Switch to Symbol for item.name

This decreases the size of `Item` from 680 to 616 bytes. It also does a
lot less work since it no longer has to copy as much.

compiler/rustc_span/src/symbol.rs

@@ -1469,6 +1469,10 @@ impl Symbol {
         self.0.as_u32()
     }
 
+    pub fn is_empty(self) -> bool {
+        self == kw::Invalid
+    }
+
     /// This method is supposed to be used in error messages, so it's expected to be
     /// identical to printing the original identifier token written in source code
     /// (`token_to_string`, `Ident::to_string`), except that symbols don't keep the rawness flag

src/librustdoc/clean/inline.rs

@@ -124,7 +124,7 @@ crate fn try_inline(
     let attrs = merge_attrs(cx, Some(parent_module), target_attrs, attrs_clone);
 
     cx.renderinfo.borrow_mut().inlined.insert(did);
-    let what_rustc_thinks = clean::Item::from_def_id_and_parts(did, Some(name.clean(cx)), kind, cx);
+    let what_rustc_thinks = clean::Item::from_def_id_and_parts(did, Some(name), kind, cx);
     ret.push(clean::Item { attrs, ..what_rustc_thinks });
     Some(ret)
 }

src/librustdoc/clean/mod.rs

@@ -169,7 +169,7 @@ impl Clean<ExternalCrate> for CrateNum {
                 for attr in attrs.lists(sym::doc) {
                     if attr.has_name(sym::keyword) {
                         if let Some(v) = attr.value_str() {
-                            keyword = Some(v.to_string());
+                            keyword = Some(v);
                             break;
                         }
                     }
@@ -253,11 +253,7 @@ impl Clean<Item> for doctree::Module<'_> {
             ModuleItem(Module { is_crate: self.is_crate, items }),
             cx,
         );
-        Item {
-            attrs,
-            source: span.clean(cx),
-            ..what_rustc_thinks
-        }
+        Item { attrs, source: span.clean(cx), ..what_rustc_thinks }
     }
 }
 
@@ -1095,7 +1091,7 @@ impl Clean<Item> for hir::TraitItem<'_> {
                     AssocTypeItem(bounds.clean(cx), default.clean(cx))
                 }
             };
-            Item::from_def_id_and_parts(local_did, Some(self.ident.name.clean(cx)), inner, cx)
+            Item::from_def_id_and_parts(local_did, Some(self.ident.name), inner, cx)
         })
     }
 }
@@ -1123,7 +1119,7 @@ impl Clean<Item> for hir::ImplItem<'_> {
                     TypedefItem(Typedef { type_, generics: Generics::default(), item_type }, true)
                 }
             };
-            Item::from_def_id_and_parts(local_did, Some(self.ident.name.clean(cx)), inner, cx)
+            Item::from_def_id_and_parts(local_did, Some(self.ident.name), inner, cx)
         })
     }
 }
@@ -1280,7 +1276,7 @@ impl Clean<Item> for ty::AssocItem {
             }
         };
 
-        Item::from_def_id_and_parts(self.def_id, Some(self.ident.name.clean(cx)), kind, cx)
+        Item::from_def_id_and_parts(self.def_id, Some(self.ident.name), kind, cx)
     }
 }
 
@@ -1770,7 +1766,7 @@ impl Clean<Item> for ty::FieldDef {
     fn clean(&self, cx: &DocContext<'_>) -> Item {
         let what_rustc_thinks = Item::from_def_id_and_parts(
             self.did,
-            Some(self.ident.name.clean(cx)),
+            Some(self.ident.name),
             StructFieldItem(cx.tcx.type_of(self.did).clean(cx)),
             cx,
         );
@@ -1846,7 +1842,7 @@ impl Clean<Item> for ty::VariantDef {
                     .fields
                     .iter()
                     .map(|field| {
-                        let name = Some(field.ident.name.clean(cx));
+                        let name = Some(field.ident.name);
                         let kind = StructFieldItem(cx.tcx.type_of(field.did).clean(cx));
                         let what_rustc_thinks =
                             Item::from_def_id_and_parts(field.did, name, kind, cx);
@@ -1858,7 +1854,7 @@ impl Clean<Item> for ty::VariantDef {
         };
         let what_rustc_thinks = Item::from_def_id_and_parts(
             self.def_id,
-            Some(self.ident.name.clean(cx)),
+            Some(self.ident.name),
             VariantItem(Variant { kind }),
             cx,
         );
@@ -2032,7 +2028,7 @@ impl Clean<Vec<Item>> for (&hir::Item<'_>, Option<Symbol>) {
                 _ => unreachable!("not yet converted"),
             };
 
-            vec![Item::from_def_id_and_parts(def_id, Some(name.clean(cx)), kind, cx)]
+            vec![Item::from_def_id_and_parts(def_id, Some(name), kind, cx)]
         })
     }
 }

src/librustdoc/clean/types.rs

@@ -70,7 +70,7 @@ crate struct ExternalCrate {
     crate src: FileName,
     crate attrs: Attributes,
     crate primitives: Vec<(DefId, PrimitiveType)>,
-    crate keywords: Vec<(DefId, String)>,
+    crate keywords: Vec<(DefId, Symbol)>,
 }
 
 /// Anything with a source location and set of attributes and, optionally, a
@@ -81,7 +81,7 @@ crate struct Item {
     /// Stringified span
     crate source: Span,
     /// Not everything has a name. E.g., impls
-    crate name: Option<String>,
+    crate name: Option<Symbol>,
     crate attrs: Attributes,
     crate visibility: Visibility,
     crate kind: ItemKind,
@@ -123,17 +123,12 @@ impl Item {
         kind: ItemKind,
         cx: &DocContext<'_>,
     ) -> Item {
-        Item::from_def_id_and_parts(
-            cx.tcx.hir().local_def_id(hir_id).to_def_id(),
-            name.clean(cx),
-            kind,
-            cx,
-        )
+        Item::from_def_id_and_parts(cx.tcx.hir().local_def_id(hir_id).to_def_id(), name, kind, cx)
     }
 
     pub fn from_def_id_and_parts(
         def_id: DefId,
-        name: Option<String>,
+        name: Option<Symbol>,
         kind: ItemKind,
         cx: &DocContext<'_>,
     ) -> Item {
@@ -334,7 +329,7 @@ crate enum ItemKind {
     AssocTypeItem(Vec<GenericBound>, Option<Type>),
     /// An item that has been stripped by a rustdoc pass
     StrippedItem(Box<ItemKind>),
-    KeywordItem(String),
+    KeywordItem(Symbol),
 }
 
 impl ItemKind {
@@ -1163,6 +1158,8 @@ crate enum Type {
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, Copy, Debug)]
+/// N.B. this has to be different from `hir::PrimTy` because it also includes types that aren't
+/// paths, like `Unit`.
 crate enum PrimitiveType {
     Isize,
     I8,
@@ -1502,6 +1499,37 @@ impl PrimitiveType {
     crate fn to_url_str(&self) -> &'static str {
         self.as_str()
     }
+
+    crate fn as_sym(&self) -> Symbol {
+        use PrimitiveType::*;
+        match self {
+            Isize => sym::isize,
+            I8 => sym::i8,
+            I16 => sym::i16,
+            I32 => sym::i32,
+            I64 => sym::i64,
+            I128 => sym::i128,
+            Usize => sym::usize,
+            U8 => sym::u8,
+            U16 => sym::u16,
+            U32 => sym::u32,
+            U64 => sym::u64,
+            U128 => sym::u128,
+            F32 => sym::f32,
+            F64 => sym::f64,
+            Str => sym::str,
+            Bool => sym::bool,
+            Char => sym::char,
+            Array => sym::array,
+            Slice => sym::slice,
+            Tuple => sym::tuple,
+            Unit => sym::unit,
+            RawPointer => sym::pointer,
+            Reference => sym::reference,
+            Fn => kw::Fn,
+            Never => sym::never,
+        }
+    }
 }
 
 impl From<ast::IntTy> for PrimitiveType {

src/librustdoc/clean/utils.rs

@@ -68,7 +68,7 @@ crate fn krate(mut cx: &mut DocContext<'_>) -> Crate {
         m.items.extend(primitives.iter().map(|&(def_id, prim)| {
             Item::from_def_id_and_parts(
                 def_id,
-                Some(prim.to_url_str().to_owned()),
+                Some(prim.as_sym()),
                 ItemKind::PrimitiveItem(prim),
                 cx,
             )

src/librustdoc/formats/renderer.rs

@@ -3,6 +3,7 @@ use std::sync::Arc;
 use rustc_data_structures::sync::Lrc;
 use rustc_session::Session;
 use rustc_span::edition::Edition;
+use rustc_span::Symbol;
 
 use crate::clean;
 use crate::config::{RenderInfo, RenderOptions};
@@ -75,7 +76,7 @@ crate fn run_format<T: FormatRenderer>(
         None => return Ok(()),
     };
 
-    item.name = Some(krate.name.clone());
+    item.name = Some(Symbol::intern(&krate.name));
 
     // Render the crate documentation
     let mut work = vec![(format_renderer.clone(), item)];

src/librustdoc/html/render/cache.rs

@@ -76,7 +76,7 @@ crate fn build_index(krate: &clean::Crate, cache: &mut Cache) -> String {
         if let Some(&(ref fqp, _)) = paths.get(&did) {
             search_index.push(IndexItem {
                 ty: item.type_(),
-                name: item.name.clone().unwrap(),
+                name: item.name.unwrap().to_string(),
                 path: fqp[..fqp.len() - 1].join("::"),
                 desc: item.doc_value().map_or_else(|| String::new(), short_markdown_summary),
                 parent: Some(did),

src/librustdoc/html/render/mod.rs

@@ -61,7 +61,7 @@ use rustc_session::Session;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::FileName;
-use rustc_span::symbol::{sym, Symbol};
+use rustc_span::symbol::{kw, sym, Symbol};
 use serde::ser::SerializeSeq;
 use serde::{Serialize, Serializer};
 
@@ -665,7 +665,7 @@ impl FormatRenderer for Context {
         if !buf.is_empty() {
             let name = item.name.as_ref().unwrap();
             let item_type = item.type_();
-            let file_name = &item_path(item_type, name);
+            let file_name = &item_path(item_type, &name.as_str());
             self.shared.ensure_dir(&self.dst)?;
             let joint_dst = self.dst.join(file_name);
             self.shared.fs.write(&joint_dst, buf.as_bytes())?;
@@ -1543,7 +1543,7 @@ impl Context {
             if !title.is_empty() {
                 title.push_str("::");
             }
-            title.push_str(it.name.as_ref().unwrap());
+            title.push_str(&it.name.unwrap().as_str());
         }
         title.push_str(" - Rust");
         let tyname = it.type_();
@@ -1815,7 +1815,7 @@ fn item_path(ty: ItemType, name: &str) -> String {
 fn full_path(cx: &Context, item: &clean::Item) -> String {
     let mut s = cx.current.join("::");
     s.push_str("::");
-    s.push_str(item.name.as_ref().unwrap());
+    s.push_str(&item.name.unwrap().as_str());
     s
 }
 
@@ -2065,9 +2065,9 @@ fn item_module(w: &mut Buffer, cx: &Context, item: &clean::Item, items: &[clean:
                 (true, false) => return Ordering::Greater,
             }
         }
-        let lhs = i1.name.as_ref().map_or("", |s| &**s);
-        let rhs = i2.name.as_ref().map_or("", |s| &**s);
-        compare_names(lhs, rhs)
+        let lhs = i1.name.unwrap_or(kw::Invalid).as_str();
+        let rhs = i2.name.unwrap_or(kw::Invalid).as_str();
+        compare_names(&lhs, &rhs)
     }
 
     if cx.shared.sort_modules_alphabetically {
@@ -2191,7 +2191,7 @@ fn item_module(w: &mut Buffer, cx: &Context, item: &clean::Item, items: &[clean:
                     add = add,
                     stab = stab.unwrap_or_else(String::new),
                     unsafety_flag = unsafety_flag,
-                    href = item_path(myitem.type_(), myitem.name.as_ref().unwrap()),
+                    href = item_path(myitem.type_(), &myitem.name.unwrap().as_str()),
                     title = [full_path(cx, myitem), myitem.type_().to_string()]
                         .iter()
                         .filter_map(|s| if !s.is_empty() { Some(s.as_str()) } else { None })
@@ -2623,7 +2623,7 @@ fn item_trait(w: &mut Buffer, cx: &Context, it: &clean::Item, t: &clean::Trait,
 
     fn trait_item(w: &mut Buffer, cx: &Context, m: &clean::Item, t: &clean::Item, cache: &Cache) {
         let name = m.name.as_ref().unwrap();
-        info!("Documenting {} on {}", name, t.name.as_deref().unwrap_or_default());
+        info!("Documenting {} on {:?}", name, t.name);
         let item_type = m.type_();
         let id = cx.derive_id(format!("{}.{}", item_type, name));
         write!(w, "<h3 id=\"{id}\" class=\"method\"><code>", id = id,);
@@ -2951,7 +2951,7 @@ fn render_assoc_item(
             AssocItemLink::GotoSource(did, provided_methods) => {
                 // We're creating a link from an impl-item to the corresponding
                 // trait-item and need to map the anchored type accordingly.
-                let ty = if provided_methods.contains(name) {
+                let ty = if provided_methods.contains(&*name.as_str()) {
                     ItemType::Method
                 } else {
                     ItemType::TyMethod
@@ -3434,10 +3434,7 @@ fn render_assoc_items(
     what: AssocItemRender<'_>,
     cache: &Cache,
 ) {
-    info!(
-        "Documenting associated items of {}",
-        containing_item.name.as_deref().unwrap_or_default()
-    );
+    info!("Documenting associated items of {:?}", containing_item.name);
     let v = match cache.impls.get(&it) {
         Some(v) => v,
         None => return,
@@ -4139,7 +4136,7 @@ fn print_sidebar(cx: &Context, it: &clean::Item, buffer: &mut Buffer, cache: &Ca
                 ty: \"{ty}\", \
                 relpath: \"{path}\"\
             }};</script>",
-        name = it.name.as_ref().map(|x| &x[..]).unwrap_or(""),
+        name = it.name.unwrap_or(kw::Invalid),
         ty = it.type_(),
         path = relpath
     );

src/librustdoc/json/conversions.rs

@@ -33,7 +33,7 @@ impl JsonRenderer {
             _ => Some(Item {
                 id: def_id.into(),
                 crate_id: def_id.krate.as_u32(),
-                name,
+                name: name.map(|sym| sym.to_string()),
                 source: self.convert_span(source),
                 visibility: visibility.into(),
                 docs: attrs.collapsed_doc_value().unwrap_or_default(),

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -668,7 +668,7 @@ fn resolve_associated_trait_item(
                     // Give precedence to methods that were overridden
                     if !impl_.provided_trait_methods.contains(&*item_name.as_str()) {
                         let mut items = impl_.items.into_iter().filter_map(|assoc| {
-                            if assoc.name.as_deref() != Some(&*item_name.as_str()) {
+                            if assoc.name != Some(item_name) {
                                 return None;
                             }
                             let kind = assoc
@@ -1942,7 +1942,14 @@ fn privacy_error(
     dox: &str,
     link_range: Option<Range<usize>>,
 ) {
-    let item_name = item.name.as_deref().unwrap_or("<unknown>");
+    let sym;
+    let item_name = match item.name {
+        Some(name) => {
+            sym = name.as_str();
+            &*sym
+        }
+        None => "<unknown>",
+    };
     let msg =
         format!("public documentation for `{}` links to private item `{}`", item_name, path_str);