diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index bb5597b5758..d28f3ce8778 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -917,6 +917,10 @@ crate struct DocFragment {
     crate indent: usize,
 }
 
+// `DocFragment` is used a lot. Make sure it doesn't unintentionally get bigger.
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+rustc_data_structures::static_assert_size!(DocFragment, 32);
+
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 crate enum DocFragmentKind {
     /// A doc fragment created from a `///` or `//!` doc comment.
@@ -1109,7 +1113,7 @@ impl Attributes {
         if self.doc_strings.is_empty() { None } else { Some(self.doc_strings.iter().collect()) }
     }
 
-    crate fn get_doc_aliases(&self) -> Box<[String]> {
+    crate fn get_doc_aliases(&self) -> Box<[Symbol]> {
         let mut aliases = FxHashSet::default();
 
         for attr in self.other_attrs.lists(sym::doc).filter(|a| a.has_name(sym::alias)) {
@@ -1117,16 +1121,16 @@ impl Attributes {
                 for l in values {
                     match l.literal().unwrap().kind {
                         ast::LitKind::Str(s, _) => {
-                            aliases.insert(s.as_str().to_string());
+                            aliases.insert(s);
                         }
                         _ => unreachable!(),
                     }
                 }
             } else {
-                aliases.insert(attr.value_str().map(|s| s.to_string()).unwrap());
+                aliases.insert(attr.value_str().unwrap());
             }
         }
-        aliases.into_iter().collect::<Vec<String>>().into()
+        aliases.into_iter().collect::<Vec<_>>().into()
     }
 }
 
diff --git a/src/librustdoc/html/render/cache.rs b/src/librustdoc/html/render/cache.rs
index 0286d2a4c81..9aa69d94215 100644
--- a/src/librustdoc/html/render/cache.rs
+++ b/src/librustdoc/html/render/cache.rs
@@ -70,7 +70,7 @@ crate fn build_index<'tcx>(krate: &clean::Crate, cache: &mut Cache, tcx: TyCtxt<
     // Set up alias indexes.
     for (i, item) in search_index.iter().enumerate() {
         for alias in &item.aliases[..] {
-            aliases.entry(alias.to_lowercase()).or_insert_with(Vec::new).push(i);
+            aliases.entry(alias.as_str().to_lowercase()).or_default().push(i);
         }
     }
 
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index dd592de41bd..ffd09663f82 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -103,7 +103,7 @@ crate struct IndexItem {
     crate parent: Option<DefId>,
     crate parent_idx: Option<usize>,
     crate search_type: Option<IndexItemFunctionType>,
-    crate aliases: Box<[String]>,
+    crate aliases: Box<[Symbol]>,
 }
 
 /// A type used for the search index.