Make dynamic XAML assembly ignore access checks

Fixes #11

src/HotAvalonia/Helpers/AvaloniaControlHelper.cs

@@ -1,5 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
+using System.Reflection.Emit;
 using Avalonia;
 using Avalonia.Markup.Xaml;
 using Avalonia.Markup.Xaml.XamlIl.Runtime;
@@ -18,13 +19,71 @@ internal static class AvaloniaControlHelper
     /// </summary>
     private static readonly FieldInfo? s_stylesAppliedField;
 
+    /// <summary>
+    /// The `Type` property of the <c>XamlX.IL.SreTypeSystem.SreType</c> class.
+    /// </summary>
+    private static readonly PropertyInfo? s_xamlTypeProperty;
+
+    /// <summary>
+    /// The <see cref="IInjection"/> instance responsible for injecting the
+    /// <see cref="OnNewSreMethodBuilder(MethodBuilder, IEnumerable{object})"/>
+    /// callback.
+    /// </summary>
+    [SuppressMessage("CodeQuality", "IDE0052", Justification = "Injections must be kept alive.")]
+    private static readonly IInjection? s_sreMethodBuilderInjection;
+
     /// <summary>
     /// Initializes static members of the <see cref="AvaloniaControlHelper"/> class.
     /// </summary>
     static AvaloniaControlHelper()
     {
         FieldInfo? stylesAppliedField = typeof(StyledElement).GetField("_stylesApplied", BindingFlags.NonPublic | BindingFlags.Instance);
         s_stylesAppliedField = stylesAppliedField?.FieldType == typeof(bool) ? stylesAppliedField : null;
+
+        Assembly xamlLoaderAssembly = typeof(AvaloniaRuntimeXamlLoader).Assembly;
+        Type? sreType = xamlLoaderAssembly.GetType("XamlX.IL.SreTypeSystem+SreType");
+        s_xamlTypeProperty = sreType?.GetProperty("Type");
+
+        BindingFlags ctorFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
+        Type? sreMethodBuilder = xamlLoaderAssembly.GetType("XamlX.IL.SreTypeSystem+SreTypeBuilder+SreMethodBuilder");
+        ConstructorInfo? sreMethodBuilderCtor = sreMethodBuilder?.GetConstructors(ctorFlags).FirstOrDefault(x => x.GetParameters().Length > 1);
+        if (sreMethodBuilderCtor is not null)
+            s_sreMethodBuilderInjection = CallbackInjector.Inject(sreMethodBuilderCtor, OnNewSreMethodBuilder);
+    }
+
+    /// <summary>
+    /// Fixes newly created <c>XamlX.IL.SreTypeSystem.SreTypeBuilder.SreMethodBuilder</c>
+    /// instances.
+    /// </summary>
+    /// <param name="methodBuilder">
+    /// The <see cref="MethodBuilder"/> used to create the
+    /// <c>SreMethodBuilder</c> instance.
+    /// </param>
+    /// <param name="parameters">
+    /// The parameters used to create the <c>SreMethodBuilder</c>
+    /// instance represented by a collection of <c>SreType</c> objects.
+    /// </param>
+    private static void OnNewSreMethodBuilder(MethodBuilder methodBuilder, IEnumerable<object> parameters)
+    {
+        // `Avalonia.Markup.Xaml.Loader` does not handle scenarios where
+        // the control population logic needs to reference private members,
+        // which are commonly used for subscribing to events (e.g., `Click`,
+        // `TextChanged`, etc.). To circumvent this problem, we need this
+        // callback to track the creation of dynamic `Populate` methods and
+        // patch their containing assembly with `IgnoresAccessChecksToAttribute`.
+        if (!AvaloniaRuntimeXamlScanner.IsDynamicPopulateMethod(methodBuilder))
+            return;
+
+        if (methodBuilder.DeclaringType?.Assembly is not AssemblyBuilder assembly)
+            return;
+
+        IEnumerable<Type> parameterTypes = parameters
+            .Where(static x => x is not null && x.GetType() == s_xamlTypeProperty?.DeclaringType)
+            .Select(static x => (Type?)s_xamlTypeProperty?.GetValue(x))
+            .Where(static x => x is not null)!;
+
+        foreach (Type parameterType in parameterTypes)
+            assembly.AllowAccessTo(parameterType);
     }
 
     /// <summary>