[swift-evolution] [Discussion] Replacing Equal Signs with Colons For Attribute Arguments

Wed Feb 17 00:46:08 CST 2016

+1 from me for proposal
On Feb 17, 2016 4:33 AM, "Erica Sadun via swift-evolution" <
swift-evolution at swift.org> wrote:

> That's beyond the scope of this proposal. If you want to discuss it, I
> encourage you to start a separate thread.
>
> -- E
>
>
> On Feb 16, 2016, at 7:54 PM, Michael Wells <michael at michaelwells.com>
> wrote:
>
> Aren’t we removing the use of snake case in Swift 3? So should
> @warn_unused_result be de-snake-cased?
>
> On Feb 16, 2016, at 6:45 PM, Ricardo Parada via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> It looks very good.
>
> Thank you Erica.
>
>
> On Feb 16, 2016, at 8:05 PM, Erica Sadun <erica at ericasadun.com> wrote:
>
> Adding:
>
> @available(*, unavailable, renamed: "MyRenamedProtocol")typealias MyProtocol = MyRenamedProtocol
> @warn_unused_result(mutable_variant: "sortInPlace")public func sort() -> [Self.Generator.Element]
> @available(*, deprecated, message: "it will be removed in Swift 3.  Use the 'generate()' method on the collection.")public init(_ bounds: Range<Element>)
>
>
> gist: https://gist.github.com/erica/d96011a5c22d9b995b91
>
> -- E
>
> On Feb 16, 2016, at 5:43 PM, Charles Kissinger <crk at akkyra.com> wrote:
>
>
> On Feb 16, 2016, at 4:08 PM, Erica Sadun via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Ricardo,
>
> This proposal is so narrow that I believe *every single example possible*
> is already in there under motivation. Just sub out each "=" for ":" and you
> have the entire extent of the change.
>
>
> Hi Erica,
>
> I think Ricardo means full examples of the new style, including @ symbol,
> attribute-name, parens, attribute argument label and example attribute
> arguments. There are no full examples in the proposal of either the
> existing or proposed style.
>
> It might seem nit-picky (and it is :-)), but that’s the only way for us to
> evaluate how it will actually look in practice. (Yes, we could look up a
> few and type them in somewhere ourselves, but it would be nice to have them
> in the proposal.)
>
> —CK
>
>
>
> -- Erica
>
> On Feb 16, 2016, at 5:03 PM, Ricardo Parada <rparada at mac.com> wrote:
>
> Hi Erica,
>
> I understand this is a draft and even though it may be obvious to many, I
> would add a few examples with the proposed solution.
>
> Thanks
> Ricardo Parada
>
>
> On Feb 16, 2016, at 5:42 PM, Erica Sadun via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Thoughts and feedback appreciated. Thank you, -- Erica
>
>
> Replacing Equal Signs with Colons For Attribute Arguments
>
>    - Proposal: TBD
>    - Author(s): Erica Sadun <http://github.com/erica>
>    - Status: TBD
>    - Review manager: TBD
>
> <https://gist.github.com/erica/d96011a5c22d9b995b91#introduction>
> Introduction
>
> Attribute arguments are unlike other Swift language arguments. At the call
> site, they use = instead of colons to distinguish argument names from
> passed values. This proposal brings attributes into compliance with Swift
> standard practices by replacing the use of "=" with ":" in this one-off
> case.
>
> *Discussion took place on the Swift Evolution mailing list in the
> [Discussion] Replacing Equal Signs with Colons For Attribute Arguments
> thread. Thanks to Doug Gregor <https://github.com/DougGregor> for
> suggesting this enhancement.*
> <https://gist.github.com/erica/d96011a5c22d9b995b91#motivation>Motivation
>
> Attributes enable developers to annotate declarations and types with
> keywords that constrain behavior. Recognizable by their at-sign
> <http://foldoc.org/strudel> "@" prefix, attributes communicate features,
> characteristics, restrictions, and expectations of types and declarations
> to the Swift compiler. Common attributes include @noescape for parameters
> that cannot outlive the lifetime of a call, @convention, to indicates
> whether a type's calling conventions follows a Swift, C, or (Objective-C)
> block model, and @available to enumerate a declaration's compatibility
> with platform and OS versions. Swift currently offers about a dozen
> distinct attributes, and is likely to expand this vocabulary in future
> language updates.
>
> Some attributes accept arguments: @attribute-name(attribute-arguments)
>  including @available and @warn_unused_result. In the current grammar, an
> equal sign separates attribute argument keywords from values:
>
> introduced=version-number
> deprecated=version-number
> obsoleted=version-number
> message=message
> renamed=new-name
> mutable_variant=method-name
>
> Using = is out of step with other Swift parameterization call-site
> patterns. Tweaking the grammar to match the rest of Swift introduces a
> small change that adds consistency across the language.
>
> parameter name: parameter value
>
> <https://gist.github.com/erica/d96011a5c22d9b995b91#detail-design>Detail
> Design
>
> This proposal replaces the use of = with : in the balanced tokens used to
> compose an attribute argument clause along the following lines:
>
> attribute → @ attribute-name attribute-argument-clause<sub>opt</sub>
> attribute-name → identifier
> attribute-argument-clause → ( balanced-tokens<sub>opt<opt> )
> balanced-tokens → balanced-token
> balanced-tokens → balanced-token, balanced-tokens
> balanced-token → attribute-argument-label : attribute argument-value
>
> This design can be summarized as "wherever current Swift attributes use =,
> use : instead".
>
> <https://gist.github.com/erica/d96011a5c22d9b995b91#alternatives-considered>Alternatives
> Considered
> There are no alternatives to put forth other than not accepting this
> proposal.
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