Description
I recently noticed that the "Important traits" feature (called "spotlight") was removed in #69514
The stated justification was a twitter poll, however from going through the responses there it seemed like people hadn't noticed it, not that people didn't find it useful. I don't think removing a feature is the right call if people aren't noticing it, that's a UX concern. It's also not that much code.
Can we reintroduce this UI as a little bubble on the return type? Putting it in the sidebar as a tiny circle was guaranteed to make it disappear. I found this feature quite useful, especially for iterators. In particular, my experience resonates with @Mark-Simulacrum's: #69514 (comment) you need to click, scroll to the iterator impl, and then compare pages and substitute return types, whereas here it's all in one place.
I think we have a good indication that we should experiment with the UI and find something that works.
Ultimately, even if a feature is useful for some and not most, we shouldn't be removing it unless it's a net negative impact on the "most", which is definitely not clear here.
(I kinda wish that removing this feature had been FCPd)
cc @GuillaumeGomez @kinnison @rust-lang/rustdoc