[dim] Interface with sealed method (mono#13501)

* '''
interface I1
{
   sealed void M1()
   {
       System.Console.WriteLine(“M1”);
   }
}

interface I2 : I1
{
   static void Test<T>(T x) where T : I2
   {
       x.M1();
   }
}

class A : I2
{
   static void Main()
   {
       I2.Test(new A());
   }
}
'''

When an interface implements a Sealed method, this method is not virtual, so it will not be available at vtable. But in the IL the call is a virtual call, but in this case we don't need to search at vtable.

Fixes mono#13466

* Change IL test.

mono/metadata/loader.c

@@ -2072,6 +2072,8 @@ get_method_constrained (MonoImage *image, MonoMethod *method, MonoClass *constra
 			return NULL;
 		}
 	} else {
+		if ((method->flags & METHOD_ATTRIBUTE_VIRTUAL) == 0)
+			return method;
 		mono_class_setup_vtable (constrained_class);
 		if (mono_class_has_failure (constrained_class)) {
 			mono_error_set_for_class_failure (error, constrained_class);

mono/tests/Makefile.am

@@ -1003,6 +1003,7 @@ TESTS_IL_SRC=			\
 	dim-sharedgenerics.il	\
 	dim-simple.il	\
 	dim-valuetypes.il \
+	dim-sealed.il \
 	tailcall-generic-cast-conservestack-il.il \
 	tailcall-generic-cast-nocrash-il.il \
 	tailcall-member-function-in-valuetype.il \

mono/tests/dim-sealed.il

@@ -0,0 +1,101 @@
+
+//  Microsoft (R) .NET Framework IL Disassembler.  Version 4.6.1055.0
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+
+
+
+// Metadata version: v4.0.30319
+.assembly extern mscorlib
+{
+  .ver 4:0:0:0
+  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) // .z\V.4..
+}
+.assembly 'sealed'
+{
+  .custom instance void class [mscorlib]System.Runtime.CompilerServices.CompilationRelaxationsAttribute::'.ctor'(int32) =  (01 00 08 00 00 00 00 00 ) // ........
+
+  .custom instance void class [mscorlib]System.Runtime.CompilerServices.RuntimeCompatibilityAttribute::'.ctor'() =  (
+		01 00 01 00 54 02 16 57 72 61 70 4E 6F 6E 45 78   // ....T..WrapNonEx
+		63 65 70 74 69 6F 6E 54 68 72 6F 77 73 01       ) // ceptionThrows.
+
+  .custom instance void class [mscorlib]System.Diagnostics.DebuggableAttribute::'.ctor'(valuetype [mscorlib]System.Diagnostics.DebuggableAttribute/DebuggingModes) =  (01 00 07 01 00 00 00 00 ) // ........
+
+  .hash algorithm 0x00008004
+  .ver  0:0:0:0
+}
+.module sealed.exe // GUID = {A4E97AD7-126F-4034-838B-627DE47F9E63}
+
+
+  .class interface private auto ansi abstract I1
+  {
+
+    // method line 1
+    .method public hidebysig 
+           instance default void M1 ()  cil managed 
+    {
+        // Method begins at RVA 0x2050
+	// Code size 13 (0xd)
+	.maxstack 8
+	IL_0000:  nop 
+	IL_0001:  ldstr "M1"
+	IL_0006:  call void class [mscorlib]System.Console::WriteLine(string)
+	IL_000b:  nop 
+	IL_000c:  ret 
+    } // end of method I1::M1
+
+  } // end of class I1
+
+  .class interface private auto ansi abstract I2
+  	implements I1  {
+
+    // method line 2
+    .method public static hidebysig 
+           default void Test<(class I2) T> (!!T x)  cil managed 
+    {
+        // Method begins at RVA 0x205e
+	// Code size 16 (0x10)
+	.maxstack 8
+	IL_0000:  nop 
+	IL_0001:  ldarga.s 0
+	IL_0003:  constrained. !!0
+	IL_0009:  callvirt instance void class I1::M1()
+	IL_000e:  nop 
+	IL_000f:  ret 
+    } // end of method I2::Test
+
+  } // end of class I2
+
+  .class private auto ansi beforefieldinit A
+  	extends [mscorlib]System.Object
+  	implements I2, I1  {
+
+    // method line 3
+    .method private static hidebysig 
+           default void Main ()  cil managed 
+    {
+        // Method begins at RVA 0x206f
+	.entrypoint
+	// Code size 13 (0xd)
+	.maxstack 8
+	IL_0000:  nop 
+	IL_0001:  newobj instance void class A::'.ctor'()
+	IL_0006:  call void class I2::Test<class A> (!!0)
+	IL_000b:  nop 
+	IL_000c:  ret 
+    } // end of method A::Main
+
+    // method line 4
+    .method public hidebysig specialname rtspecialname 
+           instance default void '.ctor' ()  cil managed 
+    {
+        // Method begins at RVA 0x207d
+	// Code size 8 (0x8)
+	.maxstack 8
+	IL_0000:  ldarg.0 
+	IL_0001:  call instance void object::'.ctor'()
+	IL_0006:  nop 
+	IL_0007:  ret 
+    } // end of method A::.ctor
+
+  } // end of class A
+