replace dynamic by Object/Object? in router.dart (#80476)

packages/flutter/lib/src/widgets/router.dart

@@ -306,7 +306,7 @@ class Router<T> extends StatefulWidget {
   ///
   ///  * [maybeOf], which is a similar function, but it will return null instead
   ///    of throwing an exception if no [Router] ancestor exists.
-  static Router<dynamic> of(BuildContext context) {
+  static Router<T> of<T extends Object?>(BuildContext context) {
     final _RouterScope? scope = context.dependOnInheritedWidgetOfExactType<_RouterScope>();
     assert(() {
       if (scope == null) {
@@ -318,7 +318,7 @@ class Router<T> extends StatefulWidget {
       }
       return true;
     }());
-    return scope!.routerState.widget;
+    return scope!.routerState.widget as Router<T>;
   }
 
   /// Retrieves the immediate [Router] ancestor from the given context.
@@ -334,9 +334,9 @@ class Router<T> extends StatefulWidget {
   ///
   ///  * [of], a similar method that returns a non-nullable value, and will
   ///    throw if no [Router] ancestor exists.
-  static Router<dynamic>? maybeOf(BuildContext context) {
+  static Router<T>? maybeOf<T extends Object?>(BuildContext context) {
     final _RouterScope? scope = context.dependOnInheritedWidgetOfExactType<_RouterScope>();
-    return scope?.routerState.widget;
+    return scope?.routerState.widget as Router<T>?;
   }
 
   /// Forces the [Router] to run the [callback] and reports the route
@@ -704,9 +704,9 @@ class _RouterScope extends InheritedWidget {
 
   final ValueListenable<RouteInformation?>? routeInformationProvider;
   final BackButtonDispatcher? backButtonDispatcher;
-  final RouteInformationParser<dynamic>? routeInformationParser;
-  final RouterDelegate<dynamic> routerDelegate;
-  final _RouterState<dynamic> routerState;
+  final RouteInformationParser<Object?>? routeInformationParser;
+  final RouterDelegate<Object?> routerDelegate;
+  final _RouterState<Object?> routerState;
 
   @override
   bool updateShouldNotify(_RouterScope oldWidget) {