Add a is_connected_to to (Unbounded)Sender (#2179)

Co-authored-by: LinkTed <LinkTed@users.noreply.github.com>

futures-channel/src/mpsc/mod.rs

@@ -481,6 +481,11 @@ impl<T> UnboundedSenderInner<T> {
         Arc::ptr_eq(&self.inner, &other.inner)
     }
 
+    /// Returns whether the sender send to this receiver.
+    fn is_connected_to(&self, inner: &Arc<UnboundedInner<T>>) -> bool {
+        Arc::ptr_eq(&self.inner, &inner)
+    }
+
     /// Returns pointer to the Arc containing sender
     ///
     /// The returned pointer is not referenced and should be only used for hashing!
@@ -657,6 +662,11 @@ impl<T> BoundedSenderInner<T> {
         Arc::ptr_eq(&self.inner, &other.inner)
     }
 
+    /// Returns whether the sender send to this receiver.
+    fn is_connected_to(&self, receiver: &Arc<BoundedInner<T>>) -> bool {
+        Arc::ptr_eq(&self.inner, &receiver)
+    } 
+
     /// Returns pointer to the Arc containing sender
     ///
     /// The returned pointer is not referenced and should be only used for hashing!
@@ -779,6 +789,14 @@ impl<T> Sender<T> {
         }
     }
 
+    /// Returns whether the sender send to this receiver.
+    pub fn is_connected_to(&self, receiver: &Receiver<T>) -> bool {
+        match (&self.0, &receiver.inner) {
+            (Some(inner), Some(receiver)) => inner.is_connected_to(receiver),
+            _ => false,
+        }
+    }
+
     /// Hashes the receiver into the provided hasher
     pub fn hash_receiver<H>(&self, hasher: &mut H) where H: std::hash::Hasher {
         use std::hash::Hash;
@@ -860,6 +878,14 @@ impl<T> UnboundedSender<T> {
         }
     }
 
+    /// Returns whether the sender send to this receiver.
+    pub fn is_connected_to(&self, receiver: &UnboundedReceiver<T>) -> bool {
+        match (&self.0, &receiver.inner) {
+            (Some(inner), Some(receiver)) => inner.is_connected_to(receiver),
+            _ => false,
+        }
+    }
+
     /// Hashes the receiver into the provided hasher
     pub fn hash_receiver<H>(&self, hasher: &mut H) where H: std::hash::Hasher {
         use std::hash::Hash;

futures-channel/tests/mpsc.rs

@@ -529,6 +529,17 @@ fn same_receiver() {
     assert!(txb1.same_receiver(&txb2));
 }
 
+#[test]
+fn is_connected_to() {
+    let (txa, rxa) = mpsc::channel::<i32>(1);
+    let (txb, rxb) = mpsc::channel::<i32>(1);
+
+    assert!(txa.is_connected_to(&rxa));
+    assert!(txb.is_connected_to(&rxb));
+    assert!(!txa.is_connected_to(&rxb));
+    assert!(!txb.is_connected_to(&rxa));
+}
+
 #[test]
 fn hash_receiver() {
     use std::hash::Hasher;