Redesign multihash::Error

Do we have other const functions that might be affected by the same problem? I wonder what a long-term solution could be here.

In the issue, you said that the problem is the io::Error in Kind? I tried previously to remove that one because it only appears in certain functions. Perhaps that is worth exploring because most functions don't actually return an io::Error.

If you'd like my opinion, you should impl From<YourErrorType> for std::io::Error, and have io functions return an io::Result, which may be InvalidData with a source = Some(YourErrorType), where YourErrorType is a slimmer Error

(This would be a breaking change.)
((I think that's fine, you're pre 1.0.0, and the API should be allowed to evolve past current limitations))

Originally posted by @aatifsyed in https://github.com/multiformats/rust-multihash/pull/331#issuecomment-1642486508

Start by reading the discussion from PR #331 and inspect the existing multihash::Error, Kind, and const-function APIs. Trace where io::Error and io::Result are used, then determine the intended breaking-change scope and how completion would be verified; the issue names no files or tests.