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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legacy	[ty] Infer type variables within generic unions (#21862)	2025-12-09 16:22:59 +01:00
pep695	[ty] Infer type variables within generic unions (#21862)	2025-12-09 16:22:59 +01:00
builtins.md	[ty] Support using legacy typing aliases for generic classes in type annotations (#18404)	2025-06-03 12:09:51 +01:00
scoping.md	[ty] Create a specialization from a constraint set (#21414)	2025-11-19 14:20:33 -05:00
specialize_constrained.md	[ty] Fix non-determinism in `ConstraintSet.specialize_constrained` (#21744)	2025-12-03 10:19:39 -05:00