[asukaminato0721]

Summary

A trailing expression in a for body can hide an uninitialized local when the iterable is empty. For example, for x in xs: y = x; time.sleep(1) can leave y undefined, but the expression incorrectly supplies termination evidence for the zero-iteration path.

Only count termination keys from branches that lack the variable. This also reports skipped elif walrus assignments and preserves the definite-uninitialized status of deleted exception targets.

This changes the default-enabled unbound-name diagnostic. It is independent of the attribute initialization check in #4326.

• I am a human, and I fully understand the code I am submitting.

Test Plan

• 479 tests passed across scope, loops, branching, and returns.
• Formatting and lint checks passed. Clippy reports existing warnings in unchanged code.

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D126824523. (Because this pull request was imported automatically, there will not be any future comments.)

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

============================================================
SUMMARY
============================================================
Total: +53 new errors, -2 fixed errors
By preset: +53/-0 (default), +53/-0 (strict)

Projects with changes (24):
  psycopg: +6 -0
  apprise: +1 -0
  pycryptodome: +1 -0
  black: +1 -0
  openlibrary: +2 -1
  isort: +1 -0
  jax: +1 -0
  scikit-learn: +3 -0
  prefect: +1 -0
  scikit-build-core: +1 -0
  freqtrade: +2 -0
  manticore: +3 -0
  cloud-init: +4 -0
  zulip: +6 -0
  static-frame: +1 -0
  mypy: +1 -0
  pandas: +5 -0
  meson: +1 -0
  pytensor: +1 -0
  sphinx: +2 -0
  core: +6 -1
  spack: +1 -0
  xarray: +1 -0
  optuna: +1 -0
============================================================

FULL DIFF DETAILS
------------------------------------------------------------

psycopg (https://github.com/psycopg/psycopg)
+ ERROR tests/test_connection.py:804:40-45: `value` may be uninitialized [unbound-name]
+ ERROR tests/test_connection.py:819:40-45: `value` may be uninitialized [unbound-name]
+ ERROR tests/test_connection_async.py:819:40-45: `value` may be uninitialized [unbound-name]
+ ERROR tests/test_connection_async.py:836:40-45: `value` may be uninitialized [unbound-name]
+ ERROR tests/test_transaction.py:613:16-19: `tx3` may be uninitialized [unbound-name]
+ ERROR tests/test_transaction_async.py:620:16-19: `tx3` may be uninitialized [unbound-name]

apprise (https://github.com/caronc/apprise)
+ ERROR apprise/plugins/pushsafer.py:711:59-67: `filename` may be uninitialized [unbound-name]

pycryptodome (https://github.com/Legrandin/pycryptodome)
+ ERROR lib/Crypto/IO/_PBES.py:693:46-66: `hmac_hash_module_oid` may be uninitialized [unbound-name]

black (https://github.com/psf/black)
+ ERROR src/blib2to3/pgen2/driver.py:75:20-25: `token` may be uninitialized [unbound-name]

openlibrary (https://github.com/internetarchive/openlibrary)
- ERROR openlibrary/core/lending.py:205:16-57: The type of `data` is unknown because it comes from an error [unknown-from-error]
+ ERROR openlibrary/core/lending.py:205:16-24: `response` may be uninitialized [unbound-name]
+ ERROR openlibrary/coverstore/archive.py:408:32-36: `item` may be uninitialized [unbound-name]

isort (https://github.com/pycqa/isort)
+ ERROR isort/api.py:202:33-45: `file_content` may be uninitialized [unbound-name]

jax (https://github.com/google/jax)
+ ERROR jax/_src/lax/control_flow/conditionals.py:755:42-50: `inst_out` may be uninitialized [unbound-name]

scikit-learn (https://github.com/scikit-learn/scikit-learn)
+ ERROR sklearn/gaussian_process/kernels.py:1899:77-81: `base` may be uninitialized [unbound-name]
+ ERROR sklearn/metrics/_plot/precision_recall_curve.py:914:23-33: `pos_label_` may be uninitialized [unbound-name]
+ ERROR sklearn/metrics/_plot/roc_curve.py:735:23-33: `pos_label_` may be uninitialized [unbound-name]

prefect (https://github.com/PrefectHQ/prefect)
+ ERROR src/integrations/prefect-gcp/prefect_gcp/workers/vertex.py:664:16-23: `job_run` may be uninitialized [unbound-name]

scikit-build-core (https://github.com/scikit-build/scikit-build-core)
+ ERROR src/scikit_build_core/build/wheel.py:523:13-17: `path` may be uninitialized [unbound-name]

freqtrade (https://github.com/freqtrade/freqtrade)
+ ERROR freqtrade/exchange/binance_public_data.py:94:38-43: `start` may be uninitialized [unbound-name]
+ ERROR freqtrade/exchange/binance_public_data.py:94:61-64: `end` may be uninitialized [unbound-name]

manticore (https://github.com/trailofbits/manticore)
+ ERROR tests/auto_generators/make_VMTests.py:217:57-68: `blockheader` may be uninitialized [unbound-name]
+ ERROR tests/ethereum/test_general.py:1020:49-66: `symbolic_address1` may be uninitialized [unbound-name]
+ ERROR tests/ethereum/test_general.py:1021:49-66: `symbolic_address2` may be uninitialized [unbound-name]

cloud-init (https://github.com/canonical/cloud-init)
+ ERROR cloudinit/net/freebsd.py:43:51-61: `net_config` may be uninitialized [unbound-name]
+ ERROR tests/unittests/config/test_cc_ntp.py:542:47-50: `cfg` may be uninitialized [unbound-name]
+ ERROR tests/unittests/config/test_cc_ntp.py:561:51-54: `cfg` may be uninitialized [unbound-name]
+ ERROR tests/unittests/config/test_cc_ntp.py:579:51-54: `cfg` may be uninitialized [unbound-name]

zulip (https://github.com/zulip/zulip)
+ ERROR zerver/lib/cache.py:118:12-18: `prefix` may be uninitialized [unbound-name]
+ ERROR zerver/tests/test_markdown.py:2604:26-42: `rendering_result` may be uninitialized [unbound-name]
+ ERROR zerver/tests/test_push_notifications.py:1233:9-18: `time_sent` may be uninitialized [unbound-name]
+ ERROR zerver/tests/test_push_notifications.py:1245:13-25: `remote_realm` may be uninitialized [unbound-name]
+ ERROR zerver/tests/test_push_notifications.py:1282:9-21: `remote_realm` may be uninitialized [unbound-name]
+ ERROR zilencer/management/commands/render_messages.py:21:43-49: `msg_id` may be uninitialized [unbound-name]

static-frame (https://github.com/static-frame/static-frame)
+ ERROR static_frame/test/unit/test_container.py:15:13-14: `c` may be uninitialized [unbound-name]

mypy (https://github.com/python/mypy)
+ ERROR mypy/semanal_main.py:173:5-10: `state` may be uninitialized [unbound-name]

pandas (https://github.com/pandas-dev/pandas)
+ ERROR pandas/io/formats/csvs.py:315:30-38: `col_line` may be uninitialized [unbound-name]
+ ERROR pandas/io/formats/style_render.py:1013:28-42: `row_body_cells` may be uninitialized [unbound-name]
+ ERROR pandas/io/parsers/python_parser.py:1343:29-41: `len_new_rows` may be uninitialized [unbound-name]
+ ERROR pandas/io/pytables.py:4170:64-70: `_start` may be uninitialized [unbound-name]
+ ERROR pandas/io/pytables.py:4170:77-82: `_stop` may be uninitialized [unbound-name]

meson (https://github.com/mesonbuild/meson)
+ ERROR mesonbuild/interpreterbase/interpreterbase.py:743:27-38: `prev_subdir` may be uninitialized [unbound-name]

pytensor (https://github.com/pymc-devs/pytensor)
+ ERROR pytensor/d3viz/formatting.py:225:69-76: `vparams` may be uninitialized [unbound-name]

sphinx (https://github.com/sphinx-doc/sphinx)
+ ERROR sphinx/ext/autodoc/importer.py:286:38-46: `qualname` may be uninitialized [unbound-name]
+ ERROR sphinx/ext/autodoc/importer.py:298:30-38: `qualname` may be uninitialized [unbound-name]

core (https://github.com/home-assistant/core)
- ERROR homeassistant/components/aws_s3/__init__.py:69:9-22: The type of this argument is unknown because it comes from an error [unknown-from-error]
+ ERROR homeassistant/components/aws_s3/__init__.py:69:16-22: `client` may be uninitialized [unbound-name]
+ ERROR homeassistant/components/cloudflare_r2/__init__.py:72:26-32: `client` may be uninitialized [unbound-name]
+ ERROR homeassistant/components/knx/config_flow.py:506:36-44: `_host_ip` may be uninitialized [unbound-name]
+ ERROR homeassistant/components/knx/config_flow.py:525:26-31: `_host` may be uninitialized [unbound-name]
+ ERROR homeassistant/components/sql/config_flow.py:185:31-52: `db_url_for_validation` may be uninitialized [unbound-name]
+ ERROR homeassistant/helpers/intent.py:1228:35-42: `service` may be uninitialized [unbound-name]

spack (https://github.com/spack/spack)
+ ERROR lib/spack/spack/test/util/filesystem.py:357:32-38: `backup` may be uninitialized [unbound-name]

xarray (https://github.com/pydata/xarray)
+ ERROR xarray/structure/concat.py:920:47-51: `name` may be uninitialized [unbound-name]

optuna (https://github.com/optuna/optuna)
+ ERROR tests/samplers_tests/tpe_tests/test_sampler.py:395:59-64: `trial` may be uninitialized [unbound-name]

[connernilsen]

Looks good, thanks for splitting this out!

[meta-codesync]

This pull request has been merged in f95c8d9.