type Stats {
    count: u32,
    total: i64,
    flag: Bool,
    bytes: [8]u8,
}

type Box<T: Type> {
    item: T,
    extra: u32,
}

fn inner(s: mutref<Stats>) -> Void {
    s.count = s.count + 1_u32
    s.total = s.total + 10
}

fn fill(s: mutref<Stats>) -> usize {
    return std.mem.copy(s.bytes, std.mem.span("zero"))
}

fn outer(s: mutref<Stats>) -> Void {
    inner(s)
    s.flag = true
}

fn bumpBox<T: Type>(b: mutref<Box<T>>) -> Void {
    b.extra = b.extra + 1_u32
}

pub fn main(world: World) -> Void raises {
    var st: Stats = Stats { count: 1_u32, total: 5, flag: false, bytes: [0_u8; 8] }
    outer(&mut st)
    let copied: usize = fill(&mut st)
    if st.count == 2_u32 {
        check world.out.write("nested count ok\n")
    }
    if st.total == 15 {
        check world.out.write("nested total ok\n")
    }
    if st.flag {
        check world.out.write("nested flag ok\n")
    }
    if copied == 4 {
        check world.out.write("nested copy ok\n")
    }
    if st.bytes[1] == 101_u8 {
        check world.out.write("nested bytes ok\n")
    }
    var bi: Box<i32> = Box { item: 5, extra: 1_u32 }
    bumpBox<i32>(&mut bi)
    if bi.extra == 2_u32 {
        check world.out.write("generic mutref ok\n")
    }
}