[swift-evolution] Smart KeyPaths

[Joe Groff]

> On Mar 17, 2017, at 3:04 PM, BJ Homer <bjhomer at gmail.com> wrote:
> 
> So then this would be disambiguated like this?
> 
> let staticValue = Foo.bar // Defaults to accessing the static value, when there is ambiguity
> 
> let value:   Bar                       = Foo.bar
> let keyPath: WritableKeyPath<Foo, Bar> = Foo.bar
> 
> It’s a little unfortunately to have to spell out WritableKeyPath<Foo, Bar> there, but as long as there’s some way to do it, I don’t think it’s a problem. This is likely a rare edge case.

You could also just write `: WritableKeyPath` and let the generic arguments be deduced. I agree that, in most situations you want a key path, you'll likely have type context that picks the right thing.

-Joe

> -BJ Homer
> 
>> On Mar 17, 2017, at 3:56 PM, Joe Groff <jgroff at apple.com <mailto:jgroff at apple.com>> wrote:
>> 
>>> 
>>> On Mar 17, 2017, at 2:53 PM, Michael LeHew <lehewjr at apple.com <mailto:lehewjr at apple.com>> wrote:
>>> 
>>> 
>>>> On Mar 17, 2017, at 2:21 PM, BJ Homer <bjhomer at gmail.com <mailto:bjhomer at gmail.com>> wrote:
>>>> 
>>>> This looks great!
>>>> 
>>>> What happens in the case when there is a static property by the same name as an instance property? e.g.
>>>> 
>>>> struct Foo {
>>>>     static var bar: Bar
>>>>     var bar: Bar
>>>> }
>>>> 
>>>> Foo.bar // What is this?
>>>> 
>>>> Is it still possible to reference both the static property and a KeyPath to the instance method? 
>>> 
>>> This is essentially the same question that I arrived at in my reply to Vladimir.  I think Joe might be best able to answer here.
>> 
>> We already encounter this situation with static vs instance methods, since `Foo.bar` can refer to either a static method `bar` or an unbound instance method `bar`. We use type context to disambiguate, favoring the static member if context doesn't help:
>> 
>> struct X {
>>   static func foo() {}
>>   func foo() {}
>> }
>> 
>> let foo1 = X.foo // Defaults to static member
>> let foo2: () -> () = X.foo // Picks static member by type context
>> let foo3: (X) -> () -> () = X.foo // Picks instance member by type context
>> 
>> -Joe
> 

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