std: Relax an assertion in oneshot selection

src/libstd/comm/oneshot.rs

@@ -339,14 +339,19 @@ impl<T: Send> Packet<T> {
             DATA => Ok(true),
 
             // If the other end has hung up, then we have complete ownership
-            // of the port. We need to check to see if there was an upgrade
-            // requested, and if so, the other end needs to have its selection
-            // aborted.
+            // of the port. First, check if there was data waiting for us. This
+            // is possible if the other end sent something and then hung up.
+            //
+            // We then need to check to see if there was an upgrade requested,
+            // and if so, the upgraded port needs to have its selection aborted.
             DISCONNECTED => {
-                assert!(self.data.is_none());
-                match mem::replace(&mut self.upgrade, SendUsed) {
-                    GoUp(port) => Err(port),
-                    _ => Ok(true),
+                if self.data.is_some() {
+                    Ok(true)
+                } else {
+                    match mem::replace(&mut self.upgrade, SendUsed) {
+                        GoUp(port) => Err(port),
+                        _ => Ok(true),
+                    }
                 }
             }
 

src/libstd/comm/select.rs

@@ -597,4 +597,56 @@ mod test {
         unsafe { h.add(); }
         assert_eq!(s.wait2(false), h.id);
     })
+
+    test!(fn oneshot_data_waiting() {
+        let (p, c) = Chan::new();
+        let (p2, c2) = Chan::new();
+        spawn(proc() {
+            select! {
+                () = p.recv() => {}
+            }
+            c2.send(());
+        });
+
+        for _ in range(0, 100) { task::deschedule() }
+        c.send(());
+        p2.recv();
+    })
+
+    test!(fn stream_data_waiting() {
+        let (p, c) = Chan::new();
+        let (p2, c2) = Chan::new();
+        c.send(());
+        c.send(());
+        p.recv();
+        p.recv();
+        spawn(proc() {
+            select! {
+                () = p.recv() => {}
+            }
+            c2.send(());
+        });
+
+        for _ in range(0, 100) { task::deschedule() }
+        c.send(());
+        p2.recv();
+    })
+
+    test!(fn shared_data_waiting() {
+        let (p, c) = Chan::new();
+        let (p2, c2) = Chan::new();
+        drop(c.clone());
+        c.send(());
+        p.recv();
+        spawn(proc() {
+            select! {
+                () = p.recv() => {}
+            }
+            c2.send(());
+        });
+
+        for _ in range(0, 100) { task::deschedule() }
+        c.send(());
+        p2.recv();
+    })
 }