perf: keep pointeesized builtin impls

Author: davidtwco

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1263,11 +1263,6 @@ fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>) -> Result<(), ErrorGuarant
     debug!(?item.owner_id);
 
     let def_id = item.owner_id.def_id;
-    if tcx.is_lang_item(def_id.into(), LangItem::PointeeSized) {
-        // `PointeeSized` is removed during lowering.
-        return Ok(());
-    }
-
     let trait_def = tcx.trait_def(def_id);
     if trait_def.is_marker
         || matches!(trait_def.specialization_kind, TraitSpecializationKind::Marker)

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -477,7 +477,11 @@ where
                     G::consider_builtin_sizedness_candidates(self, goal, SizedTraitKind::MetaSized)
                 }
                 Some(TraitSolverLangItem::PointeeSized) => {
-                    unreachable!("`PointeeSized` is removed during lowering");
+                    G::consider_builtin_sizedness_candidates(
+                        self,
+                        goal,
+                        SizedTraitKind::PointeeSized,
+                    )
                 }
                 Some(TraitSolverLangItem::Copy | TraitSolverLangItem::Clone) => {
                     G::consider_builtin_copy_clone_candidate(self, goal)

compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs

@@ -141,14 +141,15 @@ where
         // impl {Meta,}Sized for str, [T], dyn Trait
         ty::Str | ty::Slice(_) | ty::Dynamic(..) => match sizedness {
             SizedTraitKind::Sized => Err(NoSolution),
-            SizedTraitKind::MetaSized => Ok(ty::Binder::dummy(vec![])),
-            SizedTraitKind::PointeeSized => unreachable!(),
+            SizedTraitKind::MetaSized | SizedTraitKind::PointeeSized => {
+                Ok(ty::Binder::dummy(vec![]))
+            }
         },
 
         // impl {} for extern type
         ty::Foreign(..) => match sizedness {
             SizedTraitKind::Sized | SizedTraitKind::MetaSized => Err(NoSolution),
-            SizedTraitKind::PointeeSized => unreachable!(),
+            SizedTraitKind::PointeeSized => Ok(ty::Binder::dummy(vec![])),
         },
 
         ty::Alias(..) | ty::Param(_) | ty::Placeholder(..) => Err(NoSolution),

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -100,7 +100,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     );
                 }
                 Some(LangItem::PointeeSized) => {
-                    bug!("`PointeeSized` is removed during lowering");
+                    self.assemble_builtin_sized_candidate(
+                        obligation,
+                        &mut candidates,
+                        SizedTraitKind::PointeeSized,
+                    );
                 }
                 Some(LangItem::Unsize) => {
                     self.assemble_candidates_for_unsizing(obligation, &mut candidates);