Swift: regular closure vs auto closure

closure.swift

// a regular method that doesn't have any arguments
func regularClosure(str:() -> String) {
    str()
}
regularClosure{"print me!"}
// can be replaced with an @autoclosure
func autoClosure(@autoclosure str:() -> String) {
    str()
}
autoClosure("print me!")
// but one that takes an argument cannot
func regularClosureWithArgument(str:(String) -> String) {
    str("print me!")
}
regularClosureWithArgument{$0}