gh-131936: Relax assertion in _Py_CalculateSuggestions

Lib/test/test_traceback.py

@@ -4619,7 +4619,37 @@ def test_levenshtein_distance_short_circuit(self):
     @cpython_only
     def test_suggestions_extension(self):
         # Check that the C extension is available
-        import _suggestions  # noqa: F401
+        import _suggestions
+
+        self.assertEqual(
+            _suggestions._generate_suggestions(
+                ["hello", "world"],
+                "hell"
+            ),
+            "hello"
+        )
+        self.assertEqual(
+            _suggestions._generate_suggestions(
+                ["hovercraft"],
+                "eels"
+            ),
+            None
+        )
+
+        # gh-131936: _Py_CalculateSuggestions wanted exactly a list
+        class MyList(list):
+            def __getitem__(self, *_):
+                # _Py_CalculateSuggestions uses the list macros, so this
+                # shouldn't be a problem.
+                raise RuntimeError("evil")
+
+        self.assertEqual(
+            _suggestions._generate_suggestions(
+                MyList(["spanish", "inquisition"]),
+                "spani"
+            ),
+            "spanish"
+        )
 
 
 class TestColorizedTraceback(unittest.TestCase):

Python/suggestions.c

@@ -129,7 +129,7 @@ _Py_CalculateSuggestions(PyObject *dir,
                       PyObject *name)
 {
     assert(!PyErr_Occurred());
-    assert(PyList_CheckExact(dir));
+    assert(PyList_Check(dir));
 
     Py_ssize_t dir_size = PyList_GET_SIZE(dir);
     if (dir_size >= MAX_CANDIDATE_ITEMS) {