diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index 976874c7cee8..5b664e19c18c 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -1546,6 +1546,16 @@ impl<T: Idx> GrowableBitSet<T> {
         let (word_index, mask) = word_index_and_mask(elem);
         self.bit_set.words.get(word_index).map_or(false, |word| (word & mask) != 0)
     }
+
+    #[inline]
+    pub fn iter(&self) -> BitIter<'_, T> {
+        self.bit_set.iter()
+    }
+
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.bit_set.count()
+    }
 }
 
 impl<T: Idx> From<BitSet<T>> for GrowableBitSet<T> {
diff --git a/compiler/rustc_passes/src/hir_id_validator.rs b/compiler/rustc_passes/src/hir_id_validator.rs
index 23ff0a911597..b268cee96db9 100644
--- a/compiler/rustc_passes/src/hir_id_validator.rs
+++ b/compiler/rustc_passes/src/hir_id_validator.rs
@@ -1,9 +1,9 @@
-use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lock;
 use rustc_hir as hir;
 use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
 use rustc_hir::intravisit;
 use rustc_hir::{HirId, ItemLocalId};
+use rustc_index::bit_set::GrowableBitSet;
 use rustc_middle::hir::map::Map;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::TyCtxt;
@@ -40,7 +40,7 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
 struct HirIdValidator<'a, 'hir> {
     hir_map: Map<'hir>,
     owner: Option<LocalDefId>,
-    hir_ids_seen: FxHashSet<ItemLocalId>,
+    hir_ids_seen: GrowableBitSet<ItemLocalId>,
     errors: &'a Lock<Vec<String>>,
 }
 
@@ -80,7 +80,7 @@ impl<'a, 'hir> HirIdValidator<'a, 'hir> {
         if max != self.hir_ids_seen.len() - 1 {
             // Collect the missing ItemLocalIds
             let missing: Vec<_> = (0..=max as u32)
-                .filter(|&i| !self.hir_ids_seen.contains(&ItemLocalId::from_u32(i)))
+                .filter(|&i| !self.hir_ids_seen.contains(ItemLocalId::from_u32(i)))
                 .collect();
 
             // Try to map those to something more useful
@@ -106,7 +106,7 @@ impl<'a, 'hir> HirIdValidator<'a, 'hir> {
                     missing_items,
                     self.hir_ids_seen
                         .iter()
-                        .map(|&local_id| HirId { owner, local_id })
+                        .map(|local_id| HirId { owner, local_id })
                         .map(|h| format!("({:?} {})", h, self.hir_map.node_to_string(h)))
                         .collect::<Vec<_>>()
                 )