rustdoc: Remove Crate.externs and compute on-demand instead

src/librustdoc/clean/types.rs

@@ -117,7 +117,6 @@ impl From<DefId> for ItemId {
 #[derive(Clone, Debug)]
 crate struct Crate {
     crate module: Item,
-    crate externs: Vec<ExternalCrate>,
     crate primitives: ThinVec<(DefId, PrimitiveType)>,
     /// Only here so that they can be filtered through the rustdoc passes.
     crate external_traits: Rc<RefCell<FxHashMap<DefId, TraitWithExtraInfo>>>,
@@ -126,7 +125,7 @@ crate struct Crate {
 
 // `Crate` is frequently moved by-value. Make sure it doesn't unintentionally get bigger.
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-rustc_data_structures::static_assert_size!(Crate, 104);
+rustc_data_structures::static_assert_size!(Crate, 80);
 
 impl Crate {
     crate fn name(&self, tcx: TyCtxt<'_>) -> Symbol {

src/librustdoc/clean/utils.rs

@@ -7,6 +7,7 @@ use crate::clean::{
 };
 use crate::core::DocContext;
 use crate::formats::item_type::ItemType;
+use crate::visit_lib::LibEmbargoVisitor;
 
 use rustc_ast as ast;
 use rustc_ast::tokenstream::TokenTree;
@@ -24,13 +25,9 @@ use std::mem;
 mod tests;
 
 crate fn krate(cx: &mut DocContext<'_>) -> Crate {
-    use crate::visit_lib::LibEmbargoVisitor;
-
     let module = crate::visit_ast::RustdocVisitor::new(cx).visit();
 
-    let mut externs = Vec::new();
     for &cnum in cx.tcx.crates(()) {
-        externs.push(ExternalCrate { crate_num: cnum });
         // Analyze doc-reachability for extern items
         LibEmbargoVisitor::new(cx).visit_lib(cnum);
     }
@@ -76,13 +73,7 @@ crate fn krate(cx: &mut DocContext<'_>) -> Crate {
         }));
     }
 
-    Crate {
-        module,
-        externs,
-        primitives,
-        external_traits: cx.external_traits.clone(),
-        collapsed: false,
-    }
+    Crate { module, primitives, external_traits: cx.external_traits.clone(), collapsed: false }
 }
 
 fn external_generic_args(

src/librustdoc/core.rs

@@ -508,14 +508,12 @@ crate fn run_global_ctxt(
         rustc_errors::FatalError.raise();
     }
 
-    let render_options = ctxt.render_options;
-    let mut cache = ctxt.cache;
-    krate = tcx.sess.time("create_format_cache", || cache.populate(krate, tcx, &render_options));
+    krate = tcx.sess.time("create_format_cache", || Cache::populate(&mut ctxt, krate));
 
     // The main crate doc comments are always collapsed.
     krate.collapsed = true;
 
-    (krate, render_options, cache)
+    (krate, ctxt.render_options, ctxt.cache)
 }
 
 /// Due to <https://github.com/rust-lang/rust/pull/73566>,

src/librustdoc/formats/cache.rs

@@ -6,8 +6,8 @@ use rustc_middle::middle::privacy::AccessLevels;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::symbol::sym;
 
-use crate::clean::{self, ItemId, PrimitiveType};
-use crate::config::RenderOptions;
+use crate::clean::{self, ExternalCrate, ItemId, PrimitiveType};
+use crate::core::DocContext;
 use crate::fold::DocFolder;
 use crate::formats::item_type::ItemType;
 use crate::formats::Impl;
@@ -136,46 +136,47 @@ impl Cache {
 
     /// Populates the `Cache` with more data. The returned `Crate` will be missing some data that was
     /// in `krate` due to the data being moved into the `Cache`.
-    crate fn populate(
-        &mut self,
-        mut krate: clean::Crate,
-        tcx: TyCtxt<'_>,
-        render_options: &RenderOptions,
-    ) -> clean::Crate {
+    crate fn populate(cx: &mut DocContext<'_>, mut krate: clean::Crate) -> clean::Crate {
+        let tcx = cx.tcx;
+
         // Crawl the crate to build various caches used for the output
-        debug!(?self.crate_version);
-        self.traits = krate.external_traits.take();
-        let RenderOptions { extern_html_root_takes_precedence, output: dst, .. } = render_options;
+        debug!(?cx.cache.crate_version);
+        cx.cache.traits = krate.external_traits.take();
 
         // 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 &e in &krate.externs {
+        for &crate_num in cx.tcx.crates(()) {
+            let e = ExternalCrate { crate_num };
+
             let name = e.name(tcx);
+            let render_options = &cx.render_options;
             let extern_url =
                 render_options.extern_html_root_urls.get(&*name.as_str()).map(|u| &**u);
-            let location = e.location(extern_url, *extern_html_root_takes_precedence, dst, tcx);
-            self.extern_locations.insert(e.crate_num, location);
-            self.external_paths.insert(e.def_id(), (vec![name.to_string()], ItemType::Module));
+            let extern_url_takes_precedence = render_options.extern_html_root_takes_precedence;
+            let dst = &render_options.output;
+            let location = e.location(extern_url, extern_url_takes_precedence, dst, tcx);
+            cx.cache.extern_locations.insert(e.crate_num, location);
+            cx.cache.external_paths.insert(e.def_id(), (vec![name.to_string()], ItemType::Module));
         }
 
         // FIXME: avoid this clone (requires implementing Default manually)
-        self.primitive_locations = PrimitiveType::primitive_locations(tcx).clone();
-        for (prim, &def_id) in &self.primitive_locations {
+        cx.cache.primitive_locations = PrimitiveType::primitive_locations(tcx).clone();
+        for (prim, &def_id) in &cx.cache.primitive_locations {
             let crate_name = tcx.crate_name(def_id.krate);
             // Recall that we only allow primitive modules to be at the root-level of the crate.
             // If that restriction is ever lifted, this will have to include the relative paths instead.
-            self.external_paths.insert(
+            cx.cache.external_paths.insert(
                 def_id,
                 (vec![crate_name.to_string(), prim.as_sym().to_string()], ItemType::Primitive),
             );
         }
 
-        krate = CacheBuilder { tcx, cache: self }.fold_crate(krate);
+        krate = CacheBuilder { tcx, cache: &mut cx.cache }.fold_crate(krate);
 
-        for (trait_did, dids, impl_) in self.orphan_trait_impls.drain(..) {
-            if self.traits.contains_key(&trait_did) {
+        for (trait_did, dids, impl_) in cx.cache.orphan_trait_impls.drain(..) {
+            if cx.cache.traits.contains_key(&trait_did) {
                 for did in dids {
-                    self.impls.entry(did).or_default().push(impl_.clone());
+                    cx.cache.impls.entry(did).or_default().push(impl_.clone());
                 }
             }
         }