From a56116dd6471e8546a76132592a2d5bfbe38b6a0 Mon Sep 17 00:00:00 2001
From: Carl Meyer <carl@oddbird.net>
Date: Wed, 13 Sep 2023 16:45:10 -0700
Subject: [PATCH] gh-109219: propagate used free vars through type param scopes
 [v2]

---
 Lib/test/test_type_params.py | 14 ++++++++++++++
 Python/symtable.c            | 17 +++++++++++++----
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/Lib/test/test_type_params.py b/Lib/test/test_type_params.py
index b1848aee4753a1..0a61be9773ac4a 100644
--- a/Lib/test/test_type_params.py
+++ b/Lib/test/test_type_params.py
@@ -694,6 +694,20 @@ class Cls:
         cls = ns["outer"]()
         self.assertEqual(cls.Alias.__value__, "class")
 
+    def test_nested_free(self):
+        ns = run_code("""
+            def f():
+                T = str
+                class C:
+                    T = int
+                    class D[U](T):
+                        x = T
+                return C
+        """)
+        C = ns["f"]()
+        self.assertIn(int, C.D.__bases__)
+        self.assertIs(C.D.x, str)
+
 
 class TypeParamsManglingTest(unittest.TestCase):
     def test_mangling(self):
diff --git a/Python/symtable.c b/Python/symtable.c
index d737c09203d31b..b50d837a20cae3 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -784,7 +784,8 @@ drop_class_free(PySTEntryObject *ste, PyObject *free)
 static int
 update_symbols(PyObject *symbols, PyObject *scopes,
                PyObject *bound, PyObject *free,
-               PyObject *inlined_cells, int classflag)
+               PyObject *inlined_cells, int classflag,
+               PySTEntryObject *class_entry)
 {
     PyObject *name = NULL, *itr = NULL;
     PyObject *v = NULL, *v_scope = NULL, *v_new = NULL, *v_free = NULL;
@@ -836,8 +837,16 @@ update_symbols(PyObject *symbols, PyObject *scopes,
                the class that has the same name as a local
                or global in the class scope.
             */
-            if  (classflag &&
-                 PyLong_AS_LONG(v) & (DEF_BOUND | DEF_GLOBAL)) {
+            PyObject *class_v = NULL;
+            if (class_entry) {
+                class_v = PyDict_GetItemWithError(class_entry->ste_symbols, name);
+                if (!class_v && PyErr_Occurred()) {
+                    goto error;
+                }
+            }
+            if  ((classflag &&
+                  PyLong_AS_LONG(v) & (DEF_BOUND | DEF_GLOBAL)) ||
+                 (class_v && PyLong_AS_LONG(class_v) & (DEF_BOUND | DEF_GLOBAL))) {
                 long flags = PyLong_AS_LONG(v) | DEF_FREE_CLASS;
                 v_new = PyLong_FromLong(flags);
                 if (!v_new) {
@@ -1078,7 +1087,7 @@ analyze_block(PySTEntryObject *ste, PyObject *bound, PyObject *free,
         goto error;
     /* Records the results of the analysis in the symbol table entry */
     if (!update_symbols(ste->ste_symbols, scopes, bound, newfree, inlined_cells,
-                        ste->ste_type == ClassBlock))
+                        ste->ste_type == ClassBlock, class_entry))
         goto error;
 
     temp = PyNumber_InPlaceOr(free, newfree);