Allow unboxing source #505
Description
This program fails to downcast its source errors, since they are Box<MyError>, not MyError. As briefly mentioned on discord.
use snafu::ResultExt as _;
#[derive(Debug, snafu::Snafu)]
pub enum MyError {
#[snafu(display("error: {error_code:08X}"))]
LeafError { error_code: u32 },
#[snafu(display("at depth {depth}"))]
NodeError {
depth: u32,
#[snafu(source(from(MyError, Box::new)))]
source: Box<MyError>
},
}
fn main() {
let e = fake_fn(3).unwrap_err();
for e in std::iter::successors(Some(&e as &dyn std::error::Error), |e| e.source()) {
if let Some(e) = e.downcast_ref::<MyError>() {
println!("downcasted: {}", e);
} else {
println!("failed: {}", e);
}
}
}
fn fake_fn(depth: u32) -> Result<(), MyError> {
if depth == 0 {
LeafSnafu { error_code: 0xDEADBEEFu32 }.fail()
} else {
fake_fn(depth - 1).context(NodeSnafu { depth })
}
}