Put negative implementors first and apply same ordering logic to foreign implementors #142380

GuillaumeGomez · 2025-06-11T20:26:33Z

This PR changeda surprisingly small amount of things to put negative trait impls before the others: basically just adding a new information in the generated JS file for foreign implementors and a "negative marker" DOM element to know where to insert negative impls.

I also used this occasion to make the foreign implementors sort the same as the local ones by using compare_names.

You can test it here.

r? @notriddle

rustbot · 2025-06-11T20:26:40Z

Some changes occurred in HTML/CSS/JS.

cc @GuillaumeGomez, @jsha, @lolbinarycat

GuillaumeGomez · 2025-06-12T14:37:40Z

Took me a while to figure out where the typescript definition was stored to fix the error. ^^'

lolbinarycat · 2025-06-16T18:49:21Z

src/librustdoc/html/render/print_item.rs

+
+    fn insert_if_needed(&mut self, w: &mut fmt::Formatter<'_>, implementor: &Impl) -> fmt::Result {
+        if !self.inserted_negative_marker && !implementor.is_negative_trait_impl() {
+            write!(w, "<div class=\"negative-marker\"></div>")?;


Suggested change

write!(w, "<div class=\"negative-marker\"></div>")?;

write!(w, "<span class=\"negative-marker\"></span>")?;

Using a span feels more idiomatic, as it's less likely to cause weird extra linebreaks in unstyled environments.

Based on the docs/spec I read, it's exactly what div is for. From MDN:

The <div> HTML element is the generic container for flow content. It has no effect on the content or layout until styled in some way using CSS (e.g., styling is directly applied to it, or some kind of layout model like Flexbox is applied to its parent element).

As for linebreaks, I couldn't find information about how div is supposed to handle them by default.

div has a default style of display: block; so its presence can in fact change layout quite easily, as it will cause line/paragraph breaks the same way any other block element will. I'm not sure why MDN says it can't impact layout.

span is essentially the equivalent of div except it is used for inline content, which I believe a zero size marker with no impact on layout technically is?

src/librustdoc/html/render/print_item.rs

lolbinarycat · 2025-06-16T19:09:28Z

src/librustdoc/html/render/write_shared.rs

-            let part = OrderedJson::array_sorted(
+            implementors.sort_unstable();
+
+            let part = OrderedJson::array_unsorted(


This is definitely an improvement, as it eliminates an allocation, but we're still allocating an intermediate string for each element.

OrderedJson could be much more efficient if it had a method that appended using serde_json::to_writer.

I can open an issue for improving the OrderedJson interface, if you want.

An issue would be welcome indeed.

lolbinarycat · 2025-06-16T19:15:53Z

src/librustdoc/html/render/write_shared.rs

@@ -791,10 +797,12 @@ impl TraitAliasPart {
    }
 }

+#[derive(PartialEq, Eq)]


logic error: Eq and Ord impls disagree on the definition of equality, as Ord only checks the name.

this can easily be fixed by writing a PartialEq impl that defers to Ord:

impl PartialEq for Implementor { fn eq(&self, other: &Self) -> bool { self.cmp(other) == Ordering::Equal } }

Interesting approach, I like it. Adding it.

Wait, in which would it be an issue to have this difference? Ordering and equality don't have to be equivalent.

it's a correctness requirement on PartialEq.

it doesn't cause any issue with the current code, bur it could cause issues with generic datastructures like BTreeMap, so I think it would be best to try to avoid something that can cause this type of sneaky logic error.

I think this is technically the same class of error as if you had Copy and Clone diverge, not unsound, just incorrect.

lolbinarycat · 2025-06-16T19:18:32Z

src/librustdoc/html/static/css/rustdoc.css

+.negative-marker {
+	display: none;
+}


Is there any meaningful difference between an inline span with no content and the same span but hidden? if not, then I don't think this is needed.

It makes the rendering engine completely discard the element. So close to no difference. But still better to have.

lolbinarycat · 2025-06-16T19:20:41Z

src/librustdoc/html/static/js/rustdoc.d.ts

@@ -467,7 +467,7 @@ declare namespace rustdoc {
     * Provied by generated `trait.impl` files.
     */
    type Implementors = {
-        [key: string]: Array<[string, number, Array<string>]>
+        [key: string]: Array<[string, number, number, Array<string>]>


Suggested change

[key: string]: Array<[string, number, number, Array<string>]>

[key: string]: Array<[string, number, 0|1, Array<string>]>

we can be a bit more specific here.

also, it would be nice to expand the comment to mention what the meaning of each field is.

tests/rustdoc-gui/implementors.goml

src/librustdoc/html/render/print_item.rs

…ign implementors

alternate interface for OrderedJson to reduce allocations inspired by #142380 (comment) r? `@GuillaumeGomez`

bors · 2025-06-22T03:11:47Z

☔ The latest upstream changes (presumably #142667) made this pull request unmergeable. Please resolve the merge conflicts.

rustbot assigned notriddle Jun 11, 2025

GuillaumeGomez mentioned this pull request Jun 11, 2025

[rustdoc] Implementors section of Sync (and other similar traits) should separate implementors and !implementors #51129

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GuillaumeGomez force-pushed the neg-implementors branch from 27e69ca to 2b0bda6 Compare June 11, 2025 20:37

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GuillaumeGomez force-pushed the neg-implementors branch from 2b0bda6 to 2dd2db9 Compare June 11, 2025 21:26

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GuillaumeGomez force-pushed the neg-implementors branch from 2dd2db9 to cc15898 Compare June 12, 2025 12:17

lolbinarycat requested changes Jun 16, 2025

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GuillaumeGomez force-pushed the neg-implementors branch from cc15898 to 80a06df Compare June 17, 2025 14:27

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GuillaumeGomez added 2 commits June 17, 2025 16:55

Put negative implementors first and apply same ordering logic to fore…

b5b87d3

…ign implementors

Add GUI test to ensure that negative impls are correctly sorted

3028afb

GuillaumeGomez force-pushed the neg-implementors branch from 80a06df to 3028afb Compare June 17, 2025 14:55

lolbinarycat mentioned this pull request Jun 17, 2025

alternate interface for OrderedJson to reduce allocations #142634

Open

	write!(w, "<div class=\"negative-marker\"></div>")?;
	write!(w, "<span class=\"negative-marker\"></span>")?;

	[key: string]: Array<[string, number, number, Array<string>]>
	[key: string]: Array<[string, number, 0\|1, Array<string>]>

Put negative implementors first and apply same ordering logic to foreign implementors #142380

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Put negative implementors first and apply same ordering logic to foreign implementors #142380

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bors commented Jun 22, 2025

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GuillaumeGomez commented Jun 11, 2025 •

edited by rustbot

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