Track inlined items and merge their docstrings when creating clean attributes

src/librustdoc/clean/types.rs

@@ -445,12 +445,21 @@ impl Item {
         cx: &mut DocContext<'_>,
     ) -> Item {
         let ast_attrs = cx.tcx.get_attrs(def_id);
+        let mut clean_attrs = box ast_attrs.clean(cx);
+
+        if let Some(inlined_ids) = cx.cache.inlined_items.get(&def_id).cloned() {
+            tracing::debug!("extending docstrings of {:?} with {:?}", def_id, inlined_ids);
+            for &inlined_id in inlined_ids.iter() {
+                let other_attrs = cx.tcx.get_attrs(inlined_id).clean(cx);
+                clean_attrs.doc_strings.extend(other_attrs.doc_strings);
+            }
+        }
 
         Self::from_def_id_and_attrs_and_parts(
             def_id,
             name,
             kind,
-            box ast_attrs.clean(cx),
+            clean_attrs,
             cx,
             ast_attrs.cfg(cx.tcx, &cx.cache.hidden_cfg),
         )

src/librustdoc/formats/cache.rs

@@ -1,7 +1,7 @@
 use std::mem;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_INDEX};
 use rustc_middle::middle::privacy::AccessLevels;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::{sym, Symbol};
@@ -53,11 +53,16 @@ crate struct Cache {
     /// This map is used when writing out the special 'implementors'
     /// javascript file. By using the exact path that the type
     /// is declared with, we ensure that each path will be identical
+    ///
     /// to the path used if the corresponding type is inlined. By
     /// doing this, we can detect duplicate impls on a trait page, and only display
     /// the impl for the inlined type.
     crate exact_paths: FxHashMap<DefId, Vec<Symbol>>,
 
+    /// Associates every items with all of its public reexports. This is used to merge
+    /// every docstrings that are relevant to show.
+    crate inlined_items: FxHashMap<DefId, Vec<LocalDefId>>,
+
     /// This map contains information about all known traits of this crate.
     /// Implementations of a crate should inherit the documentation of the
     /// parent trait if no extra documentation is specified, and default methods

src/librustdoc/visit_ast.rs

@@ -4,7 +4,7 @@
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::DefId;
+use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::Node;
 use rustc_hir::CRATE_HIR_ID;
 use rustc_middle::middle::privacy::AccessLevel;
@@ -68,6 +68,7 @@ crate struct RustdocVisitor<'a, 'tcx> {
     /// Are the current module and all of its parents public?
     inside_public_path: bool,
     exact_paths: FxHashMap<DefId, Vec<Symbol>>,
+    inlined_items: FxHashMap<DefId, Vec<LocalDefId>>,
 }
 
 impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
@@ -78,6 +79,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
         RustdocVisitor {
             cx,
             view_item_stack: stack,
+            inlined_items: FxHashMap::default(),
             inlining: false,
             inside_public_path: true,
             exact_paths: FxHashMap::default(),
@@ -144,6 +146,8 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
             .collect();
 
         self.cx.cache.exact_paths = self.exact_paths;
+        self.cx.cache.inlined_items = self.inlined_items;
+
         top_level_module
     }
 
@@ -194,6 +198,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
         };
 
         let use_attrs = tcx.hir().attrs(id);
+
         // Don't inline `doc(hidden)` imports so they can be stripped at a later stage.
         let is_no_inline = use_attrs.lists(sym::doc).has_word(sym::no_inline)
             || use_attrs.lists(sym::doc).has_word(sym::hidden);
@@ -320,6 +325,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
                         om,
                         please_inline,
                     ) {
+                        self.inlined_items.entry(path.res.def_id()).or_default().push(item.def_id);
                         return;
                     }
                 }