solving dart migrate errors pt 2

@@ -14,12 +14,14 @@ class GetCupertinoApp extends StatelessWidget {
     this.theme,
     this.navigatorKey,
     this.home,
-    Map<String, Widget Function(BuildContext)> this.routes = const <String, WidgetBuilder>{},
+    Map<String, Widget Function(BuildContext)> this.routes =
+        const <String, WidgetBuilder>{},
     this.initialRoute,
     this.onGenerateRoute,
     this.onGenerateInitialRoutes,
     this.onUnknownRoute,
-    List<NavigatorObserver> this.navigatorObservers = const <NavigatorObserver>[],
+    List<NavigatorObserver> this.navigatorObservers =
+        const <NavigatorObserver>[],
     this.builder,
     this.translationsKeys,
     this.translations,
@@ -58,15 +60,7 @@ class GetCupertinoApp extends StatelessWidget {
     this.highContrastTheme,
     this.highContrastDarkTheme,
     this.actions,
-  })  : assert(routes != null),
-        assert(navigatorObservers != null),
-        assert(title != null),
-        assert(showPerformanceOverlay != null),
-        assert(checkerboardRasterCacheImages != null),
-        assert(checkerboardOffscreenLayers != null),
-        assert(showSemanticsDebugger != null),
-        assert(debugShowCheckedModeBanner != null),
-        routeInformationProvider = null,
+  })  : routeInformationProvider = null,
         routeInformationParser = null,
         routerDelegate = null,
         backButtonDispatcher = null,
@@ -103,7 +97,7 @@ class GetCupertinoApp extends StatelessWidget {
   final ThemeData? highContrastTheme;
   final ThemeData? highContrastDarkTheme;
   final Map<Type, Action<Intent>>? actions;
-  final Function(Routing)? routingCallback;
+  final Function(Routing?)? routingCallback;
   final Transition? defaultTransition;
   final bool? opaqueRoute;
   final VoidCallback? onInit;
@@ -169,15 +163,7 @@ class GetCupertinoApp extends StatelessWidget {
     this.defaultGlobalState,
     this.getPages,
     this.unknownRoute,
-  })  : assert(routeInformationParser != null),
-        assert(routerDelegate != null),
-        assert(title != null),
-        assert(showPerformanceOverlay != null),
-        assert(checkerboardRasterCacheImages != null),
-        assert(checkerboardOffscreenLayers != null),
-        assert(showSemanticsDebugger != null),
-        assert(debugShowCheckedModeBanner != null),
-        navigatorObservers = null,
+  })  : navigatorObservers = null,
         navigatorKey = null,
         onGenerateRoute = null,
         home = null,
@@ -248,21 +234,19 @@ class GetCupertinoApp extends StatelessWidget {
                   child: builder == null ? child! : builder!(context, child),
                 );
               },
-              title: title ?? '',
+              title: title,
               onGenerateTitle: onGenerateTitle,
               color: color,
               locale: Get.locale ?? locale,
               localizationsDelegates: localizationsDelegates,
               localeListResolutionCallback: localeListResolutionCallback,
               localeResolutionCallback: localeResolutionCallback,
-              supportedLocales:
-                  supportedLocales ?? const <Locale>[Locale('en', 'US')],
-              showPerformanceOverlay: showPerformanceOverlay ?? false,
-              checkerboardRasterCacheImages:
-                  checkerboardRasterCacheImages ?? false,
-              checkerboardOffscreenLayers: checkerboardOffscreenLayers ?? false,
-              showSemanticsDebugger: showSemanticsDebugger ?? false,
-              debugShowCheckedModeBanner: debugShowCheckedModeBanner ?? true,
+              supportedLocales: supportedLocales,
+              showPerformanceOverlay: showPerformanceOverlay,
+              checkerboardRasterCacheImages: checkerboardRasterCacheImages,
+              checkerboardOffscreenLayers: checkerboardOffscreenLayers,
+              showSemanticsDebugger: showSemanticsDebugger,
+              debugShowCheckedModeBanner: debugShowCheckedModeBanner,
               shortcuts: shortcuts,
             )
           : CupertinoApp(
@@ -295,21 +279,19 @@ class GetCupertinoApp extends StatelessWidget {
                   child: builder == null ? child! : builder!(context, child),
                 );
               },
-              title: title ?? '',
+              title: title,
               onGenerateTitle: onGenerateTitle,
               color: color,
               locale: Get.locale ?? locale,
               localizationsDelegates: localizationsDelegates,
               localeListResolutionCallback: localeListResolutionCallback,
               localeResolutionCallback: localeResolutionCallback,
-              supportedLocales:
-                  supportedLocales ?? const <Locale>[Locale('en', 'US')],
-              showPerformanceOverlay: showPerformanceOverlay ?? false,
-              checkerboardRasterCacheImages:
-                  checkerboardRasterCacheImages ?? false,
-              checkerboardOffscreenLayers: checkerboardOffscreenLayers ?? false,
-              showSemanticsDebugger: showSemanticsDebugger ?? false,
-              debugShowCheckedModeBanner: debugShowCheckedModeBanner ?? true,
+              supportedLocales: supportedLocales,
+              showPerformanceOverlay: showPerformanceOverlay,
+              checkerboardRasterCacheImages: checkerboardRasterCacheImages,
+              checkerboardOffscreenLayers: checkerboardOffscreenLayers,
+              showSemanticsDebugger: showSemanticsDebugger,
+              debugShowCheckedModeBanner: debugShowCheckedModeBanner,
               shortcuts: shortcuts,
               //   actions: actions,
             ));

@@ -13,12 +13,14 @@ class GetMaterialApp extends StatelessWidget {
     Key? key,
     this.navigatorKey,
     this.home,
-    Map<String, Widget Function(BuildContext)> this.routes = const <String, WidgetBuilder>{},
+    Map<String, Widget Function(BuildContext)> this.routes =
+        const <String, WidgetBuilder>{},
     this.initialRoute,
     this.onGenerateRoute,
     this.onGenerateInitialRoutes,
     this.onUnknownRoute,
-    List<NavigatorObserver> this.navigatorObservers = const <NavigatorObserver>[],
+    List<NavigatorObserver> this.navigatorObservers =
+        const <NavigatorObserver>[],
     this.builder,
     this.textDirection,
     this.title = '',
@@ -61,16 +63,7 @@ class GetMaterialApp extends StatelessWidget {
     this.highContrastTheme,
     this.highContrastDarkTheme,
     this.actions,
-  })  : assert(routes != null),
-        assert(navigatorObservers != null),
-        assert(title != null),
-        assert(debugShowMaterialGrid != null),
-        assert(showPerformanceOverlay != null),
-        assert(checkerboardRasterCacheImages != null),
-        assert(checkerboardOffscreenLayers != null),
-        assert(showSemanticsDebugger != null),
-        assert(debugShowCheckedModeBanner != null),
-        routeInformationProvider = null,
+  })  : routeInformationProvider = null,
         routeInformationParser = null,
         routerDelegate = null,
         backButtonDispatcher = null,
@@ -111,7 +104,7 @@ class GetMaterialApp extends StatelessWidget {
   final ThemeData? highContrastDarkTheme;
   final Map<Type, Action<Intent>>? actions;
   final bool debugShowMaterialGrid;
-  final ValueChanged<Routing>? routingCallback;
+  final ValueChanged<Routing?>? routingCallback;
   final Transition? defaultTransition;
   final bool? opaqueRoute;
   final VoidCallback? onInit;
@@ -179,16 +172,7 @@ class GetMaterialApp extends StatelessWidget {
     this.defaultGlobalState,
     this.getPages,
     this.unknownRoute,
-  })  : assert(routeInformationParser != null),
-        assert(routerDelegate != null),
-        assert(title != null),
-        assert(debugShowMaterialGrid != null),
-        assert(showPerformanceOverlay != null),
-        assert(checkerboardRasterCacheImages != null),
-        assert(checkerboardOffscreenLayers != null),
-        assert(showSemanticsDebugger != null),
-        assert(debugShowCheckedModeBanner != null),
-        navigatorObservers = null,
+  })  : navigatorObservers = null,
         navigatorKey = null,
         onGenerateRoute = null,
         home = null,
@@ -257,25 +241,23 @@ class GetMaterialApp extends StatelessWidget {
                   child: builder == null ? child! : builder!(context, child),
                 );
               },
-              title: title ?? '',
+              title: title,
               onGenerateTitle: onGenerateTitle,
               color: color,
               theme: _.theme ?? theme ?? ThemeData.fallback(),
               darkTheme: darkTheme,
-              themeMode: _.themeMode ?? themeMode ?? ThemeMode.system,
+              themeMode: _.themeMode ?? themeMode,
               locale: Get.locale ?? locale,
               localizationsDelegates: localizationsDelegates,
               localeListResolutionCallback: localeListResolutionCallback,
               localeResolutionCallback: localeResolutionCallback,
-              supportedLocales:
-                  supportedLocales ?? const <Locale>[Locale('en', 'US')],
-              debugShowMaterialGrid: debugShowMaterialGrid ?? false,
-              showPerformanceOverlay: showPerformanceOverlay ?? false,
-              checkerboardRasterCacheImages:
-                  checkerboardRasterCacheImages ?? false,
-              checkerboardOffscreenLayers: checkerboardOffscreenLayers ?? false,
-              showSemanticsDebugger: showSemanticsDebugger ?? false,
-              debugShowCheckedModeBanner: debugShowCheckedModeBanner ?? true,
+              supportedLocales: supportedLocales,
+              debugShowMaterialGrid: debugShowMaterialGrid,
+              showPerformanceOverlay: showPerformanceOverlay,
+              checkerboardRasterCacheImages: checkerboardRasterCacheImages,
+              checkerboardOffscreenLayers: checkerboardOffscreenLayers,
+              showSemanticsDebugger: showSemanticsDebugger,
+              debugShowCheckedModeBanner: debugShowCheckedModeBanner,
               shortcuts: shortcuts,
             )
           : MaterialApp(
@@ -307,25 +289,23 @@ class GetMaterialApp extends StatelessWidget {
                   child: builder == null ? child! : builder!(context, child),
                 );
               },
-              title: title ?? '',
+              title: title,
               onGenerateTitle: onGenerateTitle,
               color: color,
               theme: _.theme ?? theme ?? ThemeData.fallback(),
               darkTheme: darkTheme,
-              themeMode: _.themeMode ?? themeMode ?? ThemeMode.system,
+              themeMode: _.themeMode ?? themeMode,
               locale: Get.locale ?? locale,
               localizationsDelegates: localizationsDelegates,
               localeListResolutionCallback: localeListResolutionCallback,
               localeResolutionCallback: localeResolutionCallback,
-              supportedLocales:
-                  supportedLocales ?? const <Locale>[Locale('en', 'US')],
-              debugShowMaterialGrid: debugShowMaterialGrid ?? false,
-              showPerformanceOverlay: showPerformanceOverlay ?? false,
-              checkerboardRasterCacheImages:
-                  checkerboardRasterCacheImages ?? false,
-              checkerboardOffscreenLayers: checkerboardOffscreenLayers ?? false,
-              showSemanticsDebugger: showSemanticsDebugger ?? false,
-              debugShowCheckedModeBanner: debugShowCheckedModeBanner ?? true,
+              supportedLocales: supportedLocales,
+              debugShowMaterialGrid: debugShowMaterialGrid,
+              showPerformanceOverlay: showPerformanceOverlay,
+              checkerboardRasterCacheImages: checkerboardRasterCacheImages,
+              checkerboardOffscreenLayers: checkerboardOffscreenLayers,
+              showSemanticsDebugger: showSemanticsDebugger,
+              debugShowCheckedModeBanner: debugShowCheckedModeBanner,
               shortcuts: shortcuts,
               //   actions: actions,
             ));

-import '../../../get_core/src/get_main.dart';
+import 'package:collection/collection.dart' show IterableExtension;
 
+import '../../../get_core/src/get_main.dart';
 import '../../get_navigation.dart';
 import '../routes/get_route.dart';
-import 'package:collection/collection.dart' show IterableExtension;
 
 class RouteDecoder {
   final GetPage? route;
-  final Map<String?, String> parameters;
+  final Map<String, String?> parameters;
   const RouteDecoder(this.route, this.parameters);
 }
 
@@ -16,10 +16,10 @@ class ParseRouteTree {
   RouteDecoder matchRoute(String name) {
     final uri = Uri.parse(name);
     final route = _findRoute(uri.path);
-    final params = Map<String?, String>.from(uri.queryParameters);
+    final params = Map<String, String?>.from(uri.queryParameters);
     if (route != null) {
       final parsedParams = _parseParams(name, route.path);
-      if (parsedParams != null && parsedParams.isNotEmpty) {
+      if (parsedParams.isNotEmpty) {
         params.addAll(parsedParams);
       }
     } else {
@@ -95,13 +95,13 @@ class ParseRouteTree {
     );
   }
 
-  Map<String?, String> _parseParams(String path, PathDecoded routePath) {
-    final params = <String?, String>{};
+  Map<String, String?> _parseParams(String path, PathDecoded routePath) {
+    final params = <String, String?>{};
     Match? paramsMatch = routePath.regex.firstMatch(path);
 
     for (var i = 0; i < routePath.keys.length; i++) {
       var param = Uri.decodeQueryComponent(paramsMatch![i + 1]!);
-      params[routePath.keys[i]] = param;
+      params[routePath.keys[i]!] = param;
     }
     return params;
   }

@@ -25,9 +25,9 @@ class GetMaterialController extends GetxController {
 
   final routing = Routing();
 
-  Map<String?, String> parameters = {};
+  Map<String, String?> parameters = {};
 
-  ParseRouteTree? routeTree;
+  late ParseRouteTree routeTree;
 
   CustomTransition? customTransition;
 

@@ -416,7 +416,7 @@ class _CupertinoBackGestureDetector<T> extends StatefulWidget {
     required this.enabledCallback,
     required this.onStartPopGesture,
     required this.child,
-  })  : assert(enabledCallback != null),
+  })   : assert(enabledCallback != null),
         assert(onStartPopGesture != null),
         assert(child != null),
         super(key: key);
@@ -493,11 +493,9 @@ class _CupertinoBackGestureDetectorState<T>
         return -value;
       case TextDirection.ltr:
         return value;
+      default:
+        return value;
     }
-    // FIXME: shouldn't we return a default here?
-    //  or perhaps throw error
-    // ignore: avoid_returning_null
-    return null;
   }
 
   @override
@@ -535,7 +533,7 @@ class _CupertinoBackGestureController<T> {
   _CupertinoBackGestureController({
     required this.navigator,
     required this.controller,
-  })  : assert(navigator != null),
+  })   : assert(navigator != null),
         assert(controller != null) {
     navigator.didStartUserGesture();
   }
@@ -579,7 +577,8 @@ class _CupertinoBackGestureController<T> {
           _kMaxDroppedSwipePageForwardAnimationTime,
           0,
           controller.value,
-        )!.floor(),
+        )!
+            .floor(),
         _kMaxPageBackAnimationTime,
       );
       controller.animateTo(1.0,
@@ -597,7 +596,8 @@ class _CupertinoBackGestureController<T> {
           0,
           _kMaxDroppedSwipePageForwardAnimationTime,
           controller.value,
-        )!.floor();
+        )!
+            .floor();
         controller.animateBack(
           0.0,
           duration: Duration(milliseconds: droppedPageBackAnimationTime),