From d1190864f9fa26ad27856aa2100e3ee68c8c9457 Mon Sep 17 00:00:00 2001
From: Jungzl <13jungzl@gmail.com>
Date: Tue, 14 Apr 2026 14:20:17 +0800
Subject: [PATCH] fix: add regression test for tuple type preservation in
 snapshot

---
 packages/svelte/tests/types/state.ts | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 packages/svelte/tests/types/state.ts

diff --git a/packages/svelte/tests/types/state.ts b/packages/svelte/tests/types/state.ts
new file mode 100644
index 0000000000..6237f32075
--- /dev/null
+++ b/packages/svelte/tests/types/state.ts
@@ -0,0 +1,15 @@
+import type { ClassValue } from 'svelte/elements';
+
+// Regression test for #17117: this should not trigger deep/infinite type instantiation
+const cls = $state.raw<ClassValue[]>([]);
+const cls_snap: ReturnType<typeof $state.snapshot<ClassValue[]>> =
+	$state.snapshot<ClassValue[]>(cls);
+
+type SnapshotTuple = ReturnType<typeof $state.snapshot<[number, string]>>;
+
+const tuple_ok: SnapshotTuple = [1, 'a'];
+tuple_ok[0] === 1;
+tuple_ok[1] === 'a';
+
+// @ts-expect-error tuple element type should be preserved
+const tuple_wrong: SnapshotTuple = [1, 2];