error(transparent) on structures

[Ekleog]

Hello,

I think I haven't had yet the occasion to thank you for thiserror (as well as a lot of other crates actually), so here it is: thank you! And sorry for not having had issues with your crates earlier, which would have allowed me to thank you without just spamming 😛

I recently hit a limitation of thiserror: sometimes, I just want to hide an error type from a sub-library, and re-export it under another name, so that the implementation details don't leak.

So I originally tried this:

#[derive(Debug, thiserror::Error)]
struct E(#[error(transparent)] std::io::Error);

However, it looks like this doesn't implement Display for E.

On the other hand, this works perfectly:

#[derive(Debug, thiserror::Error)]
enum E { #[error(transparent)] Foo(std::io::Error) }

But then, it leaks the implementation detail of the inner error type.

Do you think it'd make sense to have #[error(transparent)] work on structs? Or maybe it'd be a bad idea anyway for reasons I can't think of right now?

[dtolnay]

The transparent attr goes on an enum variant or struct, not on an individual field. I think this does what you want:

#[derive(Error, Debug)]
#[error(transparent)]
struct E(std::io::Error);

[Ekleog]

Looks like that's what I was looking for indeed! I guess a diagnostic for #81 would probably have avoided that error, closing here :)

Thank you!