FP redundant_pattern (breaks code), "ref" cannot be omitted

[matthiaskrgr]

warning: the `s @ _` pattern can be written as just `s`
    --> src/librustc_resolve/imports.rs:1435:25
     |
1435 |                         ref s @ _ => bug!("unexpected import subclass {:?}", s),
     |                         ^^^^^^^^^ help: try: `s`
     |
     = note: `#[warn(clippy::redundant_pattern)]` on by default
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pattern

using just s broke the build:

error[E0507]: cannot move out of `directive.subclass` which is behind a shared reference
    --> src/librustc_resolve/imports.rs:1415:37
     |
1415 |                     let msg = match directive.subclass {
     |                                     ^^^^^^^^^^^^^^^^^^ help: consider borrowing here: `&directive.subclass`
...
1435 |                         s => bug!("unexpected import subclass {:?}", s),
     |                         -
     |                         |
     |                         data moved here
     |                         move occurs because `s` has type `imports::ImportDirectiveSubclass<'_>`, which does not implement the `Copy` trait

error: aborting due to previous error

For more information about this error, try `rustc --explain E0507`.

it needs to be ref s