error[E0308]: mismatched types --> $DIR/occurs-check-2.rs:7:9 | LL | f = Box::new(g); | ^^^^^^^^^^^ cyclic type of infinite size | help: consider unboxing the value | LL | f = *Box::new(g); | + error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0308`.