bpo-40618: Disallow invalid targets in augassign and except clauses (GH-20083)

This commit fixes the new parser to disallow invalid targets in the
following scenarios:
- Augmented assignments must only accept a single target (Name,
  Attribute or Subscript), but no tuples or lists.
- `except` clauses should only accept a single `Name` as a target.

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index 02ba8a8..e1a402e 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -1279,7 +1279,7 @@ class GrammarTests(unittest.TestCase):
     def test_try(self):
         ### try_stmt: 'try' ':' suite (except_clause ':' suite)+ ['else' ':' suite]
         ###         | 'try' ':' suite 'finally' ':' suite
-        ### except_clause: 'except' [expr ['as' expr]]
+        ### except_clause: 'except' [expr ['as' NAME]]
         try:
             1/0
         except ZeroDivisionError:
@@ -1297,6 +1297,9 @@ class GrammarTests(unittest.TestCase):
         except (EOFError, TypeError, ZeroDivisionError) as msg: pass
         try: pass
         finally: pass
+        with self.assertRaises(SyntaxError):
+            compile("try:\n    pass\nexcept Exception as a.b:\n    pass", "?", "exec")
+            compile("try:\n    pass\nexcept Exception as a[b]:\n    pass", "?", "exec")
 
     def test_suite(self):
         # simple_stmt | NEWLINE INDENT NEWLINE* (stmt NEWLINE*)+ DEDENT