json.Marshal注释里面的这2个地方怎么理解

// The nil pointer exception is not strictly necessary
// but mimics a similar, necessary exception in the behavior of
// UnmarshalJSON.
我英文水平有问题吗？翻译如下： 空指针异常不是必要的，但它在UnmarshalJSON的行为中模仿了一个相似的，必要的异常。 我怎么感觉不通顺呢？也没法理解。

// An anonymous struct field of interface type is treated the same as having
// that type as its name, rather than being anonymous.
interface类型的匿名字段？这是允许存在的吗？