diff --git a/crates/hir-def/src/adt.rs b/crates/hir-def/src/adt.rs
index af8ca8571ba..938db032fbc 100644
--- a/crates/hir-def/src/adt.rs
+++ b/crates/hir-def/src/adt.rs
@@ -151,7 +151,7 @@ pub(crate) fn struct_data_query(db: &dyn DefDatabase, id: StructId) -> Arc<Struc
     pub(crate) fn struct_data_with_diagnostics_query(
         db: &dyn DefDatabase,
         id: StructId,
-    ) -> (Arc<StructData>, Arc<Vec<DefDiagnostic>>) {
+    ) -> (Arc<StructData>, Arc<[DefDiagnostic]>) {
         let loc = id.lookup(db);
         let krate = loc.container.krate;
         let item_tree = loc.id.item_tree(db);
@@ -176,7 +176,7 @@ pub(crate) fn struct_data_with_diagnostics_query(
                 repr,
                 visibility: item_tree[strukt.visibility].clone(),
             }),
-            Arc::new(diagnostics),
+            diagnostics.into(),
         )
     }
 
@@ -187,7 +187,7 @@ pub(crate) fn union_data_query(db: &dyn DefDatabase, id: UnionId) -> Arc<StructD
     pub(crate) fn union_data_with_diagnostics_query(
         db: &dyn DefDatabase,
         id: UnionId,
-    ) -> (Arc<StructData>, Arc<Vec<DefDiagnostic>>) {
+    ) -> (Arc<StructData>, Arc<[DefDiagnostic]>) {
         let loc = id.lookup(db);
         let krate = loc.container.krate;
         let item_tree = loc.id.item_tree(db);
@@ -212,7 +212,7 @@ pub(crate) fn union_data_with_diagnostics_query(
                 repr,
                 visibility: item_tree[union.visibility].clone(),
             }),
-            Arc::new(diagnostics),
+            diagnostics.into(),
         )
     }
 }
@@ -225,7 +225,7 @@ pub(crate) fn enum_data_query(db: &dyn DefDatabase, e: EnumId) -> Arc<EnumData>
     pub(crate) fn enum_data_with_diagnostics_query(
         db: &dyn DefDatabase,
         e: EnumId,
-    ) -> (Arc<EnumData>, Arc<Vec<DefDiagnostic>>) {
+    ) -> (Arc<EnumData>, Arc<[DefDiagnostic]>) {
         let loc = e.lookup(db);
         let krate = loc.container.krate;
         let item_tree = loc.id.item_tree(db);
@@ -272,7 +272,7 @@ pub(crate) fn enum_data_with_diagnostics_query(
                 repr,
                 visibility: item_tree[enum_.visibility].clone(),
             }),
-            Arc::new(diagnostics),
+            diagnostics.into(),
         )
     }
 
diff --git a/crates/hir-def/src/data.rs b/crates/hir-def/src/data.rs
index 631ae3cf11f..2dc69b00ace 100644
--- a/crates/hir-def/src/data.rs
+++ b/crates/hir-def/src/data.rs
@@ -219,7 +219,7 @@ pub(crate) fn trait_data_query(db: &dyn DefDatabase, tr: TraitId) -> Arc<TraitDa
     pub(crate) fn trait_data_with_diagnostics_query(
         db: &dyn DefDatabase,
         tr: TraitId,
-    ) -> (Arc<TraitData>, Arc<Vec<DefDiagnostic>>) {
+    ) -> (Arc<TraitData>, Arc<[DefDiagnostic]>) {
         let tr_loc @ ItemLoc { container: module_id, id: tree_id } = tr.lookup(db);
         let item_tree = tree_id.item_tree(db);
         let tr_def = &item_tree[tree_id.value];
@@ -251,7 +251,7 @@ pub(crate) fn trait_data_with_diagnostics_query(
                 visibility,
                 skip_array_during_method_dispatch,
             }),
-            Arc::new(diagnostics),
+            diagnostics.into(),
         )
     }
 
@@ -299,7 +299,7 @@ pub(crate) fn impl_data_query(db: &dyn DefDatabase, id: ImplId) -> Arc<ImplData>
     pub(crate) fn impl_data_with_diagnostics_query(
         db: &dyn DefDatabase,
         id: ImplId,
-    ) -> (Arc<ImplData>, Arc<Vec<DefDiagnostic>>) {
+    ) -> (Arc<ImplData>, Arc<[DefDiagnostic]>) {
         let _p = profile::span("impl_data_with_diagnostics_query");
         let ItemLoc { container: module_id, id: tree_id } = id.lookup(db);
 
@@ -318,7 +318,7 @@ pub(crate) fn impl_data_with_diagnostics_query(
 
         (
             Arc::new(ImplData { target_trait, self_ty, items, is_negative, attribute_calls }),
-            Arc::new(diagnostics),
+            diagnostics.into(),
         )
     }
 
diff --git a/crates/hir-def/src/db.rs b/crates/hir-def/src/db.rs
index 93ffe29a1fe..431c8255497 100644
--- a/crates/hir-def/src/db.rs
+++ b/crates/hir-def/src/db.rs
@@ -98,38 +98,32 @@ pub trait DefDatabase: InternDatabase + AstDatabase + Upcast<dyn AstDatabase> {
     fn struct_data(&self, id: StructId) -> Arc<StructData>;
 
     #[salsa::invoke(StructData::struct_data_with_diagnostics_query)]
-    fn struct_data_with_diagnostics(
-        &self,
-        id: StructId,
-    ) -> (Arc<StructData>, Arc<Vec<DefDiagnostic>>);
+    fn struct_data_with_diagnostics(&self, id: StructId)
+        -> (Arc<StructData>, Arc<[DefDiagnostic]>);
 
     #[salsa::invoke(StructData::union_data_query)]
     fn union_data(&self, id: UnionId) -> Arc<StructData>;
 
     #[salsa::invoke(StructData::union_data_with_diagnostics_query)]
-    fn union_data_with_diagnostics(
-        &self,
-        id: UnionId,
-    ) -> (Arc<StructData>, Arc<Vec<DefDiagnostic>>);
+    fn union_data_with_diagnostics(&self, id: UnionId) -> (Arc<StructData>, Arc<[DefDiagnostic]>);
 
     #[salsa::invoke(EnumData::enum_data_query)]
     fn enum_data(&self, e: EnumId) -> Arc<EnumData>;
 
     #[salsa::invoke(EnumData::enum_data_with_diagnostics_query)]
-    fn enum_data_with_diagnostics(&self, e: EnumId) -> (Arc<EnumData>, Arc<Vec<DefDiagnostic>>);
+    fn enum_data_with_diagnostics(&self, e: EnumId) -> (Arc<EnumData>, Arc<[DefDiagnostic]>);
 
     #[salsa::invoke(ImplData::impl_data_query)]
     fn impl_data(&self, e: ImplId) -> Arc<ImplData>;
 
     #[salsa::invoke(ImplData::impl_data_with_diagnostics_query)]
-    fn impl_data_with_diagnostics(&self, e: ImplId) -> (Arc<ImplData>, Arc<Vec<DefDiagnostic>>);
+    fn impl_data_with_diagnostics(&self, e: ImplId) -> (Arc<ImplData>, Arc<[DefDiagnostic]>);
 
     #[salsa::invoke(TraitData::trait_data_query)]
     fn trait_data(&self, e: TraitId) -> Arc<TraitData>;
 
     #[salsa::invoke(TraitData::trait_data_with_diagnostics_query)]
-    fn trait_data_with_diagnostics(&self, tr: TraitId)
-        -> (Arc<TraitData>, Arc<Vec<DefDiagnostic>>);
+    fn trait_data_with_diagnostics(&self, tr: TraitId) -> (Arc<TraitData>, Arc<[DefDiagnostic]>);
 
     #[salsa::invoke(TypeAliasData::type_alias_data_query)]
     fn type_alias_data(&self, e: TypeAliasId) -> Arc<TypeAliasData>;