lldb中的Swift泛型 - 错误：无法找到与完整类型的原始类型匹配的任何类型

I have this bit of code:

我有这段代码:

class Talker:NSObject {
    func describe<T: Showable, U:Showable>(stuffs: [Blob<T, U>]) {
        let useless:Int = 71
        print("useless = \(useless)")
        for s in stuffs {
            print("s = \(s)")
        }
    }
}
class Talk