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Add else-branch narrowing for if type(a) is A when A is @final (#19925)

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Alex Waygood 2025-08-15 14:52:30 +01:00 • committed by GitHub
parent bd4506aac5
commit 6de84ed56e
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2 changed files with 48 additions and 5 deletions
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9
crates/ty_python_semantic/src/types/narrow.rs
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@ -772,13 +772,15 @@ impl<'db, 'ast> NarrowingConstraintsBuilder<'db, 'ast> {
_ => continue,
};
let is_valid_constraint = if is_positive {
let is_positive = if is_positive {
op == &ast::CmpOp::Is
} else {
op == &ast::CmpOp::IsNot
};
if !is_valid_constraint {
// `else`-branch narrowing for `if type(x) is Y` can only be done
// if `Y` is a final class
if !rhs_class.is_final(self.db) && !is_positive {
continue;
}
@ -791,7 +793,8 @@ impl<'db, 'ast> NarrowingConstraintsBuilder<'db, 'ast> {
let place = self.expect_place(&target);
constraints.insert(
place,
Type::instance(self.db, rhs_class.unknown_specialization(self.db)),
Type::instance(self.db, rhs_class.unknown_specialization(self.db))
.negate_if(self.db, !is_positive),
);
}
}