类中的私有成员和受保护成员

类中的私有成员和受保护成员会影响它们的兼容性。当检查类的实例的兼容性时，如果目标类型包含私有成员，则源类型也必须包含源自同一类的私有成员。同样，这同样适用于具有受保护成员的实例。这允许一个类的赋值与其超类兼容，但不能与来自不同继承层次结构的类兼容，否则它们具有相同的形状。

Private and protected members in a class affect their compatibility. When an instance of a class is checked for compatibility, if the target type contains a private member, then the source type must also contain a private member that originated from the same class. Likewise, the same applies for an instance with a protected member. This allows a class to be assignment compatible with its super class, but not with classes from a different inheritance hierarchy which otherwise have the same shape.