Borrow distinct fields

Borrow a field directly with & or &mut:

class Basket:
    count: i64
    items: list[str]

def main() -> Result[(), AllocError | IoError]:
    mut basket = Basket(0, []?)
    count = &mut basket.count
    *count = 2
    basket.items.append("apple")?
    basket.items.append("pear")?
    print(basket)?
    Ok(())

Basket(count=2, items=["apple", "pear"])

Distinct fields can be borrowed or changed independently. Borrowing a whole record overlaps all its fields. Collection element references such as &basket.items[0] protect the collection against changes that could invalidate the element’s address. You can replace a class-valued field by assignment, but cannot replace a whole class through *reference = new_instance yet.

class Position:
    x: i64
    y: i64

def main() -> Result[(), IoError]:
    mut position = Position(1, 2)
    x = &mut position.x
    y = &mut position.y
    *x = 10
    *y = 20
    print(*x)?
    print(*y)?
    Ok(())

10
20