message: Eq for BorrowHashed
  Summary: Needed for various experiments, but right thing to do anyway.
diff: @@ -42,7 +42,7 @@ pub struct Hashed<K> {
  }
  /// A borrowed key and its hash.
  -#[derive(Copy_, Clone_, Dupe_)]
  +#[derive(Copy_, Clone_, Dupe_, Eq, PartialEq)]
  pub struct BorrowHashed<'a, Q: ?Sized> {
  hash: StarlarkHashValue,
  key: &'a Q,
  