| error[E0277]: the size for values of type `dyn ToString` cannot be known at compilation time | |
| --> $DIR/issue-58355.rs:5:14 | |
| | | |
| LL | x = Some(Box::new(callback)); | |
| | ^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time | |
| | | |
| = help: within `fn() -> dyn ToString`, the trait `Sized` is not implemented for `dyn ToString` | |
| = note: required because it appears within the type `fn() -> dyn ToString` | |
| = note: required for the cast from `Box<fn() -> dyn ToString>` to `Box<dyn Fn() -> (dyn ToString + 'static)>` | |
| error: aborting due to 1 previous error | |
| For more information about this error, try `rustc --explain E0277`. |