fix navigator.push

com.unity.uiwidgets/Runtime/material/dropdown.cs

                 barrierLabel: MaterialLocalizations.of(context).modalBarrierDismissLabel
             );
 
-            Navigator.push(context, _dropdownRoute).then(newValue => {
+            Navigator.push<T>(context, _dropdownRoute).then(newValue => {
                 _DropdownRouteResult<T> value = newValue as _DropdownRouteResult<T>;
                 _dropdownRoute = null;
                 if (!mounted || newValue == null) {

com.unity.uiwidgets/Runtime/material/popup_menu.cs

     }
 
     public static partial class PopupMenuUtils {
-        public static Future<object> showMenu<T>(
+        public static Future<T> showMenu<T>(
             BuildContext context,
             RelativeRect position,
             List<PopupMenuEntry<T>> items,

com.unity.uiwidgets/Runtime/material/search.cs

 
 namespace Unity.UIWidgets.material {
     public class SearchUtils {
-        public static Future<object> showSearch(
+        public static Future<T> showSearch<T>(
-            SearchDelegate del,
+            SearchDelegate<T> del,
             string query = ""
         ) {
             D.assert(del != null);
             del._currentBody = _SearchBody.suggestions;
-            return Navigator.of(context).push(new _SearchPageRoute(
+            return Navigator.of(context).push<T>(new _SearchPageRoute<T>(
-    public abstract class SearchDelegate {
+    public abstract class SearchDelegate<T> {
         public abstract Widget buildSuggestions(BuildContext context);
         public abstract Widget buildResults(BuildContext context);
         public abstract Widget buildLeading(BuildContext context);
             set { _currentBodyNotifier.value = value; }
         }
 
-        internal _SearchPageRoute _route;
+        internal _SearchPageRoute<T> _route;
     }
 
     enum _SearchBody {
 
-    class _SearchPageRoute : PageRoute {
-        public _SearchPageRoute(SearchDelegate del) {
+    class _SearchPageRoute<T> : PageRoute {
+        public _SearchPageRoute(SearchDelegate<T> del) {
             D.assert(del != null);
             D.assert(del._route == null,
                 () => $"The {this.del.GetType()} instance is currently used by another active " +
             this.del._route = this;
         }
 
-        public readonly SearchDelegate del;
+        public readonly SearchDelegate<T> del;
 
         public override Color barrierColor {
             get { return null; }
             Animation<float> animation,
             Animation<float> secondaryAnimation
         ) {
-            return new _SearchPage(
+            return new _SearchPage<T>(
                 del: del,
                 animation: animation
             );
         }
     }
 
-    class _SearchPage : StatefulWidget {
+    class _SearchPage<T> : StatefulWidget {
-            SearchDelegate del,
+            SearchDelegate<T> del,
             Animation<float> animation
         ) {
             this.del = del;
-        public readonly SearchDelegate del;
+        public readonly SearchDelegate<T> del;
-            return new _SearchPageState();
+            return new _SearchPageState<T>();
-    class _SearchPageState : State<_SearchPage> {
+    class _SearchPageState<T> : State<_SearchPage<T>> {
         public override void initState() {
             base.initState();
             queryTextController.addListener(_onQueryChanged);

com.unity.uiwidgets/Runtime/widgets/navigator.cs

             return of(context).pushNamedAndRemoveUntil<T>(newRouteName, predicate, arguments: arguments);
         }
 
-        public static Future<T> push<T>(BuildContext context, Route<T> route) {
+        public static Future<T> push<T>(BuildContext context, Route route) {
             return of(context).push<T>(route);
         }
 
             return route.popped;
         }
 
-        public Future<T> push<T>(Route<T> route) {
+        public Future<T> push<T>(Route route) {
             D.assert(!_debugLocked);
             D.assert(() => {
                 _debugLocked = true;