So, are you saying that the ordering determines the keys used for hashing, in answer to OP? I expect I’ve misunderstood this, but if not, isn’t this a pretty hefty constraint? Is it not enough to have some sort of a Hashable typeclass?
Would this mean that in OP’s example, you’d need to write an instance Ord that then picks which particular field to order on - i.e. using deriving Ord in this particular case wouldn’t work?
Btw. is Ord a total order?