From 82e84a8010ede7169b5c5f6b424407997025bdac Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Fri, 18 Oct 2024 17:37:41 +0100
Subject: [PATCH] fix: migrate reactive statements with inner blocks

---
 .changeset/smooth-apes-shave.md               |  5 +++++
 packages/svelte/src/compiler/migrate/index.js |  3 ++-
 .../input.svelte                              | 17 +++++++++++++++++
 .../output.svelte                             | 19 +++++++++++++++++++
 4 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/smooth-apes-shave.md
 create mode 100644 packages/svelte/tests/migrate/samples/reactive-statements-inner-block/input.svelte
 create mode 100644 packages/svelte/tests/migrate/samples/reactive-statements-inner-block/output.svelte

diff --git a/.changeset/smooth-apes-shave.md b/.changeset/smooth-apes-shave.md
new file mode 100644
index 000000000000..18d141f4efad
--- /dev/null
+++ b/.changeset/smooth-apes-shave.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: migrate reactive statements with inner blocks
diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
index 69c840aedbac..59189e21a31e 100644
--- a/packages/svelte/src/compiler/migrate/index.js
+++ b/packages/svelte/src/compiler/migrate/index.js
@@ -570,7 +570,8 @@ const instance_script = {
 
 				const labeled_has_single_assignment =
 					labeled_statement?.body.type === 'BlockStatement' &&
-					labeled_statement.body.body.length === 1;
+					labeled_statement.body.body.length === 1 &&
+					labeled_statement.body.body[0].type === 'ExpressionStatement';
 
 				const is_expression_assignment =
 					labeled_statement?.body.type === 'ExpressionStatement' &&
diff --git a/packages/svelte/tests/migrate/samples/reactive-statements-inner-block/input.svelte b/packages/svelte/tests/migrate/samples/reactive-statements-inner-block/input.svelte
new file mode 100644
index 000000000000..fe9821b58d3b
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/reactive-statements-inner-block/input.svelte
@@ -0,0 +1,17 @@
+<script lang="ts">
+	let menuElement: HTMLUListElement | undefined = undefined;
+	let left: number;
+  let top: number;
+
+  $: {
+    if (menuElement) {
+      const rect = menuElement.getBoundingClientRect();
+      const menuHeight = 0;
+
+      left = window.innerWidth - rect.width
+      top = window.innerHeight - menuHeight;
+    }
+  }
+</script>
+
+<ul bind:this={menuElement}></ul>
diff --git a/packages/svelte/tests/migrate/samples/reactive-statements-inner-block/output.svelte b/packages/svelte/tests/migrate/samples/reactive-statements-inner-block/output.svelte
new file mode 100644
index 000000000000..4ff77477e45b
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/reactive-statements-inner-block/output.svelte
@@ -0,0 +1,19 @@
+<script lang="ts">
+  import { run } from 'svelte/legacy';
+
+	let menuElement: HTMLUListElement | undefined = $state(undefined);
+	let left: number = $state();
+  let top: number = $state();
+
+  run(() => {
+    if (menuElement) {
+      const rect = menuElement.getBoundingClientRect();
+      const menuHeight = 0;
+
+      left = window.innerWidth - rect.width
+      top = window.innerHeight - menuHeight;
+    }
+  });
+</script>
+
+<ul bind:this={menuElement}></ul>
\ No newline at end of file