[ty] Resolve type aliases in filter_union method#22989
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Typing conformance resultsNo changes detected ✅ |
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| Lint rule | Added | Removed | Changed |
|---|---|---|---|
invalid-assignment |
0 | 6 | 2 |
invalid-parameter-default |
0 | 0 | 7 |
invalid-argument-type |
0 | 2 | 2 |
invalid-return-type |
0 | 0 | 4 |
type-assertion-failure |
0 | 2 | 0 |
| Total | 0 | 10 | 15 |
This change modifies `filter_union` to resolve type aliases before checking if the type is a union. This allows `filter_union` to properly handle cases where a type alias resolves to a union type. With this change, the explicit `resolve_type_alias` call in `bind.rs` (added in #22988) is now redundant and has been removed. Added additional test cases for union type aliases with: - TypedDict dict literal inference - TypedDict dict() call inference - Set literal inference https://claude.ai/code/session_01Fsp2dSw6mnTBV1M2Fnf6gt
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carljm
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@ibraheemdev You'd mentioned this might break the current constraint solver, but if so it doesn't seem to show up in tests or in ecosystem? Is there some particular breakage you were thinking of that I should test for? |
ibraheemdev
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Jan 30, 2026
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I was thinking that eagerly resolving type aliases would change our behavior in this example:
type X[T] = list[T] | None
def _(x: X[int]):
reveal_type(x) # revealed: `list[T] | None`But it looks like we already reveal the value of the type alias instead of the type alias itself, so this seems fine.
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Summary
Update the
filter_unionmethod to resolve type aliases before checking if a type is a union. This ensures that union filtering works correctly when the type is a type alias that resolves to a union, not just direct union types.Test Plan
Added tests exercising various uses of
filter_unionthat fail without this fix.