[swift-evolution] [Pitch] Rename `AnyObject` to `AnyClass` and drop current `AnyClass`

[Austin Zheng]

Another thing to consider is that AnyObject currently has magic that allows any Objective-C method to be called upon it if Foundation is imported on an Apple platform. I think it may be desirable to have AnyObject become something like Any<class>, and have a differently-named construct take the place of an ersatz 'id' type for Objective-C interop.

Austin

> On May 20, 2016, at 11:42 PM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org> wrote:
> 
>> Fair enough.  But in that case I think we want something that does exactly that: rejects classes, rather than indicating value semantics.  We need to do this in a way that doesn’t lead to a situation where we used the word `value` to mean “value type”, and later we have the capability to very value semantics and really wish `value` could mean value semantics but that would be a breaking change we aren’t willing to make.
> 
> Exactly, `any<class>` is just a constraint that indicates which type it can hold, where `any<struct>` or `any<enum>` are two constraints and (not yet existing) counterparts to `any<class>`.
> 
> The idea behind `any<struct>` (or `any<enum>`) might look like this:
> 
> func foo(struct: any<struct, SomeProtocol>)
> 
> Where it is clear that you have to provide a custom struct which conforms to `SomeProtocol`, you’re not constrained to just a single struct, you can build as many as you want it it’s your desire. :)
> 
> Lets just imagine we already have `any<…>` and we also get `oneOf<…>` or `one<…>` which picks only one constraint at compile time and proceeds.
> 
> Here is what you could do for extendable types:
> 
> typealias AnyValue = one<any<struct>, any<enum>>
> 
> func boo(value: any<AnyValue, SomeProtocol>)
> 
> Not sure if we’ll get there or not but its a nice imagination. :)
> 
> I’m not exactly in favor of using `any<class>` instead of AnyClass but I’m openminded. :)
> 
> One problem to solve is the conformance to protocols:
> 
> If we’ll get `any<…>` and depricate `AnyClass` `AnyObject` we cannot do this directly:
> 
> protocol A: any<class> {}
> protocol B: any<ProtocolX, ProtocolY>
> 
> We still need a typealias as a workaround:
> 
> typealias AnyClass = any<class>
> typealias AnyXY = any<ProtocolX, ProtocolY>
> 
> protocol A: AnyClass {} furthermore is this protocol equivalent to protocol A: class {} ???
> protocol B: AnyXY {}
> 
> -- 
> Adrian Zubarev
> Sent with Airmail
> 
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