Add support for fragment specifiers in intra-doc-links

[Manishearth]

It should be possible to link to things like https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#indexing via [Vec#indexing].

This is pretty straightforward to implement. We already track fragment specifiers for things like methods and enum variants, which we extract here. What we can do additionally is when parsing if we come across #foo, strip it out, continue resolution, and if the resolved thing doesn't already have a fragment, use this instead.

I volunteer @sunjay to work on this, because he's the one who wanted this feature 😉

cc @QuietMisdreavus

Unsure if this needs an RFC.

[killercup]

Looks useful to me.

I agree a simplistic version of this is trivial to implement. The original idea with intra-doc-links howeve was to ensure at rustdoc-render-time that the links are valid. To implement that vision here, we'd need to ensure that the target item actually has a fragment with given name. This might not be trivial: Most fragment identifiers are generated by turning a headline into a valid HTML ID. (I'm not sure if rustdoc does anything more than that. It try to should prevent setting the same ID twice, but that is probable another issue.)

[GuillaumeGomez]

Just like @killercup said: won't be as easy as might look like. But where would be the fun otherwise? 😛

EDIT: oh and no need for an RFC, just add it to the implementation issue of the intra-links.

[Manishearth]

Don't we already support this?

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Line 578 in 3014f23

(parts[0].to_owned(), Some(parts[1].to_owned()))

[GuillaumeGomez]

We actually already do it, indeed. I'm closing this issue then.