[swift-evolution] Smart KeyPaths

[Joe Groff]

> On Mar 29, 2017, at 6:45 PM, Jonathan Hull via swift-evolution <swift-evolution at swift.org> wrote:
> 
>> 
>> On Mar 29, 2017, at 6:32 PM, Brent Royal-Gordon <brent at architechies.com> wrote:
>> 
>>> On Mar 29, 2017, at 6:21 PM, Jonathan Hull via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>>> I would love it if we found a way to retain something as concise as that shorthand.  I'm working on a library where users will specify a collection of key paths pairs.  This shorthand would be a very nice piece of sugar making the code expressing these collections (usually literals) quite a bit more readable.
>>> 
>>> +1 for this.  I think it will be somewhat common to pass around arrays of these things, and a shorthand syntax of some sort would make that nicer.  That said, I don’t want to slow down the proposal, since I will be using this feature the very second it becomes available.
>> 
>> Agreed.
>> 
>> One more thought on this: I don't think anyone really likes the #keyPath(Type, .key1.key2)` syntax; it's just the best we've come up with. If the syntax were instead this:
>> 
>> 	#keyPath(Type).key1.key2
>> 
>> I think that would look cleaner and avoid drawing distinctions based on subtle punctuation differences. I don't think it would clash with old-style key paths since you can't have a key path to a type name anyway. And support for the leading-dot syntax would fall out of it quite naturally.
> 
> I could get behind that (although it would stop us from extending KeyPaths).  One question in both cases: How do we represent keyPaths for static properties?

Static properties are members of T.Type, so you would specify T.Type as the root.

-Joe