error[E0369]: binary operation `+` cannot be applied to type `std::boxed::Box<isize>`
  --> $DIR/issue-14915.rs:16:20
   |
LL |     println!("{}", x + 1);
   |                    ^^^^^
   |
   = 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`.