Do not report redundant suppressions on trimmed members (#2999)

* Test repro + fix

* fix marked filter for events and properties

* formatting fix

* simplified Suppression constructor

* Add more tests for events and properties

2 files changed, 25 insertions, 8 deletions

diff --git a/src/linker/Linker.Steps/CheckSuppressionsDispatcher.cs b/src/linker/Linker.Steps/CheckSuppressionsDispatcher.cs
index 4bb15635c..0250dfeca 100644
--- a/src/linker/Linker.Steps/CheckSuppressionsDispatcher.cs
+++ b/src/linker/Linker.Steps/CheckSuppressionsDispatcher.cs
@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using ILLink.Shared;
+using Mono.Cecil;
 
 namespace Mono.Linker.Steps
 {
@@ -23,13 +24,30 @@ namespace Mono.Linker.Steps
 			// Suppressions targeting RedundantSuppression warning should not be reported.
 			redundantSuppressions = redundantSuppressions
 				.Where (suppression => ((DiagnosticId) suppression.SuppressMessageInfo.Id).GetDiagnosticCategory () == DiagnosticCategory.Trimming)
-				.Where (suppression => ((DiagnosticId) suppression.SuppressMessageInfo.Id) != DiagnosticId.RedundantSuppression);
+				.Where (suppression => ((DiagnosticId) suppression.SuppressMessageInfo.Id) != DiagnosticId.RedundantSuppression)
+				.Where (suppression => ProviderIsMarked (suppression.Provider));
 
 			foreach (var suppression in redundantSuppressions) {
 				var source = context.Suppressions.GetSuppressionOrigin (suppression);
 
 				context.LogWarning (new MessageOrigin (source), DiagnosticId.RedundantSuppression, $"IL{suppression.SuppressMessageInfo.Id:0000}");
 			}
+
+			bool ProviderIsMarked (ICustomAttributeProvider provider)
+			{
+				if (provider is PropertyDefinition property) {
+					return (property.GetMethod != null && context.Annotations.IsMarked (property.GetMethod))
+						|| (property.SetMethod != null && context.Annotations.IsMarked (property.SetMethod));
+				}
+
+				if (provider is EventDefinition @event) {
+					return (@event.AddMethod != null && context.Annotations.IsMarked (@event.AddMethod))
+						|| (@event.InvokeMethod != null && context.Annotations.IsMarked (@event.InvokeMethod))
+						|| (@event.RemoveMethod != null && context.Annotations.IsMarked (@event.RemoveMethod));
+				}
+
+				return context.Annotations.IsMarked (provider);
+			}
 		}
 	}
 }
diff --git a/src/linker/Linker/UnconditionalSuppressMessageAttributeState.cs b/src/linker/Linker/UnconditionalSuppressMessageAttributeState.cs
index 168b1ef72..2aff747d8 100644
--- a/src/linker/Linker/UnconditionalSuppressMessageAttributeState.cs
+++ b/src/linker/Linker/UnconditionalSuppressMessageAttributeState.cs
@@ -19,14 +19,13 @@ namespace Mono.Linker
 		public class Suppression
 		{
 			public SuppressMessageInfo SuppressMessageInfo { get; }
-			public bool Used { get; set; }
+			public bool Used { get; set; } = false;
 			public CustomAttribute OriginAttribute { get; }
 			public ICustomAttributeProvider Provider { get; }
 
-			public Suppression (SuppressMessageInfo suppressMessageInfo, bool used, CustomAttribute originAttribute, ICustomAttributeProvider provider)
+			public Suppression (SuppressMessageInfo suppressMessageInfo, CustomAttribute originAttribute, ICustomAttributeProvider provider)
 			{
 				SuppressMessageInfo = suppressMessageInfo;
-				Used = used;
 				OriginAttribute = originAttribute;
 				Provider = provider;
 			}
@@ -270,7 +269,7 @@ namespace Mono.Linker
 				if (!TryDecodeSuppressMessageAttributeData (ca, out var info))
 					continue;
 
-				yield return new Suppression (info, used: false, originAttribute: ca, provider);
+				yield return new Suppression (info, originAttribute: ca, provider);
 			}
 		}
 
@@ -297,13 +296,13 @@ namespace Mono.Linker
 
 				var scope = info.Scope?.ToLower ();
 				if (info.Target == null && (scope == "module" || scope == null)) {
-					yield return new Suppression (info, used: false, originAttribute: instance, provider);
+					yield return new Suppression (info, originAttribute: instance, provider);
 					continue;
 				}
 
 				switch (scope) {
 				case "module":
-					yield return new Suppression (info, used: false, originAttribute: instance, provider);
+					yield return new Suppression (info, originAttribute: instance, provider);
 					break;
 
 				case "type":
@@ -312,7 +311,7 @@ namespace Mono.Linker
 						break;
 
 					foreach (var result in DocumentationSignatureParser.GetMembersForDocumentationSignature (info.Target, module, _context))
-						yield return new Suppression (info, used: false, originAttribute: instance, result);
+						yield return new Suppression (info, originAttribute: instance, result);
 
 					break;
 				default: