`Self` does not work in intra-doc links for primitives

[jyn514]

I tried this code in #75807:

#![feature(lang_items)]
#![feature(no_core)]
#![no_core]

#[lang = "usize"]
/// [Self::f]
/// [usize::f]
impl usize {
    /// Some docs
    pub fn f() {}
}

I expected to see this happen: Self::f and usize::f resolve to the same thing.

Instead, this happened: Self::f gives a warning that it can't be resolved.

Meta

rustdoc --version:

rustdoc 1.47.0-nightly (de521cbb3 2020-08-21)

(but the problem is also present on master at time of writing)

[jyn514]

Marking as P-low since this only affects std and crates with #![lang_items], and there's an easy workaround.

[jyn514]

I think the issue is actually that Self doesn't work if the item is from a different crate. But it's hard to test until #74489 is fixed (since the only time this is the case is with lang items or implementing a local trait for a foreign type).

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Lines 532 to 533 in f5d7848

	// find item's parent to resolve `Self` in item's docs below
	let parent_name = self.cx.as_local_hir_id(item.def_id).and_then(|item_hir| {

[jyn514]

Ugh, this Self replacement is happening in three different places as usual.

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Lines 630 to 631 in f5d7848

	// replace `Self` with suitable item's parent name
	if path_str.starts_with("Self::") {

uses the logic I linked above,

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Line 94 in f5d7848

if f == "self" || f == "Self" {

and

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Line 264 in f5d7848

if f == "self" || f == "Self" {

use

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Lines 497 to 522 in f5d7848

	let current_item = match item.inner {
	ModuleItem(..) => {
	if item.attrs.inner_docs {
	if item.def_id.is_top_level_module() { item.name.clone() } else { None }
	} else {
	match parent_node.or(self.mod_ids.last().copied()) {
	Some(parent) if !parent.is_top_level_module() => {
	// FIXME: can we pull the parent module's name from elsewhere?
	Some(self.cx.tcx.item_name(parent).to_string())
	}
	_ => None,
	}
	}
	}
	ImplItem(Impl { ref for_, .. }) => {
	for_.def_id().map(|did| self.cx.tcx.item_name(did).to_string())
	}
	// we don't display docs on `extern crate` items anyway, so don't process them.
	ExternCrateItem(..) => {
	debug!("ignoring extern crate item {:?}", item.def_id);
	return self.fold_item_recur(item);
	}
	ImportItem(Import::Simple(ref name, ..)) => Some(name.clone()),
	MacroItem(..) => None,
	_ => item.name.clone(),
	};

[jyn514]

There's also a secondary issue: self should never mean a type. At the module level it means the current module; at the function level it means a value, but treating it the same as Self is wrong.

[jyn514]

Fixed in #76467.