Weird value of #function literal in Swift 3.1

I found out that the String returned by #function literal in Swift 3.1 is... weird. Here:

class FunctionLiteralTest {
    func weirdo() -> String {
        return #function
    }

    func weirdo(parameter: Int) -> String {
        return #function
    }

    func weirdo(_ parameter: Int) -> String {
        return #function
    }

    func weirdo(_ parameter: Int, _ anotherParameter: Int) -> String {
        return #function
    }
}

let functionLiteralTest = FunctionLiteralTest()

functionLiteralTest.weirdo()             // returns "weirdo()"
functionLiteralTest.weirdo(parameter: 1) // returns "weirdo(parameter:)"
functionLiteralTest.weirdo(1)            // returns "weirdo"
functionLiteralTest.weirdo(1, 2)         // returns "weirdo"

Parentheses are skipped entirely when all parameters are unlabeled. I would quite understand that if #function returned function name without parentheses for functions without any parameters too.

Is that justified behavior or a bug?