I alway enjoy hearing your ideas.
This is quite interesting. It's basically a way to define an ad-hoc interface
that a type doesn't need to explicitly declare it conforms to. I know Golang
works similarly; if a Go type implements all the requirements of an interface
it conforms automatically.
There are positives and negatives to allowing this sort of ad-hoc interface.
Agree. It would definitely make the language "feel" a bit more fluid. But it
doesn't add any expressive power and could have undesirable consequences.
This would make for a good standalone proposal -- both because it's complex
enough to deserve its own discussion, and because if the community is
interested someone would have to work through all the implications in order to
put together a proposal. It would be quite a big change.
I don't see how this is different from a protocol other than the lack of
requirement to declare conformance explicitly. The need to explicitly declare
conformance is a design decision that I believe the core team feels pretty
strongly about.
That said, it hasn't been debated by the community yet so if someone feels
strongly about dropping explicit conformance declarations it might be worth
pitching the idea, if for not other reason than to have a discussion about it
on the lost.
I don’t see any desire to follow Go’s path here and drop explicit conformance
in any way.
Basically such `existential` mechanism could express more than `Any<…>` could.
That said I do feel that this "could“ have some potential to exist alongside
`Any<…>`.
>From my understanding of this whole existential type thing is that it can be
>used both ways, explicitly and implicitly. As said before we only discussed
>the explicit existential types.
Just another pseudo example:
```swift
// this could also replace typealiases for (generic) existentials
existential CrazyView {
// we could introduce a way for constraints which could have a nice looking
syntax
// break `Any<…>` nesting and long very long composition lines of `Any<…>`
constraint Any<UIScrollView, Any<UITableView, Any<UIView, ProtocolA>>>
constraint ProtocolA.AssociatedType == Int
func crazyFunction()
}
existential AnyCollection<T> {
constraint Collection
constraint Collection.Element == T
}
```
But I don’t want to go any further if there is no need (yet).
--
Adrian Zubarev
Sent with Airmail
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