我的借款检查员喝醉了吗？

Question

reference must be valid for the block at 50:74... ...but borrowed value is only valid for the block at 50:74

对。那么问题是什么？

有问题的区块：

pub fn git_upload_pack(self: &mut GitConnect) -> Result<String, &str> {
    let c = format!("git-upload-pack {}[=10=]host={}[=10=]", self.repo.path, self.repo.domain);

    let mut out = String::new();
    let data = try!(self.command(c.as_slice()));

    for line in data.iter() {
        out.push_str(from_utf8(line.as_slice()).unwrap());
    }

    Ok(out)
}

self.command:

fn command(self: &mut GitConnect, command: &str) -> Result<Vec<Vec<u8>>, &str> {

完整错误：

src/protocol/git_connect.rs:54:38: 54:39 error: `c` does not live long enough
src/protocol/git_connect.rs:54         let data = try!(self.command(c.as_slice()));
                                                                    ^
<std macros>:1:1: 6:60 note: in expansion of try!
src/protocol/git_connect.rs:54:20: 54:53 note: expansion site
src/protocol/git_connect.rs:50:75: 61:6 note: reference must be valid for the anonymous lifetime #1 defined on the block at 50:74...
src/protocol/git_connect.rs:50     pub fn git_upload_pack(self: &mut GitConnect) -> Result<String, &str> {
src/protocol/git_connect.rs:51         let c = format!("git-upload-pack {}[=12=]host={}[=12=]", self.repo.path, self.repo.domain);
src/protocol/git_connect.rs:52 
src/protocol/git_connect.rs:53         let mut out = String::new();
src/protocol/git_connect.rs:54         let data = try!(self.command(c.as_slice()));
src/protocol/git_connect.rs:55 
                               ...
src/protocol/git_connect.rs:50:75: 61:6 note: ...but borrowed value is only valid for the block at 50:74
src/protocol/git_connect.rs:50     pub fn git_upload_pack(self: &mut GitConnect) -> Result<String, &str> {
src/protocol/git_connect.rs:51         let c = format!("git-upload-pack {}[=12=]host={}[=12=]", self.repo.path, self.repo.domain);
src/protocol/git_connect.rs:52 
src/protocol/git_connect.rs:53         let mut out = String::new();
src/protocol/git_connect.rs:54         let data = try!(self.command(c.as_slice()));

Answer 1

我觉得这像是一个错误。

这个签名：

fn command(self: &mut GitConnect, command: &str) -> Result<Vec<Vec<u8>>, &str>

根据lifetime elision rules，应该相当于这个：

fn command<'a, 'b>(self: &'a mut GitConnect, command: &'b str) -> Result<Vec<Vec<u8>>, &'a str>

事实上，如果您重写 command() 以使用此扩展变体，它应该可以编译。此外，如果您使用 shorthand self 参数定义：

fn command(&mut self, command: &str) -> Result<Vec<Vec<u8>>, &str>

然后它也编译。

目前看来

fn command(self: &mut GitConnect, command: &str) -> Result<Vec<Vec<u8>>, &str>

等同于

fn command<'a>(self: &'a mut GitConnect, command: &'a str) -> Result<Vec<Vec<u8>>, &'a str>

出于正确的原因给出了完全相同的错误，因为存在生命周期错误：command 参数的生命周期被断言为与 self 相同，因此它不适用于本地生命周期短于 self.

之一的变量

我的借款检查员喝醉了吗？

Is my borrow checker drunk?

rust