Address code review feedback: add annotation for field keyword detection

Co-authored-by: christophwille <344208+christophwille@users.noreply.github.com>

ICSharpCode.Decompiler/CSharp/Annotations.cs

@@ -335,4 +335,12 @@ namespace ICSharpCode.Decompiler.CSharp
 	{
 		public static readonly UseImplicitlyTypedOutAnnotation Instance = new UseImplicitlyTypedOutAnnotation();
 	}
+
+	/// <summary>
+	/// Annotates an Identifier when it was transformed from a backing field reference to the C# 14 'field' keyword.
+	/// </summary>
+	public class SemiAutoPropertyFieldKeywordAnnotation
+	{
+		public static readonly SemiAutoPropertyFieldKeywordAnnotation Instance = new SemiAutoPropertyFieldKeywordAnnotation();
+	}
 }

ICSharpCode.Decompiler/CSharp/Transforms/PatternStatementTransform.cs

@@ -677,14 +677,15 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			IProperty property = propertyDeclaration.GetSymbol() as IProperty;
 			if (property == null)
 				return;
-			// Check if any accessor body contains the 'field' keyword (which was transformed from backing field)
+			// Check if any accessor body contains an identifier with the SemiAutoPropertyFieldKeywordAnnotation
+			// (which indicates it was transformed from a backing field reference)
 			bool usesFieldKeyword = false;
 			foreach (var accessor in new[] { propertyDeclaration.Getter, propertyDeclaration.Setter })
 			{
 				if (accessor.IsNull || accessor.Body.IsNull)
 					continue;
 				usesFieldKeyword |= accessor.Body.Descendants.OfType<Identifier>()
-					.Any(id => id.Name == "field");
+					.Any(id => id.Annotation<SemiAutoPropertyFieldKeywordAnnotation>() != null);
 			}
 			if (!usesFieldKeyword)
 				return;
@@ -699,15 +700,16 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 				});
 			if (fieldDecl != null)
 			{
-				fieldDecl.Remove();
-				// Move field attributes to the property with [field: ...] target
+				// Remove compiler-generated attributes before detaching the node
 				CSharpDecompiler.RemoveAttribute(fieldDecl, KnownAttribute.CompilerGenerated);
 				CSharpDecompiler.RemoveAttribute(fieldDecl, KnownAttribute.DebuggerBrowsable);
+				// Move remaining field attributes to the property with [field: ...] target
 				foreach (var section in fieldDecl.Attributes)
 				{
 					section.AttributeTarget = "field";
 					propertyDeclaration.Attributes.Add(section.Detach());
 				}
+				fieldDecl.Remove();
 			}
 		}
 
@@ -801,7 +803,9 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 						// We're inside this property's accessor - use the field keyword if enabled
 						if (context.Settings.SemiAutoProperties)
 						{
-							return Identifier.Create("field");
+							var newIdentifier = Identifier.Create("field");
+							newIdentifier.AddAnnotation(SemiAutoPropertyFieldKeywordAnnotation.Instance);
+							return newIdentifier;
 						}
 						return null;
 					}