[Accepted with Modifications] SE-0286: Forward Scan for Trailing Closures

[Nevin]

Can we clarify the behavior of trailing closures for parameters of type Any, as per @xwu’s comment here?

@xwu

Mmm, this is interesting, and I’m not sure I’d appreciated that. Currently, Any works with trailing closure syntax:

func f(_ x: Any) -> String { "Hello, \(x)!" }
print(f { "World" })
// “Hello, (Function)!”

Unless there’s a compelling reason, I don’t know that we should break that, and I’m not sure it’s touched on in the proposal.

Edit:

The response from @Douglas_Gregor here:

@Douglas_Gregor

From the proposal:

The unlabeled trailing closure will be matched to the next parameter that is either unlabeled or has a declared type that structurally resembles a function type

so this is still well-formed.

Doug

does not seem to address what happens with labeled parameters of type Any:

func foo(f: Any) { print(f) }
foo{ return }

• • •

Also, as a forum usability issue, the fact that the proposal thread has been locked makes it very difficult to quote posts from there for the purpose of responding here. It would be nice if there were a way to quote a post from a locked thread, even without being able to post in that thread.