From 6e85c4e2d99c794e4a9172cd38468a098427c07f Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Mon, 13 Oct 2025 08:35:21 +1100
Subject: [PATCH] Remove some unused bitset code.

---
 compiler/rustc_index/src/bit_set.rs       | 51 -----------------------
 compiler/rustc_index/src/bit_set/tests.rs | 28 -------------
 2 files changed, 79 deletions(-)

diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index 85ec302a6aa9..6f207ff20ed3 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -973,48 +973,6 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
     }
 }
 
-impl<T: Idx> BitRelations<ChunkedBitSet<T>> for DenseBitSet<T> {
-    fn union(&mut self, other: &ChunkedBitSet<T>) -> bool {
-        sequential_update(|elem| self.insert(elem), other.iter())
-    }
-
-    fn subtract(&mut self, _other: &ChunkedBitSet<T>) -> bool {
-        unimplemented!("implement if/when necessary");
-    }
-
-    fn intersect(&mut self, other: &ChunkedBitSet<T>) -> bool {
-        assert_eq!(self.domain_size(), other.domain_size);
-        let mut changed = false;
-        for (i, chunk) in other.chunks.iter().enumerate() {
-            let mut words = &mut self.words[i * CHUNK_WORDS..];
-            if words.len() > CHUNK_WORDS {
-                words = &mut words[..CHUNK_WORDS];
-            }
-            match chunk {
-                Zeros => {
-                    for word in words {
-                        if *word != 0 {
-                            changed = true;
-                            *word = 0;
-                        }
-                    }
-                }
-                Ones => (),
-                Mixed(_, data) => {
-                    for (i, word) in words.iter_mut().enumerate() {
-                        let new_val = *word & data[i];
-                        if new_val != *word {
-                            changed = true;
-                            *word = new_val;
-                        }
-                    }
-                }
-            }
-        }
-        changed
-    }
-}
-
 impl<T> Clone for ChunkedBitSet<T> {
     fn clone(&self) -> Self {
         ChunkedBitSet {
@@ -1125,15 +1083,6 @@ enum ChunkIter<'a> {
     Finished,
 }
 
-// Applies a function to mutate a bitset, and returns true if any
-// of the applications return true
-fn sequential_update<T: Idx>(
-    mut self_update: impl FnMut(T) -> bool,
-    it: impl Iterator<Item = T>,
-) -> bool {
-    it.fold(false, |changed, elem| self_update(elem) | changed)
-}
-
 impl<T: Idx> fmt::Debug for ChunkedBitSet<T> {
     fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result {
         w.debug_list().entries(self.iter()).finish()
diff --git a/compiler/rustc_index/src/bit_set/tests.rs b/compiler/rustc_index/src/bit_set/tests.rs
index deddc8726143..341e0622df75 100644
--- a/compiler/rustc_index/src/bit_set/tests.rs
+++ b/compiler/rustc_index/src/bit_set/tests.rs
@@ -306,34 +306,6 @@ fn with_elements_chunked(elements: &[usize], domain_size: usize) -> ChunkedBitSe
     s
 }
 
-fn with_elements_standard(elements: &[usize], domain_size: usize) -> DenseBitSet<usize> {
-    let mut s = DenseBitSet::new_empty(domain_size);
-    for &e in elements {
-        assert!(s.insert(e));
-    }
-    s
-}
-
-#[test]
-fn chunked_bitset_into_bitset_operations() {
-    let a = vec![1, 5, 7, 11, 15, 2000, 3000];
-    let b = vec![3, 4, 11, 3000, 4000];
-    let aub = vec![1, 3, 4, 5, 7, 11, 15, 2000, 3000, 4000];
-    let aib = vec![11, 3000];
-
-    let b = with_elements_chunked(&b, 9876);
-
-    let mut union = with_elements_standard(&a, 9876);
-    assert!(union.union(&b));
-    assert!(!union.union(&b));
-    assert!(union.iter().eq(aub.iter().copied()));
-
-    let mut intersection = with_elements_standard(&a, 9876);
-    assert!(intersection.intersect(&b));
-    assert!(!intersection.intersect(&b));
-    assert!(intersection.iter().eq(aib.iter().copied()));
-}
-
 #[test]
 fn chunked_bitset_iter() {
     fn check_iter(bit: &ChunkedBitSet<usize>, vec: &Vec<usize>) {