From 9ff52bf332e03b0f0d06f3a8d8a3719b7b62c475 Mon Sep 17 00:00:00 2001
From: Zalathar <Zalathar@users.noreply.github.com>
Date: Mon, 13 Oct 2025 12:56:34 +1100
Subject: [PATCH] Clear `ChunkedBitSet` without reallocating

---
 compiler/rustc_index/src/bit_set.rs | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index f7649c5f5c55e..d5a184c259319 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -585,8 +585,7 @@ impl<T: Idx> ChunkedBitSet<T> {
     }
 
     pub fn clear(&mut self) {
-        let domain_size = self.domain_size();
-        *self = ChunkedBitSet::new_empty(domain_size);
+        self.chunks.fill_with(|| Chunk::Zeros);
     }
 
     #[cfg(test)]
@@ -684,9 +683,7 @@ impl<T: Idx> ChunkedBitSet<T> {
 
     /// Sets all bits to true.
     pub fn insert_all(&mut self) {
-        for chunk in self.chunks.iter_mut() {
-            *chunk = Ones;
-        }
+        self.chunks.fill_with(|| Chunk::Ones);
     }
 
     /// Returns `true` if the set has changed.