Function type does not implement Clone

[am0d]

I'm having some troubles with Clone for a function type.
I'm using the following function in my code:

fn(&Request, &mut ResponseWriter) -> Box<Action>

and it apparently doesn't implement Clone, nor can I implement Clone for it.

This is the code that I'm using to test: http://is.gd/3cm94D
and the output I get when trying to compile code which requires the function to be Cloneable:

<anon>:20:5: 20:35 error: failed to find an implementation of trait core::clone::Clone for fn(&Request, &mut ResponseWriter) -> Box<Action>
<anon>:20     routes: Router<RequestHandler>
              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: in expansion of #[deriving]
<anon>:18:1: 19:7 note: expansion site

@Kimundi on irc suggested the following code: http://is.gd/WJCznj which works for this specific test case, but requires a lot of other changes in my code that I haven't been to get working yet.

[huonw]

I think this is a dupe of #14820. My investigation in #15191 (comment) suggests it should be possible to work around this by providing an explicit Clone impl for Server, rather than deriving it.

[am0d]

I haven't been able to find a way to explicitly impl Clone for Server yet that works with this. I'll keep trying a bit, but may just have to wait till the fix is implemented in rustc itself.

[huonw]

impl Clone for Server {
    fn clone(&self) -> Server {
        let mut handlers = self.routes.handlers.iter().map(|x| *x);
        Server { routes: Router { handlers: handlers.collect() } }
    }
}

[am0d]

Thanks Huon. I will play with that a bit and see if I can make it work in my code.

[jjpe]

Perhaps not directly related to the posts but it is to the title: how difficult would it be to allow rust programmers to implement user-defined traits for fn types without destroying type safety guarantees?
It doesn't seem to be possible atm but would be a nice feature.

[sfackler]

It's possible right now: http://is.gd/kF8HbG.

[jjpe]

Thanks @sfackler, that helped quite a bit.