Add --disallow-str-iteration flag #20577

michaelm-openai · 2026-01-13T16:17:51Z

Fixes #11001

Related to typing python/typing#256

Expected behavior changes under this flag:

str and its subtypes are no longer treated as subtypes of Collection, Iterable, Sequence or protocols that extend them. Assignment and argument passing will be treated as errors.
The builtin iter() method has an additional overload which accepts str. This is the recommended way to iterate over characters when this flag is enabled.
Invalid assignment of str to subtypes of Container, such as Collection will not report a conflict on the __contains__ method, since this introduces noise. It is known that str does not conform to the Container protocol due to its incompatible signature for __contains__ method.

for more information, see https://pre-commit.ci

docs/source/command_line.rst

mypy/checker.py

mypy/subtypes.py

JelleZijlstra · 2026-01-13T16:29:24Z

mypy/typeshed/stdlib/builtins.pyi

    def __getitem__(self, i: int, /) -> _T_co: ...

+@overload
+def iter(object: str, /) -> Iterable[str]: ...


This needs to be in a patch file, or it will be overwritten next time we sync typeshed. Look for similar patch files in the repo (there are a few related to LiteralString).

test-data/unit/check-flags.test

for more information, see https://pre-commit.ci

mypy/checker.py

mypy/messages.py

for more information, see https://pre-commit.ci

michaelm-openai · 2026-01-14T18:38:59Z

I think the apprise diff is expected given that we added a new overload. The full diagnostic is:

apprise/config/base.py:1509: error: No overload variant of "iter" matches argument type "None"  [call-overload]
apprise/config/base.py:1509: note: Possible overload variants:
apprise/config/base.py:1509: note:     def [_SupportsNextT_co: SupportsNext[Any]] iter(SupportsIter[_SupportsNextT_co], /) -> _SupportsNextT_co
apprise/config/base.py:1509: note:     def iter(str, /) -> Iterator[str]
apprise/config/base.py:1509: note:     def [_T] iter(_GetItemIterable[_T], /) -> Iterator[_T]
apprise/config/base.py:1509: note:     def [_T] iter(Callable[[], _T | None], None, /) -> Iterator[_T]
apprise/config/base.py:1509: note:     def [_T] iter(Callable[[], _T], object, /) -> Iterator[_T]

…g_types

for more information, see https://pre-commit.ci

github-actions · 2026-01-15T19:09:26Z

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

beartype (https://github.com/beartype/beartype)
+ beartype/_data/kind/datakindtext.py:18: error: Argument 1 to "frozenset" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

spack (https://github.com/spack/spack)
+ lib/spack/spack/schema/mirrors.py:103: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Collection[object]"  [dict-item]
+ lib/spack/spack/schema/mirrors.py:107: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Collection[object]"  [dict-item]
+ lib/spack/spack/schema/modules.py:48: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Collection[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:52: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Collection[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:56: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:61: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:95: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:100: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:110: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:154: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:159: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:164: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/schema/modules.py:219: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Iterable[str]"  [dict-item]
+ lib/spack/spack/install_test.py:521: error: Argument 1 to "join" of "str" has incompatible type "Any | str"; expected "Iterable[str]"  [arg-type]
+ lib/spack/spack/test/spec_yaml.py:330: error: List item 0 has incompatible type "tuple[str, str]"; expected "tuple[str, Collection[str]]"  [list-item]
+ lib/spack/spack/test/spec_yaml.py:331: error: List item 1 has incompatible type "tuple[str, str]"; expected "tuple[str, Collection[str]]"  [list-item]
+ lib/spack/spack/cmd/info.py:151: error: Argument 1 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

CPython (Argument Clinic) (https://github.com/python/cpython)
+ Tools/clinic/libclinic/codegen.py:161: error: Argument 1 to "join" of "str" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

com2ann (https://github.com/ilevkivskyi/com2ann)
+ src/com2ann.py:436: error: Iterating over "str" is disallowed  [misc]
+ src/com2ann.py:436: note: This is because --disallow-str-iteration is enabled
+ src/com2ann.py:633: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

optuna (https://github.com/optuna/optuna)
+ tests/storages_tests/rdb_tests/test_storage.py:366: error: Argument 2 to "OperationalError" has incompatible type "str"; expected "Sequence[Sequence[Any]] | Sequence[Mapping[str, Any]] | Sequence[Any] | Mapping[str, Any] | None"  [arg-type]
+ tests/visualization_tests/test_hypervolume_history.py:26: error: Iterating over "str" is disallowed  [misc]
+ tests/visualization_tests/test_hypervolume_history.py:26: note: This is because --disallow-str-iteration is enabled
+ tests/visualization_tests/test_hypervolume_history.py:52: error: Argument "directions" to "create_study" has incompatible type "str"; expected "Sequence[str | StudyDirection] | None"  [arg-type]
+ tests/study_tests/test_study.py:177: error: Argument "directions" to "create_study" has incompatible type "str"; expected "Sequence[str | StudyDirection] | None"  [arg-type]
+ tests/samplers_tests/test_grid.py:52: error: Non-overlapping equality check (left operand type: "set[tuple[str | float | int | None, ...]]", right operand type: "set[tuple[Sequence[str | float | int | bool | None], ...]]")  [comparison-overlap]
+ optuna/visualization/_parallel_coordinate.py:289: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ optuna/visualization/_parallel_coordinate.py:297: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]

spark (https://github.com/apache/spark)
+ python/pyspark/sql/variant_utils.py:677: error: Iterating over "str" is disallowed  [misc]
+ python/pyspark/sql/variant_utils.py:677: note: This is because --disallow-str-iteration is enabled
+ python/pyspark/sql/classic/dataframe.py:1516: error: Iterating over "str | list[str]" is disallowed  [misc]
+ python/pyspark/sql/classic/dataframe.py:1516: note: This is because --disallow-str-iteration is enabled
+ python/pyspark/pandas/frame.py:7331: error: Argument 1 to "list" has incompatible type "str | list[str] | None"; expected "Iterable[str]"  [arg-type]
+ python/pyspark/pandas/frame.py:7336: error: Argument 1 to "list" has incompatible type "str | list[str] | None"; expected "Iterable[str]"  [arg-type]
+ python/pyspark/sql/connect/dataframe.py:1588: error: Iterating over "str | list[str]" is disallowed  [misc]
+ python/pyspark/sql/connect/dataframe.py:1588: note: This is because --disallow-str-iteration is enabled
+ python/pyspark/sql/connect/dataframe.py:1635: error: Argument 1 to "list" has incompatible type "str | list[str]"; expected "Iterable[str]"  [arg-type]

hydpy (https://github.com/hydpy-dev/hydpy)
+ hydpy/cythons/modelutils.py:2806: error: Iterating over "str" is disallowed  [misc]
+ hydpy/cythons/modelutils.py:2806: note: This is because --disallow-str-iteration is enabled
+ hydpy/core/timetools.py:527: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ hydpy/auxs/networktools.py:188: error: Argument 1 to "zip" has incompatible type "RiverBasinNumber"; expected "Iterable[str]"  [arg-type]
+ hydpy/auxs/networktools.py:188: error: Argument 2 to "zip" has incompatible type "RiverBasinNumber"; expected "Iterable[str]"  [arg-type]
+ hydpy/auxs/networktools.py:273: error: Iterating over "RiverBasinNumber" is disallowed  [misc]
+ hydpy/auxs/networktools.py:273: note: This is because --disallow-str-iteration is enabled
+ hydpy/auxs/networktools.py:368: error: Iterating over "RiverBasinNumber" is disallowed  [misc]
+ hydpy/auxs/networktools.py:368: note: This is because --disallow-str-iteration is enabled
+ hydpy/auxs/interptools.py:160: error: Argument 1 to "product" has incompatible type "str | list[str]"; expected "Iterable[str]"  [arg-type]
+ hydpy/auxs/interptools.py:160: error: Argument 2 to "product" has incompatible type "str | list[str]"; expected "Iterable[str]"  [arg-type]

psycopg (https://github.com/psycopg/psycopg)
+ psycopg/psycopg/errors.py:80: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/errors.py:556: error: Argument 1 to "Error" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_encodings.py:130: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/rows.py:216: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/rows.py:234: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_struct.py:49: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:183: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:277: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:302: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:306: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:321: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:325: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:338: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_py_transformer.py:355: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_conninfo_utils.py:34: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_conninfo_utils.py:42: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_conninfo_attempts_async.py:46: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_conninfo_attempts.py:48: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/conninfo.py:103: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/conninfo.py:140: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_info.py:53: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/transaction.py:239: error: Argument 1 to "OutOfOrderTransactionNesting" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_typeinfo.py:139: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_capabilities.py:110: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/waiting.py:47: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/waiting.py:160: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/waiting.py:181: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/waiting.py:221: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/waiting.py:274: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/waiting.py:285: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/waiting.py:394: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_adapters_map.py:228: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_adapters_map.py:260: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:81: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:92: error: Argument 1 to "ConnectionTimeout" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:101: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:106: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:117: error: Argument 1 to "CancellationTimeout" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:127: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:130: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:274: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/generators.py:326: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_tstrings.py:49: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_tstrings.py:74: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_tstrings.py:86: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_tstrings.py:102: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_tstrings.py:115: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_tstrings.py:141: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:141: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:161: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:238: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:418: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:424: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:429: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:441: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_queries.py:483: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_pipeline_base.py:168: error: Argument 1 to "PipelineAborted" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_copy_base.py:87: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_copy_base.py:264: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/string.py:52: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:365: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:380: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:396: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:410: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:475: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:493: error: Argument 1 to "PipelineAborted" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:496: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:500: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:603: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:606: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:613: error: Argument 1 to "PipelineAborted" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:624: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_cursor_base.py:638: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:260: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:265: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:313: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:486: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:523: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:532: error: Argument 1 to "OperationalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:534: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:574: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:580: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:594: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:600: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:638: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:644: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:653: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:657: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:672: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_connection_base.py:679: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/cursor_async.py:166: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/cursor.py:166: error: Argument 1 to "ProgrammingError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_server_cursor_base.py:167: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/client_cursor.py:62: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_server_cursor_async.py:90: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_server_cursor_async.py:105: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_server_cursor.py:91: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/_server_cursor.py:106: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/connection_async.py:145: error: Argument 1 to "Error" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/connection_async.py:597: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/connection.py:129: error: Argument 1 to "Error" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/connection.py:542: error: Argument 1 to "NotSupportedError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/range.py:441: error: Argument 1 to "InternalError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/range.py:467: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/numeric.py:342: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/json.py:280: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/enum.py:91: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:76: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:246: error: Argument 1 to "InterfaceError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:267: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:269: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:271: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:283: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:285: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]
+ psycopg/psycopg/types/datetime.py:294: error: Argument 1 to "DataError" has incompatible type "str"; expected "Sequence[Any]"  [arg-type]

... (truncated 61 lines) ...

tornado (https://github.com/tornadoweb/tornado)
+ tornado/util.py:179: error: Argument 1 to "frozenset" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ tornado/test/escape_test.py:260: error: List item 0 has incompatible type "tuple[str, str, str]"; expected "tuple[str, Sequence[object], str | None]"  [list-item]
+ tornado/test/escape_test.py:261: error: List item 1 has incompatible type "tuple[str, str, str]"; expected "tuple[str, Sequence[object], str | None]"  [list-item]
+ tornado/test/tcpserver_test.py:158: error: Argument 1 to "sorted" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ tornado/test/tcpserver_test.py:180: error: Argument 1 to "sorted" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ tornado/test/tcpserver_test.py:202: error: Argument 1 to "sorted" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ tornado/test/tcpserver_test.py:229: error: Argument 1 to "sorted" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

mongo-python-driver (https://github.com/mongodb/mongo-python-driver)
+ pymongo/saslprep.py:88: error: Iterating over "str" is disallowed  [misc]
+ pymongo/saslprep.py:88: note: This is because --disallow-str-iteration is enabled
+ bson/decimal128.py:305: error: Iterating over "str" is disallowed  [misc]
+ bson/decimal128.py:305: note: This is because --disallow-str-iteration is enabled
+ pymongo/uri_parser_shared.py:201: error: Iterating over "str" is disallowed  [misc]
+ pymongo/uri_parser_shared.py:201: note: This is because --disallow-str-iteration is enabled
+ pymongo/uri_parser_shared.py:202: error: Iterating over "str" is disallowed  [misc]
+ pymongo/uri_parser_shared.py:202: note: This is because --disallow-str-iteration is enabled
+ pymongo/helpers_shared.py:142: error: Expected iterable as variadic argument  [misc]
+ pymongo/compression_support.py:64: error: Argument 1 to "list" has incompatible type "str | Iterable[str]"; expected "Iterable[str | Any]"  [arg-type]

prefect (https://github.com/PrefectHQ/prefect)
+ src/prefect/_sdk/naming.py:110: error: Iterating over "str" is disallowed  [misc]
+ src/prefect/_sdk/naming.py:110: note: This is because --disallow-str-iteration is enabled
+ src/prefect/_sdk/naming.py:180: error: Iterating over "str" is disallowed  [misc]
+ src/prefect/_sdk/naming.py:180: note: This is because --disallow-str-iteration is enabled
+ src/prefect/utilities/urls.py:123: error: Iterating over "str | Any" is disallowed  [misc]
+ src/prefect/utilities/urls.py:123: note: This is because --disallow-str-iteration is enabled
- src/prefect/deployments/runner.py:641: error: Incompatible types in assignment (expression has type "list[Iterable[str] | Iterable[int | float | timedelta] | int | float | timedelta | None]", variable has type "Iterable[str] | Iterable[int | float | timedelta] | int | float | timedelta | None")  [assignment]
+ src/prefect/deployments/runner.py:641: error: Incompatible types in assignment (expression has type "list[Iterable[str] | str | Iterable[int | float | timedelta] | int | float | timedelta | None]", variable has type "Iterable[str] | str | Iterable[int | float | timedelta] | int | float | timedelta | None")  [assignment]
- src/prefect/deployments/runner.py:653: error: Item "None" of "Iterable[str] | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
- src/prefect/deployments/runner.py:653: error: Item "int" of "Iterable[str] | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
+ src/prefect/deployments/runner.py:653: error: Iterating over "Iterable[str] | str | Iterable[int | float | timedelta] | int | float | timedelta | None" is disallowed  [misc]
+ src/prefect/deployments/runner.py:653: note: This is because --disallow-str-iteration is enabled
- src/prefect/deployments/runner.py:653: error: Item "float" of "Iterable[str] | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
+ src/prefect/deployments/runner.py:653: error: Item "None" of "Iterable[str] | str | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
- src/prefect/deployments/runner.py:653: error: Item "timedelta" of "Iterable[str] | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
+ src/prefect/deployments/runner.py:653: error: Item "int" of "Iterable[str] | str | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
+ src/prefect/deployments/runner.py:653: error: Item "float" of "Iterable[str] | str | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
+ src/prefect/deployments/runner.py:653: error: Item "timedelta" of "Iterable[str] | str | Iterable[int | float | timedelta] | int | float | timedelta | None" has no attribute "__iter__" (not iterable)  [union-attr]
+ src/prefect/cli/cloud/__init__.py:226: error: Argument 1 to "enumerate" has incompatible type "list[str] | list[tuple[T, str]]"; expected "Iterable[Sequence[T | str]]"  [arg-type]
+ src/prefect/infrastructure/provisioners/ecs.py:1345: error: Iterating over "str | Any" is disallowed  [misc]
+ src/prefect/infrastructure/provisioners/ecs.py:1345: note: This is because --disallow-str-iteration is enabled
+ src/prefect/infrastructure/provisioners/container_instance.py:637: error: Iterating over "str | dict[str, Any]" is disallowed  [misc]
+ src/prefect/infrastructure/provisioners/container_instance.py:637: note: This is because --disallow-str-iteration is enabled

pydantic (https://github.com/pydantic/pydantic)
+ pydantic/v1/color.py:59: error: Iterating over "str" is disallowed  [misc]
+ pydantic/v1/color.py:59: note: This is because --disallow-str-iteration is enabled
+ pydantic/v1/schema.py:515: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[Collection[str]]"  [dict-item]
+ pydantic/color.py:68: error: Iterating over "str" is disallowed  [misc]
+ pydantic/color.py:68: note: This is because --disallow-str-iteration is enabled
+ pydantic/v1/_hypothesis_plugin.py:124: error: Iterating over "str" is disallowed  [misc]
+ pydantic/v1/_hypothesis_plugin.py:124: note: This is because --disallow-str-iteration is enabled

PyGithub (https://github.com/PyGithub/PyGithub)
+ github/Repository.py:1970: error: Incompatible types in assignment (expression has type "str", target has type "Sequence[Collection[str]]")  [assignment]
+ github/Repository.py:1976: error: Incompatible types in assignment (expression has type "str", target has type "Sequence[Collection[str]]")  [assignment]
+ github/Repository.py:1978: error: Incompatible types in assignment (expression has type "str", target has type "Sequence[Collection[str]]")  [assignment]

pylox (https://github.com/sco1/pylox)
+ pylox/builtins/py_builtins.py:358: error: Argument 1 to "_lox_arrayize" has incompatible type "str"; expected "Iterable[Any]"  [arg-type]
+ tests/builtins/test_loxarrayize.py:9: error: Argument 1 to "deque" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

mkosi (https://github.com/systemd/mkosi)
+ mkosi/versioncomp.py:26:35: error: Expected iterable as variadic argument  [misc]
+ mkosi/versioncomp.py:27:35: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/versioncomp.py:33:78: error: Argument 2 to "takewhile" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/versioncomp.py:36:85: error: Argument 2 to "takewhile" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/config.py:4638:18: error: Iterating over "str" is disallowed  [misc]
+ mkosi/config.py:4638:18: note: This is because --disallow-str-iteration is enabled
+ mkosi/config.py:4643:31: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/config.py:4652:31: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/config.py:4673:35: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/config.py:4679:27: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/config.py:4682:23: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mkosi/config.py:6036:91: error: Iterating over "str" is disallowed  [misc]
+ mkosi/config.py:6036:91: note: This is because --disallow-str-iteration is enabled
+ mkosi/__init__.py:2219:49: error: Iterating over "str" is disallowed  [misc]
+ mkosi/__init__.py:2219:49: note: This is because --disallow-str-iteration is enabled

bandersnatch (https://github.com/pypa/bandersnatch)
+ src/bandersnatch/configuration.py: note: In member "__init__" of class "BandersnatchConfig":
+ src/bandersnatch/configuration.py:77: error: Argument "delimiters" to "__init__" of "RawConfigParser" has incompatible type "str"; expected "Sequence[str]"  [arg-type]

aiohttp (https://github.com/aio-libs/aiohttp)
+ aiohttp/hdrs.py:114:41: error: Argument 1 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/hdrs.py:114:60: error: Argument 2 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/hdrs.py:117:41: error: Argument 1 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/hdrs.py:117:63: error: Argument 2 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/hdrs.py:120:41: error: Argument 1 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/hdrs.py:120:55: error: Argument 2 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/helpers.py:420:28: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/helpers.py:448:41: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/helpers.py:455:44: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/http_parser.py:59:33: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ aiohttp/multipart.py:77:46: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
- aiohttp/web_log.py:197: error: Unused "type: ignore" comment  [unused-ignore]
- aiohttp/web_log.py:198: error: Unused "type: ignore[has-type]" comment  [unused-ignore]
- aiohttp/web_log.py:199: error: Unused "type: ignore[has-type]" comment  [unused-ignore]
- aiohttp/web_log.py:200: error: Unused "type: ignore[has-type]" comment  [unused-ignore]

colour (https://github.com/colour-science/colour)
+ colour/utilities/verbose.py:234: error: Argument 1 to "chain" has incompatible type "*list[str | list[str]]"; expected "Iterable[str]"  [arg-type]
+ colour/geometry/primitives.py:375: error: Iterating over "Literal['-x', '+x', '-y', '+y', '-z', '+z', 'xy', 'xz', 'yz', 'yx', 'zx', 'zy']" is disallowed  [misc]
+ colour/geometry/primitives.py:375: note: This is because --disallow-str-iteration is enabled
+ colour/io/ctl.py:428: error: Incompatible types in assignment (expression has type "Collection[str]", variable has type "Sequence[str] | None")  [assignment]
+ colour/io/ctl.py:428: error: Argument 2 to "optional" has incompatible type "str"; expected "Collection[str]"  [arg-type]
+ colour/io/ctl.py:553: error: Incompatible types in assignment (expression has type "Collection[str]", variable has type "Sequence[str] | None")  [assignment]
+ colour/io/ctl.py:553: error: Argument 2 to "optional" has incompatible type "str"; expected "Collection[str]"  [arg-type]
+ colour/plotting/common.py:881: error: Iterating over "str" is disallowed  [misc]
+ colour/plotting/common.py:881: note: This is because --disallow-str-iteration is enabled
+ colour/plotting/common.py:886: error: Argument 2 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ colour/plotting/volume.py:257: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ colour/plotting/volume.py:285: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ colour/plotting/volume.py:626: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ colour/plotting/volume.py:634: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ colour/plotting/temperature.py:617: error: Argument 1 to "optional" has incompatible type "str | Sequence[str] | None"; expected "Sequence[str] | None"  [arg-type]
+ colour/utilities/tests/test_array.py:536: error: Argument 1 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

python-chess (https://github.com/niklasf/python-chess)
+ chess/__init__.py:1186: error: Iterating over "str" is disallowed  [misc]
+ chess/__init__.py:1186: note: This is because --disallow-str-iteration is enabled
+ chess/__init__.py:1213: error: Iterating over "str" is disallowed  [misc]
+ chess/__init__.py:1213: note: This is because --disallow-str-iteration is enabled
+ chess/__init__.py:2746: error: Iterating over "str" is disallowed  [misc]
+ chess/__init__.py:2746: note: This is because --disallow-str-iteration is enabled
+ chess/__init__.py:2928: error: Argument 1 to "chain" has incompatible type "str"; expected "Iterable[str | None]"  [arg-type]
+ chess/variant.py:841: error: Incompatible default for argument "symbols" (default has type "str", argument has type "Iterable[str]")  [assignment]
+ chess/variant.py:1036: error: Iterating over "str" is disallowed  [misc]
+ chess/variant.py:1036: note: This is because --disallow-str-iteration is enabled
+ chess/variant.py:1037: error: Iterating over "str" is disallowed  [misc]
+ chess/variant.py:1037: note: This is because --disallow-str-iteration is enabled
+ chess/syzygy.py:388: error: Argument 1 to "sorted" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ chess/syzygy.py:389: error: Argument 1 to "sorted" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ chess/syzygy.py:390: error: Iterating over "str" is disallowed  [misc]
+ chess/syzygy.py:390: note: This is because --disallow-str-iteration is enabled
+ chess/engine.py:2498: error: Iterating over "str" is disallowed  [misc]
+ chess/engine.py:2498: note: This is because --disallow-str-iteration is enabled

mypy_primer (https://github.com/hauntsaninja/mypy_primer)
+ mypy_primer/utils.py:92: error: Argument 1 to "join" has incompatible type "str | list[str]"; expected "Iterable[str]"  [arg-type]

zipp (https://github.com/jaraco/zipp)
+ zipp/glob.py:25: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

meson (https://github.com/mesonbuild/meson)
+ mesonbuild/depfile.py:19:18: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/depfile.py:19:18: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/utils/universal.py:1161:17: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/utils/universal.py:1161:17: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/utils/universal.py:1182:18: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/utils/universal.py:1182:18: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/utils/universal.py:1204:18: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/utils/universal.py:1204:18: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/utils/universal.py:1904:27: error: Argument 1 to "__iadd__" of "list" has incompatible type "str | list[str]"; expected "Iterable[str | Program]"  [arg-type]
+ mesonbuild/utils/universal.py:1913:27: error: Argument 1 to "__iadd__" of "list" has incompatible type "str | list[str]"; expected "Iterable[str | Program]"  [arg-type]
+ mesonbuild/cargo/cfg.py:60:27: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mesonbuild/cmdline.py:121:26: error: Argument 1 to "__init__" of "Action" has incompatible type "str"; expected "Sequence[str]"  [arg-type]
+ mesonbuild/cmdline.py:141:26: error: Argument 1 to "__init__" of "Action" has incompatible type "str"; expected "Sequence[str]"  [arg-type]
+ mesonbuild/cmake/common.py:85:14: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/cmake/common.py:85:14: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/cmake/common.py:177:56: error: Argument 1 to "join" of "str" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mesonbuild/compilers/cuda.py:219:24: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mesonbuild/compilers/cuda.py:225:24: error: Argument 1 to "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ mesonbuild/cmake/interpreter.py:287:40: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/cmake/interpreter.py:287:40: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/wrap/wrap.py:741:67: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/wrap/wrap.py:741:67: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/interpreter/type_checking.py:149:37: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/interpreter/type_checking.py:149:37: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/backend/backends.py:436:70: error: Argument 2 to "classify_unity_sources" has incompatible type "str"; expected "Sequence[File | str]"  [arg-type]
+ docs/refman/loaderbase.py:53:18: error: Iterating over "str" is disallowed  [misc]
+ docs/refman/loaderbase.py:53:18: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/modules/rust.py:79:47: error: Iterating over "str | list[Any] | None" is disallowed  [misc]
+ mesonbuild/modules/rust.py:79:47: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/modules/gnome.py:238:71: error: Iterating over "str | list[str]" is disallowed  [misc]
+ mesonbuild/modules/gnome.py:238:71: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/modules/gnome.py:1885:29: error: Argument "install_dir" to "_make_mkenum_impl" of "GnomeModule" has incompatible type "str"; expected "Sequence[str | bool] | None"  [arg-type]
+ mesonbuild/modules/gnome.py:1908:29: error: Argument "install_dir" to "_make_mkenum_impl" of "GnomeModule" has incompatible type "str"; expected "Sequence[str | bool] | None"  [arg-type]
+ mesonbuild/modules/gnome.py:2035:25: error: Argument "install_dir" to "_make_mkenum_impl" of "GnomeModule" has incompatible type "str"; expected "Sequence[str | bool] | None"  [arg-type]
+ mesonbuild/modules/cuda.py:177:66: error: Iterating over "str | list[str]" is disallowed  [misc]
+ mesonbuild/modules/cuda.py:177:66: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/mintro.py:192:17: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[str | UnknownValue]"  [dict-item]
+ mesonbuild/mintro.py:193:17: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Sequence[str | UnknownValue]"  [dict-item]
+ mesonbuild/mtest.py:96:14: error: Iterating over "str" is disallowed  [misc]
+ mesonbuild/mtest.py:96:14: note: This is because --disallow-str-iteration is enabled
+ mesonbuild/mtest.py:2243:32: error: Argument 1 to "update" of "set" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

mypy (https://github.com/python/mypy)
+ mypyc/codegen/cstring.py:29: error: Iterating over "str" is disallowed  [misc]
+ mypyc/codegen/cstring.py:29: note: This is because --disallow-str-iteration is enabled
+ mypy/server/objgraph.py:54: error: Subclass of "Iterable[Any]" and "str" cannot exist: would have inconsistent method resolution order  [unreachable]
+ mypy/server/objgraph.py:54: note: See https://mypy.rtfd.io/en/stable/_refs.html#code-unreachable for more info
+ mypy/util.py:505: error: Iterating over "str" is disallowed  [misc]
+ mypy/util.py:505: note: This is because --disallow-str-iteration is enabled
+ mypy/strconv.py:173: error: List item 0 has incompatible type "str"; expected "Sequence[object]"  [list-item]
+ mypy/strconv.py:173: note: See https://mypy.rtfd.io/en/stable/_refs.html#code-list-item for more info
+ mypy/strconv.py:185: error: Argument 2 to "insert" of "list" has incompatible type "str"; expected "Sequence[object]"  [arg-type]
+ mypy/strconv.py:189: error: Argument 2 to "insert" of "list" has incompatible type "str"; expected "Sequence[object]"  [arg-type]
+ mypy/strconv.py:193: error: Argument 2 to "insert" of "list" has incompatible type "str"; expected "Sequence[object]"  [arg-type]
+ mypy/nodes.py:3903: error: Argument 1 to "append" of "list" has incompatible type "str"; expected "Sequence[str | list[str]]"  [arg-type]
+ mypy/nodes.py:3905: error: Argument 1 to "append" of "list" has incompatible type "str"; expected "Sequence[str | list[str]]"  [arg-type]
+ mypy/config_parser.py:374: error: Iterating over "str" is disallowed  [misc]
+ mypy/config_parser.py:374: note: This is because --disallow-str-iteration is enabled
+ mypy/messages.py:3309: error: Argument "a" to "SequenceMatcher" has incompatible type "str"; expected "Sequence[str]"  [arg-type]
+ mypy/messages.py:3309: error: Argument "b" to "SequenceMatcher" has incompatible type "str"; expected "Sequence[str]"  [arg-type]
+ mypy/report.py:341: error: Argument 1 to "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]

zulip (https://github.com/zulip/zulip)
+ zerver/lib/emoji_utils.py:21: error: Iterating over "str" is disallowed  [misc]
+ zerver/lib/emoji_utils.py:21: note: This is because --disallow-str-iteration is enabled
+ tools/lib/html_branches.py:59: error: Iterating over "str" is disallowed  [misc]
+ tools/lib/html_branches.py:59: note: This is because --disallow-str-iteration is enabled
+ zerver/lib/markdown/api_arguments_table_generator.py:234: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ zerver/lib/markdown/api_arguments_table_generator.py:241: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ zerver/lib/markdown/api_arguments_table_generator.py:247: error: Argument 1 to "__iadd__" of "list" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ zerver/lib/validator.py:459: error: Argument 1 to "equals" has incompatible type "str"; expected "Sequence[Collection[str]]"  [arg-type]
+ zerver/lib/validator.py:460: error: List item 1 has incompatible type "tuple[str, Callable[[str, object], str]]"; expected "tuple[str, Callable[[str, object], Sequence[Collection[str]]]]"  [list-item]
+ zerver/openapi/python_examples.py:1747: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ zerver/openapi/python_examples.py:1760: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ zerver/openapi/python_examples.py:1761: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ zerver/openapi/python_examples.py:1763: error: Dict entry 3 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ zerver/openapi/python_examples.py:1773: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ zerver/openapi/python_examples.py:1774: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ zerver/openapi/python_examples.py:1776: error: Dict entry 3 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]
+ zerver/lib/string_validation.py:32: error: Argument 1 to "enumerate" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ zerver/lib/mobile_auth_otp.py:18: error: Argument 1 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ zerver/lib/mobile_auth_otp.py:18: error: Argument 2 to "zip" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ zerver/lib/mobile_auth_otp.py:48: error: Iterating over "str" is disallowed  [misc]
+ zerver/lib/mobile_auth_otp.py:48: note: This is because --disallow-str-iteration is enabled
+ zerver/lib/url_encoding.py:23: error: Iterating over "str" is disallowed  [misc]
+ zerver/lib/url_encoding.py:23: note: This is because --disallow-str-iteration is enabled
+ zerver/actions/default_streams.py:26: error: Iterating over "str" is disallowed  [misc]
+ zerver/actions/default_streams.py:26: note: This is because --disallow-str-iteration is enabled
+ corporate/lib/stripe.py:4403: error: List item 0 has incompatible type "str"; expected "Collection[str]"  [list-item]
+ corporate/lib/stripe.py:4847: error: List item 0 has incompatible type "str"; expected "Collection[str]"  [list-item]
+ corporate/lib/stripe.py:5296: error: List item 0 has incompatible type "str"; expected "Collection[str]"  [list-item]
+ zerver/lib/narrow.py:462: error: Argument 1 to "frozenset" has incompatible type "str"; expected "Iterable[str]"  [arg-type]
+ zerver/actions/user_settings.py:107: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Collection[str]"  [dict-item]
+ zerver/actions/user_settings.py:107: error: Dict entry 1 has incompatible type "str": "str"; expected "str": "Collection[str]"  [dict-item]
+ zerver/actions/streams.py:659: error: Dict entry 0 has incompatible type "str": "str"; expected "str": "Sequence[object]"  [dict-item]

... (truncated 2098 lines) ...```

michaelm-openai and others added 2 commits January 13, 2026 11:13

Add --disallow-str-iteration flag

ff8281b

[pre-commit.ci] auto fixes from pre-commit.com hooks

9844f81

for more information, see https://pre-commit.ci

JelleZijlstra reviewed Jan 13, 2026

View reviewed changes

This comment has been minimized.

Sign in to view

address feedback

115c1b7

This comment has been minimized.

Sign in to view

michaelm-openai and others added 2 commits January 13, 2026 15:27

actually commit the patch + more adjustments

1684059

[pre-commit.ci] auto fixes from pre-commit.com hooks

eb08cfe

for more information, see https://pre-commit.ci

JelleZijlstra reviewed Jan 13, 2026

View reviewed changes

mypy/checker.py Show resolved Hide resolved

JelleZijlstra reviewed Jan 13, 2026

View reviewed changes

mypy/messages.py Outdated Show resolved Hide resolved

address more feedback + undo reversible

4b0149a

michaelm-openai requested a review from JelleZijlstra January 14, 2026 06:05

[pre-commit.ci] auto fixes from pre-commit.com hooks

b61f340

for more information, see https://pre-commit.ci

This comment has been minimized.

Sign in to view

Swap iter overloads to preserve previous error behavior

446d5da

This comment has been minimized.

Sign in to view

fix union simplification

a6c96a1

michaelm-openai force-pushed the michaelm/disallow-str-iteration branch from 9170fb1 to 473a4a1 Compare January 15, 2026 04:14

This comment has been minimized.

Sign in to view

michaelm-openai force-pushed the michaelm/disallow-str-iteration branch from 473a4a1 to ab25cde Compare January 15, 2026 08:13

michaelm-openai added 2 commits January 15, 2026 04:00

refactor disallow_str_iteration checks and add check to is_overlappin…

d4d5ce7

…g_types

experiment enabling by default

41bb4d3

michaelm-openai force-pushed the michaelm/disallow-str-iteration branch from 09762a7 to 41bb4d3 Compare January 15, 2026 09:00

[pre-commit.ci] auto fixes from pre-commit.com hooks

8edc2d8

for more information, see https://pre-commit.ci

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Uh oh!

Add --disallow-str-iteration flag #20577

Add --disallow-str-iteration flag #20577

Uh oh!

michaelm-openai commented Jan 13, 2026 •

edited

Loading

Uh oh!

Uh oh!

Uh oh!

Uh oh!

JelleZijlstra Jan 13, 2026

Uh oh!

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

michaelm-openai commented Jan 14, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

github-actions bot commented Jan 15, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Add --disallow-str-iteration flag #20577

Are you sure you want to change the base?

Add --disallow-str-iteration flag #20577

Uh oh!

Conversation

michaelm-openai commented Jan 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

JelleZijlstra Jan 13, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

michaelm-openai commented Jan 14, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

github-actions bot commented Jan 15, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

michaelm-openai commented Jan 13, 2026 •

edited

Loading