[alexander-beedie]

Summary

Fixes #3587.

Overview

A caller of a function does not have to pass its positional-or-keyword parameters positionally - it can pass any prefix positionally, and the rest by name.

When checking whether got is assignable to want, only the one mapping where every such parameter of want is passed positionally was checked (which also requires the two signatures to agree on parameter names), so callables that satisfy want under a different mapping were rejected.

Solution

• Treat the parameter list check as a question about all of want's calling conventions rather than just one of them.

• If the as-written mapping fails, is_subset_param_list retries the check once per split, moving the positional/by-name boundary one parameter to the right each time, and accepts only if every split is assignable.

• Because Python forbids positional arguments after keyword arguments, the splits are a prefix chain, so there are only n+1 of them (rather than 2^n).

• The retry only runs when the as-written mapping fails and the comparison is not gradual, so accepting comparisons cost what they did before, and the splits speculatively pin type variables, so they run inside Solver::with_snapshot and roll back on failure 👍

Test Plan

• Existing unit tests all pass.
• Added 6-7 more tests (including the example given in the original Issue).

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D116281213. (Because this pull request was imported automatically, there will not be any future comments.)

[alexander-beedie]

Rebased/resolved 👍

[alexander-beedie]

@samwgoldman - rebased/resolved again :)
(and added an extra test, covering a duplicate-argument acceptance case) 👌

[codspeed]

Merging this PR will not alter performance

✅ 35 untouched benchmarks
⏩ 9 skipped benchmarks¹

---

_{Comparing alexander-beedie:non-constant-param-mapping (6bb93c6) with main (0e44796)}

Footnotes

1. 9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

============================================================
SUMMARY
============================================================
Total: +2 new errors, -43 fixed errors
By preset: +2/-43 (default), +2/-43 (strict)

Projects with changes (9):
  openlibrary: +0 -1
  spark: +0 -14
  scipy: +1 -0
  django-stubs: +0 -16
  hydra-zen: +0 -2
  ibis: +0 -1
  static-frame: +0 -4
  werkzeug: +0 -4
  xarray: +1 -1
============================================================

FULL DIFF DETAILS
------------------------------------------------------------

openlibrary (https://github.com/internetarchive/openlibrary)
- ERROR openlibrary/core/models.py:1052:9-28: Class member `User._get_lists_uncached` overrides parent class `Thing` in an inconsistent manner [bad-override]

spark (https://github.com/apache/spark)
- ERROR python/pyspark/sql/classic/dataframe.py:2078:9-16: Implementation signature `(self: Self@DataFrameNaFunctions, to_replace: dict[Unknown, Unknown] | list[Unknown], value: list[Unknown] | Unknown | None = ..., subset: list[str] | None = None) -> Unknown` does not accept all arguments that overload signature `(self: Self@DataFrameNaFunctions, to_replace: dict[Unknown, Unknown], subset: list[str] | None = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/context.py:369:9-24: Implementation signature `(self: Self@SQLContext, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SQLContext, data: Iterable[Unknown] | Unknown, schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/context.py:380:9-24: Implementation signature `(self: Self@SQLContext, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SQLContext, data: Unknown, samplingRatio: float | None = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/context.py:385:9-24: Implementation signature `(self: Self@SQLContext, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SQLContext, data: Unknown, schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/pandas/conversion.py:570:9-24: Implementation signature `(self: Self@SparkConversionMixin, data: Unknown, schema: list[str] | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkConversionMixin, data: Unknown, samplingRatio: float | None = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/pandas/conversion.py:575:9-24: Implementation signature `(self: Self@SparkConversionMixin, data: Unknown, schema: list[str] | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkConversionMixin, data: Unknown, samplingRatio: float | None = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/pandas/conversion.py:580:9-24: Implementation signature `(self: Self@SparkConversionMixin, data: Unknown, schema: list[str] | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkConversionMixin, data: Unknown, schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/pandas/conversion.py:588:9-24: Implementation signature `(self: Self@SparkConversionMixin, data: Unknown, schema: list[str] | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkConversionMixin, data: Unknown, schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/session.py:1386:9-24: Implementation signature `(self: Self@SparkSession, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkSession, data: Unknown, schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/session.py:1394:9-24: Implementation signature `(self: Self@SparkSession, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkSession, data: Iterable[Unknown], schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/session.py:1402:9-24: Implementation signature `(self: Self@SparkSession, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkSession, data: Unknown, samplingRatio: float | None = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/session.py:1407:9-24: Implementation signature `(self: Self@SparkSession, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkSession, data: Unknown, samplingRatio: float | None = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/session.py:1412:9-24: Implementation signature `(self: Self@SparkSession, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkSession, data: Unknown, schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]
- ERROR python/pyspark/sql/session.py:1420:9-24: Implementation signature `(self: Self@SparkSession, data: Iterable[Any] | Unknown, schema: str | Unknown | None = None, samplingRatio: float | None = None, verifySchema: bool = True) -> Unknown` does not accept all arguments that overload signature `(self: Self@SparkSession, data: Unknown, schema: str | Unknown, verifySchema: bool = ...) -> Unknown` accepts [inconsistent-overload]

scipy (https://github.com/scipy/scipy)
+ ERROR scipy/integrate/_quad_vec.py:25:9-15: Class member `LRUDict.update` overrides parent class `OrderedDict` in an inconsistent manner [bad-override]

django-stubs (https://github.com/typeddjango/django-stubs)
- ERROR django-stubs/test/client.pyi:291:9-12: Class member `Client.get` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:303:9-13: Class member `Client.post` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:316:9-13: Class member `Client.head` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:328:9-16: Class member `Client.options` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:341:9-12: Class member `Client.put` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:354:9-14: Class member `Client.patch` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:367:9-15: Class member `Client.delete` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:380:9-14: Class member `Client.trace` overrides parent class `_RequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:410:15-18: Class member `AsyncClient.get` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:422:15-19: Class member `AsyncClient.post` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:435:15-19: Class member `AsyncClient.head` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:447:15-22: Class member `AsyncClient.options` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:460:15-18: Class member `AsyncClient.put` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:473:15-20: Class member `AsyncClient.patch` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:486:15-21: Class member `AsyncClient.delete` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]
- ERROR django-stubs/test/client.pyi:499:15-20: Class member `AsyncClient.trace` overrides parent class `_AsyncRequestFactory` in an inconsistent manner [bad-override]

hydra-zen (https://github.com/mit-ll-responsible-ai/hydra-zen)
- ERROR src/hydra_zen/wrapper/_implementations.py:1472:9-17: Implementation signature `(self: Self@ZenStore, __target: F | None = None, /, **kw: Any) -> F | Self@ZenStore` does not accept all arguments that overload signature `(self: Self@ZenStore, __target: F, *, name: ((F) -> str) | str = ..., group: ((F) -> GroupName) | str | None = ..., package: ((F) -> str) | str | None = ..., provider: str | None = ..., to_config: (F) -> Any = ..., **to_config_kw: Any) -> F` accepts [inconsistent-overload]
- ERROR src/hydra_zen/wrapper/_implementations.py:1485:9-17: Implementation signature `(self: Self@ZenStore, __target: F | None = None, /, **kw: Any) -> F | Self@ZenStore` does not accept all arguments that overload signature `(self: Self@ZenStore, __target: None = None, *, name: ((Any) -> str) | str = ..., group: ((Any) -> GroupName) | str | None = ..., package: ((Any) -> str) | str | None = ..., provider: str | None = ..., to_config: (Any) -> Any = ..., **to_config_kw: Any) -> Self@ZenStore` accepts [inconsistent-overload]

ibis (https://github.com/ibis-project/ibis)
- ERROR ibis/expr/api.py:856:5-14: Implementation signature `(value_or_year: Unknown, month: Unknown | None = None, day: Unknown | None = None, hour: Unknown | None = None, minute: Unknown | None = None, second: Unknown | None = None, /, timezone: Unknown | None = None) -> Scalar | Unknown` does not accept all arguments that overload signature `(value_or_year: Any, /, timezone: str | None = None) -> TimestampValue` accepts [inconsistent-overload]

static-frame (https://github.com/static-frame/static-frame)
- ERROR static_frame/core/frame.py:5343:9-17: Implementation signature `(self: Self@Frame, row_key: TILocSelector = None, column_key: TILocSelector = None) -> Any` does not accept all arguments that overload signature `(self: Self@Frame, column_key: TILocSelectorOne) -> Series` accepts [inconsistent-overload]
- ERROR static_frame/core/frame.py:5346:9-17: Implementation signature `(self: Self@Frame, row_key: TILocSelector = None, column_key: TILocSelector = None) -> Any` does not accept all arguments that overload signature `(self: Self@Frame, column_key: TILocSelectorMany) -> Self@Frame` accepts [inconsistent-overload]
- ERROR static_frame/core/type_blocks.py:3216:9-17: Implementation signature `(self: Self@TypeBlocks, row_key: TILocSelector = None, column_key: TILocSelector = None) -> Any` does not accept all arguments that overload signature `(self: Self@TypeBlocks, column_key: TILocSelectorOne) -> TypeBlocks` accepts [inconsistent-overload]
- ERROR static_frame/core/type_blocks.py:3219:9-17: Implementation signature `(self: Self@TypeBlocks, row_key: TILocSelector = None, column_key: TILocSelector = None) -> Any` does not accept all arguments that overload signature `(self: Self@TypeBlocks, column_key: TILocSelectorMany) -> TypeBlocks` accepts [inconsistent-overload]

werkzeug (https://github.com/pallets/werkzeug)
- ERROR src/werkzeug/datastructures/headers.py:122:9-12: Implementation signature `(self: Self@Headers, key: str, default: str | T | None = None, type: ((str) -> T) | None = None) -> str | T | None` does not accept all arguments that overload signature `(self: Self@Headers, key: str, type: (str) -> T) -> T | None` accepts [inconsistent-overload]
- ERROR src/werkzeug/datastructures/structures.py:75:9-12: Implementation signature `(self: Self@_TypeConversionDict, key: K, default: V | T | None = None, type: ((V) -> T) | None = None) -> V | T | None` does not accept all arguments that overload signature `(self: Self@_TypeConversionDict, key: str, type: (V) -> T) -> T | None` accepts [inconsistent-overload]
- ERROR src/werkzeug/datastructures/structures.py:270:9-12: Implementation signature `(self: Self@MultiDict, key: K, default: V | T | None = None, type: ((V) -> T) | None = None) -> V | T | None` does not accept all arguments that overload signature `(self: Self@MultiDict, key: str, type: (V) -> T) -> T | None` accepts [inconsistent-overload]
- ERROR src/werkzeug/datastructures/structures.py:640:9-12: Implementation signature `(self: Self@CombinedMultiDict, key: K, default: V | T | None = None, type: ((V) -> T) | None = None) -> V | T | None` does not accept all arguments that overload signature `(self: Self@CombinedMultiDict, key: str, type: (V) -> T) -> T | None` accepts [inconsistent-overload]

xarray (https://github.com/pydata/xarray)
- ERROR xarray/core/resample.py:373:9-14: Class member `DataArrayResample.apply` overrides parent class `DataArrayGroupByBase` in an inconsistent manner [bad-override-param-name]
+ ERROR xarray/core/resample.py:373:9-14: Class member `DataArrayResample.apply` overrides parent class `DataArrayGroupByBase` in an inconsistent manner [bad-override]

[stroxler]

Thanks! This now needs a rebase. In addition, code review flagged a few potential issues we should look at before merge:

1. **kwargs can duplicate a positionally filled parameter. The PR accepts Want(a: int, **kwargs: int) backed by got(b: int = 0, **kwargs: int). Calling w(1, b=2) is legal through Want but raises TypeError in got. The collision check needs to consider names supplied through arbitrary kwargs.

2. Successful splits can produce an invalid generic specialization. A callback accepting str positionally and int by keyword gets inferred as Want[int | str], incorrectly allowing either type in either position. The final specialization must satisfy every split—not merely accumulate individually successful constraints.

3. Failed fallback checks leak inference state. A rejected callback pins an unrelated empty list’s element type to str, causing a subsequent xs.append(1) error. Snapshotting needs to include variables reachable through existing bounds and answers.

For cleanup, the AI reviewer also suggests recording positional bindings during the walk instead of reconstructing them afterward with zip.