scala like "if" in swift

scalaif.swift

extension Optional {
    func _else(state: () -> Wrapped) -> Wrapped {
        return self ?? state()
    }
    
    func _else_if(@autoclosure condition: () -> Bool, state: () -> Wrapped) -> Wrapped? {
        return self ?? _if(condition(), state: state)
    }
}

func _if<R>(@autoclosure condition: () -> Bool, state: () -> R) -> R? {
    if condition() {
        return state()
    }
    return nil
}

func _if_let<A, R>(@autoclosure condition: () -> A?, _where: A -> Bool = { _ in true }, state: A -> R) -> R? {
    if let a = condition() where _where(a) {
        return state(a)
    }
    return nil
}

var a = _if(true) {
    1
}

var b = _if(false) {
    1
}._else {
    2
}

var c: String?

var d = _if_let(c) { c in
    c + "B"
}

c = "A"

var e = _if_let(c, _where: { c in c == "A" }) { c in
    c + "B"
}