[swift-evolution] [Pitch] Allow trailing argument labels

Derrick Ho wh1pch81n at gmail.com
Wed Feb 22 07:19:53 CST 2017

I've read the pitch, but it isn't clear what the ask is or what benefit it
would give.
On Wed, Feb 22, 2017 at 8:05 AM Haravikk via swift-evolution <
swift-evolution at swift.org> wrote:

> On 22 Feb 2017, at 11:48, Brent Royal-Gordon <brent at architechies.com>
> wrote:
> On Feb 22, 2017, at 3:32 AM, Haravikk via swift-evolution <
> swift-evolution at swift.org> wrote:
> foo.example(foo) // What did I mean here?
> let result = foo.example(foo:) // This looks like I might be trying to
> select a function, rather than call it
> I think it would be really weird to support not one, but *two* potentially
> ambiguous sugar forms.
> Those aren't examples I think should be supported, I was thinking out
> loud. The point I was trying to make is that it's not the trailing nature
> that's a requirement, but that the real requirement for this feature to
> work is that there's at least one other, non-Void argument.
> On another note, one other alternative I did think of for declaration is
> that perhaps it might be better still to use an attribute to specify a
> label-only "argument". Think of it like an attribute on the type, except
> that it specifies that there is no type:
> func adding(_ other:Self, reportingOverflow:@labelonly) { … }
> The attribute makes it absolutely clear that this is just a label and not
> an actual, functional argument (there won't be a reportingOverflow local
> variable), and that it can be passed without a value when calling this
> method. It'll still need the trailing colon for possible disambiguation of
> variables though.
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