error-handling - 在SBCL中使用[Take New]重新启动

Question

当我尝试以导致名称冲突的方式在SBCL中重新定义软件包时，重新启动时出现NAME-CONFLICT错误

 0: [KEEP-OLD] Keep symbols already accessible FOO (shadowing others).
 1: [TAKE-NEW] Make newly exposed symbols accessible in FOO, uninterning old ones.
 2: [RESOLVE-CONFLICT] Resolve conflict.
 3: [RETRY] Retry SLIME REPL evaluation request.
 4: [*ABORT] Return to SLIME's top level.
 5: [ABORT] Abort thread (#<THREAD "new-repl-thread" RUNNING {10060E47B3}>)

我想写一些可以自动重启 TAKE-NEW的东西，这样我就可以做

(force (defpackage :foo (:use :cl :bar :baz :mumble)))

其结果应与调用 defpackage相同，然后手动调用 TAKE-NEW restart。问题是，

CL-USER> (handler-case 
         (defpackage :foo (:use :cl :bar :baz :mumble))
       (error (e) (compute-restarts e)))
(#<RESTART SWANK::RETRY {1006DC40F3}> #<RESTART ABORT {10068007E3}>
 #<RESTART ABORT {10060C7F93}>)
CL-USER> 

我似乎无法访问该特定的重新启动。正如我尝试调用它时所确认的:

CL-USER> (handler-case 
         (defpackage :foo (:use :cl :bar :baz :mumble))
       (name-conflict (e) (invoke-restart 'take-new)))

No restart TAKE-NEW is active.
   [Condition of type SB-INT:SIMPLE-CONTROL-ERROR]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [*ABORT] Return to SLIME's top level.
 2: [ABORT] Abort thread (#<THREAD "new-repl-thread" RUNNING {10060E47B3}>)

有任何想法吗？

Answer 1

handler-case在将控制权转移给处理程序之前退出重新启动的范围；您需要handler-bind。构造之间的另外两个区别是handler-bind具有不同的语法(如下所示)，并且handler-bind不传递控制权-也就是说，对于handler-bind处理程序返回其值需要显式传递控制权，例如使用return-from或invoke-restart。

类似于以下内容的东西应该起作用:

(handler-bind ((sb-ext:name-conflict
                (lambda (c)
                  (when (find-restart 'sb-impl::take-new c)
                    (invoke-restart 'sb-impl::take-new)))))
  (defpackage :foo (:use :mumble)))