[ty] disallow type variables within type variable bounds/constraints

[mtshiba]

Summary

This PR resolves https://github.com/astral-sh/ty/issues/1839.

Test Plan

mdtests updated

[astral-sh-bot[bot]]

Diagnostic diff on typing conformance tests

Changes were detected when running ty on typing conformance tests

--- old-output.txt	2025-12-23 21:37:03.629255814 +0000
+++ new-output.txt	2025-12-23 21:37:05.796265312 +0000
@@ -586,6 +586,8 @@
 generics_syntax_infer_variance.py:154:38: error[invalid-assignment] Object of type `ShouldBeInvariant5[int]` is not assignable to `ShouldBeInvariant5[int | float]`
 generics_syntax_infer_variance.py:165:45: error[invalid-assignment] Object of type `ShouldBeContravariant1[int]` is not assignable to `ShouldBeContravariant1[int | float]`
 generics_syntax_infer_variance.py:166:43: error[invalid-assignment] Object of type `ShouldBeContravariant1[int | float]` is not assignable to `ShouldBeContravariant1[int]`
+generics_syntax_scoping.py:14:20: error[invalid-type-variable-bound] Type variable bound type cannot be generic
+generics_syntax_scoping.py:18:17: error[invalid-type-variable-bound] Type variable bound type cannot be generic
 generics_syntax_scoping.py:35:7: error[unresolved-reference] Name `T` used when not defined
 generics_syntax_scoping.py:40:23: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `((**P@decorator1) -> R@decorator1, /) -> (**P@decorator1) -> R@decorator1`
 generics_syntax_scoping.py:44:17: error[unresolved-reference] Name `T` used when not defined
@@ -1033,4 +1035,4 @@
 typeddicts_usage.py:28:17: error[missing-typed-dict-key] Missing required key 'name' in TypedDict `Movie` constructor
 typeddicts_usage.py:28:18: error[invalid-key] Unknown key "title" for TypedDict `Movie`: Unknown key "title"
 typeddicts_usage.py:40:24: error[invalid-type-form] The special form `typing.TypedDict` is not allowed in type expressions
-Found 1035 diagnostics
+Found 1037 diagnostics

[astral-sh-bot[bot]]

mypy_primer results

Changes were detected when running on open source projects

websockets (https://github.com/aaugustin/websockets)
+ src/websockets/sync/client.py:553:18: error[invalid-type-variable-bound] Type variable bound type cannot be generic
- Found 44 diagnostics
+ Found 45 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`

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 `Coroutine[Any, Any, _T@cached_inject | Coroutine[Any, Any, _T@cached_inject]] | _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 `_T@cached_inject | Coroutine[Any, Any, _T@cached_inject | Coroutine[Any, Any, _T@cached_inject]]`

xarray (https://github.com/pydata/xarray)
- xarray/core/dataarray.py:5744:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `DataArray | Dataset`
+ xarray/core/dataarray.py:5744:16: 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:8873:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `DataArray | Dataset`
+ xarray/core/dataset.py:8873:16: error[invalid-return-type] Return type does not match returned value: expected `T_Xarray@map_blocks`, found `T_Xarray@map_blocks | DataArray | Dataset`

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

ibis (https://github.com/ibis-project/ibis)
+ ibis/util.py:36:18: error[invalid-type-variable-bound] Type variable bound type cannot be generic
- Found 4608 diagnostics
+ Found 4609 diagnostics

scikit-learn (https://github.com/scikit-learn/scikit-learn)
- sklearn/externals/array_api_extra/_lib/_at.py:300:17: warning[possibly-missing-attribute] Attribute `dtype` may be missing on object of type `int | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...] | slice[Any, Any, Any] | EllipsisType`
+ sklearn/externals/array_api_extra/_lib/_at.py:300:17: warning[possibly-missing-attribute] Attribute `dtype` may be missing on object of type `int | slice[Any, Any, Any] | EllipsisType | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...]`
- sklearn/externals/array_api_extra/_lib/_at.py:301:17: warning[possibly-missing-attribute] Attribute `shape` may be missing on object of type `int | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...] | slice[Any, Any, Any] | EllipsisType`
+ sklearn/externals/array_api_extra/_lib/_at.py:301:17: warning[possibly-missing-attribute] Attribute `shape` may be missing on object of type `int | slice[Any, Any, Any] | EllipsisType | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...]`
- sklearn/externals/array_api_extra/_lib/_at.py:308:25: error[invalid-argument-type] Argument to function `apply_where` is incorrect: Expected `Array`, found `int | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...] | slice[Any, Any, Any] | EllipsisType`
+ sklearn/externals/array_api_extra/_lib/_at.py:308:25: error[invalid-argument-type] Argument to function `apply_where` is incorrect: Expected `Array`, found `int | slice[Any, Any, Any] | EllipsisType | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...]`

jax (https://github.com/google/jax)
- jax/_src/tree_util.py:302:31: error[invalid-argument-type] Argument to bound method `register_node` is incorrect: Expected `(Hashable, Iterable[object], /) -> T@register_pytree_node`, found `(_AuxData@register_pytree_node, _Children@register_pytree_node, /) -> T@register_pytree_node`
- jax/_src/tree_util.py:305:31: error[invalid-argument-type] Argument to bound method `register_node` is incorrect: Expected `(Hashable, Iterable[object], /) -> T@register_pytree_node`, found `(_AuxData@register_pytree_node, _Children@register_pytree_node, /) -> T@register_pytree_node`
- jax/_src/tree_util.py:308:31: error[invalid-argument-type] Argument to bound method `register_node` is incorrect: Expected `(Hashable, Iterable[object], /) -> T@register_pytree_node`, found `(_AuxData@register_pytree_node, _Children@register_pytree_node, /) -> T@register_pytree_node`
- Found 2806 diagnostics
+ Found 2803 diagnostics

static-frame (https://github.com/static-frame/static-frame)
- static_frame/core/bus.py:671:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemLocReduces[Bus[Any], object_]`, found `InterGetItemLocReduces[Top[Index[Any]] | Top[Series[Any, Any]] | TypeBlocks | ... omitted 6 union elements, object_]`
+ static_frame/core/bus.py:671:16: error[invalid-return-type] Return type does not match returned value: expected `InterGetItemLocReduces[Bus[Any], object_]`, found `InterGetItemLocReduces[Top[Bus[Any]] | TypeBlocks | Batch | ... omitted 6 union elements, object_]`
+ static_frame/core/node_selector.py:92:5: error[invalid-type-variable-bound] Type variable bound type cannot be generic
+ static_frame/core/node_selector.py:96:5: error[invalid-type-variable-bound] Type variable bound type cannot be generic
- 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[Top[Index[Any]] | TypeBlocks | Top[Bus[Any]] | ... omitted 6 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[Top[Yarn[Any]] | TypeBlocks | Batch | ... omitted 6 union elements, generic[object]]`
- Found 1849 diagnostics
+ Found 1851 diagnostics

pandas-stubs (https://github.com/pandas-dev/pandas-stubs)
- pandas-stubs/_typing.pyi:1232:16: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- Found 5107 diagnostics
+ Found 5106 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 14413 diagnostics
+ Found 14412 diagnostics

scipy (https://github.com/scipy/scipy)
- scipy/_lib/array_api_extra/src/array_api_extra/_lib/_at.py:300:17: warning[possibly-missing-attribute] Attribute `dtype` may be missing on object of type `int | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...] | slice[Any, Any, Any] | EllipsisType`
+ scipy/_lib/array_api_extra/src/array_api_extra/_lib/_at.py:300:17: warning[possibly-missing-attribute] Attribute `dtype` may be missing on object of type `int | slice[Any, Any, Any] | EllipsisType | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...]`
- scipy/_lib/array_api_extra/src/array_api_extra/_lib/_at.py:301:17: warning[possibly-missing-attribute] Attribute `shape` may be missing on object of type `int | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...] | slice[Any, Any, Any] | EllipsisType`
+ scipy/_lib/array_api_extra/src/array_api_extra/_lib/_at.py:301:17: warning[possibly-missing-attribute] Attribute `shape` may be missing on object of type `int | slice[Any, Any, Any] | EllipsisType | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...]`
- scipy/_lib/array_api_extra/src/array_api_extra/_lib/_at.py:308:25: error[invalid-argument-type] Argument to function `apply_where` is incorrect: Expected `Array`, found `int | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...] | slice[Any, Any, Any] | EllipsisType`
+ scipy/_lib/array_api_extra/src/array_api_extra/_lib/_at.py:308:25: error[invalid-argument-type] Argument to function `apply_where` is incorrect: Expected `Array`, found `int | slice[Any, Any, Any] | EllipsisType | Array | tuple[int | slice[Any, Any, Any] | EllipsisType | Array, ...]`

No memory usage changes detected ✅

[mtshiba]

Probably unrelated to this PR, but the error messages in pydantic seem to change non-deterministically.

https://github.com/astral-sh/ruff/actions/runs/20226483261/job/58059016262?pr=21984

[astral-sh-bot[bot]]

ecosystem-analyzer results

Lint rule	Added	Removed	Changed
invalid-return-type	0	1	4
invalid-argument-type	0	3	1
invalid-type-variable-bound	4	0	0
Total	4	4	5

Full report with detailed diff (timing results)

[carljm]

Probably unrelated to this PR, but the error messages in pydantic seem to change non-deterministically.

https://github.com/astral-sh/ruff/actions/runs/20226483261/job/58059016262?pr=21984

Yes, unfortunately this non-determinism in the error messages in some projects (and occasionally non-determinism of the presence/absence of a few diagnostics also) was introduced with the Divergent PR.

[carljm]

I rebased on main, but it seems that some other recent change in main means that we no longer emit the diagnostics for typevars with self-referential bounds/constraints.