Clean middle RPITITs correctly in rustdoc

src/librustdoc/clean/mod.rs

@@ -415,6 +415,16 @@ fn clean_projection<'tcx>(
     cx: &mut DocContext<'tcx>,
     def_id: Option<DefId>,
 ) -> Type {
+    if cx.tcx.def_kind(ty.item_def_id) == DefKind::ImplTraitPlaceholder {
+        let bounds = cx
+            .tcx
+            .explicit_item_bounds(ty.item_def_id)
+            .iter()
+            .map(|(bound, _)| EarlyBinder(*bound).subst(cx.tcx, ty.substs))
+            .collect::<Vec<_>>();
+        return clean_middle_opaque_bounds(cx, bounds);
+    }
+
     let trait_ = clean_trait_ref_with_bindings(cx, ty.trait_ref(cx.tcx), ThinVec::new());
     let self_type = clean_middle_ty(ty.self_ty(), cx, None);
     let self_def_id = if let Some(def_id) = def_id {
@@ -1715,6 +1725,23 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 .iter()
                 .map(|(bound, _)| EarlyBinder(*bound).subst(cx.tcx, substs))
                 .collect::<Vec<_>>();
+            clean_middle_opaque_bounds(cx, bounds)
+        }
+
+        ty::Closure(..) => panic!("Closure"),
+        ty::Generator(..) => panic!("Generator"),
+        ty::Bound(..) => panic!("Bound"),
+        ty::Placeholder(..) => panic!("Placeholder"),
+        ty::GeneratorWitness(..) => panic!("GeneratorWitness"),
+        ty::Infer(..) => panic!("Infer"),
+        ty::Error(_) => panic!("Error"),
+    }
+}
+
+fn clean_middle_opaque_bounds<'tcx>(
+    cx: &mut DocContext<'tcx>,
+    bounds: Vec<ty::Predicate<'tcx>>,
+) -> Type {
     let mut regions = vec![];
     let mut has_sized = false;
     let mut bounds = bounds
@@ -1742,8 +1769,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
             let bindings: ThinVec<_> = bounds
                 .iter()
                 .filter_map(|bound| {
-                            if let ty::PredicateKind::Projection(proj) = bound.kind().skip_binder()
-                            {
+                    if let ty::PredicateKind::Projection(proj) = bound.kind().skip_binder() {
                         if proj.projection_ty.trait_ref(cx.tcx) == trait_ref.skip_binder() {
                             Some(TypeBinding {
                                 assoc: projection_to_path_segment(proj.projection_ty, cx),
@@ -1770,16 +1796,6 @@ pub(crate) fn clean_middle_ty<'tcx>(
     ImplTrait(bounds)
 }
 
-        ty::Closure(..) => panic!("Closure"),
-        ty::Generator(..) => panic!("Generator"),
-        ty::Bound(..) => panic!("Bound"),
-        ty::Placeholder(..) => panic!("Placeholder"),
-        ty::GeneratorWitness(..) => panic!("GeneratorWitness"),
-        ty::Infer(..) => panic!("Infer"),
-        ty::Error(_) => panic!("Error"),
-    }
-}
-
 pub(crate) fn clean_field<'tcx>(field: &hir::FieldDef<'tcx>, cx: &mut DocContext<'tcx>) -> Item {
     let def_id = cx.tcx.hir().local_def_id(field.hir_id).to_def_id();
     clean_field_with_def_id(def_id, field.ident.name, clean_ty(field.ty, cx), cx)

src/test/rustdoc/async-trait.rs

@@ -0,0 +1,16 @@
+// aux-build:async-trait-dep.rs
+// edition:2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+extern crate async_trait_dep;
+
+pub struct Oink {}
+
+// @has 'async_trait/struct.Oink.html' '//h4[@class="code-header"]' "async fn woof()"
+impl async_trait_dep::Meow for Oink {
+    async fn woof() {
+        todo!()
+    }
+}

src/test/rustdoc/auxiliary/async-trait-dep.rs

@@ -0,0 +1,9 @@
+// edition:2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+pub trait Meow {
+    /// Who's a good dog?
+    async fn woof();
+}