Add fix for generic method case

Author: buyaa-n

src/coreclr/vm/genmeth.cpp

@@ -1236,12 +1236,11 @@ MethodDesc::FindOrCreateAssociatedMethodDesc(MethodDesc* pDefMD,
         if (methodInst.GetNumArgs() != pMethod->GetNumGenericMethodArgs())
             COMPlusThrow(kArgumentException);
 
-        // we base the creation of an unboxing stub on whether the original method was one already
-        // that keeps the reflection logic the same for value types
+        // we need unboxing stubs for virtual methods on value types
         pInstMD = MethodDesc::FindOrCreateAssociatedMethodDesc(
             pMethod,
             pMT,
-            pMethod->IsUnboxingStub(),
+            instType.IsValueType() && pMethod->IsVirtual(),
             methodInst,
             FALSE,      /* no allowInstParam */
             TRUE   /* force remotable method (i.e. inst wrappers for non-generic methods on generic interfaces) */);

src/libraries/System.Runtime/tests/System/DelegateTests.cs

@@ -452,10 +452,34 @@ public static void SameMethodObtainedViaDelegateAndReflectionAreSameForStruct()
             Assert.True(m1.Equals(m2));
         }
 
+        [Fact]
+        public static void SameGenericMethodObtainedViaDelegateAndReflectionAreSameForClass()
+        {
+            var m1 = ((MethodCallExpression)((Expression<Action>)(() => new ClassG().M<string, object>())).Body).Method;
+            var m2 = new Action(new ClassG().M<string, object>).Method;
+            Assert.True(m1.Equals(m2));
+            Assert.True(m1.GetHashCode().Equals(m2.GetHashCode()));
+            Assert.Equal(m1.MethodHandle.Value, m2.MethodHandle.Value);
+        }
+
+        [Fact]
+        public static void SameGenericMethodObtainedViaDelegateAndReflectionAreSameForStruct()
+        {
+            var m1 = ((MethodCallExpression)((Expression<Action>)(() => new StructG().M<string, object>())).Body).Method;
+            var m2 = new Action(new StructG().M<string, object>).Method;
+            Assert.True(m1.Equals(m2));
+            Assert.True(m1.GetHashCode().Equals(m2.GetHashCode()));
+            Assert.Equal(m1.MethodHandle.Value, m2.MethodHandle.Value);
+        }
+
         class Class { internal void M() { } }
 
         struct Struct { internal void M() { } }
 
+        class ClassG { internal void M<Key, Value>() { } }
+
+        struct StructG { internal void M<Key, Value>() { } }
+
         private delegate void IntIntDelegate(int expected, int actual);
         private delegate void IntIntDelegateWithDefault(int expected, int actual = 7);