Make MovePreviousOrParent internal as well.

src/Avalonia.Base/Styling/ChildSelector.cs

@@ -65,6 +65,6 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (null, null);
-        protected override Selector? MovePreviousOrParent() => _parent;
+        private protected override Selector? MovePreviousOrParent() => _parent;
     }
 }

src/Avalonia.Base/Styling/DescendentSelector.cs

@@ -70,6 +70,6 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (null, null);
-        protected override Selector? MovePreviousOrParent() => _parent;
+        private protected override Selector? MovePreviousOrParent() => _parent;
     }
 }

src/Avalonia.Base/Styling/NestingSelector.cs

@@ -37,6 +37,6 @@ namespace Avalonia.Styling
             return parent is Style parentStyle ? (parentStyle.Selector, parentStyle.Parent) : (null, null);
         }
 
-        protected override Selector? MovePreviousOrParent() => null;
+        private protected override Selector? MovePreviousOrParent() => null;
     }
 }

src/Avalonia.Base/Styling/NotSelector.cs

@@ -67,6 +67,6 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (_previous, nestingParent);
-        protected override Selector? MovePreviousOrParent() => _previous;
+        private protected override Selector? MovePreviousOrParent() => _previous;
     }
 }

src/Avalonia.Base/Styling/NthChildSelector.cs

@@ -105,7 +105,7 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (_previous, nestingParent);
-        protected override Selector? MovePreviousOrParent() => _previous;
+        private protected override Selector? MovePreviousOrParent() => _previous;
 
         public override string ToString()
         {

src/Avalonia.Base/Styling/OrSelector.cs

@@ -103,7 +103,7 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (null, null);
-        protected override Selector? MovePreviousOrParent() => null;
+        private protected override Selector? MovePreviousOrParent() => null;
 
         internal override void ValidateNestingSelector(bool inControlTheme)
         {

src/Avalonia.Base/Styling/PropertyEqualsSelector.cs

@@ -90,7 +90,7 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (_previous, nestingParent);
-        protected override Selector? MovePreviousOrParent() => _previous;
+        private protected override Selector? MovePreviousOrParent() => _previous;
 
         internal static bool Compare(Type propertyType, object? propertyValue, object? value)
         {

src/Avalonia.Base/Styling/Selector.cs

@@ -95,7 +95,7 @@ namespace Avalonia.Styling
         /// <summary>
         /// Moves to the previous selector or the parent selector.
         /// </summary>
-        protected abstract Selector? MovePreviousOrParent();
+        private protected abstract Selector? MovePreviousOrParent();
 
         internal virtual void ValidateNestingSelector(bool inControlTheme)
         {

src/Avalonia.Base/Styling/TemplateSelector.cs

@@ -49,6 +49,6 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (null, null);
-        protected override Selector? MovePreviousOrParent() => _parent;
+        private protected override Selector? MovePreviousOrParent() => _parent;
     }
 }

src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs

@@ -140,7 +140,7 @@ namespace Avalonia.Styling
         }
 
         private protected override (Selector?, IStyle?) MovePrevious(IStyle? nestingParent) => (_previous, nestingParent);
-        protected override Selector? MovePreviousOrParent() => _previous;
+        private protected override Selector? MovePreviousOrParent() => _previous;
 
         private string BuildSelectorString()
         {