error[E0277]: cannot add `()` to `u32`
  --> $DIR/multiline-span-simple.rs:13:18
   |
LL |     foo(1 as u32 +
   |                  ^ no implementation for `u32 + ()`
   |
   = help: the trait `Add<()>` is not implemented for `u32`

error: aborting due to previous error

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