fix: disallow on directive with custom renderers

packages/svelte/src/compiler/phases/2-analyze/visitors/OnDirective.js

@@ -1,5 +1,6 @@
 /** @import { AST } from '#compiler' */
 /** @import { Context } from '../types' */
+import * as e from '../../../errors.js';
 import * as w from '../../../warnings.js';
 import { mark_subtree_dynamic } from './shared/fragment.js';
 
@@ -8,6 +9,10 @@ import { mark_subtree_dynamic } from './shared/fragment.js';
  * @param {Context} context
  */
 export function OnDirective(node, context) {
+	if (context.state.analysis.custom_renderer) {
+		e.incompatible_with_custom_renderer(node, '`on:`');
+	}
+
 	if (context.state.analysis.runes) {
 		const parent_type = context.path.at(-1)?.type;
 

packages/svelte/tests/custom-renderers/samples/on-directive/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	compile_error: '`on:` is not compatible with `customRenderer`'
+});

packages/svelte/tests/custom-renderers/samples/on-directive/main.svelte

@@ -0,0 +1 @@
+<button on:click={() => {}}>click me</button>