1 files changed, 80 insertions, 0 deletions
diff --git a/src/stream/stream/split.rs b/src/stream/stream/split.rs
index e2034e0..1a7fdcb 100644
--- a/src/stream/stream/split.rs
+++ b/src/stream/stream/split.rs
@@ -15,6 +15,13 @@ pub struct SplitStream<S>(BiLock<S>);
 
 impl<S> Unpin for SplitStream<S> {}
 
+impl<S> SplitStream<S> {
+    /// Returns `true` if the `SplitStream<S>` and `SplitSink<S>` originate from the same call to `StreamExt::split`.
+    pub fn is_pair_of<Item>(&self, other: &SplitSink<S, Item>) -> bool {
+        other.is_pair_of(&self)
+    }
+}
+
 impl<S: Unpin> SplitStream<S> {
     /// Attempts to put the two "halves" of a split `Stream + Sink` back
     /// together. Succeeds only if the `SplitStream<S>` and `SplitSink<S>` are
@@ -60,6 +67,13 @@ impl<S: Sink<Item> + Unpin, Item> SplitSink<S, Item> {
     }
 }
 
+impl<S, Item> SplitSink<S, Item> {
+    /// Returns `true` if the `SplitStream<S>` and `SplitSink<S>` originate from the same call to `StreamExt::split`.
+    pub fn is_pair_of(&self, other: &SplitStream<S>) -> bool {
+        self.lock.is_pair_of(&other.0)
+    }
+}
+
 impl<S: Sink<Item>, Item> SplitSink<S, Item> {
     fn poll_flush_slot(
         mut inner: Pin<&mut S>,
@@ -142,3 +156,69 @@ impl<T, Item> fmt::Display for ReuniteError<T, Item> {
 
 #[cfg(feature = "std")]
 impl<T: core::any::Any, Item> std::error::Error for ReuniteError<T, Item> {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{sink::Sink, stream::StreamExt};
+    use core::marker::PhantomData;
+
+    struct NopStream<Item> {
+        phantom: PhantomData<Item>,
+    }
+
+    impl<Item> Stream for NopStream<Item> {
+        type Item = Item;
+
+        fn poll_next(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+            todo!()
+        }
+    }
+
+    impl<Item> Sink<Item> for NopStream<Item> {
+        type Error = ();
+
+        fn poll_ready(
+            self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+        ) -> Poll<Result<(), Self::Error>> {
+            todo!()
+        }
+
+        fn start_send(self: Pin<&mut Self>, _item: Item) -> Result<(), Self::Error> {
+            todo!()
+        }
+
+        fn poll_flush(
+            self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+        ) -> Poll<Result<(), Self::Error>> {
+            todo!()
+        }
+
+        fn poll_close(
+            self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+        ) -> Poll<Result<(), Self::Error>> {
+            todo!()
+        }
+    }
+
+    #[test]
+    fn test_pairing() {
+        let s1 = NopStream::<()> { phantom: PhantomData };
+        let (sink1, stream1) = s1.split();
+        assert!(sink1.is_pair_of(&stream1));
+        assert!(stream1.is_pair_of(&sink1));
+
+        let s2 = NopStream::<()> { phantom: PhantomData };
+        let (sink2, stream2) = s2.split();
+        assert!(sink2.is_pair_of(&stream2));
+        assert!(stream2.is_pair_of(&sink2));
+
+        assert!(!sink1.is_pair_of(&stream2));
+        assert!(!stream1.is_pair_of(&sink2));
+        assert!(!sink2.is_pair_of(&stream1));
+        assert!(!stream2.is_pair_of(&sink1));
+    }
+}