Rust 1.78 added a new diagnostic::on_unimplemented attribute which can be used to add additional context in the event a trait isn't impl'd in the form of note messages that appear in the diagnostics:
https://rust-lang.github.io/rfcs/3368-diagnostic-attribute-namespace.html#guide-level-explanation
These seem very helpful for improving debugging of missing trait impls which are expected to be received via a blanket impl, i.e. the note can include the name of the other trait the user is expected to implement.
It will be awhile before we can consider Rust 1.78, however I thought I'd go ahead and open this as a tracking / planning issue for using this feature.