fix: ensure $host rune correctly compiles in variable declarations (#13127)

Fixes #13121

Author: trueadm

.changeset/heavy-cars-ring.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: ensure $host rune correctly compiles in variable declarations

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

@@ -28,7 +28,8 @@ export function VariableDeclaration(node, context) {
 				rune === '$effect.tracking' ||
 				rune === '$effect.root' ||
 				rune === '$inspect' ||
-				rune === '$state.snapshot'
+				rune === '$state.snapshot' ||
+				rune === '$host'
 			) {
 				if (init != null && is_hoisted_function(init)) {
 					context.state.hoisted.push(

packages/svelte/tests/runtime-browser/custom-elements-samples/host-rune/_config.js

@@ -16,11 +16,13 @@ export default test({
 
 		el.shadowRoot.querySelectorAll('button')[0].click();
 		el.shadowRoot.querySelectorAll('button')[1].click();
-		assert.deepEqual(events, ['greeting', 'hello', 'greeting', 'welcome']);
+		el.shadowRoot.querySelectorAll('button')[2].click();
+		assert.deepEqual(events, ['greeting', 'hello', 'greeting', 'welcome', 'greeting', 'bonjour']);
 
 		el.removeEventListener('greeting', handle_evt);
 		el.shadowRoot.querySelectorAll('button')[0].click();
 		el.shadowRoot.querySelectorAll('button')[1].click();
-		assert.deepEqual(events, ['greeting', 'hello', 'greeting', 'welcome']);
+		el.shadowRoot.querySelectorAll('button')[2].click();
+		assert.deepEqual(events, ['greeting', 'hello', 'greeting', 'welcome', 'greeting', 'bonjour']);
 	}
 });

packages/svelte/tests/runtime-browser/custom-elements-samples/host-rune/main.svelte

@@ -8,7 +8,12 @@
 	function welcome() {
 		$host().dispatchEvent(new CustomEvent('greeting', { detail: 'welcome' }))
 	}
+	function bonjour() {
+		const element = $host();
+		element.dispatchEvent(new CustomEvent('greeting', { detail: 'bonjour' }))
+	}
 </script>
 
 <button onclick={() => greet('hello')}>say hello</button>
 <button onclick={welcome}>say welcome</button>
+<button onclick={bonjour}>say bonjour</button>