bpo-40334: Correctly identify invalid target in assignment errors (GH-20076)

Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>

5 files changed, 31 insertions, 23 deletions

diff --git a/Lib/test/test_dictcomps.py b/Lib/test/test_dictcomps.py
index 16aa651b93..472e3dfa0d 100644
--- a/Lib/test/test_dictcomps.py
+++ b/Lib/test/test_dictcomps.py
@@ -77,7 +77,7 @@ class DictComprehensionTest(unittest.TestCase):
             compile("{x: y for y, x in ((1, 2), (3, 4))} = 5", "<test>",
                     "exec")
 
-        with self.assertRaisesRegex(SyntaxError, "cannot assign"):
+        with self.assertRaisesRegex(SyntaxError, "illegal expression"):
             compile("{x: y for y, x in ((1, 2), (3, 4))} += 5", "<test>",
                     "exec")
 
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 1081107ee6..348ae15aa6 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -1921,7 +1921,7 @@ SyntaxError: cannot assign to yield expression
 >>> def f(): (yield bar) += y
 Traceback (most recent call last):
   ...
-SyntaxError: cannot assign to yield expression
+SyntaxError: 'yield expression' is an illegal expression for augmented assignment
 
 
 Now check some throw() conditions:
diff --git a/Lib/test/test_genexps.py b/Lib/test/test_genexps.py
index 86e4e195f5..5c1a209b0e 100644
--- a/Lib/test/test_genexps.py
+++ b/Lib/test/test_genexps.py
@@ -158,7 +158,7 @@ Verify that syntax error's are raised for genexps used as lvalues
     >>> (y for y in (1,2)) += 10
     Traceback (most recent call last):
        ...
-    SyntaxError: cannot assign to generator expression
+    SyntaxError: 'generator expression' is an illegal expression for augmented assignment
 
 
 ########### Tests borrowed from or inspired by test_generators.py ############
diff --git a/Lib/test/test_peg_parser.py b/Lib/test/test_peg_parser.py
index 71e071940d..9614e45799 100644
--- a/Lib/test/test_peg_parser.py
+++ b/Lib/test/test_peg_parser.py
@@ -625,7 +625,7 @@ FAIL_SPECIALIZED_MESSAGE_CASES = [
     ("(a, b): int", "only single target (not tuple) can be annotated"),
     ("[a, b]: int", "only single target (not list) can be annotated"),
     ("a(): int", "illegal target for annotation"),
-    ("1 += 1", "cannot assign to literal"),
+    ("1 += 1", "'literal' is an illegal expression for augmented assignment"),
     ("pass\n    pass", "unexpected indent"),
     ("def f():\npass", "expected an indented block"),
     ("def f(*): pass", "named arguments must follow bare *"),
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index a3a1015346..60c7d9fd38 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -100,30 +100,37 @@ expression inside that contain should still cause a syntax error.
 This test just checks a couple of cases rather than enumerating all of
 them.
 
-# All of the following also produce different error messages with pegen
-# >>> (a, "b", c) = (1, 2, 3)
-# Traceback (most recent call last):
-# SyntaxError: cannot assign to literal
+>>> (a, "b", c) = (1, 2, 3)
+Traceback (most recent call last):
+SyntaxError: cannot assign to literal
 
-# >>> (a, True, c) = (1, 2, 3)
-# Traceback (most recent call last):
-# SyntaxError: cannot assign to True
+>>> (a, True, c) = (1, 2, 3)
+Traceback (most recent call last):
+SyntaxError: cannot assign to True
 
 >>> (a, __debug__, c) = (1, 2, 3)
 Traceback (most recent call last):
 SyntaxError: cannot assign to __debug__
 
-# >>> (a, *True, c) = (1, 2, 3)
-# Traceback (most recent call last):
-# SyntaxError: cannot assign to True
+>>> (a, *True, c) = (1, 2, 3)
+Traceback (most recent call last):
+SyntaxError: cannot assign to True
 
 >>> (a, *__debug__, c) = (1, 2, 3)
 Traceback (most recent call last):
 SyntaxError: cannot assign to __debug__
 
-# >>> [a, b, c + 1] = [1, 2, 3]
-# Traceback (most recent call last):
-# SyntaxError: cannot assign to operator
+>>> [a, b, c + 1] = [1, 2, 3]
+Traceback (most recent call last):
+SyntaxError: cannot assign to operator
+
+>>> [a, b[1], c + 1] = [1, 2, 3]
+Traceback (most recent call last):
+SyntaxError: cannot assign to operator
+
+>>> [a, b.c.d, c + 1] = [1, 2, 3]
+Traceback (most recent call last):
+SyntaxError: cannot assign to operator
 
 >>> a if 1 else b = 1
 Traceback (most recent call last):
@@ -131,15 +138,15 @@ SyntaxError: cannot assign to conditional expression
 
 >>> a, b += 1, 2
 Traceback (most recent call last):
-SyntaxError: invalid syntax
+SyntaxError: 'tuple' is an illegal expression for augmented assignment
 
 >>> (a, b) += 1, 2
 Traceback (most recent call last):
-SyntaxError: cannot assign to tuple
+SyntaxError: 'tuple' is an illegal expression for augmented assignment
 
 >>> [a, b] += 1, 2
 Traceback (most recent call last):
-SyntaxError: cannot assign to list
+SyntaxError: 'list' is an illegal expression for augmented assignment
 
 From compiler_complex_args():
 
@@ -346,16 +353,16 @@ More set_context():
 
 >>> (x for x in x) += 1
 Traceback (most recent call last):
-SyntaxError: cannot assign to generator expression
+SyntaxError: 'generator expression' is an illegal expression for augmented assignment
 >>> None += 1
 Traceback (most recent call last):
-SyntaxError: cannot assign to None
+SyntaxError: 'None' is an illegal expression for augmented assignment
 >>> __debug__ += 1
 Traceback (most recent call last):
 SyntaxError: cannot assign to __debug__
 >>> f() += 1
 Traceback (most recent call last):
-SyntaxError: cannot assign to function call
+SyntaxError: 'function call' is an illegal expression for augmented assignment
 
 
 Test continue in finally in weird combinations.
@@ -688,6 +695,7 @@ class SyntaxTestCase(unittest.TestCase):
     def test_assign_call(self):
         self._check_error("f() = 1", "assign")
 
+    @unittest.skipIf(support.use_old_parser(), "The old parser cannot generate these error messages")
     def test_assign_del(self):
         self._check_error("del (,)", "invalid syntax")
         self._check_error("del 1", "delete literal")