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## Summary This mostly fixes #14899 My motivation was similar to the last comment by @sharkdp there. I ran red_knot on a codebase and the most common error was patterns like this failing: ``` def foo(x: str): ... x: Any = ... if isinstance(x, str): foo(x) # Object of type `Any & str` cannot be assigned to parameter 1 (`x`) of function `foo`; expected type `str` ``` The desired behavior is pretty much to ignore Any/Unknown when resolving intersection assignability - `Any & str` should be assignable to `str`, and `str` should be assignable to `str & Any` The fix is actually very similar to the existing code in `is_subtype_of`, we need to correctly handle intersections on either side, while being careful to handle dynamic types as desired. This does not fix the second test case from that issue: ``` static_assert(is_assignable_to(Intersection[Unrelated, Any], Not[tuple[Unrelated, Any]])) ``` but that's misleading because the root cause there has nothing to do with gradual types. I added a simpler test case that also fails: ``` static_assert(is_assignable_to(Unrelated, Not[tuple[Unrelated]])) ``` This is because we don't determine that Unrelated does not subclass from tuple so we can't rule out this relation. If that logic is improved then this fix should also handle the case of the intersection ## Test Plan Added a bunch of is_assignable_to tests, most of which failed before this fix. |
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| mdtest | ||
| 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/red_knot_test/README.md for documentation of this test format.