only Swfit 1.2

gistfile1.swift

let request = GitHub.Endpoint.SearchRepositories(query: "APIKit", sort: .Stars)
GitHub.sendRequest(request)
    .success { println($0) }
    .failure { println($0) }

extension GitHub {
    func sendRequest<T: APIKit.Request>(request: T) -> Task<Float, T.Response, NSError> {
        return Task { progress, fulfill, reject, configure in
            /*
            /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc failed with exit code 1
            を回避するために必要
            */
            let fulfill = fulfill
            let reject = reject
            
            GitHub.sendRequest(request) { response in
                switch response {
                case .Success(let box):
                    fulfill(box.value)
                    
                case .Failure(let box):
                    reject(box.value)
                }
            }
        }
    }
}

これでもとおった

let a = GitHub.sendRequest(request) { response in
    switch response {
        case .Success(let box):
            fulfill(box.value)

        case .Failure(let box):
            reject(box.value)
    }
}

// NG
class A {
    func a() -> (String -> Void) {
        return { value in
            {
                println(value)
            }
        }
    }
}

// OK
class A {
    func a() -> (String -> Void) {
        return { value in
            let b = {
                println(value)
            }
        }
    }
}