rustdoc: Resolve doc links in external traits having local impls

compiler/rustc_resolve/src/lib.rs

@@ -1932,6 +1932,11 @@ pub fn macro_rules_scope(&self, def_id: LocalDefId) -> (MacroRulesScopeRef<'a>,
         }
     }
 
+    /// For rustdoc.
+    pub fn get_partial_res(&self, node_id: NodeId) -> Option<PartialRes> {
+        self.partial_res_map.get(&node_id).copied()
+    }
+
     /// Retrieves the span of the given `DefId` if `DefId` is in the local crate.
     #[inline]
     pub fn opt_span(&self, def_id: DefId) -> Option<Span> {

src/librustdoc/passes/collect_intra_doc_links/early.rs

@@ -354,7 +354,14 @@ fn visit_item(&mut self, item: &ast::Item) {
             self.parent_scope.module = old_module;
         } else {
             match &item.kind {
-                ItemKind::Impl(box ast::Impl { of_trait: Some(..), .. }) => {
+                ItemKind::Impl(box ast::Impl { of_trait: Some(trait_ref), .. }) => {
+                    if let Some(partial_res) = self.resolver.get_partial_res(trait_ref.ref_id)
+                        && let Some(res) = partial_res.full_res()
+                        && let Some(trait_def_id) = res.opt_def_id()
+                        && !trait_def_id.is_local()
+                        && self.visited_mods.insert(trait_def_id) {
+                        self.resolve_doc_links_extern_impl(trait_def_id, false);
+                    }
                     self.all_trait_impls.push(self.resolver.local_def_id(item.id).to_def_id());
                 }
                 ItemKind::MacroDef(macro_def) if macro_def.macro_rules => {

src/test/rustdoc/intra-doc/issue-104145.rs

@@ -0,0 +1,14 @@
+// Doc links in `Trait`'s methods are resolved because it has a local impl.
+
+// aux-build:issue-103463-aux.rs
+
+extern crate issue_103463_aux;
+use issue_103463_aux::Trait;
+
+pub struct LocalType;
+
+impl Trait for LocalType {
+    fn method() {}
+}
+
+fn main() {}