foo.rs

extern crate term;
use term::Terminal;

enum AdequateTerminal<T> {
    Color(Box<Terminal<T>>)
}
struct Shell<T> {
    terminal: AdequateTerminal<T>
}
impl <T: Writer + Send> Shell<T> {
    fn create(out: T) -> Option<Shell<T>> {
        let term: Option<term::TerminfoTerminal<T>> = Terminal::new(out);
        term.map(|t: term::TerminfoTerminal<T>| Shell { terminal: Color(box t as Box<Terminal<T>>) })
    }
}