fix issue + add test

Author: trueadm

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

@@ -82,7 +82,7 @@ export function SnippetBlock(node, context) {
 
 	const declaration = b.const(node.expression, snippet);
 	const local_scope = context.state.scope;
-	const can_hoist = can_hoist_snippet(node, local_scope);
+	const can_hoist = can_hoist_snippet(node, local_scope, context.state.scopes);
 
 	// Top-level snippets are hoisted so they can be referenced in the `<script>`
 	if (context.path.length === 1 && context.path[0].type === 'Fragment') {

packages/svelte/src/compiler/phases/3-transform/server/visitors/SnippetBlock.js

@@ -18,7 +18,7 @@ export function SnippetBlock(node, context) {
 	// @ts-expect-error - TODO remove this hack once $$render_inner for legacy bindings is gone
 	fn.___snippet = true;
 
-	const can_hoist = can_hoist_snippet(node, context.state.scope);
+	const can_hoist = can_hoist_snippet(node, context.state.scope, context.state.scopes);
 
 	if (context.path.length === 1 && context.path[0].type === 'Fragment' && can_hoist) {
 		context.state.hoisted.push(fn);

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

@@ -456,16 +456,17 @@ export function transform_inspect_rune(node, context) {
 
 /**
  * @param {AST.SnippetBlock} node
+ * @param {Map<SvelteNode, Scope>} scopes
  * @param {Scope} scope
  */
-export function can_hoist_snippet(node, scope) {
+export function can_hoist_snippet(node, scope, scopes, visited = new Set()) {
 	let can_hoist = true;
 
 	ref_loop: for (const [reference] of scope.references) {
 		const local_binding = scope.get(reference);
 
 		if (local_binding) {
-			if (local_binding.node === node.expression) {
+			if (local_binding.node === node.expression || local_binding.scope.function_depth === 0) {
 				continue;
 			}
 			/** @type {Scope | null} */
@@ -477,6 +478,24 @@ export function can_hoist_snippet(node, scope) {
 				}
 				current_scope = current_scope.parent;
 			}
+
+			// Recursively check if another snippet can be hoisted
+			if (local_binding.kind === 'normal') {
+				for (const ref of local_binding.references) {
+					const parent = ref.path.at(-1);
+					if (ref.node === local_binding.node && parent?.type === 'SnippetBlock') {
+						const ref_scope = scopes.get(parent);
+						if (visited.has(ref)) {
+							break;
+						}
+						visited.add(ref);
+						if (ref_scope && can_hoist_snippet(parent, ref_scope, scopes, visited)) {
+							continue ref_loop;
+						}
+						break;
+					}
+				}
+			}
 			can_hoist = false;
 			break;
 		}

packages/svelte/src/compiler/types/index.d.ts

@@ -279,7 +279,8 @@ export interface Binding {
 		| 'snippet'
 		| 'store_sub'
 		| 'legacy_reactive'
-		| 'template';
+		| 'template'
+		| 'snippet';
 	declaration_kind: DeclarationKind;
 	/**
 	 * What the value was initialized with.

packages/svelte/tests/runtime-runes/samples/snippet-hoisted-module-2/Child.svelte

@@ -0,0 +1,13 @@
+<script module>
+	const message = 'hello';
+
+	export { one };
+</script>
+
+{#snippet one()}
+	{@render two()}
+{/snippet}
+
+{#snippet two()}
+	{message}
+{/snippet}

packages/svelte/tests/runtime-runes/samples/snippet-hoisted-module-2/_config.js

@@ -0,0 +1,8 @@
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true // Render in dev mode to check that the validation error is not thrown
+	},
+	html: `hello`
+});

packages/svelte/tests/runtime-runes/samples/snippet-hoisted-module-2/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	import { one } from './Child.svelte';
+</script>
+
+{@render one()}