module main

@[heap]
struct Node {
mut:
    children []&Node
}

@[heap]
struct Tree {
mut:
    root &Node
}

fn find_leaf(mut node Node) &Node {
    for {
        if node.children.len == 0 {
            return node
        }
        node = node.children[0]
    }
    return node
}

fn test_mut_struct_arg_passed_as_pointer_keeps_original_tree_root() {
    mut n1 := &Node{}
    mut t := &Tree{
        root: n1
    }

    mut n2 := &Node{}
    t.root.children << n2
    mut n3 := &Node{}
    t.root.children[0].children << n3

    found := find_leaf(mut t.root)
    assert found == n3
    assert t.root.children.len == 1
    assert t.root.children[0] == n2
    assert t.root.children[0].children.len == 1
    assert t.root.children[0].children[0] == n3
}