From bdcc04798e20e480a018ad606e308ca30fc4abf6 Mon Sep 17 00:00:00 2001
From: Elmir Jagudin <elmir.jagudin@gmail.com>
Date: Thu, 12 Feb 2026 14:36:14 +0100
Subject: [PATCH] raise TypeError when `__iter__` method is `None`

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.
---
 Lib/test/test_typing.py     |  1 -
 crates/vm/src/types/slot.rs | 26 +++++++++++++++++++++++++-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 1038e8c1d1d..4675a1e8875 100644
--- 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
index 53750610cae..abf24bf03bd 100644
--- 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> {