Fixed compiled self binding not working from setters. Add extra tests for both reflection and compiled bindings.

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlBindingPathTransformer.cs

@@ -117,7 +117,15 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                     return parentDataContextNode.DataContextType;
                 };
 
-                XamlIlBindingPathHelper.UpdateCompiledBindingExtension(context, binding, startTypeResolver, context.ParentNodes().OfType<XamlAstConstructableObjectNode>().First().Type.GetClrType());
+                var selfType = context.ParentNodes().OfType<XamlAstConstructableObjectNode>().First().Type.GetClrType();
+                
+                // When using self bindings with setters we need to change target type to resolved selector type.
+                if (context.GetAvaloniaTypes().ISetter.IsAssignableFrom(selfType))
+                {
+                    selfType = context.ParentNodes().OfType<AvaloniaXamlIlTargetTypeMetadataNode>().First().TargetType.GetClrType();
+                }
+
+                XamlIlBindingPathHelper.UpdateCompiledBindingExtension(context, binding, startTypeResolver, selfType);
             }
 
             return node;

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs

@@ -91,6 +91,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
         public IXamlType TextDecorationCollection { get; }
         public IXamlType TextDecorations { get; }
         public IXamlType TextTrimming { get; }
+        public IXamlType ISetter { get; }
 
         public AvaloniaXamlIlWellKnownTypes(TransformerConfiguration cfg)
         {
@@ -199,6 +200,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             TextDecorationCollection = cfg.TypeSystem.GetType("Avalonia.Media.TextDecorationCollection");
             TextDecorations = cfg.TypeSystem.GetType("Avalonia.Media.TextDecorations");
             TextTrimming = cfg.TypeSystem.GetType("Avalonia.Media.TextTrimming");
+            ISetter = cfg.TypeSystem.GetType("Avalonia.Styling.ISetter");
         }
     }
 

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs

@@ -1064,6 +1064,37 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
             }
         }
 
+        [Fact]
+        public void Binds_To_Self_In_Style()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+       
+    <Window.Styles>
+        <Style Selector='Button'>
+            <Setter Property='IsVisible' Value='{CompiledBinding $self.IsEnabled}' />
+        </Style>
+    </Window.Styles>
+
+    <Button Name='button' />
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                window.ApplyTemplate();
+                window.Presenter.ApplyTemplate();
+
+                Assert.True(button.IsVisible);
+
+                button.IsEnabled = false;
+
+                Assert.False(button.IsVisible);
+            }
+        }
+
         [Fact]
         public void SupportsMethodBindingAsDelegate()
         {

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BindingTests.cs

@@ -183,6 +183,38 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             }
         }
 
+        [Fact]
+        public void Binding_To_Self_In_Style_Works()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'>
+       
+    <Window.Styles>
+        <Style Selector='Button'>
+            <Setter Property='IsVisible' Value='{Binding $self.IsEnabled}' />
+        </Style>
+    </Window.Styles>
+
+    <Button Name='button' />
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                window.ApplyTemplate();
+                window.Presenter.ApplyTemplate();
+
+                Assert.True(button.IsVisible);
+
+                button.IsEnabled = false;
+
+                Assert.False(button.IsVisible);
+            }
+        }
+
         [Fact]
         public void Stream_Binding_To_Observable_Works()
         {