### Godot version

4.1.1

### System information

windows 11

### Issue description

When registering a type with class_name and using that class name to declare a variable in code only, autocomplete works as expected anywhere in other nodes/scenes. However, if making a custom scene node that extends a script with the class_name, if that custom scene is instantiated in a different scene, even if the type is specified, it only shows the parent node's functions and not any of the extended functionality. I have made a basic project showing the issue

### Steps to reproduce

I have made a very simple project showing the issue. https://github.com/mmmmmmmmmmmmmmmmmmmdonuts/godot_4_autocomplete_issue essentially, the extended Node scene will only show the custom function when both the type is specified as well as the type afterwards following "as" 
e.g. `@onready var my_class_4: MyClass = $MyClass4 as MyClass`

### Minimal reproduction project

https://github.com/mmmmmmmmmmmmmmmmmmmdonuts/godot_4_autocomplete_issue
return _debug_error;
}
int GDScriptLanguage::debug_get_stack_level_count() const {
	if (_debug_parse_err_line >= 0) {
		return 1;
	}
	return _call_stack.stack_pos;
}
int GDScriptLanguage::debug_get_stack_level_line(int p_level) const {
	if (_debug_parse_err_line >= 0) {
		return _debug_parse_err_line;
	}
	ERR_FAIL_INDEX_V(p_level, _call_stack.stack_pos, -1);
	int l = _call_stack.stack_pos - p_level - 1;
	return *(_call_stack.levels[l].line);
}
String GDScriptLanguage::debug_get_stack_level_function(int p_level) const {