Auto merge of #80095 - jyn514:stability-on-demand, r=GuillaumeGomez

[rustdoc] Calculate stability, const_stability, and deprecation on-demand

Previously, they would always be calculated ahead of time, which bloated the size of `clean::Item`.

Builds on https://github.com/rust-lang/rust/pull/80090 and should not be merged before. Helps with https://github.com/rust-lang/rust/issues/79103 and https://github.com/rust-lang/rust/issues/76382.

cc https://github.com/rust-lang/rust/pull/80014#issuecomment-746810284

This brings `Item` down to 568 bytes, down from 616.

7 files changed, 75 insertions, 80 deletions

diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
index 40c59ed1e0b..96d19e8e17d 100644
--- a/src/librustdoc/clean/auto_trait.rs
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -123,9 +123,6 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
                     attrs: Default::default(),
                     visibility: Inherited,
                     def_id: self.cx.next_def_id(param_env_def_id.krate),
-                    stability: None,
-                    const_stability: None,
-                    deprecation: None,
                     kind: ImplItem(Impl {
                         unsafety: hir::Unsafety::Normal,
                         generics: new_generics,
diff --git a/src/librustdoc/clean/blanket_impl.rs b/src/librustdoc/clean/blanket_impl.rs
index 22496065afd..d99055e1145 100644
--- a/src/librustdoc/clean/blanket_impl.rs
+++ b/src/librustdoc/clean/blanket_impl.rs
@@ -112,9 +112,6 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                     attrs: Default::default(),
                     visibility: Inherited,
                     def_id: self.cx.next_def_id(impl_def_id.krate),
-                    stability: None,
-                    const_stability: None,
-                    deprecation: None,
                     kind: ImplItem(Impl {
                         unsafety: hir::Unsafety::Normal,
                         generics: (
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 783be6c8243..be4c62d891d 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -482,9 +482,6 @@ fn build_module(cx: &DocContext<'_>, did: DefId, visited: &mut FxHashSet<DefId>)
                         source: clean::Span::dummy(),
                         def_id: DefId::local(CRATE_DEF_INDEX),
                         visibility: clean::Public,
-                        stability: None,
-                        const_stability: None,
-                        deprecation: None,
                         kind: clean::ImportItem(clean::Import::new_simple(
                             item.ident.name,
                             clean::ImportSource {
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index cc5f68bc297..206fb739246 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -2141,9 +2141,6 @@ fn clean_extern_crate(
         source: krate.span.clean(cx),
         def_id: crate_def_id,
         visibility: krate.vis.clean(cx),
-        stability: None,
-        const_stability: None,
-        deprecation: None,
         kind: ExternCrateItem(name, orig_name),
     }]
 }
@@ -2212,9 +2209,6 @@ impl Clean<Vec<Item>> for doctree::Import<'_> {
                         source: self.span.clean(cx),
                         def_id: cx.tcx.hir().local_def_id(self.id).to_def_id(),
                         visibility: self.vis.clean(cx),
-                        stability: None,
-                        const_stability: None,
-                        deprecation: None,
                         kind: ImportItem(Import::new_simple(
                             self.name,
                             resolve_use_source(cx, path),
@@ -2233,9 +2227,6 @@ impl Clean<Vec<Item>> for doctree::Import<'_> {
             source: self.span.clean(cx),
             def_id: cx.tcx.hir().local_def_id(self.id).to_def_id(),
             visibility: self.vis.clean(cx),
-            stability: None,
-            const_stability: None,
-            deprecation: None,
             kind: ImportItem(inner),
         }]
     }
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index cd6eccea532..d7456ab5da2 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -86,9 +86,6 @@ crate struct Item {
     crate visibility: Visibility,
     crate kind: ItemKind,
     crate def_id: DefId,
-    crate stability: Option<Stability>,
-    crate deprecation: Option<Deprecation>,
-    crate const_stability: Option<ConstStability>,
 }
 
 impl fmt::Debug for Item {
@@ -102,13 +99,23 @@ impl fmt::Debug for Item {
             .field("kind", &self.kind)
             .field("visibility", &self.visibility)
             .field("def_id", def_id)
-            .field("stability", &self.stability)
-            .field("deprecation", &self.deprecation)
             .finish()
     }
 }
 
 impl Item {
+    crate fn stability<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Option<&'tcx Stability> {
+        if self.is_fake() { None } else { tcx.lookup_stability(self.def_id) }
+    }
+
+    crate fn const_stability<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Option<&'tcx ConstStability> {
+        if self.is_fake() { None } else { tcx.lookup_const_stability(self.def_id) }
+    }
+
+    crate fn deprecation(&self, tcx: TyCtxt<'_>) -> Option<Deprecation> {
+        if self.is_fake() { None } else { tcx.lookup_deprecation(self.def_id) }
+    }
+
     /// Finds the `doc` attribute as a NameValue and returns the corresponding
     /// value found.
     crate fn doc_value(&self) -> Option<&str> {
@@ -150,9 +157,6 @@ impl Item {
             source: source.clean(cx),
             attrs: cx.tcx.get_attrs(def_id).clean(cx),
             visibility: cx.tcx.visibility(def_id).clean(cx),
-            stability: cx.tcx.lookup_stability(def_id).cloned(),
-            deprecation: cx.tcx.lookup_deprecation(def_id),
-            const_stability: cx.tcx.lookup_const_stability(def_id).cloned(),
         }
     }
 
@@ -236,8 +240,8 @@ impl Item {
         }
     }
 
-    crate fn stability_class(&self) -> Option<String> {
-        self.stability.as_ref().and_then(|ref s| {
+    crate fn stability_class(&self, tcx: TyCtxt<'_>) -> Option<String> {
+        self.stability(tcx).as_ref().and_then(|ref s| {
             let mut classes = Vec::with_capacity(2);
 
             if s.level.is_unstable() {
@@ -245,7 +249,7 @@ impl Item {
             }
 
             // FIXME: what about non-staged API items that are deprecated?
-            if self.deprecation.is_some() {
+            if self.deprecation(tcx).is_some() {
                 classes.push("deprecated");
             }
 
@@ -253,15 +257,15 @@ impl Item {
         })
     }
 
-    crate fn stable_since(&self) -> Option<SymbolStr> {
-        match self.stability?.level {
+    crate fn stable_since(&self, tcx: TyCtxt<'_>) -> Option<SymbolStr> {
+        match self.stability(tcx)?.level {
             StabilityLevel::Stable { since, .. } => Some(since.as_str()),
             StabilityLevel::Unstable { .. } => None,
         }
     }
 
-    crate fn const_stable_since(&self) -> Option<SymbolStr> {
-        match self.const_stability?.level {
+    crate fn const_stable_since(&self, tcx: TyCtxt<'_>) -> Option<SymbolStr> {
+        match self.const_stability(tcx)?.level {
             StabilityLevel::Stable { since, .. } => Some(since.as_str()),
             StabilityLevel::Unstable { .. } => None,
         }
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index c21570d9716..4dedee30295 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -164,7 +164,7 @@ crate struct SharedContext<'tcx> {
     playground: Option<markdown::Playground>,
 }
 
-impl Context<'_> {
+impl<'tcx> Context<'tcx> {
     fn path(&self, filename: &str) -> PathBuf {
         // We use splitn vs Path::extension here because we might get a filename
         // like `style.min.css` and we want to process that into
@@ -176,6 +176,10 @@ impl Context<'_> {
         self.dst.join(&filename)
     }
 
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.shared.tcx
+    }
+
     fn sess(&self) -> &Session {
         &self.shared.tcx.sess
     }
@@ -1708,8 +1712,8 @@ fn print_item(cx: &Context<'_>, item: &clean::Item, buf: &mut Buffer, cache: &Ca
     write!(buf, "<h1 class=\"fqn\"><span class=\"out-of-band\">");
     render_stability_since_raw(
         buf,
-        item.stable_since().as_deref(),
-        item.const_stable_since().as_deref(),
+        item.stable_since(cx.tcx()).as_deref(),
+        item.const_stable_since(cx.tcx()).as_deref(),
         None,
         None,
     );
@@ -2061,14 +2065,20 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
         }
     }
 
-    fn cmp(i1: &clean::Item, i2: &clean::Item, idx1: usize, idx2: usize) -> Ordering {
+    fn cmp(
+        i1: &clean::Item,
+        i2: &clean::Item,
+        idx1: usize,
+        idx2: usize,
+        tcx: TyCtxt<'_>,
+    ) -> Ordering {
         let ty1 = i1.type_();
         let ty2 = i2.type_();
         if ty1 != ty2 {
             return (reorder(ty1), idx1).cmp(&(reorder(ty2), idx2));
         }
-        let s1 = i1.stability.as_ref().map(|s| s.level);
-        let s2 = i2.stability.as_ref().map(|s| s.level);
+        let s1 = i1.stability(tcx).as_ref().map(|s| s.level);
+        let s2 = i2.stability(tcx).as_ref().map(|s| s.level);
         if let (Some(a), Some(b)) = (s1, s2) {
             match (a.is_stable(), b.is_stable()) {
                 (true, true) | (false, false) => {}
@@ -2082,7 +2092,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
     }
 
     if cx.shared.sort_modules_alphabetically {
-        indices.sort_by(|&i1, &i2| cmp(&items[i1], &items[i2], i1, i2));
+        indices.sort_by(|&i1, &i2| cmp(&items[i1], &items[i2], i1, i2, cx.tcx()));
     }
     // This call is to remove re-export duplicates in cases such as:
     //
@@ -2184,7 +2194,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
                     _ => "",
                 };
 
-                let stab = myitem.stability_class();
+                let stab = myitem.stability_class(cx.tcx());
                 let add = if stab.is_some() { " " } else { "" };
 
                 let doc_value = myitem.doc_value().unwrap_or("");
@@ -2196,7 +2206,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
                          <td class=\"docblock-short\">{stab_tags}{docs}</td>\
                      </tr>",
                     name = *myitem.name.as_ref().unwrap(),
-                    stab_tags = extra_info_tags(myitem, item),
+                    stab_tags = extra_info_tags(myitem, item, cx.tcx()),
                     docs = MarkdownSummaryLine(doc_value, &myitem.links()).into_string(),
                     class = myitem.type_(),
                     add = add,
@@ -2220,7 +2230,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
 
 /// Render the stability, deprecation and portability tags that are displayed in the item's summary
 /// at the module level.
-fn extra_info_tags(item: &clean::Item, parent: &clean::Item) -> String {
+fn extra_info_tags(item: &clean::Item, parent: &clean::Item, tcx: TyCtxt<'_>) -> String {
     let mut tags = String::new();
 
     fn tag_html(class: &str, title: &str, contents: &str) -> String {
@@ -2228,7 +2238,7 @@ fn extra_info_tags(item: &clean::Item, parent: &clean::Item) -> String {
     }
 
     // The trailing space after each tag is to space it properly against the rest of the docs.
-    if let Some(depr) = &item.deprecation {
+    if let Some(depr) = &item.deprecation(tcx) {
         let mut message = "Deprecated";
         if !stability::deprecation_in_effect(
             depr.is_since_rustc_version,
@@ -2241,7 +2251,10 @@ fn extra_info_tags(item: &clean::Item, parent: &clean::Item) -> String {
 
     // The "rustc_private" crates are permanently unstable so it makes no sense
     // to render "unstable" everywhere.
-    if item.stability.as_ref().map(|s| s.level.is_unstable() && s.feature != sym::rustc_private)
+    if item
+        .stability(tcx)
+        .as_ref()
+        .map(|s| s.level.is_unstable() && s.feature != sym::rustc_private)
         == Some(true)
     {
         tags += &tag_html("unstable", "", "Experimental");
@@ -2287,7 +2300,7 @@ fn short_item_info(
     let error_codes = cx.shared.codes;
 
     if let Some(Deprecation { note, since, is_since_rustc_version, suggestion: _ }) =
-        item.deprecation
+        item.deprecation(cx.tcx())
     {
         // We display deprecation messages for #[deprecated] and #[rustc_deprecated]
         // but only display the future-deprecation messages for #[rustc_deprecated].
@@ -2327,7 +2340,7 @@ fn short_item_info(
     // Render unstable items. But don't render "rustc_private" crates (internal compiler crates).
     // Those crates are permanently unstable so it makes no sense to render "unstable" everywhere.
     if let Some((StabilityLevel::Unstable { reason, issue, .. }, feature)) = item
-        .stability
+        .stability(cx.tcx())
         .as_ref()
         .filter(|stab| stab.feature != sym::rustc_private)
         .map(|stab| (stab.level, stab.feature))
@@ -2480,8 +2493,8 @@ fn render_implementor(
         parent,
         AssocItemLink::Anchor(None),
         RenderMode::Normal,
-        implementor.impl_item.stable_since().as_deref(),
-        implementor.impl_item.const_stable_since().as_deref(),
+        implementor.impl_item.stable_since(cx.tcx()).as_deref(),
+        implementor.impl_item.const_stable_since(cx.tcx()).as_deref(),
         false,
         Some(use_absolute),
         false,
@@ -2511,8 +2524,8 @@ fn render_impls(
                 containing_item,
                 assoc_link,
                 RenderMode::Normal,
-                containing_item.stable_since().as_deref(),
-                containing_item.const_stable_since().as_deref(),
+                containing_item.stable_since(cx.tcx()).as_deref(),
+                containing_item.const_stable_since(cx.tcx()).as_deref(),
                 true,
                 None,
                 false,
@@ -2661,7 +2674,7 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
         write!(w, "<h3 id=\"{id}\" class=\"method\"><code>", id = id,);
         render_assoc_item(w, m, AssocItemLink::Anchor(Some(&id)), ItemType::Impl);
         write!(w, "</code>");
-        render_stability_since(w, m, t);
+        render_stability_since(w, m, t, cx.tcx());
         write_srclink(cx, m, w, cache);
         write!(w, "</h3>");
         document(w, cx, m, Some(t));
@@ -2768,8 +2781,8 @@ fn item_trait(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Tra
                     it,
                     assoc_link,
                     RenderMode::Normal,
-                    implementor.impl_item.stable_since().as_deref(),
-                    implementor.impl_item.const_stable_since().as_deref(),
+                    implementor.impl_item.stable_since(cx.tcx()).as_deref(),
+                    implementor.impl_item.const_stable_since(cx.tcx()).as_deref(),
                     false,
                     None,
                     true,
@@ -2950,13 +2963,18 @@ fn render_stability_since_raw(
     }
 }
 
-fn render_stability_since(w: &mut Buffer, item: &clean::Item, containing_item: &clean::Item) {
+fn render_stability_since(
+    w: &mut Buffer,
+    item: &clean::Item,
+    containing_item: &clean::Item,
+    tcx: TyCtxt<'_>,
+) {
     render_stability_since_raw(
         w,
-        item.stable_since().as_deref(),
-        item.const_stable_since().as_deref(),
-        containing_item.stable_since().as_deref(),
-        containing_item.const_stable_since().as_deref(),
+        item.stable_since(tcx).as_deref(),
+        item.const_stable_since(tcx).as_deref(),
+        containing_item.stable_since(tcx).as_deref(),
+        containing_item.const_stable_since(tcx).as_deref(),
     )
 }
 
@@ -3149,7 +3167,7 @@ fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Uni
                 shortty = ItemType::StructField,
                 ty = ty.print()
             );
-            if let Some(stability_class) = field.stability_class() {
+            if let Some(stability_class) = field.stability_class(cx.tcx()) {
                 write!(w, "<span class=\"stab {stab}\"></span>", stab = stability_class);
             }
             document(w, cx, field, Some(it));
@@ -3279,7 +3297,7 @@ fn item_enum(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, e: &clean::Enum
                 }
                 write!(w, "</div></div>");
             }
-            render_stability_since(w, variant, it);
+            render_stability_since(w, variant, it, cx.tcx());
         }
     }
     render_assoc_items(w, cx, it, it.def_id, AssocItemRender::All, cache)
@@ -3510,8 +3528,8 @@ fn render_assoc_items(
                 containing_item,
                 AssocItemLink::Anchor(None),
                 render_mode,
-                containing_item.stable_since().as_deref(),
-                containing_item.const_stable_since().as_deref(),
+                containing_item.stable_since(cx.tcx()).as_deref(),
+                containing_item.const_stable_since(cx.tcx()).as_deref(),
                 true,
                 None,
                 false,
@@ -3758,8 +3776,8 @@ fn render_impl(
         write!(w, "<a href=\"#{}\" class=\"anchor\"></a>", id);
         render_stability_since_raw(
             w,
-            i.impl_item.stable_since().as_deref(),
-            i.impl_item.const_stable_since().as_deref(),
+            i.impl_item.stable_since(cx.tcx()).as_deref(),
+            i.impl_item.const_stable_since(cx.tcx()).as_deref(),
             outer_version,
             outer_const_version,
         );
@@ -3831,8 +3849,8 @@ fn render_impl(
                     write!(w, "</code>");
                     render_stability_since_raw(
                         w,
-                        item.stable_since().as_deref(),
-                        item.const_stable_since().as_deref(),
+                        item.stable_since(cx.tcx()).as_deref(),
+                        item.const_stable_since(cx.tcx()).as_deref(),
                         outer_version,
                         outer_const_version,
                     );
@@ -3853,8 +3871,8 @@ fn render_impl(
                 write!(w, "</code>");
                 render_stability_since_raw(
                     w,
-                    item.stable_since().as_deref(),
-                    item.const_stable_since().as_deref(),
+                    item.stable_since(cx.tcx()).as_deref(),
+                    item.const_stable_since(cx.tcx()).as_deref(),
                     outer_version,
                     outer_const_version,
                 );
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index 496cc3d8560..0b22882b42e 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -17,17 +17,8 @@ use crate::json::JsonRenderer;
 impl JsonRenderer<'_> {
     pub(super) fn convert_item(&self, item: clean::Item) -> Option<Item> {
         let item_type = ItemType::from(&item);
-        let clean::Item {
-            source,
-            name,
-            attrs,
-            kind,
-            visibility,
-            def_id,
-            stability: _,
-            const_stability: _,
-            deprecation,
-        } = item;
+        let deprecation = item.deprecation(self.tcx);
+        let clean::Item { source, name, attrs, kind, visibility, def_id } = item;
         match kind {
             clean::StrippedItem(_) => None,
             _ => Some(Item {