Ios 当我尝试使用typealias类型调用静态方法时，Swift lldb rpc服务器总是崩溃

我正在一个快速的操场上尝试以下内容。因此，这里的问题基本上是

FontType.dynamicExtensionFunction（）

。这是不允许的吗

import Foundation

protocol Custom {}

extension Custom {
  static func dynamicExtensionFunction() {
    print("Add")
  }
}

@objc protocol ObjCCustom {
  associatedtype FontType: Custom
}

enum MyFont: String, Custom {
  case regular = "MyFont-Regular"
}

@objc(MyFont)
class ObjCMyFont: NSObject, ObjCCustom {
  typealias FontType = MyFont
}

extension ObjCCustom {
  static func exec() {
    FontType.dynamicExtensionFunction()
  }
}

ObjCMyFont.exec()

这通常会导致LLDB RPC服务器崩溃。此代码段来自崩溃日志

Process:               lldb-rpc-server [71615]
Path:                  /Applications/Xcode_8.3.app/Contents/SharedFrameworks/LLDBRPC.framework/Versions/A/Resources/lldb-rpc-server
Identifier:            lldb-rpc-server
Version:               2
Code Type:             X86-64 (Native)
Parent Process:        Xcode [52463]
Responsible:           lldb-rpc-server [71615]
User ID:               506

Date/Time:             2017-04-06 12:28:42.491 +0800
OS Version:            Mac OS X 10.12.4 (16E195)
Report Version:        12
Anonymous UUID:        

Sleep/Wake UUID:       

Time Awake Since Boot: 350000 seconds
Time Since Wake:       3500 seconds

System Integrity Protection: enabled

Crashed Thread:        8  RPC packet thread for client tid 028474a8 (42235048)

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000018
Exception Note:        EXC_CORPSE_NOTIFY

Termination Signal:    Segmentation fault: 11
Termination Reason:    Namespace SIGNAL, Code 0xb
Terminating Process:   exc handler [0]