Revert static interface trimming (#2784)

* Revert "Trim static interfaces (#2741)"

This reverts commit a073a68561a7f45a2dba0976083ee3e9873bf423.

* Revert "Don't remove MethodImpl if overridden method is not in a link assembly (#2771)"

This reverts commit 44610681fb096cc2b38a18689e954af24049d390.

* Revert "Fix NullReferenceException when sweeping unused static interface (#2783)"

This reverts commit 00e9a154efeb6369b1345bdafeebb686c0163841.

7 files changed, 18 insertions, 117 deletions

diff --git a/test/Mono.Linker.Tests.Cases.Expectations/Assertions/KeptOverrideAttribute.cs b/test/Mono.Linker.Tests.Cases.Expectations/Assertions/KeptOverrideAttribute.cs
deleted file mode 100644
index 62bfd0c15..000000000
--- a/test/Mono.Linker.Tests.Cases.Expectations/Assertions/KeptOverrideAttribute.cs
+++ /dev/null
@@ -1,27 +0,0 @@
-// 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;
-
-namespace Mono.Linker.Tests.Cases.Expectations.Assertions
-{
-	/// <summary>
-	/// Used to ensure that a method should keep an 'override' annotation for a method in the supplied base type.
-	/// The absence of this attribute does not enforce that the override is removed -- this is different from other Kept attributes
-	/// To enforce the removal of an override, use <see cref="RemovedOverrideAttribute"/>.
-	/// Fails in tests if the method doesn't have the override method in the original or linked assembly.
-	/// </summary>
-	/// <seealso cref="RemovedOverrideAttribute" />
-	[AttributeUsage (AttributeTargets.Method, AllowMultiple = true, Inherited = false)]
-	public class KeptOverrideAttribute : KeptAttribute
-	{
-		public Type TypeWithOverriddenMethodDeclaration;
-
-		public KeptOverrideAttribute (Type typeWithOverriddenMethod)
-		{
-			if (typeWithOverriddenMethod == null)
-				throw new ArgumentNullException (nameof (typeWithOverriddenMethod));
-			TypeWithOverriddenMethodDeclaration = typeWithOverriddenMethod;
-		}
-	}
-}
\ No newline at end of file
diff --git a/test/Mono.Linker.Tests.Cases.Expectations/Assertions/RemovedOverrideAttribute.cs b/test/Mono.Linker.Tests.Cases.Expectations/Assertions/RemovedOverrideAttribute.cs
deleted file mode 100644
index c15cf9a9e..000000000
--- a/test/Mono.Linker.Tests.Cases.Expectations/Assertions/RemovedOverrideAttribute.cs
+++ /dev/null
@@ -1,25 +0,0 @@
-// 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;
-
-namespace Mono.Linker.Tests.Cases.Expectations.Assertions
-{
-	/// <Summary>
-	/// Used to ensure that a method should remove an 'override' annotation for a method in the supplied base type.
-	/// Fails in tests if the method has the override method in the linked assembly,
-	///		or if the override is not found in the original assembly
-	/// </Summary>
-	/// <seealso cref="KeptOverrideAttribute" />
-	[AttributeUsage (AttributeTargets.Method, AllowMultiple = true, Inherited = false)]
-	public class RemovedOverrideAttribute : BaseInAssemblyAttribute
-	{
-		public Type TypeWithOverriddenMethodDeclaration;
-		public RemovedOverrideAttribute (Type typeWithOverriddenMethod)
-		{
-			if (typeWithOverriddenMethod == null)
-				throw new ArgumentException ("Value cannot be null or empty.", nameof (typeWithOverriddenMethod));
-			TypeWithOverriddenMethodDeclaration = typeWithOverriddenMethod;
-		}
-	}
-}
\ No newline at end of file
diff --git a/test/Mono.Linker.Tests.Cases/Inheritance.Interfaces/InterfaceVariants.cs b/test/Mono.Linker.Tests.Cases/Inheritance.Interfaces/InterfaceVariants.cs
index de7f5a537..bb43569b6 100644
--- a/test/Mono.Linker.Tests.Cases/Inheritance.Interfaces/InterfaceVariants.cs
+++ b/test/Mono.Linker.Tests.Cases/Inheritance.Interfaces/InterfaceVariants.cs
@@ -45,7 +45,6 @@ namespace Mono.Linker.Tests.Cases.Inheritance.Interfaces
 			internal class InterfaceMethodUsedThroughInterface : IStaticInterfaceUsed
 			{
 				[Kept]
-				[KeptOverride (typeof (IStaticInterfaceUsed))]
 				public static void StaticMethodUsedThroughInterface ()
 				{
 				}
@@ -57,7 +56,6 @@ namespace Mono.Linker.Tests.Cases.Inheritance.Interfaces
 			internal class InterfaceMethodUnused : IStaticInterfaceUsed
 			{
 				[Kept]
-				[KeptOverride (typeof (IStaticInterfaceUsed))]
 				public static void StaticMethodUsedThroughInterface ()
 				{
 				}
@@ -73,33 +71,41 @@ namespace Mono.Linker.Tests.Cases.Inheritance.Interfaces
 			// The interface methods themselves are not used, but the implementation of these methods is
 			internal interface IStaticInterfaceMethodUnused
 			{
+				// Can be removed with Static Interface trimming optimization
+				[Kept]
 				static abstract void InterfaceUsedMethodNot ();
 			}
 
-			// The interface methods themselves are not used, but the implementation of these methods is
+			// Can be removed with Static Interface Trimming
+			[Kept]
 			internal interface IStaticInterfaceUnused
 			{
+				// Can be removed with Static Interface Trimming
+				[Kept]
 				static abstract void InterfaceAndMethodNoUsed ();
 			}
 
 			[Kept]
+			[KeptInterface (typeof (IStaticInterfaceUnused))]
+			[KeptInterface (typeof (IStaticInterfaceMethodUnused))]
 			internal class InterfaceMethodUsedThroughImplementation : IStaticInterfaceMethodUnused, IStaticInterfaceUnused
 			{
 				[Kept]
-				[RemovedOverride (typeof (IStaticInterfaceMethodUnused))]
 				public static void InterfaceUsedMethodNot () { }
 
 				[Kept]
-				[RemovedOverride (typeof (IStaticInterfaceUnused))]
 				public static void InterfaceAndMethodNoUsed () { }
 			}
 
 			[Kept]
 			[KeptInterface (typeof (IStaticInterfaceMethodUnused))]
+			[KeptInterface (typeof (IStaticInterfaceUnused))]
 			internal class InterfaceMethodUnused : IStaticInterfaceMethodUnused, IStaticInterfaceUnused
 			{
+				[Kept]
 				public static void InterfaceUsedMethodNot () { }
 
+				[Kept]
 				public static void InterfaceAndMethodNoUsed () { }
 			}
 
diff --git a/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/CopyLibrary.cs b/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/CopyLibrary.cs
index 792f869fb..0f31e8277 100644
--- a/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/CopyLibrary.cs
+++ b/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/CopyLibrary.cs
@@ -13,6 +13,5 @@ namespace Mono.Linker.Tests.Cases.Libraries.Dependencies
 	{
 		static abstract void CopyLibraryStaticInterfaceMethod ();
 		static abstract void CopyLibraryExplicitImplementationStaticInterfaceMethod ();
-		public static abstract void PublicStaticInterfaceMethod ();
 	}
 }
diff --git a/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/SkipLibrary.cs b/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/SkipLibrary.cs
deleted file mode 100644
index 20f59e090..000000000
--- a/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/SkipLibrary.cs
+++ /dev/null
@@ -1,10 +0,0 @@
-// 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.
-
-namespace Mono.Linker.Tests.Cases.Libraries.Dependencies
-{
-	public interface ISkipLibraryStaticInterface
-	{
-		static abstract void StaticInterfaceMethod ();
-	}
-}
diff --git a/test/Mono.Linker.Tests.Cases/Libraries/RootLibrary.cs b/test/Mono.Linker.Tests.Cases/Libraries/RootLibrary.cs
index 03cf665de..1534573ea 100644
--- a/test/Mono.Linker.Tests.Cases/Libraries/RootLibrary.cs
+++ b/test/Mono.Linker.Tests.Cases/Libraries/RootLibrary.cs
@@ -12,9 +12,7 @@ using Mono.Linker.Tests.Cases.Libraries.Dependencies;
 namespace Mono.Linker.Tests.Cases.Libraries
 {
 	[SetupCompileBefore ("copylibrary.dll", new[] { "Dependencies/CopyLibrary.cs" })]
-	[SetupCompileBefore ("skiplibrary.dll", new[] { "Dependencies/SkipLibrary.cs" })]
 	[SetupLinkerAction ("copy", "copylibrary")]
-	[SetupLinkerAction ("skip", "skiplibrary")]
 	[SetupLinkerArgument ("-a", "test.exe", "library")]
 	[SetupLinkerArgument ("--enable-opt", "ipconstprop")]
 	[VerifyMetadataNames]
@@ -190,7 +188,6 @@ namespace Mono.Linker.Tests.Cases.Libraries
 		[KeptInterface (typeof (IInternalStaticInterface))]
 		[KeptInterface (typeof (ICopyLibraryInterface))]
 		[KeptInterface (typeof (ICopyLibraryStaticInterface))]
-		[KeptInterface (typeof (ISkipLibraryStaticInterface))]
 		public class UninstantiatedPublicClassWithInterface :
 			IPublicInterface,
 			IPublicStaticInterface,
@@ -198,8 +195,7 @@ namespace Mono.Linker.Tests.Cases.Libraries
 			IInternalStaticInterface,
 			IEnumerator,
 			ICopyLibraryInterface,
-			ICopyLibraryStaticInterface,
-			ISkipLibraryStaticInterface
+			ICopyLibraryStaticInterface
 		{
 			internal UninstantiatedPublicClassWithInterface () { }
 
@@ -221,7 +217,6 @@ namespace Mono.Linker.Tests.Cases.Libraries
 			void IInternalInterface.ExplicitImplementationInternalInterfaceMethod () { }
 
 			[Kept]
-			[RemovedOverride (typeof (IInternalStaticInterface))]
 			public static void InternalStaticInterfaceMethod () { }
 
 			static void IInternalStaticInterface.ExplicitImplementationInternalStaticInterfaceMethod () { }
@@ -245,12 +240,7 @@ namespace Mono.Linker.Tests.Cases.Libraries
 			public static void CopyLibraryStaticInterfaceMethod () { }
 
 			[Kept]
-			[KeptOverride (typeof (ICopyLibraryStaticInterface))]
 			static void ICopyLibraryStaticInterface.CopyLibraryExplicitImplementationStaticInterfaceMethod () { }
-
-			[Kept]
-			[KeptOverride (typeof (ISkipLibraryStaticInterface))]
-			static void ISkipLibraryStaticInterface.StaticInterfaceMethod () { }
 		}
 
 		[Kept]
@@ -310,7 +300,6 @@ namespace Mono.Linker.Tests.Cases.Libraries
 			void IInternalInterface.ExplicitImplementationInternalInterfaceMethod () { }
 
 			[Kept]
-			[RemovedOverride (typeof (IInternalStaticInterface))]
 			public static void InternalStaticInterfaceMethod () { }
 
 			static void IInternalStaticInterface.ExplicitImplementationInternalStaticInterfaceMethod () { }
@@ -334,7 +323,6 @@ namespace Mono.Linker.Tests.Cases.Libraries
 			public static void CopyLibraryStaticInterfaceMethod () { }
 
 			[Kept]
-			[KeptOverride (typeof (ICopyLibraryStaticInterface))]
 			static void ICopyLibraryStaticInterface.CopyLibraryExplicitImplementationStaticInterfaceMethod () { }
 		}
 
@@ -378,6 +366,7 @@ namespace Mono.Linker.Tests.Cases.Libraries
 		[Kept]
 		internal interface IInternalStaticInterface
 		{
+			[Kept] // https://github.com/dotnet/linker/issues/2733
 			static abstract void InternalStaticInterfaceMethod ();
 
 			static abstract void ExplicitImplementationInternalStaticInterfaceMethod ();
diff --git a/test/Mono.Linker.Tests/TestCasesRunner/AssemblyChecker.cs b/test/Mono.Linker.Tests/TestCasesRunner/AssemblyChecker.cs
index ccd92ca5f..aa346b38a 100644
--- a/test/Mono.Linker.Tests/TestCasesRunner/AssemblyChecker.cs
+++ b/test/Mono.Linker.Tests/TestCasesRunner/AssemblyChecker.cs
@@ -172,13 +172,12 @@ namespace Mono.Linker.Tests.TestCasesRunner
 				linkedMembers.Remove (f.FullName);
 			}
 
-			foreach (var originalMethod in original.Methods) {
-				if (verifiedEventMethods.Contains (originalMethod.FullName))
+			foreach (var m in original.Methods) {
+				if (verifiedEventMethods.Contains (m.FullName))
 					continue;
-				var methodSignature = originalMethod.GetSignature ();
-				var linkedMethod = linked?.Methods.FirstOrDefault (l => methodSignature == l.GetSignature ());
-				VerifyMethod (originalMethod, linkedMethod);
-				linkedMembers.Remove (originalMethod.FullName);
+				var msign = m.GetSignature ();
+				VerifyMethod (m, linked?.Methods.FirstOrDefault (l => msign == l.GetSignature ()));
+				linkedMembers.Remove (m.FullName);
 			}
 		}
 
@@ -213,35 +212,6 @@ namespace Mono.Linker.Tests.TestCasesRunner
 			}
 		}
 
-		void VerifyOverrides (MethodDefinition original, MethodDefinition linked)
-		{
-			if (linked is null)
-				return;
-			var expectedBaseTypesOverridden = new HashSet<string> (original.CustomAttributes
-				.Where (ca => ca.AttributeType.Name == nameof (KeptOverrideAttribute))
-				.Select (ca => (ca.ConstructorArguments[0].Value as TypeReference).FullName));
-			var originalBaseTypesOverridden = new HashSet<string> (original.Overrides.Select (ov => ov.DeclaringType.FullName));
-			var linkedBaseTypesOverridden = new HashSet<string> (linked.Overrides.Select (ov => ov.DeclaringType.FullName));
-			foreach (var expectedBaseType in expectedBaseTypesOverridden) {
-				Assert.IsTrue (originalBaseTypesOverridden.Contains (expectedBaseType),
-					$"Method {linked.FullName} was expected to keep override {expectedBaseType}::{linked.Name}, " +
-					 "but it wasn't in the unlinked assembly");
-				Assert.IsTrue (linkedBaseTypesOverridden.Contains (expectedBaseType),
-					$"Method {linked.FullName} was expected to override {expectedBaseType}::{linked.Name}");
-			}
-
-			var expectedBaseTypesNotOverridden = new HashSet<string> (original.CustomAttributes
-				.Where (ca => ca.AttributeType.Name == nameof (RemovedOverrideAttribute))
-				.Select (ca => (ca.ConstructorArguments[0].Value as TypeReference).FullName));
-			foreach (var expectedRemovedBaseType in expectedBaseTypesNotOverridden) {
-				Assert.IsTrue (originalBaseTypesOverridden.Contains (expectedRemovedBaseType),
-					$"Method {linked.FullName} was expected to remove override {expectedRemovedBaseType}::{linked.Name}, " +
-					$"but it wasn't in the unlinked assembly");
-				Assert.IsFalse (linkedBaseTypesOverridden.Contains (expectedRemovedBaseType),
-					$"Method {linked.FullName} was expected to not override {expectedRemovedBaseType}::{linked.Name}");
-			}
-		}
-
 		static string FormatBaseOrInterfaceAttributeValue (CustomAttribute attr)
 		{
 			if (attr.ConstructorArguments.Count == 1)
@@ -403,7 +373,6 @@ namespace Mono.Linker.Tests.TestCasesRunner
 			VerifySecurityAttributes (src, linked);
 			VerifyArrayInitializers (src, linked);
 			VerifyMethodBody (src, linked);
-			VerifyOverrides (src, linked);
 		}
 
 		protected virtual void VerifyMethodBody (MethodDefinition src, MethodDefinition linked)