gh-150700: Fix class-scope inline comprehensions when nested scopes reference `__class__` and friends by johnslavik · Pull Request #150735 · python/cpython

johnslavik · 2026-06-01T20:55:29Z

Follow up to GH-120295.

In inline_comprehension(), when __class__ / __classdict__ / __conditional_annotations__ appears as FREE in a comprehension's symbol table because a nested scope captured it (e.g. nested lambdas), this name is still discarded from comp_free unconditionally. This prevents drop_class_free() from seeing it, so the appropriate ste_needs_(...) flag is never set on the enclosing class. That leads to codegen_make_closure() throwing SystemError when it couldn't find __class__ / __classdict__ /
__conditional_annotations__ in the class's cellvars.

From now on we just discard from comp_free when no child scope (e.g. a lambda) still needs the name as FREE. When a child scope does need it, keep it in comp_free so drop_class_free() can set the appropriate flag and the class creates the implicit cell.

Issue: Class-scope comprehension with lambda raises SystemError #150700

…_class__` and friends In `inline_comprehension()`, when `__class__` / `__classdict__` / `__conditional_annotations__` appears as `FREE` in a comprehension's symbol table because a nested scope captured it (e.g. nested lambdas), this name is still discarded from `comp_free` unconditionally. This prevents `drop_class_free()` from seeing it, so the appropriate `ste_needs_(...)` flag is never set on the enclosing class. That leads to `codegen_make_closure()` throwing `SystemError` when it couldn't find `__class__` / `__classdict__` / `__conditional_annotations__` in the class's cellvars. From now on we just discard from `comp_free` when no child scope (e.g. a lambda) still needs the name as `FREE`. When a child scope does need it, keep it in `comp_free` so `drop_class_free()` can set the appropriate flag and the class creates the implicit cell.

…th-lambda-raises-syste

johnslavik · 2026-06-01T20:59:34Z

Updating branch to see if it fixes doc build issue.

carljm

This looks good to me. Might be nice to have some tests that validate more than "compilation doesn't fail" but actually check we are getting the right value out of __class__.

johnslavik · 2026-06-09T21:35:00Z

Might be nice to have some tests that validate more than "compilation doesn't fail" but actually check we are getting the right value out of __class__.

Excellent, added.

carljm · 2026-06-09T22:21:55Z

Thanks for the fix!

miss-islington-app · 2026-06-09T22:22:17Z

Thanks @johnslavik for the PR, and @carljm for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14, 3.15.
🐍🍒⛏🤖

bedevere-app · 2026-06-09T22:22:32Z

GH-151211 is a backport of this pull request to the 3.15 branch.

bedevere-app · 2026-06-09T22:22:38Z

GH-151212 is a backport of this pull request to the 3.14 branch.

…copes reference `__class__` and friends (GH-150735) (#151212) gh-150700: Fix class-scope inline comprehensions when nested scopes reference `__class__` and friends (GH-150735) * Fix class-scope inline comprehensions when nested scopes reference `__class__` and friends In `inline_comprehension()`, when `__class__` / `__classdict__` / `__conditional_annotations__` appears as `FREE` in a comprehension's symbol table because a nested scope captured it (e.g. nested lambdas), this name is still discarded from `comp_free` unconditionally. This prevents `drop_class_free()` from seeing it, so the appropriate `ste_needs_(...)` flag is never set on the enclosing class. That leads to `codegen_make_closure()` throwing `SystemError` when it couldn't find `__class__` / `__classdict__` / `__conditional_annotations__` in the class's cellvars. From now on we just discard from `comp_free` when no child scope (e.g. a lambda) still needs the name as `FREE`. When a child scope does need it, keep it in `comp_free` so `drop_class_free()` can set the appropriate flag and the class creates the implicit cell. * Fix tests * Fix typo * Fix formatting * Add test checking validity of `__class__` returned * Prefer 'used' to 'deferred' (cherry picked from commit ce916dc) Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>

bedevere-bot · 2026-06-09T23:06:57Z

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot aarch64 Android 3.14 (tier-3) has failed when building commit 51e83ca.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1794/builds/1170) and take a look at the build logs.
Check if the failure is related to this commit (51e83ca) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1794/builds/1170

Failed tests:

test_urllib2
test_urllibnet

Failed subtests:

test_ftp_error - test.test_urllib2.HandlerTests.test_ftp_error
test_getcode - test.test_urllibnet.urlopenNetworkTests.test_getcode

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 1529, in ftp_open
    host = socket.gethostbyname(host)
socket.gaierror: [Errno 7] No address associated with hostname
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/test/test_urllib2.py", line 798, in test_ftp_error
    urlopen("ftp://www.pythontest.net/")
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 487, in open
    response = self._open(req, data)
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 504, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
                              '_open', req)
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 464, in _call_chain
    result = func(*args)
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 1531, in ftp_open
    raise URLError(msg)
urllib.error.URLError: <urlopen error [Errno 7] No address associated with hostname>
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/test/test_urllib2.py", line 800, in test_ftp_error
    self.assertEqual(raised.reason,
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
                     f"ftp error: {exception.args[0]}")
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: gaierror(7, 'No address associated with hostname') != 'ftp error: 500 OOPS: cannot change directory:/nonexistent'
 
----------------------------------------------------------------------
Ran 80 tests in 0.085s
 
FAILED (failures=1, skipped=3)


Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 1529, in ftp_open
    host = socket.gethostbyname(host)
socket.gaierror: [Errno 7] No address associated with hostname
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/test/test_urllib2.py", line 798, in test_ftp_error
    urlopen("ftp://www.pythontest.net/")
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 487, in open
    response = self._open(req, data)
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 504, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
                              '_open', req)
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 464, in _call_chain
    result = func(*args)
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/urllib/request.py", line 1531, in ftp_open
    raise URLError(msg)
urllib.error.URLError: <urlopen error [Errno 7] No address associated with hostname>
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/test/test_urllib2.py", line 800, in test_ftp_error
    self.assertEqual(raised.reason,
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
                     f"ftp error: {exception.args[0]}")
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: gaierror(7, 'No address associated with hostname') != 'ftp error: 500 OOPS: cannot change directory:/nonexistent'
 
----------------------------------------------------------------------
Ran 80 tests in 0.047s
 
FAILED (failures=1, skipped=3)


Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/test/test_urllibnet.py", line 107, in test_getcode
    self.assertEqual(e.exception.code, 404)
                     ^^^^^^^^^^^^^^^^
AttributeError: 'URLError' object has no attribute 'code'
 
----------------------------------------------------------------------
Ran 12 tests in 0.026s
 
FAILED (errors=1, skipped=10)


Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.14/test/test_urllibnet.py", line 107, in test_getcode
    self.assertEqual(e.exception.code, 404)
                     ^^^^^^^^^^^^^^^^
AttributeError: 'URLError' object has no attribute 'code'
 
----------------------------------------------------------------------
Ran 12 tests in 0.018s
 
FAILED (errors=1, skipped=10)

…copes reference `__class__` and friends (GH-150735) (#151211) gh-150700: Fix class-scope inline comprehensions when nested scopes reference `__class__` and friends (GH-150735) * Fix class-scope inline comprehensions when nested scopes reference `__class__` and friends In `inline_comprehension()`, when `__class__` / `__classdict__` / `__conditional_annotations__` appears as `FREE` in a comprehension's symbol table because a nested scope captured it (e.g. nested lambdas), this name is still discarded from `comp_free` unconditionally. This prevents `drop_class_free()` from seeing it, so the appropriate `ste_needs_(...)` flag is never set on the enclosing class. That leads to `codegen_make_closure()` throwing `SystemError` when it couldn't find `__class__` / `__classdict__` / `__conditional_annotations__` in the class's cellvars. From now on we just discard from `comp_free` when no child scope (e.g. a lambda) still needs the name as `FREE`. When a child scope does need it, keep it in `comp_free` so `drop_class_free()` can set the appropriate flag and the class creates the implicit cell. * Fix tests * Fix typo * Fix formatting * Add test checking validity of `__class__` returned * Prefer 'used' to 'deferred' (cherry picked from commit ce916dc) Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>

johnslavik requested review from JelleZijlstra and carljm as code owners June 1, 2026 20:55

johnslavik added needs backport to 3.14 bugs and security fixes needs backport to 3.15 pre-release feature fixes, bugs and security fixes labels Jun 1, 2026

bedevere-app Bot mentioned this pull request Jun 1, 2026

Class-scope comprehension with lambda raises SystemError #150700

Open

bedevere-app Bot added the awaiting review label Jun 1, 2026

Merge branch 'main' into pythongh-150700-class-scope-comprehension-wi…

6e4dec5

…th-lambda-raises-syste

johnslavik commented Jun 1, 2026

View reviewed changes

Comment thread Lib/test/test_listcomps.py Outdated

johnslavik added 3 commits June 1, 2026 23:12

Fix tests

903f916

Fix typo

e2547b8

Fix formatting

633c54c

ZeroIntensity reviewed Jun 2, 2026

View reviewed changes

Comment thread Misc/NEWS.d/next/Core_and_Builtins/2026-06-01-19-00-00.gh-issue-150700.W8CzVR.rst

carljm approved these changes Jun 3, 2026

View reviewed changes

bedevere-app Bot added awaiting merge and removed awaiting review labels Jun 3, 2026

Add test checking validity of __class__ returned

beac186

Prefer 'used' to 'deferred'

68ee580

carljm approved these changes Jun 9, 2026

View reviewed changes

carljm merged commit ce916dc into python:main Jun 9, 2026
54 checks passed

bedevere-app Bot removed the awaiting merge label Jun 9, 2026

bedevere-app Bot removed the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label Jun 9, 2026

bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Jun 9, 2026

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

gh-150700: Fix class-scope inline comprehensions when nested scopes reference `class` and friends#150735

gh-150700: Fix class-scope inline comprehensions when nested scopes reference `class` and friends#150735
carljm merged 7 commits into
python:mainfrom
johnslavik:gh-150700-class-scope-comprehension-with-lambda-raises-syste

johnslavik commented Jun 1, 2026 •

edited

Loading

Uh oh!

johnslavik commented Jun 1, 2026

Uh oh!

Uh oh!

Uh oh!

carljm left a comment

Uh oh!

johnslavik commented Jun 9, 2026

Uh oh!

carljm commented Jun 9, 2026

Uh oh!

Uh oh!

miss-islington-app Bot commented Jun 9, 2026

Uh oh!

bedevere-app Bot commented Jun 9, 2026

Uh oh!

bedevere-app Bot commented Jun 9, 2026

Uh oh!

bedevere-bot commented Jun 9, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

Uh oh!

Conversation

johnslavik commented Jun 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

johnslavik commented Jun 1, 2026

Uh oh!

Uh oh!

Uh oh!

carljm left a comment

Choose a reason for hiding this comment

Uh oh!

johnslavik commented Jun 9, 2026

Uh oh!

carljm commented Jun 9, 2026

Uh oh!

Uh oh!

miss-islington-app Bot commented Jun 9, 2026

Uh oh!

bedevere-app Bot commented Jun 9, 2026

Uh oh!

bedevere-app Bot commented Jun 9, 2026

Uh oh!

bedevere-bot commented Jun 9, 2026

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

johnslavik commented Jun 1, 2026 •

edited

Loading