gh-135422: Fix regression in SyntaxError messages after #134036 (#135423)

Grammar/python.gram

@@ -184,8 +184,9 @@ return_stmt[stmt_ty]:
     | 'return' a=[star_expressions] { _PyAST_Return(a, EXTRA) }
 
 raise_stmt[stmt_ty]:
+    | 'raise' a=expression 'from' b=expression { _PyAST_Raise(a, b, EXTRA) }
     | invalid_raise_stmt
-    | 'raise' a=expression b=['from' z=expression { z }] { _PyAST_Raise(a, b, EXTRA) }
+    | 'raise' a=expression { _PyAST_Raise(a, NULL, EXTRA) }
     | 'raise' { _PyAST_Raise(NULL, NULL, EXTRA) }
 
 pass_stmt[stmt_ty]:

Lib/test/test_syntax.py

@@ -2872,6 +2872,13 @@ class SyntaxErrorTestCase(unittest.TestCase):
             """
         self._check_error(source, "parameter and nonlocal", lineno=3)
 
+    def test_raise_from_error_message(self):
+        source = """if 1:
+        raise AssertionError() from None
+        print(1,,2)
+        """
+        self._check_error(source, "invalid syntax", lineno=3)
+
     def test_yield_outside_function(self):
         self._check_error("if 0: yield",                "outside function")
         self._check_error("if 0: yield\nelse:  x=1",    "outside function")

Misc/NEWS.d/next/Core_and_Builtins/2025-06-12-11-19-52.gh-issue-135422.F6yQi6.rst

@@ -0,0 +1 @@
+Fix regression in :exc:`SyntaxError` messages after :gh:`134036`.