Check if the marshalling of a field is possible across all platforms.

src/coreclr/vm/comtoclrcall.cpp

@@ -1013,7 +1013,6 @@ void ComCallMethodDesc::InitNativeInfo()
                 CONSISTENCY_CHECK_MSGF(false, ("BreakOnComToClrNativeInfoInit: '%s' ", szDebugName));
 #endif // _DEBUG
 
-#ifdef TARGET_X86
             MetaSig fsig(pFD);
             fsig.NextArg();
 
@@ -1030,6 +1029,10 @@ void ComCallMethodDesc::InitNativeInfo()
 #endif
                              );
 
+            if (info.GetMarshalType() == MarshalInfo::MARSHAL_TYPE_UNKNOWN)
+                info.ThrowTypeLoadExceptionForInvalidFieldMarshal(pFD, info.GetErrorResourceId());
+
+#ifdef TARGET_X86
             if (IsFieldGetter())
             {
                 // getter takes 'this' and the output argument by-ref

src/coreclr/vm/mlinfo.h

@@ -480,6 +480,12 @@ class MarshalInfo
         return m_ms == MarshalInfo::MARSHAL_SCENARIO_FIELD;
     }
 
+    UINT GetErrorResourceId()
+    {
+        LIMITED_METHOD_CONTRACT;
+        return m_resID;
+    }
+
 private:
 
     UINT16                      GetNativeSize(MarshalType mtype);

src/tests/Interop/PInvoke/Variant/VariantTest.cs

@@ -6,7 +6,20 @@
 using TestLibrary;
 using static VariantNative;
 
-#pragma warning disable CS0612, CS0618
+// Class used to validate the IClassX generation path doesn't fail.
+// Support for this scenario is extremely limited so we simply validate
+// it continues be generated and can be marshalled to native.
+//
+// This class must be marked public in order for the IDispatch path for
+// field access to be validated.
+public class GenerateIClassX
+{
+    public int FieldPrimitive;
+    public System.Collections.Generic.List<int> FieldWithGeneric;
+    public object FieldRefType;
+    public DateTime FieldValueType;
+}
+
 partial class Test
 {
     private const byte NumericValue = 15;
@@ -41,10 +54,13 @@ private unsafe static void TestByValue(bool hasComSupport)
         Assert.IsTrue(Marshal_ByValue_Null(DBNull.Value));
         Assert.IsTrue(Marshal_ByValue_Missing(System.Reflection.Missing.Value));
         Assert.IsTrue(Marshal_ByValue_Empty(null));
+
         if (hasComSupport)
         {
             Assert.IsTrue(Marshal_ByValue_Object(new object()));
             Assert.IsTrue(Marshal_ByValue_Object_IUnknown(new UnknownWrapper(new object())));
+            Assert.IsTrue(Marshal_ByValue_Object(new GenerateIClassX()));
+            Assert.IsTrue(Marshal_ByValue_Object_IUnknown(new UnknownWrapper(new GenerateIClassX())));
         }
 
         Assert.Throws<ArgumentException>(() => Marshal_ByValue_Invalid(TimeSpan.Zero));
@@ -123,6 +139,12 @@ private unsafe static void TestByRef(bool hasComSupport)
 
             obj = new UnknownWrapper(new object());
             Assert.IsTrue(Marshal_ByRef_Object_IUnknown(ref obj));
+
+            obj = new GenerateIClassX();
+            Assert.IsTrue(Marshal_ByRef_Object(ref obj));
+
+            obj = new UnknownWrapper(new GenerateIClassX());
+            Assert.IsTrue(Marshal_ByRef_Object_IUnknown(ref obj));
         }
 
         obj = DecimalValue;
@@ -209,6 +231,12 @@ private unsafe static void TestFieldByValue(bool hasComSupport)
 
             wrapper.value = new UnknownWrapper(new object());
             Assert.IsTrue(Marshal_Struct_ByValue_Object_IUnknown(wrapper));
+
+            wrapper.value = new GenerateIClassX();
+            Assert.IsTrue(Marshal_Struct_ByValue_Object(wrapper));
+
+            wrapper.value = new UnknownWrapper(new GenerateIClassX());
+            Assert.IsTrue(Marshal_Struct_ByValue_Object_IUnknown(wrapper));
         }
     }
 
@@ -283,6 +311,12 @@ private unsafe static void TestFieldByRef(bool hasComSupport)
 
             wrapper.value = new UnknownWrapper(new object());
             Assert.IsTrue(Marshal_Struct_ByRef_Object_IUnknown(ref wrapper));
+
+            wrapper.value = new GenerateIClassX();
+            Assert.IsTrue(Marshal_Struct_ByRef_Object(ref wrapper));
+
+            wrapper.value = new UnknownWrapper(new GenerateIClassX());
+            Assert.IsTrue(Marshal_Struct_ByRef_Object_IUnknown(ref wrapper));
         }
     }
 }