Fix parsing error for propertyWrapper attributes

@propertyWrapper
struct TwelveOrLess {
    private var number: Int
    init() { self.number = 0 }
    var wrappedValue: Int {
        get { return number }
        set { number = min(newValue, 12) }
    }
}

struct SmallRectangle {
    @TwelveOrLess() // Parse error here because of empty parentheses "()"
    var height: Int
    @TwelveOrLess
    var width: Int
}

@A<Int> var a: Int
@A.Nested(withValue: 42) var a: Int