rustdoc: Move most shared fields to SharedContext

...and remove `Rc`s for the moved fields.

The only shared one that I didn't move was `cache`; see the doc-comment
I added to `cache` for details.

Author: camelid

src/librustdoc/html/render/mod.rs

@@ -111,16 +111,16 @@ crate struct Context<'tcx> {
     /// real location of an item. This is used to allow external links to
     /// publicly reused items to redirect to the right location.
     crate render_redirect_pages: bool,
-    /// The map used to ensure all generated 'id=' attributes are unique.
-    id_map: Rc<RefCell<IdMap>>,
-    /// Tracks section IDs for `Deref` targets so they match in both the main
-    /// body and the sidebar.
-    deref_id_map: Rc<RefCell<FxHashMap<DefId, String>>>,
     crate shared: Arc<SharedContext<'tcx>>,
-    all: Rc<RefCell<AllTypes>>,
-    /// Storage for the errors produced while generating documentation so they
-    /// can be printed together at the end.
-    crate errors: Rc<Receiver<String>>,
+    /// The [`Cache`] used during rendering.
+    ///
+    /// Ideally the cache would be in [`SharedContext`], but it's mutated
+    /// between when the `SharedContext` is created and when `Context`
+    /// is created, so more refactoring would be needed.
+    ///
+    /// It's immutable once in `Context`, so it's not as bad that it's not in
+    /// `SharedContext`.
+    // FIXME: move `cache` to `SharedContext`
     crate cache: Rc<Cache>,
 }
 
@@ -163,6 +163,15 @@ crate struct SharedContext<'tcx> {
     crate edition: Edition,
     crate codes: ErrorCodes,
     playground: Option<markdown::Playground>,
+    /// The map used to ensure all generated 'id=' attributes are unique.
+    id_map: RefCell<IdMap>,
+    /// Tracks section IDs for `Deref` targets so they match in both the main
+    /// body and the sidebar.
+    deref_id_map: RefCell<FxHashMap<DefId, String>>,
+    all: RefCell<AllTypes>,
+    /// Storage for the errors produced while generating documentation so they
+    /// can be printed together at the end.
+    crate errors: Receiver<String>,
 }
 
 impl<'tcx> Context<'tcx> {
@@ -478,6 +487,10 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             edition,
             codes: ErrorCodes::from(unstable_features.is_nightly_build()),
             playground,
+            id_map: RefCell::new(id_map),
+            deref_id_map: RefCell::new(FxHashMap::default()),
+            all: RefCell::new(AllTypes::new()),
+            errors: receiver,
         };
 
         // Add the default themes to the `Vec` of stylepaths
@@ -504,11 +517,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             current: Vec::new(),
             dst,
             render_redirect_pages: false,
-            id_map: Rc::new(RefCell::new(id_map)),
-            deref_id_map: Rc::new(RefCell::new(FxHashMap::default())),
             shared: Arc::new(scx),
-            all: Rc::new(RefCell::new(AllTypes::new())),
-            errors: Rc::new(receiver),
             cache: Rc::new(cache),
         };
 
@@ -558,7 +567,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         } else {
             String::new()
         };
-        let all = self.all.replace(AllTypes::new());
+        let all = self.shared.all.replace(AllTypes::new());
         let v = layout::render(
             &self.shared.layout,
             &page,
@@ -591,7 +600,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
 
         // Flush pending errors.
         Arc::get_mut(&mut self.shared).unwrap().fs.close();
-        let nb_errors = self.errors.iter().map(|err| diag.struct_err(&err).emit()).count();
+        let nb_errors = self.shared.errors.iter().map(|err| diag.struct_err(&err).emit()).count();
         if nb_errors > 0 {
             Err(Error::new(io::Error::new(io::ErrorKind::Other, "I/O error"), ""))
         } else {
@@ -670,7 +679,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             self.shared.fs.write(&joint_dst, buf.as_bytes())?;
 
             if !self.render_redirect_pages {
-                self.all.borrow_mut().append(full_path(self, &item), &item_type);
+                self.shared.all.borrow_mut().append(full_path(self, &item), &item_type);
             }
             // If the item is a macro, redirect from the old macro URL (with !)
             // to the new one (without).
@@ -1517,7 +1526,7 @@ fn settings(root_path: &str, suffix: &str, themes: &[StylePath]) -> Result<Strin
 
 impl Context<'_> {
     fn derive_id(&self, id: String) -> String {
-        let mut map = self.id_map.borrow_mut();
+        let mut map = self.shared.id_map.borrow_mut();
         map.derive(id)
     }
 
@@ -1572,8 +1581,8 @@ impl Context<'_> {
         };
 
         {
-            self.id_map.borrow_mut().reset();
-            self.id_map.borrow_mut().populate(&INITIAL_IDS);
+            self.shared.id_map.borrow_mut().reset();
+            self.shared.id_map.borrow_mut().populate(&INITIAL_IDS);
         }
 
         if !self.render_redirect_pages {
@@ -1841,7 +1850,7 @@ fn render_markdown(
     prefix: &str,
     is_hidden: bool,
 ) {
-    let mut ids = cx.id_map.borrow_mut();
+    let mut ids = cx.shared.id_map.borrow_mut();
     write!(
         w,
         "<div class=\"docblock{}\">{}{}</div>",
@@ -2319,7 +2328,7 @@ fn short_item_info(
 
         if let Some(note) = note {
             let note = note.as_str();
-            let mut ids = cx.id_map.borrow_mut();
+            let mut ids = cx.shared.id_map.borrow_mut();
             let html = MarkdownHtml(
                 &note,
                 &mut ids,
@@ -2358,7 +2367,7 @@ fn short_item_info(
         message.push_str(&format!(" ({})", feature));
 
         if let Some(unstable_reason) = reason {
-            let mut ids = cx.id_map.borrow_mut();
+            let mut ids = cx.shared.id_map.borrow_mut();
             message = format!(
                 "<details><summary>{}</summary>{}</details>",
                 message,
@@ -3513,7 +3522,8 @@ fn render_assoc_items(
                     type_.print(cx.cache())
                 )));
                 debug!("Adding {} to deref id map", type_.print(cx.cache()));
-                cx.deref_id_map
+                cx.shared
+                    .deref_id_map
                     .borrow_mut()
                     .insert(type_.def_id_full(cx.cache()).unwrap(), id.clone());
                 write!(
@@ -3819,7 +3829,7 @@ fn render_impl(
         }
 
         if let Some(ref dox) = cx.shared.maybe_collapsed_doc_value(&i.impl_item) {
-            let mut ids = cx.id_map.borrow_mut();
+            let mut ids = cx.shared.id_map.borrow_mut();
             write!(
                 w,
                 "<div class=\"docblock\">{}</div>",
@@ -4448,7 +4458,7 @@ fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &V
                 .flat_map(|i| get_methods(i.inner_impl(), true, &mut used_links, deref_mut, c))
                 .collect::<Vec<_>>();
             if !ret.is_empty() {
-                let deref_id_map = cx.deref_id_map.borrow();
+                let deref_id_map = cx.shared.deref_id_map.borrow();
                 let id = deref_id_map
                     .get(&real_target.def_id_full(cx.cache()).unwrap())
                     .expect("Deref section without derived id");