Add ILLink coverage for unused virtual method annotations

src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/UnusedVirtualMethodAnnotations.cs

@@ -0,0 +1,84 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Diagnostics.CodeAnalysis;
+using Mono.Linker.Tests.Cases.Expectations.Assertions;
+using Mono.Linker.Tests.Cases.Expectations.Helpers;
+
+namespace Mono.Linker.Tests.Cases.DataFlow
+{
+    [SkipKeptItemsValidation]
+    [ExpectedNoWarnings]
+    class UnusedVirtualMethodAnnotations
+    {
+        [UnconditionalSuppressMessage("Test", "IL2026")]
+        public static void Main()
+        {
+            _ = typeof(TypeOnlyImplementation);
+
+            IUsed used = new UsedImplementation();
+            used.Method(typeof(object));
+
+            IPartiallyUsed partiallyUsed = new PartiallyUsedImplementation();
+            partiallyUsed.Method(typeof(object));
+        }
+
+        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)]
+        interface IUnused
+        {
+            [RequiresUnreferencedCode(nameof(Method))]
+            void Method([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] Type type);
+        }
+
+        class UnusedImplementation : IUnused
+        {
+            public void Method(Type type) { }
+        }
+
+        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)]
+        interface ITypeOnly
+        {
+            [RequiresUnreferencedCode(nameof(Method))]
+            void Method([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] Type type);
+        }
+
+        class TypeOnlyImplementation : ITypeOnly
+        {
+            public void Method(Type type) { }
+        }
+
+        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)]
+        interface IUsed
+        {
+            [RequiresUnreferencedCode(nameof(Method))]
+            void Method([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] Type type);
+        }
+
+        class UsedImplementation : IUsed
+        {
+            [ExpectedWarning("IL2046")]
+            [ExpectedWarning("IL2092")]
+            public void Method(Type type) { }
+        }
+
+        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)]
+        interface IPartiallyUsed
+        {
+            [RequiresUnreferencedCode(nameof(Method))]
+            void Method([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] Type type);
+        }
+
+        class PartiallyUsedImplementation : IPartiallyUsed
+        {
+            [ExpectedWarning("IL2046")]
+            [ExpectedWarning("IL2092")]
+            public void Method(Type type) { }
+        }
+
+        class UnusedImplementationOfPartiallyUsedInterface : IPartiallyUsed
+        {
+            public void Method(Type type) { }
+        }
+    }
+}