error[E0374]: the trait `CoerceUnsized` may only be implemented for a coercion between structures --> $DIR/E0374.rs:8:1 | LL | impl CoerceUnsized> for Foo | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: expected a single field to be coerced, none found error: aborting due to previous error For more information about this error, try `rustc --explain E0374`.