Initial work to support virtual static interface methods (dotnet/link…

…er#2072)

* Initial work to support static interface methods

* commit to allow Tlakaelel help me with the il test

* support for the runtime il test

* Incorporating feedback

* reverting a file that was checked in by mistake

* test updates

* generics tests restructuring

* tests

* fixed tests

* added a comment to clarify

* FB

Commit migrated from dotnet/linker@3fc88d4

src/tools/illink/src/linker/Linker.Steps/MarkStep.cs

@@ -690,6 +690,7 @@ void ProcessOverride (OverrideInformation overrideInformation)
 			if (IsInterfaceOverrideThatDoesNotNeedMarked (overrideInformation, isInstantiated))
 				return;
 
+			// Interface static veitual methods will be abstract and will also by pass this check to get marked
 			if (!isInstantiated && !@base.IsAbstract && _context.IsOptimizationEnabled (CodeOptimizations.OverrideRemoval, method))
 				return;
 
@@ -703,14 +704,19 @@ void ProcessOverride (OverrideInformation overrideInformation)
 				MarkMethod (method, new DependencyInfo (DependencyKind.Override, @base));
 			}
 
-			ProcessVirtualMethod (method);
+			if (method.IsVirtual)
+				ProcessVirtualMethod (method);
 		}
 
 		bool IsInterfaceOverrideThatDoesNotNeedMarked (OverrideInformation overrideInformation, bool isInstantiated)
 		{
 			if (!overrideInformation.IsOverrideOfInterfaceMember || isInstantiated)
 				return false;
 
+			// This is a static interface method and these checks should all be true
+			if (overrideInformation.Override.IsStatic && overrideInformation.Base.IsStatic && overrideInformation.Base.IsAbstract && !overrideInformation.Override.IsVirtual)
+				return false;
+
 			if (overrideInformation.MatchingInterfaceImplementation != null)
 				return !Annotations.IsMarked (overrideInformation.MatchingInterfaceImplementation);
 

src/tools/illink/src/linker/Linker/TypeMapInfo.cs

@@ -166,10 +166,13 @@ void MapVirtualMethods (TypeDefinition type)
 				return;
 
 			foreach (MethodDefinition method in type.Methods) {
-				if (!method.IsVirtual)
+				// We do not proceed unless a method is virtual or is static
+				// A static method with a .override could be implementing a static interface method
+				if (!(method.IsStatic || method.IsVirtual))
 					continue;
 
-				MapVirtualMethod (method);
+				if (method.IsVirtual)
+					MapVirtualMethod (method);
 
 				if (method.HasOverrides)
 					MapOverrides (method);

src/tools/illink/test/Mono.Linker.Tests.Cases/Inheritance.Interfaces/StaticInterfaceMethods/Dependencies/TypeHierarchyBasic.il

@@ -0,0 +1,128 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+.assembly extern System.Runtime
+{
+  .publickeytoken = (B0 3F 5F 7F 11 D5 0A 3A)
+}
+
+.assembly 'library' { }
+
+.class interface public abstract auto ansi InterfaceScenario1
+{
+  .method public newslot virtual abstract static int32 Method() cil managed noinlining
+  {
+  } // end of method Method
+} // end of class InterfaceScenario1
+.class public auto ansi BaseScenario1
+       extends [System.Runtime]System.Object
+       implements InterfaceScenario1
+{
+  .method public static int32 Method() cil managed noinlining
+  {
+    .override method int32 InterfaceScenario1::Method()
+    .locals init (int32 V_O)
+    ldloca.s 0
+    initobj int32
+    ldloc.0
+    ret
+  } // end of method Method
+} // end of class BaseScenario1
+.class public auto ansi DerivedScenario1
+       extends BaseScenario1
+{
+} // end of class DerivedScenario1
+.class interface public abstract auto ansi InterfaceScenario2
+{
+  .method public newslot virtual abstract static int32 Method() cil managed noinlining
+  {
+  } // end of method Method
+} // end of class InterfaceScenario2
+.class public auto ansi BaseScenario2
+       extends [System.Runtime]System.Object
+       implements InterfaceScenario2
+{
+  .method public static int32 Method() cil managed noinlining
+  {
+    .override method int32 InterfaceScenario2::Method()
+    .locals init (int32 V_O)
+    ldloca.s 0
+    initobj int32
+    ldloc.0
+    ret
+  } // end of method Method
+} // end of class BaseScenario2
+.class public auto ansi DerivedScenario2
+       extends BaseScenario2
+       implements InterfaceScenario2
+{
+} // end of class DerivedScenario2
+.class interface public abstract auto ansi InterfaceScenario3
+{
+  .method public newslot virtual abstract static int32 Method() cil managed noinlining
+  {
+  } // end of method Method
+} // end of class InterfaceScenario3
+.class public abstract auto ansi BaseScenario3
+       extends [System.Runtime]System.Object
+       implements InterfaceScenario3
+{
+} // end of class BaseScenario3
+.class public auto ansi DerivedScenario3
+       extends BaseScenario3
+       implements InterfaceScenario3
+{
+  .method public static int32 MethodImplOnDerived() cil managed noinlining
+  {
+    .override method int32 InterfaceScenario3::Method()
+    .locals init (int32 V_O)
+    ldloca.s 0
+    initobj int32
+    ldloc.0
+    ret
+  } // end of method MethodImplOnDerived
+} // end of class DerivedScenario3
+
+.class public auto ansi TestEntrypoint
+       extends [System.Runtime]System.Object
+{
+  .method public static void Test_Scenario1() cil managed noinlining
+  {
+    constrained. DerivedScenario1
+    call int32 InterfaceScenario1::Method()
+    pop
+    ret
+  } // end of method Test_Scenario1
+  .method public static void Test_Scenario2() cil managed noinlining
+  {
+    constrained. DerivedScenario2
+    call int32 InterfaceScenario2::Method()
+    pop
+    ret
+  } // end of method Test_Scenario2
+  .method public static void Test_Scenario3() cil managed noinlining
+  {
+    constrained. DerivedScenario3
+    call int32 InterfaceScenario3::Method()
+    pop
+    ret
+  } // end of method Test_Scenario3
+  .method public static int32 Test() cil managed noinlining
+  {
+    .locals init (class [System.Runtime]System.Exception V_0)
+    .try {
+        call void TestEntrypoint::Test_Scenario1()
+        call void TestEntrypoint::Test_Scenario2()
+        call void TestEntrypoint::Test_Scenario3()
+        leave.s Scenario1Done
+    } catch [System.Runtime]System.Exception {
+        stloc.0
+        leave.s Scenario1Done
+    }
+Scenario1Done: nop
+    ret
+  } // end of method Test
+} // end of class TestEntrypoint
+
+