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` = help: the following other types implement trait `Add`: <&'a u32 as Add> <&u32 as Add<&u32>> > error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.