> On Jun 4, 2016, at 4:00 PM, Matthew Johnson via swift-evolution
> <swift-evolution@swift.org> wrote:
>
>
>>> On Jun 3, 2016, at 9:30 PM, John McCall <rjmcc...@apple.com> wrote:
>>>
>>>> On Jun 3, 2016, at 7:08 PM, Matthew Johnson <matt...@anandabits.com> wrote:
>>>>> On Jun 3, 2016, at 8:11 PM, John McCall <rjmcc...@apple.com> wrote:
>>>>>
>>>>> On Jun 3, 2016, at 5:13 PM, Matthew Johnson <matt...@anandabits.com>
>>>>> wrote:
>>>>> On Jun 3, 2016, at 6:23 PM, John McCall <rjmcc...@apple.com> wrote:
>>>>>
>>>>>>>> On Jun 3, 2016, at 4:07 PM, David Sweeris <daveswee...@mac.com> wrote:
>>>>>>>> On Jun 3, 2016, at 16:17, Matthew Johnson via swift-evolution
>>>>>>>> <swift-evolution@swift.org> wrote:
>>>>>>>>
>>>>>>>> Using an external parameter label in a declaration and allowing it to
>>>>>>>> be omitted at the call site does not feel like the right answer to me.
>>>>>>>> I think we can find a better way to present this syntactically.
>>>>>>>
>>>>>>> +eleventy gajillion
>>>>>>
>>>>>> I'm actually quite happy with the user-facing aspects of the current
>>>>>> literal protocols and see zero reason to update them for this, so if
>>>>>> that's the choice, I'll just leave this aside.
>>>>>
>>>>> Are you suggesting that preserving the current syntax of the literal
>>>>> protocols is more important than fixing this behavior so it works like
>>>>> most people seem to expect? Why not be open to other syntactic
>>>>> solutions?
>>>>
>>>> I think fixing the behavior is good, and I stand by this proposal.
>>>
>>> I agree fixing it is good and we should do it. I’m just trying to explore
>>> the solution space to see if there are any alternatives that might be more
>>> appealing. Clearly you’ve thought about this a lot but it’s a new topic to
>>> consider for the rest of us. :)
>>
>> I'm sorry if I've come across as frustrated. It's easy for me to forget
>> that things that I consider well-settled haven't always been covered in
>> depth here. The community is not intentionally re-inventing things for no
>> purpose, it's making a genuine effort to explore the constraints on a part
>> of the language that it isn't familiar with the rationale for.
>
> No problem. I know it’s not fun to revisit hard-thought decisions that
> you’re happy with! :) And I can see how it feels like we’re trying to do
> that here. That said, these discussions are the best way for the community
> to become familiar with some of the rationale for the way things currently
> are. :)
I find It helps to read the docs that has been produced (not all up to date but
still rich in background data). The source code is also a great place to do a
reality chk on ideas.
@john thank you for taking the time to share.
>
>>
>>>> There is, however, nothing glaringly wrong with the literal protocols.
>>>> They do not need to redesigned simply because we found a syntactic
>>>> interaction that needs to be cleaned up.
>>>>
>>>> There are good reasons the protocols have evolved the way they have. The
>>>> labels clearly mark the purpose of each initializer and distinguish one
>>>> from another on types that support multiple literal kinds. The labels
>>>> also clearly indicate that the initializers are not intended for general
>>>> use. The argument(s) to the initializer do not always represent a single
>>>> value of literal type. Some protocols provide multiple initializers, and
>>>> it is quite possible that that will become gradually more common as we
>>>> explore ways to grant more flexibility to code outside of the standard
>>>> library. And we actually consider it good that you can invoke these
>>>> initializers explicitly; it's only accidental use that we feel it's
>>>> important to avoid, which labels provide excellent protection against.
>>>
>>> If it is important that these initializers be callable directly I suppose
>>> the label is the only way to go. I can’t think of a reason why this is
>>> necessary though. I would consider it bad design for a type that expects
>>> to be initialized with an Int variable to require its callers to use the
>>> label, as opposed to providing an alternate initializer that doesn’t have a
>>> label with “literal” in its name. Are there specific use cases where you
>>> think this capability is important or is it just the principle that you
>>> should be able to call any initializer you write?
>>
>> Partly that principle, but partly the ability to forward
>> literal-initialization. You can forward literal-initialization to, say, a
>> BuiltinIntegerLiteralConvertible type by just appointing it your associated
>> IntegerLiteralType, but if you're wrapping another type, that doesn't work.
>> For example:
>>
>> struct MyValue : IntegerLiteralConvertible {
>> init(integerLiteral literal: JSONValue.IntegerLiteralType) {
>> json = JSONValue(integerLiteral: literal)
>> }
>> ...
>> }
>
> What is the advantage of calling the literal JSONValue initializer here
> rather than a non-literal initializer that accepts
> JSONValue.IntegerLiteralType? Is there something in the implementation that
> makes this more efficient?
>
> If forwarding is the intended use for explicit calls, wouldn’t the `@literal`
> attribute attached to the type be an alternative way to address the
> forwarding use case?
>
> Are there any non-forwarding use cases for explicit calls?
>
> If forwarding is the only intended use case of explicit calls and `@literal`
> could cover that use case then the question (in my mind) is which principle
> do we hold more sacred? The ability to call any initializer we write or the
> syntactic consistency that external argument labels are always required at
> the call site? I admit this is partly an aesthetic concern…
>
> -Matthew
>
>>
>> John.
>
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