[swift-evolution] [Discussion] func/closure parameters and tuples

Vladimir.S svabox at gmail.com
Tue Jun 21 13:28:07 CDT 2016

I wanted to ask if the below behavior of compiler/parser is bug or it is 
'feature' and 'by design' and we will not change this :

1. I was not expecting this will compile :

let ft1 : (Int,Int) -> Void = { x in print(x.0, x.1)}

ft1(1, 2)

the type of ft1 is definitely not the same as closure

2. The same. But this crashes compiler at compile time(if I understand 
correctly) :

let ft2 : (Int,Int) -> Void = { x in print(x) }

ft2(1, 2)

Unhandled conversion from exploded tuple
1.	While emitting reabstraction thunk in SIL function 
@_TTRXFo_iP___XFo_dSidSi__<unknown>:0: error: unable to execute command: 
<unknown>:0: error: compile command failed due to signal (use -v to see 

3. Was expecting closure will require a single argument, which is tuple; 
but it accepts even just x, y

typealias IntInt = (Int,Int)

func foo(block: (IntInt) -> Void) {
     let z : IntInt = (1,2)

foo { x in print(x)} // ok
foo { x, y in print(x,y)}
foo { (x, y) in print(x, y)}

I'm not sending two values to closure, I send one instance which is tuple.

Shouldn't we add consistency in Swift regarding allowed argumets of closure 
if tuple is required as parameter?

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