diff --git a/crates/hir-def/src/data.rs b/crates/hir-def/src/data.rs
index 4338163672..8cf1e15f31 100644
--- a/crates/hir-def/src/data.rs
+++ b/crates/hir-def/src/data.rs
@@ -323,7 +323,7 @@ impl TraitAliasData {
 pub struct ImplData {
     pub target_trait: Option<Interned<TraitRef>>,
     pub self_ty: Interned<TypeRef>,
-    pub items: Vec<AssocItemId>,
+    pub items: Box<[AssocItemId]>,
     pub is_negative: bool,
     pub is_unsafe: bool,
     // box it as the vec is usually empty anyways
diff --git a/crates/hir-def/src/db.rs b/crates/hir-def/src/db.rs
index eb45ad343e..0eb9e7d30b 100644
--- a/crates/hir-def/src/db.rs
+++ b/crates/hir-def/src/db.rs
@@ -193,6 +193,7 @@ pub trait DefDatabase: InternDatabase + ExpandDatabase + Upcast<dyn ExpandDataba
     #[salsa::invoke(Attrs::fields_attrs_query)]
     fn fields_attrs(&self, def: VariantId) -> Arc<ArenaMap<LocalFieldId, Attrs>>;
 
+    // should this really be a query?
     #[salsa::invoke(crate::attr::fields_attrs_source_map)]
     fn fields_attrs_source_map(
         &self,
diff --git a/crates/hir-def/src/item_tree.rs b/crates/hir-def/src/item_tree.rs
index be74d15814..7650dfe9f3 100644
--- a/crates/hir-def/src/item_tree.rs
+++ b/crates/hir-def/src/item_tree.rs
@@ -616,24 +616,30 @@ impl Index<RawVisibilityId> for ItemTree {
     type Output = RawVisibility;
     fn index(&self, index: RawVisibilityId) -> &Self::Output {
         static VIS_PUB: RawVisibility = RawVisibility::Public;
-        static VIS_PRIV_IMPLICIT: RawVisibility = RawVisibility::Module(
-            ModPath::from_kind(PathKind::SELF),
-            VisibilityExplicitness::Implicit,
-        );
-        static VIS_PRIV_EXPLICIT: RawVisibility = RawVisibility::Module(
-            ModPath::from_kind(PathKind::SELF),
-            VisibilityExplicitness::Explicit,
-        );
-        static VIS_PUB_CRATE: RawVisibility = RawVisibility::Module(
-            ModPath::from_kind(PathKind::Crate),
-            VisibilityExplicitness::Explicit,
-        );
+        static VIS_PRIV_IMPLICIT: OnceCell<RawVisibility> = OnceCell::new();
+        static VIS_PRIV_EXPLICIT: OnceCell<RawVisibility> = OnceCell::new();
+        static VIS_PUB_CRATE: OnceCell<RawVisibility> = OnceCell::new();
 
         match index {
-            RawVisibilityId::PRIV_IMPLICIT => &VIS_PRIV_IMPLICIT,
-            RawVisibilityId::PRIV_EXPLICIT => &VIS_PRIV_EXPLICIT,
+            RawVisibilityId::PRIV_IMPLICIT => VIS_PRIV_IMPLICIT.get_or_init(|| {
+                RawVisibility::Module(
+                    Interned::new(ModPath::from_kind(PathKind::SELF)),
+                    VisibilityExplicitness::Implicit,
+                )
+            }),
+            RawVisibilityId::PRIV_EXPLICIT => VIS_PRIV_EXPLICIT.get_or_init(|| {
+                RawVisibility::Module(
+                    Interned::new(ModPath::from_kind(PathKind::SELF)),
+                    VisibilityExplicitness::Explicit,
+                )
+            }),
             RawVisibilityId::PUB => &VIS_PUB,
-            RawVisibilityId::PUB_CRATE => &VIS_PUB_CRATE,
+            RawVisibilityId::PUB_CRATE => VIS_PUB_CRATE.get_or_init(|| {
+                RawVisibility::Module(
+                    Interned::new(ModPath::from_kind(PathKind::Crate)),
+                    VisibilityExplicitness::Explicit,
+                )
+            }),
             _ => &self.data().vis.arena[Idx::from_raw(index.0.into())],
         }
     }
diff --git a/crates/hir-def/src/visibility.rs b/crates/hir-def/src/visibility.rs
index e08718fc83..11d91513f1 100644
--- a/crates/hir-def/src/visibility.rs
+++ b/crates/hir-def/src/visibility.rs
@@ -2,6 +2,7 @@
 
 use std::iter;
 
+use intern::Interned;
 use la_arena::ArenaMap;
 use span::SyntaxContextId;
 use syntax::ast;
@@ -20,14 +21,17 @@ use crate::{
 pub enum RawVisibility {
     /// `pub(in module)`, `pub(crate)` or `pub(super)`. Also private, which is
     /// equivalent to `pub(self)`.
-    Module(ModPath, VisibilityExplicitness),
+    Module(Interned<ModPath>, VisibilityExplicitness),
     /// `pub`.
     Public,
 }
 
 impl RawVisibility {
-    pub(crate) const fn private() -> RawVisibility {
-        RawVisibility::Module(ModPath::from_kind(PathKind::SELF), VisibilityExplicitness::Implicit)
+    pub(crate) fn private() -> RawVisibility {
+        RawVisibility::Module(
+            Interned::new(ModPath::from_kind(PathKind::SELF)),
+            VisibilityExplicitness::Implicit,
+        )
     }
 
     pub(crate) fn from_ast(
@@ -60,7 +64,7 @@ impl RawVisibility {
             ast::VisibilityKind::PubSelf => ModPath::from_kind(PathKind::SELF),
             ast::VisibilityKind::Pub => return RawVisibility::Public,
         };
-        RawVisibility::Module(path, VisibilityExplicitness::Explicit)
+        RawVisibility::Module(Interned::new(path), VisibilityExplicitness::Explicit)
     }
 
     pub fn resolve(