dont break api.

src/Avalonia.Animation/AnimationInstance`1.cs

@@ -12,7 +12,7 @@ namespace Avalonia.Animation
     /// Handles interpolation and time-related functions 
     /// for keyframe animations.
     /// </summary>
-    internal class AnimationInstance<T> : SingleSubscriberObservableBase<T>
+    internal class AnimationInstance<T> : SingleSubscriberObservableBase<object>
     {
         private T _lastInterpValue;
         private T _firstKFValue;

src/Avalonia.Animation/Animators/Animator`1.cs

@@ -116,7 +116,7 @@ namespace Avalonia.Animation.Animators
                 clock ?? control.Clock ?? Clock.GlobalClock,
                 onComplete,
                 InterpolationHandler);
-            return control.Bind<T>((AvaloniaProperty<T>)Property, instance, BindingPriority.Animation);
+            return control.Bind(Property, instance, BindingPriority.Animation);
         }
 
         /// <summary>

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

@@ -1,4 +1,5 @@
-using Avalonia.Media;
+using System;
+using Avalonia.Media;
 using Avalonia.Media.Immutable;
 
 namespace Avalonia.Animation.Animators
@@ -6,14 +7,20 @@ namespace Avalonia.Animation.Animators
     /// <summary>
     /// Animator that handles <see cref="SolidColorBrush"/> values. 
     /// </summary>
-    public class SolidColorBrushAnimator : Animator<IBrush>
+    public class ISolidColorBrushAnimator : Animator<ISolidColorBrush>
     {
-        public override IBrush Interpolate(double progress, IBrush oldValue, IBrush newValue)
+        public override ISolidColorBrush Interpolate(double progress, ISolidColorBrush oldValue, ISolidColorBrush newValue)
         {
-            if (!(oldValue is ISolidColorBrush oldSCB) || !(newValue is ISolidColorBrush newSCB))
-                return Brushes.Transparent;
-
-            return new ImmutableSolidColorBrush(ColorAnimator.InterpolateCore(progress, oldSCB.Color, newSCB.Color));
+            return new ImmutableSolidColorBrush(ColorAnimator.InterpolateCore(progress, oldValue.Color, newValue.Color));
+        }
+    }
+    
+    [Obsolete]    
+    public class SolidColorBrushAnimator : Animator<SolidColorBrush>
+    {    
+        public override SolidColorBrush Interpolate(double progress, SolidColorBrush oldValue, SolidColorBrush newValue)
+        {
+            return new SolidColorBrush(ColorAnimator.InterpolateCore(progress, oldValue.Color, newValue.Color));
         }
     }
 }