diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index fa46f521ba5a7..77ac319547b9d 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -277,7 +277,7 @@ pub struct AssociatedItems {
 
 impl AssociatedItems {
     /// Constructs an `AssociatedItems` map from a series of `ty::AssocItem`s in definition order.
-    pub fn new(items_in_def_order: Vec<ty::AssocItem>) -> Self {
+    pub fn new(items_in_def_order: impl IntoIterator<Item = ty::AssocItem>) -> Self {
         let items = items_in_def_order.into_iter().map(|item| (item.ident.name, item)).collect();
         AssociatedItems { items }
     }
diff --git a/src/librustc_ty/ty.rs b/src/librustc_ty/ty.rs
index 916a819090c49..d466bbcca79ba 100644
--- a/src/librustc_ty/ty.rs
+++ b/src/librustc_ty/ty.rs
@@ -211,8 +211,7 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
 }
 
 fn associated_items<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx ty::AssociatedItems {
-    let items =
-        tcx.associated_item_def_ids(def_id).iter().map(|did| tcx.associated_item(*did)).collect();
+    let items = tcx.associated_item_def_ids(def_id).iter().map(|did| tcx.associated_item(*did));
     tcx.arena.alloc(ty::AssociatedItems::new(items))
 }