fix: improve createRawSnippet types with cleanup type (#12894)

* fix: improve createRawSnippet types

Add cleanup type to return value of setup function

* changeset

---------

Co-authored-by: Rich Harris <hello@rich-harris.dev>

.changeset/nasty-penguins-pump.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: add cleanup function signature to `createRawSnippet`

packages/svelte/src/internal/client/dom/blocks/snippet.js

@@ -72,7 +72,7 @@ export function wrap_snippet(component, fn) {
  * @template {unknown[]} Params
  * @param {(...params: Getters<Params>) => {
  *   render: () => string
- *   setup?: (element: Element) => void
+ *   setup?: (element: Element) => void | (() => void)
  * }} fn
  * @returns {Snippet<Params>}
  */

packages/svelte/src/internal/server/blocks/snippet.js

@@ -7,7 +7,7 @@
  * @template {unknown[]} Params
  * @param {(...params: Getters<Params>) => {
  *   render: () => string
- *   setup?: (element: Element) => void
+ *   setup?: (element: Element) => void | (() => void)
  * }} fn
  * @returns {Snippet<Params>}
  */

packages/svelte/types/index.d.ts

@@ -378,7 +378,7 @@ declare module 'svelte' {
 	 * */
 	export function createRawSnippet<Params extends unknown[]>(fn: (...params: Getters<Params>) => {
 		render: () => string;
-		setup?: (element: Element) => void;
+		setup?: (element: Element) => void | (() => void);
 	}): Snippet<Params>;
 	/** Anything except a function */
 	type NotFunction<T> = T extends Function ? never : T;