Repository navigation
Allow #[error(transparent)] on fields #103
Description
The crate I'm currently working on has code like the following:
#[derive(Debug, Clone, Error)]
pub struct Error {
pub(crate) kind: ErrorKind,
backtrack: Option<ExtBacktrace>,
}
#[derive(Debug, Error)]
pub enum ErrorKind {
// error variants go here
}If I understand correctly, this doesn't currently allow the Error impl for Error to return types from the ErrorKind variants, which seems like it would be useful. I thought I might try #[error(transparent)] on Error's kind field, but that's not allowed. Is there currently a way to support this scenario? From the description of error(transparent) it seems like it would be a good fit for this, but maybe there's a good reason not to allow this.
Activity
pjenvey commentedon Oct 27, 2023
This style was common with the
failurecrate: it recommended it as one of its patterns as it simplifies handling of extra data like the Optional backtrace here in to one centralized place (rather than within eachKind's variants).I also came across this problem hoping
#[error(transparent)]might defer the top level Error'ssourcemethod to the innerkind's. The solution was to simply not usethiserror::Errorfor the top levelErrorstruct here, instead implementing custom stdErrorandDisplaytraits for it that defer tokind's.#[derive(thiserror::Error)]is not doing a lot for the top level Error in this case otherwise: those two traits are just a few lines of code. I just use#[derive(thiserror::Error)]on theErrorKindwhich is where it's doing the heavier lifting.[-]Allow #[error(transparent)] on struct fields[/-][+]Allow #[error(transparent)] on fields[/+]