bpo-38469: Handle named expression scope with global/nonlocal keywords (GH-16755)

The symbol table handing of PEP572's assignment expressions is not resolving correctly the scope of some variables in presence of global/nonlocal keywords in conjunction with comprehensions.

1 files changed, 45 insertions, 0 deletions

diff --git a/Lib/test/test_named_expressions.py b/Lib/test/test_named_expressions.py
index b1027ce..01e26c8 100644
--- a/Lib/test/test_named_expressions.py
+++ b/Lib/test/test_named_expressions.py
@@ -1,6 +1,7 @@
 import os
 import unittest
 
+GLOBAL_VAR = None
 
 class NamedExpressionInvalidTest(unittest.TestCase):
 
@@ -470,5 +471,49 @@ spam()"""
                 self.assertEqual(ns["x"], 2)
                 self.assertEqual(ns["result"], [0, 1, 2])
 
+    def test_named_expression_global_scope(self):
+        sentinel = object()
+        global GLOBAL_VAR
+        def f():
+            global GLOBAL_VAR
+            [GLOBAL_VAR := sentinel for _ in range(1)]
+            self.assertEqual(GLOBAL_VAR, sentinel)
+        try:
+            f()
+            self.assertEqual(GLOBAL_VAR, sentinel)
+        finally:
+            GLOBAL_VAR = None
+
+    def test_named_expression_global_scope_no_global_keyword(self):
+        sentinel = object()
+        def f():
+            GLOBAL_VAR = None
+            [GLOBAL_VAR := sentinel for _ in range(1)]
+            self.assertEqual(GLOBAL_VAR, sentinel)
+        f()
+        self.assertEqual(GLOBAL_VAR, None)
+
+    def test_named_expression_nonlocal_scope(self):
+        sentinel = object()
+        def f():
+            nonlocal_var = None
+            def g():
+                nonlocal nonlocal_var
+                [nonlocal_var := sentinel for _ in range(1)]
+            g()
+            self.assertEqual(nonlocal_var, sentinel)
+        f()
+
+    def test_named_expression_nonlocal_scope_no_nonlocal_keyword(self):
+        sentinel = object()
+        def f():
+            nonlocal_var = None
+            def g():
+                [nonlocal_var := sentinel for _ in range(1)]
+            g()
+            self.assertEqual(nonlocal_var, None)
+        f()
+
+
 if __name__ == "__main__":
     unittest.main()