error[E0046]: not all trait items implemented, missing: `eq`
  --> $DIR/missing-derivable-attr.rs:13:1
   |
LL |     fn eq(&self, other: &Self) -> bool;
   |     ----------------------------------- `eq` from trait
...
LL | impl MyEq for A {}
   | ^^^^^^^^^^^^^^^ missing `eq` in implementation

error: aborting due to previous error

For more information about this error, try `rustc --explain E0046`.