// SomeType is not Send or Sync
// SomeType 没有实现 Send 和 Sync
struct SomeType {
    not_send_or_sync: *const (),
}

// but if we're confident that our impl doesn't have any data
// races we can explicitly mark it as Send and Sync using unsafe
// 倘若我们得以社会主义伟大成就的庇佑自信地写出没有数据竞争的代码
// 可以使用 unsafe 来修饰前缀，以显式地实现 Send 特性与 Sync 特性
unsafe impl Send for SomeType {}
unsafe impl Sync for SomeType {}