error[E0369]: binary operation `==` cannot be applied to type `[X; 3]`
  --> $DIR/eq-arr.rs:5:17
   |
LL |     let eq = xs == [X, X, X];
   |              -- ^^ --------- [X; 3]
   |              |
   |              [X; 3]
   |
note: an implementation of `PartialEq` might be missing for `X`
  --> $DIR/eq-arr.rs:2:5
   |
LL |     struct X;
   |     ^^^^^^^^ must implement `PartialEq`
help: consider annotating `X` with `#[derive(PartialEq)]`
   |
LL +     #[derive(PartialEq)]
LL |     struct X;
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0369`.