error[E0369]: binary operation `+` cannot be applied to type `std::boxed::Box<isize>`
  --> $DIR/issue-14915.rs:6:22
   |
LL |     println!("{}", x + 1);
   |                    - ^ - {integer}
   |                    |
   |                    std::boxed::Box<isize>
   |
   = note: an implementation of `std::ops::Add` might be missing for `std::boxed::Box<isize>`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0369`.