[swift-users] Swift 3 (Xcode 8 GM) issue with @escaping

[Shawn Erickson via swift-users]

I like and fully supported the change to @escaping away from @noescape
however in a body of code that I am porting to the latest Swift 3 variant
(as found in Xcode 8 GM) I am hitting an issue for methods that take an
optional completion closure. If optional is involved I can't find a way to
apply @escape to the escaping closure. See the following for an basic
example...

Is their a way to do what I need and/or is this an edge case in the
implementation of @escaping?

typealias MyCallback = (String)->()

// Happy
func foo1(bar: String, completion: ((String)->())) {
    completion(bar)
}

// Happy
func foo2(bar: String, completion: MyCallback) {
    completion(bar)
}

// Happy
func foo3(bar: String, completion: ((String)->())? = nil) {
    completion?(bar)
}

// Happy
func foo4(bar: String, completion: MyCallback? = nil) {
    completion?(bar)
}

// Happy
func foo5(bar: String, completion: Optional<MyCallback> = nil) {
    completion?(bar)
}

// Happy
func foo6(bar: String, completion: @escaping (String)->()) {
    completion(bar)
}

// Happy
func foo7(bar: String, completion: @escaping MyCallback) {
    completion(bar)
}

// Unhappy...
// "@escaping attribute only applies to function types"
func foo8(bar: String, completion: @escaping ((String)->())? = nil) {
    completion?(bar)
}

// Unhappy...
// "@escaping attribute only applies to function types"
func foo9(bar: String, completion: @escaping MyCallback? = nil) {
    completion?(bar)
}

// Unhappy...
// "@escaping attribute only applies to function types"
func foo10(bar: String, completion: (@escaping ((String)->()))? = nil) {
    completion?(bar)
}

// Unhappy...
// "@escaping attribute only applies to function types"
func foo11(bar: String, completion: (@escaping MyCallback)? = nil) {
    completion?(bar)
}

// Unhappy...
// "@escaping attribute only applies to function types"
func foo12(bar: String, completion: Optional<@escaping MyCallback> = nil) {
    completion?(bar)
}

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