But if ln were aliased with li, then it would break the type-safety promise implicit in the definition of li — that it is a list of integers, which is why generic types cannot be covariant.

但是如果ln是li的别名，那么这就破坏了蕴含在li定义中的类型安全承诺——它是一个整数列表，这就是泛型类型不能协变的原因。

youdao

But if ln were aliased with li, then it would break the type-safety promise implicit in the definition of li — that it is a list of integers, which is why generic types cannot be covariant.

但是如果ln是li的别名，那么这就破坏了蕴含在li定义中的类型安全承诺——它是一个整数列表，这就是泛型类型不能协变的原因。

youdao