ErrorType vs NSError

error.swift

public class func parse(data: NSData) -> (AnyObject?, NSError?) {
    do {
    	// From docs: If an error occurs, upon return contains an NSError object that describes the problem.
        let obj = try NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments)
        return (obj as AnyObject, nil)
    } catch {
    	// But here I get: ErrorType is not convertible to NSError
        return (nil, error)
    }
}

return (nil, error as NSError) thanks to ErrorType bridging to NSError. You can also catch let error as NSError because catch here is a shorthand for catch let error. Docs