fix: render `:catch` of `#await` block with correct key (#17769)

Fixes #17678

.changeset/green-sites-lead.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: render `:catch` of `#await` block with correct key

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

@@ -102,7 +102,7 @@ export function await_block(node, get_input, pending_fn, then_fn, catch_fn) {
 				(e) => {
 					resolve(() => {
 						internal_set(error, e);
-						branches.ensure(THEN, catch_fn && ((target) => catch_fn(target, error)));
+						branches.ensure(CATCH, catch_fn && ((target) => catch_fn(target, error)));
 
 						if (!catch_fn) {
 							// Rethrow the error if no catch block exists

packages/svelte/tests/runtime-runes/samples/await-immediate-fulfilled/_config.js

@@ -0,0 +1,61 @@
+import { test } from '../../test';
+import { tick } from 'svelte';
+
+export default test({
+	async test({ assert, target }) {
+		const [resolveImmediate, resolveTimeout, rejectImmediate, rejectTimeout] =
+			target.querySelectorAll('button');
+
+		rejectTimeout.click();
+		await new Promise((resolve) => setTimeout(resolve, 1));
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>Resolve (immediate)</button>
+				<button>Resolve (timeout)</button>
+				<button>Reject (immediate)</button>
+				<button>Reject (timeout)</button>
+				<p> err [Yeah] </p>
+			`
+		);
+
+		resolveImmediate.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>Resolve (immediate)</button>
+				<button>Resolve (timeout)</button>
+				<button>Reject (immediate)</button>
+				<button>Reject (timeout)</button>
+				<p> resolved [?] </p>
+			`
+		);
+
+		resolveTimeout.click();
+		await new Promise((resolve) => setTimeout(resolve, 1));
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>Resolve (immediate)</button>
+				<button>Resolve (timeout)</button>
+				<button>Reject (immediate)</button>
+				<button>Reject (timeout)</button>
+				<p> resolved [OK] </p>
+			`
+		);
+
+		rejectImmediate.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>Resolve (immediate)</button>
+				<button>Resolve (timeout)</button>
+				<button>Reject (immediate)</button>
+				<button>Reject (timeout)</button>
+				<p> err [??] </p>
+			`
+		);
+	}
+});

packages/svelte/tests/runtime-runes/samples/await-immediate-fulfilled/main.svelte

@@ -0,0 +1,34 @@
+<script>
+	let p = $state(null);
+</script>
+
+<button onclick={()=>{
+	p = new Promise((resolve, reject) => {
+		resolve("?");
+	});
+}}>Resolve (immediate)</button>
+<button onclick={()=>{
+	p = new Promise((resolve, reject) => {
+		setTimeout(() => resolve("OK"), 1);
+	});
+}}>Resolve (timeout)</button>
+<button onclick={()=>{
+	p = new Promise((resolve, reject) => {
+		reject("??");
+	});
+}}>Reject (immediate)</button>
+<button onclick={()=>{
+	p = new Promise((resolve, reject) => {
+		setTimeout(() => reject("Yeah"), 1);
+	});
+}}>Reject (timeout)</button>
+
+<p>
+	{#await p}
+		...
+	{:then v}
+		resolved [{v}]
+	{:catch err}
+		err [{err}]
+	{/await}
+</p>