Use something with interior mutability, like the Cell family; then you can hand out & references. Safe Rust precludes some safe programs, but Rust's soundness

Use something with interior mutability, like the Cell family; then you can hand out & references. Safe Rust precludes some safe programs, but Rust's soundness rules preclude far fewer. I've only seen a couple of real-world programs that you couldn't express in Rust (without unnecessary runtime checks), and that's solely due to the hierarchical lifetimes.