[swift-evolution] Remove nil and NilLiteralConvertible

[Xiaodi Wu]

It's been pointed out before that Optional being an enum type is treated
like an implementation detail. Currently, it is possible to teach the
concept of Optional without introducing enum types or generics. How would
you do so after elimination of nil?


On Wed, Jun 8, 2016 at 3:41 PM, Антон Жилин <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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