[Review] SE-0122: Use colons for subscript declarations


(James Froggatt) #1

I have mixed feelings about moving from standard parameter list syntax. I'd like to see the discussion, but it would need its own proposal. It might still be possible to get this in before the deadline, if you or anyone is up to it.

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Group: gmane.comp.lang.swift.evolution
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I like this syntax better. But do you guys think we could remove this
"subscript" prefix? Could we actually bring subscripts closer to
computed properties by doing something like "var self[externaName
internalName : ParamType] : ElemenType"? That could also support the
idea of creating named subscripts by replacing self with another name.

L

···

On 20 July 2016 at 14:17, Jose Cheyo Jimenez via swift-evolution <swift-evolution@swift.org> wrote:

On Jul 20, 2016, at 7:51 AM, Vladimir.S via swift-evolution > <swift-evolution@swift.org> wrote:

+1 to clean up the syntax of subscripts. They acts as properties, not
methods, so it is natural to express them with `:` and not with `->`.

Actually, I'd prefer additional change to use [] instead of () in
declaration like:

subscript[externalName internalName: ParamType] : ElementType {
   get { … }
   set { … }
}

I got to second this suggestion. To me this is an elegant solution.

If subscripts are so special that Swift decided to give it its own name (as
oppose to just making it two functions),
why not declare it in a special way like the above?

I think that in addition to replacing -> with : if we replaced () with []
then it would be much clearer that this is not a function or property.

subscript[externalName internalName: ParamType] : ElementType {
   get { … }
   set { … }
}

I don’t see another place in the language where [] would make more sense
than here:
Otherwise I don’t see replacing -> with : as a big win like Dmitri Gribenko
said down thread ->

I think by changing subscripts to use colons we would end in the opposite,
but
totally symmetrical situation compared to what we have now.

especially if thinking about "Future directions" and confusion with
parameterised accessor syntax(both declared with `()` but first used with
`[]` and second with `()`).

On 20.07.2016 8:50, Chris Lattner via swift-evolution wrote:

Hello Swift community,

The review of "SE-0122: Use colons for subscript declarations " begins now
and runs through July 24. The proposal is available here:

https://github.com/apple/swift-evolution/blob/master/proposals/0122-use-colons-for-subscript-type-declarations.md

Reviews are an important part of the Swift evolution process. All reviews
should be sent to the swift-evolution mailing list at

https://lists.swift.org/mailman/listinfo/swift-evolution

or, if you would like to keep your feedback private, directly to the review
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What goes into a review?

The goal of the review process is to improve the proposal under review
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When writing your review, here are some questions you might want to answer
in your review:

* What is your evaluation of the proposal?
* Is the problem being addressed significant enough to warrant a change to
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From James F