raise TypeError when __iter__ method is None

elmjag · elmjag · commit e131b7c12897 · 2026-02-12T14:38:47.000+01:00
Setting special `__iter__` method to `None` is used to mark objects as non-iterable. https://docs.python.org/3/reference/datamodel.html#special-method-names Check if `__iter__` is set to `None` and raise TypeError exception.
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
@@ -10916,7 +10916,6 @@ class TypeIterationTests(BaseTestCase):
         Annotated[T, ''],
     )
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_cannot_iterate(self):
         expected_error_regex = "object is not iterable"
         for test_type in self._UNITERABLE_TYPES:
diff --git a/crates/vm/src/types/slot.rs b/crates/vm/src/types/slot.rs
@@ -1,6 +1,7 @@
 use crate::common::lock::{
     PyMappedRwLockReadGuard, PyMappedRwLockWriteGuard, PyRwLockReadGuard, PyRwLockWriteGuard,
 };
+use crate::vm::PyMethod;
 use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
     builtins::{PyInt, PyStr, PyStrInterned, PyStrRef, PyType, PyTypeRef},
@@ -534,7 +535,30 @@ pub(crate) fn richcompare_wrapper(
 }
 
 fn iter_wrapper(zelf: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-    vm.call_special_method(&zelf, identifier!(vm, __iter__), ())
+    fn method_is_none(method: &PyMethod, vm: &VirtualMachine) -> bool {
+        match method {
+            PyMethod::Attribute(meth) => vm.is_none(meth),
+            _ => false,
+        }
+    }
+
+    //
+    // look-up '__iter__' method
+    //
+    let method_ident = identifier!(vm, __iter__);
+    let method = vm
+        .get_special_method(&zelf, method_ident)?
+        .ok_or_else(|| vm.new_attribute_error(method_ident.as_str().to_owned()))?;
+
+    //
+    // setting '__iter__' method to 'None' value is used
+    // to mark non-iterable objects, raise TypeError
+    //
+    if method_is_none(&method, vm) {
+        return Err(vm.new_type_error(format!("'{}' object is not iterable", zelf.class().name())));
+    }
+
+    method.invoke((), vm)
 }
 
 fn bool_wrapper(num: PyNumber<'_>, vm: &VirtualMachine) -> PyResult<bool> {

Original file line number	Diff line number	Diff line change
`@@ -10916,7 +10916,6 @@ class TypeIterationTests(BaseTestCase):`
`10916`	`10916`	`Annotated[T, ''],`
`10917`	`10917`	`)`
`10918`	`10918`
`10919`		`- @unittest.expectedFailure # TODO: RUSTPYTHON`
`10920`	`10919`	`def test_cannot_iterate(self):`
`10921`	`10920`	`expected_error_regex = "object is not iterable"`
`10922`	`10921`	`for test_type in self._UNITERABLE_TYPES:`