From e6ff0bac1ec1271439ed6a7dd35f861e293cd025 Mon Sep 17 00:00:00 2001
From: pierwill <pierwill@users.noreply.github.com>
Date: Tue, 7 Dec 2021 12:29:13 -0600
Subject: [PATCH] rustc `VecGraph`: require the index type to implement Ord

---
 compiler/rustc_data_structures/src/graph/scc/mod.rs       | 7 ++++---
 compiler/rustc_data_structures/src/graph/vec_graph/mod.rs | 8 +++++---
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_data_structures/src/graph/scc/mod.rs b/compiler/rustc_data_structures/src/graph/scc/mod.rs
index 508a084b311..7099ca7eb88 100644
--- a/compiler/rustc_data_structures/src/graph/scc/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/scc/mod.rs
@@ -9,6 +9,7 @@ use crate::fx::FxHashSet;
 use crate::graph::vec_graph::VecGraph;
 use crate::graph::{DirectedGraph, GraphSuccessors, WithNumEdges, WithNumNodes, WithSuccessors};
 use rustc_index::vec::{Idx, IndexVec};
+use std::cmp::Ord;
 use std::ops::Range;
 
 #[cfg(test)]
@@ -38,7 +39,7 @@ struct SccData<S: Idx> {
     all_successors: Vec<S>,
 }
 
-impl<N: Idx, S: Idx> Sccs<N, S> {
+impl<N: Idx, S: Idx + Ord> Sccs<N, S> {
     pub fn new(graph: &(impl DirectedGraph<Node = N> + WithNumNodes + WithSuccessors)) -> Self {
         SccsConstruction::construct(graph)
     }
@@ -85,7 +86,7 @@ impl<N: Idx, S: Idx> DirectedGraph for Sccs<N, S> {
     type Node = S;
 }
 
-impl<N: Idx, S: Idx> WithNumNodes for Sccs<N, S> {
+impl<N: Idx, S: Idx + Ord> WithNumNodes for Sccs<N, S> {
     fn num_nodes(&self) -> usize {
         self.num_sccs()
     }
@@ -103,7 +104,7 @@ impl<'graph, N: Idx, S: Idx> GraphSuccessors<'graph> for Sccs<N, S> {
     type Iter = std::iter::Cloned<std::slice::Iter<'graph, S>>;
 }
 
-impl<N: Idx, S: Idx> WithSuccessors for Sccs<N, S> {
+impl<N: Idx, S: Idx + Ord> WithSuccessors for Sccs<N, S> {
     fn successors(&self, node: S) -> <Self as GraphSuccessors<'_>>::Iter {
         self.successors(node).iter().cloned()
     }
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 826d0fe9ab4..3d91bcade59 100644
--- a/compiler/rustc_data_structures/src/graph/vec_graph/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/vec_graph/mod.rs
@@ -1,3 +1,5 @@
+use std::cmp::Ord;
+
 use crate::graph::{DirectedGraph, GraphSuccessors, WithNumEdges, WithNumNodes, WithSuccessors};
 use rustc_index::vec::{Idx, IndexVec};
 
@@ -17,10 +19,10 @@ pub struct VecGraph<N: Idx> {
     edge_targets: Vec<N>,
 }
 
-impl<N: Idx> VecGraph<N> {
+impl<N: Idx + Ord> VecGraph<N> {
     pub fn new(num_nodes: usize, mut edge_pairs: Vec<(N, N)>) -> Self {
         // Sort the edges by the source -- this is important.
-        edge_pairs.sort_by_key(|&edge_pairs| (edge_pairs.0.index(), edge_pairs.1.index()));
+        edge_pairs.sort();
 
         let num_edges = edge_pairs.len();
 
@@ -100,7 +102,7 @@ impl<'graph, N: Idx> GraphSuccessors<'graph> for VecGraph<N> {
     type Iter = std::iter::Cloned<std::slice::Iter<'graph, N>>;
 }
 
-impl<N: Idx> WithSuccessors for VecGraph<N> {
+impl<N: Idx + Ord> WithSuccessors for VecGraph<N> {
     fn successors(&self, node: N) -> <Self as GraphSuccessors<'_>>::Iter {
         self.successors(node).iter().cloned()
     }