Rustdoc links items in the standard library to the original crate, not the re-export

[Evian-Zhang]

In my docs, I use [`String`] or even [`std::string::String`], I expect the generated link is to the std page, but the generated link is to the alloc page.

I know maybe std re-exports some structs in alloc, core, etc. but for a beginner who does not know well about rust, he may be confused when clicking the link to String and get an unfamiliar path. So what can I do if I want to link to std page?

Meta

rustc --version --verbose:

rustc 1.49.0-nightly (a1dfd2490 2020-10-05)
binary: rustc
commit-hash: a1dfd2490a6cb456b92e469fa550dc217e20ad6d
commit-date: 2020-10-05
host: x86_64-unknown-linux-gnu
release: 1.49.0-nightly
LLVM version: 11.0

[jyn514]

This is not really supported by intra-doc links. How should it know which re-exports are canonical and which are not? The best it can do is the original place the item was defined.

[camelid]

Perhaps we could add some kind of attribute to a re-export (something like #[canonical] or #[rustdoc_canonical]) but I don't think it's necessarily worth it.

[jyn514]

Note that this is not specific to intra-doc links, if you have a function returning string, rustdoc will also link to alloc, not std.

[Nemo157]

Is the data used to decide when to inline the docs available during intra-doc links (#[doc(inline)] + whatever makes it implicitly inline)? If rustdoc knows which re-export was used in a particular link (and other locations), and has that data available, it seems like the inlining of the docs matches up with when you would want to link to the inlined docs instead of the original location.

[jyn514]

This logic is done by fn href:

rust/src/librustdoc/html/format.rs

Line 483 in 6bea76f

pub fn href(did: DefId) -> Option<(String, ItemType, Vec<String>)> {

In particular, if it's not in cache.paths, it always looks in the original crate:

rust/src/librustdoc/html/format.rs

Line 497 in 6bea76f

match cache.extern_locations[&did.krate] {

I don't know what causes something to be in paths or extern_locations.

[jyn514]

This is actually a duplicate of #22083.