Minimal example of compile eerror with recursive Snafu errors, for snafu#59 comment

snafu-recursive.rs

use snafu::{ResultExt, Snafu};

#[derive(Debug, Snafu)]
enum Error {
    #[snafu(display("Plain error"))]
    Plain {},

    #[snafu(display("Recursive variant: {}", source))]
    // #[snafu(source(from(Error, Box::new)))]
    #[snafu(source(from(Error, |e| Box::new(e))))]
    Recursive { source: Box<Error> },
}

fn main() -> Result<(), Error> {
    Plain {}
        .fail()

        //.map_err(Box::new)

        // Without the map_err above, you get the following error, regardless which of the two
        // "source(from)" invocations you use above.
        //
        // error[E0271]: type mismatch resolving `<Recursive as snafu::IntoError<Error>>::Source == Error`
        //   --> src/main.rs:22:10
        //    |
        // 22 |         .context(Recursive {})
        //    |          ^^^^^^^ expected struct `std::boxed::Box`, found enum `Error`
        //    |
        //    = note: expected type `std::boxed::Box<Error>`
        //               found type `Error`

        .context(Recursive {})
}