error[E0277]: the size for values of type `dyn Foo` cannot be known at compilation time
  --> $DIR/by-value-trait-dyn-compatibility-with-default.rs:15:9
   |
LL |     let x = *(Box::new(A) as Box<dyn Foo>);
   |         ^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `dyn Foo`
   = note: all local variables must have a statically known size
help: references are always `Sized`, even if they point to unsized data; consider not dereferencing the expression
   |
LL -     let x = *(Box::new(A) as Box<dyn Foo>);
LL +     let x = (Box::new(A) as Box<dyn Foo>);
   |

error: aborting due to 1 previous error

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