std::error::Error is not implemented for input_stream::Error

[vadimcn]

... so it isn't usable with the ? operator.

[adrian-budau]

the ? operator has nothing to do with the std::error::Error. I'm guessing you are trying to use error-chain with this library. As far as i know error-chain is being deprecated so it would be nice to migrate to failure.

If you want to obtain a std::error::Error you can call compat() on any error you obtain from this library (one of the benefits of the failure crate is this compatibility with other error handling crates).

For example to use with error-chain

extern crate input_stream;
#[macro_use]
extern crate error_chain;
extern crate failure;

use std::io::stdin;
use input_stream::InputStream;
use failure::ResultExt as FailureResultExt;

error_chain!{}

fn run() -> Result<()> {
    let stdin = stdin();
    let mut input = InputStream::new(stdin.lock());
    let a: usize = input.scan().compat().chain_err(|| "Error in input-stream")?;
    let b: usize = input.scan().compat().chain_err(|| "Error in input-stream")?;
    println!("Hello sum: {}", a + b);
    Ok(())
}

fn main() {
    run().unwrap();
}

or if I guessed wrong and you were using only Box<Error> compat() should still do the trick:

extern crate input_stream;
extern crate failure;

use std::error::Error;
use std::io::stdin;
use input_stream::InputStream;
use failure::ResultExt as FailureResultExt;

fn run() -> Result<(), Box<Error>> {
    let stdin = stdin();
    let mut input = InputStream::new(stdin.lock());
    let a: usize = input.scan().compat()?;
    let b: usize = input.scan().compat()?;
    println!("Hello sum: {}", a + b);
    Ok(())
}

fn main() {
    run().unwrap();
}