It doesn't have to be a "keyword" in the sense of reservedid, right?
Correct, it's only a keyword when used in the context of deriving,
similar to how "role" is only a keyword in the context of "type role".
You could still define, say, `id role = role` if you so wished.
Ryan S.
On Mon, Jul 18, 2016 at 10:39 AM, Andres Loeh
It might be a tongue-in-cheek suggestion, but I _really_ like it. It captures the intended semantics better than any other previous suggestion, I think. And we're already going to be appropriating a new keyword with "anyclass", so why not take "bespoke" as well? :)
It doesn't have to be a "keyword" in the sense of reservedid, right?
I thought about verbosity here, and it's not clear which one is more verbose. For example, I frequently define a new newtype and then wish to use GND to derive a whole host of instances. In this case (is it common?), `deriving (X, Y) deriving newtype (A,B,C,D,E,F)` is shorter than putting newtype on each class name.
That's a good point. Another thing to consider is that I suspect in 90% of the time, users are only going to be reaching for -XDerivingStrategies in the scenario when they enable both -XGeneralizedNewtypeDeriving and -XDeriveAnyClass. That will happen when they want to derive instances for newtypes, and as you said, you typically derive several instances at a time when defining newtypes. Therefore, it seems less noisy to factor out the deriving strategy names so that readers can tell at a glance which batch of instances are newtype-derived and which are anyclass-derived, instead of having to read a keyword before every single type.
Yes, you've convinced me that putting the strategy once in front is at least not worse.
Plus, on a superficial level, I like keeping the deriving strategy name outside of the parentheses. I think it makes clear that these keywords aren't modifying the type we're deriving, only the means by which we're deriving it. Of course, you may feel differently than I do, so please speak up if you disagree!
The very first times when I've talked to others about this feature, I think I've always used "deriving (Eq via bespoke, Monad via gnd)" as syntax, but yes, in general I agree that keeping it completely out of the parentheses may be a mild advantage.
Cheers, Andres