alt Hacker NewsIt's not uncommon to have it on the error itself, rather than a details/kind auxiliary type. AWS SDK does it, nested even [0][1], diesel[2], password_hash[3].
[0] https://docs.rs/aws-smithy-runtime-api/1.9.3/aws_smithy_runt... [1] https://docs.rs/aws-sdk-s3/1.119.0/aws_sdk_s3/operation/get_... [2] https://docs.rs/diesel/2.3.5/diesel/result/enum.Error.html [3] https://docs.rs/password-hash/0.5.0/password_hash/errors/enu...
Sure, I've done it too: https://docs.rs/ignore/latest/ignore/enum.Error.html
It's not necessarily about frequency, but about extensibility. There's lot of grey area there. If you're very certain of your error domain and what kinds of details you want to offer, then the downside of a less extensible error type may never actualize. Similarly, if you're more open to more frequent semver incompatible releases, then the downside also may never actualize.