Sent from my iPhone
> On Nov 22, 2017, at 10:12 AM, Dave DeLong <sw...@davedelong.com> wrote:
>
>
>
>> On Nov 21, 2017, at 11:51 PM, Douglas Gregor via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>> Hi all,
>>
>> We’re having a bit of a debate over the question of whether SE-0143
>> “Conditional Conformances” actually proposes any standard library changes at
>> all, or whether they should all be brought up separately. So, I’ll pitch the
>> pieces that I’d love to put into 4.1 to see if they’re as obvious as I think
>> they should be :)
>>
>> Proposal: make Optional, Array, ArraySlice, ContiguousArray, and Dictionary
>> conform to Equatable when their type parameters are Equatable (and Set
>> always conform to Equatable). Specifically, add to the standard library:
>>
>> extension Optional: Equatable where Wrapped: Equatable { /*== already
>> exists */ }
>> extension Array: Equatable where Element: Equatable { /*== already
>> exists */ }
>> extension ArraySlice: Equatable where Element: Equatable { /*== already
>> exists */ }
>> extension ContiguousArray: Equatable where Element: Equatable { /*==
>> already exists */ }
>> extension Dictionary: Equatable where Value: Equatable { /*== already
>> exists */ }
>> extension Set: Equatable { /*== already exists */ }
>>
>> Motivation: we need these for ==/!= to properly compose. It’s a
>> highly-requested feature and an obvious “first use” of conditional
>> conformances for the standard library that is unlikely to break any code.
>>
>> Implementation: https://github.com/apple/swift/pull/13046
>>
>> Thoughts?
>
> The reason these are on concrete types and not, say, Collection is because we
> can’t conditionally conform protocols yet, right?
Right. SE-0143 has a discussion of this limitation.
- Doug
>
> Dave
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