error: constant of non-structural type `&[O<B>]` in a pattern
  --> $DIR/issue-65466.rs:14:9
   |
LL | struct B;
   | -------- must be annotated with `#[derive(PartialEq)]` to be usable in patterns
LL |
LL | const C: &[O<B>] = &[O::None];
   | ---------------- constant defined here
...
LL |         C => (),
   |         ^ constant of non-structural type
   |
   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details

error: aborting due to 1 previous error