ruff/crates/ty_python_semantic at 06db474f208b826e5801b08d67f208bec0ef030b - ruff

mirror of https://github.com/astral-sh/ruff synced 2026-01-21 13:30:49 -05:00

Files

Shunsuke Shibayama 06db474f20 [ty] stabilize union-type ordering in fixed-point iteration (#22070 )

## Summary

This PR fixes https://github.com/astral-sh/ty/issues/2085.

Based on the reported code, the panicking MRE is:

```python
class Test:
    def __init__(self, x: int):
        self.left = x
        self.right = x
    def method(self):
        self.left, self.right = self.right, self.left
        if self.right:
            self.right = self.right
```

The type inference (`implicit_attribute_inner`) for `self.right`
proceeds as follows:

```
0: Divergent(Id(6c07))
1: Unknown | int | (Divergent(Id(1c00)) & ~AlwaysFalsy)
2: Unknown | int | (Divergent(Id(6c07)) & ~AlwaysFalsy) | (Divergent(Id(1c00)) & ~AlwaysFalsy)
3: Unknown | int | (Divergent(Id(1c00)) & ~AlwaysFalsy) | (Divergent(Id(6c07)) & ~AlwaysFalsy)
4: Unknown | int | (Divergent(Id(6c07)) & ~AlwaysFalsy) | (Divergent(Id(1c00)) & ~AlwaysFalsy)
...
```

The problem is that the order of union types is not stable between
cycles. To solve this, when unioning the previous union type with the
current union type, we should use the previous type as the base and add
only the new elements in this cycle (In the current implementation, this
unioning order was reversed).

## Test Plan

New corpus test

2025-12-22 16:16:03 -08:00