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

Here's a variation on Lukas's answer that avoids boxing:

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 stdin;
        let file;
        let reader = match arg.as_ref() {
            "-"  => {
                stdin = io::stdin();
                &stdin as &Read
            }
            path => {
                file = File::open(&Path::new(path)).unwrap();
                &file as &Read
            }
        };
    }
}

The trick here is to use let bindings that are only initialized on some code paths, while still having a long enough lifetime to be able to use them as the target of a borrowed pointer.