Implementors column on trait page is always empty

[aDotInTheVoid]

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

Line 2328 in 65f3f8b

buf.push_str("<h3 class=\"sidebar-title\"><a href=\"#implementors\">Implementors</a></h3>");

This leads to

when the Implementors column is empty

This is finiky to implement, cant just find the html id's for a given item cannot be determined from that item, due to the derive_id makeing the id dependent on cx state.

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

Lines 1694 to 1703 in cebd2dd

	let id = cx.derive_id(match i.inner_impl().trait_ {
	Some(ref t) => {
	if is_on_foreign_type {
	get_id_for_impl_on_foreign_type(&i.inner_impl().for_, t, cx)
	} else {
	format!("impl-{}", small_url_encode(format!("{:#}", t.print(cx))))
	}
	}
	None => "impl".to_string(),
	});

A way around this would be to add a HashMap<DefId, String> to Context, but I'm not sure if this is the best way arround this, and would apprecieate other ideas.

@rustbot claim

@rustbot modify labels: +A-rustdoc-ui +T-rustdoc

[aDotInTheVoid]

aDotInTheVoid@e3429d7 works in simple case

[camelid]

I kind of wonder if we should just remove the implementors (and implementations on foreign types) sidebar sections. They're not part of the trait's interface, and for many traits the list will be very long and fill up the sidebar. I will start a discussion on Zulip about this (EDIT: here).

[camelid]

It may not even be a bug that the section is empty; perhaps it's intended just to be a link to the beginning of the implementors section in the main body of the page. I agree that it looks confusing though.