From 90c339ebdb513a251e8acf74aa0fd28fddb69d95 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Fri, 1 Aug 2025 23:43:18 +0200
Subject: [PATCH] List.remove_at would incorrectly trigger ASAN.

---
 lib/std/collections/list.c3          |  7 ++++---
 releasenotes.md                      |  2 ++
 test/unit/stdlib/collections/list.c3 | 16 ++++++++++++++++
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/lib/std/collections/list.c3 b/lib/std/collections/list.c3
index 65369642b..c618e9cef 100644
--- a/lib/std/collections/list.c3
+++ b/lib/std/collections/list.c3
@@ -137,9 +137,10 @@ fn Type? List.pop_first(&self)
 *>
 fn void List.remove_at(&self, usz index)
 {
-	self.set_size(self.size - 1);
-	if (!self.size || index == self.size) return;
-	self.entries[index .. self.size - 1] = self.entries[index + 1 .. self.size];
+	usz new_size = self.size - 1;
+	defer self.set_size(new_size);
+	if (!new_size || index == new_size) return;
+	self.entries[index .. new_size - 1] = self.entries[index + 1 .. new_size];
 }
 
 fn void List.add_all(&self, List* other_list)
diff --git a/releasenotes.md b/releasenotes.md
index cab93b8a6..f8b2cc771 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -6,6 +6,8 @@
 - Support `alias foo = module std::io` module aliasing.
 
 ### Fixes
+- List.remove_at would incorrectly trigger ASAN.
+
 ### Stdlib changes
 
 ## 0.7.4 Change list
diff --git a/test/unit/stdlib/collections/list.c3 b/test/unit/stdlib/collections/list.c3
index 000f38757..6e5fcbc1f 100644
--- a/test/unit/stdlib/collections/list.c3
+++ b/test/unit/stdlib/collections/list.c3
@@ -20,6 +20,22 @@ fn void overaligned_type()
 	assert((usz)l.get_ref(2) - (usz)l.get_ref(1) == Overalign.sizeof);
 }
 
+fn void remove_at()
+{
+	IntList test;
+	test.init(mem);
+	defer test.free();
+	test.add_array({ 1, 2, 3, 4 });
+	test::eq(test.array_view(), (int[]){ 1, 2, 3, 4 });
+	test.remove_at(0);
+	test::eq(test.array_view(), (int[]){ 2, 3, 4 });
+	test.remove_at(1);
+	test::eq(test.array_view(), (int[]){ 2, 4 });
+	test.remove_at(1);
+	test::eq(test.array_view(), (int[]){ 2 });
+	test.remove_at(0);
+	test::eq(test.array_view(), (int[]){ });
+}
 
 fn void delete_contains_index()
 {