From c478ccc2e0678c074561de2b76578e53fa0b0b3a Mon Sep 17 00:00:00 2001
From: Siegfried Pammer <siegfriedpammer@gmail.com>
Date: Sun, 10 Nov 2024 22:07:30 +0100
Subject: [PATCH] Fix #3319: KeyDownEvent field reference was replaced with
 KeyDown event reference.

---
 .../TestCases/Pretty/TypeMemberTests.cs       | 11 +++++++++++
 .../Transforms/PatternStatementTransform.cs   | 19 ++++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/ICSharpCode.Decompiler.Tests/TestCases/Pretty/TypeMemberTests.cs b/ICSharpCode.Decompiler.Tests/TestCases/Pretty/TypeMemberTests.cs
index 4133229648..0bd6585867 100644
--- a/ICSharpCode.Decompiler.Tests/TestCases/Pretty/TypeMemberTests.cs
+++ b/ICSharpCode.Decompiler.Tests/TestCases/Pretty/TypeMemberTests.cs
@@ -925,4 +925,15 @@ public class T39_C_HideEvent : T39_B_HideEvent
 	{
 		public override event EventHandler E;
 	}
+
+	public class T40_EventVsField
+	{
+		public object KeyDownEvent;
+		private event EventHandler KeyDown;
+
+		public void UseObject()
+		{
+			Console.WriteLine(KeyDownEvent);
+		}
+	}
 }
diff --git a/ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs b/ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs
index 3605d968d7..b0f2375a28 100644
--- a/ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs
+++ b/ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs
@@ -761,7 +761,7 @@ Identifier ReplaceEventFieldAnnotation(Identifier identifier)
 			var parent = identifier.Parent;
 			var mrr = parent.Annotation<MemberResolveResult>();
 			var field = mrr?.Member as IField;
-			if (field == null)
+			if (field == null || field.Accessibility != Accessibility.Private)
 				return null;
 			foreach (var ev in field.DeclaringType.GetEvents(null, GetMemberOptions.IgnoreInheritedMembers))
 			{
@@ -999,7 +999,9 @@ EventDeclaration TransformAutomaticEvents(CustomEventDeclaration ev)
 			if (!ev.PrivateImplementationType.IsNull)
 				return null;
 			const Modifiers withoutBody = Modifiers.Abstract | Modifiers.Extern;
-			if ((ev.Modifiers & withoutBody) == 0 && ev.GetSymbol() is IEvent symbol)
+			if (ev.GetSymbol() is not IEvent symbol)
+				return null;
+			if ((ev.Modifiers & withoutBody) == 0)
 			{
 				if (!CheckAutomaticEventV4AggressivelyInlined(ev) && !CheckAutomaticEventV4(ev) && !CheckAutomaticEventV2(ev) && !CheckAutomaticEventV4MCS(ev))
 					return null;
@@ -1018,7 +1020,7 @@ EventDeclaration TransformAutomaticEvents(CustomEventDeclaration ev)
 			ed.CopyAnnotationsFrom(ev);
 
 			var fieldDecl = ev.Parent?.Children.OfType<FieldDeclaration>()
-				.FirstOrDefault(fd => CSharpDecompiler.IsEventBackingFieldName(fd.Variables.Single().Name, ev.Name, out _));
+				.FirstOrDefault(IsEventBackingField);
 			if (fieldDecl != null)
 			{
 				fieldDecl.Remove();
@@ -1033,6 +1035,17 @@ EventDeclaration TransformAutomaticEvents(CustomEventDeclaration ev)
 
 			ev.ReplaceWith(ed);
 			return ed;
+
+			bool IsEventBackingField(FieldDeclaration fd)
+			{
+				if (fd.Variables.Count > 1)
+					return false;
+				if (fd.GetSymbol() is not IField f)
+					return false;
+				return f.Accessibility == Accessibility.Private
+					&& symbol.ReturnType.Equals(f.ReturnType)
+					&& CSharpDecompiler.IsEventBackingFieldName(f.Name, ev.Name, out _);
+			}
 		}
 		#endregion