gh-136616: Improve assert syntax error messages

Author: sobolevn

Grammar/python.gram

@@ -210,7 +210,7 @@ del_stmt[stmt_ty]:
 
 yield_stmt[stmt_ty]: y=yield_expr { _PyAST_Expr(y, EXTRA) }
 
-assert_stmt[stmt_ty]: 'assert' a=expression b=[',' z=expression { z }] { _PyAST_Assert(a, b, EXTRA) }
+assert_stmt[stmt_ty]: 'assert' a=named_expression b=[',' z=named_expression { z }] { _PyAST_Assert(a, b, EXTRA) }
 
 import_stmt[stmt_ty]:
     | invalid_import

Lib/test/test_syntax.py

@@ -2686,6 +2686,57 @@ def f(x: *b)
     >>> f(x = 5, *:)
     Traceback (most recent call last):
     SyntaxError: Invalid star expression
+
+Asserts:
+
+    >>> assert 1 = 2
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?
+
+    >>> assert (1 = 2)
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?
+
+    >>> assert 'a' = a
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?
+
+    >>> assert x[0] = 1
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to subscript here. Maybe you meant '==' instead of '='?
+
+    >>> assert (yield a) = 2
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to yield expression here. Maybe you meant '==' instead of '='?
+
+    >>> assert a = 2
+    Traceback (most recent call last):
+    SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?
+
+    >>> assert (a = 2)
+    Traceback (most recent call last):
+    SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?
+
+    >>> assert a = b
+    Traceback (most recent call last):
+    SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?
+
+    >>> assert 1, 1 = b
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?
+
+    >>> assert 1, (1 = b)
+    Traceback (most recent call last):
+    SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?
+
+    >>> assert 1, a = 1
+    Traceback (most recent call last):
+    SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?
+
+    >>> assert 1, (a = 1)
+    Traceback (most recent call last):
+    SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?
+
 """
 
 import re

Misc/NEWS.d/next/Core_and_Builtins/2025-07-14-17-01-23.gh-issue-136616.FQjXE_.rst

@@ -0,0 +1,2 @@
+Improve :exc:`SyntaxError` error messages for invalid :keyword:`assert`
+usages.