test.rs

use std::io;
use std::io::Write;


fn main() {

	let mut input = String::new();
	let result = io::stdin().read_line(&mut input)
						.map(|s:usize| input)
						.and_then(|s:String| s.parse::<u32>());

	println!("{}", result.unwrap());
}

$ rustc test.rs 
test.rs:10:28: 10:44 error: mismatched types:
 expected `core::result::Result<_, std::io::error::Error>`,
    found `core::result::Result<u32, core::num::ParseIntError>`
(expected struct `std::io::error::Error`,
    found struct `core::num::ParseIntError`) [E0308]
test.rs:10                                              .and_then(|s:String| s.parse::<u32>());