manually crafted revert of PR #80653, to address issue #82465.

(update: placated tidy)
(update: rebased post PR #84707 )

merge me

2 files changed, 8 insertions, 27 deletions

diff --git a/src/librustdoc/html/render/context.rs b/src/librustdoc/html/render/context.rs
index d80b2db00ac..1898f5feed2 100644
--- a/src/librustdoc/html/render/context.rs
+++ b/src/librustdoc/html/render/context.rs
@@ -6,7 +6,7 @@ use std::rc::Rc;
 use std::sync::mpsc::{channel, Receiver};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir::def_id::{DefId, LOCAL_CRATE};
+use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_span::edition::Edition;
@@ -51,9 +51,6 @@ crate struct Context<'tcx> {
     pub(super) render_redirect_pages: bool,
     /// The map used to ensure all generated 'id=' attributes are unique.
     pub(super) id_map: RefCell<IdMap>,
-    /// Tracks section IDs for `Deref` targets so they match in both the main
-    /// body and the sidebar.
-    pub(super) deref_id_map: RefCell<FxHashMap<DefId, String>>,
     /// Shared mutable state.
     ///
     /// Issue for improving the situation: [#82381][]
@@ -74,7 +71,7 @@ crate struct Context<'tcx> {
 
 // `Context` is cloned a lot, so we don't want the size to grow unexpectedly.
 #[cfg(target_arch = "x86_64")]
-rustc_data_structures::static_assert_size!(Context<'_>, 152);
+rustc_data_structures::static_assert_size!(Context<'_>, 112);
 
 /// Shared mutable state used in [`Context`] and elsewhere.
 crate struct SharedContext<'tcx> {
@@ -486,7 +483,6 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             dst,
             render_redirect_pages: false,
             id_map: RefCell::new(id_map),
-            deref_id_map: RefCell::new(FxHashMap::default()),
             shared: Rc::new(scx),
             cache: Rc::new(cache),
         };
@@ -504,7 +500,6 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             dst: self.dst.clone(),
             render_redirect_pages: self.render_redirect_pages,
             id_map: RefCell::new(IdMap::new()),
-            deref_id_map: RefCell::new(FxHashMap::default()),
             shared: Rc::clone(&self.shared),
             cache: Rc::clone(&self.cache),
         }
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index 4b6faefc2fb..b808c6e04d8 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -1045,17 +1045,12 @@ fn render_assoc_items(
                 RenderMode::Normal
             }
             AssocItemRender::DerefFor { trait_, type_, deref_mut_ } => {
-                let id =
-                    cx.derive_id(small_url_encode(format!("deref-methods-{:#}", type_.print(cx))));
-                debug!("Adding {} to deref id map", type_.print(cx));
-                cx.deref_id_map.borrow_mut().insert(type_.def_id_full(cache).unwrap(), id.clone());
                 write!(
                     w,
-                    "<h2 id=\"{id}\" class=\"small-section-header\">\
+                    "<h2 id=\"deref-methods\" class=\"small-section-header\">\
                          Methods from {trait_}&lt;Target = {type_}&gt;\
-                         <a href=\"#{id}\" class=\"anchor\"></a>\
+                         <a href=\"#deref-methods\" class=\"anchor\"></a>\
                      </h2>",
-                    id = id,
                     trait_ = trait_.print(cx),
                     type_ = type_.print(cx),
                 );
@@ -1080,6 +1075,9 @@ fn render_assoc_items(
             );
         }
     }
+    if let AssocItemRender::DerefFor { .. } = what {
+        return;
+    }
     if !traits.is_empty() {
         let deref_impl = traits
             .iter()
@@ -1090,13 +1088,6 @@ fn render_assoc_items(
                 .any(|t| t.inner_impl().trait_.def_id_full(cache) == cx.cache.deref_mut_trait_did);
             render_deref_methods(w, cx, impl_, containing_item, has_deref_mut);
         }
-
-        // If we were already one level into rendering deref methods, we don't want to render
-        // anything after recursing into any further deref methods above.
-        if let AssocItemRender::DerefFor { .. } = what {
-            return;
-        }
-
         let (synthetic, concrete): (Vec<&&Impl>, Vec<&&Impl>) =
             traits.iter().partition(|t| t.inner_impl().synthetic);
         let (blanket_impl, concrete): (Vec<&&Impl>, _) =
@@ -2009,14 +2000,9 @@ fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &V
                 .flat_map(|i| get_methods(i.inner_impl(), true, &mut used_links, deref_mut, c))
                 .collect::<Vec<_>>();
             if !ret.is_empty() {
-                let deref_id_map = cx.deref_id_map.borrow();
-                let id = deref_id_map
-                    .get(&real_target.def_id_full(c).unwrap())
-                    .expect("Deref section without derived id");
                 write!(
                     out,
-                    "<a class=\"sidebar-title\" href=\"#{}\">Methods from {}&lt;Target={}&gt;</a>",
-                    id,
+                    "<a class=\"sidebar-title\" href=\"#deref-methods\">Methods from {}&lt;Target={}&gt;</a>",
                     Escape(&format!("{:#}", impl_.inner_impl().trait_.as_ref().unwrap().print(cx))),
                     Escape(&format!("{:#}", real_target.print(cx))),
                 );