[swift-evolution] Proposals: (1) Forbidding custom `==` for value types, (2) `dispatch` keyword, (3) `default`-result for methods with `Self`, and (4) Poor-Mans-Existentials

[L. Mihalkovic]

Regards
(From mobile)

> On Jul 18, 2016, at 9:43 PM, Austin Zheng via swift-evolution <swift-evolution at swift.org> wrote:
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>> On Mon, Jul 18, 2016 at 12:28 PM, Johannes Neubauer via swift-evolution <swift-evolution at swift.org> wrote:
>> Dear Xiaodi,
>> 
>> > Am 18.07.2016 um 20:55 schrieb Xiaodi Wu <xiaodi.wu at gmail.com>:
>> >
>> > As mentioned earlier, NaN != NaN, demonstrating that an Equatable instance that does not always equal itself is not "radical." Plainly, your proposal is unworkable.
>> 
>> 1. this is a basic internal type, so it can have a special behavior, since it is a well-designed data type created by the language designers (since there is no need to bootstrap swift from the first bits this is OK).
> 
> The problem is that this is *exactly* how Swift works. There is nothing special about e.g. Double except for the fact that it wraps a built-in type and the implementation of its operations forward to built-in functions. This is how all the stdlib types work. You can build your own refcounted COW `Array` with exactly no additional compiler support from scratch, if you want.

Well, there is something special.. The fact that the compiler will to the forwarding, and not not do something equivalent for other data types.


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