[swift-evolution] Proposal: Always flatten the single element tuple

[Brent Royal-Gordon]

> On Jun 7, 2017, at 3:03 AM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Well please no:
> 
> 
>  let fn2: ((Int, Int)) -> Void = { lhs, rhs in } 
> 
> Instead use destructuring sugar pitched by Chris Lattner on the other thread:
> 
> let fn2: ((Int, Int)) -> Void = { ((lhs, rhs)) in }
> 

I think this suggestion is better than the status quo. I'm wondering, though, if we should just drop the outer set of parentheses entirely, unless you're also putting types on the parameters. That is, a closure of type `(Int, Int) -> T` can look like this:

	{ (x: Int, y: Int) in … }

Or it can look like this:

	{ x, y in … }

But it *cannot* look like this:

	{ (x, y) in … }

The `(x, y)` form can instead be a closure of a type like `((Int, Int)) -> T`, which immediately destructures the tuple parameter into separate constants.

-- 
Brent Royal-Gordon
Architechies

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