Enable compilation on Eclipse 4.6

spring-web-reactive/src/main/java/org/springframework/web/reactive/socket/client/RxNettyWebSocketClient.java

@@ -31,6 +31,7 @@ import io.reactivex.netty.protocol.http.ws.client.WebSocketRequest;
 import io.reactivex.netty.protocol.http.ws.client.WebSocketResponse;
 import io.reactivex.netty.threads.RxEventLoopProvider;
 import reactor.core.publisher.Mono;
+import reactor.util.function.Tuple2;
 import reactor.util.function.Tuples;
 import rx.Observable;
 import rx.RxReactiveStreams;
@@ -121,12 +122,15 @@ public class RxNettyWebSocketClient extends WebSocketClientSupport implements We
 		return Mono.from(RxReactiveStreams.toPublisher(completion));
 	}
 
+	@SuppressWarnings("cast")
 	private Observable<Void> executeInternal(URI url, HttpHeaders headers, WebSocketHandler handler) {
 		String[] protocols = beforeHandshake(url, headers, handler);
 		return createRequest(url, headers, protocols)
 				.flatMap(response -> {
 					Observable<WebSocketConnection> conn = response.getWebSocketConnection();
-					return Observable.zip(Observable.just(response), conn, Tuples::of);
+					// following cast is necessary to enable compilation on Eclipse 4.6
+					return (Observable<Tuple2<WebSocketResponse<ByteBuf>, WebSocketConnection>>)
+							Observable.zip(Observable.just(response), conn, Tuples::of);
 				})
 				.flatMap(tuple -> {
 					WebSocketResponse<ByteBuf> response = tuple.getT1();