error[E0072]: recursive type `ListNode` has infinite size --> $DIR/multiline-span-E0072.rs:2:1 | LL | / struct LL | | ListNode LL | | { LL | | head: u8, LL | | tail: Option, | | ---------------- recursive without indirection LL | | } | |_^ recursive type has infinite size | help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `ListNode` representable | LL | tail: Box>, | ^^^^ ^ error: aborting due to previous error For more information about this error, try `rustc --explain E0072`.