如何修复：预期具体生命周期，但发现绑定生命周期参数

我目前正在听这个问题。我试图将其缩小到最小的可重现示例。

struct Request;

struct ResponseWriter<'a> { 
    dummy: &'a () 
}

#[deriving(Clone)]
pub struct RouteStore{
    pub routes: Vec<Route>,
}

#[deriving(Clone)]
struct Route {
    path: String,
    handler: fn(request: &Request, response: &mut ResponseWriter)
}

impl RouteStore {
    pub fn new () -> RouteStore {
        RouteStore {
            routes: Vec::new()
        }
    }

    fn add_route (&mut self, path: String, handler: fn(request: &Request, response: &mut ResponseWriter)) -> () {
        let route = Route {
            path: path,
            handler: handler
        };
        self.routes.push(route);
    }
}

fn main () {

}

这给我留下了：

error: mismatched types: expected `fn(&http::server::request::Request, &mut http::server::response::ResponseWriter<>)` but found `fn(&http::server::request::Request, &mut http::server::response::ResponseWriter<>)` (expected concrete lifetime, but found bound lifetime parameter )
src/so.rs:12     handler: fn(request: &Request, response: &mut ResponseWriter)
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

之前我存储了我的fn in a HashMap像这样HashMap<String, fn(request: &Request, response: &mut ResponseWriter)>。这很好用。

但现在我想重构一下并引入一个Route将事物构造并存储为Vec<Route>。但突然间地狱崩溃了，我不知道如何解决它:-/

对于好奇的人来说，这是我为 Rust 编写一个受expressjs启发的Web框架的一部分Floor https://github.com/cburgdorf/Floor

在使你的示例变得更加简单之后（摆脱http依赖），以及 IRC 上的一些建议（即有人指出，如果删除deriving(Clone)来自Route），您可以在下面看到一个固定版本（--cfg v2)

#[deriving(Clone)]
pub struct RouteStore{
    pub routes: Vec<Route>,
}

#[cfg(v1)]
#[deriving(Clone)]
struct Route {
    path: String,
    handler: fn(response: &mut ())
}

#[cfg(v2)]
struct Route {
    path: String,
    handler: fn(response: &mut ())
}

#[cfg(v2)]
impl Clone for Route {
    fn clone(&self) -> Route {
        Route { path: self.path.clone(), handler: self.handler }
    }
}
impl RouteStore {
    pub fn new () -> RouteStore {
        RouteStore {
            routes: Vec::new()
        }
    }

    fn add_route (&mut self, path: String, handler: fn(response: &mut ())) -> () {
        let route = Route {
            path: path,
            handler: handler
        };
        self.routes.push(route);
    }
}

fn main () {

}

这里的问题是fn不实施Clone.（编辑：嗯，它does have a clone方法，但返回的值似乎与该字段所需的不兼容。这v2上面的版本只是回避了整个问题。）

所以我怀疑您看到的错误来自自动生成的克隆实现deriving(Clone)注入。