### 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
case GDScriptParser::COMPLETION_OVERRIDE_METHOD: {
			GDScriptParser::DataType base_type = context.current_class->base_type;
			if (_lookup_symbol_from_base(base_type, p_symbol, true, r_result) == OK) {
				return OK;
			}
		} break;
		case GDScriptParser::COMPLETION_PROPERTY_DECLARATION_OR_TYPE:
		case GDScriptParser::COMPLETION_TYPE_NAME_OR_VOID:
		case GDScriptParser::COMPLETION_TYPE_NAME: {
			GDScriptParser::DataType base_type = context.current_class->get_datatype();
			if (_lookup_symbol_from_base(base_type, p_symbol, false, r_result) == OK) {
				return OK;
			}
		} break;
		case GDScriptParser::COMPLETION_ANNOTATION: {
			const String annotation_symbol = "@" + p_symbol;
			if (parser.annotation_exists(annotation_symbol)) {
				r_result.type = ScriptLanguage::LOOKUP_RESULT_CLASS_ANNOTATION;
				r_result.class_name = "@GDScript";
				r_result.class_member = annotation_symbol;
				return OK;
			}
		} break;
		default: {
		}
	}
	return ERR_CANT_RESOLVE;
}
#endif