相关疑难解决方法(0)

我写了以下代码:

use std::io::{IoResult, Writer};
use std::io::stdio;

fn main() {
    let h = |&: w: &mut Writer| -> IoResult<()> {
        writeln!(w, "foo")
    };
    let _ = h.handle(&mut stdio::stdout());
}

trait Handler<W> where W: Writer {
    fn handle(&self, &mut W) -> IoResult<()>;
}

impl<W, F> Handler<W> for F
where W: Writer, F: Fn(&mut W) -> IoResult<()> {
    fn handle(&self, w: &mut W) -> IoResult<()> { (*self)(w) }
}

然后rustc在我的终端:

$ rustc writer_handler.rs
writer_handler.rs:8:15: 8:43 error: the trait `core::marker::Sized` is not …