[swift-evolution] [Review] SE-0117: Default classes to be non-subclassable publicly

[Rod Brown]

> On 11 Jul 2016, at 12:33 PM, Jonathan Hull <jhull at gbis.com> wrote:
> 
> It is pre-breaking in that it is the exact same code that doesn’t work in both cases (only in the pre-breaking case, a bunch of other code also doesn’t work).  I know it feels different because it “was never possible” vs our change being the cause, but it is one of those things like me giving you $5 or giving you $10 and later taking back $5.  As humans we are loss averse so we devise strategies to hide the loss from ourselves.

I completely disagree with this.

 Not providing someone something due to risk of breakage is not the same thing as “giving it and taking it away”. We don’t build bridges out of spare parts and tell people “We build it but we expect it to break at some stage, so use with caution.” You either build it correctly, or you don’t let people cross the bridge. At All.

This isn’t about “loss averse”. This is about risk management.

Where does the line lie on risk? That’s ultimately something the core team will have to decide.