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 #80090 and should not be merged before. Helps with #79103 and #76382.

cc #80014 (comment)

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

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,

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: (

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 {

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),
         }]
     }

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(),
         }
     }
 
@@ -236,32 +240,32 @@ 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() {
                 classes.push("unstable");
             }
 
             // FIXME: what about non-staged API items that are deprecated?
-            if self.deprecation.is_some() {
+            if self.deprecation(tcx).is_some() {
                 classes.push("deprecated");
             }
 
             if !classes.is_empty() { Some(classes.join(" ")) } else { None }
         })
     }
 
-    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,
         }