What is the From trait for error conversion

Error Handling
2026-04-17T12:05:42+00:00
The From trait allows Rust to automatically convert one error type into another for seamless propagation.

The From trait enables automatic conversion of one error type into another, allowing the ? operator to propagate errors seamlessly. Implementing From<SourceError> for your custom error type tells Rust how to transform SourceError into your error variant.

use std::fmt;

#[derive(Debug)]
struct MyError(String);

impl fmt::Display for MyError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl std::error::Error for MyError {}

impl From<std::io::Error> for MyError {
    fn from(err: std::io::Error) -> Self {
        MyError(format!("IO error: {}", err))
    }
}

fn read_file() -> Result<String, MyError> {
    std::fs::read_to_string("data.txt")? // Automatically converts io::Error to MyError
}