rust-variance

The fragment is educational Rust variance documentation, not a covert runtime payload. Its `Sender<T>` demonstration intentionally contains an unsound contravariant channel: a borrowed message can outlive its `String`, and `Queue::drop` then invokes `drop_as`/`Box::from_raw`, causing use-after-free undefined behavior. This is a significant memory-safety risk if copied into production, but the example is explicitly labeled and explained; no malware indicators or network activity are present.