[swift-evolution] Optional comparison operators

[Jacob Bandes-Storch]

Great, thanks Mark! I look forward to it.

On Mon, Jul 11, 2016 at 4:31 PM, Mark Lacey <mark.lacey at apple.com> wrote:

> Hi Jacob,
>
> On Jul 11, 2016, at 4:23 PM, Jacob Bandes-Storch via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Bump for Swift 3.
>
> On Thu, Jul 7, 2016 at 2:37 PM, Jacob Bandes-Storch <jtbandes at gmail.com>
> wrote:
>
>> These operators cause some potential for confusion:
>>
>>     public func <<T : Comparable>(lhs: T?, rhs: T?) -> Bool
>>     public func ><T : Comparable>(lhs: T?, rhs: T?) -> Bool
>>     public func <=<T : Comparable>(lhs: T?, rhs: T?) -> Bool
>>     public func >=<T : Comparable>(lhs: T?, rhs: T?) -> Bool
>>
>> 1. The meaning of T? < T? is not immediately obvious (Why is nil <
>> .some(x) for any x? Personally, my intuition says that Optional should only
>> provide a partial order, with .none not being ordered w.r.t. .some(x).)
>>
>> 2. Even if the meaning is understood, it can be surprising when the (T?,
>> T?) -> Bool version is used instead of (T, T) -> Bool.
>>
>> Prior discussion:
>> - http://thread.gmane.org/gmane.comp.lang.swift.devel/2089
>> - http://thread.gmane.org/gmane.comp.lang.swift.evolution/10095
>> - rdar://16966712&22833869
>> - Replies to https://twitter.com/jtbandes/status/646914031433871364
>>
>> In the swift-dev thread from May, Chris said:
>>
>> One of the ideas that Joe Pamer has been discussing is whether the
>>>> implicit promotion from T to T? should be disabled when in an operator
>>>> context.  Doing so would fix problems like this, but making the code
>>>> invalid.
>>>
>>>
>>>
>> A change like this would be source-breaking, so if the core team has
>> recommendations for how to handle these issues, now is probably the time to
>> get it done.
>>
>
> I overlooked your previous message on this.
>
> I’m actually writing up a proposal for this now, and have an
> implementation that I’ve done a bit of testing with.
>
> I’m hoping to get the proposal out in the next couple days.
>
> Mark
>
>
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