Remove unnecessary null checks in flutter/widgets (#119028)

* dart fix --apply

* manual fixes

Author: goderbauer

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

@@ -431,9 +431,7 @@ class ActionListener extends StatefulWidget {
     required this.listener,
     required this.action,
     required this.child,
-  })  : assert(listener != null),
-        assert(action != null),
-        assert(child != null);
+  });
 
   /// The [ActionListenerCallback] callback to register with the [action].
   ///
@@ -548,7 +546,7 @@ class CallbackAction<T extends Intent> extends Action<T> {
   ///
   /// The `intentKey` and [onInvoke] parameters must not be null.
   /// The [onInvoke] parameter is required.
-  CallbackAction({required this.onInvoke}) : assert(onInvoke != null);
+  CallbackAction({required this.onInvoke});
 
   /// The callback to be called when invoked.
   ///
@@ -595,8 +593,6 @@ class ActionDispatcher with Diagnosticable {
     covariant Intent intent, [
     BuildContext? context,
   ]) {
-    assert(action != null);
-    assert(intent != null);
     assert(action.isEnabled(intent), 'Action must be enabled when calling invokeAction');
     if (action is ContextAction) {
       context ??= primaryFocus?.context;
@@ -651,8 +647,7 @@ class Actions extends StatefulWidget {
     this.dispatcher,
     required this.actions,
     required this.child,
-  })  : assert(actions != null),
-        assert(child != null);
+  });
 
   /// The [ActionDispatcher] object that invokes actions.
   ///
@@ -869,7 +864,6 @@ class Actions extends StatefulWidget {
   /// Will return a newly created [ActionDispatcher] if no ambient [Actions]
   /// widget is found.
   static ActionDispatcher of(BuildContext context) {
-    assert(context != null);
     final _ActionsScope? marker = context.dependOnInheritedWidgetOfExactType<_ActionsScope>();
     return marker?.dispatcher ?? _findDispatcher(context);
   }
@@ -892,8 +886,6 @@ class Actions extends StatefulWidget {
     BuildContext context,
     T intent,
   ) {
-    assert(intent != null);
-    assert(context != null);
     Object? returnValue;
 
     final bool actionFound = _visitActionsAncestors(context, (InheritedElement element) {
@@ -945,8 +937,6 @@ class Actions extends StatefulWidget {
     BuildContext context,
     T intent,
   ) {
-    assert(intent != null);
-    assert(context != null);
     Object? returnValue;
 
     _visitActionsAncestors(context, (InheritedElement element) {
@@ -1041,8 +1031,7 @@ class _ActionsScope extends InheritedWidget {
     required this.actions,
     required this.rebuildKey,
     required super.child,
-  })  : assert(child != null),
-        assert(actions != null);
+  });
 
   final ActionDispatcher? dispatcher;
   final Map<Type, Action<Intent>> actions;
@@ -1106,10 +1095,7 @@ class FocusableActionDetector extends StatefulWidget {
     this.mouseCursor = MouseCursor.defer,
     this.includeFocusSemantics = true,
     required this.child,
-  })  : assert(enabled != null),
-        assert(autofocus != null),
-        assert(mouseCursor != null),
-        assert(child != null);
+  });
 
   /// Is this widget enabled or not.
   ///
@@ -1530,7 +1516,7 @@ class PrioritizedIntents extends Intent {
   /// of intents, the first available of which will be used.
   const PrioritizedIntents({
     required this.orderedIntents,
-  })  : assert(orderedIntents != null);
+  });
 
   /// List of intents to be evaluated in order for execution. When an
   /// [Action.isEnabled] returns true, that action will be invoked and
@@ -1566,8 +1552,6 @@ class PrioritizedAction extends Action<PrioritizedIntents> {
 
   @override
   void invoke(PrioritizedIntents intent) {
-    assert(_selectedAction != null);
-    assert(_selectedIntent != null);
     _selectedAction.invoke(_selectedIntent);
   }
 }

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

@@ -130,16 +130,7 @@ class AnimatedCrossFade extends StatefulWidget {
     this.reverseDuration,
     this.layoutBuilder = defaultLayoutBuilder,
     this.excludeBottomFocus = true,
-  }) : assert(firstChild != null),
-       assert(secondChild != null),
-       assert(firstCurve != null),
-       assert(secondCurve != null),
-       assert(sizeCurve != null),
-       assert(alignment != null),
-       assert(crossFadeState != null),
-       assert(duration != null),
-       assert(layoutBuilder != null),
-       assert(excludeBottomFocus != null);
+  });
 
   /// The child that is visible when [crossFadeState] is
   /// [CrossFadeState.showFirst]. It fades out when transitioning

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

@@ -52,8 +52,7 @@ class AnimatedList extends _AnimatedScrollView {
     super.shrinkWrap = false,
     super.padding,
     super.clipBehavior = Clip.hardEdge,
-  }) : assert(itemBuilder != null),
-       assert(initialItemCount != null && initialItemCount >= 0);
+  }) : assert(initialItemCount >= 0);
 
   /// The state from the closest instance of this class that encloses the given
   /// context.
@@ -74,7 +73,6 @@ class AnimatedList extends _AnimatedScrollView {
   ///  * [maybeOf], a similar function that will return null if no
   ///    [AnimatedList] ancestor is found.
   static AnimatedListState of(BuildContext context) {
-    assert(context != null);
     final AnimatedListState? result = AnimatedList.maybeOf(context);
     assert(() {
       if (result == null) {
@@ -116,7 +114,6 @@ class AnimatedList extends _AnimatedScrollView {
   ///  * [of], a similar function that will throw if no [AnimatedList] ancestor
   ///    is found.
   static AnimatedListState? maybeOf(BuildContext context) {
-    assert(context != null);
     return context.findAncestorStateOfType<AnimatedListState>();
   }
 
@@ -217,8 +214,7 @@ class AnimatedGrid extends _AnimatedScrollView {
     super.physics,
     super.padding,
     super.clipBehavior = Clip.hardEdge,
-  })  : assert(itemBuilder != null),
-        assert(initialItemCount != null && initialItemCount >= 0);
+  })  : assert(initialItemCount >= 0);
 
   /// {@template flutter.widgets.AnimatedGrid.gridDelegate}
   /// A delegate that controls the layout of the children within the
@@ -252,7 +248,6 @@ class AnimatedGrid extends _AnimatedScrollView {
   ///  * [maybeOf], a similar function that will return null if no
   ///    [AnimatedGrid] ancestor is found.
   static AnimatedGridState of(BuildContext context) {
-    assert(context != null);
     final AnimatedGridState? result = AnimatedGrid.maybeOf(context);
     assert(() {
       if (result == null) {
@@ -294,7 +289,6 @@ class AnimatedGrid extends _AnimatedScrollView {
   ///  * [of], a similar function that will throw if no [AnimatedGrid] ancestor
   ///    is found.
   static AnimatedGridState? maybeOf(BuildContext context) {
-    assert(context != null);
     return context.findAncestorStateOfType<AnimatedGridState>();
   }
 
@@ -373,8 +367,7 @@ abstract class _AnimatedScrollView extends StatefulWidget {
     this.shrinkWrap = false,
     this.padding,
     this.clipBehavior = Clip.hardEdge,
-  }) : assert(itemBuilder != null),
-        assert(initialItemCount != null && initialItemCount >= 0);
+  }) : assert(initialItemCount >= 0);
 
   /// {@template flutter.widgets.AnimatedScrollView.itemBuilder}
   /// Called, as needed, to build children widgets.
@@ -630,8 +623,7 @@ class SliverAnimatedList extends _SliverAnimatedMultiBoxAdaptor {
     required super.itemBuilder,
     super.findChildIndexCallback,
     super.initialItemCount = 0,
-  }) : assert(itemBuilder != null),
-        assert(initialItemCount != null && initialItemCount >= 0);
+  }) : assert(initialItemCount >= 0);
 
   @override
   SliverAnimatedListState createState() => SliverAnimatedListState();
@@ -655,7 +647,6 @@ class SliverAnimatedList extends _SliverAnimatedMultiBoxAdaptor {
   ///  * [maybeOf], a similar function that will return null if no
   ///    [SliverAnimatedList] ancestor is found.
   static SliverAnimatedListState of(BuildContext context) {
-    assert(context != null);
     final SliverAnimatedListState? result = SliverAnimatedList.maybeOf(context);
     assert(() {
       if (result == null) {
@@ -695,7 +686,6 @@ class SliverAnimatedList extends _SliverAnimatedMultiBoxAdaptor {
   ///  * [of], a similar function that will throw if no [SliverAnimatedList]
   ///    ancestor is found.
   static SliverAnimatedListState? maybeOf(BuildContext context) {
-    assert(context != null);
     return context.findAncestorStateOfType<SliverAnimatedListState>();
   }
 }
@@ -782,8 +772,7 @@ class SliverAnimatedGrid extends _SliverAnimatedMultiBoxAdaptor {
     required this.gridDelegate,
     super.findChildIndexCallback,
     super.initialItemCount = 0,
-  })  : assert(itemBuilder != null),
-        assert(initialItemCount != null && initialItemCount >= 0);
+  })  : assert(initialItemCount >= 0);
 
   @override
   SliverAnimatedGridState createState() => SliverAnimatedGridState();
@@ -807,7 +796,6 @@ class SliverAnimatedGrid extends _SliverAnimatedMultiBoxAdaptor {
   ///  * [maybeOf], a similar function that will return null if no
   ///    [SliverAnimatedGrid] ancestor is found.
   static SliverAnimatedGridState of(BuildContext context) {
-    assert(context != null);
     final SliverAnimatedGridState? result = context.findAncestorStateOfType<SliverAnimatedGridState>();
     assert(() {
       if (result == null) {
@@ -844,7 +832,6 @@ class SliverAnimatedGrid extends _SliverAnimatedMultiBoxAdaptor {
   ///  * [of], a similar function that will throw if no [SliverAnimatedGrid]
   ///    ancestor is found.
   static SliverAnimatedGridState? maybeOf(BuildContext context) {
-    assert(context != null);
     return context.findAncestorStateOfType<SliverAnimatedGridState>();
   }
 }
@@ -908,8 +895,7 @@ abstract class _SliverAnimatedMultiBoxAdaptor extends StatefulWidget {
     required this.itemBuilder,
     this.findChildIndexCallback,
     this.initialItemCount = 0,
-  })  : assert(itemBuilder != null),
-        assert(initialItemCount != null && initialItemCount >= 0);
+  })  : assert(initialItemCount >= 0);
 
   /// {@macro flutter.widgets.AnimatedScrollView.itemBuilder}
   final AnimatedItemBuilder itemBuilder;
@@ -1022,8 +1008,7 @@ abstract class _SliverAnimatedMultiBoxAdaptorState<T extends _SliverAnimatedMult
   /// increases the length of the list of items by one and shifts
   /// all items at or after [index] towards the end of the list of items.
   void insertItem(int index, { Duration duration = _kDuration }) {
-    assert(index != null && index >= 0);
-    assert(duration != null);
+    assert(index >= 0);
 
     final int itemIndex = _indexToItemIndex(index);
     assert(itemIndex >= 0 && itemIndex <= _itemsCount);
@@ -1074,9 +1059,7 @@ abstract class _SliverAnimatedMultiBoxAdaptorState<T extends _SliverAnimatedMult
   /// decreases the length of items by one and shifts
   /// all items at or before [index] towards the beginning of the list of items.
   void removeItem(int index, AnimatedRemovedItemBuilder builder, { Duration duration = _kDuration }) {
-    assert(index != null && index >= 0);
-    assert(builder != null);
-    assert(duration != null);
+    assert(index >= 0);
 
     final int itemIndex = _indexToItemIndex(index);
     assert(itemIndex >= 0 && itemIndex < _itemsCount);

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

@@ -38,7 +38,7 @@ class AnimatedSize extends StatefulWidget {
     )
     TickerProvider? vsync,
     this.clipBehavior = Clip.hardEdge,
-  }) : assert(clipBehavior != null);
+  });
 
   /// The widget below this widget in the tree.
   ///
@@ -114,7 +114,7 @@ class _AnimatedSize extends SingleChildRenderObjectWidget {
     this.reverseDuration,
     required this.vsync,
     this.clipBehavior = Clip.hardEdge,
-  }) : assert(clipBehavior != null);
+  });
 
   final AlignmentGeometry alignment;
   final Curve curve;

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

@@ -19,9 +19,7 @@ class _ChildEntry {
     required this.animation,
     required this.transition,
     required this.widgetChild,
-  }) : assert(animation != null),
-       assert(transition != null),
-       assert(controller != null);
+  });
 
   // The animation controller for the child's transition.
   final AnimationController controller;
@@ -117,11 +115,7 @@ class AnimatedSwitcher extends StatefulWidget {
     this.switchOutCurve = Curves.linear,
     this.transitionBuilder = AnimatedSwitcher.defaultTransitionBuilder,
     this.layoutBuilder = AnimatedSwitcher.defaultLayoutBuilder,
-  }) : assert(duration != null),
-       assert(switchInCurve != null),
-       assert(switchOutCurve != null),
-       assert(transitionBuilder != null),
-       assert(layoutBuilder != null);
+  });
 
   /// The current child widget to display. If there was a previous child, then
   /// that child will be faded out using the [switchOutCurve], while the new

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

@@ -24,8 +24,7 @@ class AnnotatedRegion<T extends Object> extends SingleChildRenderObjectWidget {
     required Widget super.child,
     required this.value,
     this.sized = true,
-  }) : assert(value != null),
-       assert(child != null);
+  });
 
   /// A value which can be retrieved using [Layer.find].
   final T value;

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

@@ -344,9 +344,7 @@ class WidgetsApp extends StatefulWidget {
     this.actions,
     this.restorationScopeId,
     this.useInheritedMediaQuery = false,
-  }) : assert(navigatorObservers != null),
-       assert(routes != null),
-       assert(
+  }) : assert(
          home == null ||
          onGenerateInitialRoutes == null,
          'If onGenerateInitialRoutes is specified, the home argument will be '
@@ -398,15 +396,7 @@ class WidgetsApp extends StatefulWidget {
          'pageRouteBuilder must be specified so that the default handler '
          'will know what kind of PageRoute transition to build.',
        ),
-       assert(title != null),
-       assert(color != null),
-       assert(supportedLocales != null && supportedLocales.isNotEmpty),
-       assert(showPerformanceOverlay != null),
-       assert(checkerboardRasterCacheImages != null),
-       assert(checkerboardOffscreenLayers != null),
-       assert(showSemanticsDebugger != null),
-       assert(debugShowCheckedModeBanner != null),
-       assert(debugShowWidgetInspector != null),
+       assert(supportedLocales.isNotEmpty),
        routeInformationProvider = null,
        routeInformationParser = null,
        routerDelegate = null,
@@ -463,15 +453,7 @@ class WidgetsApp extends StatefulWidget {
          );
          return true;
        }()),
-       assert(title != null),
-       assert(color != null),
-       assert(supportedLocales != null && supportedLocales.isNotEmpty),
-       assert(showPerformanceOverlay != null),
-       assert(checkerboardRasterCacheImages != null),
-       assert(checkerboardOffscreenLayers != null),
-       assert(showSemanticsDebugger != null),
-       assert(debugShowCheckedModeBanner != null),
-       assert(debugShowWidgetInspector != null),
+       assert(supportedLocales.isNotEmpty),
        navigatorObservers = null,
        navigatorKey = null,
        onGenerateRoute = null,
@@ -1432,7 +1414,6 @@ class _WidgetsAppState extends State<WidgetsApp> with WidgetsBindingObserver {
         settings,
         pageContentBuilder,
       );
-      assert(route != null, 'The pageRouteBuilder for WidgetsApp must return a valid non-null Route.');
       return route;
     }
     if (widget.onGenerateRoute != null) {
@@ -1722,7 +1703,6 @@ class _WidgetsAppState extends State<WidgetsApp> with WidgetsBindingObserver {
         // parameter.
         builder: (BuildContext context) {
           final String title = widget.onGenerateTitle!(context);
-          assert(title != null, 'onGenerateTitle must return a non-null String');
           return Title(
             title: title,
             color: widget.color.withOpacity(1.0),