### 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 true;
					}
				}
				return false;
			} break;
			case GDScriptParser::DataType::BUILTIN: {
				Callable::CallError err;
				Variant tmp;
				Variant::construct(base_type.builtin_type, tmp, nullptr, 0, err);
				if (err.error != Callable::CallError::CALL_OK) {
					return false;
				}
				bool valid = false;
				Variant res = tmp.get(p_identifier, &valid);
				if (valid) {
					r_type = _type_from_variant(res);
					r_type.value = Variant();
					r_type.type.is_constant = false;
					return true;
				}
				return false;
			} break;
			default: {
				return false;
			} break;
		}
	}
	return false;
}
static void _find_last_return_in_block(GDScriptParser::CompletionContext &p_context, int &r_last_return_line, const GDScriptParser::ExpressionNode **r_last_returned_value) {