Rollup merge of #123934 - WaffleLapkin:graph-mini-refactor, r=fmease

`rustc_data_structures::graph` mini refactor

Who doesn't love to breathe dust from the ancient times?

2 files changed, 7 insertions, 13 deletions

diff --git a/compiler/rustc_data_structures/src/graph/vec_graph/mod.rs b/compiler/rustc_data_structures/src/graph/vec_graph/mod.rs
index 00f6266ce1d..26c86469fad 100644
--- a/compiler/rustc_data_structures/src/graph/vec_graph/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/vec_graph/mod.rs
@@ -1,4 +1,4 @@
-use crate::graph::{DirectedGraph, GraphSuccessors, WithNumEdges, WithNumNodes, WithSuccessors};
+use crate::graph::{DirectedGraph, NumEdges, Successors};
 use rustc_index::{Idx, IndexVec};
 
 #[cfg(test)]
@@ -80,28 +80,20 @@ impl<N: Idx + Ord> VecGraph<N> {
 
 impl<N: Idx> DirectedGraph for VecGraph<N> {
     type Node = N;
-}
 
-impl<N: Idx> WithNumNodes for VecGraph<N> {
     fn num_nodes(&self) -> usize {
         self.node_starts.len() - 1
     }
 }
 
-impl<N: Idx> WithNumEdges for VecGraph<N> {
+impl<N: Idx> NumEdges for VecGraph<N> {
     fn num_edges(&self) -> usize {
         self.edge_targets.len()
     }
 }
 
-impl<'graph, N: Idx> GraphSuccessors<'graph> for VecGraph<N> {
-    type Item = N;
-
-    type Iter = std::iter::Cloned<std::slice::Iter<'graph, N>>;
-}
-
-impl<N: Idx + Ord> WithSuccessors for VecGraph<N> {
-    fn successors(&self, node: N) -> <Self as GraphSuccessors<'_>>::Iter {
+impl<N: Idx + Ord> Successors for VecGraph<N> {
+    fn successors(&self, node: N) -> impl Iterator<Item = Self::Node> {
         self.successors(node).iter().cloned()
     }
 }
diff --git a/compiler/rustc_data_structures/src/graph/vec_graph/tests.rs b/compiler/rustc_data_structures/src/graph/vec_graph/tests.rs
index 7c866da6009..87c8d25f094 100644
--- a/compiler/rustc_data_structures/src/graph/vec_graph/tests.rs
+++ b/compiler/rustc_data_structures/src/graph/vec_graph/tests.rs
@@ -1,3 +1,5 @@
+use crate::graph;
+
 use super::*;
 
 fn create_graph() -> VecGraph<usize> {
@@ -37,6 +39,6 @@ fn successors() {
 #[test]
 fn dfs() {
     let graph = create_graph();
-    let dfs: Vec<_> = graph.depth_first_search(0).collect();
+    let dfs: Vec<_> = graph::depth_first_search(&graph, 0).collect();
     assert_eq!(dfs, vec![0, 1, 3, 4, 2]);
 }