Disable ctor calls on classes marked with ComImport when COM interop feature isn't enabled.

src/coreclr/vm/ecall.cpp

@@ -336,12 +336,9 @@ PCODE ECall::GetFCallImpl(MethodDesc * pMD, BOOL * pfSharedOrDynamicFCallImpl /*
         return CoreLibBinder::GetMethod(METHOD__DELEGATE__CONSTRUCT_DELEGATE)->GetMultiCallableAddrOfCode();
     }
 
-    // COM imported classes have special constructors
-    if (pMT->IsComObjectType()
 #ifdef FEATURE_COMINTEROP
-        && (g_pBaseCOMObject == NULL || pMT != g_pBaseCOMObject)
-#endif // FEATURE_COMINTEROP
-    )
+    // COM imported classes have special constructors
+    if (pMT->IsComObjectType() && pMT != g_pBaseCOMObject)
     {
         if (pfSharedOrDynamicFCallImpl)
             *pfSharedOrDynamicFCallImpl = TRUE;
@@ -352,6 +349,12 @@ PCODE ECall::GetFCallImpl(MethodDesc * pMD, BOOL * pfSharedOrDynamicFCallImpl /*
         // FCComCtor does not need to be in the fcall hashtable since it does not erect frame.
         return GetEEFuncEntryPoint(FCComCtor);
     }
+#else // !FEATURE_COMINTEROP
+    // This code path is taken when a class marked with ComImport is being created.
+    // If we get here and COM interop isn't suppported, throw.
+    if (pMT->IsComObjectType())
+        COMPlusThrow(kPlatformNotSupportedException, IDS_EE_ERROR_COM);
+#endif // FEATURE_COMINTEROP
 
     if (!pMD->GetModule()->IsSystem())
         COMPlusThrow(kSecurityException, BFA_ECALLS_MUST_BE_IN_SYS_MOD);

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Runtime/CompilerServices/RuntimeHelpersTests.cs

@@ -127,6 +127,22 @@ static GenericHasCctor()
             }
         }
 
+        [ComImport]
+        [Guid("00000000-0000-0000-0000-000000000000")]
+        interface ComInterface
+        {
+            void Func();
+        }
+
+        // This class is used to test the PrepareMethod API with COM interop on non-Windows platforms.
+        [ComImport]
+        [Guid("00000000-0000-0000-0000-000000000000")]
+        class ComClass : ComInterface
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            public extern void Func();
+        }
+
         [Fact]
         public static void PrepareMethod()
         {
@@ -139,6 +155,16 @@ public static void PrepareMethod()
             {
                 Assert.ThrowsAny<ArgumentException>(() => RuntimeHelpers.PrepareMethod(typeof(IList).GetMethod("Add").MethodHandle));
             }
+
+            try
+            {
+                // This is expected to either succeed or throw PlatformNotSupportedException depending on the platform
+                // and runtime flavor
+                RuntimeHelpers.PrepareMethod(typeof(ComClass).GetMethod("Func").MethodHandle);
+            }
+            catch (PlatformNotSupportedException)
+            {
+            }
         }
 
         [Fact]