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## Summary When accessing an (instance) attribute on a given class, we were previously traversing its MRO, and building a union of types (if the attribute was available on multiple classes in the MRO) until we found a *definitely bound* symbol. The idea was that possibly unbound symbols in a subclass might only partially shadow the underlying base class attribute. This behavior was problematic for two reasons: * if the attribute was definitely bound on a class (e.g. `self.x = None`), we would have stopped iterating, even if there might be a `x: str | None` declaration in a base class (the bug reported in https://github.com/astral-sh/ty/issues/1067). * if the attribute originated from an implicit instance attribute assignment (e.g. `self.x = 1` in method `Sub.foo`), we might stop looking and miss another implicit instance attribute assignment in a base class method (e.g. `self.x = 2` in method `Base.bar`). With this fix, we still iterate the MRO of the class, but we only stop iterating if we find a *definitely declared* symbol. In this case, we only return the declared attribute type. Otherwise, we keep building a union of inferred attribute types. The implementation here seemed to be the easiest fix for https://github.com/astral-sh/ty/issues/1067 that also kept the ecosystem impact low (the changes that I see all look correct). However, as the Markdown tests show, there are other things to fix in this area. For example, we should do a similar thing for *class attributes*. This is more involved, though (affects many different areas and probably involves a change to our descriptor protocol implementation), so I'd like to postpone this to a follow-up. closes https://github.com/astral-sh/ty/issues/1067 ## Test Plan Updated Markdown tests, including a regression test for https://github.com/astral-sh/ty/issues/1067. |
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| .. | ||
| 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.