> On Feb 21, 2017, at 11:05 PM, Jacob Bandes-Storch via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> Evolutioniers,
>
> Compound name syntax — foo(_:), foo(bar:), foo(bar:baz:) — is used to
> disambiguate references to functions. (You might've used it inside a
> #selector expression.) But there's currently no compound name for a function
> with no arguments.
>
> func foo() {} // no compound syntax for this one :(
> func foo(_ bar: Int) {} // foo(_:)
> func foo(bar: Int) {} // foo(bar:)
> func foo(bar: String, baz: Double) {} // foo(bar:baz:)
>
> Given these four functions, only the first one has no compound name syntax.
> And the simple reference "let myfn = foo" is ambiguous because it could refer
> to any of the four. A workaround is to specify a contextual type, e.g. "let
> myfn = foo as () -> Void".
>
> I filed SR-3550 <https://bugs.swift.org/browse/SR-3550> for this a while ago,
> and there was some discussion in JIRA about it. I'd like to continue
> exploring solutions here and then write up a formal proposal.
>
> To kick off the discussion, I'd like to propose foo(:) for nullary functions.
I like this idea.
>
> Advantages:
> - the colon marks a clear similarity to the foo(bar:) form when argument
> labels are present.
> - cutely parallels the empty dictionary literal, [:].
>
> Disadvantages:
> - violates intuition about one-colon-per-argument.
> - the parallel between #selector(foo(:)) and @selector(foo) is not quite as
> obvious as between #selector(foo(_:)) and @selector(foo:).
>
>
> For the sake of discussion, another option would be foo(_). This was my
> original choice, and I like that the number of colons matches the number of
> parameters. However, it's a little less obvious as a function reference. It
> would preclude _ from acting as an actual identifier, and might conflict with
> pattern-matching syntax (although it appears functions can't be compared with
> ~= anyway).
foo(_) looks like a pattern to me. Even if it doesn’t introduce ambiguity in
the grammar it might be confusing.
>
>
> Looking forward to everyone's bikeshed color ideas,
> Jacob
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