为什么Exception会被当成RuntimeException抛出？

为什么以下代码可以通过编译不报错？btw,运行时还是会报原有的Exception，不会吞掉

public class ThrowAsUnchecked {
  public static void main(String[] args) {
//    throwAsUnchecked(new Exception("Testing new checked exception"));
    throwAsUnchecked(new IOException());
//    throwAsUnchecked(new RuntimeException("Testing new checked exception"));
  }

  @SuppressWarnings("unchecked")
  private static  void throwAsUnchecked(Exception exception) throws E {
    throw (E) exception;
  }
}

可参考的链接：stackoverflow How Java become unchecked exception [duplicate],
以及stackoverflow A peculiar feature of exception type inference in Java 8中的sneakyThrow

目前来看，应与泛型的type inference有关，有空再来研究