Auto merge of #129244 - cjgillot:opaque-hir, r=compiler-errors

Make opaque types regular HIR nodes

Having opaque types as HIR owner introduces all sorts of complications. This PR proposes to make them regular HIR nodes instead.

I haven't gone through all the test changes yet, so there may be a few surprises.

Many thanks to `@camelid` for the first draft.
Fixes https://github.com/rust-lang/rust/issues/129023

Fixes #129099
Fixes #125843
Fixes #119716
Fixes #121422

src/librustdoc/clean/mod.rs

@@ -1828,13 +1828,8 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
             Array(Box::new(clean_ty(ty, cx)), length.into())
         }
         TyKind::Tup(tys) => Tuple(tys.iter().map(|ty| clean_ty(ty, cx)).collect()),
-        TyKind::OpaqueDef(item_id, _) => {
-            let item = cx.tcx.hir().item(item_id);
-            if let hir::ItemKind::OpaqueTy(ty) = item.kind {
-                ImplTrait(ty.bounds.iter().filter_map(|x| clean_generic_bound(x, cx)).collect())
-            } else {
-                unreachable!()
-            }
+        TyKind::OpaqueDef(ty, _) => {
+            ImplTrait(ty.bounds.iter().filter_map(|x| clean_generic_bound(x, cx)).collect())
         }
         TyKind::Path(_) => clean_qpath(ty, cx),
         TyKind::TraitObject(bounds, lifetime, _) => {
@@ -2736,9 +2731,6 @@ fn clean_maybe_renamed_item<'tcx>(
                 type_: clean_ty(ty, cx),
                 kind: ConstantKind::Local { body: body_id, def_id },
             })),
-            // clean_ty changes types which reference an OpaqueTy item to instead be
-            // an ImplTrait, so it's ok to return nothing here.
-            ItemKind::OpaqueTy(_) => return vec![],
             ItemKind::TyAlias(hir_ty, generics) => {
                 *cx.current_type_aliases.entry(def_id).or_insert(0) += 1;
                 let rustdoc_ty = clean_ty(hir_ty, cx);

src/librustdoc/html/render/span_map.rs

@@ -243,7 +243,6 @@ impl<'tcx> Visitor<'tcx> for SpanMapVisitor<'tcx> {
             | ItemKind::ExternCrate(_)
             | ItemKind::ForeignMod { .. }
             | ItemKind::GlobalAsm(_)
-            | ItemKind::OpaqueTy(_)
             // We already have "visit_mod" above so no need to check it here.
             | ItemKind::Mod(_) => {}
         }

src/librustdoc/visit_ast.rs

@@ -505,21 +505,11 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
             | hir::ItemKind::Struct(..)
             | hir::ItemKind::Union(..)
             | hir::ItemKind::TyAlias(..)
-            | hir::ItemKind::OpaqueTy(hir::OpaqueTy {
-                origin: hir::OpaqueTyOrigin::TyAlias { .. },
-                ..
-            })
             | hir::ItemKind::Static(..)
             | hir::ItemKind::Trait(..)
             | hir::ItemKind::TraitAlias(..) => {
                 self.add_to_current_mod(item, renamed, import_id);
             }
-            hir::ItemKind::OpaqueTy(hir::OpaqueTy {
-                origin: hir::OpaqueTyOrigin::AsyncFn { .. } | hir::OpaqueTyOrigin::FnReturn { .. },
-                ..
-            }) => {
-                // return-position impl traits are never nameable, and should never be documented.
-            }
             hir::ItemKind::Const(..) => {
                 // Underscore constants do not correspond to a nameable item and
                 // so are never useful in documentation.