### 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
r_result.insert(option.display, option);
					}
				}
				base_type.kind = GDScriptParser::DataType::UNRESOLVED;
			} break;
			case GDScriptParser::DataType::BUILTIN: {
				if (base.get_type() == Variant::NIL) {
					Callable::CallError err;
					Variant::construct(base_type.builtin_type, base, nullptr, 0, err);
					if (err.error != Callable::CallError::CALL_OK) {
						return;
					}
				}
				List<MethodInfo> methods;
				base.get_method_list(&methods);
				for (const MethodInfo &E : methods) {
					if (E.name == p_method) {
						r_arghint = _make_arguments_hint(E, p_argidx);
						return;
					}
				}
				base_type.kind = GDScriptParser::DataType::UNRESOLVED;
			} break;
			default: {
				base_type.kind = GDScriptParser::DataType::UNRESOLVED;
			} break;
		}
	}
}
static bool _get_subscript_type(GDScriptParser::CompletionContext &p_context, const GDScriptParser::SubscriptNode *p_subscript, GDScriptParser::DataType &r_base_type, Variant *r_base = nullptr) {