Rollup merge of #135205 - lqd:bitsets, r=Mark-Simulacrum

Rename `BitSet` to `DenseBitSet`

r? `@Mark-Simulacrum` as you requested this in https://github.com/rust-lang/rust/pull/134438#discussion_r1890659739 after such a confusion.

This PR renames `BitSet` to `DenseBitSet` to make it less obvious as the go-to solution for bitmap needs, as well as make its representation (and positives/negatives) clearer. It also expands the comments there to hopefully make it clearer when it's not a good fit, with some alternative bitsets types.

(This migrates the subtrees cg_gcc and clippy to use the new name in separate commits, for easier review by their respective owners, but they can obvs be squashed)

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/rustc_data_structures/src/graph/implementation/mod.rs b/compiler/rustc_data_structures/src/graph/implementation/mod.rs
index 43fdfe6ee0d..7724e9347d8 100644
--- a/compiler/rustc_data_structures/src/graph/implementation/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/implementation/mod.rs
@@ -22,7 +22,7 @@
 
 use std::fmt::Debug;
 
-use rustc_index::bit_set::BitSet;
+use rustc_index::bit_set::DenseBitSet;
 use tracing::debug;
 
 #[cfg(test)]
@@ -214,7 +214,7 @@ impl<N: Debug, E: Debug> Graph<N, E> {
         direction: Direction,
         entry_node: NodeIndex,
     ) -> Vec<NodeIndex> {
-        let mut visited = BitSet::new_empty(self.len_nodes());
+        let mut visited = DenseBitSet::new_empty(self.len_nodes());
         let mut stack = vec![];
         let mut result = Vec::with_capacity(self.len_nodes());
         let mut push_node = |stack: &mut Vec<_>, node: NodeIndex| {
@@ -287,7 +287,7 @@ impl<'g, N: Debug, E: Debug> Iterator for AdjacentEdges<'g, N, E> {
 pub struct DepthFirstTraversal<'g, N, E> {
     graph: &'g Graph<N, E>,
     stack: Vec<NodeIndex>,
-    visited: BitSet<usize>,
+    visited: DenseBitSet<usize>,
     direction: Direction,
 }
 
@@ -297,7 +297,7 @@ impl<'g, N: Debug, E: Debug> DepthFirstTraversal<'g, N, E> {
         start_node: NodeIndex,
         direction: Direction,
     ) -> Self {
-        let mut visited = BitSet::new_empty(graph.len_nodes());
+        let mut visited = DenseBitSet::new_empty(graph.len_nodes());
         visited.insert(start_node.node_id());
         DepthFirstTraversal { graph, stack: vec![start_node], visited, direction }
     }