gh-131936: Strengthen check in `_suggestions._generate_suggestions` (#131945)

2 files changed, 26 insertions, 2 deletions

diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index ac49278..6ae8cf5 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -4619,7 +4619,31 @@ class MiscTest(unittest.TestCase):
     @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: _generate_suggestions() doesn't accept list subclasses
+        class MyList(list):
+            pass
+
+        with self.assertRaises(TypeError):
+            _suggestions._generate_suggestions(MyList(), "")
+
+
 
 
 class TestColorizedTraceback(unittest.TestCase):
diff --git a/Modules/_suggestions.c b/Modules/_suggestions.c
index 80c7179..b8bc6db 100644
--- a/Modules/_suggestions.c
+++ b/Modules/_suggestions.c
@@ -21,7 +21,7 @@ _suggestions__generate_suggestions_impl(PyObject *module,
 /*[clinic end generated code: output=79be7b653ae5e7ca input=ba2a8dddc654e33a]*/
 {
    // Check if dir is a list
-    if (!PyList_Check(candidates)) {
+    if (!PyList_CheckExact(candidates)) {
         PyErr_SetString(PyExc_TypeError, "candidates must be a list");
         return NULL;
     }