rustdoc: skip MetaSized bounds

These should never be shown to users at the moment.

Author: davidtwco

src/librustdoc/clean/inline.rs

@@ -273,7 +273,14 @@ pub(crate) fn build_external_trait(cx: &mut DocContext<'_>, did: DefId) -> clean
     let predicates = cx.tcx.predicates_of(did);
     let generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
     let generics = filter_non_trait_generics(did, generics);
-    let (generics, supertrait_bounds) = separate_supertrait_bounds(generics);
+    let (generics, mut supertrait_bounds) = separate_supertrait_bounds(generics);
+
+    supertrait_bounds.retain(|b| {
+        // FIXME(sized-hierarchy): Always skip `MetaSized` bounds so that only `?Sized`
+        // is shown and none of the new sizedness traits leak into documentation.
+        !b.is_metasized_bound(cx)
+    });
+
     clean::Trait { def_id: did, generics, items: trait_items, bounds: supertrait_bounds }
 }
 

src/librustdoc/clean/mod.rs

@@ -39,9 +39,9 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet, IndexEntry};
 use rustc_errors::codes::*;
 use rustc_errors::{FatalError, struct_span_code_err};
-use rustc_hir::PredicateOrigin;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, LOCAL_CRATE, LocalDefId};
+use rustc_hir::{LangItem, PredicateOrigin};
 use rustc_hir_analysis::hir_ty_lowering::FeedConstTy;
 use rustc_hir_analysis::{lower_const_arg_for_rustdoc, lower_ty};
 use rustc_middle::metadata::Reexport;
@@ -892,6 +892,10 @@ fn clean_ty_generics<'tcx>(
             if b.is_sized_bound(cx) {
                 has_sized = true;
                 false
+            } else if b.is_metasized_bound(cx) {
+                // FIXME(sized-hierarchy): Always skip `MetaSized` bounds so that only `?Sized`
+                // is shown and none of the new sizedness traits leak into documentation.
+                false
             } else {
                 true
             }
@@ -1486,6 +1490,13 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                     }
                     _ => true,
                 });
+
+                bounds.retain(|b| {
+                    // FIXME(sized-hierarchy): Always skip `MetaSized` bounds so that only `?Sized`
+                    // is shown and none of the new sizedness traits leak into documentation.
+                    !b.is_metasized_bound(cx)
+                });
+
                 // Our Sized/?Sized bound didn't get handled when creating the generics
                 // because we didn't actually get our whole set of bounds until just now
                 // (some of them may have come from the trait). If we do have a sized
@@ -2321,6 +2332,12 @@ fn clean_middle_opaque_bounds<'tcx>(
                 _ => return None,
             };
 
+            // FIXME(sized-hierarchy): Always skip `MetaSized` bounds so that only `?Sized`
+            // is shown and none of the new sizedness traits leak into documentation.
+            if cx.tcx.is_lang_item(trait_ref.def_id(), LangItem::MetaSized) {
+                return None;
+            }
+
             if let Some(sized) = cx.tcx.lang_items().sized_trait()
                 && trait_ref.def_id() == sized
             {

src/librustdoc/clean/simplify.rs

@@ -134,11 +134,17 @@ pub(crate) fn sized_bounds(cx: &mut DocContext<'_>, generics: &mut clean::Generi
     // don't actually know the set of associated types right here so that
     // should be handled when cleaning associated types.
     generics.where_predicates.retain(|pred| {
-        if let WP::BoundPredicate { ty: clean::Generic(param), bounds, .. } = pred
-            && bounds.iter().any(|b| b.is_sized_bound(cx))
-        {
+        let WP::BoundPredicate { ty: clean::Generic(param), bounds, .. } = pred else {
+            return true;
+        };
+
+        if bounds.iter().any(|b| b.is_sized_bound(cx)) {
             sized_params.insert(*param);
             false
+        } else if bounds.iter().any(|b| b.is_metasized_bound(cx)) {
+            // FIXME(sized-hierarchy): Always skip `MetaSized` bounds so that only `?Sized`
+            // is shown and none of the new sizedness traits leak into documentation.
+            false
         } else {
             true
         }

src/librustdoc/clean/types.rs

@@ -1273,11 +1273,19 @@ impl GenericBound {
     }
 
     pub(crate) fn is_sized_bound(&self, cx: &DocContext<'_>) -> bool {
+        self.is_bounded_by_lang_item(cx, LangItem::Sized)
+    }
+
+    pub(crate) fn is_metasized_bound(&self, cx: &DocContext<'_>) -> bool {
+        self.is_bounded_by_lang_item(cx, LangItem::MetaSized)
+    }
+
+    fn is_bounded_by_lang_item(&self, cx: &DocContext<'_>, lang_item: LangItem) -> bool {
         if let GenericBound::TraitBound(
             PolyTrait { ref trait_, .. },
             rustc_hir::TraitBoundModifiers::NONE,
         ) = *self
-            && Some(trait_.def_id()) == cx.tcx.lang_items().sized_trait()
+            && cx.tcx.is_lang_item(trait_.def_id(), lang_item)
         {
             return true;
         }