Borrowing a field through a getter

A simple getter that directly returns a field preserves the field’s identity for the borrow checker. After the call, unrelated fields remain available:

class Pair:
    x: i64
    y: i64
    def x_ref(self: &mut Pair) -> &mut i64:
        &mut self.x

def main() -> Result[(), IoError]:
    mut pair = Pair(1, 2)
    x = pair.x_ref()
    pair.y = 7
    *x = 9
    print(pair)?
    Ok(())

Pair(x=9, y=7)

Getters that choose between fields borrow the whole argument. Indexed references also borrow the whole collection. The call still requires the access declared by the receiver type.