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[ty] narrow the right-hand side of ==, !=, is and is not conditions when the left-hand side is not narrowable (#22511)

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Co-authored-by: Alex Waygood <alex.waygood@gmail.com>
This commit is contained in:
drbh
2026-01-13 11:01:54 -05:00
committed by GitHub
parent c7b41060f4
commit d13b5db066
4 changed files with 98 additions and 0 deletions
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23
crates/ty_python_semantic/src/types/narrow.rs
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@@ -1250,6 +1250,29 @@ impl<'db, 'ast> NarrowingConstraintsBuilder<'db, 'ast> {
);
}
}
// For symmetric operators (==, !=, is, is not), if left is not a narrowable target,
// try to narrow the right operand instead by swapping the operands.
// E.g., `None != x` should narrow `x` the same way as `x != None`.
_ if matches!(
op,
ast::CmpOp::Eq | ast::CmpOp::NotEq | ast::CmpOp::Is | ast::CmpOp::IsNot
) && matches!(
right,
ast::Expr::Name(_)
| ast::Expr::Attribute(_)
| ast::Expr::Subscript(_)
| ast::Expr::Named(_)
) =>
{
if let Some(right_place) = place_expr(right)
// Swap lhs_ty and rhs_ty since we're narrowing the right operand
&& let Some(ty) =
self.evaluate_expr_compare_op(rhs_ty, lhs_ty, *op, is_positive)
{
let place = self.expect_place(&right_place);
constraints.insert(place, NarrowingConstraint::regular(ty));
}
}
_ => {}
}
}