Fix HPy test test_legacy_slots_fails_without_legacy

Author: fangerer

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/hpy/GraalHPyNodes.java

@@ -2000,6 +2000,9 @@ static Object doGeneric(GraalHPyContext context, Object typeSpec, Object typeSpe
                 // process legacy slots; this is of type 'cpy_PyTypeSlot legacy_slots[]'
                 Object legacySlots = callHelperFunctionNode.call(context, GraalHPyNativeSymbol.GRAAL_HPY_TYPE_SPEC_GET_LEGECY_SLOTS, typeSpec);
                 if (!ptrLib.isNull(legacySlots)) {
+                    if (legacy == 0) {
+                        throw raiseNode.raise(TypeError, "cannot specify .legacy_slots without setting .legacy=true");
+                    }
                     int nLegacySlots = PInt.intValueExact(ptrLib.getArraySize(legacySlots));
                     for (int i = 0; i < nLegacySlots; i++) {
                         Object legacySlotDef = ptrLib.readArrayElement(legacySlots, i);

graalpython/lib-graalpython/modules/hpy/test/test_slots_legacy.py

@@ -257,7 +257,6 @@ def test_legacy_slots_getsets(self):
         p = mod.Point()
         assert p.z == 2073
 
-    @pytest.mark.xfail
     def test_legacy_slots_fails_without_legacy(self):
         import pytest
         mod_src = """