[swift-evolution] Opt-out for first unnamed parameter instead of opt-in

[Dave Abrahams]

Just a note on terminology: we're trying to standardize on the terms
“parameter name” and “argument label”:

           func f(argumentLabel parameterName: ParameterType)

           f(argumentLabel: argument)


on Mon Feb 08 2016, Dave <swift-evolution at swift.org> wrote:

> If we decide to allow external names without an internal name, I’m
> strongly in favor of the “func doThing(with _: Int) {}“ syntax. It
> makes it crystal clear that we’re purposefully not assigning an
> internal name to that argument.
>
> - Dave Sweeris
>
>> On Feb 8, 2016, at 16:46, Jessy Catterwaul via swift-evolution
>> <swift-evolution at swift.org> wrote:
>> 
>> Sorry, I forgot about this one:
>> 
>> 5. An external, but not internal parameter name is needed. I don’t
>> think a colon is useful in these cases.
>> func doThing(with Int) {}
>> 
>> It also could satisfy a protocol requirement, without having to
>> resort to this kind of underscore usage, which should become
>> illegal:
>> func doThing(with _: Int) {}
>> 
>>> On Feb 8, 2016, at 5:32 PM, Jessy Catterwaul
>>> <mr.jessy at gmail.com
>>> <mailto:mr.jessy at gmail.com>> wrote:
>>> 
>>> How often do you find yourself wanting an internal parameter name,
>>> but not an external (case 4)? I think it’s very rare.
>>> 
>>> I doubt that the compiler’s AI will be able to deal with case 2.b,
>>> automatically, any time soon. That is okay with me, as long as we
>>> can manually type direct objects that would not be clear with only
>>> a preposition.
>>> 
>>> I think these represent the options for parameter names in order of
>>> prevalence. Case 3 has obviously never been available in Swift, but
>>> can be emulated with generic-sounding internal parameter names. If
>>> those types of names were not necessary, I believe all of these
>>> “opting” problems would go away. Is that incorrect?
>>> 
>>> 1. Internal is the same as external
>>> func function(int: Int) {}
>>> 
>>> 2. External and internal names are different 
>>> a. func doThing(with int: Int) {}
>>> b. func doThing(withGiraffe giraffe: Any) {}
>>> 
>>> 3. No parameter name is needed internally or externally
>>> func function(Int)
>>> 
>>> 4. Underscore for external, name for internal
>>> func function(_ int: Int) {}
>> 
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-- 
-Dave