Cache the styles for control types.

A lot of time was being spent calling `Attach` on styles that will never match a control. On the first pass, cache the styles that can match a particular control type and use this cache to bypass styles that will never match on subsequent passes.

src/Avalonia.Styling/Styling/ChildSelector.cs

@@ -24,6 +24,9 @@ namespace Avalonia.Styling
         /// <inheritdoc/>
         public override bool InTemplate => _parent.InTemplate;
 
+        /// <inheritdoc/>
+        public override bool IsCombinator => true;
+
         /// <inheritdoc/>
         public override Type TargetType => null;
 
@@ -43,11 +46,24 @@ namespace Avalonia.Styling
 
             if (controlParent != null)
             {
-                return _parent.Match((IStyleable)controlParent, subscribe);
+                var parentMatch = _parent.Match((IStyleable)controlParent, subscribe);
+
+                if (parentMatch.Result == SelectorMatchResult.Sometimes)
+                {
+                    return parentMatch;
+                }
+                else if (parentMatch.IsMatch)
+                {
+                    return SelectorMatch.AlwaysThisInstance;
+                }
+                else
+                {
+                    return SelectorMatch.NeverThisInstance;
+                }
             }
             else
             {
-                return SelectorMatch.False;
+                return SelectorMatch.NeverThisInstance;
             }
         }
 

src/Avalonia.Styling/Styling/DescendentSelector.cs

@@ -22,6 +22,9 @@ namespace Avalonia.Styling
             _parent = parent;
         }
 
+        /// <inheritdoc/>
+        public override bool IsCombinator => true;
+
         /// <inheritdoc/>
         public override bool InTemplate => _parent.InTemplate;
 
@@ -51,16 +54,13 @@ namespace Avalonia.Styling
                 {
                     var match = _parent.Match((IStyleable)c, subscribe);
 
-                    if (match.ImmediateResult != null)
+                    if (match.Result == SelectorMatchResult.Sometimes)
                     {
-                        if (match.ImmediateResult == true)
+                        descendantMatches.Add(match.Activator);
-                        {
-                            return SelectorMatch.True;
-                        }
                     }
-                    else
+                    else if (match.IsMatch)
                     {
-                        descendantMatches.Add(match.ObservableResult);
+                        return SelectorMatch.AlwaysThisInstance;
                     }
                 }
             }
@@ -71,7 +71,7 @@ namespace Avalonia.Styling
             }
             else
             {
-                return SelectorMatch.False;
+                return SelectorMatch.NeverThisInstance;
             }
         }
 

src/Avalonia.Styling/Styling/IStyle.cs

@@ -17,7 +17,12 @@ namespace Avalonia.Styling
         /// <param name="container">
         /// The control that contains this style. May be null.
         /// </param>
-        void Attach(IStyleable control, IStyleHost container);
+        /// <returns>
+        /// True if the style can match a control of type <paramref name="control"/>
+        /// (even if it does not match this control specifically); false if the style
+        /// can never match.
+        /// </returns>
+        bool Attach(IStyleable control, IStyleHost container);
 
         void Detach();
     }

src/Avalonia.Styling/Styling/PropertyEqualsSelector.cs

@@ -30,6 +30,9 @@ namespace Avalonia.Styling
         /// <inheritdoc/>
         public override bool InTemplate => _previous?.InTemplate ?? false;
 
+        /// <inheritdoc/>
+        public override bool IsCombinator => false;
+
         /// <summary>
         /// Gets the name of the control to match.
         /// </summary>
@@ -78,7 +81,8 @@ namespace Avalonia.Styling
             }
             else
             {
-                return new SelectorMatch((control.GetValue(_property) ?? string.Empty).Equals(_value));
+                var result = (control.GetValue(_property) ?? string.Empty).Equals(_value);
+                return result ? SelectorMatch.AlwaysThisInstance : SelectorMatch.NeverThisInstance;
             }
         }
 

src/Avalonia.Styling/Styling/Selector.cs

@@ -17,6 +17,14 @@ namespace Avalonia.Styling
         /// </summary>
         public abstract bool InTemplate { get; }
 
+        /// <summary>
+        /// Gets a value indicating whether this selector is a combinator.
+        /// </summary>
+        /// <remarks>
+        /// A combinator is a selector such as Child or Descendent which links simple selectors.
+        /// </remarks>
+        public abstract bool IsCombinator { get; }
+
         /// <summary>
         /// Gets the target type of the selector, if available.
         /// </summary>
@@ -33,25 +41,32 @@ namespace Avalonia.Styling
         /// <returns>A <see cref="SelectorMatch"/>.</returns>
         public SelectorMatch Match(IStyleable control, bool subscribe = true)
         {
-            List<IObservable<bool>> inputs = new List<IObservable<bool>>();
+            var inputs = new List<IObservable<bool>>();
-            Selector selector = this;
+            var selector = this;
+            var alwaysThisType = true;
+            var hitCombinator = false;
 
             while (selector != null)
             {
-                if (selector.InTemplate && control.TemplatedParent == null)
+                hitCombinator |= selector.IsCombinator;
-                {
-                    return SelectorMatch.False;
-                }
 
                 var match = selector.Evaluate(control, subscribe);
 
-                if (match.ImmediateResult == false)
+                if (!match.IsMatch)
+                {
+                    return hitCombinator ? SelectorMatch.NeverThisInstance : match;
+                }
+                else if (selector.InTemplate && control.TemplatedParent == null)
+                {
+                    return SelectorMatch.NeverThisInstance;
+                }
+                else if (match.Result == SelectorMatchResult.AlwaysThisInstance)
                 {
-                    return match;
+                    alwaysThisType = false;
                 }
-                else if (match.ObservableResult != null)
+                else if (match.Result == SelectorMatchResult.Sometimes)
                 {
-                    inputs.Add(match.ObservableResult);
+                    inputs.Add(match.Activator);
                 }
 
                 selector = selector.MovePrevious();
@@ -63,7 +78,9 @@ namespace Avalonia.Styling
             }
             else
             {
-                return SelectorMatch.True;
+                return alwaysThisType && !hitCombinator ? 
+                    SelectorMatch.AlwaysThisType :
+                    SelectorMatch.AlwaysThisInstance;
             }
         }
 

src/Avalonia.Styling/Styling/SelectorMatch.cs

@@ -5,51 +5,95 @@ using System;
 
 namespace Avalonia.Styling
 {
+    /// <summary>
+    /// Describes how a <see cref="SelectorMatch"/> matches a control and its type.
+    /// </summary>
+    public enum SelectorMatchResult
+    {
+        /// <summary>
+        /// The selector never matches this type.
+        /// </summary>
+        NeverThisType,
+
+        /// <summary>
+        /// The selector never matches this instance, but can match this type.
+        /// </summary>
+        NeverThisInstance,
+
+        /// <summary>
+        /// The selector always matches this type.
+        /// </summary>
+        AlwaysThisType,
+
+        /// <summary>
+        /// The selector always matches this instance, but doesn't always match this type.
+        /// </summary>
+        AlwaysThisInstance,
+
+        /// <summary>
+        /// The selector matches this instance based on the <see cref="SelectorMatch.Activator"/>.
+        /// </summary>
+        Sometimes,
+    }
+
     /// <summary>
     /// Holds the result of a <see cref="Selector"/> match.
     /// </summary>
     /// <remarks>
-    /// There are two types of selectors - ones whose match can never change for a particular
+    /// A selector match describes whether and how a <see cref="Selector"/> matches a control, and
-    /// control (such as <see cref="Selectors.OfType(Selector, Type)"/>) and ones whose result can
+    /// in addition whether the selector can ever match a control of the same type.
-    /// change over time (such as <see cref="Selectors.Class(Selector, string)"/>. For the first
-    /// category of selectors, the value of <see cref="ImmediateResult"/> will be set but for the
-    /// second, <see cref="ImmediateResult"/> will be null and <see cref="ObservableResult"/> will
-    /// hold an observable which tracks the match.
     /// </remarks>
     public class SelectorMatch
     {
-        public static readonly SelectorMatch False = new SelectorMatch(false);
+        /// <summary>
+        /// A selector match with the result of <see cref="SelectorMatchResult.NeverThisType"/>/
+        /// </summary>
+        public static readonly SelectorMatch NeverThisType = new SelectorMatch(SelectorMatchResult.NeverThisType);
 
-        public static readonly SelectorMatch True = new SelectorMatch(true);
+        /// <summary>
+        /// A selector match with the result of <see cref="SelectorMatchResult.NeverThisInstance"/>/
+        /// </summary>
+        public static readonly SelectorMatch NeverThisInstance = new SelectorMatch(SelectorMatchResult.NeverThisInstance);
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="SelectorMatch"/> class.
+        /// A selector match with the result of <see cref="SelectorMatchResult.AlwaysThisType"/>/
         /// </summary>
-        /// <param name="match">The immediate match value.</param>
+        public static readonly SelectorMatch AlwaysThisType = new SelectorMatch(SelectorMatchResult.AlwaysThisType);
-        public SelectorMatch(bool match)
-        {
-            ImmediateResult = match;
-        }
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="SelectorMatch"/> class.
+        /// Gets a selector match with the result of <see cref="SelectorMatchResult.AlwaysThisInstance"/>/
         /// </summary>
-        /// <param name="match">The observable match value.</param>
+        public static readonly SelectorMatch AlwaysThisInstance = new SelectorMatch(SelectorMatchResult.AlwaysThisInstance);
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SelectorMatch"/> class with a 
+        /// <see cref="SelectorMatchResult.Sometimes"/> result.
+        /// </summary>
+        /// <param name="match">The match activator.</param>
         public SelectorMatch(IObservable<bool> match)
         {
-            ObservableResult = match;
+            Contract.Requires<ArgumentNullException>(match != null);
+
+            Result = SelectorMatchResult.Sometimes;
+            Activator = match;
         }
 
+        private SelectorMatch(SelectorMatchResult result) => Result = result;
+
         /// <summary>
-        /// Gets the immediate result of the selector match, in the case of selectors that cannot
+        /// Gets a value indicating whether the match was positive.
-        /// change over time.
+        /// </summary>
+        public bool IsMatch => Result >= SelectorMatchResult.AlwaysThisType;
+
+        /// <summary>
+        /// Gets the result of the match.
         /// </summary>
-        public bool? ImmediateResult { get; }
+        public SelectorMatchResult Result { get; }
 
         /// <summary>
         /// Gets an observable which tracks the selector match, in the case of selectors that can
         /// change over time.
         /// </summary>
-        public IObservable<bool> ObservableResult { get; }
+        public IObservable<bool> Activator { get; }
     }
 }

src/Avalonia.Styling/Styling/Style.cs

@@ -106,20 +106,14 @@ namespace Avalonia.Styling
         /// <inheritdoc/>
         bool IResourceProvider.HasResources => _resources?.Count > 0;
 
-        /// <summary>
+        /// <inheritdoc/>
-        /// Attaches the style to a control if the style's selector matches.
+        public bool Attach(IStyleable control, IStyleHost container)
-        /// </summary>
-        /// <param name="control">The control to attach to.</param>
-        /// <param name="container">
-        /// The control that contains this style. May be null.
-        /// </param>
-        public void Attach(IStyleable control, IStyleHost container)
         {
             if (Selector != null)
             {
                 var match = Selector.Match(control);
 
-                if (match.ImmediateResult != false)
+                if (match.IsMatch)
                 {
                     var controlSubscriptions = GetSubscriptions(control);
                     
@@ -129,9 +123,10 @@ namespace Avalonia.Styling
                     {
                         foreach (var animation in Animations)
                         {
-                            IObservable<bool> obsMatch = match.ObservableResult;
+                            var obsMatch = match.Activator;
 
-                            if (match.ImmediateResult == true)
+                            if (match.Result == SelectorMatchResult.AlwaysThisType ||
+                                match.Result == SelectorMatchResult.AlwaysThisInstance)
                             {
                                 obsMatch = Observable.Return(true);
                             }
@@ -143,13 +138,15 @@ namespace Avalonia.Styling
 
                     foreach (var setter in Setters)
                     {
-                        var sub = setter.Apply(this, control, match.ObservableResult);
+                        var sub = setter.Apply(this, control, match.Activator);
                         subs.Add(sub);
                     }
 
                     controlSubscriptions.Add(subs);
                     Subscriptions.Add(subs);
                 }
+
+                return match.Result != SelectorMatchResult.NeverThisType;
             }
             else if (control == container)
             {
@@ -165,7 +162,10 @@ namespace Avalonia.Styling
                 
                 controlSubscriptions.Add(subs);
                 Subscriptions.Add(subs);
+                return true;
             }
+
+            return false;
         }
 
         /// <inheritdoc/>

src/Avalonia.Styling/Styling/Styles.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Collections;
 using Avalonia.Controls;
@@ -15,6 +16,7 @@ namespace Avalonia.Styling
     {
         private IResourceNode _parent;
         private IResourceDictionary _resources;
+        private Dictionary<Type, List<IStyle>> _cache;
 
         public Styles()
         {
@@ -34,6 +36,7 @@ namespace Avalonia.Styling
                     }
 
                     x.ResourcesChanged += SubResourceChanged;
+                    _cache = null;
                 },
                 x =>
                 {
@@ -49,6 +52,7 @@ namespace Avalonia.Styling
                     }
 
                     x.ResourcesChanged -= SubResourceChanged;
+                    _cache = null;
                 },
                 () => { });
         }
@@ -97,11 +101,46 @@ namespace Avalonia.Styling
         /// <param name="container">
         /// The control that contains this style. May be null.
         /// </param>
-        public void Attach(IStyleable control, IStyleHost container)
+        public bool Attach(IStyleable control, IStyleHost container)
         {
-            foreach (IStyle style in this)
+            if (_cache == null)
+            {
+                _cache = new Dictionary<Type, List<IStyle>>();
+            }
+
+            if (_cache.TryGetValue(control.StyleKey, out var cached))
+            {
+                if (cached != null)
+                {
+                    foreach (var style in cached)
+                    {
+                        style.Attach(control, container);
+                    }
+
+                    return true;
+                }
+
+                return false;
+            }
+            else
             {
-                style.Attach(control, container);
+                List<IStyle> result = null;
+
+                foreach (var style in this)
+                {
+                    if (style.Attach(control, container))
+                    {
+                        if (result == null)
+                        {
+                            result = new List<IStyle>();
+                        }
+
+                        result.Add(style);
+                    }
+                }
+
+                _cache.Add(control.StyleKey, result);
+                return result != null;
             }
         }
 

src/Avalonia.Styling/Styling/TemplateSelector.cs

@@ -23,6 +23,9 @@ namespace Avalonia.Styling
         /// <inheritdoc/>
         public override bool InTemplate => true;
 
+        /// <inheritdoc/>
+        public override bool IsCombinator => true;
+
         /// <inheritdoc/>
         public override Type TargetType => null;
 
@@ -46,7 +49,7 @@ namespace Avalonia.Styling
                     "Cannot call Template selector on control with null TemplatedParent.");
             }
 
-            return _parent.Match(templatedParent, subscribe) ?? SelectorMatch.True;
+            return _parent.Match(templatedParent, subscribe);
         }
 
         protected override Selector MovePrevious() => null;

src/Avalonia.Styling/Styling/TypeNameAndClassSelector.cs

@@ -68,6 +68,9 @@ namespace Avalonia.Styling
         /// <inheritdoc/>
         public override Type TargetType => _targetType ?? _previous?.TargetType;
 
+        /// <inheritdoc/>
+        public override bool IsCombinator => false;
+
         /// <summary>
         /// Whether the selector matches the concrete <see cref="TargetType"/> or any object which
         /// implements <see cref="TargetType"/>.
@@ -101,21 +104,23 @@ namespace Avalonia.Styling
                 {
                     if (controlType != TargetType)
                     {
-                        return SelectorMatch.False;
+                        return SelectorMatch.NeverThisType;
                     }
                 }
                 else
                 {
                     if (!TargetType.GetTypeInfo().IsAssignableFrom(controlType.GetTypeInfo()))
                     {
-                        return SelectorMatch.False;
+                        return SelectorMatch.NeverThisType;
                     }
                 }
             }
 
-            if (Name != null && control.Name != Name)
+            if (Name != null)
             {
-                return SelectorMatch.False;
+                return control.Name == Name ? 
+                    SelectorMatch.AlwaysThisInstance :
+                    SelectorMatch.NeverThisInstance;
             }
 
             if (_classes.IsValueCreated && _classes.Value.Count > 0)
@@ -127,12 +132,14 @@ namespace Avalonia.Styling
                 }
                 else
                 {
-                    return new SelectorMatch(Matches(control.Classes));
+                    return Matches(control.Classes) ?
+                        SelectorMatch.AlwaysThisInstance :
+                        SelectorMatch.NeverThisInstance;
                 }
             }
             else
             {
-                return SelectorMatch.True;
+                return SelectorMatch.AlwaysThisType;
             }
         }
 

src/Markup/Avalonia.Markup.Xaml/Styling/StyleInclude.cs

@@ -62,12 +62,14 @@ namespace Avalonia.Markup.Xaml.Styling
         IResourceNode IResourceNode.ResourceParent => _parent;
 
         /// <inheritdoc/>
-        public void Attach(IStyleable control, IStyleHost container)
+        public bool Attach(IStyleable control, IStyleHost container)
         {
             if (Source != null)
             {
-                Loaded.Attach(control, container);
+                return Loaded.Attach(control, container);
             }
+
+            return false;
         }
 
         public void Detach()

tests/Avalonia.Styling.UnitTests/SelectorTests_Child.cs

@@ -27,7 +27,7 @@ namespace Avalonia.Styling.UnitTests
 
             var selector = default(Selector).OfType<TestLogical1>().Child().OfType<TestLogical2>();
 
-            Assert.True(selector.Match(child).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisInstance, selector.Match(child).Result);
         }
 
         [Fact]
@@ -42,7 +42,7 @@ namespace Avalonia.Styling.UnitTests
 
             var selector = default(Selector).OfType<TestLogical1>().Child().OfType<TestLogical3>();
 
-            Assert.False(selector.Match(child).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.NeverThisInstance, selector.Match(child).Result);
         }
 
         [Fact]
@@ -54,7 +54,7 @@ namespace Avalonia.Styling.UnitTests
             child.LogicalParent = parent;
 
             var selector = default(Selector).OfType<TestLogical1>().Class("foo").Child().OfType<TestLogical2>();
-            var activator = selector.Match(child).ObservableResult;
+            var activator = selector.Match(child).Activator;
             var result = new List<bool>();
 
             Assert.False(await activator.Take(1));
@@ -70,7 +70,7 @@ namespace Avalonia.Styling.UnitTests
             var control = new TestLogical3();
             var selector = default(Selector).OfType<TestLogical1>().Child().OfType<TestLogical3>();
 
-            Assert.False(selector.Match(control).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.NeverThisInstance, selector.Match(control).Result);
         }
 
         [Fact]

tests/Avalonia.Styling.UnitTests/SelectorTests_Class.cs

@@ -40,9 +40,10 @@ namespace Avalonia.Styling.UnitTests
             };
 
             var target = default(Selector).Class("foo");
-            var activator = target.Match(control).ObservableResult;
+            var match = target.Match(control);
 
-            Assert.True(await activator.Take(1));
+            Assert.Equal(SelectorMatchResult.Sometimes, match.Result);
+            Assert.True(await match.Activator.Take(1));
         }
 
         [Fact]
@@ -54,9 +55,10 @@ namespace Avalonia.Styling.UnitTests
             };
 
             var target = default(Selector).Class("foo");
-            var activator = target.Match(control).ObservableResult;
+            var match = target.Match(control);
 
-            Assert.False(await activator.Take(1));
+            Assert.Equal(SelectorMatchResult.Sometimes, match.Result);
+            Assert.False(await match.Activator.Take(1));
         }
 
         [Fact]
@@ -69,9 +71,10 @@ namespace Avalonia.Styling.UnitTests
             };
 
             var target = default(Selector).Class("foo");
-            var activator = target.Match(control).ObservableResult;
+            var match = target.Match(control);
 
-            Assert.True(await activator.Take(1));
+            Assert.Equal(SelectorMatchResult.Sometimes, match.Result);
+            Assert.True(await match.Activator.Take(1));
         }
 
         [Fact]
@@ -80,7 +83,7 @@ namespace Avalonia.Styling.UnitTests
             var control = new Control1();
 
             var target = default(Selector).Class("foo");
-            var activator = target.Match(control).ObservableResult;
+            var activator = target.Match(control).Activator;
 
             Assert.False(await activator.Take(1));
             control.Classes.Add("foo");
@@ -96,7 +99,7 @@ namespace Avalonia.Styling.UnitTests
             };
 
             var target = default(Selector).Class("foo");
-            var activator = target.Match(control).ObservableResult;
+            var activator = target.Match(control).Activator;
 
             Assert.True(await activator.Take(1));
             control.Classes.Remove("foo");
@@ -108,7 +111,7 @@ namespace Avalonia.Styling.UnitTests
         {
             var control = new Control1();
             var target = default(Selector).Class("foo").Class("bar");
-            var activator = target.Match(control).ObservableResult;
+            var activator = target.Match(control).Activator;
 
             Assert.False(await activator.Take(1));
             control.Classes.Add("foo");
@@ -129,7 +132,7 @@ namespace Avalonia.Styling.UnitTests
             };
 
             var target = default(Selector).Class("foo");
-            var activator = target.Match(control).ObservableResult;
+            var activator = target.Match(control).Activator;
             var result = new List<bool>();
 
             using (activator.Subscribe(x => result.Add(x)))

tests/Avalonia.Styling.UnitTests/SelectorTests_Descendent.cs

@@ -26,7 +26,7 @@ namespace Avalonia.Styling.UnitTests
 
             var selector = default(Selector).OfType<TestLogical1>().Descendant().OfType<TestLogical2>();
 
-            Assert.True(selector.Match(child).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisInstance, selector.Match(child).Result);
         }
 
         [Fact]
@@ -41,7 +41,7 @@ namespace Avalonia.Styling.UnitTests
 
             var selector = default(Selector).OfType<TestLogical1>().Descendant().OfType<TestLogical3>();
 
-            Assert.True(selector.Match(child).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisInstance, selector.Match(child).Result);
         }
 
         [Fact]
@@ -56,7 +56,7 @@ namespace Avalonia.Styling.UnitTests
             child.LogicalParent = parent;
 
             var selector = default(Selector).OfType<TestLogical1>().Class("foo").Descendant().OfType<TestLogical3>();
-            var activator = selector.Match(child).ObservableResult;
+            var activator = selector.Match(child).Activator;
 
             Assert.True(await activator.Take(1));
         }
@@ -74,7 +74,7 @@ namespace Avalonia.Styling.UnitTests
             child.LogicalParent = parent;
 
             var selector = default(Selector).OfType<TestLogical1>().Class("foo").Descendant().OfType<TestLogical3>();
-            var activator = selector.Match(child).ObservableResult;
+            var activator = selector.Match(child).Activator;
 
             Assert.False(await activator.Take(1));
         }
@@ -90,7 +90,7 @@ namespace Avalonia.Styling.UnitTests
             child.LogicalParent = parent;
 
             var selector = default(Selector).OfType<TestLogical1>().Class("foo").Descendant().OfType<TestLogical3>();
-            var activator = selector.Match(child).ObservableResult;
+            var activator = selector.Match(child).Activator;
 
             Assert.False(await activator.Take(1));
             parent.Classes.Add("foo");

tests/Avalonia.Styling.UnitTests/SelectorTests_Multiple.cs

@@ -14,7 +14,7 @@ namespace Avalonia.Styling.UnitTests
     public class SelectorTests_Multiple
     {
         [Fact]
-        public void Template_Child_Of_Control_With_Two_Classes()
+        public void Named_Template_Child_Of_Control_With_Two_Classes()
         {
             var template = new FuncControlTemplate(parent =>
             {
@@ -40,9 +40,10 @@ namespace Avalonia.Styling.UnitTests
 
             var border = (Border)((IVisual)control).VisualChildren.Single();
             var values = new List<bool>();
-            var activator = selector.Match(border).ObservableResult;
+            var match = selector.Match(border);
 
-            activator.Subscribe(x => values.Add(x));
+            Assert.Equal(SelectorMatchResult.Sometimes, match.Result);
+            match.Activator.Subscribe(x => values.Add(x));
 
             Assert.Equal(new[] { false }, values);
             control.Classes.AddRange(new[] { "foo", "bar" });
@@ -51,6 +52,39 @@ namespace Avalonia.Styling.UnitTests
             Assert.Equal(new[] { false, true, false }, values);
         }
 
+        [Fact]
+        public void Named_OfType_Template_Child_Of_Control_With_Two_Classes_Wrong_Type()
+        {
+            var template = new FuncControlTemplate(parent =>
+            {
+                return new Border
+                {
+                    Name = "border",
+                };
+            });
+
+            var control = new Button
+            {
+                Template = template,
+            };
+
+            control.ApplyTemplate();
+
+            var selector = default(Selector)
+                .OfType<Button>()
+                .Class("foo")
+                .Class("bar")
+                .Template()
+                .OfType<TextBlock>()
+                .Name("baz");
+
+            var border = (Border)((IVisual)control).VisualChildren.Single();
+            var values = new List<bool>();
+            var match = selector.Match(border);
+
+            Assert.Equal(SelectorMatchResult.NeverThisType, match.Result);
+        }
+
         [Fact]
         public void TargetType_OfType()
         {

tests/Avalonia.Styling.UnitTests/SelectorTests_Name.cs

@@ -14,7 +14,7 @@ namespace Avalonia.Styling.UnitTests
             var control = new Control1 { Name = "foo" };
             var target = default(Selector).Name("foo");
 
-            Assert.True(target.Match(control).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisInstance, target.Match(control).Result);
         }
 
         [Fact]
@@ -23,7 +23,7 @@ namespace Avalonia.Styling.UnitTests
             var control = new Control1 { Name = "foo" };
             var target = default(Selector).Name("bar");
 
-            Assert.False(target.Match(control).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.NeverThisInstance, target.Match(control).Result);
         }
 
         [Fact]
@@ -33,7 +33,7 @@ namespace Avalonia.Styling.UnitTests
             var target = default(Selector).Name("foo");
             var activator = target.Match(control);
 
-            Assert.False(target.Match(control).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.NeverThisInstance, target.Match(control).Result);
         }
 
         [Fact]

tests/Avalonia.Styling.UnitTests/SelectorTests_OfType.cs

@@ -14,7 +14,7 @@ namespace Avalonia.Styling.UnitTests
             var control = new Control1();
             var target = default(Selector).OfType<Control1>();
 
-            Assert.True(target.Match(control).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisType, target.Match(control).Result);
         }
 
         [Fact]
@@ -23,7 +23,16 @@ namespace Avalonia.Styling.UnitTests
             var control = new Control2();
             var target = default(Selector).OfType<Control1>();
 
-            Assert.False(target.Match(control).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.NeverThisType, target.Match(control).Result);
+        }
+
+        [Fact]
+        public void OfType_Class_Doesnt_Match_Control_Of_Wrong_Type()
+        {
+            var control = new Control2();
+            var target = default(Selector).OfType<Control1>().Class("foo");
+
+            Assert.Equal(SelectorMatchResult.NeverThisType, target.Match(control).Result);
         }
 
         [Fact]
@@ -32,7 +41,7 @@ namespace Avalonia.Styling.UnitTests
             var control = new Control1 { TemplatedParent = new Mock<ITemplatedControl>().Object };
             var target = default(Selector).OfType<Control1>();
 
-            Assert.True(target.Match(control).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisType, target.Match(control).Result);
         }
 
         public class Control1 : TestControlBase

tests/Avalonia.Styling.UnitTests/SelectorTests_PropertyEquals.cs

@@ -16,7 +16,7 @@ namespace Avalonia.Styling.UnitTests
         {
             var control = new TextBlock();
             var target = default(Selector).PropertyEquals(TextBlock.TextProperty, "foo");
-            var activator = target.Match(control).ObservableResult;
+            var activator = target.Match(control).Activator;
 
             Assert.False(await activator.Take(1));
             control.Text = "foo";
@@ -25,6 +25,15 @@ namespace Avalonia.Styling.UnitTests
             Assert.False(await activator.Take(1));
         }
 
+        [Fact]
+        public void OfType_PropertyEquals_Doesnt_Match_Control_Of_Wrong_Type()
+        {
+            var control = new TextBlock();
+            var target = default(Selector).OfType<Border>().PropertyEquals(TextBlock.TextProperty, "foo");
+
+            Assert.Equal(SelectorMatchResult.NeverThisType, target.Match(control).Result);
+        }
+
         [Fact]
         public void PropertyEquals_Selector_Should_Have_Correct_String_Representation()
         {

tests/Avalonia.Styling.UnitTests/SelectorTests_Template.cs

@@ -29,7 +29,7 @@ namespace Avalonia.Styling.UnitTests
                 .Template()
                 .OfType<Border>();
 
-            Assert.True(selector.Match(border).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisInstance, selector.Match(border).Result);
         }
 
         [Fact]
@@ -47,7 +47,24 @@ namespace Avalonia.Styling.UnitTests
                 .Template()
                 .OfType<Border>();
 
-            Assert.False(selector.Match(border).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.NeverThisInstance, selector.Match(border).Result);
+        }
+
+        [Fact]
+        public void Control_In_Template_Of_Wrong_Type_Is_Not_Matched_With_Template_Selector()
+        {
+            var target = new Mock<IVisual>();
+            var templatedControl = target.As<ITemplatedControl>();
+            var styleable = target.As<IStyleable>();
+            BuildVisualTree(target);
+
+            var border = (Border)target.Object.GetVisualChildren().Single();
+            var selector = default(Selector)
+                .OfType<Button>()
+                .Template()
+                .OfType<Border>();
+
+            Assert.Equal(SelectorMatchResult.NeverThisInstance, selector.Match(border).Result);
         }
 
         [Fact]
@@ -64,7 +81,7 @@ namespace Avalonia.Styling.UnitTests
                 .Template()
                 .OfType<TextBlock>();
 
-            Assert.True(selector.Match(textBlock).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisInstance, selector.Match(textBlock).Result);
         }
 
         [Fact]
@@ -80,7 +97,7 @@ namespace Avalonia.Styling.UnitTests
 
             var selector = default(Selector).OfType(styleKey).Template().OfType<Border>();
 
-            Assert.True(selector.Match(border).ImmediateResult);
+            Assert.Equal(SelectorMatchResult.AlwaysThisInstance, selector.Match(border).Result);
         }
 
         [Fact]
@@ -96,7 +113,7 @@ namespace Avalonia.Styling.UnitTests
             styleable.Setup(x => x.Classes).Returns(new Classes("foo"));
             var border = (Border)target.Object.VisualChildren.Single();
             var selector = default(Selector).OfType(styleKey).Class("foo").Template().OfType<Border>();
-            var activator = selector.Match(border).ObservableResult;
+            var activator = selector.Match(border).Activator;
 
             Assert.True(await activator.Take(1));
         }
@@ -112,7 +129,7 @@ namespace Avalonia.Styling.UnitTests
             styleable.Setup(x => x.Classes).Returns(new Classes("bar"));
             var border = (Border)target.Object.VisualChildren.Single();
             var selector = default(Selector).OfType(templatedControl.Object.GetType()).Class("foo").Template().OfType<Border>();
-            var activator = selector.Match(border).ObservableResult;
+            var activator = selector.Match(border).Activator;
 
             Assert.False(await activator.Take(1));
         }
@@ -128,7 +145,7 @@ namespace Avalonia.Styling.UnitTests
             styleable.Setup(x => x.Classes).Returns(new Classes("foo"));
             var border = (Border)target.Object.VisualChildren.Single();
             var selector = default(Selector).OfType(templatedControl.Object.GetType()).Class("foo").Template().OfType<Border>();
-            var activator = selector.Match(border).ObservableResult;
+            var activator = selector.Match(border).Activator;
             var inccDebug = (INotifyCollectionChangedDebug)styleable.Object.Classes;
 
             using (activator.Subscribe(_ => { }))