error[E0072]: recursive type `Expr` has infinite size --> $DIR/issue-32326.rs:5:1 | LL | enum Expr { | ^^^^^^^^^ LL | Plus(Expr, Expr), | ---- recursive without indirection | help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle | LL | Plus(Box, Expr), | ++++ + error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0072`.