test_source.rs

#![deny(clippy::all, clippy::pedantic)]

use std::error::Error as StdError;
use std::io;
use thiserror::Error;

#[derive(Error, Debug)]
#[error("implicit source")]
pub struct ImplicitSource {
    source: io::Error,
}

#[derive(Error, Debug)]
#[error("explicit source")]
pub struct ExplicitSource {
    source: String,
    #[source]
    io: io::Error,
}

#[derive(Error, Debug)]
#[error("boxed source")]
pub struct BoxedSource {
    #[source]
    source: Box<dyn StdError + Send + 'static>,
}

#[test]
fn test_implicit_source() {
    let io = io::Error::new(io::ErrorKind::Other, "oh no!");
    let error = ImplicitSource { source: io };
    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
}

#[test]
fn test_explicit_source() {
    let io = io::Error::new(io::ErrorKind::Other, "oh no!");
    let error = ExplicitSource {
        source: String::new(),
        io,
    };
    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
}

#[test]
fn test_boxed_source() {
    let source = Box::new(io::Error::new(io::ErrorKind::Other, "oh no!"));
    let error = BoxedSource { source };
    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
}

macro_rules! error_from_macro {
    ($($variants:tt)*) => {
        #[derive(Error)]
        #[derive(Debug)]
        pub enum MacroSource {
            $($variants)*
        }
    }
}

// Test that we generate impls with the proper hygiene
error_from_macro!(#[error("Something")] Variant(#[from] io::Error));