error[E0277]: cannot add `()` to `usize`
  --> $DIR/issue-13352.rs:9:13
   |
LL |     2_usize + (loop {});
   |             ^ no implementation for `usize + ()`
   |
   = help: the trait `std::ops::Add<()>` is not implemented for `usize`

error: aborting due to previous error

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