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
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aliases.md	[ty] Complete support for `ParamSpec` (#21445)	2025-12-05 22:00:06 +05:30
classes.md	[ty] Complete support for `ParamSpec` (#21445)	2025-12-05 22:00:06 +05:30
functions.md	[ty] Infer type variables within generic unions (#21862)	2025-12-09 16:22:59 +01:00
paramspec.md	[ty] Handle various invalid explicit specializations for `ParamSpec` (#21821)	2025-12-08 05:20:41 +00:00
variables.md	[ty] Support `type[T]` with type variables (#21650)	2025-11-28 09:20:24 +01:00
variance.md	[ty] impl `VarianceInferable` for `KnownInstanceType` (#20924)	2025-10-17 21:12:19 +02:00