[XamlC] resolve generic EventArgs (#1020)

Xamarin.Forms.Build.Tasks/SetPropertiesVisitor.cs

@@ -764,14 +764,16 @@ namespace Xamarin.Forms.Build.Tasks
 
 		static bool CanConnectEvent(VariableDefinition parent, string localName)
 		{
-			return parent.VariableType.GetEvent(ed => ed.Name == localName) != null;
+			TypeReference _;
+			return parent.VariableType.GetEvent(ed => ed.Name == localName, out _) != null;
 		}
 
 		static IEnumerable<Instruction> ConnectEvent(VariableDefinition parent, string localName, INode valueNode, IXmlLineInfo iXmlLineInfo, ILContext context)
 		{
 			var elementType = parent.VariableType;
 			var module = context.Body.Method.Module;
-			var eventinfo = elementType.GetEvent(ed => ed.Name == localName);
+			TypeReference eventDeclaringTypeRef;
+			var eventinfo = elementType.GetEvent(ed => ed.Name == localName, out eventDeclaringTypeRef);
 
 //			IL_0007:  ldloc.0 
 //			IL_0008:  ldarg.0 
@@ -810,7 +812,9 @@ namespace Xamarin.Forms.Build.Tasks
 			var ctor = module.ImportReference(eventinfo.EventType.Resolve().GetConstructors().First());
 			ctor = ctor.ResolveGenericParameters(eventinfo.EventType, module);
 			yield return Instruction.Create(OpCodes.Newobj, module.ImportReference(ctor));
-			yield return Instruction.Create(OpCodes.Callvirt, module.ImportReference(eventinfo.AddMethod));
+			var adder = module.ImportReference(eventinfo.AddMethod);
+			adder = adder.ResolveGenericParameters(eventDeclaringTypeRef, module);
+			yield return Instruction.Create(OpCodes.Callvirt, module.ImportReference(adder));
 		}
 
 		static bool CanSetDynamicResource(FieldReference bpRef, INode valueNode, ILContext context)

Xamarin.Forms.Build.Tasks/TypeReferenceExtensions.cs

@@ -56,17 +56,42 @@ namespace Xamarin.Forms.Build.Tasks
 			return typeDef.BaseType.GetProperty(predicate, out declaringTypeRef);
 		}
 
-		public static EventDefinition GetEvent(this TypeReference typeRef, Func<EventDefinition, bool> predicate)
+		public static EventDefinition GetEvent(this TypeReference typeRef, Func<EventDefinition, bool> predicate,
+			out TypeReference declaringTypeRef)
 		{
+			declaringTypeRef = typeRef;
 			var typeDef = typeRef.Resolve();
 			var events = typeDef.Events.Where(predicate);
-			if (events.Any())
+			if (events.Any()) {
-				return events.Single();
+				var ev = events.Single();
+				return ev.ResolveGenericEvent(declaringTypeRef);
+			}
 			if (typeDef.BaseType == null || typeDef.BaseType.FullName == "System.Object")
 				return null;
-			return typeDef.BaseType.GetEvent(predicate);
+			return typeDef.BaseType.GetEvent(predicate, out declaringTypeRef);
 		}
 
+		//this resolves generic eventargs (https://bugzilla.xamarin.com/show_bug.cgi?id=57574)
+		static EventDefinition ResolveGenericEvent(this EventDefinition eventDef, TypeReference declaringTypeRef)
+		{
+			if (eventDef == null)
+				throw new ArgumentNullException(nameof(eventDef));
+			if (declaringTypeRef == null)
+				throw new ArgumentNullException(nameof(declaringTypeRef));
+			if (!eventDef.EventType.IsGenericInstance)
+				return eventDef;
+			if (eventDef.EventType.Resolve().FullName != "System.EventHandler`1")
+				return eventDef;
+
+			var git = eventDef.EventType as GenericInstanceType;
+			var ga = git.GenericArguments.First();
+			ga = ga.ResolveGenericParameters(declaringTypeRef);
+			git.GenericArguments[0] = ga;
+			eventDef.EventType = git;
+
+			return eventDef;
+
+		}
 		public static FieldDefinition GetField(this TypeReference typeRef, Func<FieldDefinition, bool> predicate,
 			out TypeReference declaringTypeRef)
 		{

Xamarin.Forms.Xaml.UnitTests/Issues/Bz57574.xaml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:local="clr-namespace:Xamarin.Forms.Xaml.UnitTests"
+    x:Class="Xamarin.Forms.Xaml.UnitTests.Bz57574">
+    <local:Bz57574Notificator x:Name="notificator"
+        x:TypeArguments="x:String"
+        Notified="OnNotified"/>
+</ContentPage>

Xamarin.Forms.Xaml.UnitTests/Issues/Bz57574.xaml.cs

@@ -0,0 +1,69 @@
+using System;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UnitTests;
+
+namespace Xamarin.Forms.Xaml.UnitTests
+{
+	public class Bz57574NotificationEventArgs<T> : EventArgs
+	{
+		public T Message { get; set; }
+	}
+
+	public class Bz57574Notificator<T> : View
+	{
+		public void Notify(T message)
+		{
+			Notified?.Invoke(this, new Bz57574NotificationEventArgs<T> { Message = message });
+		}
+
+		public event EventHandler<Bz57574NotificationEventArgs<T>> Notified;
+	}
+
+	public partial class Bz57574
+	{
+		public Bz57574()
+		{
+			notificator.Notified += OnNotified;
+			InitializeComponent();
+		}
+
+		public Bz57574(bool useCompiledXaml)
+		{
+			//this stub will be replaced at compile time
+		}
+
+
+		string notification;
+		public void OnNotified(object sender, Bz57574NotificationEventArgs<string> args)
+		{
+			notification = args.Message;
+		}
+
+		[TestFixture]
+		class Tests
+		{
+			[SetUp]
+			public void Setup()
+			{
+				Device.PlatformServices = new MockPlatformServices();
+			}
+
+			[TearDown]
+			public void TearDown()
+			{
+				Device.PlatformServices = null;
+				Application.Current = null;
+			}
+
+			[TestCase(true)]
+			[TestCase(false)]
+			public void EventWithGenericEventHandlers(bool useCompiledXaml)
+			{
+				var layout = new Bz57574(useCompiledXaml);
+				Assume.That(layout.notification, Is.Null);
+				layout.notificator.Notify("Foo");
+				Assert.That(layout.notification, Is.EqualTo("Foo"));
+			}
+		}
+	}
+}

Xamarin.Forms.Xaml.UnitTests/Xamarin.Forms.Xaml.UnitTests.csproj

@@ -495,6 +495,9 @@
       <DependentUpon>Bz53350.xaml</DependentUpon>
     </Compile>
     <Compile Include="XamlC\MethodDefinitionExtensionsTests.cs" />
+    <Compile Include="Issues\Bz57574.xaml.cs">
+      <DependentUpon>Bz57574.xaml</DependentUpon>
+    </Compile>
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <Import Project="..\.nuspec\Xamarin.Forms.Debug.targets" />
@@ -905,6 +908,9 @@
     </EmbeddedResource>
     <EmbeddedResource Include="Issues\Bz53350.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
+    <EmbeddedResource Include="Issues\Bz57574.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
 	</ItemGroup>
   <ItemGroup>