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[ty] Emit diagnostics for invalid base classes in type(...)#22499

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charliermarsh merged 4 commits intomainfrom
charlie/dyn-diag
Jan 14, 2026
Merged

[ty] Emit diagnostics for invalid base classes in type(...)#22499
charliermarsh merged 4 commits intomainfrom
charlie/dyn-diag

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@charliermarsh charliermarsh commented Jan 10, 2026

Summary

Tackles a few TODOs from #22291.

@charliermarsh charliermarsh added the ty Multi-file analysis & type inference label Jan 10, 2026
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astral-sh-bot bot commented Jan 10, 2026

Diagnostic diff on typing conformance tests

No changes detected when running ty on typing conformance tests ✅

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astral-sh-bot bot commented Jan 10, 2026

mypy_primer results

Changes were detected when running on open source projects
async-utils (https://github.com/mikeshardmind/async-utils)
+ src/async_utils/_graphs.py:49:18: warning[unsupported-dynamic-base] Unsupported base for class created via `type()`: Has type `<special-form 'typing.Protocol'>`
+ src/async_utils/corofunc_cache.py:58:18: warning[unsupported-dynamic-base] Unsupported base for class created via `type()`: Has type `<special-form 'typing.Protocol'>`
+ src/async_utils/task_cache.py:61:18: warning[unsupported-dynamic-base] Unsupported base for class created via `type()`: Has type `<special-form 'typing.Protocol'>`
- Found 9 diagnostics
+ Found 12 diagnostics

graphql-core (https://github.com/graphql-python/graphql-core)
+ tests/type/test_scalars.py:541:51: error[subclass-of-final-class] Class `Boolean` cannot inherit from final class `bool`
- Found 640 diagnostics
+ Found 641 diagnostics

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 | _T@next | _VT@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 | _VT@next | _T@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`

trio (https://github.com/python-trio/trio)
+ src/trio/_core/_tests/test_cancelled.py:55:27: error[subclass-of-final-class] Class `Subclass` cannot inherit from final class `Cancelled`
+ src/trio/_core/_tests/test_run.py:2368:27: error[subclass-of-final-class] Class `Subclass` cannot inherit from final class `Nursery`
+ src/trio/_core/_tests/test_run.py:2373:27: error[subclass-of-final-class] Class `Subclass` cannot inherit from final class `CancelScope`
- Found 482 diagnostics
+ Found 485 diagnostics

scikit-build-core (https://github.com/scikit-build/scikit-build-core)
+ src/scikit_build_core/build/wheel.py:99:20: error[no-matching-overload] No overload of bound method `__init__` matches arguments
- Found 47 diagnostics
+ Found 48 diagnostics

prefect (https://github.com/PrefectHQ/prefect)
- src/integrations/prefect-dbt/prefect_dbt/core/settings.py:94:28: error[invalid-assignment] Object of type `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
+ src/integrations/prefect-dbt/prefect_dbt/core/settings.py:94:28: error[invalid-assignment] Object of type `T@resolve_block_document_references | dict[str, Any]` is not assignable to `dict[str, Any]`
- src/integrations/prefect-dbt/prefect_dbt/core/settings.py:99:28: error[invalid-assignment] Object of type `T@resolve_variables | str | int | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
+ src/integrations/prefect-dbt/prefect_dbt/core/settings.py:99:28: error[invalid-assignment] Object of type `T@resolve_variables | dict[str, Any]` is not assignable to `dict[str, Any]`
- src/prefect/cli/deploy/_core.py:86:21: error[invalid-assignment] Object of type `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
+ src/prefect/cli/deploy/_core.py:86:21: error[invalid-assignment] Object of type `T@resolve_block_document_references | dict[str, Any]` is not assignable to `dict[str, Any]`
- src/prefect/cli/deploy/_core.py:87:21: error[invalid-assignment] Object of type `T@resolve_variables | str | int | ... omitted 4 union elements` is not assignable to `dict[str, Any]`
+ src/prefect/cli/deploy/_core.py:87:21: error[invalid-assignment] Object of type `T@resolve_variables` is not assignable to `dict[str, Any]`
- src/prefect/deployments/runner.py:795:70: warning[possibly-missing-attribute] Attribute `__name__` may be missing on object of type `Unknown | ((...) -> Any)`
+ src/prefect/deployments/runner.py:795:70: warning[possibly-missing-attribute] Attribute `__name__` may be missing on object of type `Unknown | (((...) -> Any) & ((*args: object, **kwargs: object) -> object))`
- src/prefect/deployments/steps/core.py:137:38: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements`
+ src/prefect/deployments/steps/core.py:137:38: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any]`
- src/prefect/flow_engine.py:812:32: error[invalid-await] `Unknown | R@FlowRunEngine | Coroutine[Any, Any, R@FlowRunEngine]` is not awaitable
- src/prefect/flow_engine.py:1401:24: error[invalid-await] `Unknown | R@AsyncFlowRunEngine | Coroutine[Any, Any, R@AsyncFlowRunEngine]` is not awaitable
- src/prefect/flow_engine.py:1482:43: error[invalid-argument-type] Argument to function `next` is incorrect: Expected `SupportsNext[Unknown]`, found `Unknown | R@run_generator_flow_sync`
- src/prefect/flow_engine.py:1490:21: warning[possibly-missing-attribute] Attribute `throw` may be missing on object of type `Unknown | R@run_generator_flow_sync`
- src/prefect/flow_engine.py:1524:44: warning[possibly-missing-attribute] Attribute `__anext__` may be missing on object of type `Unknown | R@run_generator_flow_async`
- src/prefect/flow_engine.py:1531:25: warning[possibly-missing-attribute] Attribute `throw` may be missing on object of type `Unknown | R@run_generator_flow_async`
- src/prefect/flows.py:286:34: error[unresolved-attribute] Object of type `(**P@Flow) -> R@Flow` has no attribute `__name__`
+ src/prefect/flows.py:286:34: error[unresolved-attribute] Object of type `((**P@Flow) -> R@Flow) & ((*args: object, **kwargs: object) -> object)` has no attribute `__name__`
- src/prefect/flows.py:404:68: error[unresolved-attribute] Object of type `(**P@Flow) -> R@Flow` has no attribute `__name__`
+ src/prefect/flows.py:404:68: error[unresolved-attribute] Object of type `((**P@Flow) -> R@Flow) & ((*args: object, **kwargs: object) -> object)` has no attribute `__name__`
+ src/prefect/flows.py:1750:53: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- src/prefect/utilities/templating.py:320:13: error[invalid-assignment] Invalid subscript assignment with key of type `object` and value of type `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements` on object of type `dict[str, Any]`
+ src/prefect/utilities/templating.py:320:13: error[invalid-assignment] Invalid subscript assignment with key of type `object` and value of type `T@resolve_block_document_references | dict[str, Any]` on object of type `dict[str, Any]`
- src/prefect/utilities/templating.py:323:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_block_document_references | dict[str, Any]`, found `list[T@resolve_block_document_references | dict[str, Any] | str | ... omitted 5 union elements]`
+ src/prefect/utilities/templating.py:323:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_block_document_references | dict[str, Any]`, found `list[T@resolve_block_document_references | dict[str, Any] | Unknown]`
- src/prefect/utilities/templating.py:437:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `dict[object, T@resolve_variables | str | int | ... omitted 5 union elements]`
+ src/prefect/utilities/templating.py:437:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `dict[object, T@resolve_variables | Unknown]`
- src/prefect/utilities/templating.py:442:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `list[T@resolve_variables | str | int | ... omitted 5 union elements]`
+ src/prefect/utilities/templating.py:442:16: error[invalid-return-type] Return type does not match returned value: expected `T@resolve_variables`, found `list[T@resolve_variables | Unknown]`
- src/prefect/workers/base.py:232:13: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any] | str | ... omitted 4 union elements`
+ src/prefect/workers/base.py:232:13: error[invalid-argument-type] Argument is incorrect: Expected `T@resolve_variables`, found `T@resolve_block_document_references | dict[str, Any]`
- src/prefect/workers/base.py:234:20: error[invalid-argument-type] Argument expression after ** must be a mapping type: Found `T@resolve_variables | str | int | ... omitted 4 union elements`
+ src/prefect/workers/base.py:234:20: error[invalid-argument-type] Argument expression after ** must be a mapping type: Found `T@resolve_variables`
- Found 5369 diagnostics
+ Found 5364 diagnostics

static-frame (https://github.com/static-frame/static-frame)
- static_frame/core/index.py:580:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemLocReduces[TVContainer_co@loc, TVDtype@Index]`, found `InterGetItemLocReduces[Any | Bottom[Series[Any, Any]], TVDtype@Index]`
+ static_frame/core/index.py:580:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemLocReduces[TVContainer_co@loc, TVDtype@Index]`, found `InterGetItemLocReduces[Bottom[Series[Any, Any]] | Any, TVDtype@Index]`
- static_frame/core/node_selector.py:526:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemLocReduces[TVContainer_co@InterfaceSelectQuartet, Any]`, found `InterGetItemLocReduces[Unknown | Bottom[Series[Any, Any]], Any]`
+ static_frame/core/node_selector.py:526:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemLocReduces[TVContainer_co@InterfaceSelectQuartet, Any]`, found `InterGetItemLocReduces[Bottom[Series[Any, Any]] | Unknown, Any]`
- 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] | Bottom[Index[Any]] | TypeBlocks | ... omitted 6 union elements, TVDtype@Series]`
+ 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] | Bottom[Index[Any]] | ndarray[Never, Never] | ... omitted 6 union elements, TVDtype@Series]`

rotki (https://github.com/rotki/rotki)
+ rotkehlchen/chain/decoding/tools.py:96:44: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- rotkehlchen/chain/decoding/tools.py:97:13: error[invalid-argument-type] Argument to function `decode_transfer_direction` is incorrect: Expected `BTCAddress | ChecksumAddress | SubstrateAddress | SolanaAddress`, found `A@BaseDecoderTools`
+ rotkehlchen/chain/decoding/tools.py:99:13: error[invalid-argument-type] Argument to function `decode_transfer_direction` is incorrect: Expected `Sequence[A@BaseDecoderTools]`, found `Unknown | tuple[BTCAddress, ...] | tuple[ChecksumAddress, ...] | tuple[SubstrateAddress, ...] | tuple[SolanaAddress, ...]`
- rotkehlchen/chain/decoding/tools.py:98:13: error[invalid-argument-type] Argument to function `decode_transfer_direction` is incorrect: Expected `BTCAddress | ChecksumAddress | SubstrateAddress | SolanaAddress | None`, found `A@BaseDecoderTools | None`
+ rotkehlchen/chain/decoding/tools.py:100:62: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- Found 2056 diagnostics
+ Found 2057 diagnostics

core (https://github.com/home-assistant/core)
+ homeassistant/util/variance.py:47:12: error[invalid-return-type] Return type does not match returned value: expected `(**_P@ignore_variance) -> _R@ignore_variance`, found `_Wrapped[_P@ignore_variance, _R@ignore_variance | int | float | datetime, _P@ignore_variance, _R@ignore_variance | int | float | datetime]`
- Found 14505 diagnostics
+ Found 14506 diagnostics

Memory usage changes were detected when running on open source projects
trio (https://github.com/python-trio/trio)
-     struct fields = ~12MB
+     struct fields = ~11MB

@charliermarsh charliermarsh force-pushed the charlie/dyn-diag branch 2 times, most recently from 55cf50a to 8e6b92a Compare January 11, 2026 04:41
@charliermarsh charliermarsh marked this pull request as ready for review January 11, 2026 14:27
@charliermarsh charliermarsh force-pushed the charlie/dyn branch 4 times, most recently from 05c1afb to 5a177bb Compare January 12, 2026 17:08
@charliermarsh
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Do you mean, exclusively for the protocol case? (As opposed to, e.g., inheriting from enums?) Since that one is a limitation?

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(Actually not sure if we're supposed to support final as a non-decorator, doing some research.)

@charliermarsh charliermarsh marked this pull request as ready for review January 13, 2026 16:51
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My read of https://typing.python.org/en/latest/spec/qualifiers.html is that final is only intended to work as a decorator, and not via final(type(...)). Other type checkers don't enforce that either. So I omitted final support.

```py
from typing import final

FinalClass = final(type("FinalClass", (), {}))
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can we therefore emit a diagnostic here warning the user that this has no effect? I don't like silently doing nothing in a case where the user probably expects us to do something 😄

This can be a followup.

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Will do. I think that should fire for "static" classes too.

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yeah, that makes sense.

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nice, a few more minor nits

@charliermarsh charliermarsh force-pushed the charlie/dyn-expression branch from e7f60c2 to a94d0ed Compare January 14, 2026 13:38
Base automatically changed from charlie/dyn-expression to main January 14, 2026 13:48
@charliermarsh charliermarsh merged commit e41f045 into main Jan 14, 2026
48 checks passed
@charliermarsh charliermarsh deleted the charlie/dyn-diag branch January 14, 2026 13:56
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