bpo-40334: Spacialized error message for invalid args after bare '*' (GH-19865)

When parsing things like `def f(*): pass` the old parser used to output `SyntaxError: named arguments must follow bare *`, which the new parser wasn't able to do.

3 files changed, 10 insertions, 4 deletions

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 354b3f4..d83b73a 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -242,11 +242,11 @@ class ExceptionTests(unittest.TestCase):
         check('from __future__ import doesnt_exist', 1, 1)
         check('from __future__ import braces', 1, 1)
         check('x=1\nfrom __future__ import division', 2, 1)
+        check('def f(*):\n  pass', 1, 7 if support.use_old_parser() else 8)
 
     @support.skip_if_new_parser("Pegen column offsets might be different")
     def testSyntaxErrorOffsetCustom(self):
         self.check('for 1 in []: pass', 1, 5)
-        self.check('def f(*):\n  pass', 1, 7)
         self.check('[*x for x in xs]', 1, 2)
         self.check('def f():\n  x, y: int', 2, 3)
         self.check('(yield i) = 2', 1, 1)
diff --git a/Lib/test/test_peg_parser.py b/Lib/test/test_peg_parser.py
index 1914944..d6939fd 100644
--- a/Lib/test/test_peg_parser.py
+++ b/Lib/test/test_peg_parser.py
@@ -603,6 +603,12 @@ FAIL_SPECIALIZED_MESSAGE_CASES = [
     ("1 += 1", "cannot assign to literal"),
     ("pass\n    pass", "unexpected indent"),
     ("def f():\npass", "expected an indented block"),
+    ("def f(*): pass", "named arguments must follow bare *"),
+    ("def f(*,): pass", "named arguments must follow bare *"),
+    ("def f(*, **a): pass", "named arguments must follow bare *"),
+    ("lambda *: pass", "named arguments must follow bare *"),
+    ("lambda *,: pass", "named arguments must follow bare *"),
+    ("lambda *, **a: pass", "named arguments must follow bare *"),
 ]
 
 GOOD_BUT_FAIL_TEST_CASES = [
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index e7468ca..0c0fc48 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -627,9 +627,9 @@ Corner-cases that used to fail to raise the correct error:
     Traceback (most recent call last):
     SyntaxError: cannot assign to __debug__
 
-    # >>> with (lambda *:0): pass
-    # Traceback (most recent call last):
-    # SyntaxError: named arguments must follow bare *
+    >>> with (lambda *:0): pass
+    Traceback (most recent call last):
+    SyntaxError: named arguments must follow bare *
 
 Corner-cases that used to crash: