The std::io error type is defined roughly as: type Result<T> = std::result::Result<T, io::Error>; So it's actually fine, since we're specifying it's an IO

The std::io error type is defined roughly as: type Result<T> = std::result::Result<T, io::Error>; So it's actually fine, since we're specifying it's an IO result. This is a fairly common pattern.