Remove unnecessary CrateNum from Cache.externs

It can be found from ExternalCrate.

src/librustdoc/clean/types.rs

@@ -118,7 +118,7 @@ crate struct Crate {
     crate name: Symbol,
     crate src: FileName,
     crate module: Item,
-    crate externs: Vec<(CrateNum, ExternalCrate)>,
+    crate externs: Vec<ExternalCrate>,
     crate primitives: ThinVec<(DefId, PrimitiveType)>,
     // These are later on moved into `CACHEKEY`, leaving the map empty.
     // Only here so that they can be filtered through the rustdoc passes.
@@ -133,14 +133,14 @@ crate struct TraitWithExtraInfo {
     crate is_notable: bool,
 }
 
-#[derive(Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 crate struct ExternalCrate {
     crate crate_num: CrateNum,
 }
 
 impl ExternalCrate {
     #[inline]
-    fn def_id(&self) -> DefId {
+    crate fn def_id(&self) -> DefId {
         DefId { krate: self.crate_num, index: CRATE_DEF_INDEX }
     }
 

src/librustdoc/clean/utils.rs

@@ -1,9 +1,9 @@
 use crate::clean::auto_trait::AutoTraitFinder;
 use crate::clean::blanket_impl::BlanketImplFinder;
 use crate::clean::{
-    inline, Clean, Crate, Generic, GenericArg, GenericArgs, ImportSource, Item, ItemKind, Lifetime,
+    inline, Clean, Crate, ExternalCrate, Generic, GenericArg, GenericArgs, ImportSource, Item,
-    Path, PathSegment, PolyTrait, Primitive, PrimitiveType, ResolvedPath, Type, TypeBinding,
+    ItemKind, Lifetime, Path, PathSegment, PolyTrait, Primitive, PrimitiveType, ResolvedPath, Type,
-    Visibility,
+    TypeBinding, Visibility,
 };
 use crate::core::DocContext;
 use crate::formats::item_type::ItemType;
@@ -35,11 +35,11 @@ crate fn krate(cx: &mut DocContext<'_>) -> Crate {
 
     let mut externs = Vec::new();
     for &cnum in cx.tcx.crates(()).iter() {
-        externs.push((cnum, cnum.clean(cx)));
+        externs.push(ExternalCrate { crate_num: cnum });
         // Analyze doc-reachability for extern items
         LibEmbargoVisitor::new(cx).visit_lib(cnum);
     }
-    externs.sort_by(|&(a, _), &(b, _)| a.cmp(&b));
+    externs.sort_unstable();
 
     // Clean the crate, translating the entire librustc_ast AST to one that is
     // understood by rustdoc.

src/librustdoc/formats/cache.rs

@@ -151,19 +151,18 @@ impl Cache {
 
         // Cache where all our extern crates are located
         // FIXME: this part is specific to HTML so it'd be nice to remove it from the common code
-        for &(n, ref e) in &krate.externs {
+        for &e in &krate.externs {
             let name = e.name(tcx);
             let extern_url = extern_html_root_urls.get(&*name.as_str()).map(|u| &**u);
-            let did = DefId { krate: n, index: CRATE_DEF_INDEX };
+            self.extern_locations.insert(e.crate_num, e.location(extern_url, &dst, tcx));
-            self.extern_locations.insert(n, e.location(extern_url, &dst, tcx));
+            self.external_paths.insert(e.def_id(), (vec![name.to_string()], ItemType::Module));
-            self.external_paths.insert(did, (vec![name.to_string()], ItemType::Module));
         }
 
         // Cache where all known primitives have their documentation located.
         //
         // Favor linking to as local extern as possible, so iterate all crates in
         // reverse topological order.
-        for &(_, ref e) in krate.externs.iter().rev() {
+        for &e in krate.externs.iter().rev() {
             for &(def_id, prim) in &e.primitives(tcx) {
                 self.primitive_locations.insert(prim, def_id);
             }