Remove unnecessary null checks in `flutter/{animation,semantics,scheduler}` (#118922)

* Remove unnecessary null checks in flutter/animation

* Remove unnecessary null checks in flutter/semantics

* Remove unnecessary null checks in flutter/scheduler

packages/flutter/lib/src/animation/animation.dart

@@ -269,7 +269,6 @@ abstract class Animation<T> extends Listenable implements ValueListenable<T> {
   /// * "&#x23ED;": [AnimationStatus.completed] ([value] == 1.0)
   /// * "&#x23EE;": [AnimationStatus.dismissed] ([value] == 0.0)
   String toStringDetails() {
-    assert(status != null);
     switch (status) {
       case AnimationStatus.forward:
         return '\u25B6'; // >

packages/flutter/lib/src/animation/animation_controller.dart

@@ -242,10 +242,7 @@ class AnimationController extends Animation<double>
     this.upperBound = 1.0,
     this.animationBehavior = AnimationBehavior.normal,
     required TickerProvider vsync,
-  }) : assert(lowerBound != null),
-       assert(upperBound != null),
-       assert(upperBound >= lowerBound),
-       assert(vsync != null),
+  }) : assert(upperBound >= lowerBound),
        _direction = _AnimationDirection.forward {
     _ticker = vsync.createTicker(_tick);
     _internalSetValue(value ?? lowerBound);
@@ -275,9 +272,7 @@ class AnimationController extends Animation<double>
     this.debugLabel,
     required TickerProvider vsync,
     this.animationBehavior = AnimationBehavior.preserve,
-  }) : assert(value != null),
-       assert(vsync != null),
-       lowerBound = double.negativeInfinity,
+  }) : lowerBound = double.negativeInfinity,
        upperBound = double.infinity,
        _direction = _AnimationDirection.forward {
     _ticker = vsync.createTicker(_tick);
@@ -363,7 +358,6 @@ class AnimationController extends Animation<double>
   ///  * [forward], [reverse], [animateTo], [animateWith], [fling], and [repeat],
   ///    which start the animation controller.
   set value(double newValue) {
-    assert(newValue != null);
     stop();
     _internalSetValue(newValue);
     notifyListeners();
@@ -657,7 +651,6 @@ class AnimationController extends Animation<double>
     }());
     assert(max >= min);
     assert(max <= upperBound && min >= lowerBound);
-    assert(reverse != null);
     stop();
     return _startSimulation(_RepeatingSimulation(_value, min, max, reverse, period!, _directionSetter));
   }
@@ -744,7 +737,6 @@ class AnimationController extends Animation<double>
   }
 
   TickerFuture _startSimulation(Simulation simulation) {
-    assert(simulation != null);
     assert(!isAnimating);
     _simulation = simulation;
     _lastElapsedDuration = Duration.zero;
@@ -856,9 +848,7 @@ class AnimationController extends Animation<double>
 
 class _InterpolationSimulation extends Simulation {
   _InterpolationSimulation(this._begin, this._end, Duration duration, this._curve, double scale)
-    : assert(_begin != null),
-      assert(_end != null),
-      assert(duration != null && duration.inMicroseconds > 0),
+    : assert(duration.inMicroseconds > 0),
       _durationInSeconds = (duration.inMicroseconds * scale) / Duration.microsecondsPerSecond;
 
   final double _durationInSeconds;

packages/flutter/lib/src/animation/animations.dart

@@ -271,8 +271,7 @@ class ReverseAnimation extends Animation<double>
   /// Creates a reverse animation.
   ///
   /// The parent argument must not be null.
-  ReverseAnimation(this.parent)
-    : assert(parent != null);
+  ReverseAnimation(this.parent);
 
   /// The animation whose value and direction this animation is reversing.
   final Animation<double> parent;
@@ -310,7 +309,6 @@ class ReverseAnimation extends Animation<double>
   double get value => 1.0 - parent.value;
 
   AnimationStatus _reverseStatus(AnimationStatus status) {
-    assert(status != null);
     switch (status) {
       case AnimationStatus.forward: return AnimationStatus.reverse;
       case AnimationStatus.reverse: return AnimationStatus.forward;
@@ -384,8 +382,7 @@ class CurvedAnimation extends Animation<double> with AnimationWithParentMixin<do
     required this.parent,
     required this.curve,
     this.reverseCurve,
-  }) : assert(parent != null),
-       assert(curve != null) {
+  }) {
     _updateCurveDirection(parent.status);
     parent.addStatusListener(_updateCurveDirection);
   }
@@ -518,7 +515,7 @@ class TrainHoppingAnimation extends Animation<double>
     Animation<double> this._currentTrain,
     this._nextTrain, {
     this.onSwitchedTrain,
-  }) : assert(_currentTrain != null) {
+  }) {
     if (_nextTrain != null) {
       if (_currentTrain!.value == _nextTrain!.value) {
         _currentTrain = _nextTrain;
@@ -644,8 +641,7 @@ abstract class CompoundAnimation<T> extends Animation<T>
   CompoundAnimation({
     required this.first,
     required this.next,
-  }) : assert(first != null),
-       assert(next != null);
+  });
 
   /// The first sub-animation. Its status takes precedence if neither are
   /// animating.

packages/flutter/lib/src/animation/curves.dart

@@ -35,7 +35,6 @@ abstract class ParametricCurve<T> {
   /// implementation of [transform], which delegates the remaining logic to
   /// [transformInternal].
   T transform(double t) {
-    assert(t != null);
     assert(t >= 0.0 && t <= 1.0, 'parametric value $t is outside of [0, 1] range.');
     return transformInternal(t);
   }
@@ -129,7 +128,7 @@ class SawTooth extends Curve {
   /// Creates a sawtooth curve.
   ///
   /// The [count] argument must not be null.
-  const SawTooth(this.count) : assert(count != null);
+  const SawTooth(this.count);
 
   /// The number of repetitions of the sawtooth pattern in the unit interval.
   final int count;
@@ -159,10 +158,7 @@ class Interval extends Curve {
   /// Creates an interval curve.
   ///
   /// The arguments must not be null.
-  const Interval(this.begin, this.end, { this.curve = Curves.linear })
-    : assert(begin != null),
-      assert(end != null),
-      assert(curve != null);
+  const Interval(this.begin, this.end, { this.curve = Curves.linear });
 
   /// The largest value for which this interval is 0.0.
   ///
@@ -207,7 +203,7 @@ class Threshold extends Curve {
   /// Creates a threshold curve.
   ///
   /// The [threshold] argument must not be null.
-  const Threshold(this.threshold) : assert(threshold != null);
+  const Threshold(this.threshold);
 
   /// The value before which the curve is 0.0 and after which the curve is 1.0.
   ///
@@ -307,11 +303,7 @@ class Cubic extends Curve {
   /// cubic curves in [Curves].
   ///
   /// The [a] (x1), [b] (y1), [c] (x2) and [d] (y2) arguments must not be null.
-  const Cubic(this.a, this.b, this.c, this.d)
-    : assert(a != null),
-      assert(b != null),
-      assert(c != null),
-      assert(d != null);
+  const Cubic(this.a, this.b, this.c, this.d);
 
   /// The x coordinate of the first control point.
   ///
@@ -518,9 +510,6 @@ abstract class Curve2D extends ParametricCurve<Offset> {
     // 4. Recursively sample the two parts.
     //
     // This algorithm concentrates samples in areas of high curvature.
-    assert(tolerance != null);
-    assert(start != null);
-    assert(end != null);
     assert(end > start);
     // We want to pick a random seed that will keep the result stable if
     // evaluated again, so we use the first non-generated control point.
@@ -577,7 +566,6 @@ abstract class Curve2D extends ParametricCurve<Offset> {
   /// single-valued, it will return the parameter for only one of the values at
   /// the given `x` location.
   double findInverse(double x) {
-    assert(x != null);
     double start = 0.0;
     double end = 1.0;
     late double mid;
@@ -612,7 +600,7 @@ class Curve2DSample {
   /// Creates an object that holds a sample; used with [Curve2D] subclasses.
   ///
   /// All arguments must not be null.
-  const Curve2DSample(this.t, this.value) : assert(t != null), assert(value != null);
+  const Curve2DSample(this.t, this.value);
 
   /// The parametric location of this sample point along the curve.
   final double t;
@@ -682,9 +670,7 @@ class CatmullRomSpline extends Curve2D {
         double tension = 0.0,
         Offset? startHandle,
         Offset? endHandle,
-      }) : assert(controlPoints != null),
-           assert(tension != null),
-           assert(tension <= 1.0, 'tension $tension must not be greater than 1.0.'),
+      }) : assert(tension <= 1.0, 'tension $tension must not be greater than 1.0.'),
            assert(tension >= 0.0, 'tension $tension must not be negative.'),
            assert(controlPoints.length > 3, 'There must be at least four control points to create a CatmullRomSpline.'),
            _controlPoints = controlPoints,
@@ -702,9 +688,7 @@ class CatmullRomSpline extends Curve2D {
         double tension = 0.0,
         Offset? startHandle,
         Offset? endHandle,
-      }) : assert(controlPoints != null),
-           assert(tension != null),
-           assert(tension <= 1.0, 'tension $tension must not be greater than 1.0.'),
+      }) : assert(tension <= 1.0, 'tension $tension must not be greater than 1.0.'),
            assert(tension >= 0.0, 'tension $tension must not be negative.'),
            assert(controlPoints.length > 3, 'There must be at least four control points to create a CatmullRomSpline.'),
            _controlPoints = null,
@@ -860,8 +844,7 @@ class CatmullRomCurve extends Curve {
   ///
   ///  * This [paper on using Catmull-Rom splines](http://faculty.cs.tamu.edu/schaefer/research/cr_cad.pdf).
   CatmullRomCurve(this.controlPoints, {this.tension = 0.0})
-      : assert(tension != null),
-        assert(() {
+      : assert(() {
           return validateControlPoints(
             controlPoints,
             tension: tension,
@@ -877,8 +860,7 @@ class CatmullRomCurve extends Curve {
   /// Same as [CatmullRomCurve.new], but it precomputes the internal curve data
   /// structures for a more predictable computation load.
   CatmullRomCurve.precompute(this.controlPoints, {this.tension = 0.0})
-      : assert(tension != null),
-        assert(() {
+      : assert(() {
           return validateControlPoints(
             controlPoints,
             tension: tension,
@@ -963,7 +945,6 @@ class CatmullRomCurve extends Curve {
     double tension = 0.0,
     List<String>? reasons,
   }) {
-    assert(tension != null);
     if (controlPoints == null) {
       assert(() {
         reasons?.add('Supplied control points cannot be null');
@@ -1143,7 +1124,7 @@ class FlippedCurve extends Curve {
   /// Creates a flipped curve.
   ///
   /// The [curve] argument must not be null.
-  const FlippedCurve(this.curve) : assert(curve != null);
+  const FlippedCurve(this.curve);
 
   /// The curve that is being flipped.
   final Curve curve;

packages/flutter/lib/src/animation/tween.dart

@@ -364,8 +364,7 @@ class Tween<T extends Object?> extends Animatable<T> {
 class ReverseTween<T extends Object?> extends Tween<T> {
   /// Construct a [Tween] that evaluates its [parent] in reverse.
   ReverseTween(this.parent)
-    : assert(parent != null),
-      super(begin: parent.end, end: parent.begin);
+    : super(begin: parent.end, end: parent.begin);
 
   /// This tween's value is the same as the parent's value evaluated in reverse.
   ///
@@ -544,8 +543,7 @@ class CurveTween extends Animatable<double> {
   /// Creates a curve tween.
   ///
   /// The [curve] argument must not be null.
-  CurveTween({ required this.curve })
-    : assert(curve != null);
+  CurveTween({ required this.curve });
 
   /// The curve to use when transforming the value of the animation.
   Curve curve;

packages/flutter/lib/src/animation/tween_sequence.dart

@@ -51,8 +51,7 @@ class TweenSequence<T> extends Animatable<T> {
   /// best to reuse one, rather than rebuilding it on every frame, when that's
   /// possible.
   TweenSequence(List<TweenSequenceItem<T>> items)
-      : assert(items != null),
-        assert(items.isNotEmpty) {
+      : assert(items.isNotEmpty) {
     _items.addAll(items);
 
     double totalWeight = 0.0;
@@ -113,8 +112,7 @@ class FlippedTweenSequence extends TweenSequence<double> {
   /// There's a small cost associated with building a `TweenSequence` so it's
   /// best to reuse one, rather than rebuilding it on every frame, when that's
   /// possible.
-  FlippedTweenSequence(super.items)
-    : assert(items != null);
+  FlippedTweenSequence(super.items);
 
   @override
   double transform(double t) => 1 - super.transform(1 - t);
@@ -128,9 +126,7 @@ class TweenSequenceItem<T> {
   const TweenSequenceItem({
     required this.tween,
     required this.weight,
-  }) : assert(tween != null),
-       assert(weight != null),
-       assert(weight > 0.0);
+  }) : assert(weight > 0.0);
 
   /// Defines the value of the [TweenSequence] for the interval within the
   /// animation's duration indicated by [weight] and this item's position

packages/flutter/lib/src/scheduler/binding.dart

@@ -385,7 +385,6 @@ mixin SchedulerBinding on BindingBase {
   @protected
   @mustCallSuper
   void handleAppLifecycleStateChanged(AppLifecycleState state) {
-    assert(state != null);
     _lifecycleState = state;
     switch (state) {
       case AppLifecycleState.resumed:
@@ -1026,7 +1025,6 @@ mixin SchedulerBinding on BindingBase {
   /// presentation time, and can be used to ensure that animations running in
   /// different processes are synchronized.
   Duration get currentSystemFrameTimeStamp {
-    assert(_lastRawTimeStamp != null);
     return _lastRawTimeStamp;
   }
 
@@ -1279,7 +1277,6 @@ mixin SchedulerBinding on BindingBase {
   // the error.
   @pragma('vm:notify-debugger-on-exception')
   void _invokeFrameCallback(FrameCallback callback, Duration timeStamp, [ StackTrace? callbackStack ]) {
-    assert(callback != null);
     assert(_FrameCallbackEntry.debugCurrentCallbackStack == null);
     assert(() {
       _FrameCallbackEntry.debugCurrentCallbackStack = callbackStack;

packages/flutter/lib/src/semantics/semantics.dart

@@ -211,8 +211,7 @@ class CustomSemanticsAction {
   ///
   /// The [label] must not be null or the empty string.
   const CustomSemanticsAction({required String this.label})
-    : assert(label != null),
-      assert(label != ''),
+    : assert(label != ''),
       hint = null,
       action = null;
 
@@ -221,9 +220,7 @@ class CustomSemanticsAction {
   ///
   /// The [hint] must not be null or the empty string.
   const CustomSemanticsAction.overridingAction({required String this.hint, required SemanticsAction this.action})
-    : assert(hint != null),
-      assert(hint != ''),
-      assert(action != null),
+    : assert(hint != ''),
       label = null;
 
   /// The user readable name of this custom semantics action.
@@ -371,8 +368,7 @@ class AttributedStringProperty extends DiagnosticsProperty<AttributedString> {
     super.defaultValue,
     super.level,
     super.description,
-  }) : assert(showName != null),
-       assert(level != null);
+  });
 
   /// Whether to show the property when the [value] is an [AttributedString]
   /// whose [AttributedString.string] is the empty string.
@@ -441,20 +437,12 @@ class SemanticsData with Diagnosticable {
     this.tags,
     this.transform,
     this.customSemanticsActionIds,
-  }) : assert(flags != null),
-       assert(actions != null),
-       assert(attributedLabel != null),
-       assert(attributedValue != null),
-       assert(attributedDecreasedValue != null),
-       assert(attributedIncreasedValue != null),
-       assert(attributedHint != null),
-       assert(tooltip == '' || textDirection != null, 'A SemanticsData object with tooltip "$tooltip" had a null textDirection.'),
+  }) : assert(tooltip == '' || textDirection != null, 'A SemanticsData object with tooltip "$tooltip" had a null textDirection.'),
        assert(attributedLabel.string == '' || textDirection != null, 'A SemanticsData object with label "${attributedLabel.string}" had a null textDirection.'),
        assert(attributedValue.string == '' || textDirection != null, 'A SemanticsData object with value "${attributedValue.string}" had a null textDirection.'),
        assert(attributedDecreasedValue.string == '' || textDirection != null, 'A SemanticsData object with decreasedValue "${attributedDecreasedValue.string}" had a null textDirection.'),
        assert(attributedIncreasedValue.string == '' || textDirection != null, 'A SemanticsData object with increasedValue "${attributedIncreasedValue.string}" had a null textDirection.'),
-       assert(attributedHint.string == '' || textDirection != null, 'A SemanticsData object with hint "${attributedHint.string}" had a null textDirection.'),
-       assert(rect != null);
+       assert(attributedHint.string == '' || textDirection != null, 'A SemanticsData object with hint "${attributedHint.string}" had a null textDirection.');
 
   /// A bit field of [SemanticsFlag]s that apply to this node.
   final int flags;
@@ -1721,7 +1709,6 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
   Rect get rect => _rect;
   Rect _rect = Rect.zero;
   set rect(Rect value) {
-    assert(value != null);
     assert(value.isFinite, '$this (with $owner) tried to set a non-finite rect.');
     if (_rect != value) {
       _rect = value;
@@ -1806,7 +1793,6 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
   bool get isMergedIntoParent => _isMergedIntoParent;
   bool _isMergedIntoParent = false;
   set isMergedIntoParent(bool value) {
-    assert(value != null);
     if (_isMergedIntoParent == value) {
       return;
     }
@@ -1929,7 +1915,6 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
       }
     }
     if (!sawChange && _children != null) {
-      assert(newChildren != null);
       assert(newChildren.length == _children!.length);
       // Did the order change?
       for (int i = 0; i < _children!.length; i++) {
@@ -2504,13 +2489,13 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
         platformViewId ??= node._platformViewId;
         maxValueLength ??= node._maxValueLength;
         currentValueLength ??= node._currentValueLength;
-        if (attributedValue == null || attributedValue.string == '') {
+        if (attributedValue.string == '') {
           attributedValue = node._attributedValue;
         }
-        if (attributedIncreasedValue == null || attributedIncreasedValue.string == '') {
+        if (attributedIncreasedValue.string == '') {
           attributedIncreasedValue = node._attributedIncreasedValue;
         }
-        if (attributedDecreasedValue == null || attributedDecreasedValue.string == '') {
+        if (attributedDecreasedValue.string == '') {
           attributedDecreasedValue = node._attributedDecreasedValue;
         }
         if (tooltip == '') {
@@ -2808,7 +2793,6 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
     DiagnosticLevel minLevel = DiagnosticLevel.debug,
     DebugSemanticsDumpOrder childOrder = DebugSemanticsDumpOrder.traversalOrder,
   }) {
-    assert(childOrder != null);
     return toDiagnosticsNode(childOrder: childOrder).toStringDeep(prefixLineOne: prefixLineOne, prefixOtherLines: prefixOtherLines, minLevel: minLevel);
   }
 
@@ -2835,7 +2819,6 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
 
   /// Returns the list of direct children of this node in the specified order.
   List<SemanticsNode> debugListChildrenInOrder(DebugSemanticsDumpOrder childOrder) {
-    assert(childOrder != null);
     if (_children == null) {
       return const <SemanticsNode>[];
     }
@@ -2862,10 +2845,7 @@ class _BoxEdge implements Comparable<_BoxEdge> {
     required this.isLeadingEdge,
     required this.offset,
     required this.node,
-  }) : assert(isLeadingEdge != null),
-       assert(offset != null),
-       assert(offset.isFinite),
-       assert(node != null);
+  }) : assert(offset.isFinite);
 
   /// True if the edge comes before the seconds edge along the traversal
   /// direction, and false otherwise.
@@ -2899,7 +2879,7 @@ class _SemanticsSortGroup extends Comparable<_SemanticsSortGroup> {
   _SemanticsSortGroup({
     required this.startOffset,
     required this.textDirection,
-  }) : assert(startOffset != null);
+  });
 
   /// The offset from the start edge of the parent [SemanticsNode] in the
   /// direction of the traversal.
@@ -3122,9 +3102,7 @@ class _TraversalSortNode implements Comparable<_TraversalSortNode> {
     required this.node,
     this.sortKey,
     required this.position,
-  })
-    : assert(node != null),
-      assert(position != null);
+  });
 
   /// The node whose position this sort node determines.
   final SemanticsNode node;
@@ -3263,7 +3241,6 @@ class SemanticsOwner extends ChangeNotifier {
   /// If the given `action` requires arguments they need to be passed in via
   /// the `args` parameter.
   void performAction(int id, SemanticsAction action, [ Object? args ]) {
-    assert(action != null);
     final SemanticsActionHandler? handler = _getSemanticsActionHandlerForId(id, action);
     if (handler != null) {
       handler(args);
@@ -3317,7 +3294,6 @@ class SemanticsOwner extends ChangeNotifier {
   /// If the given `action` requires arguments they need to be passed in via
   /// the `args` parameter.
   void performActionAt(Offset position, SemanticsAction action, [ Object? args ]) {
-    assert(action != null);
     final SemanticsNode? node = rootSemanticsNode;
     if (node == null) {
       return;
@@ -3419,7 +3395,6 @@ class SemanticsConfiguration {
   /// The provided `handler` is called to respond to the user triggered
   /// `action`.
   void _addAction(SemanticsAction action, SemanticsActionHandler handler) {
-    assert(handler != null);
     _actions[action] = handler;
     _actionsAsBits |= action.index;
     _hasBeenAnnotated = true;
@@ -3431,7 +3406,6 @@ class SemanticsConfiguration {
   /// The provided `handler` is called to respond to the user triggered
   /// `action`.
   void _addArgumentlessAction(SemanticsAction action, VoidCallback handler) {
-    assert(handler != null);
     _addAction(action, (Object? args) {
       assert(args == null);
       handler();
@@ -3746,7 +3720,7 @@ class SemanticsConfiguration {
     _addAction(SemanticsAction.setSelection, (Object? args) {
       assert(args != null && args is Map);
       final Map<String, int> selection = (args! as Map<dynamic, dynamic>).cast<String, int>();
-      assert(selection != null && selection['base'] != null && selection['extent'] != null);
+      assert(selection['base'] != null && selection['extent'] != null);
       value!(TextSelection(
         baseOffset: selection['base']!,
         extentOffset: selection['extent']!,
@@ -4004,7 +3978,6 @@ class SemanticsConfiguration {
   ///  * [attributedLabel], which is the [AttributedString] of this property.
   String get label => _attributedLabel.string;
   set label(String label) {
-    assert(label != null);
     _attributedLabel = AttributedString(label);
     _hasBeenAnnotated = true;
   }
@@ -4045,7 +4018,6 @@ class SemanticsConfiguration {
   ///    [value] will be after performing [SemanticsAction.decrease].
   String get value => _attributedValue.string;
   set value(String value) {
-    assert(value != null);
     _attributedValue = AttributedString(value);
     _hasBeenAnnotated = true;
   }
@@ -4091,7 +4063,6 @@ class SemanticsConfiguration {
   ///  * [attributedIncreasedValue], which is the [AttributedString] of this property.
   String get increasedValue => _attributedIncreasedValue.string;
   set increasedValue(String increasedValue) {
-    assert(increasedValue != null);
     _attributedIncreasedValue = AttributedString(increasedValue);
     _hasBeenAnnotated = true;
   }
@@ -4129,7 +4100,6 @@ class SemanticsConfiguration {
   ///  * [attributedDecreasedValue], which is the [AttributedString] of this property.
   String get decreasedValue => _attributedDecreasedValue.string;
   set decreasedValue(String decreasedValue) {
-    assert(decreasedValue != null);
     _attributedDecreasedValue = AttributedString(decreasedValue);
     _hasBeenAnnotated = true;
   }
@@ -4164,7 +4134,6 @@ class SemanticsConfiguration {
   ///  * [attributedHint], which is the [AttributedString] of this property.
   String get hint => _attributedHint.string;
   set hint(String hint) {
-    assert(hint != null);
     _attributedHint = AttributedString(hint);
     _hasBeenAnnotated = true;
   }
@@ -4217,7 +4186,7 @@ class SemanticsConfiguration {
   double get elevation => _elevation;
   double _elevation = 0.0;
   set elevation(double value) {
-    assert(value != null && value >= 0.0);
+    assert(value >= 0.0);
     if (value == _elevation) {
       return;
     }
@@ -4234,7 +4203,7 @@ class SemanticsConfiguration {
   double get thickness => _thickness;
   double _thickness = 0.0;
   set thickness(double value) {
-    assert(value != null && value >= 0.0);
+    assert(value >= 0.0);
     if (value == _thickness) {
       return;
     }
@@ -4632,7 +4601,7 @@ class SemanticsConfiguration {
     if (_currentValueLength != null && other._currentValueLength != null) {
       return false;
     }
-    if (_attributedValue != null && _attributedValue.string.isNotEmpty && other._attributedValue != null && other._attributedValue.string.isNotEmpty) {
+    if (_attributedValue.string.isNotEmpty && other._attributedValue.string.isNotEmpty) {
       return false;
     }
     return true;
@@ -4680,13 +4649,13 @@ class SemanticsConfiguration {
       otherAttributedString: child._attributedLabel,
       otherTextDirection: child.textDirection,
     );
-    if (_attributedValue == null || _attributedValue.string == '') {
+    if (_attributedValue.string == '') {
       _attributedValue = child._attributedValue;
     }
-    if (_attributedIncreasedValue == null || _attributedIncreasedValue.string == '') {
+    if (_attributedIncreasedValue.string == '') {
       _attributedIncreasedValue = child._attributedIncreasedValue;
     }
-    if (_attributedDecreasedValue == null || _attributedDecreasedValue.string == '') {
+    if (_attributedDecreasedValue.string == '') {
       _attributedDecreasedValue = child._attributedDecreasedValue;
     }
     _attributedHint = _concatAttributedString(
@@ -4880,8 +4849,7 @@ class OrdinalSortKey extends SemanticsSortKey {
   const OrdinalSortKey(
     this.order, {
     super.name,
-  }) : assert(order != null),
-       assert(order > double.negativeInfinity),
+  }) : assert(order > double.negativeInfinity),
        assert(order < double.infinity);
 
   /// Determines the placement of this key in a sequence of keys that defines
@@ -4894,7 +4862,7 @@ class OrdinalSortKey extends SemanticsSortKey {
 
   @override
   int doCompare(OrdinalSortKey other) {
-    if (other.order == null || order == null || other.order == order) {
+    if (other.order == order) {
       return 0;
     }
     return order.compareTo(other.order);

packages/flutter/lib/src/semantics/semantics_event.dart

@@ -87,9 +87,7 @@ class AnnounceSemanticsEvent extends SemanticsEvent {
 
   /// Constructs an event that triggers an announcement by the platform.
   const AnnounceSemanticsEvent(this.message, this.textDirection, {this.assertiveness = Assertiveness.polite})
-    : assert(message != null),
-      assert(textDirection != null),
-      super('announce');
+    : super('announce');
 
   /// The message to announce.
   ///