[swift-evolution] @noescape and nil

[Chris Lattner]

> On Apr 26, 2016, at 12:15 AM, Aleksandar Petrovic via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Hi Swift community, I have a question.
> 
> This is a valid Swift code:
> 
> func testFunc(times: Int, fn: ((Int)->Void)? = nil) {
> 	guard let f = fn else { return }
> 	for i in 1 ..< times {
> 		f(i)
> 	}
> }
> 
> And this is not:
> 
> func testFunc(times: Int, @noescape fn: ((Int)->Void)? = nil) {
> 	guard let f = fn else { return }
> 	for i in 1 ..< times {
> 		f(i)
> 	}
> }
> 
> I can't think of any hard reason why the @noescape parameter of the function can't be nullable (and, with default value, be optional), but maybe I'm missing something. Is there any plan to correct this in 3.0?

There are two ways to fix this: a horrible hack that special cases optionals, or the more principled solution that treats optional as the underlying enum type that it is, and making @noescape propagate through to the members of the .some case.

You can probably guess this, but I’d prefer to discuss fixing the full generality of the problem, not providing a special case in the compiler for this.

-Chris

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