问题描述
为什么调用defer func() { recover() }()成功恢复了恐慌的goroutine，但是调用defer recover()却没有成功?
Why does a call to defer func() { recover() }() successfully recover a panicking goroutine, but a call to defer recover() not?
作为一个简单的示例，此代码不会惊慌
As an minimalistic example, this code doesn't panic
package main
func main() {
defer func() { recover() }()
panic("panic")
}
但是，将匿名函数替换为直接恢复紧急情况
However, replacing the anonymous function with recover directly panics
package main
func main() {
defer recover()
panic("panic")
}
推荐答案
处理恐慌部分提到
recover功能允许程序管理紧急恐慌例程的行为.
The recover function allows a program to manage behavior of a panicking goroutine.
假设函数G 推迟了调用recover的函数D ，并且panic在执行G的同一goroutine上的函数中出现.
Suppose a function G defers a function D that calls recover and a panic occurs in a function on the same goroutine in which G is executing.
当递延函数的运行达到D时，D调用recover的返回值将是传递给panic调用的值.
如果D正常返回而没有开始新的恐慌，恐慌序列将停止.
When the running of deferred functions reaches D, the return value of D's call to recover will be the value passed to the call of panic.
If D returns normally, without starting a new panic, the panicking sequence stops.
这说明recover应该在延迟函数中调用，而不是直接调用.
出现紧急情况时，递延函数"不能是内置的recover()，而是在 defer语句中指定的函数. .
That illustrates that recover is meant to be called in a deferred function, not directly.
When it panic, the "deferred function" cannot be the built-in recover() one, but one specified in a defer statement.
DeferStmt = "defer" Expression .
除了特定的内置函数，函数和方法调用以及接收操作可以出现在语句上下文中.
With the exception of specific built-in functions, function and method calls and receive operations can appear in statement context.
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