swift - 错误: use of undeclared type '$__lldb_context' in NSAttributedString extension

Question

给定以下Swift代码，将其保存在bug.swift中，并使用Xcode 8.2.1或Xcode 8.3 beta 2:

import Foundation

protocol MyProtocol {
    func foo() -> String
}

extension MyProtocol {
    func foo() -> String {
        return "\(self)"
    }
}

extension String: MyProtocol {}
extension NSAttributedString: MyProtocol {}

let normal = "normal".foo()
let attributed = NSAttributedString(string: "attributed", attributes: [:]).foo()

运行以下命令:

swiftc -g bug.swift
lldb bug

LLDB启动。现在，运行这些命令，并观察输出。在我传递 9的地方，传递您的 bug.swift中包含 return "\(self)"的行:

(lldb) target create "bug"
Current executable set to 'bug' (x86_64).
(lldb) b 9
Breakpoint 1: where = bug`(extension in bug):bug.MyProtocol.foo () -> Swift.String + 19 at bug.swift:9, address = 0x0000000100001e53
(lldb) run
Process 16370 launched: '/Users/zev/Desktop/bug' (x86_64)
Process 16370 stopped
* thread #1: tid = 0x31730e, 0x0000000100001e53 bug`MyProtocol.foo(self="normal") -> String + 19 at bug.swift:9, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000100001e53 bug`MyProtocol.foo(self="normal") -> String + 19 at bug.swift:9
   6    
   7    extension MyProtocol {
   8        func foo() -> String {
-> 9            return "\(self)"
   10       }
   11   }
   12   
(lldb) po self
"normal"


(lldb) c
Process 16370 resuming
Process 16370 stopped
* thread #1: tid = 0x31730e, 0x0000000100001e53 bug`MyProtocol.foo(self=0x00007fff5fbff480) -> String + 19 at bug.swift:9, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
    frame #0: 0x0000000100001e53 bug`MyProtocol.foo(self=0x00007fff5fbff480) -> String + 19 at bug.swift:9
   6    
   7    extension MyProtocol {
   8        func foo() -> String {
-> 9            return "\(self)"
   10       }
   11   }
   12   
(lldb) po self
error: <EXPR>:1:11: error: use of undeclared type '$__lldb_context'
extension $__lldb_context {                            
          ^~~~~~~~~~~~~~~

error: <EXPR>:18:5: error: use of unresolved identifier '$__lldb_injected_self'
    $__lldb_injected_self.$__lldb_wrapped_expr_2(     
    ^~~~~~~~~~~~~~~~~~~~~

第一次达到断点时，我们就符合 String和 MyProtocol的要求，并且我们可以成功实现 po self。

但是，第二次达到断点时，我们处于 NSAttributedString与 MyProtocol的一致性，并且LLDB打印出乱码，而不是 po self的预期输出。

为什么LLDB有时无法打印任何有用的信息？这是一个人为的示例，但是我在日常使用LLDB时经常遇到这个问题。

Answer 1

根据Swift错误报告程序上的this answer指出，该错误已在某个时间点修复。我在Swift 5.2中进行了测试，并确认它已修复🎉