“Any”上的模式匹配为2元组？

Question

给出以下功能：

scala> def foo(x: Any) = x match { 
     |   case _: (String, Int) => "foo"
     |   case _                => "bar"
     | }

我收到以下编译时警告：

<console>:8: warning: non-variable type argument String in type pattern (String, Int) is unchecked since it is eliminated by erasure
         case _: (String, Int) => "foo"
                 ^
foo: (x: Any)String

我对JVM擦除的理解，即对List[T]的理解是，在运行时，JVM不知道T的类型。

请解释为什么以上is unchecked since it is eliminated by erasure出现在2元组上进行模式匹配的尝试。

Answer 1

元素类型只是Tuple2的类型参数。

但你可以：

scala> (("hi",42): Any) match { case (_: String, _: Int) => }