[ty] Infer generic class pattern specializations

[charliermarsh]

Summary

Follow-up to #26411.

When a generic class pattern is a subclass of the subject's class, the subject specialization constrains which pattern-class specializations can match. We previously discarded that relationship and treated members declared by the subclass as Unknown:

from typing import Generic, TypeVar

T = TypeVar("T")

class Base(Generic[T]): ...

class Child(Base[T]):
    item: T

def handle(value: Base[int]) -> None:
    match value:
        case Child(item=item):
            reveal_type(item)  # int

This PR uses the constraint solver to find every specialization of the pattern subclass whose corresponding base is compatible with the subject. It projects the captured member over the complete set of solutions instead of selecting a single preferred type argument. Separate constraint paths remain correlated, and lower and upper bounds are preserved through covariant, contravariant, and invariant member positions.

The same projection handles transformed bases, partially constrained subclasses, TypeVar bounds and constraints, and unconstrained parameters. Runtime matching continues to ignore type-parameter defaults, while generic base patterns and unrelated classes retain the existing conservative behavior.

The focused regression assertions fail on main with Unknown; the full ty_python_semantic suite, workspace Clippy, and repository hooks pass with the new inference.

[astral-sh-bot]

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]

Memory usage report

Memory usage unchanged ✅

[astral-sh-bot]

ecosystem-analyzer results

Lint rule	Added	Removed	Changed
invalid-return-type	21	0	2
invalid-argument-type	12	0	0
invalid-yield	2	0	0
Total	35	0	2

Raw diff (37 changes)

Expression (https://github.com/cognitedata/Expression)
+ expression/collections/maptree.py:503:24 error[invalid-return-type] Return type does not match returned value: expected `tuple[Key@MkIterator, Value@MkIterator]`, found `tuple[SupportsLessThan, object]`
+ expression/core/option.py:73:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Option | _TSource@default_value`, found `object`
+ expression/core/option.py:85:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Option | _TSource@default_with`, found `object`
+ expression/core/option.py:97:36 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Option`, found `object`
+ expression/core/option.py:109:36 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Option`, found `object`
+ expression/core/option.py:142:31 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Option`, found `object`
+ expression/core/option.py:173:61 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Option`, found `object`
+ expression/core/option.py:182:24 error[invalid-return-type] Return type does not match returned value: expected `list[_TSourceOut@Option]`, found `list[object]`
+ expression/core/option.py:193:24 error[invalid-return-type] Return type does not match returned value: expected `Seq[_TSourceOut@Option]`, found `Seq[object]`
+ expression/core/option.py:232:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Option | None`, found `object`
+ expression/core/option.py:242:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TSourceOut@Option, _TError@to_result]`, found `Result[object, _TError@to_result]`
+ expression/core/option.py:252:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TSourceOut@Option, _TError@to_result_with]`, found `Result[object, _TError@to_result_with]`
+ expression/core/option.py:264:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Option | None`, found `object`
+ expression/core/option.py:276:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Option`, found `object`
+ expression/core/option.py:286:31 error[invalid-yield] Yield type `object` does not match annotated yield type `_TSourceOut@Option`
+ expression/core/option.py:304:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Option`, found `object`
+ expression/core/result.py:81:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Result | _TSource@default_value`, found `object`
+ expression/core/result.py:93:24 error[invalid-return-type] Return type does not match returned value: expected `_TSource@default_with | _TSourceOut@Result`, found `object`
+ expression/core/result.py:95:31 error[invalid-argument-type] Argument is incorrect: Expected `_TErrorOut@Result`, found `object`
+ expression/core/result.py:105:63 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Result`, found `object`
+ expression/core/result.py:107:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TResult@map, _TErrorOut@Result]`, found `Result[_TResult@map, object]`
+ expression/core/result.py:121:56 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Result`, found `object`
+ expression/core/result.py:123:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TResult@map2, _TErrorOut@Result]`, found `Result[_TResult@map2, object]`
+ expression/core/result.py:133:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TSourceOut@Result, _TResult@map_error]`, found `Result[object, _TResult@map_error]`
+ expression/core/result.py:135:67 error[invalid-argument-type] Argument is incorrect: Expected `_TErrorOut@Result`, found `object`
+ expression/core/result.py:145:31 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Result`, found `object`
+ expression/core/result.py:147:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TResult@bind, _TErrorOut@Result]`, found `Result[_TResult@bind, object]`
+ expression/core/result.py:166:58 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Result`, found `object`
+ expression/core/result.py:184:58 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Result`, found `object`
+ expression/core/result.py:187:38 error[invalid-argument-type] Argument is incorrect: Expected `_TSourceOut@Result`, found `object`
+ expression/core/result.py:198:24 error[invalid-return-type] Return type does not match returned value: expected `dict[str, _TSourceOut@Result | _TErrorOut@Result | Literal["ok", "error"]]`, found `dict[str, object]`
+ expression/core/result.py:203:24 error[invalid-return-type] Return type does not match returned value: expected `dict[str, _TSourceOut@Result | _TErrorOut@Result | Literal["ok", "error"]]`, found `dict[str, object]`
+ expression/core/result.py:236:24 error[invalid-return-type] Return type does not match returned value: expected `Option[_TSourceOut@Result]`, found `Option[object]`
+ expression/core/result.py:255:31 error[invalid-yield] Yield type `object` does not match annotated yield type `_TSourceOut@Result`
+ expression/core/result.py:263:24 error[invalid-return-type] Return type does not match returned value: expected `_TSourceOut@Result`, found `object`
- expression/core/result.py:209:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TErrorOut@Result, _TSourceOut@Result]`, found `Result[_TSourceOut@Result, _TSourceOut@Result]`
+ expression/core/result.py:209:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TErrorOut@Result, _TSourceOut@Result]`, found `Result[Unknown, object]`
- expression/core/result.py:211:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TErrorOut@Result, _TSourceOut@Result]`, found `Result[_TSourceOut@Result, _TSourceOut@Result]`
+ expression/core/result.py:211:24 error[invalid-return-type] Return type does not match returned value: expected `Result[_TErrorOut@Result, _TSourceOut@Result]`, found `Result[object, Unknown]`

Full report with detailed diff (timing results)