rustdoc: "Methods from Deref" appears inconsistently

[jyn514]

I tried this code:

pub struct Bar(Baz);
impl std::ops::Deref for Bar {
    type Target = Baz;
    fn deref(&self) -> &Baz { &self.0 }
}

pub struct Baz {}
impl Baz {
    /// [prim@str]
    pub fn foo() {}
}

I expected to see this happen: Rustdoc generates a "Methods from Deref" section, the way it does if the struct derefs to Path:

Instead, this happened: Rustdoc doesn't generate the section:

Meta

rustdoc --version: rustdoc 1.58.0-nightly (936f260 2021-11-22)

cc @GuillaumeGomez

[jyn514]

I thought originally this was related to Baz being in the current crate, but I moved it to an inner crate and that still didn't generate the right section.

[jyn514]

Relevant code:

rust/src/librustdoc/html/render/mod.rs

Lines 1035 to 1076 in 207c80f

	fn render_assoc_items_inner(
	w: &mut Buffer,
	cx: &Context<'_>,
	containing_item: &clean::Item,
	it: DefId,
	what: AssocItemRender<'_>,
	derefs: &mut FxHashSet<DefId>,
	) {
	info!("Documenting associated items of {:?}", containing_item.name);
	let cache = cx.cache();
	let v = match cache.impls.get(&it) {
	Some(v) => v,
	None => return,
	};
	let (non_trait, traits): (Vec<_>, _) = v.iter().partition(|i| i.inner_impl().trait_.is_none());
	if !non_trait.is_empty() {
	let mut tmp_buf = Buffer::empty_from(w);
	let render_mode = match what {
	AssocItemRender::All => {
	tmp_buf.write_str(
	"<h2 id=\"implementations\" class=\"small-section-header\">\
	Implementations<a href=\"#implementations\" class=\"anchor\"></a>\
	</h2>",
	);
	RenderMode::Normal
	}
	AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
	let id =
	cx.derive_id(small_url_encode(format!("deref-methods-{:#}", type_.print(cx))));
	if let Some(def_id) = type_.def_id(cx.cache()) {
	cx.deref_id_map.borrow_mut().insert(def_id, id.clone());
	}
	write!(
	tmp_buf,
	"<h2 id=\"{id}\" class=\"small-section-header\">\
	<span>Methods from {trait_}&lt;Target = {type_}&gt;</span>\
	<a href=\"#{id}\" class=\"anchor\"></a>\
	</h2>",
	id = id,
	trait_ = trait_.print(cx),
	type_ = type_.print(cx),
	);

[GuillaumeGomez]

This is surprising. I'll take a look tomorrow.

[GuillaumeGomez]

This is the expected behaviour because they are not methods (they don't have a self argument). We call the function to check it here and the function itself is here.

This behaviour is tested in this test. Since this is the expected result, I'll close the issue.