Remove from S all entries whose type list is not of length argcount. #}
     {% for length, tests_methods in overloads.length_tests_methods %}
     {# 10. If i = d, then: #}
     case {{length}}:
         {# Then resolve by testing argument #}
-        {% for test, method in tests_methods %}
+        {% for test, method, typed_checked_argument_index in tests_methods %}
         {% filter runtime_enabled(not overloads.runtime_enabled_function_all and
                                   method.runtime_enabled_function) %}
         if ({{test}}) {
             {% if method.measure_as and not overloads.measure_all_as %}
             UseCounter::count(callingExecutionContext(info.GetIsolate()), UseCounter::{{method.measure_as}});
             {% endif %}
             {% if method.deprecate_as and not overloads.deprecate_all_as %}
             UseCounter::countDeprecation(callingExecutionContext(info.GetIsolate()), UseCounter::{{method.deprecate_as}});
             {% endif %}
-            {{method.name}}{{method.overload_index}}Method{{world_suffix}}(info);
+            {{method.name}}{{method.overload_index}}Method{{world_suffix}}(info, {{typed_checked_argument_index}});
             return;
         }
         {% endfilter %}
         {% endfor %}
         break;
     {% endfor %}
     default:
         {# Invalid arity, throw error #}
         {# Report full list of valid arities if gaps and above minimum #}
         {% if overloads.valid_arities %}
@@ skipping 139 matching lines @@
     return true;
 }
 {% endmacro %}
 
 
 {##############################################################################}
 {% macro generate_constructor(constructor) %}
 {% set name = '%sConstructorCallback' % v8_class
               if constructor.is_named_constructor else
               'constructor%s' % (constructor.overload_index or '') %}
-static void {{name}}(const v8::FunctionCallbackInfo<v8::Value>& info)
+static void {{name}}(const v8::FunctionCallbackInfo<v8::Value>& info{% if constructor.overload_index %}, int typeCheckedArgumentIndex{% endif %})
 {
     {% if constructor.is_named_constructor %}
     if (!info.IsConstructCall()) {
         V8ThrowException::throwTypeError(ExceptionMessages::constructorNotCallableAsFunction("{{constructor.name}}"), info.GetIsolate());
         return;
     }
 
     if (ConstructorMode::current(info.GetIsolate()) == ConstructorMode::WrapExistingObject) {
         v8SetReturnValue(info, info.Holder());
         return;
@@ skipping 55 matching lines @@
   if method.is_per_world_bindings else '0' %}
 {% set property_attribute =
   'static_cast<v8::PropertyAttribute>(%s)' % ' | '.join(method.property_attributes)
   if method.property_attributes else 'v8::None' %}
 {% set only_exposed_to_private_script = 'V8DOMConfiguration::OnlyExposedToPrivateScript' if method.only_exposed_to_private_script else 'V8DOMConfiguration::ExposedToAllScripts' %}
 static const V8DOMConfiguration::MethodConfiguration {{method.name}}MethodConfiguration = {
     "{{method.name}}", {{method_callback}}, {{method_callback_for_main_world}}, {{method.length}}, {{only_exposed_to_private_script}},
 };
 V8DOMConfiguration::installMethod({{method.function_template}}, {{method.signature}}, {{property_attribute}}, {{method.name}}MethodConfiguration, isolate);
 {%- endmacro %}