E0507 E0009 should be mutually exclusive

[Wolvereness]

E0507 E0009 should be mutually exclusive

E0009

cannot bind by-move and by-ref in the same pattern

E0507

cannot move out of borrowed content

Example

Playground

fn main() {
    Holder {
        copy_type: 0,
        almost_copy: AlmostCopy(42),
        never_copy: "Hello world".to_string(),
    }.func()
}

#[derive(Debug)]
struct AlmostCopy(usize);

#[derive(Debug)]
struct Holder {
    copy_type: usize,
    almost_copy: AlmostCopy,
    never_copy: String,
}

impl Holder {
    fn func(&self) {
        let &Holder {
            copy_type,
            almost_copy,
            ref never_copy,
        } = self;
        println!(
            "{}: {:?} -- {:?}", 
            copy_type, 
            almost_copy, 
            never_copy,
        );
    }
}

Output

   Compiling playground v0.0.1 (/playground)
error[E0009]: cannot bind by-move and by-ref in the same pattern
  --> src/main.rs:24:13
   |
24 |             almost_copy,
   |             ^^^^^^^^^^^ by-move pattern here
25 |             ref never_copy,
   |             -------------- both by-ref and by-move used

error[E0507]: cannot move out of `self.almost_copy` which is behind a shared reference
  --> src/main.rs:26:13
   |
24 |             almost_copy,
   |             -----------
   |             |
   |             data moved here
   |             move occurs because `almost_copy` has type `AlmostCopy`, which does not implement the `Copy` trait
25 |             ref never_copy,
26 |         } = self;
   |             ^^^^
help: consider removing the `&`
   |
22 |         let Holder {
23 |             copy_type,
24 |             almost_copy,
25 |             ref never_copy,
26 |         } = self;
   |

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0009, E0507.
For more information about an error, try `rustc --explain E0009`.
error: Could not compile `playground`.

To learn more, run the command again with --verbose.

Reasoning

A situation where both trigger, E0507 is a much more clear indication of something wrong in the code. In this example, the intention is that AlmostCopy implements Copy, and will subsequently trigger neither error. The presence of E0009 is misleading when it doesn't include any mention of Copy without the click-through.

[estebank]

CC #45600, which if it were fixed would also close this ticket.

[Centril]

This is now resolved when you add #![feature(move_ref_pattern)] as you only get E0507.
cc #68354.