[swift-evolution] [Proposal] Explicit Synthetic Behaviour

Nevin Brackett-Rozinsky nevin.brackettrozinsky at gmail.com
Wed Sep 6 17:43:06 CDT 2017

On Wed, Sep 6, 2017 at 5:42 PM, Haravikk via swift-evolution <
swift-evolution at swift.org> wrote:

> the issue I'm trying to raise is that when those, and similar features,
> are used in synthesised behaviour (default implementations based upon the
> concrete type), that these behaviours should be opted into explicitly,
> otherwise they open up potential for all kinds of bugs, even when the
> assumptions being made about the concrete type are simple such as in the
> case for Equatable/Hashable. There's just too much potential for this kind
> of reflective protocol implementation to overreach; to me it feels very
> much like going into a restaurant and the waiter coming across and
> force-feeding me something I don't want instead of taking my order.

I might suggest that instead it is like you have gone into a pizza shop and
said, “I’d like a large veggie pizza please.” And they made you a pizza
with their standard dough and their standard sauce and their standard
cheese and their standard selection of vegetables.

If you wanted some other dough or sauce or cheese or toppings you would
have ordered it. And the fact is you *did* order a veggie pizza (ie.
conformed to a certain protocol). It’s not like they brought you something
you didn’t order. You ordered what you wanted, and that’s what they brought

And for those times when you *do* want to customize your order, that is
perfectly fine too.

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