[DO NOT MERGE] Perf test for rustdoc

src/librustdoc/html/render/context.rs

@@ -59,6 +59,8 @@ crate struct Context<'tcx> {
     pub(super) deref_id_map: RefCell<FxHashMap<DefId, String>>,
     /// The map used to ensure all generated 'id=' attributes are unique.
     pub(super) id_map: RefCell<IdMap>,
+
+    pub(super) nixon_hack: RefCell<FxHashMap<clean::ItemId, String>>,
     /// Shared mutable state.
     ///
     /// Issue for improving the situation: [#82381][]
@@ -72,8 +74,9 @@ crate struct Context<'tcx> {
 }
 
 // `Context` is cloned a lot, so we don't want the size to grow unexpectedly.
-#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-rustc_data_structures::static_assert_size!(Context<'_>, 144);
+// FIXME: Reenable before asking for review
+// #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+// rustc_data_structures::static_assert_size!(Context<'_>, 144);
 
 /// Shared mutable state used in [`Context`] and elsewhere.
 crate struct SharedContext<'tcx> {
@@ -517,6 +520,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             render_redirect_pages: false,
             id_map: RefCell::new(id_map),
             deref_id_map: RefCell::new(FxHashMap::default()),
+            nixon_hack: RefCell::new(FxHashMap::default()),
             shared: Rc::new(scx),
             include_sources,
         };
@@ -541,6 +545,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             dst: self.dst.clone(),
             render_redirect_pages: self.render_redirect_pages,
             deref_id_map: RefCell::new(FxHashMap::default()),
+            nixon_hack: RefCell::new(FxHashMap::default()),
             id_map: RefCell::new(IdMap::new()),
             shared: Rc::clone(&self.shared),
             include_sources: self.include_sources,

src/librustdoc/html/render/mod.rs

@@ -1613,6 +1613,8 @@ fn render_impl(
             );
             write!(w, "<summary>")
         }
+
+        write!(w, "{}:{} ", file!(), line!());
         render_impl_summary(
             w,
             cx,
@@ -1624,6 +1626,7 @@ fn render_impl(
             rendering_params.is_on_foreign_type,
             aliases,
         );
+        write!(w, "{}:{} ", file!(), line!());
         if toggled {
             write!(w, "</summary>")
         }
@@ -1691,6 +1694,7 @@ pub(crate) fn render_impl_summary(
     // in documentation pages for trait with automatic implementations like "Send" and "Sync".
     aliases: &[String],
 ) {
+    // This is where the ID is created
     let id = cx.derive_id(match i.inner_impl().trait_ {
         Some(ref t) => {
             if is_on_foreign_type {
@@ -1701,6 +1705,9 @@ pub(crate) fn render_impl_summary(
         }
         None => "impl".to_string(),
     });
+
+    cx.nixon_hack.borrow_mut().insert(i.impl_item.def_id, id.clone());
+
     let aliases = if aliases.is_empty() {
         String::new()
     } else {
@@ -2215,6 +2222,7 @@ fn get_id_for_impl_on_foreign_type(
 }
 
 fn extract_for_impl_name(item: &clean::Item, cx: &Context<'_>) -> Option<(String, String)> {
+    //
     match *item.kind {
         clean::ItemKind::ImplItem(ref i) => {
             i.trait_.as_ref().map(|trait_| {
@@ -2306,6 +2314,7 @@ fn sidebar_trait(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item, t: &clean
             .filter(|i| {
                 i.inner_impl().for_.def_id(cache).map_or(false, |d| !cache.paths.contains_key(&d))
             })
+            // FIXME: Dont do the filter map dance
             .filter_map(|i| extract_for_impl_name(&i.impl_item, cx))
             .collect::<Vec<_>>();
 
@@ -2325,7 +2334,45 @@ fn sidebar_trait(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item, t: &clean
 
     sidebar_assoc_items(cx, buf, it);
 
-    buf.push_str("<h3 class=\"sidebar-title\"><a href=\"#implementors\">Implementors</a></h3>");
+    let did = it.def_id.expect_def_id();
+
+    if let Some(implementors) = cache.implementors.get(&did) {
+        let mut res = implementors
+            .iter()
+            .filter(|i| {
+                i.inner_impl().for_.def_id(cache).map_or(true, |d| cache.paths.contains_key(&d))
+                    && i.inner_impl().polarity == ty::ImplPolarity::Positive
+            })
+            // FIXME: Dont do the filter map dance
+            // .filter_map(|i| extract_for_impl_name(&i.impl_item, cx))
+            .map(|i| {
+                (
+                    format!("{:#}", i.inner_impl().for_.print(cx)),
+                    cx.nixon_hack
+                        .borrow()
+                        .get(&i.impl_item.def_id)
+                        .unwrap_or_else(|| panic!("Not in index {:#?}", i))
+                        .clone(),
+                )
+            })
+            .collect::<Vec<_>>();
+
+        if !res.is_empty() {
+            res.sort_unstable();
+
+            buf.push_str(
+                "<h3 class=\"sidebar-title\">\
+                    <a href=\"#implementors\">Implementors</a>\
+                </h3>
+                <div class=\"sidebar-links\">",
+            );
+            for (name, id) in res.into_iter() {
+                write!(buf, "<a href=\"#{}\">{}</a>", id, Escape(&name));
+            }
+            buf.push_str("</div>");
+        }
+    }
+
     if t.is_auto {
         buf.push_str(
             "<h3 class=\"sidebar-title\"><a \

src/librustdoc/html/render/print_item.rs

@@ -784,6 +784,9 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
             "Implementors",
             "<div class=\"item-list\" id=\"implementors-list\">",
         );
+
+        write!(w, "<!-- {}:{} -->", file!(), line!());
+
         for implementor in concrete {
             render_implementor(cx, implementor, it, w, &implementor_dups, &[]);
         }