Miss Dada  🏳️‍⚧️

Hey @rustlang twitter: any particular reason that there isn't an instance of std::error::Error for Arc<dyn std::error::Error>? Would be quite useful when you want a cloneable dyn error for just exploring things without being bogged down in error handling intricacies...

Arc<dyn Error> and Box<dyn Error> cannot impl Error due to the overlap rule which says currently in rust you cannot have two generic trait impls both be valid for the same type. From<T> for Arc<T> and From<T> for T would overlap if Arc<dyn Error> itself could coerce to dyn Error

This would be true if there was `impl<E: Error> From<E> for Arc<dyn Error>`, but there is no such impl. Only for Box.

Oh yea you need a concrete impl don't you, I forgot the From<T> doesn't work as a coersion site for dyn Error.

Either way, you can't meaningfully get what @klaehnr wants which is presumably a catch all error type via Arc that itself impls Error. Side question, Sian do you know if specialization is planned to allow overlap?

You definitely could write `impl<E: Error + ?Sized> Error for Arc<E>`.There's nothing incoherent about it.