ruff

dac4e356 - [ty] Use all reachable bindings for instance attributes and deferred lookups (#18955)

[ty] Use all reachable bindings for instance attributes and deferred lookups (#18955) ## Summary Remove a hack in control flow modeling that was treating `return` statements at the end of function bodies in a special way (basically considering the state *just before* the `return` statement as the end-of-scope state). This is not needed anymore now that #18750 has been merged. In order to make this work, we now use *all reachable bindings* for purposes of finding implicit instance attribute assignments as well as for deferred lookups of symbols. Both would otherwise be affected by this change: ```py def C: def f(self): self.x = 1 # a reachable binding that is not visible at the end of the scope return ``` ```py def f(): class X: ... # a reachable binding that is not visible at the end of the scope x: "X" = X() # deferred use of `X` return ``` Implicit instance attributes also required another change. We previously kept track of possibly-unbound instance attributes in some cases, but we now give up on that completely and always consider *implicit* instance attributes to be bound if we see a reachable binding in a reachable method. The previous behavior was somewhat inconsistent anyway because we also do not consider attributes possibly-unbound in other scenarios: we do not (and can not) keep track of whether or not methods are called that define these attributes. closes https://github.com/astral-sh/ty/issues/711 ## Ecosystem analysis I think this looks very positive! * We see an unsurprising drop in `possibly-unbound-attribute` diagnostics (599), mostly for classes that define attributes in `try … except` blocks, `for` loops, or `if … else: raise …` constructs. There might obviously also be true positives that got removed, but the vast majority should be false positives. * There is also a drop in `possibly-unresolved-reference` / `unresolved-reference` diagnostics (279+13) from the change to deferred lookups. * Some `invalid-type-form` false positives got resolved (13), because we can now properly look up the names in the annotations. * There are some new *true* positives in `attrs`, since we understand the `Attribute` annotation that was previously inferred as `Unknown` because of a re-assignment after the class definition. ## Test Plan The existing attributes.md test suite has sufficient coverage here.