David Peter aea2bc2308 [ty] Infer type variables within generic unions (#21862) ... ## Summary This PR allows our generics solver to find a solution for `T` in cases like the following: ```py def extract_t[T](x: P[T] | Q[T]) -> T: raise NotImplementedError reveal_type(extract_t(P[int]())) # revealed: int reveal_type(extract_t(Q[str]())) # revealed: str ``` closes https://github.com/astral-sh/ty/issues/1772 closes https://github.com/astral-sh/ty/issues/1314 ## Ecosystem The impact here looks very good! It took me a long time to figure this out, but the new diagnostics on bokeh are actually true positives. I should have tested with another type-checker immediately, I guess. All other type checkers also emit errors on these `__init__` calls. MRE [here](https://play.ty.dev/5c19d260-65e2-4f70-a75e-1a25780843a2) (no error on main, diagnostic on this branch) A lot of false positives on home-assistant go away for calls to functions like [`async_listen`](180053fe98/homeassistant/core.py (L1581-L1587)) which take a `event_type: EventType[_DataT] | str` parameter. We can now solve for `_DataT` here, which was previously falling back to its default value, and then caused problems because it was used as an argument to an invariant generic class. ## Test Plan New Markdown tests		2025-12-09 16:22:59 +01:00
..
annotations	[ty] Complete support for `ParamSpec` (#21445)	2025-12-05 22:00:06 +05:30
assignment	[ty] Avoid expression reinference for diagnostics (#21267)	2025-11-25 09:24:00 -08:00
binary	[ty] Improve the display of various special-form types (#21775)	2025-12-03 21:19:59 +00:00
boolean	Revert "[ty] Better control flow for boolean expressions that are inside if (#18010)" (#18150)	2025-05-17 08:27:32 -04:00
boundness_declaredness	[ty] Reformulation of public symbol inference test suite (#20667)	2025-10-01 14:26:17 +02:00
call	[ty] Fix overload filtering to prefer more "precise" match (#21859)	2025-12-09 20:29:34 +05:30
class	[ty] Improve the display of various special-form types (#21775)	2025-12-03 21:19:59 +00:00
comparison	[ty] Improve diagnostics for unsupported comparison operations (#21737)	2025-12-02 19:58:45 +00:00
comprehensions	[ty] fix global symbol lookup from eager scopes (#21317)	2025-11-12 10:15:51 -08:00
conditional	[ty] Support as-patterns in reachability analysis (#19728)	2025-08-04 20:13:50 +02:00
dataclasses	[ty] Suppress false positives when `dataclasses.dataclass(...)(cls)` is called imperatively (#21729)	2025-12-03 08:05:25 +00:00
declaration	[ty] Format conflicting types as an enumeration (#18956)	2025-06-26 14:29:33 +02:00
diagnostics	[ty] Add subdiagnostic hint if the user wrote `X = Any` rather than `X: Any` (#21777)	2025-12-03 20:42:21 +00:00
directives	[ty] Minor improvements to `assert_type` diagnostics (#21811)	2025-12-05 12:33:30 +00:00
doc	ty_python_semantic: add union type context to function call type errors	2025-05-09 13:40:51 -04:00
exception	[ty] Improve diagnostics for invalid exceptions (#21475)	2025-11-15 22:12:00 +00:00
expression	[ty] Check method definitions on subclasses for Liskov violations (#21436)	2025-11-23 18:08:15 +00:00
external	[ty] Infer type variables within generic unions (#21862)	2025-12-09 16:22:59 +01:00
function	[ty] Improve the display of various special-form types (#21775)	2025-12-03 21:19:59 +00:00
generics	[ty] Infer type variables within generic unions (#21862)	2025-12-09 16:22:59 +01:00
ide_support	[ty] Support `type[T]` with type variables (#21650)	2025-11-28 09:20:24 +01:00
import	[ty] cleanup test path (#21781)	2025-12-03 21:54:50 +00:00
libraries	[ty] Generic types aliases (implicit and PEP 613) (#21553)	2025-11-28 20:38:24 +01:00
literal	[ty] Type inference for genererator expressions (#21437)	2025-11-14 13:04:11 +00:00
loops	[ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995)	2025-10-27 11:19:12 +00:00
narrow	[ty] Improve the display of various special-form types (#21775)	2025-12-03 21:19:59 +00:00
regression	[ty] Avoid diagnostic when `typing_extensions.ParamSpec` uses `default` parameter (#21839)	2025-12-08 12:34:30 +00:00
scopes	[ty] Make `__getattr__` available for `ModuleType` instances (#21450)	2025-11-14 13:59:14 +01:00
shadowing	Rename Red Knot (#17820)	2025-05-03 19:49:15 +02:00
snapshots	[ty] Minor improvements to `assert_type` diagnostics (#21811)	2025-12-05 12:33:30 +00:00
stubs	[ty] Better invalid-assignment diagnostics (#21476)	2025-11-18 14:31:04 +01:00
subscript	[ty] support `type[tuple[...]]` (#21652)	2025-12-01 11:49:26 +01:00
suppressions	[ty] Add code action to ignore diagnostic on the current line (#21595)	2025-11-29 15:41:54 +01:00
type_compendium	[ty] Improve literal promotion heuristics (#21439)	2025-11-14 16:13:56 -05:00
type_of	[ty] `type[T]` is assignable to an inferable typevar (#21766)	2025-12-02 18:25:09 -05:00
type_properties	[ty] Allow `tuple[Any, ...]` to assign to `tuple[int, *tuple[int, ...]]` (#21803)	2025-12-05 19:04:23 +00:00
type_qualifiers	[ty] Avoid double-analyzing tuple in `Final` subscript (#21828)	2025-12-07 14:27:14 +00:00
unary	Update class literal display to use `<class 'Foo'>` style (#17889)	2025-05-06 20:11:25 -04:00
with	[ty] Complete support for `ParamSpec` (#21445)	2025-12-05 22:00:06 +05:30
.mdformat.toml	Rename Red Knot (#17820)	2025-05-03 19:49:15 +02:00
async.md	[ty] Generic types aliases (implicit and PEP 613) (#21553)	2025-11-28 20:38:24 +01:00
attributes.md	[ty] Support `type[T]` with type variables (#21650)	2025-11-28 09:20:24 +01:00
bidirectional.md	[ty] Improve diagnostics for unsupported comparison operations (#21737)	2025-12-02 19:58:45 +00:00
classes.md	[ty] Fix bug where ty would think all types had an `__mro__` attribute (#20995)	2025-10-27 11:19:12 +00:00
cycle.md	[ty] remove the `visitor` parameter in the `recursive_type_normalized_impl` method (#21701)	2025-12-01 08:48:43 +01:00
decorators.md	ty_python_semantic: add union type context to function call type errors	2025-05-09 13:40:51 -04:00
del.md	[ty] No union with `Unknown` for module-global symbols (#20664)	2025-10-01 16:40:30 +02:00
deprecated.md	[ty] Consistent use of American english (in rules) (#19488)	2025-07-22 16:10:38 +02:00
descriptor_protocol.md	[ty] Use the return type of `__get__` for descriptor lookups even when `__get__` is called with incorrect arguments (#21424)	2025-11-13 12:05:10 +00:00
enums.md	[ty] Support `type[T]` with type variables (#21650)	2025-11-28 09:20:24 +01:00
exhaustiveness_checking.md	[ty] Exhaustiveness checking for generic classes (#21726)	2025-12-01 13:52:36 +01:00
final.md	[ty] Improve `@override`, `@final` and Liskov checks in cases where there are multiple reachable definitions (#21767)	2025-12-03 12:51:36 +00:00
implicit_type_aliases.md	[ty] Complete support for `ParamSpec` (#21445)	2025-12-05 22:00:06 +05:30
instance_layout_conflict.md	[ty] initial support for `slots=True` in dataclasses (#20278)	2025-09-07 18:25:35 +01:00
intersection_types.md	[ty] Use "cannot" consistently over "can not" (#21255)	2025-11-03 10:38:20 -05:00
invalid_syntax.md	[ty] Avoid double-inference on non-tuple argument to `Annotated` (#21837)	2025-12-08 10:24:05 -05:00
known_constants.md	Rename Red Knot (#17820)	2025-05-03 19:49:15 +02:00
liskov.md	[ty] Carry generic context through when converting class into `Callable` (#21798)	2025-12-05 08:57:21 -05:00
literal_promotion.md	[ty] Narrow type context during literal promotion in generic class constructors (#21574)	2025-11-21 17:05:32 -05:00
mdtest_config.md	Rename Red Knot (#17820)	2025-05-03 19:49:15 +02:00
mdtest_custom_typeshed.md	[ty] Remove `Type::Tuple` (#19669)	2025-08-11 22:03:32 +01:00
metaclass.md	Update class literal display to use `<class 'Foo'>` style (#17889)	2025-05-06 20:11:25 -04:00
mro.md	[ty] Improve the display of various special-form types (#21775)	2025-12-03 21:19:59 +00:00
named_tuple.md	[ty] Improve `@override`, `@final` and Liskov checks in cases where there are multiple reachable definitions (#21767)	2025-12-03 12:51:36 +00:00
overloads.md	[ty] Infer type of `self` for decorated methods and properties (#21123)	2025-10-29 21:22:38 +00:00
override.md	[ty] Improve `@override`, `@final` and Liskov checks in cases where there are multiple reachable definitions (#21767)	2025-12-03 12:51:36 +00:00
pep613_type_aliases.md	[ty] Improve the display of various special-form types (#21775)	2025-12-03 21:19:59 +00:00
pep695_type_aliases.md	[ty] Support typevar-specialized dynamic types in generic type aliases (#21730)	2025-12-03 10:00:02 +01:00
properties.md	[ty] Use the return type of `__get__` for descriptor lookups even when `__get__` is called with incorrect arguments (#21424)	2025-11-13 12:05:10 +00:00
protocols.md	[ty] normalize typevar bounds/constraints in cycles (#21800)	2025-12-04 15:17:57 -08:00
public_types.md	[ty] Disambiguate classes that live in different modules but have the same fully qualified names (#20756)	2025-10-08 18:27:40 +01:00
statically_known_branches.md	[ty] Rename "possibly unbound" diagnostics to "possibly missing" (#20492)	2025-09-23 14:26:55 +00:00
sys_platform.md	Rename Red Knot (#17820)	2025-05-03 19:49:15 +02:00
sys_version_info.md	[ty] support PEP 613 type aliases (#21394)	2025-11-20 17:59:35 -08:00
t_strings.md	[ty] Add support for PEP 750 t-strings (#20085)	2025-08-25 18:49:49 +00:00
terminal_statements.md	[ty] improve lazy scope place lookup (#19321)	2025-07-25 07:11:11 +00:00
ty_extensions.md	[ty] Stop testing the (brittle) constraint set display implementation (#21743)	2025-12-02 09:17:29 +01:00
typed_dict.md	[ty] Preserve quoting style when autofixing `TypedDict` keys (#21682)	2025-11-28 18:40:34 +00:00
union_types.md	[ty] Introduce `TypeRelation::Redundancy` (#20602)	2025-10-03 18:35:30 +01:00
unpacking.md	[ty] Infer more precise types for collection literals (#20360)	2025-09-17 18:51:50 -04:00
unreachable.md	[ty] Add subdiagnostic hint if a variable with type `Never` is used in a type expression (#21660)	2025-11-27 12:48:18 +00:00