[ty] Fix structural pattern binding inference by charliermarsh · Pull Request #26411 · astral-sh/ruff

charliermarsh · 2026-06-26T16:36:35Z

Summary

Follow-up to #25941 and prerequisite for #25942.

The earlier PR extended successful-pattern binding inference to class and mapping patterns. This PR fixes edge cases in that analysis before the same structural machinery is reused for subject narrowing.

from typing import Literal

class IntPayload:
    tag: Literal["int"]
    payload: int

class StrPayload:
    tag: Literal["str"]
    payload: str

def handle(
    value: object,
    Pattern: type[IntPayload] | type[StrPayload],
) -> None:
    match value:
        case Pattern(tag="int", payload=item):
            reveal_type(item)  # int

Union-valued class expressions are now analyzed one class at a time, so a discriminating child pattern also selects the corresponding member types. Generic class patterns preserve specializations known from the subject, while unrelated non-final classes retain member types that can overlap through multiple inheritance. Runtime class matching uses an unknown specialization rather than a type-parameter default.

Mapping entries are extracted after the successful pattern has established the mapping interface, which keeps fully static object subjects from introducing Unknown. Later or-pattern alternatives use mutation-safe fallthrough types, so a failed sequence alternative does not leave stale shape constraints on a value captured by another alternative.

astral-sh-bot · 2026-06-26T16:38:34Z

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 94.47%. The percentage of expected errors that received a diagnostic held steady at 89.19%. The number of fully passing files held steady at 95/134.

astral-sh-bot · 2026-06-26T16:39:00Z

Memory usage report

Memory usage unchanged ✅

astral-sh-bot · 2026-06-26T16:40:17Z

`ecosystem-analyzer` results

Lint rule	Added	Removed	Changed
`invalid-argument-type`	25	0	0
`not-iterable`	5	0	0
`unresolved-attribute`	2	0	1
`invalid-return-type`	1	0	0
`type-assertion-failure`	0	1	0
Total	33	1	1

Flaky changes detected. This PR summary excludes flaky changes; see the HTML report for details.

Raw diff (35 changes)

egglog-python (https://github.com/egraphs-good/egglog-python)
- python/egglog/egraph_state.py:623:25 error[type-assertion-failure] Type `Value` is not equivalent to `Never`
+ python/egglog/egraph_state.py:150:45 error[unresolved-attribute] Attribute `id` is not defined on `None` in union `BackOffDecl | None`
+ python/egglog/thunk.py:59:24 error[invalid-return-type] Return type does not match returned value: expected `T@__call__`, found `object`

jax (https://github.com/google/jax)
+ jax/experimental/mosaic/gpu/constraints.py:638:44 error[invalid-argument-type] Argument to bound method `IsTransferableTmemRegisters.is_valid_tmem_transfer` is incorrect: Expected `TMEMLayout`, found `TiledLayout | WGSplatFragLayout | WGStridedFragLayout`
+ jax/experimental/mosaic/gpu/constraints.py:640:44 error[invalid-argument-type] Argument to bound method `IsTransferableTmemRegisters.is_valid_tmem_transfer` is incorrect: Expected `TMEMLayout`, found `TiledLayout | WGSplatFragLayout | WGStridedFragLayout`
+ jax/experimental/mosaic/gpu/constraints.py:823:18 error[unresolved-attribute] Attribute `base_tile_shape` is not defined on `WGSplatFragLayout`, `WGStridedFragLayout` in union `WGSplatFragLayout | WGStridedFragLayout | TiledLayout`

pylint (https://github.com/pycqa/pylint)
- pylint/checkers/classes/class_checker.py:946:54 error[unresolved-attribute] Attribute `name` is not defined on `NodeNG` in union `NodeNG | UninferableBase | Proxy`
+ pylint/checkers/classes/class_checker.py:946:54 error[unresolved-attribute] Attribute `name` is not defined on `NodeNG` in union `NodeNG | UninferableBase | Proxy | Any`

schema_salad (https://github.com/common-workflow-language/schema_salad)
+ src/schema_salad/dotnet_codegen.py:428:38 error[invalid-argument-type] Argument to bound method `DotNetCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/dotnet_codegen.py:438:38 error[invalid-argument-type] Argument to bound method `DotNetCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/dotnet_codegen.py:482:46 error[invalid-argument-type] Argument to function `DotNetCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/dotnet_codegen.py:491:59 error[not-iterable] Object of type `object` is not iterable
+ src/schema_salad/java_codegen.py:432:38 error[invalid-argument-type] Argument to bound method `JavaCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/java_codegen.py:449:38 error[invalid-argument-type] Argument to bound method `JavaCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/java_codegen.py:476:60 error[invalid-argument-type] Argument to function `JavaCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/java_codegen.py:479:54 error[invalid-argument-type] Argument to function `JavaCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/java_codegen.py:480:45 error[invalid-argument-type] Argument to function `JavaCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/java_codegen.py:501:46 error[invalid-argument-type] Argument to function `JavaCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/java_codegen.py:510:53 error[not-iterable] Object of type `object` is not iterable
+ src/schema_salad/python_codegen.py:394:46 error[invalid-argument-type] Argument to bound method `PythonCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/python_codegen.py:402:46 error[invalid-argument-type] Argument to bound method `PythonCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/python_codegen.py:427:28 error[not-iterable] Object of type `object` is not iterable
+ src/schema_salad/python_codegen.py:440:40 error[invalid-argument-type] Argument to function `PythonCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/python_codegen.py:442:80 error[not-iterable] Object of type `object` is not iterable
+ src/schema_salad/python_codegen.py:443:44 error[invalid-argument-type] Argument to function `PythonCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/python_codegen.py:452:40 error[invalid-argument-type] Argument to function `PythonCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/python_codegen.py:454:44 error[invalid-argument-type] Argument to function `PythonCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/python_codegen.py:468:46 error[invalid-argument-type] Argument to function `PythonCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/python_codegen.py:472:74 error[invalid-argument-type] Argument to bound method `PythonCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/typescript_codegen.py:364:46 error[invalid-argument-type] Argument to bound method `TypeScriptCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/typescript_codegen.py:373:46 error[invalid-argument-type] Argument to bound method `TypeScriptCodeGen.type_loader` is incorrect: Expected `list[Any] | dict[str, Any] | str`, found `object`
+ src/schema_salad/typescript_codegen.py:397:40 error[invalid-argument-type] Argument to function `TypeScriptCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/typescript_codegen.py:399:44 error[invalid-argument-type] Argument to function `TypeScriptCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/typescript_codegen.py:407:68 error[invalid-argument-type] Argument to function `TypeScriptCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/typescript_codegen.py:417:53 error[invalid-argument-type] Argument to function `TypeScriptCodeGen.safe_name` is incorrect: Expected `str`, found `object`
+ src/schema_salad/typescript_codegen.py:425:67 error[not-iterable] Object of type `object` is not iterable

Full report with detailed diff (timing results)

dhruvmanila

Looks good 👍

## Summary #25941 and #26411 added support for inferring the types of names bound by structural patterns, e.g., `value` in `case {"tag": "int", "value": value}`. This PR uses the same pattern analysis to narrow the match subject itself, e.g., `payload` in `match payload`: ```python from typing import Literal, TypedDict class IntPayload(TypedDict): tag: Literal["int"] value: int class StrPayload(TypedDict): tag: Literal["str"] value: str def handle(payload: IntPayload | StrPayload) -> None: match payload: case {"tag": "int", "value": value}: reveal_type(value) # int reveal_type(payload) # IntPayload ``` We analyze each possible subject type against the complete nested class, mapping, sequence, or `or` pattern, then keep the types that can match.

astral-sh-bot Bot added the ty Multi-file analysis & type inference label Jun 26, 2026

charliermarsh mentioned this pull request Jun 26, 2026

[ty] Narrow match subjects through structural patterns #25942

Merged

charliermarsh force-pushed the charlie/match-pattern-binding-followups branch from c6b372a to d7d7719 Compare June 26, 2026 18:50

[ty] Preserve generic members in overlapping patterns

336fdc2

charliermarsh force-pushed the charlie/match-pattern-binding-followups branch from d7d7719 to 5762cc5 Compare June 26, 2026 19:22

charliermarsh added 10 commits June 26, 2026 15:24

[ty] Preserve generic base pattern specialization

9b39133

[ty] Split union-valued class patterns

4f9f2f6

[ty] Extract mapping entries from narrowed subjects

fa94140

[ty] Preserve direct generic pattern members

86bb156

[ty] Avoid stale sequence facts in OR bindings

dd81a3a

[ty] Preserve default generic overlap members

dc572a9

[ty] Preserve compatible overlapping class members

df8aa85

[ty] Ignore generic defaults in class patterns

abff86d

[ty] Simplify generic pattern member lookup

dc49340

[ty] Clarify match pattern binding analysis

8335c7e

charliermarsh force-pushed the charlie/match-pattern-binding-followups branch from 5762cc5 to 8335c7e Compare June 26, 2026 19:27

charliermarsh mentioned this pull request Jun 26, 2026

[ty] Infer generic class pattern specializations #26420

Closed

charliermarsh requested a review from dhruvmanila June 26, 2026 20:01

charliermarsh marked this pull request as ready for review June 26, 2026 20:01

charliermarsh requested a review from a team as a code owner June 26, 2026 20:01

charliermarsh merged commit a582555 into main Jun 26, 2026
62 checks passed

charliermarsh deleted the charlie/match-pattern-binding-followups branch June 26, 2026 20:01

charliermarsh mentioned this pull request Jun 30, 2026

Generic type parameters not propagated to names bound in match class patterns astral-sh/ty#3879

Closed

dhruvmanila reviewed Jul 7, 2026

View reviewed changes

ShigureNyako mentioned this pull request Jul 11, 2026

⬆️ deps: Update Python dev dependencies ShigureLab/watchfs#87

Merged

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[ty] Fix structural pattern binding inference - #26411

[ty] Fix structural pattern binding inference#26411
charliermarsh merged 11 commits into
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charlie/match-pattern-binding-followups

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charliermarsh commented Jun 26, 2026 •

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