only wrap in iife if necessary

packages/svelte/src/compiler/phases/3-transform/shared/assignments.js

@@ -54,6 +54,10 @@ export function visit_assignment_expression(node, context, build_assignment) {
 			block.body.push(b.return(rhs));
 		}
 
+		if (is_standalone && !should_cache) {
+			return block;
+		}
+
 		const iife = b.arrow(should_cache ? [rhs] : [], block);
 
 		const iife_is_async =

packages/svelte/tests/snapshot/samples/destructured-assignments/_expected/client/index.svelte.js

@@ -7,12 +7,12 @@ let c = 3;
 let d = 4;
 
 export function update(array) {
-	(() => {
+	{
 		let [$$1, $$2] = array;
 
 		$.set(a, $$1, true);
 		$.set(b, $$2, true);
-	})();
+	};
 
 	[c, d] = array;
 }