rustdoc: use `LocalDefId` for inline stmt

It's never a cross-crate DefId, so save space by not storing it.

src/librustdoc/clean/inline.rs

@@ -5,7 +5,7 @@ use std::sync::Arc;
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::{DefId, DefIdSet, LocalModDefId};
+use rustc_hir::def_id::{DefId, DefIdSet, LocalDefId, LocalModDefId};
 use rustc_hir::Mutability;
 use rustc_metadata::creader::{CStore, LoadedMacro};
 use rustc_middle::ty::fast_reject::SimplifiedType;
@@ -43,7 +43,7 @@ pub(crate) fn try_inline(
     cx: &mut DocContext<'_>,
     res: Res,
     name: Symbol,
-    attrs: Option<(&[ast::Attribute], Option<DefId>)>,
+    attrs: Option<(&[ast::Attribute], Option<LocalDefId>)>,
     visited: &mut DefIdSet,
 ) -> Option<Vec<clean::Item>> {
     let did = res.opt_def_id()?;
@@ -157,7 +157,7 @@ pub(crate) fn try_inline(
         kind,
         did,
         name,
-        import_def_id.and_then(|def_id| def_id.as_local()),
+        import_def_id,
         None,
     );
     // The visibility needs to reflect the one from the reexport and not from the "source" DefId.
@@ -198,7 +198,7 @@ pub(crate) fn try_inline_glob(
                 visited,
                 inlined_names,
                 Some(&reexports),
-                Some((attrs, Some(import.owner_id.def_id.to_def_id()))),
+                Some((attrs, Some(import.owner_id.def_id))),
             );
             items.retain(|item| {
                 if let Some(name) = item.name {
@@ -372,7 +372,7 @@ fn build_type_alias(
 pub(crate) fn build_impls(
     cx: &mut DocContext<'_>,
     did: DefId,
-    attrs: Option<(&[ast::Attribute], Option<DefId>)>,
+    attrs: Option<(&[ast::Attribute], Option<LocalDefId>)>,
     ret: &mut Vec<clean::Item>,
 ) {
     let _prof_timer = cx.tcx.sess.prof.generic_activity("build_inherent_impls");
@@ -405,7 +405,7 @@ pub(crate) fn build_impls(
 pub(crate) fn merge_attrs(
     cx: &mut DocContext<'_>,
     old_attrs: &[ast::Attribute],
-    new_attrs: Option<(&[ast::Attribute], Option<DefId>)>,
+    new_attrs: Option<(&[ast::Attribute], Option<LocalDefId>)>,
 ) -> (clean::Attributes, Option<Arc<clean::cfg::Cfg>>) {
     // NOTE: If we have additional attributes (from a re-export),
     // always insert them first. This ensure that re-export
@@ -416,7 +416,7 @@ pub(crate) fn merge_attrs(
         both.extend_from_slice(old_attrs);
         (
             if let Some(item_id) = item_id {
-                Attributes::from_ast_with_additional(old_attrs, (inner, item_id))
+                Attributes::from_ast_with_additional(old_attrs, (inner, item_id.to_def_id()))
             } else {
                 Attributes::from_ast(&both)
             },
@@ -431,7 +431,7 @@ pub(crate) fn merge_attrs(
 pub(crate) fn build_impl(
     cx: &mut DocContext<'_>,
     did: DefId,
-    attrs: Option<(&[ast::Attribute], Option<DefId>)>,
+    attrs: Option<(&[ast::Attribute], Option<LocalDefId>)>,
     ret: &mut Vec<clean::Item>,
 ) {
     if !cx.inlined.insert(did.into()) {
@@ -641,7 +641,7 @@ fn build_module_items(
     visited: &mut DefIdSet,
     inlined_names: &mut FxHashSet<(ItemType, Symbol)>,
     allowed_def_ids: Option<&DefIdSet>,
-    attrs: Option<(&[ast::Attribute], Option<DefId>)>,
+    attrs: Option<(&[ast::Attribute], Option<LocalDefId>)>,
 ) -> Vec<clean::Item> {
     let mut items = Vec::new();
 
@@ -745,7 +745,7 @@ fn build_macro(
     cx: &mut DocContext<'_>,
     def_id: DefId,
     name: Symbol,
-    import_def_id: Option<DefId>,
+    import_def_id: Option<LocalDefId>,
     macro_kind: MacroKind,
     is_doc_hidden: bool,
 ) -> clean::ItemKind {
@@ -753,7 +753,7 @@ fn build_macro(
         LoadedMacro::MacroDef(item_def, _) => match macro_kind {
             MacroKind::Bang => {
                 if let ast::ItemKind::MacroDef(ref def) = item_def.kind {
-                    let vis = cx.tcx.visibility(import_def_id.unwrap_or(def_id));
+                    let vis = cx.tcx.visibility(import_def_id.map(|d| d.to_def_id()).unwrap_or(def_id));
                     clean::MacroItem(clean::Macro {
                         source: utils::display_macro_source(
                             cx,

src/librustdoc/clean/mod.rs

@@ -204,7 +204,7 @@ fn generate_item_with_correct_attrs(
 
     let name = renamed.or(Some(name));
     let mut item = Item::from_def_id_and_attrs_and_parts(def_id, name, kind, Box::new(attrs), cfg);
-    item.inline_stmt_id = import_id.map(|local| local.to_def_id());
+    item.inline_stmt_id = import_id;
     item
 }
 
@@ -2927,7 +2927,7 @@ fn clean_extern_crate<'tcx>(
         })
         && !cx.output_format.is_json();
 
-    let krate_owner_def_id = krate.owner_id.to_def_id();
+    let krate_owner_def_id = krate.owner_id.def_id;
     if please_inline {
         if let Some(items) = inline::try_inline(
             cx,
@@ -2941,7 +2941,7 @@ fn clean_extern_crate<'tcx>(
     }
 
     vec![Item::from_def_id_and_parts(
-        krate_owner_def_id,
+        krate_owner_def_id.to_def_id(),
         Some(name),
         ExternCrateItem { src: orig_name },
         cx,
@@ -2988,7 +2988,7 @@ fn clean_use_statement_inner<'tcx>(
     let inline_attr = attrs.lists(sym::doc).get_word_attr(sym::inline);
     let pub_underscore = visibility.is_public() && name == kw::Underscore;
     let current_mod = cx.tcx.parent_module_from_def_id(import.owner_id.def_id);
-    let import_def_id = import.owner_id.def_id.to_def_id();
+    let import_def_id = import.owner_id.def_id;
 
     // The parent of the module in which this import resides. This
     // is the same as `current_mod` if that's already the top
@@ -3071,7 +3071,7 @@ fn clean_use_statement_inner<'tcx>(
             )
         {
             items.push(Item::from_def_id_and_parts(
-                import_def_id,
+                import_def_id.to_def_id(),
                 None,
                 ImportItem(Import::new_simple(name, resolve_use_source(cx, path), false)),
                 cx,
@@ -3081,7 +3081,7 @@ fn clean_use_statement_inner<'tcx>(
         Import::new_simple(name, resolve_use_source(cx, path), true)
     };
 
-    vec![Item::from_def_id_and_parts(import_def_id, None, ImportItem(inner), cx)]
+    vec![Item::from_def_id_and_parts(import_def_id.to_def_id(), None, ImportItem(inner), cx)]
 }
 
 fn clean_maybe_renamed_foreign_item<'tcx>(

src/librustdoc/clean/types.rs

@@ -325,8 +325,10 @@ pub(crate) struct Item {
     /// E.g., struct vs enum vs function.
     pub(crate) kind: Box<ItemKind>,
     pub(crate) item_id: ItemId,
-    /// This is the `DefId` of the `use` statement if the item was inlined.
-    pub(crate) inline_stmt_id: Option<DefId>,
+    /// This is the `LocalDefId` of the `use` statement if the item was inlined.
+    /// The crate metadata doesn't hold this information, so the `use` statement
+    /// always belongs to the current crate.
+    pub(crate) inline_stmt_id: Option<LocalDefId>,
     pub(crate) cfg: Option<Arc<Cfg>>,
 }
 
@@ -702,7 +704,7 @@ impl Item {
             _ => {}
         }
         let def_id = match self.inline_stmt_id {
-            Some(inlined) => inlined,
+            Some(inlined) => inlined.to_def_id(),
             None => def_id,
         };
         Some(tcx.visibility(def_id))