gh-94947: Disallow parsing walrus with feature_version < (3, 8)

hauntsaninja · hauntsaninja · commit fef5536dfcb7 · 2022-07-17T21:24:50.000-07:00
diff --git a/Grammar/python.gram b/Grammar/python.gram
@@ -660,7 +660,9 @@ star_named_expression[expr_ty]:
     | named_expression
 
 assignment_expression[expr_ty]:
-    | a=NAME ':=' ~ b=expression { _PyAST_NamedExpr(CHECK(expr_ty, _PyPegen_set_expr_context(p, a, Store)), b, EXTRA) }
+    | a=NAME ':=' ~ b=expression {
+        CHECK_VERSION(expr_ty, 8, "Assignment expressions are",
+        _PyAST_NamedExpr(CHECK(expr_ty, _PyPegen_set_expr_context(p, a, Store)), b, EXTRA)) }
 
 named_expression[expr_ty]:
     | assignment_expression
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
@@ -743,6 +743,11 @@ def test_issue40614_feature_version(self):
         with self.assertRaises(SyntaxError):
             ast.parse('f"{x=}"', feature_version=(3, 7))
 
+    def test_assignment_expression_feature_version(self):
+        ast.parse('(x := 0)', feature_version=(3, 8))
+        with self.assertRaises(SyntaxError):
+            ast.parse('(x := 0)', feature_version=(3, 7))
+
     def test_constant_as_name(self):
         for constant in "True", "False", "None":
             expr = ast.Expression(ast.Name(constant, ast.Load()))
