pythongh-109114: Relax the check for invalid lambdas inside f-strings…

… to avoid false positives

Signed-off-by: Pablo Galindo <pablogsal@gmail.com>

Grammar/python.gram

@@ -1170,7 +1170,7 @@ invalid_expression:
         _PyPegen_check_legacy_stmt(p, a) ? NULL : p->tokens[p->mark-1]->level == 0 ? NULL :
         RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax. Perhaps you forgot a comma?") }
    | a=disjunction 'if' b=disjunction !('else'|':') { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "expected 'else' after 'if' expression") }
-   | a='lambda' [lambda_params] b=':' &(FSTRING_MIDDLE | fstring_replacement_field)  {
+   | a='lambda' [lambda_params] b=':' &FSTRING_MIDDLE  {
         RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "f-string: lambda expressions are not allowed without parentheses") }
 
 invalid_named_expression(memo):

Lib/test/test_fstring.py

@@ -1027,6 +1027,10 @@ def test_lambda(self):
                              "f'{lambda x:}'",
                              "f'{lambda :}'",
                              ])
+        # Ensure the detection of invalid lambdas doesn't trigger detection
+        # for valid lambdas in the second error pass
+        with self.assertRaisesRegex(SyntaxError, "invalid syntax"):
+            compile("lambda name_3=f'{name_4}': {name_3}\n1 $ 1", "<string>", "exec")
 
         # but don't emit the paren warning in general cases
         with self.assertRaisesRegex(SyntaxError, "f-string: expecting a valid expression after '{'"):

Lib/test/test_tix.py

@@ -0,0 +1,40 @@
+import sys
+import unittest
+from test import support
+from test.support import import_helper
+from test.support import check_sanitizer
+
+if check_sanitizer(address=True, memory=True):
+    raise unittest.SkipTest("Tests involving libX11 can SEGFAULT on ASAN/MSAN builds")
+
+
+# Skip this test if the _tkinter module wasn't built.
+_tkinter = import_helper.import_module('_tkinter')
+
+# Skip test if tk cannot be initialized.
+support.requires('gui')
+
+# Suppress the deprecation warning
+tix = import_helper.import_module('tkinter.tix', deprecated=True)
+from tkinter import TclError
+
+
+class TestTix(unittest.TestCase):
+
+    def setUp(self):
+        try:
+            self.root = tix.Tk()
+        except TclError:
+            if sys.platform.startswith('win'):
+                self.fail('Tix should always be available on Windows')
+            self.skipTest('Tix not available')
+        else:
+            self.addCleanup(self.root.destroy)
+
+    def test_tix_available(self):
+        # this test is just here to make setUp run
+        pass
+
+
+if __name__ == '__main__':
+    unittest.main()