[swift-evolution] Remove nil and NilLiteralConvertible

[Charlie Monroe]

My objection to this is that .none is a fairly common member in various enums (besides Optional) and it's a mess already:

enum EventDataRenderType {
	case none
	case tab
	case blockClosed
	case blockOpened
}

let data = self.data
if data.customization?.renderType == .none {
    /// Was it compared to Optional.none, or EventDataRenderType,
    /// since data.customization?.renderType == .tab is completely
    /// valid...
}

If `none` became a keyword as suggested by some, would it be allowed to have .none in other enums?


> On Jun 8, 2016, at 10:41 PM, Антон Жилин via swift-evolution <swift-evolution at swift.org> wrote:
> 
> (No joking)
> Points:
> 
> 1. When nil was added to the language, we could not infer enumeration type:
> if x != Optional.none { ... }
> 
> Now it looks like this:
> if x != .none { ... }
> 
> If at this point we had a proposal to add nil as a replacement for .none, would we accept it?
> 
> 2. nil is very generic, it only approximately allows to express the intentions.
> In case of Optional, .none is clearer. In case of JSON processing, .null is clearer. In case of a semantically nullable struct, NilLiteralConvertible usually goes to default constructor.
> 
> 3. Too many "empty" things: .none, nil; NSNull, Void, NoReturn types.
> 
> 4. There should be a single consistent terminology: no value in Swift equals none.
> 
> - Anton
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