mirror of
https://github.com/astral-sh/ruff.git
synced 2025-10-05 16:10:36 +00:00
c91b457044
## Summary The union `T | U` can be validly simplified to `U` iff: 1. `T` is a subtype of `U` OR 2. `T` is equivalent to `U` OR 3. `U` is a union and contains a type that is equivalent to `T` OR 4. `T` is an intersection and contains a type that is equivalent to `U` (In practice, the only situation in which 2, 3 or 4 would be true when (1) was not true would be if `T` or `U` is a dynamic type.) Currently we achieve these simplifications in the union builder by doing something along the lines of `t.is_subtype_of(db, u) || t.is_equivalent_to_(db, u) || t.into_intersection().is_some_and(|intersection| intersection.positive(db).contains(&u)) || u.into_union().is_some_and(|union| union.elements(db).contains(&t))`. But this is both slow and misses some cases (it doesn't simplify the union `Any | (Unknown & ~None)` to `Any`, for example). We can improve the consistency and performance of our union simplifications by adding a third type relation that sits in between `TypeRelation::Subtyping` and `TypeRelation::Assignability`: `TypeRelation::UnionSimplification`. This change leads to simpler, more user-friendly types due to the more consistent simplification. It also lead to a pretty huge performance improvement! ## Test Plan Existing tests, plus some new ones. |
||
|---|---|---|
| .. | ||
| corpus | ||
| mdtest | ||
| primer | ||
| README.md | ||
Markdown files within the mdtest/ subdirectory are tests of type inference and type checking;
executed by the tests/mdtest.rs integration test.
See crates/ty_test/README.md for documentation of this test format.