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-rw-r--r--third_party/rust/futures-util/src/stream/empty.rs45
1 files changed, 45 insertions, 0 deletions
diff --git a/third_party/rust/futures-util/src/stream/empty.rs b/third_party/rust/futures-util/src/stream/empty.rs
new file mode 100644
index 0000000000..e4fd87326b
--- /dev/null
+++ b/third_party/rust/futures-util/src/stream/empty.rs
@@ -0,0 +1,45 @@
+use super::assert_stream;
+use core::marker::PhantomData;
+use core::pin::Pin;
+use futures_core::stream::{FusedStream, Stream};
+use futures_core::task::{Context, Poll};
+
+/// Stream for the [`empty`] function.
+#[derive(Debug)]
+#[must_use = "streams do nothing unless polled"]
+pub struct Empty<T> {
+ _phantom: PhantomData<T>,
+}
+
+/// Creates a stream which contains no elements.
+///
+/// The returned stream will always return `Ready(None)` when polled.
+pub fn empty<T>() -> Empty<T> {
+ assert_stream::<T, _>(Empty { _phantom: PhantomData })
+}
+
+impl<T> Unpin for Empty<T> {}
+
+impl<T> FusedStream for Empty<T> {
+ fn is_terminated(&self) -> bool {
+ true
+ }
+}
+
+impl<T> Stream for Empty<T> {
+ type Item = T;
+
+ fn poll_next(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+ Poll::Ready(None)
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ (0, Some(0))
+ }
+}
+
+impl<T> Clone for Empty<T> {
+ fn clone(&self) -> Self {
+ empty()
+ }
+}