error[E0308]: mismatched types
  --> $DIR/unsized_coercion5.rs:16:32
   |
LL |         let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
   |                -------------   ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected trait `Send`, found trait `Trait + Send`
   |                |
   |                expected due to this
   |
   = note: expected struct `Box<dyn Send>`
              found struct `Box<dyn Trait + Send>`

error: cannot check whether the hidden type of opaque type satisfies auto traits
  --> $DIR/unsized_coercion5.rs:16:32
   |
LL |         let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
   |                                ^
   |
   = note: fetching the hidden types of an opaque inside of the defining scope is not supported. You can try moving the opaque type and the item that actually registers a hidden type into a new submodule
note: opaque type is declared here
  --> $DIR/unsized_coercion5.rs:13:19
   |
LL | fn hello() -> Box<impl Trait + ?Sized> {
   |                   ^^^^^^^^^^^^^^^^^^^
   = note: required for the cast from `Box<impl Trait + ?Sized>` to `Box<dyn Trait + Send>`

error[E0277]: the size for values of type `impl Trait + ?Sized` cannot be known at compilation time
  --> $DIR/unsized_coercion5.rs:16:32
   |
LL |         let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
   |                                ^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `impl Trait + ?Sized`
   = note: required for the cast from `Box<impl Trait + ?Sized>` to `Box<dyn Trait + Send>`

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.