[swift-evolution] [Pitch] Make the first parameter in a function declaration follow the same rules as the others

[Joe Groff]

> On Mar 9, 2016, at 5:03 PM, Jordan Rose <jordan_rose at apple.com> wrote:
> 
> This is my concern too. Our guidelines often lead to the first parameter having a label, but usually that name isn't the same as the name of the parameter—one's a preposition, the other's a noun. I'm pretty sure the common case is still unlabeled. Does that justify the complexity of the current rule?

I think it's also common under our guidelines for the second argument label to not make sense as a parameter name, since it's often also a preposition, e.g. `move(from origin: T, to destination: U)`.

-Joe

> 
> (But because Objective-C methods will now often have labeled arguments, it would at least no longer be a marker differentiating "pure Swift" code from "Cocoa" code.)
> 
> Jordan
> 
> 
>> On Mar 9, 2016, at 14:32, Radosław Pietruszewski via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Looking at my code, the majority of methods should still have the first parameter unlabeled. 
>> 
>> I like the consistency of what you’re proposing and the fact that I don’t have to write `func foo(someArgument someArgument: T)` anymore. But I also fear people won’t get it that they can (and in many, probably most, situations should) make the first parameter `_ foo`.
>> 
>> — Radek
>> 
>>> On 09 Mar 2016, at 19:58, Joe Groff via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> Our accepted naming guidelines have embraced first argument labels for functions and methods. This weakens our justification for making the first parameter declaration in a `func` declaration behave differently from the others, implicitly being unlabeled. It seems pretty clear to me we should make all of the parameter declarations behave uniformly:
>>> 
>>> func foo(x: Int, y: Int) // Should declare foo(x:y:), instead of foo(_:y:)
>>> func foo(_ x: Int, y: Int) // Explicitly declares foo(_:y:)
>>> 
>>> This would also make `init` and `func` parameters behave consistently, which is nice. There may still be hope for our keyword argument rules to one day be shorter than the Smalltalk spec…
>>> 
>>> -Joe
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