//# publish
module 0x42.A {
    struct Coin { balance: u64 }
    struct A { c: Self.Coin }

    public zero(): Self.Coin {
    label b0:
        return Coin { balance: 0 };
    }

    public new(c: Self.Coin): Self.A {
    label b0:
        return A { c: move(c) };
    }

    public destroy_a(a: Self.A) {
        let c: Self.Coin;
        let balance: u64;
    label b0:
        A { c } = move(a);
        Coin { balance } = move(c);
        return;
    }

    public mutate(a_ref: &mut Self.A) {
        let ref: &mut Self.Coin;
        let ref_balance: &mut u64;
    label b0:
        // safe to modify resources inner values (if they have drop)
        ref = &mut move(a_ref).A::c;
        ref_balance = &mut move(ref).Coin::balance;
        *move(ref_balance) = 100;
        return;
    }
}

//# run
import 0x42.A;

main() {
    let zero_resource: A.Coin;
    let s: A.A;
label b0:
    zero_resource = A.zero();
    s = A.new(move(zero_resource));
    A.mutate(&mut s);
    A.destroy_a(move(s));
    return;
}