bpo-34880: Add the LOAD_ASSERTION_ERROR opcode. (GH-15073)

Fix assert statement misbehavior if AssertionError is shadowed.

4 files changed, 20 insertions, 3 deletions

diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index 67bd1d3..671b043 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -271,6 +271,7 @@ _code_type = type(_write_atomic.__code__)
 #     Python 3.8b2  3412 (Swap the position of positional args and positional
 #                         only args in ast.arguments #37593)
 #     Python 3.8b4  3413 (Fix "break" and "continue" in "finally" #37830)
+#     Python 3.9a0  3420 (add LOAD_ASSERTION_ERROR #34880)
 #
 # MAGIC must change whenever the bytecode emitted by the compiler may no
 # longer be understood by older implementations of the eval loop (usually
@@ -279,7 +280,7 @@ _code_type = type(_write_atomic.__code__)
 # Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
 # in PC/launcher.c must also be updated.
 
-MAGIC_NUMBER = (3413).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3420).to_bytes(2, 'little') + b'\r\n'
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 
 _PYCACHE = '__pycache__'
diff --git a/Lib/opcode.py b/Lib/opcode.py
index 3fb716b..0ae0068 100644
--- a/Lib/opcode.py
+++ b/Lib/opcode.py
@@ -109,7 +109,7 @@ def_op('PRINT_EXPR', 70)
 def_op('LOAD_BUILD_CLASS', 71)
 def_op('YIELD_FROM', 72)
 def_op('GET_AWAITABLE', 73)
-
+def_op('LOAD_ASSERTION_ERROR', 74)
 def_op('INPLACE_LSHIFT', 75)
 def_op('INPLACE_RSHIFT', 76)
 def_op('INPLACE_AND', 77)
diff --git a/Lib/test/test_dis.py b/Lib/test/test_dis.py
index 03b2860..11f97e6 100644
--- a/Lib/test/test_dis.py
+++ b/Lib/test/test_dis.py
@@ -147,7 +147,7 @@ def bug1333982(x=[]):
 dis_bug1333982 = """\
 %3d           0 LOAD_CONST               1 (0)
               2 POP_JUMP_IF_TRUE        26
-              4 LOAD_GLOBAL              0 (AssertionError)
+              4 LOAD_ASSERTION_ERROR
               6 LOAD_CONST               2 (<code object <listcomp> at 0x..., file "%s", line %d>)
               8 LOAD_CONST               3 ('bug1333982.<locals>.<listcomp>')
              10 MAKE_FUNCTION            0
diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 10c1e07..4d1aa4b 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -1285,6 +1285,22 @@ class ExceptionTests(unittest.TestCase):
                 next(i)
                 next(i)
 
+    @unittest.skipUnless(__debug__, "Won't work if __debug__ is False")
+    def test_assert_shadowing(self):
+        # Shadowing AssertionError would cause the assert statement to
+        # misbehave.
+        global AssertionError
+        AssertionError = TypeError
+        try:
+            assert False, 'hello'
+        except BaseException as e:
+            del AssertionError
+            self.assertIsInstance(e, AssertionError)
+            self.assertEqual(str(e), 'hello')
+        else:
+            del AssertionError
+            self.fail('Expected exception')
+
 
 class ImportErrorTests(unittest.TestCase):