1 files changed, 59 insertions, 0 deletions
diff --git a/third_party/rust/futures-util/src/sink/drain.rs b/third_party/rust/futures-util/src/sink/drain.rs
new file mode 100644
index 0000000000..1a5480c0d6
--- /dev/null
+++ b/third_party/rust/futures-util/src/sink/drain.rs
@@ -0,0 +1,59 @@
+use super::assert_sink;
+use crate::never::Never;
+use core::marker::PhantomData;
+use core::pin::Pin;
+use futures_core::task::{Context, Poll};
+use futures_sink::Sink;
+
+/// Sink for the [`drain`] function.
+#[derive(Debug)]
+#[must_use = "sinks do nothing unless polled"]
+pub struct Drain<T> {
+    marker: PhantomData<T>,
+}
+
+/// Create a sink that will just discard all items given to it.
+///
+/// Similar to [`io::Sink`](::std::io::Sink).
+///
+/// # Examples
+///
+/// ```
+/// # futures::executor::block_on(async {
+/// use futures::sink::{self, SinkExt};
+///
+/// let mut drain = sink::drain();
+/// drain.send(5).await?;
+/// # Ok::<(), futures::never::Never>(()) }).unwrap();
+/// ```
+pub fn drain<T>() -> Drain<T> {
+    assert_sink::<T, Never, _>(Drain { marker: PhantomData })
+}
+
+impl<T> Unpin for Drain<T> {}
+
+impl<T> Clone for Drain<T> {
+    fn clone(&self) -> Self {
+        drain()
+    }
+}
+
+impl<T> Sink<T> for Drain<T> {
+    type Error = Never;
+
+    fn poll_ready(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn start_send(self: Pin<&mut Self>, _item: T) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn poll_close(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        Poll::Ready(Ok(()))
+    }
+}