Revert "Rollup merge of rust-lang#127017 - mu001999-contrib:dead/enhance, r=pnkfelix"

This reverts commit a70dc29, reversing
changes made to ceae371.

Author: compiler-errors

Diff for: compiler/rustc_passes/src/dead.rs

@@ -55,24 +55,7 @@ impl Publicness {
     }
 }
 
-fn adt_of<'tcx>(ty: &hir::Ty<'tcx>) -> Option<(LocalDefId, DefKind)> {
-    match ty.kind {
-        TyKind::Path(hir::QPath::Resolved(_, path)) => {
-            if let Res::Def(def_kind, def_id) = path.res
-                && let Some(local_def_id) = def_id.as_local()
-            {
-                Some((local_def_id, def_kind))
-            } else {
-                None
-            }
-        }
-        TyKind::Slice(ty) | TyKind::Array(ty, _) => adt_of(ty),
-        TyKind::Ptr(ty) | TyKind::Ref(_, ty) => adt_of(ty.ty),
-        _ => None,
-    }
-}
-
-fn struct_all_fields_are_public(tcx: TyCtxt<'_>, id: LocalDefId) -> bool {
+fn struct_all_fields_are_public(tcx: TyCtxt<'_>, id: DefId) -> bool {
     // treat PhantomData and positional ZST as public,
     // we don't want to lint types which only have them,
     // cause it's a common way to use such types to check things like well-formedness
@@ -97,7 +80,10 @@ fn struct_all_fields_are_public(tcx: TyCtxt<'_>, id: LocalDefId) -> bool {
 /// for enum and union, just check they are public,
 /// and doesn't solve types like &T for now, just skip them
 fn ty_ref_to_pub_struct(tcx: TyCtxt<'_>, ty: &hir::Ty<'_>) -> Publicness {
-    if let Some((def_id, def_kind)) = adt_of(ty) {
+    if let TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind
+        && let Res::Def(def_kind, def_id) = path.res
+        && def_id.is_local()
+    {
         return match def_kind {
             DefKind::Enum | DefKind::Union => {
                 let ty_is_public = tcx.visibility(def_id).is_public();
@@ -580,8 +566,10 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
     }
 
     fn impl_item_with_used_self(&mut self, impl_id: hir::ItemId, impl_item_id: LocalDefId) -> bool {
-        if let Some((local_def_id, def_kind)) =
-            adt_of(self.tcx.hir().item(impl_id).expect_impl().self_ty)
+        if let TyKind::Path(hir::QPath::Resolved(_, path)) =
+            self.tcx.hir().item(impl_id).expect_impl().self_ty.kind
+            && let Res::Def(def_kind, def_id) = path.res
+            && let Some(local_def_id) = def_id.as_local()
             && matches!(def_kind, DefKind::Struct | DefKind::Enum | DefKind::Union)
         {
             if let Some(trait_item_id) = self.tcx.associated_item(impl_item_id).trait_item_def_id
@@ -928,7 +916,7 @@ fn create_and_seed_worklist(
                     match tcx.def_kind(id) {
                         DefKind::Impl { .. } => false,
                         DefKind::AssocConst | DefKind::AssocTy | DefKind::AssocFn => !matches!(tcx.associated_item(id).container, AssocItemContainer::ImplContainer),
-                        DefKind::Struct => struct_all_fields_are_public(tcx, id) || has_allow_dead_code_or_lang_attr(tcx, id).is_some(),
+                        DefKind::Struct => struct_all_fields_are_public(tcx, id.to_def_id()) || has_allow_dead_code_or_lang_attr(tcx, id).is_some(),
                         _ => true
                     })
                 .map(|id| (id, ComesFromAllowExpect::No))