fix: prevent var name clashing for delegated events without params (#13896)

.changeset/smooth-dragons-push.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: prevent var name clashing for delegated events without params

packages/svelte/src/compiler/phases/3-transform/client/utils.js

@@ -136,7 +136,7 @@ export function build_hoisted_params(node, context) {
 	if (node.params.length === 0) {
 		if (hoisted_params.length > 0) {
 			// For the event object
-			params.push(b.id('_'));
+			params.push(b.id(context.state.scope.generate('_')));
 		}
 	} else {
 		for (const param of node.params) {

packages/svelte/tests/runtime-runes/samples/event-without-params-clash/_config.js

@@ -0,0 +1,14 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	test({ assert, target, logs }) {
+		const btn = target.querySelector('button');
+
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.deepEqual(logs, ['test']);
+	}
+});

packages/svelte/tests/runtime-runes/samples/event-without-params-clash/main.svelte

@@ -0,0 +1,6 @@
+<svelte:options runes />
+<script>
+	let _ = "test"
+</script>
+
+<button onclick={() => { console.log(_)} }></button>