dont use "not" c# preview feature

src/Avalonia.Visuals/Animation/Animators/SolidColorBrushAnimator.cs

@@ -12,7 +12,7 @@ namespace Avalonia.Animation.Animators
     {
         public override IBrush Interpolate(double progress, IBrush oldValue, IBrush newValue)
         {
-            if (oldValue is not ISolidColorBrush oldValS || newValue is not ISolidColorBrush newValS)
+            if (!(oldValue is ISolidColorBrush oldValS) || !(newValue is ISolidColorBrush newValS))
                 return Brushes.Transparent;
             
             return new ImmutableSolidColorBrush(ColorAnimator.InterpolateCore(progress, oldValS.Color, newValS.Color));

src/Avalonia.Visuals/ApiCompatBaseline.txt

@@ -1,4 +1,6 @@
 Compat issues with assembly Avalonia.Visuals:
+CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Animation.Animators.SolidColorBrushAnimator' does not inherit from base type 'Avalonia.Animation.Animators.Animator<Avalonia.Media.SolidColorBrush>' in the implementation but it does in the contract.
+MembersMustExist : Member 'public Avalonia.Media.SolidColorBrush Avalonia.Animation.Animators.SolidColorBrushAnimator.Interpolate(System.Double, Avalonia.Media.SolidColorBrush, Avalonia.Media.SolidColorBrush)' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public void Avalonia.Media.TextFormatting.DrawableTextRun.Draw(Avalonia.Media.DrawingContext)' does not exist in the implementation but it does exist in the contract.
 CannotAddAbstractMembers : Member 'public void Avalonia.Media.TextFormatting.DrawableTextRun.Draw(Avalonia.Media.DrawingContext, Avalonia.Point)' is abstract in the implementation but is missing in the contract.
 CannotSealType : Type 'Avalonia.Media.TextFormatting.GenericTextParagraphProperties' is actually (has the sealed modifier) sealed in the implementation but not sealed in the contract.
@@ -63,4 +65,4 @@ InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalon
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IGlyphRunImpl Avalonia.Platform.IPlatformRenderInterface.CreateGlyphRun(Avalonia.Media.GlyphRun)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IGlyphRunImpl Avalonia.Platform.IPlatformRenderInterface.CreateGlyphRun(Avalonia.Media.GlyphRun, System.Double)' is present in the contract but not in the implementation.
 MembersMustExist : Member 'public Avalonia.Platform.IGlyphRunImpl Avalonia.Platform.IPlatformRenderInterface.CreateGlyphRun(Avalonia.Media.GlyphRun, System.Double)' does not exist in the implementation but it does exist in the contract.
-Total Issues: 64
+Total Issues: 66

src/Avalonia.Visuals/Media/SolidColorBrush.cs

@@ -17,8 +17,8 @@ namespace Avalonia.Media
 
         static SolidColorBrush()
         {
-            Animation.Animation.RegisterAnimator<SolidColorBrushAnimator>(prop => typeof(IBrush).IsAssignableFrom(prop.PropertyType));
-            AffectsRender<SolidColorBrush>(ColorProperty);
+            Animation.Animation.RegisterAnimator<SolidColorBrushAnimator>(prop => typeof(ISolidColorBrush).IsAssignableFrom(prop.PropertyType));
+             AffectsRender<SolidColorBrush>(ColorProperty);
         }
 
         /// <summary>