1    private@
2    
3    type A =
4        var width : u32 = 0
5    
6    type B =
7        val items @dst = List<A>.new
8    
9    do
10       let button = A.new
11       let stack = B.new
12   
13       stack
14           button
15               width = 20
16   
17       assert stack.items.contains button
18       assert button.width == 20
19