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

[Adrian Zubarev]

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
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