[ty] Avoid false positive for `not-iterable` with no-positive intersection types

[charliermarsh]

Summary

When checking if list[~str] is iterable, we end up looking for a positive element to satisfy assignability to Iterable[~str]. But when there are no positive elements, we return false, rather than falling back to object.

Closes https://github.com/astral-sh/ty/issues/1880.

[astral-sh-bot[bot]]

Diagnostic diff on typing conformance tests

No changes detected when running ty on typing conformance tests ✅

[astral-sh-bot[bot]]

mypy_primer results

Changes were detected when running on open source projects

tornado (https://github.com/tornadoweb/tornado)
- tornado/gen.py:255:62: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `None | Awaitable[Unknown] | list[Awaitable[Unknown]] | dict[Any, Awaitable[Unknown]] | Future[Unknown]`, found `_T@next | _VT@next | _T@next`
+ tornado/gen.py:255:62: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `None | Awaitable[Unknown] | list[Awaitable[Unknown]] | dict[Any, Awaitable[Unknown]] | Future[Unknown]`, found `_T@next | _T@next | _VT@next`

Tanjun (https://github.com/FasterSpeeding/Tanjun)
- tanjun/dependencies/data.py:347:12: error[invalid-return-type] Return type does not match returned value: expected `_T@cached_inject`, found `_T@cached_inject | Coroutine[Any, Any, _T@cached_inject | Coroutine[Any, Any, _T@cached_inject]]`
+ tanjun/dependencies/data.py:347:12: error[invalid-return-type] Return type does not match returned value: expected `_T@cached_inject`, found `Coroutine[Any, Any, _T@cached_inject | Coroutine[Any, Any, _T@cached_inject]] | _T@cached_inject`

xarray (https://github.com/pydata/xarray)
- xarray/core/dataarray.py:5737:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `DataArray | Dataset`
+ xarray/core/dataarray.py:5737:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `T_Xarray@map_blocks | DataArray | Dataset`
- xarray/core/dataset.py:8866:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `DataArray | Dataset`
+ xarray/core/dataset.py:8866:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `T_Xarray@map_blocks | DataArray | Dataset`

openlibrary (https://github.com/internetarchive/openlibrary)
- openlibrary/core/lending.py:811:22: error[invalid-argument-type] Argument expression after ** must be a mapping type: Found `dict[Unknown | str, Unknown | str | ~AlwaysTruthy | dict[Unknown | str, Unknown] | int]`
- Found 1153 diagnostics
+ Found 1152 diagnostics

strawberry (https://github.com/strawberry-graphql/strawberry)
- strawberry/permission.py:163:35: error[not-iterable] Object of type `list[~AlwaysFalsy | Unknown]` is not iterable
- Found 393 diagnostics
+ Found 392 diagnostics

scikit-build-core (https://github.com/scikit-build/scikit-build-core)
- src/scikit_build_core/build/wheel.py:98:20: error[no-matching-overload] No overload of bound method `__init__` matches arguments
- Found 43 diagnostics
+ Found 42 diagnostics

altair (https://github.com/vega/altair)
+ altair/vegalite/v6/api.py:263:42: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `SchemaBase | Mapping[str, Any] | UndefinedType`, found `object`
- altair/vegalite/v6/api.py:263:42: error[invalid-argument-type] Argument expression after ** must be a mapping type: Found `dict[Unknown, Unknown] | dict[Unknown | str, Unknown] | dict[~Literal["values"] | Unknown, object]`
+ altair/vegalite/v6/api.py:263:42: error[invalid-argument-type] Argument expression after ** must be a mapping with `str` key type: Found `object`
- Found 1108 diagnostics
+ Found 1109 diagnostics

static-frame (https://github.com/static-frame/static-frame)
- static_frame/core/series.py:772:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[Series[Any, Any], TVDtype@Series]`, found `InterGetItemILocReduces[Series[Any, Any], generic[object]]`
+ static_frame/core/series.py:772:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[Series[Any, Any], TVDtype@Series]`, found `InterGetItemILocReduces[Series[Any, Any] | Top[Index[Any]] | TypeBlocks | ... omitted 6 union elements, generic[object]]`
- static_frame/core/series.py:4072:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[SeriesHE[Any, Any], TVDtype@SeriesHE]`, found `InterGetItemILocReduces[SeriesHE[Any, Any], generic[object]]`
+ static_frame/core/series.py:4072:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[SeriesHE[Any, Any], TVDtype@SeriesHE]`, found `InterGetItemILocReduces[SeriesHE[Any, Any] | Top[Index[Any]] | TypeBlocks | ... omitted 7 union elements, generic[object]]`
- static_frame/core/yarn.py:418:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[Yarn[Any], object_]`, found `InterGetItemILocReduces[Yarn[Any] | TypeBlocks | Batch | ... omitted 7 union elements, generic[object]]`
+ static_frame/core/yarn.py:418:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemILocReduces[Yarn[Any], object_]`, found `InterGetItemILocReduces[Yarn[Any] | Top[Index[Any]] | TypeBlocks | ... omitted 7 union elements, generic[object]]`

pandas-stubs (https://github.com/pandas-dev/pandas-stubs)
- pandas-stubs/_typing.pyi:1223:16: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- Found 5086 diagnostics
+ Found 5085 diagnostics

core (https://github.com/home-assistant/core)
- homeassistant/components/bluetooth/passive_update_coordinator.py:78:20: error[not-iterable] Object of type `GeneratorType[~None, None, None]` is not iterable
- homeassistant/helpers/update_coordinator.py:218:20: error[not-iterable] Object of type `GeneratorType[~None, None, None]` is not iterable
- Found 14425 diagnostics
+ Found 14423 diagnostics

No memory usage changes detected ✅

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #22089 will degrade performance by 29.26%

_{Comparing charlie/neg (905a38d) with main (df1552b)}

Summary

❌ 6 regressions
✅ 16 untouched
⏩ 30 skipped[^skipped]

:warning: Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	WallTime	medium[static-frame]	19.9 s	21.7 s	-8.04%
❌	WallTime	medium[colour-science]	106.8 s	151 s	-29.26%
❌	WallTime	medium[pandas]	63.8 s	70.8 s	-9.97%
❌	WallTime	small[freqtrade]	7.9 s	8.6 s	-7.48%
❌	Simulation	ty_check_file[incremental]	6.3 ms	6.8 ms	-6.47%
❌	Simulation	hydra-zen	1.2 s	1.3 s	-5.41%

[^skipped]: 30 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports.

[charliermarsh]

Ok, wasn't expecting that!

[AlexWaygood]

This does look correct, but we obviously can't merge this if it causes the benchmarks to start timing out 🙃

I think we probably need to do similar for the when_any calls in the Type::Intersection branch above this one, too

[charliermarsh]

(Looking into it...)