fix: wrap async `children` in `$$renderer.async` (#16862)

.changeset/rude-terms-confess.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: wrap async `children` in `$$renderer.async`

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

@@ -242,7 +242,12 @@ export function build_inline_component(node, expression, context) {
 			params.push(pattern);
 		}
 
-		const slot_fn = b.arrow(params, b.block(block.body));
+		const slot_fn = b.arrow(
+			params,
+			node.fragment.metadata.has_await
+				? b.block([create_async_block(b.block(block.body))])
+				: b.block(block.body)
+		);
 
 		if (slot_name === 'default' && !has_children_prop) {
 			if (

packages/svelte/tests/server-side-rendering/samples/async-children/_expected.html

@@ -0,0 +1 @@
+<!--[--><!--[--><!---->1<!--]--><!----><!--]-->

packages/svelte/tests/server-side-rendering/samples/async-children/component.svelte

@@ -0,0 +1,4 @@
+<script>
+    const { children } = $props();
+</script>
+{@render children()}

packages/svelte/tests/server-side-rendering/samples/async-children/main.svelte

@@ -0,0 +1,7 @@
+<script>
+    import Component from "./component.svelte";
+</script>
+<Component>
+    {@const one = await 1}
+    {one}
+</Component>