Result+OldCallbackHelp.swift

import Foundation
import Result

public extension Result {
    
    /// Constructs a success wrapping `value`, iff `value` is not nil and `error` is nil.
    ///
    /// Constructs a failure wrapping `error`, iff `error` is not nil and `value` is nil.
    ///
    /// Otherwise, returns nil.
    ///
    /// Example:
    ///
    ///     request(url: examplecom) { (maybeJSON, maybeError) in
    ///         guard let result = Result(value: maybeJSON, error: maybeError) else {
    ///             fatalError("invalid callback parameters")
    ///         }
    ///
    ///         // decoded : Result<String, NSError>
    ///         print(decoded)
    ///     }
    public init?(value v: T?, error e: Error?) {
        switch (v, e) {
            
        case let (.some(v), .none):
            self = .success(v)
            
        case let (.none, .some(e)):
            self = .failure(e)
            
        case (_, _):
            return nil
        }
    }
    
}