How do I overcome match arms with incompatible types for structs implementing same trait?

Question

I am attempting to write the cat command to learn Rust, but I can\'t seem to convert command line arguments into reader structs.

use std::{env,          


        

Answer 1

The accepted answer does not work with Rust v1.0 anymore. The main statement is still true though: Match arms have to return the same types. Allocating the objects on the heap solves the problem.

use std::io::{self, Read};
use std::fs::File;
use std::path::Path;

fn main() {
    if let Some(arg) = std::env::args().nth(1).as_ref() {
        let reader = match arg.as_ref() {
            "-"  => Box::new(io::stdin()) as Box,
            path => Box::new(File::open(&Path::new(path)).unwrap()) as Box,
        };
    }
}