error[E0072]: recursive type `S` has infinite size --> $DIR/issue-3779.rs:1:1 | LL | struct S { | ^^^^^^^^ LL | LL | element: Option | - recursive without indirection | help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle | LL | element: Option> | ++++ + error: aborting due to previous error For more information about this error, try `rustc --explain E0072`.