anyhow::Error to Box<dyn Error> isn't compatible with other libraries

[rkuklik]

Hello,

I have to use multiple internal crates which mix and match anyhow and eyre. When trying to convert between the two, I have convert anyhow::Error to Box<dyn Error>, which then complains that conversion requires dyn Error to be Sized (in order for Box to implement Error). This results in this ugly solution when using Result<Something, ThinError>:

result
    // Both `anyhow::Error` and `eyre::Report` support conversion into `Box`
    .map_err(Into::<Box<dyn Error + Send + Sync>>::into)
    // However, I have to stuff it into `Arc` which implements `Error` for `?Sized`
    .map_err(Into::<Arc<dyn Error + Send + Sync>>::into)?

Is there a better solution to this? If not, would it be possible to add conversion implementation from anyhow::Error into Arc or something equivalent? Unfortunately, I am unable to implement it, as it would require use of unsafe (with which I do not have enough experience) and because I am unfamiliar with techniques used in anyhow thinning.

Thank you very much in advance.

[AH-dark]

Same question, why doesn't anyhow implement std::error:Error?

[rkuklik]

Because it implements From<E> where E: Error, which would clash with blanket implementation (you can convert any type into itself). It's the same reason for Box complains about Sized constraint to implement Error.

I solved this by wrapping anyhow::Error in newtype and implementing Error for that.