error[E0594]: cannot assign to `self.0`, which is behind a `&` reference --> $DIR/issue-68049-1.rs:7:9 | LL | self.0 += 1; | ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be written error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0594`.