Fix origin for warnings due to event methods (#100500)

This fixes the warning origin to prevent warnings from being
reported on events for annotated event methods. Instead the
warning is shown at the location that introduces the dependency
on the event.

Doesn't fix the multiple warnings reported in some cases. This is
due to MarkEvent also marking event methods, unlike
MarkProperty. We might consider fixing this too, but it was
looking like a larger change than I wanted to make here.

This removes some spurious warnings that were showing up when
bubbling up RUC in winforms.

Author: sbomer

src/tools/illink/src/linker/Linker.Steps/MarkStep.cs

@@ -405,7 +405,7 @@ internal void MarkEntireType (TypeDefinition type, in DependencyInfo reason)
 
 			if (type.HasEvents) {
 				foreach (var ev in type.Events) {
-					MarkEventVisibleToReflection (ev, new DependencyInfo (DependencyKind.MemberOfType, type), ScopeStack.CurrentScope.Origin);
+					MarkEventVisibleToReflection (ev, new DependencyInfo (DependencyKind.MemberOfType, ScopeStack.CurrentScope.Origin), ScopeStack.CurrentScope.Origin);
 				}
 			}
 		}
@@ -3325,6 +3325,7 @@ static DependencyKind PropagateDependencyKindToAccessors (DependencyKind parentD
 			case DependencyKind.AlreadyMarked:
 			case DependencyKind.TypePreserve:
 			case DependencyKind.PreservedMethod:
+			case DependencyKind.DynamicallyAccessedMemberOnType:
 				return parentDependencyKind;
 
 			default:
@@ -3583,15 +3584,15 @@ protected internal virtual void MarkEvent (EventDefinition evt, in DependencyInf
 			if (!Annotations.MarkProcessed (evt, reason))
 				return;
 
+			var origin = reason.Source is IMemberDefinition member ? new MessageOrigin (member) : ScopeStack.CurrentScope.Origin;
+			DependencyKind dependencyKind = PropagateDependencyKindToAccessors (reason.Kind, DependencyKind.EventMethod);
+			MarkMethodIfNotNull (evt.AddMethod, new DependencyInfo (dependencyKind, evt), origin);
+			MarkMethodIfNotNull (evt.InvokeMethod, new DependencyInfo (dependencyKind, evt), origin);
+			MarkMethodIfNotNull (evt.RemoveMethod, new DependencyInfo (dependencyKind, evt), origin);
+
 			using var eventScope = ScopeStack.PushLocalScope (new MessageOrigin (evt));
 
 			MarkCustomAttributes (evt, new DependencyInfo (DependencyKind.CustomAttribute, evt));
-
-			DependencyKind dependencyKind = PropagateDependencyKindToAccessors (reason.Kind, DependencyKind.EventMethod);
-			MarkMethodIfNotNull (evt.AddMethod, new DependencyInfo (dependencyKind, evt), ScopeStack.CurrentScope.Origin);
-			MarkMethodIfNotNull (evt.InvokeMethod, new DependencyInfo (dependencyKind, evt), ScopeStack.CurrentScope.Origin);
-			MarkMethodIfNotNull (evt.RemoveMethod, new DependencyInfo (dependencyKind, evt), ScopeStack.CurrentScope.Origin);
-
 			DoAdditionalEventProcessing (evt);
 		}
 

src/tools/illink/test/Mono.Linker.Tests.Cases/Reflection/TypeHierarchyReflectionWarnings.cs

@@ -246,10 +246,11 @@ class AnnotatedPublicEvents
 			public delegate void MyEventHandler (object sender, int i);
 
 			[Kept]
-			[ExpectedWarning ("IL2026", "--RUC on add_RUCEvent--", ProducedBy = Tool.Trimmer)]
 			public event MyEventHandler RUCEvent {
 				[Kept]
 				[ExpectedWarning ("IL2112", nameof (AnnotatedPublicEvents), "--RUC on add_RUCEvent--")]
+				// https://github.com/dotnet/runtime/issues/100499
+				[ExpectedWarning ("IL2112", nameof (AnnotatedPublicEvents), "--RUC on add_RUCEvent--", ProducedBy = Tool.Trimmer)]
 				[KeptAttributeAttribute (typeof (RequiresUnreferencedCodeAttribute))]
 				[RequiresUnreferencedCode ("--RUC on add_RUCEvent--")]
 				add { }

src/tools/illink/test/Mono.Linker.Tests.Cases/RequiresCapability/BasicRequires.cs

@@ -137,7 +137,6 @@ static void TestRequiresFromNameOf ()
 
 		class OnEventMethod
 		{
-			[ExpectedWarning ("IL2026", "--EventToTestRemove.remove--", ProducedBy = Tool.Trimmer)]
 			static event EventHandler EventToTestRemove {
 				add { }
 				[RequiresUnreferencedCode ("Message for --EventToTestRemove.remove--")]
@@ -146,7 +145,6 @@ static event EventHandler EventToTestRemove {
 				remove { }
 			}
 
-			[ExpectedWarning ("IL2026", "--EventToTestAdd.add--", ProducedBy = Tool.Trimmer)]
 			static event EventHandler EventToTestAdd {
 				[RequiresUnreferencedCode ("Message for --EventToTestAdd.add--")]
 				[RequiresAssemblyFiles ("Message for --EventToTestAdd.add--")]

src/tools/illink/test/Mono.Linker.Tests.Cases/RequiresCapability/RequiresOnClass.cs

@@ -492,9 +492,6 @@ class MemberTypesWithRequires
 			public static int field;
 			public static int Property { get; set; }
 
-			// These should not be reported https://github.com/mono/linker/issues/2218
-			[ExpectedWarning ("IL2026", "MemberTypesWithRequires.Event.add", ProducedBy = Tool.Trimmer)]
-			[ExpectedWarning ("IL2026", "MemberTypesWithRequires.Event.remove", ProducedBy = Tool.Trimmer)]
 			public static event EventHandler Event;
 		}
 
@@ -838,24 +835,21 @@ public static void Test ()
 
 		class ReflectionAccessOnEvents
 		{
-			// Most of the tests in this run into https://github.com/dotnet/linker/issues/2218
+			// Most of the tests in this run into https://github.com/dotnet/runtime/issues/100499
 			// So for now keeping just a very simple test
 
 			[RequiresUnreferencedCode ("--WithRequires--")]
 			[RequiresDynamicCode ("--WithRequires--")]
 			class WithRequires
 			{
-				// These should be reported only in TestDirectReflectionAccess
-				// https://github.com/mono/linker/issues/2218
-				[ExpectedWarning ("IL2026", "StaticEvent.add", ProducedBy = Tool.Trimmer)]
-				[ExpectedWarning ("IL2026", "StaticEvent.remove", ProducedBy = Tool.Trimmer)]
 				public static event EventHandler StaticEvent;
 			}
 
 			[ExpectedWarning ("IL2026", "StaticEvent.add")]
 			[ExpectedWarning ("IL3050", "StaticEvent.add", ProducedBy = Tool.NativeAot)]
-			// https://github.com/mono/linker/issues/2218
-			[ExpectedWarning ("IL2026", "StaticEvent.remove", ProducedBy = Tool.Analyzer | Tool.NativeAot)]
+			// https://github.com/dotnet/runtime/issues/100499
+			[ExpectedWarning ("IL2026", "StaticEvent.add", ProducedBy = Tool.Trimmer)]
+			[ExpectedWarning ("IL2026", "StaticEvent.remove")]
 			[ExpectedWarning ("IL3050", "StaticEvent.remove", ProducedBy = Tool.NativeAot)]
 			static void TestDirectReflectionAccess ()
 			{