more fixes

com.unity.uiwidgets/Runtime/cupertino/refresh.cs

-using System.Collections.Generic;
 using Unity.UIWidgets.animation;
 using Unity.UIWidgets.async;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
 using UnityEngine;
-using Color = Unity.UIWidgets.ui.Color;
-        float refreshIndicatorLayoutExtent = 0.0f,
-        bool hasLayoutExtent = false,
+        float? refreshIndicatorLayoutExtent = 0.0f,
+        bool? hasLayoutExtent = false,
-        this.refreshIndicatorLayoutExtent = refreshIndicatorLayoutExtent;
-        this.hasLayoutExtent = hasLayoutExtent;
+        this.refreshIndicatorLayoutExtent = refreshIndicatorLayoutExtent.Value;
+        this.hasLayoutExtent = hasLayoutExtent.Value;
        }
        public readonly float refreshIndicatorLayoutExtent; 
        public readonly bool hasLayoutExtent;
        public float refreshIndicatorLayoutExtent {
            get { return _refreshIndicatorExtent; }
            set {
-               D.assert(value != null);
                D.assert(value >= 0.0);
                if (value == _refreshIndicatorExtent)
                    return;
        public bool hasLayoutExtent {
            get { return _hasLayoutExtent; }
            set {
-               D.assert(value != null);
                if (value == _hasLayoutExtent)
                    return;
                _hasLayoutExtent = value;

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

     abstract class MaterialStateProperty<T> : IMaterialStateProperty<T> {
         public abstract T resolve(HashSet<MaterialState> states);
 
-        public static T resolveAs<T>(T value, HashSet<MaterialState> states) {
-            if (value is MaterialStateProperty<T> materialStateProperty) {
-                MaterialStateProperty<T> property = materialStateProperty;
+        public static S resolveAs<S>(S value, HashSet<MaterialState> states) {
+            if (value is MaterialStateProperty<S> materialStateProperty) {
+                MaterialStateProperty<S> property = materialStateProperty;
                 return property.resolve(states);
             }
 
-        public static MaterialStateProperty<T> resolveWith<T>(material_.MaterialPropertyResolver<T> callback) =>
-            new _MaterialStateProperty<T>(callback);
+        public static MaterialStateProperty<S> resolveWith<S>(material_.MaterialPropertyResolver<S> callback) =>
+            new _MaterialStateProperty<S>(callback);
     }
 
 
 
         public override T resolve(HashSet<MaterialState> states) => _resolve(states);
 
-        public static T resolveAs<T>(T value, HashSet<MaterialState> states) {
-            if (value is MaterialStateProperty<T> materialStateProperty) {
-                MaterialStateProperty<T> property = materialStateProperty;
+        public static S resolveAs<S>(S value, HashSet<MaterialState> states) {
+            if (value is MaterialStateProperty<S> materialStateProperty) {
+                MaterialStateProperty<S> property = materialStateProperty;
                 return property.resolve(states);
             }
 
-        public static MaterialStateProperty<T> resolveWith<T>(material_.MaterialPropertyResolver<T> callback) =>
-            new _MaterialStateProperty<T>(callback);
+        public static MaterialStateProperty<S> resolveWith<S>(material_.MaterialPropertyResolver<S> callback) =>
+            new _MaterialStateProperty<S>(callback);
     }
 }

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

 
     public class VisualDensity : Diagnosticable, IEquatable<VisualDensity> {
         public VisualDensity(
-            float horizontal = 0.0f,
-            float vertical = 0.0f
+            float? horizontal = 0.0f,
+            float? vertical = 0.0f
         ) {
             D.assert(horizontal != null);
             D.assert(vertical != null);
             D.assert(horizontal >= minimumDensity);
-            this.horizontal = horizontal;
-            this.vertical = vertical;
+            this.horizontal = horizontal.Value;
+            this.vertical = vertical.Value;
         }
 
         public static readonly float minimumDensity = -4.0f;
-        public static readonly VisualDensity standard = new VisualDensity();
+        public static readonly VisualDensity standard = new VisualDensity(0.0f, 0.0f);
 
         public static readonly VisualDensity comfortable = new VisualDensity(horizontal: -1.0f, vertical: -1.0f);
 

com.unity.uiwidgets/Runtime/rendering/sliver.cs

                     hasErrors = true;
                     errorMessage.AppendLine($"  {message}");
                 });
-                void verifyFloat(float property, string name, bool mustBePositive = false, bool mustBeNegative = false) {
+                void verifyFloat(float? property, string name, bool mustBePositive = false, bool mustBeNegative = false) {
-                    if (property.isNaN()) {
+                    if (property.Value.isNaN()) {
                         string additional = ".";
                         if (mustBePositive) {
                             additional = ", expected greater than or equal to zero.";
                         verify(false, $"The \"{name}\" is NaN" + $"{additional}");
                     } else if (mustBePositive) {
-                        verify(property >= 0.0, $"The \"{name}\" is negative.");
+                        verify(property >= 0.0f, $"The \"{name}\" is negative.");
-                        verify(property <= 0.0, $"The \"{name}\" is positive.");
+                        verify(property <= 0.0f, $"The \"{name}\" is positive.");
                     }
                 }
                 verify(axis != null, "The \"axis\" is null.");

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

             PointerUpEventListener onPointerUp = null,
             PointerCancelEventListener onPointerCancel = null,
             PointerSignalEventListener onPointerSignal = null,
-            HitTestBehavior behavior = HitTestBehavior.deferToChild,
+            HitTestBehavior? behavior = HitTestBehavior.deferToChild,
             Widget child = null
         ) :
             base(key: key, child: child) {
             this.onPointerUp = onPointerUp;
             this.onPointerCancel = onPointerCancel;
             this.onPointerSignal = onPointerSignal;
-            this.behavior = behavior;
+            this.behavior = behavior.Value;
         }
 
         public readonly PointerDownEventListener onPointerDown;

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

         }
 
         _FlingGestureKind _describeFlingGesture(Velocity velocity) {
-            D.assert(widget.direction != null);
             if (_dragExtent == 0.0f) {
                 return _FlingGestureKind.none;
             }

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

             bool skipTraversal = false,
             bool canRequestFocus = true
         ) {
-            D.assert(skipTraversal != null);
-            D.assert(canRequestFocus != null);
             _skipTraversal = skipTraversal;
             _canRequestFocus = canRequestFocus;
             _onKey = onKey;