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

[Patrick Smith]

> On 9 Jun 2016, at 9:23 PM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org> wrote:
> 
> So what is the counterpart to AnyClass aka. AnyObject.Type for AnyValue? There is no and I don’t see any good name for it.
> 
You could just use AnyValue.Type?
> More confusion with generalized existentials:
> 
> Any<class> vs. AnyClass aka AnyObject.Type
> Any<class> makes it crystal clear that you’re using an instance of a class not an instance of .Type. It should be consistent.
> 
Any<…> would be used for any of a certain type. So Any<class> to me says ‘any of class’, not ‘any class’. Whereas AnyClass says to me literally ‘any class’.
> I’m not proposing for AnyStruct or AnyEnum here, it would be enough to get AnyValue in Swift, but I did considered both in my proposal. 
> 
> Lets say we also would have something like One<A, B> which picks A or B and we have generalized struct and enum. That said we could create AnyValue like this typealias AnyValue = One<struct, enum>. Again this is not the main part of the proposal.
> 
> 
> -- 
> Adrian Zubarev
> Sent with Airmail
> 
> Am 9. Juni 2016 um 13:09:28, Patrick Smith (pgwsmith at gmail.com <mailto:pgwsmith at gmail.com>) schrieb:
> 
>> I find this more confusing, not less. AnyClass suggests that will be any class, but it’s not, it’s any class instance. So I think it’s less accurate.
>> 
>> For arguments that AnyStruct and AnyEnum will come, I don’t agree with those either. AnyValue would make more sense to me. The fact that a value’s type is a struct or enum is irrelevant, just as AnyObject makes no promise about the superclass. I don’t believe there would be much or anything you could do knowing if something was a struct or enum anyway — both support properties and methods, mutations, yet cases can only be used with a concrete enum type. So AFAIK, there would no um value in having both AnyStruct and AnyEnum.
>> 
>> So I am happy staying with AnyObject, as it describes what the actual instance is. And if AnyValue comes, they would pair nicely together.
>> 
>> Patrick
>> 
>> 
>>> On 9 Jun 2016, at 8:08 PM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> I added a draft proposal here: https://github.com/DevAndArtist/swift-evolution/blob/rename_anyobject_remove_anyclass/proposals/nnnn-rename-anyobject-remove-anyclass.md <https://github.com/DevAndArtist/swift-evolution/blob/rename_anyobject_remove_anyclass/proposals/nnnn-rename-anyobject-remove-anyclass.md>
>>> Rename AnyObject and remove current AnyClass
>>> 
>>> Proposal: SE-NNNN <https://github.com/apple/swift-evolution/blob/master/proposals/nnnn-rename-anyobject-remove-anyclass.md>
>>> Author(s): Adrian Zubarev <https://github.com/DevAndArtist>
>>> Status: Awaiting review <x-msg://100/#rationale>
>>> Review manager: TBD
>>> Introduction
>>> 
>>> From the beginning AnyObject protocol and AnyClass type-alias felt wrong and confusing. This proposal aims to sort out the confusion and provide a consistency for future version of Swift.
>>> 
>>> Swift-evolution thread: [Pitch] Rename AnyObject to AnyClass and drop current AnyClass <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160516/018283.html>
>>> Motivation
>>> 
>>> In Swift 3 the standard library will correspond to a particular guideline <https://github.com/apple/swift-evolution/blob/master/proposals/0006-apply-api-guidelines-to-the-standard-library.md>. This means that the Type suffix will be removed almost everywhere. This provides good readability and makes usage of .Type more clearer and consistent. Furthermore this change is a first step towards consistency for generalized existentials <https://github.com/austinzheng/swift-evolution/blob/az-existentials/proposals/XXXX-enhanced-existentials.md>.
>>> 
>>> Short example:
>>> 
>>> -func construct(type: AnyClass) -> AnyObject?
>>> +func construct(type: AnyClass.Type) -> AnyClass? {
>>>     if let objectType = type as? NSObject.Type {
>>>         return objectType.init()
>>>     } else {
>>>         return nil
>>>     }
>>> }
>>> Proposed solution
>>> 
>>> Remove current AnyClass type-alias from the standard library and rename current AnyObject protocol to AnyClass. Then migrate existing code from AnyClass to AnyClass.Type and from AnyObject to AnyClass.
>>> 
>>> // Remove completely
>>> -public typealias AnyClass = AnyObject.Type
>>> 
>>> // Rename to AnyClass
>>> - at objc public protocol AnyObject {}
>>> + at objc public protocol AnyClass {}
>>> Impact on existing code
>>> 
>>> This change will break existing code, and will require a migrator to translate Swift 2 code into Swift 3 code.
>>> 
>>> Alternatives considered & Future consistency
>>> 
>>> Use generalized existentials with any-class requirement Any<class> instead, which won’t make it into Swift 3 in time:
>>> AnyClass equals Any<class> or typealias AnyClass = Any<class>
>>> AnyClass.Type equals Any<class>.Type
>>> Add AnyValue type-alias with generalized existentials and value keyword:
>>> AnyValue equals Any<value> or typealias AnyValue = Any<value>
>>> AnyValue.Type equals Any<value>.Type
>>> Or instead AnyValue add AnyStruct and AnyEnum type-aliases:
>>> AnyStruct equals Any<struct> or typealias AnyStruct = Any<struct>
>>> AnyEnum equals Any<enum> or typealias AnyEnum = Any<enum>
>>> AnyStruct.Type equals Any<struct>.Type
>>> AnyEnum.Type equals Any<enum>.Type
>>> Example:
>>> 
>>> // Accept any type that conforms to `SomeProtocol`
>>> func doSomething(with interface: SomeProtocol) { ... }
>>> 
>>> // Accept any class that conforms to `SomeProtocol`
>>> // We use shorthand syntax for existentials here (SE-0095)
>>> func doSomething(with interfaceReference: AnyClass & SomeProtocol) { ... }
>>> func doSomething(with interfaceReference: Any<class> & SomeProtocol) { ... }
>>> 
>>> // Accept any value that conforms to `SomeProtocol`
>>> // Missing counterpart to `AnyClass`
>>> func doSomething(with interfaceValue: AnyValue & SomeProtocol) { ... }
>>> func doSomething(with interfaceValue: Any<value> & SomeProtocol) { ... }
>>> 
>>> // Or more specific value types:
>>> func doSomething(with interfaceValue: AnyStruct & SomeProtocol) { ... }
>>> func doSomething(with interfaceValue: Any<struct> & SomeProtocol) { ... }
>>> 
>>> func doSomething(with interfaceValue: AnyEnum & SomeProtocol) { ... }
>>> func doSomething(with interfaceValue: Any<enum> & SomeProtocol) { ... }
>>> 
>>> 
>>> 
>>> -- 
>>> Adrian Zubarev
>>> Sent with Airmail
>>> 
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>> 
> 
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