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

[Stephen Celis]

I like this a lot, but how do we solve for the function case?

    func add(_ x: Int, _ y: Int) -> Int {
      return x + y
    }
    [(1, 2)].map(add)

Where does `map` with a function of `((Int, Int)) -> Int` fit in?

> On Jun 6, 2017, at 10:15 PM, Susan Cheng via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Introduction
> 
> 
> Because the painful of SE-0110, here is a proposal to clarify the tuple syntax.
> 
> Proposed solution
> 
> 1. single element tuple always be flattened
> 
> let tuple1: (((Int))) = 0  // TypeOf(tuple1) == Int
> 
> let tuple2: ((((Int))), Int) = (0, 0)  // TypeOf(tuple2) == (Int, Int)
> 
> 2. function arguments list also consider as a tuple, which means the function that accept a single tuple should always be flattened.
> 
> let fn1: (Int, Int) -> Void = { _, _ in }
> 
> let fn2: ((Int, Int)) -> Void = { _, _ in }  // always flattened
> 
> let fn3: (Int, Int) -> Void = { _ in }  // not allowed, here are two arguments
> 
> let fn4: ((Int, Int)) -> Void = { _ in }  // not allowed, here are two arguments
> 
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