[3.10] pythongh-94996: Disallow lambda pos only params with feature_version < (3, 8) (pythonGH-95934).

(cherry picked from commit a965db3)

Co-authored-by: Shantanu <[email protected]>

Author: hauntsaninja

Grammar/python.gram

@@ -552,9 +552,9 @@ lambda_params[arguments_ty]:
 #
 lambda_parameters[arguments_ty]:
     | a=lambda_slash_no_default b[asdl_arg_seq*]=lambda_param_no_default* c=lambda_param_with_default* d=[lambda_star_etc] {
-        _PyPegen_make_arguments(p, a, NULL, b, c, d) }
+        CHECK_VERSION(arguments_ty, 8, "Positional-only parameters are", _PyPegen_make_arguments(p, a, NULL, b, c, d)) }
     | a=lambda_slash_with_default b=lambda_param_with_default* c=[lambda_star_etc] {
-        _PyPegen_make_arguments(p, NULL, a, NULL, b, c) }
+        CHECK_VERSION(arguments_ty, 8, "Positional-only parameters are", _PyPegen_make_arguments(p, NULL, a, NULL, b, c)) }
     | a[asdl_arg_seq*]=lambda_param_no_default+ b=lambda_param_with_default* c=[lambda_star_etc] {
         _PyPegen_make_arguments(p, NULL, NULL, a, b, c) }
     | a=lambda_param_with_default+ b=[lambda_star_etc] { _PyPegen_make_arguments(p, NULL, NULL, NULL, a, b)}

Lib/test/test_ast.py

@@ -686,6 +686,21 @@ def test_ast_asdl_signature(self):
         expressions[0] = f"expr = {ast.expr.__subclasses__()[0].__doc__}"
         self.assertCountEqual(ast.expr.__doc__.split("\n"), expressions)
 
+    def test_positional_only_feature_version(self):
+        ast.parse('def foo(x, /): ...', feature_version=(3, 8))
+        ast.parse('def bar(x=1, /): ...', feature_version=(3, 8))
+        with self.assertRaises(SyntaxError):
+            ast.parse('def foo(x, /): ...', feature_version=(3, 7))
+        with self.assertRaises(SyntaxError):
+            ast.parse('def bar(x=1, /): ...', feature_version=(3, 7))
+
+        ast.parse('lambda x, /: ...', feature_version=(3, 8))
+        ast.parse('lambda x=1, /: ...', feature_version=(3, 8))
+        with self.assertRaises(SyntaxError):
+            ast.parse('lambda x, /: ...', feature_version=(3, 7))
+        with self.assertRaises(SyntaxError):
+            ast.parse('lambda x=1, /: ...', feature_version=(3, 7))
+
     def test_parenthesized_with_feature_version(self):
         ast.parse('with (CtxManager() as example): ...', feature_version=(3, 10))
         # While advertised as a feature in Python 3.10, this was allowed starting 3.9

Parser/parser.c

@@ -11194,7 +11194,7 @@ lambda_parameters_rule(Parser *p)
         )
         {
             D(fprintf(stderr, "%*c+ lambda_parameters[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "lambda_slash_no_default lambda_param_no_default* lambda_param_with_default* lambda_star_etc?"));
-            _res = _PyPegen_make_arguments ( p , a , NULL , b , c , d );
+            _res = CHECK_VERSION ( arguments_ty , 8 , "Positional-only parameters are" , _PyPegen_make_arguments ( p , a , NULL , b , c , d ) );
             if (_res == NULL && PyErr_Occurred()) {
                 p->error_indicator = 1;
                 p->level--;
@@ -11224,7 +11224,7 @@ lambda_parameters_rule(Parser *p)
         )
         {
             D(fprintf(stderr, "%*c+ lambda_parameters[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "lambda_slash_with_default lambda_param_with_default* lambda_star_etc?"));
-            _res = _PyPegen_make_arguments ( p , NULL , a , NULL , b , c );
+            _res = CHECK_VERSION ( arguments_ty , 8 , "Positional-only parameters are" , _PyPegen_make_arguments ( p , NULL , a , NULL , b , c ) );
             if (_res == NULL && PyErr_Occurred()) {
                 p->error_indicator = 1;
                 p->level--;