`rustup doc` can't distinguish between keywords and primitives with the same name

[cstyles]

Problem
First of all, I just want to say that I really like the recent addition of topics to the rustup doc feature! While playing around with it, I noticed that if I run rustup doc fn, it brings up the documentation for the keyword fn. However, there's also a primitive fn and I can't figure out any way to open that documentation page specifically. Am I missing something or is it just not possible?

This would also, in theory, affect any other naming collisions, not just with keywords and primitives (e.g., if some Trait and Enum had the same name and scope).

Steps

1. Run rustup doc fn
2. Observe that the keyword.fn.html page is opened in a browser.

Possible Solution(s)
I'm not super jazzed about this idea but we could add flags for --keyword, --primitive, --macro, etc. to allow the user to tell rustup exactly what they're looking for. But it would only ever be helpful in these rare situations so I don't know if it's worth A) the effort and B) making the UI more complex. It's also worth mentioning that on the page for the keyword fn, the first thing the viewer will see in the left-hand side panel is a list of primitives. So it probably wouldn't be too much of an inconvenience for them to just find fn there and click on it.

Notes

Output of rustup --version: rustup 1.20.0 (2019-10-15)
Output of rustup show:

Default host: x86_64-apple-darwin
rustup home:  /Users/collin.styles/.rustup

stable-x86_64-apple-darwin (default)
rustc 1.38.0 (625451e37 2019-09-23)

[kinnison]

I'm not sure I want to add more flags, but I also don't know how we'd distinguish them oherwise. This is an interesting idea, but as you say it's not terribly hard for someone to navigate to the other concept. I've re-labelled this help-wanted and enhancement rather than bug.

[cstyles]

The search function for the rust docs allows you to preface a search with something like fn: to restrict the search to just functions. This also works with mod, struct, enum, trait, type, macro, const. Perhaps we can do something like that here?

https://github.com/rust-lang/rust/blob/8e0007f829661e57d008d2e908c95f6e84b04b25/src/librustdoc/html/layout.rs#L134-L145

[kinnison]

Oh that is a very interesting approach yes. This feature was originally written by @dorfsmay so perhaps they might have some input on how to do this?

[dorfsmay]

And I thought we really had been through all possible conflicts 😞!

So the idea would be rustup doc primitive:fn vs rustup doc keyword:fn? It shouldn't be too difficult to implement.

What should be the default though? What should rustup doc fn bring up? My own bias is keyword over primitive but I can value in the opposite. I'd really hate that there is no default and that we'd have to use the type: for all searches.

By the way, I just checked, fn is the only conflict between primitive and keywords at this point in time!

[kinnison]

If we go based on the sort order of the results of searching the stdlib docs for fn then the keyword should win over the primitive. Do you think you can do a PR @dorfsmay ?

[dorfsmay]

The three types of docs in stdlib that are not module (which requires ::) are keyword, macro and primitive. The only conflict between those three currently is fn. IMO keyword before primitive make sense, but macro before keyword doesn't, should we future proof this a bit? Should we decide on the order and hard code it, rather than use alphabetical order?

[kinnison]

Yes, let's do that, keyword > primitive > macro I think

[dorfsmay]

Sounds good. I'll start working on it - not sure if needed or how to assign the issue to myself though.

[kinnison]

@dorfsmay I appreciate that life gets in the way sometimes, but I was wondering if you'd made a start on this? I'm currently working my way through what I might want finished before the next release and this is on the list :D