Stock: Stock-style deriving via coercion, with no Generic

You typically wouldn’t override all the fields. I’d use a library like this if I have a lot fields (10 or more perhaps) and only a few of them need overriding. And even if it would be equally long, I’d much prefer a declarative, correct by construction derived instance than code, no matter how clear, that I’d need to read to check for subtle mistakes, or would have to write boring tests for.