From 47301e2f82fb4ceaf5a830d8599fbe2a01eb9def Mon Sep 17 00:00:00 2001
From: tachsin <tachsinachmet@gmail.com>
Date: Wed, 9 Sep 2026 21:02:18 +0300
Subject: [PATCH] refactor(edmonds-karp): drop two unsafe Send impls the
 compiler already provides

---
 src/directed/edmonds_karp.rs | 4 ----
 tests/edmondskarp.rs         | 9 +++++++++
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/directed/edmonds_karp.rs b/src/directed/edmonds_karp.rs
index 2e8ed848..9c68cd43 100644
--- a/src/directed/edmonds_karp.rs
+++ b/src/directed/edmonds_karp.rs
@@ -352,8 +352,6 @@ pub struct SparseCapacity<C> {
     residuals: BTreeMap<usize, BTreeMap<usize, C>>,
 }
 
-unsafe impl<C: Send> Send for SparseCapacity<C> {}
-
 impl<C: Copy + Eq + Zero + Signed + Bounded + Ord> SparseCapacity<C> {
     fn set_value(data: &mut BTreeMap<usize, BTreeMap<usize, C>>, from: usize, to: usize, value: C) {
         let to_remove = {
@@ -479,8 +477,6 @@ pub struct DenseCapacity<C> {
     flows: Matrix<C>,
 }
 
-unsafe impl<C: Send> Send for DenseCapacity<C> {}
-
 impl<C: Copy + Zero + Signed + Ord + Bounded> EdmondsKarp<C> for DenseCapacity<C> {
     fn new(size: usize, source: usize, sink: usize) -> Self {
         assert!(source < size, "source is greater or equal than size");
diff --git a/tests/edmondskarp.rs b/tests/edmondskarp.rs
index e96ca6aa..441917c5 100644
--- a/tests/edmondskarp.rs
+++ b/tests/edmondskarp.rs
@@ -273,3 +273,12 @@ fn set_capacity_test() {
     ek.augment();
     residual_capacities_non_negative(&ek);
 }
+
+#[test]
+fn capacities_are_send_without_an_unsafe_impl() {
+    // Every field of both types is `Send` when `C` is, so the compiler derives this on its
+    // own; the assertion is here so that a field which is not can never be added silently.
+    const fn assert_send<T: Send>() {}
+    assert_send::<DenseCapacity<i32>>();
+    assert_send::<SparseCapacity<i32>>();
+}