error[E0277]: the size for values of type `dyn Trait` cannot be known at compilation time
  --> $DIR/unsized_coercion.rs:14:17
   |
LL |         let x = hello();
   |                 ^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `dyn Trait`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.