gh-128396: Fix a crash when inline comprehension has the same local variable as the outside scope (#130235)

3 files changed, 16 insertions, 2 deletions

diff --git a/Lib/test/test_frame.py b/Lib/test/test_frame.py
index 4d08606..a6e11f1 100644
--- a/Lib/test/test_frame.py
+++ b/Lib/test/test_frame.py
@@ -346,6 +346,12 @@ class TestFrameLocals(unittest.TestCase):
         self.assertEqual(x, 2)
         self.assertEqual(y, 3)
 
+    def test_closure_with_inline_comprehension(self):
+        lambda: k
+        k = 1
+        lst = [locals() for k in [0]]
+        self.assertEqual(lst[0]['k'], 0)
+
     def test_as_dict(self):
         x = 1
         y = 2
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-02-17-18-59-33.gh-issue-128396.iVtoYY.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-17-18-59-33.gh-issue-128396.iVtoYY.rst
new file mode 100644
index 0000000..4382b77
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-17-18-59-33.gh-issue-128396.iVtoYY.rst
@@ -0,0 +1 @@
+Fix a crash that occurs when calling :func:`locals` inside an inline comprehension that uses the same local variable as the outer frame scope where the variable is a free or cell var.
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 8ebcc1a..dbeee50 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -45,8 +45,15 @@ framelocalsproxy_getval(_PyInterpreterFrame *frame, PyCodeObject *co, int i)
     if (kind == CO_FAST_FREE || kind & CO_FAST_CELL) {
         // The cell was set when the frame was created from
         // the function's closure.
-        assert(PyCell_Check(value));
-        cell = value;
+        // GH-128396: With PEP 709, it's possible to have a fast variable in
+        // an inlined comprehension that has the same name as the cell variable
+        // in the frame, where the `kind` obtained from frame can not guarantee
+        // that the variable is a cell.
+        // If the variable is not a cell, we are okay with it and we can simply
+        // return the value.
+        if (PyCell_Check(value)) {
+            cell = value;
+        }
     }
 
     if (cell != NULL) {