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[ty] Assume 3-argument form for variadics in type(...)#22502

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[ty] Assume 3-argument form for variadics in type(...)#22502
charliermarsh wants to merge 3 commits intomainfrom
charlie/dyn-overload

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@charliermarsh charliermarsh commented Jan 11, 2026 •
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Summary

When we see a call like type("Foo", *args, **kwargs), the overload resolution may assume the single-argument form, even though the user likely intended the 3-argument class-creation form. We now "manually" fall back to the three-argument form. Same goes for "incorrect" calls that pass more than one argument.

@charliermarsh charliermarsh added the ty Multi-file analysis & type inference label Jan 11, 2026
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astral-sh-bot bot commented Jan 11, 2026 •
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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 11, 2026 •
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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 | _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`

pydantic (https://github.com/pydantic/pydantic)
- pydantic/fields.py:943:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
+ pydantic/fields.py:943:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
- pydantic/fields.py:983:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
+ pydantic/fields.py:983:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
- pydantic/fields.py:1026:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
+ pydantic/fields.py:1026:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
- pydantic/fields.py:1066:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
+ pydantic/fields.py:1066:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
- pydantic/fields.py:1109:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
+ pydantic/fields.py:1109:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
- pydantic/fields.py:1148:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
+ pydantic/fields.py:1148:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
- pydantic/fields.py:1188:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`
+ pydantic/fields.py:1188:5: error[invalid-parameter-default] Default value of type `PydanticUndefinedType` is not assignable to annotated parameter type `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`
- pydantic/fields.py:1567:13: error[invalid-argument-type] Argument is incorrect: Expected `dict[str, int | float | str | ... omitted 3 union elements] | ((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) | None`, found `Top[dict[Unknown, Unknown]] | (((dict[str, int | float | str | ... omitted 3 union elements], /) -> None) & ~Top[dict[Unknown, Unknown]]) | None`
+ pydantic/fields.py:1567:13: error[invalid-argument-type] Argument is incorrect: Expected `dict[str, Divergent] | ((dict[str, Divergent], /) -> None) | None`, found `Top[dict[Unknown, Unknown]] | (((dict[str, Divergent], /) -> None) & ~Top[dict[Unknown, Unknown]]) | None`

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

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]`

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: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:100:62: 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:98:13: error[invalid-argument-type] Argument to function `decode_transfer_direction` is incorrect: Expected `BTCAddress | ChecksumAddress | SubstrateAddress | SolanaAddress | None`, found `A@BaseDecoderTools | None`
- Found 2059 diagnostics
+ Found 2058 diagnostics

No memory usage changes detected ✅

@charliermarsh
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charliermarsh commented Jan 11, 2026

(Also exploring whether we can change this in overload handling directly.)

@charliermarsh charliermarsh force-pushed the charlie/dyn branch 6 times, most recently from 8df0d85 to dd2fbb3 Compare January 12, 2026 20:08
Base automatically changed from charlie/dyn to main January 12, 2026 20:20
@charliermarsh charliermarsh force-pushed the charlie/dyn-overload branch 2 times, most recently from 18c00ee to 6ff1857 Compare January 12, 2026 20:54
@charliermarsh charliermarsh changed the base branch from main to charlie/dyn-expression January 12, 2026 20:54
@charliermarsh charliermarsh marked this pull request as ready for review January 12, 2026 20:54
@charliermarsh charliermarsh force-pushed the charlie/dyn-expression branch 2 times, most recently from 17aa09f to 56b1d6f Compare January 13, 2026 02:23
@AlexWaygood

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@charliermarsh charliermarsh marked this pull request as draft January 13, 2026 14:20
@charliermarsh charliermarsh force-pushed the charlie/dyn-expression branch from 56b1d6f to fbd2949 Compare January 13, 2026 14:21
@charliermarsh charliermarsh force-pushed the charlie/dyn-expression branch from fbd2949 to 3bf7fa3 Compare January 13, 2026 14:32
@charliermarsh charliermarsh force-pushed the charlie/dyn-expression branch from 3bf7fa3 to e7f60c2 Compare January 13, 2026 16:23
@charliermarsh charliermarsh marked this pull request as ready for review January 13, 2026 16:31
ibraheemdev
ibraheemdev approved these changes Jan 14, 2026
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This makes sense to me.

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AlexWaygood commented Jan 14, 2026

This makes sense to me too but -- given that both overloads are now heavily special-cased -- I think we can both simplify our code and improve error messages for our users if we just handle both overloads at the same time. Something like #22569?

@AlexWaygood AlexWaygood mentioned this pull request Jan 14, 2026
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@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
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@ibraheemdev ibraheemdev ibraheemdev approved these changes

@carljm carljm Awaiting requested review from carljm carljm is a code owner

@AlexWaygood AlexWaygood Awaiting requested review from AlexWaygood AlexWaygood is a code owner

@sharkdp sharkdp Awaiting requested review from sharkdp sharkdp is a code owner

@dcreager dcreager Awaiting requested review from dcreager dcreager is a code owner

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