> On May 6, 2016, at 12:34 AM, Alex Hoppen via swift-evolution
> <[email protected]> wrote:
>
> Thanks for your feedback so far. Based on the discussion, I have updated the
> proposal to let `foo` refer to the zero-parameter function instead of
> `foo(_)`.
>
> The updated proposal is also available on GitHub:
> https://github.com/ahoppen/swift-evolution/blob/reference-zero-param-func/proposals/0000-refernce-zero-param-func.md
>
> <https://github.com/ahoppen/swift-evolution/blob/reference-zero-param-func/proposals/0000-refernce-zero-param-func.md>.
>
> Again comments would be greatly appreciated.
General comment: now that this proposal has pivoted to always requiring the
argument labels when referencing a function, the title and introduction are
misleading. This is a *much* larger change than Alternative 1 or Alternative 2,
and is now source-breaking.
(Personally, I still think “Alternative 1” is the right answer)
- Doug
>
> – Alex
>
> Referencing zero-parameter functions
>
> Proposal: SE-NNNN
> <https://github.com/apple/swift-evolution/blob/master/proposals/NNNN-name.md>
> Author(s): Alex Hoppen <https://github.com/ahoppen>, Pyry Jahkola
> <https://github.com/pyrtsa>
> Status: Draft
> Review manager: TBD
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#introduction>Introduction
>
> Since the approval of SE-0021
> <https://github.com/apple/swift-evolution/blob/master/proposals/0021-generalized-naming.md>
> it is possible to reference a function by its argument names using the
> foo(arg:) syntax but there is no way to reference a zero-parameter function.
> foo currently references all methods with base name foo. If there are
> multiple methods with this base name, one has to disambiguate the referenced
> function by its type using as.
>
>
> This proposal changes the behaviour of foo to always reference a
> zero-parameter function. To reference a function with more parameters, the
> argument labels have to be explicitly named (e.g. foo(arg:)).
>
> Originally, the proposal sought to introduce the new syntax foo(_) to
> reference an overloaded function with zero parameters, but was discarded
> based on the discussion on swift-evolution
> <http://thread.gmane.org/gmane.comp.lang.swift.evolution/16150>.
>
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#motivation>Motivation
>
> Consider the following example
>
> class Bar {
> func foo() {
> }
>
> func foo(arg: Int) {
> }
> }
> You can reference foo(arg: Int) using Bar.foo(arg:) but there is currently no
> syntax to reference foo() without using disambiguation by type Bar.foo as ()
> -> Void. We believe this is a major hole in the current disambiguation syntax.
>
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#proposed-solution>Proposed
> solution
>
> We propose that Bar.foo only references methods with no parameters just as
> Bar.foo(arg:) references the methods with one argument named arg.
>
> This is a breaking change since Bar.foo currently refers to all methods with
> base name foo.
>
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#detailed-design>Detailed
> design
>
> The existing syntax Bar.foo is reinterpreted to not reference any method on
> Bar with base name foo but to only reference functions named foo that take no
> parameters.
>
> If two overloads with zero-parameters exist with different return types,
> disambiguation has still to be done via as just like with the foo(arg:)
> syntax.
>
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#impact-on-existing-code>Impact
> on existing code
>
> Existing code that uses Bar.foo to reference methods with parameters needs to
> be changed. We believe this will effect many developers, so a fix-it would be
> essential.
>
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#possible-issues>Possible
> issues
>
> Bar.foo may be mistaken for a reference to a property, since all other
> references to functions will contain parenthesis if this proposal is accepted.
>
> Most functions are not overloaded and using the base name only offers a
> shorthand way to reference these functions. If this proposal is accepted,
> this shorthand is no longer available for methods with parameters.
>
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#alternatives-considered>Alternatives
> considered
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#alternative-1-barfoo-inside-selector>Alternative
> 1: Bar.foo() inside #selector
>
> Let Bar.foo() refer to the zero-parameter function only inside #selector as
> it was proposed by Doug Gregor here
> <https://github.com/apple/swift-evolution/pull/280#discussion_r61849122>.
> This requires the proposal to disallow arbitrary expressions in #selector
> (GitHub-Link
> <https://github.com/ahoppen/swift-evolution/blob/arbitrary-expressions-in-selectors/proposals/0000-arbitrary-expressions-in-selectors.md>)
> to be approved. Issues we see are:
>
> This gives the illusion that foo is actually called which it isn't
> It doesn't solve the issue of referencing a zero-parameter function in
> arbitrary expressions somewhere else in code.
>
>
> <https://github.com/ahoppen/swift-evolution/tree/reference-zero-param-func#alternative-2-barfoo_>Alternative
> 2: Bar.foo(_)
>
> The original idea of using Bar.foo(_) to refer to the zero-parameter method
> was discarded after discussion on the mailing list because of the following
> reasons:
>
> It is only a single typo away from Bar.foo(_:) which references the method
> with one unnamed argument
> In argument lists _ implies the presence of an unnamed parameter, while _ in
> Bar.foo(_) would mark the absence of a any parameters.
>
>
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