__slots__ xor __dict__

Author: youknowone

Lib/test/test_typing.py

@@ -5269,7 +5269,6 @@ def test_weakref_all(self):
         for t in things:
             self.assertEqual(weakref.ref(t)(), t)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON - __slots__ with Generic doesn't prevent new attributes
     def test_parameterized_slots(self):
         T = TypeVar('T')
         class C(Generic[T]):
@@ -5289,7 +5288,6 @@ def foo(x: C['C']): ...
         self.assertEqual(get_type_hints(foo, globals(), locals())['x'], C[C])
         self.assertEqual(copy(C[int]), deepcopy(C[int]))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON - __slots__ with Generic doesn't prevent new attributes
     def test_parameterized_slots_dict(self):
         T = TypeVar('T')
         class D(Generic[T]):

crates/vm/src/builtins/object.rs

@@ -66,10 +66,16 @@ impl Constructor for PyBaseObject {
         }
 
         // more or less __new__ operator
-        let dict = if cls.is(vm.ctx.types.object_type) {
-            None
-        } else {
+        // Only create dict if the class has HAS_DICT flag (i.e., __slots__ was not defined
+        // or __dict__ is in __slots__)
+        let dict = if cls
+            .slots
+            .flags
+            .has_feature(crate::types::PyTypeFlags::HAS_DICT)
+        {
             Some(vm.ctx.new_dict())
+        } else {
+            None
         };
 
         // Ensure that all abstract methods are implemented before instantiating instance.

crates/vm/src/builtins/type.rs

@@ -1223,7 +1223,10 @@ impl Constructor for PyType {
         // since they inherit it from type
 
         // Add __dict__ descriptor after type creation to ensure correct __objclass__
-        if !base_is_type {
+        // Only add if:
+        // 1. base is not type (type subclasses inherit __dict__ from type)
+        // 2. the class has HAS_DICT flag (i.e., __slots__ was not defined or __dict__ is in __slots__)
+        if !base_is_type && typ.slots.flags.has_feature(PyTypeFlags::HAS_DICT) {
             let __dict__ = identifier!(vm, __dict__);
             if !typ.attributes.read().contains_key(&__dict__) {
                 unsafe {

crates/vm/src/stdlib/typevar.rs

@@ -1,6 +1,6 @@
 // spell-checker:ignore typevarobject funcobj
 use crate::{
-    AsObject, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
+    AsObject, Context, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
     builtins::{PyTupleRef, PyTypeRef, pystr::AsPyStr},
     common::lock::PyMutex,
     function::{FuncArgs, IntoFuncArgs, PyComparisonValue},
@@ -972,6 +972,11 @@ pub struct Generic {}
 
 #[pyclass(flags(BASETYPE))]
 impl Generic {
+    #[pyattr]
+    fn __slots__(ctx: &Context) -> PyTupleRef {
+        ctx.empty_tuple.clone()
+    }
+
     #[pyclassmethod]
     fn __class_getitem__(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
         call_typing_args_kwargs("_generic_class_getitem", cls, args, vm)