undefined for Swift

Micro frameworks are popular now, so I'll go nano framework :-). This is all the code:

/**
 * `undefined()` pretends to be able to produce a value of any type `T` which can
 * be very useful whilst writing a program. It happens that you need a value
 * (which can be a function as well) of a certain type but you can't produce it
 * just yet. However, you can always temporarily replace it by `undefined()`.
 *
 * Inspired by Haskell's
 * [undefined](http://hackage.haskell.org/package/base-4.7.0.2/docs/Prelude.html#v:undefined).
 *
 * Invoking `undefined()` will crash your program.
 *
 * Some examples:
 *
 *  - `let x : String = undefined()
 *  - `let f : String -> Int? = undefined("string to optional int function")
 *  - `return undefined() /* in any function */`
 *  - `let x : String = (undefined() as Int -> String)(42)`
 *  - ...
 *
 * What a crash looks like:
 *
 * `fatal error: undefined: main.swift, line 131`
 *
 */
func undefined<T>(_ hint:String="", file:StaticString=__FILE__, line:UWord=__LINE__) -> T {
    let message = hint == "" ? "" : " \(hint)"
    fatalError("undefined\(message)", file:file, line:line)
}

More information

See my slides about undefined() from my Further Leveraging the Type System talk at Swift Summit 2015.