revert snippet type changes

packages/svelte/src/index.d.ts

@@ -265,10 +265,7 @@ export type ComponentType<Comp extends SvelteComponent = SvelteComponent> = (new
 	element?: typeof HTMLElement;
 };
 
-/**
- * Internal implementation details that vary between environments
- */
-export type SnippetInternals = Branded<{}, 'SnippetInternals'>;
+declare const SnippetReturn: unique symbol;
 
 // Use an interface instead of a type, makes for better intellisense info because the type is named in more situations.
 /**
@@ -285,12 +282,13 @@ export type SnippetInternals = Branded<{}, 'SnippetInternals'>;
 export interface Snippet<Parameters extends unknown[] = []> {
 	(
 		this: void,
-		internal: SnippetInternals,
 		// this conditional allows tuples but not arrays. Arrays would indicate a
 		// rest parameter type, which is not supported. If rest parameters are added
 		// in the future, the condition can be removed.
-		...args: number extends Parameters['length'] ? never : Getters<Parameters>
-	): void;
+		...args: number extends Parameters['length'] ? never : Parameters
+	): typeof SnippetReturn & {
+		_: 'functions passed to {@render ...} tags must use the `Snippet` type imported from "svelte"';
+	};
 }
 
 interface DispatchOptions {

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

@@ -51,11 +51,10 @@ export function snippet(node, get_snippet, ...args) {
  * In development, wrap the snippet function so that it passes validation, and so that the
  * correct component context is set for ownership checks
  * @param {any} component
- * @param {Snippet} fn
- * @returns {Snippet}
+ * @param {(node: TemplateNode, ...args: any[]) => void} fn
  */
 export function wrap_snippet(component, fn) {
-	return (node, ...args) => {
+	return (/** @type {TemplateNode} */ node, /** @type {any[]} */ ...args) => {
 		var previous_component_function = dev_current_component_function;
 		set_dev_current_component_function(component);
 
@@ -77,7 +76,8 @@ export function wrap_snippet(component, fn) {
  * @returns {Snippet<Params>}
  */
 export function createRawSnippet(fn) {
-	return (anchor, ...params) => {
+	// @ts-expect-error the types are a lie
+	return (/** @type {TemplateNode} */ anchor, /** @type {Getters<Params>} */ ...params) => {
 		var snippet = fn(...params);
 
 		/** @type {Element} */
@@ -95,7 +95,7 @@ export function createRawSnippet(fn) {
 				w.invalid_raw_snippet_render();
 			}
 
-			/** @type {TemplateNode} */ (/** @type {unknown} */ (anchor)).before(element);
+			anchor.before(element);
 		}
 
 		const result = snippet.setup?.(element);

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

@@ -12,9 +12,10 @@
  * @returns {Snippet<Params>}
  */
 export function createRawSnippet(fn) {
-	return (payload, ...args) => {
+	// @ts-expect-error the types are a lie
+	return (/** @type {Payload} */ payload, /** @type {Params} */ ...args) => {
 		var getters = /** @type {Getters<Params>} */ (args.map((value) => () => value));
-		/** @type {Payload} */ (/** @type {unknown} */ (payload)).out += fn(...getters)
+		payload.out += fn(...getters)
 			.render()
 			.trim();
 	};