为什么一个函数不抛出就满足抛出要求？

Question

protocol Throwing {
    func x() throws
}


class C : Throwing{
    func x(){
        print("not throwing") // no errors!
    }
}

为什么编译器不抛出任何错误？这是设计使然还是错误？

Answer 1

编译的原因是一样的：

class A {
    func x() throws {}
}
class B:A {
    override func x() {}
}

还有这个：

func f() {}
func yoho (_ f : () throws -> Void) {}
override func viewDidLoad() {
    yoho(f)
}

还有这个：

func f() {}
var fun : (() throws -> Void)!
override func viewDidLoad() {
    self.fun = f
}

Why is a function satisfying a throwing requirement without throwing?