| error[E0277]: the size for values of type `impl Tr + ?Sized` cannot be known at compilation time | |
| --> $DIR/pretty-print-opaque-no-feat.rs:9:30 | |
| | | |
| LL | let y: Box<dyn Tr> = x; | |
| | ^ doesn't have a size known at compile-time | |
| | | |
| = help: the trait `Sized` is not implemented for `impl Tr + ?Sized` | |
| = note: required for the cast from `Box<impl Tr + ?Sized>` to `Box<dyn Tr>` | |
| error: aborting due to 1 previous error | |
| For more information about this error, try `rustc --explain E0277`. |