[swift-evolution] [Review] SE-0029 Remove implicit tuple splat behavior from function applications

[Chris Lattner]

> On Feb 5, 2016, at 11:15 AM, Jessy Catterwaul via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I am fine with this proposal, except for having to name the parameter. The argument should be known as $0, within the function. Explanation and example…

Hi Jessy,

I don’t understand what you’re referring to here.  The proposal is about removing a feature, not changing existing functionality or adding new things.  If you’d like to propose a language change, please do so on a new thread.

-Chris

> 
> My single use case of where this feature might have worked, actually does not. See the double parentheses:
> 
> protocol Protocol {
>    typealias Arguments
>    func ƒ1(parameters: Arguments) -> Arguments
>    func ƒ2(parameters: Arguments)
> }
> 
> 
> struct Struct1: Protocol {
>    typealias Arguments = (goodName: String, otherGoodName: String)
>    func ƒ1(parameters: Arguments) -> Arguments {
>       return (goodName: "", otherGoodName: "")
>    }
>    func ƒ2(parameters: Arguments) {}
> }
> 
> let struct1 = Struct1()
> 
> // Too many parentheses are needed, but whatever.
> // Not a big deal.
> let struct1Arguments = struct1.ƒ1((goodName: "", otherGoodName: ""))
> 
> struct1.ƒ2(struct1Arguments)
> 
> 
> Typealiases fall apart when I need a single parameter:
> 
> struct Struct2: Protocol {
>    // Should be (goodName: String) but named 1-tuples don't work.
>    typealias Arguments = String
>    
>    func ƒ1(parameters: Arguments) -> Arguments {return ""}
>    func ƒ2(parameters: Arguments) {}
> }
> 
> let struct2 = Struct2()
> 
> // No extra parentheses are needed but I don't know what the argument is.
> // This is a big deal.
> let struct2Arguments = struct2.ƒ1("")
> 
> struct2.ƒ2(struct2Arguments)
> 
> 
> We need to be able to name the element of a single-item tuple, and we need to stop enforcing internal parameter names:
> 
> protocol Protocol {
>    typealias Arguments
>    func ƒ1(Arguments) -> Arguments
>    func ƒ2(Arguments)
> }
> 
> struct Struct: Protocol {
>    typealias Arguments = (goodName: String)
>    func ƒ1(Arguments) -> Arguments {
>       return (goodName: $0.goodName)
>    }
>    func ƒ2(Arguments) {}
> }
> 
> let `struct` = Struct()
> let structArguments = `struct`.ƒ1((goodName: ""))
> `struct`.ƒ2(structArguments)
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