Weird stuff with free function labels in Xcode 7.0 beta 2...

funcLabels.swift

import UIKit

// Running on Xcode 7.0 beta (7A121l)
// All running in a playground
// Open console (View -> Debug Area -> Show Debug Area)

// Define a non-generic free fn taking 1 arg
func notGeneric(x: String) {
  print("notGeneric called")
}

notGeneric("hello world")                 // works
//notGeneric("hello world", false)        // doesn't compile
//notGeneric("hello world", foo: false)   // doesn't compile

// Now, define a generic free fn taking 1 arg
func thisFnIsGeneric<T>(x: T) {
  print("thisFnIsGeneric called")
}

thisFnIsGeneric("hello world")                // works
thisFnIsGeneric("hello world", true)          // works
thisFnIsGeneric(foo: "hello", bar: "world")   // works

// Trying similar things with 'print()', which has an optional second argument.

// All 3 work as expected; they call the built-in 'print()' function with the correct newline behavior
//print("test")
//print("test", appendNewline: true)
//print("test", appendNewline: false)

// All of these compile and work as if they were calls to the built-in 'print()' with the correct label names
// Fun fact: if you try running this code as an actual project, these print out as tuples instead.
print("test1", appendNewLine: false)
print(foo: "test2", BAAARRRRR: true)
print("test3", false)

// Trying something else...
func print<T>(argument: T, appendNEWLINE: Bool) {
  print("Overloaded 'print' called")
}

// This calls the overloaded version of 'print' defined above
print("hello", appendNEWLINE: true)