Fix setter on metaclass

Src/IronPython/Runtime/Types/PythonType.cs

@@ -76,7 +76,6 @@ public partial class PythonType : IPythonMembersList, IDynamicMetaObjectProvider
         [MultiRuntimeAware]
         private static int MasterVersion = 1;
         private static readonly CommonDictionaryStorage _pythonTypes = new CommonDictionaryStorage();
-        internal static readonly PythonType _pythonTypeType = DynamicHelpers.GetPythonTypeFromType(typeof(PythonType));
         private static readonly WeakReference[] _emptyWeakRef = new WeakReference[0];
         private static object _subtypesLock = new object();
         internal static readonly Func<string, Exception, Exception> DefaultMakeException = (message, innerException) => new Exception(message, innerException);
@@ -514,7 +513,7 @@ public void __delattr__(CodeContext/*!*/ context, string name) {
         }
 
         [SlotField]
-        public static PythonTypeSlot __dict__ = new PythonTypeDictSlot(_pythonTypeType);
+        public static PythonTypeSlot __dict__ = new PythonTypeDictSlot(TypeCache.PythonType);
 
         [SpecialName, PropertyMethod, WrapperDescriptor]
         public static object Get__doc__(CodeContext/*!*/ context, PythonType self) {
@@ -1314,16 +1313,18 @@ internal void SetCustomMember(CodeContext/*!*/ context, string name, object valu
             Debug.Assert(context != null);
 
             PythonTypeSlot dts;
-            if (TryResolveSlot(context, name, out dts)) {
-                if (dts.TrySetValue(context, null, this, value)) {
-                    return;
-                }
+            if (TryResolveSlot(context, name, out dts) && dts.TrySetValue(context, null, this, value)) {
+                return;
             }
 
-            if (PythonType._pythonTypeType.TryResolveSlot(context, name, out dts)) {
-                if (dts.TrySetValue(context, this, PythonType._pythonTypeType, value)) {
-                    return;
-                }
+            // search the type
+            var myType = DynamicHelpers.GetPythonType(this);
+            if (myType.TryResolveSlot(context, name, out dts) && dts.TrySetValue(context, this, myType, value)) {
+                return;
+            }
+
+            if (myType != TypeCache.PythonType && TypeCache.PythonType.TryResolveSlot(context, name, out dts) && dts.TrySetValue(context, this, TypeCache.PythonType, value)) {
+                return;
             }
 
             if (IsSystemType) {

Tests/test_metaclass.py

@@ -652,4 +652,23 @@ class XM2(C2_C1, C5, metaclass=metafactory(type)):
         self.assertEqual(flags['MetaClass.__init__'], 0) # !!!
         self.assertEqual(XM2.meta_func, "processed by function meta(XM2, ...) using metabase <class 'type'>")
 
+    def test_setter_on_metaclass(self):
+        """https://github.com/IronLanguages/ironpython3/issues/1208"""
+        class MetaClass(type):
+            @property
+            def test(self):
+                return 1
+
+            @test.setter
+            def test(self, value):
+                raise Exception
+
+        class Generic(metaclass=MetaClass):
+            pass
+
+        self.assertEqual(Generic.test, 1)
+
+        with self.assertRaises(Exception):
+            Generic.test = 2
+
 run_test(__name__)