Make expression nodes sealed where possible.

src/Avalonia.Base/Data/Core/ExpressionNodes/ArrayIndexerNode.cs

@@ -8,7 +8,7 @@ namespace Avalonia.Data.Core.ExpressionNodes;
 /// A node in an <see cref="BindingExpression"/> which accesses an array with integer
 /// indexers.
 /// </summary>
-internal class ArrayIndexerNode : ExpressionNode, ISettableNode
+internal sealed class ArrayIndexerNode : ExpressionNode, ISettableNode
 {
     private readonly int[] _indexes;
 

src/Avalonia.Base/Data/Core/ExpressionNodes/AvaloniaPropertyAccessorNode.cs

@@ -4,7 +4,7 @@ using System.Text;
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class AvaloniaPropertyAccessorNode : ExpressionNode, ISettableNode
+internal sealed class AvaloniaPropertyAccessorNode : ExpressionNode, ISettableNode
 {
     private readonly EventHandler<AvaloniaPropertyChangedEventArgs> _onValueChanged;
 

src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNode.cs

@@ -2,7 +2,7 @@
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class DataContextNode : DataContextNodeBase
+internal sealed class DataContextNode : DataContextNodeBase
 {
     protected override void OnSourceChanged(object source, Exception? dataValidationError)
     {

src/Avalonia.Base/Data/Core/ExpressionNodes/FuncTransformNode.cs

@@ -7,7 +7,7 @@ namespace Avalonia.Data.Core.ExpressionNodes;
 /// A node in an <see cref="BindingExpression"/> which uses a function to transform its
 /// value.
 /// </summary>
-internal class FuncTransformNode : ExpressionNode
+internal sealed class FuncTransformNode : ExpressionNode
 {
     private readonly Func<object?, object?> _transform;
 

src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalAncestorElementNode.cs

@@ -5,7 +5,7 @@ using Avalonia.Reactive;
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class LogicalAncestorElementNode : SourceNode
+internal sealed class LogicalAncestorElementNode : SourceNode
 {
     private readonly Type? _ancestorType;
     private readonly int _ancestorLevel;

src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalNotNode.cs

@@ -5,7 +5,7 @@ using System.Text;
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class LogicalNotNode : ExpressionNode, ISettableNode
+internal sealed class LogicalNotNode : ExpressionNode, ISettableNode
 {
     public override void BuildString(StringBuilder builder)
     {

src/Avalonia.Base/Data/Core/ExpressionNodes/MethodCommandNode.cs

@@ -10,7 +10,7 @@ namespace Avalonia.Data.Core.ExpressionNodes;
 /// A node in an <see cref="BindingExpression"/> which converts methods to an
 /// <see cref="ICommand"/>.
 /// </summary>
-internal class MethodCommandNode : ExpressionNode
+internal sealed class MethodCommandNode : ExpressionNode
 {
     private readonly string _methodName;
     private readonly Action<object, object?> _execute;

src/Avalonia.Base/Data/Core/ExpressionNodes/NamedElementNode.cs

@@ -6,7 +6,7 @@ using Avalonia.Reactive;
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class NamedElementNode : SourceNode
+internal sealed class NamedElementNode : SourceNode
 {
     private readonly WeakReference<INameScope?> _nameScope;
     private readonly string _name;

src/Avalonia.Base/Data/Core/ExpressionNodes/ParentDataContextNode.cs

@@ -6,7 +6,7 @@ namespace Avalonia.Data.Core.ExpressionNodes;
 /// A node in an <see cref="BindingExpression"/> which selects the value of the visual
 /// parent's DataContext.
 /// </summary>
-internal class ParentDataContextNode : DataContextNodeBase
+internal sealed class ParentDataContextNode : DataContextNodeBase
 {
     private static readonly AvaloniaObject s_unset = new();
     private AvaloniaObject? _parent = s_unset;

src/Avalonia.Base/Data/Core/ExpressionNodes/PropertyAccessorNode.cs

@@ -10,7 +10,7 @@ namespace Avalonia.Data.Core.ExpressionNodes;
 /// A node in the binding path of an <see cref="BindingExpression"/> that reads a property
 /// via a predefined <see cref="IPropertyAccessorPlugin"/>.
 /// </summary>
-internal class PropertyAccessorNode : ExpressionNode, IPropertyAccessorNode, ISettableNode
+internal sealed class PropertyAccessorNode : ExpressionNode, IPropertyAccessorNode, ISettableNode
 {
     private readonly Action<object?> _onValueChanged;
     private readonly IPropertyAccessorPlugin _plugin;

src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginPropertyAccessorNode.cs

@@ -12,7 +12,7 @@ namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
 /// <see cref="BindingPlugins.PropertyAccessors"/>.
 /// </summary>
 [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
-internal class DynamicPluginPropertyAccessorNode : ExpressionNode, IPropertyAccessorNode, ISettableNode
+internal sealed class DynamicPluginPropertyAccessorNode : ExpressionNode, IPropertyAccessorNode, ISettableNode
 {
     private readonly Action<object?> _onValueChanged;
     private IPropertyAccessor? _accessor;

src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginStreamNode.cs

@@ -7,7 +7,7 @@ using Avalonia.Reactive;
 namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
 
 [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
-internal class DynamicPluginStreamNode : ExpressionNode
+internal sealed class DynamicPluginStreamNode : ExpressionNode
 {
     private IDisposable? _subscription;
 

src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionIndexerNode.cs

@@ -13,7 +13,7 @@ using Avalonia.Utilities;
 namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
 
 [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
-internal class ReflectionIndexerNode : CollectionNodeBase, ISettableNode
+internal sealed class ReflectionIndexerNode : CollectionNodeBase, ISettableNode
 {
     private static readonly BindingFlags InstanceFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly;
     private MethodInfo? _getter;

src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionTypeCastNode.cs

@@ -6,7 +6,7 @@ namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
 /// <summary>
 /// A node in an <see cref="BindingExpression"/> which casts a value using reflection.
 /// </summary>
-internal class ReflectionTypeCastNode : ExpressionNode
+internal sealed class ReflectionTypeCastNode : ExpressionNode
 {
     private readonly Type _targetType;
 

src/Avalonia.Base/Data/Core/ExpressionNodes/StreamNode.cs

@@ -4,7 +4,7 @@ using Avalonia.Data.Core.Plugins;
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class StreamNode : ExpressionNode, IObserver<object?>
+internal sealed class StreamNode : ExpressionNode, IObserver<object?>
 {
     private IStreamPlugin _plugin;
     private IDisposable? _subscription;

src/Avalonia.Base/Data/Core/ExpressionNodes/TemplatedParentNode.cs

@@ -3,7 +3,7 @@ using System.Text;
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class TemplatedParentNode : SourceNode
+internal sealed class TemplatedParentNode : SourceNode
 {
     public override void BuildString(StringBuilder builder)
     {         

src/Avalonia.Base/Data/Core/ExpressionNodes/VisualAncestorElementNode.cs

@@ -5,7 +5,7 @@ using Avalonia.VisualTree;
 
 namespace Avalonia.Data.Core.ExpressionNodes;
 
-internal class VisualAncestorElementNode : SourceNode
+internal sealed class VisualAncestorElementNode : SourceNode
 {
     private readonly Type? _ancestorType;
     private readonly int _ancestorLevel;