error[E0599]: the method `clone` exists for struct `Box<dyn Foo>`, but its trait bounds were not satisfied
  --> $DIR/unique-object-noncopyable.rs:24:16
   |
LL | trait Foo {
   | --------- doesn't satisfy `dyn Foo: Clone` or `dyn Foo: Sized`
...
LL |     let _z = y.clone();
   |                ^^^^^ method cannot be called on `Box<dyn Foo>` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `dyn Foo: Sized`
           which is required by `Box<dyn Foo>: Clone`
           `dyn Foo: Clone`
           which is required by `Box<dyn Foo>: Clone`
   = help: items from traits can only be used if the trait is implemented and in scope
   = note: the following trait defines an item `clone`, perhaps you need to implement it:
           candidate #1: `Clone`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0599`.