Persist printing error, NOT ErrorKind

[distortedsignal]

Reading through the Rust Book, I found this code that appears to be trying to take different actions based on the error type. Looking closer, I realized that the author changed the code (I believe, unintentionally) to log only the error type instead of the whole error when certain conditions are met.

This is a simple fix - the wildcard match for other_error is removed, and replaced with a non-binding wildcard, and the panic is changed to consuming the base error. This is better because it changes the minimal amount of functionality in the example code and it refamiliarizes readers with the non-binding wildcard matching system.

[distortedsignal]

I fired off this PR before I read the rest of the chapter - the highlight box actually calls out that the code in listing 9-6 should have the same effect as in 9-5. This PR brings the code in 9-5 into alignment with the listing in 9-6.

[distortedsignal]

Supporting documentation:

Listing 9-4:

use std::fs::File;

fn main() {
    let greeting_file_result = File::open("hello.txt");

    let greeting_file = match greeting_file_result {
        Ok(file) => file,
        Err(error) => panic!("Problem opening the file: {error:?}"), // Panics with the error
    };
}

Listing 9-6:

use std::fs::File;
use std::io::ErrorKind;

fn main() {
    let greeting_file = File::open("hello.txt").unwrap_or_else(|error| {
        if error.kind() == ErrorKind::NotFound {
            File::create("hello.txt").unwrap_or_else(|error| {
                panic!("Problem creating the file: {error:?}");
            })
        } else {
            panic!("Problem opening the file: {error:?}"); // Panics with the error
        }
    });
}

Old listing 9-5:

use std::fs::File;
use std::io::ErrorKind;

fn main() {
    let greeting_file_result = File::open("hello.txt");

    let greeting_file = match greeting_file_result {
        Ok(file) => file,
        Err(error) => match error.kind() {
            ErrorKind::NotFound => match File::create("hello.txt") {
                Ok(fc) => fc,
                Err(e) => panic!("Problem creating the file: {e:?}"),
            },
            other_error => {
                panic!("Problem opening the file: {other_error:?}"); // Panics with the result of error.kind()
            }
        },
    };
}

New listing 9-5:

use std::fs::File;
use std::io::ErrorKind;

fn main() {
    let greeting_file_result = File::open("hello.txt");

    let greeting_file = match greeting_file_result {
        Ok(file) => file,
        Err(error) => match error.kind() {
            ErrorKind::NotFound => match File::create("hello.txt") {
                Ok(fc) => fc,
                Err(e) => panic!("Problem creating the file: {e:?}"),
            },
            _ => {
                panic!("Problem opening the file: {error:?}"); // Panics with the error
            }
        },
    };
}

[chriskrycho]

Thanks for the suggestion. I agree that we should keep using error for consistency. 👍🏼

[distortedsignal]

@chriskrycho - thanks for the approval! I'll keep reading through the book and making (hopefully small) edits to make sure that a) I understand the content and b) maybe others can have an easier on-ramp with the book.