error[E0594]: cannot assign to `*input`, which is behind a `&` reference
  --> $DIR/issue-68049-2.rs:9:7
   |
LL |       *input = self.0;
   |       ^^^^^^^^^^^^^^^ `input` is a `&` reference, so the data it refers to cannot be written
   |
help: consider changing this to be a mutable reference in the `impl` method and the `trait` definition
   |
LL |   fn example(&self, input: &mut i32) {
   |                             +++

error[E0594]: cannot assign to `self.0`, which is behind a `&` reference
  --> $DIR/issue-68049-2.rs:17:5
   |
LL |     self.0 += *input;
   |     ^^^^^^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be written
   |
help: consider changing this to be a mutable reference in the `impl` method and the `trait` definition
   |
LL ~   fn example(&mut self, input: &i32);
LL | }
...
LL | impl Hello for Test2 {
LL ~   fn example(&mut self, input: &i32) {
   |

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0594`.