The utility of wildcards in the type system comes partially from the fact that generic types are not covariant.
通配符在类型系统中的作用部分来自其不会发生协变（covariant）这一特性。
The utility of wildcards in the type system comes partially from the fact that generic types are not covariant.
通配符在类型系统中的作用部分来自其不会发生协变（covariant）这一特性。
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