fix: allow await in if block consequent and alternate (#16890)

Closes #16885

Author: yuki0418

.changeset/kind-tigers-retire.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: allow await in if block consequent and alternate

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

@@ -23,7 +23,11 @@ export function IfBlock(node, context) {
 	/** @type {Statement} */
 	let statement = b.if(test, consequent, alternate);
 
-	if (node.metadata.expression.has_await) {
+	if (
+		node.metadata.expression.has_await ||
+		node.consequent.metadata.has_await ||
+		node.alternate?.metadata.has_await
+	) {
 		statement = create_async_block(b.block([statement]));
 	}
 

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

@@ -0,0 +1 @@
+3

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

@@ -0,0 +1,10 @@
+{#if false}
+  {@const one = await 1}
+  {one}
+{:else if false}
+  {@const two = await 2}
+  {two}
+{:else}
+  {@const three = await 3}
+  {three}
+{/if}