why doesn't compute_root_layout accept known_dimensions?

[Fancyflame]

What should I do if I want to put a new tree as a leaf to another tree?

compute_leaf_layout(
    inputs,
    &node.style,
    |_val, _basis| 0.0,
    |known_dimensions, available_space| {
        // where do I pass `known_dimensions`?
        compute_root_layout(&mut another_tree, another_node_id, available_space)
    },
)