In a pattern, all values that don't implement the `Copy` trait have to be bound
the same way. The goal here is to avoid binding simultaneously by-move and
by-ref.
This limitation may be removed in a future version of Rust.
Erroneous code example:
```compile_fail,E0009
struct X { x: (), }
let x = Some((X { x: () }, X { x: () }));
match x {
Some((y, ref z)) => {}, // error: cannot bind by-move and by-ref in the
// same pattern
None => panic!()
}
```
You have two solutions:
Solution #1: Bind the pattern's values the same way.
```
struct X { x: (), }
let x = Some((X { x: () }, X { x: () }));
match x {
Some((ref y, ref z)) => {},
// or Some((y, z)) => {}
None => panic!()
}
```
Solution #2: Implement the `Copy` trait for the `X` structure.
However, please keep in mind that the first solution should be preferred.
```
#[derive(Clone, Copy)]
struct X { x: (), }
let x = Some((X { x: () }, X { x: () }));
match x {
Some((y, ref z)) => {},
None => panic!()
}
```