fix: handle expression labeled statements

Author: paoloricciuti

packages/svelte/src/compiler/migrate/index.js

@@ -493,8 +493,10 @@ const instance_script = {
 				);
 
 				const labeled_has_single_assignment =
-					labeled_statement?.body.type === 'BlockStatement' &&
-					labeled_statement.body.body.length === 1;
+					(labeled_statement?.body.type === 'BlockStatement' &&
+						labeled_statement.body.body.length === 1) ||
+					(labeled_statement?.body.type === 'ExpressionStatement' &&
+						labeled_statement.body.expression.type === 'AssignmentExpression');
 
 				if (
 					possible_derived &&

packages/svelte/tests/migrate/samples/single-assignment-labeled/input.svelte

@@ -40,6 +40,9 @@
 		evenmore = count * 64;
 		evenmore_doubled = evenmore * 2;
 	}
+
+	let almost_infinity;
+	$: almost_infinity = count * 128;
 </script>
 
 <button on:click={()=>{

packages/svelte/tests/migrate/samples/single-assignment-labeled/output.svelte

@@ -40,6 +40,9 @@
 		evenmore = count * 64;
 		evenmore_doubled = evenmore * 2;
 	});
+
+	let almost_infinity = $derived(count * 128);
+	
 </script>
 
 <button onclick={()=>{