fix(client): check for dead connections in Pool

Closes #1429

tests/client.rs

@@ -954,6 +954,60 @@ mod dispatch_impl {
         assert_eq!(closes.load(Ordering::Relaxed), 1);
     }
 
+    #[test]
+    fn conn_drop_prevents_pool_checkout() {
+        // a drop might happen for any sort of reason, and we can protect
+        // against a lot of them, but if the `Core` is dropped, we can't
+        // really catch that. So, this is case to always check.
+        //
+        // See https://github.com/hyperium/hyper/issues/1429
+
+        use std::error::Error;
+        let _ = pretty_env_logger::try_init();
+
+        let server = TcpListener::bind("127.0.0.1:0").unwrap();
+        let addr = server.local_addr().unwrap();
+        let mut core = Core::new().unwrap();
+        let handle = core.handle();
+
+        let (tx1, rx1) = oneshot::channel();
+
+        thread::spawn(move || {
+            let mut sock = server.accept().unwrap().0;
+            sock.set_read_timeout(Some(Duration::from_secs(5))).unwrap();
+            sock.set_write_timeout(Some(Duration::from_secs(5))).unwrap();
+            let mut buf = [0; 4096];
+            sock.read(&mut buf).expect("read 1");
+            sock.write_all(b"HTTP/1.1 200 OK\r\nContent-Length: 0\r\n\r\n").unwrap();
+            sock.read(&mut buf).expect("read 2");
+            let _ = tx1.send(());
+        });
+
+        let uri = format!("http://{}/a", addr).parse::<hyper::Uri>().unwrap();
+
+        let client = Client::new(&handle);
+        let res = client.get(uri.clone()).and_then(move |res| {
+            assert_eq!(res.status(), hyper::StatusCode::Ok);
+            res.body().concat2()
+        });
+
+        core.run(res).unwrap();
+
+        // drop previous Core
+        core = Core::new().unwrap();
+        let timeout = Timeout::new(Duration::from_millis(200), &core.handle()).unwrap();
+        let rx = rx1.map_err(|_| hyper::Error::Io(io::Error::new(io::ErrorKind::Other, "thread panicked")));
+        let rx = rx.and_then(move |_| timeout.map_err(|e| e.into()));
+
+        let res = client.get(uri);
+        // this does trigger an 'event loop gone' error, but before, it would
+        // panic internally on a `SendError`, which is what we're testing against.
+        let err = core.run(res.join(rx).map(|r| r.0)).unwrap_err();
+        assert_eq!(err.description(), "event loop gone");
+    }
+
+
+
     #[test]
     fn client_custom_executor() {
         let server = TcpListener::bind("127.0.0.1:0").unwrap();