error[E0277]: the trait bound `(): CoerceUnsized<*const [u8]>` is not satisfied --> $DIR/issue-44861.rs:21:26 | LL | default type Data2 = (); | ^^ the trait `CoerceUnsized<*const [u8]>` is not implemented for `()` | note: required by a bound in `Smartass::Data2` --> $DIR/issue-44861.rs:12:17 | LL | type Data2: CoerceUnsized<*const [u8]>; | ^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Smartass::Data2` error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.