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[ty] Infer precise types for isinstance(…) calls involving typevars #21999

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sharkdp merged 1 commit into from
Dec 16, 2025
Merged

[ty] Infer precise types for isinstance(…) calls involving typevars #21999

sharkdp merged 1 commit into from
Dec 16, 2025

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@sharkdp sharkdp commented Dec 16, 2025 •
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Summary

Infer Literal[True] for isinstance(x, C) calls when x: T and T has a bound B that satisfies the isinstance check against C. Similar for constrained typevars.

closes astral-sh/ty#1895

Test Plan

  • New Markdown tests
  • Verified the the example in the linked ticket checks without errors

@sharkdp sharkdp requested a review from carljm as a code owner December 16, 2025 09:23
@sharkdp sharkdp added the ty Multi-file analysis & type inference label Dec 16, 2025
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astral-sh-bot bot commented Dec 16, 2025

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 Dec 16, 2025

mypy_primer results

Changes were detected when running on open source projects 
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 42 diagnostics
+ Found 41 diagnostics

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`

No memory usage changes detected ✅

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@sharkdp sharkdp merged commit 2acf1cc into main Dec 16, 2025
42 checks passed
@sharkdp sharkdp deleted the david/fix-1895 branch December 16, 2025 09:34
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dcreager added a commit that referenced this pull request Dec 16, 2025
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Merge branch 'main' into dcreager/callable-return
75b8516 
* main:
  [ty] Document `TY_CONFIG_FILE` (#22001)
  [ty] Cache `KnownClass::to_class_literal` (#22000)
  [ty] Fix benchmark assertion (#22003)
  Add uv and ty to the Ruff README (#21996)
  [ty] Infer precise types for `isinstance(…)` calls involving typevars (#21999)
  [ty] Use `FxHashMap` in `Signature::has_relation_to` (#21997)
  [ty] Avoid enforcing standalone expression for tests in f-strings (#21967)
  [ty] Use `title` for configuration code fences in ty reference documentation (#21992)
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@AlexWaygood AlexWaygood AlexWaygood approved these changes

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

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

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Self revealed as Never yet invalid-return-type error is reported

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